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Friday, 12 August 2011

Better, Faster, Cheaper: Doing Business with the Sun

Aug 12, 2011 

The change in energy policy has been decided; Germany needs more green energy. From September 5-9 in Hamburg, everything will revolve around our biggest energy supplier: the sun. At the European Photovoltaic Solar Energy Conference, in Hall B4G, Stand C12, Fraunhofer researchers will present new methods for making solar cells cheaper and more efficient.

These days, black panels can be seen on many building roofs, particularly in Southern Germany. Many of these solar collectors are used to heat water, but increasingly there are also photovoltaic systems that directly convert the light of the sun into electrical current. To date, however, only some 2% of electrical current in Germany comes from solar energy, because solar cells are costly and complicated, particularly in production. Researchers from the Fraunhofer-Gesellschaft are developing innovative production methods to change this. Lasers in particular create whole new potentials for production. Dr. Malte Schulz-Ruhtenberg of the Fraunhofer Institute for Laser Technology ILT explains the main advantage: „Laser technology permits contact-free, precise and quick processing.“ As a result, better solar cells can be produced at lower cost.

Laser Methods in Demand
One example is high-rate laser drilling, which creates tiny holes in solar cells very precisely and quickly. Why? A classic solar cell generates current through the photoelectric effect. It consists of several conducting and semiconducting layers. When light falls onto the cell, negative charge carriers are released from their bonds, and electrical current flows as a result. To date, the contacts for drawing away the electric current generated have been positioned at the front and rear of the cell. Moving all of the contacts to the rear, where they do not cast a shadow, increases the level of energy generated. The holes pave the way for this approach, which is known as „emitter wrap-through“, or EWT for short.

Special polygon scanners can be utilized to provide for even higher speeds and higher throughput rates. With these laser scanners, rotating polygonal mirrors precisely deflect millions of laser pulses per second. This allows them to process large areas very quickly. "This is a promising technology that can be used for many laser processes," Dr. Schulz-Ruhtenberg points out.
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