What Is UV Fluorescence Testing?
UV fluorescence testing (also known as UV-FLU test) is an optical method for analyzing the aging of PV modules.
It exploits the phenomenon that certain plastics – particularly the EVA encapsulation film – visibly fluoresce when exposed to UV light, meaning they "glow" at a different wavelength.
Depending on the condition of the film, a characteristic pattern emerges that allows conclusions about the age, stress, and degradation processes within the module – without opening or damaging the module.
What Exactly Does UV Fluorescence Reveal?
The fluorescent image reveals:
- Browning/discoloration of the EVA film
- Delaminations or air inclusions
- Mechanical stress at cell edges
- Inactive or damaged cell areas
- Indicators of PID (Potential Induced Degradation)
The images can be visually evaluated or analyzed using image recognition and AI – at 2nd Cycle, this is done automatically and data-driven.
How Does the UV Fluorescence Test Work at 2nd Cycle?
- UV irradiation: The module is exposed to defined UV light (wavelength ~365 nm)
- Fluorescence capture: A specialized camera records the fluorescence pattern of the encapsulation material
- AI-based analysis: The image is automatically analyzed – degradation patterns, anomalies, and defects are identified and classified
- Grading: The UV-FLU result feeds into the overall assessment and helps to differentiate between reuse-worthy and non-reuse-worthy modules
Why Is the UV Fluorescence Test So Valuable?
Unlike other methods, UV fluorescence provides a direct look at the material level of the module – particularly at the encapsulation film, which significantly affects the longevity and safety of a PV module.
The test is especially suitable for:
- Detecting age-related material changes
- Identifying delaminations before they become visible
- Evaluating the remaining useful life of the module
UV fluorescence makes what is otherwise invisible visible – without contact, without destruction.
UV Fluorescence as Part of Our Testing Line
At 2nd Cycle, UV fluorescence testing is integrated into the fully automated testing line:
Visual inspection → Flash test → UV fluorescence → Electroluminescence → Wet leakage test
It complements the other methods and provides additional information about the material condition of the module that neither the flash test nor the EL test can deliver.
Conclusion
The UV fluorescence test is a non-destructive, highly informative method for assessing the aging condition of PV modules. It makes degradation processes visible that would otherwise remain hidden – and is therefore an essential component of any professional reuse assessment.
At 2nd Cycle, we use this technology as standard – because material quality determines module lifespan.