In Situ Stability Test of a Small Amorphous Silicon Energy Harvesting Array Under Space Conditions

Amorphous silicon based thin film minimodules have been irradiated with 68 MeV protons up to a dose of 1 1012 protons cm2. During the irradiation, the solar cell current under short circuit conditions, due to the photogeneration of charge carriers by the low intensity room light and the radiation induced generation of charge carriers, has been measured. Whereas the degradation of the photo induced current can be continuously monitored during the experiment, the smaller radiation induced current is only visible in current discontinuities at the beginning and the end of the radiation period. In our experiment, we measured a very similar decrease in the photo and the radiation induced current, both due to the proton irradiation. Therefore, we can infer that the degradation of the solar cells photoelectrical properties is mainly due to the degradation of the amorphous silicon active material and only to a smaller content to the glass substrate s optical transmission properties. Directly after irradiation, we observed a continuous recovery of the photo induced current, due to the room temperature annealing of the electronic defects created in the amorphous silicon absorber laye