A supplier sends an EL image marked “PASS,” but the file does not identify the panel in your purchase order. Before using it to approve a sample or shipment, ask for the connection between the image, the actual module and the decision recorded in the report.
EL testing solar panels can provide useful evidence about features within a module. For a buyer, that evidence becomes usable when its identity, test stage and conditions are recorded, and the findings can be checked alongside the applicable electrical results.
This checklist focuses on that document review for custom crystalline-silicon panels. It separates a missing record, a finding that needs clarification and a decision under agreed acceptance criteria. It does not provide a visual crack grading scale or instructions for operating an EL tester.
Quick Answer: A solar panel EL report should identify the module, test stage, image conditions and findings behind its pass or fail statement. Match it to the relevant electrical record and agreed acceptance scope. Request missing evidence before making a decision; a dark line or a bright image alone does not establish the panel's power or cause of damage.
What an EL image can tell a panel buyer
An EL image provides information about a panel under the recorded test conditions, while an electrical test measures its electrical performance. Keep those questions separate when reviewing a supplier's report.
Electroluminescence imaging involves a module under forward bias. The free official summary of IEC TS 60904-13 covers image acquisition, processing and qualitative interpretation for modules in that condition.
A buyer does not need to infer every feature from a black-and-white screenshot. Ask the testing party to explain the locations it has marked, the interpretation it gives them and any additional checks required for the panel being supplied.
- Observation: what appears in the image and where it is located.
- Interpretation: what the testing party considers that feature to indicate.
- Decision: how the finding relates to the agreed acceptance requirement.
These entries should be distinguishable in the report. Calling every dark line a crack collapses an observation into a diagnosis; assigning a fixed power loss to its appearance adds a measurement the image has not supplied.
Likewise, an image without an obvious marked feature cannot establish lifetime performance. Image quality and test conditions affect what can be observed, and the report should state what was actually assessed.
Read the conclusion against the supplied evidence. If the report states only “PASS,” request the basis for that statement before treating it as acceptance of the ordered module.
Match the image to the panel in your order
The EL image must be traceable to the panel, sample or stated test population covered by your order. A supplier logo identifies a document's presentation, rather than the physical item that was imaged.
Start with the module model, product revision and the order or sample reference. Then look for the individual identifier used by the testing party and confirm that the image file carries the same reference.
A small custom panel may not yet have a production serial number. In that situation, agree another identifier that uniquely matches the sample to its drawing and records, instead of insisting on a serial-number format that the project has not adopted.
- Item: the module or sample represented by the image.
- Version: the product or drawing revision used for that item.
- Record: the filename or report entry connected to the identifier.
For custom mini solar panels, distinguish an image of a development sample from evidence for a later supplied variant. A change in construction or revision needs an explicit explanation of which records still apply.
If the supplier submits several images, ask for an index rather than guessing the sequence from filenames. The index should show which item each image represents and where the associated findings are recorded.
Keep an unmatched image pending. It may become useful after the identity is established, but it cannot yet support a decision about a different sample or the current batch.
Ask when and under what conditions the image was taken
An EL report needs the test stage and conditions to make its image interpretable and any comparison meaningful. Ask the testing party to record its actual method rather than filling in a universal current or camera setting.
Stage means the point at which the item was examined: before lamination, after lamination, after assembly, before shipment or after receipt. A record from one stage should retain that label when it is passed to the buyer.
The IEA PVPS imaging review published in 2018 discusses how imaging settings and applied current affect observable features. Its relevant discussion supports asking for conditions; it does not supply a universal test recipe for every custom panel.
Request the electrical excitation information, temperature information and image acquisition settings recorded for the test. If the testing party considers a field irrelevant to its method, ask it to explain that judgment and identify the method used.
Also request the file's processing history. Cropping, contrast adjustment or another presentation change should be distinguishable from the original acquisition, particularly when two images will be compared.
Retain a complete module view and any referenced detail views at a usable resolution. A chat thumbnail may locate a concern, but it can leave too little information for the testing party to explain it.
The record card illustrates the information to connect. It supplies no electrical settings and makes no claim about a panel's result.
Review the findings with the electrical record
An EL finding should be reviewed with the electrical record that applies to the same module or explicitly identified sample group. Image brightness cannot replace a measured power result.
Ask the supplier to connect the marked location, its explanation and the applicable flash or I-V test entry. Confirm the item's identifier and revision across those records before discussing whether the results support the proposed acceptance.
The records address different aspects of the panel. EL can provide clues about features within the module, while the electrical record documents measured behavior under its stated conditions; neither should be presented as a substitute for the other.
A report package should explain its test conditions and the correspondence between the files. For the underlying electrical concepts, the guide to solar-cell I-V curves covers the curve rather than EL image interpretation.
- Match: identify the physical item behind both records.
- Explain: relate the reported image finding to the electrical result.
- Resolve: identify any follow-up test or explanation needed for acceptance.
A single open-circuit voltage reading does not answer every question raised by an image. If the records appear inconsistent, ask a qualified testing party to investigate against the module's specification, rather than using one number to dismiss the concern.
Record the outcome of that review beside the original finding. Keep the evidence and the interpretation visible so an unresolved question does not disappear behind a replacement “PASS” label.
Use before-and-after records without jumping to blame
A before-and-after EL comparison requires the same module, identified stages and conditions that are comparable or have an explained difference. An image change can prompt investigation without establishing who caused it.
The cell-crack entry in the 2025 IEA PVPS failure fact sheets notes that cracks can occur at different stages and do not automatically mean module failure. A receipt image alone therefore cannot establish a production or transport cause.
Request the available earlier records for the same item and preserve their dates and stage descriptions. If an earlier record is unavailable, identify that gap rather than reconstructing a history from a photograph of another module.
Before interpreting a change, ask the testing party whether the acquisition conditions and processing allow comparison. A contrast difference, unmatched identifier or different test setup can make a visual comparison inconclusive.
Then connect the images with the handling and handover records that actually exist. Packaging information, receipt observations and the timing of the tests may inform a review, but the article establishes no liability rule.
The evidence-chain diagram shows records to connect when available. It does not imply that every stage was tested or that LinkSolar holds those images for every order.
Have the responsible parties document what the comparison supports, what remains uncertain and what further evidence is needed. Keep a technical finding separate from any later commercial decision under the order's agreed terms.
A report checklist for sample approval and shipment review
An EL report checklist should expose missing evidence, actual test coverage and the acceptance basis used for the supplied panels. Use the table as a purchasing worksheet, not as a substitute for an agreed test method.
| Check | Record to request | If unresolved |
|---|---|---|
| Identity | Item, order and product revision | Match the image to the item |
| Stage | Date and process or handover point | Clarify the represented condition |
| Conditions | Recorded excitation and acquisition method | Ask the testing party to explain |
| Image files | Complete view, details and processing | Request usable source files |
| Findings | Location and testing-party interpretation | Obtain the necessary follow-up |
| Electrical record | Matched results and test conditions | Resolve any inconsistency |
| Coverage | Items and stages actually tested | Keep untested scope separate |
| Acceptance | Applicable agreed requirement and decision | Leave the decision pending |
A missing file is a document gap; it does not by itself establish product failure. Equally, a traceable file establishes its identity without proving that the panel meets every agreed requirement.
For the wider shipment task, use the pre-shipment inspection checklist. Keep EL coverage explicit: a sample result cannot silently become confirmation that every panel in a batch was tested.
FAQ: solar panel EL test reports
A supplier's EL test report needs an identified scope and acceptance basis before a buyer can use it for an order decision. These answers address common document-review questions without adding a universal rejection rule.
Is a clean EL image enough to approve a panel?
A clean-looking EL image is one record under its stated conditions. Confirm the item's identity, acquisition quality and testing-party findings, then review the matching electrical results and agreed requirements. An unmarked image cannot establish lifetime performance or cover other checks that belong in the order's acceptance scope.
Does a visible crack always mean rejection?
A reported crack does not automatically mean module failure or rejection. Ask the qualified testing party to explain its finding and the necessary verification for the particular construction. The decision belongs to the agreed acceptance criteria; this checklist assigns no universal crack count, area threshold or power-loss percentage.
Can an old EL image represent a new batch?
An old EL image represents the item and stage identified in its record. To apply it to another delivery, require an explicit explanation of its relevance and actual coverage. Do not replace the current batch's evidence requirement with an earlier sample image because the products have similar model names.
Does every custom panel order include EL testing?
EL testing and report delivery need confirmation in the specific quotation. Ask which items and stages would be tested, what files would be supplied and what acceptance basis would apply. A panel inquiry alone does not establish included testing, independent laboratory service or testing of every supplied item.
Define the report requirement with the panel request. Request a quote with the panel outline, application, electrical target, quantity and inspection records your project needs. LinkSolar is a sourcing partner for the panel inquiry; confirm the proposed EL coverage and report deliverables as part of that quotation.
State whether the records are intended for a development sample, a shipment decision or a comparison at receipt. Ask for confirmation of the scope before treating any testing service or document as included. The result to seek is a matched panel specification and an agreed evidence requirement.