van der Waals Interaction-Induced Tunable Schottky Barriers in Metal-2D Perovskite Contacts.

We systematically study the bonding and electronic properties of metal-BAPbI contacts, which play a crucial role in affecting the device performance, based on density functional theory calculations. Tunable Schottky barrier heights (SBHs) are observed in metal-BAPbI contacts by using different metals with a moderate Fermi level pinning (FLP) effect. An interfacial van der Waals interaction-induced Pauli-exclusion effect is found to be responsible for the FLP. The unique structure of BAPbI ensures the interfacial interaction has a limited influence on the band energy of BAPbI, since the spacer cation can be seen as a naturally formed buffer layer. We also found the SBHs depend on the thickness of inorganic layers in quasi-two-dimensional (2D) BAMAPbI. A high tunneling barrier and low interfacial charge density are also observed in all contacts. The thorough understanding of the underlying mechanisms of bonding and electronic properties in these contacts is beneficial for us to promote the performance of 2D perovskite-related devices.