Potential-induced degradation: Recombination behavior, temperature coefficients and mismatch losses in crystalline silicon photovoltaic power plant

Abstract

In recent years, potential-induced degradation (PID) has gained considerable attention due to the significant negative impact on output power of photovoltaic power plant. In this paper, the recombination behavior of PID-affected solar modules dismounted from the photovoltaic power plant was investigated by the two-diode model of photovoltaic module. The mechanism of PID shunting, which is caused by sodium decorated stacking faults across n+-p junction, was further verified by analyzing changes in the quasi-neutral region and the space-charge region for PID-affected p-type crystalline silicon solar modules. It was found that the depletion region recombination increases with the extent of PID. The electroluminescence images also revealed that there exist strong ohmic shunts for PID-affected modules. Then the fundamental temperature coefficients of PID-affected solar modules were investigated. It was found that the increased depletion region recombination leads to a larger temperature coefficient of maximum power for PID-affected solar modules. The result was also verified by the thermography images of PID-affected modules. Finally, the relative mismatch losses (RML) of PID-affected module strings were analyzed. The results revealed that the RML of PID-affected module strings increase as the root-mean-square error (RMSE) of current at maximum power point progressed for the first time.