For all their promise, solar cells have frustrated scientists in one crucial regard – most are rigid. They must be deployed in stiff, often heavy, fixed panels, limiting their applications. So researchers have been trying to get photovoltaics to loosen up. The ideal: flexible, decal-like solar panels that can be peeled off like band-aids and stuck to virtually any surface, from papers to window panes.
Now the ideal is real. Stanford researchers have succeeded in developing the world's first peel-and-stick thin-film solar cells. The breakthrough is described in a paper in the December 20th issue of Scientific Reports.
Unlike standard thin-film solar cells, the peel-and-stick version from Stanford does not require any direct fabrication on the final carrier substrate. This is a far more dramatic development than it may initially seem. All the challenges associated with putting solar cells on unconventional materials are avoided with the new process, vastly expanding the potential applications of solar technology.
Thin-film photovoltaic cells are traditionally fixed on rigid silicon and glass substrates, greatly limiting their uses, says Chi Hwan Lee, lead author of the paper and a PhD candidate in mechanical engineering. And while the development of thin-film solar cells promised to inject some flexibility into the technology, explains Xiaolin Zheng, a Stanford assistant professor of mechanical engineering and senior author of the paper, scientists found that use of alternative substrates was problematic in the extreme.
"Nonconventional or 'universal' substrates are difficult to use for photovoltaics because they typically have irregular surfaces and they don't do well with the thermal and chemical processing necessary to produce today's solar cells," Zheng observes. "We got around these problems by developing this peel-and-stick process, which gives thin-film solar cells flexibility and attachment potential we've never seen before, and also reduces their general cost and weight."
Utilizing the process, Zheng continues, researchers attached their solar cells to paper, plastic and window glass among other materials.
"It's significant that we didn't lose any of the original cell efficiency," Zheng said.