Reducing V_OC loss via structure compatible and high lowest unoccupied molecular orbital nonfullerene acceptors for over 17%‐efficiency ternary organic photovoltaics

Abstract The ternary strategy is effectual to attain high‐performance organic photovoltaics (OPVs). Herein, device processing and performance of PM6:Y6:IT‐4F OPVs is improved, and ITIC‐Th with high‐lying lowest unoccupied molecular orbital is incorporated into PM6: Y6 blend. The PM6:Y6: ITIC‐Th device afforded an excellent PCE of 17.2%, surpassing PM6: Y6 device, and becoming one of the highest PCE. The resulting ITIC‐Th‐based ternary OSCs demonstrated low energy loss (E_loss) of 0.53 to 0.54 eV, as compared to their binary counterparts with either high open‐circuit voltage (V_OC) but large E_loss, or less E_loss but low V_OC. The incorporation of ITIC‐Th and IT‐4F balanced the charge mobilities, and thereby retained and improved fill factors. Increased crystalline coherence length and smaller d‐spacing of π‐π peaks are also observed in ternary blends, indicating enhanced crystallinity and thus improved active‐layer morphology. These findings demonstrate the feasibility of exploring the exciting pool of nonfullerene acceptors to pursue new breakthroughs of OPVs. image