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Nanotechnology Boosts Solar Cell Performance
Posted by
Zonk
on Tue Aug 21, 2007 05:34 PM
from the two-great-tastes dept.
from the two-great-tastes dept.
Roland Piquepaille writes "Physicists from the University of Illinois at Urbana-Champaign (UIUC) say they have improved the performance of solar cells by 60 percent. And they obtained this spectacular result by using a very simple trick. They've coated the solar cells with a film of 1-nanometer thick silicon fluorescing nanoparticles. The researchers also said that this process could be easily incorporated into the manufacturing process of solar cells with very little additional cost. Read more for additional references and a photo of a researcher holding a silicon solar cell coated with a film of silicon nanoparticles."
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Oh no, it's Roland again! (Score:3, Insightful)
Re:Try reading the article. (Score:5, Interesting)
If he was just posting an article, with a link to the EurekAlert post, it'd be all good. Instead, he has to post about his spammy blog, as well as his (paid?) blog on ZDnet.
The ratio of decent links to spam is 1:2 in this article.
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Re:Try reading the article. (Score:5, Informative)
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Hmmm... How many other blogs and sites featured at Slashdot also have ads? Nearly ALL of them?
Don't make it right. (Score:2)
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If I went around ripping off the AP, I'd get a nastygram from their lawyers. Why do we tolerate it more when it's a creepy-looking Frenchman?
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Doesn't that describe slashdot pretty well?
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Re:Try reading the article. (Score:4, Funny)
I've asked that question after every Gerard Depardieu movie.
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So mark him down (Score:2)
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Re:Try reading the article. (Score:5, Informative)
That's a whole 12 characters shorter, and leaves out the important words 'in the ultraviolet spectrum', which changes the meaning completely. Also, those emitted words are 27 characters long, so if they were properly included, his summary is actually more wordy than the original source.
It's almost word for word. And it's wrong.
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Correction (Score:5, Informative)
The nanoparticles improve efficiency by 60% in the ultraviolet spectrum. The visible light spectrum is only nominally affected.
It's still pretty cool, though.
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Re:Correction (Score:4, Interesting)
As gas prices creep ever higher and coal plants become less and less desirable a partial conversion to solar power starts to become a very possible reality. Adding just one kilowatt worth of solar power to each of America's 116 million homes would reduce the power consumption almost 1/3rd. http://www.frugalfun.com/solarfest.html [frugalfun.com] The system to get "off the grid" discussed my link costs a fair amount of money, and even a 1 KW system costs $10,000 right now, but if the solar panels can suddenly cost 60% less (by being more efficient) then the price of a 1 KW system could reasonably drop to $5000. Not a huge cost when you are talking about much of todays housing market. Five grand is less than the price difference between a Prius (22K) and a Ford Focus (15K). Solar might well become widespread after all, not because it is efficient, but because everything else is slowly rising to match solar power's high initial cost.
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Let me give you an example why. I spend about $200 for a set of solar "RV" ventilation fans, but used them in a better way -- ventilating my attic continuously when the sun is up. Each fan has about a 1W cell, but they move a fairly substantial amount of air at about 60 degrees celsius OUT of the attic. I also have about a 15 W panel pumping into an underground pipe array for "geothermal" cooling and back to t
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I would guess that the future goal is to have solar cells be able to absorb every possible frequency of sunlight.
Re:Correction (Score:4, Funny)
As the alcohol evaporated, a film of closely packed nanoparticles was left firmly fastened to the solar cell.
Whoa, whoa, whoa! Back up, bad idea!
(yeah I know it's only isopropyl alcohol. but still never something you want to hear!)
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Re:Correction (Score:4, Insightful)
Whoa, whoa, whoa! Back up, bad idea!
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Re:Correction (Score:5, Funny)
He wasn't talking about the effect it might have on the environment. He was joking about "alcohol" as in booze being left out and undrunk long enough that it evaporated.
See, in a place like Ireland it's considered near criminal to waste ale or lager. So the thought of alcohol evaporating is a disturbing thought to most Irishmen and Irishwomen. It bothers them much like the thought of global warming bothers environmentalists.
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Still something (Score:5, Informative)
However, the downside is that photons with higher energy than that bandgap, well, the extra energy is essentially wasted.
So basically, say, if you used Germanium at 0.67 EV bandgap, you'd catch more photons than with Silicium at 1.11 EV bandgap, but get less useful energy (i.e., electricity as opposed to heat) out of each photon.
And the higher frequency the photon, the more you waste as heat. So you won't waste more in the visible spectrum (well, unless the photon had less energy than the bandgap, in which case it's completely wasted), but in the UV spectrum you waste a lot.
So reducing the waste in the UV spectrum is really where it counts the most. Sure, it would be neat to gain everywhere, but the UV range is where we waste the most.
Their talk about fluorescent particles, makes me think they're essentially converting an UV photon into at least one lower frequency photon. The question is what they do with the extra energy. At the simplest imaginable way, you'd get at least two low energy photons from one UV photon.
On the other hand, it seems to be a bit more than that, from that short summary linked to. From their claim that they improve voltage, not just current, and that something happens at the interface between the particles and the substrate, it sounds like essentially they created a bunch of new junctions there. I.e., that it's a new way to make a multi-junction solar cell.
Multi-junction cells aren't exactly new, but traditionally they've been very expensive so far. If these guys invented a cheap way to make one, kudos to them.
On yet another hand, it will be interesting to see on exactly what existing cells can their film be applied. On silicon or other semiconductors, ok, I can see how it would form an extra junction. Would it also work on, say, Dye-sensitized Solar Cells? There essentially their particles would come on top of the dye, and I'm not sure how well that works. It'll be interesting to find out, eventually.
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Voltage (Score:3, Interesting)
Can't you just increase the operating voltage to capture most of the extra energy? An electron moving across a larger voltage produces more energy. How large you can set the voltage depends on the energy in the electrons being knocked out — or am I missing something?
Re:Voltage (Score:4, Informative)
--
Get solar power: http://mdsolar.blogspot.com/2007/01/slashdot-user
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Silicon Nanoparticles (Score:3, Informative)
I am a graduate student working on the synthesis of silicon nanoparticles for solar cells and other applications. While silicon nanoparticles have been syntheszed for over 20 years, and their are many ways of synthesizing them, it is still very difficult to control the size of the particles. Unlike CdSe based quantum dots where the size of the particles is determined by how long y
Silicium? (Score:4, Funny)
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the cost of making PV panels is still too high compared to the energy you can harvest using them (I choose to use "harvest" specifically because they capture energy from the sun rather than generating from oil for example) over the expected lifetime of the panels. the other problem with PV panels is the environmental cost of manufacture + transport + ancillary electronics to make them useful an
Re:Correction (Score:5, Informative)
I'm not sure if you're talking about energy cost or economic cost, but either way you are wrong. Solar panels make up their production energy cost in a fraction of their design life, and they are competitive with most non-renewables even at todays cost let alone the expected cost of those sources over the design life of the panels.
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Re:Correction (Score:4, Insightful)
Having said that. I'm not a fan of the thin film PV that contain Cd (I don't use NiCd rechargeable's either). I know its not much, but its really nasty stuff.
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Re:Correction (Score:5, Interesting)
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This 60% UV is just ONE of the configs... (Score:5, Insightful)
It's still pretty cool, though.
This whole series of "only 60% of the UV part" threads is missing the rest of the article. That was just for ONE size of naonparticle, suitable for converting light to the middle of the visible range. They ran the tests for another size, suitable for converting to visible red, and got a higher conversion result, as expected.
Solar cells completely miss photons below the bandgap energy and only peel off the bandgap energy from those above it. They have a bandgap in the infrared so they get most photons, but only take that first 0.6 electron-volt chunk of their energy and lose the rest as heat. That's great if you have an infrared photon at 0.603 eV, not so hot for visible light photons at 1.8-3.1 eV, and pretty crummy for UV photons at 3.1 to 12 or so eV.
Films of nanoparticles have an interesting property: They absorb photons of various wavelengths and emit photons of particular wavelengths related to their size. But they don't do that in the solar-cell style of chopping the right-sized hunk off a more energetic photon and throwing the rest away. Instead they are able to combine energy from multiple lower-energy photons to generate one of the desired energy, chop several desired energy photons out of a high-energy one (and keep the leftover shavings to combine with others to make more desired-energy photons), and trade energy among their neighboring particles.
So it was expected that a film of nanoparticles on a solar cell would grab the energy from photons all over the spectrum, convert it to the energy characteristic of the nanoparticle size, and re-emit that. The improvement from efficiently salami-slicing and stacking photons should be better than losses from such things as emitting the photon in the wrong direction, giving a big boost to the cell.
And to some extent that was happening: Feed UV photons to nanoparticles that chunk 'em into something in the 3 eV range and you get more out of the UV hitting the cell than you would without the film - without appreciably affecting the output from the visible light. You're averaging about 1 2/3 IR photons worth of energy, instead of 1, for each incoming photon. Feed it to nanoparticles that chunk it up finer, down to 2 eV or so, and you get more out of your UV and also start improving on even visible light.
That's a good sign for doing what you really wanted to do: Use nanoparticles that emit just a tiny squidge above the solar-cell's bandgap, chunking all the photons into the right size for the cell and wasting very little of their energy. (But maybe still losing a bunch by emitting them in the wrong direction. That might be improved by putting the nanoparticles at the bottom of wells in the cell rather than on a flat surface.)
But the experiment produced a surprise: The VOLTAGE went up! WTF?
That means one of two things:
a) The nanoparticles affected the bandgap.
b) The nanoparticles coupled directly into the cell's "circuitry" in some non-obvious way.
b) might lead to something even better: Nanoparticles that capture the photons, chunk and stack them into some desired size (voltage), and deliver them directly to the wiring. That could get virtually ALL the incoming energy into your wires.
A solar cell with efficiencies in the
Hot DAMN!
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TiO2, UV, and Solar Cubes (Score:5, Interesting)
Glass typically blocks UV. Most glazings contain glass. If this only boosts (and 60%, while a large number, is still a tiny increment in efficiency) the UV efficiency then there may be limited use... unless you count concentrator applications.
The "Sun Cube" (http://www.treehugger.com/files/2007/04/sun_cube
Just some food for thought.
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Which matters how if it still takes up 1 m2 of roof space?
Concentrator systems leave me cold because of this. They concentrate (pardon the pun) on increasing the output per cm2 of solar cell - when the real need is to increase the output per m2 of roof space occupied. (The difference is subtle, but important.)
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60% more than ~0 is hardly very much (Score:4, Interesting)
So a conventional solar cell gets ~0 energy from this part of the spectrum, but if you coat it with this special coating, it gets 60% more! And how much is that exactly?
Now if you use a different coating (2.85nm), then it improves performance "in the visible part of the spectrum" by 10%. How much energy does a conventional solar cell get from just the visible part of the spectrum? Unspecified!
Cost (Score:3, Insightful)
How about something to make solar cheaper to purchase, so that the initial investment can be recouped before the expected replacement date?
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For example[1]: if you need one $15,000 super duper efficient unit, or 10 $1,500 electric shack bargain bin units, if the savings over the life of the unit is $10,000 the inital outlay is too expensive. This doesn't cover maintenance costs over the life of the unit(s), which would decrease the savings.
[1] costs illustrative only.
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OK. Zone refining of silicon is done in large quantities now at much lower energy usage and cost than before and the high qualitity single crystal silicon ingots are cut into large wafers that are used to make things like microprocessors and solar cells. Thanks to the huge demand for semiconductors silicon solar cells are nowhere near as expensive as they were in the 1960's. There are some that are not made t
Seems best suited for non-terrestrial uses (Score:5, Insightful)
With the main advantage being in the UV spectrum, it seems to me the best application would be to UV preferential cells in orbit or on Mars, Luna, etc.. Doubly so given the difficulty in shedding excess heat in Space.
Amazing. (Score:2)
UV light (Score:2)
Refreshing (Score:2)
Yes! (Score:3, Funny)
Satellite Use? (Score:2, Interesting)
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Oh FFS, what is it with /.ers and their "Why can't I buy it at Walmart yet?" comments?
Have you people never heard of research?
A lot of these stories are of lab demonstrations, or even just theoretical breakthroughs that MAY, one day, be developed to the point that they become useful. Or they may inspire further research that may lead to further research that may eventually be commercialised in a completely different form to how they were first demonstrated.
If you want to read about new ideas and devel
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