The control of radiation resistance in space solar cells

Solar cells, powering satellites and other space vehicles, can suffer substantial degradation in performance by electron and proton irradiation experienced in orbit. These effects are first described, and the behaviour of silicon solar cells compared with cells of gallium arsenide and indium phosphide, and the more recent thin film type cells. In particular, the paper will discuss the phenomenon of ‘photon degradation’ in silicon cells, and recent progress in understanding the defect mechanisms responsible for this effect occurring after illumination of irradiated cells. Strategies for improving the radiation resistance of silicon solar cells, including the use of ‘defect gettering’ will be discussed, while the effects of annealing radiation damage will be outlined. Finally, the paper will seek to identify areas where an improved understanding of defect behaviour is necessary to produce further improvements in performance. In particular, it highlights the need for fundamental studies of advanced solar cell structures and materials, including CIS cells, where significant improvement in radiation tolerance has been found.