Turning a piece of newspaper or even tissue into a solar power device may sound like an eco-geek's impossible fantasy, but MIT researchers have done just that. They used a special vapor to coat such ordinary paper items with resilient solar cells that could still function even after being folded into a paper airplane.
The MIT team showed off that resilience by also printing a solar cell on a sheet of PET plastic, which they folded and unfolded 1,000 times without significant loss of energy production. By contrast, a commercial solar cell printed on the plastic failed after just a single folding. The new MIT method could create a wave of cheap, flexible solar cells that allow for many new solar-powered gadgets.
"Often people talk about deposition on a flexible device — but then they don’t flex it, to actually demonstrate [that it can survive the stress]," said Karen Gleason, a chemical engineer at MIT.
People have created flexible solar cells in the past, but never before so successfully with delicate paper or fabric materials. The MIT team achieved its breakthrough by gently treating the paper with vapors and temperatures of less than 120 degrees, as opposed to using liquids and higher temperatures used in normal solar cell printing.
The printing process deposits five layers of material on separate passes, with a paper mask helping to form the rectangular solar cell pattern on the surface. It also requires a vacuum chamber to ensure perfect printing conditions.
Still, the cheap vapor-deposition process could easily scale up for large-scale, inexpensive production. It essentially resembles the process used to make the silvery lining of potato chip bags.
That could slash solar installation costs by printing solar cells onto any sort of paper or cloth material that costs one thousand times less than the glass for solar windows. Paper solar cells might become window shades or wallpaper. Researchers even showed that the solar cells could be laminated for protection against the elements in outdoor use.
For now, the paper-printed solar cells have a solar power efficiency of about 1 percent. That's "good enough to power a small electric gizmo," said Vladimir Bulović, an MIT electrical engineer. But he and the rest of the MIT team expressed confidence that they can boost that efficiency with additional work on the material in the near future.
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