In the last few years, it became apparent that system voltage can lead to substantial long-term potential induced degradation (PID) of photovoltaic modules via shunting of the incorporated wafer based screen-printed solar cells. The leakage current from the module frames to the cells through the encapsulating material is supposed to cause this effect. Until now the detailed mechanism of shunting is not known although it was speculated that metal ions originating from the soda-lime glass might be responsible. In this study, experimental evidence is presented showing that PID can also be caused by other ions usually not present in photovoltaic modules indicating that the chemical nature of the ions is not relevant for PID. The conditions under which PID occurs in the field are substantiated from the analysis of leakage current data measured outdoor. Starting from these conditions, different options for accelerating a laboratory test for PID are discussed and tested experimentally.
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Schütze et al. (2011) studied this question.