An international team of scientists from King Abdullah University of Science and Technology (KAUST), University of Freiburg and Fraunhofer Institute for Solar Energy Systems ISE has achieved a significant breakthrough for the future of perovskite-silicon tandem solar cells. Their research demonstrates a practical pathway to industrial-scale production, unlocking new efficiency potential by improving surface passivation techniques on textured silicon—an industry standard for solar cell bases. Additionally, the scientists discovered that the passivation affects the entire perovskite layer – unlike silicon, where surface treatment only influences the upper layers – leading to further efficiency improvements.
Image credit: University of Freiburg / photo: Silvia Wolf
Traditionally, silicon solar cells use textured surfaces with large pyramids to boost light absorption, but this irregularity complicates the deposition and passivation of the fragile perovskite layer above. Until now, effective passivation had only worked on flat silicon architectures. This team’s innovation lies in applying 1,3-diaminopropane dihydroiodide directly onto the bumpy perovskite surface atop these textured silicon cells, successfully protecting the entire perovskite layer—not just the surface, as is the case with silicon.
This advanced passivation method led to conversion efficiencies up to 33.1%, with open-circuit voltages reaching 2.01 volts—figures that set new benchmarks for tandem solar cell performance. Notably, the passivated perovskite top cell exhibited improved conductivity and fill factor, thanks to a deep field effect influencing the absorber’s entire bulk, rather than just its surface.
“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,” said Dr. Oussama Er-Raji, the lead author of the paper and a scientist at Fraunhofer ISE.
Textured silicon bottom cells are widely used in industry due to their established fabrication processes and superior efficiency. By proving that robust passivation is feasible on these textured surfaces, the door is opened for scalable, high-performance perovskite-silicon tandem cells using existing manufacturing infrastructure.
“This realization provides a solid foundation for all future research in this area,” said Prof. Stefaan De Wolf, Professor of Materials Science and Engineering and Applied Physics at KAUST. “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.”
“Surface passivation of solar cells is not just a nice-to-have feature; it is an essential booster for their efficiency and stability,” adds Prof. Stefan Glunz, Professor of Photovoltaic Energy Conversion at the University of Freiburg and Director of the Photovoltaics Division at Fraunhofer ISE. “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.”
The researchers’ findings build on work in the Fraunhofer lighthouse project MaNiTU as well as the projects PrEsto and Perle, both funded by the Federal Ministry for Economic Affairs and Energy.
