WORLDNEWS
Fraunhofer set new
efficiency benchmark
RESEARCHERS at the Fraunhofer layers with a high crystal quality, since at
Institute for Solar Energy Systems ISE the interface of materials with different
have achieved a record efficiency of lattice constants strain is present that
41.1% for the conversion of sunlight into results in the creation of dislocations and
electricity. Sunlight is concentrated by a other crystal defects. The researchers at
factor of 454 and focused onto a small 5 Fraunhofer ISE have succeeded in structure could be chosen for the first
mm
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multi-junction solar cell made out of overcoming this obstacle. They have time that is completely current matched
GaInP/GaInAs/ Ge (gallium indium managed to localise the defects in a under the terrestrial solar spectrum. This
phosphide, gallium indium arsenide on a region of the solar cell that is not is what makes the structure so efficient for
Issue I 2009
germanium substrate). electrically active. As a result, the active solar energy conversion and is an
regions of the solar cell remain relatively important reason for the achievement of
“We are elated by this breakthrough,” free of defects – a prerequisite for the high efficiencies. At a sunlight
says Frank Dimroth, head of the group achieving the highest efficiencies. concentration factor of 454, the
“III-V – Epitaxy and Solar Cells” at researchers in Freiburg set a world record
Fraunhofer ISE. “The entire team believed This metamorphic crystal growth now of 41.1%. Even at a higher sunlight
in our concept of the metamorphic triple- enables the researchers to use a much concentration of 880, an efficiency of
-pv-management.com junction solar cells and our success today larger range of III-V compound 40.4% was measured.
is made possible only through their semiconductors for growing their multi-
.solar
committed work over the past years.” junction solar cells. For these highly Fraunhofer ISE is working together with
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efficient structures, it is decisive that the the company Azur Space in Heilbronn as
Since 1999, Fraunhofer ISE has been solar spectrum is divided into three well as Concentrix Solar GmbH in
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developing metamorphic multi-junction equally large spectral regions by a Freiburg to make this technology
solar cells, which are a special type of suitable choice of light absorbing competitive as soon as possible. “The
solar cells using III-V semiconductor materials. In this way all of the three high efficiencies of our solar cells are the
compounds. These materials are subcells generate the same amount of most effective way to reduce the
especially suitable for converting sunlight current. This is an important argument in electricity generation costs for
into electricity. They can be combined favor of a serial connected solar cell, concentrating PV systems,” says Dr.
together by applying a trick called where the device current is limited Andreas Bett, Department Head at
metamorphic growth. In contrast to ultimately by the smallest current Fraunhofer ISE. “We want it to become
conventional solar cells, the generated by one of the subcells. By competitive with conventional methods of
semiconductors in these cells do not have choosing the metamorphic electricity. With our new efficiency results,
the same lattice constant. This makes it Ga0.35In0.65P/ Ga0.83In0.17As/Ge we have moved a big step further towards
difficult to grow the III-V semiconductor material combination, a solar cell achieving this goal”
China announces PV initiative
THE CHINESE ACADEMY OF SCIENCES in selective areas” by 2015, “utilisation as The United States, Japan and European
(CAS) has launched an initiative to boost an alternative energy” by 2025 and countries began to develop solar energy
the development of solar energy “large-scale utilization” by 2035, in the 1970s. Government investment has
technology, in a bid to turn it into a major respectively. greatly promoted solar energy research
energy source in China by 2050. The and development, especially in Japan,
initiative, which was approved by CAS’s CAS experts said that China has a large Germany and Australia. Germany has
CCP committee on Dec. 23rd, 2008, was potential for solar energy development been promoting a so-called “Solar
made public at the annual meeting of both now and in the future. The duration Energy Family Programme”, and fixed
CAS officials in late January. of sunshine for two thirds of the country’s solar energy facilities on the roofs of
territory is more than 2,200 hours a year. homes. Japan has launched a
CAS had started to motivate its experts to There is also vast desert areas in China programme to accelerate the use of solar
make an action plan and to set up a where solar energy could be “harvested”. energy, and to cut the price of solar
platform to support the research in solar According to an energy industry survey energy by half within three to five years.
energy utilisation. It aims to forge by CAS experts, China has made
complete value chain including basic enormous progress in the photovoltaic Experts said that lowering the costs for
research, application research and sector. However, the research centres are using solar energy is the key for stepping
market research. The plan will be carried scattered, not co-ordinated and lack of up the use of this important renewable
out in three phases, including “utilization cutting edge technology. energy in China.
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