Dynamic Strain Regulation Via Photoresponsive Fullerenes Enables High-Performance and UV-Robust Perovskite Solar...

The long-term stability of perovskite solar cells (PSCs) is critically undermined by degradation at the buried interface, where residual tensile strain and ultraviolet (UV) irradiation act synergistically. Here, we introduce a fullerene-based photoresponsive molecule, C₆₀-azo, to construct an adaptive SnO₂/perovskite interface. Unlike static interlayers, C₆₀-azo functions as a dynamic molecular switch. Under UV illumination, its trans-to-cis isomerization actively generates a beneficial compressive stress to counteract residual tensile strain. Simultaneously, the light-enriched cis-isomer enhances dynamic defect passivation. This mechanochemical dual mechanism effectively mitigates UV-driven lattice distortion and chemical degradation. Consequently, the modified n-i-p PSCs achieve a power conversion efficiency of 26.60% and exhibit enhanced durability. Unencapsulated devices retain 92.7% of their initial performance after 488 h of continuous UV exposure. Encapsulated cells also maintain 94.7% efficiency after 1000 h of maximum power point tracking under continuous 1-sun-equivalent LED illumination. This work establishes dynamic photoresponsive interface engineering as a pioneering strategy for durable perovskite optoelectronics.