Mobile iodides capture for highly photolysis- and reverse-bias-stable perovskite solar cells

For halide perovskites that are susceptible to photolysis and ion migration, iodide-related defects, such as iodine (I₂) and iodine vacancies, are inevitable. Even a small number of these defects can trigger self-accelerating chemical reactions, posing serious challenges to the durability of perovskite solar cells. Fortunately, before I₂ can damage the perovskites under illumination, they generally diffuse over a long distance. Therefore, detrimental I₂ can be captured by interfacial materials with strong iodide/polyiodide (I_x⁻) affinities, such as fullerenes and perfluorodecyl iodide. However, fullerenes in direct contact with perovskites fail to confine I_x⁻ ions within the perovskite layer but cause detrimental iodine vacancies. Perfluorodecyl iodide, with its directional I_x⁻ affinity through halogen bonding, can both capture and confine I_x⁻. Therefore, inverted perovskite solar cells with over 10 times improved ultraviolet irradiation and thermal-light stabilities (under 85 °C and 1 sun illumination), and 1,000 times improved reverse-bias stability (under ISOS-V ageing tests) have been developed.