Electrically Confined Electroluminescence of Neutral Excitons in WSe 2 Light-emitting Transistors.

Monolayer transition metal dichalcogenides (TMDs) have drawn significant attention for their potential in optoelectronic applications due to their direct band gap and exceptional quantum yield. However, TMD-based light-emitting devices have shown low external quantum efficiencies as imbalanced free carrier injection often leads to the formation of non-radiative charged excitons, limiting practical applications. Here, we demonstrate electrically confined electroluminescence (EL) of neutral excitons in WSe 2 light-emitting transistors (LETs) based on the van der Waals (vdW) heterostructure. The WSe 2 channel is locally doped to simultaneously inject electrons and holes to the one-dimensional (1D) region by a local graphene gate. At balanced concentrations of injected electrons and holes, the WSe 2 LETs exhibited strong EL with a high external quantum efficiency (EQE) of ∼8.2% at room temperature. Our experimental and theoretical results consistently show that the enhanced EQE could be attributed to dominant exciton emission confined at the 1D region while expelling charged excitons from the active area by precise control of external electric fields. Our work shows a promising approach to enhancing the EQE of 2D light-emitting transistors and modulating the recombination of exciton complexes for excitonic devices. This article is protected by copyright. All rights reserved.