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

Raman Probe Spectroscopy as a powerful tool for analyzing the degradation behavior of encapsulants in c-Si based PV modules is reported. A non-destructive and quick testing method is needed in order to follow material changes during the aging of PV modules. Two types of c-Si PV modules with ethylene vinyl acetate (EVA) encapsulation have been aged indoors under damp-heat conditions (85% r.h./85 °C) and under combined UV/moisture conditions, respectively. The aged modules as well as a non-aged reference module for each type were analyzed by Raman Spectroscopy. The degradation of the encapsulant was observed, resulting in an increasing fluorescence background, as well as changing intensities of EVA Raman peaks. A lateral non-uniformity of the fluorescence intensity of and the EVA CH stretching vibration intensity ratios, depending on the position above the cell as well as from the aging condition, could be observed and it might be an indicator for the diffusion of water in the encapsulant.