Mitigation of Potential-Induced Degradation

Since potential-induced degradation (PID) is driven by voltage, heat, and humidity, all PV systems can be susceptible to PID and the associated power output drop of 30 percent or more [1]. The failure mechanism depends on the module's voltage potential and leakage current to facilitate ion migration through the antireflection coating (ARC) from other parts of the module such as the glass, encapsulation, mount, or frame [2]. Sodium ions are believed to be the most likely culprits but debate is ongoing concerning other ions such as aluminum, magnesium, and calcium which are present in the soda-lime glass commonly used in panels [3]. There are some recognized methods for mitigation of potential-induced degradation (PID). Replacing soda-lime glass with quartz glass ensures that the solar glass is free of the suspected PID ions [2]. At the cell level, utilizing a less than ideal higher IR silicon nitride (SiN) in the ARC minimizes PID. Here we describe the Room Temperature Wet Chemistry Growth (RTWCG) technology, a novel technology for growing highly uniform amorphous SiOX layers into silicon substrates [4]. These RTWCG SiOX layers mitigate PID when used as the first dielectric layer in a stacked SiOX / SiN ARC. Unlike some other methods for mitigating PID which lower cell performances, the inclusion of a SiOX layer to the ARC passivates the c-Si surface and thus increases cell performances.