Strategy for simple, on-site failure analysis: investigating bubbles and burn marks in backsheets of PV modules

We present a practical, field-deployable workflow for the identification and analysis of localized polymer degradation in photovoltaic modules, observed as bubbles and burn marks in three multi-MWp power plants in Brazil and Germany. The approach combines high-throughput screening—visual inspection, infrared thermography, ultraviolet fluorescence imaging, and serial-number mapping—with selective in-depth analyses of representative modules using electroluminescence, current–voltage measurements, and near-infrared absorption spectroscopy. The workflow enables efficient detection of anomalies across large installations, while confirmatory tests validate root causes on a limited subset. Defects occurred in about 3–4% of inspected modules and were concentrated in the upper and lower cell rows. Although all sites experienced similar partial shading, anomalies appeared only in PET-based backsheets with PVDF or PVF outer layers, highlighting material-dependent susceptibility. No immediate electrical or safety impact was found, but continued monitoring is advised to mitigate future reliability risks. The presented methodology offers a scalable, drone-compatible framework for early-stage field detection of polymer degradation.