Photovoltaic Properties of π-Conjugated Polymers Based on Fused Cyclic Imide and Amide Skeletons

π-Conjugated polymers P(BDT-BTI) and P(BDT-BTA) bearing cyclic imide and amide (lactam) moieties, respectively, were designed and synthesized for application in organic photovoltaics (OPVs). Introducing electron-withdrawing imide and amide moieties lowers the HOMO energy levels of the polymers, resulting in an increase in the open-circuit voltages of OPVs. Complementary photoabsorption over the entire visible range was achieved by combining P(BDT-BTI) and P(BDT-BTA) with a typical non-fullerene acceptor, IT-4F. Unlike P(BDT-BTI), P(BDT-BTA) tends to maintain high crystallinity and retains π–π stacking interactions and face-on orientation in the blend films with IT-4F. Consequently, OPVs based on P(BDT-BTA):IT-4F blends achieved power conversion efficiencies as high as 9.6% without any processing additives or post-treatments. π-Conjugated polymers P(BDT-BTI) and P(BDT-BTA), based on cyclic imide and amide skeletons, were designed and synthesized. A power conversion efficiency as high as 9.6% was obtained for organic photovoltaic devices based on P(BDT-BTA) blended with IT-4F.