Recent strategies to improve moisture stability in metal halide perovskites materials and devices

At present, the stability of the new generation of solar cells based on hybrid perovskites is the bottleneck for their practical applications. Photochemical effects, high temperature, ultraviolet light, humidity and other known or still unknown factors might cause reduction of effectiveness or even irreversible loss of materials properties due to decomposition of functional layers within perovskite solar cells (PSCs). These factors alone have a serious impact on each component of the device, while their combinations lead to much more complicated effects and consequences. This review focuses on the stability of PSCs and the degradation of the device in a humid environment. We assess the instability factors and deep-seated principles of evolution of the device structure in a humidity environment with the emphasis on the influence on their interrelations. The related solutions are reviewed from the perspective of the encapsulation, perovskite active layer, carrier transport layer and electrodes. Combined with the latest research, we believe that the waterproof strategy of PSCs requires either tight encapsulation or thorough modifications in the device itself. Therefore, it is important to develop feasible strategies to improve the overall device stability over humid according to the target characteristics of various devices.