Fully Inorganic CsSnI 3 Mesoporous Perovskite Solar Cells with High Efficiency and Stability via Coadditive Engineering

The small optical bandgap of a CsSnI3-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 SnF2−APZ complex with the aim to restrain Sn2+ oxidation and thus improve the CsSnI3-based device performance is proposed. It is found that the amino group of APZ significantly suppresses oxidation of Sn2+ through a Lewis acid–base addition reaction. Consequently, the CsSnI3-based mesoporous perovskite solar cells that use a printable c-TiO2/m-TiO2/Al2O3/NiO/carbon framework with high reproducibility achieve a power conversion efficiency of 5.12%. This is a champion efficiency for fully inorganic CsSnI3-based mesoporous devices reported up to now. Furthermore, after 60 days of storage in a N2-filled glovebox, the device still maintains an initial efficiency of 92%.