SCHOTT Solar AG and its project partners have already reached an important milestone in the research project Las VeGaS after only six months: a solar cell metalized with copper achieved an efficiency of 18.0 percent.

• Research project Las VeGaS reaches important milestone after only six months
• The manufacturing technology used can reduce the costs of front side metallization by over 50 percent
• Development successes to be transferred over to monocrystalline technology

SCHOTT Solar AG and its project partners have already reached an important milestone in the research project Las VeGaS after only six months: a solar cell metalized with copper achieved an efficiency of 18.0 percent. A multicrystalline wafer from SCHOTT Solar AG that features standard screen-printed backside metallization serves as the basis. The goal of the Las VeGaS project is to largely replace the silver contacts that are commonly used on the front side of solar cells with less expensive nickel-copper plating. This would lower the manufacturing costs of front side metallization by more than half. SCHOTT Solar is working together with RENA GmbH and CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH in order to achieve this.

Inline plating equipment from RENA

The special challenge involved in metalizing with nickel-copper plating is to prevent diffusion of the copper into the silicon solar cell, as this would reduce the carrier lifetime of the electrons and thus reduce the efficiency of the cell. For this reason, the project team has developed an electroplated nickel layer that serves as a diffusion barrier as well as the appropriate manufacturing techniques for applying both then nickel barrier and the copper contacts to the cell. 

The project team has used the new “InCellPlate” technology of RENA to manufacture rather promising prototypes on standard industrial tools. These solar cells will now be used to fabricate test modules so that they can demonstrate their long-term stability in reliability tests. Furthermore, the project team is working on transfering these development successes to monocrystalline cells. Efficiency that exceeds 19 percent are expected. 

The Las VeGaS method offers yet another advantage besides the lower costs for the raw material copper: the electroplated layers are environmentally friendly because they are free from both lead and solvents and thus meet the requirements of the European Union’s RoHS Directive. This places restrictions on the use of hazardous substances in electrical and electronic devices. It is now no longer necessary to use large amounts of expensive silver paste, because only a very thin electroplated silver layer is needed to solder the cells to the copper tabs to make a module. This, in turn, lowers the consumption of silver by at least 95 percent.