Scientists at Germany’s Fraunhofer Institute for Solar Energy Systems ISE (Fraunhofer ISE) have claimed to have produced silicon heterojunction solar cells (SHJ) with a total silver consumption of 1.4 mg per watt of peak power. This consumption would be one-tenth compared to the current industrial production standard.

The scientists said they considerably reduced the silver content in the metallization paste on the solar cells’ front side and fully replaced silver with copper paste on the rear side.

Front-side metallization refers to applying metal contacts to the front surface of a silicon solar cell to collect and conduct the electrical current generated when sunlight excites electrons within the silicon material.

The scientists also used an optimized printing process to form very fine electrical contacts. They said the copper-metallized SHJ solar cells achieved a higher efficiency than the purely silver-metallized reference cells.

In 2024, the solar industry comprised 32% of the global silver industrial use. Two milligrams of silver per watt of peak power was determined as the target for long-term sustainable production of solar cells. Fraunhofer ISE’s claimed achievement undercuts this target by 0.6 mg.

This research is part of the ‘HIT-High-quality innovative printing forms for the metallization of silicon heterojunction solar cells’ joint project. The project is funded by Germany’s Federal Ministry of Economics and Climate Protection. Solar cell and module manufacturer Meyer Burger Germany is its industrial partner.

The research team initially conducted extensive simulations using a specially developed tool called Grid Master to help optimize the composition of the metallization pastes and the screen configurations for contact printing.

Andreas Lorenz, Project Manager at Fraunhofer ISE, said, “It turned out that the selection of an optimal screen configuration plays just as important a role as the choice of the metallization paste to reduce the silver consumption.”

He added, “Using novel, ultra-fine mesh screens, we were able to print a fine-line front metallization with openings as fine as 17 μm, which is considerably thinner than a human hair.”

Recently, Fraunhofer ISE announced that its latest research has found that ultraviolet tests rate degradation of TOPCon silicon solar modules significantly higher than performance reduction in real-life conditions.