Electroluminescence-Testing Induced Crack Closure in PV Modules

Electroluminescence (EL) measurements of PV modules with cracked cells have showed some open cracks to close arbitrarily from day to day even though these modules are stored in a controlled, stressor free laboratory environment – constant temperature and no mechanical load. We have found that variations in current and temperature generated from resistive heating during EL measurements strongly influence crack closure. Because crack closure can lead to some gain in maximum power, we consider the ramifications for IEC standards, namely that performing EL measurements before I-V measurements may lead to inflated results.