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In situ Investigation of Water Interaction with Lead-Free All Inorganic Perovskite (Cs2SnIxCl6–x)

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journal contribution
posted on 22.03.2019, 00:00 by Weiguang Zhu, Tiankai Yao, Junhua Shen, Wenqian Xu, Bowen Gong, Yachun Wang, Jie Lian
Hybrid halide perovskites display a great tunability of optoelectronic properties and environmental stability by controlling the halogen anions (e.g., I, Cl, and Br). However, their water interaction and degradation mechanisms are not fully elucidated. In this work, the interaction of Cs2SnCl6 and Cl-enriched solid solution Cs2SnI0.9Cl5.1 with water was systematically studied by in situ synchrotron X-ray diffraction and micro-Raman spectra and compared with the isostructural Cs2SnI6. Unlike Cs2SnI6, which experiences a direct dissolution in water, Cs2SnCl6 displays an enhanced stability and the dissolution of the Cs2SnCl6 accompanies with the formation of an amorphous alteration phase.  Under controlled dehydration conditions, two-dimensional Cs2SnCl6 flakes can be precipitated out from water solution. Furthermore, the mixed halide perovskite (Cs2SnI0.9Cl5.1) experiences fast iodide dissolution in water solution and transforms to a more chloride-enriched perovskite which shows a behavior similar to Cs2SnCl6. The mechanistic understanding of the dissolution–precipitation process of Cs2SnIxCl6–x perovskites is useful for developing new perovskites with varied halogen and controlled environmental stability.