A critical review on the moisture stability of halide perovskite films and solar cells

In recent years, researchers have made incredible strides in raising the power conversion efficiency (PCE) to a certified PCE record of 25.5% for metal hybrid perovskite solar cells (PSCs). However, the degradation and instability of perovskite film has hindered its commercialization process. Achieving long life-span of PSCs remains to be a big challenge. As one of the notorious factors affecting the stability of PSCs, the moisture damage to the PSC devices cannot be neglected. Herein, the comprehensive effects of moisture on the halide perovskite films are discussed. First, we elucidate the peculiar structural properties of the hydrated perovskites and the corresponding degradation process. Then the carrier dynamics after water invasion are also elaborated including the free carrier density and mobility, decay kinetics and the absorption effect. We further recap the water-induced degradation through point defect processes in different hydrous compounds. On the basis of these analyses, recent measures taken to promote the moisture stability of perovskite thin films and solar cells are then summarized and discussed. Furthermore, the challenges and outlooks towards more stable PSCs are proposed. We believe this review will provide useful insights for future development of stable PSCs for commercial application.