Side chain engineering investigation of non-fullerene acceptors for photovoltaic device with efficiency over 15%

Side chain engineering plays a substantial role for high-performance organic solar cells (OSCs). Herein, a series of non-fullerene acceptor (NFA) molecules with A-D-A structures, TTCn-4F, with gradient substituent lengths of terminal side chains (T-SCs) on the molecular backbones have been designed and synthesized. The effects of T-SCs length, ranging from hydrogen atom to n-dodecyl, their optoelectronic properties, thin film molecular packing, blend film morphology, and overall photovoltaic performance have been systematically studied. The results show that among this series of molecules, TTC8-4F with n-octyl substituent, showed the best photovoltaic performance when applied with PM6 as the donor due to its favorable morphology, balanced charge mobility, effective exciton dissociation and less charge recombination. Based on this, its ternary device with F-Br as the secondary acceptor achieved a high PCE of 15.34% with the simultaneously enhancedV(oc)of 0.938 V,J(sc)of 22.66 mA cm(-2), and FF of 72.15%. These results indicate that the engineering of T-SCs is an effective strategy for designing high-performance NFAs.