First-principles study on optoelectronic properties of Cs 2 PbX 4 -PtSe 2 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, Cs 2 PbX 4 -PtSe 2 (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 Cs 2 PbX 4 -PtSe 2 heterostructures decrease rapidly. 2D Cs 2 PbCl 4 -PtSe 2 , Cs 2 PbBr 4 -PtSe 2 and Cs 2 PbI 4 -PtSe 2 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 PtSe 2 monolayer to Cs 2 PbX 4 monolayer and only the Cs 2 PbBr 4 -PtSe 2 heterostructure maintains the type-II band alignment. The Cs 2 PbBr 4 -PtSe 2 heterostructure has the strongest charge transfer among the three Cs 2 PbX 4 -PtSe 2 heterostructures because it has the lowest tunnel barrier height (Δ T ) and the highest potential difference value (ΔEP). Furthermore, the light absorption coefficient of Cs 2 PbX 4 -MSe 2 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 Cs 2 PbX 4 -PtSe 2 heterostructures increase rapidly in the visible region. Above all, the Cs 2 PbX 4 -MSe 2 heterostructures have broad application prospects in photodetectors, solar cells and other fields.