1. The idea of solar-powered packaging film

Photovoltaic encapsulation film serves the functions of enclosing photovoltaic cells between photovoltaic glass and photovoltaic backside materials, isolating air, and safeguarding cells in the photovoltaic industrial chain as one of the components of photovoltaic modules. It makes up the majority of solar modules and costs between 3% and 4% of the module price.

As the primary component of the photovoltaic module, the encapsulation film shields the solar cell from the outside environment, increases the module’s lifespan, and simultaneously allows the maximum amount of sunlight to pass through the film and reach the cell, increasing the photovoltaic module’s ability to generate electricity. The battery sheet will quickly fail and need to be discarded whenever the adhesive coating of the battery module begins to turn yellow, fracture, or delaminate. As a result, even though they only make up around 5% of the price of solar modules overall, adhesive film and other membrane materials are crucial. The most important aspect of component product life.

The categorization of photovoltaic packaging film is the second.

Ethylene vinyl acetate copolymer, or EVA

The four primary categories of EVA for solar packaging are high-transmission, high-cut-off, white, and black.

Single-glass components are often packed with white EVA and high-transmittance EVA among them. The objective is to enhance the component’s photoelectric conversion efficiency by increasing the light transmittance of the component’s front and the light reflectance of the inner layer.

Typically, high-transmission EVA + high-cut EVA + black backsheet or high-transmission EVA + black EVA + white backsheet are used to package black single-glass modules. The inner backplane is destroyed.

Photovoltaic module material composition

great cohesive force and great fluidity characterize EVA polar molecules. The structure contains ester groups, which are hydrophilic polar groups that are simple to hydrolyze. The cross-linked EVA chemical structure is rather loose, which results in a relatively high water vapor transfer rate. The component’s water vapor transmission rate should be taken into consideration while employing EVA as the encapsulant film. Low water permeability can prolong the component’s useful life.

2.2 Polyolefin (POE)

The two primary forms of POE used in photovoltaic packaging are co-extruded POE and pure POE.

Double-glass photovoltaic modules are the major use for POE for photovoltaic packaging. The cause is that PID effects are more likely to occur in double-glass modules. Glass is used for both the front and the back of the module, which increases the likelihood that metal ions will be concentrated on the cell’s surface and diminish the cell’s field passivation effect, lowering the module’s output power.

The back of the P-type cell component and the front of the N-type cell component are more likely to cause PID effects because of the differences in features between the two types of cell components. As a result, P-type double-glass components often come in EVA+POE packaging, whereas N-type modules typically come in POE+EVA packaging.

PID has significantly better hydrolysis resistance, water permeability, and resistivity than EVA, however there are some issues with the module process since its own polar additives are more likely to precipitate. Co-extruded POE has been steadily implemented by film makers to address similar issues since it can guarantee component reliability while taking cost into consideration.

A non-polar molecule, POE has a low water vapor transmission rate, a weak cohesive force, poor fluidity, a hydrophobic structure, a complicated molecular structure after cross-linking, and is easily precipitated by polar additives.

Polyvinyl butyral (PVB)

Polyvinyl butyral, a product of the condensation of polyvinyl alcohol (PVA) and butyraldehyde, serves as the primary raw material for PVB film. PVB is manufactured into PVB film by plasticization, extrusion, casting, and other procedures after being combined with plasticizer and other additives.

PVB film is being utilized often in architectural laminated glass. In terms of water penetration resistance, adhesion, acid, alkali, and salt spray resistance, high temperature resistance, and impact resistance, PVB has more glaring benefits over EVA and POE. PVB may end up being the chosen encapsulation film material for photovoltaic curtain wall (BIPV) because it has been utilized for 70 years in the building curtain wall sector.

The majority of the worldwide construction-grade, automotive-grade, and photovoltaic-grade PVB markets are monopolized by Solutia Corporation of the United States, Sekisui Chemical of Japan, DuPont of the United States, and Kuraray of Japan in terms of PVB film supply. Although domestic businesses only make up a tiny portion of the market for high-performance photovoltaic grade PVB, demand for domestic BVP film will climb quickly as BIPV develops further. It will encourage domestic businesses to expand their research, development, and manufacture of photovoltaic grade PVB film, and it is anticipated that the localization process for PVB film would quicken.

3. Typical flaws in packaging film

3.1 Fading

The adhesive film will experience “yellowing” and “browning” during the operation of solar modules if it is left outside for an extended period of time.

movie coloring
The discolouration lowers the photocurrent of the solar cell, lowers the light transmittance of the encapsulation layer, and ultimately causes the photovoltaic module to lose power. The creation of unsaturated polyene chromophores as a consequence of the chemical composition of the packing material changing as a result of the combined effects of UV light and water penetration is the primary cause of this phenomena. The hue of EVA progressively deepens from bright yellow to dark brown when unsaturated polyene molecules build up in it.

Unsaturated carbonyl compounds that alter the light transmission of EVA and lower component efficiency are produced by the deterioration of EVA packaging materials. Chromophore production raises the opacity index and partially obstructs sunlight from reaching the solar module.

3.2 Delamination

The adhesive force between the cover glass and the solar cell and/or between the solar cell and the back sheet material is lost as a result of delamination caused by the breakdown of the encapsulation layer brought on by water vapor or ultraviolet radiation.

movie lamination

The system as a whole suffers from output power loss, increased light reflection, increased water penetration, and solar module delamination.

Delamination can occur for several reasons. The primary cause, in addition to process variables, is EVA’s deterioration with use. As EVA ages, the interface connections break down, causing gaps to emerge between EVA and other layers. Light, heat, oxygen, and water are used in this process. Additionally, there are additional aspects that are significant. A usually hot and humid atmosphere will speed up stratification.

3.3 Swelling

Similar to delamination, blistering is a smaller-scale phenomenon that is brought on by EVA’s lack of adhesion. A chemical reaction results in the release of gases, which frequently emerge on the back of the module and gather in the package but sporadically appear on the front between the glass and the cell.

The high temperature within the battery and the varied adherence of EVA are the main causes of the bubbles that frequently occur in the battery’s center. Inhibited heat dissipation from the battery caused by air bubbles increases overheating and shortens component life.