New technique offers spray-on solar power

December 5, 2014
Credit: University of Toronto

Pretty soon, powering your tablet could be as simple as wrapping it in cling wrap.

That's Illan Kramer's hope. Kramer and colleagues have just invented a new way to spray solar cells onto flexible surfaces using miniscule light-sensitive materials known as colloidal quantum dots (CQDs)—a major step toward making spray-on solar cells easy and cheap to manufacture.

"My dream is that one day you'll have two technicians with Ghostbusters backpacks come to your house and spray your roof," says Kramer, a post-doctoral fellow with The Edward S. Rogers Sr. Department of Electrical & Computer Engineering at the University of Toronto and IBM Canada's Research and Development Centre.

Solar-sensitive CQDs printed onto a flexible film could be used to coat all kinds of weirdly shaped surfaces, from patio furniture to an airplane's wing. A surface the size of your car's roof wrapped with CQD-coated film would produce enough energy to power three 100-Watt light bulbs—or 24 compact fluorescents.

He calls his system sprayLD, a play on the manufacturing process called ALD, short for atomic layer deposition, in which materials are laid down on a surface one atom-thickness at a time.

Until now, it was only possible to incorporate light-sensitive CQDs onto surfaces through batch processing—an inefficient, slow and expensive assembly-line approach to chemical coating. SprayLD blasts a liquid containing CQDs directly onto flexible surfaces, such as film or plastic, like printing a newspaper by applying ink onto a roll of paper. This roll-to-roll coating method makes incorporating into existing manufacturing processes much simpler. In two recent papers in the journals Advanced Materials and Applied Physics Letters, Kramer showed that the sprayLD method can be used on flexible materials without any major loss in solar-cell efficiency.

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Kramer built his sprayLD device using parts that are readily available and rather affordable—he sourced a spray nozzle used in steel mills to cool steel with a fine mist of water, and a few regular air brushes from an art store.

"This is something you can build in a Junkyard Wars fashion, which is basically how we did it," says Kramer. "We think of this as a no-compromise solution for shifting from to roll-to-roll."

"As quantum dot solar technology advances rapidly in performance, it's important to determine how to scale them and make this new class of solar technologies manufacturable," said Professor Ted Sargent, vice dean, research in the Faculty of Applied Science & Engineering at University of Toronto and Kramer's supervisor. "We were thrilled when this attractively manufacturable spray-coating process also led to superior performance devices showing improved control and purity."

In a third paper in the journal ACS Nano, Kramer and his colleagues used IBM's BlueGeneQ supercomputer to model how and why the sprayed CQDs perform just as well as—and in some cases better than—their batch-processed counterparts. This work was supported by the IBM Canada Research and Development Centre, and by King Abdullah University of Science and Technology.

Explore further: New nanoparticles make solar cells cheaper to manufacture

More information: Advanced Materials: DOI: 10.1002/adma.201403281/abstract

Applied Physics Letters: DOI: 10.1063/1.4898635

ACS Nano: DOI: 10.1021/nn505343e

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JamesG
3 / 5 (2) Dec 05, 2014
Sweet stuff. I've read about this before. It's fun to see it progress knowing we will soon get the benefits. Love to read about this kind of science.
dirk_bruere
not rated yet Dec 06, 2014
If only we knew the average surface area of a car roof we could work out the efficiency...
pntaylor
not rated yet Dec 06, 2014
This looks very promising but, after years of watching "Seinfeld", it's
difficult to take anyone named Kramer seriously. };^)
Thank God his name isn't Cosmo! LOL.
PS3
not rated yet Dec 06, 2014
That's like scifi cool.

Now they just need solar to adapt to harvesting the force from rain drops. :D

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