First-principles study on optoelectronic properties of Cs₂PbX₄-PtSe₂ van der Waals heterostructures

In order to achieve low-cost, high efficiency and stable photoelectric devices, two-dimensional (2D) inorganic halide perovskite photosensitive layers need to cooperate with other functional layers. Here, we investigate the structure, stability and optical properties of perovskite and transition metal dichalcogenide (TMD) heterostructures using first-principles calculations. Firstly, Cs₂PbX₄-PtSe₂ (X = Cl, Br, I) heterostructures are stable because of negative interface binding energy. With the halogen varying from Cl to I, the interface binding energies of Cs₂PbX₄-PtSe₂ heterostructures decrease rapidly. 2D Cs₂PbCl₄-PtSe₂, Cs₂PbBr₄-PtSe₂ and Cs₂PbI₄-PtSe₂ heterostructures have an indirect bandgap with the value of 1.28, 1.02, and 1.29 eV, respectively, which approach the optimal bandgap (1.34 eV) for solar cells. In the contact state, the electrons transfer from the PtSe₂ monolayer to Cs₂PbX₄ monolayer and only the Cs₂PbBr₄-PtSe₂ heterostructure maintains the type-II band alignment. The Cs₂PbBr₄-PtSe₂ heterostructure has the strongest charge transfer among the three Cs₂PbX₄-PtSe₂ heterostructures because it has the lowest tunnel barrier height (ΔT) and the highest potential difference value (ΔEP). Furthermore, the light absorption coefficient of Cs₂PbX₄-MSe₂ heterostructures is at least two times higher than that of monolayer 2D inorganic halide perovskites. With the halogen varying from Cl to I, the light absorption coefficients of the Cs₂PbX₄-PtSe₂ heterostructures increase rapidly in the visible region. Above all, the Cs₂PbX₄-MSe₂ heterostructures have broad application prospects in photodetectors, solar cells and other fields.