By Kari Williamson
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, using a multicrystalline wafer from SCHOTT Solar featuring standard screen-printed backside metallisation as the basis.
The special challenge involved in metalising 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, SCHOTT Solar says.
The project team has used the InCellPlate technology of RENA to manufacture prototypes on standard industrial tools. These solar cells will now be used to fabricate test modules to test long-term stability.
Furthermore, the project team is working on transferring the development successes to monocrystalline cells, expecting efficiencies exceeding 19 %.
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.