Electroluminescence imaging – EL photos, is the technology that allows to penetrate inside the PV modules and detect any invisible defects. Such defects cannot be detected with bare eyes or by any other means such us thermography or I-V characteristics. Electroluminescence is such an X-ray photo, and shows the inside defects of the PV modules (solar cells), such as cracks, micro-cracks, disoldering problems, etching and dead cells. More