Electroluminescence (EL) is an imaging diagnostic method in which solar modules are forward-biased with current, causing them to emit infrared radiation (approx. 1,150 nm). Defective cell areas appear dark because they conduct little or no current.
EL images reveal: cell fractures (micro-cracks to macro-cracks), PID-affected cells, inactive cell areas, solder joint defects, finger interruptions, and degradation patterns. The method is standardized per IEC 60904-13.
EL is the standard method for defect assessments, warranty disputes, and damage evaluations. In combination with IV curve measurements and thermography, it provides a complete defect profile at the cell level.
Yes, outdoor EL is possible in darkness. PV-BESS-Assessor performs field EL measurements using specialized InGaAs cameras. For large systems, the combination of drone thermography (daytime) and sample-based EL (nighttime) is the most efficient method.
Electroluminescence: 847 Hidden Cell Cracks After Hailstorm
Real anonymized investigation case with measurement data, timeline, and economic evaluation.