UVF is used on solar modules because it can reveal degradation and material failures that are not always visible through electrical testing or infrared scans. It is especially helpful for identifying encapsulant discoloration, moisture intrusion patterns, backsheet and seal integrity issues, delamination, and aging effects that can reduce long term module reliability. UVF can also highlight early stage changes that may precede hotspots or electrical failure, making it valuable for preventive maintenance and warranty evaluation.