Introduction of a conjugated side chain as an effective approach to improving donor–acceptor photovoltaic polymers

We report a simple, effective approach to modifying two kinds of D–A type polymers; copolymerization with thiophene containing tris(thienylenevinylene) (TTV) conjugated side chain. The resulting copolymers, TTV1 and TTV2, showed significant improvement (25% and 43%) of power conversion efficiency in comparison to the original polymers. The short-circuit current of TTV2 reached 22.6 mA cm−2 that is the highest record for organic photovoltaic devices to date. This design strategy opens up a new possibility to modify the existing D–A type photovoltaic polymers for better performance.