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  Neumann, B.; Bierau, F.; Johnson, B.; Kaufmann, C.A.; Ellmer, K.; Tributsch, H.: Niobium-doped TiO₂ films as window layer for chalcopyrite solar cells. Physica Status Solidi B 245 (2008), p. 1849-1857

10.1002/pssb.200879538

Abstract:
Smooth and semitransparent NbxTi1-xOy (x=0.03, y=1.84-1.91) films have been prepared by reactive magnetron sputtering at temperatures below 420 K. Structural investigations by RAMAN-spectroscopy together with resistivity- and temperature-dependent Hall-measurements were used in order to analyze the film structure and the nature of the charge transport in this material. These films can be used as a window layer (TCO) for thin film solar cells. Cu(In,Ga)Se2 solar cells equipped with the new window layer keep their functionality which excludes first, the presence of strong energetic barriers and second, a strong interfacial recombination. The development of TiO2-based window layers is expected to make thin film solar cells less sensitive against corrosion after contact with humidity.