Figure 2 shows the electroluminescence images of the cells. Figure 2a shows the electroluminescence image of the
reference cell, Fig. 2b the image of a cell with paste A and Fig. 2c the image of a cell with paste B. The images
were taken with the cells lying sunny side up. Bright areas in the electroluminescence image correspond to areas
with a high lifetime. Dark areas correspond to areas with a decreased lifetime. The images show that the lifetime at
the bus bars generally is lower compared to areas without metallization. The metal increases the surface
recombination and thus lowers the lifetime [7, 8]. Figure 2d shows the influence of copper metallization on the
lifetime of a wafer. Compared to silver the solubility of copper is considerably higher in silicon. Already at room
temperature, the lifetime decreases spaciously. Our base metal replacing silver does not influence the lifetime
negatively. Figure 2b and 2c show no difference compared to the reference indicating an influence to the lifetime.