Emerging 2D Materials and Van der Waals Heterostructures for Advanced NIR, SWIR, and MWIR Emitters.

Infrared (IR) emitters have drawn considerable attention for applications in deep-tissue imaging, optical communication, and thermal sensing. While III-V and II-VI semiconductors are traditionally used in these emitters, their reliance on complex epitaxial growth to overcome lattice mismatch and thermal expansion challenges leads to intricate device structures and limits their integrability. In contrast, 2D materials provide a more flexible solution, offering diverse optical bandgaps and the ability to be vertically restacked in arbitrary crystal orientations to form complex van der Waals (vdW) heterostructures, which can be further integrated onto diverse device platforms. This review highlights recent advancements in 2D-based IR emitters, focusing on the NIR, SWIR, and MWIR regions. It discusses the photoluminescence properties of 2D materials and innovative vdW engineering techniques used to develop IR light-emitting diodes (LEDs). The review also explores how external stimuli, such as electric fields and strain, can enable tunable emission wavelengths and examines the integration of 2D-based emitters with photonic structures, like cavities and waveguides, to create hybrid photonic devices. Finally, the review addresses the challenges and prospects of 2D-based IR technologies, highlighting their potential to transform IR light sources across various applications.