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

Abstract

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.