Inorganic CsSnI3 Perovskite Solar Cells with an Efficiency above 13.6%

Abstract

Due to the high Lewis acidity of Sn²⁺, it is a major challenge to prepare high-quality CsSnI₃ films. To solve this critical problem, here we propose a pseudohalide anion alloying process to regulate the crystallization of inorganic CsSnI₃ perovskite and achieve large grain sizes in the micron range. The introduction of a pseudohalide anion changes the phase transition pathways through the formation of intermediates, thereby slowing the rate of CsSnI₃ crystallization. The substitutional alloying of HCOO^– in the CsSnI₃ crystal lattice further improves the oxidation resistance of Sn²⁺ due to the strong bonding between the HCOO^– anions and Sn²⁺ cations. The fabricated CsSnI₃-based planar perovskite solar cell with an inverted configuration and active area of 4.05 mm² exhibits certified power conversion efficiency of 13.68% at AM 1.5 solar irradiation (100 mW cm^–2), which is among the best reported for CsSnI₃-based inorganic perovskite cells.