ECN publication
Title:
Strategies for ultra-low Ag consumption of industrial n-type cells
 
Author(s):
Geerligs, L.J.; Lamers, M.W.P.E.; Burgers, A.R.; Dovrat, M.; Eytan, G.; Bertens, J.; Kivits, M.; O'Sullivan, B.; Debucquoy, M.
 
Published by: Publication date:
ECN Solar Energy 20-5-2014
 
ECN report number: Document type:
ECN-M--14-022 Conference Paper
 
Number of pages: Full text:
7 Download PDF  

Abstract:
For cost reduction as well as reduction of environmental footprint of solar cells, it is important to reduce the use of silver (Ag) in metallisation. In this work we report on large reduction of Ag consumption for industrial high-efficiency bifacial n-type cells with front and rear Ag grid, by modest process changes. Both front-and-rear contacted, as well as metal-wrap-through cells, are considered. The approaches explored are, for the front, seeding with a small amount of Ag fire-through ink or paste, and plate the thus formed contact grid with copper (Cu). For the rear we use the same approach, or replace the Ag grid by a sputtered Al layer. Front Ag consumption of 10mg per wafer and rear Ag consumption of 12mg per wafer were demonstrated for inkjet seeding. The front finger width after inkjet seed&plate is about 55um. With screen print or stencil print seeding a significant Ag reduction can be obtained too, but not to the same level as with inkjet printing. The replacement of a rear Ag grid by a sputtered Al contact layer requires optimisation of the rear dielectric in order to obtain good rear internal reflection. We model and experimentally demonstrate that a small modification of the rear dielectric already yields an acceptable reflection. In all experiments we find approximately equal or better efficiency than in the reference process; and also the cost of ownership estimates are favorable. This shows that a better environmental footprint can be well combined with improved production cost.


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