Fraunhofer Sets CPV Efficiency Record of 41.1%

By using the test modules, sunlight is concentrated by a factor of 454 and focused onto a 5mm² multi-junction solar cell made out of  gallium indium phosphide, gallium indium arsenide on a germanium substrate (GaInP/GaInAs/Ge). In contrast to conventional solar cells, the semiconductors in these cells do not have the same lattice constant (the distance between atoms in a crystalline structure).

This makes it difficult to grow the semiconductor layers with a high crystal quality, since at the interface of materials with different lattice constants strain is present that results in the creation of dislocations and other crystal defects.

The researchers at Fraunhofer ISE have overcome this obstacle, managing to localize the defects in a region of the solar cell that is not electrically active. As a result, the active regions of the solar cell remain relatively free of defects. Even at a concentration of 880 suns, an efficiency of 40.4% was measured, Fraunhofer reported.

“This is an especially good example of how the control of crystal defects in semiconductors can lead to a breakthrough in technology,” said Eicke Weber, director of Fraunhofer ISE.

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.