Fraunhofer ISE Sets World Records With 34.2% And 31.3% Efficient Tandem Solar Modules

Scientists at the Fraunhofer Institute for Solar Energy Systems ISE have set new world records in solar module efficiency by developing two advanced tandem photovoltaic modules. The research team announced that a III-V germanium PV module achieved a record efficiency of 34.2 percent, making it the most efficient solar module in the world to date. At the same time, a III-V silicon PV module reached 31.3 percent efficiency, marking a record in its category and highlighting the potential of combining high-performance materials with established silicon technology.

The 34.2 percent efficient module was developed using triple III-V germanium solar cells supplied and further refined by AZUR SPACE Solar Power GmbH. These cells were specially adapted for terrestrial solar conditions, so they can now be produced in similar quantities and wafer formats as space solar cells. The module, measuring 833 square centimeters, was created as part of the “Vorfahrt” research project. To further enhance performance, temicon GmbH applied a nano-imprinted stochastic surface structure onto the glass surface of the module. This innovation reduces reflection losses and increases the amount of sunlight entering the solar cells.

The second breakthrough came from the “Mod30plus” project, where researchers developed a 218 square centimeter III-V silicon tandem module with an efficiency of 31.3 percent. This module builds on earlier achievements, including a silicon-based III-V solar cell that previously reached 36.1 percent efficiency at the cell level. For the first time, the team managed small-scale production of these advanced solar cells and adapted them for interconnection using shingle technology, which helps improve module performance and reliability.

According to Prof. Dr. Andreas Bett, Director of Fraunhofer ISE, both tandem technologies could help fill the gap between conventional, cost-effective rooftop or ground-mounted solar systems and the highly efficient but expensive solar cells typically used in space applications. He explained that III-V silicon technology offers a more affordable solution, while III-V germanium provides slightly higher efficiency. These options could be particularly useful in applications where installation space is limited and higher energy output per area is required.

Conventional silicon solar cells are approaching their physical efficiency limit of about 29.4 percent, while commercial modules currently operate at around 24 percent efficiency. Researchers believe that stacking multiple semiconductor materials in tandem structures is a promising way to move beyond these limits. Dr. Laura Stevens, project leader of “Vorfahrt,” noted that replacing single-junction cells with multi-junction designs significantly boosts performance. Dr. Jonas De Rose, who leads “Mod30plus,” added that tandem photovoltaics is one of the fastest-growing areas in solar research today.

Several industry and research partners contributed to the development of the III-V silicon module, including Karlsruhe Institute of Technology, LPKF Laser & Electronics SE, and SUNSET Energietechnik GmbH, among others. The germanium-based record module also involved partners such as Audi AG and additional technology firms. Both projects received funding support from the German Federal Ministry for Economic Affairs and Energy, reflecting Germany’s continued investment in next-generation solar innovation.