Strong electron–phonon coupling in vacancy-ordered Cs2SnBr6 double perovskite

Abstract

Vacancy-ordered double perovskites (VODPs), such as Cs₂SnBr₆, are emerging as eco-friendly and stable alternatives to lead halide perovskites (LHPs). Recently, Cs₂SnBr₆ functionalities have been explored for application in light-emitting diodes. In this paper, we systematically studied the temperature-dependent optical properties of the Cs₂SnBr₆ VODP. Our analysis reveals a strong electron–phonon (EP) coupling at room temperature, as evidenced by multiphonon scattering, leading to intense overtones up to the fourth-order. Such strength of the EP coupling was confirmed by a Huang–Rhys factor S = 24.4. Additionally, we observe that the EP interaction induces the formation of self-trapped excitons (STEs), which are the main source of its photoluminescence. Our results offer insights into influences of EP coupling on multiphonon scattering and STE emergence, guiding the design of Cs₂SnBr₆-based materials for light-harvesting applications.