<p>The density of trap states at the donor–acceptor interface increases charge recombination, limiting the efficiency of organic solar cells (OSCs). Ternary organic solar cells (TOSCs) overcome this issue by incorporating a third material to modify the interfacial energetics. Prior studies have predominantly focused on complex organic semiconductors as third materials to mitigate interface recombination. In contrast, boron-based compounds have emerged as promising materials owing to their structural versatility, tunable optoelectronic properties, and simple fabrication. In this work, we introduce an easily synthesized boron-based small molecule as a practical third component in a PTB7-Th:PC₇₁BM bulk heterojunction system. Trap density-of-states revealed that including the boron compound in the TOSCs suppresses the density of deep interface trap states, while maintaining bulk trap densities. Consequently, this interface-defect passivation enhances the solar cell’s fill factor. Numerical simulations of the recombination rate corroborated the reduced charge-carrier recombination losses.</p>