Impact of humidity exposure during device fabrication on CZTSSe solar cell performance

The effect of exposing Cu₂ZnSn(S,Se)₄ films to ambient humidity during various stages of device fabrication was studied. Cu₂ZnSn(S,Se)₄ films were made via solution-based processing of binary and ternary metal-chalcogenide nanoparticle precursors. Following the formation of precursor films, storage conditions between successive steps for device completion were varied. The performance of finished devices showed little sensitivity to overnight storage conditions with the exception of exposure to high relative humidity prior to the p-n junction formation, which resulted in catastrophic efficiency loss. The time evolution of the moisture degradation was exponential, with a characteristic time of approximately 2 hours.