Prediction of Band Structure of $Bi_2Te_3$-related Binary and Ternary Thermoelectric Materials

TL;DR

This study uses density functional calculations to analyze the band structures of $Bi_2Te_3$-related thermoelectric materials, revealing how doping affects band gaps and degeneracies to guide high-performance material design.

Contribution

It provides detailed insights into how Sb and Se doping alter band structures and degeneracies in $Bi_2Te_3$-related compounds, aiding the design of better thermoelectric materials.

Findings

Sb doping increases band gap

Se doping monotonically increases band gap

Degeneracy of valence band maximum remains at 6

Abstract

Density functional calculations have performed to study the band structures of $Bi_2Te_3$-related binary ($Bi_2Te_3$, $Sb_2Te_3$, $Bi_2Se_3$, and $Sb_2Se_3$) and $Sb$/$Se$ doped ternary compounds [$(Bi_{1-x}Sb_x)_2Te_3$ and $Bi_2(Te_{1-y}Se_y)_3$]. It is found that the band gap can be increased by $Sb$ doping and it is monotonically increased by $Se$ doping. In ternary compounds, the change of the conduction band structure is more significant, as compared to the change of valence band. The band degeneracy of valence band maximum is maintained to be 6 in binaries and ternaries. However, as going from $Bi_2Te_3$ to $Sb_2Te_3$ ($Bi_2Se_3$), the degeneracy of conduction band minimum is reduced from 6 to 2(1). Based on the results of band structures, we suggest the suitable stoichiometries of ternary compounds for high thermoelectric performance.