Modulation of the optoelectronic properties of h-BN/ WTe2 heterostructures with different twist angles by biaxial strain

Abstract

Constructing a vertical van der Waals heterostructure can effectively regulate the properties of a single 2D material. This paper constructs a vertical h-BN/WTe₂ heterostructure and uses first-principles methods based on density functional theory to explore the effects of twist angle and biaxial strain on its stability, electronic properties, and optical performance. The results show that the twist angle does not change the direct bandgap and type-I band alignment of the h-BN/WTe₂ heterostructure, but it affects the bandgap size and the positions of the conduction band minimum (CBM) and valence band maximum (VBM). The maximum value of the bandgap occurs at twist angles of 8.9° and 51.1°, with a value of 1.21 eV. Additionally, for the h-BN/WTe₂ heterostructure at a twist angle of 0°, the maximum optical absorption coefficient is 9.5 × 10⁵ cm⁻¹ at 5.38 eV. As the twist angle changes from 0° to 8.9° and 30°, the optical absorption spectrum redshifts, and the absorption coefficient decreases. Furthermore, within the strain range of −12 % to +12 %, the bandgap type of the h-BN/WTe₂ heterostructure changes from indirect to direct and then back to indirect, and a semiconductor-metal phase transition also occurs. The research results provide theoretical guidance for the use of the h-BN/WTe₂ heterostructure in optoelectronic devices, aiding its further development in the field of optoelectronic device applications.