Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te: PBE + U approach.

The electronic, vibrational and thermoelectric transport characteristics of AgInTe and AgGaTe with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe and AgGaTe are much larger than previous standard GGA functional results and agree well with the existing experimental data. The effective mass of the hole and the shape of density of states near the edge of the valence band indicate AgInTe and AgGaTe are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe and AgGaTe. The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe and AgGaTe in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe and AgGaTe at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 10 cm and 1.97 × 10 cm carrier concentrations, respectively. This indicates p-type AgGaTe is a potential thermoelectric material at high temperature.