A room-temperature polariton light-emitting diode based on monolayer WS2

Abstract

Half-light half-matter quasiparticles termed exciton-polaritons arise through the strong coupling of excitons and cavity photons. They have been used to demonstrate a wide array of fundamental phenomena and potential applications ranging from Bose-Einstein like condensation 1-3 to analog Hamiltonian simulators 4,5 and chip-scale interferometers 6 . Recently the two dimensional transition metal dichalcogenides (TMDs) owing to their large exciton binding energies, oscillator strength and valley degree of freedom have emerged as a very attractive platform to realize exciton-polaritons at elevated temperatures 7 . Achieving electrical injection of polaritons is attractive both as a precursor to realizing electrically driven polariton lasers 8,9 as well as for high speed light-emitting diodes (LED) for communication systems 10 . Here we demonstrate an electrically driven polariton LED operating at room temperature using monolayer tungsten disulphide (WS2) as the emissive material. To realize this device, the monolayer WS2 is sandwiched between thin hexagonal boron nitride (hBN) tunnel barriers with graphene layers acting as the electrodes 11,12 . The entire tunnel LED structure is embedded inside a one-dimensional distributed Bragg reflector (DBR) based microcavity structure. The extracted external quantum efficiency is ~0.1% and is comparable to recent demonstrations of bulk organic 13 and carbon nanotube based polariton electroluminescence (EL) devices 14 . The possibility to realize electrically driven polariton LEDs in atomically thin semiconductors at room temperature presents a promising step towards achieving an inversionless electrically driven laser in these systems as well as for ultrafast microcavity LEDs using van der Waals materials.

Polariton panorama

“…The first polaritonic systems are also emerging and include QSs and networks for neuromorphic computers [416]. TMDC material WSe 2 integrated into microcavity devices acts as efficient light emitting device [417].…”

Engineering photonic environments for two-dimensional materials

“…(G) The schematic for the sample structure to study the strong interactions in polaron polaritons [146]. (H) The schematic for the sample device to realize the polariton LED in a monolayer WS 2 [147]. (I) A typical example of plasmonic cavity samples for the strong coupling in a monolayer WSe 2 [148].…”

“…As an example, a gating device could be embedded into the FP cavities to unravel the correlation between the strong coupling and carrier doping [145,146] and even reveal the strong interactions of polaron-polaritons with excessive carriers ( Figure 3G) [146]. In addition, FP cavities could be integrated with heterostructured 2D materials for LEDs as Figure 3H [147], opening up the possibilities of electrical pumping for these EPs. Indeed, FP cavities are the most straightforward and convenient option to research the strong coupling of 2D TMDs, and therefore prospect the most possibilities to realize striking phenomena and applications ahead, such as valley polariton Bose-Einstein condensation (BEC), electrically pumped EP laser and valleytronics devices [54,58,59].…”

Ultrafast Response of a Hybrid Device Based on Strongly Coupled Monolayer WS2and Photonic Crystals: The Effect of Photoinduced Coulombic Screening

“…[ 22,40,56–58 ] To date, strong coupling has been widely observed in various hybrid photonic devices consisting of TMDs and optical cavities of various shapes, including Fabry–Pérot (FP) cavities or distributed Bragg reflectors, [ 59,60 ] metallic nanoparticles, [ 61–66 ] and plasmonic arrays, [ 67–72 ] accompanied by alternative fascinating phenomena such as valley‐polarized exciton–polaritons [ 28,73–76 ] as well as polariton light‐emitting diodes. [ 77 ] Benefiting from the delocalized nature of their Bloch modes and their designable properties, photonic crystals (PhCs) are becoming an important platform for approaching the strong exciton–photon coupling regime with TMDs, [ 78 ] an approach that is regarded as flexible, practical, and ultracompact in on‐chip science.…”