Recent Progress on the Stability of Perovskite Solar Cells in a Humid Environment

In recent years, photovoltaic devices based on inorganic–organic hybrid perovskite materials have become one of the most promising research subjects in the field of energy conversion. CH3NH3PbI3 stands out among a wide variety of perovskite structural materials with the advantages of a suitable band structure, small exciton binding energy, long carrier diffusion distance, and so on. Unfortunately, the CH3NH3PbI3 perovskite undergoes severe degradation under humid conditions, which limits the service life of the device. To address this issue, researchers have recently discovered that the humidity stability of perovskite solar cells (PSCs) can be improved through doping or interfacial engineering. Here, we have reviewed the state of the research progress in improving the humidity stability of PSCs, including (a) improving the structural stability of perovskite material itself by doping or element substitutions; (b) interface engineering between the hole transport layer and the perovskite active layer; (c) interface modification between the electron transport layer and the perovskite layer; and (d) encapsulation. The strategy of improving the humidity stability of CH3NH3PbI3 by optimizing the device structure and developing new materials is summarized. We also make constructive suggestions for improving the stability of PSCs in humid environments.