Simultaneously enhancing the photovoltaic parameters of ternary organic solar cells by incorporating a fused ring electron acceptor.

The ternary strategy has been recognized as an effective method to improve the photovoltaic performance of organic solar cells (OSCs). In ternary OSCs, the complementary or broadened absorption spectrum, optimized morphology, and enhanced photovoltaic performance could be obtained by selecting a third rational component for the host system. In this work, a fused ring electron acceptor named BTMe-C8-2F, which possesses a high-lying lowest unoccupied molecular orbital (LUMO) energy level and a complementary absorption spectrum to PM6:Y6, was introduced to a PM6:Y6 binary system. The ternary blend film PM6:Y6:BTMe-C8-2F showed high and more balanced charge mobilities, and low charge recombination. Therefore, the OSC based on the PM6:Y6:BTMe-C8-2F (1 : 1.2 : 0.3, w/w/w) blend film achieved the highest power conversion efficiency (PCE) of 17.68%, with an open-circuit voltage (VOC) of 0.87 V, a short-circuit current (JSC) of 27.32 mA cm-2, and a fill factor (FF) of 74.05%, which are much higher than the binary devices of PM6:Y6 (PCE = 15.86%) and PM6:BTMe-C8-2F (PCE = 11.98%). This work provides more insight into the role of introducing a fused ring electron acceptor with a high-lying LUMO energy level and complementary spectrum for simultaneously enhancing the VOC and JSC to promote the performance of ternary OSCs.