Bright and Efficient Light-Emitting Devices Based on 2D Transition Metal Dichalcogenides

2D monolayer transition metal dichalcogenides (TMDCs) show great promise for the development of next-generation light-emitting devices owing to their unique electronic and optoelectronic properties. The dangling-bond-free surface and direct-bandgap structure of monolayer TMDCs allow for near-unity photoluminescence quantum efficiencies. The excellent mechanical and optical characteristics of 2D TMDCs offer great potential to fabricate TMDC-based light-emitting diodes (LEDs) featuring good flexibility and transparency. Great progress has been made in the fabrication of bright and efficient LEDs with varying device structures. In this review, the aim is to provide a comprehensive summary of the state-of-the-art progress made in the construction of bright and efficient LEDs based on 2D TMDCs. After a brief introduction to the research background, the preparation of 2D TMDCs used for LEDs is briefly discussed. The requirements and the corresponding challenges to achieve bright and efficient LEDs based on 2D TMDCs are introduced. Thereafter, various strategies to enhance the brightness of monolayer 2D TMDCs are described. Following that, the carrier-injection schemes enabling bright and efficient TMDC-based LEDs along with the device performance are summarized. Finally, the challenges and future prospects regarding the accomplishment of TMDC-LEDs with ultimate brightness and efficiency are discussed.