Photoisomeric Molecule-Mediated Ion Anchoring and UV Resistance in Metal Halide Perovskites

Halide perovskites are novel photovoltaic materials with soft ionic lattice that are continuously exposed to sunlight during operation. High-energy ultraviolet (UV) irradiation will cause halide ion oxidation within the perovskite layer, accelerating halide ion migration and component loss, which results in a marked degradation in the device’s photovoltaic performance. Here, we introduce a 2,3-bis(2,4,5-trimethyl-3-thienyl) maleimide (BTTM) molecule capable of interconversion between UV and visible light into the perovskite structure, intensifying the light stability of the perovskite layer via ion anchoring. Meanwhile, the incorporation of BTTM promotes the growth of perovskite crystals and efficiently passivates defects within the perovskite film, significantly boosting the open-circuit voltage of the perovskite solar cells. This results in a power conversion efficiency increase from 22.07% to 24.71%. Under UV irradiation (365 nm), BTTM molecules mitigate the degradation of perovskite by suppressing the ion migration of iodide ions. After cumulative exposure to 5 kWh/m 2 of continuous UV irradiation, BTTM-based devices retain over 90% of their initial power conversion efficiency, demonstrating significantly enhanced UV stability. This study offers a straightforward approach to UV protection, providing novel insights for the environmental application of perovskite solar cells under intense UV irradiation.