Stress Free Application of Glass Covers for Radiation Hardened Solar Cells and Arrays.
Final technical rept. Jan 74-Jul 76,
SIMULATION PHYSICS INC BEDFORD MA
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This report describes a two and one half year program to develop a practical integral protective cover for silicon solar cells. The report discusses the electrostatic bonding process, methods for its utilization and selection of a satisfactory glass over material for use with the process. Excellent results have been achieved in demonstrating integral covers 150 micrometers to more than 500 micrometers thick onto several types of 2 x 2 cm cells with SiO sub x or Ta2O5 antireflective coatings. The most difficult problem in applying electrostatically bonded covers to silicon solar cells involves the raised metallization pattern on the otherwise essentially planar cell surface. Cover glasses can either be plastically deformed around the material pattern or can be mechanically grooved to accept the grid material. The plastic deformation approach requires higher bonding process temperatures, to as high as 600 C, but should be more practical in production. Representative integral cover cell samples have exhibited excellent stability under environmental testing. An automated facility has been constructed to demonstrated production feasibility for application of integral covers. Cells covered using the automated facility have exhibited some contact integrity problems which have been identified as associated with the presence of an oxidizing atmosphere during bonding. Facility correction will be required. The electrostatic bonding process shows promise for major technical and economic advantages over conventional glued covers. Author
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