Tunable Emissions in Zero-Dimensional (C6H5CH2NH3)3InBr6 Enabled by Controlled Structural Amorphization

Zero-dimensional (0D) hybrid metal halides (HMHs) hold great promise as multifunctional emitters. However, precise functionalization of organic moieties and controlled modulation of self-trapped exciton (STE) emission from inorganic polyhedra remain challenging. This study introduces 0D (PMA)₃InBr₆ (PMA⁺ = C₆H₅CH₂NH₃⁺) as a multifunctional emitter, leveraging pressure-induced structural regulation to control photoluminescence properties. Increasing pressure leads to simultaneous contraction and distortion of InBr₆³⁻ octahedra, shifting the STE emission color from orange to green. At high compression, structural amorphization quenches STE emission, but upon pressure release, a bright cyan emission from the PMA⁺ cation emerges, with intensity approximately 21 times stronger than that of the initial STE emission. The enhanced emission is attributed to altered molecular configurations, disrupted intermolecular contacts, and reduced lattice vibrations, collectively suppressing excimeric coupling and minimizing nonradiative losses in the recovered amorphous phase. Furthermore, emission conversion is also achieved via laser-induced structural amorphization, expanding the potential of (PMA)₃InBr₆ for direct laser writing and sensitive laser detection applications.