MECHANISM OF ANOMALOUS DEGRADATION OF SILICON SOLAR-CELLS SUBJECTED TO HIGH-FLUENCE IRRADIATION

We have found anomalous degradation of electrical performance in silic on solar cells designed for space use due to high-fluence irradiation of charged particles, e.g., 1MeV-electrons of similar to 10(17) e/cm(2 ) and 10MeV-protons of similar to 10(14) p/cm(2). This anomalous degra dation has two typical features, i.e., sudden-drop-down of electrical performances and slight recovery of the short circuit current I-SC jus t before the sudden-drop-down, which cannot be explained by a conventi onal model based on decrease of the minority-carrier life-time. In ord er to account for these features, we propose a new model, in which dec reases of the majority-carrier concentration and the minority-carrier mobility are considered in addition to that of the minority-carrier li fe-time. The anomalous degradation observed is well represented by thi s model.