Tailoring the optical and thermodynamic response of bulk Cs2 GeTmI6 via vacuum Thickness: First principle study

To improve the efficiency of optoelectronic and thermoelectric devices, it is necessary to understand the effect of vacuum thickness on the physical properties of low-dimensional halide perovskites. In this paper, Density Functional Theory (DFT)-based simulation was used to explore the thermodynamic properties of bulk Cs 2 GeTmI 6 double perovskites and their associated vacuum thicknesses. It focuses on how vacuum thickness affects the optical and thermodynamic parameters and their energetic performance. The Struct Gen program in WIEN2K code was utilized to generate three distinct vacuum thicknesses ([Formula: see text], [Formula: see text], [Formula: see text]) of bulk Cs 2 GeTmI 6 double perovskites. The PBE-GGA potential was used to investigate the optical properties. The Gibbs2 code was used to explore the thermodynamic properties of bulk Cs 2 GeTmI 6 double perovskite compound and its associated vacuum thickness. Further, the thermodynamic behavior was studied at high-pressure–temperature conditions. The results show that the thermal expansion coefficient, entropy and enthalpy properties are significantly affected by vacuum thickness. Our findings elucidate the basic impact of vacuum thickness on the thermodynamic properties of Cs2GeTmI6, delivering critical insights for its prospective uses in energy harvesting and optoelectronic devices.