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New roles of fused-ring electron acceptors in organic solar cells

Cao, Huan, Qin, Dashan, Wang, Jing, Li, Tengfei, Zhu, Jingshuai, Jiang, Haotian, Zhang, Mingyu, Liu, Kuan, Tang, Zheng, Zhan, Xiaowei
Journal of materials chemistry A 2019 v.7 no.9 pp. 4766-4770
cathodes, electron transfer, polyethyleneimine, solar cells, zinc oxide
Recently, we developed fused-ring electron acceptors (FREAs) as a class of high-performance nonfullerene acceptors, which have been widely used in organic solar cells (OSCs). Here, we explore new functions of FREAs in addition to being an acceptor in a photoactive layer, and use them as an interfacial layer, which significantly improves the performance of OSCs. Compared with the conventional cathode modifying layers (CMLs) of ZnO and ZnO/polyethylenimine ethoxylated (PEIE), a novel CML of ZnO/FREA/PEIE enhances the optical mode and absorption of the device and suppresses geminate recombination via charge separation, both of which increase the short-circuit current density. In addition, FREAs passivate the surface defects of ZnO and then facilitate electron transport. The OSCs based on ZnO/FREA/PEIE exhibit a power conversion efficiency of 13.04%, higher than those based on ZnO and ZnO/PEIE (12.15% and 12.12%).