Distinct conducting layer edge states in two-dimensional (2D) halide perovskite

Two-dimensional (2D) lead halide perovskite with a natural "multiple quantum well" (MQW) structure has shown great potential for optoelectronic applications. Continuing advancement requires a fundamental understanding of the charge and energy flow in these 2D heterolayers, particularly at the layer edges. Here, we report the distinct conducting feature at the layer edges between the insulating bulk terrace regions in the (C₄H₉NH₃)₂PbI₄ 2D perovskite single crystal. The edges of the 2D exhibit an extraordinarily large carrier density of ~10²¹ cm^-3. By using various mapping techniques, we found the layer edge electrons are not related to the surface charging effect; rather, they are associated with the local nontrivial energy states of the electronic structure at the edges. This observation of the metal-like conducting feature at the layer edge of the 2D perovskite provides a different dimension for enhancing the performance of the next-generation optoelectronics and developing innovative nanoelectronics.