Small 2-D Material Has Big Potential

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.