Structural transition and emission enhancement in vacancy ordered halide double perovskite Cs$_2$TeCl$_6$ under pressure

TL;DR

This study investigates how applying pressure affects the structure and optical properties of Cs$_2$TeCl$_6$, revealing structural transitions and enhanced photoluminescence that could inform optoelectronic applications.

Contribution

It provides a systematic analysis of pressure-induced structural and optical changes in Cs$_2$TeCl$_6$, including phase transitions and optical band gap modulation.

Findings

Structural transition from cubic to monoclinic below 1 GPa.

Enhanced photoluminescence intensity under pressure.

Reversion to cubic structure at around 3.4 GPa.

Abstract

The effect of pressure on the structural evolution, enhancement of photoluminescence intensity and optical band gap of a vacancy ordered double halide perovskite Cs$_2$TeCl$_6$ is investigated systematically. We use synchrotron x-ray diffraction, Raman spectroscopy, optical band gap and photoluminescence measurements to explore the structural and the optical properties of Cs$_2$TeCl$_6$ under pressure up to 30.0 GPa. We find that Cs$_2$TeCl$_6$ undergoes a structural transition from cubic Fm$\bar{3}$m to monoclinic P2$_1$/n at very low pressure below 1.0 GPa. A significant increase in photoluminescence intensity and a rapid decrease in optical band gap are observed, which are related to the octahedral distortion and structural transition. Interestingly, with increasing pressure, the sample regains its ambient Fm$\bar{3}$m structure at around 3.4 GPa maintaining the cubic phase up to 30.0 GPa. The sample undergoes an iso-structural transition at around 14.1 GPa pressure with a slight decrease in compressibility.