Using Module Leakage Current Modeling to Understand Corrosion Chemistry

When fielded, modules are exposed to high voltages in the presence of moisture and/or elevated temperature this allows significant leakage currents to flow between the cell and ground. When current changes from an electronic to an ionic form, electrochemical reactions are promoted creating the potential for a wide variety of degradation reactions. This work investigates the nature of this current flow to gain a better understanding of the effect. At the cell surface, current preferentially flows to the metallization and under negative bias will split water to form OH- ions. It is found that transient effects occur in the leakage current as a result of some capacitive and electrochemical effects. This work seeks to provide important insight into the nature of the charge transfer species and the factors that most strongly affect leakage rates to provide better correlation to module performance.