Biaxial Strain Improving the Thermoelectric Performance of a Two-Dimensional MoS2/WS2 Heterostructure

The strain-sensitive heterostructure, as a type of low-dimensional technique, has attracted extensive attention, but the influence mechanism of the biaxial strain on its thermoelectric properties is still unclear. In this paper, the first principles based on density functional theory and the BoltzTrap transport equation with relaxation time calculated by deformation potential theory are employed to figure out the biaxial strain effect on the band structure and transport performance of the MoS2/WS2 heterostructure. The lattice thermal conductivity under different strains is also investigated through nonequilibrium molecular dynamics. The results indicate that the strain-induced convergence of the valence and conduction bands can significantly improve the Seebeck coefficient of p- and n-type doping systems, respectively. The effective mass also changes with a tunable band structure, which increases the electrical conductivity under the tensile strain. Additionally, the biaxial strain is beneficial to reduce the lattice thermal conductivity. The final figure of merit significantly increases at large strains or at strains where band convergence can be achieved. This work shows that the biaxial strain is a highly efficient strategy to increase the thermoelectric properties of heterostructures.