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Laser Marking of Solar Cells: Technologies and Potential

In this work, laser marking processes for wafer identification have been investigated on mono-crystalline silicon wafers with respect to the laser-induced damage using small Data Matrix codes with a code size of 0.8 x 3.2 mm2 and a brick slice code. The experiment focuses on the identification of shunts, the breakdown characteristics and the recombination losses of Al BSF solar cells to check if a purely geometric specification of a front-side marking is sufficient for the ongoing standardization procedure. The analysis of photoluminescence images shows that recombination losses which affect the finished solar cell are only detectable after ARC. Thermography revealed that a severe hot spot risk only arises for codes with the too deep structures. However, all laser marks resulted in sites of slightly increased energy dissipation under reverse bias. So the proposed purely geometric SEMI specification for Data Matrix codes at the front side of the cell seems to be sufficient to exclude marking-induced efficiency losses in standard industrial solar.