Optoelectronic properties of two-dimensional lead-free perovskite Cs3Sb2I9/InX (X = S, Se) van der Waals heterostructures

Abstract

Low-dimensional halide perovskite semiconductor materials have attracted much attention from researchers due to their unique physicochemical properties that distinguish them from conventional semiconductor materials, but most of the current low-dimensional metal halide perovskite materials contain elemental lead, which hinders their large-scale use. Here, we introduce a two-dimensional lead-free perovskite Cs₃Sb₂I₉ and further construct a Cs₃Sb₂I₉/InX (X = S, Se) heterostructure based on the density-functional theory to investigate its electrical and optical properties. The magnitude of van der Waals forces between the layers of the heterostructure was analyzed by calculating the variation of the binding energy with the layer spacing. The projected energy bands and projected density of states of the heterostructures show that both heterostructures have a type-II energy band alignment at the interface. The calculated differential charge densities show the charge transfer process in the heterostructures, and the results indicate that the charge transfer mainly occurs at the interface and the electrons mainly accumulate in the InX layer. In addition, the light absorption coefficient and dielectric function of the heterostructure are significantly improved compared with those of the isolated material. Especially in the ultraviolet (UV) region, the peak absorption coefficient of the heterojunction can reach 4.16 × 10⁵ cm⁻¹. Subsequently, the response behavior of the heterostructure devices to different wavelengths of incident light was investigated, and the two devices showed peak responsivity of 21 mA/W and 34 mA/W at 3.4 eV and 3.95 eV, respectively. The results of our study suggest that the Cs₃Sb₂I₉/InX (X = S, Se) heterostructure has the potential to be applied in UV photodetector devices.