The first-principles study on the halogen-doped graphene/MoS2 heterojunction

Monolayer graphene has a zero band gap, and monolayer MoS2 has a direct band gap of 1.80 eV. In the form of van der Waals heterostructure, the combination can open the Dirac point of graphene. In this paper, the graphene/MoS2 heterojunctions were doped with the elements of F, Cl, Br and I to construct four systems. The defect formation energies, electronic structures and optical properties of four doped systems were calculated based on the first-principles. According to the defect formation energies, S vacancy became the best choice of doping site. The band structures of the doped heterojunctions changed significantly and appeared new energy levels. In addition, the MoS2 layers in the four heterojunctions produced some density of states near the Fermi surface. By calculating the optical properties that are the dielectric functions of the four halogen-doped graphene/MoS2 heterojunctions, the optical absorption range of the halogen-doped heterojunctions expanded from the visible light range to the infrared light range. This phenomenon indicates that the doping of halogen in the graphene/MoS2 heterojunction can expand the light absorption range of the heterojunction and improve the utilization rate of the heterojunction to infrared light.