Electronic, optical, and thermoelectric properties of multifunctional zintl compound BaAg2Te2 for energy conversion

Abstract

Using the FP-APW + lo method, the structural, electronic, and optical properties of the Zintl BaAg2Te2 compound were investigated. The calculated unit cell parameters are well matching with the experimental results. In addition, the study of electronic properties reveals that BaAg2Te2 is a semiconductor with a direct bandgap of about 1.445 eV. The optical constants such as loss energy, refractive index, reflectivity, and absorption coefficient have been calculated and analyzed. These constants show a clear anisotropy caused by the different electron polarizability in the x-, y-, and z-directions. Moreover, the direct bandgap and good optical absorption make BaAg2Te2 promising candidates for photovoltaic applications. The thermoelectric properties of the BaAg2Te2 compound in the x, y, and z directions have been studied to obtain the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, power factor, and figure of merit (ZT) against temperature and carrier concentrations. Our investigations showed an improvement in the ZT values of BaAg2Te2 with increase in temperature. Moreover, the BaAg2Te2 demonstrated optimal ZT values along the y-axis.