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Boffins build substrate for 'peel and stick' solar cells

Technique suitable for LEDs and printed circuits

A team of scientists from Stanford University has developed a "peel and stick" solar cell to demonstrate a new flexible substrate with the potential to be used by the wider electronics industry.

Thin-film solar cells can be printed on an increasing variety of rigid surfaces but the team noted that it might be possible to remove the substrate that requires rigidity, in a paper published in Scientific Reports. Once removed from their base, the solar cells show very little loss of generating power and the flexible end-result can be stuck onto almost any surface, even the Microsoft one.

"Now you can put them on helmets, cell phones, convex windows, portable electronic devices, curved roofs, clothing – virtually anything," said Stanford assistant professor of mechanical engineering Xiaolin Zheng.

The substrate is uses a rigid silicon base, with a specially-constructed silicon dioxide topping, onto which is deposited a 300 nanometer-thick layer of nickel. Thin-film solar cells are then printed onto the unit using industry-standard fabrication equipment, the whole thing is covered with a transparent protection layer of plastic and then sealed up with a strip of thermally-bonded tape.

solar sticker

Peel and stick solar strip

Once ready for attachment the strip is dumped in water for a few seconds, allowing water to seep into the gaps between the nickel and the silicon substrate and help detach the two by encouraging cracking between them. The thermal tape is then peeled off and the flexible solar cell is stuck onto something using commercial double-sided adhesive tape.

The paper reports that the silicon substrate can be recovered and reused if necessary (El Reg would suggest printing a discount coupon on the back) to bring costs and the environmental impact down further. Solar cell efficiency wasn't noticeably harmed by the process and the team reports negligible loss of power after the units were bent up to 23mm more than 3,000 times.

bendy solar

Bendy cells hold up well

The thin-film solar cells aren't anywhere near as efficient as more rigid alternatives, but the new substrate could be adapted to carry other electronics and LED panels, Zheng explained. In addition the process could be applied to substrates using other types of materials to fit specific electronics manufacturing needs.

"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," she said.

"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 Ni/SiO2. It's likely many other material interfaces demonstrate similar qualities." ®

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