Time-resolved photoluminescence analysis shows that as-grown Cu 2 ZnSnSe 4 (CZTSe) thin films degrade when they are exposed to air. The analysis of the films prior to degradation reveals relatively long carrier lifetimes. The increase of the recombination rates significantly affects the performance of the related solar cells. Among all the chemical treatments tested to recover the lifetime of the carrier after air exposure, the KCN etching seems to be the most efficient.