Temperature effects on the thermoelectric properties of PbTe: a first-principles study*

Thermoelectric materials are of intense interest for energy harvesting applications, because they convert waste heat into electricity. PbTe is one of the most efficient thermoelectric materials. It has a direct narrow gap that increases strongly with temperature [1]. Here we study how the temperature dependence of the electronic bands influences the thermoelectric transport properties of PbTe from first principles. The calculated temperature variation of the direct gap accounts for both thermal expansion and electron-phonon coupling [2]. The temperature dependence of the electronic bands is modeled using a two band Kane model. We also build accurate models of phonon bands and electron-phonon scattering from first principles [3]. By solving the Boltzmann equation, we calculate the thermoelectric transport properties of PbTe in very good agreement with experiments. We find that the temperature variation of the direct gap has substantial effects on these properties, leading to a high figure of merit zT over a broader range of doping concentrations at high temperatures.

[1] Z. M. Gibbs et al, Appl. Phys. Lett. 103, 262109 (2013)
[2] J. D. Querales-Flores et al, 1809.02643
[3] J. Cao et al, arXiv:1809.03799