Non-Fullerene Organic Solar Cells Based on Benzo[1,2-b:4,5-b′]difuran-Conjugated Polymer with 14% Efficiency

The development of high-performance donor polymers is important for obtaining high power conversion efficiencies (PCEs) of non-fullerene polymer solar cells (PSCs). Currently, most high-efficiency PSCs are fabricated with benzo[1,2-b:4,5-b′]dithiophene (BDT)-based conjugated polymers. The photovoltaic performance of benzo[1,2-b:4,5-b′]difuran (BDF)-based copolymers has lagged far behind that of BDT-based counterparts. In this study, a novel BDF-based copolymer L2 is designed and synthesized, in which BDF and benzotriazole (BTz) building blocks have been used as the electron-sufficient and deficient units, respectively. When blending with a non-fullerene small molecule acceptor (SMA), TTPT-T-4F, the L2-based device exhibits a remarkably high PCE of 14.0%, which is higher than that of the device fabricated by its analogue BDT copolymer (12.72%). Moreover, PSCs based on the L2:TTPT-T-4F blend demonstrate excellent ambient stability with 92% of its original PCE remaining after storage in air for 1800 h. Thus, BDF is a promising electron-donating unit, and the BDF-based copolymers can be competitive or even surpass the performance of BDT-based counterparts.