Current-Resolved Electroluminescence Imaging for Assessing Potential Induced Degradation Shunting Recovery in c-Si PV Modules

Potential-Induced Degradation Shunting (PID-s) is a severe form of degradation that creates a short-circuit path within the p–n junction of a solar cell under negative bias voltage, which typically develops in large arrays of photovoltaic (PV) modules with respect to the grounded frame. PID-s leads to a significant drop in power output and adversely affects the long-term reliability of PV systems. Although PID-s can be mitigated using advanced bills of materials (BOMs), these materials are expensive and have not been extensively field-tested over long durations. As a result, they may introduce other forms of degradation in the future. Furthermore, existing PV deployments in the field remain susceptible to PID-s. While PID-s recovery techniques are available—typically involving the application of a reverse polarity potential to facilitate the out-diffusion of sodium ions from the p-n junction, however complete recovery is rarely achieved. Therefore, applying reverse polarity recovery techniques indiscriminately to all PID-s-affected PV modules may lead to unnecessary resource consumption. Hence, in this work, current-resolved electroluminescence (EL) imaging is explored as a tool to assess the recovery potential of modules prior to implementing recovery procedures. Since PID-s recovery is directly influenced by the depth and concentration of sodium ions across the p–n junction, EL intensity reflects the net current flowing through the bulk. This current is directly affected by the shunted path, whether it behaves as a resistor or a diode—commonly referred to as linear and nonlinear shunts, respectively.