Thermoelectric properties of isoelectronically substituted bismuth compounds: a computational study

Abstract

This work focuses on using isoelectronic substitution to modify electronic density of states (DOS) of bismuth (Bi) compounds for thermoelectric property modification. The calculations include first-principle density functional theory (DFT) and analytical calculations based on Mott formula. The thermoelectric materials selected in the present study are Bi compounds, i.e. Bi2Te3, Bi2Se3, Bi2Se2Te, Bi2Te2Se, Bi2O2Te, and Bi2O2Se. The results reveal that isoelectronic substitution of Se and Te atoms with O atoms (Bi2O2Te and Bi2O2Se) introduces changes in DOS around the valence band maximum and the conduction band minimum, exhibiting the figure of merit (ZT) approaching the values 0.004 and 0.03 at room temperature, for Bi2O2Se and Bi2O2Te, respectively. Though the ZT of these oxide compounds are inferior to conventional thermoelectric materials, it is known that they show better stability and less toxicity which could be the alternative materials.