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

Ga(0.5)In(0.5)P/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 Isc, however, did limit the device performance as is traditionally documented. The final-to-initial maximum power ratio (P/P(0)) of 3J cells was near 0.833 at a fluence of 1x10(15) e(-)/cm(2), and matches Spectrolab's presently established value of 0.83 for standard production of space-qualified dual-junction cells.