Across deserts, on blue seas, and atop urban rooftops, dark blue photovoltaic (PV) modules quietly convert sunlight into clean electricity. These seemingly robust "power panels" are actually composed of delicate silicon cells, glass covers, backsheets, and interconnected circuits. Ensuring their overall sealing and protection against external erosion is critical for longevity and performance. Besides the front-side EVA or POE encapsulant films, edge encapsulation plays a crucial yet often overlooked role in safeguarding these components. In this role, silicone rubber stands out due to its exceptional weather resistance, elasticity, and reliable adhesion, making it the material of choice for high-end PV systems, especially in double-glass modules, Building-Integrated Photovoltaics (BIPV), and installations in harsh environments.

Design Lifespan and Environmental Challenges

PV modules are designed to last 25–30 years, during which they must withstand extreme climatic conditions: temperature swings exceeding 80°C in desert areas, high humidity and salt spray near coastlines, intense UV radiation at high altitudes, and snow loads in cold regions. If moisture penetrates through the edges, it can lead to a cascade of failures including corrosion of cell grid lines, yellowing and delamination of EVA, exacerbated Potential Induced Degradation (PID), and ultimately a sharp decline or complete failure in power generation efficiency. Thus, edge encapsulation is not just about physical sealing but also serves as a lifeline for electrical and chemical protection.

Advantages of Silicone Rubber in PV Edge Sealing

1. Exceptional Weather Resistance: As previously mentioned, silicone rubber naturally resists UV, ozone, and moisture-heat exposure. High-quality silicone sealants maintain over 90% of their adhesive strength after rigorous aging tests (such as IEC 61215 damp heat cycles and UV pre-treatment), without chalking or cracking. In contrast, polyurethane or acrylic sealants tend to harden and fail within a few years, failing to meet the 25-year lifespan requirement.

2. Excellent Elasticity and Movement Capability: Due to different coefficients of thermal expansion (CTE) between glass, aluminum frames, and backsheets, relative movement occurs with temperature changes. Silicone rubber's low modulus and high elongation rate (>300%) allow it to dynamically stretch and contract with joints without losing adhesion, effectively relieving interfacial stress and preventing micro-cracks in glass or frame deformation caused by "hard connections".

3. Strong Adhesion to Glass and Metals: Silicone sealants form stable Si–O–Si or Si–O–Al chemical bonds with glass and anodized aluminum via surface hydroxyl groups. Even under prolonged immersion in water or wet heat conditions, their adhesion performance degrades minimally. Some high-end products enhance adhesion to fluorocarbon backsheets or coated glass using primers.

In frameless double-glass modules, silicone rubber becomes even more essential. Without aluminum frames, edge sealant takes on all environmental protection responsibilities. Liquid silicone rubber (LSR) dispensing or extrusion processes create fully enclosed elastic seals around the perimeter, reducing weight, enhancing aesthetics, and avoiding electrochemical corrosion risks associated with metal frames—ideal for coastal or chemical industry zones.

4. Hydrophobicity and Low Water Vapor Transmission Rate (WVTR): Silicone rubber’s hydrophobic nature and low WVTR further block moisture intrusion. Its large contact angle causes rainwater to bead and roll off easily, while its dense cross-linked network restricts water molecule diffusion. Proper joint design (width ≥5mm, appropriate depth) minimizes edge moisture penetration.

Certification and Special Requirements

Photovoltaic-grade silicone rubber must pass stringent certifications such as TÜV Rheinland’s IEC 61730 fire rating, UL 1703 safety standards, and specialized tests for PID suppression, ammonia corrosion (for agrivoltaic applications), and sand abrasion. Some manufacturers have developed conductive or flame-retardant silicones for specific safety requirements.

Construction techniques also play a vital role in success. On-site application requires controlled environmental temperature and humidity, ensuring substrate cleanliness; factory pre-encapsulation relies on automated dispensing equipment to ensure uniform glue application and eliminate air bubbles. Any flaw could become a potential entry point for moisture.

Conclusion

The use of silicone rubber in PV module edge encapsulation exemplifies how material science supports the promise of "reliable energy". Though it doesn’t generate power itself, silicone rubber safeguards every kilowatt-hour of green electricity, ensuring purity and longevity. Under the dual challenges of sunlight and time, this transparent silicon-based defense line silently upholds the grand vision of global energy transition with its enduring resilience.