Thermoelectric properties of quaternary (Bi,Sb)2(Te,Se)3 compound

• Sb and Se spin–orbit coupling play a key role in the band structure.
• Substituted Bi/Sb and Te/Se have a limited impact on the transport coefficients.
• n-Type doping will be preferred for quaternary (Bi,Sb)2(Te,Se)3 compound.

The quaternary (Bi,Sb)2(Te,Se)3 compounds are investigated using first-principles study and Boltzmann transport theory. The energy band structure and density of states are studied in detail. The electronic transport coefficients are then calculated as a function of chemical potential. The figure of merit ZT is obtained assuming a constant relaxation time and an averaged thermal conductivity. Our theoretical result agrees well with previous experimental data.