Efficient Solar Cells Based on a Polymer Donor with β-Branching in Trialkylsilyl Side Chains

Side-chain engineering is an important strategy in designing novel polymer semiconductor materials for high-efficient organic solar cells. The use of trialkylsilyl side chains can improve the photovoltaic efficiency by decreasing energy HOMO and improving its crystallinity hole mobility. Compared to simple linear derivatives, α-branching alkyl groups causes strong aggregation excessive phase separation photoactive layer, leading poor device performance. β-Branching has not yet been used chains. Herein, we describe a new (J77) with triisobutylsilyl investigate effect β-branching on molecular aggregation, optical properties, levels, properties. We find that compared α-branching, significantly reduces aggregation. This enables J77 form blend morphologies films provide cells combination different non-fullerene acceptors. Moreover lowers level increases open-circuit voltage J77-based without sacrificing short-circuit current density or fill factor.