Perylene and naphthalene diimide copolymers for all‐polymer solar cells: Effect of perylene/naphthalene ratio

We report the synthesis of a series of copolymers, having 2,2′‐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%.