Koray Aydin, a new assistant professor of electrical engineering and computer science at the McCormick School at Northwestern University, has developed a new material that absorbs a wide range of wavelengths and could lead to more efficient and less expensive solar technology.

The paper published in Nature Communications entitled, ‘Broadband Polarization-Independent Resonant Light Absorption Using Ultrathin Plasmonic Super Absorbers’ says in the abstract, “Our super absorber yields broadband and polarization-independent resonant light absorption over the entire visible spectrum (400–700 nm) with an average measured absorption of 0.71 and simulated absorption of 0.85.”

That’s right – the claim is the entire visible spectrum leaving some infrared and ultraviolet yet to be gathered.

Aydin explains, “The solar spectrum is not like a laser – it’s very broadband, starting with UV and going up to near-infrared. To capture this light most efficiently, a solar cell needs to have a broadband response. This design allows us to achieve that.”

Solar cells are only as efficient as the amount of sunlight they collect.  Collect a small percent and the efficiency is a small percent.  Collect a larger percent and the efficiency rockets up.

Light Absorption Grate. Click image for more info.

Aydin and his team used two unconventional materials, metal and silicon oxide – to create thin but complex, trapezoid-shaped metal gratings on the nanoscale that can trap a wider range of visible light. The use of these materials is unusual because on their own, they do not absorb light; however, they worked together on the nanoscale to achieve very high absorption rates

The uniquely shaped grating captured a wide range of wavelengths due to the local optical resonances, causing light to spend more time inside the material until it gets absorbed. This composite metamaterial was also able to collect light from many different angles – a useful quality when dealing with sunlight, which hits solar cells at different angles as sun moves from east to west throughout the day.

The catch is as Aydin explains, is the research is not directly applicable to solar cell technology because metal and silicon oxide cannot convert light to electricity. In fact, the photons are converted to heat and might allow novel ways to control the heat flow at the nanoscale. However, the innovative trapezoid shape could be replicated in semiconducting materials that could be used in solar cells.

But, if the geometry and technique can be applied to semiconducting materials, the technology could lead to thinner, lower-cost, and more efficient solar cells.  Aydin thinks it can be done.

Aydin has taken light physics and materials chemistry together to control light absorption and refraction at the nanoscale with an impressive result.  Collecting all the visible light is a significant achievement with materials that seem to be likely to make the transition to the solar cell research area.

Solar electrical generation is in a low spot with a certain widely publicized bankruptcy dragging down a business that is intermittent in performance and very difficult to make completive with things a simple as thermal solar.  The industry needs a shot of innovation and the Aydin’s team at Northwestern might have the answer for the industry and the energy independence minded consumer.


3 Comments so far

  1. Al Fin on November 3, 2011 7:48 AM

    Very interesting technology, and useful in its own light.

    In many ways, heat is a more useful and workable form of energy than electricity, on a local scale.

  2. Unconventional Approaches to Solar Energy Capture | RefineryNews.com on November 11, 2011 11:19 PM

    […] Another type of plasmonic super-absorption device comes from Northwestern U. Brian Westenhaus has more. […]

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