Solar cell degradation experiments on the Lincoln laboratory LES-4 and LES-5 satellites

The Lincoln Laboratory satellites LES-4 and LES-5 each carry solar cell experiments consisting of the following. V
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Measurement of 10 Ω . cm silicon cell with 30-mil cover slide. I
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Measurement of 10 Ω . cm silicon cell with 30-mil cover slide. I
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Measurement of 10 Ω . cm silicon cell with 6-mil cover slide. I
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Measurement of two CdTe thin-film cells (LES-4 only). I
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Measurement of two CdS thin-film cells (LES-5 only). LES-4 was orbited in December 1965 in a highly elliptical orbit with an 18 000-mi apogee and a 100-mi perigee; LES-5 was injected into a quasi-synchronous orbit in July 1967. In the LES-5 experiment, the Si cells exhibit an I
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degradation of eight percent per year plus an initial short term degradation of four percent; V
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is relatively unaffected. The CdS cells have an I
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degradation of 20 percent per year plus an initial degradation of five percent. In the LES-4 experiment, the Si cell with the 6-mil cover slide shows two rates of degradation, with the break point occurring at about 100 days; the cell with the 30-mil cover slide shows substantially less degradation. After 700 days, the short-circuit currents of these two cells are 60 percent and 78 percent of their initial AMO values. One CdTe cell has decayed to 38 percent of its initial AMO value after 700 days; the second sample gives anomalous results. In each experiment AM0 to AM1 short-circuit current ratios of approximately 1.09 were noted.