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Lasers, for more efficient solar cells
said. “Breakage is a primary cost factor in
production.”
On the other hand, however, with
“selective laser soldering” the contacts are
pressed on to the cells with compressed
air and then soldered with the laser. The
mechanical stress approaches zero and the
temperature can be precisely regulated.
The result: Optimal contacts and almost
no rejects.
Laser technology is also helping to
optimize the manufacture of thin film solar
cells. The extremely thin film packages
made of semiconducting oxide, amorphous
silicon, and metal that are deposited
onto the glass panels still have a market
share of only ten percent. But as Gillner
knows, “This could be higher, because
thin film solar cells can be used anywhere
that non-transparent glass panels can be
mounted, for example, on house facades
or sound-insulating walls. But the degrees
of efficiency are comparable low at five to
eight percent, and the production costs are
comparatively high.”
“The tiny holes in the
wafer—their diameter
only 50 micrometers—
open up undreamt-of
possibilities for solar cell
developers.”
The laser researchers are working
to improve these costs. Until now, the
manufacturers have used mechanical
methods or solid-state lasers in the
nanosecond range in order to structure the
active layers on the glass panels. In order to
produce electric connections between the
semiconductor and the metal, grooves only
a few micrometers wide must be created.
The ILT researchers have developed
a 400-watt ultrashort pulse laser that
processes thin-film solar modules ten times
faster than conventional diode-pumped
solid-state lasers. “The ultrashort pulse
laser is an ideal tool for ablating thin
layers: It works very precisely, does not heat
the material and, working with a pulse
frequency of 80 MHz, can process a 2-by-3
meter glass panel in under two minutes,”
Gillner explained. “The technology is still
very new, and high-performance scanning
systems and optical systems adapted to the
process must be developed first. In the
medium term, however, this technology
will be able to reduce production costs.”
The rise of laser technology in solar
technology is just taking off, and it still
has a long way to go. “Lasers simplify and
optimize the manufacture of classic silicon
and thin-film cells, and they allow the
development of new design alternatives,”
Gillner said. “And so laser technology is
making an important contribution towards
allowing renewable energy sources to
penetrate further into the energy market.”
Innovation
that
matters …
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Global Solar Technology – July/August 2009 – 17