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Abstract
This work deals with the characterization of the chemical and elektronical proporties of the
absober/buffer interface in a Cu(In,Ga)Se 2 solar cell with a standard CdS buffer layer and an
alternative ZnO 1−x S x buffer layer on industry-oriented samples. The methods of choice are X-ray
photoelectron spectroscopy and Impedance spectroscopy.
The X-ray photoelectron spectroscopy results show the electronical structure of the valence band
maximum of the different materials. Using the valence band offset and the band gaps of the
used materials, the offset in the conduction band is determined. With the help of the Auger
Parameter, the composition of the ZnO 1−x S x buffer layer is determined. Together with the known
properties of the materials from literature, potential band diagrams could be derived and help
to interpretate the performance of the cells.
The performed Impedance measurements show a transient behaviour of the impedance, which
is assigned to the diffusion of copper defects in the absorber layer. With this mechanism the well
known phenomenon by applying a reverse bias on the cell could be explained. Other metastable
effects could not be explained with this theory, but the different effects aren’t bound to originate
from the same defect and can be considered detached.
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