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ECN publication
What makes a high-performing screen-printed Ag contact? Realities and idealities from microscopical insight
Olibet, S.; Rudolph, D.; Cabrera, E.; Hoornstra, J.; Carr, A.J.; Weeber, A.W.; Fu, Y.; Kopecek, R.
Published by: Publication date:
ECN Solar Energy 22-7-2012
ECN report number: Document type:
ECN-M--12-039 Conference Paper
Number of pages: Full text:
5 Download PDF  

Presented at: 22nd Workshop on Crystalline Silicon Solar Cells & Modules: Materials and Processes, Vail, Colorado, USA, , 22-25 juli 2012.

High-performing screen-printed and co-fired Ag contacts feature Ag-crystallites grown into Si. Our experiments show that the commonly observed benefit of ultra-fast firing may be the enhancement of direct or close contact formation of these Ag-crystallites to the bulk of the Ag-finger. While so far these Ag-crystallites grown into Si are needed for low contact resistivity, they lead to contact induced recombination losses as exemplarily shown by model pastes etching deeply into the emitter. Advances such as high-performing emitters being able to be contacted by newest generation Ag-pastes lead to standard c-Si solar cells being fully limited by the Al back metallization besides the bulk quality. But for advanced high-efficiency concepts like PERC and n-type cells, contact induced recombination becomes the main efficiency limiting factor. Based on our large microscopic contact database together with resulting solar cell data, we intend to quantify these losses and give guidelines for process optimization within current industrial cost-efficient process limits, i.e. using screen-printing and costeffective emitters. Finally, the ideal contact should avoid any metal grown into Si. By temperaturedependent contact resistivity measurements, current conduction mechanisms can be identified. We apply such measurements to two different microscopic current conduction path systems.

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