Electronic Structure and Thermoelectric Properties of Semiconductors K2GeSiX6 (X=F, Cl, Br and I) Compounds: Ab-Initio Investigation

Abstract

In this work, we have studied the structural, optoelectronic, elastic and thermoelectric properties for halides doubles perovskites compounds K2GeSiX6 ([Formula: see text], Cl, Br and I). Based on the linearized augmented plane wave method with full potential (FP-LAPW) method, the previous properties are treated within GGA-PBE and the modified Beck–Johnson correction (mBJ-GGA) approximations. The results show that these compounds are stable in the nonmagnetic phase (NM). Due to the electronic properties, our results indicate that all these compounds have a semiconductor behavior with a direct bandgap at [Formula: see text]-[Formula: see text] direction with values of 2.30[Formula: see text]eV, 0.632[Formula: see text]eV, 0.259[Formula: see text]eV and 0.124[Formula: see text]eV for K2GeSiF6, K2GeSiCl6, K2GeSiBr6 and K2GeSiI6, respectively. In addition, the high dielectric constant, high absorption coefficient and high optical conductivity suggest that the materials have the potential for a wide absorption range that starts from the visible to the ultraviolet of optoelectronic applications, including solar or photovoltaic cells. Finally, the thermoelectric properties, through the calculation of the various related parameters (Seebeck coefficient, electrical conductivity, thermal conductivity, power factor and figure of merit), show that the materials K2GeSiBr6 and K2GeSiI6 can be promising for predispositions thermoelectric and by comparing the thermoelectric parameters of the two materials mentioned above, at room temperature, the material K2GeSiI6 has better performance than the material K2GeSiBr6, due to a significantly higher Seebeck coefficient (234.32[Formula: see text][Formula: see text]V/°K), a fairly substantial power factor ([Formula: see text][Formula: see text]Wk[Formula: see text]m[Formula: see text]s[Formula: see text]) and a fairly low thermal conductivity ([Formula: see text][Formula: see text]WK[Formula: see text]m[Formula: see text]s[Formula: see text]).