Fraunhofer ISE approaches 50 percent efficiency for solar cells

According to their own statements, it is the most efficient solar cell in the world, as confirmed by researchers at the Fraunhofer Institute for Solar Energy Systems (ISE). Because the new cell from Freiburg achieves a whopping 47.6 percent efficiency – with a four-celled solar cell with a concentration of 665 times that of the Sun. In doing so, they broke the previous record for such cells, which was 46.1%. Hence they are getting close to 50 percent, which is the goal they have been pursuing for two years as part of a similar project.

Optimizing communication layers

Researchers achieve higher efficiency with a new and improved anti-reflective coating. They have also improved the other layers of the multi-junction solar cell. In addition, there are technical improvements to the process in the metal joints. “We are pleased with this result, which was achieved just one year after the opening of our new high-efficiency solar cell center,” says Frank Demmeroth, Head of III-V Photovoltaics and Capacitor Technology at Fraunhofer ISE. “Through our work, we want to contribute to making concentrated photovoltaics more efficient and competitive, because we believe this is the most sustainable form of renewable electricity generation.”

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As early as 2016, Freiburg researchers and their French colleagues from Soitec developed the core layer structure of the current recording cell. The basis is a tandem solar cell with gallium indium phosphide (GaInP) and aluminum gallium arsenide (AlGaAs) as semiconductor materials. Soitec developers chose a low-end tandem solar cell made of indium gallium arsenide phosphide (GaInAsP) and gallium indium arsenide (GaInAs). III-V compound semiconductor multi-junction solar cells have long been among the most efficient solar cells in the world.

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Wide spectral band absorption

Researchers have been working on this multi-layered structure for years. Colleagues at the Fraunhofer ISE Center for High Efficiency Solar Cells have now fitted the cell with improved contact layers and a 4-layer anti-reflection coating. This reduces resistance and reflection losses at the front of the cell, which is sensitive in a wide spectral range from 300 to 1780 nm. For comparison: conventional silicon solar cells absorb only sunlight with a wavelength of 1,200 nanometers. But you don’t need an extensive anti-reflective coating.

concentrated sunlight

In addition, sunlight is collected through the lenses on solar cells only a few square millimeters in size. This allows III-V compound semiconductors to develop their highest potential. “Possible applications for such highly efficient tandem solar cells include concentrated photovoltaic systems, which contribute to efficient power generation in sunny countries,” says Stefan Glones, head of photovoltaic research at Fraunhofer ISE. He predicts that “with tandem photovoltaic cells, it is possible to leave the limits of single solar cells behind and ultimately achieve a reduction in solar electricity costs.” (see below)

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