Fraunhofer ISE develops 23.4%-efficient PERC solar cells with limited silver amount

Researchers from Germany’s Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) developed a reproducible method to make ultra-fine contact fingers measuring just 14 µm. They applied the process in passivated emitter and rear cell (PERC) cell fabrication with the aim of reducing silver consumption without compromising the device’s performance.

“The power conversion efficiency was 23.4%, verified and confirmed by Fraunhofer ISE CalLab,” the research project manager Elmar Lohmüller told pv magazine, adding that the Fraunhofer group has a 30-year track record in optimizing PERC processes.

The result represents an internal record-breaking achievement after the group’s previously reported 20 µm front side contact milestone, according to Andreas Lorenz, who heads up the PV printing technology group at Fraunhofer ISE.

The team used a commercially available PERC silver paste, in a screen printer from German equipment provider ASYS Automatisierungssysteme. The screen printer relied on a fine mesh screen supplied by Japan’s Asada Mesh Co. Ltd.

Looking ahead, Lorenz sees room for further improvement to reduce silver consumption by further reducing the finger width and by replacing silver paste with other materials, such as copper, for a range of high-efficiency cell technologies, including tunnel oxide passivated contacts (TOPCon), silicon heterojunction and perovskite tandem solar cells.

The research will be presented at the 41st European Photovoltaic Solar Energy Conference (EUPVSEC) in Vienna in September. The research project, dubbed “Guten Morgen”, was funded by Germany’s Federal Ministry of Economic Affairs and Climate Action (BMWK).

The Fraunhofer ISE collaborated with ASYS Automatisierungssysteme on solar cell metallization projects in the past as well as with other partners to develop processes that reduce silver consumption.