Thermoreflectance and multimode imaging for defect location in silicon solar cells

Silicon solar cells suffer from defects such as microcracks and shunts that limit performance and reliability. We describe a new family of imaging techniques, including lock-in thermoreflectance and mechanoreflectance, which offer much higher spatial resolution and lower cost than current methods for inspection of solar cells. These techniques are based on advanced image processing algorithms for detection of very small variations in optical reflectance, using ordinary visible light CCD cameras. The image data can be merged with conventional techniques such as electroluminescence, in one camera system. Experimental results and comparison with conventional techniques for evaluation of solar cells are presented.

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