Patchwork EL pattern

A patchwork EL pattern is an electroluminescence image of a module that looks more and more uneven, with cells or areas of different brightness and no clear crack-type signature. In some cases it shows that light induced degradation (LID or LeTID) is going on in crystalline silicon modules. That degradation shows up mainly as a drop in STC output power, and also as lower short-circuit current and open-circuit voltage early in the system's life, with no visible defect. IV measurement is the main way to detect it, and EL and IR imaging give supporting evidence. EL images are taken with the module in forward bias from a DC power supply that can drive the module's short-circuit current, in a dark setting or at sunset or night in the field. One EL image at a single bias current and temperature often cannot pin down the physical cause, so images at two bias currents or other methods such as thermography or photoluminescence help. Modules with higher power losses generally have an EL intensity distribution shifted toward lower intensities, but no clear link to specific defect types has been found yet.

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• sentence 1: support check: partial - The passages say increasing non-uniformity of EL images is called a patchwork pattern, but nothing about cells or areas of different brightness or the absence of a crack-type signature (cracks are said to have recognizable signature elsewhere).
• sentence 4: support check: partial - Detection lists IV with EL and IRT in parentheses, which implies IV primary and EL/IRT secondary, but the passages do not explicitly say IV is the main method or that EL/IR give supporting evidence. -->