What is eva used for in photovoltaics?

In the manufacturing process of photovoltaic modules, EVA (ethylene vinyl acetate copolymer) is an indispensable key material. Its main functions include encapsulating, bonding and protecting solar cells to ensure that photovoltaic modules remain efficient, stable and durable during long-term outdoor use. The following will provide a detailed analysis of EVA’s characteristics, functions, application scenarios and industry development trends.

### 1. Characteristics of EVA and basics of photovoltaic applications
EVA is a transparent or translucent thermoplastic material made from the copolymer of ethylene and vinyl acetate. In the photovoltaic field, EVA with a vinyl acetate content of 28%-33% is usually used because it has the following characteristics:
1. **High transmittance**: The transmittance of EVA can reach more than 90%, which can minimize the blocking of sunlight and ensure the photoelectric conversion efficiency of the cells.
2. **Excellent adhesion**: During the heating lamination process, EVA can form strong chemical bonds with the glass, backsheet (such as TPT, PET) and the surface of the battery sheet to avoid interlayer peeling.
3. **Weather resistance and anti-aging**: By adding additives such as anti-UV agents and antioxidants, EVA can resist environmental erosion such as ultraviolet rays, high temperatures, moisture, etc., extending the life of components to more than 25 years.
4. **Elasticity and buffering effect**: Its flexibility can alleviate the expansion of micro-cracks in battery cells under thermal expansion, contraction or mechanical stress, and reduce the risk of hidden cracks.

### 2. The core functions of EVA in photovoltaic modules
1. **Encapsulation protection**
EVA, as an encapsulating film, covers the upper and lower sides of the battery cell. It is melted and solidified through a lamination process (temperature is about 140-150°C) to form a dense protective layer. This process can isolate oxygen, water vapor and other external pollutants, and prevent battery cell corrosion or PID (potential induced decay). For example, in areas with high humidity and high salt spray such as deserts or coastal areas, the barrier properties of EVA directly determine the reliability of components.

2. **Optical enhancement**
Some high-end EVAs use surface modification technology (such as adding light scattering particles) to improve light capture capabilities and refract more light to the battery surface, thereby increasing component power output. According to industry tests, optimized EVA can increase module efficiency by 0.5%-1%.

3. **Electrical insulation**
The dielectric strength of EVA exceeds 20kV/mm, which can effectively isolate the direct contact between battery cells and metal wires to avoid leakage or short circuit accidents.

### 3. EVA’s technological evolution and industry challenges
1. **Material upgrade**
Traditional EVA has the problem of yellowing caused by the hydrolysis of vinyl acetate. The new formula significantly improves the anti-aging performance by introducing cross-linking agents (such as peroxide) and stabilizers. For example, the "anti-PID EVA" developed by some manufacturers can control the component power attenuation rate below 1% per year.

2. Competition and complementarity between ** and POE**
In recent years, polyolefin elastomers (POE) have attracted attention due to their lower water vapor transmission rate, but their costs are high and processing is difficult. The industry mostly adopts the "EVA+POE" double-layer structure solution, taking into account cost-effectiveness and performance. According to the "Photovoltaic Industry White Paper" data, EVA will still account for more than 70% of the global packaging materials market share in 2024.

3. **Recycling problems**
The EVA layer of retired components is difficult to peel off, and thermal decomposition will produce harmful gases. At present, scientific research institutions are exploring biodegradable EVA or low-temperature degumming technology to meet the requirements of green circular economy.

### 4. Industrial chain and market dynamics
China is the world's largest producer of photovoltaic EVA, with major suppliers including Swick, Foster and other companies. With the popularity of N-type batteries (such as TOPCon, HJT), the requirements for high temperature resistance and low acidity of EVA have further increased. In early 2025, some manufacturers have launched special EVA adhesive films suitable for N-type batteries, which have a wider melting temperature range and shorten lamination time by 10%-15%.

### 5. Future Outlook
Driven by the "double carbon" goal, photovoltaic installed capacity continues to grow, and global EVA demand is expected to exceed 2 million tons in 2025. Technological innovation will focus on:
- **Multifunctional integration**: such as self-healing EVA, which can automatically repair micro-cracks in battery cells；
- **Intelligent packaging**: EVA film embedded with sensors monitors component health in real time；
- **Low-carbon process**: Reduce production energy consumption and reduce carbon emissions throughout the life cycle.

In short, as the "invisible guardian" of photovoltaic modules, EVA's performance optimization and technological innovation will continue to promote the industry's cost reduction and efficiency improvement, providing key support for the development of renewable energy.