GaAs component cells, representative of the middle cell in Ga0.5In0.5P/GaAs/Ge triple junction solar cells, were irradiated with protons and electrons of various energies and fluences. The local ideality factor, calculated from the measured dark J‐V curves, exhibits a characteristic signature of the irradiating particle. With the help of an analytical model based on Shockley‐Read‐Hall statistics, the recombination current in the space‐charge region is calculated, and the local diode ideality factor is reproduced accurately. The inclusion of defect levels away from the intrinsic Fermi level in the bandgap is found to be essential, since a classical two‐diode model fails to describe the experimental data. On the basis of literature data of known defect levels in irradiated GaAs, the associated lifetimes and defect introduction rates are derived.

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Admittance spectroscopy combined with non-ionizing energy loss (NIEL) analysis is shown to be a powerful tool for analyzing solar cell radiation degradation, not relying on the change of macroscopic cell parameters. GaAs component cells, representative of the middle sub-cell in Ga 0.5 In 0.5 P/GaAs/Ge solar cells, were irradiated with protons and electrons in the 0.5-3 MeV energy range. Four irradiation-induced defects are identified in the p-type base layer. The nature of each defect is assessed by analyzing the dependence of its introduction rate on the NIEL deposited by electrons in the semiconductor. The expected linear relationship is only achieved if a unique threshold energy E d is ascribed to each defect, which ranges from 9 to 38 eV. An electron NIEL with E d = 21 eV, customarily used for GaAs-based solar cell degradation analysis, is an approximation of the relative abundance of these four defects. The 21 eV value is thus a GaAs material-specific parameter, independent of the electrical device design. In addition, the type and energy of the incident particle is correlated with the relative abundance of high E d defects. The impact of each defect on the macroscopic electrical parameters of the cell, namely the open-circuit voltage V OC , the short-circuit current density J SC and the recombination current density J 02 , is assessed with the help of a Pearson analysis. The different effectiveness of electron and proton irradiation on parameters dominated by recombination in the depleted region, such as V OC or J 02 , is attributed in part to the influence of the particle recoil spectra on the defect capture cross-section.