A team of scientists from Germany and Saudi Arabia has achieved 33.1% efficiency with 2.01 V open-circuit voltage in perovskite–silicon tandem cells
They used PDAI treatment to passivate the texturized cell surface, solving key deposition challenges and boosting conductivity
This enhanced field effect and reduced defects to improve charge transport, fill factor, and overall device stability
Researchers at King Abdullah University of Science and Technology (KAUST), Fraunhofer Institute for Solar Energy Systems (ISE), and the University of Freiburg have achieved a ‘record’ 33.1% efficiency in perovskite–silicon tandem solar cells, and an open-circuit voltage of 2.01 V.
To achieve this level, the team developed a new method by treating the perovskite surface of the tandem solar cells with a single molecule – 1,3-diaminopropane dihydroiodide (PDAI) – and depositing it. This deals with the challenges emanating from the texturization of the silicon solar cell used as the bottom layer, which is necessary to increase its surface area. Complications also arise during the deposition of the perovskite layer.
“So far, effective passivation has not been fully harnessed on textured perovskite silicon tandem solar cells, with prior success largely confined to flat-front architectures. But we have now managed excellent passivation by depositing 1,3-diaminopropane dihydroiodide on the uneven perovskite surface,” explained the Lead Author of the paper and a Scientist at Fraunhofer ISE, Dr. Oussama Er-Raji.
They also found that while PDAI passivation improved the conductivity and fill factor of the cell, it also created a deep field effect, enhancing the bulk properties of the perovskite layer and improving the overall performance.
“This realization provides a solid foundation for all future research in this area,” explained Professor of Materials Science and Engineering and Applied Physics at KAUST, Prof. Stefaan De Wolf. “It enhances our understanding of the processes occurring in the top cell while converting light into electricity, enabling scientists to leverage this knowledge to develop better tandem solar cells.”
“For today’s silicon solar cells, surface passivation was the key for high efficiencies in industrial production, and it is encouraging that the PV industry will benefit from these positive effects for perovskite silicon tandem solar cells as well,” added Prof. Stefan Glunz, Professor of Photovoltaic Energy Conversion at the University of Freiburg and Director of the Photovoltaics Division at Fraunhofer ISE.
According to the team, this single-molecule treatment with PDAI reduces defects and enhances charge transport across the perovskite surface, resulting in better efficiency and stability. The breakthrough could accelerate the commercial deployment of perovskite–silicon tandem cells, cutting production costs and saving billions for nations transitioning to renewable energy, like Saudi Arabia, stated KAUST.
The full research paper, titled Electron accumulation across the perovskite layer enhances tandem solar cells with textured silicon, has been published in the Science journal.
Previously, in June 2025, KAUST and Fraunhofer ISE reported 27.8% perovskite-silicon tandem solar cell efficiency using a hybrid fabrication technique that replaced spin-coating (see Fraunhofer ISE & KAUST's Scalable Tandem Cell Production Breakthrough).
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