Solar Cell Degradation under 1-Mev Electron Bombardment

The effect of radiation damage on the important parameters of solar cells has been evaluated for groups of blue-sensitive n-on-p, normal p-on-n, and blue-sensitive p-on-n cells using 1-Mev electrons. The outer space short circuit current, maximum power, junction characteristic, and spectral response are presented quantitatively as a function of radiation flux along with the bulk minority-carrier diffusion length. The rate of change of inverse squared diffusion length with flux is found to be 1.22 × 10 ⁻⁸ for the p-on-n cells, as compared to 1.7 × 10 ⁻¹⁰ for the n-on-p. The degradation of the spectral response is consistent with the measured diffusion length for both types of cells if one assumes a total effective front layer of 1 μ thickness for the p-on-n cells. As a result of the less rapid degradation of their minority-carrier lifetime, the n-on-p cells exhibit a greater resistance to radiation than the p-on-n cells. Comparing only the two types of blue-sensitive cells, after prolonged bombardment, the flux ratios required to achieve equal values of short-circuit current and maximum power are 17 and 9.5 respectively.