Nature Energy reports perovskite silicon tandem mini modules pass IEC 61215 stress tests

A consortium led by the Swiss Federal Institute of Technology Lausanne and Fraunhofer Institute for Solar Energy Systems reports that perovskite silicon tandem mini modules completed the full IEC 61215 accelerated stress sequence with limited degradation. The study, published this week in Nature Energy by Christoph Ballif at EPFL and Stefan Glunz at Fraunhofer ISE, found less than 5 percent drop in output after damp heat, thermal cycling, and UV exposure on glass glass mini modules. The work targets the main barrier to deployment, durability under standardized tests.

The team sent devices for independent evaluation at Fraunhofer ISE CalLab PV Modules and at TÜV Rheinland to remove lab bias. Module makers and project developers have cited these tests as a prerequisite for procurement decisions on tandem products expected in late decade roadmaps.

Methods and results Researchers built 100 to 200 square centimeter mini modules that pair a high quality silicon heterojunction bottom cell with a wide bandgap perovskite top cell. The stack used a tunnel recombination junction on textured silicon, a tin oxide electron contact, and a self assembled passivation layer to limit ion migration at grain boundaries.

Devices were encapsulated in glass glass with UV filtering EVA and edge seals, then subjected to damp heat at 85 degrees Celsius and 85 percent relative humidity for 1000 hours, thermal cycling from minus 40 to 85 degrees Celsius for 200 cycles, mechanical load, and UV preconditioning. Independent labs measured stabilized efficiencies near 28 percent at the start, then recorded power loss below 5 percent after the full sequence under maximum power tracking.

The authors used in situ photoluminescence and grazing incidence X ray scattering to monitor halide phase stability during stress. Time of flight secondary ion mass spectrometry tracked iodine and mobile cation profiles before and after tests. Henry Snaith at the University of Oxford, a co author, reports that interfacial chemistry and a thin two dimensional capping layer were key to suppressing defect formation during heat and moisture exposure.

Why this matters for industry Perovskite silicon tandems have set cell efficiency records above 33 percent, but bankability depends on module reliability and safety, including IEC 61215 and 61730. Prior studies cleared subsets of tests or relied on small area cells. Mini module passage under third party supervision narrows the gap to product qualification, although field data across climates, potential induced degradation, and manufacturing yield still need proof.

Module manufacturers in China and Europe have mapped tandem introductions to 2027 and 2028, but financing has hinged on durability evidence. If results hold for full size modules and production lines, capital plans will shift toward tandem compatible coatings, encapsulants, and lead capture layers to address end of life regulations. For the wider technology landscape, credible lifetime metrics unlock competition on efficiency per area, which shapes factory siting, supply chains for perovskite precursors, and system design for constrained rooftops and land.