First principles study of optoelectronic, thermoelectric, and mechanical features of double perovskites K₂AgGaZ₆ (Z = Cl, Br) for energy harvesting perspectives

Potassium-based perovskites hold the potential to substantially modify renewable technology by developing eco-friendly devices. A thorough analysis of structural, electronic, optical, transport, and mechanical characteristics of the double perovskites K₂AgGaZ₆ (Z = Cl, Br) has been executed using the Wein2K code. The stability has been verified by analyzing optimization curves, tolerance factor, and the enthalpy of formation energy. The AIMD simulation further confirms the thermodynamic stability of both compounds. The analysis of electronic band structures indicates that the perovskite K₂AgGaCl₆ has a bandgap of 1.85 eV, which is reduced to 1.14 eV for K₂AgGaBr₆. The Kramer-Kronig relation is used to evaluate optical characteristics, which exhibit extensive absorption within the visible spectrum for both materials, enabling their utilization in photovoltaics and optoelectronics. The Boltzmann semi-classical framework is employed to calculate thermoelectric properties. These materials have great potential for renewable energy applications due to their high ZT values, supported by their high Seebeck coefficients and electrical conductivities. The demonstrated mechanical attributes confirm ductility, stiffness, anisotropy, and higher melting temperature. Hence, this study provides theoretical evidence that these perovskite compounds are well-suited for green energy harvesting.