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The German research institute is investigating the use of commercially available vacuum evaporation equipment to fabricate perovskite thin films and contact layers in the manufacturing of perovskite-silicon tandem cells.
Researchers at the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Germany are currently investigating vacuum deposition to fabricate perovskite thin films and contact layers for perovskite-silicon tandem solar cells.
Until now, the highest efficiency tandem cells, measuring 1 cm² or even smaller, are typically made with a wet spin chemical coating tool. “It is a good method for rapid testing, but it is not scalable to industrial-sized substrates,” Juliane Borchert, a scientist at Fraunhofer ISE, told pv magazine .
Another point against chemical spin coating is that it cannot be used on substrates with a pyramidal texture, typical of the front face of silicon solar cells.
Vacuum deposition is one of the two main processing routes for perovskite-silicon tandem solar cells on an industrial scale. The other is a solution-based process.
“There is a wide variety of methods for deposition of perovskite thin films. Some rely exclusively on wet chemical processes, such as spin coating, knife coating, and printing. Others are solvent-free evaporation processes in a vacuum, such as physical vapor deposition or pulsed laser deposition,” explains Borchert.
The researchers are using M12-sized wafers for their experiments, which are being carried out as part of a three-year, €6.5 million ($7.0 million) research project called Liverpool.
“At Liverpool we use a hybrid deposition method that combines the best aspects of both approaches. It involves a vacuum evaporation process to deposit the inorganic components and then a second wet chemical step to convert this inorganic scaffold into the complete perovskite film. Our goal is to produce several M12 wafers per hour, or 40 per day,” explains Borchert.
To put Liverpools research in context, Fraunhofer ISE has several perovskite-silicon tandem solar cell projects underway. For example, the Pero-Si-Scale project focuses on the construction of a pilot line composed solely of scalable processes and technologies, including the characterization and testing steps of M12 tandem cells and modules. Both were launched in the spring of last year and are funded by the Federal Ministry for Economic Affairs and Climate Action (BMWK). The Liverpool project will run until April 2026.
In November, a group of researchers at Fraunhofer ISE published a study estimating that the practical potential power conversion efficiency of perovskite-silicon tandem solar cells could reach up to 39.5%.
In late January, the German institute and UK-based Oxford PV announced the manufacture of a perovskite-silicon tandem solar module with a glass-glass design and a power conversion efficiency of 25%. |
