Interfacial Interactions and Enhanced Optoelectronic Properties in CsSnI3-Black Phosphorus van der Waals Heterostructures

Vertical Van der Waals (vdW) heterostructures, characterized by two-dimensional materials and halide perovskites, have drawn extensive attention to differences in novel optoelectronic properties for isolated materials. In this paper, the structural, electronic, and optical properties of vdW heterostructures based on gamma-CsSnI3 and black phosphorus (BP) monolayers are investigated using first-principle calculations. The calculated results show that the I-Cs are investigated interface heterostructure contacting the BP monolayer has a type-I band alignment, while the I-Sn interface contacting the BP monolayer heterostructure has a type-II alignment. In addition, CsSnI3-BP heterostructures show superior optical performance compared to CsSnI3 slabs in visible and ultraviolet spectra. This surprising result is traced to the smaller bandgap of heterostructures compared to that of isolated structures, as well as the inner electric field caused by the potential across the interface, which produces a charge redistribution at the interface and a separation of electron-hole pairs. This work offers a new view to shed light on the interface charge transfer mechanism for hybrid heterostructures with enhanced optical absorption. Therefore, a bandgap-tunable inorganic perovskite may be attractive for optoelectric applications.