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carbon nanotube  (Source:
Nanotubes concentrate solar energy 100 times more and can be used for a variety of applications

MIT chemical engineers have developed a way to concentrate solar energy 100 times more than a traditional photovoltaic cell through the use of carbon nanotubes. 

Jae-Hee Han, postdoctoral associate and lead author; Geraldine Paulus, graduate student and lead author; and Michael Strano, leader of the research team have devised a way to use carbon nanotubes (hollow tubes of carbon atoms) to form antennas that capture and focus light energy, resulting in more powerful and smaller solar arrays. 

"Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antenna's that would drive photons into them," said Strano. 

Traditional solar panels convert photons into an electric current to generate electricity, but with the use of the nanotube antenna, the number of photons being captured increases and light is transformed into energy that can be funneled into the solar cell. 

These new antenna's are called "solar funnels," and can be used in various other applications such as telescopes or night-vision goggles, where light needs to be concentrated. They contain a fibrous rope that is 10 micrometers long and four micrometers thick, and consist of 30 million carbon nanotubes. The fiber is made up of two layers of nanotubes with different bandgaps, which is the difference in energy levels between an electron and the hole it leaves behind. When photons strike a surface, this excites the electron to a higher degree depending on the material, and interactions between the electron and the hole it leaves behind is an exciton.

The outer layer of the nanotubes have a higher bandgap while the inner layer has a lower bandgap, and the excitons flow from the higher to lower energy. When light strikes the material, the excitons become more concentrated, flowing to the center of the fiber. 

What makes this study such a significant advancement is that it's the first to construct nanotube fibers where the properties of different layers can be controlled. Costs of carbon nanotubes originally prohibited this kind of experimentation, but prices have fallen and made the nanotubes more accessible. 

The next step is to build a photovoltaic device using the antenna, where the antenna would concentrate photons before they are converted into an electrical current by the photovoltaic cell. The antenna would be constructed around a core of semiconducting material and the system would generate electricity by separating the electron from the hole and collecting electrons at one electrode on the inner semiconductor and collecting holes at the other electrode touching the nanotubes. 

The research team is also looking to increase the number of excitons per photon, and to decrease the energy lost as excitons "flow through the fiber."

This study was published in Nature Materials on September 12. 

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Small Detail
By GruntboyX on 9/14/2010 7:28:16 AM , Rating: 2
Great news... However is it manufacturable? My understanding is carbon nano-tubes are still very expensive to produce and can only be synthesized in a lab environment.

Right now they created something, for all intensive purposes, from a unobtainium.

RE: Small Detail
By Kiffberet on 9/14/2010 8:45:23 AM , Rating: 2
If they used unobtanium, the solar panels would float above your house as well...

RE: Small Detail
By TSS on 9/14/2010 9:39:10 AM , Rating: 3
It'd be silly to wait for prices to drop to develop uses that take advantage of a lower price. As developing takes time, it's better to be ahead of the curve then behind it.

RE: Small Detail
By Ammohunt on 9/14/2010 2:39:47 PM , Rating: 4
I look forward to consumer products using this tech in 2041 by then I will be retired and won't give a damn.

Great news
By TechIsGr8 on 9/14/2010 11:33:06 AM , Rating: 1
China will be so happy we found another way for them to make more money. The USA can't be bothered with making this crap here. Now, let me get back to my job as Walmart greeter.

RE: Great news
By FITCamaro on 9/14/2010 12:17:07 PM , Rating: 2
Well it involves carbon so clearly its evil and needs heavy taxes on it. So yeah pretty much.

The only industrial jobs that are good anymore are those which are the direct result of government initiatives. Wind turbines, solar cells, batteries, and the like. Of course globally most of those are built in China.

RE: Great news
By Kurz on 9/15/2010 8:37:42 AM , Rating: 2
You should definitely look why we need those inscentives.
A clue they are the some of the biggest pricks in the world.

Solar cells DO NOT CONCENTRATE light!
By SolarDon on 9/15/2010 4:38:14 PM , Rating: 2
It may be nice to actually know a little bit about what you are reporting on!! Solar cells do not concentrate light. Typically there are optics the direct concentrated light to the solar cell like Sol Focus ( or Amonix ( or in the case of a Rainbow Concentrator will separate and concentrate the light like Sol Solution (

Using carbon nanotubes in solar energy is so ridiculously expensive that it is laughable.

By fic2 on 9/16/2010 12:51:40 PM , Rating: 2
When solar cell research began it was so ridiculously expensive that it was laughable. Now solar is just laughably expensive.

That's odd...
By chagrinnin on 9/14/2010 9:13:41 AM , Rating: 2
...and the hole it leaves behind is an exciton.

...I always get my exciton over the hole I'm about to enter. :P

Bye :)
By Akdor 1154 on 9/14/2010 1:05:12 PM , Rating: 1
I'm sorry, but the standard of English in this article would not pass a first year science lab report.
Goodbye DT, I'm going back to Ars.

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