Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 5: Photovoltaic
HL 5.6: Vortrag
Montag, 26. März 2007, 12:15–12:30, H14
Deposition and characterization of (Zn,Mg)O buffer layers on CIGSSe thin film solar cells — •Felix Erfurth1, Thomas Niesen2, Jörg Palm2, and Eberhard Umbach1 — 1University of Würzburg, Experimental Physics II, Am Hubland, 97070 Würzburg, Germany — 2Avancis GmbH, München, Germany
The replacement of the CdS buffer layer in thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe), and the use of dry physical deposition methods, would be beneficial for high volume mass production. (Zn,Mg)O buffer layers deposited by radio frequency magnetron sputtering can result in efficiencies comparable to those of CdS containing solar cells. Using two separated ZnO and MgO sputter targets we are able to control the Zn/Mg – ratio of the buffer layer. A higher Mg content enhances the optical band–gap of (Zn,Mg)O, which is expected to have a great influence on the solar cell parameters by changing the electronic band alignment, too. In our experimental setup the sputter preparation chamber is connected with a UHV analysis system which allows in–situ characterization even during the layer deposition by interrupting the sputter process.
To understand the impact of sputter parameters, such as Mg content, on the cell efficiency, we investigated the buffer layer and the absorber–buffer interface by photoelectron spectroscopy (XPS, UPS) and inverse photoelectron spectroscopy (IPES). The combination of both techniques allows determining the buffer layer stoichiometry as well as the alignment of the conduction and valence band at the heterojunction interface.