Dark cell edges in EL

In an electroluminescence image, the borders of the cells look darker, while the cell centers stay brighter. To take the image, a DC current is fed through the module and a camera records the light it gives off. This is done in a dark environment, usually at night, because daylight drowns out the signal. With metallization corrosion, the dark cell borders show moisture moving in through the module's rear side and the gaps between cells. The front side of each cell then corrodes, starting at its edges. With potential induced degradation, EL shows dark cells at the module boundaries, with the cell edges darkest near the frame. This is commonly blamed on current flowing through a lowered parallel resistance instead of the PN junction. Night-time field EL of modules with PID has been taken with a consumer DSLR camera, using an accumulated exposure of around four minutes. In PID-tested heterojunction glass/glass mini-modules, the damage started at the cell edges and spread inward over time. This was linked to moisture ingress helping sodium move through the module. Corrosion often appears together with delamination and yellowed encapsulant, so check the module visually as well.

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• sentence 1: support check: partial - Passages say dark areas at cell borders occur in EL under certain circumstances (corrosion, PID edges), not as a general EL feature, and don't say centers stay brighter.
• sentence 2: support check: partial - DC current and camera in a dark environment/night are stated, but u2 says darkness is useful but not necessary, and u22 says reverse current while u2 says dc current; the 'daylight drowns signal' reason is supported by u22.
• sentence 7: support check: partial - Passages say corrosion is very often observed with delamination and encapsulant discolouration, but the advice to check visually is not stated (though detection lists VI). -->