18.7% Efficiency Ternary Organic Solar Cells Using Two Non-Fullerene Acceptors with Excellent Compatibility

In this work, a series of ternary organic solar cells (OSCs) were prepared with polymer PM6 as a donor and two non-fullerene materials, BTP-eC9 and ITIC-Th, with excellent compatibility as acceptors. The open-circuit voltage ( V OC ) of ternary OSCs is found to monotonically increase with increasing content of ITIC-Th, implying the formation of an alloying state between BTP-eC9 and ITIC-Th. Furthermore, the incorporation of ITIC-Th can effectively minimize energy loss, which effectively improves the V OC of ternary OSCs. Consequently, a remarkable power conversion efficiency (PCE) of 18.7% with a short-circuit current density ( J SC ) of 28.0 mA cm –2, a V OC of 0.87 V, and a fill factor (FF) of 77.0% is achieved from the optimal ternary OSCs with 15 wt % ITIC-Th in acceptors. Comprehensive characterizations show that the enhanced J SC and FF are likely due to enhanced photon harvesting, effective exciton dissociation, and balanced charge transport in the optimal ternary active layers. The findings provide a hopeful way to further improve the OSC performance by employing a ternary strategy with two compatible non-fullerene materials as acceptors.