Degradation Analysis of Field-Exposed Photovoltaic Modules with Non-Fluoropolymer-Based Backsheets

Neelkanth G. Dhere, Keiichiro Sakurai, Michael D. Kempe, Andrew Fairbrother, Scott Julien, Kai Tak Wan, Liang Ji, Kenneth Boyce, Sebastien Merzlic, Amy Lefebvre, Greg O'Brien, Yu Wang, Laura Bruckman, Roger French, Michael Kempe, Xiaohong Gu

Research output: Contribution to conferencePaperpeer-review

10 Scopus Citations


The selection of polymeric materials utilized in photovoltaic (PV) modules has changed relatively little since the inception of the PV industry, with ethylene-vinyl acetate (EVA), polyethylene terephthalate (PET), and fluoropolymer-based laminates being the most widely adopted primary components of the encapsulant and backsheet materials. The backsheet must serve to electrically insulate the solar cells and protect them from the effects of weathering. Due to continued downward pressure on cost, other polymeric materials are being formulated to withstand outdoor exposure for use in backsheets to replace either the PET film, the fluoropoymer film, or both. Because of their relatively recent deployment, less is known about their reliability and if they are durable enough to fulfill the ≥25 year warranties of current PV modules. This work presents a degradation analysis of field-exposed modules with polyamide-and polyester-based backsheets. Modules were exposed for up to five years in different geographic locations: USA (Maryland, Ohio), China, and Italy. Surface and cross-sectional analysis included visual inspection, colorimetry, glossimetry, and Fourier-Transform infrared spectroscopy. Each module experienced different types of degradation depending on the exposure site, even for the same material and module brand. For instance, the polyamide-based backsheet experienced hairline cracking and greater yellowing and chemical changes in China (Changsu, humid subtropical climate), while in Italy (Rome, hot-summer Mediterranean climate) it underwent macroscopic cracking and greater losses in gloss. Spectroscopic studies have permitted identification of degradation products and changes in polymer structure over time. Comparisons are made to fielded modules with fluoropolymer-based backsheets, as well as backsheet materials in accelerated laboratory exposures. Implications for qualification testing and service life prediction of the non-fluoropolymer-based backsheets are discussed.

Original languageAmerican English
Number of pages13
StatePublished - 2017
Externally publishedYes
EventReliability of Photovoltaic Cells, Modules, Components, and Systems X 2017 - San Diego, United States
Duration: 6 Aug 20177 Aug 2017


ConferenceReliability of Photovoltaic Cells, Modules, Components, and Systems X 2017
Country/TerritoryUnited States
CitySan Diego

Bibliographical note

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© COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

NREL Publication Number

  • NREL/CP-5J00-68229


  • backsheet
  • degradation
  • failure analysis
  • photovoltaic module
  • polyamide
  • polyethylene naphthalate
  • polyethylene terephthalate
  • polymeric materials
  • reliability


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