Influence of strain on anisotropic thermoelectric transport in Bi2Te3 and Sb2Te3

On the basis of detailed first-principles calculations and semiclassical Boltzmann transport, the anisotropic thermoelectric transport properties of Bi2Te3 and Sb2Te3 under strain were investigated. It was found that due to compensation effects of the strain-dependent thermopower and electrical conductivity, the related power factor will decrease under applied in-plane strain for Bi2Te3, while being stable for Sb2Te3. A clear preference for thermoelectric transport under hole doping, as well as for the in-plane transport direction was found for both tellurides. In contrast to the electrical conductivity anisotropy, the anisotropy of the thermopower was almost robust under applied strain. The assumption of an anisotropic relaxation time for Bi2Te3 suggests that already in the single crystalline system strong anisotropic scattering effects should play a role.