F R A U N H OF E R I N S T I T U T E F O R L A S E R T E C H N O L O G Y I L T
PRESS RELEASE
PRESS RELEASE
September 10, 2012 || Page 1 | 6
The solar industry could gain sizeable cost advantages
by using the right lasers
Contactless and material-selective laser processes are of critical importance for the
production of sensitive electronic components such as solar cells. Lasers can
achieve a decisive step to greater efficiencies and lower manufacturing costs for
crystalline and thin-film photovoltaics. With this goal in mind, the Fraunhofer
Institute for Laser Technology ILT is developing industrial-scale processes, e.g. for
the high-resolution structuring of thin layers, along with corresponding
mechanical components to raise production throughput rates. Selecting the most
suitable laser to optimize such processes plays a predominant role in these
research activities.
Competitive process engineering for the production of electronic components
calls for high speeds, small structure sizes, and large-scale applicability. In organic
electronics, structured printing currently allows feature sizes as small as 10
micrometers at high speeds. A significantly higher resolution and productivity can
be obtained with structuring by laser. Especially important here is choosing a laser
that is ideally suited to the requirements of the particular application. “Most
companies in the solar industry don’t know how much time and costs they can
save by using the right laser for manufacturing thin-film solar modules or
crystalline solar cells,” explains Dr. Malte Schulz-Ruthenberg, project manager at
Fraunhofer ILT. “For example, completely different beam guiding and shaping
Editorial Notes
Dipl.-Phys. Axel Bauer Head of Marketing and Communications | Phone +49 241 8906-194 | axel.bauer@ilt.fraunhofer.de
Petra Nolis M.A. | PR Consultant | Phone +49 241 8906-662 | petra.nolis@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT | Steinbachstraße 15 | 52074 Aachen, Germany | www.ilt.fraunhofer.de
F R A U N H OF E R I N S T I T U T E F O R L A S E R T E C H N O L O G Y I L T
approaches are required for high-speed drilling of back-contact solar cells than
those used to create complex structures on electronic circuits at high processing
rates .”
Consequently, researchers at Fraunhofer ILT are investigating different approaches
to improve process efficiency in a range of different projects. One of these
projects is exploring the possibility of multiple beam splitting using diffractive
optical elements, which can dramatically increase production throughput rates. A
polygon scanner is also being developed, which enables two-dimensional
structuring of thin layers at extremely high speeds of several hundred meters a
second. Fraunhofer ILT will be presenting the demonstrator of this polygon
scanner to a professional audience at the joint Fraunhofer booth in Hall 3/G22 at
the European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC, in
Frankfurt from September 24 – 28, 2012. Combined with modern beam sources
working at high repetition rates, the polygon scanner can significantly increase
production throughput. It can be used for processing both thin-film solar modules
and crystalline solar cells.
Series connection for rigid and flexible solar modules
In addition to machine technology, one focus of research at Fraunhofer ILT is on
further developing structuring processes for thin-film solar modules. These
modules require small strips of cells connected in series in order to reduce current
densities, which in turn reduces electrical losses within the module. What many
companies are still carrying out by means of mechanical scribing can be done
quicker and more cleanly by means of laser radiation. The challenge ILT
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F R A U N H OF E R I N S T I T U T E F O R L A S E R T E C H N O L O G Y I L T
researchers now face is to do this without impairing the functionality of the layers
of conducting, semi-conducting, or insulating materials, which have thicknesses
ranging from a few nanometers to a few micrometers. If, for example, residues of
ablated material or thermal damage to neighboring areas occur during
processing, the extreme thinness of these layers can lead to their degradation and
cause the entire solar module not to work. The laser structuring processes
therefore have to be adapted to the different characteristics of each individual
layer. Ultrashort pulse lasers can be used for physical processes that are not
feasible at longer pulse durations. This opens up new process windows, and paves
the way towards new industrial-scale processes.
In the FlexLas project, funded by the European Commission and the state
government of North Rhine-Westphalia, a laser structuring technique for organic
solar cells on flexible film substrates is being developed at Fraunhofer ILT. This
type of solar module is considered an economical, forward-looking product in the
field of solar energy. It might well be possible one day to make textiles or
handbags with flexible solar cells, which could be used to charge a cell phone. The
laser structuring processes being developed in Aachen can also be applied to
other products with multiple-layer systems, such as smart phone screens and flat
lighting elements.
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F R A U N H OF E R I N S T I T U T E F O R L A S E R T E C H N O L O G Y I L T
Production technology for crystalline solar cells
Scientists in research and development are currently working on a variety of laser
processes for manufacturing crystalline solar cells. For example, a technique
developed at Fraunhofer ILT allows you to drill upward of 10,000 holes a second
into silicon wafers. Thin passivation layers can be removed with scarcely any effect
on electrical functionality. And thanks to innovative beam-shaping optics, laserbased module manufacturing drives soldering times down to less than a second.
Using the right beam source here can significantly improve the production
process. ILT researchers are currently testing a variety of different beam sources in
order to fulfill the widest possible range of parameters relating to pulse duration,
wavelength, process-adapted intensity distribution, etc. while minimizing laserrelated damage.
The researchers in Aachen are also busy devising innovative approaches to
producing high-efficiency cells. To create a texture that reduces reflection and
maximizes use of the sun’s radiation, an ablation-free laser process is combined
with a subsequent etching stage. This reduces laser-related material damage to a
minimum and maximizes process speed, contributing in turn to a significant
reduction in production costs.
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F R A U N H OF E R I N S T I T U T E F O R L A S E R T E C H N O L O G Y I L T
Fig. 1:
Process for selective
bild 11
ablation of a silicon nitride
layer on a silicon wafer.
Source:
Fraunhofer ILT, Aachen.
Fig. 2:
Silicon-based thin-film
Bild 22
module, structured using
laser radiation.
Source:
Fraunhofer ILT, Aachen.
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PRESS RELEASE
September 10, 2012 || Page 6 | 6
The Fraunhofer-Gesellschaft is the leading organization for applied research in Europe. Its research activities are conducted by 60
Fraunhofer Institutes at over 40 different locations throughout Germany. The Fraunhofer-Gesellschaft employs a staff of around 20,000,
who work with an annual research budget totaling 1,8 billion euros. Roughly two thirds of this sum is generated through contract research
on behalf of industry and publicly funded research projects. Branches in the USA and Asia serve to promote international cooperation.
For further information
Dr. Malte Schulz-Ruthenberg | Group Micro and Nanostructuring | Phone +49 241 8906-604
malte.schulz-ruhtenberg@ilt.fraunhofer.de | Fraunhofer Institute for Laser Technology ILT, Aachen | www.ilt.fraunhofer.de
Dr. Alexander Olowinsky | Head of the Group Micro Joining | Phone +49 241 8906-491 |
alexander.olowinsky@ilt.fraunhofer.de | Fraunhofer Institute for Laser Technology ILT, Aachen | www.ilt.fraunhofer.de
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