Detailed numerical simulation of the effect of defects created by electron irradiation on the performance degradation of a p+–n–n+ GaAs solar cell

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 following 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. A strategy is adopted to check the truthfulness of this by simulating the effect of each single trap level separately on the output parameters of the cell. The simulation results show that only the shallowest deep electron trap is responsible for the degradation of Jsc while Voc is mostly affected by other electron and hole traps especially the deepest one. This more detailed study is an extension of another work in which the effect of a group instead of individual levels is investigated.