This paper reports the fabrication of efficient thick-film organic solar cells (OSCs) with an active layer consisting of one polymer donor and two non-fullerene acceptors. The use of two acceptors with enlarged exciton diffusion length, coupled with a layer-by-layer approach to optimize vertical phase separation, resulted in a 300 nm-thick OSC with a certified efficiency of 16.9% (17.31% un-certified). A 500 nm-thick device also showed an efficiency of 15.21%. These results highlight the importance of exciton diffusion length and graded vertical phase separation for achieving high-efficiency thick-film OSCs.

Yunhao Cai, Qian Li, Guanyu Lu, Hwa Sook Ryu, Yun Li, Hui Jin, Zhihao Chen, Zheng Tang, Guanghao Lu, Xiaotao Hao, Han Young Woo, Chunfeng Zhang, Yanming Sun