High-energy and high-fluence proton irradiation effects in silicon solar cells

We have examined proton irradiation damage in high-energy (1-10 MeV) and high-fluence (>10(13) cm(-2)) Si n(+)-p-p(+) structure space solar cells. Radiation testing has revealed an anomalous increase in short-circuit current I-sc followed by an abrupt decrease and cell failure, induced by high-fluence proton irradiation. We propose a model to explain these phenomena by expressing the change in carrier concentration p of the base region as a function of the proton fluence in addition to the well-known model where the short-circuit current is decreased by minority-carrier lifetime reduction after irradiation. The reduction in carrier concentration due to majority-carrier trapping by radiation-induced defects has two effects. First, broadening of the depletion layer increases both the generation-recombination current and also the contribution of the photocurrent generated in this region to the total photocurrent. Second, the resistivity of the base layer is increased, resulting in the abrupt decrease in the short circuit current and failure of the solar cells. (C) 1996 American Institute of Physics.