<p><?tk 4?>Ternary blending represents a promising strategy for advancing polymer solar cell performance, yet the mechanisms underlying slight efficiency enhancement often remain elusive. Herein, based on the binary PM6:IT-4F blend, we constructed a ternary photovoltaic system, PM6:IT-4F:PC₇₁BM, demonstrating that 20% PC₇₁BM incorporation in acceptors yields 12.17% efficiency, a slight 2.44% improvement driven predominantly by open-circuit voltage enhancement despite short-circuit current reduction. Compared to conventional complementary absorption strategies, PC₇₁BM functions primarily as a morphology regulator, transforming the active layer from a honeycomb-like porous structure into a fibrous entangled network. This optimization enhances charge mobility and suppresses bimolecular recombination, effectively compensating for the slight reduction in PM6 exciton dissociation efficiency (photoluminescence quenching: 91.5% to 88.0%). These findings highlight that morphology engineering can regulate the dynamic behavior of exciton and charge, offering new design principles for ternary organic photovoltaics.</p>