To demonstrate such feasibility, Cu/Ge/Pd and Cu/Pt/Ti/Pt
structures were applied to the half wafer of the InGaP/InGaAs/Ge
triple-junction solar cells as frontside and backside contacts.
Conventional n-type ohmic metal (Au/Ni/Ge/Au) and p-type ohmic
metal (Au/Pt/Ti) were deposited on the other half of the same
wafer for direct comparison. To reduce the total series resistance
losses at high current densities, the fingers and busbars were plated
to 1 lm and 5 lm thicknesses. Table 2 lists the three types of
metallized electrodes evaluated. Sample A is a conventional
Au-metallized solar cell (Au/Ni/Ge/Au with 1 lm of Au as the front
electrode metal and Ti/Pt/Au as the back electrode metal). Sample
B and sample C are Cu-metallized solar cells (sample B with 1 lm
and sample C with 5 lm Cu layer on Cu/Ge/Pd as the front electrode
metal and both use Cu/Pt/Ti/Pt as the back electrode metal).