Researchers in Austria found that the fluorine and fluoropolymer content in PV backsheets has decreased significantly over the past thirty years, due to a shift from fluorine-rich multilayer structures to fluorine-free or coated alternatives. Despite this decline, fluoropolymer backsheets remain important for end-of-life management due to environmental conservation concerns.
Researchers from the Austrian Research Institute for Chemistry and Technology have evaluated how the fluorine (F) content has evolved in the backplates of PV modules over the past thirty years and found that both the relative and absolute fluoropolymer content in recently installed PV systems have decreased significantly.
F-containing polymers are often associated with environmental and health concerns as they may belong to the PFAS family, which is very persistent in the environment and can accumulate in living organisms, increasing the risks of long-term toxicity and pollution.
“Many PV backsheet types are known to contain fluoropolymers. However, quantitative data on their fluorine content are limited,” corresponding author Anika Gassner told us. pv magazine. “Using a combination of low-resolved material identification, thickness measurements and elemental analysis, we determined the F content of complete backsheet structures.”
The scientists explained that previous backplate designs primarily used three-layer polyvinyl fluoride (PVF)/polyethylene terephthalate (PET)/polyvinyl fluoride (PVF) structures, later supplemented with polyvinylidene fluoride (PVDF)-based and other fluoropolymer variants. However, from around 2010, fluorine-free alternatives such as PET/polyethylene (PE) and coated PET systems became increasingly common due to cost and environmental benefits, driving a market shift from durable but fluorine-rich multilayer systems to simpler coated or fluorine-free designs.
To determine the F content of backsheet materials, the research team conducted qualitative and quantitative analyses, including layer specific composition, layer thickness and density, and the fluorine content of each layer. Small samples of 1 cm × 1 cm were cut from PV backsheets, embedded in epoxy resin, and polished to obtain planar cross-sections for analysis.
Optical microscopy was used to measure layer thicknesses, while attenuated total reflection infrared (ATR-IR) imaging with Fourier transform infrared (FTIR) spectroscopy was used to identify the polymer composition of each layer. Furthermore, scanning electron microscopy (SEM) was combined with energy dispersive X-ray spectroscopy (EDX) to estimate surface element composition.
“We analyzed 23 representative backsheet samples from modules manufactured between 1988 and 2024,” Gassner said. “This allowed us to compare the F content of older and newer designs and of different materials.”
The analysis showed that the fluorine contents in the individual layers varied widely, with PVF reaching about 30 wt%, PVDF about 42 wt% and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride (THV) up to 71.5 wt%. The outer coatings ranged from fluorine-free to low-fluorine, reflecting the wide variability between backplate designs.
Additionally, the academics found that the total fluorine content of full backsheets varied widely from 0 wt% to approximately 17 wt%, decreasing in newer designs due to thinner fluoropolymer layers, thicker PET cores and the increasing use of fluorine-free layers or coatings, to 0.04-0.8 wt%.
Combined with estimated market shares, the results indicate an overall decline in the use of fluoropolymers in recent years, although older PV systems with higher fluorine content will continue to dominate end-of-life waste streams in the coming decades.
“We found that older backsheets with PVF outer and inner layers can have an F content of up to 12% by weight,” Gassner points out. “This value dropped to 2.8-4.7 wt% when the inner layer was replaced by PE or a coating in many backsheet designs between 2010 and 2020.”
“Additionally, we linked the measured results to the estimated market share of backsheet designs as reported by industry surveys,” she continued. “This can help estimate the impact of backsheets on the end-of-life and, in particular, on the recycling practices of PV modules. Although backsheets represent only 2-3% of PV modules, there are strict regulatory limits due to the formation of HF during the thermal treatment of fluoropolymers, making this a major concern for recyclers.”
The research work was presented in “Evolution of the fluorine content in the backplates of photovoltaic modules”, published in Solar energy materials and solar cells.
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