Nature study reports perovskite on silicon tandem cells pass key stability tests, moving closer to bankable solar products

A team led by Helmholtz Zentrum Berlin and the University of Oxford reports today in Nature that perovskite on silicon tandem solar cells retained most of their output after standard accelerated aging protocols, a milestone for stability that the technology has struggled to meet. The study, led by Steve Albrecht at HZB with collaborators in Henry J. Snaith’s group at Oxford, addresses damp heat and thermal cycling failure modes that have limited bankability.

The most consequential detail is third party verification. Fraunhofer ISE CalLab PV Cells confirmed efficiency values before and after testing, reducing uncertainty that has trailed earlier claims.

The researchers fabricated perovskite on silicon tandem cells using a passivated contact silicon bottom cell and a wide bandgap formamidinium based perovskite top cell. They applied interface passivation and compositional alloying to suppress ion migration, then used low temperature encapsulation with edge seals compatible with perovskites.

Devices were held at 85 degrees Celsius and 85 percent relative humidity for one thousand hours, and subjected to two hundred thermal cycles between minus 40 and 85 degrees Celsius, following IEC 61215 style protocols at cell level. Maximum power point tracking under one sun illumination showed output retention above 90 percent after the combined tests, according to the paper.

The team used time of flight secondary ion mass spectrometry and photoluminescence mapping to monitor halide movement and defect states before and after aging. They report that surface passivation reduced non radiative recombination, and that alumina based barrier layers deposited by atomic layer deposition limited moisture ingress without impairing carrier extraction.

The paper does not claim full size module certification. The work focuses on cell level and mini module devices, and the authors note that lamination, ultraviolet exposure over longer periods, and mechanical reliability in large area glass to glass builds still require study. Scale up to wafer sized tandems with uniform layers remains a manufacturing challenge.

Oxford PV, a spin out linked to Snaith’s lab, already ships commercial perovskite on silicon cells, and large module makers such as Longi and Jinko have disclosed pilot tandem lines. Evidence that tandems can clear standard stress tests at the device level will influence procurement models, insurance underwriting, and factory capex decisions as developers weigh higher efficiency against process risk in a market shaped by data center power demand and land constrained projects.