The effects of electron irradiation on triple-junction Ga0.5 In0.5P/GaAs/Ge solar cells

Ga_0.5In_0.5P/GaAs/Ge solar cells have been fabricated at Spectrolab under the Multijunction Solar Cell Manufacturing Technology (Mantech) program, sponsored by the US Air Force and NASA. The cells were irradiated with increasing 1 MeV electron fluences, and the degradation of their PV parameters was characterized using light I-V and external QE. Analysis of the PV parameters of the GaInP top subcell showed little degradation, and was not a limitation for triple junction (3J) cell performance. Furthermore, the radiation degradation of the Ge subcell PV parameters was almost negligible. The GaAs subcell I_sc, however, did limit the device performance as is traditionally documented. The final-to-initial maximum power ratio (P/P₀) of 3J cells was near 0.833 at a fluence of 1×10 ¹⁵ e^-/cm², and matches Spectrolab´s presently established value of 0.83 for standard production of space-qualified dual-junction cells