研究目的
To demonstrate a proof of principle for electrochemical screen printing (ESP) as a patterning process for thin metal stacks that can be employed in interdigitated back contact (IBC) or silicon heterojunction (SHJ) solar cells.
研究成果
The ESP process was demonstrated on 125 × 125 mm2 100‐nm aluminum layers as well as on Al (100 nm)/Cu (20 nm) stacks on Si wafers and on foils, where single layers could be removed selectively. The achieved electrochemical etched trenches on the metal stacks were in average 110 μm wide on Si substrate and 150 μm wide on foil substrate. These trenches were free of any residues in microscope inspection. Still, no full electrical contact separation was achieved on Si substrate, which has to be investigated in more detail. The patterned copper seed layer was thickened in average to a height of 7 μm by copper plating.
研究不足
The inhomogeneous current distribution is one big challenge while patterning single metal layers with the ESP process. The amount of metal residuals in the patterned trenches can be controlled to a certain degree by the used squeegee pressure and process parameters. A chemical posttreatment is beneficial to remove metal residuals in these trenches.
