Lattice dynamics and self-trapped excitons in the Cs2SnBr6 double perovskites

Abstract

Abstract Our study delved into the detailed investigation of Cs2SnBr6 double perovskites, focusing on their electrical properties, lattice dynamics, and stability. The direct bandgap for Cs2SnBr6 was estimated to be at 2.93 eV. One external translational mode of the Cs+ lattice with T 2g symmetry and three internal modes of the octahedral with A 1g, E g, and T 2g symmetries are defined by calculated lattice dynamics, experimental micro-Raman scattering. We show a correlation with first-principles calculations, validating using a band-structured electronic approach to understanding the behavior of charge carriers, and electron–phonon interactions in Cs2SnBr6. We propose that electron-vibration interactions result in self-trapped excitons (STEs) displaying significant Stokes shifts (0.508 eV) and broad-spectrum emission. Understanding the behavior of STEs is fundamental for their optoelectronic applications.