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M Knausz, G Oreski, K Berger, G Eder, Y Voronko, T. Koch, G. Pinter:
"Reliability testing of backsheets: comparison between module and free aged films";
Poster: 29th European Photovoltaic Solar Energy Conference and Exhibition, Amsterdam; 09-22-2014 - 09-26-2014; in: "EU PVSEC Proceedings", (2014), ISBN: 3-936338-34-5; Paper ID 5BV.4.4.

In PV industry discussions about reliability testing of materials/modules are still holding on. Of special interest is the question, whether the materials should be tested alone or laminated within a PV module. In case of solar cell encapsulants testing of whole modules is preferred as some interactions (e.g. PID, snail tracks, corrosion, yellowing...) can`t be reproduced by weathering of the single materials. Merely a principal applicability, pre-selection or process unit improvements can be done very well in case of testing encapsulants as single materials. Weathering and testing of backsheet films instead seem to be less critical due to fewer failure/degradation mechanisms which occur in combination with other PV module components. However, in scientific literature no proof of this assumption was published so far. Therefore the main objective of this study was to compare test results of weathered single backsheets with backsheets aged within PV modules. In this study the aging behaviour of four different types of backsheets from three different producers was investigated, all of them containing polyethylene terephthalate (PET) middle layers. The outside/inside layers of the backsheets were in case of symmetric composition out of fluoropolymers or for the asymmetric ones PET on the outer with EVA as primer on the inner side. Test modules using the same components (encapsulant, solar cells etc.) have been produced, varying only in the backsheet types. Single backsheet films and the test modules were exposed to damp heat conditions at 85°C and 85% relative humidity for 1000 and 2000h.

photovoltaic module, backsheet, artificial ageing,damp heat