Dynamic Strain Regulation Via Photoresponsive Fullerenes Enables High‐Performance and UV‐Robust Perovskite Solar Cells

ABSTRACT 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, C 60 ‐azo, to construct an adaptive SnO 2 /perovskite interface. Unlike static interlayers, C 60 ‐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.