Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 17: Poster I
HL 17.31: Poster
Monday, February 25, 2008, 16:30–19:00, Poster D
Co-Sputtering of (Zn,Mg)O buffer layers on CIGSSe thin film solar cells — •Felix Erfurth1, Benjamin Hußmann1, Thomas Niesen2, Jörg Palm2, Alexander Grimm3, Achim Schöll1, and Eberhard Umbach1 — 1Universität Würzburg, Experimentelle Physik II — 2Avancis GmbH, München — 3Hahn-Meitner-Institut, Berlin
To better meet the environmental requirements of thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe), the substitution of the CdS buffer layer by using a dry physical deposition method is of great interest. (Zn,Mg)O buffer layers deposited by rf-magnetron sputtering can result in efficiencies comparable with CdS containing solar cells. The properties of these layers depend on a multitude of parameters like sputter power, sputter pressure, and layer thickness, which therefore affect the characteristics of the entire solar cell. Of prime interest is the impact of the Mg/Zn-ratio, which in principle allows to tailor the optical band gap of the buffer layer. We are able to vary the Zn/Mg-ratio by controlling the sputter power of two separated ZnO and MgO sputter targets. By varying one specific parameter while leaving all others constant we have optimised the sputter deposition in order to achieve high efficiency solar cells. We present the influence of various parameters on cell properties like efficiency, filling factor, open circuit voltage, and short circuit current. In-situ X-Ray Photoelectron Spectroscopy measurements have been performed to investigate the direct impact of the sputter parameters on the chemical and stoichiometric properties of the buffer layer and of the absorber-buffer interface.