A highly crystalline small molecule donor based on bithiazole units enabling efficient ternary all-small-molecule organic solar cells

Abstract

All-small-molecule organic solar cells (ASM-OSCs) have garnered widespread attention in recent years. However, their power conversion efficiencies (PCEs) still fall behind those of polymer donor-based devices, primarily due to the challenge of realizing optimized morphology in ASM-OSCs. Here, a highly crystalline small molecule donor (SMD) named ZW2 is synthesized and incorporated into the ZnP-TSEH:6TIC system. The addition of ZW2 synergistically regulates the morphology, molecular crystallinity, and molecular packing of blends, facilitating efficient charge transport and suppressing charge recombination. Consequently, an impressive PCE of 16.30% was delivered in the ternary device. This work highlights the significance of employing a highly crystalline SMD as the third component in tuning the crystallinity and morphology of blends, providing feasibility for achieving high-efficiency ASM-OSCs.