Have you ever wondered what happens when a solar module is pushed to its limits?

While we often focus on efficiency and power output, a module’s true value lies in its ability to withstand the physical stresses of a 25-year lifespan—from transportation and installation to decades of wind and snow.

The truth is, significant damage can occur that is completely invisible to the naked eye. This hidden damage, in the form of microscopic cracks in the solar cells, silently compromises performance and reliability. In this article, we’ll shine a light on this invisible threat, exploring how a module’s fundamental structure—a rigid glass backing versus a flexible polymer backsheet—can mean the difference between long-term durability and gradual decline.

The Core Dilemma: Structural Strength vs. Handling Flexibility

At its heart, a solar module is a protective sandwich designed to shield fragile silicon cells from the elements. Today’s two most common designs approach this challenge from different angles.

1. The Glass-Glass (G2G) Module: This design, often seen in bifacial and premium modules, encases the solar cells between two layers of glass. It’s built like a fortress—rigid, durable, and incredibly stable.

2. The Transparent Backsheet Module: This more traditional and lightweight design uses a single layer of glass on the front and a flexible, transparent polymer backsheet on the rear. This makes the module lighter and easier to handle but introduces a trade-off in structural rigidity.

Here’s a look at how they stack up structurally:

We captured an EL image of each module before the test to confirm they were free of defects. Then, after applying the 6000 Pa load, we took another set of EL images. The results were startling.

The Revealing Results: An EL Image Tell-All

The EL images taken after the load test tell a clear and compelling story.

The glass-glass module on the left looks nearly identical to its pre-test image. Its rigid, dual-glass structure distributed the stress evenly and effectively shielded the cells from harm. Virtually no new microcracks formed.

The module with the transparent backsheet on the right tells a different story. The image is covered in a web of new lines and dark spots, each one representing a microcrack or a damaged cell area. The module’s flexibility allowed the mechanical load to be transferred directly to the fragile cells, causing widespread, permanent damage.

„Rigidity isn’t just a structural feature; it’s a performance guarantee. Our tests consistently show that the sandwich-like structure of a Glass-Glass module acts as a protective shield for the cells, directly translating to lower degradation rates and higher lifetime energy yield.“

• Patrick Thoma, PV Process Specialist

The Trade-Off Explained: What Does This Mean for You?

This experiment highlights a critical trade-off in module design. While a transparent backsheet offers advantages in weight and handling, its flexibility creates a significant risk of cell damage during transport, installation, and throughout its operational life.

For anyone developing new solar module concepts, this is a crucial consideration. A G2G structure’s inherent cell protection can provide a more reliable path to long-term bankability and performance. The decision isn’t just about initial cost or weight; it’s about the lifetime value and durability of the final product.

This is why objective material testing is so vital. Understanding how different backsheets, encapsulants, and glass types behave under real-world industrial conditions allows developers to make informed decisions before committing to mass production.

Frequently Asked Questions (FAQ)

What are microcracks in solar cells?

Microcracks are tiny, often microscopic, fractures that form in the silicon wafer of a solar cell due to mechanical or thermal stress. They disrupt the flow of electricity and reduce the cell’s ability to produce power.

Can you see microcracks without EL testing?

No. The vast majority of microcracks are completely invisible to the naked eye. Electroluminescence imaging is the industry-standard method for reliably detecting and diagnosing them.

Does this mean all modules with backsheets are bad?

Not at all. High-quality backsheets and careful manufacturing can produce reliable modules. However, this test demonstrates that a flexible backsheet structure is inherently more susceptible to mechanical stress-induced microcracking than a rigid G2G structure. The choice depends on the application, climate conditions, and long-term performance goals.

Are Glass-Glass modules always the better choice?

For applications where long-term durability, minimal degradation, and resistance to harsh weather (like heavy snow or high winds) are paramount, G2G modules offer a clear advantage in cell protection. However, their heavier weight can be a factor in certain rooftop installations. It’s a trade-off between robustness and installation logistics.

How much power is lost due to microcracks?

The power loss can range from negligible to severe, depending on the number, location, and orientation of the cracks. A few small, isolated cracks might have a minimal impact initially, but a dense network of cracks, like that seen in our test, can lead to an immediate power loss of 5-10% or more and significantly accelerated degradation over time.

From Insight to Innovation: What’s Next?

Choosing the right module structure is more than an engineering decision—it’s an investment in 25 years of reliable energy production. As this comparison shows, the foundational design of a module has a direct and measurable impact on the health of its solar cells.

Understanding these hidden dynamics is the first step toward building better, more durable solar technology. The next step is to put your own materials, designs, and concepts to the test in a real-world industrial environment. Only by connecting theory with real-world results can we accelerate innovation and build the next generation of solar modules.