Flexographic Printing – High Throughput Technology for Fine Line Seed Layer Printing on Silicon Solar Cells

Within this work, seed layer grids for solar cell front side metallization were applied using flexographic printing which represents an innovative, high-throughput approach for solar cell front side metallization. Fine line seed layer contact grids with a silver consumption lower than 10 mg per cell could be realized on alkaline textured Czochralski-grown silicon wafers with an edge length of 156 mm. Subsequently, the seed layer has been reinforced with silver using light induced plating (LIP). In order to determine the optimum LIP process, three groups were plated with different amounts of silver deposition. The results were analyzed before and after plating regarding silver consumption, contact finger geometry and interruptions. Solar cell parameters were determined after plating. It was demonstrated, that a homogeneous front side seed layer metallization without interruptions down to a line width of 25 μm can be realized using flexographic printing. The best cell reached a conversion efficiency of 18 % after silver LIP which is comparable to standard screen printed cells on the used Si wafer material. Furthermore, an economic comparison was carried out to illustrate the potential of solar cell metallization using rotational printing methods with subsequent Ag-LIP or Ni/Cu/Ag-LIP compared to state-of-the-art screen printing technology.