Probably the more detailed piece on QA of Solar Cells read thus far.
https://www.pv-tech.cn/news/Electroluminescence_detection?
https://en.wikipedia.org/wiki/Electroluminescence
Excerb (Google translated)
In fact, electroluminescence analysis will qualitatively, quickly and directly reveal healthy or defective areas in the inspected sample, and present different series and parallel resistances. Adjusting the current injection level will show different resistance states, so it helps to understand what is happening in the battery or component under test. Therefore, any low-EL image contrast feature will usually be inferred that there are hidden defects in its structure
The interpretation of EL images has always been biased or subjective, which stems from the industry's lack of consensus on the definition of EL defects. In addition, the many unknown physical and chemical mechanisms behind the defects found on damaged solar cells and the subsequent short- to long-term effects make the consequences of EL analysis more complicated. In this regard, the TC82 working group of the International Electrotechnical Commission (IEC), which specializes in solar energy systems and equipment, recently released the IEC TS 60904-13:2018 document [8], which aims to establish a series of methods for collecting, processing and interpreting EL images. The operating method serves as a preliminary guide for the final standards applicable to the photovoltaic industry.
In any case, even if the mainstream market may no longer adopt these standard guidelines, EL inspection may eventually become a universal, non-conflict and unbiased defect detection and classification method, which is used in EL inspection to combine images with photovoltaic module performance This is especially important in the context of association, although some interesting attempts have been made so far [8]. In some cases, extrapolating EL-based results to financial or legal consequences does cause EL inspection to be supplemented by other well-known component specific methods, such as IV curve measurement or infrared thermal imaging, which can be completely solved. The mechanism behind the defect then draws more accurate and fair conclusions, especially when it involves penalties or warranty claims.
Taking into account those defects that can only be found through EL inspection that are not detectable by the naked eye, there are big differences in the definition and judgment of defects among Tier 1 component manufacturers. Due to the rapid development and release of new photovoltaic cell and module designs, this trend is currently very obvious. All in all, the release of these new products has taken us a few steps forward, and the corresponding EL quality standards need to be updated.
Through online testing, it can be seen that there are huge differences in EL test equipment between different suppliers (even different production lines of the same supplier).
This inconsistency is patent-protected in terms of the classification of defect severity (minor, major, critical) and its individual description, so that most vendors have been using almost the same EL standard for many years, regardless of the introduction of new ones
https://www.enertis.com
https://www.enertis.com/clients/
https://www.enertis.com/testing-quality-control-inspection-solar-pv/
Module Quality Assurance and Onsite Testing.
Also ACU.V site finally reflect their whole suite of products.
https://aurorasolartech.com/product/insight/
https://aurorasolartech.com/product/aurora-visualize/
https://aurorasolartech.com/product/aurora-dm-321/
Videos are also neat.
https://aurorasolartech.com/videos/