| New Material Can Absorb More Infrared, Increase Solar Efficiency |
| Written by Jaymi Heimbuch | ||
| Tuesday, 05 August 2008 | ||
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The new material provides a “stepping-stone” for electrons to move from a low energy level to an intermediate energy level as they absorb photons, allowing more photons of lower energy levels (and thus different parts of the light spectrum) to be utilized. So while some efficiency research goes into breaking down what is absorbed into specific wavelengths or trapping light for greater absorption, this technology basically helps to cast a really wide net to increase how much light can be captured and turned into energy. The new material hasn’t been tested yet for just how much it can gather, but it has a theoretical absorption rate of 63% so the scientists reason that the actual absorption will be higher than conventional semiconductor solar cells. This is a step up from the first “stepping-stone” solar cells that achieved a theoretical capture rate of 57%. In geek-speak: Calculations for indium thiospinel semiconductors substituted at octahedral sites with isolated transition metals (M=Ti,V) show an isolated partially filled narrow band containing three t2g-type states per M atom inside the usual semiconductor band gap. Thanks to this electronic structure feature, these materials will allow the absorption of photons with energy below the band gap, in addition to the normal light absorption of a semiconductor... leading to an enhancement of the absorption coefficient in both infrared and visible ranges of the solar spectrum. This electronic structure feature could be applied for developing a new third-generation photovoltaic cell. So, the early versions of the materials match the properties predicted by the researchers to enable it to absorb infrared. Now we just have to wait for the material to be turned into an actual solar cell so we can know just what the size of this improvement is. Via TreeHugger, New Scientist, Physical Review Letters; photo via vogelium
Comments
(7)
The Next Level
written by Sustainable Home Design , August 05, 2008
I agree
written by Clinch , August 05, 2008
This is good, and I like hearing stories like this, but the link to the 57% capture rate cell was from 2004! And there hasn't been any news on that since then, does this mean that in 4 years time, this new material will just be gathering dust in the back of some laboratory?
I really hope not. And I'm also curious about the cost of this as well, efficiency is great, but if it's not affordable, then it wont be successful (possibly the problem the 57% from 2004 had)
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written by check your facts , August 05, 2008
Learn how to copy guys:
http://technology.newscientist.com/channel/tech/dn14436-solarcell-material-can-soak-up-more-sun.html?feedId=online-news_rss20 at least they give a link to the original research, which you fail to provide (at least mention who'd done it). Also solar cells don't have a maximum theoretical efficiency of 40%. A single bandgap material is limited to just above 30%, and you could go up to ~ 80% with an infinite number of gaps. In any case 40% has already been experimentally demonstrated in three junction cells.
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written by check your facts , August 05, 2008
oh and one more thing - I am not sure how you are defining ultraviolet or infrared, but here is how solar energy is distributed. it is even color coded. Silicon solar cells absorb up to 1.1 micron wavelengths (so infrared or near infrared if you want to call it that):
http://www.lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html
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written by Karkus , August 06, 2008
Check you facts is correct. Your post contains MANY errors and just doesn't make much sense.
Please remove it and just provide a link to the original article. Here's some of the other issues. 1) The materials used by these guys are still semiconductors. They just modify the semiconductor material by adding dopants. 2)The problems isn't necessary the low absorption rate of semiconductors (for example, low bandgap semiconductors actually absorb almost all the photons.) So the main issue is not % absorption, but rather how much of the energy you can turn into useable eletrical energy. That depends on the bandgap, and there's a tradeoff between not absorbing photons with energy below the bandgap vs. wasting excess energy off photons with energy above the bandgap. This research is one way to try to get around this tradeoff.
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written by Karkus , August 06, 2008
In addition to the many problems with paragraph 3, the first sentence has issues too. Some semiconductors absorb just fine in the IR, and they also absorb the photons in the visible and UV - but then most of that energy gets wasted as heat. (Silicon actually absorbs part of the IR spectrum). Then there are other semiconductors that absorb only UV (such as TiO2) but then the visible and IR photons don't get absorbed.
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written by NS , August 06, 2008
The issue here is the efficiency of the conversion of the absorbed energy into work. While generation of intermediate energy levels via metal doping is an interesting development, the more difficult problem is coupling the energy released as the material relaxes back down to the ground state, into useful energy that can be used to perform work. Just because a state exists does not mean it is easily coupled.
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Charles Precht
Sustainable Design
www.sustainablehomeplans.com