Manufacturing Methods for Silicon Solar Cells with Integral Coverslips.
Final technical progress rept. 1 Jun 70-30 Mar 72,
HELIOTEK SYLMAR CA
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A pilot production line employing both an 18 and 42 inch diameter vacuum system was run producing 1600 cells with integral covers up to 150 micrometers thickness. Cells with 50 micrometers covers yielded approx 10 percent average efficiency under AMO, 28 C, conditions while 100 micrometers covers showed greater than 9 percent efficiency. These cells successfully passed typical space type thermal cycling and high temperature storage tests. The integral cover demonstrated behavior at least equivalent to conventional fused silica covers when subjected to 1 MeV electrons and ultraviolet radiation. Electron beam evaporation techniques were used to rapidly deposit up to 150 micrometers thick integral covers. The aluminosilicate glass source material yielded highly transparent 90 percent transmission covers provided the glass was premelted to remove volatile materials and then deposited with a background oxygen pressure of approx 0.00005 torr. Cover stresses of approx 3 x 10 to the 8th power dynessq cm were routinely achieved by using high condensation rates approx 300 Asec.. The stress was shown to be inversely related to condensation rate, but the high oxygen background pressures necessary for good optical transmission prevented higher rates from being achieved. A new TiO antireflection coating, better matched for glass covers than SiO, was implemented.
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