Regensburg 2004 – scientific programme
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HL: Halbleiterphysik
HL 24: Photovoltaik I
HL 24.2: Talk
Tuesday, March 9, 2004, 18:00–18:15, H15
Investigation of the chemical and electronic properties of the ZnO/Cu(In,Ga)(S,Se)2 interface in thin film solar cells — •G. Storch1, L. Weinhardt1, C. Heske1, E. Umbach1, S. Visbeck2, T.P. Niesen2, and F. Karg2 — 1Experimentelle Physik II, Universität Würzburg, Am Hubland, D-97074 Würzburg — 2Shell Solar, 81739 München
Thin film solar cells based on Cu(In,Ga)(S,Se))2 (CIGSSe) commonly contain a CdS buffer layer between the absorber and the (i-ZnO/n-ZnO) window layer. For environmental reasons, it is desirable to replace the Cd-containing buffer, either by alternative materials or by direct deposition of the window layer on the absorber. However, depositing the standard window layer directly on the absorber results in poor efficiencies. In contrast, the use of (Zn,Mg)O instead of i-ZnO leads to cells showing satisfactory performance. Until today, the reason for this discrepancy is unknown. As a first step towards an understanding, we have investigated the i-ZnO/CIGSSe interface by using X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and UV-photoelectron spectroscopy (UPS) combined with inverse photoemission (IPES). The resulting chemical and electronic picture of the interface, including the band alignment in both the valence and conduction band, will be discussed and compared to results from related interfaces (e.g., i-ZnO/CdS) as well as alternative preparation methods.