Silicon solar cells have an approximately 90% share on the global photovoltaic market. And every small improvement in their efficiency has a significant impact on material consumption and costs. R&D work is therefore being undertaken to boost the efficiency of these cells, so as to generate as much electricity as possible using as little material as possible. A silicon-based multi-junction solar cell , developed by the Fraunhofer Institute for Solar Energy Systems ISE in collaboration with the Austrian EV Group , has raised the efficiency bar to a record high: This cell converts exactly one third of the energy contained in sunlight into electrical energy.
This extremely high value is possible thanks to 0.002 mm-thin layers of III-V compound semiconductors, bonded directly onto the silicon. In the resulting complex structure, the visible sunlight is absorbed in a gallium-indium-phosphide top cell, the infrared light in gallium-arsenide (GaAs), and the longer wavelengths in the silicon sub-cell. The cell thereby achieves far greater efficiency than conventional silicon solar cells, but can still be easily integrated into PV modules, just like conventional cells.