Synthesis and Soft Crystal Structure-Induced Broad Emission in (NH3C6H12NH3)InBr5·2H2O

Abstract

We report a simple synthesis of a new lead-free zero-dimensional (0D) hybrid halide compound, (5P1)InBr5∙2H2O [(5P1) = NH3C6H12NH3], which hosts isolated and distorted octahedra of [InBr5(H2O)]2-, surrounded by bulky asymmetric organic cation [(5P1)2+] and H2O molecule. Upon photoexcitation, the hybrid crystals exhibit pink emission with two emission peaks, high energy band to band emission and slightly lower energy self-trapped excitonic (STE) emission, respectively. Strong anharmonicity and soft lattice indicated by Raman spectroscopy, low temperature heat capacity and sound velocity measurements, are responsible for the broad STE emission.