Soitec and CEA-Leti, France, together with the Fraunhofer Institute for Solar Energy System ISE, Germany, achieved a new world record of 46 percent efficiency for the direct conversion of sunlight into electricity using a multi-junction solar cell.
Multi-junction solar cells are based on a selection of III-V compound semiconductor materials. This new world record cell is a four-junction cell, with each of its sub-cells converting precisely one quarter of the incoming photons in the wavelength range between 300 and 1750 nm into electricity.
When applied in concentrator PV, a very small cell is used with a Fresnel lens, which concentrates the sunlight onto the cell. The 46 percent efficiency was measured at a concentration of 508 suns and has been confirmed by the Japanese AIST (National Institute of Advanced Industrial Science and Technology), one of the leading centers for independent verification of solar cell performance results under standard-testing conditions. The uniqueness of this cell is its requirement for the exact distribution of the photons among the four sub-cells and this has been achieved by precise tuning of the composition and thicknesses of each layer inside the cell structure.
"This is a major milestone for our French-German collaboration. We are extremely pleased to hear that our result of 46 percent efficiency has now been independently confirmed by AIST in Japan", explains Frank Dimroth, project manager for the cell development at the German Fraunhofer Institute for Solar Energy Systems ISE. "CPV is the most efficient solar technology today and suitable for all countries with high direct normal irradiance."
Jocelyne Wasselin, vp solar cell product development for Soitec, a company headquartered in France says: "We are very proud of this new world record. It confirms we made the right technology choice when we decided to develop this four-junction solar cell, and clearly indicates that we can demonstrate a 50 percent efficiency in the near future".
She adds: "To produce this new generation of solar cells, we have already installed a line in France. It uses our bonding and layer-transfer technologies and already employs more than 25 engineers and technicians. I have no doubt that this successful cooperation with our French and German partners will drive further increase of CPV technology efficiency and competitiveness."