ANOMALOUS DEGRADATION IN SILICON SOLAR-CELLS SUBJECTED TO HIGH-FLUENCE PROTON AND ELECTRON IRRADIATIONS

Distinct from the well-known logarithmic degradation in electrical per formances of a crystalline silicon solar cell, an anomalous degradatio n of short-circuit current density (I-sc) was observed in a cell irrad iated by energetic protons and electrons at high fluence. From results of proton irradiations with various energies (0.4-10 MeV) and high fr equency (1 MHz) capacitance measurements, the anomalous drop of I-sc i s found to be caused by (1) the p-type substrate changes into the intr insiclike layer (Fermi level shift) by the irradiations, followed by a n extension of the depletion layer, and (2) the drift length of the mi nority carrier becomes shorter than the depletion layer. (C) 1997 Amer ican Institute of Physics.