A solar module that converts a third of incoming light into electricity was long considered a technical utopia. The Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg achieved exactly that in February 2026: 34.2 percent efficiency on a tandem module, more than ever measured on a solar module worldwide. A second record followed shortly after, a silicon tandem module at 31.3 percent.
What the Records Mean
To understand the scale: conventional silicon solar cells run into a physical limit at 29.4 percent, the so-called Shockley-Queisser limit for single-junction cells. Commercially available modules today sit at an average of roughly 24 percent. The Fraunhofer ISE tandem module therefore exceeds typical commercial products by more than ten percentage points and simultaneously breaks the physical ceiling of classical silicon technology.
The 34.2 percent record was achieved on an 833-square-centimetre module based on III-V semiconductor compounds and germanium. The cells for this module were supplied by AZUR SPACE, a company specialized in high-performance photovoltaics for space applications. The second world record, 31.3 percent on a 218-square-centimetre module, emerged from the Mod30plus project using silicon tandem technology.
How Tandem Modules Work
The efficiency of a solar module is limited because each semiconductor layer efficiently absorbs only a specific wavelength range of light. Tandem modules stack two or more layers on top of each other, each optimized for a different part of the light spectrum. A larger share of the incoming solar energy can therefore be used than any single layer ever could.
III-V tandem cells use compound semiconductors from the third and fifth groups of the periodic table, such as gallium arsenide or indium gallium phosphide. These materials are more complex to manufacture than silicon but achieve significantly higher efficiencies. Until now they were primarily used in space, where weight and area are expensive and efficiency is the top priority.
Between Lab and Market
The record numbers come from controlled laboratory conditions. For broad commercial use of III-V tandem modules, the high material cost and elaborate manufacturing processes stand in the way of scaling. Fraunhofer ISE operates both projects within research programmes aimed at long-term cost reduction.
Silicon tandem cells, as in the Mod30plus project, are closer to commercial application. Several manufacturers are working on production lines for silicon-perovskite tandem modules that could reach the market within a few years. The 31.3 percent efficiency gives the industry a new reference point.
Significance for the Energy Transition
Efficiency gains have direct practical consequences. A module with 34 instead of 24 percent efficiency generates 42 percent more electricity on the same area. For densely populated regions, rooftops or agrivoltaics, where space is scarce, that is a substantial advantage. The International Energy Agency (IEA) identified solar energy as the most important driver of the global energy transition in its 2025 World Energy Report.
Fraunhofer ISE institute director Andreas Bett called the result in February a milestone that shows how far tandem module technology has advanced. The next challenge is certification of the measurements by independent institutes and the transfer of the technology into scalable manufacturing processes. The institute expects commercial tandem modules with efficiencies above 30 percent to reach the market by the end of the decade.