A new solar cell conversion efficiency world record has been set — an impressive 44.7% conversion efficiency was achieved by a solar cell created by researchers at the Fraunhofer Institute for Solar Energy Systems ISE, with help from Soitec, CEA-Leti, and the Helmholtz Center Berlin. The new record surpasses the previous one of 44.4%, that was set just a couple of months ago by the Sharp Corporation.

The new solar cells — which are based on the utilization of a new solar cell structure with four solar subcells — are another step towards the widely shared (in the industry) goal of a solar cell possessing a conversion efficiency of at least 50%. Conversion efficiency refers to the percentage of the solar spectrum that is harnessed and converted into electrical energy — a 44.7% conversion efficiency means that 44.7% of the total solar spectrum, including infrared and ultraviolet, are converted into electricity by the new solar cells.

The Fraunhofer Institute for Solar Energy Systems provides more:

Surpassing competition after only over three years of research, and entering the roadmap at world class level, a new record efficiency of 44.7% was measured at a concentration of 297 suns. Back in May 2013, the German-French team of Fraunhofer ISE, Soitec, CEA-Leti and the Helmholtz Center Berlin had already announced a solar cell with 43.6% efficiency. Building on this result, further intensive research work and optimization steps led to the present efficiency of 44.7%.

These 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 so-called III-V multi-junction solar cells, which originally came from space technology, has prevailed to realize highest efficiencies for the conversion of sunlight to electricity. In this multi-junction 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.

“We are incredibly proud of our team which has been working now for three years on this four-junction solar cell,” states 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. With this technology, we are able to connect two semiconductor crystals, which otherwise cannot be grown on top of each other with high crystal quality. In this way we can produce the optimal semiconductor combination to create the highest efficiency solar cells.”