Power conversion efficiency (PCE) of single-junction polymer solar cells (PSCs) has made a remarkable breakthrough recently. Plenty of work was reported to achieve PCEs higher than 16% derived from the PM6:Y6 binary system. To further increase the PCEs of binary OSCs incorporating small molecular acceptor (SMA) Y6, we substituted PM6 with PM7 due to the deeper highest occupied molecular orbital (HOMO) of PM7. Consequently, the PM7:Y6 has achieved PCEs as high as 17.0% by the hotcast method, due to the improved open-circuit voltage (V OC ). Compared with PM6, the lower HOMO of PM7 increases the gap between E LUMO-donor and E HOMO-acceptor , which is proportional to V OC . This research provides a high PCE for single-junction binary PSCs, which is meaningful for device fabrication related to PM7 and commercialization of PSCs.

Regulating side-chain orientations of Y-series NFAs is a promising strategy to achieve favorable morphology, and high charge mobility and solar cell performances, which enables high-performance devices with efficiency approaching 18%.