Monitoring crosslinking inhomogeneities in ethylene vinyl acetate photovoltaic encapsulants using Raman microscopy

Crosslinked ethylene vinyl acetate (EVA) resin is the preferred material for encapsulation of photovoltaic (PV) modules. Yet, profiling the spatial homogeneity of crosslinking in a quantitative and non-destructive way still remains a challenge. With the aid of reference techniques and using carefully prepared and well characterized model systems we have developed a protocol for Raman microscopy, which can determine the degree of crosslinking in EVA sheets in a quantitative manner. The new method has then been applied to characterize inhomogeneities with regard to crosslinking in EVA samples on various length scales, going down to a few mm. Finally, this method has been used to study crosslinking in EVA/glass laminates. The applicability and limitations of measuring crosslinking under glass was probed.