Directional Exciton-Energy Transport in a Lateral Heteromonolayer of WSe₂–MoSe₂

Abstract

Controlling the direction of exciton-energy flow in two-dimensional (2D) semiconductors is crucial for developing future high-speed optoelectronic devices using excitons as the information carriers. However, intrinsic exciton diffusion in conventional 2D semiconductors is omnidirectional, and efficient exciton-energy transport in a specific direction is difficult to achieve. Here we demonstrate directional exciton-energy transport across the interface in tungsten diselenide (WSe2)–molybdenum diselenide (MoSe2) lateral heterostructures. Unidirectional transport is spontaneously driven by the built-in asymmetry of the exciton-energy landscape with respect to the heterojunction interface. At excitation positions close to the interface, the exciton photoluminescence (PL) intensity was substantially decreased in the WSe2 region and enhanced in the MoSe2 region. In PL excitation spectroscopy, it was confirmed that the observed phenomenon arises from lateral exciton-energy transport from WSe2 to MoSe2. This directional exciton-energy flow in lateral 2D heterostructures can be exploited in future optoelectronic devices.

Exciton spectroscopy and unidirectional transport in MoSe2-WSe2 lateral heterostructures encapsulated in hexagonal boron nitride

“…This behavior shows that the junction acts as an exciton diode, allowing excitons to cross from WSe 2 to MoSe 2 but not the other way around. This non reciprocal behavior is in agreement with the excitonic energy landscape at the interface and previously observed behavior in far field measurement 72 . Indeed as illustrated in Fig.…”

Quantum Spin Hall States in 2D Monolayer WTe2/MoTe2 Lateral Heterojunctions for Topological Quantum Computation

“…28 The fabrication of lateral heterojunctions of 2H−MoSe 2 and 1T′−ReSe 2 has also been reported, 29 although the atomic and electronic structures of 1T′−ReSe 2 , a group VII TMDC, are different from those of group VI TMDCs, such as 1T′−WTe 2 . 30 Besides those including 1T′ phases, several heterojunctions of monolayer TMDCs have been experimentally realized: WS 2 /MoS 2 , 31,32 MoSe 2 /WSe 2 , 33,34 MoS 2 /MoSe 2 , 35 WS 2 /WSe 2 , 35 and WSe 2 / MoS 2 . 36,37 The formation of 2D lateral junctions with different monolayer TMDCs can result in properties that differ from the intrinsic properties of each material.…”

Electronic property modulation in two-dimensional lateral superlattices of monolayer transition metal dichalcogenides

“…61 Interestingly, MoS 2x Se 2(1−x) -MoS 2y Se (1−y) exhibits a wide bandgap tunability of 0.32 eV. 53,59 These synthesized 2D lateral TMD-HSs have been assembled into devices for electronic and optoelectronic applications such as lateral p-n diodes, 46,56 photodiodes, 42 photodetectors, 62 high-repetition excitonic devices 63 and fieldeffect transistors (FETs). 9 Meanwhile, the theoretical studies of lateral TMD-HSs were mainly focused on the electronic band structures and band offsets.…”