Back in May 2013, the
German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Building on this result, further intensive
research work and optimization steps led to the present efficiency of
44.7%.
These solar cells are used in concentrator photovoltaics (CPV), a
technology which achieves more than twice the efficiency of conventional
PV power plants in sun-rich locations. The terrestrial use of so-called
III-V multi-junction solar cells, which originally came from space
technology, has prevailed to realize highest efficiencies for the
conversion of sunlight to electricity. In this multi-junction solar
cell, several cells made out of different III-V semiconductor materials
are stacked on top of each other. The single subcells absorb different
wavelength ranges of the solar spectrum.
"We are incredibly proud of our team which has been working now for
three years on this four-junction solar cell," says Frank Dimroth,
Department Head and Project Leader in charge of this development work at
Fraunhofer ISE. "This four-junction solar cell contains our collected
expertise in this area over many years. Besides improved materials and
optimization of the structure, a new procedure called wafer bonding
plays a central role. With this technology, we are able to connect two
semiconductor crystals, which otherwise cannot be grown on top of each
other with high crystal quality. In this way we can produce the optimal
semiconductor combination to create the highest efficiency solar cells."
"This world record increasing our efficiency level by more than 1
point in less than 4 months demonstrates the extreme potential of our
four-junction solar cell design which relies on Soitec bonding
techniques and expertise," says André-Jacques Auberton-Hervé, Soitec's
Chairman and CEO. "It confirms the acceleration of the roadmap towards
higher efficiencies which represents a key contributor to
competitiveness of our own CPV systems. We are very proud of this
achievement, a demonstration of a very successful collaboration."
"This new record value reinforces the credibility of the direct
semiconductor bonding approaches that is developed in the frame of our
collaboration with Soitec and Fraunhofer ISE. We are very proud of this
new result, confirming the broad path that exists in solar technologies
for advanced III-V semiconductor processing," said Leti CEO Laurent
Malier. Concentrator modules are produced by Soitec (started in 2005
under the name Concentrix Solar, a spin-off of Fraunhofer ISE). This
particularly efficient technology is employed in solar power plants
located in sun-rich regions with a high percentage of direct radiation.
Presently Soitec has CPV installations in 18 different countries
including Italy, France, South Africa and California.
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