Tandem PV Module Fraunhofer ISE Achieves A Module Efficiency of 34.2 Percent

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Researchers at Fraunhofer ISE have set two efficiency records for tandem PV modules under laboratory conditions. The III-V germanium module achieved a world record of 34.2%, while a III-V silicon PV module set a new class record with an efficiency of 31.3%.

The Fraunhofer Institute for Solar Energy Systems ISE has set two world records for tandem photovoltaic modules: a III-V germanium module achieved an efficiency of 34.2%, and a III-V silicon module reached 31.3%. Both values significantly exceed the theoretical limit of conventional silicon solar cells. These laboratory results mark an important milestone on the path to highly efficient next-generation solar technologies.

The III-V germanium module, with an area of 129 in² is based on triple-junction III-V cells from AZUR SPACE Solar Power, specifically adapted to the terrestrial solar spectrum. Additionally, antireflective nanostructures from Temicon are used to minimize reflection losses, further increasing efficiency. The second record-breaking module combines III-V materials with silicon over an area of 34 in², achieving an efficiency of 31.3%.

Semiconductor Materials With Different Bandgaps

The physics behind this breakthrough lies in the combination of different semiconductor materials with varying bandgaps. While conventional silicon solar cells are limited to a maximum of 33.2% efficiency by the Shockley-Queisser limit, tandem cells overcome this barrier through their multi-junction design. The III-V materials absorb the visible spectral range with higher energies, while germanium or silicon utilize the infrared range with lower energies. This layer architecture allows for much more efficient use of the entire solar spectrum compared to single-junction solar cells.

Professor Andreas Bett, director of the Fraunhofer ISE, views tandem technologies as an important bridge between cost-effective standard photovoltaic modules and expensive space solar cells. The III-V silicon variant offers a better cost-benefit ratio for terrestrial applications, while III-V germanium modules excel in applications with extreme space constraints. However, both record-breaking modules are still laboratory demonstrators developed in research projects and are not commercially available.

Higher Efficiency And Limited Area

The currently best commercially available solar modules achieve efficiencies of up to 24.8%, meaning the new laboratory values are 1.4 times higher. The tandem modules were developed in the projects Vorfahrt and Mod30plus, which involved the Fraunhofer ISE as well as industry partners such as Azur Space, Temicon, Gochermann Solar, and Audi. The participation of the automobile manufacturer already points to an important target direction: highly efficient solar cells for integration into electric vehicles, where every square centimeter of space must be utilized optimally.

For electronics developers, these advancements open up new design possibilities in the medium term, particularly for space-critical applications. With limited installation space, the higher efficiencies enable more compact system designs, which is especially relevant for electromobility, mobile electronics with solar integration, industrial IoT sensors with energy harvesting, as well as aerospace and satellite applications. Although module costs are higher than standard technologies, system costs can be improved through fewer modules needed per kilowatt, reduced balance-of-system components, and lower installation costs.

Market Readiness Will Take A Few More Years

The path to market maturity will, however, take several more years. III-V semiconductors are extremely expensive and require highly precise manufacturing processes, similar to those in space solar cell technology. In the short term, these modules will therefore first be used in niche markets such as automotive integration or specialized industrial applications before potentially becoming affordable for broader applications with appropriate scaling. As a more cost-effective alternative, other research groups are developing perovskite tandem cells, which are already achieving commercial efficiencies of around 25%.

With the surpassing of the 30 percent mark in module efficiency in the laboratory, tandem photovoltaics is emerging as a forward-looking key technology for the next generation of solar energy systems and demonstrates the enormous potential that lies beyond the physical limits of conventional silicon solar cells. (heh)

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