Electroluminescence (EL) Testing for solar modules
Perform Electroluminescence (EL) testing on solar modules at our Accredited PV Laboratory.
What is the Electroluminescence (EL) imaging test?
Electroluminescence (EL) imaging is used to test the manufactured solar modules for cell inherent defects, such as micro cracks, debris, bad soldering, and for instance to detect an inactive string inside a solar modules. EL imaging is becoming more and more important for quality testing of solar cells, as the defects can be severe but are not visible to the naked eye.
How is the Electroluminescence (EL) test performed?
An electroluminescence tester is a machine which can identify cell breakage, surface cracks and fissures that can’t be identified by visual or naked eye inspection.
Electroluminescence shares the same concept as the LED ( light emitting diode). Current flows into the solar cells which basically act as a large diode, then radiative recombination of carriers causes light emission. For the indirect bandgap semiconductor, the majority of recombination in silicon occurs due to defects or Auger recombination.
The percentage of band-to-band recombination which produces radiative emission is comparatively low. Yet, there is still a small quantity of radiative recombination that occur even in silicon and this signal can be detected using an external sensor. This technique requires electrical contact and thus can only be used after the metallization has been applied to the cell and the cell is substantially complete.
Electroluminescence provides a lot of important data about the area related uniformity of solar cells or modules. It is a non destructive technique and fairly fast with possible measurement times of 1 s.
What defects can the Electroluminescence (EL) testing detect?
With the help of the Electroluminescence (EL) test, a manufacturer can detect defects that are normally not visually detectable.
Defects that can be found with an Electroluminescence (EL) testing are:
- Broken cells and micro-cracks in the cells.
- Detection of busbar contact defects
- Detection of missing or interrupted screen-printed fingers
- Detection of non-homogeneity and foreign matter in the crystalline silicone
- Short circuit in solar cells
Electroluminescence (EL) Testing and IEC 61215
The Electroluminescence (EL) test main purpose is ensuring the quality standards of the production line and meeting customer requirements. Electroluminescence (EL) testing helps in qualification of integrity of PV modules along with the tests required by the IEC 61215 standard.
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