SprayLD coats various surfaces with energy-producing solar cells

In the next decade, people may be able to convert almost any surface into a solar power generator. 

Scientists have built a device that can spray on solar cells, the first step toward quickly and easily coating variously shaped objects that could range from airplane wings and road surfaces to the roof of your house.

"My dream is that you could have a couple of technicians with Ghostbuster backpacks show up at your house and spray paint your roof," says Illan Kramer, a University of Toronto and IBM researcher funded through a collaborative program between the company, the Canadian government and various universities.

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While he admits that dream is still a long way from reality, Kramer and other U of T researchers have made the first step toward a spray-on solar power future with the creation of what they call sprayLD.

​The sprayLD deposits solar cells (specifically, colloidal quantum dots or CQDs) onto a flexible film that can then be used to wrap very large, awkwardly shaped surfaces. It could be used to cover kilometres of road, an airplane wing or a car fender.

The film can be used to cover anything "that's bent in funny ways, that's not a standard shape," says Kramer, who tested the process on different materials, including one similar to the plastic sheets used for overhead projectors.

The process is much better for these types of shaped surfaces than standard assembly-line style batch processing, he says, which doesn't allow for continuous coating.

"If your hope is to coat every road or ... make many, many, many kilometres worth of solar cells, you need to be able to coat very large areas in a ... quick amount of time and in a uniform way," he explains.

$1,000 to build sprayLD

The approach requires a way to produce inexpensive, spray-paintable solar cells.

"We started by buying a few art store airbrushes," Kramer says, "and it kind of grew from there."

The scientists stopped by an art store near the university and purchased a few airbrushes for a little over $100. They also bought three spray nozzles, including one fine-mist type from a vendor who mostly services the steel mill industry.

The device they created, which looks like something constructed during a Junkyard Wars episode, cost a little less than $1,000 to build  — solar cells not included.

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Next, the scientists want to build a bigger version of the sprayLD device to test whether increased size will affect its performance.

They also need to improve the efficiency of the solar cell material. The performance benchmark for solar energy is typically a product that can convert 10 per cent of the sun's energy into electrical energy, he says.

"We're close," Kramer says. Their best measured efficiency is 8.1 per cent.

"So, we're getting there."