Radiation Hardness of Ultra-thin GaAs Solar Cells with Rear-side Silver Mirror

For space solar cells, thinner is better: indeed reducing the absorber thickness enables mass savings and radiation hardness improvements. However if the solar cells absorber thickness is simply reduced, the end-of-life (EOL) performance advantage of ultra-thin cells compared to bulk counterpart will only happen at very high fluences. By combining thinner absorber with efficient light trapping structures, ultra-thin solar cells can have superior EOL performances (efficiency, W/kg, W/m2) at moderate fluences. Recent advances have shown that ~ 200nm thin GaAs cells with a nanostructured back mirror can reach ~ 20% BOL efficiency. In this study, we review the potential of such ultra-thin GaAs cell technology for space applications. The first experimental results of 1 MeV electron irradiation tests on ultra-thin GaAs solar cells with Ag back mirror will be presented, and the radiation hardness will be compared with bulk GaAs solar cells.