Irradiation of monolithic InP/Ga/sub 0.47/In/sub 0.53/As tandem solar cells

Prototype three-terminal, two-junction, monolithic InP/Ga/sub 0.47/In/sub 0.53/As tandem solar cells were grown by the National Renewable Energy Laboratory (NREL) using metal-organic chemical vapor deposition (MOCVD). The tandem cells have been irradiated at room temperature with incremental fluences of 1-MeV electrons. One sun, AM0, 25 degrees C I-V measurements and deep level transient spectroscopy (DLTS) measurements are reported for each fluence step. The results are presented and compared with similar measurements on electron-irradiated single-homojunction (SHJ) InP solar cells. Even though the tandem cells were prototype cells, they displayed excellent radiation responses. The InP top cell of the tandem device degraded no more than the SHJ InP. Also, the Ga/sub 0.47/In/sub 0.53/As bottom and the InP top cell were nearly current-matched throughout the fluence range studied. The preliminary conclusion is that the InP/Ga/sub 0.47/In/sub 0.53/As tandem cell will display the radiation resistance of an SHJ InP cell while producing the high power output of a tandem solar cell.<>