Transition metal dichalcogenide (TMDC) monolayers are promising materials for next-generation nanoscale optoelectronics, including high-speed light sources and detectors. However, most past reports on TMDC light-emitting diodes are limited to operation in high vacuum, while most applications require operation under ambient conditions. In this work, we study the time-resolved electroluminescence of monolayer WSe2 p-n junctions under ambient conditions and identify the decay in current over time as the main issue preventing stable device operation. We show that pulsed voltage bias overcomes this issue and results in bright electroluminescence under ambient conditions. This is achieved in a simple single-gate structure, without the use of dual gates, heterostructures, or doping methods. Internal quantum efficiency of electroluminescence reaches ∼1%, close to the photoluminescence quantum efficiency, indicating efficient exciton formation with injected carriers. Emission intensity is stable over hours of device operation. Finally, our device exhibits ∼15 ns rise and fall times, the fastest direct modulation speed reported for TMDC light-emitting diodes.
Bibliographical noteFunding Information:
Device fabrication and characterization were funded by the Center for Energy Efficient Electronics Science through a grant from the National Science Foundation (NSF Award No. ECCS-0939514). K.H. was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program. WSe 2 growth was supported by the Electronic Materials Program funded by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the U.S. Department of Energy, under Contract No. DE-AC02-05Ch11231.
© 2019 Author(s).
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)