You’ve invested in high-performance bifacial or glass-glass solar modules, which promise decades of clean energy production, superior durability, and a lower levelized cost of energy. But a subtle threat lurks at the very edge of these advanced modules—one that can quietly undermine their long-term performance and reliability: edge delamination.
Though it often starts as a microscopic failure, invisible to the naked eye, this separation of layers can eventually lead to moisture ingress, corrosion, and significant power loss, turning a state-of-the-art asset into a potential liability.
Understanding and preventing this issue isn’t just good practice—it’s essential for anyone involved in developing, manufacturing, or investing in next-generation solar technology.
What is Edge Delamination and Why Does It Matter?
Think of a modern solar module as a high-tech sandwich: glass on the outside, delicate solar cells in the middle, and a polymer encapsulant that acts as the „glue“ holding it all together. Delamination occurs when that glue fails and the layers start to come apart.
This problem is particularly critical at the module’s most vulnerable point: the edge, where it’s exposed to the elements.
For glass-glass and bifacial modules, this vulnerability is amplified. Unlike traditional modules with a robust aluminum frame and polymer backsheet to provide a seal, these newer designs often rely entirely on the integrity of the encapsulant’s bond right to the edge of the glass.
When this bond weakens, it creates a pathway for failure:
- Moisture Ingress: Water vapor from the air can seep into the module, corroding cell interconnects and reducing electrical output.
- Accelerated Aging: The presence of moisture dramatically speeds up the degradation of module components.
- Safety Risks: Severe delamination can compromise the module’s electrical insulation, creating potential safety hazards.
- Financial Impact: These issues can lead to underperformance, voided warranties, and costly field replacements.
The Main Culprit: When Moisture Attacks Your Module’s Edge
The primary cause of edge delamination is a loss of adhesion between the glass and the encapsulant. This chemical breakdown, known as hydrolysis, is triggered and accelerated by moisture.
Different encapsulants react to moisture differently:
- EVA (Ethylene Vinyl Acetate): For years, EVA has been the industry’s cost-effective and well-understood standard. It is, however, susceptible to hydrolysis. Over time, moisture and heat can cause it to break down and produce acetic acid, which further weakens the bond to the glass and can corrode cell parts.
- POE (Polyolefin Elastomer): POE is known for its excellent resistance to moisture. It doesn’t break down via hydrolysis in the same way EVA does, making it a promising choice for durable modules like bifacial and glass-glass designs. Yet POE can be more challenging to work with. It often has lower initial adhesion to glass and requires a more finely tuned lamination process to achieve a strong, lasting bond.
„Choosing the right encapsulant is only half the battle,“ notes Patrick Thoma, PV Process Specialist at PVTestLab. „We’ve seen high-quality POE fail simply because the lamination parameters weren’t optimized for that specific material and glass combination. The entire system has to work together.“
How to Predict and Prevent Catastrophic Failure
You can’t wait 25 years in the field to see if a module design is robust. To ensure long-term reliability, you have to accurately simulate decades of environmental stress in a matter of weeks. That’s where a systematic, two-step validation process comes in.
Step 1: Simulating a Lifetime of Stress with Damp Heat Testing
The Damp Heat (DH) test is the industry-standard method for accelerating the aging process caused by humidity and high temperatures. In this test, a module or material sample is placed in a climate chamber and subjected to harsh conditions—typically 85°C and 85% relative humidity—for 1,000 to 2,000 hours.
This test aggressively challenges the adhesive bonds within the module, revealing weaknesses that would otherwise take years to appear in the field. It’s the ultimate stress test for evaluating how well a chosen encapsulant will resist moisture-driven degradation. But passing a visual inspection after DH isn’t enough—you need to quantify the bond strength.
Step 2: Measuring What Matters with the Mechanical Peel Test
After the sample has been aged in the damp heat chamber, the true test of adhesion begins. The mechanical peel test is a precise, objective method for measuring the force required to separate the encapsulant from the glass.
In a typical 90-degree peel test, a strip of the encapsulant/glass laminate is clamped while a machine pulls the encapsulant layer away from the glass at a constant speed and angle. The force required for this separation is measured in Newtons per centimeter (N/cm).
A high peel strength value after Damp Heat testing is the gold standard. It provides concrete, quantitative data proving that the bond is strong enough to withstand long-term environmental stress. This test is fundamental to successful solar module prototyping, as it validates material choices before committing to mass production.
It’s Not the Materials, It’s the Recipe
A common mistake is assuming that using premium materials like POE encapsulants automatically guarantees a reliable module. The process is just as important as the components.
Think of it like baking a cake. You can have the best flour, sugar, and eggs, but if your oven temperature is wrong or you don’t mix the ingredients correctly, the result will be a disaster.
The same is true for solar modules. The lamination cycle—the specific profile of temperature, pressure, and time used to cure the encapsulant and bond the layers—is critical. A suboptimal process can lead to weak adhesion, even with the best materials on the market.
This is why true reliability comes from holistic process optimization. It means testing the complete system: the specific glass, the chosen encapsulant, and the precise lamination parameters, then validating the result with DH aging and peel tests.
Frequently Asked Questions (FAQ) about Edge Delamination
Is edge delamination visible to the naked eye?
In its early stages, no. It often begins as a micro-separation at the molecular level. By the time it becomes visible as bubbles or separated layers at the edge, significant and potentially irreversible damage may have already occurred inside the module.
Can you fix a module that has started to delaminate?
Unfortunately, field repairs for delamination are generally not feasible or lasting. The process requires re-establishing a perfect, void-free bond under vacuum and heat—conditions that can’t be replicated outside a production environment. Prevention is the only reliable strategy.
Does the type of glass surface or coating affect delamination risk?
Absolutely. Different glass coatings (like anti-reflective coatings) or surface treatments can have a major impact on how well an encapsulant adheres. This is another reason it’s crucial to test the exact combination of materials you plan to use in production.
How long does this type of validation testing take?
A full Damp Heat test can take 1,000 hours (about 6 weeks) or more, depending on the standard being followed. While this sounds like a long time, it’s a small investment compared to preventing massive warranty claims and reputational damage down the line.
From Lab Insights to Long-Term Reliability
Preventing edge delamination isn’t about finding a single „magic bullet“ material; it’s about adopting a rigorous, scientific approach to validation. By combining accelerated aging tests with quantitative mechanical measurements, module developers and material manufacturers can move beyond assumptions and make data-driven decisions.
Understanding the intricate dance between your materials and your process parameters is the key to building solar modules that not only perform well on day one but continue to deliver clean, reliable energy for decades to come.
If you’re developing a new module design or evaluating new materials, protecting the long-term integrity of your product is paramount. For questions about setting up a reliable testing protocol, book a consultation with our process engineering team to discuss your specific challenges.