Electroluminescence from Megasonically Solution-Processed MoS2 Nanosheet Films

Due to their superior optoelectronic properties, monolayertwo-dimensional(2D) transition metal dichalcogenides (TMDs) have attracted significantattention for electroluminescent devices. However, challenges in isolatingoptoelectronically active TMD monolayers using scalable liquid phaseexfoliation have precluded electroluminescence in large-area, solution-processedTMD films. Here, we overcome these limitations and demonstrate electroluminescencefrom molybdenum disulfide (MoS2) nanosheet films by employinga monolayer-rich MoS2 ink produced by electrochemical intercalationand megasonic exfoliation. Characteristic monolayer MoS2 photoluminescence and electroluminescence spectral peaks at 1.88-1.90eV are observed in megasonicated MoS2 films, with the emissionintensity increasing with film thickness over the range 10-70nm. Furthermore, employing a vertical light-emitting capacitor architectureenables uniform electroluminescence in large-area devices. These resultsindicate that megasonically exfoliated MoS2 monolayersretain their direct bandgap character in electrically percolatingthin films even following multistep solution processing. Overall,this work establishes megasonicated MoS2 inks as an additivemanufacturing platform for flexible, patterned, and miniaturized lightsources that can likely be expanded to other TMD semiconductors.