POE is utilized as a single substance, primarily in the adhesive film used as photovoltaic module packaging.
To enclose and safeguard the solar cells in photovoltaic modules, an adhesive film is positioned between the tempered glass/backsheet of the module and the solar cells.
Structure of a photovoltaic module
Although the absolute value of the film is not high in the components, its quality directly determines the product quality and life of the comp. since the packaging process for solar cells is irreversible and the operating life of modules is typically required to be more than 25a. As a result, once the light transmittance of the adhesive film decreases or failure problems like yellowing occur while operation, the solar cells will be scrapped, rendering the modules unusable.
Currently, POE film and EVA film are the two most common types of encapsulation film used for solar modules. EVA adhesive film is a thermosetting adhesive film that has poor weather resistance, a high rate of water vapor transfer, and low strength. Water vapor will still be able to travel through the film normally, which will atomize the film and change its permeability. Additionally, the EVA film easily breaks down and releases molecules of acetic acid, which corrodes glass, the backplane, and other components and reduces their useful lives.
In recent years, it has also been discovered that there is a major potential-induced degradation (PID) phenomena in the EVA film, which causes a dramatic decrease in the output power of solar power plants.
In recent years, it has also been discovered that there is a substantial potential-induced degradation (PID) problem in the EVA film, which causes a significant decrease in the power plant’s output.
Low water vapor transmission rate and high volume resistivity of POE film over EVA film ensure the safety and long-term aging resistance of photovoltaic modules in high temperature and high humidity environments, allowing for the modules’ long-lasting and effective use.
Performance evaluation of POE and EVA
EVA and POE each have advantages and disadvantages in the realm of photovoltaics. EVA is inexpensive, simple to produce, storage resistant, quick to crosslink, and performs well when bonded to glass and the backplane; the benefits of POE are mostly related to its superior material performance and anti-PID performance. Excellent, high resistivity, strong resistance to water vapor, low temperature resistance, and resistance to yellowing.
The primary drawbacks of EVA are that vinyl acetate is prone to hydrolysis in hot, humid, and oxygen-rich situations, creating acetic acid that corrodes soldering strips and battery sheet surfaces and also interacts with sodium in glass to produce a significant amount of free movement. Na ions, which results in power attenuation; concurrently, EVA is prone to yellowing in the light and heat environment, which lowers the light transmittance and results in the module’s overall power loss.
The processing is too difficult, the film lip is easy to hang, and the overall price of POE particles is more expensive than that of EVA. POE’s disadvantages include its low polarity, which causes the polar additive solvent to precipitate to the surface of the film during processing, making it smooth and easy to shift. According to common consensus, the following variables will cause the fraction of POE particles in the application of film particles to increase during the next several years:
1. N-type battery: While the upper limit of photoelectric conversion efficiency for P-type batteries is currently close to 24.5%, it is higher for N-type batteries; the boron-oxygen complex doped in P-type batteries’ silicon wafers will cause the potential decay to speed up, and N-type batteries mixed with scale will perform better against attenuation. N-type cells have a PID effect that is more sensitive to the light-receiving surface. After the light is restored, N-type components with significant PID attenuation will likewise sustain permanent harm. Therefore, selecting POE film for packaging can lower the module’s total water vapor transmission rate and increase the module’s useful life. As a result, encouraging the use of N-type batteries can boost POE.
2. Battery power on a large scale: In recent years, the power of various battery component types has substantially improved, and heat generation has grown. The demands for electrical performance will be increased.
3. The reduction in cover glass thickness and the rise in double-glass components: According to CPIA statistics, there are now three primary grades of glass thickness: 2.5mm, 2.8mm, and 3.2mm; of these, the market share of 2.5mm glass cover plates is 32%. By 2025, it’s anticipated that the percentage would reach about 50%. The performance requirements for packaging materials will rise as glass becomes thinner, and POE offers strong mechanical strength and toughness.
