Tearing and reliability of photovoltaic module backsheets

Journal Article · 29 May 2019 · Progress in Photovoltaics

DOI: https://doi.org/10.1002/pip.3144 · OSTI ID:1560684

Yuen, Pak Yan ^[1]; Moffitt, Stephanie L.  ^[2]; Novoa, Fernando D. ^[3]; Schelhas, Laura T.  ^[2]; Dauskardt, Reinhold H.  ^[1]

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1. Stanford Univ., CA (United States)
2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
3. SolarCity, Fremont, CA (United States)

We report that the backsheet in photovoltaic modules belongs to an important class of layered materials where the tearing behavior of the individual layers does not necessarily represent the tearing behavior of the entire backsheet. Such characteristic arises from the interaction between the individual layers during the tearing process, where one layer of the backsheet is mechanically constrained by its neighboring layers and the layers may debond from each other. The mechanical constraint and debonding change the amount of energy dissipated during tearing and affect the overall tearing energy. In this article, we exposed a wide selection of backsheets with polymers including ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), and ethylene tetrafluoroethylene (ETFE) to damp heat (85°C/85%RH) for up to 2000 hours. We report on the effect of damp heat on the tearing energy as a function of damp heat exposure. We developed a model that describes the tearing energy of a layered structure by accounting for the tearing of the individual layers in the backsheet, the effect of mechanical constraint, and the adhesive debonding between the layers. Additionally, we explore the relationship between the microstructural change in the polymers which resulted from the damp heat exposure and the mechanical properties using modulated differential scanning calorimetry (MDSC), small and wide angle X-ray scattering (SAXS and WAXS), and tensile testing.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC02‐76SF00515; ECCS‐1542152
• OSTI ID: 1560684
• Alternate ID(s): OSTI ID: 1523542
• Journal Information: Progress in Photovoltaics, Vol. 27, Issue 8; ISSN 1062-7995
• Publisher: WileyCopyright Statement
• Country of Publication: United States
• Language: English