Doping-dependent thermoelectric properties of BiSb3Te6 from first-principle calculations

The influence of electronic structure and doping level on the thermoelectric transport properties of BiSb3Te6 compound was investigated using first-principle calculations and Boltzmann transport theory. The calculation results indicate that BiSb3Te6 is a narrow gap semiconductor with an indirect band gap of 0.113 eV. The calculated band structures of the compound present nonparabolic curves with multi-valley band property. The density of states is enhanced below a few tenths of Fermi energy and the bands are flatted with heavy effective mass. The calculated thermoelectric coefficients of BiSb3Te6 are anisotropic and mainly dependent on the doping concentrations. The dopant dependences of ZT values are given with the optimal carrier concentrations ∼1019 cm−3. This theoretical investigation gives a valuable insight into the relationship between the electronic structure and thermoelectric transport properties of BiSb3Te6 material, and provides a quantificational doping level to improve the thermoelectric performance.