Ester-substituted copolymer-based ternary semitransparent polymer solar cells with enhanced FF and PCE

Ternary polymer solar cells (PSCs) are one of the most promising high-efficiency photovoltaic devices with advantages of simple solution fabrication and single-junction structure. Herein, we fabricated ternary PSCs with PC71BM as the third component, and ester-polymer PFTzTT-3TC as donor and ITIC as host acceptor. So after treatment-annealing, ternary devices based on PFTzTT-3TC: ITIC: PC71BM (1:1:0.05) exhibited a prominently increased VOC of 0.93 V and PCE of 8.87%. The optimal devices (1:1:0.30) delivers a state of art FF of 71.76%, which is over 22% higher than the value of 58.40% in binary devices. Ternary semitransparent solar cells (1:1:0.25, 15 and 20 nm Ag as cathode) produced a PCE of 6.49% and 7.18% and an AVT of 11.91% and 9.29%, respectively. Our work demonstrated that ternary strategy is a promising solution to improve photovoltaic parameters simultaneously though rational selection of matched fullerene and non-fullerene acceptors.