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, ultrathin solar cells can have superior EOL performances (efficiency, W/kg, W/m(2)) at moderate fluences. Recent advances have shown that similar to 200nm thin GaAs cells with a nanostructured back mirror can reach similar to 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.