Evolution of a self-organized molecular packing at the microscopic scale in a bulk heterojunction active layer is critical for improving the performance of organic solar cells. We demonstrate that the molecular-shape-induced effects improve the morphology of the ternary thin films as PC₆₁BM molecules were added to the host binary blend, PTB7-Th:PC₇₁BM. Compared to the binary PTB7-Th:PC₇₁BM devices, the ternary devices with 20% PC₆₁BM content (relative to PC₇₁BM) exhibited an enhanced efficiency, from 6.4% to 8.5%. In particular, we find that the spherical PC₆₁BM molecules with better precipitation kinetics than ellipsoidal PC₇₁BM alter the morphology of ternary thin film and modulate interfaces to expedite charge transport and collection by reducing various recombination losses.