UV Degradation of Formamidinium-Cesium Lead Halide Perovskite Solar Cells

Perovskite solar cells show great promise for cost-effective and efficient solar energy production, but their stability remains a challenge. Understanding the degradation mechanisms of perovskite solar cells is essential for their successful implementation and widespread use. Here, we study the degradation mechanism of formamidinium-cesium lead halide perovskite solar cells under ultraviolet (UV) radiation. We measure the UV-induced device performance degradation and characterize the changes in the structural and optoelectronic properties of perovskite films after UV radiation. Further analysis reveals that UV-induced halide photo-redox reactions create iodine vacancies at the buried interface of perovskite films, leading to phase segregation and crystal reconstruction to form photoinactive CsI-rich defects, increasing non-radiative recombination and reducing the efficiency of the UV-exposed cells. Understanding the degradation mechanism will aid in directing attention toward developing encapsulants and the design of more stable perovskites.