Effect of bias voltage application on potential-induced degradation for crystalline silicon photovoltaic modules

Abstract

To analyze the dynamic behavior of Na ions in the p–n junction of crystalline Si photovoltaic (PV) cells during potential-induced degradation (PID), a bias voltage was applied between the electrodes of the testing PV modules. During the PID test with a negative high voltage stress (HVS), PID was suppressed by the simultaneous loading of a forward bias voltage, although that of a reverse bias voltage accelerated the progression of PID. However, in the recovery stage after the PID test, the opposite loading effects of the bias voltage with a positive HVS were found. In other words, the extent of recovery from PID was suppressed or enhanced by forward or reverse bias loading, respectively. Similar effects of bias loading were observed even under the recovery conditions without the positive HVS. The effect of Na ions within a depletion layer on the evolution of PID will be discussed for the interpretation of these results.