Inorganic CsSnI3 Perovskite Solar Cells with an Efficiency above 13.6%

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.