光致发光(photoluminescence，PL)检测过程大致包括激光被样品吸收、能量传递、光发射及CCD成像四个阶段。通常利用激光作为激发光源，提供一定能量的光子，Si片中处于基态的电子在吸收这些光子后而进入激发态，处于激发态的电子属于亚稳态，在短时间内会回到基态，并发出以1150 nm的红外光为波峰的荧光。利用冷却的照相机镜头进行感光，将图像通过计算机显示出来。发光的强度与本位置的非平衡少数载流子的密度成正比，而缺陷处会成为少数载流子的强复合中心，因此该区域的少数载流子密度变小导致荧光效应减弱，在图像上表现出来就成为暗色的点、线，或一定的区域，而在电池片内复合较少的区域则表现为比较亮的区域。
因此，通过观察光致发光成像能够判断Si片或电池片是否存在缺陷
操作界面如下图
测试样本实例如下图：
PL测试设备性能参数
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Parameter |
Specification |
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General |
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Measurement System: |
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Sample Type |
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Solar Cells: |
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Busbar Configurations: |
2 busbars and 3 busbars and Back-Contact ( |
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Defect Types Found: (for both mono- and poly-cell material) |
Micro Cracks / Large Cracks / Dark Areas / Low efficiency areas / Whole Cell defect |
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Max. Throughput: |
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Inspection Cycle Time: |
3000 cells / h |
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Operation: |
Stop & Go measurement |
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Optics |
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Camera: |
1 x 1 Megapixel Camera (Black & White sensor) à | |
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Lens: |
NIR optimized lens + cut-off filters for PL |
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Camera specifications |
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Image device: |
1MP Deep depletion cooled CCD sensor |
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Picture size: |
1024 H x 1024 V |
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Pixel size: |
13 µm x 13 µm (large pixel for best SNR) |
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Resolution depth: |
16 bit |
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Lens mount: |
C-Mount |
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Frame rates: |
2,25 fps (full resolution) |
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Illumination |
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PL excitation source: |
Laser | |
