Researchers at the University of New South Wales (UNSW), working with SunDrive and Shenzhen APG, have found that the characteristics of nickel powder can determine whether it effectively replaces some silver in TOPCon solar cell metallization. Their tests showed that an optimized nickel blend lowered rear-finger raw-metal costs by 6.8% with little change in cell efficiency.
The team tested two commercial nickel powders, with particle sizes of about 1.5 μm and 3.8 μm, in screen-printed pastes for the rear side of industrial n-type TOPCon cells. Nickel made up 5% to 15% of the metal-powder fraction. The researchers compared electrical performance and printing behavior, and measured paste consumption to assess the cost impact.
A paste containing 10% of the coarser Ni-4000 powder achieved an efficiency of 26.325%, compared with 26.349% for the silver-only baseline. It reduced raw-metal costs for the rear fingers by 6.8%, equivalent to $561,500 per gigawatt, according to the study.
Results varied with the powder used. The finer Ni-1500 formulation showed greater resistive losses at the same nickel loading; at 10% nickel, cell efficiency fell to 26.124%. The researchers also observed that nickel substitution could widen printed fingers and increase paste consumption.
Raising the Ni-4000 content to 15% kept efficiency at 26.302%, but increased paste consumption by 17% against the silver-only baseline. As a result, the cost saving fell to 0.3%, showing that higher nickel content does not necessarily deliver greater savings.
The study, published in Solar Energy Materials and Solar Cells, concludes that cost and performance assessments need to account for powder properties, electrode formation and actual paste use. The researchers also identified interactions with glass-frit chemistry and paste rheology, as well as long-term metallization reliability, as areas for further optimization.
Sources: pv magazine.