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

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.