Band gap modulation and improved optoelectronic and thermoelectric properties in Sn-doped RbCaCl3 perovskites

Perovskite compounds are widely studied for their structural versatility and tunable properties, making them ideal for optoelectronic and energy applications. This study employs first-principles calculations to investigate the optoelectronic and thermoelectric properties of RbCa${}_{1-x}$Sn${}_x$Cl${}_3$ ($x$ = 0, 0.25, 0.50, 0.75, 1) halide perovskites. Elastic constants confirm the mechanical stability of all compounds except RbCaCl${}_3$, while Pugh’s and Poisson’s ratios indicate their ductile nature. RbCaCl${}_3$ exhibits an indirect band gap of 4.95 eV, whereas Sn doping induces a direct band gap, ranging from 2.36 eV to 0.96 eV. Optical analysis reveals strong absorption in the visible to ultraviolet range, along with enhanced dielectric constants and optical conductivity in Sn-rich compositions. However, Sn doping reduces lattice thermal conductivity and electrical conductivity. These findings highlight Sn-doped RbCaCl${}_3$ perovskites as promising candidates for solar cells, thermoelectric devices, and energy harvesting applications due to their tunable band gaps, strong optical absorption, and enhanced thermoelectric performance.