• • Ternary all-polymer solar cells with PM6:PCN3:PY-IT achieved a PCE of 19.41%, surpassing the binary PM6:PY-IT system (18.67%) by 0.74 percentage points, demonstrating the efficacy of dual-compatibility interfacial modifiers in enhancing photovoltaic performance.
• • At an active layer thickness of 200 nm, the device retained a high PCE of 18.25%, indicating thickness-insensitive behavior critical for roll-to-roll manufacturing where uniform thick films are challenging to produce.
• • The interfacial modifier PCN3 suppressed excessive phase separation and optimized vertical phase separation, leading to extended exciton diffusion length and improved exciton dissociation efficiency, which are essential for mitigating recombination losses in thick active layers.
• • The strategy effectively suppressed trap-assisted recombination, a major loss mechanism in thick-film devices, thereby enabling high fill factors and open-circuit voltages even at increased thicknesses.