Ternary organic solar cells with PCEs of up to 16.6% by two complementary acceptors working in alloy-like model

Nowadays, improving the power conversion efficiency (PCE) of organic solar cells (OSCs) is still the most concerned issue. Ternary strategy can effectively improve the PCE while maintaining the single junction device structure from well-developed material systems. Herein, a brominated non-fullerene acceptor of ITC-2Br1 is used as the third component to optimize the efficient PM6:Y6 binary system with highly complementary absorption and higher LUMO value as compared with Y6. With 15% wt ITC-2Br1 in the ternary system, the device achieved a best PCE of 16.6%, which is significantly higher than that of its binary counterpart (15.6%). Through the study of neat and blend films, it is found that ITC-2Br1 and Y6 show good miscibility and the absorption of ternary blend film almost cover the whole range from visible and near-IR regions. The optimized ternary device shows an alloy-like working model with improved carrier lifetime and enhanced charge collection efficiency. This work provides a good example for the third component selection in ternary system, and the ternary strategy is a facile and effective method to boost the device performance of OSCs.