TPT is the abbreviation of Tedlar Polyester Tedlar and is a composite-layer film used as covering foil on the backs of solar modules.
What is Tedlar?
Tedlar is the brand name of the US-American chemical company DuPont and refers to Polyvinyl fluoride (PVF), a thermoplastic fluoropolymer material which features high weather-resistance and inherent strength, has low permeability of moisture, vapor, oil and can be used in a wide temperature range of between -70°C to +110°C.
Beyond these material qualities, Tedlar - if transparent - allows for a high degree of light spectrum permeability.
Solar panel layers: TPT layer as backsheet
TPT and solar panels
The Tedlar Polyester Tedlar material combination strengthens the material qualities of Tedlar and is therefore used as backsheet of solar panels to enhance the longevity of the panels.
TPT is one of the mostly applied polymer multi-laminates for solar panels as there are only very few materials with comparably material qualities.
Regarding tradtional solar panel manufacturing, TPT along with the glass layer on the front side are the key barriers against damaging externalities, most importantly water, vapor and dirt.
Alternatives to TPT
Tedlar is a comparably expensive material and therefore one of the cost factors manufacturers seek to reduce by using alternative materials or even new panel types not requiring TPT at all.
Common alternatives to TPT are TPE (Tedlar/ Polyethylene terephthalate (PET)/ EVA), another composite-layer film and PET-based backsheets.