Abstract
On basis of our first principle calculations, we suggest lead free defective perovskites Cs2SeCl6 and Cs2TeCl6 as efficient high temperature thermoelectric materials. Our calculations predict high stability of these materials. The calculated flat valence bands in these compounds results high values of Seebeck coefficient. The density of states predicts the p-type conductivity in both compounds which was confirmed from positive value of Seebeck coefficient. The calculated thermal conductivity was found as low, 1.068 and 0.697 W/mK for Cs2SeCl6 and Cs2TeCl6, respectively at 800 K. This results high ZT values in comparison of lead halide pemvskites. The combination of high electrical conductivity with Seebeck coefficient give rise to reasonable values of power factor 0.81 x 10(-3) W/mK(2) for Cs2SeCl6 and 0.83 x 10(-3) W/mK(2) for Cs2TeCl6 at 800 K. Furthermore, our calculated mechanical properties predicted the studied compounds as ductile. The ductile nature along with high values of thermoelectric parameters makes Cs2SeCl6 and Cs2TeCl6 compounds more promising for thermoelectric power generation at high temperatures.