Performance of proton- and electron-irradiated, two-terminal, monolithic InP/Ga0.47In0.53As tandem solar cells

Radiation damage results are presented for two-terminal InP/Ga_0.47In_0.53As tandem solar cells irradiated with 1 MeV electrons and 3 MeV protons. The performance of the irradiated tandem cells are compared with each other which are, subsequently, described in terms of the component cells. The current mismatch appearing in the tandems are almost nonexistent compared to previous electron-irradiated cells. This is explained in terms of the thickness of the InP top subcell for a top cell-limited tandem. At high fluences, the proton-irradiated cell showed very good radiation resistance compared to a shallow homojunction InP cell. The increase in the recombination current appears to be the major degradation mechanism as revealed by the degradation of the open circuit voltage for the proton-irradiated cells. Annealing of the tandems showed partial recovery for the PV parameters in general but the short circuit current and the fill factor decrease at elevated temperatures for the cell irradiated with protons