Researchers have successfully developed devices to convert infrared radiation into light usable by solar cells.
Solar cells absorb visible and near-infrared light – but the infrared portion is not absorbed, going right through them.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg; University of Bern, Switzerland, and the Heriot-Watt University in Edinburgh, Scotland, have made a portion of infrared radiation usable by solar cells with the assistance of a practical up-converter.
The up-converter consists primarily of a microcrystalline powder made of sodium yttrium fluoride embedded in a polymer. Part of the yttrium has been replaced with erbium, which is active in the optical range and ultimately responsible in the end for the up-conversion.
Infrared light falling on this up-converter excites the erbium ions resulting in so much energy that the solar cells can “see” it and utilize it to create electricity.
“We equipped the solar cells with metal lattices on the front and rear sides so that IR light can pass through the solar cells. In addition, the light can be used by both faces of the cell – we call this a bi-facial solar cell,” says Stefan Fischer happily, a scientist at ISE.
The researchers also applied specialized coatings to the front and rear sides of the solar cell to cancel reflections and allow that the cells absorb as much light as possible.
“We have been able to adapt both the solar cells and the up-converter so as to obtain the biggest improvement in efficiency so far.”
The Fraunhofer Institute says up-converters could increase silicon solar cell efficiency to a theoretical level of forty percent.
Fraunhofer is Europe’s largest application-oriented research organization. The Fraunhofer-Gesellschaft maintains 66 institutes and independent research units staffed by a workforce of 22,000; the majority of whom are qualified scientists and engineers.
