Anew world record was set when 44.7% of sunlight was converted into elec- tricity by a photovoltaic panel using a new solar cell structure with four solar subcells last month, says German research organi- sation Fraunhofer Institute for Solar Energy Systems department head and development project leader Dr Frank Dimroth.

Semiconductor and solar company Soitec, French Alternative Energies and Atomic Energy Commission nanotechnology and photonics research and technology institute Leti and German materials and energy company Helmholtz Centre Berlin jointly participated in the project.

“These high-efficiency solar cells are used in concentrator photovoltaics (CPV), a technology which achieves more than twice the efficiency of conventional PV power plants in sun-rich locations. The terrestrial use of III-V multijunction solar cells, which originates from space technology, has prevailed to realise the highest efficiencies for the conversion of sunlight into electricity,” says Dimroth.

In this multijunction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other. The single subcells absorb different wavelength ranges of the solar spectrum.

“This four-junction solar cell contains our collected expertise in this area. Besides improved materials and optimisating the structure, a new procedure, called wafer- bonding, plays a central role. With this technology, we can connect two semiconductor crystals, which can otherwise not be grown on top of each other with high crystal quality. In this way, we can produce an optimal semiconductor combination to create the high-efficiency solar cells.”

Concentrator modules are produced by Soitec, which started to produce these modules in 2005 under the name Concentrix Solar, a spin-off of the Fraunhofer Institute. This efficient technology is employed in solar power plants in sun-rich regions with a high percentage of direct radiation. Presently, Soitec has CPV installations in 18 different countries, including Italy, France, South Africa and California.

“This world record confirms the acceleration towards higher efficiencies, which represents a key contributor to the competitiveness of our own CPV systems. We are very proud of this achievement – a demonstration of a very successful collaboration,” says Soitec chairperson and CEO André-Jacques Auberton-Hervé.

“This new record value reinforces the credibility of the direct semiconductor bonding approaches that were developed in collaboration with Soitec and Fraunhofer. We are very proud of this new result, confirming the broad path that exists in solar technologies for advanced III-V semiconductor processing,” concludes Leti CEO Laurent Malier.