@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={Abstract Ultrathin 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{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={Abstract Due 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{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{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={Abstract Solution‐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{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={Abstract To 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 (μ e ) as high as 2.22 cm 2 V −1 s −1 and a hole/electron mobility ratio (μ h /μ e ) 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{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 the organic cations to simultaneously improve the device performance and stability of 2D OIHP solar cells is rarely reported. Here, we demonstrate that by introducing a classic noncovalent aryl-perfluoroaryl interaction, 2D OIHP solar cells with 1:1 mixed phenethylammonium (PEA) and perfluorophenethylammonium (F5-PEA) can achieve an efficiency of >10% with much enhanced stability using a simple deposition at low temperature without using any additives. The competing effects of surface morphology and crystal orientation with an increased amount of F5-PEA result in the highest efficiency at a 1:1 ratio, while single-crystal studies reveal the expected aryl-perfluoroaryl interaction, accounting for the highest device stability of 2D OIHP solar cell at 1:1 ratio as well. This work provides an example where tuning the interactions of organic cations via molecular engineering can have a profound effect on device performance and stability of 2D OIHP solar cells.}, 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{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={<h2>Summary</h2> 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{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={Abstract The 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 ( E loss ) and maximum external quantum efficiency (EQE max ), 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 E loss of 0.57 eV and a high EQE max (>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{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={Two-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{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={Layered 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{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={Abstract N‐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 (C 16 ) (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 cm 2 V −1 s −1 for IDTTIC in OFET devices than for IDTIC (0.15 cm 2 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} }