Efficient and Chiral Electroluminescence from In‐Plane Heterostructure of Transition Metal Dichalcogenide Monolayers

Atomically thin transition metal dichalcogenides (TMDCs) are attractive materials for future optoelectronic applications because of their excellent electrical, optical, and quantum (spin‐valley) properties. In particular, in‐plane heterostructures based on TMDC monolayers provide opportunities to directly modulate band structures and lattice strains by the spatial distribution of constituent elements, leading to efficient control of their carrier transport and recombination. However, it is still challenging to create light‐emitting devices using such in‐plane heterostructures because of the technical difficulties associated with sample/device fabrication. This study demonstrated interfacial electroluminescence (EL) in diverse TMDC monolayer in‐plane heterostructures. Various combinations of large‐area, single‐crystalline in‐plane heterostructures with sharp interfaces are grown by chemical vapor deposition, followed by the adoption of electrolyte‐based light‐emitting devices to observe EL. The fine heterostructures enabled the capture of the linear‐shaped EL fixed along the junction interfaces. Significantly, the WS2/WSe2 in‐plane heterostructures exhibited circularly polarized EL with polarizability of 10% at room temperature. This can be explained by the interfacial strain‐mediated electronic structure evolution, in which the combination of electric fields and strain‐induced valley drifts realizes selective EL from the K/K’ valley. These findings pave the way for expanding the potential of monolayer in‐plane heterostructures for use in functional optoelectronic devices. In‐plane heterostructure light‐emitting diode is realized using various combinations of chemical vapor deposition‐grown transition metal dichalcogenide monolayers. The sharp and strained heterostructure makes it possible to capture the electroluminescence (EL) fixed along the heterojunction interfaces, which results in circularly polarized EL at room temperature. These results pave the way to expand the potential of monolayer in‐plane heterostructures for use in quantum optoelectronic devices.