French research institute Institut Photovoltaïque d’Île-de-France (IPVF) and the Delft University of Technology (TU Delft) in the Netherlands have jointly achieved a power conversion efficiency of 31% for a 4 cm2 perovskite-silicon tandem solar cells.

The two therminal (2T) monolithic device combines nanotextured silicon heterojunction bottom cells developed at TU Delft with perovskite top cells fabricated at IPVF using ambient air slot-die coating. The performance improvement came from the integration of nanotextured silicon bottom cells, along with the fine-tuning of the ink and slot-die conditions, and the addition of an antireflection coating.

“Achieving 31% efficiency on a 4 cm² two-terminal (2T) perovskite/silicon tandem cell, with all the manufacturing processes compatible with industrial scale-up, represents a significant step towards the next generation of photovoltaic technologies,” Gilles Goaer, Chief Technology Officer (CTO) at IPVF, told pv magazine.

“Our work on the silicon heterojunction bottom cell focused on developing advanced nano-textures together with tailored plasma treatments to improve the quality of the recombination junction, which is critical for achieving high-efficiency tandem devices,” added Liqi Cao, researcher at TU Delft.

Last year, the research team reported a 24% efficiency for 10 cm2 monolithic tandem devices using planar silicon heterojunction bottom cells developed by France’s CNRS – École Polytechnique. That was an important step toward scalable tandem technology, although the planar bottom cell suffered from reflection losses, which limited the current density. “

“By combining nanotextured silicon bottom cells from TU Delft with our ambient-air slot-die-coated perovskite top cells, we were able to push the efficiency beyond 30%,” said IPVF researcher Chandralina Patra. “Several groups have already demonstrated tandem solar cells above 30% efficiency, but many of those results rely on laboratory-scale deposition methods. In our case, the perovskite layer was deposited by slot-die coating in ambient air, which is much closer to industrial manufacturing. Demonstrating this level of performance with a scalable deposition process is an important step toward commercialization.”

“Reaching 31% efficiency is an exciting result, but the most important point is that it was achieved using ambient-air slot-die coating,” she emphasized.

Looking forward, IPVF and its partners intend to further advance the scientific understanding of perovskite/silicon tandem solar cells and the mechanisms that enable such high levels of performance. Building on this achievement, IPVF is now leading efforts to transfer these innovations to larger-area devices and industrially relevant photovoltaic modules. “These developments represent an important step toward the commercialization of high-efficiency tandem technologies and reinforce IPVF’s position at the forefront of next-generation photovoltaic research and scale-up,” Patra said.

No more technical details about the tandem device were provided.

Recently, IPVF took delivery of a solar simulator with advanced electroluminescence (EL) analysis from Italy’s Ecoprogetti for testing perovskite solar cells and modules. It also has an ongoing collaboration focused on perovskite-silicon tandem solar panels with French solar manufacturer Voltec Solar.