Solar cells created with a twist
2008-10-06 11:09
Chicago - US researchers have found a
way to make efficient silicon-based solar cells that are
flexible enough to be rolled around a pencil and transparent
enough to be used to tint windows on buildings or cars.
The finding, reported on Sunday in the journal Nature
Materials, offers a new way to process conventional silicon by
slicing the brittle wafers into ultrathin bits and carefully
transferring them onto a flexible surface.
"We can make it thin enough that we can put it on plastic
to make a rollable system. You can make it gray in the form of
a film that could be added to architectural glass," said John
Rogers of the University of Illinois at Urbana-Champaign, who
led the research.
"It opens up spaces on the fronts of buildings as
opportunities for solar energy," Rogers said in a telephone
interview.
Converted into electricity
Solar cells, which convert solar energy into electricity,
are in high demand because of higher oil prices and concerns
over climate change.
Many companies, including Japanese consumer electronics
maker Sharp Corp and Germany's Q-Cells are making thin-film
solar cells, but they typically are less efficient at
converting solar energy into electricity than conventional
cells.
Rogers said his technology uses conventional single crystal
silicon. "It's robust. It's highly efficient. But in its
current form, it's rigid and fragile," he said.
Rogers' team uses a special etching method that slices
chips off the surface of a bulk silicon wafer. The sliced chips
are 10 to 100 times thinner than the wafer, and the size can be
adapted to the application.
Once sliced, a device picks up the bits of silicon chips
"like a rubber stamp" and transfers them to a new surface
material, Rogers said.
'Like an inking pad'
"These silicon solar cells become like a solid ink pad for
that rubber stamp. The surface of the wafers after we've done
this slicing become almost like an inking pad," he said.
"We just print them down onto a target surface."
The final step is to electrically connect these cells to
get power out of them, he said.
Adding flexibility to the material would make the cells far
easier to transport. Rogers envisions the material being
"rolled up like a carpet and thrown on the truck."
He said the technology has been licensed to a startup
company called Semprius Inc in Durham, North Carolina, which is
in talks to license the technology.
"It's just a way to use thing we already know well," Rogers
said.