Density functional modelling of lead-free Sn-based AmSnX3 (Am=Rb, Cs; X=Cl, Br, I) perovskites as sustainable materials for optoelectronics and solar cell applications.

This research uses density functional theory to examine the structural, electronic, optical, mechanical, thermodynamic, thermoelectric, magnetic, and photovoltaic properties of Sn-based AmSnX3 (Am = Rb, Cs; X = Cl, Br, I) perovskites. The tolerance factor (0.71-1.04) and the negative cohesive energy confirm the materials' structural and thermodynamic stability. The electronic properties show semiconducting behavior, with energy band gaps of 0.42 eV for RbSnBr3 and 1.02 eV for CsSnCl3. The maximum absorption values (7.16 × 104 cm-1 to 8.11 × 104 cm-1) in the visible region indicate efficient light harvesting for solar cell applications. Mechanical properties suggest mechanical stability and ductility. The Debye temperature (146.08-190.78 K) offers insights into heat capacity and thermal behavior at different temperatures. The Seebeck coefficient at room temperature classifies RbSnBr3, RbSnI3, and CsSnCl3 as p-type materials, while RbSnCl3, CsSnBr3, and CsSnI3 are n-type. The calculated power conversion efficiencies, from 12.47 % for CsSnI3 to 29.54 % for CsSnCl3, emphasize the novelty of this work, which combines structural, mechanical, electronic, and optical analyses for the first time to thoroughly evaluate the potential of RbSnX3 and CsSnX3 perovskites in optoelectronic and energy applications.