Silver-lean screen-printing metallisation for industrial TOPCon solar cells: Enabling an 80 % reduction in silver consumption

The photovoltaic (PV) industry is transitioning from Passivated Emitter and Rear Contact (PERC) technology to Tunnel Oxide Passivated Contact (TOPCon) solar cells, which offer higher efficiency but require significantly more silver for screen-printed metallisation. This increased silver demand presents challenges for both manufacturing costs and resource sustainability, particularly as PV production scales towards the terawatt level. To address this, we present a silver-lean screen-printing metallisation technology that substantially reduces silver consumption in industrial TOPCon solar cells while maintaining their excellent efficiencies. Our approach utilises a two-step printing process, where a small amount of silver paste is printed as dashes to form contacts with the silicon surface, followed by the printing of floating fingers and busbars with alternative silver-lean pastes. Using this approach, we achieved an 85 % reduction in rear-side silver usage in 25 %-efficient TOPCon cells, with only a marginal efficiency gap (∼0.1 %) compared to TOPCon cells with industrial standard metallisation design. We also demonstrated an ultra-low silver consumption of 2 mg/W by implementing our design on both sides of TOPCon cells. With further optimisations in dash pattern design and printing processes, we expect these cells to reach efficiencies comparable to industrial TOPCon cells with standard metallisation designs. Additionally, we identified a negative interaction between Ag dashes and Al fingers during co-firing, highlighting the need for paste development to take full advantage of this metallisation approach. This work demonstrates a practical and industry-relevant approach to reducing silver consumption in screen-printed metallisation, paving the way for more sustainable and cost-effective manufacturing of TOPCon solar cells. • The high silver consumption in industrial TOPCon solar cells presents substantial challenges to the PV industry. • This work presents a silver-lean screen-printing metallisation technology for TOPCon solar cells. • Several silver-lean paste materials, such as Ag-coated Cu, pure Cu and Al, have been tested with our design. • Up to 85 % reductions in rear-side silver consumption has been demonstrated without significant losses in efficiency. • An ultra-low silver consumption of 2 mg/W has also been demonstrated on fabricated TOPCon cells.