Electron irradiation study of metamorphic 1.7eV GaAsP solar cells

We investigated the effects of 1 MeV electron irradiation on uncoated metamorphic −1.7eV GaAsP solar cells on GaP and on GaP/Si. Effects of junction polarity, base thickness, and threading dislocation density on radiation hardness were investigated using the AM0 solar simulator at NASA Glenn Research Center. Degradation of solar cell efficiency after irradiation was dominated by reduced minority carrier diffusion length in the base, leading to loss of long-wavelength carrier collection. Designs with higher base diffusion length or thinner base were favored, and accordingly, devices with
$n^{+}/p$
junction polarity were more radiation-hard than those with
$p^{+}/n$
junction polarity.