aMetal organic chemical vapor deposition is carefully optimized for the growth of pure CuCrO 2 delafossite coatings on glass substrates. The pulsed direct liquid delivery is demonstrated to be an efficient process technology for the controlled supply of the precursor solution in the evaporation chamber, which is shown to be one of the main process parameters to tailor the thin-film properties.We investigated the influence of the precursor concentration ratio Cu(thd) 2 (bis[2,2,6,6-tetramethyl-3,5-heptanedionato]copper(II)) and Cr(thd) 3 (tris[2,2,6,6-tetramethyl-3,5-heptanedionato]chromium(III)) on the crystal structure, morphology and electrical conductivity, at a reduced temperature of 370 1C. We observe for a low ratio, a pure delafossite phase with a constant Cu-poor/Cr-rich chemical composition, while at a high ratio a mixture of copper oxides and CuCrO 2 was found. The as-grown 140 nm-thick pure delafossite films exhibit an exceptional high electrical conductivity for a non-intentionally doped CuCrO 2 , S cm À1, and a near 50% transparency in the visible spectral range.

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Off-stoichiometric copper chromium oxide delafossite received lately a great interest due to its high p-type electrical conductivity and adequate optical transmittance in the visible range. However, for a suitable integration in active devices such as p-n junctions, transistors or optoelectronic devices, the electronic properties must be efficiently tailored. Here, post-deposition thermal treatment is proven as an adequate approach for finely controlling the electrical properties of this former degenerate semiconducting material. The energetics of the annealing process are investigated using two different approaches, as a function of the annealing temperature and as a function of the annealing time, allowing the accurate determination of the activation energy of the annealing of defects. By using this method, the electrical carrier concentration was varied in the 1021 – 1017 cm−3 range while the recorded changes in the drift mobility covered three orders of magnitude. Moreover, we demonstrate the ability to accurately manipulate the Fermi level of such materials, which is of great importance in controlling the carrier injection and extraction in optoelectronic active layers.

Transparent conductive oxides (TCOs) constitute a class of materials that combine high electrical conductivity and optical transparency. These features led to the development of the transparent electronics applications, such as flat panel displays, “smart” windows or functional glasses. N-type TCOs dominate the applications market, and the lack of a suitable p-type counterpart limits the fabrication of a completely transparent active device, which might be considered as a technological breakthrough. Among the wide range of p-type candidates, delafossite CuCrO2 (and its out-of-stoichiometry derivatives) is a promising material to achieve the desired p-type TCO properties as, up to date, it is presenting the foremost trade-off between optical and electrical properties. The present paper covers the research work and the major achievements related to copper chromium delafossite. A comprehensive overview of fabrication methods and opto-electronic properties is presented. The source of doping and the charge carriers transport mechanism are also thoroughly discussed. Graphical abstract