Two polymer donors PPAF and PPAT with phenylacetates as pendant side chains were designed and synthesized. The pendants of PPAF and PPAT are furan and thiophene, respectively. Relative to the sulfur in thiophene pendants, the oxygen in furan pendants can induce more intermolecular interactions. Thus, in neat films, PPAF shows more ordered packing than PPAT
but in blended films, the over-interaction between PPAF and BTP-eC9 acceptor mutually disturbs their packing, resulting in reduced crystallinity and thereby hindering the device performance. The power conversion efficiencies of PPAF:BTP-eC9 and PPAT:BTP-eC9 based devices are 4.26% and 15.6%, respectively. This work provides a new side chain engineering strategy to optimize the performance of polymer donors.