Abstract
The capabilities of light-emitting diodes (LEDs) based on two-dimensional materials are restricted by efficiency roll-off, which is induced by exciton-exciton annihilation, at high current densities. Dielectric or strain engineering can be used to reduce exciton-exciton annihilation rates in monolayer transition metal dichalcogenides, but achieving electroluminescence in two-dimensional LEDs without efficiency roll-off is challenging. Here we describe pulsed LEDs that are based on intercalated transition metal dichalcogenides and offer suppressed exciton-exciton annihilation at high exciton generation rates. We intercalate oxygen plasma into few-layer molybdenum disulfide (MoS2) and tungsten disulfide (WS2) to create LEDs with a suppressed efficiency roll-off in both photo-excitation and electro-injection luminescence at all exciton densities up to around 1020 cm-2 s-1. We attribute this suppression to a reduced exciton Bohr radius and exciton diffusion coefficient, as extracted from optical spectroscopy measurements. LEDs based on intercalated MoS2 and WS2 operate at maximum external quantum efficiencies of 0.02% and 0.78%, respectively, at a generation rate of around 1020 cm-2 s-1.
Light-emitting diodes with suppressed efficiency roll-off can be created by intercalating oxygen plasma into few-layer molybdenum disulfide and tungsten disulfide.