Channel cracking fragmentation testing and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were utilized to study mechanical and chemical degradation of a multilayered backsheet after outdoor and accelerated laboratory aging. A model sample of commercial PPE backsheet, namely polyethylene terephthalate/polyethylene terephthalate/ethylene vinyl acetate (PET/PET/EVA) was investigated. Outdoor aging was performed in Gaithersburg, Maryland, USA for up to 510 days, and complementary accelerated laboratory aging was conducted on the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure). Fracture energy, mode I stress intensity factor and film strength were analyzed using an analytical model based on channel cracking fragmentation testing results. The correlation between mechanical and chemical degradation was discussed for both outdoor and accelerated laboratory aging. The results of this work provide preliminary understanding on failure mechanism of backsheets after weathering, laying the groundwork for linking outdoor and indoor accelerated laboratory testing for multilayer photovoltaic backsheets.

Date Published: 26 September 2016
PDF: 11 pages
Proc. SPIE 9938, Reliability of Photovoltaic Cells, Modules, Components, and Systems IX, 99380H (26 September 2016); doi: 10.1117/12.2238216

Published in SPIE Proceedings Vol. 9938:
Reliability of Photovoltaic Cells, Modules, Components, and Systems IX
Neelkanth G. Dhere; John H. Wohlgemuth; Keiichiro Sakurai, Editor(s)