Analytical techniques used to determine chemical degradation of polymeric materials used in PV modules after sustained exposure to partial discharge voltages

Partial Discharge is one of a number of tests defined in IEC61730-2, which specifies properties of photovoltaic modules and components to assure safe electrical operation during their expected lifetimes. From the perspective of backsheet/ frontsheet designers and developers, the test is of practical importance because of the criteria it places on material choice and film thickness. Our objective is to study the chemistry of electrically induced degradation of PV front/backsheet materials, in order to improve the linkage of the partial discharge test with electrical safety. We have used ESCA to determine extent of chemical degradation of several polymeric films after exposure to voltage greater than V_i for 24 hours; we´ve shown that degradation occurs in the annulus of the electrode, presumably at the distance given by the Paschen´s law minimum. The relative rates of degradation in decreasing order are polypropylene >; PET >; THV, with no measurable degradation to the THV film.