upconverter materials
© Fraunhofer ISE
The upconverter materials are placed at the rear of the silicon solar cells. In the mirror, one can see how an upconverter shines brightly under illumination by an infrared laser. The infrared has passed the silicon solar cell unutilized and is now converter into usable radiation.

Because the solar spectrum contains photons with energy below the band gap of silicon, for silicon solar cells some 20 percent of the incident energy are lost, as these photons pass through the silicon unused. Their energy can be utilized, however, when several such photons are converted into one single photon with an energy above the silicon band gap.

New system architectures are thus being investigated at Fraunhofer ISE that enable efficient upconversion.

This work ranges from developing concepts through characterizing materials and theoretical description to realizing and characterizing complete solar cell and upconverter systems.