Early Detection of Encapsulant Discoloration by UV Fluorescence Imaging and Yellowness Index Measurements

The early detection of encapsulant discoloration in the indoor accelerated UV-stressed mini-modules were carried out using non-destructive methods, such as UV fluorescence (UVf) imaging, yellowness index (YI), and IV measurements. Eight labfabricated 9-cell mini-modules having glass/backsheet construction with two kinds of EVA, UV-cut EVA and UV-pass EVA, were experimented. Mini-modules with UV-cut EVA suffered from yellowing, which is clearly evident from UVf images and ΔYI (not to the naked eyes), whereas mini-modules with UV-pass EVA showed the signs of delamination above the cell area without any discoloration in the UVf images. Also, the activation energy for encapsulant discoloration was determined based on %I
_sc
drop and ΔYI data.