Photovoltaic modules are exposed to extremely harsh conditions of heat, humidity, high voltage, mechanical stress,
thermal cycling and ultraviolet (UV) radiation. The current qualification tests (e.g. IEC 61215) do not require sufficient
UV exposure to evaluate lifespans of 30 years. Recently, photovoltaic panel manufacturers have been using glass that
does not contain Cerium. This has the advantage of providing about 1.3% to 1.8% more photon transmission but
potentially at the expense of long term stability. The additional transmission of light in the 300 nm to 340 nm range can
cause delamination to occur about 3.8 times faster. Similarly, UV radiation will cause polymeric encapsulants, such as
ethylene vinyl-acetate (EVA), to turn yellow faster losing photon transmission. Silicones do not suffer from light
induced degradation as hydrocarbon based polymers do, therefore if silicone encapsulants are used, a 1.6% to 1.9%
increase in photon transmission can be obtained from removal of Ce from glass, with no tradeoff in long term stability.
Additionally antimony can be added to non-Ce containing glass to further improve photon transmission (principally in
the IR range) by an additional 0.4% to 0.7%; however, this does not significantly affect UV transmission so the same
UV induced reliability concerns will still exist with common hydrocarbon-based encapsulants.
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