DFT Investigation of Optoelectronic, Transport, and Elastic Properties of Double Perovskites K₂AgTlX₆ (X = Cl, Br) for Green Energy Technologies

Herein, a detailed exploration of the structural, electronic, optical, transport, and elastic characteristics of K₂AgTlX₆ (X = Cl, Br) is provided by implementing density functional theory (DFT). The calculated tolerance factors and formation energies verify the structural and thermal stability. The structural attributes have been predicted by utilizing PBE-GGA approximation and the Murnaghan equation of state. The direct band gaps for K₂AgTlCl₆ and K₂AgTlBr₆ calculated by TB-mBJ potential are 1.68 eV and 1.13 eV, respectively. Optical characteristics have been thoroughly examined for visible-ultraviolet regions between 0 and 8 eV energies. The absorption peaks of 10⁵/cm in the visible region and lowest reflectivity suggest their suitability for photovoltaic applications. Transport features are also described against temperature, revealing that both materials are p-type semiconductors. K₂AgTlCl₆ and K₂AgTlBr₆ demonstrate moderate ZT values of 0.60 and 0.55, respectively. The elastic features have been explored to determine the mechanical stability, nature of the material, and anisotropy. These features of the investigated compounds demonstrate their reliability as alternatives for green energy applications.