Small 2-D Material Has Big Potential
CAMBRIDGE, Mass., March 14, 2014 — Although small and just a few atoms thick, a new material has big possibilities for the field of optoelectronics.
A 2-D material called tungsten diselenide (WSe2), which could potentially manipulate light and electricity interactions, has already demonstrated improved efficiency and spectral properties in a variety of applications, including lighting, displays, optical interconnects, logics and sensors.
Researchers from MIT say this novel material could also lead to the creation of ultrathin, lightweight, flexible photovoltaic cells, enhanced LEDs and other optoelectronic devices.
Researchers supplied electricity to a small piece of tungsten selenide through two gold wires, causing it to emit light and demonstrate its potential as an LED material. Courtesy of MIT.
The team produced working diodes using the WSe2 material, which was electrically doped, half n-type and half p-type. In turn, basic optoelectronic devices (photodetectors, photovoltaic cells and LEDs) can be produced.
Electroluminescence is a factor, the researchers said, and has been observed from existing 2-D MoS2 devices already. However, it has low efficiency and broad linewidth, as MoS2 has poor optical quality.
This recent study has found electroluminescence from lateral p-n junctions in the 2-D WSe2, which touts a high optical quality. It was induced electrostatically using a thin boron nitride support as a dielectric layer with multiple metal gates beneath.
The structure allows effective injection of electrons and holes. Combined with the high optical quality of WSe2, it yields bright electroluminescence with 1,000-times-smaller injection current and 10-times-smaller linewidth than in MoS2.
This system has the necessary components for development of new types of optoelectronic devices, such as spin- and valley-polarized LEDs, on-chip lasers, and 2-D electro-optic modulators, the researchers said. They noted that it could also be possible to use the WSe2 material for solar cell or display devices, which could then be used in windows on buildings or vehicles, or even clothing.
The work was supported by the U.S. Office of Naval Research Packard fellowship and a Pappalardo fellowship. It was published in Nature Nanotechnology.
For more information, visit: www.web.mit.edu.
- The nonthermal conversion of electrical energy into light in a liquid or solid substance. The photon emission resulting from electron-hole recombination in a PN junction is one example. This is the mechanism employed by the injection laser.
- A sub-field of photonics that pertains to an electronic device that responds to optical power, emits or modifies optical radiation, or utilizes optical radiation for its internal operation. Any device that functions as an electrical-to-optical or optical-to-electrical transducer. Electro-optic often is used erroneously as a synonym.
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