Encapsulant

The encapsulant is a polymer film that bonds the module layers together during lamination. Common types are EVA, PVB, POE and TPU. EVA is the most widely used encapsulant. Alternatives include PVB, ionomers, polyolefins and co-extruded EPE films, which combine EVA outer layers with a POE core. The encapsulant and backsheet have to work together. Their combination affects discoloration, delamination that lets moisture in, and corrosion of the cell metallization. As EVA degrades it releases acetic acid, which corrodes ribbons and cell fingers and promotes potential induced degradation and delamination. Polyolefin encapsulants do not produce acetic acid. The encapsulant's volume resistivity and water vapour transmission rate strongly affect potential induced degradation. A more resistive encapsulant gives a lower leakage current. Front delamination looks like bubbles or bright, milky areas and is usually found by visual inspection. It can lead to leakage currents, loss of insulation and inverter shutdowns. Hot cells and hot spots can overheat the encapsulant, causing browning, delamination, gas formation, and bubbles and deformation in the backsheet. The IEC 61215 qualification test has no pass or fail criterion for encapsulant discoloration. Read the full test report for discoloration remarks.

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• sentence 6: support check: partial - Appearance, visual inspection detection, leakage currents and inverter shutdown are stated, but loss of insulation is only 'reduced insulation' and leakage/shutdown are conditional possibilities, not usual outcomes.
• sentence 7: support check: partial - Passages support browning, delamination, gas formation and backsheet bubbles/deformation, but bubbles/deformation require above 170°C and the effects are attributed to different temperature levels, not simply overheating the encapsulant. -->