@article{dong_lee_song_neu_kashani_you_ade_2025, title={Control Over Vertical Composition in Low Complexity Polymer Solar Cells}, volume={1}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202404962}, DOI={10.1002/aenm.202404962}, abstractNote={Abstract Inverted organic solar cells are promising due to their better stability compared to conventional structures. Donors with low synthetic complexity are desirable to lower costs. However, inverted devices are rarely used in low‐complexity systems. To investigate the reasons, the low‐complexity PTQ10:BTP‐eC9 binary system is benchmarked against the high‐complexity PM6:BTP‐eC9 system. In PTQ10:BTP‐eC9, where the efficiency of inverted devices lags the conventional structure significantly, distinct wetting layers are observed in conventional and inverted device structures. Conversely, the vertical distribution of PM6:BTP‐eC9 remains unaffected by changes in interlayer materials. The surface is always enriched in BTP‐eC9, but less for PM6. Importantly, the addition of PC 71 BM reduces the nonuniform vertical composition gradients. As the PC 71 BM concentration increases, the efficiency of the inverted PTQ10 devices approach that of the conventional devices and PTQ10:BTP‐eC9:PC 71 BM (1:1.2:0.4) exhibits negligible efficiency differences between inverted (14.01%) and conventional (14.49%) architectures. The concentration‐gradients aredriven by the interfacial energy between the active layer and interlayer materials and the casting kinetics in the case of the surface. Understanding the thermodynamic and kinetic aspects provides valuable insights for optimizing the performance of inverted organic solar cells, bringing them closer to practical applications.}, journal={ADVANCED ENERGY MATERIALS}, author={Dong, Xinyun and Lee, Byongkyu and Song, Runqiao and Neu, Justin and Kashani, Somayeh and You, Wei and Ade, Harald}, year={2025}, month={Jan} } @article{qin_tu_woodward_chauhan_thapa_amassian_neuf_you_yin_ade_2025, title={Low‐Cost, High‐Efficiency Organic Solar Cells Based on Ecofriendly Processing Solvent}, url={https://doi.org/10.1002/aesr.202400268}, DOI={10.1002/aesr.202400268}, journal={Advanced Energy and Sustainability Research}, author={Qin, Yunpeng and Tu, Haoran and Woodward, Nathan and Chauhan, Mihirsinh and Thapa, Gaurab J. and Amassian, Aram and Neuf, Justin and You, Wei and Yin, Haipeng and Ade, Harald}, year={2025}, month={Jan} } @article{yu_wang_kwok_zhou_yao_mukherjee_sergeev_hu_fu_ng_et al._2024, title={A polymer acceptor with double-decker configuration enhances molecular packing for high-performance all-polymer solar cells}, volume={8}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2024.06.010}, number={8}, journal={JOULE}, author={Yu, Han and Wang, Yan and Kwok, Chung Hang and Zhou, Rongkun and Yao, Zefan and Mukherjee, Subhrangsu and Sergeev, Aleksandr and Hu, Haixia and Fu, Yuang and Ng, Ho Ming and et al.}, year={2024}, month={Aug} } @article{shanahan_yan_olanrewaju_kashani_ade_so_you_2024, title={Acid-Triggered Side Chain Cleavage Leads to Doped Conjugated Polymers of High Conductivity}, volume={10}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.4c09843}, abstractNote={Cleavable side chain based conjugated polymers (CSCPs) represent a unique approach to offering solution processability with added benefits via the elimination of insulating side chains. This work highlights an optimally designed polythiophene-carboxylic acid based CSCP, POET-T2-COOH, which achieves a conductivity exceeding 350 S/cm in molecularly doped and side chain cleaved films, 100-100,000 times higher than three other structurally isomeric CSCPs. The high conductivity of POET-T2-COOH is accomplished via a new "cleavage with doping" methodology, synergistically combining a strong acid and a primary dopant. This hybrid method achieves the greatest conductivity in all isomeric CSCPs over conventional doping or cleavage techniques. The doped and side chain cleaved POET-T2-COOH displays a stable conductivity in inert atmospheres and a high work function of 5.3 eV, opening up new applications.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Shanahan, Jordan and Yan, Liang and Olanrewaju, Yusuf and Kashani, Somayeh and Ade, Harald and So, Franky and You, Wei}, year={2024}, month={Oct} } @article{arneson_huang_huang_fan_gao_ye_ade_li_forrest_2024, title={Erratum: "Relationship between charge transfer state electroluminescence and the degradation of organic photovoltaics" [Appl. Phys. Lett. 118, 063301 (2021)]}, volume={125}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0237612}, DOI={10.1063/5.0237612}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Arneson, Claire and Huang, Xinjing and Huang, Xiaheng and Fan, Dejiu and Gao, Mengyuan and Ye, Long and Ade, Harald and Li, Yongxi and Forrest, Stephen R.}, year={2024}, month={Sep} } @article{schrickx_kashani_buck_ding_rech_flagg_li_kudenov_you_richter_et al._2024, title={Exceptional Alignment in a Donor-Acceptor Conjugated Polymer via a Previously Unobserved Liquid Crystal Mesophase}, volume={4}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202315183}, abstractNote={AbstractOrienting polymer semiconductors is desirable to optimize device characteristics, provide insight into microstructure, and magnify subtle phase behavior. Here, a combination of uniaxial strain and subsequent heating of the donor–acceptor (DA) polymer PBnDT‐FTAZ is discovered to lead to exceptional optical dichroic ratios of up to 38 (and close to 50 near the polymer's absorption edge). This alignment is achieved due to the existence of a previously undetected thermotropic liquid crystal (LC) mesophase. The LC transition, not discernable through calorimetry, is uncovered through a combination of in situ UV–vis spectroscopy, X‐ray scattering, and dynamic mechanical analysis (DMA). Comparing PBnDT‐FTAZ to the non‐fluorinated PBnDT‐HTAZ and the homo polymer PBnDT, all of which show similar thermal transitions, reveals that exceptional alignment is only found in PBnDT‐FTAZ. This is attributed to the PBnDT‐FTAZ film having two distinct liquid crystal populations, and the polymer templating to a highly aligned, high‐clearing temperature population when heated. The DMA thermal relaxation behavior observed here is also seen in other DA conjugated polymers suggesting that such thermotropic LC mesophases may be common in these materials. These findings demonstrate a polymer semiconductor with remarkable alignment and uncover phase behavior with broad implications for process‐structure‐property relationships in polymer semiconductors.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Schrickx, Harry M. and Kashani, Somayeh and Buck, Lauren and Ding, Kan and Rech, Jeromy J. and Flagg, Lucas Q. and Li, Ruipeng and Kudenov, Michael W. and You, Wei and Richter, Lee J. and et al.}, year={2024}, month={Apr} } @article{pacalaj_dong_ramirez_mackenzie_hosseini_bittrich_heger_kaienburg_mukherjee_wu_et al._2024, title={From generation to collection - impact of deposition temperature on charge carrier dynamics of high-performance vacuum-processed organic solar cells}, volume={10}, ISSN={["1754-5706"]}, DOI={10.1039/d4ee03623a}, abstractNote={Vacuum-processed organic solar cells (VP-OSCs) possess many advantages for scalability. However, as the academic community focusses on high performing solution-processed OSCs, detailed studies about the relation between morphology and device...}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Pacalaj, Richard Adam and Dong, Yifan and Ramirez, Ivan and Mackenzie, Roderick C. I. and Hosseini, Seyed Mehrdad and Bittrich, Eva and Heger, Julian Eliah and Kaienburg, Pascal and Mukherjee, Subhrangsu and Wu, Jiaying and et al.}, year={2024}, month={Oct} } @article{henry_ade_2024, title={Melt Expansion and Thermal Transitions of Semiconducting Polymers in Thin Films}, volume={11}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202409465}, abstractNote={Abstract The molecular self‐organization and reorganization and thus volumetric and density changes during structural relaxation and melting of modern organic semi‐conducting materials remains largely unknown, particularly in the device relevant thin film geometry where the initial state may be structurally quenched away from equilibrium. Here, the apparent mass‐thickness of a range of semi‐conducting polymeric or molecular model materials systems is measured through in situ ellipsometry. Surprisingly, the volume changes upon melting correlate inversely, with a few exceptions, to the quality of crystallinity found via x‐ray methods (i.e., directly correlate with the paracrystalline g‐parameter) rather than the melting enthalpy that is possibly a proxy for the degree of crystallinity. This study also observes changes in orientation and/or density due to segmental relaxation during the first heat, thus complementing other characterization methods that measure relaxation or reorganization transitions. Semiconducting materials exhibit very large melt expansion and a richer phase‐behavior compared to commodity polymers, presumably due to their complex chemical structure. The results delineate an important and novel structure‐function relation that, together with simulations constrained by these results, will lead to better rational design of semi‐conducting materials.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Henry, Reece and Ade, Harald}, year={2024}, month={Nov} } @article{kim_ng_pan_lai_li_li_ding_lu_ade_cui_et al._2024, title={Modification of the Electron-Deficient Core on Unfused-Ring Acceptors Enabling High Open-Circuit Voltage of Organic Solar Cells}, volume={1}, ISSN={["2367-198X"]}, DOI={10.1002/solr.202300997}, abstractNote={Unfused‐ring acceptors with different electron‐deficient central units, dithieno[3,2‐f:2′,3′‐h]quinoxaline (KS40) and dithieno[3,2‐e:2′,3′‐g]‐2,1,3‐benzoxadiazole (KS41) are synthesized and characterized. When blended with PM6, KS40 with a weaker electron‐accepting quinoxaline exhibits a much higher open‐circuit voltage (VOC) of 0.945 V. As a result, the KS40‐based device achieves a power conversion efficiency (PCE) of 12.2%. PM6:KS41‐based devices, in contrast, afford improved charge mobilities as well as suppressed recombination behavior, which eventually leads to an improvement in the fill factor (72.4%). Consequently, the device is able to achieve a PCE of 11.6%.}, journal={SOLAR RRL}, author={Kim, Ha Kyung and Ng, Ho Ming and Pan, Mingao and Lai, Joshua Yuk Lin and Li, Xingye and Li, Yuhao and Ding, Kan and Lu, Xinhui and Ade, Harald and Cui, Bo and et al.}, year={2024}, month={Jan} } @article{neu_ding_liu_ade_xu_you_2024, title={Optimized Incorporation of Furan into Diketopyrrolopyrrole-Based Conjugated Polymers for Organic Field-Effect Transistors}, volume={4}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.202400171}, abstractNote={AbstractFlexible electronics have received considerable attention in the past decades due to their promising application in rollable display screens, wearable devices, implantable devices, and other electronic applications. In particular, conjugated polymers are favored for flexible electronics due to their mechanical flexibility and potential for solution‐processed fabrication techniques, such as blade‐coating, roll‐to‐roll printing, and high‐throughput printing allowing for high‐performance transistor devices. Thiophene is the prevailing conjugated unit to construct these conjugated polymers due to its favorable electronic properties. On the other hand, furans are among the few conjugated moieties that are easily derived from bio renewable resources. To promote sustainability, we selectively introduced furan into the conjugated backbone of a high‐mobility polymer scaffold and systematically studied the effect on the microstructure and charge transport. We show that partially and selectively replacing thiophene units with furan can yield nearly comparable performance compared to the all‐thiophene polymer. This strategy offers an improvement in the sustainability of the polymer by incorporating bio‐sourced furan without sacrificing the high‐performance characteristics. Meanwhile, polymers with incorrect or complete furan incorporation show reduced mobilities. This work serves to develop coherent structure–morphology–performance relationships; such knowledge will establish guidelines for the future development of sustainable, furan‐based conjugated materials.}, journal={CHEMSUSCHEM}, author={Neu, Justin and Ding, Kan and Liu, Shubin and Ade, Harald and Xu, Jie and You, Wei}, year={2024}, month={Apr} } @article{zou_ng_yu_ding_yao_chen_pun_hu_ding_ma_et al._2024, title={Precisely Controlling Polymer Acceptors with Weak Intramolecular Charge Transfer Effect and Superior Coplanarity for Efficient Indoor All-Polymer Solar Cells with over 27% Efficiency}, volume={6}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202405404}, abstractNote={Abstract Indoor photovoltaics (IPVs) are garnering increasing attention from both the academic and industrial communities due to the pressing demand of the ecosystem of Internet‐of‐Things. All‐polymer solar cells (all‐PSCs), emerging as a sub‐type of organic photovoltaics, with the merits of great film‐forming properties, remarkable morphological and light stability, hold great promise to simultaneously achieve high efficiency and long‐term operation in IPV's application. However, the dearth of polymer acceptors with medium‐bandgap has impeded the rapid development of indoor all‐PSCs. Herein, a highly efficient medium‐bandgap polymer acceptor (PYFO‐V) is reported through the synergistic effects of side chain engineering and linkage modulation and applied for indoor all‐PSCs operation. As a result, the PM6:PYFO‐V‐based indoor all‐PSC yields the highest efficiency of 27.1% under LED light condition, marking the highest value for reported binary indoor all‐PSCs to date. More importantly, the blade‐coated devices using non‐halogenated solvent ( o ‐xylene) maintain an efficiency of over 23%, demonstrating the potential for industry‐scale fabrication. This work not only highlights the importance of fine‐tuning intramolecular charge transfer effect and intrachain coplanarity in developing high‐performance medium‐bandgap polymer acceptors but also provides a highly efficient strategy for indoor all‐PSC application.}, journal={ADVANCED MATERIALS}, author={Zou, Bosen and Ng, Ho Ming and Yu, Han and Ding, Pengbo and Yao, Jia and Chen, Dezhang and Pun, Sai Ho and Hu, Huawei and Ding, Kan and Ma, Ruijie and et al.}, year={2024}, month={Jun} } @article{kwon_giridharagopal_neu_kashani_chen_quezada_guo_ade_you_ginger_2024, title={Quantifying Doping Efficiency to Probe the Effects of Nanoscale Morphology and Solvent Swelling in Molecular Doping of Conjugated Polymers}, volume={2}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.4c00153}, abstractNote={We study the doping of conjugated polymers from droplets of molecular dopant solutions, as might be used in additive manufacturing approaches. We compare the doping efficiency of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) solutions between two model conjugated polymers, regioregular poly(3-hexylthiophene) (P3HT) and poly(bithiophene-thienothiophene) copolymer with a triethylene glycol side chain (P(g32T-TT)). We find that F4TCNQ dopes P(g32T-TT) more efficiently from solution, producing films with >103 times higher conductivity. Using spectroelectrochemistry to calibrate polaron spectra to known hole injection levels, we quantify the doping efficiency (polarons created/dopant molecule added) to be higher than 170% for P(g32T-TT) but only 47.2% for P3HT. We further explore the differences in molecular doping using a combination of scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (cAFM). We explore doping efficiency and aggregation as a function of the solvent of the dopant solution, side chain, and regioregularity of conjugated polymers; we show that the doping efficiency and dopant aggregation are both correlated with the ability of the dopant/solvent solution to swell the conjugated polymer, with combinations that swell, resulting in more efficient doping and smoother films with less aggregation.}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kwon, Sung-Joo and Giridharagopal, Rajiv and Neu, Justin and Kashani, Somayeh and Chen, Shinya E. and Quezada, Ramsess J. and Guo, Jiajie and Ade, Harald and You, Wei and Ginger, David S.}, year={2024}, month={Feb} } @article{chen_zhao_yu_sergeev_zhu_ding_fu_ng_kwok_zou_et al._2024, title={Tailoring Cyano Substitutions on Quinoxaline-based Small-Molecule Acceptors Enabling Enhanced Molecular Packing for High-Performance Organic Solar Cells}, volume={5}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202400285}, abstractNote={Abstract Cyanation is a common chemical modification strategy to fine‐tune the energy levels and molecular packing of organic semiconductors, especially materials used in organic solar cells (OSCs). Generally, cyanation is used to modify the end groups of high‐performance small‐molecule acceptors (SMAs). However, the cyanation strategy has not been investigated on the central backbone of SMAs, which could introduce stronger intermolecular interaction and enhance the π–π stacking for rapid charge transport. This paper, for the first time, reports a new cyanation strategy on the central benzo‐quinoxaline core and synthesizes two novel A‐DA'D‐A type SMAs, named BQx‐CN and BQx‐2CN, with mono‐ and di‐cyanide groups, respectively. Through tailoring the number of CN groups, the BQx‐CN‐based OSC exhibits the best device performance of 18.8%, which is significantly higher than the non‐cyano BQx‐based one. The reason for the superior performance of BQx‐CN‐based devices can be attributed to the fine‐tuned energy level, stronger packing, and ideal phase segregation, which lead to superior exciton dissociation, faster charge transport, and suppressed recombination, therefore the highest fill factor (FF) and power conversion efficiencies (PCE). The research demonstrates the effectiveness of the cyanation strategy on the central core of SMAs for enhanced molecular packing and better performance of OSCs.}, journal={ADVANCED ENERGY MATERIALS}, author={Chen, Li and Zhao, Chaoyue and Yu, Han and Sergeev, Aleksandr and Zhu, Liangxiang and Ding, Kan and Fu, Yuang and Ng, Ho Ming and Kwok, Chung Hang and Zou, Xinhui and et al.}, year={2024}, month={May} } @article{wang_guo_liu_shu_han_ding_mukherjee_zhang_yip_yi_et al._2024, title={The role of interfacial donor-acceptor percolation in efficient and stable all-polymer solar cells}, volume={15}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-024-45455-0}, abstractNote={AbstractPolymerization of Y6-type acceptor molecules leads to bulk-heterojunction organic solar cells with both high power-conversion efficiency and device stability, but the underlying mechanism remains unclear. Here we show that the exciton recombination dynamics of polymerized Y6-type acceptors (Y6-PAs) strongly depends on the degree of aggregation. While the fast exciton recombination rate in aggregated Y6-PA competes with electron-hole separation at the donor–acceptor (D–A) interface, the much-suppressed exciton recombination rate in dispersed Y6-PA is sufficient to allow efficient free charge generation. Indeed, our experimental results and theoretical simulations reveal that Y6-PAs have larger miscibility with the donor polymer than Y6-type small molecular acceptors, leading to D–A percolation that effectively prevents the formation of Y6-PA aggregates at the interface. Besides enabling high charge generation efficiency, the interfacial D–A percolation also improves the thermodynamic stability of the blend morphology, as evident by the reduced device “burn-in” loss upon solar illumination.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Wang, Zhen and Guo, Yu and Liu, Xianzhao and Shu, Wenchao and Han, Guangchao and Ding, Kan and Mukherjee, Subhrangsu and Zhang, Nan and Yip, Hin-Lap and Yi, Yuanping and et al.}, year={2024}, month={Feb} } @article{peng_stingelin_ade_michels_2023, title={A materials physics perspective on structure–processing–function relations in blends of organic semiconductors}, url={https://doi.org/10.1038/s41578-023-00541-5}, DOI={10.1038/s41578-023-00541-5}, journal={Nature Reviews Materials}, author={Peng, Zhengxing and Stingelin, Natalie and Ade, Harald and Michels, Jasper J.}, year={2023}, month={Mar} } @article{du_luong_sabury_therdkatanyuphong_chae_welton_jones_zhang_peng_zhu_et al._2023, title={Additive-free molecular acceptor organic solar cells processed from a biorenewable solvent approaching 15% efficiency}, volume={10}, ISSN={["2051-6355"]}, DOI={10.1039/d3mh01133j}, abstractNote={We report on the use of molecular acceptors and donor polymers processed with a biomass-derived solvent 2-methyltetrahydrofuran to facilitate bulk heterojunction organic photovoltaics with power conversion efficiency approaching 15%.}, journal={MATERIALS HORIZONS}, author={Du, Zhifang and Luong, Hoang Mai and Sabury, Sina and Therdkatanyuphong, Pattarawadee and Chae, Sangmin and Welton, Claire and Jones, Austin L. and Zhang, Junxiang and Peng, Zhengxing and Zhu, Ziyue and et al.}, year={2023}, month={Oct} } @article{luo_li_zhang_zou_zhao_ding_huang_song_yi_yu_et al._2023, title={Auxiliary sequential deposition enables 19%-efficiency organic solar cells processed from halogen-free solvents}, volume={14}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-023-41978-0}, abstractNote={AbstractHigh-efficiency organic solar cells are often achieved using toxic halogenated solvents and additives that are constrained in organic solar cells industry. Therefore, it is important to develop materials or processing methods that enabled highly efficient organic solar cells processed by halogen free solvents. In this paper, we report an innovative processing method named auxiliary sequential deposition that enables 19%-efficiency organic solar cells processed by halogen free solvents. Our auxiliary sequential deposition method is different from the conventional blend casting or sequential deposition methods in that it involves an additional casting of dithieno[3,2-b:2’,3’-d]thiophene between the sequential depositions of the donor (D18-Cl) and acceptor (L8-BO) layers. The auxiliary sequential deposition method enables dramatic performance enhancement from 15% to over 18% compared to the blend casting and sequential deposition methods. Furthermore, by incorporating a branched-chain-engineered acceptor called L8-BO-X, device performance can be boosted to over 19% due to increased intermolecular packing, representing top-tier values for green-solvent processed organic solar cells. Comprehensive morphological and time-resolved characterizations reveal that the superior blend morphology achieved through the auxiliary sequential deposition method promotes charge generation while simultaneously suppressing charge recombination. This research underscores the potential of the auxiliary sequential deposition method for fabricating highly efficient organic solar cells using environmentally friendly solvents.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Luo, Siwei and Li, Chao and Zhang, Jianquan and Zou, Xinhui and Zhao, Heng and Ding, Kan and Huang, Hui and Song, Jiali and Yi, Jicheng and Yu, Han and et al.}, year={2023}, month={Oct} } @article{zhao_kim_ding_jung_li_ade_lee_forrest_2023, title={Control of Host-Matrix Morphology Enables Efficient Deep-Blue Organic Light-Emitting Devices}, volume={2}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202210794}, abstractNote={AbstractMixing a sterically bulky, electron‐transporting host material into a conventional single host–guest emissive layer is demonstrated to suppress phase separation of the host matrix while increasing the efficiency and operational lifetime of deep‐blue phosphorescent organic light‐emitting diodes (PHOLEDs) with chromaticity coordinates of (0.14, 0.15). The bulky host enables homogenous mixing of the molecules comprising the emissive layer while suppressing single host aggregation; a significant loss channel of nonradiative recombination. By controlling the amorphous phase of the host‐matrix morphology, the mixed‐host device achieves a significant reduction in nonradiative exciton decay, resulting in 120 ± 6% increase in external quantum efficiency relative to an analogous, single‐host device. In contrast to single host PHOLEDs where electrons are transported by the host and holes by the dopants, both charge carriers are conducted by the mixed host, reducing the probability of exciton annihilation, thereby doubling of the deep‐blue PHOLED operational lifetime. These findings demonstrate that the host matrix morphology affects almost every aspect of PHOLED performance.}, journal={ADVANCED MATERIALS}, author={Zhao, Haonan and Kim, Jongchan and Ding, Kan and Jung, Mina and Li, Yongxi and Ade, Harald and Lee, Jun Yeob and Forrest, Stephen R.}, year={2023}, month={Feb} } @article{charles_edwards_ravishankar_calero_henry_rech_saravitz_you_ade_o'connor_et al._2023, title={Emergent molecular traits of lettuce and tomato grown under wavelength-selective solar cells}, volume={14}, ISSN={["1664-462X"]}, DOI={10.3389/fpls.2023.1087707}, abstractNote={The integration of semi-transparent organic solar cells (ST-OSCs) in greenhouses offers new agrivoltaic opportunities to meet the growing demands for sustainable food production. The tailored absorption/transmission spectra of ST-OSCs impacts the power generated as well as crop growth, development and responses to the biotic and abiotic environments. To characterize crop responses to ST-OSCs, we grew lettuce and tomato, traditional greenhouse crops, under three ST-OSC filters that create different light spectra. Lettuce yield and early tomato development are not negatively affected by the modified light environment. Our genomic analysis reveals that lettuce production exhibits beneficial traits involving nutrient content and nitrogen utilization while select ST-OSCs impact regulation of flowering initiation in tomato. These results suggest that ST-OSCs integrated into greenhouses are not only a promising technology for energy-neutral, sustainable and climate-change protected crop production, but can deliver benefits beyond energy considerations.}, journal={FRONTIERS IN PLANT SCIENCE}, author={Charles, Melodi and Edwards, Brianne and Ravishankar, Eshwar and Calero, John and Henry, Reece and Rech, Jeromy and Saravitz, Carole and You, Wei and Ade, Harald and O'Connor, Brendan and et al.}, year={2023}, month={Feb} } @article{kashani_rech_liu_baustert_ghaffari_angunawela_xiong_dinku_you_graham_et al._2023, title={Exciton Binding Energy in Organic Polymers: Experimental Considerations and Tuning Prospects}, volume={12}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202302837}, abstractNote={AbstractDiscrepancies in reported values of exciton binding energy (Eb) for organic semiconductors (OSs) necessitate a comprehensive study. Traditionally, Eb is defined as the difference between the transport gap (Et) and the optical gap (Eopt). Here, the Eb values of PBnDT‐TAZ polymer variants are determined using two commonly employed methods: a combination of ultraviolet photoemission spectroscopy and low‐energy inverse photoemission spectroscopy (UPS‐LEIPS) and solid‐state cyclic voltammetry (CV). Eb values obtained by UPS‐LEIPS show low dispersion and no clear correlation with the polymer structure and thedielectric properties. In contrast, CV reveals a larger dispersion (200 meV‐1 eV) and an apparent qualitative Eb‐molecular structure correlation, as the lowest Eb values are observed for oligo‐ethylene glycol side chains. This discrepancy is discussed by examining the implications of the traditional definition of Eb. Additionally, the impact of both intrinsic and extrinsic factors contributing to the derived experimental values of Et is discussed. The differences in intrinsic and extrinsic factors highlight the context‐dependent nature of measurement when drawing global conclusions. Notably, the observed Eb trend derived from CV is not intrinsic to the pure materials but likely linked to electrolyte swelling and associated changes in dielectric environment, suggesting that high‐efficiency single‐material organic photovoltaics with low Eb may be possible via high dielectric materials.}, journal={ADVANCED ENERGY MATERIALS}, author={Kashani, Somayeh and Rech, Jeromy James and Liu, Tuo and Baustert, Kyle and Ghaffari, Abbas and Angunawela, Indunil and Xiong, Yuan and Dinku, Abay and You, Wei and Graham, Kenneth and et al.}, year={2023}, month={Dec} } @article{henry_balar_ade_2023, title={In-Situ Ellipsometry for the Determination of Thermal Transitions and Relaxations in Organic Photovoltaic Materials}, volume={35}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.3c00714}, abstractNote={Characterization of thermodynamic transitions and kinetic processes in optoelectronic materials is critical for understanding the optimized processing conditions and final device structural stability. Differential scanning calorimetry (DSC) is traditionally used to determine melting, crystallization, and glass transition temperatures as well as additional transitions, such as polymorphic solid–solid transitions. These transition temperatures are utilized to understand the general structure–property relations of materials and can be used to inform processing protocols in device fabrication in order to facilitate the formation of preferable microstructures for optimized electronic properties. However, traditional DSC experiments are limited to bulk-like samples and cannot characterize device relevant, controlled thin film geometries. Here we demonstrate that ellipsometry is at least as capable as traditional DSC experiments to determine relevant thermal transitions through a direct comparison using a range of optoelectronic and benchmarking materials. In addition, ellipsometry measurement protocols can uncover kinetic characteristics and possible additional transitions that are not observed in traditional DSC. Furthermore, ellipsometry observes density changes associated with free volume and molecular packing and associated hysteresis during temperature sweeps directly, an avenue of inquiry underutilized to date. We anticipate that ellipsometry protocols will allow for a more widely used, powerful complement to DSC characterization.}, number={18}, journal={CHEMISTRY OF MATERIALS}, author={Henry, Reece and Balar, Nrup and Ade, Harald}, year={2023}, month={Sep}, pages={7406–7421} } @article{wu_jiang_li_zhang_ding_zhuo_guo_li_meng_ade_et al._2023, title={Introducing a Phenyl End Group in the Inner Side Chains of A-DA'D-A Acceptors Enables High-Efficiency Organic Solar Cells Processed with Nonhalogenated Solvent}, volume={10}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202302946}, abstractNote={AbstractPower conversion efficiency (PCE) of organic solar cells (OSCs) processed by nonhalogenated solvents is unsatisfactory due to the unfavorable morphology. Herein, two new small molecule acceptors (SMAs) Y6‐Ph and L8‐Ph are synthesized by introducing a phenyl end group in the inner side chains of the SMAs of Y6 and L8‐BO, respectively, for overcoming the excessive aggregation of SMAs in the long‐time film forming processed by nonhalogenated solvents. First, the effect of the film forming time on the aggregation property and photovoltaic performance of Y6, L8‐BO, Y6‐Ph, and L8‐Ph is studied by using the commonly used solvents: chloroform (CF) (rapid film forming process) and chlorobenzene (CB) (slow film forming process). It is found that Y6‐ and L8‐BO‐based OSCs exhibit a dramatic drop in PCE from CF‐ to CB‐processed devices owing to the large phase separation, while the Y6‐Ph and L8‐Ph based OSCs show obviously increased PCEs Furthermore, L8‐Ph‐based OSCs processed by nonhalogenated solvent o‐xylene (o‐XY) achieved a high PCE of 18.40% with an FF of 80.11%. The results indicate that introducing a phenyl end group in the inner side chains is an effective strategy to modulate the morphology and improve the photovoltaic performance of the OSCs processed by nonhalogenated solvents.}, journal={ADVANCED MATERIALS}, author={Wu, Xiangxi and Jiang, Xin and Li, Xiaojun and Zhang, Jinyuan and Ding, Kan and Zhuo, Hongmei and Guo, Jing and Li, Jing and Meng, Lei and Ade, Harald and et al.}, year={2023}, month={Oct} } @article{siddika_peng_balar_dong_zhong_you_ade_oconnor_2023, title={Molecular interactions that drive morphological and mechanical stabilities in organic solar cells}, volume={7}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2023.06.002}, abstractNote={Morphological and mechanical stabilities of organic solar cells (OSCs) are of paramount importance to ensure long-lived devices. However, the fundamental drivers of these stability metrics and their competing relationship have yet to be well defined. Here, several high-performance polymers and small molecule acceptors (SMAs) are considered to assist in the development of a comprehensive view of the molecular drivers of, and interrelationships between, morphological and mechanical stabilities. We find that the SMAs drive much of the embrittlement and diffusion characteristics in the blend films. However, the heterointeraction of the SMA and polymer, probed through dynamic mechanical analysis, is a key contributing factor to the film toughness. The heterointeraction energy is ideally maximally negative (i.e., repulsive), deviating from the geometric mean of the homointeraction energy. These findings assist in introducing a framework to understand the active layer stability and highlight material properties that lead to morphologically stable and physically robust OSCs.}, number={7}, journal={JOULE}, author={Siddika, Salma and Peng, Zhengxing and Balar, Nrup and Dong, Xinyun and Zhong, Xiaowei and You, Wei and Ade, Harald and OConnor, Brendan T.}, year={2023}, month={Jul}, pages={1593–1608} } @article{jia_ma_chen_meng_jain_angunawela_qin_kong_li_yang_et al._2023, title={Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells}, volume={14}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-023-36917-y}, abstractNote={AbstractReducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm−2 and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Jia, Zhenrong and Ma, Qing and Chen, Zeng and Meng, Lei and Jain, Nakul and Angunawela, Indunil and Qin, Shucheng and Kong, Xiaolei and Li, Xiaojun and Yang, Yang and et al.}, year={2023}, month={Mar} } @article{neu_samson_ding_rech_ade_you_2023, title={Oligo(ethylene glycol) Side Chain Architecture Enables Alcohol-Processable Conjugated Polymers for Organic Solar Cells}, volume={56}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.2c02259}, abstractNote={Achieving green-solvent solubility of conjugated polymers in truly green solvents such as alcohols has proven to be a significant challenge. In this work, we report the synthesis and characterization of three conjugated polymers derived from poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)] (PTQ10) with the goal of developing derivates which are more green-solvent-processable. The traditional alkyl side chains are replaced by various oligo(ethylene glycol) (OEG) side chains of different architectures, including one linear and two branched, all of which contain six ethylene glycol repeating units. It is determined that the linear OEG side chain architecture, even when sufficiently long, will not give desired green-solvent solubility shown by a small solubility capacity (R0). However, branched OEG side chains significantly improve solubility as R0 was increased from 4.7 of PTQ10 to 11.9 of PTQ-6bO/6bO2. Although the solution states of the polymers were vastly different, the solid-state morphologies were more similar as all three OEG-based polymers retained a predominately face-on molecular orientation similar to PTQ10. It was demonstrated that PTQ-6O devices showed the most comparable power conversion efficiencies (PCEs) to PTQ10 in bulk heterojunction solar cells, while PTQ-6bO2 and PTQ-6bO showed poorer performances. With one extra carbon in the side chain, PTQ-6bO2 showed higher PCE than PTQ-6bO, attributed to the improved aggregation properties and solid-state morphology of PTQ-6bO2, highlighting the importance of OEG side chain architecture. This work serves to develop important guidelines for future alcohol-soluble materials for green-solvent-processed OPVs.}, number={5}, journal={MACROMOLECULES}, author={Neu, Justin and Samson, Stephanie and Ding, Kan and Rech, Jeromy James and Ade, Harald and You, Wei}, year={2023}, month={Mar}, pages={2092–2103} } @article{zhuo_li_zhang_zhu_he_ding_li_meng_ade_li_2023, title={Precise synthesis and photovoltaic properties of giant molecule acceptors}, volume={14}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-023-43846-3}, DOI={10.1038/s41467-023-43846-3}, abstractNote={AbstractSeries of giant molecule acceptors DY, TY and QY with two, three and four small molecule acceptor subunits are synthesized by a stepwise synthetic method and used for systematically investigating the influence of subunit numbers on the structure-property relationship from small molecule acceptor YDT to giant molecule acceptors and to polymerized small molecule acceptor PY-IT. Among these acceptors-based devices, the TY-based film shows proper donor/acceptor phase separation, higher charge transfer state yield and longer charge transfer state lifetime. Combining with the highest electron mobility, more efficient exciton dissociation and lower charge carrier recombination properties, the TY-based device exhibits the highest power conversion efficiency of 16.32%. These results indicate that the subunit number in these acceptors has significant influence on their photovoltaic properties. This stepwise synthetic method of giant molecule acceptors will be beneficial to diversify their structures and promote their applications in high-efficiency and stable organic solar cells.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Zhuo, Hongmei and Li, Xiaojun and Zhang, Jinyuan and Zhu, Can and He, Haozhe and Ding, Kan and Li, Jing and Meng, Lei and Ade, Harald and Li, Yongfang}, year={2023}, month={Dec} } @article{al shafe_schrickx_ding_ade_brendan t. o'connor_2023, title={Rubber-Toughened Organic Solar Cells: Miscibility-Morphology-Performance Relations}, volume={8}, ISSN={["2380-8195"]}, DOI={10.1021/acsenergylett.3c01124}, abstractNote={Tough organic solar cell (OSC) active layers are necessary to achieve robust, flexible, and stretchable devices. A major challenge is that the brittle small molecule acceptor (SMA) in polymer/SMA bulk heterojunctions results in films prone to mechanical failure. To improve mechanical toughness, we investigate the use of a thermoplastic elastomer (styrene-b-ethylene-butylene-styrene) (SEBS) as an additive in high-performance photoactive layers. We find a consistent transition of all measured parameters [e.g., fracture energy (Gc) and power conversion efficiency (PCE)] at a SEBS concentration of 5–10 wt %, which is driven by the miscibility of the SEBS. We use this insight to optimize the SEBS loading for PCE and toughness. Optimized OSCs are found to increase Gc significantly with a marginal decrease in PCE, resulting in a record Gc·PCE metric, considering all OSC photoactive layers. The pronounced miscibility–function relationship provides a framework to optimize elastomer addition in OSCs for performance and toughness.}, journal={ACS ENERGY LETTERS}, author={Al Shafe, Abdullah and Schrickx, Harry M. and Ding, Kan and Ade, Harald and Brendan T. O'Connor}, year={2023}, month={Aug} } @article{singh_kim_henry_ade_mitzi_2023, title={Study of Glass Formation and Crystallization Kinetics in a 2D Metal Halide Perovskite Using Ultrafast Calorimetry}, volume={8}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.3c06342}, abstractNote={While crystalline 2D metal halide perovskites (MHPs) represent a well-celebrated semiconductor class, supporting applications in the fields of photovoltaics, emitters, and sensors, the recent discovery of glass formation in an MHP opens many new opportunities associated with reversible glass-crystalline switching, with each state offering distinct optoelectronic properties. However, the previously reported [S-(-)-1-(1-naphthyl)ethylammonium]2PbBr4 perovskite is a strong glass former with sluggish glass-crystal transformation time scales, pointing to a need for glassy MHPs with a broader range of compositions and crystallization kinetics. Herein we report glass formation for low-melting-temperature 1-MeHa2PbI4 (1-MeHa = 1-methyl-hexylammonium) using ultrafast calorimetry, thereby extending the range of MHP glass formation across a broader range of organic (fused ring to branched aliphatic) and halide (bromide to iodide) compositions. The importance of a slight loss of organic and hydrogen iodide components from the MHP in stabilizing the glassy state is elucidated. Furthermore, the underlying kinetics of glass-crystal transformation, including activation energies, crystal growth rate, Angell plot, and fragility index, is studied using a combination of kinetic, thermodynamic, and rheological modeling techniques. An inferred fast crystal growth rate of 0.21 m/s for 1-MeHa2PbI4 shows promise toward suitability in extended application spaces, for example, in metamaterials, nonvolatile memory, and optical and neuromorphic computing devices.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Singh, Akash and Kim, Yongshin and Henry, Reece and Ade, Harald and Mitzi, David B.}, year={2023}, month={Aug} } @article{wang_peng_balar_ade_2023, title={Suppressing pre-aggregation to increase polymer solar cell ink shelf life}, volume={11}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta06617g}, abstractNote={An approach to slow down the polymer solar cell ink aging by employing an additive (i.e., PCBM variants) was developed. It is inferred that PCBMs in the ink act as a co-solvent and slow down the polymer pre-aggregation.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Wang, Zhen and Peng, Zhengxing and Balar, Nrup and Ade, Harald}, year={2023}, month={Nov} } @article{ng_kwok_qi_wang_chen_liu_zhao_ade_zhang_yan_et al._2023, title={Synergistic effect of benzoselenadiazole core and alkoxy side chain substitution on the photovoltaic performance of non-fullerene acceptors}, volume={10}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta04364a}, abstractNote={We developed a novel Y-series small molecule acceptor by adopting benzoselenadiazole central core and alkoxy side chains on the β-position of thiophene moieties, inducing a boost in performance due to upshifted energy levels and optimized morphology.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Ng, Ho Ming and Kwok, Chung Hang and Qi, Zhenyu and Wang, Zhen and Chen, Li and Liu, Wei and Zhao, Wenchao and Ade, Harald and Zhang, Chen and Yan, He and et al.}, year={2023}, month={Oct} } @article{peng_ade_2023, title={Unveiling re-entrant phase behavior and crystalline-amorphous interactions in semi-conducting polymer:small molecule blends}, volume={4}, ISSN={["2051-6355"]}, DOI={10.1039/d3mh00034f}, abstractNote={It is revealed that the re-entrant phase behavior of the conjugated polymer:small molecule systems is indeed a result of thermodynamics. The composition difference (Δϕ) between liquidus and binodal reflects the crystalline–amorphous interaction.}, journal={MATERIALS HORIZONS}, author={Peng, Zhengxing and Ade, Harald}, year={2023}, month={Apr} } @article{zhang_sun_angunawela_meng_qin_zhou_li_zhuo_yang_zhang_et al._2022, title={16.52% Efficiency All-Polymer Solar Cells with High Tolerance of the Photoactive Layer Thickness}, volume={4}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202108749}, abstractNote={AbstractAll‐polymer solar cells (all‐PSCs) have drawn growing attention and achieved tremendous progress recently, but their power conversion efficiency (PCE) still lags behind small‐molecule‐acceptor (SMA)‐based PSCs due to the relative difficulty on morphology control of polymer photoactive blends. Here, low‐cost PTQ10 is introduced as a second polymer donor (a third component) into the PM6:PY‐IT blend to finely tune the energy‐level matching and microscopic morphology of the polymer blend photoactive layer. The addition of PTQ10 decreases the π–π stacking distance, and increases the π–π stacking coherence length and the ordered face‐on molecular packing orientation, which improves the charge separation and transport in the photoactive layer. Moreover, the deeper highest occupied molecular orbital energy level of the PTQ10 polymer donor than PM6 leads to higher open‐circuit voltage of the ternary all‐PSCs. As a result, a PCE of 16.52% is achieved for ternary all‐PSCs, which is one of the highest PCEs for all‐PSCs. In addition, the ternary devices exhibit a high tolerance of the photoactive layer thickness with high PCEs of 15.27% and 13.91% at photoactive layer thickness of ≈205 and ≈306 nm, respectively, which are the highest PCEs so far for all‐PSCs with a thick photoactive layer.}, journal={ADVANCED MATERIALS}, author={Zhang, Wenqing and Sun, Chenkai and Angunawela, Indunil and Meng, Lei and Qin, Shucheng and Zhou, Liuyang and Li, Shaman and Zhuo, Hongmei and Yang, Guang and Zhang, Zhi-Guo and et al.}, year={2022}, month={Apr} } @article{yi_pan_chen_chen_angunawela_luo_zhang_zeng_chen_qi_et al._2022, title={A Benzo[1,2-b:4,5-b']Difuran Based Donor Polymer Achieving High-Performance (>17%) Single-Junction Organic Solar Cells with a Fill Factor of 80.4%}, volume={7}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202201850}, abstractNote={AbstractIn the field of non‐fullerene organic solar cells (OSCs), most of the promising polymer donors are based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) units while benzo[1,2‐b:4,5‐b′]difuran (BDF)‐based polymers have drawn less attention since the efficiencies of BDF polymer‐based devices are generally lower than those of BDT polymer‐based ones. In this contribution, the BDT unit in a polymer donor named D18 is replaced with a BDF unit, and a new polymer named D18‐Fu is synthesized. As a highly‐crystalline molecule named Y6‐1O is chosen as the acceptor, the efficiency of binary devices based on D18‐Fu can reach 16.38%. Furthermore, when one of fullerene derivatives PC71BM is added, the ternary devices based on D18‐Fu achieve an efficiency of 17.07% and a high fill factor (FF) of 80.4%, both of which are the highest values among those of BDF polymer‐based devices. For comparison, D18‐based ternary devices show an inferior efficiency of 15.61% mainly due to the lower FF of 73.9%. Subsequent characterization reveals that D18‐Fu possesses a more coplanar molecular geometry, leading to better morphology and higher charge mobility for a promising FF. The high performance shown in this work demonstrates the potential role of BDF units in the design of polymer donors for highly efficient OSCs.}, journal={ADVANCED ENERGY MATERIALS}, author={Yi, Jicheng and Pan, Mingao and Chen, Lu and Chen, Yuzhong and Angunawela, Indunil Chathurangani and Luo, Siwei and Zhang, Ting and Zeng, Anping and Chen, Jian and Qi, Zhenyu and et al.}, year={2022}, month={Jul} } @article{fu_peng_fan_lin_qi_ran_wu_fan_jiang_woo_et al._2022, title={A Top-Down Strategy to Engineer ActiveLayer Morphology for Highly Efficient and Stable All-Polymer Solar Cells}, volume={7}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202202608}, abstractNote={AbstractA major challenge hindering the further development of all‐polymer solar cells (all‐PSCs) employing polymerized small‐molecule acceptors is the relatively low fill factor (FF) due to the difficulty in controlling the active‐layer morphology. The issues typically arise from oversized phase separation resulting from the thermodynamically unfavorable mixing between two macromolecular species, and disordered molecular orientation/packing of highly anisotropic polymer chains. Herein, a facile top‐down controlling strategy to engineer the morphology of all‐polymer blends is developed by leveraging the layer‐by‐layer (LBL) deposition. Optimal intermixing of polymer components can be achieved in the two‐step process by tuning the bottom‐layer polymer swelling during top‐layer deposition. Consequently, both the molecular orientation/packing of the bottom layer and the molecular ordering of the top layer can be optimized with a suitable top‐layer processing solvent. A favorable morphology with gradient vertical composition distribution for efficient charge transport and extraction is therefore realized, affording a high all‐PSC efficiency of 17.0% with a FF of 76.1%. The derived devices also possess excellent long‐term thermal stability and can retain >90% of their initial efficiencies after being annealed at 65 °C for 1300 h. These results validate the distinct advantages of employing an LBL processing protocol to fabricate high‐performance all‐PSCs.}, journal={ADVANCED MATERIALS}, author={Fu, Huiting and Peng, Zhengxing and Fan, Qunping and Lin, Francis R. and Qi, Feng and Ran, Yixin and Wu, Ziang and Fan, Baobing and Jiang, Kui and Woo, Han Young and et al.}, year={2022}, month={Jul} } @article{gao_qi_peng_lin_jiang_zhong_kaminsky_guan_lee_marks_et al._2022, title={Achieving 19% Power Conversion Efficiency in Planar-Mixed Heterojunction Organic Solar Cells Using a Pseudosymmetric Electron Acceptor}, volume={7}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202202089}, abstractNote={AbstractA record power conversion efficiency (PCE) of over 19% is realized in planar‐mixed heterojunction (PMHJ) organic solar cells (OSCs) by adopting the asymmetric selenium substitution strategy in making a pseudosymmetric electron acceptor, BS3TSe‐4F. The combined molecular asymmetry with more polarizable selenium substitution increases the dielectric constant of the D18/BS3TSe‐4F blend, helping lower the exciton binding energy. On the other hand, dimer packing in BS3TSe‐4F is facilitated to enable free charge generation, helping more efficient exciton dissociation and lowering the radiative recombination loss (ΔE2) of OSCs. As a result, PMHJ OSCs based on D18/BS3TSe‐4F achieve a PCE of 18.48%. By incorporating another mid‐bandgap acceptor Y6‐O into D18/BS3TSe‐4F to form a ternary PMHJ, a higher open‐circuit voltage (VOC) can be achieved to realize an impressive PCE of 19.03%. The findings of using pseudosymmetric electron acceptors in enhancing device efficiency provides an effective way to develop highly efficient acceptor materials for OSCs.}, journal={ADVANCED MATERIALS}, author={Gao, Wei and Qi, Feng and Peng, Zhengxing and Lin, Francis R. and Jiang, Kui and Zhong, Cheng and Kaminsky, Werner and Guan, Zhiqiang and Lee, Chun-Sing and Marks, Tobin J. and et al.}, year={2022}, month={Jul} } @article{charles_edwards_ravishankar_calero_henry_rech_saravitz_you_ade_brendan_et al._2022, title={Beyond energy balance in agrivoltaic food production: Emergent crop traits from wavelength-selective solar cells}, url={https://doi.org/10.1101/2022.03.10.482833}, DOI={10.1101/2022.03.10.482833}, abstractNote={AbstractThe integration of semi-transparent organic solar cells (ST-OSCs) in greenhouses offers new agrivoltaic opportunities to meet the growing demands for sustainable food production. The tailored absorption/transmission spectra of ST-OSCs impacts the power generated as well as crop growth, development and responses to the biotic and abiotic environments. We grew lettuce and tomato, traditional greenhouse crops, under three ST-OSC filters that create different light spectra. Lettuce yield and early tomato development are not negatively affected by the modified light environment. Our genomic analysis reveals that lettuce production exhibits beneficial traits involving nutrient content and nitrogen utilization while select ST-OSCs impact regulation of flowering initiation in tomato. ST-OSCs integrated into greenhouses are not only a promising technology for energy-neutral, sustainable and climate-change protected crop production, but can deliver benefits beyond energy considerations.}, author={Charles, Melodi and Edwards, Brianne and Ravishankar, Eshwar and Calero, John and Henry, Reece and Rech, Jeromy and Saravitz, Carole and You, Wei and Ade, Harald and Brendan, O’Connor and et al.}, year={2022}, month={Mar} } @article{ho_pei_qin_zhang_peng_angunawela_jones_yin_iqbal_reynolds_et al._2022, title={Importance of Electric-Field-Independent Mobilities in Thick-Film Organic Solar Cells}, volume={10}, ISSN={["1944-8252"]}, url={http://dx.doi.org/10.1021/acsami.2c11265}, DOI={10.1021/acsami.2c11265}, abstractNote={In organic solar cells (OSCs), a thick active layer usually yields a higher photocurrent with broader optical absorption than a thin active layer. In fact, a ∼300 nm thick active layer is more compatible with large-area processing methods and theoretically should be a better spot for efficiency optimization. However, the bottleneck of developing high-efficiency thick-film OSCs is the loss in fill factor (FF). The origin of the FF loss is not clearly understood, and there a direct method to identify photoactive materials for high-efficiency thick-film OSCs is lacking. Here, we demonstrate that the mobility field-dependent coefficient is an important parameter directly determining the FF loss in thick-film OSCs. Simulation results based on the drift-diffusion model reveal that a mobility field-dependent coefficient smaller than 10-3 (V/cm)-1/2 is required to maintain a good FF in thick-film devices. To confirm our simulation results, we studied the performance of two ternary bulk heterojunction (BHJ) blends, PTQ10:N3:PC71BM and PM6:N3:PC71BM. We found that the PTQ10 blend film has weaker field-dependent mobilities, giving rise to a more balanced electron-hole transport at low fields. While both the PM6 blend and PTQ10 blend yield good performance in thin-film devices (∼100 nm), only the PTQ10 blend can retain a FF = 74% with an active layer thickness of up to 300 nm. Combining the benefits of a higher JSC in thick-film devices, we achieved a PCE of 16.8% in a 300 nm thick PTQ10:N3:PC71BM OSC. Such a high FF in the thick-film PTQ10 blend is also consistent with the observation of lower charge recombination from light-intensity-dependent measurements and lower energetic disorder observed in photothermal deflection spectroscopy.}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Ho, Carr Hoi Yi and Pei, Yusen and Qin, Yunpeng and Zhang, Chujun and Peng, Zhengxing and Angunawela, Indunil and Jones, Austin L. and Yin, Hang and Iqbal, Hamna F. and Reynolds, John R. and et al.}, year={2022}, month={Oct} } @article{luginbuhl_ko_ran_hu_becwar_karki_seifrid_okubo_wang_ade_et al._2022, title={Low Voltage-Loss Organic Solar Cells Light the Way for Efficient Semitransparent Photovoltaics}, volume={3}, ISSN={["2367-198X"]}, url={https://doi.org/10.1002/solr.202200135}, DOI={10.1002/solr.202200135}, abstractNote={Organic solar cells that are transparent to visible light are highly desirable for applications such as window treatments or solar greenhouse panels. A key challenge is to simultaneously transmit most photons between 400 and 700 nm while retaining a high short‐circuit current and power conversion efficiency (PCE). Here, organic bulk heterojunction (BHJ) solar cells consisting of a donor polymer (PM2) is reported and the non‐fullerene acceptor ITIC‐Th achieves a PCE of 9.3%, and the BHJ thin films exhibit an average visible transmittance over 40%. This value is achieved primarily due to a very high open‐circuit voltage (VOC) of 0.93 V, which represents a voltage loss of only 0.50 V relative to the material optical bandgap, Eopt. In PM2:PC61BM devices, this voltage loss increases to 0.62 V (VOC = 0.82 V). It is found that this difference in VOC is due to higher nonradiative recombination in the fullerene‐based solar cell, suggesting that non‐fullerene acceptors may lead to better performance in semi‐transparent devices. The optoelectronic properties associated with PM2:ITIC‐Th and PM2:PC61BM blends are further corroborated by different morphological features and local structures at the donor‐acceptor interfaces characterized by atomic force microscopy, X‐ray scattering, and solid‐state NMR spectroscopy techniques.}, journal={SOLAR RRL}, publisher={Wiley}, author={Luginbuhl, Benjamin R. and Ko, Seo-Jin and Ran, Niva A. and Hu, Huawei and Becwar, Shona M. and Karki, Akchheta and Seifrid, Martin and Okubo, Takashi and Wang, Ming and Ade, Harald W. and et al.}, year={2022}, month={Mar} } @article{luo_bai_zhang_zhao_angunawela_zou_li_luo_feng_yu_et al._2022, title={Optimizing spectral and morphological match of nonfullerene acceptors toward efficient indoor organic photovoltaics with enhanced light source adaptability}, volume={98}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2022.107281}, abstractNote={High-performance indoor organic photovoltaics (IOPV) require large-bandgap material systems to absorb visible light efficiently and reduce energy loss. However, state-of-the-art non-fullerene acceptors (NFAs) have absorptions in the near-infrared region and are thus not suitable for IOPV applications. Herein, we report a series of large-bandgap (>1.70 eV) NFAs named FCC-Cl-C8, FCC-Cl-4Ph and FCC-Cl-6Ph by modifying the alkyl side chains with alkylphenyl chains partially or completely. Results show that the bulky alkylphenyl side chains can finely tune the absorption properties of the NFAs and also affect their morphological properties. Interestingly, the best-performing NFA is the one (named FCC-Cl-4Ph) with partial alkyl and alkylphenyl substitutions, which blue-shift the absorption of the NFAs while minimizing the negative morphological effect of the bulky alkylphenyl chains. As a result, FCC-Cl-4Ph can achieve excellent indoor efficiencies over 29% under a 3000 K LED lamp at 1000 lux and show better solution processability over FCC-Cl-C8. More importantly, FCC-Cl-4Ph can maintain high indoor performance (29.7–26.8% at 1000 lux) under a wide range of indoor lighting spectra (2600, 3000, 4000, and 6500 K LED lamps), which should be due to the blue-shifted spectra of FCC-Cl-4Ph and better matching with various indoor conditions. This work reveals an interesting structure-property relationship and offers useful strategies for the further design of NFAs toward efficient IOPV devices.}, journal={NANO ENERGY}, author={Luo, Siwei and Bai, Fujin and Zhang, Jianquan and Zhao, Heng and Angunawela, Indunil and Zou, Xinhui and Li, Xiaojun and Luo, Zhenghui and Feng, Kui and Yu, Han and et al.}, year={2022}, month={Jul} } @article{ravishankar_booth_hollingsworth_ade_sederoff_decarolis_brendan t. o'connor_2022, title={Organic solar powered greenhouse performance optimization and global economic opportunity}, volume={15}, ISSN={["1754-5706"]}, url={https://doi.org/10.1039/D1EE03474J}, DOI={10.1039/D1EE03474J}, abstractNote={This work integrates greenhouse energy demand, solar power production, and plant growth modeling to assess the economic opportunity of organic solar powered greenhouses. Results show these systems have positive economic outlook across broad climates.}, number={4}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, publisher={Royal Society of Chemistry (RSC)}, author={Ravishankar, Eshwar and Booth, Ronald E. and Hollingsworth, Joseph A. and Ade, Harald and Sederoff, Heike and DeCarolis, Joseph F. and Brendan T. O'Connor}, year={2022}, month={Mar} } @article{kashani_wang_risko_ade_2022, title={Relating reorganization energies, exciton diffusion length and non-radiative recombination to the room temperature UV-vis absorption spectra of NF-SMA}, volume={12}, ISSN={["2051-6355"]}, url={https://doi.org/10.1039/D2MH01228F}, DOI={10.1039/D2MH01228F}, abstractNote={Multiparameter Franck–Condon analyses of absorption spectra of Y6 in dilute solutions reveals that Y6 exhibits a high conformation uniformity and the smallest intra-molecular reorganization energy among the materials studied.}, journal={MATERIALS HORIZONS}, author={Kashani, Somayeh and Wang, Zhen and Risko, Chad and Ade, Harald}, year={2022}, month={Dec} } @article{fang_wang_chen_zhang_zhang_zhu_zhang_cui_wei_ade_et al._2022, title={Revealing aggregation of non-fullerene acceptors in intermixed phase by ultraviolet-visible absorption spectroscopy}, volume={3}, ISSN={["2666-3864"]}, DOI={10.1016/j.xcrp.2022.100983}, abstractNote={Non-fullerene acceptor (NFA) aggregation is crucial in determining bulk-heterojunction (BHJ) organic photovoltaic (OPV) performance. However, it is still a big challenge to characterize the nanostructure of NFAs in the disordered donor-acceptor intermixed phase. Here, we demonstrate a method to characterize NFA aggregation and composition in the intermixed phase by measuring NFA concentration-dependent ultraviolet-visible (UV-vis) absorption spectroscopy of BHJ films. In various polymer:NFA films, an absorption shift as a function of increasing molecular concentration (ASIMC) phenomenon is observed, and different NFA aggregation behaviors can be distinguished. The ASIMC method was then applied to study the influence of processing conditions on the NFA concentration in the intermixed phase of devices to establish a correlation with device efficiency. The current work provides a feasible tool to study the nanostructure of NFAs in the complex polymer matrix and to understand the variations in the NFA concentration in the intermixed phase under non-equilibrium conditions.}, number={7}, journal={CELL REPORTS PHYSICAL SCIENCE}, author={Fang, Jin and Wang, Zhen and Chen, Yiyao and Zhang, Qing and Zhang, Jianqi and Zhu, Lingyun and Zhang, Maojie and Cui, Zheng and Wei, Zhixiang and Ade, Harald and et al.}, year={2022}, month={Jul} } @article{booth_schrickx_hanby_liu_qin_ade_zhu_brendan t. o'connor_2022, title={Silver Nanowire Composite Electrode Enabling Highly Flexible, Robust Organic Photovoltaics}, volume={6}, ISSN={["2367-198X"]}, DOI={10.1002/solr.202200264}, abstractNote={Using Ag nanowires (NWs) is a promising approach to make flexible and transparent conducting electrodes for organic photovoltaics (OPVs). However, the roughness of the NWs can decrease device performance. Herein, a Ag NW electrode embedded in a UV‐curable epoxy that uses a simple mechanical lift‐off process resulting in highly planar electrodes is demonstrated. A bimodal blend of Ag NWs with varying aspect ratios is used to optimize the transparency and conductivity of the electrode. In addition, a ZnO layer is coated on the Ag NWs prior to the embedding process to ensure low contact resistance in the OPV cells. The resulting resin‐embedded ZnO‐encapsulated silver nanowire (REZEN) electrode is found to have excellent mechanical stability. REZEN electrode‐based OPV cells exhibit comparable performance with reference devices, achieving maximum power conversion efficiency (PCE) of 13.5% and 13.6% respectively. The REZEN‐based OPV cells are also mechanically robust, retaining 97% of their PCE after 5000 cycles at R = 1.2 mm and 94% PCE after 1000 cycles at R = 0.55 mm. This flexibility is among the highest reported for freestanding devices. Thus, the REZEN electrode is a promising and simple strategy to achieve mechanically robust ITO‐free flexible OPV cells.}, journal={SOLAR RRL}, author={Booth, Ronald E. and Schrickx, Harry M. and Hanby, Georgia and Liu, Yuxuan and Qin, Yunpeng and Ade, Harald and Zhu, Yong and Brendan T. O'Connor}, year={2022}, month={Jun} } @article{li_kong_chen_angunawela_zhu_li_meng_ade_li_2022, title={Small-Molecule Acceptor with Unsymmetric Substituents and Fused Rings for High-Performance Organic Solar Cells with Enhanced Mobility and Reduced Energy Losses}, volume={11}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.2c17235}, abstractNote={A new unsymmetric small-molecule acceptor (SMA) BTPOSe-4F was designed by unsymmetric structure modification to Y6 with an alkyl upper side chain replaced by an alkoxy side chain and a sulfur atom in its central fused ring replaced by a selenium atom, for the application as an acceptor to fabricate organic solar cells (OSCs). BTPOSe-4F exhibits a higher lowest unoccupied molecular orbital (LUMO) energy level, a reduced nonradiation energy loss, and better charge extraction properties in its binary OSCs with a higher Voc of 0.886. Furthermore, the ternary OSCs with the addition of PC71BM demonstrated a higher power conversion efficiency (PCE) of 17.33% with Voc of 0.890 V. This work reveals that the unsymmetric modification strategy can further give impetus to the photovoltaic performance promotion of OSCs for Y6-series SMAs.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Li, Zechen and Kong, Xiaolei and Chen, Zeng and Angunawela, Indunil and Zhu, Haiming and Li, Xiaojun and Meng, Lei and Ade, Harald and Li, Yongfang}, year={2022}, month={Nov} } @article{hu_zhu_ding_qin_lai_du_zhang_wei_li_zhang_et al._2022, title={Solid additive tuning of polymer blend morphology enables non-halogenated-solvent all-polymer solar cells with an efficiency of over 17%}, volume={8}, ISSN={["1754-5706"]}, DOI={10.1039/d2ee01727j}, abstractNote={The treatment of toluene solvent and DTT additive enables the PBQ6:PYF-T-o-based all-PSC devices with PCE up to 17.06%, which is one of the highest value in non-halogenated-processed all-PSCs to date.}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Hu, Ke and Zhu, Can and Ding, Kan and Qin, Shucheng and Lai, Wenbin and Du, Jiaqi and Zhang, Jianqi and Wei, Zhixiang and Li, Xiaojun and Zhang, Zhanjun and et al.}, year={2022}, month={Aug} } @article{jiang_zhang_zhong_lin_qi_li_peng_kaminsky_jang_yu_et al._2022, title={Suppressed recombination loss in organic photovoltaics adopting a planar-mixed heterojunction architecture}, volume={7}, ISSN={["2058-7546"]}, DOI={10.1038/s41560-022-01138-y}, number={11}, journal={NATURE ENERGY}, author={Jiang, Kui and Zhang, Jie and Zhong, Cheng and Lin, Francis R. and Qi, Feng and Li, Qian and Peng, Zhengxing and Kaminsky, Werner and Jang, Sei-Hum and Yu, Jianwei and et al.}, year={2022}, month={Nov}, pages={1076–1086} } @article{steckmann_angunawela_kashani_zhu_nahid_ade_gadisa_2022, title={Ultrathin P(NDI2OD-T2) Films with High Electron Mobility in Both Bottom-Gate and Top-Gate Transistors}, volume={3}, ISSN={["2199-160X"]}, url={https://doi.org/10.1002/aelm.202101324}, DOI={10.1002/aelm.202101324}, abstractNote={AbstractUltrathin organic films (typically < 10 nm) attracted great attention due to their (semi)transparency and unique optoelectronic properties that benefit applications such as sensors and flexible electronics. At the core of that, achieving high mobility in an ultrathin film is essential for the efficient operation of relevant electronic devices. While the state‐of‐the‐art material systems, e.g., P(NDI2OD‐T2) also known as N2200 can achieve high mobility in a thin film (typically > 20 nm), multitudinous challenges remain in processing an ultrathin film exhibiting desired charge transport morphology within a preferred thickness limit. Here, high electron mobility (a tenfold increase compared to annealed spin‐coated films) is reported in both the top and bottom‐gate configuration organic field‐effect transistors comprising ultrathin N2200 films produced with a water‐floating film transfer method. A range of characterization techniques are used to investigate these ultrathin films and their microstructure, and conclude that favorable edge‐on polymer orientation at the top as well as throughout the ultrathin film thickness and the quality of π–π ordering as captured by the largest coherences length resulted in this high mobility in N2200 ultrathin films, in stark contrast to the commonly observed microstructural gradient in spin‐coated thin films. The results provide new insight into the electronic and microstructural properties of thin films of organic semiconductors.}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Steckmann, Thomas and Angunawela, Indunil and Kashani, Somayeh and Zhu, Youqin and Nahid, Masrur M. and Ade, Harald and Gadisa, Abay}, year={2022}, month={Mar} } @article{zeng_ma_pan_chen_ma_zhao_zhang_kim_shang_luo_et al._2021, title={A Chlorinated Donor Polymer Achieving High-Performance Organic Solar Cells with a Wide Range of Polymer Molecular Weight}, volume={6}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202102413}, abstractNote={AbstractIn the field of non‐fullerene organic solar cells (OSCs), compared to the rapid development of non‐fullerene acceptors, the progress of high‐performance donor polymers is relatively slow. The property and performance of donor polymers in OSCs are often sensitive to the molecular weight of the polymers. In this study, a chlorinated donor polymer named D18‐Cl is reported, which can achieve high performance with a wide range of polymer molecular weight. The devices based on D18‐Cl show a higher open‐circuit voltage (VOC) due to the slightly deeper energy levels and an outstanding short‐circuit current density (JSC) owing to the appropriate long periods of blend films and less ([6,6]‐phenyl‐C71‐butyric acid methyl ester) (PC71BM) in mixed domains, leading to the higher efficiency of 17.97% than those of the D18‐based devices (17.21%). Meanwhile, D18‐Cl can achieve high efficiencies (17.30–17.97%) when its number‐averaged molecular weight (Mn) is ranged from 45 to 72 kDa. In contrast, the D18‐based devices only exhibit relatively high efficiencies in a narrow Mn range of ≈70 kDa. Such property and performance make D18‐Cl a promising donor polymer for scale‐up and low‐cost production.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Zeng, Anping and Ma, Xiaoling and Pan, Mingao and Chen, Yuzhong and Ma, Ruijie and Zhao, Heng and Zhang, Jianquan and Kim, Ha Kyung and Shang, Ao and Luo, Siwei and et al.}, year={2021}, month={Jun} } @article{yu_luo_sun_angunawela_qi_peng_zhou_han_wei_pan_et al._2021, title={A Difluoro-Monobromo End Group Enables High-Performance Polymer Acceptor and Efficient All-Polymer Solar Cells Processable with Green Solvent under Ambient Condition}, volume={31}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202100791}, abstractNote={AbstractIn this paper, a difluoro‐monobromo end group is designed and synthesized, which is then used to construct a novel polymer acceptor (named PY2F‐T) yielding high‐performance all‐polymer solar cells with 15.22% efficiency. The fluorination strategy can increase the intramolecular charge transfer and interchain packing of the previous PY‐T based acceptor, and significantly improve photon harvesting and charge mobility of the resulting polymer acceptor. In addition, detailed morphology investigations reveal that the PY2F‐T‐based blend shows smaller domain spacing and higher domain purity, which significantly suppress charge recombination as supported by time‐resolved techniques. These polymer properties enable simultaneously enhanced JSC and FF of the PY2F‐T‐based devices, eventually delivering device efficiencies of over 15%, significantly outperforming that of the devices based on the non‐fluorinated PY‐T polymer (13%). More importantly, the PY2F‐T‐based active layers can be processed under ambient conditions and still achieve a 14.37% efficiency. They can also be processed using non‐halogenated solvent o‐xylene (no additive) and yield a decent performance of 13.05%. This work demonstrates the success of the fluorination strategy in the design of high‐performance polymer acceptors, which provide guidelines for developing new all‐PSCs with better efficiencies and stabilities for commercial applications.}, number={25}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Yu, Han and Luo, Siwei and Sun, Rui and Angunawela, Indunil and Qi, Zhenyu and Peng, Zhengxing and Zhou, Wentao and Han, Han and Wei, Rong and Pan, Mingao and et al.}, year={2021}, month={Jun} } @misc{armin_li_sandberg_xiao_ding_nelson_neher_vandewal_shoaee_wang_et al._2021, title={A History and Perspective of Non-Fullerene Electron Acceptors for Organic Solar Cells}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202003570}, abstractNote={AbstractOrganic solar cells are composed of electron donating and accepting organic semiconductors. Whilst a significant palette of donors has been developed over three decades, until recently only a small number of acceptors have proven capable of delivering high power conversion efficiencies. In particular the fullerenes have dominated the landscape. In this perspective, the emergence of a family of materials–the non‐fullerene acceptors (NFAs) is described. These have delivered a discontinuous advance in cell efficiencies, with the significant milestone of 20% now in sight. Intensive international efforts in synthetic chemistry have established clear design rules for molecular engineering enabling an ever‐expanding number of high efficiency candidates. However, these materials challenge the accepted wisdom of how organic solar cells work and force new thinking in areas such as morphology, charge generation and recombination. This perspective provides a historical context for the development of NFAs, and also addresses current thinking in these areas plus considers important manufacturability criteria. There is no doubt that the NFAs have propelled organic solar cell technology to the efficiencies necessary for a viable commercial technology–but how far can they be pushed, and will they also deliver on equally important metrics such as stability?}, number={15}, journal={ADVANCED ENERGY MATERIALS}, author={Armin, Ardalan and Li, Wei and Sandberg, Oskar J. and Xiao, Zuo and Ding, Liming and Nelson, Jenny and Neher, Dieter and Vandewal, Koen and Shoaee, Safa and Wang, Tao and et al.}, year={2021}, month={Apr} } @article{ghasemi_balar_peng_hu_qin_kim_rech_bidwell_mask_mcculloch_et al._2021, title={A molecular interaction-diffusion framework for predicting organic solar cell stability}, volume={20}, ISSN={["1476-4660"]}, DOI={10.1038/s41563-020-00872-6}, abstractNote={Rapid increase in the power conversion efficiency of organic solar cells (OSCs) has been achieved with the development of non-fullerene small-molecule acceptors (NF-SMAs). Although the morphological stability of these NF-SMA devices critically affects their intrinsic lifetime, their fundamental intermolecular interactions and how they govern property-function relations and morphological stability of OSCs remain elusive. Here, we discover that the diffusion of an NF-SMA into the donor polymer exhibits Arrhenius behaviour and that the activation energy E a scales linearly with the enthalpic interaction parameters χ H between the polymer and the NF-SMA. Consequently, the thermodynamically most unstable, hypo-miscible systems (high χ) are the most kinetically stabilized. We relate the differences in E a to measured and selectively simulated molecular self-interaction properties of the constituent materials and develop quantitative property-function relations that link thermal and mechanical characteristics of the NF-SMA and polymer to predict relative diffusion properties and thus morphological stability.}, number={4}, journal={NATURE MATERIALS}, author={Ghasemi, Masoud and Balar, Nrup and Peng, Zhengxing and Hu, Huawei and Qin, Yunpeng and Kim, Taesoo and Rech, Jeromy J. and Bidwell, Matthew and Mask, Walker and McCulloch, Iain and et al.}, year={2021}, month={Apr}, pages={525-+} } @article{zhang_bai_angunawela_xu_luo_li_chai_yu_chen_hu_et al._2021, title={Alkyl-Chain Branching of Non-Fullerene Acceptors Flanking Conjugated Side Groups toward Highly Efficient Organic Solar Cells}, volume={10}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202102596}, abstractNote={AbstractSide‐chain modifications of non‐fullerene acceptors (NFAs) are essential for harvesting their full potential in organic solar cells (OSC). Here, an effective alkyl‐chain‐branching approach of the Y‐series NFAs flanking meta‐substituted phenyl side groups at the outer positions is demonstrated. Compared to BTP‐4F‐PC6 with linear m‐hexylphenyl chains, two new acceptors named BTP‐4F‐P2EH and BTP‐4F‐P3EH are developed with bulkier alkyl chains branched at the β and γ positions, respectively. These branched chains result in altered molecular packing of the NFAs and afford higher open‐circuit voltage of the devices. Despite the blue‐shifted absorption of the branched‐chain NFAs, their blends with PBDB‐T‐2F enable improved short‐circuit current density for the corresponding devices owing to the more suitable phase separation and better exciton dissociation. Consequently, the OSCs based on BTP‐4F‐P2EH and BTP‐4F‐P3EH yield enhanced device performance of 18.22% and 17.57%, respectively, outperforming the BTP‐4F‐PC6‐based ones (17.22%). These results highlight that the side‐chain branching design of NFAs has great potential in optimizing molecular properties and promoting photovoltaic performance.}, journal={ADVANCED ENERGY MATERIALS}, author={Zhang, Jianquan and Bai, Fujin and Angunawela, Indunil and Xu, Xiaoyun and Luo, Siwei and Li, Chao and Chai, Gaoda and Yu, Han and Chen, Yuzhong and Hu, Huawei and et al.}, year={2021}, month={Oct} } @article{ravishankar_charles_xiong_henry_swift_rech_calero_cho_booth_kim_et al._2021, title={Balancing crop production and energy harvesting in organic solar-powered greenhouses}, volume={2}, ISSN={["2666-3864"]}, DOI={10.1016/j.xcrp.2021.100381}, abstractNote={Adding semitransparent organic solar cells (ST-OSCs) to a greenhouse structure enables simultaneous plant cultivation and electricity generation, thereby reducing the greenhouse energy demand. However, there is a need to establish the impact of such systems on plant growth and indoor climate and to optimize system tradeoffs. In this work, we consider plant growth under OSCs and system-relevant design. We evaluate the growth of red leaf lettuce under ST-OSC filters and compare the impact of three different OSC active layers that have unique transmittance. We find no significant differences in the fresh weight and chlorophyll content of the lettuce grown under these OSC filters. In addition, OSCs provide an opportunity for further light and thermal management of the greenhouse through device design and optical coatings. The OSCs can thus affect plant growth, power generation, and thermal load of the greenhouse, and this design trade space is reviewed and exemplified.}, number={3}, journal={CELL REPORTS PHYSICAL SCIENCE}, publisher={Elsevier BV}, author={Ravishankar, Eshwar and Charles, Melodi and Xiong, Yuan and Henry, Reece and Swift, Jennifer and Rech, Jeromy and Calero, John and Cho, Sam and Booth, Ronald E. and Kim, Taesoo and et al.}, year={2021}, month={Mar} } @article{zheng_sun_zhang_chen_peng_wu_yuan_yu_wang_wu_et al._2021, title={Baseplate Temperature-Dependent Vertical Composition Gradient in Pseudo-Bilayer Films for Printing Non-Fullerene Organic Solar Cells}, volume={10}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202102135}, abstractNote={AbstractNumerous previous reports on the sequential deposition (SD) technique have demonstrated that this approach can achieve a p‐i‐n active layer architecture with an ideal vertical composition gradient, which is one of the critical factors that can influence the physical processes that determine the photovoltaic performance of organic solar cells. Herein, a commonly used photovoltaic system comprised of PM6 as a donor and Y6 as an acceptor is investigated with respect to sequential blade‐processing deposition to comprehensively explore the morphology characteristics as a function of baseplate temperature. A systematic study of the temperature‐dependent blend morphology elucidates the SD‐processed configuration merits and device physics behind temperature‐controlled degree of vertical composition gradient, and constructs the temperature‐microstructure‐property relationship for the corresponding photovoltaic parameters. The result shows, as the temperature increases, the morphology of the active layer has undergone a distinct evolution from the pseudo‐bulk heterojunction to a pseudo‐planar heterojunction and then to a pseudo‐planar bilayer, leading to a non‐monotonic correlation between baseplate temperature and device performance. This investigation not only reveals the importance of precisely controlling baseplate temperature for gaining vertical morphology control, but also provides a path toward rational optimization of device performance in the lab‐to‐fab transition.}, journal={ADVANCED ENERGY MATERIALS}, author={Zheng, Yina and Sun, Rui and Zhang, Meng and Chen, Zhihao and Peng, Zhengxing and Wu, Qiang and Yuan, Xinxin and Yu, Yue and Wang, Tao and Wu, Yao and et al.}, year={2021}, month={Oct} } @article{zhong_kirmani_lan_carpenter_rong-hui chew_awartani_yu_niazi_voznyy_hu_et al._2022, title={Conjugated polymers with controllable interfacial order and energetics enable tunable heterojunctions in organic and colloidal quantum dot photovoltaics}, volume={10}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/D1TA09544G}, DOI={10.1039/d1ta09544g}, abstractNote={Top and bottom surfaces of polymer films are used to construct interfaces in heterojunction based devices, affecting device figure of merit significantly with their different aggregation states.}, number={4}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Zhong, Yufei and Kirmani, Ahmad R. and Lan, Xinzheng and Carpenter, Joshua and Rong-Hui Chew, Annabel and Awartani, Omar and Yu, Liyang and Niazi, Muhammad R. and Voznyy, Oleksandr and Hu, Hanlin and et al.}, year={2022}, pages={1788–1801} } @article{rech_neu_qin_samson_shanahan_josey_ade_you_2021, title={Designing Simple Conjugated Polymers for Scalable and Efficient Organic Solar Cells}, volume={6}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.202100910}, abstractNote={AbstractConjugated polymers have a long history of exploration and use in organic solar cells, and over the last twenty‐five years, marked increases in the solar cell efficiency have been achieved. However, the synthetic complexity of these materials has also drastically increased, which makes the scalability of the highest‐efficiency materials difficult. If conjugated polymers could be designed to exhibit both high efficiency and straightforward synthesis, the road to commercial reality would be more achievable. For that reason, a new synthetic approach was designed towards PTQ10 (=poly[(thiophene)‐alt‐(6,7‐difluoro‐2‐(2‐hexyldecyloxy)quinoxaline)]). The new synthetic approach to make PTQ10 brought a significant reduction in cost (1/7th the original) and could also easily accommodate different side chains to move towards green processing solvents. Furthermore, high‐efficiency organic solar cells were demonstrated with a PTQ10:Y6 blend exhibiting approximately 15 % efficiency.}, journal={CHEMSUSCHEM}, author={Rech, Jeromy James and Neu, Justin and Qin, Yunpeng and Samson, Stephanie and Shanahan, Jordan and Josey, Richard F., III and Ade, Harald and You, Wei}, year={2021}, month={Jun} } @article{schopp_brus_lee_dixon_karki_liu_peng_graham_ade_bazan_et al._2021, title={Effect of Palladium-Tetrakis(Triphenylphosphine) Catalyst Traces on Charge Recombination and Extraction in Non-Fullerene-based Organic Solar Cells}, volume={31}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202009363}, abstractNote={AbstractThe effect of the cross‐coupling catalyst tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) on the performance of a model organic bulk‐heterojunction solar cell composed of a blend of poly([2,6′‐4,8‐di(5‐ethylhexylthienyl)benzo[1,2‐b;3,3‐b]dithiophene]{3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) (PTB7‐Th) donor and 3,9‐bis(2‐methylene‐((3‐(1,1‐dicyanomethylene)‐6,7‐difluoro)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (IOTIC‐4F) non‐fullerene acceptor is investigated. The effect of intentional addition of different amounts of Pd(PPh3)4 on morphology, free charge carrier generation, non‐geminate bulk trap‐ and surface trap‐assisted recombination as well as bimolecular recombination and charge extraction is quantified. This work shows that free charge carrier generation is affected significantly, while the impact of Pd(PPh3)4 on non‐geminate recombination processes is limited because the catalyst does not facilitate efficient trap‐assisted recombination. The studied system shows substantial robustness towards the addition of Pd(PPh3)4 in small amounts.}, number={15}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Schopp, Nora and Brus, Viktor V. and Lee, Jaewon and Dixon, Alana and Karki, Akchheta and Liu, Tuo and Peng, Zhengxing and Graham, Kenneth R. and Ade, Harald and Bazan, Guillermo C. and et al.}, year={2021}, month={Apr} } @article{zhang_zhu_deng_wang_zhang_li_zhang_lv_liu_zhang_et al._2021, title={High Miscibility Compatible with Ordered Molecular Packing Enables an Excellent Efficiency of 16.2% in All-Small-Molecule Organic Solar Cells}, volume={12}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202106316}, abstractNote={AbstractIn all‐small‐molecule organic solar cells (ASM‐OSCs), a high short‐circuit current (Jsc) usually needs a small phase separation, while a high fill factor (FF) is generally realized in a highly ordered packing system. However, small domain and ordered packing always conflicted each other in ASM‐OSCs, leading to a mutually restricted Jsc and FF. In this study, alleviation of the previous dilemma by the strategy of obtaining simultaneous good miscibility and ordered packing through modulating homo‐ and heteromolecular interactions is proposed. By moving the alkyl‐thiolation side chains from the para‐ to the meta‐position in the small‐molecule donor, the surface tension and molecular planarity are synchronously enhanced, resulting in compatible properties of good miscibility with acceptor BTP‐eC9 and strong self‐assembly ability. As a result, an optimized morphology with multi‐length‐scale domains and highly ordered packing is realized. The device exhibits a long carrier lifetime (39.8 μs) and fast charge collection (15.5 ns). A record efficiency of 16.2% with a high FF of 75.6% and a Jsc of 25.4 mA cm−2 in the ASM‐OSCs is obtained. These results demonstrate that the strategy of simultaneously obtaining good miscibility with high crystallinity could be an efficient photovoltaic material design principle for high‐performance ASM‐OSCs.}, journal={ADVANCED MATERIALS}, author={Zhang, Lili and Zhu, Xiangwei and Deng, Dan and Wang, Zhen and Zhang, Ziqi and Li, Yi and Zhang, Jianqi and Lv, Kun and Liu, Lixuan and Zhang, Xuning and et al.}, year={2021}, month={Dec} } @article{jia_qin_meng_ma_angunawela_zhang_li_he_lai_li_et al._2021, title={High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-020-20431-6}, abstractNote={AbstractTandem organic solar cells are based on the device structure monolithically connecting two solar cells to broaden overall absorption spectrum and utilize the photon energy more efficiently. Herein, we demonstrate a simple strategy of inserting a double bond between the central core and end groups of the small molecule acceptor Y6 to extend its conjugation length and absorption range. As a result, a new narrow bandgap acceptor BTPV-4F was synthesized with an optical bandgap of 1.21 eV. The single-junction devices based on BTPV-4F as acceptor achieved a power conversion efficiency of over 13.4% with a high short-circuit current density of 28.9 mA cm−2. With adopting BTPV-4F as the rear cell acceptor material, the resulting tandem devices reached a high power conversion efficiency of over 16.4% with good photostability. The results indicate that BTPV-4F is an efficient infrared-absorbing narrow bandgap acceptor and has great potential to be applied into tandem organic solar cells.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Jia, Zhenrong and Qin, Shucheng and Meng, Lei and Ma, Qing and Angunawela, Indunil and Zhang, Jinyuan and Li, Xiaojun and He, Yakun and Lai, Wenbin and Li, Ning and et al.}, year={2021}, month={Jan} } @article{du_mainville_vollbrecht_dixon_schopp_schrock_peng_huang_chae_ade_et al._2021, title={Insights into Bulk-Heterojunction Organic Solar Cells Processed from Green Solvent}, volume={5}, ISSN={["2367-198X"]}, url={https://doi.org/10.1002/solr.202100213}, DOI={10.1002/solr.202100213}, abstractNote={The environmental impact of solution processed organic solar cells (OSCs) can be mitigated by introducing so‐called green solvents during the fabrication processes. However, the effects of such green solvents on the molecular‐level structures and optoelectronic properties lack in‐depth characterization. Here, insights into the structure–processing–property correlation of a PPDT2FBT:PC61BM bulk‐heterojunction (BHJ) system processed from a green solvent, ortho‐xylene (o‐XY), is investigated in comparison with the same blend processed from a traditional halogenated solvent, chlorobenzene (CB). The BHJ blends are characterized with various techniques probing at difference length scales, and an increased donor:acceptor (D:A) interfacial area as well as well‐mixed features in the bulk morphologies of the active layer are observed for the o‐XY processed BHJ blend. Furthermore, molecular‐level differences in the D–A intermolecular interactions at the BHJ interfaces in o‐XY and CB cast films are elucidated by 2‐dimensional solid‐state nuclear magnetic resonance (ssNMR) measurements and analysis. These results are consistent with the device properties, suggesting that the green‐solvent‐processed devices have longer charge carrier lifetimes and faster charge carrier extraction. The optimized PPDT2FBT:PC61BM devices processed from o‐XY can achieve a noteworthy higher power conversion efficiency (PCE) owing to a higher short‐circuit current density and fill factor.}, journal={SOLAR RRL}, publisher={Wiley}, author={Du, Zhifang and Mainville, Mathieu and Vollbrecht, Joachim and Dixon, Alana L. and Schopp, Nora and Schrock, Max and Peng, Zhengxing and Huang, Jianfei and Chae, Sangmin and Ade, Harald and et al.}, year={2021}, month={Jun} } @article{zhou_meng_zhang_zhu_qin_angunawela_wan_ade_li_2021, title={Introducing Low-Cost Pyrazine Unit into Terpolymer Enables High-Performance Polymer Solar Cells with Efficiency of 18.23%}, volume={11}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202109271}, abstractNote={AbstractRecently, a random ternary copolymerization strategy has become a promising and efficient approach to develop high‐performance polymer donors for polymer solar cells (PSCs). In this study, a low‐cost electron‐withdrawing unit, 2,5‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)pyrazine (PZ‐T), is incorporated into the polymer backbone of PM6 as the third component, and three D‐A1‐D‐A2 type terpolymers PMZ‐10, PMZ‐20, and PMZ‐30 are synthesized by the random copolymerization strategy, with the PZ‐T proportion of 10%, 20%, and 30%, respectively. The terpolymers exhibit downshifted highest occupied molecular orbital energy levels than PM6, which is beneficial for obtaining higher open‐circuit voltage (Voc) of the PSCs with the polymer as a donor. Importantly, the PSCs based on PMZ‐10:Y6 demonstrate efficient exciton dissociation, higher and balanced electron/hole mobilities, desirable aggregation, and high power conversion efficiency of 18.23%, which is the highest efficiency among the terpolymer‐based PSCs so far. The results indicate that the ternary copolymerization strategy with PZ‐T as the second A‐unit is an efficient approach to further improve the photovoltaic performance and reduce the synthetic cost of the D‐A copolymer donors.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Zhou, Liuyang and Meng, Lei and Zhang, Jinyuan and Zhu, Can and Qin, Shucheng and Angunawela, Indunil and Wan, Yan and Ade, Harald and Li, Yongfang}, year={2021}, month={Nov} } @article{peng_jiang_qin_li_balar_brendan t. o'connor_ade_ye_geng_2021, title={Modulation of Morphological, Mechanical, and Photovoltaic Properties of Ternary Organic Photovoltaic Blends for Optimum Operation}, volume={11}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202003506}, DOI={10.1002/aenm.202003506}, abstractNote={AbstractTernary solar cells comprising both fullerene and nonfullerene acceptors have shown a rapid increase in power conversion efficiency, which holds promise in commercial applications. Despite the rapid progress, there is still a lack of fundamental understanding of the relations between microstructure and (photovoltaic/mechanical) properties in these ternary blend systems. In this work, the dependence of molecular packing, phase separation, mechanical properties, and photovoltaic performance on acceptor composition of a recently certificated ternary system is thoroughly investigated by combined scattering and microscopy characterizations. It is demonstrated that incorporating a small amount (20% by weight) PC71BM to the PM6:N3 binary blend can afford the best device efficiency and the highest ductility simultaneously. This maximum performance is due to the optimized molecular order, orientational texture, and phase separation. Additionally, increasing the amount of PC71BM results in higher elastic modulus, as probed by two distinct methods. A more crucial observation is that the elastic modulus of ternary blends can be well captured by an extended Halpin–Tsai model. This finding is expected to enable the prediction of the elastic modulus of various kinds of ternary blends that are widely used in solar cells and other electronics.}, number={8}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Peng, Zhongxiang and Jiang, Kui and Qin, Yunpeng and Li, Miaomiao and Balar, Nrup and Brendan T. O'Connor and Ade, Harald and Ye, Long and Geng, Yanhou}, year={2021}, month={Feb} } @article{li_huang_ding_sheriff_ye_liu_li_ade_forrest_2021, title={Non-fullerene acceptor organic photovoltaics with intrinsic operational lifetimes over 30 years}, volume={12}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-021-25718-w}, DOI={10.1038/s41467-021-25718-w}, abstractNote={AbstractOrganic photovoltaic cells (OPVs) have the potential of becoming a productive renewable energy technology if the requirements of low cost, high efficiency and prolonged lifetime are simultaneously fulfilled. So far, the remaining unfulfilled promise of this technology is its inadequate operational lifetime. Here, we demonstrate that the instability of NFA solar cells arises primarily from chemical changes at organic/inorganic interfaces bounding the bulk heterojunction active region. Encapsulated devices stabilized by additional protective buffer layers as well as the integration of a simple solution processed ultraviolet filtering layer, maintain 94% of their initial efficiency under simulated, 1 sun intensity, AM1.5 G irradiation for 1900 hours at 55 °C. Accelerated aging is also induced by exposure of light illumination intensities up to 27 suns, and operation temperatures as high as 65 °C. An extrapolated intrinsic lifetime of > 5.6 × 104 h is obtained, which is equivalent to 30 years outdoor exposure.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Li, Yongxi and Huang, Xiaheng and Ding, Kan and Sheriff, Hafiz K. M., Jr. and Ye, Long and Liu, Haoran and Li, Chang-Zhi and Ade, Harald and Forrest, Stephen R.}, year={2021}, month={Sep} } @article{zou_ma_chan_zhang_li_shang_wang_arunagiri_qi_ade_et al._2021, title={Optically Probing Field-Dependent Charge Dynamics in Non-Fullerene Organic Photovoltaics with Small Interfacial Energy Offsets}, volume={125}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.0c09663}, abstractNote={Current non-fullerene organic photovoltaics (OPVs) can achieve high photocurrent generation yields with small donor/acceptor energy offsets. However, the effect of varying energy offset on the char...}, number={3}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Zou, Xinhui and Ma, Chao and Chan, Christopher C. S. and Zhang, Jianquan and Li, Yunke and Shang, Ao and Wang, Zhen and Arunagiri, Lingeswaran and Qi, Zhenyu and Ade, Harald and et al.}, year={2021}, month={Jan}, pages={1714–1722} } @article{an_qin_zhang_lv_qin_zhang_he_ade_hou_2021, title={Optimization of active layer morphology by small-molecule donor design enables over 15% efficiency in small-molecule organic solar cells}, volume={4}, ISSN={["2050-7496"]}, DOI={10.1039/d0ta12242d}, abstractNote={Two conjugated small molecules with different conjugated side chains were synthesized to study their photovoltaic performances.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={An, Cunbin and Qin, Yunpeng and Zhang, Tao and Lv, Qianglong and Qin, Jinzhao and Zhang, Shaoqing and He, Chang and Ade, Harald and Hou, Jianhui}, year={2021}, month={Apr} } @article{mukherjee_gann_nahid_mcafee_herzing_delongchamp_ade_2021, title={Orientational Ordering within Semiconducting Polymer Fibrils}, volume={31}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202102522}, abstractNote={AbstractDue to a general paucity of suitable characterization methods, the internal orientational ordering of polymer fibrils has rarely been measured despite its importance particularly for semi‐conducting polymers. An emerging tool with sensitivity to bond orientation is polarized resonant soft X‐ray scattering (P‐RSoXS). Here, P‐RSoXS reveals the molecular arrangement within fibrils (if type I or type II fibrils), the extent of orientation in the fibril crystal, and an explicit crystal‐amorphous interphase. Neat films as well as binary blends with a fullerene derivative are characterized for three different polymers, that are prototypical materials widely used in organic electronics applications. Anisotropic P‐RSoXS patterns reveal two different fibril types. Analysis of the q‐dependence of the anisotropy from simulated and experimental scattering patterns reveal that neat polymer fibrillar systems likely comprise more than two phases, with the third phase in addition to crystal and amorphous likely being an interphase with distinct density and orientation. Intriguingly, the fibril type correlates to the H‐ or J‐aggregation signature in ultraviolet‐visible (UV–vis) spectroscopy, revealing insight into the fibril formation. Together, the results will open the door to develop more sophisticated structure‐function relationships between chemical design, fibril type, formation pathways and kinetics, interfacial ordering, and eventually device functions.}, number={28}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Mukherjee, Subhrangsu and Gann, Eliot and Nahid, Masrur Morshed and McAfee, Terry and Herzing, Andrew A. and DeLongchamp, Dean M. and Ade, Harald}, year={2021}, month={Jul} } @article{du_hu_zhang_meng_yue_angunawela_yan_qin_kong_zhang_et al._2021, title={Polymerized small molecular acceptor based all-polymer solar cells with an efficiency of 16.16% via tuning polymer blend morphology by molecular design}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-021-25638-9}, abstractNote={AbstractAll-polymer solar cells (all-PSCs) based on polymerized small molecular acceptors (PSMAs) have made significant progress recently. Here, we synthesize two A-DA’D-A small molecule acceptor based PSMAs of PS-Se with benzo[c][1,2,5]thiadiazole A’-core and PN-Se with benzotriazole A’-core, for the studies of the effect of molecular structure on the photovoltaic performance of the PSMAs. The two PSMAs possess broad absorption with PN-Se showing more red-shifted absorption than PS-Se and suitable electronic energy levels for the application as polymer acceptors in the all-PSCs with PBDB-T as polymer donor. Cryogenic transmission electron microscopy visualizes the aggregation behavior of the PBDB-T donor and the PSMA in their solutions. In addition, a bicontinuous-interpenetrating network in the PBDB-T:PN-Se blend film with aggregation size of 10~20 nm is clearly observed by the photoinduced force microscopy. The desirable morphology of the PBDB-T:PN-Se active layer leads its all-PSC showing higher power conversion efficiency of 16.16%.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Du, Jiaqi and Hu, Ke and Zhang, Jinyuan and Meng, Lei and Yue, Jiling and Angunawela, Indunil and Yan, Hongping and Qin, Shucheng and Kong, Xiaolei and Zhang, Zhanjun and et al.}, year={2021}, month={Sep} } @article{jiang_zhang_peng_lin_wu_li_chen_yan_ade_zhu_et al._2021, title={Pseudo-bilayer architecture enables high-performance organic solar cells with enhanced exciton diffusion length}, volume={12}, ISSN={["2041-1723"]}, url={https://doi.org/10.1038/s41467-020-20791-z}, DOI={10.1038/s41467-020-20791-z}, abstractNote={AbstractSolution-processed organic solar cells (OSCs) are a promising candidate for next-generation photovoltaic technologies. However, the short exciton diffusion length of the bulk heterojunction active layer in OSCs strongly hampers the full potential to be realized in these bulk heterojunction OSCs. Herein, we report high-performance OSCs with a pseudo-bilayer architecture, which possesses longer exciton diffusion length benefited from higher film crystallinity. This feature ensures the synergistic advantages of efficient exciton dissociation and charge transport in OSCs with pseudo-bilayer architecture, enabling a higher power conversion efficiency (17.42%) to be achieved compared to those with bulk heterojunction architecture (16.44%) due to higher short-circuit current density and fill factor. A certified efficiency of 16.31% is also achieved for the ternary OSC with a pseudo-bilayer active layer. Our results demonstrate the excellent potential for pseudo-bilayer architecture to be used for future OSC applications.}, number={1}, journal={NATURE COMMUNICATIONS}, publisher={Springer Science and Business Media LLC}, author={Jiang, Kui and Zhang, Jie and Peng, Zhengxing and Lin, Francis and Wu, Shengfan and Li, Zhen and Chen, Yuzhong and Yan, He and Ade, Harald and Zhu, Zonglong and et al.}, year={2021}, month={Jan} } @article{xu_xue_stuard_ade_zhang_yao_li_li_2021, title={Reducing Energy Disorder of Hole Transport Layer by Charge Transfer Complex for High Performance p-i-n Perovskite Solar Cells}, volume={33}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202006753}, abstractNote={AbstractSolution‐processed organic semiconductor charge‐transport layers (OS‐CTLs) with high mobility, low trap density, and energy level alignment have dominated the important progress in p–i–n planar perovskite solar cells (pero‐SCs). Unfortunately, their inevitable long chains result in weak molecular stacking, which is likely to generate high energy disorder and deteriorate the charge‐transport ability of OS‐CTLs. Here, a charge‐transfer complex (CTC) strategy to reduce the energy disorder in the OS‐CTLs by doping an organic semiconductor, 4,4′‐(4,8‐bis(5‐(trimethylsilyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(N,N‐bis(4‐methoxyphenyl)aniline) (BDT‐Si), in a commercial hole‐transport layer (HTL), poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl)amine (PTAA), is proposed. The formation of the CTC makes the PTAA conjugated backbone electron‐deficient, resulting in a quinoidal and stiffer character, which is likely to planarize the PTAA backbone and enhance the ordering of the film in nanoscale. The resultant HTL exhibits a reduced energy disorder, which simultaneously promotes hole transport in the HTL, hole extraction at the interface, energy level alignment, and quasi‐Fermi level splitting in the device. As a result, the p–i–n planar pero‐SCs with optimized HTL exhibit the best power conversion efficiency of 21.87% with good operating stability. This finding demonstrates that the CTC strategy is an effective way to reduce the energy disorder in HTLs and to improve the performance of planar pero‐SCs.}, number={13}, journal={ADVANCED MATERIALS}, author={Xu, Guiying and Xue, Rongming and Stuard, Samuel J. and Ade, Harald and Zhang, Chenjie and Yao, Jianlin and Li, Yaowen and Li, Yongfang}, year={2021}, month={Apr} } @article{yu_pan_sun_agunawela_zhang_li_qi_han_zou_zhou_et al._2021, title={Regio-Regular Polymer Acceptors Enabled by Determined Fluorination on End Groups for All-Polymer Solar Cells with 15.2 % Efficiency}, volume={60}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202016284}, abstractNote={AbstractPolymerization sites of small molecule acceptors (SMAs) play vital roles in determining device performance of all‐polymer solar cells (all‐PSCs). Different from our recent work about fluoro‐ and bromo‐ co‐modified end group of IC‐FBr (a mixture of IC‐FBr1 and IC‐FBr2), in this paper, we synthesized and purified two regiospecific fluoro‐ and bromo‐ substituted end groups (IC‐FBr‐o & IC‐FBr‐m), which were then employed to construct two regio‐regular polymer acceptors named PYF‐T‐o and PYF‐T‐m, respectively. In comparison with its isomeric counterparts named PYF‐T‐m with different conjugated coupling sites, PYF‐T‐o exhibits stronger and bathochromic absorption to achieve better photon harvesting. Meanwhile, PYF‐T‐o adopts more ordered inter‐chain packing and suitable phase separation after blending with the donor polymer PM6, which resulted in suppressed charge recombination and efficient charge transport. Strikingly, we observed a dramatic performance difference between the two isomeric polymer acceptors PYF‐T‐o and PYF‐T‐m. While devices based on PM6:PYF‐T‐o can yield power conversion efficiency (PCE) of 15.2 %, devices based on PM6:PYF‐T‐m only show poor efficiencies of 1.4 %. This work demonstrates the success of configuration‐unique fluorinated end groups in designing high‐performance regular polymer acceptors, which provides guidelines towards developing all‐PSCs with better efficiencies.}, number={18}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Yu, Han and Pan, Mingao and Sun, Rui and Agunawela, Indunil and Zhang, Jianquan and Li, Yuhao and Qi, Zhenyu and Han, Han and Zou, Xinhui and Zhou, Wentao and et al.}, year={2021}, month={Apr}, pages={10137–10146} } @article{arneson_huang_huang_fan_gao_ye_ade_li_forrest_2021, title={Relationship between charge transfer state electroluminescence and the degradation of organic photovoltaics}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0037710}, DOI={10.1063/5.0037710}, abstractNote={The degradation of archetype organic photovoltaics comprising both vacuum and solution-deposited bulk heterojunction active regions is investigated and quantified using a theory based on detailed balance, which relates the open-circuit voltage to the efficiency of charge transfer state emission. To describe this relationship, we account for the difference between electroluminescent external quantum efficiency and the charge transfer emission efficiency. An empirical factor, m, is introduced to distinguish between nonradiative defect sites both within, m = 1, and outside, m >1, of the photoactive heterojunction. The m-factor is used to determine the primary sources of degradation for archetype solution- and vacuum-processed material systems. We conclude that degradation occurs primarily within the donor–acceptor heterojunction for the vacuum-processed devices (where m = 1.020 ± 0.002) and outside of the photoactive heterojunction for the solution-processed devices studied, both with and without an anode buffer layer (where m = 2.93 ± 0.09 and m = 1.90 ± 0.01, respectively).}, number={6}, journal={APPLIED PHYSICS LETTERS}, author={Arneson, Claire and Huang, Xinjing and Huang, Xiaheng and Fan, Dejiu and Gao, Mengyuan and Ye, Long and Ade, Harald and Li, Yongxi and Forrest, Stephen R.}, year={2021}, month={Feb} } @article{balar_rech_siddika_song_schrickx_sheikh_ye_bonilla_awartani_ade_et al._2021, title={Resolving the Molecular Origin of Mechanical Relaxations in Donor-Acceptor Polymer Semiconductors}, volume={32}, ISSN={["1616-3028"]}, url={https://doi.org/10.1002/adfm.202105597}, DOI={10.1002/adfm.202105597}, abstractNote={AbstractThe thermomechanical behavior of polymer semiconductors plays an important role in the processing, morphology, and stability of organic electronic devices. However, donor–acceptor‐based copolymers exhibit complex thermal relaxation behavior that is not well understood. This study uses dynamic mechanical analysis (DMA) to probe thermal relaxations of a systematic set of polymers based around the benzodithiophene (BDT) moiety. The loss tangent curves are resolved by fitting Gaussian functions to assign and distinguish different relaxations. Three prominent transitions are observed that correspond to: i) localized relaxations driven primarily by the side chains (γ ), ii) relaxations along the polymer backbone (β  ), and iii) relaxations associated with aggregates (α  ). The side chains are found to play a clear role in dictating Tγ, and that mixing the side chain chemistry of the monomer to include alkyl and oligo(ethylene glycol) moieties results in splitting the γ ‐relaxation. The β relaxations are shown to be associated with backbone elements along with the monomer. In addition, through processing, it is shown that the α‐relaxation is due to aggregate formation. Finally, it is demonstrated that the thermal relaxation behavior correlates well with the stress–strain behavior of the polymers, including hysteresis and permanent set in cyclically stretched films.}, number={4}, journal={ADVANCED FUNCTIONAL MATERIALS}, publisher={Wiley}, author={Balar, Nrup and Rech, Jeromy James and Siddika, Salma and Song, Runqiao and Schrickx, Harry M. and Sheikh, Nadeem and Ye, Long and Bonilla, Anthony Megret and Awartani, Omar and Ade, Harald and et al.}, year={2021}, month={Oct} } @article{marina_gutierrez-fernandez_gutierrez_gobbi_ramos_solano_rech_you_hueso_tercjak_et al._2021, title={Semi-paracrystallinity in semi-conducting polymers}, volume={12}, ISSN={["2051-6355"]}, DOI={10.1039/d1mh01349a}, abstractNote={We introduce a new structural model for polymer materials: the semi-paracrystallinity. The assessment of structural order in semi-paracrystalline materials requires to consider the quality of ordering of the paracrystalline lattice and the degree of paracrystallinity.}, journal={MATERIALS HORIZONS}, author={Marina, Sara and Gutierrez-Fernandez, Edgar and Gutierrez, Junkal and Gobbi, Marco and Ramos, Nicolas and Solano, Eduardo and Rech, Jeromy and You, Wei and Hueso, Luis and Tercjak, Agnieszka and et al.}, year={2021}, month={Dec} } @article{nevola_bataller_kumar_sridhar_frick_o'donnell_ade_maggard_kemper_gundogdu_et al._2021, title={Timescales of excited state relaxation in alpha-RuCl3 observed by time-resolved two-photon photoemission spectroscopy}, volume={103}, ISSN={["2469-9969"]}, url={https://doi.org/10.1103/PhysRevB.103.245105}, DOI={10.1103/PhysRevB.103.245105}, abstractNote={The nonequilibrium properties of strongly correlated materials present a target in the search for new phases of matter. It is important to observe the types of excitations that exist in these materials and their associated relaxation dynamics. We have studied the photoexcitations in a spin-orbit assisted Mott insulator $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Ru}{\mathrm{Cl}}_{3}$ using time-resolved two-photon photoemission spectroscopy and transient reflection spectroscopy. We find that photoexcited carriers (doublons) in the upper Hubbard band rapidly relax to Mott-Hubbard excitons on a timescale of less than 200 fs. Subsequently, further relaxation of these lower-energy quasiparticles occurs with an energy-dependent time constant of that ranges from 370 to 600 fs due to exciton cooling. The population of Mott-Hubbard excitons persists for timescales up to several microseconds.}, number={24}, journal={PHYSICAL REVIEW B}, author={Nevola, Dan and Bataller, Alexander and Kumar, Ankit and Sridhar, Samanvitha and Frick, Jordan and O'Donnell, Shaun and Ade, Harald and Maggard, Paul A. and Kemper, Alexander F. and Gundogdu, Kenan and et al.}, year={2021}, month={Jun} } @article{peng_ye_ade_2021, title={Understanding, quantifying, and controlling the molecular ordering of semiconducting polymers: from novices to experts and amorphous to perfect crystals}, volume={12}, ISSN={["2051-6355"]}, url={https://doi.org/10.1039/D0MH00837K}, DOI={10.1039/d0mh00837k}, abstractNote={Molecular packing of semiconducting polymers is often critical to the performance of devices using these materials. The degree and quality of ordering are revealed by grazing-incidence wide-angle X-ray scattering and thermal analysis.}, number={2}, journal={MATERIALS HORIZONS}, publisher={Royal Society of Chemistry (RSC)}, author={Peng, Zhengxing and Ye, Long and Ade, Harald}, year={2021}, month={Dec} } @article{peng_balar_ghasemi_ade_2021, title={Upper and Apparent Lower Critical Solution Temperature Branches in the Phase Diagram of Polymer:Small Molecule Semiconducting Systems}, volume={12}, ISSN={["1948-7185"]}, DOI={10.1021/acs.jpclett.1c02848}, abstractNote={Solution-processable semiconducting materials are complex materials with a wide range of applications. Despite their extensive study and utility, their molecular interactions as manifested, for example, in phase behavior are poorly understood. Here, we aim to understand the phase behavior of conjugated systems by determining phase diagrams spanning extensive temperature ranges for various combinations of the highly disordered semiconducting polymer (PTB7-Th) with crystallizable (IT-M and PC61BM) and noncrystallizable (di-PDI) small molecule acceptors (SMAs), with polystyrene as an amorphous control, a nonsemiconducting commodity polymer. We discover that the apparent binodal of the studied blends frequently consists of an upper critical solution temperature (UCST) and lower critical solution temperature (LCST) branch, exhibiting a sharp kink where the branches join. Our work suggests that phase diagrams might be a probe in combination with sophisticated models to understand the complexity of semiconducting materials, including microstructure and molecular interactions.}, number={44}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Peng, Zhengxing and Balar, Nrup and Ghasemi, Masoud and Ade, Harald}, year={2021}, month={Nov}, pages={10845–10853} } @article{zhang_yu_zhou_wang_tang_xie_xie_hu_yip_ye_et al._2020, title={3,4-Dicyanothiophene-a Versatile Building Block for Efficient Nonfullerene Polymer Solar Cells}, volume={10}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/32099461/}, DOI={10.1002/aenm.201904247}, abstractNote={AbstractIn this contribution, a versatile building block, 3,4‐dicyanothiophene (DCT), which possesses structural simplicity and synthetic accessibility for constructing high‐performance, low‐cost, wide‐bandgap conjugated polymers for use as donors in polymer solar cells (PSCs), is reported. A prototype polymer, PB3TCN‐C66, and its cyano‐free analogue polymer PB3T‐C66, are synthesized to evaluate the potential of using DCT in nonfullerene PSCs. A stronger aggregation property in solution, higher thermal transition temperatures with higher enthalpies, a larger dipole moment, higher relative dielectric constant, and more linear conformation are exhibited by PB3TCN‐C66. Solar cells employing IT‐4F as the electron acceptor offer power conversion efficiencies (PCEs) of 11.2% and 2.3% for PB3TCN‐C66 and PB3T‐C66, respectively. Morphological characterizations reveal that the PB3TCN‐C66:IT‐4F blend exhibits better π–π paracrystallinity, a contracted domain size, and higher phase purity, consistent with its higher molecular interaction parameter, derived from thermodynamic calculations. Moreover, PB3TCN‐C66 offers a higher open‐circuit voltage and reduced energy loss than most state‐of‐the‐art wide‐bandgap polymers, without the need of additional electron‐withdrawing substituents. Two additional polymers derived from DCT also demonstrate promising performance with a higher PCE of 13.4% being achieved. Thus, DCT represents a versatile and promising building block for constructing high‐performance, low‐cost, conjugated polymers for application in PSCs.}, number={12}, journal={ADVANCED ENERGY MATERIALS}, author={Zhang, Bo and Yu, Yonggao and Zhou, Jiadong and Wang, Zhenfeng and Tang, Haoran and Xie, Shenkun and Xie, Zengqi and Hu, Liuyong and Yip, Hin-Lap and Ye, Long and et al.}, year={2020}, month={Mar} } @article{jiang_huang_sun_li_gao_ye_ade_forrest_fan_2020, title={A 3D nonfullerene electron acceptor with a 9,9 ' -bicarbazole backbone for high -efficiency organic solar cells}, volume={84}, ISSN={["1878-5530"]}, url={https://publons.com/wos-op/publon/32099481/}, DOI={10.1016/j.orgel.2020.105784}, abstractNote={One-dimensional ladder-type nonfullerene electron acceptors (NFAs) with large fused ring cores have been widely used in highly efficient organic solar cells (OSCs). Recent studies have demonstrated that small molecule acceptors with three-dimensional (3D) structures may exhibit low energy loss, and hence can lead to improved OSC performance. In this study, a new 3D NFA (99CZ-8F) with a 9,9′-bicarbazole backbone was designed, synthesized, and characterized, where two linear A-D-A architectures were linked by a single N–N bond. 99CZ-8F showed strong absorption in the range of 500–800 nm in the solid state, which is complementary to the absorption of the donor material PM6. After regulating the morphology of the active layer via binary solvent mixture, the optimized device exhibited a maximum power conversion efficiency (PCE) of 6.6 ± 0.1%, which is among the best reported values for 3D nonfullerene electron acceptor based OSCs.}, journal={ORGANIC ELECTRONICS}, author={Jiang, Chao and Huang, Xinjing and Sun, Bangjin and Li, Yongxi and Gao, Mengyuan and Ye, Long and Ade, Harald and Forrest, Stephen R. and Fan, Jian}, year={2020}, month={Sep} } @article{ravishankar_booth_saravitz_sederoff_ade_brendan t. o'connor_2020, title={Achieving Net Zero Energy Greenhouses by Integrating Semitransparent Organic Solar Cells}, volume={4}, ISSN={["2542-4351"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85079138223&partnerID=MN8TOARS}, DOI={10.1016/j.joule.2019.12.018}, abstractNote={Greenhouses vastly increase agricultural land-use efficiency. However, they also consume significantly more energy than conventional farming due in part to conditioning the greenhouse space. One way to mitigate the increase in energy consumption is to integrate solar modules onto the greenhouse structure. Semitransparent organic solar cells (OSCs) are particularly attractive given that their spectral absorption can be tuned to minimize the attenuation of sunlight over the plants photosynthetically active spectrum. Here, the benefits of integrating OSCs on the net energy demand of greenhouses within the U.S. are determined through a detailed energy balance model. We find that these systems can have an annual surplus of energy in warm and moderate climates. Furthermore, we show that sunlight reduction entering the greenhouse can be minimized with appropriate design. These results demonstrate that OSCs are an excellent candidate for implementing in greenhouses and provide an opportunity to diversify sustainable energy generation technology.}, number={2}, journal={JOULE}, author={Ravishankar, Eshwar and Booth, Ronald E. and Saravitz, Carole and Sederoff, Heike and Ade, Harald W. and Brendan T. O'Connor}, year={2020}, month={Feb}, pages={490–506} } @article{chen_bai_peng_zhu_zhang_zou_qin_kim_yuan_ma_et al._2021, title={Asymmetric Alkoxy and Alkyl Substitution on Nonfullerene Acceptors Enabling High-Performance Organic Solar Cells}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202003141}, abstractNote={AbstractIn this paper, a strategy of asymmetric alkyl and alkoxy substitution is applied to state‐of‐the‐art Y‐series nonfullerene acceptors (NFAs), and it achieves great performance in organic solar cell (OSC) devices. Since alkoxy groups can have a significant influence on the material properties of NFAs, alkoxy substitution is applied to the Y6 molecule in a symmetric manner. The resulting molecule (named Y6‐2O), despite showing improved open‐circuit voltage (Voc), yields extremely poor performance due to low solubility and excessive aggregation properties, a change that is due to the conformational locking effect of alkoxy groups. In contrast, asymmetric alkyl and alkoxy substitution on Y6, yields a molecule named Y6‐1O that can maintain the positive effect of Voc improvement and obtain reasonably good solubility. The resulting molecule Y6‐1O enables highly efficient nonfullerene OSCs with 17.6% efficiency and the asymmetric side‐chain strategy has the potential to be applied to other NFA‐material systems to further improve their performance.}, number={3}, journal={ADVANCED ENERGY MATERIALS}, author={Chen, Yuzhong and Bai, Fujin and Peng, Zhengxing and Zhu, Lei and Zhang, Jianquan and Zou, Xinhui and Qin, Yunpeng and Kim, Ha Kyung and Yuan, Jun and Ma, Lik-Kuen and et al.}, year={2021}, month={Jan} } @article{guo_lin_liu_dong_guo_ye_ma_tang_ade_zhang_et al._2020, title={Asymmetrically noncovalently fused-ring acceptor for high-efficiency organic solar cells with reduced voltage loss and excellent thermal stability}, volume={74}, ISSN={["2211-3282"]}, url={https://publons.com/wos-op/publon/32099469/}, DOI={10.1016/j.nanoen.2020.104861}, abstractNote={Simultaneously broadening the spectral response and reducing the energy loss are challenging tasks in the material design of organic solar cells (OSCs). Herein, a novel asymmetrically noncovalently fused-ring electron acceptor (NFEA) with unilateral alkylthio-substituted thiophene π-bridge, namely IDST-4F, is synthesized. IDST-4F exhibits a broader absorption, higher-lying energy levels, larger dipole moments and suppressed crystallinity than its symmetric counterpart (ID-4F) without the π-bridge. Compared to the devices of PM6:ID-4F, the optimized PM6:IDST-4F-based devices display simultaneously enhanced current density and photovoltage, resulting in an excellent power conversion efficiency (PCE) of 14.3%, which is the highest value among the OSCs based on NFEAs reported in the literature to date. More importantly, the PM6:IDST-4F-based OSCs possess excellent thermal stability with 82% of the initial PCE after thermal treatment at 150 °C for 1200 min. In summary, this study indicates that asymmetrically NFEAs are promising to achieve high efficiency with excellent thermal stability.}, journal={NANO ENERGY}, author={Guo, Qing and Lin, Ji and Liu, Haiqin and Dong, Xingliang and Guo, Xia and Ye, Long and Ma, Zaifei and Tang, Zheng and Ade, Harald and Zhang, Maojie and et al.}, year={2020}, month={Aug} } @article{szymanski_henry_stuard_vongsaysy_courtel_vellutini_bertrand_ade_chambon_wantz_2020, title={Balanced Charge Transport Optimizes Industry-Relevant Ternary Polymer Solar Cells}, volume={4}, ISSN={["2367-198X"]}, url={https://doi.org/10.1002/solr.202000538}, DOI={10.1002/solr.202000538}, abstractNote={Bulk heterojunction polymer solar cells based on a novel combination of materials are fabricated using industry‐compliant conditions for large area manufacturing. The relatively low‐cost polymer PTQ10 is paired with the nonfullerene acceptor 4TIC‐4F. Devices are processed using a nonhalogenated solvent to comply with industrial usage in absence of any thermal treatment to minimize the energy footprint of the fabrication. No solvent additive is used. Adding the well‐known and low‐cost fullerene derivative PC61BM acceptor to this binary blend to form a ternary blend, the power conversion efficiency (PCE) is improved from 8.4% to 9.9% due to increased fill factor (FF) and open‐circuit voltage (VOC) while simultaneously improving the stability. The introduction of PC61BM is able to balance the hole–electron mobility in the ternary blends, which is favourable for high FF. This charge transport behavior is correlated with the bulk heterojunction (BHJ) morphology deduced from grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), atomic force microscopy (AFM), and surface energy analysis. In addition, the industrial figure of merit (i‐FOM) of this ternary blend is found to increase drastically upon addition of PC61BM due to an increased performance–stability–cost balance.}, number={11}, journal={SOLAR RRL}, publisher={Wiley}, author={Szymanski, Robin and Henry, Reece and Stuard, Samuel and Vongsaysy, Uyxing and Courtel, Stephanie and Vellutini, Luc and Bertrand, Melanie and Ade, Harald and Chambon, Sylvain and Wantz, Guillaume}, year={2020}, month={Nov} } @article{szymanski_henry_stuard_vongsaysy_courtel_vellutini_bertrand_ade_chambon_wantz_2020, title={Balanced Charge Transport Optimizes Industry‐Relevant Ternary Polymer Solar Cells}, volume={4}, url={https://doi.org/10.1002/solr.202070111}, DOI={10.1002/solr.202070111}, abstractNote={Polymer Solar Cells In article number 2000538, Harald Ade, Guillaume Wantz, and co-workers develop novel, cost-effective ternary polymer solar cells printed in semi-industrial conditions from a relatively benign ink, which do not require any further processing. These solar cells show good stability and efficiency due to balanced charge carrier mobilities achieved by optimizing the composition and morphology.}, number={11}, journal={Solar RRL}, publisher={Wiley}, author={Szymanski, Robin and Henry, Reece and Stuard, Samuel and Vongsaysy, Uyxing and Courtel, Stéphanie and Vellutini, Luc and Bertrand, Mélanie and Ade, Harald and Chambon, Sylvain and Wantz, Guillaume}, year={2020}, month={Nov}, pages={2070111} } @article{wu_fan_xiong_wang_chen_liu_gao_ye_guo_fang_et al._2021, title={Carboxylate substituted pyrazine: A simple and low-cost building block for novel wide bandgap polymer donor enables 15.3% efficiency in organic solar cells}, volume={82}, ISSN={["2211-3282"]}, url={https://publons.com/wos-op/publon/33566889/}, DOI={10.1016/j.nanoen.2020.105679}, abstractNote={In addition to high power conversion efficiency (PCE) and good stability, the low-cost of photovoltaic materials is also very important for the practical application of organic solar cells (OSCs). Herein, we synthesized a carboxylate substituted pyrazine-based electron-deficient building block (DTCPz) with a simple structure and low synthetic cost, and then developed a novel wide bandgap polymer donor PFBCPZ. Due to the synergistic electron-withdrawing effects of the fluorination in donor unit (BDT-TF) and esterification and C=N double-bond in DTCPz unit, PFBCPZ shows a deeper HOMO level of −5.60 eV, a strong intermolecular π-π interaction, good crystallinity and stacking, and high hole-mobility of 2.11 × 10−3 cm2 V−1 s−1. Matched with a low bandgap acceptor IT-4F, excellent charge transfer, weak recombination, and small non-radiative energy loss in OSCs was achieved, resulting in an impressive fill factor of 0.785 and a high open-circuit voltage of 0.92 V. As a result, a PCE of up to 15.3% is obtained in OSCs, which is the highest value in the IT-4F-based binary OSCs so far and indicates that low-cost DTCPz with a simple structure is a promising building block to construct high-performance polymer donors for application in efficient OSCs.}, journal={NANO ENERGY}, author={Wu, Jingnan and Fan, Qunping and Xiong, Minghai and Wang, Qiutang and Chen, Kai and Liu, Haiqin and Gao, Mengyuan and Ye, Long and Guo, Xia and Fang, Jin and et al.}, year={2021}, month={Apr} } @article{li_guo_peng_qu_yan_ade_zhang_forrest_2020, title={Color-neutral, semitransparent organic photovoltaics for power window applications}, volume={117}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.2007799117}, abstractNote={Significance We demonstrate a semitransparent organic photovoltaic cell that achieves a power conversion efficiency of 10.8% and visible transparency of ∼50% using a nonfullerene acceptor (NFA) featuring strong near-infrared (NIR) absorption and simple synthesis. Contrary to expectations, stronger NIR absorption and closer molecular packing are obtained by employing an additive in these partially, instead of fully fused, rigid NFAs. By combining NIR-absorbing material sets with an optical outcoupling structure as well as transparent electrode, we overcome the trade-offs between efficiency, transparency, and device appearance. These results surpass other semitransparent solar cell technologies based on organic and other thin-film materials systems, showing a promising future for ST-OPVs as power-generating windows and other solar energy harvesting applications.}, number={35}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Li, Yongxi and Guo, Xia and Peng, Zhengxing and Qu, Boning and Yan, Hongping and Ade, Harald and Zhang, Maojie and Forrest, Stephen R.}, year={2020}, month={Sep}, pages={21147–21154} } @article{yi_peng_xu_seyitliyev_ho_danilov_kim_reynolds_amassian_gundogdu_et al._2020, title={Critical Role of Polymer Aggregation and Miscibility in Nonfullerene-Based Organic Photovoltaics}, volume={10}, ISSN={["1614-6840"]}, url={http://dx.doi.org/10.1002/aenm.201902430}, DOI={10.1002/aenm.201902430}, abstractNote={AbstractUnderstanding the correlation between polymer aggregation, miscibility, and device performance is important to establish a set of chemistry design rules for donor polymers with nonfullerene acceptors (NFAs). Employing a donor polymer with strong temperature‐dependent aggregation, namely PffBT4T‐2OD [poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3″′‐di(2‐octyldodecyl)‐2,2′;5′,2″;5″,2″′‐quaterthiophen‐5,5‐diyl)], also known as PCE‐11 as a base polymer, five copolymer derivatives having a different thiophene linker composition are blended with the common NFA O‐IDTBR to investigate their photovoltaic performance. While the donor polymers have similar optoelectronic properties, it is found that the device power conversion efficiency changes drastically from 1.8% to 8.7% as a function of thiophene content in the donor polymer. Results of structural characterization show that polymer aggregation and miscibility with O‐IDTBR are a strong function of the chemical composition, leading to different donor–acceptor blend morphology. Polymers having a strong tendency to aggregate are found to undergo fast aggregation prior to liquid–liquid phase separation and have a higher miscibility with NFA. These properties result in smaller mixed donor–acceptor domains, stronger PL quenching, and more efficient exciton dissociation in the resulting cells. This work indicates the importance of both polymer aggregation and donor–acceptor interaction on the formation of bulk heterojunctions in polymer:NFA blends.}, number={8}, journal={ADVANCED ENERGY MATERIALS}, author={Yi, Xueping and Peng, Zhengxing and Xu, Bing and Seyitliyev, Dovletgeldi and Ho, Carr Hoi Yi and Danilov, Evgeny O. and Kim, Taesoo and Reynolds, John R. and Amassian, Aram and Gundogdu, Kenan and et al.}, year={2020}, month={Feb} } @article{bin_angunawela_ma_nallapaneni_zhu_leenaers_saes_wienk_yan_ade_et al._2020, title={Effect of main and side chain chlorination on the photovoltaic properties of benzodithiophene-alt-benzotriazole polymers}, volume={8}, ISSN={["2050-7534"]}, DOI={10.1039/d0tc03095c}, abstractNote={Introduction of chlorine in the conjugated side chains significantly improves open-circuit voltage and power conversion efficiency, benefiting from a lower HOMO energy level, well-balanced charge transport and superior nanoscale morphology.}, number={43}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Bin, Haijun and Angunawela, Indunil and Ma, Ruijie and Nallapaneni, Asritha and Zhu, Chenhui and Leenaers, Pieter J. and Saes, Bart W. H. and Wienk, Martijn M. and Yan, He and Ade, Harald and et al.}, year={2020}, month={Nov}, pages={15426–15435} } @article{li_angunawela_chang_zhou_huang_zhong_liebman-pelaez_zhu_meng_xie_et al._2020, title={Effect of the chlorine substitution position of the end-group on intermolecular interactions and photovoltaic performance of small molecule acceptors}, volume={13}, ISSN={["1754-5706"]}, DOI={10.1039/d0ee02251a}, abstractNote={Differences in the intermolecular interactions of small molecule acceptors with different chlorine substitution positions affect their molecular packing and photovoltaic properties.}, number={12}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Li, Xiaojun and Angunawela, Indunil and Chang, Yuan and Zhou, Jiadong and Huang, He and Zhong, Lian and Liebman-Pelaez, Alex and Zhu, Chenhui and Meng, Lei and Xie, Zengqi and et al.}, year={2020}, month={Dec}, pages={5028–5038} } @article{lei_seyitliyev_stuard_mendes_dong_fu_chen_he_yi_zhu_et al._2020, title={Efficient Energy Funneling in Quasi-2D Perovskites: From Light Emission to Lasing}, volume={32}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201906571}, abstractNote={AbstractQuasi‐2D Ruddlesden–Popper halide perovskites with a large exciton binding energy, self‐assembled quantum wells, and high quantum yield draw attention for optoelectronic device applications. Thin films of these quasi‐2D perovskites consist of a mixture of domains having different dimensionality, allowing energy funneling from lower‐dimensional nanosheets (high‐bandgap domains) to 3D nanocrystals (low‐bandgap domains). High‐quality quasi‐2D perovskite (PEA)2(FA)3Pb4Br13 films are fabricated by solution engineering. Grazing‐incidence wide‐angle X‐ray scattering measurements are conducted to study the crystal orientation, and transient absorption spectroscopy measurements are conducted to study the charge‐carrier dynamics. These data show that highly oriented 2D crystal films have a faster energy transfer from the high‐bandgap domains to the low‐bandgap domains (<0.5 ps) compared to the randomly oriented films. High‐performance light‐emitting diodes can be realized with these highly oriented 2D films. Finally, amplified spontaneous emission with a low threshold 4.16 µJ cm−2 is achieved and distributed feedback lasers are also demonstrated. These results show that it is important to control the morphology of the quasi‐2D films to achieve efficient energy transfer, which is a critical requirement for light‐emitting devices.}, number={16}, journal={ADVANCED MATERIALS}, author={Lei, Lei and Seyitliyev, Dovletgeldi and Stuard, Samuel and Mendes, Juliana and Dong, Qi and Fu, Xiangyu and Chen, Yi-An and He, Siliang and Yi, Xueping and Zhu, Liping and et al.}, year={2020}, month={Apr} } @article{chai_chang_peng_jia_zou_yu_yu_chen_chow_wong_et al._2020, title={Enhanced hindrance from phenyl outer side chains on nonfullerene acceptor enables unprecedented simultaneous enhancement in organic solar cell performances with 16.7% efficiency}, volume={76}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2020.105087}, abstractNote={Inner side-chain engineering on Y6 has been proven successful in improving short-circuit current density (JSC) through fine-tuning aggregated structures of acceptors. However, it fails in tuning the lowest unoccupied molecular orbital level (LUMO) and open-circuit voltage (VOC). In this paper, we turn to focus on engineering the outer side chains on the flanking thienothiophene units with 4-hexylphenyl (PhC6) and 6-phenylhexyl (C6Ph) chains. Use of PhC6 enhances the steric effect between the attached phenyl and the ending group, which in combination with the additional conjugation effect provided by the linking phenyl leads to upshifted energy levels and increased VOC as a result. Again, substitution with the bulkier PhC6 unprecedentedly improves film-morphology with reduced paracrystalline disorder and long period and increased root-mean-square composition variations as well, leading to increased electron and hole mobilities and suppressed monomolecular recombination with JSC and fill-factor (FF) simultaneously enhanced. The PM6:BTP-PhC6-based devices yield a higher efficiency value of 16.7% than the PM6:BTP-C6Ph-based one (15.5%). Therefore, this study shows a conceptual advance in materials design towards reducing the conflict between VOC and JSC in binary blended organic solar cells, which can be achieved by introducing bulkier chains to twist the backbone and simultaneously enhance the packing order.}, journal={NANO ENERGY}, author={Chai, Gaoda and Chang, Yuan and Peng, Zhengxing and Jia, Yanyan and Zou, Xinhui and Yu, Dian and Yu, Han and Chen, Yuzhong and Chow, Philip C. Y. and Wong, Kam Sing and et al.}, year={2020}, month={Oct} } @article{islam_liu_boyd_zhong_nahid_henry_taussig_ko_nguyen_myers_et al._2020, title={Enhanced mid-wavelength infrared refractive index of organically modified chalcogenide (ORMOCHALC) polymer nanocomposites with thermomechanical stability}, volume={108}, ISSN={["1873-1252"]}, url={http://dx.doi.org/10.1016/j.optmat.2020.110197}, DOI={10.1016/j.optmat.2020.110197}, abstractNote={Abstract Organically modified chalcogenide (ORMOCHALC) polymers have proven to be alternatives to the conventional inorganic materials for mid-wavelength infrared (MWIR, λ = 3–5 μm) optical components. While the refractive index of ORMOCHALC can be reinforced by the content of chalcogenides such as sulfur (S) and selenium (Se), the increased portion of the S or Se deteriorate the thermomechanical stabilities. As a remedy, this study utilizes ZnS nanoparticles to reinforce both optical and thermomechanical properties of the sulfur-based ORMOCHALC polymer, poly(S-random-1,3-diisopropenylbenzene). The refractive index n and extinction coefficient k of the nanocomposites were characterized by Infrared Variable Angle Spectroscopic Ellipsometry (IR-VASE). The results show a significant increment in the refractive index of Δn = 6.58% at the wavelength of 4 μm by adding 20 wt% ZnS (or 7.29 vol%) in the ORMOCHALC polymer. The low extinction coefficient of the nanocomposites (}, journal={OPTICAL MATERIALS}, author={Islam, Md Didarul and Liu, Sipan and Boyd, Darryl A. and Zhong, Yaxu and Nahid, Masrur Morshed and Henry, Reece and Taussig, Laine and Ko, Yeongun and Nguyen, Vinh Q. and Myers, Jason D. and et al.}, year={2020}, month={Oct} } @article{rech_yan_wang_zhang_bradshaw_ade_you_2021, title={Functionalization of Benzotriazole-Based Conjugated Polymers for Solar Cells: Heteroatom vs Substituents}, volume={3}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.0c00761}, abstractNote={With the recent remarkable advances in the efficiency of organic solar cells, the need to distill key structure–property relationships for semiconducting materials cannot be understated. The fundam...}, number={1}, journal={ACS APPLIED POLYMER MATERIALS}, author={Rech, Jeromy James and Yan, Liang and Wang, Zhen and Zhang, Qianqian Q. and Bradshaw, Spencer and Ade, Harald and You, Wei}, year={2021}, month={Jan}, pages={30–41} } @article{huang_li_sun_angunawela_qiu_du_qin_meng_zhang_ade_et al._2020, title={Green solvent-processed organic solar cells based on a low cost polymer donor and a small molecule acceptor}, volume={8}, ISSN={["2050-7534"]}, DOI={10.1039/d0tc01313g}, abstractNote={High-performance OSCs were fabricated based on polymer PTQ10 as donor and HO-IDIC-2F as acceptor, using non-halogen tetrahydrofuran as processing solvent and the PCE of the as-cast OSCs reached 12.20% which is competitive with regular chloroform.}, number={23}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Huang, He and Li, Xiaojun and Sun, Chenkai and Angunawela, Indunil and Qiu, Beibei and Du, Jiaqi and Qin, Shucheng and Meng, Lei and Zhang, Zhanjun and Ade, Harald and et al.}, year={2020}, month={Jun}, pages={7718–7724} } @article{du_hu_meng_angunawela_zhang_qin_liebman-pelaez_zhu_zhang_ade_et al._2020, title={High-Performance All-Polymer Solar Cells: Synthesis of Polymer Acceptor by a Random Ternary Copolymerization Strategy}, volume={59}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202005357}, abstractNote={AbstractDemonstrated in this work is a simple random ternary copolymerization strategy to synthesize a series of polymer acceptors, PTPBT‐ETx, by polymerizing a small‐molecule acceptor unit modified from Y6 with a thiophene connecting unit and a controlled amount of an 3‐ethylesterthiophene (ET) unit. Compared to PTPBT of only Y6‐like units and thiophene units, PTPBT‐ETx (where x represents the molar ratio of the ET unit) with an incorporated ET unit in the ternary copolymers show up‐shifted LUMO energy levels, increased electron mobilities, and improved blend morphologies in the blend film with the polymer donor PBDB‐T. And the all‐polymer solar cell (all‐PSC) based on PBDB‐T:PTPBT‐ET0.3 achieved a high power conversion efficiency over 12.5 %. In addition, the PTPBT‐ET0.3‐based all‐PSC also exhibits long‐term photostability over 300 hours.}, number={35}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Du, Jiaqi and Hu, Ke and Meng, Lei and Angunawela, Indunil and Zhang, Jinyuan and Qin, Shucheng and Liebman-Pelaez, Alex and Zhu, Chenhui and Zhang, Zhanjun and Ade, Harald and et al.}, year={2020}, month={Aug}, pages={15181–15185} } @article{ho_kim_xiong_firdaus_yi_dong_rech_gadisa_booth_brendan t. o'connor_et al._2020, title={High-Performance Tandem Organic Solar Cells Using HSolar as the Interconnecting Layer}, volume={10}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202000823}, DOI={10.1002/aenm.202000823}, abstractNote={AbstractTandem structure provides a practical way to realize high efficiency organic photovoltaic cells, it can be used to extend the wavelength coverage for light harvesting. The interconnecting layer (ICL) between subcells plays a critical role in the reproducibility and performance of tandem solar cells, yet the processability of the ICL has been a challenge. In this work the fabrication of highly reproducible and efficient tandem solar cells by employing a commercially available material, PEDOT:PSS HTL Solar (HSolar), as the hole transporting material used for the ICL is reported. Comparing with the conventional PEDOT:PSS Al 4083 (c‐PEDOT), HSolar offers a better wettability on the underlying nonfullerene photoactive layers, resulting in better charge extraction properties of the ICL. When FTAZ:IT‐M and PTB7‐Th:IEICO‐4F are used as the subcells, a power conversion efficiency (PCE) of 14.7% is achieved in the tandem solar cell. To validate the processability of these tandem solar cells, three other research groups have successfully fabricated tandem devices using the same recipe and the highest PCE obtained is 16.1%. With further development of donor polymers and device optimization, the device simulation results show that a PCE > 22% can be realized in tandem cells in the near future.}, number={25}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Ho, Carr Hoi Yi and Kim, Taesoo and Xiong, Yuan and Firdaus, Yuliar and Yi, Xueping and Dong, Qi and Rech, Jeromy J. and Gadisa, Abay and Booth, Ronald and Brendan T. O'Connor and et al.}, year={2020}, month={Jul} } @article{yang_fan_wang_yan_dong_cui_ade_li_2020, title={Impact of Isomer Design on Physicochemical Properties and Performance in High-Efficiency All-Polymer Solar Cells}, volume={53}, ISBN={1520-5835}, DOI={10.1021/acs.macromol.0c01405}, abstractNote={Combining the acceptor–donor–acceptor-type fused ring-based molecular architecture into a polymeric backbone is a promising strategy to design polymer acceptors for high-performance all-polymer sol...}, number={20}, journal={MACROMOLECULES}, author={Yang, Hang and Fan, Hongyu and Wang, Zhen and Yan, Hongping and Dong, Yingying and Cui, Chaohua and Ade, Harald and Li, Yongfang}, year={2020}, pages={9026–9033} } @article{firdaus_le corre_karuthedath_liu_markina_huang_chattopadhyay_nahid_nugraha_lin_et al._2020, title={Long-range exciton diffusion in molecular non-fullerene acceptors}, volume={11}, ISBN={2041-1723}, DOI={10.1038/s41467-020-19029-9}, abstractNote={AbstractThe short exciton diffusion length associated with most classical organic semiconductors used in organic photovoltaics (5-20 nm) imposes severe limits on the maximum size of the donor and acceptor domains within the photoactive layer of the cell. Identifying materials that are able to transport excitons over longer distances can help advancing our understanding and lead to solar cells with higher efficiency. Here, we measure the exciton diffusion length in a wide range of nonfullerene acceptor molecules using two different experimental techniques based on photocurrent and ultrafast spectroscopy measurements. The acceptors exhibit balanced ambipolar charge transport and surprisingly long exciton diffusion lengths in the range of 20 to 47 nm. With the aid of quantum-chemical calculations, we are able to rationalize the exciton dynamics and draw basic chemical design rules, particularly on the importance of the end-group substituent on the crystal packing of nonfullerene acceptors.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Firdaus, Yuliar and Le Corre, Vincent M. and Karuthedath, Safakath and Liu, Wenlan and Markina, Anastasia and Huang, Wentao and Chattopadhyay, Shirsopratim and Nahid, Masrur Morshed and Nugraha, Mohamad I. and Lin, Yuanbao and et al.}, year={2020} } @article{qin_xu_peng_hou_ade_2020, title={Low Temperature Aggregation Transitions in N3 and Y6 Acceptors Enable Double-Annealing Method That Yields Hierarchical Morphology and Superior Efficiency in Nonfullerene Organic Solar Cells}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202005011}, abstractNote={AbstractThermal transition of organic solar cells (OSCs) constituent materials are often insufficiently researched, resulting in trial‐and‐error rather than rational approaches to annealing strategies to improve domain purity to enhance the power conversion efficiency. Despite the potential utility, little is known about the thermal transitions of the modern high‐performance acceptors Y6 and N3. Here, by using an optical method, it is discovered that the acceptor N3 has a clear solid‐state aggregation transition at 82 °C. This unusually low transition not only explains prior optimization protocols, but the transition informs and enables a double‐annealing method that can fine‐tune aggregation and the device morphology. Compared with 16.6% efficiency for PM6:N3:PC71BM control devices, higher efficiency of 17.6% is obtained through the improved protocol. Morphology characterization with x‐ray scattering methods reveals the formation of a multilength scale morphology. Moreover, the double‐annealing method is illustrated and easily transferred and validated with Y6‐based devices, using the transition of Y6 at 102 °C. As a result, the PCE improved from 16.0% to 16.8%. Design of high‐performance acceptors with yet lower aggregation transitions might be required for OSCs to successfully transition to low thermal budget industrial processing methods where annealing temperatures on plastic substrates have to be kept low.}, number={46}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Qin, Yunpeng and Xu, Ye and Peng, Zhengxing and Hou, Jianhui and Ade, Harald}, year={2020}, month={Nov} } @article{yu_qi_li_wang_zhou_ade_yan_chen_2020, title={Modulating Energy Level on an A-D-A '-D-A-Type Unfused Acceptor by a Benzothiadiazole Core Enables Organic Solar Cells with Simple Procedure and High Performance}, volume={4}, ISSN={["2367-198X"]}, DOI={10.1002/solr.202000421}, abstractNote={Unfused‐ring acceptors (UFAs) have gained considerable research attention as they offer simple chemical structures through simplified synthesis methods, which would boost the commercialization of organic solar cells (OSCs). Recently, a new small molecule acceptor (SMA) named Y6 was reported, yielding high‐performance OSCs. Herein, the Y6‐like A‐DA′D‐A framework is developed to A‐D‐A′‐D‐A‐type backbone adopted in constructing UFAs. Two new Y6‐like UFAs are synthesized within four steps and the effect of noncovalent atoms at the central electron‐deficient core on material properties and device performances is studied. It is found that the introduction of fluorine atoms can bring larger red‐shift in the absorption spectra and better aggregation of the resulting UFA film states compared with those of oxygen atoms. Interestingly, the variations in the noncovalent interaction atoms induce different intermolecular charge transfer between donors and UFAs. When blended with another economical donor, PTQ10, F substitution at the benzothiadiazole ring is more effective than O substitution, leading to the increased short‐circuit current density (JSC) and higher efficiency of over 12%, among the best performances of UFA‐based OSCs. This contribution demonstrates the appropriate introduction of noncovalent interaction is a promising method for tuning energy levels, absorption, and aggregation of UFAs for high‐performance OSCs.}, number={11}, journal={SOLAR RRL}, author={Yu, Han and Qi, Zhenyu and Li, Xingye and Wang, Zhen and Zhou, Wentao and Ade, Harald and Yan, He and Chen, Kai}, year={2020}, month={Nov} } @article{kim_kim_gadisa_stuard_nahid_kwon_bae_kim_park_won_et al._2020, title={Morphological-Electrical Property Relation in Cu(In,Ga)(S,Se)(2) Solar Cells: Significance of Crystal Grain Growth and Band Grading by Potassium Treatment}, volume={16}, ISSN={["1613-6829"]}, DOI={10.1002/smll.202003865}, abstractNote={AbstractSolution‐processed Cu(In,Ga)(S,Se)2 (CIGS) has a great potential for the production of large‐area photovoltaic devices at low cost. However, CIGS solar cells processed from solution exhibit relatively lower performance compared to vacuum‐processed devices because of a lack of proper composition distribution, which is mainly instigated by the limited Se uptake during chalcogenization. In this work, a unique potassium treatment method is utilized to improve the selenium uptake judiciously, enhancing grain sizes and forming a wider bandgap minimum region. Careful engineering of the bandgap grading structure also results in an enlarged space charge region, which is favorable for electron–hole separation and efficient charge carrier collection. Besides, this device processing approach has led to a linearly increasing electron diffusion length and carrier lifetime with increasing the grain size of the CIGS film, which is a critical achievement for enhancing photocurrent yield. Overall, 15% of power conversion efficiency is achieved in solar cells processed from environmentally benign solutions. This approach offers critical insights for precise device design and processing rules for solution‐processed CIGS solar cells.}, number={48}, journal={SMALL}, author={Kim, Joo-Hyun and Kim, Min Kyu and Gadisa, Abay and Stuard, Samuel J. and Nahid, Masrur Morshed and Kwon, Soyeong and Bae, Soohyun and Kim, Byoungwoo and Park, Gi Soon and Won, Da Hye and et al.}, year={2020}, month={Dec} } @article{zhang_li_peng_bai_ma_ade_li_yan_2020, title={Near-infrared electron acceptors with fused nonacyclic molecular backbones for nonfullerene organic solar cells}, volume={4}, ISSN={["2052-1537"]}, DOI={10.1039/c9qm00754g}, abstractNote={Two strong electron-donating moieties were fused into the molecular backbone of small molecular acceptors showing dramatically extended absorption beyond 900 nm.}, number={6}, journal={MATERIALS CHEMISTRY FRONTIERS}, author={Zhang, Jianquan and Li, Yunke and Peng, Zhengxing and Bai, Fujin and Ma, Lik-Kuen and Ade, Harald and Li, Zhengke and Yan, He}, year={2020}, month={Jun}, pages={1729–1738} } @article{liang_li_wang_qin_stuard_peng_deng_ade_ye_geng_2020, title={Optimization Requirements of Efficient Polythiophene:Nonfullerene Organic Solar Cells}, volume={4}, ISSN={["2542-4351"]}, url={https://publons.com/wos-op/publon/33106087/}, DOI={10.1016/j.joule.2020.04.014}, abstractNote={Polythiophene (PT) and its derivatives have attracted long-standing attention in the organic photovoltaic community for their low cost and high scalability of synthesis. However, due to the lack of rational guidelines in controlling morphology and matching materials, the power conversion efficiencies (PCEs) based on PTs reported so far are generally below 10%. Here, we establish the first-ever relationship between miscibility, morphology, and device performance of binary blends, based on various nonfullerene acceptors (ITIC-Th1, ITIC, IT4F, IDIC, and Y6) and a PT derivative named PDCBT-Cl by scattering and calorimetric characterizations. Benefiting from a properly quenched mixed phase, PDCBT-Cl:ITIC-Th1 system shows the best efficiency of over 12%. Conversely, the blend of PDCBT-Cl and the star acceptor Y6 remained in a homogeneous state due to their high miscibility, resulting in abysmal performance with PCE of 0.5%. Specific guidelines are also proposed to remediate the performance of PDCBT-Cl:Y6, which are crucial for advancing their practical applications.}, number={6}, journal={JOULE}, author={Liang, Ziqi and Li, Miaomiao and Wang, Qi and Qin, Yunpeng and Stuard, Sam J. and Peng, Zhongxiang and Deng, Yunfeng and Ade, Harald and Ye, Long and Geng, Yanhou}, year={2020}, month={Jun}, pages={1278–1295} } @article{guo_fan_wu_li_peng_su_lin_hou_qin_ade_et al._2021, title={Optimized Active Layer Morphologies via Ternary Copolymerization of Polymer Donors for 17.6 % Efficiency Organic Solar cells with Enhanced Fill Factor}, volume={60}, ISSN={["1521-3773"]}, url={https://publons.com/wos-op/publon/36593750/}, DOI={10.1002/anie.202010596}, abstractNote={AbstractRegulating molecular structure to optimize the active layer morphology is of considerable significance for improving the power conversion efficiencies (PCEs) in organic solar cells (OSCs). Herein, we demonstrated a simple ternary copolymerization approach to develop a terpolymer donor PM6‐Tz20 by incorporating the 5,5′‐dithienyl‐2,2′‐bithiazole (DTBTz, 20 mol%) unit into the backbone of PM6 (PM6‐Tz00). This method can effectively tailor the molecular orientation and aggregation of the polymer, and then optimize the active layer morphology and the corresponding physical processes of devices, ultimately boosting FF and then PCE. Hence, the PM6‐Tz20: Y6‐based OSCs achieved a PCE of up to 17.1% with a significantly enhanced FF of 0.77. Using Ag (220 nm) instead of Al (100 nm) as cathode, the champion PCE was further improved to 17.6%. This work provides a simple and effective molecular design strategy to optimize the active layer morphology of OSCs for improving photovoltaic performance.}, number={5}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Guo, Xia and Fan, Qunping and Wu, Jingnan and Li, Guangwei and Peng, Zhongxiang and Su, Wenyan and Lin, Ji and Hou, Lintao and Qin, Yunpeng and Ade, Harald and et al.}, year={2021}, month={Feb}, pages={2322–2329} } @article{samson_rech_perdigon-toro_peng_shoaee_ade_neher_stolterfoht_you_2020, title={Organic Solar Cells with Large Insensitivity to Donor Polymer Molar Mass across All Acceptor Classes}, volume={2}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.0c01041}, abstractNote={Donor polymer number-average molar mass (Mn) has long been known to influence organic photovoltaic (OPV) performance via changes in both the polymer properties and the resulting bulk heterojunction...}, number={11}, journal={ACS APPLIED POLYMER MATERIALS}, author={Samson, Stephanie and Rech, Jeromy and Perdigon-Toro, Lorena and Peng, Zhengxing and Shoaee, Safa and Ade, Harald and Neher, Dieter and Stolterfoht, Martin and You, Wei}, year={2020}, month={Nov}, pages={5300–5308} } @article{bin_angunawela_qiu_colberts_li_dyson_wienk_ade_li_janssen_2020, title={Precise Control of Phase Separation Enables 12% Efficiency in All Small Molecule Solar Cells}, volume={10}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202001589}, DOI={10.1002/aenm.202001589}, abstractNote={AbstractCompared to conjugated polymers, small‐molecule organic semiconductors present negligible batch‐to‐batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small‐molecular organic solar cells (SM‐OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small‐molecular donors H13 and H14, created by fluorine and chlorine substitution of the original donor molecule H11, are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open‐circuit voltage with IDIC‐4F as acceptor. Due to kinetic and thermodynamic reasons, H13‐based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14‐based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14‐based SM‐OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM‐OSCs using IDIC‐4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine‐tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.}, number={34}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Bin, Haijun and Angunawela, Indunil and Qiu, Beibei and Colberts, Fallon J. M. and Li, Mengmeng and Dyson, Matthew J. and Wienk, Martijn M. and Ade, Harald and Li, Yongfang and Janssen, Rene A. J.}, year={2020}, month={Sep} } @article{liang_pan_chai_peng_zhang_luo_han_chen_shang_bai_et al._2020, title={Random Polymerization Strategy Leads to a Family of Donor Polymers Enabling Well-Controlled Morphology and Multiple Cases of High-Performance Organic Solar Cells}, volume={32}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202003500}, abstractNote={AbstractDeveloping high‐performance donor polymers is important for nonfullerene organic solar cells (NF‐OSCs), as state‐of‐the‐art nonfullerene acceptors can only perform well if they are coupled with a matching donor with suitable energy levels. However, there are very limited choices of donor polymers for NF‐OSCs, and the most commonly used ones are polymers named PM6 and PM7, which suffer from several problems. First, the performance of these polymers (particularly PM7) relies on precise control of their molecular weights. Also, their optimal morphology is extremely sensitive to any structural modification. In this work, a family of donor polymers is developed based on a random polymerization strategy. These polymers can achieve well‐controlled morphology and high‐performance with a variety of chemical structures and molecular weights. The polymer donors are D–A1–D–A2‐type random copolymers in which the D and A1 units are monomers originating from PM6 or PM7, while the A2 unit comprises an electron‐deficient core flanked by two thiophene rings with branched alkyl chains. Consequently, multiple cases of highly efficient NF‐OSCs are achieved with efficiencies between 16.0% and 17.1%. As the electron‐deficient cores can be changed to many other structural units, the strategy can easily expand the choices of high‐performance donor polymers for NF‐OSCs.}, number={52}, journal={ADVANCED MATERIALS}, author={Liang, Jiaen and Pan, Mingao and Chai, Gaoda and Peng, Zhengxing and Zhang, Jianquan and Luo, Siwei and Han, Qi and Chen, Yuzhong and Shang, Ao and Bai, Fujin and et al.}, year={2020}, month={Dec} } @article{balar_siddika_kashani_peng_rech_ye_you_ade_brendan t. o'conner_2020, title={Role of Secondary Thermal Relaxations in Conjugated Polymer Film Toughness}, volume={32}, ISSN={["1520-5002"]}, url={https://publons.com/wos-op/publon/35208553/}, DOI={10.1021/acs.chemmater.0c01910}, abstractNote={Conjugated polymers have proven to be an important class of materials for flexible and stretchable electronics. To ensure long term thermal and mechanical stability of associated devices, there is ...}, number={15}, journal={CHEMISTRY OF MATERIALS}, author={Balar, Nrup and Siddika, Salma and Kashani, Somayeh and Peng, Zhengxing and Rech, Jeromy James and Ye, Long and You, Wei and Ade, Harald and Brendan T. O'Conner}, year={2020}, month={Aug}, pages={6540–6549} } @article{arunagiri_peng_zou_yu_zhang_wang_lai_zhang_zheng_cui_et al._2020, title={Selective Hole and Electron Transport in Efficient Quaternary Blend Organic Solar Cells}, volume={4}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2020.06.014}, abstractNote={Multi-component organic solar cells (OSCs) comprising more than two donor and acceptor materials have attracted significant research attention, as they can offer broader and better absorption, hence increasing solar cell performance. However, the morphology of multi-component OSCs is exceptionally complicated and challenging to control. Here, we develop a highly efficient (near 17.7%) quaternary OSC (q-OSC) using two polymer donors (namely PM6 and PTQ10) along with a fullerene (PC71BM) and a non-fullerene acceptor (N3). Our quaternary system demonstrates a new type of “rivers and streams” functional hierarchical (multi-length scale) morphology, where small domains of PTQ10 and PC71BM act as separators that spatially separate PM6 and N3, which effectively suppressed charge recombination, enhanced hole transport, and balanced charge transportation. These improvements in the quaternary system contribute to the increased internal quantum efficiency (IQE) and, thus, lead to an excellent JSC and device performance, which surpass their respective binary and ternary OSCs.}, number={8}, journal={JOULE}, author={Arunagiri, Lingeswaran and Peng, Zhengxing and Zou, Xinhui and Yu, Han and Zhang, Guangye and Wang, Zhen and Lai, Joshua Yuk Lin and Zhang, Jianquan and Zheng, Yan and Cui, Chaohua and et al.}, year={2020}, month={Aug}, pages={1790–1805} } @article{king_melville_rice_kashani_tonnele_raboui_swaraj_grant_mcafee_bender_et al._2021, title={Silicon Phthalocyanines for n-Type Organic Thin-Film Transistors: Development of Structure-Property Relationships}, volume={3}, ISSN={["2637-6113"]}, DOI={10.1021/acsaelm.0c00871}, abstractNote={Silicon phthalocyanines (SiPcs) have shown great potential as n-type or ambipolar organic semiconductors in organic thin-film transistors (OTFTs) and organic photovoltaics. Although properly design...}, number={1}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={King, Benjamin and Melville, Owen A. and Rice, Nicole A. and Kashani, Somayeh and Tonnele, Claire and Raboui, Hasan and Swaraj, Sufal and Grant, Trevor M. and McAfee, Terry and Bender, Timothy P. and et al.}, year={2021}, month={Jan}, pages={325–336} } @article{liu_kumagai_manzhos_chen_angunawela_nahid_feron_bottle_bell_ade_et al._2020, title={Synergistic Use of Pyridine and Selenophene in a Diketopyrrolopyrrole-Based Conjugated Polymer Enhances the Electron Mobility in Organic Transistors}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202000489}, abstractNote={AbstractTo achieve semiconducting materials with high electron mobility in organic field‐effect transistors (OFETs), low‐lying energy levels (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) and favorable molecular packing and ordering are two crucial factors. Here, it is reported that the incorporation of pyridine and selenophene into the backbone of a diketopyrrolopyrrole (DPP)‐based copolymer produces a high‐electron‐mobility semiconductor, PDPPy‐Se. Compared with analogous polymers based on other DPP derivatives and selenophene, PDPPy‐Se features a lower LUMO that can decrease the electron transfer barrier for more effective electron injection, and simultaneously a lower HOMO that, however, can increase the hole transfer barrier to suppress the hole injection. Combined with thermal annealing at 240 °C for thin film morphology optimization to achieve large‐scale crystallite domains with tight molecular packing for effective charge transport along the conducting channel, OFET devices fabricated with PDPPy‐Se exhibit an n‐type‐dominant performance with an electron mobility (μe) as high as 2.22 cm2 V−1 s−1 and a hole/electron mobility ratio (μh/μe) of 0.26. Overall, this study demonstrates a simple yet effective approach to boost the electron mobility in organic transistors by synergistic use of pyridine and selenophene in the backbone of a DPP‐based copolymer.}, number={34}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Liu, Qian and Kumagai, Shohei and Manzhos, Sergei and Chen, Yingqian and Angunawela, Indunil and Nahid, Masrur Morshed and Feron, Krishna and Bottle, Steven E. and Bell, John and Ade, Harald and et al.}, year={2020}, month={Aug} } @article{yu_qi_zhang_wang_sun_chang_sun_zhou_min_ade_et al._2020, title={Tailoring non-fullerene acceptors using selenium-incorporated heterocycles for organic solar cells with over 16% efficiency}, volume={8}, ISSN={["2050-7496"]}, DOI={10.1039/d0ta06658c}, abstractNote={The selenium substitution strategy was applied to develop two new A′-DAD-A′-type small molecular acceptors. The resulting selenium-incorporated molecules exhibit red-shifted absorption and an enhanced photon response, leading to high device efficiencies of over 16%.}, number={45}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Yu, Han and Qi, Zhenyu and Zhang, Jianquan and Wang, Zhen and Sun, Rui and Chang, Yuan and Sun, Huiliang and Zhou, Wentao and Min, Jie and Ade, Harald and et al.}, year={2020}, month={Dec}, pages={23756–23765} } @article{hu_ghasemi_peng_zhang_rech_you_yan_ade_2020, title={The Role of Demixing and Crystallization Kinetics on the Stability of Non-Fullerene Organic Solar Cells}, volume={32}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.202005348}, DOI={10.1002/adma.202005348}, abstractNote={AbstractWith power conversion efficiency now over 17%, a long operational lifetime is essential for the successful application of organic solar cells. However, most non‐fullerene acceptors can crystallize and destroy devices, yet the fundamental underlying thermodynamic and kinetic aspects of acceptor crystallization have received limited attention. Here, room‐temperature (RT) diffusion coefficients of 3.4 × 10−23 and 2.0 × 10−22 are measured for ITIC‐2Cl and ITIC‐2F, two state‐of‐the‐art non‐fullerene acceptors. The low coefficients are enough to provide for kinetic stabilization of the morphology against demixing at RT. Additionally profound differences in crystallization characteristics are discovered between ITIC‐2F and ITIC‐2Cl. The differences as observed by secondary‐ion mass spectrometry, differential scanning calorimetry (DSC), grazing‐incidence wide‐angle X‐ray scattering, and microscopy can be related directly to device degradation and are attributed to the significantly different nucleation and growth rates, with a difference in the growth rate of a factor of 12 at RT. ITIC‐4F and ITIC‐4Cl exhibit similar characteristics. The results reveal the importance of diffusion coefficients and melting enthalpies in controlling the growth rates, and that differences in halogenation can drastically change crystallization kinetics and device stability. It is furthermore delineated how low nucleation density and large growth rates can be inferred from DSC and microscopy experiments which could be used to guide molecular design for stability.}, number={49}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Hu, Huawei and Ghasemi, Masoud and Peng, Zhengxing and Zhang, Jianquan and Rech, Jeromy James and You, Wei and Yan, He and Ade, Harald}, year={2020}, month={Dec} } @article{karki_vollbrecht_gillett_xiao_yang_peng_schopp_dixon_yoon_schrock_et al._2020, title={The role of bulk and interfacial morphology in charge generation, recombination, and extraction in non-fullerene acceptor organic solar cells}, volume={13}, ISSN={["1754-5706"]}, DOI={10.1039/d0ee01896a}, abstractNote={This study provides insight into the detailed bulk and interfacial morphological features critical in achieving high PCEs in polymer:NFA OSCs.}, number={10}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Karki, Akchheta and Vollbrecht, Joachim and Gillett, Alexander J. and Xiao, Steven Shuyong and Yang, Yali and Peng, Zhengxing and Schopp, Nora and Dixon, Alana L. and Yoon, Sangcheol and Schrock, Max and et al.}, year={2020}, month={Oct}, pages={3679–3692} } @article{wang_peng_xiao_seyitliyev_gundogdu_ding_ade_2020, title={Thermodynamic Properties and Molecular Packing Explain Performance and Processing Procedures of Three D18:NFA Organic Solar Cells}, volume={32}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202005386}, abstractNote={AbstractOrganic solar cells (OSCs) based on D18:Y6 have recently exhibited a record power conversion efficiency of over 18%. The initial work is extended and the device performance of D18‐based OSCs is compared with three non‐fullerene acceptors, Y6, IT‐4F, and IEICO‐4Cl, and their molecular packing characteristics and miscibility are studied. The D18 polymer shows unusually strong chain extension and excellent backbone ordering in all films, which likely contributes to the excellent hole‐transporting properties. Thermodynamic characterization indicates a room‐temperature miscibility for D18:Y6 and D18:IT‐4F near the percolation threshold. This corresponds to an ideal quench depth and explains the use of solvent vapor annealing rather than thermal annealing. In contrast, D18:IEICO‐4Cl is a low‐miscibility system with a deep quench depth during casting and poor morphology control and low performance. A failure of ternary blends with PC71BM is likely due to the near‐ideal miscibility of Y6 to begin with and indicates that strategies for developing successful ternary or quaternary solar cells are likely very different for D18 than for other high‐performing donors. This work reveals several unique property–performance relations of D18‐based photovoltaic devices and helps guide design or fabrication of yet higher efficiency OSCs.}, number={49}, journal={ADVANCED MATERIALS}, author={Wang, Zhen and Peng, Zhengxing and Xiao, Zuo and Seyitliyev, Dovletgeldi and Gundogdu, Kenan and Ding, Liming and Ade, Harald}, year={2020}, month={Dec} } @article{karki_vollbrecht_gillett_selter_lee_peng_schopp_dixon_schrock_nadazdy_et al._2020, title={Unifying Charge Generation, Recombination, and Extraction in Low-Offset Non-Fullerene Acceptor Organic Solar Cells}, volume={10}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202001203}, abstractNote={AbstractEven though significant breakthroughs with over 18% power conversion efficiencies (PCEs) in polymer:non‐fullerene acceptor (NFA) bulk heterojunction organic solar cells (OSCs) have been achieved, not many studies have focused on acquiring a comprehensive understanding of the underlying mechanisms governing these systems. This is because it can be challenging to delineate device photophysics in polymer:NFA blends comprehensively, and even more complicated to trace the origins of the differences in device photophysics to the subtle differences in energetics and morphology. Here, a systematic study of a series of polymer:NFA blends is conducted to unify and correlate the cumulative effects of i) voltage losses, ii) charge generation efficiencies, iii) non‐geminate recombination and extraction dynamics, and iv) nuanced morphological differences with device performances. Most importantly, a deconvolution of the major loss processes in polymer:NFA blends and their connections to the complex BHJ morphology and energetics are established. An extension to advanced morphological techniques, such as solid‐state NMR (for atomic level insights on the local ordering and donor:acceptor ππ interactions) and resonant soft X‐ray scattering (for donor and acceptor interfacial area and domain spacings), provide detailed insights on how efficient charge generation, transport, and extraction processes can outweigh increased voltage losses to yield high PCEs.}, number={29}, journal={ADVANCED ENERGY MATERIALS}, author={Karki, Akchheta and Vollbrecht, Joachim and Gillett, Alexander J. and Selter, Philipp and Lee, Jaewon and Peng, Zhengxing and Schopp, Nora and Dixon, Alana L. and Schrock, Max and Nadazdy, Vojtech and et al.}, year={2020}, month={Aug} } @article{wu_zhong_hu_li_zhang_li_zhang_ade_jiang_liao_2019, title={A decacyclic indacenodithiophene-based non-fullerene electron acceptor with meta-alkyl-phenyl substitutions for polymer solar cells}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta11972d}, abstractNote={ Meta-alkyl-phenyl substitutions and fluorination approach selectively optimizes a decacyclic indacenodithiophene-based fused electron acceptor (p-IDTIDT-IC), improving PCE from 6.48% to 11.32%.}, number={8}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Wu, Fupeng and Zhong, Lian and Hu, Huawei and Li, Yun and Zhang, Zhanjun and Li, Yongxi and Zhang, Zhi-Guo and Ade, Harald and Jiang, Zuo-Quan and Liao, Liang-Sheng}, year={2019}, month={Feb}, pages={4063–4071} } @article{jiang_wei_lai_peng_kim_yuan_ye_ade_zou_yan_2019, title={Alkyl Chain Tuning of Small Molecule Acceptors for Efficient Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, url={https://publons.com/wos-op/publon/27161014/}, DOI={10.1016/j.joule.2019.09.010}, abstractNote={The field of organic solar cells has seen rapid developments after the report of a high-efficiency (15.7%) small molecule acceptor (SMA) named Y6. In this paper, we design and synthesize a family of SMAs with an aromatic backbone identical to that of Y6 but with different alkyl chains to investigate the influence of alkyl chains on the properties and performance of the SMAs. First, we show that it is beneficial to use branched alkyl chains on the nitrogen atoms of the pyrrole motif of the Y6. In addition, the branching position of the alkyl chains also has a major influence on material and device properties. The SMA with 3rd-position branched alkyl chains (named N3) exhibits optimal solubility and electronic and morphological properties, thus yielding the best performance. Further device optimization using a ternary strategy allows us to achieve a high efficiency of 16.74% (and a certified efficiency of 16.42%).}, number={12}, journal={JOULE}, author={Jiang, Kui and Wei, Qingya and Lai, Joshua Yuk Lin and Peng, Zhengxing and Kim, Ha Kyung and Yuan, Jun and Ye, Long and Ade, Harald and Zou, Yingping and Yan, He}, year={2019}, month={Dec}, pages={3020–3033} } @article{hu_oswald_hu_stuard_nahid_yan_chen_ade_neilson_you_2019, title={Aryl-Perfluoroaryl Interaction in Two-Dimensional Organic-Inorganic Hybrid Perovskites Boosts Stability and Photovoltaic Efficiency}, volume={1}, ISSN={["2639-4979"]}, DOI={10.1021/acsmaterialslett.9b00102}, abstractNote={Two-dimensional (2D) organic–inorganic hybrid perovskites (OIHPs) have showed impressive stability, compared to their three-dimensional (3D) counterparts. However, tuning the chemical structure of ...}, number={1}, journal={ACS MATERIALS LETTERS}, author={Hu, Jun and Oswald, Iain W. H. and Hu, Huamin and Stuard, Samuel J. and Nahid, Masrur Morshed and Yan, Liang and Chen, Zheng and Ade, Harald and Neilson, James R. and You, Wei}, year={2019}, month={Jul}, pages={171–176} } @article{yang_ye_yao_jin_ade_chen_2019, title={Black phosphorus nanoflakes as morphology modifier for efficient fullerene-free organic solar cells with high fill-factor and better morphological stability}, volume={12}, ISSN={["1998-0000"]}, url={https://publons.com/wos-op/publon/19724081/}, DOI={10.1007/s12274-019-2288-9}, number={4}, journal={NANO RESEARCH}, author={Yang, Weitao and Ye, Long and Yao, Fenfa and Jin, Chuanhong and Ade, Harald and Chen, Hongzheng}, year={2019}, month={Apr}, pages={777–783} } @article{zhang_li_hu_zhang_ade_yan_2019, title={Chlorinated Thiophene End Groups for Highly Crystalline Alkylated Non-Fullerene Acceptors toward Efficient Organic Solar Cells}, volume={31}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.9b00980}, abstractNote={End group engineering is critical for developing A-D-A-type non-fullerene acceptors with suitable absorption properties and high crystallinity for organic solar cells. Here, we report the synthesis of a novel chlorinated thiophene end group and its application in A-D-A-type acceptors. When combined with a tetraoctyl-substituted indacenodithieno[3,2-b]thiophene core, the resulting C8-ITCC-Cl acceptor exhibited red-shifted absorption and downshifted energy levels relative to those of the nonchlorinated analogue, C8-ITCC, due to the strong electron-withdrawing ability of the chlorine atoms as revealed by theoretical calculations. Moreover, the noncovalent interactions induced by the chlorine atoms enabled improved lamellar and π–π stacking of C8-ITCC-Cl, leading to a higher electron mobility of 6.6 × 10–4 cm2 V–1 s–1 and a fill factor of 73% of the PBDB-TF:C8-ITCC-Cl devices. Consequently, a high power conversion efficiency of 12.7% was achieved by the C8-ITCC-Cl-based devices, which outperformed the C8-ITCC...}, number={17}, journal={CHEMISTRY OF MATERIALS}, author={Zhang, Jianquan and Li, Yunke and Hu, Huawei and Zhang, Guangye and Ade, Harald and Yan, He}, year={2019}, month={Sep}, pages={6672–6676} } @article{wu_fan_liu_chen_yang_ye_ade_zhu_2019, title={Conjugation-Curtailing of Benzodithionopyran-Cored Molecular Acceptor Enables Efficient Air-Processed Small Molecule Solar Cells}, volume={15}, ISSN={["1613-6829"]}, url={https://publons.com/wos-op/publon/29105600/}, DOI={10.1002/smll.201902656}, abstractNote={AbstractSmall molecule solar cells (SMSCs) lag a long way behind polymer solar cells. A key limit is the less controllable morphology of small molecule materials, which can be aggravated when incorporating anisotropic nonfullerene acceptors. To fine‐tune the blending morphology within SMSCs, a π‐conjunction curtailing design is applied, which produces a efficient benzodithionopyran‐cored molecular acceptor for nonfullerene SMSCs (NF‐SMSCs). When blended with a molecular donor BDT3TR‐SF to fabricate NF‐SMSCs, the π‐conjunction curtailed molecular acceptor NBDTP‐M obtains an optimal power conversion efficiency (PCE) of up to 10.23%, which is much higher than that of NBDTTP‐M of longer π‐conjunction. It retains 93% of the PCE of devices fabricated in a glove box when all spin‐coating and post‐treating procedures are conducted in ambient air with relative humidity of 25%, which suggests the good air‐processing capability of π‐conjunction curtailed molecules. Detailed X‐ray scattering investigations indicate that the BDT3TR‐SF:NBDTP‐M blend exhibits a blend morphology featuring fine interpenetrating networks with smaller domains and higher phase purity, which results in more efficient charge generation, more balanced charge transport, and less recombination compared to the low‐performance BDT3TR‐SF:NBDTTP‐M blend. This work provides a guideline for molecular acceptors' design toward efficient, low‐cost, air‐processed NF‐SMSCs.}, number={44}, journal={SMALL}, author={Wu, Hao and Fan, Haijun and Liu, Wuyue and Chen, Shanshan and Yang, Changduk and Ye, Long and Ade, Harald and Zhu, Xiaozhang}, year={2019}, month={Oct} } @article{ghasemi_hu_peng_rech_angunawela_carpenter_stuard_wadsworth_mcculloch_you_et al._2019, title={Delineation of Thermodynamic and Kinetic Factors that Control Stability in Non-fullerene Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2019.03.020}, abstractNote={Although non-fullerene small molecular acceptors (NF-SMAs) are dominating current research in organic solar cells (OSCs), measurements of thermodynamics drivers and kinetic factors determining their morphological stability are lacking. Here, we delineate and measure such factors in crystallizable NF-SMA blends and discuss four model systems with respect to their meta-stability and degree of vitrification. We determine for the first time the amorphous-amorphous phase diagram in an NF-SMA system and show that its deep quench depth can result in severe burn-in degradation. We estimate the relative phase behavior of four other materials systems. Additionally, we derive room-temperature diffusion coefficients and conclude that the morphology needs to be stabilized by vitrification corresponding to diffusion constants below 10−22 cm2/s. Our results show that to achieve stability via rational molecular design, the thermodynamics, glass transition temperature, diffusion properties, and related structure-function relations need to be more extensively studied and understood.}, number={5}, journal={JOULE}, author={Ghasemi, Masoud and Hu, Huawei and Peng, Zhengxing and Rech, Jeromy James and Angunawela, Indunil and Carpenter, Joshua H. and Stuard, Samuel J. and Wadsworth, Andrew and McCulloch, Iain and You, Wei and et al.}, year={2019}, month={May}, pages={1328–1348} } @article{song_gasparini_nahid_paleti_wang_ade_baran_2019, title={Dual Sensitizer and Processing-Aid Behavior of Donor Enables Efficient Ternary Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2019.01.009}, abstractNote={

Summary

Herein, we report ternary organic solar cells with a power conversion efficiency (PCE) of 14.0%. By incorporating 10 wt % of BIT-4F-T in the PTB7-Th:IEICO-4F blend, we obtain an enhancement of all photovoltaic parameters compared to the binary devices, leading to a 15% performance improvement in ternary blend. The high photocurrent in 10% BIT-4F-T blend results from a complementary absorption profile of donor components and a hole transfer from BIT-4F-T to PTB7-Th. Morphological and device characterizations reveal that the addition of 10% BIT-4F-T acts not only as a sensitizer but also as a solid processing aid, which is beneficial for charge generation and transport. The effect of the third component is observed in different non-fullerene and fullerene OSCs. Our study demonstrates that careful selection of a third component, where dual sensitizing and processing-aid effects are observed, can be a design strategy to achieve a concomitant improvement in all photovoltaic parameters.}, number={3}, journal={JOULE}, author={Song, Xin and Gasparini, Nicola and Nahid, Masrur Morshed and Paleti, Sri Harish Kumar and Wang, Jin-Liang and Ade, Harald and Baran, Derya}, year={2019}, month={Mar}, pages={846–857} } @article{zhang_rech_yan_liang_peng_ade_wu_you_2019, title={Effect of Cyano Substitution on Conjugated Polymers for Bulk Heterojunction Solar Cells}, volume={1}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.9b00767}, abstractNote={The design of polymer structures has played a vital role in improving the efficiency of organic solar cells (OSCs). A common approach to increase solar cell efficiency is to add a specific substitu...}, number={12}, journal={ACS APPLIED POLYMER MATERIALS}, author={Zhang, Qianqian and Rech, Jeromy James and Yan, Liang and Liang, Quanbin and Peng, Zhengxing and Ade, Harald and Wu, Hongbin and You, Wei}, year={2019}, month={Dec}, pages={3313–3322} } @article{zhong_bin_angunawela_jia_qiu_sun_li_zhang_ade_li_2019, title={Effect of Replacing Thiophene by Selenophene on the Photovoltaic Performance of Wide Bandgap Copolymer Donors}, volume={52}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.9b00484}, abstractNote={Two polymers J75 and J76 with selenophene instead of thiophene on the conjugated side chain of benzodithiophene (BDT) unit or π bridges of polymer J71 were designed and synthesized, for investigating the effect of selenophene substitution on the photovoltaic performance of the conjugated polymer donors in comparison with J71. The selenophene π bridges in J76 can narrow optical band gap and red-shift absorption of the polymer film by ca. 25 nm, but the highest occupied molecular orbital (HOMO) energy level (EHOMO) of J76 is up-shifted slightly by 0.04 eV. Two typical electron acceptors of fullerene derivative PC71BM and the nonfullerene acceptor m-ITIC were used to investigate photovoltaic performance of the polymer donors. For the PC71BM-based polymer solar cells (PSCs), J76 with selenophene π bridges shows the best power-conversion efficiency (PCE) of 8.40% in comparison with the J71-based device (PCE = 6.79%), benefitted from the red-shifted absorption, larger coherence length, purer average domains, an...}, number={12}, journal={MACROMOLECULES}, author={Zhong, Lian and Bin, Haijun and Angunawela, Indunil and Jia, Zhenrong and Qiu, Beibei and Sun, Chenkai and Li, Xiaojun and Zhang, Zhanjun and Ade, Harald and Li, Yongfang}, year={2019}, month={Jun}, pages={4776–4784} } @article{li_huang_angunawela_zhou_du_liebman-pelaez_zhu_zhang_meng_xie_et al._2020, title={Effects of Short-Axis Alkoxy Substituents on Molecular Self-Assembly and Photovoltaic Performance of Indacenodithiophene-Based Acceptors}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201906855}, abstractNote={AbstractThe effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA‐based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single‐crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self‐assembly. The short‐circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self‐assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.}, number={3}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Li, Xiaojun and Huang, He and Angunawela, Indunil and Zhou, Jiadong and Du, Jiaqi and Liebman-Pelaez, Alex and Zhu, Chenhui and Zhang, Zhanjun and Meng, Lei and Xie, Zengqi and et al.}, year={2020}, month={Jan} } @article{yao_bai_hu_arunagiri_zhang_chen_yu_chen_liu_lai_et al._2019, title={Efficient All-Polymer Solar Cells based on a New Polymer Acceptor Achieving 10.3% Power Conversion Efficiency}, volume={4}, ISSN={["2380-8195"]}, DOI={10.1021/acsenergylett.8b02114}, abstractNote={Here we demonstrate efficient all-polymer solar cells (all-PSCs) based on a polymer acceptor named PFBDT-IDTIC. By combining PFBDT-IDTIC with a fluorinated donor polymer (PM6), a high power conversion efficiency of 10.3% can be achieved, which is the highest value reported to date for single-junction all-PSCs. This performance can be attributed to its good absorption property (absorption coefficient: 2.74 × 105 cm–1) and high electron mobility of PFBDT-IDTIC. It is also found that the choice of donor polymer has major impacts on the performance of the cell. By replacing PBDB-T with its fluorinated counterpart, PM6, the VOC, JSC, and FF of the devices were all improved, which can be attributed to the deeper HOMO level of PM6 and more crystalline and pure domains of the active layer blends. Our study provides a promising polymer acceptor for all-PSCs and also shows that selecting a matching donor polymer is important in achieving the optimal all-PSC performance.}, number={2}, journal={ACS ENERGY LETTERS}, author={Yao, Huatong and Bai, Fujin and Hu, Huawei and Arunagiri, Lingeswaran and Zhang, Jianquan and Chen, Yuzhong and Yu, Han and Chen, Shangshang and Liu, Tao and Lai, Joshua Yuk Lin and et al.}, year={2019}, month={Feb}, pages={417–422} } @article{song_gasparini_nahid_paleti_li_li_ade_baran_2019, title={Efficient DPP Donor and Nonfullerene Acceptor Organic Solar Cells with High Photon-to-Current Ratio and Low Energetic Loss}, volume={29}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201902441}, abstractNote={AbstractThe high crystallinity and ability to harvest near‐infrared photons make diketopyrrolopyrrole (DPP)‐based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP‐based OSC devices still suffer from the trade‐off between energetic loss (Eloss) and maximum external quantum efficiency (EQEmax), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP‐donor‐based solar cells due to severe charge recombination issues. In this work, efficient DPP‐based solar cells are reported using low bandgap fused ring electron acceptor, IEICO‐4F. PBDTT‐DPP:IEICO‐4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low Eloss of 0.57 eV and a high EQEmax (>70%).}, number={34}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Song, Xin and Gasparini, Nicola and Nahid, Masrur Morshed and Paleti, Sri Harish Kumar and Li, Cheng and Li, Weiwei and Ade, Harald and Baran, Derya}, year={2019}, month={Aug} } @article{duan_peng_colberts_pang_ye_awartani_hendriks_ade_wienk_janssen_et al._2019, title={Efficient Thick-Film Polymer Solar Cells with Enhanced Fill Factors via Increased Fullerene Loading}, volume={11}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.9b00337}, DOI={10.1021/acsami.9b00337}, abstractNote={Developing effective methods to make efficient bulk-heterojunction polymer solar cells at roll-to-roll relevant active layer thickness is of significant importance. We investigate the effect of fullerene content in polymer:fullerene blends on the fill factor (FF) and on the performance of thick-film solar cells for four different donor polymers PTB7-Th, PDPP-TPT, BDT-FBT-2T, and poly[5,5′-bis(2-butyloctyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-5,5′-2,2′-bithiophene] (PDCBT). At a few hundreds of nanometers thickness, increased FFs are observed in all cases and improved overall device performances are obtained except for PDCBT upon increasing fullerene content in blend films. This fullerene content effect was studied in more detail by electrical and morphological characterization. The results suggest enhanced electron mobility and suppressed bimolecular recombination upon increasing fullerene content in thick polymer:fullerene blend films, which are the result of larger fullerene aggregates and improved interconnectivity of the fullerene phases that provide continuous percolating pathways for electron transport in thick films. These findings are important because an effective and straightforward method that enables fabricating efficient thick-film polymer solar cells is desirable for large-scale manufacturing via roll-to-roll processing and for multijunction devices.}, number={11}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Duan, Chunhui and Peng, Zhengxing and Colberts, Fallon J. M. and Pang, Shuting and Ye, Long and Awartani, Omar M. and Hendriks, Koen H. and Ade, Harald and Wienk, Martijn M. and Janssen, Rene A. J. and et al.}, year={2019}, month={Mar}, pages={10794–10800} } @article{yang_liang_ye_ade_yuan_hou_2019, title={Enhanced JSC of P3HT-based non-fullerene polymer solar cells by modulating aggregation effect of P3HT in solution state}, volume={68}, ISSN={1566-1199}, url={http://dx.doi.org/10.1016/J.ORGEL.2019.01.047}, DOI={10.1016/J.ORGEL.2019.01.047}, abstractNote={Poly(3-hexylthiophene) (P3HT) is a broadly used donor material for polymer solar cells (PSCs) due to its simple molecular structure and low production cost. In recent years, the P3HT-based non-fullerene PSCs have been extensively studied as the rapid development of the non-fullerene small molecular acceptors (NFSMAs). However, the active layers based on the P3HT and NFSMAs blend usually exhibit unfavorable phase separation morphologies, resulting in relatively low short-circuit currents (JSCs) and power conversion efficiencies (PCEs) of the corresponding PSC devices. Herein, we utilized the chloroform (CF)/anisole solvent mixture to adjust the aggregation effect of P3HT in solution state to optimize the phase separation morphology of the active layers. As a result, the combination of CF, anisole, and 1,8-diiodooctane (DIO) affords an enhanced JSC of 14.23 mA cm−2 for a P3HT:IEICO-based PSC.}, journal={Organic Electronics}, publisher={Elsevier BV}, author={Yang, Chenyi and Liang, Ningning and Ye, Long and Ade, Harald and Yuan, Xiaotao and Hou, Jianhui}, year={2019}, month={May}, pages={15–21} } @article{ma_xue_zhong_angunawela_chen_ade_huo_zhang_li_2019, title={High voltage all polymer solar cells with a polymer acceptor based on NDI and benzotriazole}, volume={7}, ISSN={["2050-7534"]}, DOI={10.1039/c9tc01922g}, abstractNote={A new n-type conjugated copolymer LA03 based on naphthalene diimide and benzotriazole with thiophene π-bridges was synthesized, and the all polymer solar cells with PBDB-T as donor and LA03 as acceptor achieved a power conversion efficiency of 6.49%.}, number={29}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Ma, Qing and Xue, Xiaonan and Zhong, Lian and Angunawela, Indunil and Chen, Shanshan and Ade, Harald and Huo, Lijun and Zhang, Zhanjun and Li, Yongfang}, year={2019}, month={Aug}, pages={9031–9037} } @article{hu_ye_ghasemi_balar_rech_stuard_you_brendan t. o'connor_ade_2019, title={Highly Efficient, Stable, and Ductile Ternary Nonfullerene Organic Solar Cells from a Two-Donor Polymer Blend}, volume={31}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.201808279}, DOI={10.1002/adma.201808279}, abstractNote={AbstractOrganic solar cells (OSCs) are one of the most promising cost‐effective options for utilizing solar energy, and, while the field of OSCs has progressed rapidly in device performance in the past few years, the stability of nonfullerene OSCs has received less attention. Developing devices with both high performance and long‐term stability remains challenging, particularly if the material choice is restricted by roll‐to‐roll and benign solvent processing requirements and desirable mechanical durability. Building upon the ink (toluene:FTAZ:IT‐M) that broke the 10% benchmark when blade‐coated in air, a second donor material (PBDB‐T) is introduced to stabilize and enhance performance with power conversion efficiency over 13% while keeping toluene as the solvent. More importantly, the ternary OSCs exhibit excellent thermal stability and storage stability while retaining high ductility. The excellent performance and stability are mainly attributed to the inhibition of the crystallization of nonfullerene small‐molecular acceptors (SMAs) by introducing a stiff donor that also shows low miscibility with the nonfullerene SMA and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer. The study indicates that improved stability and performance can be achieved in a synergistic way without significant embrittlement, which will accelerate the future development and application of nonfullerene OSCs.}, number={17}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Hu, Huawei and Ye, Long and Ghasemi, Masoud and Balar, Nrup and Rech, Jeromy James and Stuard, Samuel J. and You, Wei and Brendan T. O'Connor and Ade, Harald}, year={2019}, month={Apr} } @article{zhang_bai_li_hu_liu_zou_yu_huang_pan_ade_et al._2019, title={Intramolecular pi-stacked perylene-diimide acceptors for non-fullerene organic solar cells}, volume={7}, ISSN={["2050-7496"]}, DOI={10.1039/c9ta00343f}, abstractNote={Two isomeric perylene diimide acceptors with both intra- and intermolecular π–π stacking are developed for non-fullerene organic solar cells.}, number={14}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Zhang, Jianquan and Bai, Fujin and Li, Yunke and Hu, Huawei and Liu, Bin and Zou, Xinhui and Yu, Han and Huang, Jiachen and Pan, Ding and Ade, Harald and et al.}, year={2019}, month={Apr}, pages={8136–8143} } @article{roy_knapp_miller_gadisa_ade_wu_2020, title={Millimeter wave direct-current transmission and reflection spectral data of some organic photo-responsive materials}, volume={28}, ISSN={["2352-3409"]}, DOI={10.1016/j.dib.2019.104996}, abstractNote={Voltage data acquired after probe signal transmitted through the organic film and reflected off the film surface as a function of 0.36 mW millimeter wave signal frequency in the range 110-160 GHz. Five different organic photovoltaic (OPV) materials and one 95:5 blend produced at 2 spin rates are used. These materials are a) fluorinated 2-alkyl-benzol[d] [1-3]triazole (FTAZ), a high hole-mobility polymer used for transistors and photovoltaics, b) diketopyrrolopyrrole (DPP3T), an acceptor polymer used in field-effect transistors (FET), c) Y5(PffBT4T-2OD) film that possesses remarkable temperature controllable morphology, d) a neat conjugated polymer P3HT, Poly(3-(hexylthiophene-2,5diyl) film that is used in optoelectronic devices and as a conductive binder for Li-ion batteries, e) phenyl-C61-butyric acid methyl ester (PCBM) films and its soluble derivatives used as n-type organic semiconductors, and f) excitonic photovoltaic material 95%:5% donor-acceptor blend P3HT:PCBM produced by 2 different spin rates. Measurement of direct-current (dc) transmitted and reflected power (RF voltage signal) are measured using a newly developed continuous wave (CW) D-waveguide band probe (110-160 GHz) apparatus named time-resolved millimeter wave conductivity (TR-mmWC) [1]. Transmission and first surface reflection voltages are captured by a zero-bias Schottky barrier diode (ZBD) and converted to relevant dc voltages. Original voltage signal datasets attached with this can be utilized for photovoltaic, dielectric property estimation, and other semiconductor physics applications. A manually collected dataset of transmission and reflection coefficient at incident probe power level ∼0.9 mW for 95:5 P3HT:PCBM films produced at 2 different spin rates, and one separately only for the neat P3HT film are also presented here in tabular form.}, journal={DATA IN BRIEF}, author={Roy, Biswadev and Knapp, Taylor and Miller, Corinne and Gadisa, Abay and Ade, Harald W. and Wu, Marvin H.}, year={2020}, month={Feb} } @article{ye_li_guo_zhang_ade_2019, title={Polymer Side-Chain Variation Induces Microstructural Disparity in Nonfullerene Solar Cells}, volume={31}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/ACS.CHEMMATER.9B00174}, DOI={10.1021/ACS.CHEMMATER.9B00174}, abstractNote={In addition to the innovation of nonfullerene acceptors, the development of highly efficient nonfullerene organic solar cells requires the design of new polymer donors and fundamental understanding of their structural and morphological properties. Utilizing meta-alkoxy-phenyl-substituted benzodithiophene and benzodithiophene-4,8-dione building blocks, we designed and prepared a new class of structurally similar photovoltaic polymers named PBDx (x = 1–4), which are capable of being processed from nonchlorinated solvents. From PBD1 to PBD4, the total carbon number of the alkyl side chains in each repeat unit increased by four in turn. The effect of side chain structure variation on the molecular aggregation, molecular arrangement, mesoscale phase separation, charge transport, and nonfullerene solar cell performance was systematically studied. Our hard and soft X-ray scattering results indicate that small side chain variation yields vastly different molecular packing and mesoscale morphology for these analog...}, number={17}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={Ye, Long and Li, Wanbin and Guo, Xia and Zhang, Maojie and Ade, Harald}, year={2019}, month={Feb}, pages={6568–6577} } @article{rosenthal_hughes_luginbuhl_ran_karki_ko_hu_wang_ade_nguyen_2019, title={Quantifying and Understanding Voltage Losses Due to Nonradiative Recombination in Bulk Heterojunction Organic Solar Cells with Low Energetic Offsets}, volume={9}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201901077}, DOI={10.1002/aenm.201901077}, abstractNote={AbstractOpen‐circuit voltage (VOC) losses in organic photovoltaics (OPVs) inhibit devices from reaching VOC values comparable to the bandgap of the donor–acceptor blend. Specifically, nonradiative recombination losses (∆Vnr) are much greater in OPVs than in silicon or perovskite solar cells, yet the origins of this are not fully understood. To understand what makes a system have high or low loss, an investigation of the nonradiative recombination losses in a total of nine blend systems is carried out. An apparent relationship is observed between the relative domain purity of six blends and the degree of nonradiative recombination loss, where films exhibiting relatively less pure domains show lower ∆Vnr than films with higher domain purity. Additionally, it is shown that when paired with a fullerene acceptor, polymer donors which have bulky backbone units to inhibit close π–π stacking exhibit lower nonradiative recombination losses than in blends where the polymer can pack more closely. This work reports a strategy that ensures ∆Vnr can be measured accurately and reports key observations on the relationship between ∆Vnr and properties of the donor/acceptor interface.}, number={27}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Rosenthal, Katie D. and Hughes, Michael P. and Luginbuhl, Benjamin R. and Ran, Niva A. and Karki, Akchheta and Ko, Seo-Jin and Hu, Huawei and Wang, Ming and Ade, Harald and Nguyen, Thuc-Quyen}, year={2019}, month={Jul} } @article{zhu_gadisa_peng_ghasemi_ye_xu_zhao_ade_2019, title={Rational Strategy to Stabilize an Unstable High-Efficiency Binary Nonfullerene Organic Solar Cells with a Third Component}, volume={9}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201900376}, DOI={10.1002/aenm.201900376}, abstractNote={AbstractLong device lifetime is still a missing key requirement in the commercialization of nonfullerene acceptor (NFA) organic solar cell technology. Understanding thermodynamic factors driving morphology degradation or stabilization is correspondingly lacking. In this report, thermodynamics is combined with morphology to elucidate the instability of highly efficient PTB7‐Th:IEICO‐4F binary solar cells and to rationally use PC71BM in ternary solar cells to reduce the loss in the power conversion efficiency from ≈35% to <10% after storage for 90 days and at the same time improve performance. The hypomiscibility observed for IEICO‐4F in PTB7‐Th (below the percolation threshold) leads to overpurification of the mixed domains. By contrast, the hypermiscibility of PC71BM in PTB7‐Th of 48 vol% is well above the percolation threshold. At the same time, PC71BM is partly miscible in IEICO‐4F suppressing crystallization of IEICO‐4F. This work systematically illustrates the origin of the intrinsic degradation of PTB7‐Th:IEICO‐4F binary solar cells, demonstrates the structure–function relations among thermodynamics, morphology, and photovoltaic performance, and finally carries out a rational strategy to suppress the degradation: the third component needs to have a miscibility in the donor polymer at or above the percolation threshold, yet also needs to be partly miscible with the crystallizable acceptor.}, number={20}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Zhu, Youqin and Gadisa, Abay and Peng, Zhengxing and Ghasemi, Masoud and Ye, Long and Xu, Zheng and Zhao, Suling and Ade, Harald}, year={2019}, month={May} } @article{qin_zhang_xu_ye_wu_kong_xu_yao_ade_hou_et al._2019, title={Reduced Nonradiative Energy Loss Caused by Aggregation of Nonfullerene Acceptor in Organic Solar Cells}, volume={9}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/28504183/}, DOI={10.1002/aenm.201901823}, abstractNote={AbstractReducing energy loss (Eloss) is of critical importance to improving the photovoltaic performance of organic solar cells (OSCs). Although nonradiative recombination () is investigated in quite a few works, the method for modulating is seldom reported. Here, a new method of depressing Eloss is reported for nonfullerene OSCs. In addition to ternary‐blend bulk heterojunction (BHJ) solar cells, it is proved that a small molecular material (NRM‐1) can be selectively dispersed into the acceptor phase in the PBDB‐T:IT‐4F‐based OSC, resulting in lower and , and hence a significant improvement in the open‐circuit voltage (VOC); under an optimal feed ratio of NRM‐1, an enhanced power conversion efficiency can also be gained. Moreover, the role of NRM‐1 in the method is illustrated and its applicability for several other representative OSCs is validated. This work paves a new pathway to reduce the Eloss for nonfullerene OSCs.}, number={35}, journal={ADVANCED ENERGY MATERIALS}, author={Qin, Yunpeng and Zhang, Shaoqing and Xu, Ye and Ye, Long and Wu, Yi and Kong, Jingyi and Xu, Bowei and Yao, Huifeng and Ade, Harald and Hou, Jianhui and et al.}, year={2019}, month={Sep} } @article{ye_xiong_chen_zhang_fei_henry_heeney_o’connor_you_ade_et al._2019, title={Sequential Deposition of Organic Films with Eco-Compatible Solvents Improves Performance and Enables Over 12%-Efficiency Nonfullerene Solar Cells}, volume={31}, ISSN={["1521-4095"]}, url={https://doi.org/10.1002/adma.201808153}, DOI={10.1002/adma.201808153}, abstractNote={AbstractCasting of a donor:acceptor bulk‐heterojunction structure from a single ink has been the predominant fabrication method of organic photovoltaics (OPVs). Despite the success of such bulk heterojunctions, the task ofcontrolling the microstructure in a single casting process has been arduous and alternative approaches are desired. To achieve OPVs with a desirable microstructure, a facile and eco‐compatible sequential deposition approach is demonstrated for polymer/small‐molecule pairs. Using a nominally amorphous polymer as the model material, the profound influence of casting solvent is shown on the molecular ordering of the film, and thus the device performance and mesoscale morphology of sequentially deposited OPVs can be tuned. Static and in situ X‐ray scattering indicate that applying (R)‐(+)‐limonene is able to greatly promote the molecular order of weakly crystalline polymers and form the largest domain spacing exclusively, which correlates well with the best efficiency of 12.5% in sequentially deposited devices. The sequentially cast device generally outperforms its control device based on traditional single‐ink bulk‐heterojunction structure. More crucially, a simple polymer:solvent interaction parameter χ is positively correlated with domain spacing in these sequentially deposited devices. These findings shed light on innovative approaches to rationally create environmentally friendly and highly efficient electronics.}, number={17}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Ye, Long and Xiong, Yuan and Chen, Zheng and Zhang, Qianqian and Fei, Zhuping and Henry, Reece and Heeney, Martin and O’Connor, Brendan T. and You, Wei and Ade, Harald and et al.}, year={2019}, month={Apr} } @article{pan_sun_bin_angunawela_lai_meng_ade_li_2020, title={Side-chain engineering of medium bandgap polymer donors for efficient polymer solar cells}, volume={78}, ISSN={["1878-5530"]}, DOI={10.1016/j.orgel.2019.105603}, abstractNote={Polymer solar cells (PSCs) have received widespread attentions recently due to the significant innovations of narrow bandgap n-type organic semiconductor (n-OS) acceptors. To obtain efficient PSCs, it is crucial to employ suitable donor/acceptor pair with matched electronic energy levels, complementary absorption spectra, appropriate molecular self-assembly behavior and preferred blend film morphology, which can be achieved by rational molecular structure optimization. Here we develop three D-A copolymer donors J55, J65 and J75 based on identical building blocks of bithienyl-benzodithiophene (BDTT) D-unit and bifluorine substituted benzotriazole A-unit with different flexible side-chains on BDTT unit to regulate the molecular electronic energy levels and molecular aggregation features, for further improving photovoltaic performance of the PSCs. The three D-A copolymers showed similar absorption profiles due to the identical building blocks. In comparison with the alkyl side-chain substituted polymer J55, the polymers J65 and J75 with alkylthio side-chain and alkylsilyl side-chain showed gradually down-shifted highest occupied molecular orbital energy levels (EHOMO) of −5.38 and −5.43 eV, respectively, which is beneficial for obtaining high open-circuit voltage (Voc). The favorable morphology with preferred face-on orientation and stronger integrated intensity of the π-π stacking peak was formed in J75 blend, which contributes to charge transport, thus enhancing the fill factor (FF) and Jsc. The PSC with J75 as donor and ITIC as acceptor exhibits an efficient PCE of 11.07%, with a Voc of 0.94 V, an enhanced Jsc of 16.99 mA cm−2 and a high FF of 69.29%.}, journal={ORGANIC ELECTRONICS}, author={Pan, Fei and Sun, Chenkai and Bin, Haijun and Angunawela, Indunil and Lai, Wenbin and Meng, Lei and Ade, Harald and Li, Yongfang}, year={2020}, month={Mar} } @article{hu_oswald_stuard_nahid_zhou_williams_guo_yan_hu_chen_et al._2019, title={Synthetic control over orientational degeneracy of spacer cations enhances solar cell efficiency in two-dimensional perovskites}, volume={10}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-019-08980-x}, abstractNote={AbstractTwo-dimensional perovskites have emerged as more intrinsically stable materials for solar cells. Chemical tuning of spacer organic cations has attracted great interest due to their additional functionalities. However, how the chemical nature of the organic cations affects the properties of two-dimensional perovskites and devices is rarely reported. Here we demonstrate that the selection of spacer cations (i.e., selective fluorination of phenethylammonium) affects the film properties of two-dimensional perovskites, leading to different device performance of two-dimensional perovskite solar cells (average n = 4). Structural analysis reveals that different packing arrangements and orientational disorder of the spacer cations result in orientational degeneracy and different formation energies, largely explaining the difference in film properties. This work provides key missing information on how spacer cations exert influence on desirable electronic properties and device performance of two-dimensional perovskites via the weak and cooperative interactions of these cations in the crystal lattice.}, journal={NATURE COMMUNICATIONS}, author={Hu, Jun and Oswald, Iain W. H. and Stuard, Samuel J. and Nahid, Masrur Morshed and Zhou, Ninghao and Williams, Olivia F. and Guo, Zhenkun and Yan, Liang and Hu, Huamin and Chen, Zheng and et al.}, year={2019}, month={Mar} } @article{arunagiri_zhang_hu_yao_zhang_li_chow_ade_yan_2019, title={Temperature-Dependent Aggregation Donor Polymers Enable Highly Efficient Sequentially Processed Organic Photovoltaics Without the Need of Orthogonal Solvents}, volume={29}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201902478}, abstractNote={AbstractThe conventional method to prepare bulk‐heterojunction organic photovoltaics (OPVs) is a one‐step method from the blend solution of donor and acceptor materials, known as blend‐casting (BC). Recently, an alternative method was demonstrated to achieve high efficiencies (13%) comparable to state‐of‐the‐art BC devices. This two‐step‐coating method, known as “sequential processing,” (SqP) involves sequential deposition of the donor and then the acceptor from two orthogonal solvents. However, the requirement of orthogonal solvents to process the donor and acceptor constrains the choice of materials and processing solvents. In this paper, an improved version of SqP method without the need for using orthogonal solvents is reported. The success is based on donor polymers with strong temperature‐dependent aggregation properties whose solution can be processed at a high temperature, but the resulting film becomes completely insoluble at room temperature, which allows for the processing of overlying acceptors from a wide range of nonorthogonal solvents. With this approach, efficient SqP OPVs is demonstrated based on a range of donor/acceptor materials and processing solvents, and, in every single case, SqP OPVs can outperform their BC counterparts. The results broaden the solvent choices and open a much larger window to optimize the processing parameters of SqP method.}, number={33}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Arunagiri, Lingeswaran and Zhang, Guangye and Hu, Huawei and Yao, Huatong and Zhang, Kai and Li, Yunke and Chow, Philip C. Y. and Ade, Harald and Yan, He}, year={2019}, month={Aug} } @article{rech_bauer_dirkes_kaplan_peng_zhang_ye_liu_gao_ade_et al._2019, title={The crucial role of end group planarity for fused-ring electron acceptors in organic solar cells}, volume={3}, url={https://doi.org/10.1039/C9QM00314B}, DOI={10.1039/C9QM00314B}, abstractNote={Planar acceptor moieties in FREAs are necessary, as expanding the π–π stacking by only 1 Å disrupts the packing and decreases performance.}, number={8}, journal={Materials Chemistry Frontiers}, publisher={Royal Society of Chemistry (RSC)}, author={Rech, Jeromy J. and Bauer, Nicole and Dirkes, David and Kaplan, Joseph and Peng, Zhengxing and Zhang, Huotian and Ye, Long and Liu, Shubin and Gao, Feng and Ade, Harald and et al.}, year={2019}, pages={1642–1652} } @article{bauer_zhang_rech_dai_peng_ade_wang_zhan_you_2019, title={The impact of fluorination on both donor polymer and non-fullerene acceptor: The more fluorine, the merrier}, volume={12}, ISSN={["1998-0000"]}, DOI={10.1007/s12274-019-2362-3}, number={9}, journal={NANO RESEARCH}, author={Bauer, Nicole and Zhang, Qianqian and Rech, Jeromy James and Dai, Shuixing and Peng, Zhengxing and Ade, Harald and Wang, Jiayu and Zhan, Xiaowei and You, Wei}, year={2019}, month={Sep}, pages={2400–2405} } @article{lin_fang_zhao_shao_stuard_nahid_ade_wang_shield_zhou_et al._2019, title={Unveiling the operation mechanism of layered perovskite solar cells}, volume={10}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-019-08958-9}, abstractNote={AbstractLayered perovskites have been shown to improve the stability of perovskite solar cells while its operation mechanism remains unclear. Here we investigate the process for the conversion of light to electrical current in high performance layered perovskite solar cells by examining its real morphology. The layered perovskite films in this study are found to be a mixture of layered and three dimensional (3D)-like phases with phase separations at micrometer and nanometer scale in both vertical and lateral directions. This phase separation is explained by the surface initiated crystallization process and the competition of the crystallization between 3D-like and layered perovskites. We further propose that the working mechanisms of the layered perovskite solar cells involve energy transfer from layered to 3D-like perovskite network. The impact of morphology on efficiency and stability of the hot-cast layered perovskite solar cells are also discussed to provide guidelines for the future improvement.}, journal={NATURE COMMUNICATIONS}, author={Lin, Yun and Fang, Yanjun and Zhao, Jingjing and Shao, Yuchuan and Stuard, Samuel J. and Nahid, Masrur Morshed and Ade, Harald and Wang, Qi and Shield, Jeffrey E. and Zhou, Ninghao and et al.}, year={2019}, month={Mar} } @article{rech_yan_peng_dai_zhan_ade_you_2019, title={Utilizing Difluorinated Thiophene Units To Improve the Performance of Polymer Solar Cells}, volume={52}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.9b01168}, abstractNote={While there are numerous approaches to functionalize conjugated polymers for organic solar cells (OSCs), one widely adopted approach is fluorination. Of the many different locations for fluorinatio...}, number={17}, journal={MACROMOLECULES}, author={Rech, Jeromy J. and Yan, Liang and Peng, Zhengxing and Dai, Shuixing and Zhan, Xiaowei and Ade, Harald and You, Wei}, year={2019}, month={Sep}, pages={6523–6532} } @article{li_ye_li_yao_ade_hou_2018, title={A High-Efficiency Organic Solar Cell Enabled by the Strong Intramolecular Electron Push-Pull Effect of the Nonfullerene Acceptor}, volume={30}, ISSN={["1521-4095"]}, url={https://publons.com/wos-op/publon/7528271/}, DOI={10.1002/adma.201707170}, abstractNote={AbstractBesides broadening of the absorption spectrum, modulating molecular energy levels, and other well‐studied properties, a stronger intramolecular electron push–pull effect also affords other advantages in nonfullerene acceptors. A strong push–pull effect improves the dipole moment of the wings in IT‐4F over IT‐M and results in a lower miscibility than IT‐M when blended with PBDB‐TF. This feature leads to higher domain purity in the PBDB‐TF:IT‐4F blend and makes a contribution to the better photovoltaic performance. Moreover, the strong push–pull effect also decreases the vibrational relaxation, which makes IT‐4F more promising than IT‐M in reducing the energetic loss of organic solar cells. Above all, a power conversion efficiency of 13.7% is recorded in PBDB‐TF:IT‐4F‐based devices.}, number={16}, journal={ADVANCED MATERIALS}, author={Li, Wanning and Ye, Long and Li, Sunsun and Yao, Huifeng and Ade, Harald and Hou, Jianhui}, year={2018}, month={Apr} } @article{song_gasparini_nahid_chen_macphee_zhang_norman_zhu_bryant_ade_et al._2018, title={A Highly Crystalline Fused-Ring n-Type Small Molecule for Non-Fullerene Acceptor Based Organic Solar Cells and Field-Effect Transistors}, volume={28}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201802895}, abstractNote={AbstractN‐type organic small molecules (SMs) are attracting attention in the organic electronics field, due to their easy purification procedures with high yield. However, only a few reports show SMs that perform well in both organic field‐effect transistors (OFETs) and organic solar cells (OSCs). Here, the synthesis and characterization of an n‐type small molecule with an indacenodithieno[3,2‐b]thiophene (IDTT) core unit and linear alkylated side chain (C16) (IDTTIC) are reported. Compared to the state‐of‐the‐art n‐type molecule IDTIC, IDTTIC exhibits smaller optical bandgap and higher absorption coefficient, which is due to the enhanced intramolecular effect. After mixing with the polymer donor PBDB‐T, IDTIC‐based solar cells deliver a power conversion efficiency of only 5.67%. In stark contrast, the OSC performance of IDTTIC improves significantly to 11.2%. It is found that the superior photovoltaic properties of PBDB‐T:IDTTIC blends are mainly due to reduced trap‐assisted recombination and enhanced molecular packing coherence length and higher domain purity when compared to IDTIC. Moreover, a significantly higher electron mobility of 0.50 cm2 V−1 s−1 for IDTTIC in OFET devices than for IDTIC (0.15 cm2 V−1 s−1) is obtained. These superior performances in OSCs and OFETs demonstrate that SMs with extended π‐conjugation of the backbone possess a great potential for application in organic electronic devices.}, number={35}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Song, Xin and Gasparini, Nicola and Nahid, Masrur Morshed and Chen, Hu and Macphee, Sky Marie and Zhang, Weimin and Norman, Victoria and Zhu, Chenhui and Bryant, Daniel and Ade, Harald and et al.}, year={2018}, month={Aug} } @article{kang_ye_xu_an_stuard_zhang_yao_ade_hou_2019, title={A Printable Organic Cathode Interlayer Enables over 13% Efficiency for 1-cm(2) Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, url={https://publons.com/wos-op/publon/17838771/}, DOI={10.1016/j.joule.2018.10.024}, abstractNote={Currently, most cathode interlayer (CIL) materials for organic solar cells (OSCs) cannot be processed by printing techniques, which severely limits their use in practical productions. Herein, we report a naphthalene diimide (NDI)-based small-molecular compound (N,N-dimethylamino)propyl naphthalene diimide (NDI-N) as printable CIL for OSCs. NDI-N exhibits a unique advantage that combines the merits of high crystallinity and good film-forming property in one material, endowing the semiconductor with excellent electron-transport properties and good processability. By using the NDI-N as CIL, a high power-conversion efficiency (PCE) of 13.9% was achieved in a PBDB-T-2F:IT-4F-based OSC device. More importantly, a large-area OSC device of 1 cm2 was fabricated by using the blade-coated NDI-N CIL and an outstanding PCE of 13.2% was achieved, which represents the highest efficiency of large-area OSCs. The results in this work may pave the way for low-cost and mass production of OSCs.}, number={1}, journal={JOULE}, author={Kang, Qian and Ye, Long and Xu, Bowei and An, Cunbin and Stuard, Samuel J. and Zhang, Shaoqing and Yao, Huifeng and Ade, Harald and Hou, Jianhui}, year={2019}, month={Jan}, pages={227–239} } @article{li_ye_zhao_yan_yang_liu_li_ade_hou_2018, title={A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells}, volume={140}, ISSN={["0002-7863"]}, url={https://doi.org/10.1021/jacs.8b02695}, DOI={10.1021/jacs.8b02695}, abstractNote={To simultaneously achieve low photon energy loss ( Eloss) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. -5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low Eloss of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π-π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory-Huggins interaction parameter (χ), surface-directed phase separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. These results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.}, number={23}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher={American Chemical Society (ACS)}, author={Li, Sunsun and Ye, Long and Zhao, Wenchao and Yan, Hongping and Yang, Bei and Liu, Delong and Li, Wanning and Ade, Harald and Hou, Jianhui}, year={2018}, month={Jun}, pages={7159–7167} } @article{qin_ye_zhang_zhu_yang_ade_hou_2018, title={A polymer design strategy toward green solvent processed efficient non-fullerene polymer solar cells}, volume={6}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C8TA00368H}, DOI={10.1039/c8ta00368h}, abstractNote={This work suggests an effective material design strategy to prepare efficient PSCs with a green solvent, which is important in PSCs.}, number={10}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Qin, Yunpeng and Ye, Long and Zhang, Shaoqing and Zhu, Jie and Yang, Bei and Ade, Harald and Hou, Jianhui}, year={2018}, month={Mar}, pages={4324–4330} } @article{roy_jones_vlahovic_ade_wu_2018, title={A time-resolved millimeter wave conductivity (TR-mmWC) apparatus for charge dynamical properties of semiconductors}, volume={89}, ISSN={["1089-7623"]}, url={https://doi.org/10.1063/1.5026848}, DOI={10.1063/1.5026848}, abstractNote={This article demonstrates a contactless, time-resolved, millimeter wave conductivity apparatus capable of measuring photoconductivity of a diverse range of materials. This cavity-less system determines the time-dependent magnitude of a sample’s charge carrier density-mobility product by monitoring the response of a continuous, millimeter-wave probe beam following excitation of the sample by an ultrafast laser pulse. The probe beam is tunable from 110 GHz to 170 GHz and the sample response data can be obtained over the sub-nanosecond to millisecond time interval. This system has been tested on silicon wafers, S-I GaAs, perovskite thin films, SiO2-Ge(nc), and CdSxSe1−x nanowire samples. We demonstrate a minimum detectable photoconductance change of ∼1 µS, an estimated time resolution for conductance decay of ∼100 ps, and a dynamic range greater than 57 dB. The calibration constant of the system, needed for quantitative calculation of photoconductivity from experimental data, has been determined using silicon wafers. This system has several advantages over currently used microwave and terahertz techniques, such as facile tunability of probe frequency and substantially wider time range for study of decay kinetics, while maintaining an open sample environment that enables characterization of a wide range of sample sizes under controlled environmental conditions.}, number={10}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, publisher={AIP Publishing}, author={Roy, Biswadev and Jones, Charles R. and Vlahovic, B. and Ade, Harald W. and Wu, Marvin H.}, year={2018}, month={Oct} } @article{chen_zhang_ma_meng_zhang_zhang_li_chow_ma_wang_et al._2018, title={Alkyl Chain Regiochemistry of Benzotriazole-Based Donor Polymers Influencing Morphology and Performances of Non-Fullerene Organic Solar Cells}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201702427}, abstractNote={AbstractThe effects of alkyl chain regiochemistry on the properties of donor polymers and performances of non‐fullerene organic solar cells are investigated. Two donor polymers (PfBTAZ and PfBTAZS) are compared that have nearly identical chemical structures except for the regiochemistry of alkyl chains. The optical properties and crystallinity of two polymers are nearly identical yet the PfBTAZ:O‐IDTBR blend exhibits nearly double domain size compared to the blend based on PfBTAZS:O‐IDTBR. To reveal the origins of the very different domain size of two blends, the morphology of neat polymer films is characterized, and it is found that PfBTAZ tends to aggregate into much larger polymer fibers without the presence of O‐IDTBR. This indicates that it is not the polymer:O‐IDTBR interactions but the intrinsic aggregation properties of two polymers that determine the morphology features of neat and blend films. The stronger aggregation tendency of PfBTAZ could be explained by its more co‐planar geometry of the polymer backbone arising from the different alkyl chain regiochemistry. Combined with the similar trend observed in another set of donor polymers (PTFB‐P and PTFB‐PS), the results provide an important understanding of the structure–property relationships that could guide the development of donor polymers for non‐fullerene organic solar cells.}, number={11}, journal={ADVANCED ENERGY MATERIALS}, author={Chen, Shangshang and Zhang, Lin and Ma, Chao and Meng, Dong and Zhang, Jianquan and Zhang, Guangye and Li, Zhengke and Chow, Philip C. Y. and Ma, Wei and Wang, Zhaohui and et al.}, year={2018}, month={Apr} } @article{liu_ma_sheong_zhang_hu_zhang_zhang_li_ma_han_et al._2018, title={Carboxylate substitution position influencing polymer properties and enabling non-fullerene organic solar cells with high open circuit voltage and low voltage loss}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta04935a}, abstractNote={A novel polymer P3TAE enables a high VOC of 1.20 V and a PCE of 8.10% for non-fullerene OSCs.}, number={35}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Liu, Jing and Ma, Lik-Kuen and Sheong, Fu Kit and Zhang, Lin and Hu, Huawei and Zhang, Jing-Xuan and Zhang, Jianquan and Li, Zhengke and Ma, Chao and Han, Xu and et al.}, year={2018}, month={Sep}, pages={16874–16881} } @article{carpenter_ghasemi_gann_angunawela_stuard_rech_ritchie_brendan t. o'connor_atkin_you_et al._2019, title={Competition between Exceptionally Long-Range Alkyl Sidechain Ordering and Backbone Ordering in Semiconducting Polymers and Its Impact on Electronic and Optoelectronic Properties}, volume={29}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201806977}, abstractNote={AbstractIntra‐ and intermolecular ordering greatly impacts the electronic and optoelectronic properties of semiconducting polymers. The interrelationship between ordering of alkyl sidechains and conjugated backbones has yet to be fully detailed, despite much prior effort. Here, the discovery of a highly ordered alkyl sidechain phase in six representative semiconducting polymers, determined from distinct spectroscopic and diffraction signatures, is reported. The sidechain ordering exhibits unusually large coherence lengths (≥70 nm), induces torsional/twisting backbone disorder, and results in a vertically multilayered nanostructure with ordered sidechain layers alternating with disordered backbone layers. Calorimetry and in situ variable temperature scattering measurements in a model system poly{4‐(5‐(4,8‐bis(3‐butylnonyl)‐6‐methylbenzo[1,2‐b:4,5‐b′]dithiophen‐2‐yl)thiophen‐2‐yl)‐2‐(2‐butyloctyl)‐5,6‐difluoro‐7‐(5‐methylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole} (PBnDT‐FTAZ) clearly delineate this competition of ordering that prevents simultaneous long‐range order of both moieties. The long‐range sidechain ordering can be exploited as a transient state to fabricate PBnDT‐FTAZ films with an atypical edge‐on texture and 2.5× improved field‐effect transistor mobility. The observed influence of ordering between the moieties implies that improved molecular design can produce synergistic rather than destructive ordering effects. Given the large sidechain coherence lengths observed, such synergistic ordering should greatly improve the coherence length of backbone ordering and thereby improve electronic and optoelectronic properties such as charge transport and exciton diffusion lengths.}, number={5}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Carpenter, Joshua H. and Ghasemi, Masoud and Gann, Eliot and Angunawela, Indunil and Stuard, Samuel J. and Rech, Jeromy James and Ritchie, Earl and Brendan T. O'Connor and Atkin, Joanna and You, Wei and et al.}, year={2019}, month={Feb} } @article{song_gasparini_ye_yao_hou_ade_baran_2018, title={Controlling Blend Morphology for Ultrahigh Current Density in Nonfullerene Acceptor-Based Organic Solar Cells}, volume={3}, ISSN={2380-8195 2380-8195}, url={http://dx.doi.org/10.1021/ACSENERGYLETT.7B01266}, DOI={10.1021/ACSENERGYLETT.7B01266}, abstractNote={In this Letter, we highlight a system with a well-known polymer donor (PTB7-Th) blended with a narrow band gap nonfullerene acceptor (IEICO-4F) as the active layer and 1-chloronaphthalene (CN) as the solvent additive. Optimization of the photoactive layer nanomorphology yields a short-circuit current density value of 27.3 mA/cm2, one of the highest values in organic solar cells reported to date, which competes with other types of solution-processed solar cells such as perovskite or quantum dot devices. Along with decent open-circuit voltage (0.71 V) and fill factor values (66%), a power conversion efficiency of 12.8% is achieved for the champion devices. Morphology characterizations elucidate that the origin of this high photocurrent is mainly the increased π–π coherence length of the acceptor, the domain spacing, as well as the mean-square composition variation of the blend. Optoelectronic measurements confirm a balanced hole and electron mobility and reduced trap-assisted recombination for the best devices.}, number={3}, journal={ACS Energy Letters}, publisher={American Chemical Society (ACS)}, author={Song, Xin and Gasparini, Nicola and Ye, Long and Yao, Huifeng and Hou, Jianhui and Ade, Harald and Baran, Derya}, year={2018}, month={Jan}, pages={669–676} } @article{liu_ma_li_hu_sheong_zhang_ade_yan_2018, title={Donor polymer based on alkylthiophene side chains for efficient non- fullerene organic solar cells: insights into fluorination and side chain effects on polymer aggregation and blend morphology}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta08769e}, abstractNote={The synergistic effects of overfluorination and alkylthiophene side chain strategies led to 10.60% efficiency for non-fullerene organic solar cells.}, number={46}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Liu, Jing and Ma, Lik-Kuen and Li, Zhengke and Hu, Huawei and Sheong, Fu Kit and Zhang, Guangye and Ade, Harald and Yan, He}, year={2018}, month={Dec}, pages={23270–23277} } @article{hu_li_zhang_peng_ma_xin_huang_ma_jiang_zhang_et al._2018, title={Effect of Ring-Fusion on Miscibility and Domain Purity: Key Factors Determining the Performance of PDI-Based Nonfullerene Organic Solar Cells}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201800234}, abstractNote={AbstractCompared to the rapid development of nonfullerene organic solar cells (OSCs) based on the state‐of‐the‐art indacenodithiophene (IDT)‐based small molecule acceptors (SMAs), the progress for perylene diimide (PDI)‐based electron acceptors has lagged behind owing to the lack of understanding on the structure–morphology–performance relationship of PDI SMAs. Given the ease of synthesis for PDIs and their high intrinsic electron mobility, it is crucial to identify key material parameters that influence the polymer:PDI blend morphology and to develop rational approaches for molecular design toward high‐performance PDI‐based SMAs. In this study, three pairs of PDI‐based SMAs with and without ring‐fusion are investigated and it is found that ring‐fusion and domain purity are the key structural and morphological factors determining the fill factors (FFs) and efficiencies of PDI‐based nonfullerene OSCs. This data shows that nonfullerene OSCs based on the ring‐fused PDI‐based SMAs exhibit much higher average domain purity and thus increased charge mobilities, which lead to enhanced FFs compared to those solar cells based on nonfused PDIs. This is explained by higher Florry Huggins interaction parameters as observed by melting point depression measurements. This study suggests that increasing repulsive molecular interactions to lower the miscibility between the polymer donor and PDI acceptor is the key to improve the FF and performance of PDI‐based devices.}, number={26}, journal={ADVANCED ENERGY MATERIALS}, author={Hu, Huawei and Li, Yunke and Zhang, Jianquan and Peng, Zhengxing and Ma, Lik-kuen and Xin, Jingming and Huang, Jiachen and Ma, Tingxuan and Jiang, Kui and Zhang, Guangye and et al.}, year={2018}, month={Sep} } @article{huang_bin_peng_qiu_sun_liebman-pelaez_zhang_zhu_ade_zhang_et al._2018, title={Effect of Side-Chain Engineering of Bithienylbenzodithiophene-alt-fluorobenzotriazole-Based Copolymers on the Thermal Stability and Photovoltaic Performance of Polymer Solar Cells}, volume={51}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.8b01036}, abstractNote={Side-chain engineering of conjugated polymer donor materials is an important way for improving photovoltaic performances of polymer solar cells (PSCs). On the basis of the polymer J61 synthesized in our group, here, we design and synthesize three new 2D-conjugated polymers J62, J63, and J64 with different types of side chains to further investigate the effect of side chain on their physicochemical and photovoltaic properties. With the narrow bandgap n-type organic semiconductor (n-OS) ITIC as acceptor, the optimized PSCs based on polymer donor of J62 with linear octyl, J63 with linear unsaturated hexylene, and J64 with cyclohexane side chains display power conversion efficiency (PCE) of 10.81%, 8.13%, and 8.59%, respectively. After thermal treatment at 200 °C for 2 h on the active layer,the PCE of the PSC based on J63 still keeps 92% of the original value, which verifies that the cross-linking of the polymer can improve the thermal stability of PSCs. Morphological studies show that the active layer based ...}, number={15}, journal={MACROMOLECULES}, author={Huang, He and Bin, Haijun and Peng, Zhengxing and Qiu, Beibei and Sun, Chenkai and Liebman-Pelaez, Alex and Zhang, Zhi-Guo and Zhu, Chenhui and Ade, Harald and Zhang, Zhanjun and et al.}, year={2018}, month={Aug}, pages={6028–6036} } @article{li_huang_peng_sun_yang_zhou_liebman-pelaez_zhu_zhang_zhang_et al._2018, title={Effects of fused-ring regiochemistry on the properties and photovoltaic performance of n-type organic semiconductor acceptors}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta05920a}, abstractNote={The effects of fused-ring regiochemistry on the physicochemical and photovoltaic properties of n-type organic semiconductor (n-OS) acceptors are investigated.}, number={33}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Li, Xiaojun and Huang, He and Peng, Zhengxing and Sun, Chenkai and Yang, Dengchen and Zhou, Jiadong and Liebman-Pelaez, Alex and Zhu, Chenhui and Zhang, Zhi-Guo and Zhang, Zhanjun and et al.}, year={2018}, month={Sep}, pages={15933–15941} } @article{bin_yao_yang_angunawela_sun_gao_ye_qiu_xue_zhu_et al._2018, title={High-Efficiency All-Small-Molecule Organic Solar Cells Based on an Organic Molecule Donor with Alkylsilyl-Thienyl Conjugated Side Chains}, volume={30}, ISSN={["1521-4095"]}, url={https://publons.com/wos-op/publon/7528268/}, DOI={10.1002/adma.201706361}, abstractNote={AbstractTwo medium‐bandgap p‐type organic small molecules H21 and H22 with an alkylsily‐thienyl conjugated side chain on benzo[1,2‐b:4,5‐b′]dithiophene central units are synthesized and used as donors in all‐small‐molecule organic solar cells (SM‐OSCs) with a narrow‐bandgap n‐type small molecule 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC) as the acceptor. In comparison to H21 with 3‐ethyl rhodanine as the terminal group, H22 with cyanoacetic acid esters as the terminal group shows blueshifted absorption, higher charge‐carrier mobility and better 3D charge pathway in blend films. The power conversion efficiency (PCE) of the SM‐OSCs based on H22:IDIC reaches 10.29% with a higher open‐circuit voltage of 0.942 V and a higher fill factor of 71.15%. The PCE of 10.29% is among the top efficiencies of nonfullerene SM‐OSCs reported in the literature to date.}, number={27}, journal={ADVANCED MATERIALS}, author={Bin, Haijun and Yao, Jia and Yang, Yankang and Angunawela, Indunil and Sun, Chenkai and Gao, Liang and Ye, Long and Qiu, Beibei and Xue, Lingwei and Zhu, Chenhui and et al.}, year={2018}, month={Jul} } @article{yi_gautam_constantinou_cheng_peng_klump_ba_ho_dong_marder_et al._2018, title={Impact of Nonfullerene Molecular Architecture on Charge Generation, Transport, and Morphology in PTB7-Th-Based Organic Solar Cells}, volume={28}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201802702}, DOI={10.1002/ADFM.201802702}, abstractNote={AbstractDespite the rapid development of nonfullerene acceptors (NFAs), the fundamental understanding on the relationship between NFA molecular architecture, morphology, and device performance is still lacking. Herein, poly[[4,8‐bis[5‐(2‐ethylhexyl)thiophene‐2‐yl]benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]‐thieno[3,4‐b]thiophenediyl]] (PTB7‐Th) is used as the donor polymer to compare an NFA with a 3D architecture (SF‐PDI4) to a well‐studied NFA with a linear acceptor–donor–acceptor (A–D–A) architecture (ITIC). The data suggest that the NFA ITIC with a linear molecular structure shows a better device performance due to an increase in short‐circuit current (  Jsc) and fill factor (FF) compared to the 3D SF‐PDI4. The charge generation dynamics measured by femtosecond transient absorption spectroscopy (TAS) reveals that the exciton dissociation process in the PTB7‐Th:ITIC films is highly efficient. In addition, the PTB7‐Th:ITIC blend shows a higher electron mobility and lower energetic disorder compared to the PTB7‐Th:SF‐PDI4 blend, leading to higher values of Jsc and FF. The compositional sensitive resonant soft X‐ray scattering (R‐SoXS) results indicate that ITIC molecules form more pure domains with reduced domain spacing, resulting in more efficient charge transport compared with the SF‐PDI4 blend. It is proposed that both the molecular structure and the corresponding morphology of ITIC play a vital role for the good solar cell device performance.}, number={32}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Yi, Xueping and Gautam, Bhoj and Constantinou, Iordania and Cheng, Yuanhang and Peng, Zhengxing and Klump, Erik and Ba, Xiaochu and Ho, Carr Hoi Yi and Dong, Chen and Marder, Seth R. and et al.}, year={2018}, month={Jun}, pages={1802702} } @article{li_yao_angunawela_sun_xue_liebman-pelaez_zhu_yang_zhang_ade_et al._2018, title={Improvement of Photovoltaic Performance of Polymer Solar Cells by Rational Molecular Optimization of Organic Molecule Acceptors}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201800815}, abstractNote={AbstractTwo n‐type organic semiconductor (n‐OS) small molecules m‐ITIC‐2F and m‐ITIC‐4F with fluorinated 2‐(2,3‐dihydro‐3‐oxo‐1H‐inden‐1‐ylidene)propanedinitrile (IC) terminal moieties are prepared, for the application as an acceptor in polymer solar cells (PSCs), to further improve the photovoltaic performance of the n‐OS acceptor 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene) indanone) ‐5,5,11,11‐tetrakis(3‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐sindaceno[1,2‐b:5,6‐b′]‐dithiophene (m‐ITIC). Compared to m‐ITIC, these two new acceptors show redshifted absorption, higher molecular packing order, and improved electron mobilities. The power conversion efficiencies (PCE) of the as‐cast PSCs with m‐ITIC‐2F or m‐ITIC‐4F as an acceptor and a low‐cost donor–acceptor (D–A) copolymer PTQ10 as a donor reach 11.57% and 11.64%, respectively, which are among the highest efficiency for the as‐cast PSCs so far. Furthermore, after thermal annealing treatment, improved molecular packing and enhanced phase separation are observed, and the higher PCE of 12.53% is achieved for both PSCs based on the two acceptors. The respective and unique advantage with the intrinsic high degree of order, molecular packing, and electron mobilities of these two acceptors will be suitable to match with different p‐type organic semiconductor donors for higher PCE values, which provide a great potential for the PSCs commercialization in the near future. These results indicate that rational molecular structure optimization is of great importance to further improve photovoltaic properties of the photovoltaic materials.}, number={23}, journal={ADVANCED ENERGY MATERIALS}, author={Li, Xiaojun and Yao, Jia and Angunawela, Indunil and Sun, Chenkai and Xue, Lingwei and Liebman-Pelaez, Alexander and Zhu, Chenhui and Yang, Chunhe and Zhang, Zhi-Guo and Ade, Harald and et al.}, year={2018}, month={Aug} } @article{li_mangalore_zhao_carpenter_yan_ade_yan_muellen_blom_pisula_et al._2018, title={Integrated circuits based on conjugated polymer monolayer}, volume={9}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-017-02805-5}, abstractNote={AbstractIt is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm2 V−1 s−1. The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.}, journal={NATURE COMMUNICATIONS}, author={Li, Mengmeng and Mangalore, Deepthi Kamath and Zhao, Jingbo and Carpenter, Joshua H. and Yan, Hongping and Ade, Harald and Yan, He and Muellen, Klaus and Blom, Paul W. M. and Pisula, Wojciech and et al.}, year={2018}, month={Jan} } @article{wu_fan_xu_ye_guo_yi_ade_zhu_2019, title={Isomery-Dependent Miscibility Enables High-Performance All-Small-Molecule Solar Cells}, volume={15}, ISSN={["1613-6829"]}, url={https://publons.com/wos-op/publon/14860771/}, DOI={10.1002/smll.201804271}, abstractNote={AbstractNonfullerene polymer solar cells develop quickly. However, nonfullerene small‐molecule solar cells (NF‐SMSCs) still show relatively inferior performance, attributing to the lack of comprehensive understanding of the structure–performance relationship. To address this issue, two isomeric small‐molecule acceptors, NBDTP‐Fout and NBDTP‐Fin, with varied oxygen position in the benzodi(thienopyran) (BDTP) core are designed and synthesized. When blended with molecular donor BDT3TR‐SF, devices based on the two isomeric acceptors show disparate photovoltaic performance. Fabricated with an eco‐friendly processing solvent (tetrahydrofuran), the BDT3TR‐SF:NBDTP‐Fout blend delivers a high power conversion efficiency of 11.2%, ranked to the top values reported to date, while the BDT3TR‐SF:NBDTP‐Fin blend almost shows no photovoltaic response (0.02%). With detailed investigations on inherent optoelectronic processes as well as morphological evolution, this performance disparity is correlated to the interfacial tension of the two combinations and concludes that proper interfacial tension is a key factor for effective phase separation, optimal blend morphology, and superior performance, which can be achieved by the “isomerization” design on molecular acceptors. This work reveals the importance of modulating the materials miscibility by interfacial‐tension‐oriented molecular design, which provides a general guideline toward efficient NF‐SMSCs.}, number={1}, journal={SMALL}, author={Wu, Hao and Fan, Haijun and Xu, Shengjie and Ye, Long and Guo, Yuan and Yi, Yuanping and Ade, Harald and Zhu, Xiaozhang}, year={2019}, month={Jan} } @article{ziffer_jo_zhong_ye_liu_lin_zhang_li_ade_jen_et al._2018, title={Long-Lived, Non-Geminate, Radiative Recombination of Photogenerated Charges in a Polymer/Small-Molecule Acceptor Photovoltaic Blend}, volume={140}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/JACS.8B05834}, DOI={10.1021/JACS.8B05834}, abstractNote={Minimization of open-circuit-voltage ( VOC) loss is required to transcend the efficiency limitations on the performance of organic photovoltaics (OPV). We study charge recombination in an OPV blend comprising a polymer donor with a small molecule nonfullerene acceptor that exhibits both high photovoltaic internal quantum efficiency and relatively high external electroluminescence quantum efficiency. Notably, this donor/acceptor blend, consisting of the donor polymer commonly referred to as PCE10 with a pseudoplanar small molecule acceptor (referred to as FIDTT-2PDI) exhibits relatively bright delayed photoluminescence on the microsecond time scale beyond that observed in the neat material. We study the photoluminescence decay kinetics of the blend in detail and conclude that this long-lived photoluminescence arises from radiative nongeminate recombination of charge carriers, which we propose occurs via a donor/acceptor CT state located close in energy to the singlet state of the polymer donor. Additionally, crystallographic and spectroscopic studies point toward low subgap disorder, which could be beneficial for low radiative and nonradiative losses. These results provide an important demonstration of photoluminescence due to nongeminate charge recombination in an efficient OPV blend, a key step in identifying new OPV materials and materials-screening criteria if OPV is to approach the theoretical limits to efficiency.}, number={31}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Ziffer, Mark E. and Jo, Sae Byeok and Zhong, Hongliang and Ye, Long and Liu, Hongbin and Lin, Francis and Zhang, Jie and Li, Xiaosong and Ade, Harald W. and Jen, Alex K.-Y. and et al.}, year={2018}, month={Jul}, pages={9996–10008} } @article{peng_jiao_ye_li_rech_you_hou_ade_2018, title={Measuring Temperature-Dependent Miscibility for Polymer Solar Cell Blends: An Easily Accessible Optical Method Reveals Complex Behavior}, volume={30}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.8b00889}, DOI={10.1021/acs.chemmater.8b00889}, abstractNote={In bulk-heterojunction polymer solar cells (PSC), the molecular-level mixing between conjugated polymer donors and small-molecule acceptors plays a crucial role in obtaining a desirable morphology and good device stability. It has been recently shown that the thermodynamic limit of this mixing can be quantified by the liquidus miscibility, the composition of the small-molecule acceptor in amorphous phases in the presence of small-molecule crystals, and then converted to the Flory–Huggins interaction parameter χ. This conversion maps out the amorphous miscibility. Moreover, the quantitative relations between χ and the fill factor of PSC devices were established recently. However, the commonly used measurement of this liquidus miscibility, scanning transmission X-ray microscopy, is not easily and readily accessible. Here, we delineate a method based on common visible light microscopy and ultraviolet–visible absorption spectroscopy to replace the X-ray measurements. To demonstrate the feasibility of this tec...}, number={12}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Peng, Zhengxing and Jiao, Xuechen and Ye, Long and Li, Sunsun and Rech, Jeromy James and You, Wei and Hou, Jianhui and Ade, Harald}, year={2018}, month={Jun}, pages={3943–3951} } @article{ye_collins_jiao_zhao_yan_ade_2018, title={Miscibility-Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation}, volume={8}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201703058}, DOI={10.1002/aenm.201703058}, abstractNote={AbstractPolymer solar cells (PSCs) continue to be a promising low‐cost and lead‐free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X‐ray microscopy method, the temperature dependences of “molecular miscibility” in the presence of fullerene crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high‐efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, an approach is outlined to convert liquidus miscibility to an effective Flory–Huggins interaction parameter χ. Crucially, determination of temperature‐dependent amorphous miscibility paves a way to rationally optimize the stability and mixing behaviors of PSCs at actual processing and operating temperatures.}, number={28}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Ye, Long and Collins, Brian A. and Jiao, Xuechen and Zhao, Jingbo and Yan, He and Ade, Harald}, year={2018}, month={Oct} } @article{chen_liu_hu_ma_lai_zhang_ade_yan_2018, title={Modulation of End Groups for Low-Bandgap Nonfullerene Acceptors Enabling High-Performance Organic Solar Cells}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201801203}, abstractNote={AbstractThe field of nonfullerene organic solar cells (OSCs) has seen an impressive progress, largely due to advances in high‐performance small molecule acceptors (SMAs). As a large portion of the solar energy is located in the near‐infrared region, it is important to develop ultralow‐bandgap SMAs that have extended absorption in the spectral range of 800–1000 nm to maximize light absorption and efficiencies. In this work, three low‐bandgap SMAs, namely, IXIC, IXIC‐2Cl, and IXIC‐4Cl, are designed and synthesized with same fused terthieno[3,2‐b]thiophene donor unit and different end groups (EGs). The three SMAs all have low optical bandgap (Eg) of 1.35, 1.30, and 1.25 eV, respectively. The chlorination on EGs can lower the energy level and broaden absorption range of the SMAs. As a result, the Voc of the devices is reduced but the Jsc is significantly increased. In addition, the addition of chlorine atoms can enhance π–π stacking and crystallinity of the SMAs, which result in high fill factors. Overall, the optimum EGs are monochlorine‐substituted IC and OSCs based on PBDB‐T:IXIC‐2Cl that can achieve remarkable power conversion efficiencies (PCEs) of 12.2%, which is one of the highest PCEs for nonfullerene organic solar cells based on low‐bandgap SMAs.}, number={27}, journal={ADVANCED ENERGY MATERIALS}, author={Chen, Yuzhong and Liu, Tao and Hu, Huawei and Ma, Tingxuan and Lai, Joshua Yuk Lin and Zhang, Jianquan and Ade, Harald and Yan, He}, year={2018}, month={Sep} } @article{suranagi_singh_kim_kim_ade_cho_2018, title={Molecular engineering of perylene-diimide-based polymer acceptors containing heteroacene units for all-polymer solar cells}, volume={58}, ISSN={["1878-5530"]}, DOI={10.1016/j.orgel.2018.02.015}, abstractNote={Polymer acceptors based on perylene diimide (PDI) with three symmetrical S-heteroacene backbone units of different sizes were synthesized for use in all-polymer solar cells (all-PSCs). The effects of varying the size of the heteroacene unit on the backbone of the PDI polymer are evident in the absorption spectra and their energy level offsets, which are correlated with their morphological and photovoltaic properties. These newly synthesized polymers were employed as acceptors with the polymer poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c]-[1,2,5]thiadiazole)] (PPDT2FBT) as the donor in all-PSCs that were found to exhibit modest power conversion efficiencies. The variations in photovoltaic properties of all-PSCs are investigated by characterizing the charge generation, carrier mobilities and recombination. The morphological disorder at the polymer/PPDT2FBT interface and average composition variations are revealed by using grazing incidence wide angle X-ray scattering (GIWAXS) and resonance soft X-ray scattering (R-SoXS) characterizations.}, journal={ORGANIC ELECTRONICS}, author={Suranagi, Sanjaykumar R. and Singh, Ranbir and Kim, Joo-Hyun and Kim, Min and Ade, Harald and Cho, Kilwon}, year={2018}, month={Jul}, pages={222–230} } @article{angunawela_ye_bin_zhang_gadisa_li_ade_2019, title={Multi-length scale morphology of nonfullerene all-small molecule blends and its relation to device function in organic solar cells}, volume={3}, ISSN={["2052-1537"]}, url={https://doi.org/10.1039/C8QM00503F}, DOI={10.1039/c8qm00503f}, abstractNote={Device characteristics of a pair of nonfullerene small molecule solar cells were well correlated to their mesoscale morphologyviaresonant soft X-ray scattering.}, number={1}, journal={MATERIALS CHEMISTRY FRONTIERS}, publisher={Royal Society of Chemistry (RSC)}, author={Angunawela, Indunil and Ye, Long and Bin, Haijun and Zhang, Zhi-Guo and Gadisa, Abay and Li, Yongfang and Ade, Harald}, year={2019}, month={Jan}, pages={137–144} } @article{ye_collins_jiao_zhao_yan_ade_2018, title={Polymer Solar Cells: Miscibility-Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation (Adv. Energy Mater. 28/2018)}, volume={8}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201870124}, DOI={10.1002/AENM.201870124}, abstractNote={In article number 1703058, Harald Ade and co-workers present the determination of liquidus miscibility and its temperature dependence of organic films by scanning transmission X-ray microscopy and outline an approach to convert liquidus miscibility to an effective Flory-Huggins interaction parameter χ, which will pave a way to predict morphology and processing strategies of polymer solar cells.}, number={28}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Ye, Long and Collins, Brian A. and Jiao, Xuechen and Zhao, Jingbo and Yan, He and Ade, Harald}, year={2018}, month={Oct}, pages={1870124} } @article{awartani_gautam_zhao_younts_hou_gundogdu_ade_2018, title={Polymer non-fullerene solar cells of vastly different efficiencies for minor side-chain modification: impact of charge transfer, carrier lifetime, morphology and mobility}, volume={6}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA01746D}, DOI={10.1039/c7ta01746d}, abstractNote={The performance of the 11.25% efficient PBDB-T : ITIC system degraded to 4.35% after a minor side-chain modification in PBDB-O : ITIC. In this study, the underlying reasons behind this vast difference in efficiencies are investigated.}, number={26}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Awartani, Omar M. and Gautam, Bhoj and Zhao, Wenchao and Younts, Robert and Hou, Jianhui and Gundogdu, Kenan and Ade, Harald}, year={2018}, month={Jul}, pages={12484–12492} } @article{ye_hu_ghasemi_wang_collins_kim_jiang_carpenter_li_li_et al._2018, title={Quantitative relations between interaction parameter, miscibility and function in organic solar cells}, volume={17}, ISSN={["1476-4660"]}, url={https://doi.org/10.1038/s41563-017-0005-1}, DOI={10.1038/s41563-017-0005-1}, abstractNote={Although it is known that molecular interactions govern morphology formation and purity of mixed domains of conjugated polymer donors and small-molecule acceptors, and thus largely control the achievable performance of organic solar cells, quantifying interaction-function relations has remained elusive. Here, we first determine the temperature-dependent effective amorphous-amorphous interaction parameter, χ aa (T), by mapping out the phase diagram of a model amorphous polymer:fullerene material system. We then establish a quantitative 'constant-kink-saturation' relation between χ aa and the fill factor in organic solar cells that is verified in detail in a model system and delineated across numerous high- and low-performing materials systems, including fullerene and non-fullerene acceptors. Our experimental and computational data reveal that a high fill factor is obtained only when χ aa is large enough to lead to strong phase separation. Our work outlines a basis for using various miscibility tests and future simulation methods that will significantly reduce or eliminate trial-and-error approaches to material synthesis and device fabrication of functional semiconducting blends and organic blends in general.}, number={3}, journal={NATURE MATERIALS}, publisher={Springer Nature}, author={Ye, Long and Hu, Huawei and Ghasemi, Masoud and Wang, Tonghui and Collins, Brian A. and Kim, Joo-Hyun and Jiang, Kui and Carpenter, Joshua H. and Li, Hong and Li, Zhengke and et al.}, year={2018}, month={Mar}, pages={253–260} } @article{ye_li_liu_zhang_ghasemi_xiong_hou_ade_2019, title={Quenching to the Percolation Threshold in Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, url={https://doi.org/10.1016/j.joule.2018.11.006}, DOI={10.1016/j.joule.2018.11.006}, abstractNote={The general lack of knowing the quench depth and the convolution with key kinetic factors has confounded deeper understanding of the respective importance of these factors in the morphology development of organic solar cells. Here, we determine the quench depth of a high-efficiency system and delineate the need to kinetically quench the mixed domains to a composition close to the percolation threshold. Importantly, the ability to achieve such a quench is very sensitive to structural parameters in polymer solar cells (PSCs) of the polymer PBDB-TF. Only the highest-molecular-weight polymer is able of earlier liquid-solid transition to “lock in” a high-performing PSC morphology with a composition above the miscibility limit and with an efficiency of over 13%. Systems with deep quench depths are therefore sensitive to molecular weight and the kinetic factors of the casting, likely impacting fabrication yield and reliability. They also need to be vitrified for stable performance.}, number={2}, journal={JOULE}, publisher={Elsevier BV}, author={Ye, Long and Li, Sunsun and Liu, Xiaoyu and Zhang, Shaoqing and Ghasemi, Masoud and Xiong, Yuan and Hou, Jianhui and Ade, Harald}, year={2019}, month={Feb}, pages={443–458} } @article{xiong_ye_gadisa_zhang_rech_you_ade_2018, title={Revealing the Impact of F4-TCNQ as Additive on Morphology and Performance of High-Efficiency Nonfullerene Organic Solar Cells}, volume={29}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201806262}, DOI={10.1002/adfm.201806262}, abstractNote={AbstractFluorinated molecule 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ) and its derivatives have been used in polymer:fullerene solar cells primarily as a dopant to optimize the electrical properties and device performance. However, the underlying mechanism and generality of how F4‐TCNQ affects device operation and possibly the morphology is poorly understood, particularly for emerging nonfullerene organic solar cells. In this work, the influence of F4‐TCNQ on the blend film morphology and photovoltaic performance of nonfullerene solar cells processed by a single halogen‐free solvent is systematically investigated using a set of morphological and electrical characterizations. In solar cells with a high‐performance polymer:small molecule blend FTAZ:IT‐M, F4‐TCNQ has a negligibly small effect on the molecular packing and surface characteristics, while it clearly affects the electronic properties and mean‐square composition variation of the bulk. In comparison to the control devices with an average power conversion efficiency (PCE) of 11.8%, inclusion of a trace amount of F4‐TCNQ in the active layer has improved device fill factor and current density, which has resulted into a PCE of 12.4%. Further increase in F4‐TCNQ content degrades device performance. This investigation aims at delineating the precise role of F4‐TCNQ in nonfullerene bulk heterojunction films, and thereby establishing a facile approach to fabricate highly optimized nonfullerene solar cells.}, number={1}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Xiong, Yuan and Ye, Long and Gadisa, Abay and Zhang, Qianqian and Rech, Jeromy James and You, Wei and Ade, Harald}, year={2018}, month={Nov}, pages={1806262} } @article{nevola_hoffman_bataller_ade_gundogdu_dougherty_2019, title={Rigid valence band shift due to molecular surface counter-doping of MoS2}, volume={679}, ISSN={["1879-2758"]}, DOI={10.1016/j.susc.2018.09.016}, abstractNote={Adsorption of the acceptor material tetracyanoquinodimethane can control optoelectronic properties of MoS2 by accepting defect generated excess negative charge from the surface that would otherwise interfere with radiative decay processes. Angle Resolved Photoelectron Spectroscopy measurements show that the MoS2 band structure near the Γ point shifts rigidly upward by ∼0.2 eV for a complete surface coverage of acceptor species as expected for an upward Fermi level shift due to charge transfer to the TCNQ. The molecular adsorbate orbitals visible in photoemission are indicative of an anionic species, consistent with interfacial charge transfer but without evidence for hybrid states arising from covalent adsorbate-surface interactions. Thus, our interface studies support the notion that molecular adsorbates are a useful tool for controlling optoelectronic functionality in 2D materials without fundamentally modifying their favorable band structures.}, journal={SURFACE SCIENCE}, author={Nevola, D. and Hoffman, B. C. and Bataller, A. and Ade, H. and Gundogdu, K. and Dougherty, D. B.}, year={2019}, month={Jan}, pages={254–258} } @article{sen_xiong_zhang_park_you_ade_kudenov_brendan t. o'connor_2018, title={Shear-Enhanced Transfer Printing of Conducting Polymer Thin Films}, volume={10}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.8b09968}, abstractNote={Polymer conductors that are solution-processable provide an opportunity to realize low-cost organic electronics. However, coating sequential layers can be hindered by poor surface wetting or dissolution of underlying layers. This has led to the use of transfer printing where solid film inks are transferred from a donor substrate to partially fabricated devices using a stamp. This approach typically requires favorable adhesion differences between the stamp, ink, and receiving substrate. Here, we present a shear-assisted organic printing (SHARP) technique that employs a shear load on a post-less polydimethylsiloxane (PDMS) elastomer stamp to print large-area polymer films that can overcome large unfavorable adhesion differences between the stamp and receiving substrate. We explore the limits of this process by transfer printing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films with varied formulation that tune the adhesive fracture energy. Using this platform, we show that the SHARP process is able to overcome a 10-fold unfavorable adhesion differential without the use of a patterned PDMS stamp, enabling large-area printing. The SHARP approach is then used to print PEDOT:PSS films in the fabrication of high-performance semitransparent organic solar cells.}, number={37}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Sen, Pratik and Xiong, Yuan and Zhang, Qanqian and Park, Sungjune and You, Wei and Ade, Harald and Kudenov, Michael W. and Brendan T. O'Connor}, year={2018}, month={Sep}, pages={31560–31567} } @article{ade_2018, title={Soft X-ray Microscopy: History, Status, and Future}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618005494}, DOI={10.1017/S1431927618005494}, abstractNote={Photon-in, photon-out X-ray microscopy traces its roots all the way back to Nobel Laureate Wilhelm Röntgen, who has as one of the first applications used X-rays in 1895-1897 to image the internal structures of various objects, one of the most famous being the hand of his wife (see Figure 1). Since then, X-ray microscopy has yielded many unique developments and blossomed into many specialized techniques.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Ade, Harald}, year={2018}, month={Aug}, pages={1000–1001} } @article{ye_xiong_zhang_li_wang_jiang_hou_you_ade_2018, title={Surpassing 10% Efficiency Benchmark for Nonfullerene Organic Solar Cells by Scalable Coating in Air from Single Nonhalogenated Solvent}, volume={30}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201705485}, DOI={10.1002/ADMA.201705485}, abstractNote={AbstractThe commercialization of nonfullerene organic solar cells (OSCs) critically relies on the response under typical operating conditions (for instance, temperature and humidity) and the ability of scale‐up. Despite the rapid increase in power conversion efficiency (PCE) of spin‐coated devices fabricated in a protective atmosphere, the efficiencies of printed nonfullerene OSC devices by blade coating are still lower than 6%. This slow progress significantly limits the practical printing of high‐performance nonfullerene OSCs. Here, a new and relatively stable nonfullerene combination is introduced by pairing the nonfluorinated acceptor IT‐M with the polymeric donor FTAZ. Over 12% efficiency can be achieved in spin‐coated FTAZ:IT‐M devices using a single halogen‐free solvent. More importantly, chlorine‐free, blade coating of FTAZ:IT‐M in air is able to yield a PCE of nearly 11% despite a humidity of ≈50%. X‐ray scattering results reveal that large π–π coherence length, high degree of face‐on orientation with respect to the substrate, and small domain spacing of ≈20 nm are closely correlated with such high device performance. The material system and approach yield the highest reported performance for nonfullerene OSC devices by a coating technique approximating scalable fabrication methods and hold great promise for the development of low‐cost, low‐toxicity, and high‐efficiency OSCs by high‐throughput production.}, number={8}, journal={Advanced Materials}, publisher={Wiley}, author={Ye, Long and Xiong, Yuan and Zhang, Qianqian and Li, Sunsun and Wang, Cheng and Jiang, Zhang and Hou, Jianhui and You, Wei and Ade, Harald}, year={2018}, month={Jan}, pages={1705485} } @article{ye_xiong_zhang_li_wang_jiang_hou_you_ade_2018, title={Surpassing 10% efficiency benchmark for nonfullerene organic solar cells by scalable coating in air from single nonhalogenated solvent}, volume={30}, DOI={10.1002/adma.201870054}, abstractNote={Realizing over 10% efficiency in printed organic solar cells via scalable materials and less toxic solvents remains a grand challenge. In article number 1705485, Harald Ade and co-workers report chlorine-free, in-air blade-coating of a new photoactive combination, FTAZ:IT-M, which is able to yield an efficiency of nearly 11%, despite a high humidity of ≈50%.}, number={8}, journal={Advanced Materials}, author={Ye, Long and Xiong, Y. and Zhang, Q. Q. and Li, S. S. and Wang, C. and Jiang, Z. and Hou, J. H. and You, W. and Ade, Harald}, year={2018} } @article{kim_schaefer_ma_zhao_turner_ghasemi_constantinou_so_yan_gadisa_et al._2019, title={The Critical Impact of Material and Process Compatibility on the Active Layer Morphology and Performance of Organic Ternary Solar Cells}, volume={9}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201802293}, DOI={10.1002/aenm.201802293}, abstractNote={AbstractAlthough ternary solar cells (TSCs) offer a cost‐effective prospect to expand the absorption bandwidth of organic solar cells, only few TSCs have succeeded in surpassing the performance of binary solar cells (BSCs) primarily due to the complicated morphology of the ternary blends. Here, the key factors that create and limit the morphology and performance of the TSCs are elucidated. The origin of morphology formation is explored and the role of kinetic factors is investigated. The results reveal that the morphology of TSC blends considered in this study are characterized with either a single length‐scale or two length‐scale features depending on the composition of the photoactive polymers in the blend. This asymmetric morphology development reveals that TSC blend morphology critically depends on material compatibility and polymer solubility. Most interestingly, the fill factor (FF) of TSCs is found to linearly correlate with the relative standard deviation of the fullerene distribution at small lengths. This is the first time that such a correlation has been shown for ternary systems. The criteria that uniform sized and highly pure amorphous domains are accomplished through the correct kinetic path to obtain a high FF for TSCs are specifically elucidated. The findings provide a critical insight for the precise design and processing of TSCs.}, number={2}, journal={ADVANCED ENERGY MATERIALS}, author={Kim, Joo-Hyun and Schaefer, Charley and Ma, Tingxuan and Zhao, Jingbo and Turner, Johnathan and Ghasemi, Masoud and Constantinou, Iordania and So, Franky and Yan, He and Gadisa, Abay and et al.}, year={2019}, month={Jan} } @article{gautam_younts_carpenter_ade_gundogdu_2018, title={The Role of FRET in Non-Fullerene Organic Solar Cells: Implications for Molecular Design}, volume={122}, ISSN={["1089-5639"]}, url={https://doi.org/10.1021/acs.jpca.7b12807}, DOI={10.1021/acs.jpca.7b12807}, abstractNote={Non-fullerene acceptors (NFAs) have been demonstrated to be promising candidates for highly efficient organic photovoltaic (OPV) devices. The tunability of absorption characteristics of NFAs can be used to make OPVs with complementary donor-acceptor absorption to cover a broad range of the solar spectrum. However, both charge transfer from donor to acceptor moieties and energy (energy) transfer from high-bandgap to low-bandgap materials are possible in such structures. Here, we show that when charge transfer and exciton transfer processes are both present, the coexistence of excitons in both domains can cause a loss mechanism. Charge separation of excitons in a low-bandgap material is hindered due to exciton population in the larger bandgap acceptor domains. Our results further show that excitons in low-bandgap material should have a relatively long lifetime compared to the transfer time of excitons from higher bandgap material in order to contribute to the charge separation. These observations provide significant guidance for design and development of new materials in OPV applications.}, number={15}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, publisher={American Chemical Society (ACS)}, author={Gautam, Bhoj R. and Younts, Robert and Carpenter, Joshua and Ade, Harald and Gundogdu, Kenan}, year={2018}, month={Apr}, pages={3764–3771} } @article{kelly_zhang_peng_noman_zhu_ade_you_2018, title={The finale of a trilogy: comparing terpolymers and ternary blends with structurally similar backbones for use in organic bulk heterojunction solar cells}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta05132a}, abstractNote={Comparing the efficiency of terpolymers vs. ternary blends, this study focuses on two polymers with structurally similar backbones (monoCNTAZ and FTAZ) yet markedly different open circuit voltages.}, number={39}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Kelly, Mary Allison and Zhang, Qianqian and Peng, Zhengxing and Noman, Victoria and Zhu, Chenhui and Ade, Harald and You, Wei}, year={2018}, month={Oct}, pages={19190–19200} } @article{bin_yang_zhang_ye_ghasem_chen_zhang_zhang_sun_xue_et al._2017, title={9.73% Efficiency Nonfullerene All Organic Small Molecule Solar Cells with Absorption-Complementary Donor and Acceptor}, volume={139}, ISSN={["0002-7863"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=MEDLINE&KeyUT=MEDLINE:28322045&KeyUID=MEDLINE:28322045}, DOI={10.1021/jacs.6b12826}, abstractNote={In the last two years, polymer solar cells (PSCs) developed quickly with n-type organic semiconductor (n-OSs) as acceptor. In contrast, the research progress of nonfullerene organic solar cells (OSCs) with organic small molecule as donor and the n-OS as acceptor lags behind. Here, we synthesized a D-A structured medium bandgap organic small molecule H11 with bithienyl-benzodithiophene (BDTT) as central donor unit and fluorobenzotriazole as acceptor unit, and achieved a power conversion efficiency (PCE) of 9.73% for the all organic small molecules OSCs with H11 as donor and a low bandgap n-OS IDIC as acceptor. A control molecule H12 without thiophene conjugated side chains on the BDT unit was also synthesized for investigating the effect of the thiophene conjugated side chains on the photovoltaic performance of the p-type organic semiconductors (p-OSs). Compared with H12, the 2D-conjugated H11 with thiophene conjugated side chains shows intense absorption, low-lying HOMO energy level, higher hole mobility and ordered bimodal crystallite packing in the blend films. Moreover, a larger interaction parameter (χ) was observed in the H11 blends calculated from Hansen solubility parameters and differential scanning calorimetry measurements. These special features combined with the complementary absorption of H11 donor and IDIC acceptor resulted in the best PCE of 9.73% for nonfullerene all small molecule OSCs up to date. Our results indicate that fluorobenzotriazole based 2D conjugated p-OSs are promising medium bandgap donors in the nonfullerene OSCs.}, number={14}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, publisher={American Chemical Society (ACS)}, author={Bin, Haijun and Yang, Yankang and Zhang, Zhi-Guo and Ye, Long and Ghasem, Masoud and Chen, Shanshan and Zhang, Yindong and Zhang, Chunfeng and Sun, Chenkai and Xue, Lingwei and et al.}, year={2017}, month={Apr}, pages={5085–5094} } @article{yao_li_hu_chow_chen_zhao_li_carpenter_lai_yang_et al._2018, title={A Facile Method to Fine-Tune Polymer Aggregation Properties and Blend Morphology of Polymer Solar Cells Using Donor Polymers with Randomly Distributed Alkyl Chains}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201701895}, abstractNote={AbstractThe device performance of polymer solar cells (PSCs) is strongly dependent on the blend morphology. One of the strategies for improving PSC performance is side‐chain engineering, which plays an important role in controlling the aggregation properties of the polymers and thus the domain crystallinity/purity of the donor–acceptor blends. In particular, for a family of high‐performance donor polymers with strong temperature‐dependent aggregation properties, the device performances are very sensitive to the size of alkyl chains, and the best device performance can only be achieved with an optimized odd‐numbered alkyl chain. However, the synthetic route of odd‐numbered alkyl chains is costly and complicated, which makes it difficult for large‐scale synthesis. Here, this study presents a facile method to optimize the aggregation properties and blend morphology by employing donor polymers with a mixture of two even‐numbered, randomly distributed alkyl chains. In a model polymer system, this study suggests that the structural and electronic properties of the random polymers comprising a mixture of 2‐octyldodecyl and 2‐decyltetradecyl alkyl chains can be systematically tuned by varying the mixing ratio, and a high power conversion efficiency (11.1%) can be achieved. This approach promotes the scalability of donor polymers and thus facilitates the commercialization of PSCs.}, number={6}, journal={ADVANCED ENERGY MATERIALS}, author={Yao, Huatong and Li, Yunke and Hu, Huawei and Chow, Philip C. Y. and Chen, Shangshang and Zhao, Jingbo and Li, Zhengke and Carpenter, Joshua H. and Lai, Joshua Yuk Lin and Yang, Guofang and et al.}, year={2018}, month={Feb} } @article{liu_ma_li_hu_ma_zhu_ade_yan_2017, title={A random donor polymer based on an asymmetric building block to tune the morphology of non-fullerene organic solar cells}, volume={5}, ISSN={["2050-7496"]}, DOI={10.1039/c7ta07830g}, abstractNote={The introduction of an asymmetric unit enables a fine-tuned morphology and thus up to 10.4% efficiency for non-fullerene organic solar cells.}, number={43}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Liu, Jing and Ma, Lik-Kuen and Li, Zhengke and Hu, Huawei and Ma, Tingxuan and Zhu, Chenhui and Ade, Harald and Yan, He}, year={2017}, month={Nov}, pages={22480–22488} } @article{zhong_ye_chen_jo_chueh_carpenter_ade_jen_2017, title={A regioregular conjugated polymer for high performance thick-film organic solar cells without processing additive}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA02391J}, DOI={10.1039/c7ta02391j}, abstractNote={Regioregular PTB7-Th with pre-designated repeat units achieves over 10% efficiency in thick-film solar cells without the assistance of a solvent additive.}, number={21}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Zhong, Hongliang and Ye, Long and Chen, Jung-Yao and Jo, Sae Byeok and Chueh, Chu-Chen and Carpenter, Joshua H. and Ade, Harald and Jen, Alex K. -Y.}, year={2017}, month={Jun}, pages={10517–10525} } @article{yao_ye_hou_jang_han_cui_su_wang_gao_yu_et al._2017, title={Achieving Highly Efficient Nonfullerene Organic Solar Cells with Improved Intermolecular Interaction and Open-Circuit Voltage}, volume={29}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201700254}, DOI={10.1002/ADMA.201700254}, abstractNote={A new acceptor–donor–acceptor‐structured nonfullerene acceptor ITCC (3,9‐bis(4‐(1,1‐dicyanomethylene)‐3‐methylene‐2‐oxo‐cyclopenta[b]thiophen)‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d′:2,3‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]‐dithiophene) is designed and synthesized via simple end‐group modification. ITCC shows improved electron‐transport properties and a high‐lying lowest unoccupied molecular orbital level. A power conversion efficiency of 11.4% with an impressive V OC of over 1 V is recorded in photovoltaic devices, suggesting that ITCC has great potential for applications in tandem organic solar cells.}, number={21}, journal={Advanced Materials}, publisher={Wiley}, author={Yao, Huifeng and Ye, Long and Hou, Junxian and Jang, Bomee and Han, Guangchao and Cui, Yong and Su, Gregory M. and Wang, Cheng and Gao, Bowei and Yu, Runnan and et al.}, year={2017}, month={Mar}, pages={1700254} } @article{roland_yan_zhang_jiao_hunt_ghasemi_ade_you_neher_2017, title={Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene}, volume={121}, ISSN={1932-7447 1932-7455}, url={http://dx.doi.org/10.1021/ACS.JPCC.7B02288}, DOI={10.1021/ACS.JPCC.7B02288}, abstractNote={Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene–C60 bisadduct (ICBA) has been regarded as a promising candidate, as it provides high open-circuit voltage in BHJ solar cells; however, the photovoltaic performance of such ICBA-based devices is often inferior when compared to cells with the omnipresent PCBM electron acceptor. Here, by pairing the high performance polymer (FTAZ) as the donor with either PCBM or ICBA as the acceptor, we explore the physical mechanism behind the reduced performance of the ICBA-based device. Time delayed collection field (TDCF) experiments reveal reduced, yet field-independent free charge generation in the FTAZ:ICBA system, explaining the overall lower photocurrent in its cells. Through the analysis of the photoluminescence, photogeneration, and electroluminescence, we find that the lower generation efficiency is neither caused by inefficient exciton splitting, nor ...}, number={19}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Roland, Steffen and Yan, Liang and Zhang, Qianqian and Jiao, Xuechen and Hunt, Adrian and Ghasemi, Masoud and Ade, Harald and You, Wei and Neher, Dieter}, year={2017}, month={May}, pages={10305–10316} } @article{ran_love_heiber_jiao_hughes_karki_wang_brus_wang_neher_et al._2018, title={Charge Generation and Recombination in an Organic Solar Cell with Low Energetic Offsets}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201701073}, abstractNote={AbstractOrganic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short‐circuit currents (JSC) and fill factors (FF). However, it is necessary to reduce the energetic offsets to achieve high open‐circuit voltages (VOC). Recently, reports have highlighted BHJ blends that are pushing at the accepted limits of energetic offsets necessary for high efficiency. Unfortunately, most of these BHJs have modest FF values. How the energetic offset impacts the solar cell characteristics thus remains poorly understood. Here, a comprehensive characterization of the losses in a polymer:fullerene BHJ blend, PIPCP:phenyl‐C61‐butyric acid methyl ester (PC61BM), that achieves a high VOC (0.9 V) with very low energy losses (Eloss = 0.52 eV) from the energy of absorbed photons, a respectable JSC (13 mA cm−2), but a limited FF (54%) is reported. Despite the low energetic offset, the system does not suffer from field‐dependent generation and instead it is characterized by very fast nongeminate recombination and the presence of shallow traps. The charge‐carrier losses are attributed to suboptimal morphology due to high miscibility between PIPCP and PC61BM. These results hold promise that given the appropriate morphology, the JSC, VOC, and FF can all be improved, even with very low energetic offsets.}, number={5}, journal={ADVANCED ENERGY MATERIALS}, author={Ran, Niva A. and Love, John A. and Heiber, Michael C. and Jiao, Xuechen and Hughes, Michael P. and Karki, Akchheta and Wang, Ming and Brus, Viktor V. and Wang, Hengbin and Neher, Dieter and et al.}, year={2018}, month={Feb} } @article{bauer_zhang_zhao_ye_kim_constantinou_yan_so_ade_yan_et al._2017, title={Comparing non-fullerene acceptors with fullerene in polymer solar cells: a case study with FTAZ and PyCNTAZ}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C6TA10450A}, DOI={10.1039/c6ta10450a}, abstractNote={Non-fullerene acceptors (NFAs) are becoming a serious contender to fullerene-based electron acceptors in organic photovoltaics, due to their structural versatility and easily tunable optical and electronic properties.}, number={10}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Bauer, Nicole and Zhang, Qianqian and Zhao, Jingbo and Ye, Long and Kim, Joo-Hyun and Constantinou, Iordania and Yan, Liang and So, Franky and Ade, Harald and Yan, He and et al.}, year={2017}, month={Mar}, pages={4886–4893} } @article{urquhart_martinson_eger_murcia_ade_collins_2017, title={Connecting Molecular Conformation to Aggregation in P3HT Using Near Edge X-ray Absorption Fine Structure Spectroscopy}, volume={121}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.7b07143}, abstractNote={Carbon 1s near edge X-ray absorption fine structure (NEXAFS) and UV–vis spectroscopy are used to examine differences between highly aggregated and poorly aggregated forms of the polymer poly(3-hexylthiophene) (P3HT), based on as-cast and annealed regiorandom and regioregular P3HT samples. UV–vis spectra show characteristic signatures of unaggregated P3HT in regiorandom P3HT, and of H-aggregation in regioregular P3HT samples. Distinct spectroscopic differences, including energy shifts, are observed in the NEXAFS spectra of aggregated P3HT relative to the unaggregated forms. These differences are reproduced with transition-potential density functional theory (TP-DFT) calculations which explore aggregation and molecular conformation. Differences in the NEXAFS spectra of P3HT are assigned to thiophene backbone twisting in the unaggregated forms of P3HT, and to various degrees of chain planarization in aggregated forms of P3HT that also correlate to the exciton bandwidth. These results open up the prospect of ...}, number={39}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Urquhart, Stephen G. and Martinson, Mercedes and Eger, Shaylin and Murcia, Victor and Ade, Harald and Collins, Brian A.}, year={2017}, month={Oct}, pages={21720–21728} } @article{du_jiao_rechberger_perea_meyer_kazerouni_spiecker_ade_brabec_fink_et al._2017, title={Crystallization of Sensitizers Controls Morphology and Performance in Si-/C-PCPDTBT-Sensitized P3HT:ICBA Ternary Blends}, volume={50}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b02699}, abstractNote={Organic solar cells based on multinary components are promising to further boost the device performance. The complex interplay of the morphology and functionality needs further investigations. Here, we report on a systematic study on the morphology evolution of prototype ternary systems upon adding sensitizers featuring similar chemical structures but dramatically different crystallinity, namely poly(3-hexylthiophene) (P3HT) and indene-C60-bis-adduct (ICBA) blends with poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadi-azole)-5,5′-diyl] (Si-PCPDTBT) and poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (C-PCPDTBT), employing energy-filtered transmission electron microscopy (EFTEM) and resonant soft X-ray scattering (RSoXS). In addition, a combined density functional theory (DFT) and artificial neuronal network (ANN) computational approach has been utilized to calculate the solubility paramet...}, number={6}, journal={MACROMOLECULES}, author={Du, Xiaoyan and Jiao, Xuechen and Rechberger, Stefanie and Perea, Jose Dario and Meyer, Markus and Kazerouni, Negar and Spiecker, Erdmann and Ade, Harald and Brabec, Christoph J. and Fink, Rainer H. and et al.}, year={2017}, month={Mar}, pages={2415–2423} } @article{li_ye_zhao_liu_zhu_ade_hou_2017, title={Design of a New Small‐Molecule Electron Acceptor Enables Efficient Polymer Solar Cells with High Fill Factor}, volume={29}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/ADMA.201704051}, DOI={10.1002/ADMA.201704051}, abstractNote={AbstractImproving the fill factor (FF) is known as a challenging issue in organic solar cells (OSCs). Herein, a strategy of extending the conjugated area of end‐group is proposed for the molecular design of acceptor–donor–acceptor (A–D–A)‐type small molecule acceptor (SMA), and an indaceno[1,2‐b:5,6‐b′]dithiophene‐based SMA, namely IDTN, by end‐capping with the naphthyl fused 2‐(3‐oxocyclopentylidene)malononitrile is synthesized. Benefiting from the π‐conjugation extension by fusing two phenyls, IDTN shows stronger molecular aggregation, more ordered packing structure, thus over one order of magnitude higher electron mobility relative to its counterpart. By utilizing the fluorinated polymer (PBDB‐TF) as the electron donor, the corresponding device exhibits a high efficiency of 12.2% with a record‐high FF of 0.78, which is approaching the theoretical limit of OSCs. Compared with the reference molecule, such a high FF in the IDTN system can be mainly attributed to the more ordered π–π packing of acceptor aggregates, higher domain purity and symmetric carrier transport in the blend. Hence, enlarging the conjugated area of the terminal‐group in these A–D–A‐type SMAs is a promising approach not only for enhancing the electron mobility, but also for improving the blend morphology, and both of them are conducive to the fill‐factor breakthrough.}, number={46}, journal={Advanced Materials}, publisher={Wiley}, author={Li, Sunsun and Ye, Long and Zhao, Wenchao and Liu, Xiaoyu and Zhu, Jie and Ade, Harald and Hou, Jianhui}, year={2017}, month={Oct}, pages={1704051} } @article{bauer_zhang_zhu_peng_yan_zhu_ade_zhan_you_2017, title={Donor polymer fluorination doubles the efficiency in non-fullerene organic photovoltaics}, volume={5}, ISSN={["2050-7496"]}, DOI={10.1039/c7ta07882j}, abstractNote={Donor polymer fluorination in ITIC-based device led to a large increase in the current and an efficiency twice that of the non-fluorinated polymer based device.}, number={43}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Bauer, Nicole and Zhang, Qianqian and Zhu, Jingshuai and Peng, Zhengxing and Yan, Long and Zhu, Chenhui and Ade, Harald and Zhan, Xiaowei and You, Wei}, year={2017}, month={Nov}, pages={22536–22541} } @article{bin_yang_peng_ye_yao_zhong_sun_gao_huang_li_et al._2017, title={Effect of Alkylsilyl Side-Chain Structure on Photovoltaic Properties of Conjugated Polymer Donors}, volume={8}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201702324}, DOI={10.1002/AENM.201702324}, abstractNote={AbstractSide‐chain engineering is an important strategy for optimizing photovoltaic properties of organic photovoltaic materials. In this work, the effect of alkylsilyl side‐chain structure on the photovoltaic properties of medium bandgap conjugated polymer donors is studied by synthesizing four new polymers J70, J72, J73, and J74 on the basis of highly efficient polymer donor J71 by changing alkyl substituents of the alkylsilyl side chains of the polymers. And the photovoltaic properties of the five polymers are studied by fabricating polymer solar cells (PSCs) with the polymers as donor and an n‐type organic semiconductor (n‐OS) m‐ITIC as acceptor. It is found that the shorter and linear alkylsilyl side chain could afford ordered molecular packing, stronger absorption coefficient, higher charge carrier mobility, thus results in higher Jsc and fill factor values in the corresponding PSCs. While the polymers with longer or branched alkyl substituents in the trialkylsilyl group show lower‐lying highest occupied molecular orbital energy levels which leads to higher Voc of the PSCs. The PSCs based on J70:m‐ITIC and J71:m‐ITIC achieve power conversion efficiency (PCE) of 11.62 and 12.05%, respectively, which are among the top values of the PSCs reported in the literatures so far.}, number={8}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Bin, Haijun and Yang, Yankang and Peng, Zhengxing and Ye, Long and Yao, Jia and Zhong, Lian and Sun, Chenkai and Gao, Liang and Huang, He and Li, Xiaojun and et al.}, year={2017}, month={Dec}, pages={1702324} } @article{zhang_yang_yan_kim_ade_wu_xu_duan_peng_2017, title={Efficient Nonfullerene Polymer Solar Cells Enabled by a Novel Wide Bandgap Small Molecular Acceptor}, volume={29}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201606054}, abstractNote={A wide bandgap small molecular acceptor, SFBRCN, containing a 3D spirobifluorene core flaked with a 2,1,3‐benzothiadiazole (BT) and end‐capped with highly electron‐deficient (3‐ethylhexyl‐4‐oxothiazolidine‐2‐yl)dimalononitrile (RCN) units, has been successfully synthesized as a small molecular acceptor (SMA) for nonfullerene polymer solar cells (PSCs). This SMA exhibits a relatively wide optical bandgap of 2.03 eV, which provides a complementary absorption to commonly used low bandgap donor polymers, such as PTB7‐Th. The strong electron‐deficient BT and RCN units afford SFBRCN with a low‐lying LUMO (lowest unoccupied molecular orbital) level, while the 3D structured spirobifluorene core can effectively suppress the self‐aggregation tendency of the SMA, thus yielding a polymer:SMA blend with reasonably small domain size. As the results of such molecular design, SFBRCN enables nonfullerene PSCs with a high efficiency of 10.26%, which is the highest performance reported to date for a large bandgap nonfullerene SMA.}, number={18}, journal={ADVANCED MATERIALS}, author={Zhang, Guangjun and Yang, Guofang and Yan, He and Kim, Joo-Hyun and Ade, Harald and Wu, Wenlin and Xu, Xiaopeng and Duan, Yuwei and Peng, Qiang}, year={2017}, month={May} } @article{zhao_ye_li_liu_zhang_zhang_ghasemi_he_ade_hou_et al._2017, title={Environmentally-friendly solvent processed fullerenefree organic solar cells enabled by screening halogen-free solvent additives}, volume={60}, ISSN={["2199-4501"]}, url={https://publons.com/wos-op/publon/5290953/}, DOI={10.1007/s40843-017-9080-x}, abstractNote={Though the power conversion efficiencies (PCEs) of organic solar cells (OSCs) have been boosted to 12%, the use of highly pollutive halogenated solvents as the processing solvent significantly hinders the mass production of OSCs. It is thus necessary to achieve high-efficiency OSCs by utilizing the halogen-free and environmentally-friendly solvents. Herein, we applied a halogen-free solvent system (oxylene/1-phenylnaphthalene, XY/PN) for fabricating fullerene-free OSCs, and a high PCE of 11.6% with a notable fill factor (FF) of 72% was achieved based on the PBDB-T:IT-M blend, which is among the top efficiencies of halogen-free solvent processed OSCs. In addition, the influence of different halogen-free solvent additives on the blend morphology and device performance metrics was studied by synchrotron-based tools and other complementary methods. Morphological results indicate the highly ordered molecular packing and highest average domain purity obtained in the blend films prepared by using XY/PN co-solvent are favorable for achieving increased FFs and thus higher PCEs in the devices. Moreover, a lower interaction parameter (χ) of the IT-M:PN pair provides a good explanation for the more favorable morphology and performance in devices with PN as the solvent additive, relative to those with diphenyl ether and N-methylpyrrolidone. Our study demonstrates that carefully screening the non-halogenated solvent additive plays a vital role in realizing the efficient and environmentally-friendly solvent processed OSCs.}, number={8}, journal={SCIENCE CHINA-MATERIALS}, author={Zhao, W. C. and Ye, Long and Li, S. S. and Liu, X. Y. and Zhang, S. Q. and Zhang, Y. and Ghasemi, M. and He, C. and Ade, H. and Hou, J. H. and et al.}, year={2017}, month={Aug}, pages={697–706} } @article{yu_chung_shewmon_ho_carpenter_larrabee_sun_jones_ade_o'connor_et al._2017, title={Flexible Inorganic Ferroelectric Thin Films for Nonvolatile Memory Devices}, volume={27}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201700461}, DOI={10.1002/ADFM.201700461}, abstractNote={Next‐generation wearable electronics call for flexible nonvolatile devices for ubiquitous data storage. Thus far, only organic ferroelectric materials have shown intrinsic flexibility and processability on plastic substrates. Here, it is shown that by controlling the heating rate, ferroelectric hafnia films can be grown on plastic substrates. The resulting highly flexible capacitor with a film thickness of 30 nm yields a remnant polarization of 10 µC cm−2. Bending tests show that the film ferroelectricity can be retained under a bending radius below 8 mm with up to 1000 bending cycles. The excellent flexibility is due to the extremely thin hafnia film thickness. Using the ferroelectric film as a gate insulator, a low voltage nonvolatile vertical organic transistor is demonstrated on a plastic substrate with an extrapolated date retention time of up to 10 years.}, number={21}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Yu, Hyeonggeun and Chung, Ching-Chang and Shewmon, Nate and Ho, Szuheng and Carpenter, Joshua H. and Larrabee, Ryan and Sun, Tianlei and Jones, Jacob L. and Ade, Harald and O'Connor, Brendan T. and et al.}, year={2017}, month={Apr}, pages={1700461} } @article{zhang_yan_jiao_peng_liu_rech_klump_ade_so_you_2017, title={Fluorinated Thiophene Units Improve Photovoltaic Device Performance of Donor–Acceptor Copolymers}, volume={29}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/ACS.CHEMMATER.7B01683}, DOI={10.1021/acs.chemmater.7b01683}, abstractNote={Fluorinated conjugated polymers leading to enhanced photovoltaic device performance has been widely observed in a variety of donor–acceptor copolymers; however, almost all these polymers have fluorine substituents on the acceptor unit. Building upon our previously reported PBnDT-FTAZ, a fluorinated donor–acceptor conjugated polymer with impressive device performance, we set this study to explore the effect of adding the fluorine substituents onto the flanking thiophene units between the donor unit (BnDT) and the acceptor unit (TAZ). We developed new synthetic approaches to control the position of the fluorination (3′ or 4′) on the thiophene unit, and synthesized four additional PBnDT-TAZ polymers incorporating the fluorine-substituted-thiophene (FT) units, 3′-FT-HTAZ, 4′-FT-HTAZ, 3′-FT-FTAZ, and 4′-FT-FTAZ. We discover that relocating the fluorine substituents from the acceptor to the flanking thiophene units have a negligible impact on the device characteristics (short circuit current, open circuit volta...}, number={14}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={Zhang, Qianqian and Yan, Liang and Jiao, Xuechen and Peng, Zhengxing and Liu, Shubin and Rech, Jeromy James and Klump, Erik and Ade, Harald and So, Franky and You, Wei}, year={2017}, month={Jul}, pages={5990–6002} } @article{min_gueldal_guo_fang_jiao_hu_heumueller_ade_brabec_2017, title={Gaining further insight into the effects of thermal annealing and solvent vapor annealing on time morphological development and degradation in small molecule solar cells}, volume={5}, ISSN={["2050-7496"]}, DOI={10.1039/c7ta04769j}, abstractNote={Morphology evolution mechanisms of thermal and solvent vapor annealing in small-molecule solar cells have been investigated systematically.}, number={34}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Min, Jie and Gueldal, Nusret S. and Guo, Jie and Fang, Chao and Jiao, Xuechen and Hu, Huawei and Heumueller, Thomas and Ade, Harald and Brabec, Christoph J.}, year={2017}, month={Sep}, pages={18101–18110} } @article{feng_yang_xu_zhang_yan_awartani_ye_ade_li_peng_et al._2018, title={High-Performance Wide Bandgap Copolymers Using an EDOT Modified Benzodithiophene Donor Block with 10.11% Efficiency}, volume={8}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/7528267/}, DOI={10.1002/aenm.201602773}, abstractNote={AbstractNewly developed benzo[1,2‐b:4,5‐b′]dithiophene (BDT) block with 3,4‐ethylenedioxythiophene (EDOT) side chains is first employed to build efficient photovoltaic copolymers. The resulting copolymers, PBDTEDOT‐BT and PBDTEDOTFBT, have a large bandgap more than 1.80 eV, which is attributed to the increased steric hindrance between the BDT and EDOT skeletons. Both copolymers possess the satisfied absorptions, low‐lying highest occupied molecular orbital (HOMO) levels and high crystallinity. Using the fluorination strategy, PBDTEDOT‐FBT exhibits a wider and stronger absorption and a deeper HOMO level than those of PBDTEDOT‐BT. PBDTEDOT‐FBT:[6,6]‐Phenyl C71 butyric acid methyl ester (PC71BM) blend also shows the higher hole mobility and better surface morphology compared with the PBDTEDOTBT:PC71BM blend. Combination of above advantages, PBDTEDOT‐FBT devices exhibit much higher power conversion efficiency (PCE) of 10.11%, with an improved open circuit voltage (Voc) of 0.86 V, short circuit current densities (Jsc) of 16.01 mA cm−2, and fill factor (FF) of 72.6%. This work not only provides a newly efficient candidate of BDT donor block modified with EDOT conjugated side chains, but also achieves high‐performance large bandgap copolymers for polymer solar cells (PSCs) via the synergistic effect of fluorination and side chain engineering strategies.}, number={6}, journal={ADVANCED ENERGY MATERIALS}, author={Feng, K. and Yang, G. F. and Xu, X. P. and Zhang, G. J. and Yan, H. and Awartani, O. and Ye, Long and Ade, H. and Li, Y. and Peng, Q. and et al.}, year={2018}, month={Feb} } @article{lee_giridhar_choi_kim_kim_kim_lee_cho_wang_ade_et al._2017, title={Importance of 2D Conjugated Side Chains of Benzodithiophene-Based Polymers in Controlling Polymer Packing, Interfacial Ordering, and Composition Variations of All-Polymer Solar Cells}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.7b03495}, abstractNote={We delineate the important role of 2D conjugated alkylthiophene side chains of polymers in manipulating the molecular orientation and ordering at the polymer donor/polymer acceptor (PD/PA) interface as well as the composition variations in the blend active layer of all-polymer solar cells (all-PSCs). To systematically investigate the impact of 2D conjugated side chains on the performance of all-PSCs, we synthesized a series of poly(benzo[1,2-b:4,5-b]-dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with different contents of alkoxy and alkylthiophene side chains, from 0 to 100% (PBDT-TPD (P1, 100% alkoxy side chain), PBDTT0.29-TPD (P2), PBDTT0.59-TPD (P3), PBDTT0.76-TPD (P4), and PBDTT-TPD (P5, 100% alkylthiophene side chain). The P1–P5 polymer donors produced similar PCEs of ∼6% in fullerene-based PSCs. In contrast, for the all-PSC systems, the changes in the side chain composition of the polymers induced a strong increasing trend in the power conversion efficiencies (PCEs), from 2.8...}, number={21}, journal={CHEMISTRY OF MATERIALS}, author={Lee, Changyeon and Giridhar, Thota and Choi, Joonhyeong and Kim, Seonha and Kim, Youngwoong and Kim, Taesu and Lee, Wonho and Cho, Han-Hee and Wang, Cheng and Ade, Harald and et al.}, year={2017}, month={Nov}, pages={9407–9415} } @article{guo_li_awartani_han_zhao_ade_yan_zhao_2017, title={Improved Performance of All-Polymer Solar Cells Enabled by Naphthodiperylenetetraimide-Based Polymer Acceptor}, volume={29}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201700309}, abstractNote={A new polymer acceptor, naphthodiperylenetetraimide‐vinylene (NDP‐V), featuring a backbone of altenating naphthodiperylenetetraimide and vinylene units is designed and applied in all‐polymer solar cells (all‐PSCs). With this polymer acceptor, a new record power‐conversion efficiencies (PCE) of 8.59% has been achieved for all‐PSCs. The design principle of NDP‐V is to reduce the conformational disorder in the backbone of a previously developed high‐performance acceptor, PDI‐V, a perylenediimide‐vinylene polymer. The chemical modifications result in favorable changes to the molecular packing behaviors of the acceptor and improved morphology of the donor–acceptor (PTB7‐Th:NDP‐V) blend, which is evidenced by the enhanced hole and electron transport abilities of the active layer. Moreover, the stronger absorption of NDP‐V in the shorter‐wavelength range offers a better complement to the donor. All these factors contribute to a short‐circuit current density (J sc) of 17.07 mA cm−2. With a fill factor (FF) of 0.67, an average PCE of 8.48% is obtained, representing the highest value thus far reported for all‐PSCs.}, number={26}, journal={ADVANCED MATERIALS}, author={Guo, Yikun and Li, Yunke and Awartani, Omar and Han, Han and Zhao, Jingbo and Ade, Harald and Yan, He and Zhao, Dahui}, year={2017}, month={Jul} } @article{hu_jiang_chow_ye_zhang_li_carpenter_ade_yan_2018, title={Influence of Donor Polymer on the Molecular Ordering of Small Molecular Acceptors in Nonfullerene Polymer Solar Cells}, volume={8}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/7528287/}, DOI={10.1002/aenm.201701674}, abstractNote={AbstractNonfullerene polymer solar cells (PSCs) based on polymer donors and nonfullerene small molecular acceptors (SMAs) have recently attracted considerable attention. Although much of the progress is driven by the development of novel SMAs, the donor polymer also plays an important role in achieving efficient nonfullerene PSCs. However, it is far from clear how the polymer donor choice influences the morphology and performance of the SMAs and the nonfullerene blends. In addition, it is challenging to carry out quantitative analysis of the morphology of polymer:SMA blends, due to the low material contrast and overlapping scattering features of the π–π stacking between the two organic components. Here, a series of nonfullerene blends is studied based on ITIC‐Th blended with five different donor polymers. Through quantitative morphology analysis, the (010) coherence length of the SMA is characterized and a positive correlation between the coherence length of the SMA and the device fill factor (FF) is established. The study reveals that the donor polymer can significantly change the molecular ordering of the SMA and thus improve the electron mobility and domain purity of the blend, which has an overall positive effect that leads to the enhanced device FF for nonfullerene PSCs.}, number={5}, journal={ADVANCED ENERGY MATERIALS}, author={Hu, Huawei and Jiang, Kui and Chow, Philip C. Y. and Ye, Long and Zhang, Guangye and Li, Zhengke and Carpenter, Joshua H. and Ade, Harald and Yan, He}, year={2018}, month={Feb} } @article{popescu_younts_hoffman_mcafee_dougherty_ade_gundogdu_bondarev_2017, title={Monitoring Charge Separation Processes in Quasi-One-Dimensional Organic Crystalline Structures}, volume={17}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/ACS.NANOLETT.7B02471}, DOI={10.1021/ACS.NANOLETT.7B02471}, abstractNote={We perform the transient absorption spectroscopy experiments to investigate the dynamics of the low-energy collective electron-hole excitations in α-copper phthalocyanine thin films. The results are interpreted in terms of the third-order nonlinear polarization response function. It is found that, initially excited in the molecular plane, the intramolecular Frenkel exciton polarization reorients with time to align along the molecular chain direction to form coupled Frenkel-charge-transfer exciton states, the eigenstates of the one-dimensional periodic molecular lattice. The process pinpoints the direction of the charge separation in α-copper phthalocyanine and similar organic molecular structures. Being able to observe and monitor such processes is important both for understanding the physical principles of organic thin film solar energy conversion device operation and for the development of organic optoelectronics in general.}, number={10}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Popescu, Adrian and Younts, Robert A. and Hoffman, Benjamin and McAfee, Terry and Dougherty, Daniel B. and Ade, Harald W. and Gundogdu, Kenan and Bondarev, Igor V.}, year={2017}, month={Sep}, pages={6056–6061} } @misc{mukherjee_herzing_zhao_wu_yu_ade_delongchamp_richter_2017, title={Morphological characterization of fullerene and fullerene-free organic photovoltaics by combined real and reciprocal space techniques}, volume={32}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2017.131}, abstractNote={Abstract}, number={10}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Mukherjee, Subhrangsu and Herzing, Andrew A. and Zhao, Donglin and Wu, Qinghe and Yu, Luping and Ade, Harald and DeLongchamp, Dean M. and Richter, Lee J.}, year={2017}, month={May}, pages={1921–1934} } @article{liu_ye_zhao_zhang_li_su_wang_ade_hou_2017, title={Morphology control enables thickness-insensitive efficient nonfullerene polymer solar cells}, volume={1}, ISSN={["2052-1537"]}, url={https://doi.org/10.1039/C7QM00182G}, DOI={10.1039/c7qm00182g}, abstractNote={Thermal annealing can be used to achieve thickness-insensitive non-fullerene polymer solar cells.}, number={10}, journal={MATERIALS CHEMISTRY FRONTIERS}, publisher={Royal Society of Chemistry (RSC)}, author={Liu, Xiaoyu and Ye, Long and Zhao, Wenchao and Zhang, Shaoqing and Li, Sunsun and Su, Gregory M. and Wang, Cheng and Ade, Harald and Hou, Jianhui}, year={2017}, month={Oct}, pages={2057–2064} } @article{jiang_zhang_yang_zhang_li_ma_hu_ma_ade_yan_2018, title={Multiple Cases of Efficient Nonfullerene Ternary Organic Solar Cells Enabled by an Effective Morphology Control Method}, volume={8}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201701370}, DOI={10.1002/aenm.201701370}, abstractNote={AbstractTernary organic solar cells (OSCs) have attracted much research attention, as they can maintain the simplicity of the single‐junction device architecture while broadening the absorption range of OSCs. However, one main challenge that limits the development of ternary OSCs is the difficulty in controlling the morphology of ternary OSCs. In this paper, an effective approach to control the morphology is presented that leads to multiple cases of efficient nonfullerene ternary OSCs with efficiencies of up to 11.2%. This approach is based on a donor polymer with strong temperature dependent aggregation properties processed from hot solutions without any solvent additives and a pair of small molecular acceptors (SMAs) that have similar surface tensions and thus low propensity to form discrete phases. Such a ternary blend exhibits a simplified bulk‐heterojunction morphology that is similar to the morphology of previously reported binary blends. As a result, an almost linear relationship between VOC and film composition is observed for all nonfullerene ternary devices. Meanwhile, by carefully designing a control system with a large interfacial tension, a different phase separation and VOC dependence is demonstrated. This morphology control approach can be applicable to more material systems and accelerates the development of the ternary OSC field.}, number={9}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Jiang, Kui and Zhang, Guangye and Yang, Guofang and Zhang, Jianquan and Li, Zhengke and Ma, Tingxuan and Hu, Huawei and Ma, Wei and Ade, Harald and Yan, He}, year={2018}, month={Mar} } @article{ghasemi_ye_zhang_yan_kim_awartani_you_gadisa_ade_2017, title={Polymer Solar Cells: Panchromatic Sequentially Cast Ternary Polymer Solar Cells (Adv. Mater. 4/2017)}, volume={29}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201770022}, DOI={10.1002/ADMA.201770022}, abstractNote={To increase the range of light absorption in polymer solar cells, two absorber donor polymers (blue and red, respectively) are utilized. In article 1604603, H. Ade and co-workers mix these polymers separately with a fullerene acceptor (grey) and process them using a new deposition strategy to create sequentially cast ternary (SeCaT) polymer solar cells that exhibit a bilayer structure without an interlayer.}, number={4}, journal={Advanced Materials}, publisher={Wiley}, author={Ghasemi, Masoud and Ye, Long and Zhang, Qianqian and Yan, Liang and Kim, Joo-Hyun and Awartani, Omar and You, Wei and Gadisa, Abay and Ade, Harald}, year={2017}, month={Jan} } @article{ye_xiong_li_ghasemi_balar_turner_gadisa_hou_o’connor_ade_et al._2017, title={Precise Manipulation of Multilength Scale Morphology and Its Influence on Eco-Friendly Printed All-Polymer Solar Cells}, volume={27}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201702016}, DOI={10.1002/adfm.201702016}, abstractNote={Significant efforts have lead to demonstrations of nonfullerene solar cells (NFSCs) with record power conversion efficiency up to ≈13% for polymer:small molecule blends and ≈9% for all‐polymer blends. However, the control of morphology in NFSCs based on polymer blends is very challenging and a key obstacle to pushing this technology to eventual commercialization. The relations between phases at various length scales and photovoltaic parameters of all‐polymer bulk‐heterojunctions remain poorly understood and seldom explored. Here, precise control over a multilength scale morphology and photovoltaic performance are demonstrated by simply altering the concentration of a green solvent additive used in blade‐coated films. Resonant soft X‐ray scattering is used to elucidate the multiphasic morphology of these printed all‐polymeric films and complements with the use of grazing incidence wide‐angle X‐ray scattering and in situ spectroscopic ellipsometry characterizations to correlate the morphology parameters at different length scales to the device performance metrics. Benefiting from the highest relative volume fraction of small domains, additive‐free solar cells show the best device performance, strengthening the advantage of single benign solvent approach. This study also highlights the importance of high volume fraction of smallest domains in printed NFSCs and organic solar cells in general.}, number={33}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Ye, Long and Xiong, Yuan and Li, Sunsun and Ghasemi, Masoud and Balar, Nrup and Turner, Johnathan and Gadisa, Abay and Hou, Jianhui and O’Connor, Brendan T. and Ade, Harald and et al.}, year={2017}, month={Jul}, pages={1702016} } @article{jiao_ye_ade_2017, title={Quantitative Morphology-Performance Correlations in Organic Solar Cells: Insights from Soft X-Ray Scattering}, volume={7}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.201700084}, DOI={10.1002/aenm.201700084}, abstractNote={Organic/polymer semiconductors provide unique possibilities and flexibility in tailoring their optoelectronic properties to match specific application demands. One of the key factors contributing to the rapid and continuous progress of organic photovoltaics (OPVs) is the control and optimization of photoactive‐layer morphology. The impact of morphology on photovoltaic parameters has been widely observed. However, the highly complex and multilength‐scale morphology often formed in efficient OPV devices consisting of compositionally similar components impose obstacles to conventional morphological characterizations. In contrast, due to the high compositional and orientational sensitivity, resonant soft X‐ray scattering (R‐SoXS), and related techniques lead to tremendous progress of characterization and comprehension regarding the complex mesoscale morphology in OPVs. R‐SoXS is capable of quantifying the domain characteristics, and polarized soft X‐ray scattering (P‐SoXS) provides quantitative information on orientational ordering. These morphological parameters strongly correlate the fill factor (FF), open‐circuit voltage (Voc), as well as short‐circuit current (Jsc) in a wider range of OPV devices, including recent record‐efficiency polymer:fullerene solar cells and 12%‐efficiency fullerene‐free OPVs. This progress report will delineate the soft X‐ray scattering methodology and its future challenges to characterize and understand functional organic materials and provide a non‐exhaustive overview of R‐SoXS characterization and its implication to date.}, number={18}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Jiao, Xuechen and Ye, Long and Ade, Harald}, year={2017}, month={Sep} } @article{zhang_li_huang_hu_zhang_ma_chow_ade_pan_yan_2017, title={Ring-Fusion of Perylene Diimide Acceptor Enabling Efficient Nonfullerene Organic Solar Cells with a Small Voltage Loss}, volume={139}, ISSN={["0002-7863"]}, DOI={10.1021/jacs.7b09998}, abstractNote={We report a novel small molecule acceptor (SMA) named FTTB-PDI4 obtained via ring-fusion between the thiophene and perylene diimide (PDI) units of a PDI-tetramer with a tetrathienylbezene (TTB) core. A small voltage loss of 0.53 V and a high power conversion efficiency of 10.58% were achieved, which is the highest value reported for PDI-based devices to date. By comparing the fused and nonfused SMAs, we show that the ring-fusion introduces several beneficial effects on the properties and performances of the acceptor material, including more favorable energy levels, enhanced light absorption and stronger intermolecular packing. Interestingly, morphology data reveal that the fused molecule yields higher domain purity and thus can better maintain its molecular packing and electron mobility in the blend. Theoretical calculations also demonstrate that FTTB-PDI4 exhibits a "double-decker" geometry with two pairs of mostly parallel PDI units, which is distinctively different from reported PDI-tetramers with highly twisted geometries and can explain the better performance of the material. This work highlights the promising design of PDI-based acceptors by the ring-fusion strategy.}, number={45}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Zhang, Jianquan and Li, Yunke and Huang, Jiachen and Hu, Huawei and Zhang, Guangye and Ma, Tingxuan and Chow, Philip C. Y. and Ade, Harald and Pan, Ding and Yan, He}, year={2017}, month={Nov}, pages={16092–16095} } @article{balar_xiong_ye_li_nevola_dougherty_hou_ade_o’connor_2017, title={Role of Polymer Segregation on the Mechanical Behavior of All-Polymer Solar Cell Active Layers}, volume={9}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/ACSAMI.7B13719}, DOI={10.1021/ACSAMI.7B13719}, abstractNote={An all-polymer bulk heterojunction (BHJ) active layer that removes the use of commonly used small molecule electron acceptors is a promising approach to improve the thermomechanical behavior of organic solar cells. However, there has been limited research on their mechanical properties. Here, we report on the mechanical behavior of high-performance blade-coated all-polymer BHJ films cast using eco-friendly solvents. The mechanical properties considered include the elastic modulus, crack onset strain, and cohesive fracture energy. We show that the mechanical behavior of the blend is largely unaffected by significant changes in the segregation characteristics of the polymers, which was varied systematically through solvent formulation. In comparison to a polymer:fullerene BHJ counterpart, the all-polymer films were found to have lower stiffness and increased ductility. Yet, the fracture energy of the all-polymer films is not significantly improved compared to that of the polymer:fullerene films. This study highlights that improved mechanical behavior of all-polymer systems cannot be assumed, and that details of the molecular structure, molecular weight, and film morphology play an important role in both the optoelectronic and mechanical properties. Furthermore, we show that simple composite modeling provides a predictive tool for the mechanical properties of the polymer blend films, providing a framework to guide future optimization of the mechanical behavior.}, number={50}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Balar, Nrup and Xiong, Yuan and Ye, Long and Li, Sunsun and Nevola, Daniel and Dougherty, Daniel B. and Hou, Jianhui and Ade, Harald and O’Connor, Brendan T.}, year={2017}, month={Dec}, pages={43886–43892} } @article{guo_li_awartani_han_zhang_ade_yan_zhao_2017, title={Side-chain engineering of perylenediimide-vinylene polymer acceptors for high-performance all-polymer solar cells}, volume={1}, ISSN={["2052-1537"]}, DOI={10.1039/c6qm00355a}, abstractNote={The performance of a PDI-vinylene polymer acceptor in an all-PSC is optimized by side-chain engineering. The best average PCE of 7.40% is obtained with a medium side-chain length.}, number={7}, journal={MATERIALS CHEMISTRY FRONTIERS}, author={Guo, Yikun and Li, Yunke and Awartani, Omar and Han, Han and Zhang, Guangye and Ade, Harald and Yan, He and Zhao, Dahui}, year={2017}, month={Jul}, pages={1362–1368} } @article{li_ye_zhao_zhang_ade_hou_2017, title={Significant Influence of the Methoxyl Substitution Position on Optoelectronic Properties and Molecular Packing of Small-Molecule Electron Acceptors for Photovoltaic Cells}, volume={7}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/5290958/}, DOI={10.1002/aenm.201700183}, abstractNote={Molecular engineering of nonfullerene electron acceptors is of great importance for the development of organic photovoltaics. In this study, a series of methoxyl‐modified dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐based small‐molecule acceptor (SMA) isomers are synthesized and characterized to determine the effect of substitution position of the terminal group in these acceptor–donor–acceptor‐type SMAs. Minor changes in the substitution position are demonstrated to greatly influence the optoelectronic properties and molecular packing of the isomers. Note that SMAs with planar molecular backbones show more ordered molecular packing and smaller π–π stacking distances, thus dramatically higher electron mobilities relative to their counterparts with distorted end‐groups. By utilizing polymer poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophen)‐co‐(1,3‐di(5‐thiophene‐2‐yl)‐5,7‐bis(2‐ethylhexyl)benzo[1,2‐c:4,5‐c′]dithiophene‐4,8‐dione)] (PBDB‐T) as an electron donor, an optimum power conversion efficiency (PCE) of 11.9% is achieved in the device based on PBDB‐T:IT‐OM‐2, which is among the top efficiencies reported as of yet. Moreover, the PCE stays above 10% as the film thickness increases to 250 nm, which is very advantageous for large‐area printing. Overall, the intrinsic molecular properties as well as the morphologies of blends can be effectively modulated by manipulating the substituent position on the terminal groups, and the structure–property relationships gleaned from this study will aid in designing more efficient SMAs for versatile applications.}, number={17}, journal={ADVANCED ENERGY MATERIALS}, author={Li, Sunsun and Ye, Long and Zhao, Wenchao and Zhang, Shaoqing and Ade, Harald and Hou, Jianhui}, year={2017}, month={Sep} } @article{kim_gadisa_schaefer_yao_gautam_balar_ghasemi_constantinou_so_o'connor_et al._2017, title={Strong polymer molecular weight-dependent material interactions: impact on the formation of the polymer/fullerene bulk heterojunction morphology}, volume={5}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/C7TA03052E}, DOI={10.1039/c7ta03052e}, abstractNote={The morphological evolution is initiated by L–L or L–S phase separation (left) and further developed by molecular mobility, governed by polymer–solvent interactions which determine the final domain size of the BHJ layer (right).}, number={25}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Kim, Joo-Hyun and Gadisa, Abay and Schaefer, Charley and Yao, Huifeng and Gautam, Bhoj R. and Balar, Nrup and Ghasemi, Masoud and Constantinou, Iordania and So, Franky and O'Connor, Brendan T. and et al.}, year={2017}, pages={13176–13188} } @article{chen_yao_li_awartani_liu_wang_yang_zhang_ade_yan_2017, title={Surprising Effects upon Inserting Benzene Units into a Quaterthiophene-Based D-A Polymer-Improving Non-Fullerene Organic Solar Cells via Donor Polymer Design}, volume={7}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201602304}, abstractNote={S. Chen, H. Yao, Z. Li, Y. Liu, Z. Wang, G. Yang, J. Zhang, Prof. H. Yan Department of Chemistry and Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction Hong Kong University of Science and Technology Clear Water Bay, Kowloon, Hong Kong E-mail: hyan@ust.hk S. Chen, H. Yao, Z. Li, Prof. H. Yan Hong Kong University of Science and Technology-Shenzhen Research Institute No. 9 Yuexing 1st RD, Hi-tech Park, Nanshan, Shenzhen 518057, P. R. China Dr. O. M. Awartani, Prof. H. Ade Department of Physics and Organic and Carbon Electronics Laboratory North Carolina State University Raleigh, NC 27695, USA E-mail: harald_ade@ncsu.edu Prof. H. Yan Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and Devices South China University of Technology Guangzhou 510640, P. R. China}, number={12}, journal={ADVANCED ENERGY MATERIALS}, author={Chen, Shangshang and Yao, Huatong and Li, Zhengke and Awartani, Omar M. and Liu, Yuhang and Wang, Zheng and Yang, Guofang and Zhang, Jianquan and Ade, Harald and Yan, He}, year={2017}, month={Jun} } @article{li_huang_bin_peng_zhu_xue_zhang_zhang_ade_li_2017, title={Synthesis and Photovoltaic Properties of a Series of Narrow Bandgap Organic Semiconductor Acceptors with Their Absorption Edge Reaching 900 nm}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.7b03928}, abstractNote={Three n-OS acceptors with Eg values of <1.4 eV were synthesized by introducing double-bond π-bridges into ITIC (ITVIC) and ITIC with monofluorine (ITVfIC) or bifluorine (ITVffIC) substituents on its end groups, and the structure–property relationships of the acceptors were systematically studied. The three n-OS films show broad absorption covering the wavelength range of 550–900 nm with narrow Eg values of 1.40 eV for ITVIC, 1.37 eV for ITVfIC, and 1.35 eV for ITVffIC. Additionally, the fluorine substitution downshifted the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the compounds. The photovoltaic properties of the n-OS acceptors were investigated by using a medium bandgap conjugated polymer J71 as a donor. The optimized polymer solar cells (PSCs) based on J71:ITVffIC demonstrated a power conversion efficiency (PCE) of 10.54% with a high Jsc of 20.60 mA cm–2 and a Voc of 0.81 V, and the highest Jsc reached 22.83 mA cm–2. The high Jsc values of...}, number={23}, journal={CHEMISTRY OF MATERIALS}, author={Li, Xiaojun and Huang, He and Bin, Haijun and Peng, Zhengxing and Zhu, Chenhui and Xue, Lingwei and Zhang, Zhi-Guo and Zhang, Zhanjun and Ade, Harald and Li, Yongfang}, year={2017}, month={Dec}, pages={10130–10138} } @article{di pietro_erdmann_carpenter_wang_shivhare_formanek_heintze_voit_neher_ade_et al._2017, title={Synthesis of High-Crystallinity DPP Polymers with Balanced Electron and Hole Mobility}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.7b04423}, abstractNote={We review the Stille coupling synthesis of P(DPP2OD-T) (Poly[[2,5-di(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-3,6-diyl]-alt-[2,2′:5′,2″-terthiophene-5,5″-diyl]]) and show that high-quality, high molecular weight polymer chains are already obtained after as little as 15 min of reaction time. The results of UV–vis spectroscopy, grazing incidence wide-angle X-ray scattering (GIWAXS), and atomic force microscopy show that longer reaction times are unnecessary and do not produce any improvement in film quality. We achieve the best charge transport properties with polymer batches obtained from short reaction times and demonstrate that the catalyst washing step is responsible for the introduction of charge-trapping sites for both holes and electrons. These trap sites decrease the charge injection efficiency, strongly reducing the measured currents. The careful tuning of the synthesis allows us to reduce the reaction time by more than 100 times, achieving a more environmentally friendly, less costly ...}, number={23}, journal={CHEMISTRY OF MATERIALS}, author={Di Pietro, Riccardo and Erdmann, Tim and Carpenter, Joshua H. and Wang, Naixiang and Shivhare, Rishi Ramdas and Formanek, Petr and Heintze, Cornelia and Voit, Brigitte and Neher, Dieter and Ade, Harald and et al.}, year={2017}, month={Dec}, pages={10220–10232} } @article{guo_li_awartani_zhao_han_ade_zhao_yan_2016, title={A Vinylene-Bridged Perylenediimide-Based Polymeric Acceptor Enabling Efficient All-Polymer Solar Cells Processed under Ambient Conditions}, volume={28}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201602387}, abstractNote={All-polymer solar cells with 7.57% power conversion efficiency are achieved via a new perylenediimide-based polymeric acceptor. Furthermore, the device processed in ambient air without encapsulation can still reach a high power conversion efficiency (PCE) of 7.49%, which is a significant economic advantage from an industrial processing perspective. These results represent the highest PCE achieved from perylenediimide-based polymers.}, number={38}, journal={ADVANCED MATERIALS}, author={Guo, Yikun and Li, Yunke and Awartani, Omar and Zhao, Jingbo and Han, Han and Ade, Harald and Zhao, Dahui and Yan, He}, year={2016}, month={Oct}, pages={8483–8489} } @article{mukherjee_jiao_ade_2016, title={Charge Creation and Recombination in Multi-Length Scale Polymer:Fullerene BHJ Solar Cell Morphologies}, volume={6}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201600699}, abstractNote={While the extremes in organic photovoltaic bulk heterojunction morphology (finely mixed or large pure domains) are easily understood and known to be unfavorable, efficient devices often exhibit a complex multi‐length scale, multi‐phase morphology. The impact of such multiple length scales and their respective purities and volume fractions on device performance remains unclear. Here, the average spatial composition variations, i.e., volume‐average purities, are quantified at multiple size scales to elucidate their effect on charge creation and recombination in a complex, multi‐length scale polymer:fullerene system (PBDTTPD:PC71BM). The apparent domain size as observed in TEM is not a causative parameter. Instead, a linear relationship is found between average purity at length scales <50 nm and device fill‐factor. Our findings show that a high volume fraction of pure phases at the smallest length scales is required in multi‐length scale systems to aid charge creation and diminish recombination in polymer:fullerene solar cells.}, number={18}, journal={ADVANCED ENERGY MATERIALS}, author={Mukherjee, Subhrangsu and Jiao, Xuechen and Ade, Harald}, year={2016}, month={Sep} } @article{gautam_younts_li_yan_danilov_klump_constantinou_so_you_ade_et al._2016, title={Charge photogeneration in organic photovoltaics: Role of hot versus cold charge-transfer excitons}, volume={6}, DOI={10.1002/aenm.201670002}, abstractNote={In article number 1501032, Kenan Gundogdu and co-workers present hot and cold exciton charge separation at the polymer/fullerene interface. On the left of the image high energy photons create excitons with excess energy. On the right of the image low energy photons create solely low energy charge transfer excitons. Both types separate into free charges effectively.}, number={1}, journal={Advanced Energy Materials}, author={Gautam, B. R. and Younts, R. and Li, W. T. and Yan, L. and Danilov, E. and Klump, E. and Constantinou, I. and So, Franky and You, W. and Ade, Harald and et al.}, year={2016} } @article{zhang_kelly_hunt_ade_you_2016, title={Comparative Photovoltaic Study of Physical Blending of Two Donor-Acceptor Polymers with the Chemical Blending of the Respective Moieties}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.5b02586}, abstractNote={A regularly alternating terpolymer and a random terpolymer were synthesized from the constituent units of two donor–acceptor polymers with complementary absorption. They were then compared to a physical blend of these two donor–acceptor polymers in order to investigate the best means of extending the light absorption range in bulk heterojunction (BHJ) solar cells. While all three methods broadened the light absorption, the physical blend provided the best improvement in power conversion efficiency (4.10% vs 3.63% and 2.67% for the random and regular terpolymers, respectively). This is due to the increase in aggregation in the physical blend, as demonstrated in the UV–vis spectra, which likely leads to higher local mobility and less recombination. This study shows that in order to effectively increase the light absorption (and therefore performance) of a polymer:fullerene based BHJ solar cell, a terpolymer must retain a structure which allows sufficient aggregation.}, number={7}, journal={MACROMOLECULES}, author={Zhang, Qianqian and Kelly, Mary Allison and Hunt, Adrian and Ade, Harald and You, Wei}, year={2016}, month={Apr}, pages={2533–2540} } @article{ye_jiao_zhang_yao_qin_ade_hou_2017, title={Control of Mesoscale Morphology and Photovoltaic Performance in Diketopyrrolopyrrole-Based Small Band Gap Terpolymers}, volume={7}, ISSN={["1614-6840"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85005777590&partnerID=MN8TOARS}, DOI={10.1002/aenm.201601138}, abstractNote={Morphology control is one of the key strategies in optimizing the performance of organic photovoltaic materials, particularly for diketopyrrolopyrrole (DPP)‐based donor polymers. The design of DPP‐based polymers that provide high power conversion efficiency (PCE) presents a significant challenge that requires optimization of both energetics and morphology. Herein, a series of high performance, small band gap DPP‐based terpolymers are designed via two‐step side chain engineering, namely introducing alternating short and long alkyls for reducing the domain spacing and inserting alkylthio for modulating the energy levels. The new DPP‐based terpolymers are compared to delineate how the side chain impacts the mesoscale morphology. By employing the alkylthio‐substituted terpolymer PBDPP‐TS, the new polymer solar cell (PSC) device realizes a good balance of a high Voc of 0.77 V and a high Jsc over 15 mA cm−2, and thus realizes desirable PCE in excess of 8% and 9.5% in single junction and tandem PSC devices, respectively. The study indicates better control of domain purity will greatly improve performance of single junction DPP‐based PSCs toward 10% efficiency. More significantly, the utility of this stepwise side chain engineering can be readily expanded to other classes of well‐defined copolymers and triggers efficiency breakthroughs in novel terpolymers for photovoltaic and related electronic applications.}, number={3}, journal={ADVANCED ENERGY MATERIALS}, author={Ye, Long and Jiao, Xuechen and Zhang, Shaoqing and Yao, Huifeng and Qin, Yunpeng and Ade, Harald and Hou, Jianhui}, year={2017}, month={Feb} } @article{gueldal_berlinghof_kassar_du_jiao_meyer_ameri_osvet_li_li destri_et al._2016, title={Controlling additive behavior to reveal an alternative morphology formation mechanism in polymer : fullerene bulk-heterojunctions}, volume={4}, ISSN={["2050-7496"]}, DOI={10.1039/c6ta07023j}, abstractNote={The high solubility of DPP-TT-T in 1,8-diiodooctane leads the microstructure formation towards thermodynamic equilibrium.}, number={41}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Gueldal, Nusret S. and Berlinghof, Marvin and Kassar, Thaer and Du, Xiaoyan and Jiao, Xuechen and Meyer, Markus and Ameri, Tayebeh and Osvet, Andres and Li, Ning and Li Destri, Giovanni and et al.}, year={2016}, pages={16136–16147} } @article{di pietro_nasrallah_carpenter_gann_koelln_thomsen_venkateshvaran_o'hara_sadhanala_chabinyc_et al._2016, title={Coulomb Enhanced Charge Transport in Semicrystalline Polymer Semiconductors}, volume={26}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201602080}, abstractNote={Polymer semiconductors provide unique possibilities and flexibility in tailoring their optoelectronic properties to match specific application demands. The recent development of semicrystalline polymers with strongly improved charge transport properties forces a review of the current understanding of the charge transport mechanisms and how they relate to the polymer's chemical and structural properties. Here, the charge density dependence of field effect mobility in semicrystalline polymer semiconductors is studied. A simultaneous increase in mobility and its charge density dependence, directly correlated to the increase in average crystallite size of the polymer film, is observed. Further evidence from charge accumulation spectroscopy shows that charges accumulate in the crystalline regions of the polymer film and that the increase in crystallite size affects the average electronic orbitals delocalization. These results clearly point to an effect that is not caused by energetic disorder. It is instead shown that the inclusion of short range coulomb repulsion between charge carriers on nanoscale crystalline domains allows describing the observed mobility dependence in agreement with the structural and optical characterization. The conclusions that are extracted extend beyond pure transistor characterization and can provide new insights into charge carrier transport for regimes and timescales that are relevant to other optoelectronic devices.}, number={44}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Di Pietro, Riccardo and Nasrallah, Iyad and Carpenter, Joshua and Gann, Eliot and Koelln, Lisa Sophie and Thomsen, Lars and Venkateshvaran, Deepak and O'Hara, Kathryn and Sadhanala, Aditya and Chabinyc, Michael and et al.}, year={2016}, month={Nov}, pages={8011–8022} } @article{gasparini_jiao_heumueller_baran_matt_fladischer_spiecker_ade_brabec_ameri_2016, title={Designing ternary blend bulk heterojunction solar cells with reduced carrier recombination and a fill factor of 77%}, volume={1}, ISSN={2058-7546}, url={http://dx.doi.org/10.1038/NENERGY.2016.118}, DOI={10.1038/NENERGY.2016.118}, number={9}, journal={Nature Energy}, publisher={Springer Science and Business Media LLC}, author={Gasparini, Nicola and Jiao, Xuechen and Heumueller, Thomas and Baran, Derya and Matt, Gebhard J. and Fladischer, Stefanie and Spiecker, Erdmann and Ade, Harald and Brabec, Christoph J. and Ameri, Tayebeh}, year={2016}, month={Aug} } @article{zheng_awartani_gautam_liu_qin_li_bataller_gundogdu_ade_hou_et al._2016, title={Efficient Charge Transfer and Fine-Tuned Energy Level Alignment in a THF-Processed Fullerene-Free Organic Solar Cell with 11.3% Efficiency}, volume={29}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/adma.201604241}, DOI={10.1002/adma.201604241}, abstractNote={Fullerene-free organic solar cells show over 11% power conversion efficiency, processed by low toxic solvents. The applied donor and acceptor in the bulk heterojunction exhibit almost the same highest occupied molecular orbital level, yet exhibit very efficient charge creation.}, number={5}, journal={Advanced Materials}, publisher={Wiley}, author={Zheng, Z. and Awartani, O. M. and Gautam, B. and Liu, D. L. and Qin, Y. P. and Li, W. N. and Bataller, Alexander and gundogdu and Ade, H. and Hou, J. H. and et al.}, year={2016}, month={Nov}, pages={1604241} } @article{zhao_li_yang_jiang_lin_ade_ma_yan_2016, title={Efficient organic solar cells processed from hydrocarbon solvents}, volume={1}, ISSN={2058-7546}, url={http://dx.doi.org/10.1038/nenergy.2015.27}, DOI={10.1038/nenergy.2015.27}, number={2}, journal={Nature Energy}, publisher={Springer Science and Business Media LLC}, author={Zhao, Jingbo and Li, Yunke and Yang, Guofang and Jiang, Kui and Lin, Haoran and Ade, Harald and Ma, Wei and Yan, He}, year={2016}, month={Jan} } @article{li_ye_zhao_zhang_mukherjee_ade_hou_2016, title={Energy-Level Modulation of Small-Molecule Electron Acceptors to Achieve over 12% Efficiency in Polymer Solar Cells}, volume={28}, ISSN={["1521-4095"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=MEDLINE&KeyUT=MEDLINE:27606970&KeyUID=MEDLINE:27606970}, DOI={10.1002/adma.201602776}, abstractNote={Fine energy-level modulations of small-molecule acceptors (SMAs) are realized via subtle chemical modifications on strong electron-withdrawing end-groups. The two new SMAs (IT-M and IT-DM) end-capped by methyl-modified dicycanovinylindan-1-one exhibit upshifted lowest unoccupied molecular orbital (LUMO) levels, and hence higher open-circuit voltages can be observed in the corresponding devices. Finally, a top power conversion efficiency of 12.05% is achieved.}, number={42}, journal={ADVANCED MATERIALS}, author={Li, Sunsun and Ye, Long and Zhao, Wenchao and Zhang, Shaoqing and Mukherjee, Subhrangsu and Ade, Harald and Hou, Jianhui}, year={2016}, month={Nov}, pages={9423-+} } @article{liu_chen_qian_gautam_yang_zhao_bergqvist_zhang_ma_ade_et al._2016, title={Fast charge separation in a non-fullerene organic solar cell with a small driving force}, volume={1}, ISSN={2058-7546}, url={http://dx.doi.org/10.1038/nenergy.2016.89}, DOI={10.1038/nenergy.2016.89}, number={7}, journal={Nature Energy}, publisher={Springer Science and Business Media LLC}, author={Liu, Jing and Chen, Shangshang and Qian, Deping and Gautam, Bhoj and Yang, Guofang and Zhao, Jingbo and Bergqvist, Jonas and Zhang, Fengling and Ma, Wei and Ade, Harald and et al.}, year={2016}, month={Jun} } @article{ye_xiong_yao_dinku_zhang_li_ghasemi_balar_hunt_o'connor_et al._2016, title={High Performance Organic Solar Cells Processed by Blade Coating in Air from a Benign Food Additive Solution}, volume={28}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/ACS.CHEMMATER.6B03083}, DOI={10.1021/acs.chemmater.6b03083}, abstractNote={Solution processable conjugated organic materials have gained tremendous interest motivated by their potential of low cost, lightweight and especially easy manufacturing of large-area and flexible electronics. Toxic halogen-containing solvents have been widely used in the processing of organic electronics, particularly organic photovoltaics (OPVs). To transition this technology to more commercially attractive manufacturing approaches, removing these halogenated solvents remains one of the key challenges. Our morphological (hard/soft X-ray scattering) and calorimetric characterizations reveal that using o-methylanisole, a certified food additive, as processing solvent can achieve similar crystalline properties and domain spacing/purity with that achieved by widely used binary halogenated solvents (chlorobenzene and 1,8-diiodooctane), thus yielding comparable photovoltaic performance in spin-casted films. To move a step forward, we further present the potential of o-methylanisole as processing solvent in th...}, number={20}, journal={Chemistry of Materials}, publisher={Link}, author={Ye, L. and Xiong, Y. and Yao, H. and Dinku, A.G. and Zhang, H. and Li, S. and Ghasemi, M. and Balar, N. and Hunt, A. and O'Connor, B.T. and et al.}, year={2016}, pages={7451–7458} } @article{min_jiao_sgobba_kan_heumueller_rechberger_spiecker_guldi_wan_chen_et al._2016, title={High efficiency and stability small molecule solar cells developed by bulk microstructure fine-tuning}, volume={28}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2016.08.047}, abstractNote={Morphological control over the bulk heterojunction (BHJ) microstructure of a high-efficiency small molecule photovoltaic system composed of a quinquethiophene based molecule (DRCN5T) as electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as electron acceptor is demonstrated using three different post-processing strategies, including thermal annealing (TA), solvent vapor annealing (SVA), and two-step annealing (TA-SVA) treatments. We systematically analyze the processing condition-microstructure-device property relationships, explore the corresponding morphology evolution and their effects on carrier transport and recombination dynamics in BHJs as well as understand the nature of phase-separation process resulting in light-induced degradation mechanisms. Within the investigated results, the causative relations between annealing sequence, photovoltaic parameters, morphology evolution and charge carrier dynamics are for the first time delineated. In addition, the observed trade-offs in device efficiency and stability with respect to the well-defined morphologies are highlighted. The in-depth picture of the bulk microstructure formation and its kinetic evolution as a function of the specific post-processing approaches is a valuable asset for the design of new photovoltaic materials and thin film nanoscale architectures that are more efficient and better aid future commercialization efforts.}, journal={NANO ENERGY}, author={Min, Jie and Jiao, Xuechen and Sgobba, Vito and Kan, Bin and Heumueller, Thomas and Rechberger, Stefanie and Spiecker, Erdmann and Guldi, Dirkm M. and Wan, Xiangjian and Chen, Yongsheng and et al.}, year={2016}, month={Oct}, pages={241–249} } @article{ye_zhao_li_mukherjee_carpenter_awartani_jiao_hou_ade_2017, title={High-Efficiency Nonfullerene Organic Solar Cells: Critical Factors that Affect Complex Multi-Length Scale Morphology and Device Performance}, volume={7}, ISSN={["1614-6840"]}, url={https://publons.com/wos-op/publon/5290907/}, DOI={10.1002/aenm.201602000}, abstractNote={Organic solar cells (OSCs) made of donor/acceptor bulk‐heterojunction active layers have been of widespread interest in converting sunlight to electricity. Characterizing of the complex morphology at multiple length scales of polymer:nonfullerene small molecular acceptor (SMA) systems remains largely unexplored. Through detailed characterizations (hard/soft X‐ray scattering) of the record‐efficiency polymer:SMA system with a close analog, quantitative morphological parameters are related to the device performance parameters and fundamental morphology–performance relationships that explain why additive use and thermal annealing are needed for optimized performance are established. A linear correlation between the average purity variations at small length scale (≈10 nm) and photovoltaic device characteristics across all processing protocols is observed in ≈12%‐efficiency polymer:SMA systems. In addition, molecular interactions as reflected by the estimated Flory–Huggins interaction parameters are used to provide context of the room temperature morphology results. Comparison with results from annealed devices suggests that the two SMA systems compared show upper and lower critical solution temperature behavior, respectively. The in‐depth understanding of the complex multilength scale nonfullerene OSC morphology may guide the device optimization and new materials development and indicates that thermodynamic properties of materials systems should be studied in more detail to aid in designing optimized protocols efficiently.}, number={7}, journal={ADVANCED ENERGY MATERIALS}, author={Ye, Long and Zhao, Wenchao and Li, Sunsun and Mukherjee, Subhrangsu and Carpenter, Joshua H. and Awartani, Omar and Jiao, Xuechen and Hou, Jianhui and Ade, Harald}, year={2017}, month={Apr} } @article{hu_jiang_kim_yang_li_ma_lu_qu_ade_yan_2016, title={Influence of fluorination on the properties and performance of isoindigo-quaterthiophene-based polymers}, volume={4}, ISSN={["2050-7496"]}, DOI={10.1039/c6ta00006a}, abstractNote={Isoindigo–quaterthiophene-based polymers are synthesized and compared to investigate the relationship between the fluorination position and photovoltaic properties.}, number={14}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Hu, Huawei and Jiang, Kui and Kim, Joo-Hyun and Yang, Guofang and Li, Zhengke and Ma, Tingxuan and Lu, Guanghao and Qu, Yongquan and Ade, Harald and Yan, He}, year={2016}, pages={5039–5043} } @article{hoffman_mcafee_conrad_loth_anthony_ade_dougherty_2016, title={Intrinsic Charge Trapping Observed as Surface Potential Variations in diF-TES-ADT Films}, volume={8}, ISSN={["1944-8244"]}, DOI={10.1021/acsami.6b03886}, abstractNote={Spatial variations in surface potential are measured with Kelvin probe force microscopy for thin films of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophenes (diF-TES-ADT) grown on SiO2 and silane-treated SiO2 substrates by organic molecular beam deposition. The variations are observed both between and within grains of the polycrystalline organic film and are quantitatively different than electrostatic variations on the substrate surfaces. The skewness of surface potential distributions is larger on SiO2 than on HMDS-treated substrates. This observation is attributed to the impact of substrate functionalization on minimizing intrinsic crystallographic defects in the organic film that can trap charge.}, number={33}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Hoffman, Benjamin C. and McAfee, Terry and Conrad, Brad R. and Loth, Marsha A. and Anthony, John E. and Ade, Harald W. and Dougherty, Daniel B.}, year={2016}, month={Aug}, pages={21490–21496} } @article{bondarev_popescu_younts_hoffman_mcafee_dougherty_gundogdu_ade_2016, title={Lowest energy Frenkel and charge transfer exciton intermixing in one-dimensional copper phthalocyanine molecular lattice}, volume={109}, ISSN={["1077-3118"]}, DOI={10.1063/1.4968821}, abstractNote={We report the results of the combined experimental and theoretical studies of the low-lying exciton states in crystalline copper phthalocyanine. We derive the eigen energy spectrum for the two lowest intramolecular Frenkel excitons coupled to the intermolecular charge transfer exciton state and compare it with temperature dependent optical absorption spectra measured experimentally, to obtain the parameters of the Frenkel-charge-transfer exciton intermixing. The two Frenkel exciton states are spaced apart by 0.26 eV, and the charge transfer exciton state is 50 meV above the lowest Frenkel exciton. Both Frenkel excitons are strongly mixed with the charge transfer exciton, showing the coupling constant 0.17 eV which agrees with earlier experimental measurements. These results can be used for the proper interpretation of the physical properties of crystalline phthalocyanines.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Bondarev, I. V. and Popescu, A. and Younts, R. A. and Hoffman, B. and McAfee, T. and Dougherty, D. B. and Gundogdu, K. and Ade, H. W.}, year={2016}, month={Nov} } @article{ye_jiao_zhao_zhang_yao_li_ade_hou_2016, title={Manipulation of Domain Purity and Orientational Ordering in High Performance All-Polymer Solar Cells}, volume={28}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000383318500021&KeyUID=WOS:000383318500021}, DOI={10.1021/acs.chemmater.6b02222}, abstractNote={All-polymer solar cells (All-PSCs) are of great interest as a renewable and economically viable energy technology, which has shown potential advantages in practical photovoltaic applications due to the highly tunable optical, electronic, and mechanical properties. A quantitative understanding of the domain composition variations and orientational ordering of all-polymeric films affected by solvent additives had been unattainable until now. This study demonstrates how the use of trace amount solvent additive can indeed manipulate domain purity and molecular orientational ordering as revealed by polarized soft X-ray scattering (P-SoXS). Additionally, the BDDT/PNDI all-polymeric blend exhibits enhanced average domain purity with the use of a trace amount of solvent additive and thus improved charge mobility, device fill factor and power conversion efficiency. A high power conversion efficiency of ∼7.1% was obtained in the All-PSC mainly contributed by this morphology control strategy. Manipulation of domain ...}, number={17}, journal={CHEMISTRY OF MATERIALS}, author={Ye, Long and Jiao, Xuechen and Zhao, Wenchao and Zhang, Shaoqing and Yao, Huifeng and Li, Sunsun and Ade, Harald and Hou, Jianhui}, year={2016}, month={Sep}, pages={6178–6185} } @article{mcafee_hoffman_you_atkin_ade_dougherty_2016, title={Morphological, Optical, and Electronic Consequences of Coexisting Crystal Orientations in beta-Copper Phthalocyanine Thin Films}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.6b05043}, abstractNote={The crystal structure of the β phase of copper phthalocyanine (CuPc) is a monoclinic herringbone, which is commonly created in thin films by either thermal annealing of α-CuPc at ∼300 °C or deposition on heated substrates. Of the several known CuPc crystal polymorphs, the β phase is of particular interest due to its thermodynamic stability. We observe three coexisting crystal orientations for thin films of β-CuPc to be (101), (105), and (502) using grazing incidence wide-angle X-ray scattering. Each of the three crystal orientations have distinct surface roughness, as measured by atomic force microscopy, but are electrostatically similar by Kelvin probe force microscopy. However, local optical properties, as measured by micro-UV–vis spectroscopy, are very different in the different domains.}, number={33}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={McAfee, Terry and Hoffman, Benjamin C. and You, Xiao and Atkin, Joanna M. and Ade, Harald and Dougherty, Daniel B.}, year={2016}, month={Aug}, pages={18616–18621} } @article{ro_downing_engmann_herzing_delongchamp_richter_mukherjee_ade_abdelsamie_jagadamma_et al._2016, title={Morphology changes upon scaling a high-efficiency, solution-processed solar cell}, volume={9}, ISSN={["1754-5706"]}, DOI={10.1039/c6ee01623e}, abstractNote={Optimized spin-coating and blade-coating are found to produce similar performance yet notably different morphologies.}, number={9}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Ro, Hyun Wook and Downing, Jonathan M. and Engmann, Sebastian and Herzing, Andrew A. and DeLongchamp, Dean M. and Richter, Lee J. and Mukherjee, Subhrangsu and Ade, Harald and Abdelsamie, Maged and Jagadamma, Lethy K. and et al.}, year={2016}, pages={2835–2846} } @article{ghasemi_ye_zhang_yan_kim_awartani_you_gadisa_ade_2017, title={Panchromatic Sequentially Cast Ternary Polymer Solar Cells}, volume={29}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201604603}, DOI={10.1002/adma.201604603}, abstractNote={A sequential-casting ternary method is developed to create stratified bulk heterojunction (BHJ) solar cells, in which the two BHJ layers are spin cast sequentially without the need of adopting a middle electrode and orthogonal solvents. This method is found to be particularly useful for polymers that form a mechanically alloyed morphology due to the high degree of miscibility in the blend.}, number={4}, journal={Advanced Materials}, publisher={Wiley}, author={Ghasemi, Masoud and Ye, Long and Zhang, Qianqian and Yan, Liang and Kim, Joo-Hyun and Awartani, Omar and You, Wei and Gadisa, Abay and Ade, Harald}, year={2017}, month={Jan}, pages={1604603} } @article{brady_ku_perez_cochran_schmidt_weiss_toney_ade_hexemer_wang_et al._2016, title={Role of Solution Structure in Self-Assembly of Conjugated Block Copolymer Thin Films}, volume={49}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.6b01686}, abstractNote={Conjugated block copolymers provide a pathway to achieve thermally stable nanostructured thin films for organic solar cells. We characterized the structural evolution of poly(3-hexylthiophene)-block-poly(diketopyrrolopyrrole–terthiophene) (P3HT-b-DPPT-T) from solution to nanostructured thin films. Aggregation of the DPPT-T block of P3HT-b-DPPT-T was found in solution by small-angle X-ray scattering with the P3HT block remaining well-solvated. The nanostructure in thin films was determined using a combination of wide and small-angle X-ray scattering techniques as a function of processing conditions. The structure in solution controlled the initial nanostructure in spin-cast thin films, allowing subsequent thermal annealing processes to further improve the ordering. In contrast to the results for thin films, nanostructural ordering was not observed in the bulk samples by small-angle X-ray scattering. These results suggest the importance of controlling solvent induced aggregation in forming nanostructured th...}, number={21}, journal={MACROMOLECULES}, author={Brady, Michael A. and Ku, Sung-Yu and Perez, Louis A. and Cochran, Justin E. and Schmidt, Kristin and Weiss, Thomas M. and Toney, Michael F. and Ade, Harald and Hexemer, Alexander and Wang, Cheng and et al.}, year={2016}, month={Nov}, pages={8187–8197} } @article{min_jiao_ata_osvet_ameri_baeuerle_ade_brabec_2016, title={Time-Dependent Morphology Evolution of Solution-Processed Small Molecule Solar Cells during Solvent Vapor Annealing}, volume={6}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201502579}, abstractNote={Morphological modification using solvent vapor annealing (SVA) provides a simple and widely used fabrication option for improving the power conversion efficiencies of solution‐processed bulk heterojunction (BHJ) small molecule solar cells. Previous reports on SVA have shown that this strategy influences the degree of donor/acceptor phase separation and also improves molecular donor ordering. A blend composed of a dithienopyrrole containing oligothiophene as donor (named UU07) and [6,6]‐phenyl‐C61‐butyric acid methyl ester as acceptor is investigated with respect to SVA treatment to explore the dynamics of the BHJ evolution as a function of annealing time. A systematic study of the time dependence of morphology evolution clarifies the fundamental mechanisms behind SVA and builds the structure–property relation to the related device performance. The following two‐stage mechanism is identified: Initially, as SVA time increases, donor crystallinity is improved, along with enhanced domain purity resulting in improved charge transport properties and reduced recombination losses. However, further extending SVA time results in domains that are too large and a few large donor crystallites, depleting donor component in the mixed domain. Moreover, the larger domain microstructure suffers from enhanced recombination and overall lower bulk mobility. This not only reveals the importance of precisely controlling SVA time on gaining morphological control, but also provides a path toward rational optimization of device performance.}, number={10}, journal={ADVANCED ENERGY MATERIALS}, author={Min, Jie and Jiao, Xuechen and Ata, Ibrahim and Osvet, Andres and Ameri, Tayebeh and Baeuerle, Peter and Ade, Harald and Brabec, Christoph J.}, year={2016}, month={May} } @article{ye_jiao_zhang_li_yao_ade_hou_2015, title={2D-Conjugated Benzodithiophene-Based Polymer Acceptor: Design, Synthesis, Nanomorphology, and Photovoltaic Performance}, volume={48}, ISSN={["1520-5835"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000362921500041&KeyUID=WOS:000362921500041}, DOI={10.1021/acs.macromol.5b01537}, abstractNote={All polymer photovoltaic cells offer unique potentials owing to the chemical and electronic tunability of both polymer donors and polymer acceptors. Compared with the numerous π-conjugated polymer donors, choices of π-conjugated polymer acceptors are limited for photovoltaic applications. Although 2D-conjugated benzo[1,2-b:4,5-b′]dithiophene (BDT) units are widely used as building blocks in highly efficient donor polymers in recent years, polymer acceptors based on these units have not been reported yet. Herein, a novel 2D-conjugated polymer acceptor (PBDTNDI-T) based on naphthalene diimide (NDI) and alkylthiothiophene-substituted BDT was designed, synthesized, and in-depth characterized. The polymers’ photophysical, electrical, crystallinity, and morphological properties are addressed in homopolymer and blend films and well correlated with device performance. Under the weight ratio of 1.5:1 and 3 vol % of 1-chloronaphthalene, the PBDTNDI-T-based all polymer photovoltaic device exhibited a desirable PCE o...}, number={19}, journal={MACROMOLECULES}, author={Ye, Long and Jiao, Xuechen and Zhang, Hao and Li, Sunsun and Yao, Huifeng and Ade, Harald and Hou, Jianhui}, year={2015}, month={Oct}, pages={7156–7163} } @article{zhao_li_hunt_zhang_yao_li_zhang_huang_ade_yan_2016, title={A Difluorobenzoxadiazole Building Block for Efficient Polymer Solar Cells}, volume={28}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201504611}, abstractNote={A difluorobenzoxadiazole building block is synthesized and utilized to construct a conjugated polymer leading to high-performance thick-film polymer solar cells with a V(OC) of 0.88 V and a power conversion efficiency of 9.4%. This new building block can be used in many possible polymer structures for various organic electro-nic applications.}, number={9}, journal={ADVANCED MATERIALS}, author={Zhao, Jingbo and Li, Yunke and Hunt, Adrian and Zhang, Jianquan and Yao, Huatong and Li, Zhengke and Zhang, Jie and Huang, Fei and Ade, Harald and Yan, He}, year={2016}, month={Mar}, pages={1868–1873} } @article{zhang_guo_ma_ade_hou_2015, title={A Large-Bandgap Conjugated Polymer for Versatile Photovoltaic Applications with High Performance}, volume={27}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201502110}, abstractNote={A new copolymer PM6 based on fluorothienyl-substituted benzodithiophene is synthesized and characterized. The inverted polymer solar cells based on PM6 exhibit excellent performance with Voc of 0.98 V and power conversion efficiency (PCE) of 9.2% for a thin-film thickness of 75 nm. Furthermore, the single-junction semitransparent device shows a high PCE of 5.7%.}, number={31}, journal={ADVANCED MATERIALS}, author={Zhang, Maojie and Guo, Xia and Ma, Wei and Ade, Harald and Hou, Jianhui}, year={2015}, month={Aug}, pages={4655–4660} } @article{zhu_xue_he_jiang_hu_bai_zhang_xiao_gundogdu_gautam_et al._2016, title={A PCBM Electron Transport Layer Containing Small Amounts of Dual Polymer Additives that Enables Enhanced Perovskite Solar Cell Performance}, volume={3}, ISSN={["2198-3844"]}, DOI={10.1002/advs.201500353}, abstractNote={A polymer/PCBM hybrid electron transport layer is reported that enables high‐performance perovskite solar cells with a high power conversion efficiency of 16.2% and with negligible hysteresis. Unlike previous approaches of reducing hysteresis by thermal annealing or fullerene passivation, the success of our approach can be mainly attributed to the doping of the PCBM layer using an insulating polymer (polystyrene) and an amine‐containing polymeric semiconductor named PFNOX.}, number={9}, journal={ADVANCED SCIENCE}, author={Zhu, Zonglong and Xue, Qifan and He, Hexiang and Jiang, Kui and Hu, Zhicheng and Bai, Yang and Zhang, Teng and Xiao, Shuang and Gundogdu, Kenan and Gautam, Bhoj Raj and et al.}, year={2016}, month={Sep} } @article{carpenter_hunt_ade_2015, title={Characterizing morphology in organic systems with resonant soft X-ray scattering}, volume={200}, ISSN={0368-2048}, url={http://dx.doi.org/10.1016/J.ELSPEC.2015.05.006}, DOI={10.1016/J.ELSPEC.2015.05.006}, abstractNote={Resonant soft X-ray scattering (R-SoXS) has proven to be a highly useful technique for studying the morphology of soft matter thin films due to the large intrinsic contrast between organic materials and the anisotropic nature of the resonant electronic state transitions from which the contrast originates. This allows R-SoXS users to measure spatial composition correlations from crystalline and amorphous phases in heterogeneous organic samples, infer relative domain purity, and determine average local molecular ordering correlations. R-SoXS has been used to study the morphology of organic photovoltaics, organic thin film transistors, biological systems, and block copolymer engineering applications. The mesoscopic morphological information compliments molecular packing information determined with hard X-rays, so that complex structure–property relationships can be elucidated over a large range of length scales. Extensions of R-SoXS have also emerged that make use of more advanced sample setups or different experimental geometries than normal transmission, such as θ–2θ reflectivity or grazing incidence.}, journal={Journal of Electron Spectroscopy and Related Phenomena}, publisher={Elsevier BV}, author={Carpenter, Joshua H. and Hunt, Adrian and Ade, Harald}, year={2015}, month={Apr}, pages={2–14} } @article{gautam_younts_li_yan_danilov_klump_constantinou_so_you_ade_et al._2015, title={Charge Photogeneration in Organic Photovoltaics: Role of Hot versus Cold Charge-Transfer Excitons}, volume={6}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201501032}, DOI={10.1002/AENM.201501032}, abstractNote={The role of excess excitation energy on long‐range charge separation in organic donor/acceptor bulk heterojunctions (BHJs) continues to be unclear. While ultrafast spectroscopy results argue for efficient charge separation through high‐energy charge‐transfer (CT) states within the first picosecond (ps) of excitation, charge collection measurements suggest excess photon energy does not increase the current density in BHJ devices. Here, the population dynamics of charge‐separated polarons upon excitation of high‐energy polymer states and low‐energy interfacial CT states in two polymer/fullerene blends from ps to nanosecond time scales are studied. It is observed that the charge‐separation dynamics do not show significant dependence on excitation energy. These results confirm that excess exciton energy is not necessary for the effective generation of charges.}, number={1}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Gautam, Bhoj R. and Younts, Robert and Li, Wentao and Yan, Liang and Danilov, Evgeny and Klump, Erik and Constantinou, Iordania and So, Franky and You, Wei and Ade, Harald and et al.}, year={2015}, month={Oct}, pages={1301032} } @article{gautam_barrette_mai_yan_zhang_danilov_you_ade_gundogdu_2015, title={Direct Optical Observation of Stimulated Emission from Hot Charge Transfer Excitons in Bulk Heterojunction Polymer Solar Cells}, volume={119}, ISSN={["1932-7447"]}, DOI={10.1021/acs.jpcc.5b06557}, abstractNote={Charge transfer excitons (CTEs) play an important role in semiconducting polymer-based optoelectronic applications. In organic photovoltaics, they are an intermediate step between tightly bound excitons and free charges. Although CT state energies at the interface of bulk heterojunction organic solar cells have been reported using quantum chemical calculations and by sensitive external quantum efficiency (EQE) measurements, direct optical observation of CT states was limited to relaxed, low energy, CT levels. Here we used polarization anisotropy transient absorption experiments to measure emission from high-energy CT levels. These experimental methods provide means to study high energy CT state dynamics in BHJs with controlled molecular orientations and complement theoretical calculations of interfacial CT state energies.}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Gautam, Bhoj R. and Barrette, Andy and Mai, Cong and Yan, Liang and Zhang, Qianqian and Danilov, Eygeny and You, Wei and Ade, Harald and Gundogdu, Kenan}, year={2015}, month={Aug}, pages={19697–19702} } @article{li_lin_jiang_carpenter_li_liu_hu_zhao_ma_ade_et al._2015, title={Dramatic performance enhancement for large bandgap thick-film polymer solar cells introduced by a difluorinated donor unit}, volume={15}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2015.05.016}, abstractNote={We report a large bandgap (1.9 eV) donor–acceptor copolymer (named PffT2-FTAZ) that enables polymer solar cells with a high power conversion efficiency of 7.8%. An important structural feature of the PffT2-FTAZ polymer is a difluorinated donor unit (3,3′-difluoro-2,2′-bithiophene, or, ffT2) that introduces several surprising and/or beneficial effects. By comparing PffT2-FTAZ with the analog polymer (PT2-FTAZ) without fluorination on the bithiophene donor unit, it is found that the ffT2 unit effectively lowers the HOMO and LUMO energy levels of the polymer and slightly reduces optical bandgap. It also introduces strong interchain aggregation for the polymer in solution, which leads to a highly crystalline polymer film and reasonably high hole transport mobility. On the other hand, the PffT2-FTAZ: fullerene blend still exhibits a reasonably small polymer domain size suitable for polymer solar cell operation. All these positive factors combined leads to dramatically enhanced performance for the polymer solar cells with the power conversion efficiency increasing from 2.8% for PT2-FTAZ to 7.8% for f PffT2-FTAZ. The high PSC performance of PffT2-FTAZ makes it a promising candidate for high efficiency tandem PSCs.}, journal={NANO ENERGY}, author={Li, Zhengke and Lin, Haoran and Jiang, Kui and Carpenter, Joshua and Li, Yunke and Liu, Yuhang and Hu, Huawei and Zhao, Jingbo and Ma, Wei and Ade, Harald and et al.}, year={2015}, month={Jul}, pages={607–615} } @article{mcafee_apperson_ade_dougherty_2016, title={Growth of thermally stable crystalline C60 films on flat-lying copper phthalocyanine}, volume={4}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/C5TA06820G}, DOI={10.1039/C5TA06820G}, abstractNote={We observe thermally stable growth of fcc(111) films of fullerene-C60 on top of crystalline, flat-lying, CuPc film structures on graphite using combined grazing incidence wide-angle X-ray scattering and atomic force microscopy.}, number={3}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={McAfee, Terry and Apperson, Aubrey and Ade, Harald and Dougherty, Daniel B.}, year={2016}, pages={1028–1032} } @article{lin_chen_li_lai_yang_mcafee_jiang_li_liu_hu_et al._2015, title={High-Performance Non-Fullerene Polymer Solar Cells Based on a Pair of Donor-Acceptor Materials with Complementary Absorption Properties}, volume={27}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201502775}, abstractNote={A 7.3% efficiency non-fullerene polymer solar cell is realized by combining a large-bandgap polymer PffT2-FTAZ-2DT with a small-bandgap acceptor IEIC. The complementary absorption of donor polymer and small-molecule acceptor is responsible for the high-performance of the solar-cell device. This work provides important guidance to improve the performance of non-fullerene polymer solar cells.}, number={45}, journal={ADVANCED MATERIALS}, author={Lin, Haoran and Chen, Shangshang and Li, Zhengke and Lai, Joshua Yuk Lin and Yang, Guofang and McAfee, Terry and Jiang, Kui and Li, Yunke and Liu, Yuhang and Hu, Huawei and et al.}, year={2015}, month={Dec}, pages={7299-+} } @article{huang_carpenter_li_yu_ade_jen_2016, title={Highly Efficient Organic Solar Cells with Improved Vertical Donor-Acceptor Compositional Gradient Via an Inverted Off-Center Spinning Method}, volume={28}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201504014}, abstractNote={A novel, yet simple solution fabrication technique to address the trade-off between photocurrent and fill factor in thick bulk heterojunction organic solar cells is described. The inverted off-center spinning technique promotes a vertical gradient of the donor-acceptor phase-separated morphology, enabling devices with near 100% internal quantum efficiency and a high power conversion efficiency of 10.95%.}, number={5}, journal={ADVANCED MATERIALS}, author={Huang, Jiang and Carpenter, Joshua H. and Li, Chang-Zhi and Yu, Jun-Sheng and Ade, Harald and Jen, Alex K. -Y.}, year={2016}, month={Feb}, pages={967–974} } @article{ma_yang_jiang_carpenter_wu_meng_mcafee_zhao_zhu_wang_et al._2015, title={Influence of Processing Parameters and Molecular Weight on the Morphology and Properties of High-Performance PffBT4T-2OD:PC71BM Organic Solar Cells}, volume={5}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201501400}, DOI={10.1002/AENM.201501400}, abstractNote={The influences of various processing parameters and polymer molecular weight on the morphology and properties of poly[(5,6‐difluoro‐2,1,3‐benzothiadiazol‐4,7‐diyl)‐alt‐(3,3′′′‐di(2‐octyldodecyl) 2,2′;5′,2″;5″,2′′′‐quaterthiophen‐5,5′′′‐diyl)] (PffBT4T‐2OD)‐based polymer solar cells (PSCs) are investigated. High spin rate/high temperature conditions are found to significantly reduce polymer crystallinity and change polymer backbone orientation from face‐on to edge‐on. Most surprisingly, it is found that the median domain sizes of PffBT4T‐2OD:PC71BM blends processed at different temperatures/spin rates are nearly identical, while the average domain purity and the molecular orientation relative to polymer:fullerene interfaces can be significantly changed by the processing conditions. A systematic study is carried out to identify the roles of individual processing parameters including processing temperature, spin rate, concentration, and solvent mixtures. Furthermore, the effect of molecular weight on morphology control is also examined. These detailed studies provide important guidance to control and optimize various morphological parameters and thus electrical properties of PffBT4T‐2OD‐type materials for the application in PSC.}, number={23}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Ma, Wei and Yang, Guofang and Jiang, Kui and Carpenter, Joshua H. and Wu, Yang and Meng, Xiangyi and McAfee, Terry and Zhao, Jingbo and Zhu, Chenhui and Wang, Cheng and et al.}, year={2015}, month={Sep}, pages={1501400} } @article{zhong_li_carpenter_ade_jen_2015, title={Influence of Regio- and Chemoselectivity on the Properties of Fluoro-Substituted Thienothiophene and Benzodithiophene Copolymers}, volume={137}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.5b04209}, abstractNote={By studying the regio- and chemoselectivity of fluoro-substituted thienothiophene and benzodithiophene copolymers, we found polymers made from conventional one-pot polycondensation reaction consist of two distinctly different segments with a ratio of 0.36/0.64. Through further comparative studies of neat regioregular polymers based on each individual segment, we have identified the specific segment that contributes to the superior absorption, packing order, and charge mobility in the corresponding polymers. The unique structure-property relationships are the result of cooperative molecular arrangements of the key segment and noncovalent interaction between the fluoro group and the aromatic proton on the thiophene side-chain of the polymers.}, number={24}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Zhong, Hongliang and Li, Chang-Zhi and Carpenter, Joshua and Ade, Harald and Jen, Alex K. -Y.}, year={2015}, month={Jun}, pages={7616–7619} } @article{ma_yang_jiang_carpenter_wu_meng_mcafee_zhao_zhu_wang_et al._2015, title={Influence of processing parameters and molecular weight on the morphology and properties of high-performance PffBT4T-2OD:PC71BM organic solar cells}, volume={5}, DOI={10.1002/aenm.201570126}, abstractNote={The detailed morphology of high efficiency polymer ( PffBT4T-2OD) based organic solar cells is investigated by Wei Ma, Harald Ade, He Yan and co-workers in article number 1501400. It is found that the median domain sizes of PffBT4T-2OD:PC71BM blends processed at different temperatures/ spin rates are nearly identical, while the average domain purity and the molecular orientation relative to polymer:fullerene interfaces can be significantly changed by the processing conditions.}, number={23}, journal={Advanced Energy Materials}, author={Ma, W. and Yang, G. F. and Jiang, K. and Carpenter, J. H. and Wu, Y. and Meng, X. Y. and McAfee, T. and Zhao, J. B. and Zhu, C. H. and Wang, C. and et al.}, year={2015} } @article{ye_jiao_zhou_zhang_yao_zhao_xia_ade_hou_2015, title={Manipulating Aggregation and Molecular Orientation in All-Polymer Photovoltaic Cells}, volume={27}, ISSN={["1521-4095"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=MEDLINE&KeyUT=MEDLINE:26315155&KeyUID=MEDLINE:26315155}, DOI={10.1002/adma.201503218}, abstractNote={Manipulating molecular orientation at the donor/acceptor interface is the key to boosting charge separation properties and efficiencies of anisotropic-materials-based organic photovoltaics (OPVs). By replacing the polymeric donor PBDTBDD with its 2D-conjugated polymer PBDTBDD-T, the power conversion efficiency of OPVs featuring the anisotropic polymer acceptor PNDI is drastically boosted from 2.4% up to 5.8%.}, number={39}, journal={ADVANCED MATERIALS}, author={Ye, Long and Jiao, Xuechen and Zhou, Meng and Zhang, Shaoqing and Yao, Huifeng and Zhao, Wenchao and Xia, Andong and Ade, Harald and Hou, Jianhui}, year={2015}, month={Oct}, pages={6046–6054} } @article{gann_collins_tang_tumbleston_mukherjee_ade_2016, title={Origins of polarization-dependent anisotropic X-ray scattering from organic thin films}, volume={23}, ISSN={["1600-5775"]}, DOI={10.1107/s1600577515019074}, abstractNote={Organic thin films that have no overall in-plane directional ordering often nonetheless produce anisotropic scattering patterns that rotate with the polarization of incident resonant X-rays. Isotropic symmetry is broken by local correlations between molecular orientation and domain structure. Such examples of molecular alignment at domain interfaces and within the bulk of domains, which are both critical to fields such as organic electronics, are simulated and compared with experimental scattering. Anisotropic scattering patterns are found to allow unambiguous identification of the mechanism of local molecular orientation correlations and, as such, promise to be both distinct and complementary to isotropic scattering intensity as a general measure of thin film microstructure.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Gann, Eliot and Collins, Brian A. and Tang, Maolong and Tumbleston, John R. and Mukherjee, Subrangsu and Ade, Harald}, year={2016}, month={Jan}, pages={219–227} } @article{zhong_wu_li_carpenter_chueh_chen_ade_jen_2016, title={Rigidifying Nonplanar Perylene Diimides by Ring Fusion Toward Geometry-Tunable Acceptors for High-Performance Fullerene-Free Solar Cells}, volume={28}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201504120}, abstractNote={Rigid fused perylene diimide (PDI) dimers bridged with heterocycles exhibit superior photovoltaic performance compared to their unfused semiflexible analogues. Changing the chalcogen atoms in the aromatic bridges gradually increases the twist angles between the two PDI planes, leading to a varied morphology in which the one bridged by thiophene achieves a balance and shows the best efficiency of 6.72%.}, number={5}, journal={ADVANCED MATERIALS}, author={Zhong, Hongliang and Wu, Chen-Hao and Li, Chang-Zhi and Carpenter, Joshua and Chueh, Chu-Chen and Chen, Jung-Yao and Ade, Harald and Jen, Alex K. -Y.}, year={2016}, month={Feb}, pages={951–958} } @article{mukherjee_proctor_bazan_nguyen_ade_2015, title={Significance of Average Domain Purity and Mixed Domains on the Photovoltaic Performance of High-Efficiency Solution-Processed Small-Molecule BHJ Solar Cells}, volume={5}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201500877}, DOI={10.1002/AENM.201500877}, abstractNote={Whereas the role of molecularly mixed domains in organic photovoltaic devices for charge generation is extensively discussed in the literature, the impact on charge recombination and thus fill factor is largely unexplored. Here, a combination of soft X‐ray techniques enables the quantification of phases at multiple length scales to reveal their role regarding charge recombination in a highly efficient solution processed small molecule system 7,7′‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(6‐fluoro‐4‐(5′‐hexyl‐[2,2′‐bithiophen]‐5‐yl)benzo[c][1,2,5]thiadiazole) (p‐DTS(FBTTh2)2) . A quantitative (linear) relationship between the average composition variations and the device fill‐factor is observed. The results establish the complex interrelationship between average phase purity, domain size, and structural order and highlight the requirement of achieving sufficient phase purities to diminish bimolecular and geminate recombination in solution processed small molecule solar cells.}, number={21}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Mukherjee, Subhrangsu and Proctor, Christopher M. and Bazan, Guillermo C. and Nguyen, Thuc-Quyen and Ade, Harald}, year={2015}, month={Jul}, pages={1500877} } @article{mukherjee_proctor_bazan_nguyen_ade_2015, title={Significance of average domain purity and mixed domains on the photovoltaic performance of high-efficiency solution-processed small-molecule bhj solar cells}, volume={5}, DOI={10.1002/aenm.201570111}, abstractNote={In article 1500877, Thuc-Quyen Nguyen, Harald Ade, and co-workers demonstrate the connection between device performance and morphological parameters in organic photovoltaics. The results demonstrate the complex correlation between domain purity, size, and molecular ordering, and highlight the requirement of achieving sufficient average phase purity of donor and acceptor domains to diminish charge recombination losses in solution-processed small-molecule bulk heterojunction solar cells.}, number={21}, journal={Advanced Energy Materials}, author={Mukherjee, S. and Proctor, C. M. and Bazan, G. C. and Nguyen, T. Q. and Ade, Harald}, year={2015} } @article{zhao_li_zhang_zhang_lai_jiang_mu_li_chan_hunt_et al._2015, title={The influence of spacer units on molecular properties and solar cell performance of non-fullerene acceptors}, volume={3}, ISSN={["2050-7496"]}, DOI={10.1039/c5ta05339k}, abstractNote={The position of methyl groups causes a dramatic change in molecular properties and solar cell performance.}, number={40}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Zhao, Jingbo and Li, Yunke and Zhang, Jianquan and Zhang, Lu and Lai, Joshua Yuk Lin and Jiang, Kui and Mu, Cheng and Li, Zhengke and Chan, Chun Lam Clement and Hunt, Adrian and et al.}, year={2015}, pages={20108–20112} } @article{ma_reinspach_zhou_diao_mcafee_mannsfeld_bao_ade_2015, title={Thin Films: Tuning Local Molecular Orientation-Composition Correlations in Binary Organic Thin Films by Solution Shearing (Adv. Funct. Mater. 21/2015)}, volume={25}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201570140}, DOI={10.1002/ADFM.201570140}, abstractNote={On page 3131, Z. Bao, H. Ade, and colleagues demonstrate that the solution shearing can control molecular orientation at donor/acceptor interface of BHJ organic solar cells with polarized soft X-ray scattering. This effect is further extended to binary organic blend in which one of the components forms fibrils or aggregates.}, number={21}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Ma, Wei and Reinspach, Julia and Zhou, Yan and Diao, Ying and McAfee, Terry and Mannsfeld, Stefan C. B. and Bao, Zhenan and Ade, Harald}, year={2015}, month={Jun}, pages={3106–3106} } @article{ma_reinspach_zhou_diao_mcafee_mannsfeld_bao_ade_2015, title={Tuning Local Molecular Orientation-Composition Correlations in Binary Organic Thin Films by Solution Shearing}, volume={25}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201500468}, abstractNote={A general impact of solution shearing on molecular orientation correlation is observed in polymer:fullerene organic solar cells in which one of the components forms fibrils or aggregates. Further investigation with polarized soft X‐ray scattering reveals that solution shearing induces more face‐to‐face orientation relative to the interface of two components compared to spin‐coating. This impact is shearing speed dependent, that is, slow shearing speed can induce more face‐to‐face orientation than a fast shearing speed. These results demonstrate that solution shearing is an effective method to control the relative molecular orientation. Solution shearing can also modify the domain size and average composition variations.}, number={21}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Ma, Wei and Reinspach, Julia and Zhou, Yan and Diao, Ying and McAfee, Terry and Mannsfeld, Stefan C. B. and Bao, Zhenan and Ade, Harald}, year={2015}, month={Jun}, pages={3131–3137} } @article{kitchen_awartani_kline_mcafee_ade_brendan t. o'connor_2015, title={Tuning Open-Circuit Voltage in Organic Solar Cells with Molecular Orientation}, volume={7}, ISSN={["1944-8244"]}, DOI={10.1021/am508855s}, abstractNote={The role of molecular orientation of a polar conjugated polymer in polymer-fullerene organic photovoltaic (OPV) cells is investigated. A planar heterojunction (PHJ) OPV cell composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is used as a model system to isolate the effect of the interfacial orientation on the photovoltaic properties. The molecular orientation of the aggregate P3HT relative to the PCBM layer is varied from highly edge-on (conjugated ring plane perpendicular to the interface plane) to appreciably face-on (ring plane parallel to the interface). It is found that as the P3HT stacking becomes more face-on there is a positive correlation to the OPV open-circuit voltage (V(OC)), attributed to a shift in the highest occupied molecular orbital (HOMO) energy level of P3HT. In addition, the PHJ OPV cell with a broad P3HT stacking orientation distribution has a V(OC) comparable to an archetypal bulk heterojunction (BHJ) device. These results suggest that, in the BHJ OPV cell, the hole energy level in the charge transfer state is defined in part by the orientation distribution of the P3HT at the interface with PCBM. Finally, the photoresponses of the devices are also shown to have a dependence on P3HT stacking orientation.}, number={24}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Kitchen, Brent and Awartani, Omar and Kline, R. Joseph and McAfee, Terry and Ade, Harald and Brendan T. O'Connor}, year={2015}, month={Jun}, pages={13208–13216} } @article{zhang_guo_ma_ade_hou_2014, title={A Polythiophene Derivative with Superior Properties for Practical Application in Polymer Solar Cells}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201401494}, abstractNote={A polythiophene derivative called PDCBT, which has a backbone of thiophene units and just carboxylate functional groups to modulate its properties, exhibits properties superior to those of poly(3-hexylthiophene), the classic polythiophene derivative, when used as an electron donor in polymer solar cells (PSCs). The best device, based on PDCBT/PC71BM (1:1), develops a good power conversion efficiency of 7.2%.}, number={33}, journal={ADVANCED MATERIALS}, author={Zhang, Maojie and Guo, Xia and Ma, Wei and Ade, Harald and Hou, Jianhui}, year={2014}, month={Sep}, pages={5880–5885} } @article{liu_zhao_li_mu_ma_hu_jiang_lin_ade_yan_2014, title={Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells}, volume={5}, ISSN={["2041-1723"]}, DOI={10.1038/ncomms6293}, abstractNote={AbstractAlthough the field of polymer solar cell has seen much progress in device performance in the past few years, several limitations are holding back its further development. For instance, current high-efficiency (>9.0%) cells are restricted to material combinations that are based on limited donor polymers and only one specific fullerene acceptor. Here we report the achievement of high-performance (efficiencies up to 10.8%, fill factors up to 77%) thick-film polymer solar cells for multiple polymer:fullerene combinations via the formation of a near-ideal polymer:fullerene morphology that contains highly crystalline yet reasonably small polymer domains. This morphology is controlled by the temperature-dependent aggregation behaviour of the donor polymers and is insensitive to the choice of fullerenes. The uncovered aggregation and design rules yield three high-efficiency (>10%) donor polymers and will allow further synthetic advances and matching of both the polymer and fullerene materials, potentially leading to significantly improved performance and increased design flexibility.}, journal={NATURE COMMUNICATIONS}, author={Liu, Yuhang and Zhao, Jingbo and Li, Zhengke and Mu, Cheng and Ma, Wei and Hu, Huawei and Jiang, Kui and Lin, Haoran and Ade, Harald and Yan, He}, year={2014}, month={Nov} } @article{li_yang_tumbleston_yan_ade_you_2014, title={Controlling Molecular Weight of a High Efficiency Donor-Acceptor Conjugated Polymer and Understanding Its Significant Impact on Photovoltaic Properties}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201305251}, abstractNote={The molecular weight (MW) of PBnDT-FTAZ can be precisely controlled by adjusting the stoichiometric ratio of the two monomers, following the Carothers equation. The study of a set of PBnDT-FTAZ polymers with different MWs reveals that the MW significantly influences the morphology and structural order of PBnDTFTAZ in its bulk heterojunction solar cells, with the highest efficiency (over 7%) achieved with the use of a MW of 40 000 g mol(-1) .}, number={26}, journal={ADVANCED MATERIALS}, author={Li, Wentao and Yang, Liqiang and Tumbleston, John R. and Yan, Liang and Ade, Harald and You, Wei}, year={2014}, month={Jul}, pages={4456-+} } @article{schubert_collins_mangold_howard_schindler_vandewal_roland_behrends_kraffert_steyrleuthner_et al._2014, title={Correlated Donor/Acceptor Crystal Orientation Controls Photocurrent Generation in All-Polymer Solar Cells}, volume={24}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/ADFM.201304216}, DOI={10.1002/ADFM.201304216}, abstractNote={New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all‐polymer solar cells have struggled to keep up with the steadily increasing power conversion efficiency of polymer:fullerene cells. The lack of knowledge about the dominant recombination process as well as the missing concluding picture on the role of the semi‐crystalline microstructure of conjugated polymers in the free charge carrier generation process impede a systematic optimization of all‐polymer solar cells. These issues are examined by combining structural and photo‐physical characterization on a series of poly(3‐hexylthiophene) (donor) and P(NDI2OD‐T2) (acceptor) blend devices. These experiments reveal that geminate recombination is the major loss channel for photo‐excited charge carriers. Advanced X‐ray and electron‐based studies reveal the effect of chloronaphthalene co‐solvent in reducing domain size, altering domain purity, and reorienting the acceptor polymer crystals to be coincident with those of the donor. This reorientation correlates well with the increased photocurrent from these devices. Thus, efficient split‐up of geminate pairs at polymer/polymer interfaces may necessitate correlated donor/acceptor crystal orientation, which represents an additional requirement compared to the isotropic fullerene acceptors.}, number={26}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Schubert, Marcel and Collins, Brian A. and Mangold, Hannah and Howard, Ian A. and Schindler, Wolfram and Vandewal, Koen and Roland, Steffen and Behrends, Jan and Kraffert, Felix and Steyrleuthner, Robert and et al.}, year={2014}, month={Apr}, pages={4068–4081} } @article{huston_wang_mcafee_loth_anthony_ade_conrad_dougherty_2015, title={Disruption of Molecular Ordering over Several Layers near the Au/2,8-Difluoro-5,11-bis(triethylsilylethynyl) Anthradithiophene Interface}, volume={15}, ISSN={["1528-7505"]}, DOI={10.1021/cg501621k}, abstractNote={The transition from an electrode-dominated ordered monolayer structure to a bulk-like thin film crystal structure of 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT) is observed to occur over at least the first four molecular layers near the electrode surface. Scanning tunneling microscopy studies of the growth of diF-TES-ADT on Au(111) show that the first two molecular layers assemble with aromatic planes parallel to the substrate surface. The monolayer structures are highly stable and well-ordered, while the bilayer structures are more loosely packed and poorly ordered. Subsequent diF-TES-ADT growth results in a more bulk-like layer containing standing up molecular configurations approaching the (001) crystal face as observed by grazing incidence wide angle X-ray scattering measurements. However, the third and fourth monolayers also show poor long-range ordering and an apparent height modulation that indicate significant strain effects from the substrate still persist.}, number={2}, journal={CRYSTAL GROWTH & DESIGN}, author={Huston, Shawn M. and Wang, Jiuyang and McAfee, Terry and Loth, Marsha and Anthony, John E. and Ade, Harald W. and Conrad, Brad R. and Dougherty, Daniel B.}, year={2015}, month={Feb}, pages={822–828} } @article{guo_zhang_ma_ye_zhang_liu_ade_huang_hou_2014, title={Enhanced Photovoltaic Performance by Modulating Surface Composition in Bulk Heterojunction Polymer Solar Cells Based on PBDTTT-C-T/PC71BM}, volume={26}, ISSN={["1521-4095"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903160839&partnerID=MN8TOARS}, DOI={10.1002/adma.201400411}, abstractNote={For the blend film of PBDTTT-C-T:PC71 BM, the use of 1,8-diiodooctane as the solvent additive enriches the polymer at the top surface, so that a power conversion efficiency of 9.13% is recorded in the inverted polymer solar cell based on the blend, which is much higher than that of the device with conventional structure.}, number={24}, journal={ADVANCED MATERIALS}, author={Guo, Xia and Zhang, Maojie and Ma, Wei and Ye, Long and Zhang, Shaoqing and Liu, Shengjian and Ade, Harald and Huang, Fei and Hou, Jianhui}, year={2014}, month={Jun}, pages={4043–4049} } @article{roland_schubert_collins_kurpiers_chen_facchetti_ade_neher_2014, title={Fullerene-Free Polymer Solar Cells with Highly Reduced Bimolecular Recombination and Field-Independent Charge Carrier Generation}, volume={5}, ISSN={1948-7185}, url={http://dx.doi.org/10.1021/JZ501506Z}, DOI={10.1021/JZ501506Z}, abstractNote={Photogeneration, recombination, and transport of free charge carriers in all-polymer bulk heterojunction solar cells incorporating poly(3-hexylthiophene) (P3HT) as donor and poly([N,N'-bis(2-octyldodecyl)-naphthelene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)) (P(NDI2OD-T2)) as acceptor polymer have been investigated by the use of time delayed collection field (TDCF) and time-of-flight (TOF) measurements. Depending on the preparation procedure used to dry the active layers, these solar cells comprise high fill factors (FFs) of up to 67%. A strongly reduced bimolecular recombination (BMR), as well as a field-independent free charge carrier generation are observed, features that are common to high performance fullerene-based solar cells. Resonant soft X-ray measurements (R-SoXS) and photoluminescence quenching experiments (PQE) reveal that the BMR is related to domain purity. Our results elucidate the similarities of this polymeric acceptor with the superior recombination properties of fullerene acceptors.}, number={16}, journal={The Journal of Physical Chemistry Letters}, publisher={American Chemical Society (ACS)}, author={Roland, Steffen and Schubert, Marcel and Collins, Brian A. and Kurpiers, Jona and Chen, Zhihua and Facchetti, Antonio and Ade, Harald and Neher, Dieter}, year={2014}, month={Aug}, pages={2815–2822} } @article{zhou_kurosawa_ma_guo_fang_vandewal_diao_wang_yan_reinspach_et al._2014, title={High Performance All-Polymer Solar Cell via Polymer Side-Chain Engineering}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201306242}, abstractNote={Acknowledge support from the Office of Naval Research (N00014-14-1-0142), KAUST Center for Advanced Molecular Photovoltaics at Stanford and the Stanford Global Climate and Energy Program, NSF DMR-1303742 and the National Natural Science Foundation of China (Projects 21174004 and 21222403). Soft X-ray characterization and analysis by NCSU supported by the U.S. Department of Energy, Office of Science, Basic Energy Science, Division of Materials Science and Engineering under Contract DE-FG02-98ER45737. Soft X-ray data was acquired at beamlines 11.0.1.2 at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U. S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank Professor Michael D. McGehee, Dr. George F. Burkhard and Dr. Eric T. Hoke for their help in discussion of the recombination mechanism.}, number={22}, journal={ADVANCED MATERIALS}, author={Zhou, Yan and Kurosawa, Tadanori and Ma, Wei and Guo, Yikun and Fang, Lei and Vandewal, Koen and Diao, Ying and Wang, Chenggong and Yan, Qifan and Reinspach, Julia and et al.}, year={2014}, month={Jun}, pages={3767–3772} } @article{mu_liu_ma_jiang_zhao_zhang_chen_wei_yi_wang_et al._2014, title={High-Efficiency All-Polymer Solar Cells Based on a Pair of Crystalline Low-Bandgap Polymers}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201402473}, abstractNote={All-polymer solar cells based on a pair of crystalline low-bandgap polymers (NT and N2200) are demonstrated to achieve a high short-circuit current density of 11.5 mA cm-2 and a power conversion efficiency of up to 5.0% under the standard AM1.5G spectrum with one sun intensity. The high performance of these NT:N2200-based cells can be attributed to the low optical bandgaps of the polymers and the reasonably high and balanced electron and hole mobilities of the NT:N2200 blends due to the crystalline nature of the two polymers.}, number={42}, journal={ADVANCED MATERIALS}, author={Mu, Cheng and Liu, Peng and Ma, Wei and Jiang, Kui and Zhao, Jingbo and Zhang, Kai and Chen, Zhihua and Wei, Zhanhua and Yi, Ya and Wang, Jiannong and et al.}, year={2014}, month={Nov}, pages={7224–7230} } @article{huang_wen_mukherjee_ade_kramer_bazan_2014, title={High-Molecular-Weight Insulating Polymers Can Improve the Performance of Molecular Solar Cells}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201400497}, abstractNote={The addition of small quantities of polystyrene (PS) is a simple and economically viable process that improves the power conversion efficiency of one of the most efficient small molecule donors. Addition of PS increases the solution viscosity, thereby providing thicker layers, and allows the formation of a desirable bulk heterojunction morphology. Moreover, the PS spontaneously accumulates as phase separated domains, away from the electrodes, so as not to interfere with charge extraction.}, number={24}, journal={ADVANCED MATERIALS}, author={Huang, Ye and Wen, Wen and Mukherjee, Subhrangsu and Ade, Harald and Kramer, Edward J. and Bazan, Guillermo C.}, year={2014}, month={Jun}, pages={4168–4172} } @article{mukherjee_proctor_tumbleston_bazan_nguyen_ade_2015, title={Importance of Domain Purity and Molecular Packing in Efficient Solution-Processed Small-Molecule Solar Cells}, volume={27}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201404388}, abstractNote={Connections are delineated between solar-cell performance, charge-carrier mobilities, and morphology in a highperformance molecular solar cell. The observations show that maximizing the relative phase purity and structural order while simultaneously limiting the domain size may be essential for achieving optimal solar-cell performances in solution-processed small-molecule solar cells .}, number={6}, journal={ADVANCED MATERIALS}, author={Mukherjee, Subhrangsu and Proctor, Christopher M. and Tumbleston, John R. and Bazan, Guillermo C. and Nguyen, Thuc-Quyen and Ade, Harald}, year={2015}, month={Feb}, pages={1105–1111} } @article{he_mukherjee_watkins_chen_qin_thomsen_ade_mcneill_2014, title={Influence of Fluorination and Molecular Weight on the Morphology and Performance of PTB7:PC71BM Solar Cells}, volume={118}, ISSN={["1932-7447"]}, DOI={10.1021/jp501222w}, abstractNote={The device performance and microstructure of a series of PTB7-based polymers with varied molecular weight and degree of fluorination are investigated. Although the energy level of the highest occupied molecular orbital is found to increase with degree of fluorination, a strong relative molecular weight dependence of device performance dominates any underlying fluorination-dependent trend on overall performance. Microstructural investigation using a combination of X-ray techniques reveals a striking effect of polymer molecular characteristics on film morphology, with the size of PC71BM domains systematically decreasing with increasing polymer molecular weight. Furthermore, the relative purity of the mixed PTB7:PC71BM domain is found to systematically decrease with increasing molecular weight. When domain sizes with and without the use of the solvent additive diiodooctane (DIO) are compared, the effectiveness of DIO in reducing PC71BM domain sizes is also found to be strongly dependent on the molecular weig...}, number={19}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={He, Xiaoxi and Mukherjee, Subhrangsu and Watkins, Scott and Chen, Ming and Qin, Tianshi and Thomsen, Lars and Ade, Harald and McNeill, Christopher R.}, year={2014}, month={May}, pages={9918–9929} } @article{love_collins_nagao_mukherjee_ade_bazan_nguyen_2014, title={Interplay of Solvent Additive Concentration and Active Layer Thickness on the Performance of Small Molecule Solar Cells}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201402403}, abstractNote={A relationship between solvent additive concentration and active layer thickness in small-molecule solar cells is investigated. Specifically, the additive concentration must scale with the amount of semiconductor material and not as absolute concentration in solution. Devices with a wide range of active layers with thickness up to 200 nm can readily achieve efficiencies close to 6% when the right concentration of additive is used.}, number={43}, journal={ADVANCED MATERIALS}, author={Love, John A. and Collins, Samuel D. and Nagao, Ikuhiro and Mukherjee, Subhrangsu and Ade, Harald and Bazan, Guillermo C. and Nguyen, Thuc-Quyen}, year={2014}, month={Nov}, pages={7308–7316} } @article{li_abrecht_yang_roland_tumbleston_mcafee_yan_kelly_ade_neher_et al._2014, title={Mobility-Controlled Performance of Thick Solar Cells Based on Fluorinated Copolymers}, volume={136}, ISSN={["0002-7863"]}, DOI={10.1021/ja5067724}, abstractNote={Developing novel materials and device architectures to further enhance the efficiency of polymer solar cells requires a fundamental understanding of the impact of chemical structures on photovoltaic properties. Given that device characteristics depend on many parameters, deriving structure-property relationships has been very challenging. Here we report that a single parameter, hole mobility, determines the fill factor of several hundred nanometer thick bulk heterojunction photovoltaic devices based on a series of copolymers with varying amount of fluorine substitution. We attribute the steady increase of hole mobility with fluorine content to changes in polymer molecular ordering. Importantly, all other parameters, including the efficiency of free charge generation and the coefficient of nongeminate recombination, are nearly identical. Our work emphasizes the need to achieve high mobility in combination with strongly suppressed charge recombination for the thick devices required by mass production technologies.}, number={44}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Li, Wentao and Abrecht, Steve and Yang, Liqiang and Roland, Steffen and Tumbleston, John R. and McAfee, Terry and Yan, Liang and Kelly, Mary Allison and Ade, Harald and Neher, Dieter and et al.}, year={2014}, month={Nov}, pages={15566–15576} } @article{tumbleston_yang_you_ade_2014, title={Morphology linked to miscibility in highly amorphous semi-conducting polymer/fullerene blends}, volume={55}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2014.07.051}, abstractNote={Molecular miscibility is a defining property of mixtures of electron-donating polymers and electron-accepting fullerenes used in the photoactive layer of bulk heterojunction (BHJ) organic solar cells. Even though miscibility of fullerene in the polymer is a commonly observed property, quantitative measurements have unknown connections with other morphological properties such as domain size and domain purity. By varying the amount of fullerene loading in BHJ thin films, we show that morphological properties are related to miscibility via straightforward relationships. In particular, miscibility influences the sensitivity of domain spacing to fullerene loading and determines the domain volume fractions and the residual fullerene content in the mixed polymer-rich phase in devices. Not only does this work show the relationships between miscibility and morphology, but it also highlights the general importance in determining miscibility levels in BHJ systems in order to target optimum morphologies and domain purities.}, number={19}, journal={POLYMER}, author={Tumbleston, John R. and Yang, Liqiang and You, Wei and Ade, Harald}, year={2014}, month={Sep}, pages={4884–4889} } @article{albrecht_vandewal_tumbleston_fischer_douglas_fréchet_ludwigs_ade_salleo_neher_2014, title={On the Efficiency of Charge Transfer State Splitting in Polymer:Fullerene Solar Cells}, volume={26}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201305283}, DOI={10.1002/ADMA.201305283}, abstractNote={The field dependence and yield of free charge carrier generation in polymer:fullerene blends with varying energetic offsets is not affected when the excitation energy is varied from above band-gap to direct CT state excitation. Instead, the ability of the CT state to split is dictated by the energetic offset between the relaxed CT state and the charge separated (CS) state.}, number={16}, journal={Advanced Materials}, publisher={Wiley}, author={Albrecht, Steve and Vandewal, Koen and Tumbleston, John R. and Fischer, Florian S. U. and Douglas, Jessica D. and Fréchet, Jean M. J. and Ludwigs, Sabine and Ade, Harald and Salleo, Alberto and Neher, Dieter}, year={2014}, month={Feb}, pages={2533–2539} } @article{albrecht_vandewal_tumbleston_fischer_douglas_fréchet_ludwigs_ade_salleo_neher_2014, title={Organic Solar Cells: On the Efficiency of Charge Transfer State Splitting in Polymer:Fullerene Solar Cells (Adv. Mater. 16/2014)}, volume={26}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201470107}, DOI={10.1002/ADMA.201470107}, abstractNote={A so called “energy river” originates in the active layer of a bulk-heterojunction solar cell as described in work by D. Neher, K. Vandewal, and co-workers on page 2533. This river contains polymer chains and cools down from its hot origin to a cold front. The riverbank is created by “fullerene walls” with different heights. Flashes create hot electrons in the energy river. These electrons need to decrease in temperature during their refrigerating evolution in the river. The cold electrons on the right side cannot escape the river, hidden by the big fullerene wall, and get lost. The cold electrons on the left side are the “good guys”. They are able to splash out of the river and generate electrical power.}, number={16}, journal={Advanced Materials}, publisher={Wiley}, author={Albrecht, Steve and Vandewal, Koen and Tumbleston, John R. and Fischer, Florian S. U. and Douglas, Jessica D. and Fréchet, Jean M. J. and Ludwigs, Sabine and Ade, Harald and Salleo, Alberto and Neher, Dieter}, year={2014}, month={Apr}, pages={2607–2607} } @article{ma_tumbleston_ye_wang_hou_ade_2014, title={Photovoltaics: Quantification of Nano- and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency,Jsc, and FF in Polymer:Fullerene Solar Cells (Adv. Mater. 25/2014)}, volume={26}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/ADMA.201470171}, DOI={10.1002/ADMA.201470171}, abstractNote={On page 4234, J. Hou, H. Ade, and co-workers quantify the composition variations in a complex three-phase, hierarchical morphology of polymer/fullerene devices and establish novel structure–function relations by combining different X-ray scattering techniques. Anti-correlated composition variations between meso- and nanoscale separation are observed and impacted by the solvent mixture.}, number={25}, journal={Advanced Materials}, publisher={Wiley}, author={Ma, Wei and Tumbleston, John R. and Ye, Long and Wang, Cheng and Hou, Jianhui and Ade, Harald}, year={2014}, month={Jul}, pages={4399–4399} } @article{ma_tumbleston_ye_wang_hou_ade_2014, title={Quantification of Nano- and Mesoscale Phase Separation and Relation to Donor and Acceptor Quantum Efficiency, J(SC), and FF in Polymer:Fullerene Solar Cells}, volume={26}, ISSN={["1521-4095"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903724646&partnerID=MN8TOARS}, DOI={10.1002/adma.201400216}, abstractNote={Dr. W. Ma, Dr. J. R. Tumbleston, Prof. H. Ade Department of Physics North Carolina State University Raleigh , NC 27695 , USA E-mail: harald_ade@ncsu.edu L. Ye, Prof. J. Hou State Key Laboratory of Polymer Physics and Chemistry Beijing National Laboratory for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 , China E-mail: hjhzlz@iccas.ac.cn L. Ye University of Chinese Academy of Sciences Beijing 100049, China Dr. C. Wang Advanced Light Source Laurence Berkeley National Laboratory Berkeley , California 94720 , USA}, number={25}, journal={ADVANCED MATERIALS}, author={Ma, Wei and Tumbleston, John R. and Ye, Long and Wang, Cheng and Hou, Jianhui and Ade, Harald}, year={2014}, month={Jul}, pages={4234–4241} } @article{albrecht_tumbleston_janietz_dumsch_allard_scherf_ade_neher_2014, title={Quantifying Charge Extraction in Organic Solar Cells: The Case of Fluorinated PCPDTBT}, volume={5}, ISSN={["1948-7185"]}, DOI={10.1021/jz500457b}, abstractNote={We introduce a new and simple method to quantify the effective extraction mobility in organic solar cells at low electric fields and charge carrier densities comparable to operation conditions under one sun illumination. By comparing steady-state carrier densities at constant illumination intensity and under open-circuit conditions, the gradient of the quasi-Fermi potential driving the current is estimated as a function of external bias and charge density. These properties are then related to the respective steady-state current to determine the effective extraction mobility. The new technique is applied to different derivatives of the well-known low-band-gap polymer PCPDTBT blended with PC70BM. We show that the slower average extraction due to lower mobility accounts for the moderate fill factor when solar cells are fabricated with mono- or difluorinated PCPDTBT. This lower extraction competes with improved generation and reduced nongeminate recombination, rendering the monofluorinated derivative the most efficient donor polymer.}, number={7}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Albrecht, Steve and Tumbleston, John R. and Janietz, Silvia and Dumsch, Ines and Allard, Sybille and Scherf, Ullrich and Ade, Harald and Neher, Dieter}, year={2014}, month={Apr}, pages={1131–1138} } @article{steyrleuthner_di pietro_collins_polzer_himmelberger_schubert_chen_zhang_salleo_ade_et al._2014, title={The Role of Regioregularity, Crystallinity, and Chain Orientation on Electron Transport in a High-Mobility n-Type Copolymer}, volume={136}, ISSN={["0002-7863"]}, DOI={10.1021/ja4118736}, abstractNote={We investigated the correlation between the polymer backbone structural regularity and the charge transport properties of poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)], a widely studied semiconducting polymer exhibiting high electron mobility and an unconventional micromorphology. To understand the influence of the chemical structure and crystal packing of conventional regioregular P(NDI2OD-T2) [RR-P(NDI2OD-T2)] on the charge transport, the corresponding regioirregular polymer RI-P(NDI2OD-T2) was synthesized. By combining optical, X-ray, and transmission electron microscopy data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of all of the polymer films, which were then correlated to the electron mobilities in electron-only diodes. By carefully selecting the preparation conditions, we were able to obtain RR-P(NDI2OD-T2) films with similar crystalline structure along the three crystallographic axes but with different orientations of the polymer chains with respect to the substrate surface. RI-P(NDI2OD-T2), though exhibiting a rather similar LUMO structure and energy compared with the regioregular counterpart, displayed a very different packing structure characterized by the formation of ordered stacks along the lamellar direction without detectible π-stacking. Vertical electron mobilities were extracted from the space-charge-limited currents in unipolar devices. We demonstrate the anisotropy of the charge transport along the different crystallographic directions and how the mobility depends on π-stacking but is insensitive to the degree or coherence of lamellar stacking. The comparison between the regioregular and regioirregular polymers also shows how the use of large planar functional groups leads to improved charge transport, with mobilities that are less affected by chemical and structural disorder with respect to classic semicrystalline polymers such as poly(3-hexylthiophene).}, number={11}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Steyrleuthner, Robert and Di Pietro, Riccardo and Collins, Brian A. and Polzer, Frank and Himmelberger, Scott and Schubert, Marcel and Chen, Zhihua and Zhang, Shiming and Salleo, Alberto and Ade, Harald and et al.}, year={2014}, month={Mar}, pages={4245–4256} } @article{tumbleston_collins_yang_stuart_gann_ma_you_ade_2014, title={The influence of molecular orientation on organic bulk heterojunction solar cells}, volume={8}, ISSN={["1749-4893"]}, DOI={10.1038/nphoton.2014.55}, number={5}, journal={NATURE PHOTONICS}, author={Tumbleston, John R. and Collins, Brian A. and Yang, Liqiang and Stuart, Andrew C. and Gann, Eliot and Ma, Wei and You, Wei and Ade, Harald}, year={2014}, month={May}, pages={385–391} } @article{gann_watson_tumbleston_cochran_yan_wang_seok_chabinyc_ade_2014, title={Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique}, volume={90}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.90.245421}, abstractNote={The internal structures of thin films, particularly interfaces between different materials, are critical to system properties and performance across many disciplines, but characterization of buried interface topography is often unfeasible. In this work, we demonstrate that grazing resonant soft x-ray scattering (GRSoXS), a technique measuring diffusely scattered soft x rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces. By controlling and predicting the x-ray electric field intensity throughout the depth of the film and simultaneously the scattering contrast between materials, we are able to unambiguously identify the microstructure at different interfaces of a model polymer bilayer system. We additionally demonstrate the use of GRSoXS to selectively measure the topography of the surface and buried polymer-polymer interface in an organic thin-film transistor, revealing different microstructure and markedly differing evolution upon annealing. In such systems, where only indirect control of interface topography is possible, accurate measurement of the structure of interfaces for feedback is critically important. While we demonstrate the method here using organic materials, we also show that the technique is readily extendable to any thin-film system with elemental or chemical contrasts exploitable at absorption edges.}, number={24}, journal={PHYSICAL REVIEW B}, author={Gann, Eliot and Watson, Anne and Tumbleston, John R. and Cochran, Justin and Yan, Hongping and Wang, Cheng and Seok, Jaewook and Chabinyc, Michael and Ade, Harald}, year={2014}, month={Dec} } @article{mcafee_gann_guan_stuart_rowe_dougherty_ade_2014, title={Toward Single-Crystal Hybrid-Carbon Electronics: Impact of Graphene Substrate Defect Density on Copper Phthalocyanine Film Growth}, volume={14}, ISSN={["1528-7505"]}, DOI={10.1021/cg500504u}, abstractNote={Graphene has long been recognized as a potential replacement for indium tin oxide as a transparent conducting substrate that may not only be cheaper to manufacture but also may provide mechanical flexibility and templating for preferential organic film growth. Here, we report the discovery that the thin film growth mode and crystal structure of copper phthalocyanine (CuPc), a prototype organic semiconductor, is extremely sensitive to even atomic-scale defects (e.g., steps) on the graphene surface and that high quality films can be grown with a well-defined crystal orientation that should be favorable for optimized solar cell applications. The initial growth involves flat-lying copper phthalocyanine molecules in a triclinic brickstone crystal with (012) orientation. Thicker films on pristine graphite, as well as thin films on lower quality graphene, show an orientational transition to the flat-lying (112)-oriented brickstone, which nucleates near film defects and grows in more compact 3D islands. The thi...}, number={9}, journal={CRYSTAL GROWTH & DESIGN}, author={McAfee, Terry and Gann, Eliot and Guan, Tianshuai and Stuart, Sean C. and Rowe, Jack and Dougherty, Daniel B. and Ade, Harald}, year={2014}, month={Sep}, pages={4394–4401} } @article{yan_wang_mccarn_ade_2013, title={Accurate and Facile Determination of the Index of Refraction of Organic Thin Films Near the Carbon 1s Absorption Edge}, volume={110}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.110.177401}, abstractNote={A practical and accurate method to obtain the index of refraction, especially the decrement δ, across the carbon 1s absorption edge is demonstrated. The combination of absorption spectra scaled to the Henke atomic scattering factor database, the use of the doubly subtractive Kramers-Kronig relations, and high precision specular reflectivity measurements from thin films allow the notoriously difficult-to-measure δ to be determined with high accuracy. No independent knowledge of the film thickness or density is required. High confidence interpolation between relatively sparse measurements of δ across an absorption edge is achieved. Accurate optical constants determined by this method are expected to greatly improve the simulation and interpretation of resonant soft x-ray scattering and reflectivity data. The method is demonstrated using poly(methyl methacrylate) and should be extendable to all organic materials.}, number={17}, journal={PHYSICAL REVIEW LETTERS}, author={Yan, Hongping and Wang, Cheng and McCarn, Allison R. and Ade, Harald}, year={2013}, month={Apr} } @article{buchaca-domingo_ferguson_jamieson_mccarthy-ward_shoaee_tumbleston_reid_yu_madec_pfannmöller_et al._2014, title={Additive-assisted supramolecular manipulation of polymer:fullerene blend phase morphologies and its influence on photophysical processes}, volume={1}, ISSN={2051-6347 2051-6355}, url={http://dx.doi.org/10.1039/C3MH00125C}, DOI={10.1039/C3MH00125C}, abstractNote={The role of intermixed phases in organic solar cell blends is evaluated through manipulation of their number of phases.}, number={2}, journal={Mater. Horiz.}, publisher={Royal Society of Chemistry (RSC)}, author={Buchaca-Domingo, E. and Ferguson, A. J. and Jamieson, F. C. and McCarthy-Ward, T. and Shoaee, S. and Tumbleston, J. R. and Reid, O. G. and Yu, L. and Madec, M.-B. and Pfannmöller, M. and et al.}, year={2014}, pages={270–279} } @article{zhang_guo_ma_zhang_huo_ade_hou_2014, title={An Easy and Effective Method to Modulate Molecular Energy Level of the Polymer Based on Benzodithiophene for the Application in Polymer Solar Cells}, volume={26}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201304631}, abstractNote={Attaching meta-alkoxy-phenyl groups as conjugated side chains is an easy and effective way to modulate the molecular energy level of D-A polymer for photovoltaic application, and the polymer solar cells based on the polymer consisting meta-alkoxy-phenyl groups as conjugated side chain, PBT-OP, shows an enhanced open circuit voltage and thus higher efficiency of 7.50%, under the illumination of AM 1.5G, 100 mW/cm(2) .}, number={13}, journal={ADVANCED MATERIALS}, author={Zhang, Maojie and Guo, Xia and Ma, Wei and Zhang, Shaoqing and Huo, Lijun and Ade, Harald and Hou, Jianhui}, year={2014}, month={Apr}, pages={2089–2095} } @article{ma_ye_zhang_hou_ade_2013, title={Competition between morphological attributes in the thermal annealing and additive processing of polymer solar cells}, volume={1}, ISSN={2050-7526 2050-7534}, url={http://dx.doi.org/10.1039/C3TC30679H}, DOI={10.1039/C3TC30679H}, abstractNote={Thermal annealing and additive processing are employed and compared using alkoxy substituted (QxO) and extended π conjugated alkythienyl substituted (QxT) benzo[1,2-b:4,5 b′]dithiophene based heterojunction (BHJ) solar cells. The characteristic median length of the morphology, average composition fluctuations, interface structure, crystallinity and molecular miscibility are investigated based on these two processes. Our results suggest that focusing on single structural, morphological or thermodynamic measurements is not sufficient to explain differences in device performance. In the current work, no blends are close to the ideal morphology containing either domains that are too large, too mixed or too pure. An optimization strategy is proposed to improve those devices. Importantly, we find that domain size and relative domain purity are overall correlated with molecular miscibility, i.e. the more immiscible system induces larger and purer domains irrespective of the processing and even in non-equilibrium structures. This indicates that the relative domain size and purity, and device performance can be potentially predicted by the donor–acceptor molecular miscibility, a factor not yet widely considered when designing new materials for BHJ devices.}, number={33}, journal={Journal of Materials Chemistry C}, publisher={Royal Society of Chemistry (RSC)}, author={Ma, Wei and Ye, Long and Zhang, Shaoqing and Hou, Jianhui and Ade, Harald}, year={2013}, pages={5023} } @article{swaraj_ade_2013, title={Differences in NEXAFS of odd/even long chain n-alkane crystals}, volume={191}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2013.10.006}, abstractNote={We present the near edge X-ray absorption fine structure (NEXAFS) spectra of several long chain n-alkanes crystallites formed on Silicon nitride (Si3N4) windows. Dichroic signature was investigated with the CC backbone aligned perpendicular to the substrate. Significant changes in the dichroic signature of spectral intensities at energies below the ionization edge (287.5 and 288.1 eV) have been observed. While the dichroic ratio corresponding to the spectral feature at 287.5 eV remains relatively unaffected by the overall length of CC backbone, it is noticeably affected by the parity (odd or even) of the number of Carbon atoms in the n-alkane backbone. Data obtained provide evidence of the influence of interaction of molecular orbitals with periodic lattice structure.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Swaraj, Sufal and Ade, Harald}, year={2013}, month={Dec}, pages={60–64} } @article{ma_tumbleston_wang_gann_huang_ade_2013, title={Domain Purity, Miscibility, and Molecular Orientation at Donor/Acceptor Interfaces in High Performance Organic Solar Cells: Paths to Further Improvement}, volume={3}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201200912}, abstractNote={AbstractDomain purity and interface structure are known to be critical for fullerene‐based bulk heterojunction (BHJ) solar cells, yet have been very difficult to study. Using novel soft X‐ray tools, we delineate the importance of these parameters by comparing high performance cells based on a novel naphtha[1,2‐c:5,6‐c]bis[1,2,5]thiadiazole (NT) material to cells based on a 2,1,3‐benzothiadiazole (BT) analogue. BT‐based devices exhibit ∼15 nm, mixed domains that differ in composition by at most 22%, causing substantial bimolecular recombination. In contrast, NT‐based devices have more pure domains that are >80 nm in size, yet the polymer‐rich phase still contains at least 22% fullerene. Power conversion efficiency >6% is achieved for NT devices despite a domain size much larger than the nominal exciton diffusion length due to a favourable trade‐off in the mixed domain between exciton harvesting, charge transport, and bimolecular recombination. The miscibility of the fullerene with the NT and BT polymer is measured and correlated to the purity in devices. Importantly, polarized x‐ray scattering reveals preferential face‐on orientation of the NT polymer relative to the PCBM‐rich domains. Such ordering has previously not been observed in fullerene‐based solar cells and is shown here to be possibly a controlling or contributing factor to high performance.}, number={7}, journal={ADVANCED ENERGY MATERIALS}, author={Ma, Wei and Tumbleston, John R. and Wang, Ming and Gann, Eliot and Huang, Fei and Ade, Harald}, year={2013}, month={Jul}, pages={864–872} } @article{tumbleston_stuart_gann_you_ade_2013, title={Fluorinated Polymer Yields High Organic Solar Cell Performance for a Wide Range of Morphologies}, volume={23}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.201300093}, DOI={10.1002/adfm.201300093}, abstractNote={AbstractDevice performance is recognized to be generally sensitive to morphology in bulk heterojunction solar cells. Through the use of quantitative morphological measurements, it is demonstrated that devices based on benzodithiophene and fluorinated benzotriazole moieties constitute an exception to this design rule and exhibit a range of morphologies that yield similar high performance. In particular, the fill factor (FF) remains above 65% even with factor of two changes in domain size and factor of two changes in relative domain purity. Devices with active layer thicknesses of 250 nm are employed, which are capable of increasing optical absorption to produce high photocurrent. The general insensitivity to both morphology and thickness is likely related to the measured low equilibrium miscibility of fullerene in the polymer of 3‐4%. The materials and processes investigated therefore provide insights into functional material design that yield increased processing latitude and may be more amenable to roll‐to‐roll processing.}, number={27}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Tumbleston, John R. and Stuart, Andrew C. and Gann, Eliot and You, Wei and Ade, Harald}, year={2013}, month={Feb}, pages={3463–3470} } @article{stuart_tumbleston_zhou_li_liu_ade_you_2013, title={Fluorine Substituents Reduce Charge Recombination and Drive Structure and Morphology Development in Polymer Solar Cells}, volume={135}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/ja309289u}, DOI={10.1021/ja309289u}, abstractNote={Three structurally identical polymers, except for the number of fluorine substitutions (0, 1, or 2) on the repeat unit (BnDT-DTBT), are investigated in detail, to further understand the impact of these fluorine atoms on open circuit voltage (V(oc)), short circuit current (J(sc)), and fill factor (FF) of related solar cells. While the enhanced V(oc) can be ascribed to a lower HOMO level of the polymer by adding more fluorine substituents, the improvement in J(sc) and FF are likely due to suppressed charge recombination. While the reduced bimolecular recombination with raising fluorine concentration is confirmed by variable light intensity studies, a plausibly suppressed geminate recombination is implied by the significantly increased change of dipole moment between the ground and excited states (Δμ(ge)) for these polymers as the number of fluorine substituents increases. Moreover, the 2F polymer (PBnDT-DTffBT) exhibits significantly more scattering in the in-plane lamellar stacking and out-of-plane π-π stacking directions, observed with GIWAXS. This indicates that the addition of fluorine leads to a more face-on polymer crystallite orientation with respect to the substrate, which could contribute to the suppressed charge recombination. R-SoXS also reveals that PBnDT-DTffBT has larger and purer polymer/fullerene domains. The higher domain purity is correlated with an observed decrease in PCBM miscibility in polymer, which drops from 21% (PBnDT-DTBT) to 12% (PBnDT-DTffBT). The disclosed "fluorine" impact not only explains the efficiency increase from 4% of PBnDT-DTBT (0F) to 7% with PBnDT-DTffBT (2F) but also suggests fluorine substitution should be generally considered in the future design of new polymers.}, number={5}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Stuart, Andrew C. and Tumbleston, John R. and Zhou, Huaxing and Li, Wentao and Liu, Shubin and Ade, Harald and You, Wei}, year={2013}, month={Jan}, pages={1806–1815} } @article{tumbleston_gadisa_liu_collins_samulski_lopez_ade_2013, title={Modifications in Morphology Resulting from Nanoimprinting Bulk Heterojunction Blends for Light Trapping Organic Solar Cell Designs}, volume={5}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/AM402363R}, DOI={10.1021/am402363r}, abstractNote={Nanoimprinting the photoactive layer of bulk heterojunction (BHJ) organic solar cells is a promising technique for enhancing device performance via improved light absorption. Here, we demonstrate that imprinting poly(3-hexylthiophene) (P3HT) and fullerene BHJ blends leads to adverse morphological changes within the photoactive nanopattern which have been previously overlooked. In particular, nanoimprinting induces a factor of 2 difference in polymer:fullerene composition between the nanopattern posts and interconnecting flash layer that inadvertently moves the composition outside the range for optimal performance. This occurs because of the strong tendency of regioregular P3HT to crystallize since imprinting blends based on amorphous regiorandom P3HT have uniform nanopattern composition. Based on these results, we outline promising design strategies, such as nanoimprinting amorphous polymers, to serve as guidelines for fabricating high-performance nanopatterned BHJ solar cells capable of maximized light absorption.}, number={16}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Tumbleston, John R. and Gadisa, Abay and Liu, Yingchi and Collins, Brian A. and Samulski, Edward T. and Lopez, Rene and Ade, Harald}, year={2013}, month={Aug}, pages={8225–8230} } @article{qian_ma_li_guo_zhang_ye_ade_tan_hou_2013, title={Molecular Design toward Efficient Polymer Solar Cells with High Polymer Content}, volume={135}, ISSN={["1520-5126"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878954003&partnerID=MN8TOARS}, DOI={10.1021/ja402971d}, abstractNote={A novel polythiophene derivative, PBT1, was designed, synthesized, and applied in polymer solar cells (PSCs). This work provides a successful example of using molecular structure as a tool to realize optimal photovoltaic performance with high polymer content, thus enabling the realization of efficient photoabsorption in very thin films. As a result, an efficiency of 6.88% was recorded in a PSC with a 75 nm active layer.}, number={23}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Qian, Deping and Ma, Wei and Li, Zhaojun and Guo, Xia and Zhang, Shaoqing and Ye, Long and Ade, Harald and Tan, Zhan'ao and Hou, Jianhui}, year={2013}, month={Jun}, pages={8464–8467} } @article{westacott_tumbleston_shoaee_fearn_bannock_gilchrist_heutz_demello_heeney_ade_et al._2013, title={On the role of intermixed phases in organic photovoltaic blends}, volume={6}, ISSN={1754-5692 1754-5706}, url={http://dx.doi.org/10.1039/C3EE41821A}, DOI={10.1039/C3EE41821A}, abstractNote={Recently, an intermixed phase has been identified within organic photovoltaic (OPV) bulk heterojunction (BHJ) systems that can exist in addition to relatively phase-pure regions, highlighting the need for a refined picture of the solid-state microstructure of donor–acceptor blends and for gaining further understanding of the exact nature and role such intermixed phases play in such devices. Here we manipulate the microstructure of polymer–fullerene systems via processing means and the selection of the molecular weight of the donor polymer. This manipulation is used as a tool to vary the fraction of intermixed phase present and its effects on the structure and subsequently the opto-electronic processes. We find clear relationships between the state of mixing and amount of exciton quenching and number of polarons generated per absorbed photon. Furthermore, we observe that blend systems incorporating higher molecular weight polymer result in a greater yield of dissociated polarons, likely due to the increase of the intermixed fraction.}, number={9}, journal={Energy & Environmental Science}, publisher={Royal Society of Chemistry (RSC)}, author={Westacott, Paul and Tumbleston, John R. and Shoaee, Safa and Fearn, Sarah and Bannock, James H. and Gilchrist, James B. and Heutz, Sandrine and deMello, John and Heeney, Martin and Ade, Harald and et al.}, year={2013}, pages={2756} } @article{collins_li_tumbleston_gann_mcneill_ade_2013, title={Organic Solar Cells: Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in PTB7:PC71BM Solar Cells (Adv. Energy Mater. 1/2013)}, volume={3}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/aenm.201370001}, DOI={10.1002/aenm.201370001}, abstractNote={The front cover represents the morphology and resulting device dynamics in organic solar cell blend films of PTB7 and PC71BM, as revealed by combined resonant X-ray scattering and microscopy. Harald Ade and co-workers find on page 65 that the fullerene molecules (red) are miscible in the polymer (blue) up to 30 wt.%, above which they begin to agglomerate (bottom). This agglomeration is important for the optoelectronic processes within the device, but the agglomerates must be kept to small sizes by the solvent processing additive diiodooctane (DIO). Correlation of this morphology with the spectrally resolved quantum efficiency shows that the yellow excitons created upon photoabsorption must arrive at the agglomerate interface for charge separation to occur. The blue electrons and green holes can then percolate through appropriate molecules in the mixed matrix to the electrodes for harvesting of electrical energy.}, number={1}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Collins, Brian A. and Li, Zhe and Tumbleston, John R. and Gann, Eliot and McNeill, Christopher R. and Ade, Harald}, year={2013}, month={Jan}, pages={1–1} } @article{ma_tumbleston_wang_gann_huang_ade_2013, title={Organic Solar Cells: Domain Purity, Miscibility, and Molecular Orientation at Donor/Acceptor Interfaces in High Performance Organic Solar Cells: Paths to Further Improvement (Adv. Energy Mater. 7/2013)}, volume={3}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/AENM.201370029}, DOI={10.1002/AENM.201370029}, abstractNote={The importance of domain purity and molecular orientation are investigated for solar cell devices based on naphtha[1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT) or 2,1,3-benzothiadiazole-based conjugated polymers. Harald Ade and co-workers show on page 864 that the domain purity, domain size and the nature of the interface structure in BHJ organic solar cells are critical for their performance and provide for the first time a quantitative comparison of domain purity between devices based on polymers with a different backbone.}, number={7}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Ma, Wei and Tumbleston, John R. and Wang, Ming and Gann, Eliot and Huang, Fei and Ade, Harald}, year={2013}, month={Jul}, pages={826–826} } @article{wu_li_ma_huang_huo_guo_zhang_ade_hou_2013, title={PDT-S-T: A New Polymer with Optimized Molecular Conformation for Controlled Aggregation and pi-pi Stacking and Its Application in Efficient Photovoltaic Devices}, volume={25}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201301174}, abstractNote={The correlation among molecular conformation, the crystallinity of the morphology, propensity for π-π stacking, J- versus H-aggregation, and photovoltaic performance have been studied based on two newly designed polymers, PBDTTT-S-T and PDT-S-T. The results show that more linear backbone structure is helpful to improve photovoltaic properties of the polymer, and therefore, molecular conformation should be considered for molecular design of photovoltaic polymers.}, number={25}, journal={ADVANCED MATERIALS}, author={Wu, Yue and Li, Zhaojun and Ma, Wei and Huang, Ye and Huo, Lijun and Guo, Xia and Zhang, Maojie and Ade, Harald and Hou, Jianhui}, year={2013}, month={Jul}, pages={3449–3455} } @article{mcafee_gann_ade_dougherty_2013, title={Thermally Induced Dewetting in Ultrathin C-60 Films on Copper Phthalocyanine}, volume={117}, ISSN={["1932-7447"]}, DOI={10.1021/jp4067372}, abstractNote={The evolution of thermally annealed ultrathin fullerene–C60 layers on copper phthalocyanine is examined by atomic force microscopy and near-edge X-ray absorption fine structure spectroscopy. Annealing causes C60 films to dewet the copper phthalocyanine substrate surface via lateral surface mass transport. Coarsening of C60 clusters is observed that creates mounds that exceed the nominal C60 thickness by more than an order of magnitude and is consistent with surface diffusion-mediated mass transport. Implications for thermal morphology control in organic solar cells, such as the destabilization of multilayered C60:CuPc with individual layers only ∼5–10 nm thick, are discussed.}, number={49}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={McAfee, T. and Gann, E. and Ade, H. and Dougherty, D. B.}, year={2013}, month={Dec}, pages={26007–26012} } @article{liu_zhao_tumbleston_wang_gu_wang_briseno_ade_russell_2014, title={Understanding the Morphology of PTB7: PCBM Blends in Organic Photovoltaics}, volume={4}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201301377}, abstractNote={The structure–property relationships of PTB7‐phenyl‐C61‐butyric acid methyl ester (PCBM)‐based organic photovoltaics are investigated. The morphology is investigated in an active layer setting where a multi‐length‐scale morphology is observed using a solvent additive‐assisted film processing. This multi‐length‐scale structure consists of a phase separated morphology with a characteristic length scale of ≈30 nm, which is critical for producing large currents in devices; a second length scale of ≈130 nm, arises from face‐on PTB7 crystalline aggregates. This latter morphological feature is also observed in films prepared without the use of an additive. By observing the structure formation in situ during solvent evaporation for blade coated thin films, the additive is found to promote the formation of ordered domains of the PTB7 at an earlier stage during the solvent evaporation, which is critical in the development of the final morphology. In studies on PTB7/PCBM bilayers, PCBM is found to diffuse into the PTB7 layer. However, the performance of devices prepared in this manner is low. This diffusion leads to a swelling of the PTB7 and a reduction in the crystallinity of the PTB7, reflecting the strong miscibility of PCBM with PTB7. The morphology resulting from the interdiffusion is single‐length‐scale with slightly large phase separation. This leads to devices with poor performance.}, number={5}, journal={ADVANCED ENERGY MATERIALS}, author={Liu, Feng and Zhao, Wei and Tumbleston, John R. and Wang, Cheng and Gu, Yu and Wang, Dong and Briseno, Alejandro L. and Ade, Harald and Russell, Thomas P.}, year={2014}, month={Apr} } @article{kanel_ade_delongchamp_chabinyc_wang_guo_snell_ralston_2012, title={2011 ALS User Meeting and Workshops}, volume={25}, ISSN={0894-0886 1931-7344}, url={http://dx.doi.org/10.1080/08940886.2012.645416}, DOI={10.1080/08940886.2012.645416}, abstractNote={A record 461 people registered for this year's ALS User Meeting, packing the plenary sessions, workshops, and meals that took place from October 3–5, 2011. Berkeley Lab Deputy Director Horst Simon welcomed guests to the meeting, touching on the looming challenge of data storage and processing. ALS Director Roger Falcone gave an in-depth overview of ALS progress and prospects, highlighting the new AMBER beamline, a controls upgrade, and a new user processing system as the top priorities for the coming year.}, number={1}, journal={Synchrotron Radiation News}, publisher={Informa UK Limited}, author={Kanel, Shauna and Ade, Harald and Delongchamp, Dean and Chabinyc, Michael and Wang, Cheng and Guo, Jinghua and Snell, Gyorgy and Ralston, Corie}, year={2012}, month={Jan}, pages={4–8} } @article{collins_li_tumbleston_gann_mcneill_ade_2012, title={Absolute Measurement of Domain Composition and Nanoscale Size Distribution Explains Performance in PTB7:PC71BM Solar Cells}, volume={3}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/aenm.201200377}, DOI={10.1002/aenm.201200377}, abstractNote={AbstractThe importance of morphology to organic solar cell performance is well known, but to date, the lack of quantitative, nanoscale and statistical morphological information has hindered obtaining direct links to device function. Here resonant X‐ray scattering and microscopy are combined to quantitatively measure the nanoscale domain size, distribution and composition in high efficiency solar cells based on PTB7 and PC71BM. The results show that the solvent additive diiodooctane dramatically shrinks the domain size of pure fullerene agglomerates that are embedded in a polymer‐rich 70/30 wt.% molecularly mixed matrix, while preserving the domain composition relative to additive‐free devices. The fundamental miscibility between the species – measured to be equal to the device's matrix composition – is likely the dominant factor behind the overall morphology with the additive affecting the dispersion of excess fullerene. As even the molecular ordering measured by X‐ray diffraction is unchanged between the two processing routes the change in the distribution of domain size and therefore increased domain interface is primarily responsible for the dramatic increase in device performance. While fullerene exciton harvesting is clearly one significant cause of the increase owing to smaller domains, a measured increase in harvesting from the polymer species indicates that the molecular mixing is not the reason for the high efficiency in this system. Rather, excitations in the polymer likely require proximity to a pure fullerene phase for efficient charge separation and transport. Furthermore, in contrast to previous measurements on a PTB7‐based system, a hierarchical morphology was not observed, indicating that it is not necessary for high performance.}, number={1}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Collins, Brian A. and Li, Zhe and Tumbleston, John R. and Gann, Eliot and McNeill, Christopher R. and Ade, Harald}, year={2012}, month={Oct}, pages={65–74} } @article{yang_tumbleston_zhou_ade_you_2013, title={Disentangling the impact of side chains and fluorine substituents of conjugated donor polymers on the performance of photovoltaic blends}, volume={6}, ISSN={["1754-5706"]}, DOI={10.1039/c2ee23235a}, abstractNote={Side chains and fluorine (F) substituents on conjugated polymers have shown significant impact on the photovoltaic properties of polymer-based bulk heterojunction (BHJ) solar cells, but their respective impact is largely studied independently. In order to disentangle the effect of side chains and F substituents, we comprehensively investigate a series of conjugated polymers with an identical backbone (PNDT–DTBT) but different combinations of side chains and F substituents. Surprisingly, these seemingly marginal changes to the polymer backbone strongly influence the morphology and structure in BHJ thin films (e.g., domain size/purity and the relative orientation of polymer crystallites), as manifested by resonant soft X-ray scattering (R-SoXS) and grazing-incidence wide-angle X-ray scattering (GI-WAXS), thereby exerting significant impact on the photovoltaic properties of these conjugated polymer-based BHJ cells. Devices based on the polymer with long bulky side chains and F substituents (C8,4-C6,2F) simultaneously exhibit large open circuit voltage (Voc), high short circuit current (Jsc) and good fill factor (FF), with an efficiency as high as 5.6% for this series of PNDT–DTBT polymers.}, number={1}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Yang, Liqiang and Tumbleston, John R. and Zhou, Huaxing and Ade, Harald and You, Wei}, year={2013}, month={Jan}, pages={316–326} } @article{pack_bobo_muir_yang_swaraj_ade_cao_korach_kashiwagi_rafailovich_2012, title={Engineering biodegradable polymer blends containing flame retardant-coated starch/nanoparticles}, volume={53}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2012.08.007}, abstractNote={We have shown that the addition of resorcinol di(phenyl phosphate) (RDP)-coated starch can improve the compatibility to either Ecoflex or poly(lactic acid) (PLA). The increased compatibilization enhanced the tensile properties such as yield strength and impact toughness. In particular, we examined the effect of addition of RDP-coated starch on thermal responses of a blend of Ecoflex/PLA. We found that the combination of RDP-coated starches with nanoclays could render the blends self-extinguishing since they are formed as a shell-like chars on the exposure surface against heat, which can prevent the melt polymers against dripping. With an examination on the scanning transmission X-ray microscopy (STXM) images of the blends, the Ecoflex domains were well dispersed in the PLA matrix, while the domains became smaller when the RDP-coated starch was added. Moreover, we demonstrated that the introduction of either flat-like or tube-like clays could provide an increase of interfacial area on the RDP-coated starch surfaces, where each polymer chain preferentially segregates to either the starch or the clay surface. Thus, large complex in-situ grafts with polymers can be formed at the interfaces. Additionally, the complex in-situ grafts could influence flammability of the blends. We have shown that the addition of RDP-coated clays can decrease the mass loss rate of Ecoflex/Starch blends, while a lot of nanofiber are formed on the chars surface, which are entangled each other with the clay platelets. The mechanical properties of the chars structures were examined by nano-indentation, where a good elastic chars formation could keep the internal pressures built up with decomposed gases from melt polymers as well as ductility of the chars could play an important role on releasing the internal gases through small vents on its surface, steadily where a good elastic and ductile chars formation could require keeping the internal pressures built up with decomposed gases from melt polymers.}, number={21}, journal={POLYMER}, author={Pack, Seongchan and Bobo, Ezra and Muir, Neil and Yang, Kai and Swaraj, Sufal and Ade, Harald and Cao, Changhong and Korach, Chad S. and Kashiwagi, Takashi and Rafailovich, Miriam H.}, year={2012}, month={Sep}, pages={4787–4799} } @article{yan_schuettfort_kronemeijer_mcneill_ade_2012, title={Erratum: “Influence of dielectric-dependent interfacial widths on device performance in top-gate P(NDI2OD-T2) field-effect transistors” [Appl. Phys. Lett. 101, 093308 (2012)]}, volume={101}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4762831}, DOI={10.1063/1.4762831}, abstractNote={First Page}, number={17}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Yan, Hongping and Schuettfort, Torben and Kronemeijer, Auke J. and McNeill, Christopher R. and Ade, Harald W.}, year={2012}, month={Oct}, pages={179901} } @article{ye_zhang_ma_fan_guo_huang_ade_hou_2012, title={From Binary to Ternary Solvent: Morphology Fine-tuning of D/A Blends in PDPP3T-based Polymer Solar Cells}, volume={24}, ISSN={["1521-4095"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84870872663&partnerID=MN8TOARS}, DOI={10.1002/adma.201202855}, abstractNote={For the PDPP3T/PCBM system investigated here, atomic force microscopy, resonant soft X-ray scattering, and grazing incidence wide angle X-ray scattering are used as an initial set of tools to determine the surface texture, the bulk compositional morphology, and the crystallization behavior, respectively. We find systematic variations and relate them to device performance. A solvent mixture of DCB/CF/DIO = 76:19:5 (v/v/v) yields a PCE of 6.71%.}, number={47}, journal={ADVANCED MATERIALS}, author={Ye, Long and Zhang, Shaoqing and Ma, Wei and Fan, Benhu and Guo, Xia and Huang, Ye and Ade, Harald and Hou, Jianhui}, year={2012}, month={Dec}, pages={6335–6341} } @article{yan_schuettfort_kronemeijer_mcneill_ade_2012, title={Influence of dielectric-dependent interfacial widths on device performance in top-gate P(NDI2OD-T2) field-effect transistors}, volume={101}, ISSN={["1077-3118"]}, DOI={10.1063/1.4748976}, abstractNote={Resonant soft x-ray reflectivity (R-SoXR) is employed to determine the interfacial widths of the semiconductor/dielectric interface in P(NDI2OD-T2)-based top-gate organic field-effect transistors (OFETs). It is shown that the deposition of a polymer dielectric on top of a semiconducting polymer layer can affect the interface structure, even when cast from an orthogonal solvent. The observed differences in the interfacial widths for different dielectrics explain the insensitivity of OFET performance to dielectric choice for OFETs fabricated using an identical fabrication protocol. The R-SoXR results demonstrate that differences in the physical interface structure should be taken into account when considering the influence of polymer dielectrics on the performance of all solution-processed OFETs. Specifically, the importance of the choice of solvent for the deposition is highlighted.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Yan, Hongping and Schuettfort, Torben and Kronemeijer, Auke J. and McNeill, Christopher R. and Ade, Harald W.}, year={2012}, month={Aug} } @article{yan_schuettfort_kronemeijer_mcneill_ade_2012, title={Influence of dielectric-dependent interfacial widths on device performance in top-gate P(NDI2OD-T2) field-effect transistors (vol 101, 093308, 2012)}, volume={101}, number={17}, journal={Applied Physics Letters}, author={Yan, H. P. and Schuettfort, T. and Kronemeijer, A. J. and McNeill, C. R. and Ade, H. W.}, year={2012} } @article{watts_ade_2012, title={NEXAFS imaging of synthetic organic materials}, volume={15}, ISSN={1369-7021}, url={http://dx.doi.org/10.1016/S1369-7021(12)70068-8}, DOI={10.1016/S1369-7021(12)70068-8}, abstractNote={The utilization of near edge x-ray absorption fine structure spectroscopy (NEXAFS) in achieving strong, novel contrast for soft x-ray microscopy and scattering methods has been afforded significant success in elucidating outstanding issues in organic materials systems due to the unique combination of high sensitivity to chemical functionality and thus composition, moderately high spatial resolution and moderate radiation damage. We illustrate the basic operating principles of NEXAFS spectroscopy, scanning transmission x-ray microscopy, and resonant soft x-ray scattering, and exemplify the impact by discussing a few recent applications. The focus of this perspective will be the characterization of synthetic organic materials, with a further emphasis on applications involving semi-conducting polymers. We also provide a brief perspective of future instrument and method developments.}, number={4}, journal={Materials Today}, publisher={Elsevier BV}, author={Watts, Ben and Ade, Harald}, year={2012}, month={Apr}, pages={148–157} } @article{collins_cochran_yan_gann_hub_fink_wang_schuettfort_mcneill_chabinyc_et al._2012, title={Polarized X-ray scattering reveals non-crystalline orientational ordering in organic films}, volume={11}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/nmat3310}, DOI={10.1038/nmat3310}, abstractNote={Molecular orientation critically influences the mechanical, chemical, optical and electronic properties of organic materials. So far, molecular-scale ordering in soft matter could be characterized with X-ray or electron microscopy techniques only if the sample exhibited sufficient crystallinity. Here, we show that the resonant scattering of polarized soft X-rays (P-SoXS) by molecular orbitals is not limited by crystallinity and that it can be used to probe molecular orientation down to size scales of 10 nm. We first apply the technique on highly crystalline small-molecule thin films and subsequently use its high sensitivity to probe the impact of liquid-crystalline ordering on charge mobility in polymeric transistors. P-SoXS also reveals scattering anisotropy in amorphous domains of all-polymer organic solar cells where interfacial interactions pattern orientational alignment in the matrix phase, which probably plays an important role in the photophysics. The energy and q-dependence of the scattering anisotropy allows the identification of the composition and the degree of orientational order in the domains.}, number={6}, journal={Nature Materials}, publisher={Springer Nature}, author={Collins, B. A. and Cochran, J. E. and Yan, H. and Gann, E. and Hub, C. and Fink, R. and Wang, C. and Schuettfort, T. and McNeill, C. R. and Chabinyc, M. L. and et al.}, year={2012}, month={Apr}, pages={536–543} } @article{collins_ade_2012, title={Quantitative compositional analysis of organic thin films using transmission NEXAFS spectroscopy in an X-ray microscope}, volume={185}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2012.05.002}, abstractNote={Near edge X-ray absorption fine structure (NEXAFS) spectroscopy is well suited for the quantitative determination of the composition of soft matter thin films. Combined with the high spatial resolution of a scanning transmission X-ray microscope, compositional maps of submicron morphologies can be derived and have been used successfully to characterize a number of materials systems. However, multiple sources of known systematic errors limit the accuracy and are frequently not taken into account. We show that these errors can be significant (more than 10%) and demonstrate simple methods to eliminate them. With suitable precautions, a compositional measurement can be made on a thin film sample in a matter of minutes with sub-micron spatial resolution and sub-percent compositional precision. NEXAFS measurements are furthermore known to be sensitive to anisotropic molecular orientation and a strategy to account for that and extract preferential molecular orientation relative to a reference is presented. The spatial resolution of the measurement can be increased to below 100 nm at the expense of compositional precision, depending on the point spread function of the zone plate focusing optics of the microscope.}, number={5-7}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Collins, Brian A. and Ade, Harald}, year={2012}, month={Aug}, pages={119–128} } @article{ade_2012, title={Soft X-ray Imaging of Polymers and Polymer Composites}, volume={18}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927612009919}, DOI={10.1017/S1431927612009919}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Ade, H.}, year={2012}, month={Jul}, pages={1612–1613} } @article{mcneill_ade_2013, title={Soft X-ray characterisation of organic semiconductor films}, volume={1}, ISSN={["2050-7534"]}, DOI={10.1039/c2tc00001f}, abstractNote={Organic semiconductor devices such as organic solar cells and organic field-effect transistors are based on blended and/or multilayered structures. Many organic semiconductors used in high-performance devices are also semicrystalline or liquid crystalline with a complex relationship between film microstructure and device performance. Unravelling structure–function relationships in organic semiconductor devices therefore requires structural probes that have high chemical specificity, sensitivity to molecular orientation and order and high spatial resolution. Soft X-rays have proven to be versatile in spectroscopy, microspectroscopy and scattering experiments providing contrast derived from differences in the near-edge X-ray absorption spectra of different organic semiconductors. Furthermore, the sensitivity of polarised soft X-ray beams to the orientation of bonds in organic materials makes them a unique probe of molecular orientation. This feature article provides an overview of the range of microscopy, reflectivity and scattering techniques based on soft X-rays that have been developed in recent years and their utility for providing new insight into the complex structure of organic semiconductor thin films.}, number={2}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={McNeill, Christopher R. and Ade, Harald}, year={2013}, pages={187–201} } @article{gann_young_collins_yan_nasiatka_padmore_ade_hexemer_wang_2012, title={Soft x-ray scattering facility at the Advanced Light Source with real-time data processing and analysis}, volume={83}, ISSN={["1089-7623"]}, DOI={10.1063/1.3701831}, abstractNote={We present the development and characterization of a dedicated resonant soft x-ray scattering facility. Capable of operation over a wide energy range, the beamline and endstation are primarily used for scattering from soft matter systems around the carbon K-edge (∼285 eV). We describe the specialized design of the instrument and characteristics of the beamline. Operational characteristics of immediate interest to users such as polarization control, degree of higher harmonic spectral contamination, and detector noise are delineated. Of special interest is the development of a higher harmonic rejection system that improves the spectral purity of the x-ray beam. Special software and a user-friendly interface have been implemented to allow real-time data processing and preliminary data analysis simultaneous with data acquisition.}, number={4}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Gann, E. and Young, A. T. and Collins, B. A. and Yan, H. and Nasiatka, J. and Padmore, H. A. and Ade, H. and Hexemer, A. and Wang, C.}, year={2012}, month={Apr} } @article{he_collins_watts_ade_mcneill_2012, title={Studying Polymer/Fullerene Intermixing and Miscibility in Laterally Patterned Films with X-Ray Spectromicroscopy}, volume={8}, ISSN={["1613-6810"]}, DOI={10.1002/smll.201102382}, abstractNote={AbstractFilms of the fullerene derivatives [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM) are patterned on silicon nitride membranes using photolithography to study, with X‐ray spectromicroscopy, the lateral, solid‐state diffusion of fullerene derivatives into conjugated polymer films. After patterning of the fullerene film, a film of conjugated polymer is laminated on top and the structure is annealed in order to study lateral intermixing and facilitate measurement of fullerene miscibility. Lateral intermixing of polymer and fullerene readily occurs for poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and regiorandom poly(3‐hexylthiophene) (RRa‐P3HT). A 42 wt.% miscibility of PC61BM in PBTTT is measured, while miscibilities of 20 and 41 wt.% are measured for PC61BM and PC71BM, respectively, in RRa‐P3HT, thereby demonstrating a significant difference in the miscibilities of these two fullerene derivatives. For regioregular poly(3‐hexylthiophene) (RR‐P3HT), incomplete lateral intermixing of fullerene and RR‐P3HT is observed with PCBM crystallite formation competing with the lateral diffusion of PCBM molecules into the polymer film.}, number={12}, journal={SMALL}, author={He, Xiaoxi and Collins, Brian A. and Watts, Benjamin and Ade, Harald and McNeill, Christopher R.}, year={2012}, month={Jun}, pages={1920–1927} } @article{cochran_amir_sivanandan_ku_seo_collins_tumbleston_toney_ade_hawker_et al._2013, title={Synthesis, solid-state, and charge-transport properties of conjugated polythiophene-S,S-dioxides}, volume={51}, ISSN={["1099-0488"]}, DOI={10.1002/polb.23167}, abstractNote={AbstractAn alkylated semiconducting polymer comprising alternating bithiophene‐[all]‐S,S‐dioxide and aromatic monothiophene units in the polymer backbone was synthesized with the intent of modifying the energy gap and lowest unoccupied molecular orbital for use as a stable n‐type semiconductor. Films spun from this semiconducting polymer were characterized utilizing X‐ray scattering, near edge X‐ray absorption fine structure spectroscopy, ultraviolet photoelectron spectroscopy, and thin‐film field effect transistors to determine how oxidation of the thiophene ring systems impacts the structural and electronic properties of the polymer. The thiophene‐S,S‐dioxide polymers have lower optical and electrical band gaps than corresponding thiophene polymers. X‐ray scattering results indicate that the polymers are well ordered with the π–π stacking distances increased by 0.4 Å relative to analogous thiophene polymers. The electrical stability of these polymers is poor in transistors with a drop in the field effect mobility by approximately one order of magnitude upon addition of just 5% of the thiophene‐S,S‐dioxide unit in a copolymer with thiophene. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013}, number={1}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Cochran, Justin E. and Amir, Elizabeth and Sivanandan, Kulandaivelu and Ku, Sung-Yu and Seo, Jung Hwa and Collins, Brian A. and Tumbleston, John R. and Toney, Michael F. and Ade, Harald and Hawker, Craig J. and et al.}, year={2013}, month={Jan}, pages={48–56} } @article{bartelt_beiley_hoke_mateker_douglas_collins_tumbleston_graham_amassian_ade_et al._2013, title={The Importance of Fullerene Percolation in the Mixed Regions of Polymer-Fullerene Bulk Heterojunction Solar Cells}, volume={3}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201200637}, abstractNote={AbstractMost optimized donor‐acceptor (D‐A) polymer bulk heterojunction (BHJ) solar cells have active layers too thin to absorb greater than ∼80% of incident photons with energies above the polymer's band gap. If the thickness of these devices could be increased without sacrificing internal quantum efficiency, the device power conversion efficiency (PCE) could be significantly enhanced. We examine the device characteristics of BHJ solar cells based on poly(di(2‐ethylhexyloxy)benzo[1,2‐b:4,5‐b′]dithiophene‐co‐octylthieno[3,4‐c]pyrrole‐4,6‐dione) (PBDTTPD) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) with 7.3% PCE and find that bimolecular recombination limits the active layer thickness of these devices. Thermal annealing does not mitigate these bimolecular recombination losses and drastically decreases the PCE of PBDTTPD BHJ solar cells. We characterize the morphology of these BHJs before and after thermal annealing and determine that thermal annealing drastically reduces the concentration of PCBM in the mixed regions, which consist of PCBM dispersed in the amorphous portions of PBDTTPD. Decreasing the concentration of PCBM may reduce the number of percolating electron transport pathways within these mixed regions and create morphological electron traps that enhance charge‐carrier recombination and limit device quantum efficiency. These findings suggest that (i) the concentration of PCBM in the mixed regions of polymer BHJs must be above the PCBM percolation threshold in order to attain high solar cell internal quantum efficiency, and (ii) novel processing techniques, which improve polymer hole mobility while maintaining PCBM percolation within the mixed regions, should be developed in order to limit bimolecular recombination losses in optically thick devices and maximize the PCE of polymer BHJ solar cells.}, number={3}, journal={ADVANCED ENERGY MATERIALS}, author={Bartelt, Jonathan A. and Beiley, Zach M. and Hoke, Eric T. and Mateker, William R. and Douglas, Jessica D. and Collins, Brian A. and Tumbleston, John R. and Graham, Kenneth R. and Amassian, Aram and Ade, Harald and et al.}, year={2013}, month={Mar}, pages={364–374} } @article{watts_swaraj_nordlund_lüning_ade_2011, title={Calibrated NEXAFS spectra of common conjugated polymers}, volume={134}, ISSN={0021-9606 1089-7690}, url={http://dx.doi.org/10.1063/1.3506636}, DOI={10.1063/1.3506636}, abstractNote={Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has evolved into a powerful characterization tool for polymeric materials and is increasingly being used to elucidate composition and orientation in thin films of relevance to organic electronic devices. For accurate quantitative compositional analysis, insight into the electronic structure and the ability to assess molecular orientation, reliable reference spectra with known energy resolution and calibrated energy scale are required. We report a set of such NEXAFS spectra from 23 semiconducting polymers and some related materials that are frequently used in organic device research.}, number={2}, journal={The Journal of Chemical Physics}, publisher={AIP Publishing}, author={Watts, B. and Swaraj, S. and Nordlund, D. and Lüning, J. and Ade, H.}, year={2011}, month={Jan}, pages={024702} } @article{yan_collins_gann_wang_ade_mcneill_2012, title={Correlating the Efficiency and Nanomorphology of Polymer Blend Solar Cells Utilizing Resonant Soft X-ray Scattering}, volume={6}, ISSN={["1936-086X"]}, DOI={10.1021/nn204150f}, abstractNote={Enhanced scattering contrast afforded by resonant soft X-ray scattering (R-SoXS) is used to probe the nanomorphology of all-polymer solar cells based on blends of the donor polymer poly(3-hexylthiophene) (P3HT) with either the acceptor polymer poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2',2"-diyl) (F8TBT) or poly([N,N'-bis(2-octyldodecyl)-11-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-12-bithiophene)) (P(NDI2OD-T2)). Both P3HT:F8TBT and P3HT:P(NDI2OD-T2) blends processed from chloroform with subsequent annealing exhibit complicated morphologies with a hierarchy of phase separation. A bimodal distribution of domain sizes is observed for P3HT:P(NDI2OD-T2) blends with small domains of size ~5-10 nm that evolve with annealing and larger domains of size ~100 nm that are insensitive to annealing. P3HT:F8TBT blends in contrast show a broader distribution of domain size but with the majority of this blend structured on the 10 nm length scale. For both P3HT:P(NDI2OD-T2) and P3HT:F8TBT blends, an evolution in device performance is observed that is correlated with a coarsening and purification of domains on the 5-10 nm length scale. Grazing-incidence wide-angle X-ray scattering (GI-WAXS) is also employed to probe material crystallinity, revealing P(NDI2OD-T2) crystallites 25-40 nm in thickness that are embedded in the larger domains observed by R-SoXS. A higher degree of P3HT crystallinity is also observed in blends with P(NDI2OD-T2) compared to F8TBT with the propensity of the polymers to crystallize in P3HT:P(NDI2OD-T2) blends hindering the structuring of morphology on the sub-10 nm length scale. This work also underscores the complementarity of R-SoXS and GI-WAXS, with R-SoXS measuring the size of compositionally distinguishable domains and GI-WAXS providing information regarding crystallinity and crystallite thickness.}, number={1}, journal={ACS NANO}, author={Yan, Hongping and Collins, Brian A. and Gann, Eliot and Wang, Cheng and Ade, Harald and McNeill, Christopher R.}, year={2012}, month={Jan}, pages={677–688} } @article{wang_lee_hexemer_kim_zhao_hasegawa_ade_russell_2011, title={Defining the Nanostructured Morphology of Triblock Copolymers Using Resonant Soft X-ray Scattering}, volume={11}, ISSN={["1530-6992"]}, DOI={10.1021/nl2020526}, abstractNote={The morphologies of a poly(1,4-isoprene)-block-polystyrene-block-poly(2-vinyl pyridine) (IS2VP) copolymer were investigated using resonant soft X-ray scattering (RSoXS) together with scanning force microscopy, small-angle X-ray scattering, and electron microscopy. Differences in the nanoscopic morphologies in the bulk and thin film samples were observed arising from the competition between segmental interactions between the blocks and the substrate and the surface energies of each block. Using soft X-rays at selected photon energies to isolate the scattering contribution from different polymer blocks, RSoXS unambiguously defined the complex morphology of the triblock copolymer. In the bulk sample, two nested, hexagonal arrays of P2VP and PI cylindrical microdomains residing in the PS matrix were observed. The cylindrical microdomains of one component were found to be located at the interstitial sites of the hexagonal array of the other component that has the larger d spacing. In solvent-annealed thin films with 40 nm in thickness, a hexagonal array of core-shell microdomains of P2VP cores with PS shells that reside in a PI matrix were observed.}, number={9}, journal={NANO LETTERS}, author={Wang, Cheng and Lee, Dong Hyun and Hexemer, Alexander and Kim, Myung Im and Zhao, Wei and Hasegawa, Hirokazu and Ade, Harald and Russell, Thomas P.}, year={2011}, month={Sep}, pages={3906–3911} } @article{collins_li_mcneill_ade_2011, title={Fullerene-Dependent Miscibility in the Silole-Containing Copolymer PSBTBT-08}, volume={44}, ISSN={["1520-5835"]}, DOI={10.1021/ma201883a}, abstractNote={A high fullerene molecular miscibility of over 40 wt % is found in the copolymer poly((4,4-octyldithieno(3,2-b:2′,3′-d)silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl) (PSBTBT-08)—a member of the PSBTBT low-bandgap polymer family that have produced power conversion efficiencies as high as 5.9% in solar cells. This observation suggests molecular miscibility plays a key role in the photovoltaic effect in this system. The level of miscibility is additionally measured to be highly dependent on the fullerene species with significant differences between C60- and C70-based fullerenes, highlighting a new parameter to be monitored and controlled when considering different fullerene moieties and species in organic solar cells. Surprisingly, a wide-angle X-ray scattering study reveals no significant crystallinity in the PSBTBT with octyl side chains, potentially the cause of low mobilities and in stark contrast to dodecyl and ethylhexyl PSBTBTs, which demonstrates the importance of the side chain in device mo...}, number={24}, journal={MACROMOLECULES}, author={Collins, Brian A. and Li, Zhe and McNeill, Christopher R. and Ade, Harald}, year={2011}, month={Dec}, pages={9747–9751} } @article{yan_wang_garcia_swaraj_gu_mcneill_schuettfort_sohn_kramer_bazan_et al._2011, title={Interfaces in organic devices studied with resonant soft x-ray reflectivity}, volume={110}, ISSN={["1089-7550"]}, DOI={10.1063/1.3661991}, abstractNote={Interfaces between donor and acceptor semiconducting polymers are critical to the performance of polymer light-emitting diodes and organic solar cells. Similarly, interfaces between a conjugated polymer and a dielectric play a critical role in organic thin-film transistors. Often, these interfaces are difficult to characterize with conventional methods. Resonant soft x-ray reflectivity (R-SoXR) is a unique and relatively simple method to investigate such interfaces. R-SoXR capabilities are exemplified by presenting or discussing results from systems spanning all three device categories. We also demonstrate that the interfacial widths between active layers can be controlled by annealing at elevated temperature, pre-annealing of the bottom layer, or casting from different solvent mixtures. The extension of R-SoXR to the fluorine K absorption edge near 698 eV is also demonstrated.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Yan, Hongping and Wang, Cheng and Garcia, Andres and Swaraj, Sufal and Gu, Ziran and McNeill, Christopher R. and Schuettfort, Torben and Sohn, Karen E. and Kramer, Edward J. and Bazan, Guillermo C. and et al.}, year={2011}, month={Nov} } @article{collins_tumbleston_ade_2011, title={Miscibility, Crystallinity, and Phase Development in P3HT/PCBM Solar Cells: Toward an Enlightened Understanding of Device Morphology and Stability}, volume={2}, ISSN={["1948-7185"]}, DOI={10.1021/jz2014902}, abstractNote={Rapid improvements in organic solar cell efficiency have brought these devices into the spotlight as a potential source of abundant electricity. Despite much empirical progress, fundamental understanding is still lacking. Due to the required three-dimentional nanoscale morphology, determining structure–performance relationships has been a major challenge, and a convergent understanding has yet to emerge. We discuss recent major advances in delineating the characteristics of the most common organic solar cells. The large variations in device performance reported, the contradictory morphologies observed, and the determination of the underlying driving forces need to be resolved. Deeper understanding that can provide a roadmap to improved devices will only occur through refined consideration of material characteristics and fabrication procedures in conjunction with increased use of advanced characterization. We additionally highlight the recently discovered partial miscibility of the component materials, its...}, number={24}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Collins, Brian A. and Tumbleston, John R. and Ade, Harald}, year={2011}, month={Dec}, pages={3135–3145} } @inproceedings{kilcoyne_ade_attwood_hitchcock_mckean_mitchell_monteiro_tyliszczak_warwick_garrett_et al._2010, title={A new Scanning Transmission X-ray Microscope at the ALS for operation up to 2500eV}, url={http://dx.doi.org/10.1063/1.3463241}, DOI={10.1063/1.3463241}, abstractNote={We report on the design and construction of a higher energy Scanning Transmission X‐ray Microscope on a new bend magnet beam line at the Advanced Light Source. Previously we have operated such an instrument on a bend magnet for C, N and O 1s NEXAFS spectroscopy. The new instrument will have similar performance at higher energies up to and including the S 1s edge at 2472eV. A new microscope configuration is planned. A more open geometry will allow a fluorescence detector to count emitted photons from the front surface of the sample. There will be a capability for zone plate scanning in addition to the more conventional sample scanning mode. This will add the capability for imaging a massive sample at high resolution over a limited field of view, so that heavy reaction cells may be used to study processes in‐situ, exploiting the longer photon attenuation length and the longer zone plate working distances available at higher photon energy. The energy range will extend down to include the C1s edge at 300eV, t...}, publisher={AIP}, author={Kilcoyne, David and Ade, Harald and Attwood, David and Hitchcock, Adam and McKean, Pat and Mitchell, Gary and Monteiro, Paulo and Tyliszczak, Tolek and Warwick, Tony and Garrett, R. and et al.}, year={2010} } @article{jeong_kwon_choi_ade_han_2010, title={Improved efficiency of bulk heterojunction poly(3-hexylthiophene):[6,6]-phenyl-C-61-butyric acid methyl ester photovoltaic devices using discotic liquid crystal additives}, volume={96}, ISSN={["0003-6951"]}, DOI={10.1063/1.3395391}, abstractNote={Well established poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) bulk-heterojunction organic photovoltaics (BHJ OPVs) were improved by incorporating a small portion of the discotic liquid crystal (DLC) additives with a strong self-assembling ability and high mobility. Under simulated solar illumination of AM 1.5 (100 mW/cm2), the devices fabricated using P3HT:PC61BM (1:1.2 w:w) layer blended with 3 wt % of 2,3,6,7,10,11-hexaacetoxytriphenylene (DLC 2) achieved an average power conversion efficiency (PCE) of 3.97% after thermal annealing, compared to the reference cells with PCE=3.03%. DLCs have been proven here to be a promising new type of additive that can remain embedded in the active layer of high efficiency P3HT:PC61BM BHJ OPVs.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Jeong, Seonju and Kwon, Younghwan and Choi, Byeong-Dae and Ade, Harald and Han, Yoon Soo}, year={2010}, month={May} } @article{yan_swaraj_wang_hwang_greenham_groves_ade_mcneill_2010, title={Influence of Annealing and Interfacial Roughness on the Performance of Bilayer Donor/Acceptor Polymer Photovoltaic Devices}, volume={20}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201001292}, abstractNote={AbstractThrough controlled annealing of planar heterojunction (bilayer) devices based on the polyfluorene copolymers poly(9,9‐dioctylfluorene‐co‐bis(N,N′‐(4,butylphenyl))bis(N,N′‐phenyl‐1,4‐phenylene)diamine) (PFB) and poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT) we study the influence of interface roughness on the generation and separation of electron–hole pairs at the donor/acceptor interface. Interface structure is independently characterized by resonant soft X‐ray reflectivity with the interfacial width of the PFB/F8BT heterojunction observed to systematically increase with annealing temperature from 1.6 nm for unannealed films to 16 nm with annealing at 200 °C for ten minutes. Photoluminescence quenching measurements confirm the increase in interface area by the three‐fold increase in the number of excitons dissociated. Under short‐circuit conditions, however, unannealed devices with the sharpest interface are found to give the best device performance, despite the increase in interfacial area (and hence the number of excitons dissociated) in annealed devices. The decrease in device efficiency with annealing is attributed to decreased interfacial charge separation efficiency, partly due to a decrease in the bulk mobility of the constituent materials upon annealing but also (and significantly) due to the increased interface roughness. We present results of Monte Carlo simulations that demonstrate that increased interface roughness leads to lower charge separation efficiency, and are able to reproduce the experimental current‐voltage curves taking both increased interfacial roughness and decreased carrier mobility into account. Our results show that organic photovoltaic performance can be sensitive to interfacial order, and heterojunction sharpness should be considered a requirement for high performance devices.}, number={24}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Yan, Hongping and Swaraj, Sufal and Wang, Cheng and Hwang, Inchan and Greenham, Neil C. and Groves, Chris and Ade, Harald and McNeill, Christopher R.}, year={2010}, month={Dec}, pages={4329–4337} } @article{collins_gann_guignard_he_mcneill_ade_2010, title={Molecular Miscibility of Polymer-Fullerene Blends}, volume={1}, ISSN={["1948-7185"]}, DOI={10.1021/jz101276h}, abstractNote={The device function of polymer bulk heterojunction (BHJ) solar cells has been commonly interpreted to arise from charge separation at discrete interfaces between phase-separated materials and subsequent charge transport through these phases without consideration of phase purity. To probe composition, the miscibility of poly(3-hexylthiophene) (P3HT) and poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) with phenyl-C61-butyric acid methyl ester (PCBM) has been determined, while the effects of polymer crystallinity on miscibility are probed using P3HT grades of varying regioregularity. It is found that, while no intercalation occurs in P3HT crystals, amorphous portions of P3HT and MDMO-PPV contain significant concentrations of PCBM, calling into question models based on pure phases and discrete interfaces. Furthermore, depth profiles of P3HT/PCBM bilayers reveal that even short annealing causes significant interdiffusion of both materials, showing that under no conditions do pure am...}, number={21}, journal={JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, author={Collins, Brian A. and Gann, Eliot and Guignard, Lewis and He, Xiaoxi and McNeill, Christopher R. and Ade, Harald}, year={2010}, month={Nov}, pages={3160–3166} } @article{swaraj_wang_yan_watts_lüning jan_mcneill_ade_2010, title={Nanomorphology of Bulk Heterojunction Photovoltaic Thin Films Probed with Resonant Soft X-ray Scattering}, volume={10}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl1009266}, DOI={10.1021/nl1009266}, abstractNote={The bulk nanomorphology of organic bulk heterojunction devices, particularly of all-polymer devices, is difficult to characterize due to limited electron density contrast between constituent materials. Resonant soft X-ray scattering can overcome this problem and is used to show that the morphologies in chloroform cast and subsequently annealed polyfluorene copolymer poly(9,9'-dioctylfluorene-co-bis(N,N'-(4,butylphenyl))bis(N,N'-phenyl-1,4-phenylene)diamine) (PFB) and poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) blends exhibit a hierarchy of length scales with impure domains in as-cast films. With annealing, these domains first become purer at the smallest length scale and only then evolve in size with annealing. Even optimized cells using present fabrication methods are found to have a dominant domain size much larger than the exciton diffusion length. The observed morphology is far from ideal for efficient solar cell operation and very different from those achieved in high-efficiency fullerene-based devices. This strongly implies that lack of morphological control contributes to the relatively poor performance of the all-polymer PFB/F8BT devices and may be problematic for all-polymer devices in general. Novel processing strategies will have to be employed to harness the full potential these high open circuit voltage devices offer.}, number={8}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Swaraj, Sufal and Wang, Cheng and Yan, Hongping and Watts, Benjamin and Lüning Jan and McNeill, Christopher R. and Ade, Harald}, year={2010}, month={Aug}, pages={2863–2869} } @article{wang_zou_araki_luening_kilcoyne_sokolov_ade_rafailovich_2010, title={Probing the Chain and Crystal Lattice Orientation in Polyethylene Thin Films by Near Edge X-ray Absorption Fine Structure (NEXAFS) Spectroscopy}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma101213h}, abstractNote={The chain and the crystal unit cell orientation of linear low density polyethylene (LLDPE) were measured with near edge X-ray absorption fine structure (NEXAFS) spectroscopy. A strongly attractive substrate, silicon, and a weakly attractive substrate, mica, were used. For a 100 nm thick LLDPE film on the silicon substrate, the crystals exhibit an edge-on lamellar morphology, with the chains predominantly parallel to the substrate, and the orthorhombic unit cell ⟨a, b, c⟩ in the following approximate orientation: b and c are in the film plane with b along the crystal fibril direction and c perpendicular to the fibril direction and a perpendicular to the film plane. On the mica substrates, LLDPE films with thickness below 180 nm completely dewet the surface and form isolated droplets, while a film 366 nm thick crystallizes as spherulites with most of the chains perpendicular to the substrate before annealing and with a twisted lamellar structure after isothermal crystallization at 60 °C. The results demonst...}, number={19}, journal={MACROMOLECULES}, author={Wang, Yantian and Zou, Ying and Araki, Tohru and Luening, Jan and Kilcoyne, A. L. D. and Sokolov, Jonathan and Ade, Harald and Rafailovich, Miriam}, year={2010}, month={Oct}, pages={8153–8161} } @article{ade_2010, title={Quantitative Soft X-ray Microscopy of Soft Matter}, volume={16}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927610058174}, DOI={10.1017/S1431927610058174}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Ade, H}, year={2010}, month={Jul}, pages={888–889} } @article{hub_wenzel_raabe_ade_fink_2010, title={Surface sensitivity in scanning transmission x-ray microspectroscopy using secondary electron detection}, volume={81}, ISSN={["0034-6748"]}, DOI={10.1063/1.3360813}, abstractNote={The successful integration of electron detection into an existing scanning transmission x-ray microspectroscope (STXM) at the Swiss Light Source is demonstrated. In conventional x-ray detection using a photomultiplier, STXM offers mainly bulk sensitivity combined with high lateral resolution. However, by implementation of a channeltron electron multiplier, the surface sensitivity can be established by the detection of secondary electrons emitted from the sample upon resonant excitation. We describe the experimental setup and discuss several relevant aspects, in particular the schemes to correct for self-absorption in the specimen due to back illumination in case of thicker films.}, number={3}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Hub, C. and Wenzel, S. and Raabe, J. and Ade, H. and Fink, R. H.}, year={2010}, month={Mar} } @article{zhang_lin_winesett_dhez_kilcoyne_ade_rubinstein_shafi_ulman_gersappe_et al._2011, title={The use of functionalized nanoparticles as non-specific compatibilizers for polymer blends}, volume={22}, ISSN={["1099-1581"]}, DOI={10.1002/pat.1875}, abstractNote={AbstractThe ability to form blends of polymers offers the opportunity of creating a new class of materials with enhanced properties. In addition to the polymer components, recent advances in nanoengineering have resulted in the development of nanosized inorganic particles that can be used to improve the properties of the blend, such as the flammability and the mechanical properties. While traditional methods using copolymer compatibilizers have been used to strengthen polymer blends, here, we show that the inorganic nanosized filler additive can also serve as a compatibilizer as it can localize to the interface between the polymers. We use experimental and theoretical studies to show the fundamental mechanisms by which inorganic fillers with large aspect ratio and at least one‐dimension in the nanometer range, can act as non‐specific compatibilizers for polymer blends. We examine a series of nanosized fillers, ranging from nanotubes to nanoclays (with varying aspect ratios) in a model polystyrene (PS)/poly(methylmethacyralate) (PMMA) blend. Using a number of experimental techniques such as transmission electron microscopy (TEM), scanning tunneling X‐ray microscopy (STXM), and atomic force microscopy (AFM) we postulate that the mechanism of compatibilization occurs as a result of the fillers forming in situ grafts with the immiscible polymers. We also use theoretical studies to show that the aspect ratio and the bending energy of the fillers play a key role in the compatibilization process. Our results indicate that the compatibilization is a general phenomenon, which should occur with all large aspect ratio nanofiller additives to polymer blends. Copyright © 2010 John Wiley & Sons, Ltd.}, number={1}, journal={POLYMERS FOR ADVANCED TECHNOLOGIES}, author={Zhang, W. and Lin, M. and Winesett, A. and Dhez, O. and Kilcoyne, A. Ld. and Ade, H. and Rubinstein, M. and Shafi, K. V. P. M. and Ulman, A. and Gersappe, D. and et al.}, year={2011}, month={Jan}, pages={65–71} } @article{watts_belcher_thomsen_ade_dastoor_2009, title={A Quantitative Study of PCBM Diffusion during Annealing of P3HT: PCBM Blend Films}, volume={42}, ISSN={["1520-5835"]}, DOI={10.1021/ma901444u}, abstractNote={Scanning transmission X-ray microscopy has been used to quantitatively map the composition of P3HT:PCBM blend films in the vicinity of PCBM crystals formed during annealing at 140 °C. The observed PCBM concentration profiles around these crystals have been fitted to Fick’s second law of diffusion and the diffusion constant found to be 2.5 × 10−14 m2 s−1. The PCBM concentration at the crystal boundary was found to be 19% (v/v) and is interpreted, together with the annealing temperature of 140 °C, as a point on the bimodal line of the composition−temperature phase diagram. The diffusion of PCBM through P3HT is observed to be bulk-dominated, in contrast to the surface/interface-dominated diffusion observed in MDMO-PPV:PCBM blend films by Yang et al.(1, 2)}, number={21}, journal={MACROMOLECULES}, author={Watts, Benjamin and Belcher, Warwick J. and Thomsen, Lars and Ade, Harald and Dastoor, Paul C.}, year={2009}, month={Nov}, pages={8392–8397} } @article{ade_wang_garcia_yan_sohn_hexemer_bazan_nguyen_kramer_2009, title={Characterization of multicomponent polymer trilayers with resonant soft X-ray reflectivity}, volume={47}, ISSN={0887-6266 1099-0488}, url={http://dx.doi.org/10.1002/polb.21730}, DOI={10.1002/polb.21730}, abstractNote={AbstractResonant soft X‐ray reflectivity (RSoXR) has been used to quantify the layer thicknesses and the interfacial widths of a single, complex thin film with three polymeric layers supported on an inorganic substrate. By adjusting the photon energy, the sensitivity to particular interfaces within the trilayer can be selectively enhanced. The results significantly improve and broaden the capabilities of RSoXR, which has previously only been demonstrated and used for bilayers on silicon substrates. The capability of RSoXR to characterize polymer trilayers was not readily predictable from prior bilayer results, as the RSoXR characterization of bilayers benefits from a strong X‐ray reflection from the substrate that serves as a reference beam with which the reflections from the other interfaces interfere with. The impact of having the capability to investigate trilayers is exemplified by discussing the utility of RSoXR to characterize organic electronic light emitting multilayers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1291–1299, 2009}, number={13}, journal={Journal of Polymer Science Part B: Polymer Physics}, publisher={Wiley}, author={Ade, H. and Wang, C. and Garcia, A. and Yan, H. and Sohn, K. E. and Hexemer, A. and Bazan, G. C. and Nguyen, T.-Q. and Kramer, E. J.}, year={2009}, month={Jul}, pages={1291–1299} } @article{mcneill_watts_thomsen_belcher_greenham_dastoor_ade_2009, title={Evolution of Laterally Phase-Separated Polyfluorene Blend Morphology Studied by X-ray Spectromicroscopy}, volume={42}, ISSN={["1520-5835"]}, DOI={10.1021/ma801816r}, abstractNote={The morphological evolution of laterally phase-separated polyfluorene blends composed of poly(9,9′-dioctylfluorene-co-bis-N,N′-(4-butylphenyl)-bis-N,N′-phenyl-1,4-phenylenediamine) (PFB) and poly(9...}, number={9}, journal={MACROMOLECULES}, author={McNeill, Christopher R. and Watts, Benjamin and Thomsen, Lars and Belcher, Warwick J. and Greenham, Neil C. and Dastoor, Paul C. and Ade, Harald}, year={2009}, month={May}, pages={3347–3352} } @article{fujii_dupin_araki_armes_ade_2009, title={First Direct Imaging of Electrolyte-Induced Deswelling Behavior of pH-Responsive Microgels in Aqueous Media Using Scanning Transmission X-ray Microscopy}, volume={25}, ISSN={["0743-7463"]}, DOI={10.1021/la804212y}, abstractNote={Lightly cross-linked sterically stabilized poly(2-vinylpyridine) latexes exhibit pH-responsive behavior, undergoing a latex-to-microgel transition below pH 4.1 as a result of protonation of the pyridine pendent groups. We have examined both the latex and microgel states of such particles directly in aqueous solution using scanning transmission X-ray microscopy (STXM). Moreover, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy studies confirm that the nitrogen atoms of the microgel particles are fully protonated at low pH. The addition of salt causes partial deswelling of these microgel particles, but spectroscopic analysis confirms the retention of their cationic character. This is the first direct visualization of the effect of electrolyte screening on microgel dimensions in aqueous solution. In each case, the observed particle dimensions are consistent with dynamic light scattering characterization, especially when polydispersity effects are taken into consideration.}, number={5}, journal={LANGMUIR}, author={Fujii, Syuji and Dupin, Damien and Araki, Tohru and Armes, Steven P. and Ade, Harald}, year={2009}, month={Mar}, pages={2588–2592} } @article{martin_jimenez_angeles gomez_ade_kilcoyne_2010, title={Interfacial Interactions in PP/MMT/SEBS Nanocomposites}, volume={43}, ISSN={["0024-9297"]}, DOI={10.1021/ma901952p}, abstractNote={The intercalation capability of poly(styrene-b-ethylene butylene-b-styrene) (SEBS) in nanocomposites of isotactic polypropylene (PP) with 5 wt % of organically modified montmorillonite (C20A), prepared by melt blending, has been investigated. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies have shown the presence of intercalated structures in the nanocomposite. In a previous research, we studied the intercalation capability of a commercial compatibilizer.(1) Those results, with the study we present in this work, allow us a better understanding of the mechanism of compatibilization and a deeper characterization of the structure and morphology of the nanocomposite. Scanning transmission X-ray microscopy (STXM) has been used. Because of the excellent chemical sensitivity and the high spatial resolution (∼40 nm) of this technique, we have proved that C20A is not in direct contact with the PP phase because the clay is always located inside the elastomer domains. The elastomer is surr...}, number={1}, journal={MACROMOLECULES}, author={Martin, Zulima and Jimenez, Ignacio and Angeles Gomez, M. and Ade, Harald and Kilcoyne, David A.}, year={2010}, month={Jan}, pages={448–453} } @article{wang_garcia_yan_sohn_hexemer_nguyen_bazan_kramer_ade_2009, title={Interfacial widths of conjugated polymer bilayers}, volume={131}, DOI={10.1021/ja905293m}, abstractNote={The interfaces of conjugated polyelectrolyte (CPE)/poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) bilayers cast from differential solvents are shown by resonant soft X-ray reflectivity (RSoXR) to be very smooth and sharp. The chemical interdiffusion due to casting is limited to less than 0.6 nm, and the interface created is thus nearly "molecularly" sharp. These results demonstrate for the first time and with high precision that the nonpolar MEH-PPV layer is not much disturbed by casting the CPE layer from a polar solvent. A baseline is established for understanding the role of interfacial structure in determining the performance of CPE-based polymer light-emitting diodes. More broadly, we anticipate further applications of RSoXR as an important tool in achieving a deeper understanding of other multilayer organic optoelectronic devices, including multilayer photovoltaic devices.}, number={35}, journal={Journal of the American Chemical Society}, author={Wang, C. and Garcia, A. and Yan, H. P. and Sohn, K. E. and Hexemer, A. and Nguyen, T. Q. and Bazan, G. C. and Kramer, E. J. and Ade, Harald}, year={2009}, pages={12538-} } @article{ade_watts_swaraj_mcneill_thomsen_belcher_dastoor_2009, title={NEXAFS microscopy of polymeric materials: Successes and challenges encountered when characterizing organic devices}, volume={186}, ISBN={["*****************"]}, ISSN={["1742-6596"]}, DOI={10.1088/1742-6596/186/1/012102}, abstractNote={We summarize recent developments in x-ray microscopy of polymers by focusing on the characterization of organic electronic devices. The quantitative compositions of model polymer blends have been mapped at a resolution of ∼35 nm. Since it could be inferred that these devices have structures smaller than 35 nm, quantitative compositional mapping at length scales below the present resolution limit of x-ray microscopy is required. Organic devices thus serve to both highlight the success of NEXAFS microscopy to date, but to also outline the very real need for higher spatial resolution. New approaches to create improved optics or different acquisition modalities are required if x-ray microscopy is to make sustained contributions to such an important area of research as organic devices.}, journal={9TH INTERNATIONAL CONFERENCE ON X-RAY MICROSCOPY}, author={Ade, H. and Watts, B. and Swaraj, S. and McNeill, C. and Thomsen, L. and Belcher, W. and Dastoor, P. C.}, year={2009} } @article{ade_stoll_2009, title={Near-edge X-ray absorption fine-structure microscopy of organic and magnetic materials}, volume={8}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/nmat2399}, DOI={10.1038/nmat2399}, abstractNote={Many high-performance materials and novel devices consist of multiple components and are naturally or intentionally nano-structured for optimal properties and performance. To understand their structure-property relationships fully, quantitative compositional analysis at length scales below 100 nm is required, a need that is often uniquely addressed using soft X-ray microscopy. Similarly, the interaction of X-rays with magnetic materials provides unique element-specific contrast that allows the determination of magnetic properties in multi-element antiferromagnetic and ferromagnetic materials. Pump-probe-type experiments can even investigate magnetic domain dynamics. Here we review and exemplify the ability of soft X-ray microscopy to provide information that is otherwise inaccessible, and discuss a perspective on future developments.}, number={4}, journal={Nature Materials}, publisher={Springer Nature}, author={Ade, Harald and Stoll, Herman}, year={2009}, month={Apr}, pages={281–290} } @article{burke_belcher_thomsen_watts_mcneill_ade_dastoor_2009, title={Role of Solvent Trapping Effects in Determining the Structure and Morphology of Ternary Blend Organic Devices}, volume={42}, ISSN={["1520-5835"]}, DOI={10.1021/ma802632y}, abstractNote={We present results of scanning transmission X-ray microscopy (STXM) measurements of bulk heterojunction organic solar cells built from a ternary blend of poly(3-hexylthiophene) (P3HT), [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), and [2,3,12,13-tetracyano-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrinato]copper(II) (Cu(CN)4P) porphyrin. These results show evidence of solvent trapping due to porphyrin in the film. Upon annealing, submicrometer depressions are observed in the ternary blend films, corresponding to the evolution of solvent that is associated with the small porphyrin aggregates that phase segregate in the middle of the depressions. The areal density and size of the depressions change systematically with porphyrin concentration in the ternary blend. The relationship of the observed morphologies to the previously measured device performance is discussed.}, number={8}, journal={MACROMOLECULES}, author={Burke, Kerry B. and Belcher, Warwick J. and Thomsen, Lars and Watts, Benjamin and McNeill, Christopher R. and Ade, Harald and Dastoor, Paul C.}, year={2009}, month={Apr}, pages={3098–3103} } @article{watts_queen_kilcoyne_tyliszczak_hellman_ade_2009, title={Soft X-Ray Beam Induced Current Technique}, volume={186}, ISBN={["*****************"]}, ISSN={["1742-6596"]}, DOI={10.1088/1742-6596/186/1/012023}, abstractNote={Direct mapping of the charge transport efficiency of polymer solar cell devices using a soft X-ray beam induced current (SoXBIC) method is described. By fabricating a polymer solar cell on an x-ray transparent substrate, we demonstrate the ability to map polymer composition and nanoscale structure within an operating solar cell device and to simultaneously measure the local charge transport efficiency via the short-circuit current. A simple model is calculated and compared to experimental SoXBIC data of a PFB:F8BT bulk-heterojunction device in order to gain greater insight into the device operation and physics.}, journal={9TH INTERNATIONAL CONFERENCE ON X-RAY MICROSCOPY}, author={Watts, B. and Queen, D. and Kilcoyne, A. L. D. and Tyliszczak, T. and Hellman, F. and Ade, H.}, year={2009} } @article{martin_jimenez_angeles gomez_ade_kilcoyne_hernadez-cruz_2009, title={Spectromicroscopy Study of Intercalation and Exfoliation in Polypropylene/Montmorillonite Nanocomposites}, volume={113}, ISSN={["1520-6106"]}, DOI={10.1021/jp9049999}, abstractNote={We present a combined study by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission X-ray microscopy (STXM) of the successful formation of nanocomposites of polypropylene with montmorillonite by melt processing, providing a complete picture of the intercalation and exfoliation processes taking place. The nanocomposites contained 5 wt % of an organically modified montmorillonite, and different amounts of polypropylene-graft-maleic anhydride, used as a polar compatibilizer. Microscopy reveals a complex morphology, with partial intercalation/exfoliation, which depends on the concentration of compatibilizer. STXM spectromicroscopy provides direct information of the presence of different polymer components at the polymer-silicate interfaces and details on the intercalation mechanism.}, number={32}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Martin, Zulima and Jimenez, Ignacio and Angeles Gomez, M. and Ade, Harald W. and Kilcoyne, David A. and Hernadez-Cruz, Daniel}, year={2009}, month={Aug}, pages={11160–11165} } @article{meyer_ade_2009, title={The effect of angle of incidence on the optical field distribution within thin film organic solar cells}, volume={106}, ISSN={["0021-8979"]}, DOI={10.1063/1.3253718}, abstractNote={The optical field within an organic solar cell is the result of thin film interference effects which become more complex at higher angles of incidence. We use optical modeling to study the optical field at oblique incidence. Our findings include an expansion of the interference pattern, a significant intensity of p-polarized light at the cathode interface, and a strong dependence on indium tin oxide and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) thicknesses for single wavelengths. Applications to current research are presented including recent misconceptions in the literature and suggestions for new research.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Meyer, A. and Ade, H.}, year={2009}, month={Dec} } @article{swaraj_wang_araki_mitchell_liu_gaynor_deshmukh_yan_mcneill_ade_2009, title={The utility of resonant soft x-ray scattering and reflectivity for the nanoscale characterization of polymers}, volume={167}, ISSN={["1951-6355"]}, DOI={10.1140/epjst/e2009-00946-3}, journal={EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS}, author={Swaraj, S. and Wang, C. and Araki, T. and Mitchell, G. and Liu, L. and Gaynor, S. and Deshmukh, B. and Yan, H. and McNeill, C. R. and Ade, H.}, year={2009}, month={Feb}, pages={121–126} } @article{mcneill_watts_swaraj_ade_thomsen_belcher_dastoor_2008, title={Evolution of the nanomorphology of photovoltaic polyfluorene blends: sub-100 nm resolution with x-ray spectromicroscopy}, volume={19}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/19/42/424015}, abstractNote={We investigate the influence of annealing on the morphology of intimately mixed blends of the conjugated polymers poly(9,9′-dioctylfluorene-co-bis-N,N′-(4-butylphenyl)-bis-N,N′-phenyl-1,4-phenylene-diamine) (PFB) and poly(9,9′-dioctylfluorene-co-benzothiadiazole) (F8BT) with scanning transmission x-ray microscopy (STXM). Through the use of a zone plate with theoretical Rayleigh resolution of 30 nm, we are able to resolve sub-100 nm bulk structure in these films. Surprisingly, for unannealed films spin-coated from chloroform we observe features with an average diameter of 85 nm. The high degree of photoluminescence quenching in these as-spun films (>95%) implies that there is significant intermixing within the 85 nm structures, indicating that a hierarchy of phase separation exists even on the length scale of less than 100 nm. With annealing up to 160 °C, close to the Tg of the components, there is little change in the feature sizes observed by STXM, although an increase in variation of the composition is observed. With annealing above 160 °C the imaged features begin to evolve in size, increasing to 225 nm in extent, alongside large changes in composition with annealing to 200 °C. Comparing the evolution of morphology imaged by STXM with the change in photoluminescence quenching with annealing, we propose that phase separation first evolves via the evolution of relatively pure phases on the length scale of a few to tens of nanometres within the larger 85 nm structures. Once the length scale of compositional fluctuations exceeds 85 nm (for anneal temperatures above 160 °C) the hierarchy of phase separation is lost and the subsequent morphological evolution is readily imaged by STXM. Applying the results of an exciton diffusion and quenching model, we find good agreement between the size of the domains measured by STXM (above 180 °C) and the results of the model for an exciton diffusion length of 15 nm. The growth in domain size and towards purer structures has also been observed with resonant soft x-ray scattering.}, number={42}, journal={NANOTECHNOLOGY}, author={McNeill, C. R. and Watts, B. and Swaraj, S. and Ade, H. and Thomsen, L. and Belcher, W. and Dastoor, P. C.}, year={2008}, month={Oct} } @article{cody_alexander_yabuta_kilcoyne_araki_ade_dera_fogel_militzer_mysen_2008, title={Organic thermometry for chondritic parent bodies}, volume={272}, ISSN={["0012-821X"]}, DOI={10.1016/j.epsl.2008.05.008}, abstractNote={Abstract A unique spectroscopic feature has been identified in a study of twenty-five different samples of meteoritic insoluble organic matter (IOM) spanning multiple chemical classes, groups, and petrologic types, using carbon X-ray Absorption Near Edge Structure (XANES) spectroscopy. The intensity of this feature, a 1s − σ⁎ exciton, appears to provide a precise measure of parent body metamorphism. The intensity of this exciton is also shown to correlate well with a large negative paramagnetic shift observed through solid state 13C NMR. Experiments reveal that upon heating primitive IOM is transformed into material that is indistinguishable from that in thermally processed chondrites, including the development of the 1s − σ⁎ exciton. A thermo-kinetic expression is derived from the experimental data that allows the intensity of the 1s − σ⁎ exciton to be used to estimated the effective temperature integrated over time. A good correlation is observed between the intensity of the 1s − σ⁎ exciton and previously published microRaman spectral data. These data provide a self-consistent organic derived temperature scale for the purpose of calibrating Raman based thermometric expressions.}, number={1-2}, journal={EARTH AND PLANETARY SCIENCE LETTERS}, author={Cody, G. D. and Alexander, C. M. O'D. and Yabuta, H. and Kilcoyne, A. L. D. and Araki, T. and Ade, H. and Dera, R. and Fogel, M. and Militzer, B. and Mysen, B. O.}, year={2008}, month={Jul}, pages={446–455} } @article{raabe_tzvetkov_flechsig_boege_jaggi_sarafimov_vernooij_huthwelker_ade_kilcoyne_et al._2008, title={PolLux: A new facility for soft x-ray spectromicroscopy at the Swiss Light Source}, volume={79}, ISSN={["1089-7623"]}, DOI={10.1063/1.3021472}, abstractNote={We report on the successful installation and operation of a scanning transmission x-ray microspectroscope (STXM) at the PolLux facility at the Swiss Light Source. This integration of an advanced STXM with improved sample handling capabilities and a novel beamline provides unique capabilities. PolLux uses linearly or circularly polarized x-rays from a bending magnet with an extended photon energy range (200–1400 eV). It is therefore well suited to determine a sample’s quantitative chemical composition, molecular orientation, or thickness of organic as well as condensed matter materials. The local magnetic state of magnetic thin films is accessible through fast helicity switching by steering the electron beam off axis through the bending magnet. Ex vacuo girder movers allow fast and highly reproducible (<1 μm) alignment of the instrument with respect to the photon beam. The present spatial resolution is ∼20 nm, limited by the zone plates utilized. The instrument has the stability and positional resolution to operate with much higher resolution optics as it becomes available. In addition to characterization experiments, we present several typical examples from materials research and environmental science to exemplify the capabilities.}, number={11}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Raabe, J. and Tzvetkov, G. and Flechsig, U. and Boege, M. and Jaggi, A. and Sarafimov, B. and Vernooij, M. G. C. and Huthwelker, T. and Ade, H. and Kilcoyne, D. and et al.}, year={2008}, month={Nov} } @article{cody_ade_alexander_araki_butterworth_fleckenstein_flynn_gilles_jacobsen_kilcoyne_et al._2008, title={Quantitative organic and light-element analysis of comet 81P/Wild 2 particles using C-, N-, and O-mu-XANES}, volume={43}, ISSN={["1945-5100"]}, DOI={10.1111/j.1945-5100.2008.tb00627.x}, abstractNote={Abstract— Synchrotron‐based soft X‐ray micro‐analysis was performed on particles extracted from the Stardust aerogel collector in order to obtain detailed organic functional group information on any organic solids captured as part of the Principal Examination suite of analyses for samples from comet 81P/Wild 2. It is observed that cometary organic carbon captured in aerogel is present in a number of different manifestations and often intimately associated with silicates. Carbon X‐ray absorption near edge structure (XANES) spectra reveal considerable chemical complexity in all of the organic particles studied so far. Universally, the comet 81P/Wild 2 organic particles contain low concentrations of aromatic and/or olefinic carbon relative to aliphatic and heteroatom‐containing functional groups, e.g., amide, carboxyl, and alcohol/ethers. N‐XANES confirms the presence and assignments of these functional groups. In general, the XANES data record considerable chemical complexity across the range of organic samples currently analyzed. The atomic ratios, N/C and O/C, derived from XANES data reveal a wide range in heteroatom content; in all cases these elemental ratios are higher than that of primitive meteoritic organic matter. The wide range in chemistry, both in elemental abundances and specific organic functional groups, suggests that the comet 81P/Wild 2 organic solids may have multiple origins.}, number={1-2}, journal={METEORITICS & PLANETARY SCIENCE}, author={Cody, George D. and Ade, Harald and Alexander, Conel M. O'D. and Araki, Tohru and Butterworth, Anna and Fleckenstein, Holger and Flynn, George and Gilles, Mary K. and Jacobsen, Chris and Kilcoyne, A. L. D. and et al.}, year={2008}, pages={353–365} } @article{ade_2008, title={X-ray Microscopy of Soft Matter}, volume={14}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927608084092}, DOI={10.1017/S1431927608084092}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Ade, H}, year={2008}, month={Aug}, pages={58–59} } @article{watts_ade_2008, title={A simple method for determining linear polarization and energy calibration of focused soft X-ray beams}, volume={162}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2007.08.008}, abstractNote={Although critical to quantitative linear dichroism studies of molecular orientation, the degree of linear polarization of focused soft X-ray beams delivered by X-ray microscopes has not been previously measured. Here, we present a scaled-down version of a recently developed technique in which the π∗ near edge X-ray absorption fine structure (NEXAFS) resonance of highly oriented pyrolytic graphite (HOPG) is used to probe the electric field intensity in each direction and hence deduce the degree of linear polarization of the incident X-ray beam. Applying this technique to the soft X-ray microscope at beamline 5.3.2 of the Advanced Light Source in Berkeley, CA, yielded a measured value of 79±11%, for the first Stokes parameter of 0.79±0.11 or as a Stöhr P factor of 0. 89±0.06. It is expected that the error margin could be significantly reduced via the use of an in-vacuum rotation actuator. We have also calibrated the energy of the graphite exciton to be 291.65±0.025 eV, improving the utility of graphite as an energy calibration standard for NEXAFS and allowing the convenience of both energy calibration and polarization determination with a single inexpensive sample.}, number={2}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Watts, B. and Ade, H.}, year={2008}, month={Feb}, pages={49–55} } @article{harton_zhu_stevie_aoyama_ade_2007, title={Carbon-13 labeling for quantitative analysis of molecular movement in heterogeneous organic materials using secondary ion mass spectrometry}, volume={79}, ISSN={["1520-6882"]}, DOI={10.1021/ac070437q}, abstractNote={Secondary ion mass spectrometry (SIMS) is used to probe the movement of macromolecules in heterogeneous organic systems. Using 13C tracer labeling and two model systems, polystyrene/poly(2-vinylpyridine) (PS/P2VP) and polystyrene/poly(4-bromostyrene) (PS/P4BrS), the diffusion of 13C-labeled PS has been investigated near the respective heterogeneous interfaces using a CAMECA-IMS-6F magnetic sector mass spectrometer. 13C labeling has been shown to greatly minimize matrix effects (i.e., changes in secondary ion yields due to changing chemical environment) in heterogeneous systems. P2VP is a nitrogen-rich polymer (C7H7N monomer composition), making it an excellent model polymer for exploration of this technique for potential future use in biological applications, and probing the PS/P4BrS interface demonstrates the versatility of this technique for analysis of various heteroatom-containing materials. Results confirm that the 13C-labeling method does indeed allow for quantitative analysis of molecular movement in heterogeneous organic systems containing matrix-enhancing heteroatoms such as nitrogen. Therefore, extension of this method to more complicated biological systems involving multiple heteroatoms (oxygen, nitrogen, etc.), layers, and heterogeneous interfaces, as well as two- and three-dimensional profiling and imaging using SIMS, can be envisaged.}, number={14}, journal={ANALYTICAL CHEMISTRY}, author={Harton, Shane E. and Zhu, Zhengmao and Stevie, Frederick A. and Aoyama, Yoko and Ade, Harald}, year={2007}, month={Jul}, pages={5358–5363} } @article{hub_harton_hunt_fink_ade_2007, title={Influence of sample preparation and processing on observed glass transition temperatures of polymer nanocomposites}, volume={45}, ISSN={["1099-0488"]}, DOI={10.1002/polb.21249}, abstractNote={AbstractPolymer composites composed of poly(methyl methacrylate) (PMMA) and silica (14 nm diameter) have been investigated. The influences of sample preparation and processing have been probed. Two types of sample preparation methods were investigated: (i) solution mixture of PMMA and silica in methyl ethyl ketone and (ii) in situ synthesis of PMMA in the presence of silica. After removing all solvent or monomer, as confirmed using thermogravimetric analysis, and after compression molding, drops in Tg of 5–15 °C were observed for all composites (2–12% w/w silica) and even pure polymer reference samples. However, after additional annealing for 72 h at 140 °C, all previously observed drops in Tg disappeared, and the intrinsic Tg of bulk, pure PMMA was again observed. This is indicative of nonequilibrium trapped voids being present in the as‐molded samples. Field‐emission scanning electron microscopy was used to show well‐dispersed particles, and dynamic mechanical analysis was used to probe the mechanical properties (i.e., storage modulus) of the fully equilibrated composites. Even though no equilibrium Tg changes were observed, the addition of silica to the PMMA matrices was observed to improve the mechanical properties of the glassy polymer host. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2270–2276, 2007}, number={16}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Hub, Christian and Harton, Shane E. and Hunt, Marcus A. and Fink, Rainer and Ade, Harald}, year={2007}, month={Aug}, pages={2270–2276} } @article{harton_zhu_stevie_griffis_ade_2007, title={Mass fractionation of carbon and hydrogen secondary ions upon Cs+ and O-2(+) bombardment of organic materials}, volume={25}, ISSN={["1520-8559"]}, DOI={10.1116/1.2718957}, abstractNote={A phenomenon known as mass fractionation has been probed in organic materials using secondary ion mass spectrometry (SIMS). Mass fractionation occurs because two isotopes of a particular species (i.e., identical number of protons, but different number of neutrons) do not have identical secondary ion yields in a constant chemical environment. Two primary ion probes, Cs+ and O2+, have been utilized with detection of negative and positive secondary ions, respectively, using a magnetic sector mass spectrometer. These two analysis conditions have been found to yield considerably different mass fractionation effects as a result of different sputtering and ionization mechanisms. Also, as determined previously with SIMS analysis of inorganic materials, the lower molecular weight species carbon and hydrogen are particularly susceptible to mass fractionation effects. Because organic materials are primarily composed of carbon and hydrogen, and because isotopic labeling is often utilized to accurately analyze such materials, knowledge of these effects in organic materials is essential for quantitative SIMS analysis.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Harton, Shane E. and Zhu, Zhengmao and Stevie, Frederick A. and Griffis, Dieter P. and Ade, Harald}, year={2007}, pages={480–484} } @misc{ade_hitchcock_2008, title={NEXAFS microscopy and resonant scattering: Composition and orientation probed in real and reciprocal space}, volume={49}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2007.10.030}, abstractNote={Near Edge X-ray Absorption Fine Structure (NEXAFS) spectromicroscopy, resonant scattering and resonant reflectivity are specialized, synchrotron radiation based, soft X-ray characterization tools that provide moiety-specific contrast and either real-space imaging at ∼30 nm spatial resolution, or scattering signals which can be inverted to provide chemically sensitive information at an even higher spatial resolution (<5 nm). These X-ray techniques complement other real and reciprocal space characterization tools such as various microscopies and conventional electron, X-ray and neutron scattering. We provide an overview of these synchrotron based tools, describe their present state-of-the-art and discuss a number of applications to exemplify their unique aspects.}, number={3}, journal={POLYMER}, author={Ade, Harald and Hitchcock, Adam P.}, year={2008}, month={Feb}, pages={643–675} } @article{wang_araki_watts_harton_koga_basu_ade_2007, title={Resonant soft x-ray reflectivity of organic thin films}, volume={25}, ISSN={["0734-2101"]}, DOI={10.1116/1.2731352}, abstractNote={At photon energies close to absorption edges in the soft x-ray range, the complex index of refraction, n=1−δ−iβ, of organic materials varies rapidly as a function of photon energy in a manner that strongly depends on the chemical moieties and functionalities present in the material. The authors present details of how these molecular structure specific variations in the complex index of refraction can be utilized to enhance and tune the contrast in reflectivity experiments of organic films. This near edge contrast enhancement mimics the specific contrast achieved through deuterium labeling in neutron reflectivity (NR). This relatively new x-ray approach, resonant soft x-ray reflectivity (RSoXR), thus combines aspects of NR and conventional x-ray reflectivity (XR), yet does not require special chemical procedures. The capabilities of RSoXR are exemplified using a number of polymeric bi- and multilayers. Furthermore, a direct comparison of RSoXR to conventional x-ray reflectivity and NR for polystyrene and poly(methyl methacrylate) bilayers verifies that RSoXR is an excellent alternative tool for the characterization of organic thin films. The influence of the longitudinal and transverse coherence properties as well as the divergence of the x-ray or neutron beam on the capabilities and limitations of each reflectivity variant is discussed.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Wang, Cheng and Araki, Tohru and Watts, Benjamin and Harton, Shane and Koga, Tadanori and Basu, Saibal and Ade, Harald}, year={2007}, pages={575–586} } @article{mcneill_watts_thomsen_ade_greenham_dastoor_2007, title={X-ray microscopy of photovoltaic polyfluorene blends: Relating nanomorphology to device performance}, volume={40}, ISSN={["1520-5835"]}, DOI={10.1021/ma070132d}, abstractNote={The composition of blend films of poly(9,9‘-dioctylfluorene-co-bis-N,N‘-(4-butylphenyl)-bis-N,N‘-phenyl-1,4-phenylenediamine) (PFB) and poly(9,9‘-dioctylfluorene-co-benzothiadiazole) (F8BT) used in prototype polymer solar cells has been quantitatively mapped using scanning transmission X-ray microscopy (STXM). The resolution of the STXM technique is 50 nm or better, allowing the first nanoscale lateral chemical mapping of this blend system. For 1:1 blend films spin-coated from xylene we find that the F8BT-rich domain is over 90% pure (by weight) and the PFB-rich domain contains 70% PFB. For 5:1 and 1:5 blend films processed from xylene, the minority phases are found to be intermixed, containing as much as 50% by weight of the majority polymer. Films prepared from chloroform with a 1:1 weight ratio have also been imaged but show no features on the length scale of 50 nm or greater. Additionally, the performance of photovoltaic devices fabricated using films prepared in an identical fashion to those prepared...}, number={9}, journal={MACROMOLECULES}, author={McNeill, Christopher R. and Watts, Benjamin and Thomsen, Lars and Ade, Harald and Greenham, Neil C. and Dastoor, Paul C.}, year={2007}, month={May}, pages={3263–3270} } @article{hoedl_young_ade_lozano_2006, title={An electron transparent proton detector for neutron decay studies}, volume={99}, ISSN={0021-8979}, DOI={10.1063/1.2186970}, abstractNote={We have developed an ultrathin (<100nm), very strong polyimide foil which can span more than 6×6cm2 and is ideal for the fabrication of low energy proton detectors. We have produced a proton detector geometry in which protons incident on the foil with kinetic energies greater than about 25keV produce, on average, more than ten secondary electrons in a conversion crystal evaporated on the back face of the foil. These secondary electrons can be “postaccelerated” and counted in a variety of detectors. The polyimide foils are much more durable than carbon foils previously used in similar detection geometries. LiF was chosen as the conversion crystal, which is relatively insensitive to exposure to air, improving their secondary electron yield under typical operating conditions. In addition, we describe the operation of a very simple, small scale proton accelerator and detector testing chamber capable of providing up to 10kHz of beam with energies between 10 and 50keV onto a biased target with a maximum ion contamination of 0.5%.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Hoedl, SA and Young, AR and Ade, H and Lozano, A}, year={2006}, month={Apr}, pages={084904} } @article{harton_stevie_zhu_ade_2006, title={Carbon-13 labeled polymers: An alternative tracer for depth profiling of polymer films and multilayers using secondary ion mass spectrometry}, volume={78}, ISSN={["1520-6882"]}, DOI={10.1021/ac060133o}, abstractNote={13C labeling is introduced as a tracer for depth profiling of polymer films and multilayers using secondary ion mass spectrometry (SIMS). Deuterium substitution has traditionally been used in depth profiling of polymers but can affect the phase behavior of the polymer constituents with reported changes in both bulk-phase behavior and surface and interfacial interactions. SIMS can provide contrast by examining various functional groups, chemical moieties, or isotopic labels. 13C-Labeled PS (13C-PS) and unlabeled PS (12C-PS) and PMMA were synthesized using atom-transfer radical polymerization and assembled in several model thin-film systems. Depth profiles were recorded using a Cameca IMS-6f magnetic sector mass spectrometer using both 6.0-keV impact energy Cs+ and 5.5-keV impact energy O2+ primary ion bombardment with detection of negative and positive secondary ions, respectively. Although complete separation of 12C1H from 13C is achieved using both primary ion species, 6.0-keV Cs+ clearly shows improved detection sensitivity and signal-to-noise ratio for detection of 12C, 12C1H, and 13C secondary ions. The use of Cs+ primary ion bombardment results in somewhat anomalous, nonmonotonic changes in the 12C, 12C1H, and 13C secondary ion yields through the PS/PMMA interface; however, it is shown that this behavior is not due to sample charging. Through normalization of the 13C secondary ion yield to the total C (12C + 13C) ion yield, the observed effects through the PS/PMMA interface can be greatly minimized, thereby significantly improving analysis of polymer films and multilayers using SIMS. Mass spectra of 13C-PS and 12C-PS were also analyzed using a PHI TRIFT I time-of-flight mass spectrometer, with 15-keV Ga+ primary ion bombardment and detection of positive secondary ions. The (12)C7(1)H7 ion fragment and its 13C-enriched analogues have significant secondary ion yields with negligible mass interferences, providing an early indication of the potential for future use of this technique for cluster probe depth profiling of high molecular weight 13C-labeled fragments.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Harton, S. E. and Stevie, F. A. and Zhu, Z. and Ade, H.}, year={2006}, month={May}, pages={3452–3460} } @article{harton_stevie_ade_2006, title={Carbon-13 labeling for improved tracer depth profiling of organic materials using secondary ion mass spectrometry}, volume={17}, ISSN={["1879-1123"]}, DOI={10.1016/j.jasms.2006.03.018}, abstractNote={13C labeling is introduced as an alternative to deuterium labeling for analysis of organic materials using secondary ion mass spectrometry (SIMS). A model macromolecular system composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA) was used to compare the effects of isotopic labeling using both deuterium substitution (dPS) and 13C labeling (13C-PS). Clear evidence is shown that deuterium labeling does introduce changes in the thermodynamic properties of the system, with the observation of segregation of dPS to an hPS:dPS/hPMMA interface. This type of behavior could significantly impact many types of investigations due to the potential for improper interpretation of experimental results as a consequence of labeling-induced artifacts. 13C labeling is shown to provide a true tracer for analysis using SIMS.}, number={8}, journal={JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY}, author={Harton, S. E. and Stevie, F. A. and Ade, H.}, year={2006}, month={Aug}, pages={1142–1145} } @article{harton_stevie_zhu_ade_2006, title={Changes in Thermodynamic Interactions at Highly Immiscible Polymer/Polymer Interfaces due to Deuterium Labeling}, volume={110}, ISSN={1520-6106 1520-5207}, url={http://dx.doi.org/10.1021/jp061811d}, DOI={10.1021/jp061811d}, abstractNote={Deuterium labeling has been shown previously to affect thermodynamic interactions at polymer surfaces, polymer/polymer heterogeneous interfaces, and in bulk (away from a surface or interface). However, the changes in polymer-polymer interactions due to deuterium labeling have not been thoroughly investigated for highly immiscible systems. It is shown here that deuterium labeling can influence polymer-polymer interactions at heterogeneous interfaces with highly immiscible systems, namely, polystyrene/poly(2-vinylpyridine) (PS/P2VP), polystyrene/poly(4-vinylpyridine) (PS/P4VP), and polystyrene/poly(methyl methacrylate) (PS/PMMA). Using secondary ion mass spectrometry, segregation of deuterium labeled polystyrene (dPS) in a dPS + unlabeled PS (dPS:hPS) blend layer was observed at the dPS:hPS/hP2VP, dPS:hPS/hP4VP, and dPS:hPS/hPMMA heterogeneous interfaces. However, a reference system involving PS on a PS brush shows no segregation of dPS to the interface.}, number={22}, journal={The Journal of Physical Chemistry B}, publisher={American Chemical Society (ACS)}, author={Harton, Shane E. and Stevie, Frederick A. and Zhu, Zhengmao and Ade, Harald}, year={2006}, month={Jun}, pages={10602–10605} } @article{si_araki_ade_kilcoyne_fisher_sokolov_rafailovich_2006, title={Compatibilizing bulk polymer blends by using organoclays}, volume={39}, ISSN={["1520-5835"]}, DOI={10.1021/ma060125+}, abstractNote={We have studied the morphology of blends of PS/PMMA, PC/SAN24, and PMMA/EVA and compared the morphologies with and without modified organoclay Cloisite 20A or Cloisite 6A clays. In each case we found a large reduction in domains size and the localization of the clay platelets along the interfaces of the components. The increased miscibility was accompanied in some cases, with the reduction of the system from multiple values of the glass transition temperatures to one. In addition, the modulus of all the systems increased significantly. A model was proposed where it was proposed that in-situ grafts were forming on the clay surfaces during blending and the grafts then had to be localized at the interfaces. This blending mechanism reflects the composition of the blend and is fairly nonspecific. As a result, this may be a promising technology for use in processing recycled blends where the composition is often uncertain and price is of general concern.}, number={14}, journal={MACROMOLECULES}, author={Si, Mayu and Araki, Tohru and Ade, Harald and Kilcoyne, A. L. D. and Fisher, Robert and Sokolov, Jonathan C. and Rafailovich, Miriam H.}, year={2006}, month={Jul}, pages={4793–4801} } @article{ennis_betz_ade_2006, title={Direct spincasting of polystyrene thin films onto poly(methyl methacrylate)}, volume={44}, ISSN={["1099-0488"]}, DOI={10.1002/polb.20976}, abstractNote={AbstractThe low vapor pressure solvent 1‐chloropentane was used to directly spincast polystyrene (PS) films onto poly(methyl methacrylate) (PMMA) with smooth surfaces and sharp interfaces. Interface roughness after removal of the PS layer with cyclohexane was determined with scanning force microscopy to be <1 nm. Dynamic secondary mass spectroscopy revealed an interfacial width below the resolution limit of ∼10 nm. Large area bilayers with smooth surfaces could be created. In addition, direct spincasting with 1‐chloropentane allows the production of thin PS films (<15 nm) and films of low molecular weight (<5 kDa) PS, all of which would be impossible to produce for this important model system by the traditional water‐transfer method. 1‐chloropentane was confirmed to be a sufficiently selective solvent for PS by measuring the Flory–Hugginsχparameters of 1‐chloropentane with PS and PMMA, respectively, with inverse gas chromatography. In the search for a suitable selective solvent, the authors have also examined the role of vapor pressure in spin casting smooth films over a wider molecular weight (4.3–190 kDa) and thickness range (∼5–500 nm) than previously reported. Only solvents with low vapor pressure produced high quality PS films. Methylcyclohexene can also be used to produce excellent, directly cast PS/PMMA bilayers, but with a smaller molecular weight and thickness window compared with 1‐chloropentane. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3234–3244, 2006}, number={22}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Ennis, David and Betz, Heike and Ade, Harald}, year={2006}, month={Nov}, pages={3234–3244} } @article{harton_stevie_ade_2006, title={Investigation of the effects of isotopic labeling, at a PS/PMMA interface using SIMS and mean-field theory}, volume={39}, ISSN={["1520-5835"]}, DOI={10.1021/ma052236z}, abstractNote={Isotopic labeling (deuteration) is known to affect the phase behavior of polystyrene (PS) and poly- (methyl methacrylate) (PMMA) blends, but little is known regarding the changes in the interfacial properties at the PS/PMMA interface due to deuteration of PS and/or PMMA. To investigate these potential changes, secondary ion mass spectrometry (SIMS) was used to measure real-space depth profiles of dPS in hPS:dPS/hPMMA bilayers, with the hPS:dPS blend being well within the single-phase region of the phase diagram. Profound changes in the thermodynamic behavior of this system at the polymer/polymer interface are observed in the form of significant segregation of dPS to the hPS:dPS/hPMMA interface. The observation of a depletion hole during the formation of an equilibrium excess of dPS implies that the energetic gain at the interface per dPS chain has to be >kT. These results cannot be described, even qualitatively, using previously reported changes in for PS/PMMA due to isotopic labeling. The previously reported values of for dPS/hPMMA and hPS/hPMMA actually predict a depletion of dPS at the hPS:dPS/hPMMA interface rather than the observed segregation. The observed interfacial excess is quantified by generating theoretical profiles, using self-consistent mean-field theory (SCMF), and fitting an effective interaction energy parameter ¢ p as a function of temperature. This parameter represents the asymmetry in dPS/hPMMA and hPS/PMMA interactions. The temperature dependency of ¢ p was found to be a factor of 3-4 greater than any of those reported for of PS/PMMA. It was also found that SCMF theory accurately describes the concentration dependency of dPS segregation at a constant dPS molecular weight using a concentration-independent ¢ p; however, ¢ p was found to be dependent on dPS molecular weight.}, number={4}, journal={MACROMOLECULES}, author={Harton, SE and Stevie, FA and Ade, H}, year={2006}, month={Feb}, pages={1639–1645} } @article{harton_luning_betz_ade_2006, title={Polystyrene/poly(methyl methacrylate) blends in the presence of cyclohexane: Selective solvent washing or equilibrium adsorption?}, volume={39}, ISSN={["0024-9297"]}, DOI={10.1021/ma061401n}, abstractNote={Cyclohexane has been frequently used as a selective solvent to remove PS layers or domains from polystyrene:poly(methyl methacrylate) (PS:PMMA) blends and for reorganization or self-assembly of polymer brushes and block copolymers. We have found that cyclohexane is not efficient at PS removal, observing significant residual PS at PMMA surfaces. In contrast, 1-chloropentane was found to be a far greater selective solvent (i.e., residual PS was essentially nonexistent). These results were compared to PMMA surfaces after PS was allowed to adsorb to the surface from a dilute theta solution in cyclohexane. Using near-edge X-ray absorption fine structure spectroscopy and inverse gas chromatography, coupled with self-consistent mean-field theory calculations, we have demonstrated that selectively washing a polymer from a polymer blend is nearly identical to adsorption of a polymer to a "soft" surface from a dilute solution. Improved knowledge about the effects of selective solvents will improve experimental analysis of washed systems as well as manipulation of block copolymers and polymer brushes for reorganization or self-assembly.}, number={22}, journal={MACROMOLECULES}, author={Harton, Shane E. and Luning, Jan and Betz, Heike and Ade, Harald}, year={2006}, month={Oct}, pages={7729–7733} } @article{araki_ade_stubbs_sundberg_mitchell_kortright_kilcoyne_2006, title={Resonant soft x-ray scattering from structured polymer nanoparticles}, volume={89}, DOI={10.1063/1.2356306}, abstractNote={The application of resonant soft x-ray scattering to chemically heterogeneous soft condensed matter materials is presented. Two structured styrene-acrylic polymer composite latex particles ∼230nm in diameter were utilized to delineate the potential utility of this technique. Angular scans at photon energies corresponding to strong scattering contrast between specific chemical moieties made it possible to infer the effective radii that correspond to the two polymer phases in the nanoparticles. The results show that resonant soft x-ray scattering should be a powerful complementary tool to neutron and hard x-ray scattering for the characterization of structured soft condensed matter nanomaterials.}, number={12}, journal={Applied Physics Letters}, author={Araki, T. and Ade, Harald and Stubbs, J. M. and Sundberg, D. C. and Mitchell, G. E. and Kortright, J. B. and Kilcoyne, A. L. D.}, year={2006} } @article{harton_stevie_griffis_ade_2006, title={SIMS depth profiling of deuterium labeled polymers in polymer multilayers}, volume={252}, ISSN={["0169-4332"]}, DOI={10.1016/j.apsusc.2006.02.146}, abstractNote={Abstract Thin planar polymer films are model systems for probing physical phenomena related to molecular confinement at polymer surfaces and polymer/polymer interfaces. Existing experimental techniques such as forward recoil spectrometry (FRES) and neutron reflectometry (NR) have been used extensively for analysis of these systems, although they suffer from relatively low depth resolution (FRES) or difficulties associated with inversion to real space (NR). In contrast, secondary ion mass spectrometry (SIMS) can provide real-space depth profiles of tracer labeled polymers directly with sufficient depth resolution for optimal analyses of these systems. Deuterated polystyrene (dPS) has been employed as the tracer polymer and has been embedded in a matrix of either unlabeled polystyrene (PS) or poly(cyclohexyl methacrylate) (PCHMA). These doped films have been placed on either poly(methyl methacrylate) (PMMA) or poly(2-vinyl pyridine) (P2VP) and thermally annealed. Varied analysis conditions for a magnetic sector SIMS instrument (CAMECA IMS-6f) were used to optimize the depth resolution and detection sensitivity while minimizing matrix effects and sample charging. Both Cs+ and O2+ primary ions have been used along with detection of negative and positive secondary ions, respectively. Impact energy and primary ion species have been shown to affect matrix secondary ion count rate for the various films studied.}, number={19}, journal={APPLIED SURFACE SCIENCE}, author={Harton, Shane E. and Stevie, Fred A. and Griffis, Dieter P. and Ade, Harald}, year={2006}, month={Jul}, pages={7224–7227} } @article{zou_araki_appel_kilcoyne_ade_2006, title={Solid state effects in the NEXAFS spectra of alkane-based van der Waals crystals: Breakdown of molecular model}, volume={430}, ISSN={["1873-4448"]}, DOI={10.1016/j.cplett.2006.08.110}, abstractNote={Experimental data conclusively shows that the weak van der Waals interactions between alkane molecules, <1.5% the strength of covalent bonding on a per carbon atom basis, modify the carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectrum significantly in ordered solids, both in intensity, spectral shape, peak position, and dichroic signature. This constitutes a further breakdown of the ‘building block’ model, or, more precisely, even a molecular model in interpreting NEXAFS spectra. These observations have significant implications for the interpretation and use of NEXAFS spectra from any crystalline or semi-crystalline macromolecules, small molecules, or other weakly interacting systems.}, number={4-6}, journal={CHEMICAL PHYSICS LETTERS}, author={Zou, Y. and Araki, T. and Appel, G. and Kilcoyne, A. L. D. and Ade, H.}, year={2006}, month={Oct}, pages={287–292} } @article{wang_rafailovich_sokolov_gersappe_araki_zou_kilcoyne_ade_marom_lustiger_2006, title={Substrate effect on the melting temperature of thin polyethylene films}, volume={96}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.96.028303}, abstractNote={Strong dependence of the crystal orientation, morphology, and melting temperature (Tm) on the substrate is observed in the semicrystalline polyethylene thin films. The Tm decreases with the film thickness decrease when the film is thinner than a certain critical thickness, and the magnitude of the depression increases with increasing surface interaction. We attribute the large Tm depression to the decrease in the overall free energy on melting, which is caused by the substrate attraction force to the chains that competes against the interchain force which drives the chains to crystallization.}, number={2}, journal={PHYSICAL REVIEW LETTERS}, author={Wang, Y and Rafailovich, M and Sokolov, J and Gersappe, D and Araki, T and Zou, Y and Kilcoyne, ADL and Ade, H and Marom, G and Lustiger, A}, year={2006}, month={Jan} } @article{lucovsky_hong_fulton_stoute_zou_nemanich_aspnes_ade_schlom_2005, title={Conduction band states of transition metal (TM) high-k gate dielectrics as determined from X-ray absorption spectra}, volume={45}, ISSN={["0026-2714"]}, DOI={10.1016/j.microrel.2004.11.038}, abstractNote={This paper uses X-ray absorption spectroscopy to study the electronic structure of the high-k gate dielectrics including TM and RE oxides. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d∗ states, which define the optical band gap, Eg, and the conduction band offset energy with respect to crystalline Si, EB. Eg and EB scale with the atomic properties of the TM and RE atoms providing important insights for identification high-k dielectrics that meet performance targets for advanced CMOS devices.}, number={5-6}, journal={MICROELECTRONICS RELIABILITY}, author={Lucovsky, G and Hong, JG and Fulton, CC and Stoute, NA and Zou, Y and Nemanich, RJ and Aspnes, DE and Ade, H and Schlom, DG}, year={2005}, pages={827–830} } @article{lucovsky_fulton_zhang_zou_luning_edge_whitten_nemanich_ade_schlom_et al._2005, title={Conduction band-edge states associated with the removal of d-state degeneracies by the Jahn-Teller effect}, volume={5}, ISSN={["1558-2574"]}, DOI={10.1109/TDMR.2005.845804}, abstractNote={X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-/spl kappa/ transition metal (TM) and trivalent lanthanide rare earth (RE) oxide gate dielectrics. The lowest conduction band d/sup */-states in TiO/sub 2/, ZrO/sub 2/ and HfO/sub 2/ are correlated with: 1) features in the O K/sub 1/ edge, and 2) transitions from occupied Ti 2p, Zr 3p and Hf 4p states to empty Ti 3d-, Zr 4d-, and Hf 5d-states, respectively. The relative energies of d-state features indicate that the respective optical bandgaps, E/sub opt/ (or equivalently, E/sub g/), and conduction band offset energy with respect to Si, E/sub B/, scale monotonically with the d-state energies of the TM/RE atoms. The multiplicity of d-state features in the Ti L/sub 2,3/ spectrum of TiO/sub 2/, and in the derivative of the O K/sub 1/ spectra for ZrO/sub 2/ and HfO/sub 2/ indicate a removal of d-state degeneracies that results from a static Jahn-Teller effect in these nanocrystalline thin film oxides. Similar removals of d-state degeneracies are demonstrated for complex TM/RE oxides including Zr and Hf titanates, and La, Gd and Dy scandates. Analysis of XAS and band edge spectra indicate an additional band edge state that is assigned Jahn-Teller distortions at internal grain boundaries. These band edges defect states are electronically active in photoconductivity (PC), internal photoemission (IPE), and act as bulk traps in metal oxide semiconductor (MOS) devices, contributing to asymmetries in tunneling and Frenkel-Poole transport that have important consequences for performance and reliability in advanced Si devices.}, number={1}, journal={IEEE TRANSACTIONS ON DEVICE AND MATERIALS RELIABILITY}, author={Lucovsky, G and Fulton, CC and Zhang, Y and Zou, Y and Luning, J and Edge, LF and Whitten, JL and Nemanich, RJ and Ade, H and Schlom, DG and et al.}, year={2005}, month={Mar}, pages={65–83} } @article{ge_rafailovich_sokolov_zou_ade_lüning_lustiger_marom_2005, title={Crystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density Polyethylene}, volume={38}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma0501601}, DOI={10.1021/ma0501601}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionCrystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density PolyethyleneS. Ge, M. Rafailovich*, J. Sokolov, Y. Zou, H. Ade, J. Lüning, A. Lustiger, and G. MaromCite this: Macromolecules 2005, 38, 5, 2022Publication Date (Web):February 8, 2005Publication History Published online8 February 2005Published inissue 1 March 2005https://pubs.acs.org/doi/10.1021/ma0501601https://doi.org/10.1021/ma0501601correctionACS PublicationsCopyright © 2005 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views330Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (43 KB) Get e-Alertsclose Get e-Alerts}, number={5}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Ge, S. and Rafailovich, M. and Sokolov, J. and Zou, Y. and Ade, H. and Lüning, J. and Lustiger, A. and Marom, G.}, year={2005}, month={Mar}, pages={2022–2022} } @article{harton_stevie_ade_2005, title={Diffusion-controlled reactive coupling at polymer-polymer interfaces}, volume={38}, ISSN={["0024-9297"]}, DOI={10.1021/ma047421b}, abstractNote={Reactive coupling of an end-functionalized polymer A with another endor chain-functionalized polymer B at an A-B interface is technologically referred to as reactive compatibilization. It is a proven means by which to reduce interfacial tension and improve adhesion between domains in polymer blends.1 In reactive systems, whether small-molecule or macromolecular in nature, the two regimes that generally describe the ratelimiting mechanism of the reaction are classified as diffusionand reaction-controlled (DC and RC, respectively) regimes.2 A dimensionless Damkohler number (NDa) as defined below can be used to determine which regime dominates a particular reaction.3}, number={9}, journal={MACROMOLECULES}, author={Harton, SE and Stevie, FA and Ade, H}, year={2005}, month={May}, pages={3543–3546} } @article{fujii_armes_araki_ade_2005, title={Direct imaging and spectroscopic characterization of stimulus-responsive microgels}, volume={127}, ISSN={["1520-5126"]}, DOI={10.1021/ja056589p}, abstractNote={Scanning transmission X-ray microscopy has been employed to visualize pH-responsive acid-swellable microgel particles directly in their swollen state in aqueous acidic solution. Moreover, NEXAFS studies confirm that the nitrogen atoms of these cationic microgel particles are completely protonated at low pH.}, number={48}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Fujii, S and Armes, SP and Araki, T and Ade, H}, year={2005}, month={Dec}, pages={16808–16809} } @article{lucovsky_zhang_fulton_zou_nemanich_ade_whitten_2005, title={Final state effects in VUV and soft X-ray absorption spectra of transition metal oxides and silicate alloys: comparisons between experiment and ab initio calculations}, volume={144}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2005.01.251}, abstractNote={This paper uses X-ray absorption spectroscopy and vacuum ultra-violet spectroscopic ellipsometry to study the electronic structure of high-k transition metal (TM) oxide gate dielectrics. The results are applicable to TM and rare earth (RE) silicate and aluminate alloys, as well as complex oxides comprised of mixed TM/TM and TM/RE oxides. These studies identify the nature of the lowest conduction band d* states, which define the optical band gap, including their relationship to the band gap, Eg, of the oxide.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Lucovsky, G and Zhang, Y and Fulton, CC and Zou, Y and Nemanich, RJ and Ade, H and Whitten, JL}, year={2005}, month={Jun}, pages={917–919} } @article{harton_koga_stevie_araki_ade_2005, title={Investigation of blend miscibility of a ternary PS/PCHMA/PMMA system using SIMS and mean-field theory}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma051595r}, abstractNote={Poly(cyclohexyl methacrylate) (PCHMA) and polystyrene (PS) are miscible with each other, but each is highly immiscible with PMMA. Identifiable by the asymmetries in the binary mean-field interaction parameters χ, PS preferentially segregates to the PCHMA/PMMA interface. Secondary ion mass spectrometry was used to provide real-space depth profiles of deuterated PS (dPS) in a miscible blend with PCHMA. The initial dPS concentration was varied from 5 to 20% (v/v), and the blend film was annealed at 150 °C on a film of PMMA for 42 h. X-ray reflectometry was used to determine the interfacial width between PCHMA and PMMA at 150 °C. Using self-consistent mean-field theory, good agreement was found between the experimental and theoretical interfacial excess Z* of dPS at each concentration. Because of their similar glass transition temperatures (∼100 °C for PS and PCHMA) and the ability of PS and PCHMA to be controllably synthesized with low polydispersities, we anticipate this blend to be a model system for futur...}, number={25}, journal={MACROMOLECULES}, author={Harton, SE and Koga, T and Stevie, FA and Araki, T and Ade, H}, year={2005}, month={Dec}, pages={10511–10515} } @article{harton_stevie_spontak_koga_rafailovich_sokolov_ade_2005, title={Low-temperature reactive coupling at polymer–polymer interfaces facilitated by supercritical CO2}, volume={46}, ISSN={0032-3861}, url={http://dx.doi.org/10.1016/j.polymer.2005.07.085}, DOI={10.1016/j.polymer.2005.07.085}, abstractNote={Supercritical CO2 (scCO2) has been used to facilitate reactions in thin film bilayers between functionalized polystyrene and poly(methyl methacrylate) at temperatures far below the glass transition temperatures of the respective polymers. Secondary ion mass spectrometry (SIMS) is used to monitor the reaction progression directly by measuring the interfacial excess of deuterated PS. Complementary X-ray reflectometry (XR) yields the interfacial width and surface roughness of bilayer films for reactive systems with and without the addition of scCO2, and comparisons are made with unreactive reference systems. From XR and SIMS analyses, the interfacial width and roughness have been found to be effectively independent of the reaction conditions employed here, and the primary impact of incorporated scCO2 is enhanced mobility of the reactive polymer chains. The use of scCO2 can change polymer mobility significantly enough over a very small temperature range (DTw15 8C) so that both diffusion- and reaction-controlled type behavior can be observed for otherwise identical systems. q 2005 Elsevier Ltd. All rights reserved.}, number={23}, journal={Polymer}, publisher={Elsevier BV}, author={Harton, S.E. and Stevie, F.A. and Spontak, R.J. and Koga, T. and Rafailovich, M.H. and Sokolov, J.C. and Ade, H.}, year={2005}, month={Nov}, pages={10173–10179} } @article{wang_araki_ade_2005, title={Soft x-ray resonant reflectivity of low-Z material thin films}, volume={87}, ISSN={["1077-3118"]}, DOI={10.1063/1.2136353}, abstractNote={Soft x-ray resonant reflectivity, a method for low-Z materials that combines aspects of neutron reflectivity and x-ray reflectivity, is presented. Resonant reflectivity provides enhanced and selective sensitivity to specific chemical moieties near the absorption edges of constituent elements and was demonstrated through the characterization of a bilayer polymer thin film. The relative reflectivity of a particular interface could be tuned by adjusting the incident photon energy near the carbon 1s absorption edge. The resulting chemical specificity is analogous to using deuteration as a tracer or marker in neutron reflectivity, but without requiring special sample synthesis or preparation.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Wang, C and Araki, T and Ade, H}, year={2005}, month={Nov} } @article{fulton_lucovsky_zhang_zou_nemanich_ade_whitten_2005, title={Studies of the coupling of final d*-states in mixed Hf and Ti oxides (HfO2)(x)(TiOx)(1-x) and other complex oxides}, volume={144}, ISSN={["1873-2526"]}, DOI={10.1016/j.elspec.2005.01.098}, abstractNote={Abstract X-ray absorption spectroscopy and vacuum ultra-violet spectroscopic ellipsometry are used to study the electronic structure of complex oxides comprised of mixed TM/TM and TM/RE oxides. Experimental spectra for HfTiO 4 and Gd(Dy)ScO 3 indicate multiple d-state features in the O K 1 edge. These are compared with the empirical models for atomic d-state mixing. It is concluded that a mean field, virtual alloy model does not apply, and that the effects associated with the differences in atomic coordination and deviations from ideal octahedral or cubic bonding play a determinant role in d-state atom mixing. The results are applied band edge engineering options for high- k dielectric applications.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Fulton, CC and Lucovsky, G and Zhang, Y and Zou, Y and Nemanich, RJ and Ade, H and Whitten, JL}, year={2005}, month={Jun}, pages={913–916} } @article{wang_ge_rafailovich_sokolov_zou_ade_luning_lustiger_maron_2004, title={Crystallization in the thin and ultrathin films of poly(ethylene-vinyl acetate) and linear low-density polyethylene}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma030456b}, abstractNote={The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness from 460 to 10 nm was studied. The lamellar thickness was measured using small-angle X-ray scattering (SAXS) and found to increase from 14 to 21 nm for films thinner than 100 nm. The morphology of LLDPE measured by scanning probe microscopy (SPM) showed an edge-on lamellae for the films thicker than 30 nm and flat-on lamellae for the films thinner than 15 nm. A pseudo-“shish-kebab” tiny crystal structure was observed in between the larger lamellae. Crystallinity was confirmed using attenuated total reflectance−Fourier transformed infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The shear modulation force microscopy technique (SMFM) was used to measure the melting point, Tm, which was found to decrease for films thinner than 100 nm. The rate of decrease was a function of the annealing pr...}, number={9}, journal={MACROMOLECULES}, author={Wang, Y and Ge, S and Rafailovich, M and Sokolov, J and Zou, Y and Ade, H and Luning, J and Lustiger, A and Maron, G}, year={2004}, month={May}, pages={3319–3327} } @article{tyliszczak_kilcoyne_liddle_warwick_hitchcock_ade_shuh_2004, title={Scanning Transmission X-ray Microscopes at the Advanced Light Source: Performance and Experimental Capabilities}, volume={10}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927604883855}, DOI={10.1017/S1431927604883855}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.}, number={S02}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Tyliszczak, Tolek and Kilcoyne, A. L. David and Liddle, J. Alexander and Warwick, Tony and Hitchcock, Adam P. and Ade, Harald and Shuh, David K.}, year={2004}, month={Aug}, pages={1018–1019} } @article{yang_ade_nemanich_2004, title={Shape stability of TiSi2 islands on Si (111)}, volume={95}, ISSN={["1089-7550"]}, DOI={10.1063/1.1636526}, abstractNote={The evolution of the shape and size of TiSi2 islands on Si (111) surfaces is explored with real time ultraviolet photoelectron emission microscopy. During continuous deposition of Ti at elevated temperatures, individual islands in a dilute surface distribution grow larger without island–island interactions. As they increase in size, symmetric islands transform into elongated shaped islands with high length-to-width aspect ratios. An extremely elongated island shows a ratio of 85:1 and is ∼17 μm long and ∼0.2 μm wide. The individual elongated islands have different widths regardless of their length. The width of the growing islands is determined at the initial transition stage and remains essentially constant with increasing length. We propose that the various widths of the elongated islands are determined by the degree of strain relaxation, possibly through the nucleation of dislocations at the island interface. In addition, it is found that the elongated islands display a prism-like shape or a truncated prism-like shape. We propose that the shape evolution of the elongated islands is related to both strain relaxation and growth kinetics.}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Yang, WC and Ade, H and Nemanich, RJ}, year={2004}, month={Feb}, pages={1572–1576} } @article{lucovsky_hong_fulton_zou_nemanich_ade_scholm_freeouf_2004, title={Spectroscopic studies of metal high-k dielectrics: transition metal oxides and silicates, and complex rare earth/transition metal oxides}, volume={241}, ISSN={["1521-3951"]}, DOI={10.1002/pssb.200404938}, abstractNote={AbstractThis paper uses X‐ray absorption spectroscopy to the study of electronic structure of the transition metal oxides TiO2, ZrO2 and HfO2, Zr and Hf silicate alloys, and the complex oxides, GdScO3, DyScO3 and HfTiO4. Qualitative and quantitative differences are identified between dipole allowed intra‐atomic transitions from core p‐states to empty d*‐ and s*‐states, and inter‐atomic transitions from transition metal and oxide 1s states to O 2p* that are mixed with transition metal d*‐ and s*‐states for transition metal oxides and silicate alloys. The complex oxide studies have focused on the O K1 edge spectra. Differences between the spectral peak energies of the lowest d*‐features in the respective O K1 spectra are demonstrated to scale with optical band gap differences for TiO2, ZrO2 and HfO2, as well as the complex oxides providing important information relevant to applications of TM oxides as high‐k gate dielectrics in advanced Si devices. This is demonstrated through scaling relationships between (i) conduction band offset energies between Si and the respective dielectrics, and the optical band gaps, and (ii) the optical band gaps, the conduction band offset energies, and the electron tunneling masses as functions of the atomic d‐state energies of the transition metal atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)}, number={10}, journal={PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS}, author={Lucovsky, G and Hong, JG and Fulton, CC and Zou, Y and Nemanich, RJ and Ade, H and Scholm, DG and Freeouf, JL}, year={2004}, month={Aug}, pages={2221–2235} } @article{yang_ade_nemanich_2004, title={Stability and dynamics of Pt-Si liquid microdroplets on Si(001)}, volume={69}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.69.045421}, abstractNote={The formation and dynamics of Pt-Si liquid droplets on Si (001) surfaces are explored with real-time ultraviolet photoelectron emission microscopy. PtSi islands of micrometer lateral diameter begin to melt and are transformed into molten Pt-Si alloy islands below the melting point of bulk PtSi. In particular, at ∼1100 °C surface migration of the liquid microdroplets is observed, where the droplets move directionally from the cold to the hot regions of the surface following the temperature gradient across the substrate. It is proposed that the droplet surface migration is due to dissolution-diffusion-deposition flow of Si through the droplet driven by the Si concentration difference in the droplet. In addition, the migration rate of the droplet is measured as a function of temperature and droplet diameter. Above a minimum diameter, the migration velocity is independent of the droplet size, which indicates that Si diffusivity through the droplet is the primary factor determining the rate of migration. The activation energy for the Si diffusion in the droplet is found to be ∼0.57 eV. We conclude that the thermal and chemical stability of the droplet-substrate interface significantly affects the evolution and dynamics of the liquid island on the surface.}, number={4}, journal={PHYSICAL REVIEW B}, author={Yang, WC and Ade, H and Nemanich, RJ}, year={2004}, month={Jan} } @article{ade_zou_kilcoyne_wang_rafailovich_sokolov_2004, title={X-ray Linear Dichroism Microscopy of Crystalline Short Chain Alkanes and Semi-crystalline Polyethylene Thin Films}, volume={10}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927604881595}, DOI={10.1017/S1431927604881595}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.}, number={S02}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Ade, Harald and Zou, Ying and Kilcoyne, A.D.L. and Wang, Yantian and Rafailovich, Miriam and Sokolov, J.}, year={2004}, month={Aug}, pages={1020–1021} } @article{lucovsky_hong_fulton_zou_nemanich_ade_2004, title={X-ray absorption spectra for transition metal high-kappa dielectrics: Final state differences for intra- and inter-atomic transitions}, volume={22}, ISSN={["2166-2746"]}, DOI={10.1116/1.1771670}, abstractNote={This article applies x-ray absorption spectroscopy to a study of the electronic structure of the high-k gate dielectrics, TiO2, ZrO2, and HfO2. Qualitative and quantitative differences are identified between intra-atomic transitions such as the Zr 3p-state, M2,3 core state absorptions which terminate in TM 4d*- and 5s*-states, and inter-atomic transitions such as the Zr 1s- and O 1s-state K1 absorptions which terminate in Zr 4d*- and 5s*-states that are mixed with O atom 2p* states through nearest neighbor bonding interactions. Differences between the spectral peak energies of the lowest d*-features in the O K1 spectra are demonstrated to scale with optical band gap differences for TiO2, ZrO2, and HfO2, providing important information relevant to applications of TM oxides as high-κ gate dielectrics in advanced Si devices. This is demonstrated through additional scaling relationships between (i) conduction band offset energies between Si and the respective dielectrics, and the optical band gaps, and (ii) the conduction band offset energies, and the electron tunneling masses as well.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Lucovsky, G and Hong, JG and Fulton, CC and Zou, Y and Nemanich, RJ and Ade, H}, year={2004}, pages={2132–2138} } @article{winesett_ade_smith_urquhart_dias_stevens_2003, title={Application of scanning transmission X-ray microscopy to the rubber industry}, volume={76}, ISSN={["1943-4804"]}, DOI={10.5254/1.3547773}, abstractNote={Abstract Materials of commercial significance in the rubber industry are usually multi-component systems composed of several elastomers and various fillers. Elucidating the complex morphology that can arise from blending and understanding how this affects the various properties are essential. A technique advantageous to the study of multi-component elastomeric systems is Scanning Transmission X-ray Microscopy (STXM). STXM utilizes the chemical sensitivity of Near Edge X-ray Absorption Fine Structure (NEXAFS) and combines with relatively high spatial resolution and low beam damage to allow the successful characterization of multi-component materials that may be difficult or impossible with other techniques. An overview of the technique and example applications for the rubber industry is presented.}, number={4}, journal={RUBBER CHEMISTRY AND TECHNOLOGY}, author={Winesett, DA and Ade, H and Smith, AP and Urquhart, SG and Dias, AJ and Stevens, P}, year={2003}, pages={803–811} } @article{yang_zeman_ade_nemanich_2003, title={Attractive migration and coalescence: A significant process in the coarsening of TiSi2 islands on the Si(111) surface}, volume={90}, ISSN={["0031-9007"]}, DOI={10.1103/physrevlett.90.136102}, abstractNote={The dynamics and coarsening of TiSi2 islands on Si(111) surfaces are studied in real time with photoelectron emission microscopy. A significant fraction of events are observed in which nearby islands move attractively toward each other and subsequently coalesce. It is proposed that attractive island migration is due to the growth-decay flow of the island edges driven by a nonuniform surface concentration around the islands. The local surface concentration is induced by the neighboring islands. This coarsening mechanism should significantly affect the evolution of the island distribution.}, number={13}, journal={PHYSICAL REVIEW LETTERS}, author={Yang, WC and Zeman, M and Ade, H and Nemanich, RJ}, year={2003}, month={Apr} } @article{lucovsky_raynor_zhang_fulton_nemanich_appel_ade_whitten_2003, title={Electronic structure of transition metal high-k dielectrics: interfacial band offset energies for microelectronic devices}, volume={212}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(03)00055-2}, abstractNote={Transition metal silicates, (ZrO2)x(SiO2)1� x, have dielectric constants k > 10 that make them attractive for advanced Si devices. Band offset energies relative to Si are an important factor in determining tunneling leakage current, and internal photoemission. Studies by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and X-ray absorption spectroscopy (XAS) are combined with ab initio calculations to identify the compositional variation of the band-gap, and valence and conduction band offset energies of Zr silicate alloys with respect to Si. The minimum conduction band offset, due to}, number={2003 May 15}, journal={APPLIED SURFACE SCIENCE}, author={Lucovsky, G and Raynor, GB and Zhang, Y and Fulton, CC and Nemanich, RJ and Appel, G and Ade, H and Whitten, JL}, year={2003}, month={May}, pages={563–569} } @article{kilcoyne_tyliszczak_steele_fakra_hitchcock_franck_anderson_harteneck_rightor_mitchell_et al._2003, title={Interferometer-controlled scanning transmission X-ray microscopes at the Advanced Light Source}, volume={10}, ISSN={["1600-5775"]}, DOI={10.1107/S0909049502017739}, abstractNote={Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned. Interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample. Long-term positional stability and compensation for transverse displacement during translations of the zone plate have been achieved. The interferometer also provides low-distortion orthogonal x, y imaging. Two different control systems have been developed: a digital control system using standard VXI components at beamline 7.0, and a custom feedback system based on PC AT boards at beamline 5.3.2. Both microscopes are diffraction limited with the resolution set by the quality of the zone plates. Periodic features with 30 nm half period can be resolved with a zone plate that has a 40 nm outermost zone width. One microscope is operating at an undulator beamline (7.0), while the other is operating at a novel dedicated bending-magnet beamline (5.3.2), which is designed specifically to illuminate the microscope. The undulator beamline provides count rates of the order of tens of MHz at high-energy resolution with photon energies of up to about 1000 eV. Although the brightness of a bending-magnet source is about four orders of magnitude smaller than that of an undulator source, photon statistics limited operation with intensities in excess of 3 MHz has been achieved at high energy resolution and high spatial resolution. The design and performance of these microscopes are described.}, number={2003 Mar}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Kilcoyne, ALD and Tyliszczak, T and Steele, WF and Fakra, S and Hitchcock, P and Franck, K and Anderson, E and Harteneck, B and Rightor, EG and Mitchell, GE and et al.}, year={2003}, month={Mar}, pages={125–136} } @article{appel_ade_guerek_stadler_mikalo_schmeisser_2003, title={Orientation studies of Si-phthalocyanine sulfonic acids cast on SiOx substrates}, volume={76}, ISSN={["1432-0630"]}, DOI={10.1007/s003390201320}, number={2}, journal={APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING}, author={Appel, G and Ade, H and Guerek, AG and Stadler, S and Mikalo, RP and Schmeisser, D}, year={2003}, month={Feb}, pages={177–182} } @article{ade_kilcoyne_tyliszczak_hitchcock_anderson_harteneck_rightor_mitchell_hitchcock_warwick_2003, title={Scanning transmission X-ray microscopy at a bending magnet beamline at the Advanced Light Source}, volume={104}, ISSN={["1155-4339"]}, DOI={10.1051/jp4:200300017}, abstractNote={During the last two decades, scanning transmission x-ray microscopy (STXM) has evolved into a powerful characterization tool. For best performance, STXM's are located at undulator sources at synchrotron facilities. The scarcity and expense of undulator sources and associated heamlines limits the number of available STXMs. We have successfully re-examined the use of bending magnets as a source for a STXM and implemented a interferometer controlled STXM with excellent performance at the beamline 5.3,2, at the Advanced Light Source Near the carbon K-edge, periodic features with 30 nm half-period could be resolved with a zone plate that has a 40 nm outermost zone width with an energy resolution corresponding to 100 meV and an intensity of about 1 MHz The design and perforormance of the microscope are described.}, number={2003 Mar}, journal={JOURNAL DE PHYSIQUE IV}, author={Ade, H and Kilcoyne, ALD and Tyliszczak, T and Hitchcock, P and Anderson, E and Harteneck, B and Rightor, EG and Mitchell, GE and Hitchcock, AP and Warwick, T}, year={2003}, month={Mar}, pages={3–8} } @article{harris_appel_ade_2003, title={Surface morphology of annealed polystyrene and poly(methyl methacrylate) thin film blends and bilayers}, volume={36}, ISSN={["0024-9297"]}, DOI={10.1021/ma0257043}, abstractNote={Thin films of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were spun-cast onto silicon substrates, annealed, and analyzed by atomic force microscopy (AFM), total electron yield (TEY), and partial electron yield (PEY) near-edge X-ray absorption fine structure (NEXAFS) spectroscopy in order to resolve conflicting prior literature regarding the tendency of PS to form a wetting layer or overlayer on top of PMMA. From the comparison of the three methods of analysis and on the basis of the extraordinary surface sensitivity of PEY NEXAFS, we conclude that PS does not form an overlayer in samples with morphologies near thermodynamic equilibrium. The PS forms droplets of a large size range on top of a PMMA layer that wets the hydrophilic SiOx substrate. From our results, the maximum thickness of a continuous PS wetting layer would be about 0.25 nm. This is in contrast to recent experiments that imply an equivalent PS wetting layer of about 5−10 nm is forming during annealing.}, number={9}, journal={MACROMOLECULES}, author={Harris, M and Appel, G and Ade, H}, year={2003}, month={May}, pages={3307–3314} } @article{scholl_fink_umbach_mitchell_urquhart_ade_2003, title={Towards a detailed understanding of the NEXAFS spectra of bulk polyethylene copolymers and related alkanes}, volume={370}, ISSN={["0009-2614"]}, DOI={10.1016/S0009-2614(03)00215-X}, abstractNote={High energy resolution C 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of ethylene-1-alkene copolymers with systematic variations in comonomer content and thus systematic changes in branch length, branching ratio, and degree of crystallinity are presented. Spectral changes of the σ*C–H/Rydberg and σ*C–C features in these ideal model systems provide unambiguous experimental evidence for intermolecular interactions with profound effects on the spectral intensity, but only very small energy shifts. Ab initio calculations reproduce the experimental results in detail. The intermolecular interaction observed suggests that interpretation of NEXAFS spectra based on calculations of isolated molecules can be insufficient even in relatively weakly interacting macromolecules.}, number={5-6}, journal={CHEMICAL PHYSICS LETTERS}, author={Scholl, A and Fink, R and Umbach, E and Mitchell, GE and Urquhart, SG and Ade, H}, year={2003}, month={Mar}, pages={834–841} } @article{winesett_story_luning_ade_2003, title={Tuning substrate surface energies for blends of polystyrene and poly(methyl methacrylate)}, volume={19}, ISSN={["0743-7463"]}, DOI={10.1021/la030129x}, abstractNote={We compare the efficacies of three preparation methods intended to create in an easy and inexpensive way a nonpreferential surface for a two-component homopolymer blend of polystyrene and poly(methyl methacrylate). The first method is to physically absorb two different high molecular weight copolymers of styrene and methyl methacrylate onto hydroxylated silicon oxide. The second method consists of covalently bonding octyltrichlorosilane onto hydroxylated silicon oxide with gradient coverage to create a region with a neutral surface. The third method utilizes hydroxyl terminated, miscible, low molecular weight homopolymers of polystyrene and poly(methyl methacrylate) covalently attached to the substrate. We characterize the relative effectiveness of all three methods and their temporal stability using optical microscopy, atomic force microscopy, contact angle measurements, as well as near edge X-ray absorption fine structure (NEXAFS) microscopy and spectroscopy. The preparation methods explored should be extendable to a number of polymer systems.}, number={20}, journal={LANGMUIR}, author={Winesett, DA and Story, S and Luning, J and Ade, H}, year={2003}, month={Sep}, pages={8526–8535} } @article{zhang_ge_wang_rafailovich_dhez_winesett_ade_shafi_ulman_popovitz-biro_et al._2003, title={Use of functionalized WS2 nanotubes to produce new polystyrene/polymethylmethacrylate nanocomposites}, volume={44}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(03)00053-3}, abstractNote={Multiwall WS2 nanotubes of 40–50 nm diameter were functionalized with n-octadecyl phosphonic acid by sonication in toluene and blended with mixtures of polystyrene (PS) and polymethylmethacrylate (PMMA) to form new nanocomposite (NC) materials. The surface and domain structures were studied by atomic force microscopy (AFM), scanning transmission X-ray microscopy (STXM) and transmission electron microscopy (TEM) for various levels of loading of nanotubes up to 20 wt%. Phase-separated domain size and surface roughness of the nanocomposite films were found to be dramatically reduced relative to the pure homopolymer blend and good dispersal of the nanotubes in the blend matrix was attained.}, number={7}, journal={POLYMER}, author={Zhang, W and Ge, S and Wang, Y and Rafailovich, MH and Dhez, O and Winesett, DA and Ade, H and Shafi, KVPM and Ulman, A and Popovitz-Biro, R and et al.}, year={2003}, month={Mar}, pages={2109–2115} } @article{warwick_ade_kilcoyne_kritscher_tylisczcak_fakra_hitchcock_hitchcock_padmore_2002, title={A new bend-magnet beamline for scanning transmission X-ray microscopy at the Advanced Light Source}, volume={9}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049502005502}, abstractNote={The high brightness of the bend magnets at the Advanced Light Source has been exploited to illuminate a scanning transmission X-ray microscope (STXM). This is the first diffraction-limited scanning X-ray microscope to operate with a useful count rate on a synchrotron bend-magnet source. A simple dedicated beamline has been built covering the range of photon energy from 250 eV to 600 eV. The beamline is always available and needs little adjustment. Use of this facility is much easier than that of installations that share undulator beams. This facility provides radiation for C 1s, N 1s and O 1s near-edge X-ray absorption spectromicroscopy with STXM count rates in excess of 1 MHz and with spectral resolution typically 1:2000, limited to about 1:5000.}, number={2002 Jul}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Warwick, T and Ade, H and Kilcoyne, D and Kritscher, M and Tylisczcak, T and Fakra, S and Hitchcock, A and Hitchcock, P and Padmore, H}, year={2002}, month={Jul}, pages={254–257} } @article{dhez_ade_urquhart_2003, title={Calibrated NEXAFS spectra of some common polymers}, volume={128}, ISSN={["0368-2048"]}, DOI={10.1016/S0368-2048(02)00237-2}, abstractNote={Near edge X-ray absorption fine structure (NEXAFS) microscopy has evolved into a powerful characterization tool for polymeric materials. The foundation of this utility depends crucially on the sensitivity of NEXAFS to the specific chemical structure of the polymer. Furthermore, for quantitative compositional analysis, reliable reference spectra with known energy resolution and calibrated energy scale are required. We report a set of NEXAFS spectra from 24 common polymers that represent a range of chemical functionalities in order to create a database of calibrated polymer NEXAFS spectra to be used for compositional analysis. These spectra illustrate the sensitivity of NEXAFS spectroscopy to the polymer composition, illustrating the potential of NEXAFS for chemical analysis.}, number={1}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Dhez, O and Ade, H and Urquhart, SG}, year={2003}, month={Jan}, pages={85–96} } @article{coffey_urquhart_ade_2002, title={Characterization of the effects of soft X-ray irradiation on polymers}, volume={122}, ISSN={["1873-2526"]}, DOI={10.1016/S0368-2048(01)00342-5}, abstractNote={The physical and chemical effects of the soft X-ray irradiation of polymers have been systematically evaluated for photon energies just above the C 1s binding energy. This exposure causes radiation damage in the form of the loss of mass and changes to the chemical structure of the polymers. These effects are evident in the Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of the exposed polymers, posing a fundamental limit to the sensitivity of NEXAFS spectroscopy for chemical microanalysis. Quantitative understanding of the chemistry and kinetics of radiation damage in polymers is necessary for the successful and validated application of NEXAFS microscopy. This paper outlines a method for quantifying this radiation damage as a function of X-ray dose, and applies these methods to characterize the loss of mass and loss of carbonyl group functionality from a diverse series of polymers. A series of simple correlations are proposed to rationalize the observed radiation damage propensities on the basis of the polymer chemical structure. In addition, NEXAFS spectra of irradiated and virgin polymers are used to provide a first-order identification of the radiation chemistry.}, number={1}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Coffey, T and Urquhart, SG and Ade, H}, year={2002}, month={Jan}, pages={65–78} } @article{zhang_fu_seo_schrag_hsiao_mather_yang_xu_ade_rafailovich_et al._2002, title={Effect of methyl methacrylate/polyhedral oligomeric silsesquioxane random copolymers in compatibilization of polystyrene and poly(methyl methacrylate) blends}, volume={35}, ISSN={["0024-9297"]}, DOI={10.1021/ma020725i}, abstractNote={Random copolymers of methyl methacrylate with polyhedral oligomeric silsesquioxane (POSS) were synthesized and blended with PS and PMMA homopolymer thin films. The effects of the POSS on phase segregation were studied using a variety of complementary techniques. The results showed that these copolymers were efficient at compatibilizing immiscible polymer blends. Compatibilization occurred when the POSS was grafted onto the backbone and a favorable interaction existed between the POSS functional groups and the PS homopolymers. The consequences of this compatibilization were studied using a comprehensive array of characterization methods and found to be as follows: reduced domain size, increased interfacial width, and greatly improved fracture toughness. This compatibilization is due to the increased site functionality provided by the POSS molecule without the entropic penalty associated with introducing functionalities via grafting directly onto the polymer chains.}, number={21}, journal={MACROMOLECULES}, author={Zhang, WH and Fu, BX and Seo, Y and Schrag, E and Hsiao, B and Mather, PT and Yang, NL and Xu, DY and Ade, H and Rafailovich, M and et al.}, year={2002}, month={Oct}, pages={8029–8038} } @article{lucovsky_zhang_rayner_appel_ade_whitten_2002, title={Electronic structure of high-k transition metal oxides and their silicate and aluminate alloys}, volume={20}, number={4}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Lucovsky, G. and Zhang, Y. and Rayner, G. B. and Appel, G. and Ade, H. and Whitten, J. L.}, year={2002}, pages={1739–1747} } @article{rightor_urquhart_hitchcock_ade_smith_mitchell_priester_aneja_appel_wilkes_et al._2002, title={Identification and quantitation of urea precipitates in flexible polyurethane foam formulations by X-ray spectromicroscopy}, volume={35}, ISSN={["1520-5835"]}, DOI={10.1021/ma0122627}, abstractNote={Scanning transmission X-ray microscopy (STXM) and atomic force microscopy have been used to study the morphology and chemical composition of macrophase-segregated block copolymers in plaque formulations based on water-blown flexible polyurethane foams. Although there has been a large body of indirect evidence indicating that the observed macrophase-segregated features in water-rich polyurethane foams are due principally to urea components, this work provides the first direct, spatially resolved spectroscopic proof to support this hypothesis. The STXM results are consistent with a segregation model where urea segments segregate, forming enriched phases with the majority of the polyether- polyol and urethane groups at the chain ends of the urea hard segments. Chemical mapping of the urea, urethane, and polyether distribution about the urea-rich segregated phases showed that the urea concentration changes gradually (across several hundred nanometers) in a butylene oxide-based foam. This mapping also showed the urea-rich segregated phases present as a partial network in an ethylene oxide/propylene oxide sample.}, number={15}, journal={MACROMOLECULES}, author={Rightor, EG and Urquhart, SG and Hitchcock, AP and Ade, H and Smith, AP and Mitchell, GE and Priester, RD and Aneja, A and Appel, G and Wilkes, G and et al.}, year={2002}, month={Jul}, pages={5873–5882} } @article{urquhart_ade_2002, title={Trends in the carbonyl core (C 1s, O 1s) -> pi*c=o transition in the near-edge X-ray absorption fine structure spectra of organic molecules}, volume={106}, ISSN={["1520-6106"]}, DOI={10.1021/jp0255379}, abstractNote={Carbonyl core (C 1s, O 1s) → π*CO transitions are distinctive in the near-edge X-ray absorption fine structure (NEXAFS) spectra of species containing carbonyl groups. These features are used for the chemical microanalysis of organic materials using X-ray microscopy. We have explored the chemical sensitivity of these features in C 1s and O 1s NEXAFS spectra for a series of polymers containing the carbonyl group in a range of different bonding environments. Ab initio calculations are used to explain the origin of the observed trends and to explore the effect that orbital interactions have on the energy of these core (C 1s, O 1s) → π*CO features. The differences between the experimental and the calculated carbonyl core (C 1s, O 1s) → π*CO transition energies are systematic and can be used to develop a semiempirical method for predicting the absolute (experimental) transition energies from the calculated transition energies. This relationship is applied to a large body of calculated transition energy data to ...}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Urquhart, SG and Ade, H}, year={2002}, month={Aug}, pages={8531–8538} } @article{smith_ade_smith_koch_spontak_2001, title={Anomalous phase inversion in polymer blends prepared by cryogenic mechanical alloying}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma001151p}, abstractNote={offer alternative strategies for producing highly dis-persed multicomponent polymer blends. By their verynature, these processes yield fine powders, which mustbe subsequently consolidated or melt-processed to formobjects. While nanoscale dispersion of one polymerwithin the matrix of another has been achieved withoutcompatibilizing agents in binary blends produced byCMA,}, number={6}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Smith, SD and Koch, CC and Spontak, RJ}, year={2001}, month={Mar}, pages={1536–1538} } @article{smith_ade_koch_spontak_2001, title={Cryogenic mechanical alloying as an alternative strategy for the recycling of tires}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(00)00804-1}, abstractNote={Cryogenic mechanical alloying (CMA) is investigated as a viable strategy by which to produce highly dispersed blends composed of thermoplastics and tire, thereby providing a potentially new route by which to recycle discarded tires. Morphological characterization of these blends by near-edge X-ray absorption fine structure (NEXAFS) microscopy demonstrates that, upon CMA, ground tire is highly dispersed within poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET) matrices at sub-micron size scales. Incorpo-ration of polyisoprene (PI) homopolymer into the blends to improve dispersion efficacy is also examined. Neither PI nor the tire is found to interact chemically with PMMA or PET under the milling conditions employed here.}, number={9}, journal={POLYMER}, author={Smith, AP and Ade, H and Koch, CC and Spontak, RJ}, year={2001}, month={Apr}, pages={4453–4457} } @article{zhang_ge_tang_koga_rafailovich_sokolov_peiffer_li_dias_mcelrath_et al._2001, title={Effect of carbon black and silica fillers in elastomer blends}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma010183p}, abstractNote={The effects of carbon black and pyrogeneous silica fillers on the interfacial properties of a homopolymer [polybutadiene, (PB)] and a terpolymer [brominated poly(isobutylene-co-p-methylstyrene), (BIMS)] are reported. Neutron reflectivity (NR) was used to study the interfacial structure. The results are complemented by scanning transmission X-ray microscopy (STXM) and lateral force microscopy (LFM), which were used to probe the morphology and surface lateral force. Small-angle neutron scattering (SANS) was used to characterize the size and surface properties of the filler aggregates in elastomers. Our results show that the interfacial behavior of PB/BIMS is more sensitive to carbon black than to silica. The interfacial broadening is significantly slowed down with addition of merely φCB = 0.01 (volume fraction) carbon black fillers. This volume level is much lower than that used in bulk rubbers (φCB ≥ 0.1). Pyrogeneous silica has a less pronounced effect on the interfacial characteristics. When both carbon ...}, number={20}, journal={MACROMOLECULES}, author={Zhang, YM and Ge, S and Tang, B and Koga, T and Rafailovich, MH and Sokolov, JC and Peiffer, DG and Li, Z and Dias, AJ and McElrath, KO and et al.}, year={2001}, month={Sep}, pages={7056–7065} } @article{lucovsky_rayner_kang_appel_johnson_zhang_sayers_ade_whitten_2001, title={Electronic structure of noncrystalline transition metal silicate and aluminate alloys}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1404997}, abstractNote={A localized molecular orbital description (LMO) for the electronic states of transition metal (TM) noncrystalline silicate and aluminate alloys establishes that the lowest conduction band states are derived from d states of TM atoms. The relative energies of these states are in agreement with the LMO approach, and have been measured by x-ray absorption spectroscopy for ZrO2–SiO2 alloys, and deduced from an interpretation of capacitance–voltage and current–voltage data for capacitors with Al2O3–Ta2O5 alloy dielectrics. The LMO model yields a scaling relationship for band offset energies providing a guideline for selection of gate dielectrics for advanced Si devices.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Lucovsky, G and Rayner, GB and Kang, D and Appel, G and Johnson, RS and Zhang, Y and Sayers, DE and Ade, H and Whitten, JL}, year={2001}, month={Sep}, pages={1775–1777} } @article{zhang_li_tang_ge_hu_rafailovich_sokolov_gersappe_peiffer_li_et al._2001, title={Interfacial properties of elastomer blends as studied by neutron reflectivity}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(01)00370-6}, abstractNote={The interfacial properties of a homopolymer (polybutadiene (PB)) and a terpolymer (brominated poly(isobutylene-co-p-methylstyrene) (BIMS)) are reported. Neutron reflectivity was used to study the interfacial structure. The results were complemented by scanning transmission X-ray microscopy and atomic force microscopy, which were used to probe the morphology of these binary blends. Our results show that the interfacial behavior of these elastomeric blends is a direct function of the BIMS chemical composition. The interfacial width decreased with increasing bromide functionality. At levels below 8 mol%, the para-methylstyrene concentration had a less pronounced effect on the compatibility and interfacial characteristics. We also studied the effect of styrene butadiene random copolymers on the miscibility of the PB/BIMS blends. The results showed that styrene-butadiene rubber (SBR) was not fully miscible with BIMS and PB on an individual basis, but addition of relatively small amount of SBR enhances the compatibilization of the PB/BIMS interface. Self-consistent field (SCF) modeling was used to determine the optimum copolymer composition. The calculations are consistent with the experimental results.}, number={21}, journal={POLYMER}, author={Zhang, YM and Li, W and Tang, B and Ge, S and Hu, X and Rafailovich, MH and Sokolov, JC and Gersappe, D and Peiffer, DG and Li, Z and et al.}, year={2001}, month={Oct}, pages={9133–9141} } @article{sloop_ade_fornes_gilbert_smith_2001, title={Near-edge X-ray absorption fine structure (NEXAFS) microscopy of a polycarbonate/poly (acrylonitrile/butadiene/styrene) blend}, volume={39}, ISSN={["1099-0488"]}, DOI={10.1002/1099-0488(20010301)39:5<531::AID-POLB1026>3.0.CO;2-Q}, abstractNote={Blends of polycarbonate (PC), poly(styrene/acrylonitrile) (SAN), and polybutadiene (PB), commonly called PC/acrylonitrile–butadiene–styrene (ABS) blends, are complex mixtures. The ABS component consists of free SAN copolymer and SAN grafted onto PB (SAN-g-PB). PC/ABS blends are materials that typically require heavy metal staining to differentiate the separate phases at a high spatial resolution in an electron microscope. Our eventual goal is the characterization of blends of PC and ABS as a function of increasing thermomechanical cycles. Because heavy metal staining is not directly sensitive to potential compositional changes in these polymers, we explored the characterization of PC/ABS blends with a directly sensitive imaging technique: near-edge X-ray absorption fine structure (NEXAFS) microscopy. Here we report NEXAFS spectra of the carbon K shell of PC, SAN, and SAN-gPB, and we evaluate the contrast in a PC/ABS blend across an energy range of 280–295 eV in the presence of TiO2 additives. We unambiguously observed free SAN in the PC matrix. NEXAFS spectroscopy exhibits spectral variations that are sensitive to numerous chemical functionalities and permits the characterization of the composition of organic materials. The information is analogous to what can be obtained in the near edge of core loss features in electron energy loss spectroscopy. During the last few years, the combination of NEXAFS and a high spatial resolution of about 50 nm has been achieved. The resolution has not reached a fundamental limit and is expected to approach 10 nm in the future. NEXAFS microscopy has already been used to image biological systems and examine the morphology and orientation of polymer systems near the K-shell absorption edge of carbon, oxygen, and nitrogen. NEXAFS spectroscopy without spatial resolution has also been successfully used to investigate various polymer surfaces (see refs. 19–26). One advantage of NEXAFS microscopy in imaging polymer systems is that materials of similar electron density and elemental chemistry can be differentiated and complex compositions can be quantified at much higher spatial resolutions than are possible with IR or Raman microscopy. In addition, organic materials can be differentiated directly on the basis of differences in chemical composition rather than through the indirect and aggressive Correspondence to: C. C. Sloop (E-mail: ccsloop@us. ibm.com) Present Address: National Institute of Standards and Technology, Gaithersburg, MD *Present Address: IBM Corporation, Research Triangle Park, NC}, number={5}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Sloop, CC and Ade, H and Fornes, RE and Gilbert, RD and Smith, AP}, year={2001}, month={Mar}, pages={531–535} } @article{smith_spontak_ade_2001, title={On the similarity of macromolecular responses to high-energy processes: mechanical milling vs. irradiation}, volume={72}, ISSN={["0141-3910"]}, DOI={10.1016/S0141-3910(01)00055-6}, abstractNote={Recent efforts to blend and compatibilize intrinsically immiscible polymers in the solid state by high-energy methods have shown that macromolecules may undergo scission, crosslinking or amorphization, depending on the chemical nature of the repeat unit, the processing temperature and the initial degree of polymer crystallinity. Identical process-induced molecular and structural modifications have been previously observed in polymers exposed to large doses of electron and γ radiation, suggesting that the responses of polymers to high-energy processes may be mechanistically similar. In this work, we explore a variety of similarities between mechanically-milled and irradiated polymers in terms of molecular characteristics, process temperature and polymer crystallinity, and we demonstrate that these similarities provide predictive guidance for the selection of polymers to be subjected to solid-state processing.}, number={3}, journal={POLYMER DEGRADATION AND STABILITY}, author={Smith, AP and Spontak, RJ and Ade, H}, year={2001}, pages={519–524} } @article{hitchcock_koprinarov_tyliszczak_rightor_mitchell_dineen_hayes_lidy_priester_urquhart_et al._2001, title={Optimization of scanning transmission X-ray microscopy for the identification and quantitation of reinforcing particles in polyurethanes}, volume={88}, ISSN={["1879-2723"]}, DOI={10.1016/S0304-3991(00)00113-3}, abstractNote={The morphology, size distributions, spatial distributions, and quantitative chemical compositions of co-polymer polyol-reinforcing particles in a polyurethane have been investigated with scanning transmission X-ray microscopy (STXM). A detailed discussion of microscope operating procedures is presented and ways to avoid potential artifacts are discussed. Images at selected photon energies in the C 1s, N 1s and O 1s regions allow unambiguous identification of styrene-acrylonitrile-based (SAN) copolymer and polyisocyanate polyaddition product-based (PIPA) reinforcing particles down to particle sizes at the limit of the spatial resolution (50 nm). Quantitative analysis of the chemical composition of individual reinforcing particles is achieved by fitting C 1s spectra to linear combinations of reference spectra. Regression analyses of sequences of images recorded through the chemically sensitive ranges of the C 1s, N 1s and O 1s spectra are used to generate quantitative compositional maps, which provide a fast and effective means of investigating compositional distributions over a large number of reinforcing particles. The size distribution of all particles determined by STXM is shown to be similar to that determined by TEM. The size distributions of each type of reinforcing particle, which differ considerably, were obtained by analysis of STXM images at chemically selective energies.}, number={1}, journal={ULTRAMICROSCOPY}, author={Hitchcock, AP and Koprinarov, I and Tyliszczak, T and Rightor, EG and Mitchell, GE and Dineen, MT and Hayes, F and Lidy, W and Priester, RD and Urquhart, SG and et al.}, year={2001}, month={Jun}, pages={33–49} } @article{mitchell_wilson_dineen_urquhart_hayes_rightor_hitchcock_ade_2002, title={Quantitative characterization of microscopic variations in the cross-link density of gels}, volume={35}, ISSN={["1520-5835"]}, DOI={10.1021/ma010840d}, abstractNote={We report the visualization and quantitative analysis of the cross-link structure in model core/shell hydrogel polymers on the microscopic scale, in a fully swollen state, using soft X-ray microscopy. The cross-link density in these materials and their microscopic or even nanoscopic variation critically influence materials characteristics, yet the cross-link density is difficult to characterize by conventional methods. By the use of soft X-ray microscopy, one can investigate these materials in a fully swollen state and thus directly visualize and quantitatively determine the cross-link structure on a microscopic scale. Materials that were cross-linked by different methods were shown to give rise to differently shaped profiles. Abrupt and gradient cross-link density profiles have been investigated, and the spatial variation in their cross-link density has been determined quantitatively.}, number={4}, journal={MACROMOLECULES}, author={Mitchell, GE and Wilson, LR and Dineen, MT and Urquhart, SG and Hayes, F and Rightor, EG and Hitchcock, AP and Ade, H}, year={2002}, month={Feb}, pages={1336–1341} } @article{smith_urquhart_winesett_mitchell_ade_2001, title={Use of near edge X-ray absorption fine structure spectromicroscopy to characterize multicomponent polymeric systems}, volume={55}, DOI={10.1366/0003702011954008}, abstractNote={ The merits of a polymer characterization technique, near edge X-ray absorption fine structure (NEXAFS) spectromicroscopy, are demonstrated through the characterization of a multilayer polymer film with partially unknown chemical composition. The combination of chemical speciation through NEXAFS spectroscopy with the high spatial resolution available in X-ray microscopy allows the characterization of polymeric materials not possible with conventional techniques. Analysis of a multilayer with layers as thin as 4 μm has yielded results that differ from those previously obtained by infrared microscopy. Layers below the spatial resolution limit of infrared microscopy were characterized. }, number={12}, journal={Applied Spectroscopy}, author={Smith, A. P. and Urquhart, S. G. and Winesett, D. A. and Mitchell, G. and Ade, Harald}, year={2001}, pages={1676–1681} } @article{morin_ikeura-sekiguchi_tyliszczak_cornelius_brash_hitchcock_scholl_nolting_appel_winesett_et al._2001, title={X-ray spectromicroscopy of immiscible polymer blends: polystyrene-poly(methyl methacrylate)}, volume={121}, DOI={10.1016/S0368-2048(01)00335-8}, abstractNote={Abstract Spun cast thin films of blends of low and high molecular weight mono-disperse polystyrene (PS) and poly(methyl methacrylate) (PMMA) with nominal compositions ranging from 66/33 wt.%/wt.% (w/w) up to 10/90 w/w PS/PMMA have been studied, as-made and after annealing. Two synchrotron-based X-ray microscopies — scanning transmission X-ray microscopy (STXM) and X-ray photoemission electron microscopy (X-PEEM) — as well as several variants of atomic force microscopy (AFM) were used to probe the composition and morphology of the bulk and surface of these blends. The chemical sensitivities and spatial resolutions of these three techniques are compared. All samples are observed to have a PS signal in the C 1s X-ray absorption spectrum of the surface of the PMMA-rich domains as measured in the X-PEEM. A continuous thin PS layer is not expected at a PMMA surface since neither polymer should wet the other at thermodynamic equilibrium. The likely origin of this PS surface signal is from a bimodal distribution of PS domain sizes with the PS signal arising from domains at the surface which are smaller than the ∼200-nm resolution of the X-PEEM. High resolution AFM and STXM provide direct evidence for this explanation.}, number={1-3}, journal={Journal of Electron Spectroscopy and Related Phenomena}, author={Morin, C. and Ikeura-Sekiguchi, H. and Tyliszczak, T. and Cornelius, R. and Brash, J. L. and Hitchcock, A. P. and Scholl, A. and Nolting, F. and Appel, G. and Winesett, D. A. and et al.}, year={2001}, pages={203–224} } @article{smith_ade_koch_smith_spontak_2000, title={Addition of a block copolymer to polymer blends produced by cryogenic mechanical alloying}, volume={33}, ISSN={["0024-9297"]}, DOI={10.1021/ma9915475}, abstractNote={Cryogenic mechanical alloying is used to incorporate a poly(methyl methacrylate-b-isoprene) (MI) diblock copolymer into blends of poly(methyl methacrylate) (PMMA) and polyisoprene (PI). Mechanical milling of the copolymer promotes a reduction in the molar mass of the M block, as discerned from glass transition temperature measurements performed by thermal calorimetry, and induces chemical cross- linking of the I block, as determined from sol-gel analysis. These effects become more pronounced with increasing milling time. Morphological characterization of PMMA-rich PI/MI/PMMA blends by X-ray and electron microscopies reveals that the characteristic size scale of the minority phase decreases with increasing MI content, as well as milling time. The nanostructural features observed in such blends are retained at relatively high MI concentrations during subsequent melt-pressing. Impact testing demon- strates that the blends become tougher upon addition of the MI copolymer, even at relatively low copolymer concentrations. Blend toughness likewise increases with increasing milling time up to a point, beyond which phase inversion occurs within the ternary blends (the PI becomes continuous) and impact strength sharply decreases.}, number={4}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Feb}, pages={1163–1172} } @inbook{mitchell_wilson_rightor_dineen_hayes_urquhart_hitchcock_ade_2000, title={Characterization of microscopic variation in crosslink density in polymer gels using scanning transmission X-ray microscopy}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Mitchell, G. and Wilson, L. R. and Rightor, E. G. and Dineen, M. T. and Hayes, F. and Urquhart, S. and Hitchcock, A. and Ade, H.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={113–114} } @article{urquhart_ade_rafailovich_sokolov_zhang_2000, title={Chemical and vibronic effects in the high-resolution near-edge X-ray absorption fine structure spectra of polystyrene isotopomers}, volume={322}, DOI={10.1016/s0009-2614(00)00441-3}, abstractNote={This Letter presents the high-resolution C 1s near-edge X-ray absorption fine structure (NEXAFS) spectra of hydrogenated and deuterated polystyrene. The differences between these spectra provide unambiguous evidence for the presence of a significant vibronic contribution to the shape and structure of the C 1s(C–H) →1π∗CC transition in polystyrene. High-resolution NEXAFS spectra, spectroscopic simulations and ab initio calculations are used to help resolve the relative contributions of chemical shifts and vibronic excitation to the shape of the characteristic C 1s(C–H) →1π∗CC transition.}, number={5}, journal={Chemical Physics Letters}, author={Urquhart, S. G. and Ade, Harald and Rafailovich, M. and Sokolov, J. S. and Zhang, Y.}, year={2000}, pages={412–418} } @article{smith_ade_balik_koch_smith_spontak_2000, title={Cryogenic mechanical alloying of poly(methyl methacrylate) with polyisoprene and poly(ethylene-alt-propylene)}, volume={33}, ISSN={["1520-5835"]}, DOI={10.1021/ma991453v}, abstractNote={Mechanical alloying is performed at cryogenic temperatures to incorporate polyisoprene (PI) or its hydrogenated analogue poly(ethylene-alt-propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy solid-state blending. Morphological characterization of the blends by X-ray and electron microscopies confirms that the degree of dispersion of the constituent polymers improves with increasing milling time. Such dispersion in the PEP/PMMA blends is, however, ultimately compromised by phase coarsening when the materials are postprocessed above the PMMA glass transition temperature in the melt. Milling-induced PI cross-linking serves to suppress phase coarsening in PI/ PMMA blends, which remain relatively well-dispersed even after postprocessing. These blends are generally less fracture-resistant than the as-received PMMA due mainly to the accompanying reduction in PMMA molecular weight. Their optical transparency is observed to decrease dramatically with increasing PEP or PI concentration until they appear opaque. An overall improvement in blend properties by mechanical alloying is, however, anticipated upon judicious selection of more degradation-resistant polymers.}, number={7}, journal={MACROMOLECULES}, author={Smith, AP and Ade, H and Balik, CM and Koch, CC and Smith, SD and Spontak, RJ}, year={2000}, month={Apr}, pages={2595–2604} } @article{slep_asselta_rafailovich_sokolov_winesett_smith_ade_anders_2000, title={Effect of an interactive surface on the equilibrium contact angles in bilayer polymer films}, volume={16}, ISSN={["0743-7463"]}, DOI={10.1021/la990031b}, abstractNote={Scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and photoemission electron microscopy (PEEM) were used to obtain the three-dimensional concentration profiles and the late-stage morphology of liquid bilayer thin films of the two imiscible polymers polystyrene (PS) and (polybromostyrene) (PBrx=0.79S), where x = fraction of monomers brominated) as a function of the lower PS film thickness. The results showed that the apparent contact angle at the polymer/air interface decreases exponentially with increasing PS film thickness with a constant that scales with the PS radius of gyration (Rg). In contrast, the Neuman angle, as determined from the PBrS STXM images, increases with substrate thickness. NEXAFS and PEEM data show that the droplets consist of a PBrS core fully encapsulated by PS for substrate thicknesses greater than Rg. Only partial encapsulation is seen for substrates less than Rg. These results could not b...}, number={5}, journal={LANGMUIR}, author={Slep, D and Asselta, J and Rafailovich, MH and Sokolov, J and Winesett, DA and Smith, AP and Ade, H and Anders, S}, year={2000}, month={Mar}, pages={2369–2375} } @article{smith_shay_spontak_balik_ade_smith_koch_2000, title={High-energy mechanical milling of poly(methyl methacrylate), polyisoprene and poly(ethylene-alt-propylene)}, volume={41}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(99)00830-7}, abstractNote={High-energy mechanical milling has been performed on poly(methyl methacrylate) (PMMA) at ambient and cryogenic temperatures, as well as on polyisoprene (PI) and poly(ethylene-alt-propylene) (PEP) at cryogenic conditions only. Milling conducted at ambient temperature has a substantially greater impact on the molecular characteristics of PMMA than milling at cryogenic temperatures. An increase in the milling time is accompanied by substantial reductions in PMMA molecular weight and, hence, glass transition temperature and impact strength under both sets of experimental conditions. An unexpected trend identified here is that the PMMA molecular weight distribution initially broadens and subsequently narrows with increasing milling time. Solid-state mechanical milling promotes comparable decreases in molecular weight and glass transition temperature in PEP (at a slower rate relative to PMMA), but induces chemical crosslinking in PI, as confirmed by FTIR spectroscopy. Charlesby–Pinner analysis yields not only the degree of PI crosslinking, but also the relative crosslinking and scission rates of PI, during cryogenic milling.}, number={16}, journal={POLYMER}, author={Smith, AP and Shay, JS and Spontak, RJ and Balik, CM and Ade, H and Smith, SD and Koch, CC}, year={2000}, month={Jul}, pages={6271–6283} } @article{winn_ade_buckley_feser_howells_hulbert_jacobsen_kaznacheyev_kirz_osanna_et al._2000, title={Illumination for coherent soft X-ray applications: the new X1A beamline at the NSLS}, volume={7}, ISSN={["1600-5775"]}, DOI={10.1107/S0909049500012942}, abstractNote={The X1A soft X-ray undulator beamline at the NSLS has been rebuilt to serve two microscopy stations operating simultaneously. Separate spherical-grating monochromators provide the resolving power required for XANES spectroscopy at the C, N and O absorption edges. The exit slits are fixed and define the coherent source for the experiments. The optical design and the operational performance are described.}, number={2000 Nov.}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Winn, B and Ade, H and Buckley, C and Feser, M and Howells, M and Hulbert, S and Jacobsen, C and Kaznacheyev, K and Kirz, J and Osanna, A and et al.}, year={2000}, month={Nov}, pages={395–404} } @inbook{ade_2000, title={Quantitation of composition in inhomogeneous polymers with NEXAFS microscopy}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Ade, H.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={109–110} } @inbook{rightor_urquhart_hitchcock_ade_mitchell_dineen_hayes_priester_lidy_2000, title={Segregated phases in flexible polyurethanes by x-ray spectromicroscopy}, volume={165}, ISBN={0750306858}, number={2000}, booktitle={Microbeam Analysis 2000: proceedings of the Second Conference of the International Union of Microbeam Analysis Societies held in Kailua-Kona, Hawaii, 9-14 July 2000}, publisher={Bristol: Institute of Physics Publishing}, author={Rightor, E. and Urquhart, S. and Hitchcock, A. and Ade, H. and Mitchell, G. and Dineen, M. T. and Hayes, F. and Priester, R. and Lidy, W.}, editor={Williams, D. B. and Shimizu, R.Editors}, year={2000}, pages={111–112} } @article{winesett_ade_sokolov_rafailovich_zhu_2000, title={Substrate dependence of morphology in thin film polymer blends of polystyrene and poly(methyl methacrylate)}, volume={49}, DOI={10.1002/(sici)1097-0126(200005)49:5<458::aid-pi373>3.0.co;2-5}, abstractNote={We studied the effects of different substrates on the development of the morphologies in thin film polymer blends in as-spun and annealed films. We have utilized thin films of blends of polystyrene and poly(methyl methacrylate) spun cast on Si, Au and Co surfaces, and produced quantitative composition maps with near edge X-ray absorption fine structure (NEXAFS) microscopy as a function of annealing time. We observed a marked dependence of the morphologies and the qualitative dynamics on the surface composition. # 2000 Society of Chemical Industry}, number={5}, journal={Polymer International}, author={Winesett, D. A. and Ade, Harald and Sokolov, J. and Rafailovich, M. and Zhu, S.}, year={2000}, pages={458–462} } @article{smith_spontak_koch_smith_ade_2000, title={Temperature-induced morphological evolution in polymer blends produced by cryogenic mechanical alloying}, volume={274}, DOI={10.1002/(sici)1439-2054(20000101)274:1<1::aid-mame1>3.3.co;2-r}, number={1}, journal={Macromolecular Materials and Engineering}, author={Smith, A. P. and Spontak, Richard and Koch, C. C. and Smith, S. D. and Ade, Harald}, year={2000}, pages={1–12} } @article{winesett_zhu_sokolov_rafailovich_ade_2000, title={Time-temperature superposition of phase separating polymer blend films}, volume={12}, ISSN={["0954-0083"]}, DOI={10.1088/0954-0083/12/4/315}, abstractNote={ We have examined the structure formations in symmetric blend films of polystyrene and poly(methyl methacrylate) during phase separation and coalescence in the melt. We qualitatively verify the principle of time–temperature superposition by observing morphology development in which characteristic structures develop independently of annealing temperature and initial morphology. Domain structures proceed to qualitatively similar morphologies regardless of the initial morphology due to the intrinsic viscosity of the blend films. }, number={4}, journal={HIGH PERFORMANCE POLYMERS}, author={Winesett, DA and Zhu, S and Sokolov, J and Rafailovich, M and Ade, H}, year={2000}, month={Dec}, pages={599–602} } @article{zhu_liu_rafailovich_sokolov_gersappe_winesett_ade_1999, title={Confinement-induced miscibility in polymer blends}, volume={400}, number={6739}, journal={Nature}, author={Zhu, S. and Liu, Y. and Rafailovich, M. H. and Sokolov, J. and Gersappe, D. and Winesett, D. A. and Ade, H.}, year={1999}, pages={49–51} } @article{smith_spontak_ade_smith_koch_1999, title={High-energy cryogenic blending and compatibilizing of immiscible polymers}, volume={11}, ISSN={["1521-4095"]}, DOI={10.1002/(SICI)1521-4095(199910)11:15<1277::AID-ADMA1277>3.0.CO;2-9}, abstractNote={ciency Z in solid films of PA-PPV and MEH-PPV has been determined by xerographic discharge experiments over two orders of magnitude in field and for different illumination wavelengths. Onsager's theory with a Gaussian distribution of electron±hole radii describes the electric field dependences of Z well. The large distribution parameter a is a characteristic of a small electron±hole pair binding energy of approximately 0.1±0.2 eV. For both polymers, high efficiencies of up to 20 % at a field of 100 V/mm were measured. Within the polymer absorption, Z was found to be nearly independent of wavelength. This is in agreement with the well established picture of a fast vibronic and energetic relaxation following photoexcitation. Addition of C60 to PA-PPV increases the primary quantum yield to unity and photogeneration efficiencies of up to 50 % are measured.}, number={15}, journal={ADVANCED MATERIALS}, author={Smith, AP and Spontak, RJ and Ade, H and Smith, SD and Koch, CC}, year={1999}, month={Oct}, pages={1277-+} } @article{nemanich_english_hartman_sowers_ward_ade_davis_1999, title={Imaging electron emission from diamond and III-V nitride surfaces with photo-electron emission microscopy}, volume={146}, ISSN={["0169-4332"]}, DOI={10.1016/S0169-4332(99)00021-5}, abstractNote={Wide bandgap semiconductors such as diamond and the III–V nitrides (GaN, AlN, and AlGaN alloys) exhibit small or even negative electron affinities. Results have shown that different surface treatments will modify the electron affinity of diamond to cause a positive or negative electron affinity (NEA). This study describes the characterization of these surfaces with photo-electron emission microscopy (PEEM). The PEEM technique is unique in that it combines aspects of UV photoemission and field emission. In this study, PEEM images are obtained with either a traditional Hg lamp or with tunable UV excitation from a free electron laser. The UV-free electron laser at Duke University provides tunable emission from 3.5 to greater than 7 eV. PEEM images of boron or nitrogen (N)-doped diamond are similar to SEM of the same surface indicating relatively uniform emission. For the N-doped samples, PEEM images were obtained for different photon energies ranging from 5.0 to 6.0 eV. In these experiments, the hydrogen terminated surface showed more intense PEEM images at lower photon energy indicating a lower photothreshold than annealed surfaces which are presumed to be adsorbate free. For the nitrides, the emission properties of an array of GaN emitter structures is imaged. Emission is observed from the peaks, and relatively uniform emission is observed from the array. The field at the sample surface is approximately 10 V/μm which is sufficient to obtain an image without UV light. This process is termed field emission electron microscopy (FEEM).}, number={1-4}, journal={APPLIED SURFACE SCIENCE}, author={Nemanich, RJ and English, SL and Hartman, JD and Sowers, AT and Ward, BL and Ade, H and Davis, RF}, year={1999}, month={May}, pages={287–294} } @article{urquhart_hitchcock_smith_ade_lidy_rightor_mitchell_1999, title={NEXAFS spectromicroscopy of polymers: overview and quantitative analysis of polyurethane polymers}, volume={100}, ISSN={["1873-2526"]}, DOI={10.1016/S0368-2048(99)00043-2}, abstractNote={The successful application of X-ray spectromicroscopy to chemical analysis of polymers is reviewed and a detailed application to quantitative analysis of polyurethanes is presented. Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is the basis of chemical sensitive X-ray imaging, as well as qualitative and quantitative micro-spectroscopy. These capabilities are demonstrated by a review of recent work, and by presentation of new results outlining a methodology for quantitative speciation of polyurethane polymers. C 1s inner-shell excitation spectra of a series of molecular and polymeric model compounds, recorded by gas phase inelastic electron scattering (ISEELS) and solid phase NEXAFS techniques, are used to understand the spectroscopic basis for chemical analysis of polyurethanes. These model species contain the aromatic urea, aromatic urethane (carbamate) and aliphatic ether functionalities that are the main constituents of polyurethane polymers. Ab initio calculations of several of the model molecular compounds are used to support spectral assignments and give insight into the origin and relative intensities of characteristic spectral features. The model polymer spectra provide reference standards for qualitative identification and quantitative analysis of polyurethane polymers. The chemical compositions of three polyurethane test polymers with systematic variation in urea/urethane content are measured using the spectra of model toluene diisocyanate (TDI) urea, TDI-carbamate, and poly(propylene oxide) polymers as reference standards.}, number={1999 Oct.}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Urquhart, SG and Hitchcock, AP and Smith, AP and Ade, HW and Lidy, W and Rightor, EG and Mitchell, GE}, year={1999}, month={Oct}, pages={119–135} } @article{urquhart_smith_ade_hitchcock_rightor_lidy_1999, title={Near-edge X-ray absorption fine structure spectroscopy of MDI and TDI polyurethane polymers}, volume={103}, ISSN={["1089-5647"]}, DOI={10.1021/jp990059w}, abstractNote={The sensitivity of near-edge X-ray absorption fine structure (NEXAFS) to differences in key chemical components of polyurethane polymers is presented. Carbon 1s NEXAFS spectra of polyurethane polymers made from 4,4‘-methylene di-p-phenylene isocyanate (MDI) and toluene diisocyanate (TDI) isocyanate monomers illustrate that there is an unambiguous spectroscopic fingerprint for distinguishing between MDI-based and TDI-based polyurethane polymers. NEXAFS spectra of MDI and TDI polyurea and polyurethane models show that the urea and carbamate (urethane) linkages in these polymers can be distinguished. The NEXAFS spectroscopy of the polyether component of these polymers is discussed, and the differences between the spectra of MDI and TDI polyurethanes synthesized with polyether polyols of different molecular composition and different molecular weight are presented. These polymer spectra reported herein provide appropriate model spectra to represent the pure components for quantitative microanalysis.}, number={22}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Urquhart, SG and Smith, AP and Ade, HW and Hitchcock, AP and Rightor, EG and Lidy, W}, year={1999}, month={Jun}, pages={4603–4610} } @article{giebler_schulz_reiche_brehmer_wuhn_woll_smith_urquhart_ade_unger_1999, title={Near-edge X-ray absorption fine structure spectroscopy on ordered films of an amphiphilic derivate of 2,5-diphenyl-1,3,4-oxadiazole}, volume={15}, ISSN={["0743-7463"]}, DOI={10.1021/la980888t}, abstractNote={The surfaces of ordered films formed from an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole by the Langmuir−Blodgett (LB) technique and organic molecular beam deposition (OMBD) were investigated by the use of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. For the assignment of the spectral features of the C, N, and O K-edge absorption spectra, fingerprint spectra of poly(p-phenylene terephthalamide) (Kevlar), poly(ethylene terephthalate), poly(p-phenylene-1,3,4-oxadiazole), and 2,5-di(pentadecyl)-1,3,4-oxadiazole, which contain related chemical moieties, were recorded. Ab initio molecular orbital calculations, performed with explicit treatment of the core hole, are used to support the spectral interpretations. Angle-resolved NEXAFS spectroscopy at the C, N, and O K-edges suggests a preferentially upright orientation of the oxadiazole derivative in the outermost layer of the films. X-ray specular reflectivity data and molecular modeling results suggest a similar interpretation.}, number={4}, journal={LANGMUIR}, author={Giebler, R and Schulz, B and Reiche, J and Brehmer, L and Wuhn, M and Woll, C and Smith, AP and Urquhart, SG and Ade, HW and Unger, WES}, year={1999}, month={Feb}, pages={1291–1298} } @article{ade_winesett_smith_qu_ge_sokolov_rafailovich_1999, title={Phase segregation in polymer thin films: Elucidations by X-ray and scanning force microscopy}, volume={45}, ISSN={["0295-5075"]}, DOI={10.1209/epl/i1999-00198-7}, abstractNote={We have used quantitative X-ray microscopy in combination with Scanning Force Microscopy to monitor the phase separation of spun cast thin films of polystyrene and poly(methyl methacrylate) blends upon annealing. Both techniques complement and enhance each other in elucidating the complicated structures that develop as a function of annealing time. We have determined the composition of the mixed phases that result from solvent spin casting. We subsequently observe the sudden rearrangement into domains much smaller than those originally formed. Unique, intricate hydrodynamic mass flow patterns form during coarsening which are in qualitative agreement with recent simulations of phase segregation in two-dimensional viscous fluids. Complicated polymer-polymer interfaces persist even in the later stages that are explained in terms of the geometric constraints of a thin film and the dependance of polymer viscosity on film thickness.}, number={4}, journal={EUROPHYSICS LETTERS}, author={Ade, H and Winesett, DA and Smith, AP and Qu, S and Ge, S and Sokolov, J and Rafailovich, M}, year={1999}, month={Feb}, pages={526–532} } @article{ade_yang_english_hartman_davis_nemanich_litvinenko_pinayev_wu_madey_1998, title={A free electron laser-photoemission electron microscope system (FEL-PEEM)}, volume={5}, ISSN={["0218-625X"]}, DOI={10.1142/S0218625X98001596}, abstractNote={ We report first results from our effort to couple a high resolution photoemission electron microscope (PEEM) to the OK-4 ultraviolet free electron laser at Duke University (OK-4/Duke UV FEL). The OK-4/Duke UV FEL is a high intensity source of tunable monochromatic photons in the 3–10 eV energy range. This tunability is unique and allows us to operate near the photoemission threshold of any samples and thus maximize sample contrast while keeping chromatic berrations in the PEEM minimal. We have recorded first images from a variety of samples using spontaneous radiation from the OK-4/ Duke UV FEL in the photon energy range of 4.0–6.5 eV. Due to different photothreshold emission from different sample areas, emission from these areas could be turned on (or off) selectively. We have also observed relative intensity reversal with changes in photon energy which are interpreted as density-of-state contrast. Usable image quality has been achieved, even though the output power of the FEL in spontaneous emission mode was several orders of magnitude lower than the anticipated full laser power. The PEEM has achieved a spatial resolution of 12 nm. }, number={6}, journal={SURFACE REVIEW AND LETTERS}, author={Ade, H and Yang, W and English, SL and Hartman, J and Davis, RF and Nemanich, RJ and Litvinenko, VN and Pinayev, IV and Wu, Y and Madey, JMJ}, year={1998}, month={Dec}, pages={1257–1268} } @article{warwick_franck_kortright_meigs_moronne_myneni_rotenberg_seal_steele_ade_et al._1998, title={A scanning transmission x-ray microscope for materials science spectromicroscopy at the advanced light source}, volume={69}, ISSN={["0034-6748"]}, DOI={10.1063/1.1149041}, abstractNote={Design and performance of a scanning transmission x-ray microscope (STXM) at the Advanced Light Source is described. This instrument makes use of a high brightness undulator beamline and extends the STXM technique to new areas of research. After 2.5 years of development it is now an operational tool for research in polymer science, environmental chemistry, and magnetic materials.}, number={8}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Warwick, T and Franck, K and Kortright, JB and Meigs, G and Moronne, M and Myneni, S and Rotenberg, E and Seal, S and Steele, WF and Ade, H and et al.}, year={1998}, month={Aug}, pages={2964–2973} } @article{ade_winesett_smith_anders_stammler_heske_slep_rafailovich_sokolov_stohr_1998, title={Bulk and surface characterization of a dewetting thin film polymer bilayer}, volume={73}, ISSN={["0003-6951"]}, DOI={10.1063/1.122891}, abstractNote={We have monitored the progression of the dewetting of a partially brominated polystyrene (PBrS) thin film on top of a polystyrene (PS) thin film with scanning transmission x-ray microscopy (STXM) as well as photoemission electron microscopy (PEEM). We mapped the projected thickness of each constituent polymer species and the total thickness of the film with STXM, while we determined the surface composition with PEEM. Our data show that the PBrS top layer becomes encapsulated during the later stages of dewetting and that atomic force microscopy topographs cannot be utilized to determine the contact angle between PBrS and PS.}, number={25}, journal={APPLIED PHYSICS LETTERS}, author={Ade, H and Winesett, DA and Smith, AP and Anders, S and Stammler, T and Heske, C and Slep, D and Rafailovich, MH and Sokolov, J and Stohr, J}, year={1998}, month={Dec}, pages={3775–3777} } @article{cody_ade_wirick_mitchell_davis_1998, title={Determination of chemical-structural changes in vitrinite accompanying luminescence alteration using C-NEXAFS analysis}, volume={28}, ISSN={["0146-6380"]}, DOI={10.1016/S0146-6380(98)00010-2}, abstractNote={The phenomenon of luminescence alteration has been shown to correlate with the thermal maturity of Type III kerogens (vitrinites). In order to establish a chemical structural basis for this correlation, carbon near edge X-ray absorption fine structure (C-NEXAFS) spectroscopy is used to monitor the gain and loss of organic functionality in ultra-thin sections of vitrinite following time incremental exposure to blue light (390–490 nm) irradiation in air. These data are compared with luminescence alteration behavior measured at 600 nm. Three samples are studied; low maturity (% R0=0.29), medium maturity (% R0=0.73), and high maturity (% R0=1.35) vitrinite. These exhibit “positive”, “dual”, and “negative” luminescence alteration, respectively. It has been previously established that the luminescence alteration of vitrinites is the result of photo–oxidation. C-NEXAFS data are used to identify the types of reactions and correlate the chemical structural changes with luminescence alteration behavior. The unaltered C-NEXAFS spectrum of each vitrinite is significantly different, reflecting the broad range in vitrinite maturity. The dominant reaction is the formation of COOH groups, through the attack of singlet oxygen on, predominantly, benzylic carbon. Carbonyl substituted aromatics are the dominant photo–oxidation product of the most mature vitrinite. The photo–chemical oxidation pathways and kinetics vary significantly between the three samples. Virtually all of the major spectral trends (excluding the formation of COOH groups) reverse, moving from low to high maturity, i.e. gains in absorption at a given energy at one maturity level are observed to be losses at a different maturity level. The spectral changes reveal that in the lower maturity samples aromatic acids, aliphatic ketones, and hydroxylated aromatic compounds are formed; aliphatic and aldehydic carbon are lost. In the more mature vitrinite, aryl–ketones and aromatic acids are formed, whereas polycyclic aromatic compounds are lost. Strong correlations exist between the development of “positive” alteration and the formation of COOH functionality. No obvious correlation could be made between the C-NEXAFS data and the “negative” luminescence alteration, suggesting that the lumophor participating in this reaction is below the detection limit of C-NEXAFS spectroscopy. The maturity of a given vitrinite sample, hence its molecular structure, strongly controls the specific reaction pathways as well as the total extent of reaction.}, number={7-8}, journal={ORGANIC GEOCHEMISTRY}, author={Cody, GD and Ade, H and Wirick, S and Mitchell, GD and Davis, A}, year={1998}, pages={441–455} } @article{warwick_ade_cerasari_denlinger_franck_garcia_hayakawa_hitchcock_kikuma_klingler_et al._1998, title={Development of scanning X-ray microscopes for materials science spectromicroscopy at the Advanced Light Source}, volume={5}, ISSN={["0909-0495"]}, DOI={10.1107/S0909049597014283}, abstractNote={The development of two zone-plate microscopes for X-ray spectroscopic analysis of materials is described. This pair of instruments will provide imaging NEXAFS analysis of samples in transmission at atmospheric pressure and imaging XPS and NEXAFS analysis of sample surfaces in a UHV environment.}, number={3}, journal={JOURNAL OF SYNCHROTRON RADIATION}, author={Warwick, T and Ade, H and Cerasari, S and Denlinger, J and Franck, K and Garcia, A and Hayakawa, S and Hitchcock, A and Kikuma, J and Klingler, S and et al.}, year={1998}, month={May}, pages={1090–1092} } @article{nemanich_baumann_benjamin_nam_sowers_ward_ade_davis_1998, title={Electron emission properties of crystalline diamond and III-nitride surfaces}, volume={130}, ISSN={["0169-4332"]}, DOI={10.1016/s0169-4332(98)00140-8}, abstractNote={Wide bandgap semiconductors have the possibility of exhibiting a negative electron affinity (NEA) meaning that electrons in the conduction band are not bound by the surface. The surface conditions are shown to be of critical importance in obtaining a negative electron affinity. UV-photoelectron spectroscopy can be used to distinguish and explore the effect. Surface terminations of molecular adsorbates and metals are shown to induce an NEA on diamond. Furthermore, a NEA has been established for epitaxial AlN and AlGaN on 6H–SiC. Field emission measurements from flat surfaces of p-type diamond and AlN are similar, but it is shown that the mechanisms may be quite different. The measurements support the recent suggestions that field emission from p-type diamond originates from the valence band while for AlN on SiC, the field emission results indicate emission from the AlN conduction band. We also report PEEM (photo-electron emission microscopy) and FEEM (field electron emission microscopy) images of an array of nitride emitters.}, number={1998 June}, journal={APPLIED SURFACE SCIENCE}, author={Nemanich, RJ and Baumann, PK and Benjamin, MC and Nam, OH and Sowers, AT and Ward, BL and Ade, H and Davis, RF}, year={1998}, month={Jun}, pages={694–703} } @article{slep_asselta_rafailovich_sokolov_winesett_smith_ade_strzhemechny_schwarz_sauer_1998, title={Phase separation of polystyrene and bromo-polystyrene mixtures in equilibrium structures in thin films}, volume={14}, ISSN={["0743-7463"]}, DOI={10.1021/la9804132}, abstractNote={Scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), and dynamic secondary ion mass spectrometry (DSIMS) were used to obtain the true three-dimensional concentration profiles of polystyrene (PS) and bromo−polystyrene (PBrx=0.79S where x = fraction of monomers brominated) blend films as a function of PBrx=0.79S concentration. Upon annealing, it is found that the PBrS becomes encapsulated by the PS. The encapsulation provides for a continuous PS phase for all blend compositions and explains the observed structures that are formed for different PBrS volume fractions. The encapsulation allows us to estimate the dispersive contribution of the PBrS surface energy to be less than 20.6 dyn/cm.}, number={17}, journal={LANGMUIR}, author={Slep, D and Asselta, J and Rafailovich, MH and Sokolov, J and Winesett, DA and Smith, AP and Ade, H and Strzhemechny, Y and Schwarz, SA and Sauer, BB}, year={1998}, month={Aug}, pages={4860–4864} } @article{smith_bai_ade_spontak_balik_koch_1998, title={X-ray microscopy characterization of a thermoplastic / liquid crystalline polymer blend produced by mechanical alloying}, volume={19}, DOI={10.1002/marc.1998.030191104}, abstractNote={Incorporation of liquid crystalline polymers (LCPs) into commodity polymers remains a challenge in the design of high-performance, low-cost polymeric blends. Blends of a thermoplastic polymer and a nematic LCP are produced here by mechanical alloying. Functionality sensitive X-ray microscopy reveals LCP dispersions as small as 100 nm in diameter. Intimate mixing remains upon subsequent melt processing, indicating that mechanical alloying is suited for applications such as recycling.}, number={1998}, journal={Macromolecular Rapid Communications}, author={Smith, A. P. and Bai, C. and Ade, Harald and Spontak, Richard and Balik, C. M. and Koch, C. C.}, year={1998}, pages={557} } @article{yang_jedema_ade_nemanich_1997, title={Correlation of morphology and electrical properties of nanoscale TiSi2 epitaxial islands on Si (001)}, volume={308}, ISSN={["1879-2731"]}, DOI={10.1016/S0040-6090(97)00431-8}, abstractNote={The morphology and electrical properties of nanoscale epitaxial islands of TiSi2 are explored. The TiSi2 islands are prepared by ultra-high vacuum (UHV) deposition of ultra-thin Ti (0.3–2 nm) on both smooth and roughened Si (001) substrates. The roughened substrates are prepared by etching with atomic H produced in a plasma. The island formation is initiated by annealing to 800–1000°C. The morphologies of the substrate before and after island formation are examined by atomic force microscopy (AFM). In particular, the influence of surface-roughness on both the formation of islands and the size distribution of islands is investigated. Islands with a lateral dimension of ~35 nm and a vertical dimension of ~2.5 nm on a roughened substrate (RMS=12 nm) were observed, with a uniform distribution of 120 nm spacing between the islands. It was found that for similar processing conditions the size distribution of islands formed on a rough surface was smaller than islands formed on smooth surfaces. The results are discussed in terms of surface energy, diffusion and the strain field around the islands. The island structures can affect the electrical characteristics of the interface and the Schottky barrier was obtained from diodes formed with a Pt layer deposited over the islanded interface. The Schottky barrier was lowest for interfaces with the smaller TiSi2 islands.}, number={1997 Oct. 31}, journal={THIN SOLID FILMS}, author={Yang, W and Jedema, FJ and Ade, H and Nemanich, RJ}, year={1997}, month={Oct}, pages={627–633} } @article{urquhart_hitchcock_smith_ade_rightor_1997, title={Inner-shell excitation spectroscopy of polymer and monomer isomers of dimethyl phthalate}, volume={101}, ISSN={["1520-6106"]}, DOI={10.1021/jp963419d}, abstractNote={The C 1s X-ray absorption spectra (XAS) of poly(diallyl phthalate), poly(diallyl isophthalate), and poly(ethylene terephthalate) (PET) have been recorded using transmission detection. The phthalate segments of these polymers are isomers with different patterns of substitution (ortho, meta, para) of the methyl carboxylate groups on the phenyl ring. The C 1s and O 1s electron energy loss spectra (EELS) of the corresponding isomeric monomers, dimethyl phthalate, dimethyl isophthalate, and dimethyl terephthalate, have also been recorded in the gas phase using inelastic electron scattering under conditions dominated by electric dipole transitions. Good agreement is found in overall shape and in the energies of the spectral features of the same isomer in monomeric (EELS) versus polymeric (XAS) form. Ab initio calculations are used to provide a detailed interpretation of the spectra, in particular the origin of the isomeric variations. The analytical potential for using inner shell excitation spectroscopy to ide...}, number={13}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Urquhart, SG and Hitchcock, AP and Smith, AP and Ade, H and Rightor, EG}, year={1997}, month={Mar}, pages={2267–2276} } @article{warwick_ade_hitchcock_padmore_rightor_tonner_1997, title={Soft x-ray spectromicroscopy development for materials science at the advanced light source}, volume={84}, ISSN={["0368-2048"]}, DOI={10.1016/S0368-2048(97)00026-1}, abstractNote={Several third generation synchrotron radiation facilities are now operational, and the high brightness of these photon sources offers new opportunities for X-ray microscopy. Well developed synchrotron radiation spectroscopy techniques are being applied in new instruments capable of imaging the surface of a material with a spatial resolution smaller than 1 μm. There are two aspects to this. One is to further the field of surface science by exploring the effects of spatial variations across a surface on a scale not previously accessible to X-ray measurements. The other is to open up new analytical techniques in materials science using X-rays on a spatial scale comparable with that of the processes or devices to be studied. The development of the spectromicroscopy program at the Advanced Light Source will employ a variety of instruments, some of which are already operational. Their development and use will be discussed, and recent results will be presented to illustrate their capabilities.}, number={1-3}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Warwick, T and Ade, H and Hitchcock, AP and Padmore, H and Rightor, EG and Tonner, BP}, year={1997}, month={Mar}, pages={85–98} } @article{rightor_hitchcock_ade_leapman_urquhart_smith_mitchell_fischer_shin_warwick_1997, title={Spectromicroscopy of poly(ethylene terephthalate): Comparison of spectra and radiation damage rates in x-ray absorption and electron energy loss}, volume={101}, ISSN={["1520-5207"]}, DOI={10.1021/jp9622748}, abstractNote={The C 1s and O 1s X-ray absorption spectra of poly(ethylene terephthalate) (PET) have been recorded using transmission, fluorescence, and electron yield detection. The corresponding electron energy loss spectra (EELS) have been recorded in a scanning transmission electron microscope. These results are compared to the C 1s and O 1s spectra of gas phase 1,4-dimethyl terephthalate (the monomer of PET) recorded using EELS. The comparison of monomer and polymer materials in different phases and with different techniques has aided the understanding of the relative strengths and limitations of each technique as well as assisting the spectral interpretation. Good agreement is found in the overall shape and the energies of the spectral features. Relatively minor differences in intensities can be understood in terms of the properties of the individual spectroscopic techniques. The critical dose for radiation damage by 100 keV electrons incident on PET at 100 K is found to be (1.45 ± 0.15) × 103 eV nm-3. In contrast...}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Rightor, EG and Hitchcock, AP and Ade, H and Leapman, RD and Urquhart, SG and Smith, AP and Mitchell, G and Fischer, D and Shin, HJ and Warwick, T}, year={1997}, month={Mar}, pages={1950–1960} } @article{ade_1997, title={Spectromicroscopy: preface}, volume={84}, number={1-3}, journal={Journal of Electron Spectroscopy and Related Phenomena}, author={Ade, H.}, year={1997}, pages={R9} } @article{smith_laurer_ade_smith_ashraf_spontak_1997, title={X-ray microscopy and NEXAFS spectroscopy of macrophase-separated random block copolymer/homopolymer blends}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma9612687}, abstractNote={Morphological characterization of bulk polymer blends or compatibilized alloys at submicron spatial resolution has almost exclusively relied upon electron microscopy techniques. Since, however, most organic polymers are composed of carbon and light elements, an arsenal of methods to enhance phase contrast has been developed to facilitate discrimination and analysis of propertygoverning morphological features.1 For transmission electron microscopy (TEM), chemical modification of polymeric specimens through, for example, functionality-specific incorporation of heavy-metal staining agents (typically OsO4 or RuO4) may result in ambiguous results due to an inadequate understanding of the staining reaction or competing reaction kinetics. While microanalytical techniques such as light-element energydispersive X-ray mapping2 and electron spectroscopic (energy-filtered) imaging3-5 can potentially eliminate the need for chemical modification in TEM and have proven highly valuable in identifying morphological characteristics in unmodified multiphase polymer systems, they are typically only capable of distinguishing among constituent elements. In addition, appropriate steps must be exercised during data acquisition to minimize specimen damage due to electron beam irradiation. Another microscopy technique recently applied to the morphological characterization of multiphase polymers is X-ray microscopy (XRM),6-9 in which chemical sensitivity is based on the principles of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.10 This technique utilizes a diffractive optical element (zone plate) to focus highly monochromatic soft X-rays in the energy range of 200-600 eV generated by a synchrotron radiation source onto an ultrathin polymer specimen (typically 100-200 nm in thickness). The transmitted flux is detected as a function of specimen position as the specimen is raster-scanned by piezoelectric transducers. A detailed description of the microscope employed in this work is provided elsewhere.11 The practical spatial resolution of XRM is dictated by zone plate technology, with the smallest available probe presently limited to a full width at half-maximum of about 55 nm, resulting in a minimum feature resolution of about 35 nm. Recent XRM studies of multiphase polymers have successfully elucidated the morphological characteristics of a binary blend composed of polypropylene (PP) and poly(styrene-r-acrylonitrile) (SAN).6,8 Such blends are expected a priori to be highly demixed due to the chemical dissimilarity of the constituent polymers. Moreover, SAN (unlike PP) contains nitrogen, in which case the SAN spatial distribution can be discerned by either XRM or the element-specific techniques mentioned earlier. In this work, we explore the sensitivity of XRM by examining a polymer blend in which the constituent materials are identical in terms of the elements present (C and H only) and, moreover, differ only in terms of their fraction of the same chemical moiety (polystyrene, PS). As a consequence, blends of this type have been found12,13 to exhibit complex phase behavior that is highly dependent on both blend composition and molecular weight considerations. Results obtained here from XRM are compared with TEM micrographs of the same blend after functionalityspecific OsO4 staining. The polymers employed in this work were PS with Mh n ) 120 000 andMh w/Mh n≈ 1.04 and a “random” diblock copolymer (RBC) synthesized by living anionic polymerization in the presence of sec-butyllithium and a potassium alkoxide. A detailed description of the copolymer synthesis and molecular characterization (in terms of monomer sequencing) is provided elsewhere14-16 and is not addressed, for the sake of brevity, in this communication. The RBC was a poly[(styrene-r-isoprene)′-b-(styrene-r-isoprene)′′], (S/I)′-b-(S/I)′′, copolymer, where the ′ and ′′ denote different block compositions, namely, 75/25 and 50/50 (wt %) S/I. The overall composition of the RBC was 68 wt % S, as measured by 1H NMR, and the block lengths were approximately 40 000 each. Two RBC/PS blends, one consisting of 20 wt % RBC and 80 wt % PS and the other 80 wt % RBC and 20 wt % PS, were prepared by solution casting from toluene, as described elsewhere.13 Upon slow solvent evaporation and subsequent annealing, the resultant films were sectioned in a Reichert-Jung Ultracut-S cryoultramicrotome maintained at -100 °C. Sections for TEM analysis, nominally 100-120 nm in thickness and stained with the vapor of OsO4(aq) for 90 min, were imaged on a Zeiss EM902 electron spectroscopic microscope operated at 80 kV and ∆E ) 50 eV. The XRM analysis was performed on the X-1A Beamline of the National Synchrotron Light Source at Brookhaven National Laboratory.}, number={3}, journal={MACROMOLECULES}, author={Smith, AP and Laurer, JH and Ade, HW and Smith, SD and Ashraf, A and Spontak, RJ}, year={1997}, month={Feb}, pages={663–666} } @article{ade_smith_zhang_zhuang_kirz_rightor_hitchcock_1997, title={X-ray spectromicroscopy of polymers and tribological surfaces at beamline X1A at the NSLS}, volume={84}, ISSN={["1873-2526"]}, DOI={10.1016/S0368-2048(97)00013-3}, abstractNote={We provide a general overview of microspectroscopy and spectromicroscopy for materials characterization at beamline X1A at the national synchrotron light source (NSLS). Two instruments, the scanning transmission X-ray microscope (STXM) and scanning photoemission microscope (SPEM), are available. The STXM has been able to provide a spatial resolution of better than 50 nm for several years and near edge X-ray absorption fine structure (NEXAFS) spectroscopy is performed in transmission from thin samples at an energy resolution of typically 0.3 eV at the carbon K-edge. Numerous applications in polymer science and biology have been performed to date. We restrict our review to polymer science applications and present new results of several polymer systems. The SPEM has a spatial resolution of about 250 nm in routine operation and was recently upgraded with a hemispherical sector analyzer to improve the data throughput. We present the latest SPEM results, which were generated from a tribological sample.}, number={1-3}, journal={JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA}, author={Ade, H and Smith, AP and Zhang, H and Zhuang, GR and Kirz, J and Rightor, E and Hitchcock, A}, year={1997}, month={Mar}, pages={53–71} } @article{ade_hsiao_1993, title={X-ray Linear Dichroism Microscopy}, volume={262}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.262.5138.1427}, DOI={10.1126/science.262.5138.1427}, abstractNote={ Chemical-specific x-ray linear dichroism was observed in an x-ray microscope as evidenced by changes in relative contrast upon azimuthal rotation of the sample. As a demonstration, thin sections of a partially ordered polymer fiber were examined with a transmission x-ray microscope near the carbon K -shell absorption edge to provide chemical-specific imaging at 50-nanometer spatial resolution. The observed dichroism and change in contrast upon rotation arise from the polarization dependence of the near-edge x-ray absorption cross section and can be used to image the orientation of specific chemical bonds. }, number={5138}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Ade, H. and Hsiao, B.}, year={1993}, month={Nov}, pages={1427–1429} } @article{ade_zhang_cameron_costello_kirz_williams_1992, title={Chemical contrast in X-ray microscopy and spatially resolved XANES spectroscopy of organic specimens}, volume={258}, ISSN={0036-8075 1095-9203}, url={http://dx.doi.org/10.1126/science.1439809}, DOI={10.1126/science.1439809}, abstractNote={ The scanning transmission x-ray microscope at the National Synchrotron Light Source has been used to record x-ray absorption near-edge structure (XANES) spectra from 0.01-square-micrometer regions of organic specimens. The spectral features observed reflect the molecular structure of the dominant absorbing atoms and provide the contrast mechanism for high-resolution imaging with chemical sensitivity. This technique was used with x-ray energies near the carbon K absorption edge to identify and map separate phases in various polymer blends and to map the DNA distribution in chromosomes with a spatial resolution of 55 nanometers. }, number={5084}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Ade, H and Zhang, X and Cameron, S and Costello, C and Kirz, J and Williams, S}, year={1992}, month={Nov}, pages={972–975} }