Exploring the physical properties of Rb₂TlSbM₆ (M = Cl, Br) inorganic halide perovskites for solar cell applications: A DFT study

We studied Rb₂TlSbM₆ (M = Cl, Br) halides using density functional theory calculations to determine their potential thermoelectric and optoelectronic properties. The stability of cubic phase halides was analyzed through Goldsmith's tolerance factor and enthalpy of formation calculations. By analyzing the electronic characteristics, the bandgap of Rb₂TlSbCl₆ (E_g=1.713eV) and Rb₂TlSbBr₆ (E_g=1.713eV) were calculated with GGA-PBE potentials for improved accuracy and comparison with reported values. The high absorption coefficient of Rb₂TlSbM₆ (M = Cl, Br) perovskite halides in the ultraviolet spectrum and low reflectivity in the order of 20 % make them promising for optoelectronics and photovoltaic applications. The Poisson and Pugh ratio calculations suggested the ductile nature of these materials. The Boltz-TraP code was employed to investigate the thermoelectric properties of Rb₂TlSbM₆ (M = Cl, Br) perovskites within the temperature range of (200–850 K). The findings demonstrate that Rb₂TlSbM₆ (M = Cl, Br) is a promising candidate for thermoelectric applications based on its exceptional thermoelectric properties. The SLME analysis performed on Rb₂TlSbCl₆ and Rb₂TlSbBr₆ at 293 K indicates an SLME of 31.04 % and 27.53 %, respectively. This finding suggests that these materials have great potential for utilization in solar cells.