Theoretical investigations of optoelectronic and thermoelectric properties of halide based double perovskite halides: K₂TeX₆

The double perovskite halides owing to their environmental stability, non-toxicity and remarkable efficiency are emerging as a potential candidate for photovoltaic, solar cell and thermoelectric applications. The tolerance factor and formation energy are computed for structural, and thermodynamic existence in cubic phase. The electron density regulates the charge transfer and bonding. Here we report a comprehensive study of optical, electronic, and thermoelectric properties of K₂TeX₆ (X = Cl, Br, and I). The electronic band structure analysis reveals indirect semiconducting band gap lying within 3.2–1.68 eV. The substitution of Cl with Br and I reduces band gap with a shift of maximum absorption from ultraviolet to visible region. The optical characteristics are analyzed for the incident energy range 0–5eV by computing dielectric constant, absorption, reflection, and optical loss. Moreover, transport properties are also explained in terms of the exotic variations in the calculated Seebeck coefficient, electronic and thermal conductivities. Figure of merit is elaborated to reveal their potential for thermoelectric applications.