Impact of permeation properties and back sheet/encapsulation interactions on the reliability of PV modules

The interaction of different types of new encapsulation and back sheet materials for PV modules was investigated. Therefore, various types of laminates were made in order to examine the environmental impact on such materials during the materials aging process with special attention to the permeability of the back sheet. The laminates were characterized by Raman Spectroscopy, FT-IR/VIS reflectance measurements before and after different accelerated aging procedures. The water vapor and oxygen permeation properties were measured. A clear correlation between the permeation properties and the observed aging behavior was found. The degradation, especially of the encapsulant, resulted in increasing background fluorescence in the Raman Spectra and in a change of transmittance of the encapsulants which is also known as yellowing. It could be shown that the encapsulation/cell/back-sheet system should be optimized in order to minimize the stress on the PV-module components. Copyright