This week researchers from the National University of Singapore (NUS) and the Singapore University of Technology and Design and Imperial College (SUTD) announced a significant stride towards more efficient optoelectronics.

A press release by NUS proclaims that a team of researchers has succeeded in enhancing the photoluminescence efficiency of the compound tungsten diselenide (WSe2).
Tungsten diselenide is a chemical compound used as a single-molecule (2D) semiconductor. It is identified as a transition metal dichalcogenide (TMDC) monolayer, which means that it is a functional semiconductor at only a single molecule thick. Because these semiconductors are so small, they are often known as 2D, or two-dimensional, semiconductors.

2D semiconductors have been gaining attention over the past several years for their ability to efficiently conduct electricity due to their direct band gap, much faster than silicon.

 

Stick-and-ball graphical representation of tungsten disulfide's lattice structure from above (left) and two views in profile (right) showing a single-molecule layer. Image courtesy of Nature Physics.

 

One obstacle to using TDMC monolayer semiconductors in electronics has been the limited amount of energy absorption that they are capable of. The team at NUS has taken steps to solving this problem by pairing tungsten diselenide with gold substrates on the nano level known as plasmonic nanostructures.

By combining the tungsten diselenide monolayers with these gold plasmonic substructures (which function as tiny trenches), the researchers found that its photoluminescence was up to 20,000 times its initial capacities.

The researchers, led by Physics Professor Andrew Wee and PhD candidate Wang Zhuo, pioneered this usage of gold plasmonic nanostructures as they combine with 2D semiconductors.

The team plans to continue their research by pairing the gold plasmonic nanostructures with other TMDC monolayers, such as molybdenum disulphide (MoS2).

Continuing research in 2D semiconductors will allow for more robust and far more compact optoelectronics.

Tungsten diselenide and molybdenum disulphide were combined in 2014 by researchers from the Vienna Institute of Research Technology to create a semiconductor structure that showed promise in solar cell technology. Tungsten diselenide is capable of turning light into electric energy and also of the reverse, but by combining it with molybdenum disulphide, the researchers were able to achieve these results in a much more compact manner.

 

Two semiconductor layers used in a solar cell layer system. Image courtesy of Phys.org.

 

At the end of last year, researchers from the Department of Energy’s Lawrence Berkeley National Laboratory embedded tungsten diselenide into a microdisk resonator, allowing for high-quality, visible excitonic lasing. This could allow for on-chip 2D applications for high-efficiency computing.

The uses of tungsten diselenide in future projects could span several industries. 

 

Comments

1 Comment


  • roderick young 2016-05-15

    Might be better to have a more 3-D picture of the lattice.  The picture shows an equal number of each kind of atom in the large matrix, belying the fact that there are actually two layers of sulfur.  Perhaps it would be useful to note that although sulfur is shown in the picture, selenium would have a similar structure.

    • Kate Smith 2016-05-15

      You’re absolutely right, Roderick. I’ve replaced the image and labeled it more thoroughly and accurately. Thanks very much for pointing that out. And thank you for the comment!