Non-destructive monitoring of ethylene vinyl acetate crosslinking in PV-modules by luminescence spectroscopy

This work reports on the prospects of using luminescence spectroscopy as a non-destructive method for the characterization of ethylene vinyl acetate copolymer (EVA) crosslinking in photovoltaic (PV) modules. Luminescence has the potential to be easily applied in-line for monitoring purposes, e.g. during manufacturing. We investigate the correlation of luminescence, Raman spectroscopy and differential scanning calorimetry with the EVA crosslinking. We show that all these methods, including the luminescence method, show a good correlation with the hold time during the lamination process. Furthermore, time-dependent luminescence measurements are introduced. These make use of the fact that the luminescence decreases upon the ultraviolet irradiation during the measurement. In contrast to steady-state luminescence, this facilitates measurements that are inherently less dependent on possible interfering signal artifacts, as these may occur in industrial PV modules due to other components of the PV module.