Delamination behaviour of multi-layer films for PV encapsulation

This paper focuses on the description and evaluation of the delamination behaviour of multi layer films, which are used for encapsulation of photovoltaic (PV) cells. The materials investigated include polyethylene terephthalate (PET), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) and ethylene vinylacetate copolymer (EVA). To describe the delamination behaviour a new energy-based fracture mechanics approach was applied. Problems due to testing conditions that influence the adhesive strength value were eliminated by the fracture mechanics approach. Delamination investigations indicated that the energy-based fracture mechanics approach is much more sensitive to describe the delamination behaviour compared to the usually applied load based analysis. In comparison to common thermoplastic laminates which are used for packaging purposes the tested laminates showed equal or higher adhesion values. For the investigated laminates a delamination within the backsheet material may be more likely than delamination between backsheet material and EVA solar cells encapsulation material.