Computational screening of appealing perspectives of indium-based halide double perovskites In₂AgSbX₆ (X = Cl, Br, and I) for energy harvesting technologies

Halide double perovskites have attracted considerable attention for their potential use in solar cells and thermoelectric devices, as they are ecologically benign and possess band gap tunability. Herein, the stability, optoelectronic, and thermal transport characteristics of In₂AgSbX₆ (X = Cl, Br, and I) were examined using density functional theory (DFT). <i>Ab initio</i> molecular dynamics (AIMD) analysis was conducted, which verified the dynamic stability of In₂AgSbX₆ up to 700 K. The estimated elastic parameters further confirmed their mechanical stability. Through mechanical analysis, the asymmetric characteristics of In₂AgSbX₆ were revealed. The above-mentioned materials were ductile, validating their utilization in flexible or foldable technologies. Analyses of the electrical properties of In₂AgSbCl₆, In₂AgSbBr₆, and In₂AgSbI₆ showed indirect band gaps (<i>E</i> _g) of 1.95 eV, 1.35 eV, and 0.78 eV, respectively. These electronic <i>E</i> _g values were ideal for solar cell applications. The lower effective masses and binding energies of excitons of In₂AgSbCl₆, In₂AgSbBr₆, and In₂AgSbI₆ than those of the perspective solar cell candidates CsPbI₃ and Cs₂AgBiBr₆ provided evidence for their effectiveness as absorber layer materials. The optical analysis of the dielectric constant, absorption, reflection, and loss demonstrated higher absorption, lower reflection, and minimal energy loss within the visible and ultraviolet spectra. The thermal transport features were analyzed for various temperatures up to 600 K and chemical potentials. In₂AgSbCl₆, In₂AgSbBr₆, and In₂AgSbI₆ demonstrated p-type nature, higher Seebeck coefficient, and <i>ZT</i> values of 0.75, 0.77, and 0.76, respectively. Thus, In₂AgSbCl₆, In₂AgSbBr₆, and In₂AgSbI₆ possessed feasible characteristics for applications in solar cells and thermal energy transformation, demonstrating that they can be utilized in future energy harvesting technologies.