High-Performance Ternary Organic Solar Cells through Incorporation of a Series of A2-A1-D-A1-A2 Type Nonfullerene Acceptors with Different Terminal Groups

A ternary strategy has been considered to be a simple and efficient method to further improve the performance of organic solar cells (OSCs). Here, three benzotriazole-based nonfullerene acceptors (NFAs) with similar A2-A1-D-A1-A2 backbones except for different terminal groups, are utilized as guest components to a classic PM6:BTP-BO-4F binary host. Excitingly, BTA1–3 all realize much better photovoltaic performance in ternary devices with a minimized energy loss (Eloss) and improved open-circuit voltage (VOC), suggesting that it is the bridge A1 unit that plays the decisive role. Additionally, the short-circuit current density (JSC) and fill factor (FF) of BTA2-/BTA3-incorporated devices can be enhanced simultaneously, resulting from more efficient photon harvesting, increased exciton dissociation, improved charge transport, and reduced charge recombination. The highest efficiency of 18.27% is obtained in the BTA2 device, one of the top values for PM6-based OSCs. This work suggests that A2-A1-D-A1-A2 type NFAs are effective in further improving the performance of ternary OSCs.