Strain engineering of electronic and thermoelectric properties in MoS2/WSe2 bilayer Heterostructure

Two-dimensional transition metal dichalcogenides (2D TMDs) and their van der Waals (vdW) heterostructures exhibit a lot of outstanding properties based on their like-graphene structures and tunable band gaps, which can address some serious environmental issues as potential candidates for energy conversion and storage devices. Among these materials, MoS₂ and WSe₂ are popular study subjects. The systematic modulation of the electronic structure and bandgap in bilayer (BL) MoS₂/WSe₂ heterostructure via biaxial and vertical strain engineering remains poorly understood. Therefore, we study the electronic structure and the band gap of MoS₂/WSe₂ heterostructure under the vertical and biaxial strains, and found that both biaxial and vertical strains significantly enhance the thermoelectric performance of the BL MoS₂/WSe₂ heterostructure, with biaxial strain being particularly effective. The results indicate that biaxial strain and compressive vertical strain are effective engineering methods to reduce the band gap of the heterostructure. Furthermore, this work shows that the biaxial strain is a highly efficient and useful strategy to increase the thermoelectric properties of MoS₂/WSe₂ heterostructure. At the certain carrier concentration, when −8 % biaxial strain is applied to the heterostructure, the $S^2\sigma /\tau$ will be significantly improved compared with that of the heterostructure without strain. Among them, the p-type doping increases 65.5 %, and the n-type doping increases 94.3 %. This suggests a promising strategy for optimizing vdW heterostructures.