10-07/08 :: July/August 2010

nanotimes News in Brief

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the more homogeneous the material becomes. It has now become apparent that gallium-rich CIGS is always less homogeneous than indium-rich CIGS. Because of this lack of homogeneity, the optoelectro- nic properties of the gallium-rich material are poorer, resulting in the low efficiency levels of gallium-rich CIGS cells - an effect that has now been explained for the first time. The calculations also provide a con- crete indication of the best way to manufacture CIGS solar cells. If it is produced at higher temperatures, the material is significantly more homogeneous. To retain the desired homogeneity, the material then needs to be cooled down sufficiently rapidly.

In practice, it was the limited heat resistance of the glass used as a substrate for solar cells that has always restricted process temperatures, but a significant bre- akthrough has also recently been made here.

Schott AG has developed a special glass with which the process temperature can be increased to well above 600° C (1,112° F). The cells that result from this process are considerably more homogeneous, meaning that the production of cells with a much greater efficiency level has become possible. But the comCIGS project researchers are already thinking ahead of this.

“We are currently working on large-format solar cells which should outperform conventional cells in terms

of efficiency,“ states Gruhn. “The prospects look promising.“

Christian D. R. Ludwig, Thomas Gruhn, Claudia Felser, Tanja Schilling, Johannes Windeln, Peter Kratzer: Indium- Gallium Segregation in CuInx

Ga1-x Se2

: An Ab Initio–Ba-

sed Monte Carlo Study, In: Physical Review Letters, Vol. 105(2010), Issue 2, July 09, 2010, Article 025702 [4 pages], DOI:10.1103/PhysRevLett.105.025702: http://dx.doi.org/10.1103/PhysRevLett.105.025702

http://www.staff.uni-mainz.de/gruhn/gruhn.html http://www.superconductivity.de/