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.