Researchers at the Fraunhofer Institute for Solar Energy Systems ISE, using a new antireflection coating, have successfully increased the efficiency of the best four-junction solar cell to date from 46.1 to 47.6% at a concentration of 665 suns. The layer structure of the new solar cell was developed back in 2016 together with the French company Soitec Inc., that designs and manufactures semiconductor materials. The upper tandem solar cell is made of gallium indium phosphide (GaInP) and aluminum gallium arsenide (AlGaAs), which was bonded by Soitec onto a lower tandem solar cell made of gallium indium arsenide phosphide (GaInAsP) and gallium indium arsenide (GaInAs). Now an improved contact layer and a 4-layer antireflection coating were applied to the tandem cell structure in Fraunhofer ISE’s Center for High Efficiency Solar Cells. These measures reduce the resistance losses and the reflection on the front side of the cell, which is spectrally sensitive within a broad range of 300 and 1780 nanometers.
Fraunhofer Institute for Solar Energy Systems ISE | http://www.ise.fraunhofer.de/en