Researchers Achieve 33.1% Efficiency with Passivated Perovskite-on-Textured-Silicon Tandem Cells

An international team of photovoltaic researchers from King Abdullah University of Science and Technology (KAUST), the University of Freiburg, and the Fraunhofer Institute for Solar Energy Systems ISE have achieved a key step toward the industrialization of perovskite-silicon tandem solar cells. The group demonstrated that the perovskite top layer can be effectively passivated even when combined with textured silicon bottom cells—which feature pyramid-shaped surfaces and represent the industry standard.

Unlike passivation in silicon, which only influences upper layers, the treatment applied to the perovskite enhances the entire active layer, leading to further efficiency improvements. The passivated tandem cells reached an efficiency of 33.1% and an open-circuit voltage of 2.01V.

Tandem cells combine a perovskite top layer with a silicon bottom layer. This technology offers notable advances in photovoltaics, as traditional silicon cells max out at around 29.4% efficiency—near, near their current physical limit.

For large-scale production, it is advantageous to use industry-standard textured silicon cells as the bottom layer, given their well-established manufacturing processes. These cells have a textured structure that increases surface area and improves efficiency, but complicates the deposition of the perovskite layer. Until now, high-quality passivation had not been achieved on pyramidal silicon surfaces.

The group also noted that passivation improves conductivity and fill factor. This enhancement stems from a deep field effect that influences the entire perovskite layer—unlike in silicon, where only surface layers benefit.

Dr. Oussama Er-Raji, lead author of the study and a researcher at Fraunhofer ISE, stated that effective passivation on fully textured tandem cells had not been previously realized, with earlier progress limited to flat surfaces. The team achieved high-quality passivation by depositing 1,3-diaminopropane-dihydroiodide on the uneven perovskite surface.

Professor Stefaan De Wolf of KAUST mentioned that the finding provides a solid basis for future research and improves understanding of light-conversion processes within the top layer, supporting the development of improved tandem cells.

Professor Stefan Glunz of the University of Freiburg and head of photovoltaics at Fraunhofer ISE added that surface passivation is not merely supplemental but essential for improving cell efficiency and stability. He noted that passivation has been key for high performance in industrial silicon cell production, and the photovoltaic industry is likely to see similar benefits with perovskite-silicon tandem cells.

The results are based on work carried out within the Fraunhofer flagship project “MaNiTU” and the “PrEsto” and “Perle” projects, funded by the German Federal Ministry for Economic Affairs and Energy.