Pressure-Induced Enhancement of Broad-Band White Light Emission in Butylammonium Lead Bromide.

Two-dimensional (2D) perovskites with inorganic layers sandwiched between hydrophobic organic cations possess excellent lighting properties and moisture stability. However, broad-band white light (BWL) is limited to a selected class of perovskites. Our understanding of the intrinsic relationship of BWL and structure and the systemic study of their mechanism of photoluminescence (PL) emission caused by self-trapped excitons in 2D perovskites are still lacking. Here, we show a pressure-induced PL enhancement (PIPE) and a remarkable BWL emission covering the whole visible spectrum in BA2PbBr4. Synchrotron X-ray diffraction shows cooperative octahedral tilting below 1 GPa and a Jahn-Teller-like octahedral distortion above 5.3(1) GPa driving the PIPE and BWL emission, respectively. The BWL and structural distortion are retained down to 1.8(1) GPa. Our study provides important insights into the intrinsic correlation between optical properties and structural changes and establishes pressure as a new means for tailoring the use of perovskites in lighting devices.