Breakthrough promises significantly more efficient solar cells

March 7, 2013
Breakthrough promises significantly more efficient solar cells

A new technique developed by U of T Engineering Professor Ted Sargent and his research group could lead to significantly more efficient solar cells, according to a recent paper published in the journal Nano Letters.

The paper, "Jointly-tuned plasmonic-excitonic using ," describes a new technique to improve efficiency in colloidal quantum dot photovoltaics, a technology which already promises inexpensive, more efficient . Quantum dot photovoltaics offers the potential for low-cost, large-area solar power – however these devices are not yet highly efficient in the infrared portion of the sun's spectrum, which is responsible for half of the sun's power that reaches the Earth.

The solution? Spectrally tuned, solution-processed plasmonic nanoparticles. These particles, the researchers say, provide unprecedented control over light's propagation and absorption.

The new technique developed by Sargent's group shows a possible 35 per cent increase in the technology's efficiency in the near-infrared spectral region, says co-author Dr. Susanna Thon. Overall, this could translate to an 11 per cent solar increase, she says, making quantum dot photovoltaics even more attractive as an alternative to current solar cell technologies.

"There are two advantages to colloidal ," Thon says. "First, they're much cheaper, so they reduce the cost of measured in cost per watt of power. But the main advantage is that by simply changing the size of the quantum dot, you can change its light-. Changing the size is very easy, and this size-tunability is a property shared by plasmonic materials: by changing the size of the plasmonic particles, we were able to overlap the absorption and scattering spectra of these two key classes of nanomaterials."

Sargent's group achieved the increased efficiency by embedding gold nanoshells directly into the quantum dot absorber film. Though gold is not usually thought of as an economical material, other, lower-cost metals can be used to implement the same concept proved by Thon and her co-workers.

She says the current research provides a proof of principle. "People have tried to do similar work but the problem has always been that the metal they use also absorbs some light and doesn't contribute to the photocurrent - so it's just lost light."

More work needs to be done, she adds. "We want to achieve more optimization, and we're also interested in looking at cheaper metals to build a better cell. We'd also like to better target where photons are absorbed in the cell – this is important photovoltaics because you want to absorb as many photons as you can as close to the charge collecting electrode as you possibly can."

The research is also important because it shows the potential of tuning nanomaterial properties to achieve a certain goal, says Paul Weiss, Director of the California NanoSystems Institute at the University of California, Los Angeles (UCLA).

"This work is a great example of fulfilling the promise of nanoscience and nanotechnology," Weiss says. "By developing the means to tune the properties of nanomaterials, Sargent and his co-workers have been able to make significant improvements in an important device function, namely capturing a broader range of the solar spectrum more effectively."

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4.3 / 5 (6) Mar 07, 2013
Yet another break through ......
2.5 / 5 (8) Mar 07, 2013
beat me to it.....i wish the wolf would actually show up.
1 / 5 (4) Mar 07, 2013
"collodial plasmonic particles" have large surface area, so they're doing the whole solar cell technology sensitive to photooxydation and degradation in humid air. Such inventions work well in lab for few weeks, but from long term perspective they're just salary generators for researchers involved without practical value.
2 / 5 (8) Mar 07, 2013
If scientists took all the "breakthroughs" I've read about in the last couple of years and put them together we should have 80 efficient solar cells by now available at wally world. It's always 10 years down the road though......
2.9 / 5 (8) Mar 07, 2013
Perhaps if they tried platinum plating the gold dots and placed them on a Rhodium substrate under a vapour deposited diamond glass front... Or they could power a stering engine by burning dolar bills.
2.3 / 5 (7) Mar 07, 2013
HoHum, whatever...when I see 5kw systems at Lowes for a couple of thousand, or less, dollars I will start believing some of these claims...
3.8 / 5 (4) Mar 07, 2013
The cost of solar panels has fallen dramatically in the past decade - falling from $1.81 per watt to $0.62 per watt in less than three years. http://cleantechn...-graphs/ The fall continues - and we should be looking at below $0.50 per watt shortly. Why are you guys not able to appreciate the amazing advances that have been made - all of which started in the lab. Today's breakthroughs translate to tomorrow's technology. You guys are so sad...
1.6 / 5 (8) Mar 07, 2013

None of those price changes are caused by new technology. That's caused by economy of scale and government subsidies.

EyeNStein has a point. Many of these supposed breakthroughs involve obscenely complicated processes, in many cases using Gold, Platinum, or some other precious metal, or a composite material with nanomaterial precision, in order to make it work...and there's no evidence they are going to market anyway.

The "Platinum plated gold dots" joke isn't far from the truth.
1 / 5 (6) Mar 07, 2013
Where do you get solar for 62 cents a watt?
I see plenty of news articles claiming that, but no one selling for that!
5 / 5 (1) Mar 07, 2013
It's similar to the problem with "Quadraphonic Audio". Several competing approaches, and the customer base waiting to see which one took over. Eventually, none of them did. In building automation, the same situation occurred with competing companies producing spectacular (sometimes) software which was compatable with nothing else. Eventually, a standard called BACNET was developed, and the competing manufacturers switched to it. I propose that it doesn't matter who develops what or what efficiency they're wringing out of it. What is important is that voltage and current standards be established and maintained to allow PV panels from anyone's technology to safely interconnect with anyone elses. This will encourage investment and installation; if "Sunlight Inc." wants to compete with "Brilliantcorp" for who is making the best/cheapest/most efficient PV, let'em, and more power to them. Or from them, as it were...
4.5 / 5 (2) Mar 08, 2013
None of those price changes are caused by new technology. That's caused by economy of scale and government subsidies

Not true Lurker - there is a lot of technological innovation going in to the process of reducing the cost of the panels. There is massive amounts of research going on - looking for more efficient ways to make the panels.
5 / 5 (2) Mar 08, 2013
Where do you get solar for 62 cents a watt?
I see plenty of news articles claiming that, but no one selling for that!

Well, how about 65 cents/watt? This is a spot price from Trina Solar as posted in this link:
The spot price is taken from this file:

The catch is that you have to buy megawatt quantities of the panels, and the price is only for the panels. The mounting hardware, wiring, and control systems cost extra.

For what it's worth, a 5 kw system, installed, can be purchased for under $15,000. Less than most new cars or trucks. And a lot less than a kitchen makeover... So you can skip buying the new wheels, pay for your solar in 3-5 years, and be done with your power bills.

As a bonus, the market value of you building will rise as conventional energy sources become more costly.

What's not to like about that?

3.3 / 5 (3) Mar 08, 2013
If scientists took all the "breakthroughs" I've read about in the last couple of years and put them together

That's not very logical, as many of the breakthroughs aren't complementary.

It's alo a matter of cost. Sure you can create very high efficiency solar cells, but they are enormously expensive (and hence only used in very special circumstances where their cost is not the predominant factor - like on spacecraft)

None of those price changes are caused by new technology.

Whut? Moving from expensive monocrystalline wafer solar cells to polycristalline isn't new technology? Thin film solar cells aren't new technology? The efficiency of commercially available cells at least doubling in the past 20 years (any type) isn't new technology?

What WOULD be new technology in your book?
1 / 5 (5) Mar 08, 2013
Useful new Tech = Any advance that will make PV panels pay for their installation in under 5 years without needing subsidies. (Over subsidisation means that more energy is expended making the cells than they EVER recover.)
1 / 5 (5) Mar 08, 2013
The cost of solar panels has fallen dramatically in the past decade - falling from $1.81 per watt to $0.62 per watt in less than three years
Note that these solar panels don't use any innovations, proposed for solar cells in last twenty years from good reason - they would make these panels less stable and more expensive.
1 / 5 (3) Mar 10, 2013
The problem with technological advances and media is that the media reports everything as a break through, while it may be a break through, it does not have direct bearing on the consumer in its break through form. People have to realize this and look at things like Wikipedia which gives a view of the overall trend of developments over the last 50 years. It will probably be another 10 years before solar reaches a point at which it can compete with coal for price without subsidies. This does NOT mean we should invest in it. ON the contrary we should. It's necessary for the future. At the same time we should be investing in other technologies like LFTR's which I heavily promote as being part of balanced solution which is required to eliminate CO2 from the output of the US and the world. Go to and look over my extensive library about LFTR reactors, Air Carbon Capture, paying for conversion from Coal to LFTR reactors without taxation and much more.

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