PET based backsheets is Polyethylene Terephthalte film which is a material used in production of composite layer film which is used as a backsheet material in solar modules.
The backsheet consists of multiple layers of barrier films and adhesives. The construction of the backsheet is instrumental in protecting the solar cells from different environmental conditions like moisture, UV exposure and other performance threats while also improving solar module efficiency by aiding the reduction of partial discharge. To accomplish this, the solar panel material should be of a robust construction, typically a three layer laminate, and possess high dielectric properties. Most backsheets consist of combinations of films chosen for their different properties. Examples of standard films include: PET or EVA, Tedlar and Kynar. Combinations can be TPT (Tedlar/PET/Tedlar), KPK (Kynar/PET/Kynar) or PPE (PET/PET/EVA) among other combinations.
What is PET?
PET is the Polyethylene Terephthalte. PET Polyethylene commonly abbreviated PET is the most common thermoplastic polymer resin of the polyester range of products and is widely used in different products like clothing fiber, liquid and food containers, thermoforming for manufacturing, and for engineering resins in combination with fiber glass. It may has some well known names that are used to refer to it, like Dacron in the US, Terylene and Lavsan in Europe.
PET based materials are used in Solar panels as backsheet material.
PET based backsheets use in solar panels
PET based backsheets are one of the most used backsheets materials in order to reduce the cost of Tedlar-based material. PET based backsheets have a range of properties that makes suitable to use as backsheet materials, mainly transparency, good thermal resistance, mechanical and chemical resistance. Yet, the lifetime and ageing performance of the PET is not better than the more expensive alternatives, as PET based backsheets can be affected by yellowing and cracking after periods of outdoor exposure to environmental conditions.
Among newer outer layer backsheet materials, non-fluoropolymer backsheets –mainly PET and PEN based– constituted nearly 60% of the global backsheet PV market by area in 2014 (Global Market Insights, 2017).
Backsheets approximately cost $2 to $7/m2, which makes around 3% to 5% of the total module cost. The fluoropolymer-based sheets are more expensive than non-fluoropolymer-based backsheets, yet Fluoropolymer backsheets have better properties as they can withstand weather conditions quite well, even after years, while non-fluoropolymer backsheets tend to be more susceptible to environmental degradation.