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

Abstract

The strain-sensitive heterostructure, as a type of lowdimensional 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 MoS 2 /WS 2 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 ntype 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.

Excellent Medium-Temperature Thermoelectric Performance of Monolayer BiOCl

“…The TE transport coefficients with respect to the tensile strains of 0, 1, and 1.5% as a function of the carrier concentration are plotted in Figure a–e. Clearly, S is insensitive to the variation of strain (Figure a), similar to the previous studies in monolayer GeSe and MoS 2 /WS 2 heterostructures . However, the electrical conductivity slightly decreases with increasing tensile strain (Figure b), which is consistent with the tendency of the electronic thermal conductivity (Figure c).…”

High thermoelectric performance of two-dimensional SiPGaS/As heterostructures

“…Our designed heterostructure's thermoelectric performance is better than those of reported heterostructures and monolayers, as depicted in Fig. 11(a) and S4 † 22,69–89 . It is highly anticipated that TE materials with ZT avg > 1 can be practically used in a large temperature range.…”

“…To optimize the thermoelectric efficiency, tensile strain is highly efficient strategy to enlarge bond length signifies weaker bonding leads to smaller lattice thermal conductivity, thus enhance ZT. 71,94 In addition, Fig. S5(a-d) † depicts the ZT values as a function of carrier concentrations (n).…”

A van der Waals p–n heterostructure of GaSe/SnS2: a high thermoelectric figure of merit and strong anisotropy

“…It is evident that the ZT value of GaSe/SnS 2 vdWH is not only better than those of its constituents owing to the longer relaxation time of the electron in the y-direction resulting in a higher power factor, 27,28 but also higher than those of the reported vdWHs. 22,53,61,62 On the whole, the experimentally synthesized GaSe/SnS 2 vdWH is applicable as an optional substitute for medium-temperature thermoelectric materials, irrespective of the p-type or n-type.…”