@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={Abstract}, 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{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{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{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{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{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{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{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_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{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{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} }