News #11

Silicon Heterojunction Solar Cells Realized with Record Savings in Silver

Without a significant reduction in silver content, the global demand for photovoltaics to ensure a sustainable, climate-neutral energy system cannot be met. Scientists at the Fraunhofer Institute for Solar Energy Systems ISE have now produced silicon heterojunction solar cells (SHJ) with a total silver consumption of just 1.4 milligrams per watt peak. This is about one tenth of the current standard in industrial production. To achieve this, they strongly reduced the silver content in the metallization paste for the front side metallization and completely replaced silver with copper paste on the rear side. An optimized printing process also ensured very fine electrical contacts. The copper-metallized SHJ solar cells even achieved a higher efficiency than their reference cells with traditional silver contacts.

© Fraunhofer ISE / Photo: Andreas Lorenz
Solar cell with screen-printed copper paste metallization.

To enable PV production on a multi-terawatt scale, solar cell and module manufacturer must significantly reduce their silver consumption. In 2024, the PV industry, which continues to grow, already accounted for 32 percent of the silver used industrially worldwide. In order to be able to produce sustainably in the long term, 2 milligrams of silver per watt of peak power were calculated as the target for a long-term sustainable global PV production. Scientists at Fraunhofer ISE have now succeeded in undercutting this limit for the first time, using screen printing for the solar cell metallization.

“Thanks to the balanced combination of silver-copper paste on the front side and pure copper paste on the rear side in conjunction with an optimized fine-line printing process, we were able to produce highly efficient silicon heterojunction solar cells with a minimal silver consumption of only 1.4 milligrams of silver per watt peak,” explains Sebastian Pingel, research associate at Fraunhofer ISE. “In our experiment, the solar cells even achieved a higher efficiency than the purely silver-metallized reference cells.”

© Fraunhofer ISE / Photo: Oumaima Mhirsi
Colorized scanning electron microscope image of a contact printed with silver-coated copper paste, developed at Fraunhofer ISE.

The research result is part of the joint project “HIT - High-quality innovative printing forms for the metallization of silicon heterojunction solar cells”, funded by the Federal Ministry of Economics and Climate Protection BMWK. The solar cell and module manufacturer Meyer Burger Germany GmbH is involved in the project as an industrial partner.

To optimize the composition of the metallization pastes and the screen configurations for printing the contacts, the research team initially carried out extensive simulations using the specially developed simulation tool “GridMaster”. “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,” says Andreas Lorenz, project manager at Fraunhofer ISE. “Using novel, ultra-fine mesh screens, we were able to print a fine-line front metallization with openings as fine as 17 micrometers, which is considerably thinner than a human hair.”

Visitors to The Smarter E / Intersolar trade fair in Munich can view the largely copper-metallized solar cell at the Fraunhofer ISE stand in Hall A1 from May 7 to 9, 2025.

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