Reducing VOC 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 excel-lent 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 (Eloss) of 0.53 to 0.54 eV, as compared to their binary counterparts with either high open-circuit voltage (VOC) but large Eloss, or less Eloss but low VOC. 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 find-ings demonstrate the feasibility of exploring the exciting pool of nonfullerene acceptors to pursue new breakthroughs of OPVs.