Improved Photovoltaic Properties of Donor–Acceptor Copolymers by Introducing Quinoxalino[2,3-b′]porphyrin as a Light-Harvesting Unit

Donor–acceptor (D–A) copolymerization is an effective approach to construct low bandgap polymers with tunable electronic energy levels for the application as donor materials in polymer solar cells (PSCs). Usually, D–A copolymers possess an intramolecular charge transfer absorption band at long wavelength direction, so that the absorption of the polymers is broadened. However, absorption at short wavelength direction is also important and should be broadened and enhanced to increase the short-circuit current density (Jsc) of the PSCs. In this study, a series of low bandgap conjugated polymers, P(QP4-BT-DPP1), P(QP1-BT-DPP1), and P(QP1-BT-DPP4), based on two acceptor units quinoxalino[2,3-b′]porphyrin (QP) and diketopyrrolopyrrole (DPP) connected by oligothiophene donor units, were designed and synthesized by palladium-catalyzed Stille-coupling polymerization. As a complementary light-harvesting unit, QP was first introduced into the D–A conjugated polymers for improving the photovoltaic performance of PSCs...