You’ve specified bifacial modules for your project, counting on higher energy yields and a lower LCOE. The datasheets look promising, and the IEC certifications are in order. But a troubling reality is emerging from the field: standard tests are no longer a reliable predictor of long-term performance.
Recent industry benchmarks are sounding the alarm. In PVEL’s 2025 stress tests, a staggering 66% of PV module manufacturers experienced at least one failure—the highest rate ever recorded. This isn’t about minor deviations; it’s about systemic risks in new module designs that outdated standards simply weren’t built to catch.
For asset owners and investors, this creates a critical evaluation challenge: how do you validate the 25-year bankability of a technology when its unique failure modes are invisible to conventional testing?
This reality demands a shift from certification to applied reliability testing. It means moving beyond pass/fail checks to understand the interconnected physics of how modern bifacial modules degrade. At PVTestLab, we’ve developed a comprehensive diagnostic protocol that simulates these real-world failure pathways, providing the data you need to de-risk your investment with confidence.
Mechanical Failure: The Glass Fracture Epidemic in Dual-Glass Designs
The move to larger formats and thinner, heat-strengthened glass has created a perfect storm for mechanical failure. While dual-glass designs have their advantages, they also introduce critical new vulnerabilities. Field reports confirm this, with one DNV study documenting a rear glass breakage rate of over 15% at a single tracker-mounted project. These are not isolated incidents but evidence of a systemic industry problem.
The Mechanism: Low-Energy Cracks and Frame-Induced Stress
Unlike the flexible backsheet on a monofacial module, the rear glass on a bifacial module is rigid. This rigidity means that subtle, low-energy impacts during transport or installation—or even dynamic wind and snow loads that cause frame torsion—can initiate microcracks.
These cracks may not be visible initially but can propagate over time, leading to catastrophic failure and safety hazards. Standard static load tests (like IEC 61215) often miss this vulnerability because they don’t replicate the dynamic, cyclical, and torsional stresses experienced in the field.
PVTestLab’s Applied Testing Approach: Predictive Failure Analysis
We go beyond standard static tests to understand a module’s true mechanical resilience. Our protocol combines dynamic mechanical load (DML) testing with climatic chamber cycles to simulate years of environmental stress in a matter of weeks.
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Test-to-Failure Protocol: We don’t just test to a prescribed limit; we apply increasing cyclical loads until failure, identifying the precise weak points in the module’s design—whether in the glass, frame, or cell interconnections.
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High-Resolution EL Imaging: After each load cycle, we use electroluminescence (EL) imaging to detect the formation and propagation of microcracks at the cellular level, long before they become visible or cause power loss.
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Weibull Analysis: This statistical method uses test-to-failure data to predict the probability of breakage over the module’s lifetime under specific field conditions.
This approach provides a clear, data-driven assessment of a module’s mechanical bankability, enabling you to compare different bills of materials and avoid designs prone to premature field failure. By understanding these limits, you can refine your own Prototyping & Module Development cycle.
Electrochemical Degradation: Rear-Side PID in New Cell Architectures
While Potential-Induced Degradation (PID) is a well-known issue, the threat has evolved in bifacial modules, especially those using advanced TOPCon and HJT cells. The rear side, now an active power-generating surface, introduces a new pathway for leakage currents and electrochemical corrosion that standard PID tests often overlook.
The Mechanism: PID-p vs. PID-c on the Rear Side
Traditional PID testing focuses on PID-s (shunting) in p-type PERC cells. Bifacial modules introduce two new dominant forms:
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PID-p (Polarization): Occurs when sodium ions from the glass migrate into the cell’s passivation layers, neutralizing the surface charge and crippling efficiency. This is a major risk for n-type TOPCon and HJT cells.
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PID-c (Corrosion): Moisture ingress, combined with system voltage bias, can lead to the electrochemical corrosion of the Transparent Conductive Oxide (TCO) layers essential for HJT cell performance.
The choice of encapsulant and the quality of the edge seal are paramount in preventing these failure modes, yet their long-term performance can only be validated through multi-stressor testing.
PVTestLab’s Applied Testing Approach: Simulating Real-World Bias
Our climate-controlled production line allows us to conduct Material Testing & Lamination Trials that replicate the exact conditions leading to bifacial PID. We don’t just test a coupon; we build full-sized modules with your proposed bill of materials and subject them to tailored stress sequences in our advanced environmental chambers.
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Multi-Stressor Environment: We combine damp heat (85°C / 85% RH) with a high system voltage bias (-1500V) to accelerate both polarization and corrosion mechanisms.
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Targeted Diagnostics: We use high-resolution EL and quantum efficiency (QE) measurements to differentiate between PID-p and PID-c, providing precise feedback on whether the failure is due to the encapsulant, the cell, or the lamination process.
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Encapsulant Validation: By testing various EVA and POE formulations under these conditions, we provide definitive data on which materials offer the highest long-term PID resistance for your specific cell technology.
Emergent Defects: The Hidden Threat of UV-Induced Degradation (UVID)
As module technology advances, new and unexpected degradation modes are appearing in the field. One of the most concerning is UV-Induced Degradation (UVID), a phenomenon particularly relevant to bifacial modules because of rear-side UV exposure from albedo.
The Mechanism: Encapsulant and Backsheet Interaction
A recent field study in ScienceDirect analyzing bifacial modules in Northern Europe found a mean degradation rate of 0.63% per year, significantly higher than the 0.5%/a benchmark. The study identified UVID as a primary culprit, which appears as „dark imprints on EL images.“
This degradation is attributed to a photochemical reaction between certain encapsulant formulations and other materials in the module laminate when exposed to UV light, leading to the formation of power-degrading chromophores. As a recently identified mechanism, it is not covered by any standard certification test.
PVTestLab’s Applied Testing Approach: Advanced Spectroscopic Characterization
Detecting emergent defects like UVID requires looking beyond standard flash tests and EL imaging. Our R&D facility is equipped with a suite of advanced characterization tools to identify these latent threats before they impact your assets.
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UV Fluorescence (UVF) Imaging: This technique is highly effective at detecting chemical changes in encapsulants and other polymer materials. UVID-affected areas show a distinct fluorescence signature, allowing us to map the degradation precisely.
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Accelerated UV Stress Testing: We use specialized UV chambers to deliver a high dose of UV radiation, simulating decades of field exposure in a controlled environment to assess the stability of different encapsulant and backsheet combinations.
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Process Parameter Optimization: By identifying the root cause, we can work with you to optimize your lamination process or select more UV-stable materials, ensuring your modules are robust against this emerging threat. Our Process Optimization & Training services can then help transfer this knowledge to your production line.
Image description: A high-resolution electroluminescence (EL) image of a solar cell, with distinct dark, grid-like patterns clearly showing the imprints characteristic of UV-induced degradation (UVID).
Frequently Asked Questions (FAQ)
Isn’t my supplier’s IEC certification enough to guarantee reliability?
IEC 61215 is a crucial baseline for safety and design qualification, but it is not a reliability or bankability test. It was designed years ago for older technologies and doesn’t adequately stress the unique failure modes of modern bifacial modules, such as dynamic mechanical loads, rear-side PID in n-type cells, or UVID. Our protocol is specifically designed to find the failures that IEC certification misses.
How does the PVTestLab protocol differ from other third-party testing?
Many labs focus on one piece of the puzzle, like PID or mechanical loads. Our strength lies in our holistic, interconnected approach. We understand that these failure modes don’t happen in isolation. Mechanical stress can create pathways for moisture ingress, which accelerates PID. UV degradation of polymers can compromise mechanical integrity. Our protocol is a comprehensive audit that tests for this trifecta of risks—mechanical, electrochemical, and emergent—using real industrial equipment under one roof.
What is the ROI of conducting this level of advanced testing?
The cost of advanced reliability testing is a fraction of the potential loss from widespread field failures. A single project experiencing a 15% glass breakage rate or an additional 0.2% of annual degradation can result in millions in lost revenue and warranty claims. Our testing provides the data to mitigate that risk by helping you select more robust bills of materials, reject problematic batches, and enforce stronger quality controls in your supply chain. It’s an investment in certainty.
Secure the Bankability of Your Bifacial Assets
Relying on datasheets and outdated certifications for next-generation bifacial technology is no longer a viable risk management strategy. The evidence from the field is clear: new designs are susceptible to a new class of interconnected failure modes that require a more sophisticated, applied approach to testing.
PVTestLab provides the bridge between laboratory research and industrial reality. Our full-scale R&D production line—operated by experienced German process engineers—offers unparalleled insight into the long-term reliability of your modules. We empower you to move beyond speculation and make procurement decisions based on objective, scientific data.
Don’t wait for field failures to reveal the weaknesses in your assets. Contact our process specialists today to design a custom reliability audit that validates the true performance of your bifacial modules.