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Researchers develop cheap and easy to mass-produce "solar-paint"

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December 21, 2011

Mixtures using cadmium sulfide produced yellow paint, cadmium selenide produced dark brown...

Mixtures using cadmium sulfide produced yellow paint, cadmium selenide produced dark brown, while a mixture of the two - which offered the best conversion efficiency - was light brown (Photo: ACS Nano)

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A team of researchers from the University of Notre Dame in Indiana is reporting the creation of a "solar paint" that could mark an important milestone on the road to widespread implementation of renewable energy technology. Although the new material is still a long way off the conversion efficiencies of commercial silicon solar cells, the researchers say it is cheap to make and can be produced in large quantities.

In an effort to find an alternative to silicon-based solar cells, the Notre Dame researchers turned to quantum dot materials. They started with nanoparticles of titanium dioxide (TiO2) and coated them with either cadmium sulfide or cadmium selenide - both compounds that can absorb photons. A photon of the right energy hitting the cadmium compounds causes an electron to escape, which is absorbed by the TiO2.

The resultant particles were then suspended in a water-alcohol mixture to create a paste. The cadmium sulfide mixture produced a yellow paste, while the cadmium selenide mix produced a dark brown. The most efficient was a mixture of the two that produced a light brown paste.

Titanium dioxide nanoparticles coated with cadmium sulfide produced a yellow paste that, w...

When the paste was brushed onto a transparent conducting material and exposed to light, it created electricity. To replenish the electrons lost by the cadmium and test the conversion efficiency of the paint-on electrode, cathodes made from other materials and additional compounds were used.

"The best light-to-energy conversion efficiency we've reached so far is 1 percent, which is well behind the usual 10 to 15 percent efficiency of commercial silicon solar cells," explains Prashant Kamat, an investigator in Notre Dame's Center for Nano Science and Technology (NDnano). "But this paint can be made cheaply and in large quantities. If we can improve the efficiency somewhat, we may be able to make a real difference in meeting energy needs in the future."

Kama and his team have christened the new paint "Sun-Believable" and plan to study ways to increase its conversion efficiency and improve its stability. The Notre Dame team's paper is published in the journal ACS Nano.

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
11 Comments

Cadmium is highly toxic. I truly hope this never reaches production phase...

Bart Viaene
21st December, 2011 @ 10:23 pm PST

Same concern as Bart Viaene. Cadmium is very toxic. It is in the same family as zinc though. Maybe zinc would work? Zinc selenide is also a colored compound, so my guess is that it would maybe work...

Frank191
22nd December, 2011 @ 06:58 am PST

cadmium may be highly toxic, but is cadmium sulphide? after all chlorine and sodium are extremely dangerous as well, but you still put them on your chips in the form of sodium chloride. Lets not confuse elements and compounds composed of those elements, the chemical properties may be completely different

Michael1986
22nd December, 2011 @ 07:19 am PST

I'm trying to think what 'transparent conducting materials' they may be talking about.

I got nothin' here.

Larry Hooten
22nd December, 2011 @ 09:34 am PST

Sweet. If they can get efficiency up to even 3% at about the same cost and durability of current paints, it would be well worth it to paint houses and roofs with this. If I have 5x the surface area facing the sun as I do with a PV panel, then I've effectively got the equivalent of a solar-tracking 15% efficient solar panel for a pittance.

Heck, put up a picket fence and paint that....

Tysto
22nd December, 2011 @ 12:22 pm PST

The dawn is drawing near when we will have the ability to de-centralize the power grid and break our dependence on fossil fuels. These breakthroughs will free our debt based money system from the con game of OPEC too. We will also be freed from the maniacs enslaving all of us into fighting their wars of resources and oil commodities. We are literally being drowned by the filthy oil politics and pollution of fossil fuels. It is high time we push the fossils, politicians and their ilk included, back into the ground, and bask in the glorious warmth and cleansing properties of the sun.

zackzelmo
22nd December, 2011 @ 12:48 pm PST

Cadmium sulfide is very toxic. I am not so gung ho about this development. cadmium pigments also lacks stability. I wonder if there is a corelation between the lack of stability and the reactivity to light. I suppose that it might be appropriate for certain types of instalations. The reactivity also seems like a terrible thing for a paint to have. Soon, it will turn into a flaky, toxic mess. Cadmium pigments in oil last pretty well, but even those are not fully light fast.

Jonathon Sauer
22nd December, 2011 @ 04:47 pm PST

Has anybody tried Cadmium Arsenide? It may have better results, please inform me of any developments.

Saul Abundo Sr.
28th December, 2011 @ 06:26 pm PST

As a developmental stage in proof-of-concept for a generative paint, this is very promising, the toxicity and stability notwithstanding- since these are quantum dots, the actual level of Cd can be miniscule, and encapsulation can minimize leaching and maximize stability. The CdAs idea is worthwhile pursuing, and I can readily see SoS at the nano level as an alternate material for examination, as Si is relatively innocuous, although that wasn't the original empiric justification.

Thierry M Phillips
2nd January, 2012 @ 08:00 am PST

Toxic? Mcdonalds is toxic. Dont smoke it and you'll be fine.

Brainfarth
6th January, 2012 @ 12:27 pm PST

How has this been coming along? Great tech and a 2 year old article? Have they had any advances? Will it be put into production yet?

Bmak1225
1st July, 2013 @ 01:36 am PDT
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