Multi-crystalline solar cells with inexpensive metal contacts at 18 percent efficiency

MAINZ, GERMANY: SCHOTT Solar AG has reached and its project partners after only six months a major milestone in the research project in Las Vegas: A metallized with copper solar cell achieved a high efficiency of 18.0 percent. Base is a multi-crystalline wafers with screen-printed standard backside of SCHOTT Solar AG.

The aim of the project in Las Vegas is now the standard silver contacts largely replaced on the front side of solar cells by a cheaper nickel-copper-plating. This allows the production costs for the front-side will be more than halved. SCHOTT Solar is so, RENA GmbH and the Research Institute for Micro Sensors CiS and PV GmbH.

The principal challenge in the metallization with a nickel-copper-plating, is to prevent the diffusion of copper into the silicon solar cell. There would be the lifetime of the electrons and thus the efficiency of reducing the cell. The project team has therefore developed a galvanic nickel layer as a diffusion barrier and appropriate production techniques to create this and the copper contacts on the cell.

With the new "InCellPlate" technology of the project team RENA promising prototypes to standard industry equipment has made. These solar cells will now be installed in test modules and make their long-term stability in hardness tests to the test. In addition, the project aims to transfer the development team successes now on mono-crystalline cells. Efficiencies of over 19 percent are to be expected.

Besides lower costs for the raw material is copper, the Las Vegas method has another advantage: the galvanic coatings are environmentally friendly because they are free of lead and solvents, and meet the real needs of the RoHS Directive of the European Union. This restricts the use of hazardous substances in electrical and electronic equipment. The use of relatively expensive silver paste is avoided, it is only a very thin galvanic silver-plating required in order to solder the cells to the copper strips laminated to form a module. As a result, the silver consumption is reduced by at least 95 percent.