Dark regions in EL image

In an EL image, damaged parts of a module look dark or give off less light than healthy areas. A broken or weak cell interconnection is hard to see by eye. In EL it shows as a dark region where the failed interconnect would otherwise collect carriers, and in IR it often shows as a hot spot. Other causes give different patterns. Cracks show as dark grey lines and can cut off parts of a cell. A badly connected busbar can make a whole cell dimmer. PID darkens cells along the module edges next to the frame. EL alone does not show how much power a dark area costs, so combine it with IR thermography and IV curve analysis to separate interconnection faults from cracks or diode failures. In the field, use IR first to find the abnormal modules, then take EL images of them on site in the dark or in a lab. If you need to know whether an isolated cell part really costs power, take the EL image at about one tenth of rated current. At rated current, isolated parts may only show as noise, and their power impact cannot be judged.

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• sentence 2: support check: partial - Passages support hard to see by eye, dark region in EL, and hot spot in IR, but do not say the IR hot spot is 'often' seen; they say 'or as a hot spot'. -->