Back Sheet

Solar Back sheet - The solar panel back sheet serves as the outermost layer of a photovoltaic module, serving multiple crucial roles. It is primarily designed to shield the photovoltaic cells and internal electrical components while also providing electrical insulation.

Additionally, the back sheet acts as a robust weatherproof barrier, safeguarding the module against environmental elements such as rain, moisture, and other adverse conditions.

Type of back sheet -

1.Two-side Fluoropolymer layered Back sheet:This consists mainly of PVDF or PVF on either side of the PET based back sheet at the core.

2.Single-side Fluoropolymer layered Back sheet:One way of reducing the cost of the back sheet while maintaining satisfactory behavior and durability is to reduce the number of fluoropolymer layers from two to one. In this case, the layered structure is formed mainly with PVF or PVDF on the airside and with PET or EVA layers on the inner side.

3.Non-Fluoropolymer layered Back sheet:This consists of a specialized H-PET (Hydrolysed PET) on Air-side, with PET disposed on the central followed by EVA/Polyolefinic layer on the cell side.

A typical backsheet is composed of three core layers

Outer Protective Layer (Weathering Layer): For optimal weather resistance, the outer layer material usually contains fluorine. PVF and PVDF are well-known polymers with high weather resistance.

Middle Layer: This layer provides support and must withstand temperature fluctuations. It should have stable mechanical properties, excellent electrical insulation, and low gas and vapor permeability. Modified PET material is commonly used.

Lamination Adhesive Layer: Unmodified fluorine films and PET have poor adhesion to EVA, so modified fluorine materials or adhesives like EVA, PE, or PA films are used.

Functions Of Solar Panel Back Sheets-

1. Mechanical Stress Resistance :The backsheet plays a critical role in fortifying the structural integrity of solar modules. It serves as a protective shield against various mechanical stresses that could potentially inflict harm.
2. Protection from Water and Dust Ingress : - One of the key functions of the backsheet is to act as a barrier against water and dust infiltration.It also safeguards against dust accumulation on the cell surface
3. Ultraviolet Radiation Shield:UV rays can cause semiconductor materials within the solar cells to degrade, diminishing their performance and efficiency. The backsheet acts as a shield, protecting the cells from UV radiation.
4. 4.Temperature Stress Management: Backsheets also serve a critical function in managing temperature-related stress in photovoltaic modules. Solar cells are subject to thermal stress when exposed to extreme heat or cold, which can impact their efficiency.
5. Dielectric Integrity: backsheet serves as a protective shield, preventing electrical conductivity between the solar cell and its environment.

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