US-based startup Bert Thin Films, Inc. (BFT) has developed a new front-side copper metallization paste for solar cell manufacturing.
“Our CuBert copper-based paste can be integrated into existing manufacturing lines and be formulated to work with the Laser Enhanced Contact Optimization (LECO) process,” the company's chief sales officer, Matthew Healy, told pv magazine, noting that the new product is particularly suitable with TOPCon solar cell manufacturing, where LECO requires twice as much silver.
“The new product has been formulated to etch through the silicon nitride layer during the firing process at peak temperatures of around 600 C,” he went on to say. “The patented formulation keeps the copper from oxidizing during the air-firing process while at the same time keeping the copper from making direct contact with the silicon, with the LECO process finalizing the contact.”
Healy also explained that any diffusion of the copper into the silicon would damage the cell and stressed that BTF has verified through accelerated testing that this does not occur with the proposed product, without providing further details.

Image: Berth Thin Films
The company has also revealed that a TOPCon cell based on an M10 wafer and metallized with the new copper paste achieved a power conversion efficiency of over 24%.
“The combination of the paste formulation and LECO process has also achieved an open-circuit voltage that is the same as a sister cell that featured silver as the back side contact,” Healy stated. “This demonstrates the viability of replacing a silver paste with a screen printable air-fired contact on a high-efficiency full-sized TOPCon solar cell.”
The company believes that, with careful control of the paste formulation and firing conditions, the performance of the cell can be further increased. It is currently working with manufacturing partners to improve the performance and optimize processing parameters. Partnerships for scaling the pastes for industry needs are also being established.
“We believe that the product should be ready for pilot-scale deployment by 2026,” Healy concluded.
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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