Nanotechnology Boosts Solar Cell Performance

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."

Re:Try reading the article.

[Baddas]

It only bothers me because he linkjacks it with his blog.

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.

TiO2, UV, and Solar Cubes

[purduephotog]

While at Purdue one of my friends worked on a process to increase solar cell efficiency by etching TiO2 coatings into long, thin whiskers that helped 'whisk' photons down into the surface of the material. It basically doubled the efficiency of a 3% cell in the visible range. Solar hasn't taken off.

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_ by_gre_1.php [treehugger.com] uses lenses to concentrate light onto small, very efficient space-grade solar panels. Each panel (if memory serves) was on the order of 1 sqcm, allowing these very expensive but very efficient (25%+) panels to be used. The overall effect was to to take 1 m2 down to 10 sqcm of chips.. and yet have the power output be about the same. Combine that concentrator technology with higher utilization of UV bands AND ultra-efficient space grade panels and you've got a winner (concentrators work ONLY in direct sun- no clouds).

Just some food for thought.

Re:Correction

[sl70]

Yeah, but the efficiency is so low to start with, anyway, that increasing it by 60% may not make much of a difference. Amorphous silicon cells have an efficiency of about 6%. Increase that by 60% and we get ... 9.6%! Nothing to write home about.

60% more than ~0 is hardly very much

[Chalex]

So I RTFA, and here's the bit: "improves power performance by 60 percent in the ultraviolet range of the spectrum" and "in conventional solar cells, ultraviolet light is either filtered out or absorbed by the silicon and converted into potentially damaging heat, not electricity."

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!

Re:Correction

[hedwards]

That's correct, but what you failed to note is that the UV spectrum contains a much larger amount of energy than either the visible or the infrared spectra do. Shorter wavelength, higher energy. And the higher energy particles are the ones that are the most desirable anyways.

Re:Correction

[Original Replica]

9.6%! Nothing to write home about.

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.

Voltage

[benhocking]

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.

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:Correction

[IConrad01]

A 60% increase in photovoltaic conversion efficiency -- assuming the process as a $0.00 cost, which it will not -- that would represent a roughly 37.5% reduction in cost. Given that this process is, as yet, not self-assembling, the cost is likely to be well into the thousands as-is -- precision alignment of forcibly assembled nanoparticles is expensive ; then you also have to consider the durability issues and the like; any medium of protection for the coating, in the interests of durability for anything resembling a reasonable life-span, will likely again further increase costs. All in all, this is not a solution. We're likely to get more out of the use of self-assembling chlorophyll-based photovoltaic polymers.

Re:now what to do

[ILuvRamen]

but wait, I drive a Mercury so that counts too lol. But seriously, look on ebay for 150-200 watt solar panels. They're not very large, only about five and a half by three and a half feet. I found a 200 watt one that exact size that claims 12.6% module conversion efficiency which I think isn't so good but let's say this one gets the added bonus from the nano-layer and gets up to like 300 watts. So with a transformer or whatever to get it down to 12 volts from 30-ish volts, that's 25 amps it's putting out in the best sunlight. And my battery charger can charge an entire average car battery in 2 hours at 6 amps and 12 volts. So parked outside of work for 8 hours with a solar panel the size of the roof, hood, and trunk of my car (i.e. 3x the one mentioned above), I could charge empty to full a hybrid car battery with such a large capacity that none like it even exist yet. It'd be somewhere in the neighborhood of like a 600 amp hour battery charged from empty to full, which is about 25x the capacity of a normal car battery I think

Satellite Use?

[Yehooti]

If we could shed about 60% of the solar panels on our space vehicles, that would be a tremendous boost in our ability to launch neat stuff cheaper. The question that comes up though is, how well will this new coating survive the rigors of the space environment? If it degrades faster than our current choice then we probably cannot qualify it as a replacement for our current cells. Until that question is addressed, flown and tested, this remains as only a neat future potential. Space drives the race.

Re:Correction

[CodeShark]

That's because a 1 KW system in silicon is silly expensive, not to mention a poor use of "juice".

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 the house -- so I have a total of about 20W providing literally many KW of cooling.

Once I have time I build a test rig for at least one of the attic fans out to pump it's share of hot air through an insulated water /radiator panel -- and build the interface to function right through the same hole in the roof -- and watch my hot water bill go way down.

Net investment? Maybe $500.