Achieving High‐Efficiency and Thick‐Film‐Insensitive Organic Solar Cells with a Functional Aid <sup>†</sup>
Ruizhi Zhang, Linghui Qi, Maoheng Wu, Bing Sun, Longfei Jia, Jiaqi Hu, Chengcheng Li, Sunsun Li, Lina Zhou, Vakhobjon Kuvondikov, Sherzod Nematov, Changlei Xia, Wenchao Zhao, Long Ye
Abstract
Comprehensive Summary Presently, few methods offer broad applicability for optimizing thick‐film organic solar cells (OSCs). Here, we identify and implement a functional aid, 4‐iodobiphenyl (IBP), in OSCs to optimize active layer morphology and significantly boost device efficiency. In the PM6:A4T‐16 system, the optimized volatility of IBP promotes acceptor recrystallization and ordered molecular alignment during thermal annealing, leading to the formation of large aggregates and a fibrous morphology that facilitates efficient charge transport. As a result, the power conversion efficiency (PCE) of IBP‐treated devices increases by 20% compared with those using conventional additives such as DIO and DIB. Notably, IBP exhibits broad compatibility, delivering substantial efficiency enhancements in PM6:BTP‐eC9 and PM6:D18:L8‐BO systems, with the latter reaching a high PCE of 20%. Furthermore, IBP enables thickness‐insensitive performance, maintaining a PCE of ~17% at an active layer thickness exceeding 360 nm. These results demonstrate IBP as a highly effective processing aid for multiple donor:acceptor pairs, offering a promising strategy for morphology engineering and advancing the fabrication of high‐performance OSCs.