German researchers break solar record

A German research team last week announced they had broken the conversion efficiency record for a photovoltaic solar cell, in a move scientists claimed represented a "big step" towards delivering solar energy at a lower cost than conventional energy sources.

The team at the Fraunhofer Institute for Solar Energy Systems ISE said that they had managed to achieve a record efficiency of 41.1 per cent for the conversion of sunlight into electricity, breaking the Institute's previous record of 39.7 per cent efficiency.

The breakthrough was acheived after the sun's rays were concentrated to a factor of 454 onto a small five milimetre squared multi-junction solar cell made out of gallium indium phosphide and gallium indium arsenide on a germanium substrate.

The results follow almost 10 years of research on so-called metamorphic multi-junction solar cells - a special type of thin film solar cells made using semiconductor compounds.

The research team said that while it has been known for years that gallium indium-based cells can deliver relatively high conversion efficiency rates their adoption has been hampered by difficulties in combining the cells together into workable solar panels.

The researchers said this can only be acheived through a process called metamorphic growth, but because the distance between the atoms in the semiconductors varies it is difficult to grow the cells without defects and weaknesses occuring.

This obstacle has been overcome, according to the German researchers, through the development of a technique that concentrates the defects in a region of the cell that is not electrically active.

Fraunhofer ISE said it is now working with two solar firms, Azur Space in Heilbronn and Concentrix Solar GmbH in Freiburg, on commercialising the technology for use in large-scale concentrated solar p hotovoltaic plants.

Dr. Andreas Bett, Department Head at Fraunhofer ISE said that the new cells would help lower costs for solar technologies making them competitive with traditional grid energy.

"The high efficiencies of our solar cells are the most effective way to reduce the electricity generation costs for concentrating PV systems," he said. "We want that photovoltaics becomes competitive with conventional methods of electricity production as soon as possible. With our new efficiency results, we have moved a big step further towards achieving this goal."