Material Characterization of Seven Photovoltaic Backsheets Using Seven Accelerated Test Conditions: Article No. 112726

Sona Ulicna, Rachael Arnold, Jimmy Newkirk, Archana Sinha, Kent Terwilliger, Laura Schelhas, Peter Pasmans, Christopher Thellen, David Miller

Research output: Contribution to journalArticlepeer-review


A variety of polymeric backsheet materials can be found in fielded photovoltaic (PV) modules, mostly based on fluoropolymer and polyethylene terephthalate (PET) materials. Cost reduction and sustainability considerations drive the recent development of alternative backsheet materials and designs [1]. In some fielded PV installations, polymeric materials are susceptible to environmental degradation in the form of backsheet cracking. To prevent backsheet degradation that can result in a module failure, thorough laboratory reliability testing is needed. Here, we studied the durability of seven commercial and experimental PV backsheets through accelerated stress testing using seven photolytic, hygrometric, and custom tests with the goal to understand if novel fluoropolymer-free backsheets are sufficiently environmentally durable to be commercialized. We divided the mechanisms observed during aging into two categories: core degradation and surface degradation. Although core degradation due to hydrolysis was observed in all commercial PET-, and polyamide (PA)-based backsheets aged with 85 degrees C/85% relative humidity, this test is unlikely to be field relevant. Photo-oxidative reactions on the exposed surface during UV weathering affected all seven backsheets regardless of the outer layer polymer material and additives. This degradation was limited to the outermost micrometers of the surface, except for backsheets containing PA-12, which resulted in surface cracking. A custom test combining UV with water spray caused the most severe backsheet degradation, including surface erosion and loss of insulating properties in polyolefin (PO)- and PA-based backsheets. This highlights the importance of combined accelerated stress testing to screen for complex backsheet degradation mechanisms. We also showed that, with material and design optimization, coextruded experimental PO-based backsheets have the potential to be a durable alternative to commercial PET- and fluoropolymer-based PV backsheets.
Original languageAmerican English
Number of pages13
JournalSolar Energy Materials and Solar Cells
StatePublished - 2024

NREL Publication Number

  • NREL/JA-5900-88632


  • backsheet
  • damp heat testing
  • durability
  • DuraMAT
  • IEC TS 62788-7-2
  • PET
  • polyamide
  • polyolefin
  • UV weathering


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