Electroluminescence from Megasonically Solution-Processed MoS<sub>2</sub> Nanosheet Films
Sonal V. Rangnekar, Vinod K. Sangwan, Mengru Jin, Maryam Khalaj, Beata M. Szydłowska, Anushka Dasgupta, Lidia Kuo, Heather Kurtz, Tobin J. Marks, Mark C. Hersam
Abstract
Due to their superior optoelectronic properties, monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention for electroluminescent devices. However, challenges in isolating optoelectronically active TMD monolayers using scalable liquid phase exfoliation have precluded electroluminescence in large-area, solution-processed TMD films. Here, we overcome these limitations and demonstrate electroluminescence from molybdenum disulfide (MoS 2 ) nanosheet films by employing a monolayer-rich MoS 2 ink produced by electrochemical intercalation and megasonic exfoliation. Characteristic monolayer MoS 2 photoluminescence and electroluminescence spectral peaks at 1.88–1.90 eV are observed in megasonicated MoS 2 films, with the emission intensity increasing with film thickness over the range 10–70 nm. Furthermore, employing a vertical light-emitting capacitor architecture enables uniform electroluminescence in large-area devices. These results indicate that megasonically exfoliated MoS 2 monolayers retain their direct bandgap character in electrically percolating thin films even following multistep solution processing. Overall, this work establishes megasonicated MoS 2 inks as an additive manufacturing platform for flexible, patterned, and miniaturized light sources that can likely be expanded to other TMD semiconductors.