Light-emitting diodes based on intercalated transition metal dichalcogenides with suppressed efficiency roll-off at high generation rates
摘要
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.