High-Temperature Ferroelasticity and Photoluminescence in a 2D Monolayer Perovskite Compound: (C₅NH₈Br)₂PbBr₄

Anew 2D lead-based organo-inorganic hybrid perovskite (C5NH13Br)(2)PbBr4 (1) (C5NH13Br = 5-bromoamylamine cation) hasbeen reported. Hybrid organic-inorganic perovskites (HOIPs) haveattractedmuch attention due to their excellent properties and easy synthesis.As far as we know, most documented ferroelastics mainly focus on the3D (three-dimensional) perovskites, the 2D monolayer perovskite ferroelasticsare rarely reported before. In this work, we synthesized a 2D lead-basedperovskite (C5NH13Br)(2)PbBr4 (1) (C5NH13Br = 5-bromoamylaminecation) by introducing flexible chain organic cations. The evolutionof ferroelastic domains observed by a polarized light microscope confirmsthat compound 1 undergoes a ferroelastic phase transitionat 392/384 K. In addition, its direct band gap is 2.877 eV. Interestingly,the material emits an attractive blue light (quantum yield 5.06%)under UV light. Three structural descriptors are introduced to quantitativelyanalyze the relationship between structural distortion and the shapeof emission peak. This work provides a way to design multifunctionalperovskite-type materials.