News
New technology could capture solar energy now wasted
time: 2011-12-21  chick£º[2918] ´Î

Existing silicon solar panels harvest light from the visible part of the spectrum, and their efficiency is improving, but much of the sun¡¯s energy that reaches Earth comes in the form of infrared energy.

Wouldn¡¯t it be grand if we could find a way to harvest this lost energy? It could go a long way toward making solar energy competitive with other energy sources, such as coal and natural gas.

 

A new discovery described in the journal Science (see abstract) by local researchers brings us closer to this goal. The Rice University scientists appear to have discovered a way to create tiny antennas out of silicon that capture infrared light.

It comes from the lab of Naomi Halas, who did some of the early and critical work with nanoshells. Her primary focus now is on the emerging field of plasmonics, a complex field that might imperfectly be described as the behavior of light at the nanoscale.

I caught up with Halas to get the scoop on her new paper.

What are nanoscale antennas? Are they at all like a very, very tiny radio antenna that picks up light waves?

Nanoscale antennas are remarkably similar to radio frequency antennas. Since radio waves are large, antennas that detect them are also large, on the same size scale as the wavelength of the wave. Because optical frequencies have wavelengths that are more than a million times smaller than radio waves, the antennas that detect them are more than a million times smaller too.

As I understand it, these antennas might be attached to existing solar cells to capture infrared light and convert it to energy, is that correct? If so, what must still be tested to see if this will work?

They can¡¯t be attached to existing solar panels as is, but close: they would need to be incorporated into the manufacturing of the solar cell as it is being made, in order to deliver additional current to the existing circuit. We still have a way to go with optimizing our current design for increased efficiency, but the principle should work.

Theoretically how much might a nanoscale antenna improve existing silicon solar cells?

Approximately 1/3 of the solar spectrum incident on a silicon solar cell are infrared wavelengths that the cell cannot use to convert to electricity.  We would be able to harvest a fraction of this currently unused part of the solar spectrum, which means an automatic increase in efficiency.

Are the materials and processes used to make your antennas costly?

In the research lab, we use gold to make our antennas, and precise nanoscale lithographic patterning to make them the right size.  For commercialization one would move both to lower-cost metals and to inexpensive, large-area patterning processes.  There are highly promising strategies for both.

Were you actively searching for a way to capture infrared light, or something else entirely?

No we were not.  This is an excellent example of how basic research can have important payoffs for technologies that can benefit society.  We were actually designing a device that would allow us to detect ¡°hot electrons¡± that are generated when you excite the current in an optical nanoantenna.  Once we figured out a way to detect hot electons directly, we realized that this method could greatly improve the way that we harvest infrared light, in a variety of different types of devices from solar cells to infrared imaging detectors.

retrun    print
ÕãICP±¸ 03052623 ºÅ    © Copyright 2009-2012 Zhejiang Xinyuan Lighting Co., Ltd All Rights Reserved Design By:nbsms