Yuan Meng, Bowen Cheng, Dongcheng Jiang, Jiangkai Sun, Jiawei Qiao, Beibei Shi, Haisheng Ma, Jingtian Zhu, Lianbo Wang, R. Y. Gu, Pengfei Lu, Yanna Sun, Yanna Sun, Xia Guo, Xia Guo, Ke Gao, He Yan, Maojie Zhang, Feng Chen, Yanming Sun, Yanming Sun, Xiaotao Hao, Hang Yin
The commercialization of organic solar cells (OSCs) requires thick-film active layers, yet current thick-film-compatible acceptor selection based on zero-field mobility is unreliable due to methodological inconsistencies in experimental protocols, fitting models, and single-carrier device configurations. Existing literature indicates that the zero-field mobility in high-performance thick-film devices shows negligible differences compared to thin-film counterparts, thereby invalidating its significance as a selection criterion. This study introduces a protocol identifying critical length - an intrinsic property distinct from zero-field mobility - as the decisive factor for thick-film OSC performance. Comparative studies reveal that enlarged acceptor domains with high critical length yield increased hopping frequency, improved charge mobility and reduced field-dependent, collectively enhancing performance. Applying this criterion, we identify BTP-eC9 as a general acceptor, achieving 19.0% efficiency in thick-film D18:L8-BO:BTP-eC9 OSCs. This work not only demonstrates the fabrication of high-performance thick-film OSCs, but fundamentally advances material screening methodology specifically tailored for thick-film-compatible organic semiconductors.