Light‐Emission Devices Based on Transition Metal Dichalcogenide: Quantum Efficiency Progress and Influencing Factors

ABSTRACT Different from conventional compound semiconductors, transition metal dichalcogenides (TMDCs) exhibit unique excitonic luminescence due to weak dielectric screening effects and strong geometric confinement. The atomic monolayer thickness, combined with the characteristics of van der Waals crystals, TMDCs provide a platform to develop novel excitonic light‐emitting devices with advantages such as easy integration, flexibility, and low threshold. Quantum efficiency represents one of the most critical metrics for assessing the performance of light‐emitting devices. Over the past decade, the external quantum efficiency (EQE) of TMDC‐based electroluminescent devices has improved significantly, rising four orders from an initially reported value of approximately 0.001% to nearly 10%. Nevertheless, when compared to commercial light‐emitting diode (LED) devices, this EQE still offers considerable room for further enhancement. From a device‐level perspective, in this review, we discuss the latest advancements in four types of TMDC‐based electroluminescent devices, namely PN (or PIN) junctions, quantum wells (QW), metal‐insulator‐semiconductor (MIS) structures, and alternating current (AC) injection, categorized by carrier injection mechanisms and spatial confinement of carriers. Moreover, we summarize the current challenges and provide an outlook on the future development of these technologies.