Thin film PID field failures and root cause determination

Potential Induced Degradation (PID) manifests itself as a pre-mature degradation of solar module performance that is dependent on the relative position of the module in a series connected string of modules. In this paper we describe a particular type of PID not previously documented that was experienced in an actual field installation. Measurements and analysis show that the PID originates from current shunt paths in the laser scribes of the monolithically integrated thin-film modules. Root cause of the shunt paths are found to be field driven sodium migration from the glass substrate into the scribe lines causing a severe degradation of the module shunt resistance.