Reduced fill factor

A reduced fill factor shows up when you trace a module or string IV curve. The curve gives lower power than its Isc and Voc would suggest. For reference, typical fill factors at STC are 0.75 to 0.80 for polycrystalline cells and 0.80 to 0.85 for monocrystalline cells. In severe metallization corrosion, the fill factor drops because series resistance rises, and short-circuit current also falls. The corrosion is usually visible by eye, and EL imaging can confirm it. In light induced degradation, Isc, fill factor and Voc all fall together. Check early-life flash-test and IV results against the nameplate rating. Cell cracks raise series resistance only modestly. In one stress test, a module that lost about a tenth of its power showed a fill factor drop of 2% absolute. Potential induced degradation and cell interconnection failure can also change the IV curve. Use EL, IR thermography and Voc checks to tell them apart from cracks or diode faults. Check first: look for corrosion and encapsulant damage, then use EL and thermography to find the affected cells.

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• sentence 1: support check: partial - IV tracing shows FF decrease in corrosion and LID, but the passages never say the curve gives lower power than Isc and Voc suggest, and they do not specifically describe module or string traces.
• sentence 6: support check: partial - The passages give EL, thermography and Voc checks for PID and EL/IR for separating interconnection failures from cracks or diode failures, and a PID IV signature figure, but they do not state that interconnection failure changes the IV curve or that the same combination applies to both.
• sentence 7: support check: partial - Visual inspection then electrical confirmation (EL, thermography) is stated for corrosion, but encapsulant damage is not tied to EL and thermography locating affected cells, and the 'check first' framing is an extrapolation. -->