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Totally Transparent Solar Cells Could Turn Our Windows Into Solar Panels

"Ultimately, we want to make solar harvesting surfaces that you do not even know are there."

In the future, you'll be able to charge your phone just by placing it in the sun, and you'll generate electricity through your windows, not just from the panels on the roof. How? By covering glass in a material that captures energy from the invisible parts of the light spectrum, but still lets in visible light. In other words: translucent solar cells.

"When you look at tall buildings, there is a tremendous amount of surface area. They can act as efficient collectors throughout the day," says Richard Lunt, an assistant professor of chemical engineering at Michigan State University. "In many buildings, we are already installing films to reject infrared light to reduce [heating and cooling] costs. We aim to do something similar while also generating power."

Molecules in the film absorb energy and "glow." The glowing infrared light is then pushed to the sides, where it's converted to electricity using edge-mounted strips of solar cells.

Lunt has co-founded a company, Ubiquitous Energy, to commercialize his team's work. He reckons we could see the first applications within five years.

It's likely the films won't be as efficient as solar panels, even today's relatively inefficient versions. At the moment, they convert only about 1% of incoming energy, compared to a typical rate of 20% for today solar panels. But the films could be cost-effective if spread over large areas—say on the side of skyscrapers. They could also be a useful addition to tablets and smartphones.

"Ultimately we want to make solar harvesting surfaces that you do not even know are there," Lunt says.