Fraunhofer ISE redesigns silicon solar cells with ‘record’ low level of silver

29 Apr 2025

Sustainable heterojunction system uses only 10% of the silver required by conventional devices.

Solar cell with screen-printed copper paste metallization.

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 developed 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 significantly 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 fine electrical contacts. The copper-metallized SHJ solar cells even achieved a higher efficiency than their reference cells with traditional silver contacts.

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.

Screen printing metallization

In order to be able to produce sustainably in the long term, 2 mg of silver per watt of peak power were calculated as the target (according to the Royal Society of Chemistry’s Energy & Environmental Science journal) for a long-term sustainable global PV production. Scientists at 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,” said Sebastian Pingel, research associate at ISE. “In our experiment, the solar cells even achieved a higher efficiency than the purely silver-metallized reference cells.”

SEM image of a contact printed with silver-coated copper paste.

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 Germany’s Federal Ministry of Economics and Climate Protection (BMWK). The solar cell and module manufacturer Meyer Burger Germany is also 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 called “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,” said Andreas Lorenz, project manager at 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.