Exploring physical characteristics of double perovskites Na2CuAsX6 (X = F, Cl, Br, and I) for solar energy harvesting and wasted heat recovery applications

•Na2CuAsX6 (X = F, Cl, Br, and I) double perovskites (DPs) are stable in the cubic phase.•They have indirect band gaps of 1.28, 1.14, 0.85, and 0.52 eV, respectively.•These materials are appropriate for solar cell applications exhibiting a significant absorption in the visible region.•Na2CuAsX6 (X = F, Cl, Br, and I) exhibit p-type semiconductor characteristics.•These perovskites possess exceptional physical features to serve as sustainable green energy alternatives. The current research is intended to investigate the physical properties of the Na2CuAsX6 (X = F, Cl, Br, and I) double perovskites using the density functional theory (DFT) framework implemented in the WIEN2k code. Herein, the structural configuration, electronic, optical, thermoelectric, and thermodynamic features are thoroughly discussed. The structural investigation utilized the Murnaghan equation of state (EOS) and the generalized gradient approximation (GGA). The thermal and phase stability has been verified by the formation enthalpy and tolerance factor. The perovskites Na2CuAsF6, Na2CuAsCl6, Na2CuAsBr6, and Na2CuAsI6 exhibit semiconductor properties characterized by indirect band gaps of 1.28, 1.14, 0.85, and 0.52 eV, respectively. An extensive examination of the optical characteristics suggests the possible appropriateness of these materials for photovoltaic applications. Double perovskites exhibit a significant absorption in the visible spectrum. Thermodynamic properties have demonstrated the thermal stability of analyzed perovskites even at high temperatures. Additionally, the thermoelectric properties have been determined at specific temperatures and chemical potentials, indicating the p-type nature of studied perovskites. The figure of merit (ZT) values at 300 K are determined to be 0.79, 0.76, 0.77, and 0.80, suggesting Na2CuAsX6 may be sustainable thermoelectric materials with excellent performance. Consequently, the examined materials can serve as sustainable candidates for solar energy and wasted heat recovery applications.