Cell ARC layer optimization

Cell ARC layer optimization is a preventive measure against Potential Induced Degradation (PID). It works on the anti-reflective coating (ARC) of the solar cell. It is a cell manufacturing measure, not a field repair. On site, it matters mainly when choosing modules. It targets the sodium path behind PID shunting. Sodium ions in a standard ARC layer help the degradation along. Sodium ions from the glass also move into the ARC layer, build up there and enter defects in the cell junction. Two cell designs have been shown to reduce PID. One raises the silicon-to-nitrogen ratio of the ARC to lower its sodium content. The other adds a silicon oxide layer between the cell and the ARC. Other cell-level factors that affect PID are the thickness and evenness of the ARC and its silicon-to-nitrogen ratio. Reported results: cells with no ARC show no PID, and a conductive coating on top of the ARC stops PID. There is a trade-off. A silicon nitride coating with a higher refractive index lowers PID but increases reflective losses. This cell-level step is one of four groups of PID prevention measures. The others cover the environment (regular cleaning), the system (frame potential and PV offset boxes) and the module (encapsulant and front glass).

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• sentence 2: support check: partial - u11 labels it a cell (manufacturing) level factor, but the passages say nothing about field repair or about its mattering on site when choosing modules.
• sentence 3: support check: partial - The passages say sodium in the standard ARC assists PID and that Na+ migrates, accumulates in the ARC layer and enters junction defects. However, they say the sodium comes from the glass plate and that the Si/N increase reduces sodium in the ARC. They do not describe sodium being 'targeted' beyond that, and the layer naming is muddled. -->