Sequentially Fluorinated Polythiophene Donors for High‐Performance Organic Solar Cells with 16.4% Efficiency

Polythiophenes (PTs) have attracted considerable interest for application in organic solar cells (OSCs) owing to their simple molecular structures and low‐cost synthesis. However, the power conversion efficiencies (PCEs) of PT‐based OSCs are lower than those of state‐of‐the‐art OSCs. Herein, the development of two sequentially fluorinated PT donors (PT‐2F and PT‐4F) is reported for realizing highly efficient OSCs. PT‐2F and PT‐4F are designed to contain two and four fluorine atoms, respectively, per repeating unit to decrease their highest occupied molecular orbital energy levels and increase the open‐circuit voltages of the OSCs. Importantly, the PT‐4F polymers exhibit high backbone rigidity and the desired temperature‐dependent aggregation behavior, affording well‐developed crystalline structures in thin films for efficient charge transport. These beneficial features promote the construction of an optimal blend morphology of PT‐4F:small‐molecule acceptor with a suitable energy offset and low energetic disorder. Thus, the PT‐4F‐based binary and ternary OSCs achieve high PCEs of 15.6% and 16.4%, respectively. A high‐performance polythiophene organic solar cell with a power conversion efficiency of 16.4% is demonstrated, which is enabled by sequentially fluorinated thiophene‐based polymers with a low‐lying highest occupied molecular orbital level, high crystalline properties, and the desired temperature‐dependent aggregation behavior. These beneficial features afford an optimal bulk heterojunction morphology with a suitable energy offset and low energetic disorder.