Achieving efficient and stable inorganic CsSnI3 mesoporous perovskite solar cells via galvanic displacement reaction

Reducing the toxicity of hybrid halide perovskites is critical in the path toward perovskite photovoltaic commercialization. In this regard, Sn-based halide perovskite compounds, especially inorganic CsSnI3, are emerging as promising alternatives. However, the instability of Sn-based perovskites originated from Sn2+ oxidation remains a serious problem that needs to be addressed. Herein, we propose a facile yet effective galvanic displacement reaction (GDR) method to solve this issue. Using zinc metal powder as an example, the Sn4+ species can be spontaneously and completely reduced via the GDR in precursor solutions in a short time. Meanwhile, this procedure introduces a certain number of external divalent Zn2+ metal ions into the inorganic CsSnI3 perovskite lattice. The introduced Zn2+ is found to weaken the adsorption of water and oxygen molecules on the CsSnI3 crystalline surface, therefore enhancing the ambient stability of the resulting perovskite films. A power conversion efficiency of 8.27% was achieved for inorganic CsSnI3 mesoporous solar cells using a fully printable TiO2/Al2O3/NiO/carbon framework. To the best of our knowledge, this is the highest efficiency for fully inorganic CsSnI3-based mesoporous devices reported so far. Moreover, the devices without encapsulation maintained 86.3% of the initial efficiency after being stored in ambient air for 216 hours.