Hyperspectral photoluminescence imaging of silicon wafers and solar cells

Hyperspectral photoluminescence imaging is a non-destructive characterization method used to study radiative defects in crystalline silicon wafers and solar cells. It provides both spatial distribution and spectral response of these crystal imperfections and impurities. The goal of this research has been to establish hyperspectral photoluminescence imaging as a characterization method. The objectives of this research have been three-fold; to optimize, verify and apply the method. In the optimizing process, an oscillation in the background noise was identified. An enhanced noise removal algorithm was developed, drastically increasing the camera’s sensitivity, allowing even weakly emitting defects to be detected. By application of a macro-lens, the spatial resolution has been improved from 200 to 27 µm. Verification of the method was done by comparing results with several complementary characterization techniques and on various materials. In addition to multicrystalline silicon wafers and solar cells, samples of mono and mono-like crystalline silicon have been characterized with success. The results show that hyperspectral photoluminescence imaging correlates well and in some instances, compared with electroluminescence, yields richer data output. The third objective of this research was to show that the method might be applied as a characterization method in line with other existing methods. This objective has been achieved in two studies. One of these studies has led to a patent application. The conclusion is that Hyperspectral photoluminescence imaging is a method that may be used on par with other characterization methods