Sunlight is concentrated by a factor of 454 and focused onto a small 5mm² multi-junction solar cell made out of GaInP/GaInAs/ Ge (gallium indium phosphide, gallium indium arsenide on a germanium substrate).

By choosing a metamorphic Ga0.35In0.65P/Ga0.83In0.17As/Ge material combination, a solar cell structure could be chosen for the first time that is completely matched under the terrestrial solar spectrum. This enables the achievement of the high efficiencies.

At a sunlight concentration factor of 454, the researchers in Freiburg set a “world record” of 41.1%. Even at a higher sunlight concentration of 880, an efficiency of 40.4% was measured.

The high efficiency multi-junction solar cells are used in concentrating PV systems for solar power stations in countries with a large fraction of direct solar radiation.

Fraunhofer ISE is working together with the company Azur Space in Heilbronn as well as Concentrix Solar GmbH in Freiburg to make this technology competitive “as soon as possible.”

“The high efficiencies of our solar cells are the most effective way to reduce the electricity generation costs for concentrating PV systems,” says Dr. Andreas Bett, Department Head at Fraunhofer ISE.