Broadband Photoelectric Performance Of 2D SePtTe/InS Van Der Waals Heterojunction

Since the successful fabrication of graphene in 2004,two-dimensional?2D?materials have attracted much attention due to their optoelectronics properties.Among of them,transition metal dichalcogenides?TMDs?has attracted much attention due to its asymmetric electronic structure and excellent properties in the field of optoelectronics.Recently,the 1T phase PtSe₂ has aroused great attention in the sulfur group compounds of Pt.Although The single-layer 1T-PtSe₂ is an indirect band gap semiconductor like most other TMDs,it has high carrier mobility,moderate band gap and high optical absorption coefficient.Previous studies have shown that the Janus structure of PtSe₂ also has excellent optical properties.However,both PtSe₂and its Janus structure are indirect band-gap semiconductors,which greatly limits its application in the field of optoelectronics.Actually,constructing van der Waals heterojunction is an effective approach to tune the band structures.In this paper,we use the first-principles calculation method to explore the van der Waals heterojunction between 1T-PtSe₂ or Janus structure and III-VI compound.And the research contents and main conclusions of this paper are as followed:?1?The van der Waals heterojunction has been constructed based on monolayer SePtTe and InS.We systematically studied four possible stacking structures of the SePtTe/InS heterojunction,and finally established a new van der Waals heterojunction with AA2 stacking pattern via comparing the bandgap types and binding energies.Our studies show that the SePtTe/InS heterojunction possess direct band gap and Type-II band alignment.In addition,compared with monolayer SePtTe and InS,the SePtTe/InS heterojunction maintains the excellent optical properties of both SePtTe and InS,and its optical absorption spectrum combined the advantages of the two monolayer materials.The optical absorption coefficient of the heterojunction can reach 10⁵ and a wider spectral response.?2?The effects of the stress on the photoelectric properties of the SePtTe/InS van der Waals heterojunction is studied by the first-principles method.We studied the stability of the electrical and optical properties of the SePtTe/InS van der Waals heterojunction under biaxial strain.It is found that the in-plane strain which may be caused by lattice mismatch will not affect the electronic properties,such as direct band-gap and type-II band alignment.Under the vertical stress applied by changing interlayer distance of the heterojunction,the band offset and band alignment can be effectively regulated which can strengthen the photoelectric conversion efficiency?PCE?.?3?The effects of external electric field on the photoelectric properties of SePtTe/InS van der Waals heterojunction are also studied.Results show that the charge transfer in the heterojunction can be promoted or inhibited by controlling the direction and size of external electric field,which means that can modulate the charge density distribution.As a result,the type,size of the band gap and band alignment can be modulated by the external electric field.Interestingly,both vertical strain and external electric field can modulate the size of bandgap and band offsets?0.3e V<E_g<3e V,?E_c<1.0e V?which can improve the photoelectric performance,such as promote the separation of electron hole pairs and improve the PCE.At the same time,the heterojunction maintains a high optical absorption coefficient and a wide absorption spectrum.These properties are very helpful for the wide application of PtSe₂ and its Janus in the field of optoelectronic devices.