Patterning the Front Polysilicon Contact for Silicon Solar Cells using Laser Oxidation

The use of 'poly-Si/SiO
2
carrier selective contacts has pushed up the efficiencies of commercial large-area silicon solar cells, primarily driven by their excellent passivation properties. However, the high absorption in the visible spectrum has restricted their use only to the rear side of the solar cell. The ability to pattern poly-Si on the front of the solar cells to restrict them only under the screen-printed metal fingers can significantly mitigate the detrimental effect of parasitic absorption while providing all the advantages of excellent passivation. In this paper, we demonstrate a novel laser oxidation process as a rapid and scalable for patterning poly-Si, achieving fingers as narrow as 35 μm. We also observe that the laser irradiation of in-situ doped poly-Si can increase the concentration of active dopants. The patterning process with laser modifies the morphology and the properties of the poly-Si layer, which is visible as a change in the solar cell parameters and SEM imaging. In selective area front contact cell design with
$< 5\%$
laser processed region, any negative impact will be limited relative to the benefit of rapid low-cost patterning and efficiency enhancement from selective TOPCon. We also used this method to fabricate a preliminary 19.8 % efficient rear junction solar cell with ex-situ poly-Si contacts on both sides.