Optimizing the thermoelectric performance of low-temperature SnSe compounds by electronic structure design

Abstract

Recently, the SnSe compound was reported to have a peak thermoelectric figure-of-merit (ZT) of ∼2.62 at 923 K, but the ZT values at temperatures below 750 K are relatively low. In this work, the electronic structures of SnSe are calculated using the density functional theory, and the electro- and thermo-transport properties upon carrier density are evaluated by the semi-classic Boltzmann transport theory, revealing that the calculated ZT values along the a- and c-axes below 675 K are in agreement with reported values, but that along the b-axis can be as high as 2.57 by optimizing the carrier concentration to n ∼ 3.6 × 10¹⁹ cm⁻³. It is suggested that a mixed ionic–covalent bonding and heavy-light band overlapping near the valence band are the reasons for the higher thermoelectric performance.