Fraunhofer ISE has reported two record efficiencies for tandem photovoltaic modules, underlining the rapid progress of multi-junction concepts beyond the physical limits of conventional silicon.
A III-V-on-germanium module achieved 34.2 percent efficiency, while a III-V-on-silicon module reached 31.3 percent. The former sets a new benchmark for terrestrial modules, the latter establishing a class record based on established silicon technology.
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For context, standard crystalline silicon modules are approaching commercial efficiencies of around 24 percent, with a theoretical cell limit of 29.4 percent. Tandem architectures aim to overcome this ceiling by stacking semiconductors with complementary bandgaps, increasing energy yield per square metre rather than relying solely on cost reductions.
Scaling tandem technology
The 31.3 percent module, measuring 218 square centimetres, was produced within the “Mod30plus” project and marks a step from laboratory cell records towards small-scale module production compatible with shingle interconnection. A previous III-V silicon cell had reached 36.1 percent, but scaling these results from laboratory cells to functional modules has proved difficult in practical implementation.
The larger 833 square centimetre III-V-on-germanium module was developed under the “Vorfahrt” project, German for “right of way”. It uses triple-junction cells supplied by AZUR SPACE and anti-reflection structures from temicon, applied to the glass surface to reduce reflection losses.
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Fraunhofer ISE’s Director, Prof. Dr. Andreas Bett, says tandem PV technologies could help bridge the gap between conventional ground-mounted or rooftop systems and high-performance space solar cells. “III-V on silicon offers a more cost-sensitive pathway, while III-V on germanium delivers higher efficiency at greater material expense,” he explains.
From an industry perspective, tandem photovoltaics is among the fastest-moving areas of solar research. The challenge now is to improve manufacturing yield and reduce costs to compete with mainstream utility and commercial installations. (TF)
