Mechanism for the anomalous degradation of Si solar cells induced by high fluence 1 MeV electron irradiation

Abstract

An anomalous increase in the short-circuit current Isc of n-on-p Si space solar cells, followed by an abrupt decrease in Isc and cell failure has been observed under high fluence (≳1016 cm −2) 1 MeV electron irradiation. A model to explain these phenomena by expressing the change in carrier concentration p, of the base region as a function of the electron fluence is proposed in addition to the well-known model where Isc decreases by minority-carrier lifetime reduction under irradiation. The reduction in p due to majority-carrier trapping by radiation-induced defects has two effects: broadening of the depletion layer which increases the generated photocurrent, and also an increase in the resistivity of the base layer, resulting in the abrupt decrease of Isc and failure of the solar cells.