solar adhesive film is mostly utilized in the solar module packaging process within the photovoltaic manufacturing chain. It is among the essential building blocks used in the photovoltaic sector. Changes in the solar cell technology route have no effect on its demand. solar films continue to be in high demand due to the solar industry’s rapid development. The demand for photovoltaic films is predicted to rise to almost 4 billion square meters globally in 2025, a 209.77% growth from 2020. By 2025, the photovoltaic film market is projected to have grown to a conservative 20 billion yuan worldwide. What function does photovoltaic film serve, then? Which kinds and features distinguish typical photovoltaic films?
1. Photovoltaic films’ function
In the intermediate stages of the solar industrial chain, photovoltaic film is employed. Photovoltaic glass and photovoltaic backsheets are required to cover the upper and bottom sides of crystalline silicon cells in order to seal and preserve them, as crystalline silicon cells are relatively delicate and cannot be directly exposed to the air. The crystalline silicon cells, the backsheet, and the glass are not connected. In practical application, vibration and other factors can quickly degrade the crystalline silicon cells.Consequently, the solar glass, crystalline silicon cells, and photovoltaic backsheet must be separated using photovoltaic adhesive film. Bonding and fixing, which add 3% to 4% to the module’s cost, also contribute to air isolation and battery cell protection.
2. Photovoltaic film types
At the moment, the market offers four popular packaging adhesives.
1)Clear EVA plastic. Its light transmittance is excellent. EVA resin and several modifiers serve as the raw components. Once everything has been uniformly stirred in the mixer, combine it in a covered container and leave it to stand for a while. After being extracted, the mixture is sent into the film production process where it is cast and extruded into a molten film. The edges of the molten film are cut and formed into rolls after it has been cooled by several cooling rollers. Light stabilizers and ultraviolet absorbers are crucial components of the translucent EVA film composition. They can significantly lengthen the transparent film’s service life resistant to weather.
2) EVA film in white. It is highly reflective. As the bottom adhesive film, it can effectively increase the transmitted light of the module and the reflection of incident light in the cell gap, boosting the module efficiency by 1W to 3W. The production process is comparable to that of transparent EVA film; to make the EVA film white, 5% to 20% of white filler is added.
3)The POE film. Low water vapor transfer rate and high volume resistivity are two benefits of POE film that guarantee the long-term aging resistance and safety of the module in high-temperature and high-humidity situations, thereby extending its useful life. Right now, it’s the double-sided double glass. The primary film used in component and thin-film packaging. Octene and ethylene copolymerize to form POE film. Its chemical chain contains less aging-prone tertiary carbon atoms and a saturated fatty chain structure.It has exceptional resistance to heat, low temperatures, and UV aging in addition to outstanding weather resilience. performance, POE film is more resistant to aging than EVA film. POE is not polar by nature, but it can be modified to improve its adherence to materials like glass and backplanes by grafting polar monomers, plasma surface treatment, or reactive graft modification. This gives POE good interface bonding capabilities.
Furthermore, polyolefin POE film exhibits a strong resistance to PID. Module power attenuation results from the potential-induced attenuation effect (PID), which is particularly prone to the backside of batteries due to the unique design of monocrystalline PERC bifacial cells and their double-sided power generation characteristics. PID attenuation is especially noticeable in double-glass modules.
4)EPE film, or multi-layer co-extruded POE film (EVA/POE/EVA structure). POE needs to be polarized because it lacks polarity and adheres to glass, backplane, and other materials quite poorly. Through the upper and lower EVA layers with stronger polarity, the EPE film strengthens the bonding strength with the base material. In addition, the middle POE layer minimizes the usage of POE in order to save costs because it has low water vapor transmission rate and anti-PID performance. Boost productivity.
High-quality film content, primarily multi-layer co-extruded POE and white improved EVA films, is steadily rising as producers of solar modules raise the bar for power production efficiency. The percentage of double-sided cells and double-glass modules is also used to increase the market share of premium adhesive films.
