World record solar cell with 44.7 percent efficiency

Engineers at the Fraunhofer Institute, Soitec, CEA-Leti and the Helmholtz Center Berlin joined forces to achieve a new world record for the conversion of sunlight into electricity. Using a new solar cell structure with four solar subcells, they managed to set a new record efficiency of 44.7% was measured at a concentration of 297 suns and their full spectrum from ultraviolet through to the infrared.

Back in May 2013, the German-French team consisting out of Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE), Soitec, CEA-Leti and the Helmholtz Center Berlin managed to use the same approach to create a solar cell with 43.6% efficiency. Combination of further intensive research and optimization of the system led to the present efficiency of 44.7%.

These solar cells are used in concentrator photovoltaics (CPV) – a technology that can achieve more than double the efficiency of conventional PV power plants in sun-rich locations. In this multi-junction solar cell, several cells made out of different III-V semiconductor materials are stacked on top of each other in a way where a single subcell absorbs different wavelength range of the solar spectrum.

“We are incredibly proud of our team which has been working now for three years on this four-junction solar cell”, says Frank Dimroth, Department Head and Project Leader in charge of this development work at Fraunhofer ISE. “This four-junction solar cell contains our collected expertise in this area over many years. Besides improved materials and optimization of the structure, a new procedure called wafer bonding plays a central role.”

Wafer bonding lets them to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. That allows them to combine semiconductors to create solar cells with highest efficiency.

“This world record increasing our efficiency level by more than 1 point in less than 4 months demonstrates the extreme potential of our four-junction solar cell design which relies on Soitec bonding techniques and expertise”, said André-Jacques Auberton-Hervé, Soitec’s Chairman and CEO. “It confirms the acceleration of the roadmap towards higher efficiencies which represents a key contributor to competitiveness of our own CPV systems. We are very proud of this achievement, a demonstration of a very successful collaboration.”

The goal engineers have set to themselves is to pump-up the efficiency up to 50 percent. While these solar cells aren’t going to find their use around our homes in near future, they are suitable for use in satellites and power plants where slight increase of efficiency leads to larger supply and profit.

Concentrator photovoltaic modules are produced by Soitec (a spin-off of Fraunhofer ISE), a company with CPV installations in 18 different countries including Italy, France, South Africa and California.