The photovoltaic front sheet and back sheet are very important for the solar panels encapsulation. In general, the photovoltaic backsheet is mostly PET based polymer materials, while the front plate is mostly photovoltaic glass. Photovoltaic backsheet mainly has three layers, the outer layer is mostly fluorine-containing polymer film, which has good environmental corrosion resistance; the middle layer is PET layer, which has good insulation performance, and the inner layer has good bonding effect with EVA and so on.

ETFE is a kind of fluorine-containing polymer thermoplastic material, the chemical name ethylene tetrafluoroethylene copolymer, in the 1970s, by the United States NASA and DuPont company jointly developed, and applied in the field of space. Because ETFE has strong light transmission and heat insulation, it is soon widely used in various fields.