Fully Inorganic CsSnI3 Mesoporous Perovskite Solar Cells with High Efficiency and Stability via Coadditive Engineering

The small optical bandgap of a CsSnI 3 ‐based inorganic perovskite film makes it a hopeful candidate as an absorber layer in solar cell applications. Herein, a coadditive 2‐aminopyrazine (APZ) in the precursor solution to form SnF 2 −APZ complex with the aim to restrain Sn 2+ oxidation and thus improve the CsSnI 3 ‐based device performance is proposed. It is found that the amino group of APZ significantly suppresses oxidation of Sn 2+ through a Lewis acid–base addition reaction. Consequently, the CsSnI 3 ‐based mesoporous perovskite solar cells that use a printable c‐TiO 2 /m‐TiO 2 /Al 2 O 3 /NiO/carbon framework with high reproducibility achieve a power conversion efficiency of 5.12%. This is a champion efficiency for fully inorganic CsSnI 3 ‐based mesoporous devices reported up to now. Furthermore, after 60 days of storage in a N 2 ‐filled glovebox, the device still maintains an initial efficiency of 92%.