First-principles study of lead-free double perovskites K2Pt(Cl/Br)6 for optoelectronic and renewable energy applications

The density functional theory-based calculations investigate the structural, electronic, elastic, optical, and thermoelectric properties of K2Pt (Cl/Br)6 for renewable energy applications. The tolerance factor, formation energy, and positive frequencies of phonon dispersions ensure structural and thermodynamic stabilities. The structural parameters and elastic constants analysis show the studied compounds are anisotropic and ductile. The computed direct band gaps 2.6 ​eV and 2.2 ​eV for K2PtCl6 and K2PtBr6 make sure the absorption of light in ultraviolet and visible regions. Therefore, these materials are extensively used in solar cells and other optoelectronic applications. Thermoelectric properties are explored in terms of electrical conductivity, thermal conductivity, and Seebeck coefficient to enhance the figure of merit. The room temperature ZT values 0.68 and 0.72 emphasize their importance for thermoelectric applications.