Solar cell analysis system

Electroluminescence imaging

These images show the near-bandgap light that a solar cell emits when it is driven in forward bias. The intensity depends mainly on the local minority carrier concentration, so a number of effects that are affecting it become visible: inhomogeneous recombination properties in the base volume and at the rear surface, voltage drops due to series resistance, and cracks. The acquisition of a high-current image takes only a few seconds and should generally accompany IV measurements to reveal e.g. poor contacting quality which may affect the fill factor measurement. Images of series resistance and saturation current are calculated from images under different bias conditions.

The camera's height and focus settings are motorized and automatically adjusted to the sample size. A zoom mode uses the minimum possible object distance for high resolution close-ups. The images are scaled to mm.