Nature study reports perovskite silicon tandem cells clearing key stability tests needed for bankability

A team led by Christophe Ballif at EPFL and Steve Albrecht at Helmholtz Zentrum Berlin reports in Nature today that perovskite silicon tandem solar cells maintained output through several industry standard accelerated stress tests. The study, which includes Oxford PV and other European partners, targets the durability gap that has kept high efficiency tandems out of mass deployment.

The most important result is stability under damp heat and thermal cycling that mirrors parts of IEC 61215 certification. The authors report independently certified efficiencies above 33 percent on small area devices and retention near 95 percent of initial power after 2,000 hours at 85 degrees Celsius and 85 percent relative humidity under maximum power point tracking with a UV filter, along with less than 5 percent loss after 200 thermal cycles between minus 40 and 85 degrees.

What the study shows The group built tandems on industrial grade silicon heterojunction bottom cells and used a wide bandgap perovskite top cell with interface passivation and compositional tuning to suppress ion migration. The stack employed ultrathin oxide passivation, a self assembled monolayer for the hole contact, and a two dimensional perovskite capping layer to reduce halide movement at grain boundaries.

Encapsulated test coupons ran at one sun equivalent using spectrally matched illumination while holding the device at maximum power. The team monitored degradation with electroluminescence imaging, time of flight secondary ion mass spectrometry, and transmission electron microscopy to track interdiffusion and phase changes at buried interfaces.

The authors state that not all certification elements are complete. Large area modules, humidity freeze, mechanical load, and potential induced degradation remain open. “This work shows that specific failure modes can be mitigated with interface and encapsulation design, but it does not yet guarantee 25 year outdoor lifetimes,” Ballif said in a statement released by EPFL. Albrecht said the results close a gap between record efficiencies and reliability data that investors require.

Why this matters now Manufacturers in Europe and Asia plan pilot lines for tandem modules in 2026 and 2027. Bankability depends on repeatable stability data under standard protocols, not only headline efficiencies. The Nature report provides a detailed test recipe and failure analysis that equipment makers and material suppliers can use to prioritize coatings, adhesives, and UV filtering for first products.

For the broader technology landscape, the data signals that high efficiency tandems are moving from lab curiosity toward engineering programs constrained by certification and supply chain choices. That shift will pressure module makers to integrate reliability analytics into cell design and it will expand demand for metrology, encapsulants, and barrier films across the solar manufacturing stack.