The degradation and recovery behavior of mixed-cation perovskite solar cells in moisture and a gas mixture environment

Metal halide perovskites are not only established as champion materials for conversion of solar energy to electricity but are also one of the promising candidates for solar driven fuel generation. In this paper, we report the photovoltaic devices' operational stability investigation in dry and humid nitrogen (N₂) and carbon dioxide (CO₂) environments. By monitoring the behavior of a mixed-cation mixed-halide perovskite solar cell under constant 1-sun illumination in a gas mixture, we find that relative humidity plays a central role in expediting degradation. Interestingly, rapid degradation is a recoverable process once the light source is removed at the same humidity level. After a detailed analysis of the current-voltage characteristics, an increase in the series resistance is observed when exposed to continuous illumination. This is validated by surface resistivity measurements on both sides of the device. Photoluminescence (PL) characterization indicates a temporary decrease in the PL intensity and can be expedited by higher relative humidity levels. Our study reports behavior of perovskite solar cells in dry and wet N₂ and CO₂ environments that is necessary for solar-to-fuel applications like CO₂ reduction and water splitting in the gas phase.