Arcing of negatively biased solar cells in low earth orbit

A set of experiments is described in which the arcing of negatively biased solar cells is examined and characterized in terms of the primary factors that cause such behavior. The experiments are conducted in an ultrahigh vacuum chamber, and an image-intensified CCD camera is employed to monitor UV emission from arc events at the interfacial edge between the cover slip and the solar cell. A bead of encapsulant along the interfacial edge is noted which can be removed to reduce arc frequency, and water contamination is found to further enhance arcing. Frequency of arcing is found to vary indirectly with temperature and directly with exposure to H2O, but no other significant correlations are noted. The sensitivity to H2O vapor is eliminated by simply removing the adhesive/encapsulant, and the corresponding arc-rate performance is low.