Prediction for electronic, vibrational and thermoelectric properties of chalcopyrite AgX(X=In,Ga)Te2: PBE + U approach.

Jianhui Yang,Xinlu Cheng,Qiang Fan

doi:10.1098/rsos.170750

Abstract

The electronic, vibrational and thermoelectric transport characteristics of AgInTe2 and AgGaTe2 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 AgInTe2 and AgGaTe2 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 AgInTe2 and AgGaTe2 are considerable p-type thermoelectric materials. An analysis of lattice dynamics shows the low thermal conductivities of AgInTe2 and AgGaTe2. The thermoelectric transport properties' dependence on carrier concentration for p-type AgInTe2 and AgGaTe2 in a wide range of temperatures has been studied in detail. The results show that p-type AgInTe2 and AgGaTe2 at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 1020 cm−3 and 1.97 × 1020 cm−3 carrier concentrations, respectively. This indicates p-type AgGaTe2 is a potential thermoelectric material at high temperature.

Highlights

Thermoelectric material, which can be used in thermoelectric devices to convert waste heat into electricity without any2017 The Authors
The results show that p-type AgInTe2 and AgGaTe2 at 800 K can achieve the merit values of 0.91 and 1.38 at about 2.12 × 1020 cm−3 and 1.97 × 1020 cm−3 carrier concentrations, respectively
We find that the phonon density of states (DOS) of AgGaTe2 is a little wider than that of AgInTe2 in the low-frequency range of up to 50 cm−1 and the Ga atom contributes to moving towards a lower frequency because of the lighter mass

Summary

Introduction

The ZT value can be improved by increasing the power factor (PF = S2σ ) or decreasing thermal conductivity. The PF can be improved by using ‘band engineering’ to increase the effective mass and carrier concentration optimization [2,3,4,5,6]. Because of the dependent interrelation of the Seebeck coefficient, electrical conductivity via carrier concentration and effective mass poses a great challenge to regulate the thermal and electrical properties of thermoelectric material

Methods

Results

Conclusion