Lattice dynamics and self-trapped excitons in the Cs₂SnBr₆double perovskites

Our study delved into the detailed investigation of Cs₂SnBr₆double perovskites, focusing on their electrical properties, lattice dynamics, and stability. The direct bandgap for Cs₂SnBr₆was estimated to be at 2.93 eV. One external translational mode of the Cs⁺lattice withT_2gsymmetry and three internal modes of the octahedral withA_1g,E_g, andT_2gsymmetries 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.