A type-II WSe2/HfSe2 van der Waals heterostructure with adjustable electronic and optical properties

The construction of van der Waals (vdW) heterostructures is an efficient strategy for attaining more desired specifications. According to first-principles calculations, the WSe2/HfSe2 vdW heterostructure has an indirect band gap from K point to M point with the value of 0.21 eV. A conventional type-II band alignment is constructed for the WSe2/HfSe2 heterostructure, where the electrons and holes are placed in HfSe2 and WSe2 layers, respectively, facilitating the efficient separation of photo-generated electron and hole pairs. Although both WSe2 and HfSe2 monolayers were highly insulating, Kashiwabara group found that WSe2/HfSe2 heterostructure were highly conducting [Adv. Funct. Mater. 2019, 29, 1900354]. Our calculated results suggest that the strain and external electric field can lead to the transition from semiconductor to metal, resulting in high conductivity. The band alignment transition from type-II to type-I can also be obtained by means of in-plane strains and external electric field. The interlayer coupling only affects the values of band gap. Moreover, the investigation on the optical properties shows that the optical absorption intensity of WSe2/HfSe2 heterostructure can attain the order of 10(5). These findings indicate that the WSe2/HfSe2 vdW heterostructure is promising for efficient optoelectronic nanodevices.