Unusual Contact Properties at the Metal-2D Perovskite Interface: The Crucial Role of Naturally Formed Buffer Layer in 2D Perovskite

The contact properties of two-dimensional (2D) perovskites with electrode can severely affect the device performance. In this work, we studied the contact properties of Cs2PbI2Cl2 with different metals (Al, Ag, Au, Pd, Ir, and Pt). A naturally formed buffer layer in Cs2PbI2Cl2 at the interface plays a crucial role in affecting the interface electronic properties. Two stacking patterns are constructed according to their symmetry. Typical Schottky contacts are observed in type II contacts with a strong Fermi level pinning (FLP) effect, while unusual FLP is observed in type I contacts. Remarkably, Ohmic contacts are obtained in Pd/Ir/Pt- Cs2PbI2Cl2 type I contacts. The influence of interfacial coupling behaviors to the FLP is revealed. This study shows that through judicious device architecture design, tunable interfacial tunneling and Schottky barriers can be achieved in metal-Cs2PbI2Cl2 contacts, which would provide guidance in developing more effective electronic nanodevices based on Cs2PbI2Cl2 and its analogues.