2D conjugated polymers with enhanced intralayer π-π interactions to facilitate exciton diffusion and charge transport are also promising candidates for photovoltaics, which can utilize solar irradiation to produce electricity directly. Usually, a p-type polymer and a n-type small molecule working as the donor and acceptor, respectively, assemble the optically active layer of organic photovoltaics (Figure a) . Here, a rather small band gap (an optimum region of 1.1~1.4 eV) allows for a broad absorption spectrum, and sufficient energy level offset between the LUMO of donor and acceptor guarantees effective exciton dissociation . Benzodithiophene-based 2D polymers (Figure ) have been widely studied as donors and acceptors in photovoltaics .