French-German collaborators claim solar cell efficiency world record

December 02, 2014 // By Paul Buckley
A new world record for the direct conversion of sunlight into electricity has been set by a multi-junction solar cell that converts 46% of the solar light into electrical energy.

The solar cell has been developed by Soitec and CEA-Leti, France, together with the Fraunhofer Institute for Solar Energy Systems ISE, Germany.  

Multi-junction solar cells are based on a selection of III-V compound semiconductor materials. The world record cell is a four-junction cell, and each of its sub-cells converts precisely one quarter of the incoming photons in the wavelength range between 300 and 1750 nm into electricity. When applied in concentrator PV, a small cell is used with a Fresnel lens, which concentrates the sunlight onto the cell. The new record 46.0% 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.

A special challenge that had to be met by this cell is the exact distribution of the photons among the four sub-cells. 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% efficiency has now been independently confirmed by AIST in Japan", explained Dr. 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, Vice President Solar Cell Product Development for Soitec, a company headquartered in France and a world leader in high performance semiconductor materials, said: "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% efficiency in the near future.  To produce this new generation of solar cells, we have already installed a line in France. It uses our bonding and