Encapsulant photobleaching

Photobleaching works against encapsulant yellowing: the encapsulant stays clear along cell cracks and around cell borders, while the rest of the encapsulant turns yellow or brown. Oxygen in the encapsulant drives the effect, so a discolored glass/backsheet module typically shows a transparent ring or frame around each cell or crack, with browning in the cell centers. In glass/backsheet modules, these clearer patterns usually line up with cell cracks, so photobleaching is a visible clue to cracks that the eye would otherwise miss. It points to two failure modes: encapsulant discoloration (the browning itself) and cell cracks (the lines where bleaching follows the cracks). Do not confuse it with snail tracks: a snail track is discolored silver paste on the gridlines, while photobleaching is clear encapsulant along the crack. In lab tests, colored compounds that form under heat and humidity break down under light, which is why this kind of yellowing does not appear in modules exposed to sun, heat and humidity together in the field.

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• sentence 3: support check: partial - Passages say clearer patterns generally correlate with cell cracks in glass/backsheet modules and that photobleaching makes micro-cracks visible, though 'usually' and 'clue' are slightly stronger framing.
• sentence 4: support check: partial - Passages link photobleaching to both encapsulant discoloration and cell cracks, but do not state that it 'points to two failure modes' as such.
• sentence 6: support check: partial - Passage states chromophores formed under temperature and humidity decompose under irradiation and that this does not occur in real life, but it concerns PO encapsulant/PO backsheet incompatibility specifically, and the statement generalizes it to this kind of yellowing. -->