研究了正负偏压下的组件PID行为，组件的PID效应好偏压的正、负有很大的关系。负偏压会导致更快、更明显的组件ＰＩＤ效应。This is associated with significant shunting of individual cells. A positive system bias is associated with Ag gridfinger corrosion and ion migration from the cell or interconnect metallization to the grounded module frame,
especially in areas of high moisture ingress and weakened encapsulant. Based on the measured
activation energy for module leakage current of 0.86 eV,
ion transport through glass is the dominant mechanism at 30% RH (25°–85°C), and the magnitude of the leakage
current is generally independent of bias direction except in a module design with high moisture ingress and
weakened encapsulant adhesion. The threshold for severe degradation of 1–10 C/cm is still applicable per the work of the Jet Propulsion Laboratory (1985) for (+) bias to active layer, but we additionally find that 0.1–1.0 C/cm leads to ~5% degradation. A 0.02–0.2 C/cm threshold is proposed for (-) bias to active layer based on measurements of six commercial crystalline-silicon modules. Some types of degradation observed, such as electrolytic corrosion, will happen after many years in hot/humid environments, but others, such as ion migration, happen more quickly and are of pressing concern. Higher electrical resistance packaging will help reduce electrolytic and ion migration-related degradation, which can be controlled by choices including the glass and its coatings, the encapsulant, and the frame. |
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