Non-destructive degradation analysis of encapsulants in PV modules by Raman Spectroscopy

Simulation of water ingress into PV-modules: IEC-testing versus outdoor exposure

“…Especially the polymeric materials used in PV-modules are affected by water ingress under elevated temperatures. Thus, DH testing can cause degradation of the encapsulant between glass and solar cell which can be correlated with a lateral diffusion of water (Peike et al, 2011). Other works stated a reduction of optical properties by increasing absorption that was translated in a reduction of light transmission (McIntosh and et al, 2011) and as well as changes in yellowness-index (Hsu and et al, 2010).…”

Chemical depth profiling of photovoltaic backsheets after accelerated laboratory weathering

“…[28][29][30][31][32][33] Note that the bands at 1727 cm -1 and 631 cm -1 are solely from vinyl acetate (VA) of EVA copolymer. [28][29] Obviously, the EVA outer layer has relatively lower VA content compared with EVA inner layer and pigmented-EVA layer, so that the EVA outer layer is supposed to be an adhesion promotion layer.…”

“…However, the photo-and thermal degradation of the EVA, and the interaction between polymeric matrix and additives during accelerated laboratory aging can provide the main contribution of the enhanced fluorescence background to Raman spectra for aged samples. 10,14,[32][33] Therefore, fluorescence intensity can represent overall chemical property and be used as an index to study chemical depth profiling as discussed in the following. An example of Raman mapping spectra, which are the constructing elements of Raman image, is shown in Figure 3.…”

“…Because of the low intensity of the C=O band, the aliphatic CH band region around 2800 cm -1 to 3000 cm -1 was chosen to study the degradation of EVA. 32,33 As shown in Figures 9(a) through 9(d), the results imply: (1) the lower C-H intensity of the middle pigmented EVA layer in comparison to other EVA layers is probably due to the diluted C-H concentration in the presence of the pigments; (2) the distribution profile of C-H intensity across three EVA layers for the sample aged in the low humidity is similar to that of the fresh sample, only the surface of EVA outer layer has slightly lower C-H intensity, which could be due to chemical degradation of the EVA surface; (3) in high humidity conditions, the thickness of the pigmented-EVA layer is visibly decreased, and the C-H intensity in this layer is lower than the fresh and the low humidity aged samples. Even though these changes could be due to water-assisted degradation of pigmented PET, the detailed mechanism is yet unclear; (4) the vicinity of EVA inner/PET core interfacial region shows a lower C-H intensity, which is consistent with Figures 7 and 8 showing chemical and topographic changes after exposure in high humidity; (5) the strong contrast of Raman image of the fluorescence intensity at 1660 cm -1 further confirms that chemical degradation has occurred in pigmented EVA layer during exposure in high humidity.…”

Cross-linking characterization of polymers based on their optical dispersion utilizing a white-light interferometer

“…Faster and non-destructive measurements can be obtained by using optical measurement technologies. One state-of-the-art technology is Raman spectroscopy, [8]. The analysis of spectral features of reactional groups and bonds before, as well as, after the curing process are utilized to calculate the degree of cross-linking.…”