Defect‐Mediated Efficient and Tunable Emission in van der Waals Integrated Light Sources at Room Temperature

Abstract

Despite defect‐mediated states in monolayer semiconductors have been considered as efficient emitters in cryogenic conditions, they are severely quenched at room temperature (RT) because of multiple thermal‐induced non‐radiative channels, hindering their practical use. Here, robust and tunable defect‐mediated emissions at RT, designated as D1 (1.82 eV) and D2 (1.62 eV), are discovered in monolayer WS2 through argon plasma treatment, which, via multiple corroborative experiments, are attributed to distinct physical processes: bound excitons associated with sulfur vacancies (Vs) and the band‐to‐acceptor recombination, respectively. Remarkably, the defective sample exhibits over ten‐fold increase in both photoluminescence quantum yield and full‐width at half‐maximum (FWHM) compared to its intrinsic counterpart. Leveraging these pronounced edges, light‐emitting diodes (LEDs) functioning at RT achieve broadband (FWHM: 490 meV) and continuously tunable emission from 1.6 to 2.0 eV, as well as the highest electroluminescence (EL) external quantum efficiency (EQE) of ≈1.39% among transient LEDs based on monolayer semiconductors to date, thereby unveiling a new strategy for emission tailoring at the atomic‐scale limit.