Trifluoromethylation in the Design and Synthesis of High-Performance Wide Bandgap Polymer Donors for Quasiplanar Heterojunction Organic Solar Cells.

New strategies for the molecular design to construct efficient electron-deficient units for D-A-type donor copolymers are urgently needed. Halogenation of electron-deficient units (A) has been shown to be the most effective strategy reported to date with which to produce high-performance donor polymers. Herein, we have constructed two different trifluoromethyl-substituted polymer donors, PBQP-CF 3 and PBQ-CF 3 . The trifluoromethylation process typically involves complex protocols, which are not widely used in the synthesis of polymer donors. Accordingly, we have developed a single-step, one-pot synthesis of the new trifluoromethyl-substituted electron-deficient unit (A) of PBQ-CF 3 . The strong electron-withdrawing ability of the trifluoromethyl group ensures deeper highest occupied molecular orbital (HOMO) energy levels, and the non-covalent bonding interactions of the fluorine atoms are beneficial to the regulation of aggregation properties. Thus, both of the trifluoromethyl-substituted polymer donors obtained much higher power conversion efficiency (PCE) than PBDP-H (6.66%). PBQ-CF 3 exhibits a deeper HOMO energy level, better aggregation behavior, and higher hole mobility than PBQP-CF 3 . PBQ-CF 3 -based quasiplanar heterojunction (Q-PHJ) devices therefore achieve simultaneously enhanced open-circuit voltage ( V OC ), short-circuit current density ( J SC ), and fill factor (FF) and an impressive PCE (16.02%), which is much higher than that obtained by PBQP-CF 3 -based devices (12.57%). This work reveals a promising path to synthesis of the trifluoromethylation polymer donors and demonstrates that the trifluoromethylation strategy can be used to enhance the photovoltaic performance.