Ternary Polymer Solar Cells with High Efficiency of 14.24% by Integrating Two Well‐Complementary Nonfullerene Acceptors

Ternary polymer solar cells (PSCs) are one of the most promising device architectures that maintains the simplicity of single‐junction devices and provides an important platform to better tailor the multiple performance parameters of PSCs. Herein, a ternary PSC system is reported employing a wide bandgap polymeric donor (PBTA‐PS) and two small molecular nonfullerene acceptors (labeled as LA1 and 6TIC). LA1 and 6TIC keep not only well‐matched absorption profiles but also the rational crystallization properties. As a result, the optimal ternary PSC delivers a state of the art power conversion efficiency (PCE) of 14.24%, over 40% higher than the two binary devices, resulting from the prominently increased short‐circuit current density (Jsc) of 22.33 mA cm−2, moderate open‐circuit voltage (Voc) of 0.84 V, and a superior fill factor approaching 76%. Notably, the outstanding PCE of the ternary PSC ranks one of the best among the reported ternary solar cells. The greatly improved performance of ternary PSCs mainly derives from combining the complementary properties such as absorption and crystallinity. This work highlights the great importance of the rational design of matched acceptors toward highly efficient ternary PSCs. High‐performance ternary‐blend solar cells are fabricated by incorporating two nonfullerene acceptors. The enhanced power conversion efficiency mainly benefits from the broadened light harvesting and the optimized morphology. This work demonstrates that elaborately selecting a suitable third component with complementary basic properties is critical for the development of high‐performance ternary solar cells.