Metasurfaces Enhancing Excitonic Emission from 2D Materials: Hybrid Structures, Mechanisms, and Applications.

Two-dimensional (2D) materials feature strong excitonic emission, holding great promise for excitonic and optoelectronic applications. However, the atomic thickness restricts the light-matter interaction and largely limits their optical performance. The hybrid structures integrated by 2D materials and metasurfaces not only provide an effective means for optimizing and extending the functionalities of 2D optoelectronic devices but also offer an ideal platform for exploring diverse physical phenomena. In this review, we focus on recent progress in metasurface-enhanced excitonic emission from 2D materials, comprehensively examining the underlying physical mechanisms, enhanced properties, and relevant device applications. We first outline the working principles, which are organized into coupling-regime mechanisms along with effects beyond coupling strength. Second, we introduce various hybrid structure types of 2D materials, including perovskites, transition metal dichalcogenides (TMDs), and other 2D materials such as graphene, hexagonal boron nitride (hBN), indium selenide (InSe), etc. For each configuration, the corresponding functional applications are discussed and evaluated in detail. Finally, we summarize the review and point out remaining challenges and future research directions. It is anticipated that metasurface-enhanced excitonic emission from 2D materials will continue to significantly impact the development of emerging excitonic and optoelectronic applications.