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Research: Waveguide tapers boost thin-film solar cells

Posted: 02 Apr 2014 ?? ?Print Version ?Bookmark and Share

Keywords:University at Buffalo? solar cell? waveguide taper? microchip?

A team of scientists at the University at Buffalo has created a multilayered waveguide taper array that claims to improve the ability to trap and absorb light. According to them, the nanoscale microchip component promises to advance the performance of thin-film solar cell technology.

The work explores the use of waveguide tapers to slow and ultimately absorb each frequency of light at different places vertically to catch a 'rainbow' of wavelengths, or broadband light.

We previously predicted the multilayered waveguide tapers would more efficiently absorb light, and now we've proved it with these experiments, explained lead researcher Qiaoqiang Gan, PhD, UB assistant professor of electrical engineering. This advancement could prove invaluable for thin-film solar technology, as well as recycling waste thermal energy that is a by-product of industry and everyday electronic devices such as smartphones and laptops.

Each multilayered waveguide taper is made of ultrathin layers of metal, semiconductors and/or insulators. The tapers absorb light in metal dielectric layer pairs, the so-called hyperbolic metamaterial. By adjusting the thickness of the layers and other geometric parameters, the tapers can be tuned to different frequencies including visible, near-infrared, mid-infrared, terahertz and microwaves.

The structure could lead to advancements in a number of applications.

The multilayered waveguide taper array could improve thin-film photovoltaic cells, which are less expensive and more flexible than traditional solar cells, noted the researchers.

The drawback with thin-film solar cells is that they do not absorb as much light as traditional cells. Because the multilayered waveguide taper structure array can efficiently absorb the visible spectrum, as well as the infrared spectrum, it could potentially boost the amount of energy that thin-film solar cells generate.

In the field of on-chip optical communications there is the crosstalk phenomenon, in which an optical signal transmitted on one waveguide channel creates an undesired scattering or coupling effect on another waveguide channel. The multilayered waveguide taper structure array could potentially prevent crosstalk.

The multilayered waveguide taper array could help recycle waste heat generated by power plants and other industrial processes, as well as electronic devices such as televisions, smartphones and laptop computers.

It could be useful as an ultra compact thermal-absorption, collection and liberation device in the mid-infrared spectrum, said Dengxin Ji, a PhD student in Gans lab and first author of the paper.

It could even be used as a stealth, or cloaking, material for airplanes, ships and other vehicles to avoid radar, sonar, infrared and other forms of detection. The multilayered waveguide tapers can be scaled up to tune the absorption band to a lower frequency domain and absorb microwaves efficiently, added Haomin Song, another PhD student in Gans lab and the papers second author.

- Paul Buckley
??EE Times Europe

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