Binary non-fullerene-based polymer solar cells with a 430 nm thick active layer showing 15.39% efficiency and 73.38% fill factor

作者：Pan, Feilong; Luo, Mei; Liu, Xuncheng; Jiang, Haiying; Wang, Zhen; Yuan, Dong; Wang, Qian; Qing, Lechi; Zhang, Zesheng; Zhang, Lianjie; Zou, Yingping^*; Chen, Junwu^*

来源：Journal of Materials Chemistry A, 2021, 9(11): 7129-7136.

DOI：10.1039/d1ta00287b

• HIGH HOLE MOBILITY
• ACCEPTOR
• ENABLES

Thickness-sensitive fill factor (FF) is usually encountered by organic active layers with a thickness of several hundred nanometers, which significantly deteriorate the photovoltaic performance of thick-film polymer solar cells (PSCs). Here, paring of high-hole mobility (mu(h)) polymer donor Si25 with benzotriazole-fused Y-series non-fullerene acceptor Y14 is proposed to overcome this challenge. Relative to the electron mobility (mu(e)) of 8.17 x 10(-4) cm(2) V-1 s(-1) for the Y14 pristine film, much higher mu(e) values up to 3.79 x 10(-3) cm(2) V-1 s(-1) were demonstrated using Si25:Y14 binary blend films, achieving mu(h)/mu(e) of 2.31-3.56. The Si25-induced closer packing of Y14 molecules was observed with the blend film. The high and fairly balanced charge transport-enabled PSCs with 320-600 nm thick active layers to show a low FF decay from 74.69% to 67.46%. Power conversion efficiencies (PCEs) of 15.39% and 15.03% were achieved for 430 nm and 600 nm thick active layers, respectively. The device performances can supply a wide processing window with high efficiency. Delightedly, green solvent o-xylene cast active layers of 400 nm and 530 nm thickness exhibited PCEs of 14.43% and 14.25%, respectively. This study indicates that high mu(h) polymers and benzotriazole-fused Y-series non-fullerene acceptors are promising candidates to overcome the thickness sensitivity of FF.