Besides, the junction temperature will increase when the solar
cell is irradiated at high intensities. Ju et al. analyzed the InGaP/
GaAs/Ge triple-junction solar cell operating at the concentration
ratios in the range of 1–1000 suns [11], the same approach was
used to calculate the Cu-based solar cell in this work, the junction
temperatures were estimated to be around 25 C at 1 sun and 72 C
at 120 suns. However, his study also indicated that the junction
temperature will increase to 120 C with 1000 suns irradiation.
This temperature is only half of the tested temperature (250 C)
of our study, which means the Cu contacts will remain quite stable
at high concentration operation. Accordingly, the performance of
Cu contacts should remain stable at high irradiation intensity
and would not be the primary factor for the cell degradation.