The encapsulating film, a crucial part of photovoltaic modules, acts as a barrier between the cells and the glass or backsheet, preventing water vapor from entering the cells and providing protection. Indicators including the film’s light transmittance, volume resistivity, weather resistance, and PID resistance are critical to the solar modules’ operational life and power production efficiency.
In order to increase the dependability of components, the encapsulation film POE (polyolefin polymer) is extensively employed because to its performance advantages in resistance to PID, water vapor transfer rate, aging yellowing, etc. Nevertheless, there are a number of difficulties with using traditional POE in the component production process. The additives readily precipitate and induce slippage because of the POE film’s low compatibility with them, which makes it simple for the components to create bubbles and issues such cell slipping and paralleling.
Both EVA and POE have benefits and drawbacks in the realm of photovoltaics. EVA has excellent bonding performance with glass and backplane, is less expensive, simple to produce, resistant to storage, and has a quick cross-linking speed. PID resistance and high material qualities are the key benefits of POE. Outstanding features include low temperature resistance, high resistivity, a high water vapor barrier rate, and resistance to yellowing.
The primary drawback of EVA is its susceptibility to hydrolysis in light, oxygen, humid, and hot environments. This results in the production of acetic acid, which corrodes battery cells, solder ribbons, and other components. Additionally, EVA reacts with Na in glass to generate a significant amount of freely moving Na ions, which attenuates power. In addition, EVA is susceptible to yellowing in light and heat environments, which reduces light transmittance and increases the component’s overall power loss.
One of POE’s drawbacks is its low polarity. The polar additive solvent precipitates to the film surface during the processing process, making the surface smooth and easily shifted; processing complexity is relatively high, and the film lip is easily accessible for material hanging; POE particles are more expensive overall than EVA particles. The application fraction of POE particles in film particles is expected to increase during the next several years, mostly due to the following factors:
1. N-type batteries: The current photoelectric conversion efficiency of P-type batteries is close to the upper limit of 24.5%, while the upper limit of the conversion efficiency of N-type batteries is higher; the doped boron-oxygen complex of P-type batteries in the silicon wafer will cause the potential to decay faster , N-type batteries are mixed with scale and have better anti-attenuation performance. N-type batteries have a more sensitive PID impact on the surface that receives light. After the light is restored, N-type components with significant PID attenuation will likewise result in permanent damage. Simultaneously, the backplane exhibits inadequate water vapor barrier characteristics when N-type batteries are packed with a single piece of glass. As a result, selecting POE film for packaging can decrease the module’s total water vapor transfer rate and increase its usable life. As a result, encouraging N-type batteries may result in a rise in POE use.
2. Large-scale battery power: Different battery component types have seen considerable power improvements and an increase in heat generation in recent years. The temperature will have a bigger effect on the battery’s open circuit voltage, peak power, and other electrical characteristics. As a result, the packaging components The standards for electrical performance are rising steadily.
3. The number of double-glass components is rising while cover glass is decreasing: CPIA data indicates that there are now three different glass thickness levels: <2.5mm, 2.8mm, and 3.2mm. Of these, glass cover plates with a thickness of <2.5mm make up 32% of the market, and by 2025, that percentage is predicted to rise to almost 50%. Glass thinning will result in ever-higher performance standards for packaging materials. POE is robust and mechanically strong.
EVA and POE are the two distinct particles that make up co-extruded POE. The molecular structure accounts for a significant variation in performance. POE is a non-polar substance that is a saturated hydrocarbon polymer. It cannot be combined with water molecules to produce hydrogen bonds because it lacks an acetic acid structure. Vinyl acetate and polar groups, which are easily able to absorb water vapor, are present in the EVA compound. Since POE has a more stable molecular structure than EVA, the material performance is impacted by the co-extruded POE intermediate layer POE dose design.
Co-extruded POE is increasingly replacing conventional POE in order to address the drawbacks of the current technology.
The exceptional properties of both traditional POE and EVA are combined in the co-extruded POE composite film.
1. The module’s long-term dependability is not only on par with traditional POE, but it can also effectively increase the PID resistance of the module and lower water vapor penetration when the module is in use.
2. More significantly, when it comes to component manufacture, it may enhance the laminates’ appearance yield rate.
3. The use of co-extruded POE has also been growing quickly under the general trend of cost reduction and efficiency improvement in the solar industry, and it is a significant future growth path for adhesive films.
The benefits of POE and EVA may be combined in EPE film, which is a significant avenue for future film development.
