研究目的
Demonstrating an electrically driven polariton LED that operates at room temperature using monolayer tungsten disulfide (WS2) as the emissive material.
研究成果
The demonstration of room-temperature polariton EL from a vdW heterostructure embedded in a microcavity is an important step towards realizing electrically driven integrated microcavity light emitters using 2D vdW materials for potential applications as ultrafast LEDs and low threshold lasers.
研究不足
The presence of graphene in the cavity layer lowered the quality factor and the larger thickness of the cavity increased the mode volume, reducing the Rabi splitting compared to previous reports. The observed EQE is lower than that reported for similar tunnelling devices not confined to a cavity geometry, probably due to poor light extraction from the cavity.
1:Experimental Design and Method Selection:
The device consists of a 12-period bottom distributed Bragg reflector (DBR) and a 40 nm silver film acting as the bottom and top mirrors, respectively, of the microcavity. The active region includes a tunnel area and two more hBN-encapsulated monolayers of WS2 to increase the overall exciton density. A capping layer of PMMA is spin coated on the vdW heterostructure to tune the cavity mode.
2:Sample Selection and Data Sources:
Monolayer WS2, graphene, and multilayer hBN were exfoliated from bulk crystals and stacked using the polypropylene carbonate transfer technique.
3:List of Experimental Equipment and Materials:
A homemade spectroscopy set-up with a white light source and a laser for PL measurement, coupled with a Princeton Instruments monochromator with a PIXIS: 256 EMCCD camera. A ×100, 0.7 numerical aperture objective was used for all measurements.
4:7 numerical aperture objective was used for all measurements.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Angle-resolved spectra were recorded to ascertain the strong coupling regime. EL measurements were carried out under an external d.c. bias applied using a Keithley 2400 source meter.
5:Data Analysis Methods:
The Rabi splitting and cavity detuning were derived using a coupled oscillator mode fit to the EL experiment.
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