Nature: Perovskite silicon tandem solar cell hits 35% certified efficiency with IEC‑relevant durability

An international team led by Helmholtz‑Zentrum Berlin reported on Wednesday in Nature that a perovskite silicon tandem solar cell reached a certified 35.0 percent efficiency and maintained performance after 2,000 hours of damp‑heat exposure. The collaboration, which includes École Polytechnique Fédérale de Lausanne and Oxford PV, paired record efficiencies with stability tests aligned to industry standards.

The results arrive as manufacturers prepare pilot production of tandem modules in Europe and Asia in 2026 and 2027. The study targets the central question that has held back procurement, whether high efficiency can be retained under heat and humidity conditions used in IEC 61215 qualification.

Methods and measurements The authors, led by Steve Albrecht at Helmholtz‑Zentrum Berlin and Christophe Ballif at EPFL, combined a wide bandgap perovskite top cell with a textured silicon heterojunction bottom cell. They report reduced halide phase segregation using a mixed‑cation, mixed‑halide perovskite with a bulky organic passivation layer formed from a 2D perovskite capping treatment.

To improve contact stability, the group introduced a chemically anchored self‑assembled monolayer on the hole transport side and a low‑damage sputtered indium tin oxide with a thin buffer to limit ion migration. Accelerated aging included 2,000 hours at 85 degrees Celsius and 85 percent relative humidity on encapsulated devices, along with 1,000 hours of light soaking at maximum power point.

Fraunhofer ISE CalLab certified a 1 square centimeter aperture efficiency of 35.0 percent. The team also fabricated a tiled mini module of 16 square centimeters that delivered 28 percent under standard test conditions and retained more than 95 percent of initial output after damp‑heat exposure. The paper does not present full‑size modules, outdoor exposure beyond several weeks, or hail and UV preconditioning, which remain part of IEC type approval.

“We focused on interfaces that limit ion migration and on processes compatible with established silicon lines,” Albrecht said in a statement released by Helmholtz‑Zentrum Berlin. Ballif added that the deposition routes were designed to be transferable to larger areas, while acknowledging that uniformity and encapsulation are unresolved at module scale.

Industry context and limits Oxford PV, which operates a perovskite silicon tandem factory in Brandenburg an der Havel, Germany, has said it aims to ship commercial modules in 2026. The Nature study provides process details that cell makers can evaluate, but it does not address lead management, long‑term field reliability beyond a few thousand hours, or cost models for gigawatt‑scale lines.

Policy and procurement hurdles also persist. European regulators continue to assess end‑of‑life handling for lead‑containing modules, and financiers typically require multi‑year outdoor data before offering warranty backstops. The authors note that their chemistry choices reduce but do not eliminate ion migration under stress.

For technology buyers, the signal is that tandem performance gains are moving in parallel with durability work, which could lower balance‑of‑system costs if validated at module scale. If similar stability can be replicated on full‑size panels, perovskite silicon tandems would factor into utility procurement and rooftop upgrades, reshaping materials supply chains for specialty coatings, glass, and encapsulants.