UV Fluorescence Imaging of Defects and Bill of Materials Variations in Bifacial Solar Panels

UV Fluorescence (UVF) is a high-throughput, non-contact method of imaging defects and bill of material variations in solar panels. Cracks in silicon solar cells are easily seen by this technique since oxygen can diffuse through polymer backsheets, through the cracks in the cells, and then quench the fluorescence in the front encapsulant above the crack lines. Most of the reported data on UVF imaging in the literature shows images of panels with polymeric backsheets, but bifacial panels with rear glass layers are steadily taking market share, and oxygen cannot penetrate the rear glass in such panels except through the junction box penetrations and the perimeter edges. We therefore ask the question, “Does UVF have a useful role in imaging glass/glass panels?” Here we present data from several different glass/glass bifacial panels installed in desert climate (Qatar), showing effective UVF imaging of varying levels of oxygen ingress from the frame edges, varying oxygen ingress from the junction box penetrations, encapsulant bill of materials variations, hot spots, and cell cracks. We therefore conclude that a use case does exist for UVF in at least certain glass/glass solar panel models.