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Encapsulating adhesive film serves as the fundamental component of photovoltaic modules, shielding delicate solar cells from the elements so they can function without interference from the outside world. This increases the modules’ service life while also maximizing the amount of sunlight that can pass through the glue. When the film reaches the cell sheet, the solar module’s power generation efficiency increases. In the photovoltaic industry, photovoltaic encapsulation film is an essential auxiliary material that must guarantee the 25-year service life of solar modules.
When looking at the product composition, the encapsulation film is mostly constructed of two films: POE (polyolefin elastomer) and EVA (ethylene-vinyl acetate copolymer), which are made primarily of POE and EVA resin. By including the proper Melt extrusion and casting are the methods used to make cross-linking agents, anti-aging agents, etc.
Regarding product attributes, POE film has strong resistance to PID (potential induced decay), which is the term used to describe the photovoltaic module’s susceptibility to UV yellowing caused by moisture and heat, and high light transmittance. System bias and external factors will cause the power generation efficiency to rapidly decline throughout operation until it fails entirely.) Performance as well as additional benefits. For solar modules, both adhesive films are essential components.They cover the upper and lower sides of the cell sheet, the upper glass, and the lower back during the lamination process of battery module packaging. A photovoltaic module is created using vacuum lamination, which bonds the panels (or glass) together.
2. Features of the product
1. EVA
Right now, the primary packing material is EVA. It is a film created by combining a number of modifying ingredients with melted EVA resin as a raw material.
Feature 1: Since EVA resin is polar, it can fuse more easily with polar additives to form EVA film. Its low processing temperature, good processing characteristics, and outstanding melt fluidity are all present.
Feature 2: Inadequate protection against PID. The hydrophilic group in the EVA polymer is vinyl acetate. Water vapor entering the component’s edge can hydrolyze EVA, producing acetic acid. When the acetic acid and glass combine, a significant amount of sodium ions are produced on their own. The silver grid lines on the battery sheet’s surface are contacted by the sodium ions on the glass surface as they move to the battery’s surface. This corrosion of the battery grid lines raises series resistance and reduces module performance.
Feature 3: EVA is not very stable. The vinyl acetate group in EVA film contributes to its aging and deterioration from UV light and wet heat oxidation. This aging and degradation causes the film to yellow and delaminate, reducing the film’s service life and image component efficiency.
2. POE
Polyolefin elastomer, or POE for short, is a random copolymer made of ethylene and ฮฑ-olefins, primarily those with 4โ8 carbon atoms, including 1-butene, 1-hexene, and 1-octene. It performs well at low temperatures, has outstanding heat aging resistance, excellent mechanical and physical qualities, and is UV resistant.
POE resin is the primary raw material used in POE film; it is then modified by adding different additives, heated, and formed into the desired shape. POE resin performs exceptionally well, which gives it the following qualities:
Feature 1: Good PID resistance, high volume resistivity, and low water vapor transfer rate. Since POE resin is non-polar, it is unable to establish hydrogen bonds with molecules of water. Its water vapor transmission rate is minimal, and it does not absorb water vapor like polymers with polar groups like EVA. Furthermore, POE film has a high volume resistivity. Compared to EVA film, POE film’s volume resistivity diminishes more slowly as temperature rises. These properties enable the POE film to have strong PID resistance, partially minimize the PID effect, and inhibit the rate at which positively charged ions (such Na+) migrate to the cell surface.
Feature 2: The possibility of additive migration and poor processing qualities. The material POE resin is non-polar. Adhesive film preparation now involves the addition of polar chemicals, which are not well suited to POE resin. The module lamination yield is low, POE adhesive films have a smooth and easily shifted surface that reduces module manufacturing efficiency, and they have a number of other issues such additive precipitation and easy bubble formation after application.
Feature 3: There is a shortage and high POE expenses. Solution polymerization is the method used in the manufacturing of POE resin. The fundamental technique involves high-carbon ฮฑ-olefins, primarily those with 4 to 8 carbons, like 1-butene, 1-hexene, and 1-octene, as well as catalysts (metallocene catalyst production). has a comparatively small supply, and when demand and supply are tight, the price is high.
3. Co-extruded film with several layers (EPE)
Although it requires less POE resin and has superior PID resistance than EVA film, processing this film is more challenging. Currently, EPE adhesive films, which are created by co-extrusion and melt processing of EVA and POE resin, are a representation of multi-layer co-extruded adhesive films.
Feature 1: POE resin usage is lower and anti-PID performance is superior to that of EVA film. Co-extruded film has the high PID resistance performance of POE film and co-extrudes EVA and POE resin in a certain proportion. EVA film can be used to encapsulate the front side of PERC double-sided modules because the outer layer is composed of this material. When compared to the “POE-POE” packaging structure, the “EVA-EPE” packaging structure drastically reduces the amount of POE resin, which helps somewhat ease the shortage of POE resin and lower component packaging costs.
Feature 2: Complexity of processing. The co-extruded film is made up of several layers. POE resin is a non-polar material and EVA resin is a polar material, hence there is little compatibility between the two and little surface adhesion. Fusing the POE and EVA layers together is challenging.
