Mechanism of Pressure‐Modulated Self‐Trapped Exciton Emission in Cs₂TeCl₆ Double Perovskite

Abstract

Pressure‐modulated self‐trapped exciton (STE) emission mechanism in all‐inorganic lead‐free metal halide double perovskites characterized by large Stokes‐shifted broadband emission, has attracted much attention across various fields such as optics, optoelectronics, and biomedical sciences. Here, by employing the all‐inorganic lead‐free metal halide double perovskite Cs2TeCl6 as a paradigm, the authors elucidate that the performance of STE emission can be modulated by pressure, attributable to the pressure‐induced evolution of the electronic state (ES). Two ES transitions happen at pressures of 1.6 and 5.8 GPa, sequentially. The electronic behaviors of Cs2TeCl6 can be jointly modulated by both pressure and ES transitions. When the pressure reaches 1.6 GPa, the Huang–Rhys factor S, indicative of the strength of electron‐phonon coupling, attains an optimum value of ≈12.0, correlating with the pressure‐induced photoluminescence (PL) intensity of Cs2TeCl6 is 4.8‐fold that of its PL intensity under ambient pressure. Through analyzing the pressure‐dependent STE dynamic behavioral changes, the authors have revealed the microphysical mechanism underlying the pressure‐modulated enhancement and quenching of STE emission in Cs2TeCl6.