Exploring Electronic Coupling and Interface Energetics of a Magnetic Two-dimensional Perovskite with Metal Interfaces

Understanding the interfacial energetics between low-dimensional semiconductors and metal electrodes is pivotal for optimizing charge injection and extraction in optoelectronic devices. In this work, we systematically investigate the energy-level alignment at the interface between the two-dimensional (2D) Ruddlesden-Popper perovskite (PEA)₂CrCl₄ and metal substrates with contrasting work functions (WFs), namely silver (Ag) and gold (Au). Kelvin probe force microscopy (KPFM) is performed to acquire surface potential maps of the perovskite between bulk and atomic thicknesses, revealing pronounced thickness-dependent modulation of interfacial energetics. These measurements also uncover a complex interplay between interfacial dipoles, defect states, and metal-induced gap states, leading to varied degrees of Fermi-level pinning (FLP). Temperature-dependent KPFM further reveals thermally induced shifts in the interfacial energetics. The Au interface exhibits strong FLP and stable electronic coupling, while the Ag interface manifests higher sensitivity to thermally activated interfacial dipoles and defect states. These findings underscore the sensitivity of 2D perovskite interfaces to metal WF and surface chemistry, offering important insights for tailoring contact properties in perovskite-based optoelectronic devices.