Designing the weak Fermi pinning and p-type Ohmic contacts to monolayer halide perovskite Cs3Bi2I9

The contact between two-dimensional (2D) perovskite and metal electrodes is often plagued by strong Fermi-level pinning (FLP) effects, which limit the electronic performance of devices. By utilizing van der Waals design strategies, the contact performance between Cs3Bi2I9 and 1T/H-XA2 (X = V, Nb, Ta; A = S, Se) was investigated. P-type Schottky contacts are obtained in all 1T/H-XA2 contacts to Cs3Bi2I9, and the contacts can be engineered from Schottky to Ohmic contacts via external electric fields. Furthermore, a large pinning factor to suppress the FLP effects was observed to approach the Schottky–Mott limit, and the origin is elucidated. In addition, the transport properties of various 2D metals contacts to Cs3Bi2I9 were calculated and screened out. Finally, Curie temperature (Tc) of magnetic systems were calculated using the Monte Carlo method, and the Tc of 1H-VS2/Cs3Bi2I9 significantly enhances largely to surpass room temperature, thereby expanding the application field of spintronic devices. This study provides potential guidance for the design of efficient 2D Cs3Bi2I9-based nanodevices as well as high-temperature spintronic devices.