Effect of relative humidity during the preparation of perovskite solar cells: Performance and stability

Humidity is one of the main environmental factors that limits performance and stability of perovskite solar cells (PSC); it plays a critical role during the preparation of the perovskite film, influencing the crystal growth. In this work, it is investigated the effect of the relative humidity (RH) and type of atmosphere (nitrogen vs air) used during the deposition of both perovskite layer and hole extraction layer (HEL). While humidity and oxygen seem not to affect the HEL deposition step, the perovskite layer is notoriously influenced by the RH and by the presence of oxygen during its deposition. Until 10% of RH, the performance of devices prepared with a triple-cation perovskite layer deposited under a nitrogen environment was mostly unaffected, whilst for devices deposited in air that limit is lower. On the other hand, for high RH values (above 30%), devices prepared with a triple-cation perovskite layer deposited under N2 presented slightly better stability over time than the ones prepared under air. The best-performing device was prepared with a triple-cation perovskite layer deposited under dry air, presenting a power conversion efficiency of 16.7%. These results are of critical value when designing a plant for fabricating PSC showing that the perovskite layer may be deposited under a simple dry air atmosphere (RH < 1%).