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Arthur T Knackerbracket has found the following story:

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE have once again succeeded in raising the efficiency value of monolithic triple-junction solar cells made of silicon and III-V semiconductor materials. Using a combination of multiple absorber materials, these multi-junction photovoltaic cells exploit the energy from the solar spectrum significantly better than conventional silicon solar cells. The world record for a monolithic multi-junction solar cell manufactured by wafer bonding has been increased to 34.1% and an efficiency record of 24.3% achieved for a solar cell with the III-V semiconductor layers deposited directly on the silicon.

“Monolithic multi-junction solar cells are a source of hope for the further development of the silicon solar cells dominating the field today because they can lead to significantly higher efficiency values when converting sunlight into electrical power. We believe that we can achieve efficiency values of 36%, which would substantially exceed the physical limit of 29.4% offered by a pure silicon solar cell,” explains Dr. Andreas Bett, Institute Director of Fraunhofer ISE. The high efficiency allows for more output per surface area, thus creating a savings of solar cell and module materials — an important aspect in regard to the sustainability of photovoltaics.

Triple-junction solar cells made of III-V semiconductors and silicon have the potential to take photovoltaics to a new level of efficiency.

For the production of multi-junction photovoltaic cells, thin III-V semiconductor layers only a few micrometers thick are deposited on a silicon solar cell. In order to optimally exploit the sun’s rays, the different layers absorb light from different spectral ranges: gallium indium phosphide in the 300–660 nm range (visible light), aluminum gallium arsenide in the 600–840 nm range (near infrared light) and silicon in the 800–1200 nm range (long-wavelength light).

This enables significantly increased efficiencies compared to single-junction silicon solar cells. Like today’s conventional silicon solar cells, these cells each have a contact on the front and rear sides, which allows for easy integration in solar modules.

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