Structure\nEvolution and Optical Tuning of One-Dimensional\nPost-perovskite (TDMP)PbBr<sub>4</sub> under High Pressure

Optimizing the structure and tuning the optical properties\nin low-dimensional\norganic–inorganic halide perovskites are crucial to practical\napplications for stable solid-state lighting. Herein, we performed\nhigh-pressure investigations on one-dimensional (1D) postperovskite\n(TDMP)PbBr<sub>4</sub> (TDMP = <i>trans</i>-2,5-dimethylpiperaziniium),\nand structure and optical properties under pressure are studied. (TDMP)PbBr<sub>4</sub> exhibits color tunable emission from cool white light to\nyellow orange as the pressure increases from atmospheric pressure\nto 20.0 GPa. It was found that high pressure would facilitate trapping\nthe free exciton (free exciton) to form a self-trapped exciton (STE)\nstate due to increased electron–phonon interaction, thus enhancing\nSTE emission in the pressure range of 4.0–7.0 GPa. At above\n7.0 GPa, the STE emission is quenched, which is due to the phonon-assisted\nnonradiative relaxation. Meanwhile, (TDMP)PbBr<sub>4</sub> displays\nreversible piezochromism from colorless to yellow under pressure as\na result of the compound undergoing a reversible structural transformation.\nThis work provides an insightful perspective on revealing the relationship\nbetween structure and optical properties of 1D postperovskites under\nhigh pressure.