Figure 1a shows the measured cell efficiencies on cells with three different rear bus bar pastes. We compare
cells with a reference paste (60 % silver content) with two batches with silver reduced pastes (Paste A and B: ~ 40
% silver content). Paste A shows a higher efficiency than the reference paste, which we attribute to the inherent
variation in the production line. Paste B shows a drop in measured efficiency which is due to the increased line
resistance. Figure 1b shows the measured fill factor FF of the cells. Reference cells and cells with paste A get a fill
factor FFref = FFA = 77.6 % whereas cells with paste B loose around 0.5 % getting a fill factor FFB = 77 %. Thus
the silver reduction has no influence on the series resistance, regarding the result of paste A. The fill factor loss of
paste B is based on a different paste recipe, resulting in an increase of the series resistance and thus a drop in fill
factor. Figure 1c presents the measured Voc values of the cells. The figure shows a slight variation in Voc between
the batches. We explain this variation with variations in the production line. Nevertheless Voc values Voc > 625 mV
in all batches and a variation between the result of the reference cells and cells with pastes A and B Voc < 2 mV
show, that the used base material in the paste, replacing the silver particles, does not influence the lifetime of the
silicon material of the solar cell. Electroluminescence images confirm this result.