Structure and basic properties of photovoltaic module backsheet films

In this paper commercially relevant backsheets are characterized as to their material and laminate structure and basic optical and mechanical properties. Various multilayer backsheet materials were selected and analysed by optical microscopy, Raman spectroscopy, infrared spectroscopy (FTIR-ATR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), ultra violet visible near infrared spectroscopy (UV/VIS/NIR) and monotonic tensile testing. By Raman and infrared spectroscopy and DSC the polymeric materials of the various layers were identified. Furthermore it was shown for the thermoplastic ethylene vinylacetate copolymer (EVA) layers that three different vinylacetate (VA) contents were used. By TGA a content of inorganic fillers and pigments from about 6%m to approximately 20%m was detected. The hemispherical solar reflectance of the white pigmented backsheets was ranging from 0.695 to 0.838. The highest Young׳s modulus was found in polyvinylfluoride based multilayers while the lowest values were detected for polyamide based structures.