Pressure-Induced Enhancement of Broad-Band White Light\nEmission in Butylammonium Lead Bromide

Abstract

Two-dimensional (2D)\nperovskites with inorganic layers sandwiched\nbetween hydrophobic organic cations possess excellent lighting properties\nand moisture stability. However, broad-band white light (BWL) is limited\nto a selected class of perovskites. Our understanding of the intrinsic\nrelationship of BWL and structure and the systemic study of their\nmechanism of photoluminescence (PL) emission caused by self-trapped\nexcitons in 2D perovskites are still lacking. Here, we show a pressure-induced\nPL enhancement (PIPE) and a remarkable BWL emission covering the whole\nvisible spectrum in BA₂PbBr₄. Synchrotron X-ray\ndiffraction shows cooperative octahedral tilting below 1 GPa and a\nJahn–Teller-like octahedral distortion above 5.3(1) GPa driving\nthe PIPE and BWL emission, respectively. The BWL and structural distortion\nare retained down to 1.8(1) GPa. Our study provides important insights\ninto the intrinsic correlation between optical properties and structural\nchanges and establishes pressure as a new means for tailoring the\nuse of perovskites in lighting devices.