Sodium Outdiffusion from Stacking Faults as Root Cause for the Recovery Process of Potential-induced Degradation (PID)

Potential-induced degradation (PID) is currently one of the most important and prominent module degradation mechanisms leading to significant yield losses. It was shown that Na decorated stacking faults are responsible for this degradation mechanism of the solar modules. Additionally, PID can be recovered by an applied reversed voltage to the one causing PID. In this contribution both a thermal and an electrical recovery were performed. By in-situ thermal recovery and subsequent microscopic investigations the recovery process will be clarified. It is shown that Na causing PID diffuses out of the stacking fault during the thermal recovery process resulting in vanishing of the PID-s shunts. The stacking fault originally causing PID-s can still be verified by its atomic structure after recovery, now without any Na decoration. The clean stacking fault is not electrically active and thus is not influencing the electronic properties of the solar cells anymore. Finally, a qualitative process explaining the recovery is proposed.