Structural, optoelectronic, photocatalytic and thermoelectric properties of M₂ZAuBr₆ double perovskites: Insights for energy conversion applications

Double perovskites of the M 2 ZAuBr 6 (where M [Formula: see text] K, Rb, Cs and Z [Formula: see text] Sc, Y) have shown strong potential for energy conversion, capable of harvesting both solar and thermal energy to generate electricity. This study employs density functional theory (DFT) to investigate their structural, mechanical, optoelectronic, thermodynamic and thermoelectric properties. Structural stability was confirmed through tolerance and octahedral factors, phonon dispersion spectra, Born mechanical stability criteria for cubic structures and Gibbs free energy calculations. Electronic structure analysis using the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential revealed wide energy band gaps (2.27, 2.94, 2.18, 2.92, 2.26 and 2.77[Formula: see text]eV) for the respective compounds. Mechanical properties, assessed through Poisson’s and Pugh’s ratios, confirmed ductility and favorable mechanical behavior. Optical parameters, including refractive index, reflectivity, extinction coefficient and optical conductivity, indicate their suitability for optoelectronic applications. Thermoelectric performance, evaluated via the semi-classical Boltzmann transport method over a temperature range of 200–1000[Formula: see text]K, showed promising results with figure-of-merit (ZT) values at 1000[Formula: see text]K of 0.92, 0.89, 0.91, 0.84, 0.84 and 0.73. These findings establish M 2 ZAuBr 6 compounds as viable candidates for future optoelectronic and thermoelectric energy harvesting technologies.