Pressure-induced enhancement in the thermoelectric properties of monolayer and bilayer SnSe ₂

Abstract

The electronic structures of monolayer and bilayer SnSe₂ under pressure were investigated by using first-principles calculations including van der Waals interactions. For monolayer SnSe₂, the variation of electronic structure under pressure is controlled by pressure-dependent lattice parameters. For bilayer SnSe₂, the changes in electronic structure under pressure are dominated by intralayer and interlayer atomic interactions. The <i>n</i>-type thermoelectric properties of monolayer and bilayer SnSe₂ under pressure were calculated on the basis of the semi-classical Boltzmann transport theory. It was found that the electrical conductivity of monolayer and bilayer SnSe₂ can be enhanced under pressure, and such dependence can be attributed to the pressure-induced changes of the Se-Sn antibonding states in conduction band. Finally, the doping dependence of power factors of <i>n</i>-type monolayer and bilayer SnSe₂ at three different pressures were estimated, and the results unveiled that thermoelectric performance of <i>n</i>-type monolayer and bilayer SnSe₂ can be improved by applying external pressure. This study benefits to understand the nature of the transport properties for monolayer and bilayer SnSe₂ under pressure, and it offers valuable insight for designing high-performance thermoelectric few-layered SnSe₂ through strain engineering induced by external pressure.