As silver prices approach $50 per ounce, researchers from the University of New South Wales (UNSW) and the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) say pv magazine that efforts to reduce silver use in solar cells will not compromise the quality of the modules if they are designed properly.
Silver traded around $49 an ounce on Thursday, compared to around $44 in the last week of September. The price increase and the possible crossing of the $50 threshold in the coming weeks or months are prompting the PV industry to intensify efforts to implement “thrift,” or reducing the silver content in cells and modules.
But how much can this process be promoted without affecting the quality of the PV products?
“This doesn’t necessarily have to happen,” said Ning Song, a researcher at UNSW pv magazine. “If silver reduction is properly designed with good design and process control, it need not compromise the quality of solar cells and modules. The key is to adopt appropriate approaches rather than simply reducing silver content.”
Andreas Lorenz, a researcher at Germany’s Fraunhofer ISE, also said that the quality of sun products will not be affected by the silver reduction.
“A reduction in the quality of solar cells and modules would not be acceptable. I don’t see any indication of a reduction in quality, despite a significant silver reduction per cell,” said Lorenz.
Song noted that if silver reduction is not implemented correctly, potential problems could include higher series resistance, reduced solder quality and long-term reliability issues. “These are technical challenges that can be managed effectively through good metallization design and process optimization,” she said.
Lorenz explained that cell interconnection using busbarless cells with multiwire interconnection could become challenging if the finger height becomes too low, potentially causing local connection problems between wires and printed or fired contacts. “However, I am confident that these challenges will be resolved in mass production,” he added.
Song said researchers are focusing on replacing silver with cheaper metals such as copper, aluminum or nickel and optimizing interconnect designs.
“For example, multi-busbar (MBB) and railless layouts at the module level can help reduce silver consumption while maintaining performance,” she explains. “Additionally, fine line full-open stencil screen printing and copper electroplating are being actively explored as potential silver reduction technologies.”
The scientists told it pv magazine that they are convinced that in the coming years the industry will intensify efforts to reduce or even replace silver with copper.
“We believe rising silver prices are driving strong interest in alternative metallization approaches, including copper, nickel, aluminum and various hybrid solutions,” Song said. “This is currently a very active area of both research and industrial development. In fact, some hybrid copper-silver methods have already been applied in commercial heterojunction (HJT) solar cells. At the same time, any large-scale market shift in mainstream cell products will ultimately depend on ensuring that cell and module efficiency, long-term reliability, as well as processing costs and impact on environment, can be properly managed.”
Lorenz said screen-printable copper or copper-containing pastes are the most promising method to significantly reduce silver use.
“Given the currently ongoing massive increase in the price level of silver, the pressure on the PV industry to reduce silver is currently very high,” explains the Fraunhofer ISE researcher. “This will accelerate the development of new metallization pastes to replace silver with alternative materials such as copper and nickel.”
Lorenz added that replacing silver pastes with copper-containing pastes in tunnel oxide passivated contact (TOPCon) solar panels is more difficult due to oxidation, copper in-diffusion, cross-contamination and panel-level reliability issues.
“My expectation is that the very rapid development of new screen/stencil generations to print increasingly finer contacts with less silver, especially on the front, will continue for some time,” says Lorenz. “However, there are limitations to further reduction of the finger width, as the printed fingers are already very narrow. Very interesting are the current developments of fire-permeable copper paste for TOPCon cells, with initial tests showing promising results on TOPCon cells. This could be a way to replace silver with copper in the long term.”
This content is copyrighted and may not be reused. If you would like to collaborate with us and reuse some of our content, please contact: editors@pv-magazine.com.
