Highly Red Emissive Lead‐Free Indium‐Based Perovskite Single Crystal for Sensitive Water Detection

Low dimensional luminescent lead halide perovskites recently have attracted tremendous attention for their fascinating optoelectronic properties, while the toxicity of lead is still considered as a drawback. Herein we report a novel lead‐free zero‐dimensional (0D) indium‐based perovskite Cs2InBr5·H2O single crystal that is red luminescent with a high photoluminescence quantum yield (PLQY) of 33%. Experimental and computational studies reveal that the strong PL emission might originate from self‐trapping excitons (STEs) as a result of an excited‐state structural deformation. More importantly, the in situ transformation between hydrated Cs2InBr5·H2O and the dehydrated form is accompanied with a switchable dual emission, which favorably enables it as a PL water‐sensor in humidity detection or traces of water detection in organic solvents.

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