Researchers at the Stanford School of Engineering have succeeded in developing the world’s first peel-and-stick thin-film solar cells.
The idea will allow the cells to be applied to almost any surface, with successful tests having been conducted on paper, plastic and window glass. This opens up significant opportunities for alternative applications for solar technology, previously limited by traditional solar cells, which must be mounted on stiff, often heavy, fixed panels.
Though fabricating thin-film solar panels on flexible substrates has been successfully achieved before, previous efforts have required modifications of existing processes or materials. The Stanford researchers’ solution has been achieved without modifying any existing processes, facilities or materials, making them viable commercially.
The decal-like application process provides the real difference from existing thin-film photovoltaic cells as they do not require any direct fabrication on the final carrier substrate.
“Non-conventional 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,” said Xiaolin Zheng, a Stanford assistant professor of mechanical engineering and senior author of the paper. “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.”
The new process involves a unique silicon, silicon dioxide and nickel “sandwich” covered with a protective polymer. A thermal release tape aids the peeling process when the cell is submerged in water at room temperature. The cell comes away, attached to the tape, and is then heated to 90 degrees for several seconds. The cell can then be applied to virtually any surface simply using double-side tape or other adhesive and the thermal release tape is then removed.
The researchers were able to reliably attach the cells to helmets, cell phones, convex windows, portable electronic devices, curved roofs, clothing and more, and without losing any of the original cell efficiency. There is also no waste. The cell can be simply peeled off and reused somewhere else.
The researchers believe the process can also be applied to thin-film electronics, including printed circuits, ultra-thin transistors and LCDs.
“Obviously, a lot of new products – from ‘smart’ clothing to new aerospace systems – might be possible by combining both thin-film electronics and thin-film solar cells,” said Zheng. “And for that matter, we may be just at the beginning of this technology. The peel-and-stick qualities we’re researching probably aren’t restricted to nickel and silicon dioxide. It’s likely many other material interfaces demonstrate similar qualities, and they may have certain advantages for specific applications. We have a lot left to investigate.”