Fraunhofer ISE reports ‘record efficiencies’ for two tandem PV modules

17 Feb 2026

III-V germanium module at 34.2%, and III-V silicon module at 31.3% are “world beating”.

ISE PV developers Laura Stevens and Leonhard Böck.

A III-V germanium PV module with an efficiency of 34.2 percent, incorporating solar cells from Azur Space, a producer of multi-junction solar cells for space photovoltaics, and anti-reflection structures from Temicon, a producer of nano and micro structured films for displays, LED, solar or optics applications, has become what ISE calls “the most efficient solar module in the world”.

In the second PV development, announced simultaneously, a new III-V silicon PV module has achieved an efficiency of 31.3 percent, setting a record in its class, and is based on established, cost-effective silicon technology.

“Both tandem PV technologies have the potential to fill application gaps between conventional, cost-effective ground-mounted and rooftop systems on the one hand, and high-performance but more expensive space solar cells on the other,” said Prof. Dr. Andreas Bett, director of ISE. “III-V in tandem with silicon as a more affordable option, III-V on germanium as a slightly more efficient alternative, are both interesting technology routes for integrated PV applications wherever space is limited.”

Small-scale production

A few years ago, researchers at the Fraunhofer ISE achieved a new efficiency record for silicon-based solar cells with a III-V silicon solar cell reaching 36.1 percent. As part of the research project Mod30plus, they have now, for the first time, realized a small-scale production of these solar cells, adapted for interconnection with shingle technologies.

A module produced by the research team in this way, measuring 218 cm², has now achieved a record efficiency of 31.3 percent. A 833 cm² tandem module with an efficiency of 34.2 percent was built by a second ISE research team as part of the Vorfahrt project. It consists of triple III-V germanium cells, which the project coordinator Azur Space further developed for the new module technology.

For this purpose, the solar cell manufacturer adapted its triple solar cell technology to the terrestrial solar spectrum, so that it can now be produced in comparable quantities and in the same wafer formats as space solar cells. Temicon further improved the module's efficiency through a stochastic surface structure transferred onto the glass surface using nano-imprint, which minimizes reflection losses at this interface of the record module.

Conventional silicon solar cells cannot exceed a physical efficiency limit of 29.4 percent; currently commercially available PV modules already have efficiencies around 24 percent. “That is why we are conducting intensive research to replace single solar cells with multiple solar cells in modules,” said Dr. Laura Stevens, scientist at ISE and project leader of Vorfahrt. “The fact that we achieved a world record with the III-V germanium module shows the great potential in combining multiple semiconductors,” she said.