Sequentially Fluorinated Polythiophene Donors for High-Performance Organic Solar Cells with 16.4% Efficiency
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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 a sequentially fluorinated PT donor, PT-4F, is reported for realizing highly efficient OSCs. PT-4F contains four fluorine atoms, respectively, per repeating unit to decrease their highest occupied molecular orbital 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 and 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.