Asymmetric chlorination of A₂–A₁–D–A₁–A₂ type non-fullerene acceptors for high-voltage organic photovoltaics

Herein, we synthesized an asymmetric A₂–A₁–D–A₁–A₂ type small molecule nonfullerene acceptor (NFA), HCl-BTA3, by chlorination on one side of A₁. The synergistic effect of the asymmetric structure and chlorination endows HCl-BTA3 with a large dipole moment, close molecular packing, and high-efficiency charge transfer and transport. After being blended with a carboxylate-based polymer donor, TTC-Cl, HCl-BTA3 achieved a high open-circuit voltage (V_OC) of 1.20 V and a satisfactory power conversion efficiency (PCE) of 11.2%, which are among the highest values for high-voltage carboxylate-based polymers.