Optoelectronic Properties Of Two-dimensional Materials And Their Heterostructures

Two dimensional(2D)materials have many unique physical properties different from three-dimensional materials.van der Waals(vd W)heterostructures is formed by stacking of two or more 2D materials,which can not only combine the advantages of2D materials but also form a new 2D electronic system at the interface of vd W heterojunction.In addition,there is only a weak vd W force between the layers of 2D materials,so it is not necessary to consider the lattice mismatch and directional mismatch in traditional heterostructures.Therefore,vd W heterostructures provides a new opportunity for the study of new physical phenomena and the development of new nano devices.In this paper,the photoelectric properties of 2D materials and their vd W heterostructures are studied based on density functional theory.We found through first principles calculations that the S orbitals and P orbitals of layered black phosphorus(BP)phosphorus atoms play an important role in the formation of covalent bonds,and the P_zorbital contributes the most near the Fermi plane.The photoelectric properties of BP with different layer numbers are systematically explored,and it is found that the photoelectric properties are very sensitive to the layer numbers,and the metal properties are found in the high frequency region.Our theoretical study shows that the electronic and optical properties of BP can be regulated by interlayer interactions.The more layers of BP,the more suitable it is for its technical application in UV protection and detection,which provides a theoretical basis for experimental synthesis and technical application.The electronic structure and optical properties of Arsenene/MoTe₂vd W heterojunction have been systematically studied by first principles.It is found that in the absence of electric field,the heterojunction is a classical indirect bandgap type-I heterojunction system,and the conduction and valence bands are mainly contributed by MoTe₂.By applying an applied electric field to the heterojunction,the band gap size of the heterojunction can be effectively controlled.Through simulation,it is found that the band edge of the heterojunction shifts under the applied electric field,leading to the transition from type-I heterojunction to type-II heterojunction.The biggest advantage of type-II heterostructures is that it can effectively prevent the recombination of electrons and holes.In addition,we found that type-II heterojunction has excellent light absorption performance under solar irradiation,which provides the possibility for the application of vd W heterostructures in optical devices and photocatalysis.