30% Less Silver For Silicon PV Cells: Fraunhofer ISE

• Researchers at Fraunhofer ISE along with Koenen GmbH, Murakami and Kissel+Wolf GmbH have created contact fingers with a width of 19 µm and height of 18 µm for fine-line metallization screens
• This process was accomplished by metallizing PERC solar cells using optimal screen parameters and with a nominal finger width of 24 µm, the team achieved an efficiency of h=22.1%
• According to the team, highly engineered screen and paste systems for fine-line metallization could help manufacture solar cells with nearly invisible contact fingers on an industrial scale in the near future

Germany's Fraunhofer ISE claims an innovative technique of specially developed fine-line metallization screens helped it create contact fingers with a width of merely 19 µm and a height of 18 µm in a single printing step which ensures 30% less silver is needed in the production of silicon solar cells, thereby reducing manufacturing costs significantly.

Fraunhofer ISE's team worked with its industry partners – screen manufacturers Koenen GmbH and Murakami Co. Ltd. along with screen chemical supplier Kissel+Wolf GmbH – for the test that helped bring down the contact fingers' width to less than 20 µm. The FINALE project ran from December 2016 to March 2019. Details about the project can be viewed on the Fraunhofer ISE website.

Using a traditional screen printing process for fine-line metallization of silicon solar cells, the team selected a nominal finger width of 24 µm and used optimal screen parameters, which resulted in PERC cells with 22.1% efficiency.

"Using highly engineered screen and paste systems for fine-line metallization, it could be possible to start manufacturing solar cells with nearly invisible contact fingers on an industrial scale in the near future," said Dr. Florian Clement, head of Production Technology at the Structuring and Metallization Department at Fraunhofer ISE. "This would represent a great advantage for applications in integrated photovoltaics, where aesthetic, homogeneous module surfaces are in demand."

According to the team, the contact fingers when integrated into modules — particularly with newer technologies such as multi-busbar interconnection with 8 to 15 busbars — enable a notable reduction of the power loss in the contact fingers.

Results of the FINALE project will be shared at the 36th EU PVSEC in Marseille, France in September and the 29th Asian PVSEC in Xi'an, China in November.