Radiation-Resistant Solar Cell Coverglass

The problem of the continual loss of output power from solar cells on spacecraft is attributed to damage to the cell covers caused by exposure to energetic particulate and UV irradiation. Reduced lifetime limits the space mission and requires replacement at very high expense. Multi-layer coatings on the cover glasses function to increase transmission, reject damaging UV, and prevent the accumulation of static charges. The causes for radiation-induced transmission loss are not understood. Our approach introduces advanced high-energy deposition and improved material technologies to the manufacture of the cover glasses, with the goal of producing coatings that have greater immunity to contamination and lower defect densities than are produced by the current coating techniques. In Phase I, we evaluated several coating materials deposited as single layers using ion assisted deposition, and we successfully demonstrated improved thin-film layer density. Analytical techniques developed for evaluating film properties and relating those properties to radiation tolerance will be enhanced. Our experience with the new technologies and with the effects of the space radiation environment on optics are focused on the. As we expand the work in Phase II, we hope to contribute to the understanding of the mechanisms responsible for radiation darkening. Domestic and military applications will benefit from an end of life extension that would result from increasing the radiation resistance of the optical coatings deposited on the cover glasses. Our development of a domestic supplier of coated cell covers would reduce the dependence on off-shore sources.