The U.S. startup has introduced a screen-printable copper paste for backside solar cell metallization that can be fired in air and co-fired with standard silver frontside pastes using conventional manufacturing processes. Tested on TOPCon cells, the paste contributed to achieve a 25% efficiency and passed 2,000-hour damp heat testing.
Image: Bert Thin Films
US-based Bert Thin Films (BTF) has unveiled a new copper paste for backside solar cell metallization.
According to the manufacturer, the new paste can be screen printed and fired in air, and can also be co-fired with commercial silver pastes for frontside metallization.
“The metallization process followed the conventional industry operation,” the company’s chief sales officer, Matthew Healy, told pv magazine. “A standard M10 wafer is initially printed using an automated screen printer with CuBert™ copper pastes on the rear side and subsequently dried. The wafer is then flipped and printed with a standard silver paste on the front side and dried. The wafer is next transported to a belt furnace for a thirty-second firing profile having a peak temperature exceeding 700 C. The cells are finally processed using aLaser Enhanced Contact Optimization (LECO) tool.”
The company tested the new metallization product on a TOPCon architecture using typical industry screen printing and high temperature fire furnaces.  The co-fire was performed in air at one of its facility and also at an undisclosed independent site. For the backside metallization it used unspecified commercial silver pastes.
“In December, we achieved a 25% efficiency on sequential fire TOPCon as well as successful 2,000 h damp heat data,” Healy said, without providing further details. “These results demonstrate that high efficiency devices can be fabricated using silver frontside and BTF copper backside pastes.”
In April, BTF launched a front-side copper metallization paste. The CuBert copper-based paste can be integrated into existing manufacturing lines and be formulated to work with the LEGO process.
Based in Kentucky, Bert Thin Films, Inc. focuses on enabling copper-based solar cell production across a range of device architectures. It was awarded $1 million in funding by the U.S. Department of Energy in 2021.
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