Created by M.L., OST, on 19.03.2025
- Description: Light emission from cells is measured, like for EL, but using light (instead of current) as excitation source. Lock-in amplification is used to filter out the sunlight, modulating the signal with a high power LED array [1–3]. As for EL, regions with high signal are intact, whereas damaged areas will remain dark, allowing for defect localization.
- Equipment: InGaAs-camera, high power LED array, computer for image processing.
- Requirements: Stable sunny conditions.
- Gained insights: Cell (micro-) cracks, shunts, potential induced degradation (PID) defects, failed bypass diode.
Due to the combination of low temperatures and heavy mechanical loads (wind and snow), defects such as micro-cracks are expected to be more common in alpine regions [4–6]. - Advantages: No need to electrically contact the modules.
- Disadvantages: Comparison between modules is limited, since illumination might change between measurements.
- Effort:
- Global: high.
- Costs: high.
- Time: high; 1 hour per 100 solar modules.
- Providers (non-exhaustive list): – (couldn’t find any provider offering this field measurement as a common service)
- Links:
- Brief explanation of PL: https://pv-manufacturing.org/metrology/photoluminescence-imaging/
- Additional notes: Other variations of PL measurements exist. We chose here to describe the optically modulated approach, since it doesn’t require electrical connection to the modules, providing an advantage compared to EL.
References
- Hermann W, Eder G, Farnung B, Friesen G, Köntges M, Kubicek B, et al. Qualification of Photovoltaic (PV) Power Plants using Mobile Test Equipment. International Energy Agency (IEA); 2021.
- Bhoopathy R, Kunz O, Juhl M, Trupke T, Hameiri Z. Outdoor photoluminescence imaging of photovoltaic modules with sunlight excitation. Prog Photovolt Res Appl 2018;26:69–73. https://doi.org/10.1002/pip.2946.
- Kunz O, Weber JW, Rey G, Juhl M, Trupke T. Daylight Photoluminescence Imaging via Optical String Switching. Sol RRL 2024;8:2400385. https://doi.org/10.1002/solr.202400385.
- Gassner A. Alpine PV: Stressors and module testing strategies 2025.
- Seigneur H, Schneller E, Lincoln J, Ebrahimi H, Ghosh R, Gabor AM, et al. Microcrack Formation in Silicon Solar Cells during Cold Temperatures. 2019 IEEE 46th Photovolt. Spec. Conf. PVSC, Chicago, IL, USA: IEEE; 2019, p. 1–6. https://doi.org/10.1109/PVSC40753.2019.9198968.
- Schneller EJ, Seigneur H, Lincoln J, Gabor AM. The Impact of Cold Temperature Exposure in Mechanical Durability Testing of PV Modules. 2019 IEEE 46th Photovolt. Spec. Conf. PVSC, Chicago, IL, USA: IEEE; 2019, p. 1521–4. https://doi.org/10.1109/PVSC40753.2019.8980533.
