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

Our study delved into the detailed investigation of Cs 2 SnBr 6 double perovskites, focusing on their electrical properties, lattice dynamics, and stability. The direct bandgap for Cs 2 SnBr 6 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 Cs 2 SnBr 6 . 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.