Fast illuminated Lock-In Thermography: An inline shunt detection measurement tool

This paper focuses on the fast spatially resolved detection of material and / or processing induced shunting using fast illuminated Lock-In Thermography (iLIT). With this technique shunting can be detected spatially resolved within a measurement time of only 1 s and thus the method in principle can be used for inline characterisation. Points addressed are the influence of Lock-In frequency on spatial resolution and the effect of a lowered illumination intensity for a better selectivity between shunting and recombination induced generation of heat. The method is tested for different common sources of shunting in standard industrial-type solar cells (points like shunts, cracks, poor edge isolation, contaminations) and all major types of shunts under investigation can be detected in times relevant for inline characterisation.