Automated in-line defect classification and localization in solar cells for laser-based repair
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Defective crystalline silicon solar cells may be repaired using laser-based techniques if the problem is properly identified and characterized. This paper presents a novel system for the automation of solar cells repair that carries out the following tasks: 1) It detects and localizes cracks and shunts in solar cells from electroluminescence images; 2) It takes a decision on the laser process to repair faulty cells; 3) It automates the operation of a laser machine for processing solar cells. Regarding the analysis of electroluminescence images of solar cells, the proposed solution is able to discriminate the type of defect, which means a step-forward compared to state-of-the-art approaches. Moreover, it is to our knowledge the first solution that takes the results of such analysis to automate a process of laser-based repair. The proposed system paves the way for waste reduction in the production of solar cells by using repaired cells in custom-made solar modules.
Automated in-line defect classification and localization in solar cells for laser-based repair
- 1. Automated in-Line Defect Classification and Localization in Solar Cells for Laser-Based Repair Jorge Rodr鱈guez Ara炭jo, Ant坦n Garc鱈a-D鱈az AIMEN Technology Center, Porri単o, Spain ISIE 2014, Istambul, 2-6-2014
- 2. www.aimen.es | aimen@aimen.es 2 Index 1. Motivation and Innovative Character. 2. Proposed Solution. 3. Diagnostic and Defect Segmentation. 4. Repair Process Decision. 5. Experimental Results. 6. Conclusions and future work. Index
- 3. www.aimen.es | aimen@aimen.es 3 Motivation and Innovative Character
- 4. 4www.aimen.es | aimen@aimen.es Motivation and Innovative Character Solar cells are made of silicon (156x156mm). Monocrystalline and Polycrystalline silicon (more common materials). The manufacturing process produces defects. Photovoltaic solar cells busbars front back
- 5. 5www.aimen.es | aimen@aimen.es Motivation and Innovative Character Electroluminescence imaging. Shunts and Cracks (most important).(> 50%) Lacks of metallization (less frequent) (< 20%). Finger interruptions (reduced effects). (> 58%) Shunts and Cracks may be repaired. Cutting or isolating using laser technology. New pieces of cells are obtained. Defects Detection
- 6. www.aimen.es | aimen@aimen.es 6 Proposed Solution
- 7. 7www.aimen.es | aimen@aimen.es Proposed Solution Laser Repair System (laser process). Defects Inspector (defects identification and laser control). Data Input Block (electroluminescence provider). Solar cell repair system
- 8. 8www.aimen.es | aimen@aimen.es Proposed Solution Cell Diagnostic (defects segmentation from EL). Repairing Decision (laser process decision). Cell Alignment (laser process correction). Defects inspector
- 9. www.aimen.es | aimen@aimen.es 9 Diagnostic and Defect Segmentation
- 10. 10www.aimen.es | aimen@aimen.es Diagnostic and Defect Segmentation Human experts examine EL images. Changes on texture. Changes on the shape of texture boundaries. Defect Diagnostic (texture based) Decomposition: for automatic features generation. Adaptation: for enhancement of features. Pixel level classification: for multiclass identification. Bio-inspired texture approach Texture approach Defects Log Gabor filters
- 11. 11www.aimen.es | aimen@aimen.es Diagnostic and Defect Segmentation Trained with only 4 images. 4 cracks presents. 4 shunts presents. Type of defect and boundary contour are identified. Some examples of identified defects. Pixel level identification
- 12. www.aimen.es | aimen@aimen.es 12 Repair Process Decision
- 13. 13www.aimen.es | aimen@aimen.es Repair Process Decision Decision rules:. Isolate shunts not on a busbar. Cut shunts on a busbar or close to one. Cut pieces to remove cracks. Solar cell repair decision Examples of repair decision.
- 14. 14www.aimen.es | aimen@aimen.es Repair Process Decision Closing morphological operation. Inversion and thresholding. Edge detection and contour. Bounding box localization. Cell location and alignment Steps on cell localization.
- 15. www.aimen.es | aimen@aimen.es 15 Experimental results
- 16. Experimental Results www.aimen.es | aimen@aimen.es 16 Laser-based repair unit Camera perspective. Scanner working area. Laser repair system.
- 17. Experimental results www.aimen.es | aimen@aimen.es 17 Laser scanner calibration Galvo-scanner working area.
- 18. 18www.aimen.es | aimen@aimen.es Experimental results Calibration pictures
- 19. 19www.aimen.es | aimen@aimen.es Experimental results Processing pictures
- 20. 20www.aimen.es | aimen@aimen.es Experimental results Results pictures
- 21. 21www.aimen.es | aimen@aimen.es Experimental Results 47 cells considered. 45 cells repaired. 69% waste reduction. Processing results Defect type # of Defects TP FP FN Repaired Shunts 43 43 4 0 42 Cracks 38 36 6 2 36 All 81 79 10 2 45* * This value refers to the number of cells repaired.
- 22. www.aimen.es | aimen@aimen.es 22 Conclusions and Future Work
- 23. 23www.aimen.es | aimen@aimen.es Conclusions and Future work Defect segmentation and classification. In-line solar cells repair system. Able to isolate and cut defects. 69% of rejected cells reutilization. Discriminate more defects, like metallization. More complex repair strategies. Isolation based on efficiency estimation. Conclusions Future work
- 24. www.aimen.es | aimen@aimen.es 24 AIMEN Central y Laboratorios c/ Relva 27 A 36410 O PORRIO (Pontevedra) Telf.+34 986 344 000 Fax. +34 986 337 302 Delegaci坦n Tecnol坦gica Madrid Avda. del General Per坦n, 32, 8 A 28020 MADRID (Madrid) Telf.+34 687 448 915 Delegaci坦n Tecnol坦gica A Coru単a Fundaci坦n Mans Paideia Pol. Pocomaco - Parcela D-22 - Oficina 20A 15190 A CORUA (A Coru単a) Telf. +34 617 395 153 Thank you for your attention Jorge Rodr鱈guez Araujo | Research Engineer Ph +34 986 344 000 | jorge.rodriguez@aimen.es