Ionic Liquid Surface Treatment-Induced Crystal Growth of CsPbIBr2 Perovskite for High-Performance Solar Cells

Inorganic CsPbIBr2 perovskite has been attracting ever-increasing attention in the photovoltaic field owing to its high stability and good optoelectronic properties. The high-quality CsPbIBr2 perovskite is an essential prerequisite for fabricating efficient inorganic CsPbIBr2 perovskite solar cells. Herein, we report the preparation of high-quality CsPbIBr2 perovskites through an ionic liquid surface treatment-induced crystal growth strategy. The CsPbIBr2 precursor is deposited on the substrate by a spin-coating method and then treated through spin-coating the isopropanol solution of 1-ethyl-3-methylimidazolium iodide ionic liquid atop it. This surface treatment results in the formation of perovskite crystals with a well-developed structure within the obtained precursor film. These well-developed perovskite crystals can induce perovskite crystallization during the subsequent annealing process and lead to the formation of a dense and high-crystallinity CsPbIBr2 perovskite film with reduced defect density. The fabricated carbon-based CsPbIBr2 cell achieves a conversion efficiency of up to 10.13% and displays a good long-term stability while retaining ∼88% of the original efficiency after being stored for 816 h in ambient air.