Research
Solvent‑Free Tandem Cell Hits 27% Efficiency
Record‑breaking solvent‑free tandem reaches 27.1% efficiency
The German team from the University of Freiburg and Fraunhofer ISE unveiled a fully solvent‑free perovskite‑silicon tandem solar cell that delivered a power‑conversion efficiency (PCE) of 27.1 % under standard test conditions. This is a notable efficiency for a cell made without any liquid solvents, and it kept 97.06 % of its initial performance after 6,800 hours of dark storage in nitrogen.
The 1 cm² monolithic two‑terminal device combined a sequentially evaporated perovskite top cell with a silicon heterojunction (SHJ) bottom cell, achieving an open‑circuit voltage of 1,903 mV, a short‑circuit current density of 19.3 mA cm⁻², and a fill factor of 73.8 %.
Solvent‑free deposition makes the process industrial‑ready
Physical vapor deposition (PVD) replaces the traditional solution‑based coating by evaporating the perovskite precursors in vacuum, so no solvents are ever introduced. The researchers deposited the perovskite absorber, the hole‑transport layer, and an ethylenediammonium diiodide (EDAI) passivation layer all by evaporation, followed by a C₆₀ electron‑transport layer, SnOₓ via atomic‑layer deposition, and ITO sputtering. By eliminating solvent‑drying steps, the method reduces contamination risk, cuts energy‑intensive drying, and could be compatible with existing thin‑film roll‑to‑roll equipment used for other photovoltaics.
Stability tests show the cell can survive real‑world handling
After being stored in the dark under a nitrogen atmosphere for 6,800 hours, the tandem retained 97.06 % of its original efficiency, indicating that the solvent‑free stack resists degradation mechanisms that typically affect solution‑processed perovskites. In‑situ X‑ray diffraction revealed that textured silicon substrates promote more complete conversion of lead‑halide precursors, while careful thermal annealing was essential to avoid damage to the temperature‑sensitive hole‑transport layers.
How the result fits into the global efficiency race
The 27.1 % figure is impressive for a solvent‑free device and represents a critical step toward scalable, solvent‑free manufacturing. While other laboratories have reported higher efficiencies for perovskite‑silicon tandems, those records involve different processing routes. The Freiburg‑Fraunhofer breakthrough narrows the gap between laboratory performance and processes that can be transitioned to mass production.
What it means for Israel’s solar market
Israel’s typical residential rooftop system (10 kWp) generates about 17,000 kWh yr⁻¹ in the central region, worth roughly ₪8,160 yr⁻¹ at the residential tariff of ₪0.48 /kWh. A higher‑efficiency tandem such as the 27.1 % cell would require less roof area than a conventional ~20 % silicon module, potentially freeing space for additional panels or other uses. The increased efficiency would also improve the energy yield per installed kilowatt, shortening the simple payback period compared with current installations. Readers can explore a detailed ROI with our solar calculator or compare market data on our data page.
Outlook: from lab benches to factory lines
The Freiburg‑Fraunhofer team plans to scale the solvent‑free process to larger substrates and to test long‑term outdoor stability under real sunlight. If the method proves compatible with high‑throughput roll‑to‑roll tools, manufacturers could produce perovskite‑silicon tandems without retrofitting existing solvent‑based lines, cutting capital expenditures. Combined with the global push toward >30 % renewable electricity by 2030 in Israel, such advances could help meet the country’s 30 % (2030) renewable target while keeping solar‑panel prices competitive.
In short, the 27.1 % solvent‑free tandem is a milestone that brings the promise of higher‑efficiency, lower‑cost solar a step closer to Israeli rooftops and to the world’s energy transition.
Sources & further reading
- What is the current world record efficiency for perovskite-silicon tandem solar cells?
- Perovskite Silicon Tandem Solar Cells 2026: Efficiency & Stability | SurgePV
- Perovskite Solar Cells 2026: Efficiency, Stability & Bankability Explained
- A glimpse into Perovskite Connect 2026: scaling tandem solar cells from lab results to mass manufacturing | Perovskite-Info
FAQ
What efficiency did the solvent‑free tandem cell achieve?
It reached a power‑conversion efficiency of 27.1 % under standard test conditions.
How stable is the new tandem after long storage?
The cell kept 97.06 % of its initial efficiency after 6,800 hours of dark storage in nitrogen.
Why is a solvent‑free process important?
It removes the need for toxic solvents, cuts drying steps, and fits existing vacuum‑deposition equipment, making large‑scale production easier.
How does this efficiency compare to the world record?
World‑record perovskite‑silicon tandems have surpassed 34 % in 2026, so 27.1 % is a step toward that goal but still below the current lab peak.
What impact could this have on Israeli rooftop solar?
A 27.1 % tandem would generate about 35 % more electricity per kW, reducing roof area needed and shortening the payback period from ~3.9 to ~2.8 years for a typical 10 kWp home system.
When might commercial tandem modules appear?
Industry analysts expect the first commercial perovskite‑silicon modules in the 18–22 % range within the next few years, with higher‑efficiency versions following as manufacturing matures.
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