Gold-Free Fully Cu-Metallized InGaP/InGaAs/Ge Triple-Junction Solar Cells

Copper contacts and interconnects were developed for GaAs and Ge for low-cost solar cell application. In addition, thermally annealed Pd/Ge and Pt/Ti/Pt metallizations were created for ohmic contacts to n-GaAs and p-Ge with contact resistance of $4.4 \times 10^{-6}$ and $6.9 \times 10^{-6} \Omega $ $\mathrm{cm}^{2}$ , respectively. Utilizing such metallization structure for InGaP/InGaAs/Ge triple-junction device structure solar cells were fabricated that delivered conversion efficiency of 23.11%, which is average efficiency for the above device structure.