Lead-free Cs₂InAsX₆ (X = Cl, Br) halide double perovskites: A DFT perspective on their potential for sustainable energy applications

In response to the escalating global demand for efficient energy harvesting materials, this study investigates the halide double perovskites (HDPs),Cs2InAsX6 and Cs2InAsX6 , as promising candidates. The exploration focuses on their structural stability, optoelectronic characteristics, and superior thermoelectric properties. Through comprehensive first principles calculations, stable cubic geometries consistent with the Fm3m space group are revealed for considered HDPs. Thermodynamically, these compounds exhibit significant thermodynamic stability with negative formation enthalpy values. The HDPs exhibit bandgaps of 1.02 eV and 0.41 eV for corresponding Cs2InAsX6 and Cs2InAsX6 , showcasing their potential for optoelectronic applications. Optically, Cs2InAsX6 display high absorptive nature with minimal reflectivity, indicating their suitability for IR sensors and visible light absorbers. The thermoelectric investigation unveils impressive ZT values, similar to 0.9 at 300 K, positioning Cs2InAsX6 as efficient thermoelectric materials with potential applications in energy conversion and sustainable technologies. The study contributes valuable insights into the comprehensive theoretical characterization of Cs2InAsX6 HDPs, advancing the exploration of lead-free and environmentally friendly materials for diverse energy applications.