Mid-Infrared Light-Emitting Diodes Based on Black Phosphorus with Asymmetric Electrodes

The mid-infrared light-emitting devices are crucial components in free-space optical communication, gas sensing, and military applications. Two-dimensional (2D) narrow-bandgap semiconductors offer opportunities for low-cost and tunable miniaturized mid-infrared light sources. Current 2D light-emitting devices face challenges in the effective injection of carriers and complex device structures. In this paper, we report a black phosphorus-based mid-infrared light-emitting diode (LED) with a simple structure of asymmetric contacts of gold and few-layer graphene. The narrow band gap of black phosphorus and tunable Fermi energy of graphene facilitate electron and hole injection simultaneously. Hot carrier injection and band filling under high injection current conditions are further revealed in the heterojunction device. This study demonstrates a simple and effective strategy for constructing 2D mid-infrared LEDs and shows potential for scalable applications.