Electronic, optical, and thermoelectric investigations of Zintl phase AAg2Se2 (A=Sr, Ba) compounds: A first-principle approach

We have studied the structural, optoelectronic, and thermoelectric properties of AAg(2)Se(2) (A = Sr, Ba) compounds using first-principles calculations. We found that these compounds are dynamically stable in trigonal structure with no negative frequencies in Phonon spectra. The electronic properties reveal that both the compounds possess a direct bandgap of 1.76 eV and 1.35 eV for AAg(2)Se(2) (A = Sr, Ba) respectively. The optical response has been studied in terms of dielectric constants, reflectivity absorption, and energy loss function. The presence of high absorption peaks in the visible region confirms the direct transition of electrons from the valence band conduction band. The thermoelectric properties of the materials have been studied using BoltzTrap code to obtain the Seebeck coefficient, electrical and thermal conductivities, and figure of merit (ZT) as a function of temperature and carrier concentrations. The calculated excellent optoelectronic properties and the stunning ZT values predict this family could be promising for applications in optoelectronics and thermal devices.