A first-principle investigation of the effect of S, Se, and Te impurities on the optical and thermoelectric properties of LaAlO₃ and KNbO₃ compounds for photovoltaic applications

The electronic, optical, and thermoelectric properties of the pure and (S, Se, and Te)-doped into the oxygen site of LaAlO₃ and KNbO₃ compounds have been investigated using the Locale Density Approximation with modified Becke and Johnson, based on the density functional theory. These doped structures represent p-type semiconductors with a direct band gap, since the concentration of chalcogens impurities increases to 16.66% for LaAlO₃ and up to 12.5% for KNbO₃, respectively. Furthermore, the optical properties for the doped systems are favorable in the visible region, especially for KNbO₃ doped with 8.33 and 12.5% of Te making KNbO₃Te more favorable for photovoltaic application compared to LaAlO₃Te_. Moreover, the thermoelectric properties indicate that the electrical conductivity increases with increasing temperature. However, it decreases after doping compounds with varying S/Se/Te concentrations compared to pure ones, indicating an increase in the collision between atomic vibration and the movements of electrons. All examined compounds exhibit an increase of the thermal conductivity as temperature increase.