Polymer solar cells(PSCs)have attracted much attention due to their potential for the fabrication of light-weight,large-area,and flexible photovoltaic devices through low-cost solution processing.Compared to most symmetry copolymerized monomers,the strategy of symmetry-breaking applicable in building blocks was employed by us to design new lightharvesting polymers.A series of asymmetric benzodithiophenes(BDTs)with alkoxyl(1D)and aromatic(2D)substituted groups were designed as the electron-rich units for constructing donor-acceptor copolymers.