We report the synthesis of a series of copolymers, having 2,20-bithiophene as electron-donating moiety, and perylene diimide (PDI) and/or naphthalene diimide (NDI) as electron-accepting moiety, and employed as non-fullerene acceptors in polymer solar cells (PSCs). All the copolymers show wide absorption varying from 300 to 850 nm in the visible and NIR spectrum. When changing the PDI/NDI ratio in the polymer backbone, The LUMO energy levels vary in the range of -3.90 to -3.80 eV and the HOMO energy levels vary in the range of -6.10 to -5.85 eV. Among PSCs based on PTB7-Th donor and these polymer acceptors, the devices based on PTB7-Th/NDI100 yield the best power conversion efficiency (PCE) of 4.67%, while the PTB7-Th/PDI100-based devices yield a PCE of 1.03%. (C) 2016 Wiley Periodicals, Inc.