Prediction of the performance degradation of GaAs solar cells by electron irradiation

Abstract

Solar cells exposed to irradiation undergo severe degradation in their performance due to induced structural defects. To predict this effect, the current-voltage characteristics under AM0 illumination for a constant dose of electron irradiation are numerically calculated. From these characteristics the solar cell output parameters: the short circuit current density Jsc, the open circuit voltage Voc, the fill factor FF and the conversion efficiency η are extracted. The irradiation induced defects introduce in the energy gap either recombination centres or traps. The irradiation induced degradation is widely attributed to the first type of defects. We have adopted a strategy to find out which defects are responsible for the degradation. This consists of simulating the effect of each defect separately on the output parameters. The simulation results show that traps are mainly responsible for the degradation of Jsc while recombination centres are responsible the degradation of Voc. The other parameters (FF and η) are degraded by the combination of the traps and recombination centres.