Nature study reports perovskite–silicon tandem cells maintain performance under IEC‑relevant damp‑heat stress

A team led by the École Polytechnique Fédérale de Lausanne reported today in Nature that perovskite–silicon tandem solar cells retained more than 95 percent of their initial efficiency after 2,000 hours of damp heat at 85 degrees Celsius and 85 percent relative humidity. The study, conducted with Helmholtz Zentrum Berlin and Fraunhofer ISE, targets the reliability concerns that have slowed industry adoption of tandems.

The findings matter because module buyers require evidence that new materials can meet or approach IEC 61215 stress tests. With Oxford PV scaling tandems in Europe and Chinese and US manufacturers planning pilot lines, durability data now influences procurement and financing decisions.

What the study shows

The researchers introduced an ionic crosslinker in the perovskite absorber to suppress halide ion migration, then added an ultrathin atomic layer deposition alumina interlayer at the hole‑selective contact to block moisture ingress and interfacial reactions. They verified reduced ionic mobility and structural stability using time‑of‑flight secondary ion mass spectrometry and grazing‑incidence X‑ray scattering, including operando measurements at the BESSY II synchrotron in Berlin.

On 1 square centimeter perovskite–silicon tandem cells with initial power conversion efficiencies above 32 percent, maximum power output dropped by less than 5 percent after 2,000 hours of damp heat with one sun illumination and maximum power point tracking. Mini‑modules of 16 square centimeters retained about 90 percent of initial output after 1,000 hours under the same conditions. Michael Grätzel at EPFL and Eva Unger at Helmholtz Zentrum Berlin are corresponding authors.

What it does not prove

The devices were laminated under glass with standard encapsulants, not integrated into full‑size modules that complete the entire IEC test matrix including thermal cycling, humidity freeze, and extended UV exposure. The work does not demonstrate high‑throughput manufacturing compatibility or yield on commercial lines. Fraunhofer ISE performed independent stress testing, but certification has not been issued.

Implications for manufacturers

If the crosslinker and interlayer stack translate to larger areas and automated coating, manufacturers could address a primary failure mode in perovskites without major process changes. That would reduce qualification risk for tandem pilots scheduled for 2026 and 2027, increase confidence among project developers, and intensify competition for incumbent silicon suppliers weighing efficiency upgrades against line conversions.