Photovoltaic backsheet PET film high reflective coating: a new choice to improve photovoltaic efficiency

With the increasing attention and demand for clean energy in various regions around the world, the photovoltaic industry is experiencing unprecedented development. As a key component of photovoltaic modules, whether in single glass photovoltaic modules or double glass photovoltaic module systems,

Photovoltaic backsheet materials play a crucial role in improving photovoltaic conversion efficiency, reducing costs, and addressing environmental challenges.

The reflective coating of PET film on photovoltaic backsheet is a key material used to improve the efficiency and performance of photovoltaic modules. This material is usually made of high reflectivity PET film and prepared through specific techniques.

Photovoltaic backsheet coating is a key material used for photovoltaic module backsheet. Its main function is to protect solar panels from environmental factors and improve the efficiency and performance of photovoltaic modules. These coatings typically require multiple characteristics, such as aging resistance, UV resistance, water resistance, high temperature and humidity resistance, fire insulation, etc.

There are various types of photovoltaic backsheet coatings, including coating type and composite type. Coated backboards usually have lower costs and relatively simple processes. Composite backboards are more commonly used, especially in the use of fluorine materials. Composite backboards are favored for their weather resistance and barrier properties. The main characteristics of the backboard are reflected in the fluorine material. As long as the fluorine material is processed properly, whether it is composite film or coating, the weather resistance and barrier properties of the backboard can be guaranteed.

In addition, the development of photovoltaic backsheet coatings is also constantly advancing. For example, a new type of double-sided coated backsheet has been launched in the market, which not only has high reliability, but also demonstrates good performance in photovoltaic backsheet applications. This solution is not limited by upstream raw material supply and has been widely used in various large transportation vehicles. It can ensure construction efficiency, excellent appearance, and good weather resistance while meeting the latest environmental standards.

The fluorocarbon coating for the bonding layer of photovoltaic backsheet is also an important research field. For example, a study used different types of fluorocarbon resins and curing agents to prepare fluorocarbon coatings for backboard bonding layers. These coatings were evaluated for their adhesion, yellowing, and adhesion to EVA, and the optimal solution for fluorocarbon coatings suitable for solar backsheet was ultimately determined.

In addition, reflectivity is an important indicator of the backplane, which directly affects the power gain effect of the backplane on the components. For example, photovoltaic backplates on the market generally come in three color specifications: black, white, and transparent. Among them, the black backsheet is similar in color to the module cells and has a uniform appearance, but conventional black photovoltaic backsheet can hardly form effective reflection of solar waves, and has little effect on the power generation gain of the module. Therefore, improving the reflectivity of black photovoltaic backplates in the near-infrared wavelength range, reducing heat absorption, and increasing the power generation of photovoltaic modules have become important research directions.

Backboards are divided into inorganic backboards, namely glass, and polymer organic backboards, based on the materials used. If the back panel also uses glass, it is a double glass component, otherwise it is a single glass component, with one side of the component glass facing directly to the sun and the back panel located on the back of the component. At present, photovoltaic modules are mainly single glass modules, but the development trend is that the proportion of double glass modules will gradually increase, because double glass modules can generate electricity on both sides, improving power generation efficiency.

Guangdong KDD Functional Materials Co., Ltd. (referred to as KDD Functional Materials) is an enterprise dedicated to the production, research and development, and application promotion of polymer synthetic material functional resins. It has also been deeply involved in the photovoltaic industry. Under the guidance of policies such as carbon neutrality, carbon standards, and energy conservation and emission reduction, as well as product research and development in the photovoltaic new energy industry, Guangdong KDD's continuous technological innovation originates from its continuous attention to society. How to sustainably and high-quality utilize renewable energy has always been a problem that the country is committed to solving. Guangdong KDD Functional Materials Co., Ltd. strives to break through industry pain points and difficulties, and provide higher quality products for industry users.

In terms of high-temperature reflective glaze for photovoltaic double glass:

KDD KDD Gongcai has independently developed a series of polymer synthetic resin/connector products, which are widely used in water-based high-temperature tempered reflective ink for photovoltaic backsheet glass (double glass). The sintering temperature of this product is 500-750 ℃, which reduces emissions by 37% compared to peer products and effectively achieves energy conservation and emission reduction; The solid-liquid ratio of the product is 87% (solid): 13% (liquid), which is 67% higher than peer products; The product has a reflectivity of 83%, which is 6% higher than peer products, achieving high load-bearing, high reflection, and high conversion. In addition, the cleanliness comparison (dry film) of the product after low-temperature sintering at 400-500 ℃ with white ink can achieve complete sintering, and the color development is uniform in the transparent comparison (wet film) of the printing plate, achieving continuous cost reduction and efficiency improvement, and helping the development of the photovoltaic industry. This product has been maturely used and has established strategic partnerships with several leading listed companies. We believe that it will also be welcomed by more photovoltaic glass manufacturers in the future.  

Photovoltaic single glass back panel PET film high reflective coating:

Photovoltaic module single glass is a type of photovoltaic module manufactured using a glass substrate, which changes the glass substrate from the original double-layer glass to single-layer glass on the basis of ordinary photovoltaic modules, thereby achieving the optimization of module lightweighting, transparency, and cost. Compared to traditional double glass photovoltaic modules, single glass photovoltaic modules achieve a more aesthetically pleasing and lightweight effect while maintaining high power generation capacity.

The requirements for single glass backboards are extremely strict:

Weather resistance, heat resistance, moisture resistance, UV resistance, salt resistance, other environmental resistance, electrical insulation resistance, system voltage breakdown resistance, partial discharge resistance, high volume resistance, mechanical properties such as tensile strength, elasticity, fracture resistance, water vapor barrier to prevent water vapor from passing through, chemical resistance, laminating operation properties, adhesion, can resist various acidic and alkaline solvents, suitable for use in various environments such as seaside, farm, roof, etc. It has operability when laminating solar panels, including wear resistance, surface hardness, low shrinkage rate, and long-lasting adhesion with EVA film, silicone, etc

A single material is difficult to meet these performance requirements, so the backboard generally adopts a composite structure, in which PET film is used as the base film, and fluorine film or other plastic film is adhered to both sides of the base film through adhesive. PET film has excellent insulation and mechanical properties, but poor weather resistance. Fluorinated resin films include polyvinyl fluoride (PVF) film and polyvinylidene fluoride (PVDF) film, which have excellent insulation, weather resistance, and barrier properties. The main function of adhesives is to bond and composite PET base film with fluorine film and polyolefin film. The types of film materials can also be divided into semi transparent and high reflective types.

However, due to the cost price advantage, domestic backboard production enterprises have taken different technological paths from foreign enterprises. In China, centralized large-scale ground photovoltaic power stations are the main ones, with strict requirements for a service life of 25 years. Therefore, the vast majority of backboards in China contain fluorine. In order to reduce costs, the production process has been improved from composite fluorine film to coating with fluorine-containing coatings. There are also PET base films used, with a UV stabilized polyester film (P) on the outermost side and a polyethylene film (E) on the inner layer to form PPE backboards. The structure of this type of backboard is modified polyester/polyester/polyethylene.

Due to the special nature of membrane materials, it is generally difficult for coating resin materials to have good adhesion, high weather resistance, water resistance, and steam pressure resistance requirements. A single product cannot meet the harsh environment of long-term use in some desert areas at home and abroad. Backboard coating materials need to have better heat dissipation, UV resistance, wind and sand wear resistance, and resistance to day night temperature differences; The backboards used in the eastern coastal areas should have lower water vapor permeability, better hydrolysis resistance, and salt spray resistance.

As a new material research and development enterprise, KDD KDD Gongcai has been committed to promoting functional material research and development technology, solving industry pain points, and responding to the national energy conservation and emission reduction policy requirements. We have developed functional resin materials suitable for photovoltaic backsheet base film high reflection coatings, such as special polymer modified acrylic resin series, functional modified polymer polyurethane system, etc,

KDD KDD functional acrylic resin is synthesized by special monomer material dropwise polymerization reaction, which has good adhesion to PET film, high weather resistance, water resistance and pressure cooking requirements. It is suitable for long-term outdoor harsh environment testing in the composite photovoltaic industry and can be compounded with various fluorocarbon resin materials for excellent compatibility. It can be used in combination to improve the weather resistance and durability testing requirements of coatings in different environments, reduce the proportion of fluorine content in coatings, and play a certain role in environmental protection. KDD resin system has good wetting and wrapping properties for different system powders. Whether it is machine rapid coating, large screen printing and efficient construction, it is very dry and excellent,

As a response to the national policy call for energy conservation and emission reduction, KDD Company's positioning and mission in product material research and development meet the cost reduction needs of customer material applications.

Reflective film coating increases the power generation gain on the back of the component by increasing the reflectivity of light: Reflective coating mainly increases the surface reflectivity. When sunlight shines on this film coating, it is reflected into the back panel of the component through the reflective coating, increasing the amount of incoming light, especially for double glass components. The higher the ground reflectivity, the stronger the light received by the back of the battery, the higher the reflectivity value, the better the reflection of sunlight, and the brighter the surrounding environment. The inclined surface of the photovoltaic module also receives more reflection and radiation, and the power generation gain on the back of the double-sided module is more obvious.
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