Effects of irradiation beam conditions on radiation degradation of solar cells

We have investigated the effects of irradiation on space solar cell degradation characteristic. We examined the effects of beam conditions such as fluence rate and beam expansion method. For the fluence rate experiment, in the case of proton irradiations, the degradation did not depend on fluence rate. Meanwhile, in the case of electron irradiation, Si cell results showed degradation dependent on fluence rate, and the dependency is found to be due to temperature increase during irradiation. From the comparison of cell degradation by irradiation with defocused and scanned 10 MeV proton beams, no significant difference in degradation has been observed. We plan to reflect these findings into the ISO standard for irradiation test methods.