A Review of the Intrinsic Chemical Stability Challenge in Operational Perovskite Photovoltaics

Although the power conversion efficiency of perovskite photovoltaics (PVs) has achieved significant progress, the operational stability is still a critical issue for their commercialization. Compared to inorganic semiconductor materials, organic species in perovskites are intrinsically unstable under long-term illumination, heat, and bias stresses. These organic species exhibit higher chemical reactivity, which can complicate the degradation mechanisms or model of perovskite PVs. In this review, we analyzed the types of chemical reactions for different organic species. The chemical instability mainly stems from the deprotonation of A-site ammonium cations, X-site halide ion migration, and oxidation of halide ions, which can even mutually influence one another. We systematically discuss the effect of this chemical instability on perovskite structure degradation under device operation. These special chemical evolutions will accelerate perovskite PVs' degradation. Then, strategies to mitigate these reactions for enhanced operational stability are introduced. Despite substantial progress in the operational stability of perovskite PVs, achieving an operational lifetime comparable to crystalline silicon remains challenging. Therefore, a deep understanding of intrinsic perovskite structure degradation should become a research focus, contributing to improvement in the operational lifetime of perovskite PVs.