Novel Patterning Techniques for Copper Electroplated Metallization on Silicon Heterojunction Solar Cells

37th European Photovoltaic Solar Energy Conference and Exhibition; 228-232
For the current PV production about 2000 tons of silver are consumed per year. This is already 10% of the entire world annual silver supply. The PV production is expected to grow significantly in the next decades in order to enable the energy transition to 100% renewables. Annual production volumes in the terawatt range are predicted already for 2030 and this may lead to higher silver price and put more pressure on the industry to replace silver by copper. With the currently available processes the cost advantage of copper plating over screen printing is relatively small and the implementation of plating in production is slowed down by the high up-front investment for equipment. The highest cost share of the process sequence has the patterning and research activities focus on new, i.e. more cost competitive patterning techniques. Within the Ameliz project several approaches are investigated: firstly, patterning by printing a metal seed grid with a dielectric layer as plating mask and secondly masking by a monolayer of self-assembling molecules. These molecules consist of a phosphonic acid group and a hydrocarbon chain. They are bonded to the ITO surface and form a monolayer of well-ordered, densely packed hydrophobic chains, which protects the ITO surface against plating solutions. Furthermore, methods for selective formation of a copper seed layer by electrografting and for improved adhesion by ITO reduction are being investigated.