Analysis of Radiation Damage to Si Solar Cells under High-Fluence Electron Irradiation

Abstract

Radiation testing of Si n⁺–p–p⁺ space solar cells has revealed an anomalous increase in short-circuit current I _sc, followed by an abrupt decrease and cell failure, induced by high-fluence (>10¹⁶ cm^-2) electron irradiation. A model which can be used to explain these phenomena by expressing the change in majority-carrier concentration p of the base region as a function of the electron fluence has been proposed in addition to the well-known model in which I _sc is decreased due to minority-carrier lifetime reduction with irradiation. The reduction in p due to majority-carrier trapping by radiation-induced defects has two effects; one is broadening of the depletion layer which contributes to the increase in the generated photocurrent and that in the recombination-generation current in the depletion layer, and the second is an increase in the resistivity of the base layer resulting in an abrupt decrease of I _sc and failure of the solar cells.