New Medium-Bandgap Nonfused Ring Guest Acceptor with a Higher-Lying LUMO Level Enables High-Performance Ternary Organic Solar Cells

Adding another constituent into a binary system, known as a ternary strategy, represents a simple and effective approach to boosting the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, we have prepared a new nonfused ring small-molecule acceptor with a medium bandgap, named DFTQA-2FIC, which possesses a high-lying lowest unoccupied molecular orbital energy level and a strong intramolecular charge-transfer effect. We elaborately utilized it as a third component in a typical PM6:Y6 blend to obtain high-performance ternary OSCs. The resulting ternary blend film exhibited superior and balanced hole/electron mobility, enhanced favorable aggregation morphology, and reduced charge carrier recombination. Consequently, an optimized ternary OSC presented a distinctly increased PCE of 17.29%, accompanied by synchronous enhancements in crucial parameters, representing a 7.46% improvement over the binary OSC based on PM6:Y6 with a PCE of 16.09%. This study highlights that incorporating DFTQA-2FIC as a third component in a binary system is suitable for optimizing photovoltaic performance.