Year: 2026
Type: report
Abstract: Crystalline-silicon (c-Si) solar cells account for over 95% of the PV market with most of these cells utilizing metal contacts produced by screen printing silver (Ag) metallization pastes. The application and processing of these contacts is a critical step in producing high efficiency (η) devices and is also the highest non-Si material cost in cell manufacturing. The pastes typically contain over 85% Ag and are thus subject to the volatility of this highly priced metal. These prices cut into the cell manufacturer’s profit margins with the costs eventually passed on to consumers; potentially impacting the Solar Energy Technology Office’s (SETO) 2030 target of 3¢/kWh. The PV industry is also competing against other consumer goods for supply, so Ag is projected to become an expensive bottleneck on the route to reach multi-terawatt production; thus, alternative metallization routes are being actively sought. Bert Thin Films (BTF) Inc.’s approach was to develop a screen printable copper (Cu) based paste (CuBertTM) that can be fired in atmospheric IR belt furnaces without the use of additional steps. In other words, producing a direct drop-in replacement for the Ag pastes. The primary goals of this project were to demonstrate that CuBertTM could be delivered to market at a 90% cost reduction of the established Ag pastes, as well as demonstrating the performance and durability of the Cu contacts on high η Si solar cells. Cu contacts made with BTF’s air fired CuBertTM metallization pastes achieved a maximum η of 21.4% when used as the front contacts on PERC cells, and an η of 24.4% when used as the rear contact on TOPCon cells. Thus, resulting in a relative η of 94% for PERC and 96% for TOPCon, when compared to the same structures commercially metallized with Ag. These results were achieved by improvements to the paste composition and processing conditions. The reliability of the Cu contacts was studied by thermally stressing the bare cells at 200°C, as well as damp heat (85°C/85%RH) testing of mini-modules containing these cells. This work was also supported by micro-structural and elemental analysis of the interface. As part of this project, domestic and non-US based suppliers of the main components of the paste were sourced to produce a more robust supply chain for the product. The findings from this project allowed BTF to reduce the risk of switching from Ag to Cu pastes; thus, creating an opportunity to produce metallization pastes in the US. BTF continues to actively work with industrial partners to improve and demonstrate the product at scale.
DOI: 10.2172/3409809
Authors: USDOE Office of Critical Minerals and Energy Innovation (CMEI), Ruvini Dharmadasa, USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office, Thad Druffel, Krishnamraju Ankireddy, Kevin Elmer, Hugo Apolo Nambo Salgado, Dustin Williams, Erin Yenney, Abasifreke Ebong, Sandra Huneycutt, Donald Intal, Ajeet Rohatgi, Vijay Upadhyaya
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Award: G8042686370
OpenAlex ID: W7204103010
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