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These Cheap, Invisible Solar Cells Can Be Spray-Painted On Anything

The solar cells can be rolled up like wallpaper and then unrolled onto any surface.

Most solar panels, made of expensive electronics encased in glass, are awkward to use anywhere other than a rooftop or solar farm. But in the near future, spray-on solar cells will be able to turn almost anything–from cars, to patio furniture, to airplane wings–into mini power plants.

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Researchers at the University of Toronto have figured out how to make the process both cheap and fast. Light-sensitive dots, so tiny they’re invisible to the eye, can be sprayed onto a flexible film and then wrapped on anything with access to sunlight.

“We start with something like an ink, so it can be deposited using really cheap manufacturing methods, as opposed to traditional solar panels, which are made using the microelectronics industry model,” says Illan Kramer, a post-doctoral fellow who works for a lab at the University of Toronto through a partnership with IBM.

“The advantage here is that if you want to start coating giant areas–like the kinds of areas you’d be interested in coating if you really want to solve the world’s energy problems–you have to be thinking about coating square kilometers worth of space, not just 12 inches at a time,” he says.

The project isn’t the first to experiment with spray-on solar power, but it uses a process that’s cheaper. In the past, surfaces were coated using slow, labor-intensive assembly lines. Now, the researchers use a method that prints directly onto a film, similar to the way ink prints onto newspapers.

“We decided to build ourselves a little mini-model of a newspaper printing press,” says Kramer. “We don’t need an expensive solar cell kind of factory, so there are much lower barriers to entry in terms of infrastructure.”

After a solution filled with the nano-sized solar cells is printed on a flexible film, it can be rolled up and carried away to wrap on anything. “They wind up like a roll of wallpaper you might buy from a hardware store,” Kramer explains. “Then you could unroll them and mount them on any surface you like.”

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Though the individual cells are invisible, the printing process creates a dark surface, so this wouldn’t be the kind of thing that can be used on windows, unlike some other spray-on solar projects. But Kramer argues that windows aren’t the best place to put solar panels anyway–since you’re either limiting light in a room or not generating much power. “We want to absorb as much sunlight as possible, and we want to create as much electricity as possible,” Kramer says.

The spray-on solar cells, which the researchers says will be ready for the market in five to 10 years, aren’t yet as efficient as traditional solar panels. The current prototype of the spray-on solar cell only converts 8.1% of sunlight to power, compared to 15%-20% for most common rooftop panels. But Kramer says that may not be a problem: “We’re working on making them more efficient, but we think of ourselves as operating in a slightly different paradigm, where we don’t have to be quite as efficient because we’re so much less expensive.”

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About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley.

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