Thin GaAs Solar Cells For High Irradiation Levels

GaAs is an attractive material for space solar cells due to it possessing the highest photovoltaic efficiency among semiconductors. However, material vulnerability to radiation damage is a limiting factor, which should be resolved. This can be done through the optimization of solar cell geometry. Specifically, ultra-thin GaAs solar cells possess increased radiation hardness in combination with high specific power (W/kg) making them desirable for space applications. In this research, modeling of single-junction thin GaAs based solar cells with an active device thickness < 1.6 µm is performed to evaluate cell performance at high irradiation levels (1 MeV electrons with a fluence of 1E15 e-/cm2) associated with high energy orbits. The radiation tolerance of two configurations is evaluated; conventional and rear junction (thick emitter) with a backside gold reflective coating. In addition, solar cell structures utilizing n- and p-type base are simulated. The Hovel model, modified to include the photon recycling effect, is used for modeling. The effect of radiation on GaAs electronic properties is counted through degradation of minority carrier lifetime and changes in the carrier concentration. It’s found that conventional n-emitter/p-base and the rear junction with p-type thick emitter configurations with a heavily doped absorber ~5E18 [cm-3] and thickness below 800 nm have increased radiation hardness with a degradation rate