Pressure induced emergence of visible luminescence in $Cs_3Bi_2Br_9$: Effect of structural distortion in optical behaviour

TL;DR

This study demonstrates that applying high pressure to Cs3Bi2Br9 induces visible photoluminescence at room temperature, driven by structural distortions and phase transitions, with implications for tunable optical properties.

Contribution

It reveals pressure-induced luminescence in Cs3Bi2Br9 linked to structural distortions and phase changes, providing new insights into pressure-tunable optical behavior of halide perovskites.

Findings

Photoluminescence appears at high pressure in Cs3Bi2Br9.

Luminescence intensity increases with pressure due to structural distortions.

The high-pressure phase is an indirect band gap semiconductor.

Abstract

We report emergence of photoluminescence at room temperature in trigonal $Cs_3Bi_2Br_9$ at high pressures. Enhancement in intensity with pressure is found to be driven by increase in distortion of $BiBr_6$ octahedra and iso-structural transitions. Electronic band structure calculations show the sample in the high pressure phase to be an indirect band gap semiconductor. The luminescence peak profile show signatures related to the recombination of free and self trapped excitons, respectively. Blue shift of the both peaks till about 4.4 GPa are due to the exciton recombination before relaxation due to the decrease in exciton lifetime with scattering from phonons