NREL and Stanford Team up on Peel-and-Stick Solar Cells
January 10, 2013
It may be possible soon to charge cell phones, change the tint on windows, or power
small toys with peel-and-stick versions of solar cells, thanks to a partnership between
Stanford University and the U.S. Department of Energy’s National Renewable Energy
A scientific paper, “Peel and Stick: Fabricating Thin Film Solar Cells on Universal
Substrates,” appears in the online version of Scientific Reports, a subsidiary of the British scientific journal Nature.
Peel-and-stick, or water-assisted transfer printing (WTP), technologies were developed
by the Stanford group and have been used before for nanowire based electronics, but
the Stanford-NREL partnership has conducted the first successful demonstration using
actual thin film solar cells, NREL principal scientist Qi Wang said.
The university and NREL showed that thin-film solar cells less than one-micron thick
can be removed from a silicon substrate used for fabrication by dipping them in water
at room temperature. Then, after exposure to heat of about 90°C for a few seconds,
they can attach to almost any surface.
Wang met Stanford’s Xiaolin Zheng at a conference last year where Wang gave a talk
about solar cells and Zheng talked about her peel-and-stick technology. Zheng realized
that NREL had the type of solar cells needed for her peel-and-stick project.
NREL’s cells could be made easily on Stanford’s peel off substrate. NREL’s amorphous
silicon cells were fabricated on nickel-coated Si/SiO2 wafers. A thermal release tape
attached to the top of the solar cell serves as a temporary transfer holder. An optional
transparent protection layer is spin-casted in between the thermal tape and the solar
cell to prevent contamination when the device is dipped in water. The result is a thin strip much like a bumper sticker: the user can peel off the
handler and apply the solar cell directly to a surface.
“It’s been a quite successful collaboration,” Wang said. “We were able to peel it
off nicely and test the cell both before and after. We found almost no degradation
in performance due to the peel-off.”
Zheng said the partnership with NREL is the key for this successful work. “NREL has
years of experience with thin film solar cells that allowed us to build upon their
success,” Zheng said. “Qi Wang and (NREL engineer) William Nemeth are very valuable
and efficient collaborators.”
Zheng said cells can be mounted to almost any surface because almost no fabrication
is required on the final carrier substrates.
The cells’ ability to adhere to a universal substrate is unusual; most thin-film cells
must be affixed to a special substrate. The peel-and-stick approach allows the use
of flexible polymer substrates and high processing temperatures. The resulting flexible,
lightweight, and transparent devices then can be integrated onto curved surfaces such
as military helmets and portable electronics, transistors and sensors.
In the future, the collaborators will test peel-and-stick cells that are processed
at even higher temperatures and offer more power.
NREL is the U.S. Department of Energy's primary national laboratory for renewable
energy and energy efficiency research and development. NREL is operated for DOE by
the Alliance for Sustainable Energy, LLC.