Most Popular Backsheet Material for Solar Panels

What is a backsheet?

A backsheet is a layer inside of the solar panel that enhances it’s functionality. A backsheet provides the following functions:

  • Dissipate heat for a longer lifespan and more efficient solar panels
  • Protect the solar panel from UV rays
  • Protection from mechanical damage
  • Added electrical insulation

Different backsheets for different applications:

  • Backsheets for crystalline modules (mono and polycrystalline)
  • Backsheets for flexible solar panels
  • Backsheets for thin-film solar panels
  • Backsheets for bifacial panels

The different layers of a solar panel

A solar panel has 5 main layers, which are the following beginning from the top:

Layers of a solar panel with backsheet
Layers of a solar panel
  1. Glass
  2. Encapsulant
  3. Solar cells
  4. Encapsulant
  5. Frame
  6. Backsheet

We can see that the backsheet is located (not surprisingly) at the back. And that there is only one backsheet for one solar panel.

How many layers does a backsheet have?

A backsheet can have many layers depending on the manufacturer and the intended use. Therefore, the chosen materials will be different for solar panels. Normally this consists of three layers. Two specialized layers on the top and bottom and one PET layer in the middle.

TPT and TPE backsheets from Dupont
Image from dupont.com

How to check if your backsheet is damaged

We can do three checks to see if the backsheet is still okay. These are:

  • Visual inspections
  • Hotspot detection
  • The power output of the panel

If you see a discrepancy in one or more of these tests, you might be eligible to talk to the manufacturer or installer to use your warranty. Manufacturers now give 20 to 25 years of warranty on their solar panels. Sometimes to reduce the price, the material of the backpanel is of lesser quality. Depending on the damage, you might receive new panels.

What is the most popular Backsheet Material?

The most popular backsheet is called TPT. This abbreviation is Tedlar Polyester Tedlar. It is a product from DuPont. It consists of several layers.

layers of a TPT backpanel
TPT layers
  1. Tedlar
  2. Adhesive
  3. PET
  4. Adhesive
  5. Tedlar

Some cheaper solar panel manufacturers use another material to reduce costs. Make sure they offer a long warranty on their panels because the backsheet will be one of the first components to fail on a solar panel.

The thickness of a backsheet will only be a few millimeters. The color is mostly white to help reduce the solar panel’s temperature. If it were black, the temperature would be higher, and the solar panel would be less efficient.

What kind of backsheet does my solar panel have?

To find the backsheet of your solar panel, you need to do some digging. This is because this is often overlooked in the marketing material. For example, I couldn’t find the kind of backsheet Renogy used for their panels on the datasheet. But I found it in the description on their website. Their 200W 12V panels uses TPT.

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