@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{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{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", {:sub=>"a"}, " scales linearly with the enthalpic interaction parameters χ", {:sub=>"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", {:sub=>"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{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={In 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{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{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={Conjugated 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 we are able to design conjugated polymers which can exhibit both high efficiency and straightforward synthesis, the road to commercial reality would be more achievable. For that reason, we designed a new synthetic approach towards PTQ10. Our new synthetic approach to make PTQ10 has a significant reduction in cost (1/7 th the original) and is also able to easily accommodate different side chains to move towards green processing solvents. Furthermore, high efficiency organic solar cells are demonstrated with a PTQ10:Y6 blend exhibiting ~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{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={Ternary 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{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{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={Nowadays, the commercially available polymer donor PM6 has been applied widely in organic solar cells (OSCs) and achieved the state-of-the-art power conversation efficiencies (PCEs). To fully explore its photovoltaic potential in OSCs, fine regulating the molecular structure to further optimize the related active layer morphologies is of considerable significance. Herein, we demonstrated a simple random ternary copolymerization approach to develop a terpolymer donor PM6-Tz20 by carefully incorporating the third 5,5'-dithienyl-2,2'-bithiazole (DTBTz, 20 mol%) unit into the molecular backbone of PM6 (PM6-Tz00). It is found that this method can properly tailor the molecular ordering, orientation, and aggregation properties without obviously affecting absorption and energy levels of polymer donors, and then effectively optimize the active layer morphology with a small molecule acceptor Y6, as well as the electrical properties of the related devices, ultimately improving fill factor (FF) and thus boosting PCE. As a result, the PM6-Tz20-based OSCs achieved a PCE of up to 17.1% with a significantly enhanced FF of 0.77, which is much higher than that of the controlled OSCs based on PM6 (PCE=15.7% and FF=0.72). Notable, using Ag (220 nm) instead of Al (100 nm) as cathode, the champion PCE was further improved to 17.6% due to the increase of photocurrent. These are among the best results for the binary OSCs reported to date. Our work provides a simple but effective approach to optimize blend morphologies of OSCs for higher 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{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={Thermal 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{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} }