Electronic structure and stability of lead-free CsSnBr3 perovskites: Insights from density functional theory

The use of lead-free tin-based halide perovskite materials is an alternative to the widespread use of lead-based materials in photovoltaics because of their favourable optoelectronic properties, good mechanical properties and reduced environmental impact. Using density functional theory and molecular dynamic simulations allowed for a systematic and thorough investigation of the structural, electronic and mechanical characteristics of the CsSnBr 3 perovskite. Mechanical properties of the CsSnBr 3 perovskite demonstrated that it meets the Born stability criteria for cubic crystals and that it has moderate bulk and shear moduli with a Poisson ratio, which suggests that it is ductile enough to be suitable for use in a device. The interaction of oxygen and water at the surface was studied and very strong interaction was found for all orientations with the adsorption energies of −1.13 to −1.55 eV, which facilitates tin oxidation and defect creation. Molecular dynamics simulations indicated that high temperatures disorder the surface layers more, whereas the bulk lattice remained almost unchanged. The findings demonstrated how temperature affects the material's mechanical characteristics. The water molecule shows stronger negative adsorption than oxygen on all surfaces, according to the adsorption energy. The Mulliken population data unequivocally show that significant electron redistribution among Cs, Sn, and Br 3 atoms is caused by environmental exposure. CsSnBr 3 's optical characteristics, including its dielectric function, loss function, reflectivity and refractive index, demonstrated that it could be the ideal material for solar cells.