High-Performance Ternary Organic Solar Cells with Morphology-Modulated Hole Transfer and Improved Ultraviolet Photostability

A ternary bulk-heterojunction (BHJ) strategy that synergistically combines the merits of fullerene and nonfullerene acceptors has been regarded as a promising approach to enhance the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Herein, the fullerene derivative ICBA as the morphology regulator is incorporated into a nonfullerene-based PBDB-T-2F:BTP-4Cl (PM6:BTP-4Cl) system to fabricate the high-performance ternary OSCs. The amorphous ICBA prefers to homogeneously distribute in the BTP-4Cl phase to form the well-mixed acceptor domains due to their better miscibility, which distinctly reduces the exciton decay loss driven by the unfavorable phase separation and enhances BHJ morphology stability of ternary blends. The appropriate addition of ICBA induces the efficient long-range Forster resonance energy transfer to BTP-4Cl and facilitates the ultrafast hole transfer process from BTP-4Cl to PM6, thereby contributing to charge carrier generation in the actual devices. Ultimately, the optimal ternary OSCs not only yield an average PCE higher than 16.5% but also show the superior ultraviolet photostability relative to binary control devices due to the increased harvesting of ultraviolet photons, boosted charge transfer, more balanced charge transport, and more stable nanostructural morphology. The results provide new insights to enable the simultaneously improved device performance and ultraviolet durability in state-of-the-art ternary OSCs.