Enhancing intermolecular packing and light harvesting through asymmetric non-fullerene acceptors for achieving 18.7% efficiency ternary organic solar cells

Abstract

In recent years, the ternary strategy has been proven to be an effective way to improve the performance of organic solar cells (OSCs). Herein, an asymmetric medium-band gap non-fullerene acceptor (AFIC) is synthesized and added as the third component into the PM6:BTP-eC9 binary blend for a highly efficient ternary OSC. AFIC exhibits a well-complementary absorption spectrum with the host binary blend, which benefits light harvesting of the active layer. Furthermore, AFIC shows a large dipole moment and good miscibility with BTP-eC9, which facilitates the formation of a stable well-mixed phase and enhances molecular packing in the blend, leading to improved charge transport and suppressed charge recombination in ternary devices. As a result, the ternary OSC based on PM6:BTP-eC9:AFIC demonstrates a significantly improved power conversion efficiency (PCE) of 18.7% while the binary OSC based on PM6:BTP-eC9 shows a PCE of 17.5%, which is attributed to the synergistic enhancement of the open-circuit voltage (V_oc), short-circuit current density (J_sc), and fill factor (FF).