Graphene/Cs2PbI2Cl2 van der Waals heterostructure with tunable Schottky barriers and contact types

Abstract

Two-dimensional halide perovskite Cs2PbI2Cl2 with the Ruddlesden–Popper structure has attracted much interest in both experiment and theory, owing to its excellent structural stability and electronic and optical properties. Here, we design the graphene/Cs2PbI2Cl2 van der Waals (vdW) heterostructure (HS) and comprehensively investigate its structural, electronic, and contact properties by using first principle calculations. Four types of graphene/Cs2PbI2Cl2 HSs are considered, and the most stable one is identified. Because the composed system has weak vdW interaction, the intrinsic band structures of both graphene and Cs2PbI2Cl2 are well maintained. Meanwhile, the graphene opens a minute energy gap of about 68 meV, which may have resulted from a broken sublattice inversion symmetry and tiny structure distortion. Moreover, it is found that graphene/Cs2PbI2Cl2 forms a p-type Schottky contact. The HS undergoes a contact-type transition to p-type Ohmic contact and n-type Ohmic contact from the original p-type Schottky contact under positive and negative electric fields, respectively. When interlayer coupling strength increases or decreases, a contact-type transition to the p-type Ohmic contact from the original p-type Schottky contact occurs. These findings provide a meaningful guidance for tuning the electronic properties and constructing high-performance graphene/Cs2PbI2Cl2 HS-based Schottky devices.