Low Cost, Single Layer Replacement for the Back-Sheet and Encapsulant Layers

Michael D. Kempe, Prem Thapa

Research output: Contribution to conferencePaperpeer-review

5 Scopus Citations


Ethylene propylene diene monomer (EPDM) based polymers have been formulated for specific use in photovoltaic modules to produce better performance and longer term stability at a lower cost than standard materials. EPDM formulations are advantageous over ethylene vinyl-acetate (EVA) because they can use the same lamination/cure cycle as EVA, they do not need a second back-sheet protective material (e.g. PET/Tedlar), they have a lower glass transition temperature, no melting transition, more constant mechanical moduli as a function of temperature, they are less polar than EVA (provides better corrosion protection), and they have excellent damp heat (85°C/85% relative humidity) resistance against delamination. Module designs typically use EVA on the back side of cells despite the fact that transparency is not advantageous. We have developed a single encapsulant layer that will replace standard module back-sheet constructions consisting of EVA/PET/Tedlar. Because a single low-cost material layer is used, it will provide a significant materials cost savings of about $6 to $8/m2 as compared to traditional back-sheets. Electrical insulation tests were conducted using 0.85 mm thick stainless steel sheets as a model for a cell. It was found that a polymer layer thickness of about 0.33mm provided better high voltage electrical insulation than a combined film of Tedla (0.038 mm) / PET (0.051 mm) / EVA (0.55 mm). When formulated with a white pigment, reflectivity was comparable to Tedlar TM. Upon accelerated exposure to light at 60C and 60% RH it was found that an EVA layer in front of these materials would decompose before significant yellowing and delamination of the back EPDM layer occurs.

Original languageAmerican English
Number of pages12
StatePublished - 2008
EventReliability of Photovoltaic Cells, Modules, Components, and Systems - San Diego, CA, United States
Duration: 11 Aug 200813 Aug 2008


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

Bibliographical note

For preprint version, see NREL/CP-520-42795

NREL Publication Number

  • NREL/CP-520-44858


  • efficiency
  • photovoltaic
  • solar cell


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