LAUSR

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.