Low bandgap polymers with benzodithiophene and bisthienylacrylonitrile units for photovoltaic applications

► Novel copolymers having benzodithiophene and bisthienylacrylonitrile were synthesized. ► Copolymers were applied as an electron donor material in polymer solar cells. ► Copolymers showed good thermal stabilities, broad absorption bands, and low bandgaps. ► Polymer solar cells based on P2 exhibited a high power conversion efficiency of 4.17%.