Improved Charge Transport and Reduced Nonradiative Energy Loss Enable Over 16% Efficiency in Ternary Polymer Solar Cells.

Recent advances in the material design and synthesis of nonfullerene acceptors (NFAs) have revealed a new landscape for polymer solar cells (PSCs) and have boosted the power conversion efficiencies (PCEs) to over 15%. Further improvements of the photovoltaic performance are a significant challenge in NFA-PSCs based on binary donor:acceptor blends. In this study, ternary PSCs are fabricated by incorporating a fullerene derivative, PC61 BM, into a combination of a polymer donor (PBDB-TF) and a fused-ring NFA (Y6) and a very high PCE of 16.5% (certified as 16.2%) is recorded. Detailed studies suggest that the loading of PC61 BM into the PBDB-TF:Y6 blend can not only enhance the electron mobility but also can increase the electroluminescence quantum efficiency, leading to balanced charge transport and reduced nonradiative energy losses simultaneously. This work suggests that utilizing the complementary advantages of fullerene and NFAs is a promising way to finely tune the detailed photovoltaic parameters and further improve the PCEs of PSCs.