Edge shunt passivation in silicon solar cells by chemical etching investigated by lock-in thermography and CELLO

Shunts in solar cells are often localized at the edges. Some of these edge shunts have a linear (ohmic) behavior and some of them have a non-linear (diode-like) one. At least the linear edge shunts, which are the most dangerous ones, can be removed by local etching. Two proven nondestructive techniques for shunt imaging are lock-in thermography and CELLO. Lock-in thermography detects local heat sources under forward or reverse bias in the dark, whereas CELLO measures the small signal electrical response to a pulsed laser beam at different voltages. These two techniques are compared with respect to their ability to investigate the influence of edge etching procedures on the shunt activity.