Scientists at the Fraunhofer Institute of Solar Energy (ISE) have developed a new laser technique to reduce the amount of silver used in the production of solar panels and achieve maximum module efficiency using a thin aluminum foil.

In the new technique called FoilMet, the ISE researchers interconnected the neighboring solar cells in a module using a thin strip of aluminum foil. The team observed that the process hardly takes less than a tenth per wafer per second. The scientists connected the aluminum film to the conductor paths using a unique laser micro-welding mechanism while bonding it to the silicon nitride surface in the intermediate finger area.

The interconnection with aluminum foil served to be resource-saving as the scientists did not use conductive adhesive or soldering to bind the cells. The contact resistances between the film and electrodes were very low, yielding higher efficiencies in the solar modules part of the experiment. The string design pursued in the experiment was curved.

The team successfully used aluminum as the potential substitute for copper connectors with lead-containing solder or adhesive with silver. The use of silver in solar module manufacturing and its related concerns are being studied by researchers worldwide.

The use of silver leads to concerns in interconnecting the solar cells. The solid mechanical adhesion deployed by the ISE scientists in their module goes beyond the potential of a metal foil. The aluminum foil helped the team establish an interconnection in shingle construction, in which the solar cells form a slight overlap while arranging the cells close to each other.

According to ISE scientists, the FoilMet technique is cost-efficient for mass production of solar modules, maintaining higher efficiencies.

Head of Structuring and Metallization in ISE Jan Nekarda observed, “The fascinating thing about our technology is that it promises high module efficiencies and aesthetics owing to low electrical resistance. The possibility of shingling combined with the very high mechanical flexibility of the string appears predestined for niche applications in integrated photovoltaics. On the other hand, the high potential for cost and material savings makes the process even more interesting for the PV mass market.”

In February 2022, ISE scientists collaborated with researchers from the Fraunhofer Center for Silicon Photovoltaics and a Germany-based solar modules recycler Reiling GmBH to develop a method to recycle discarded solar modules. The team of scientists fabricated wafers made of recycled silicon into PERC solar cells, which had a conversion efficiency of 19.7%.

Researchers worldwide are conducting experiments to discover a potential alternative for silver in solar modules. Metals like silver, indium, and bismuth are scarce on earth. According to a report by researchers from the School of Photovoltaic Renewable Energy and Engineering (SPREE), University of New South Wales, such scarcity is likely to obstruct the sustainable production of photovoltaics on a multi-terawatt scale.