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

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Off-stoichiometric copper chromium delafossites demonstrate the highest values of electric conductivity among the p-type transparent conducting oxides. Morphological and structural changes in cu 0.66 cr 1.33 o 2 upon annealing processes are investigated. chained copper vacancies were previously suggested as source of the high levels of doping in this material. High resolution Helium ion Microscopy, Secondary ion Mass Spectrometry and transmission electron Microscopy reveal a significant rearrangement of copper and chromium after the thermal treatments. Furthermore, positron Annihilation Spectroscopy evidences the presence of vacancy defects within the delafossite layers which can be assigned to the cu vacancy chains whose concentration decreases during the thermal process. These findings further confirm these chained vacancies as source of the p-type doping and suggest that the changes in electrical conductivities within the off-stoichiometric copper based delafossites are triggered by elemental rearrangements. P-type transparent conductive oxides (TCOs) have lately attracted attention due to their promising applications in various fields such as flat panel displays, solar cells, photovoltaics and transparent electronic devices. The development of such material, with properties similar to its n-type counterpart (electric conductivity 10 3 S cm −1 , optical transmittance in the visible range well above 80%) will unlock the fabrication of a complete transparent active device (like a diode or a transistor) 1,2. Among the others TCOs, copper based delafossites (with general formula CuM 3+ O 2 , where M = Al, Cr, B, Ga or In) have shown attractive performances with a record value of electric conductivity of 280 S cm −1 (with a visible transmittance of 50%) 3,4. In such delafossites, the mixing of Cu 3d states and O 2p states forming the valence band leads to higher holes mobility. Tailoring the edge of the valence band by mixing molecular orbitals of the cations was proposed by Hosono and co-workers and demonstrated for CuAlO 2 as the first p-type transparent delafossite 5,6. Among delafossite materials, a special focus was given to CuCrO 2 due to its highest density of 3d cations near the maximum of valence band and the covalent mixing between chromium and oxygen ions 7. These two properties shall promote larger holes mobility and hence greater conductivities are expected for this material. However, intrinsic CuCrO 2 presents a relatively low conductivity (10 −4 S cm −1) and doping is required for obtaining decent electrical conductivity larger than 1 S cm −1 8. Higher values started to be lately reported for delafossite films demonstrating peculiar off-stoichiometric ratios. Tens of

The most promising materials to replace indium tin oxide (ITO) in transparent electrodes could be silver nanowires. One of the challenges is, however, the large-scale deposition of silver nanowires. This study provides a solution to deposit silver nanowires on large substrate area by spray deposition. The new concept is to spray on a heated glass substrate in vertical position with a flat spray beam instead of the basic conic beam. After optimization of the spray parameters such as the substrate cleaning, the droplets size, the pressure, and the spray distance, a surface of 100 cm 2 was fully covered with a very good homogeneity, and it was demonstrated that the concept can be extended on a much higher substrate area. The electrical and the optical properties of such a large sample were investigated by sheet resistance, transmittance, and haze factor measurements. A silver nanowire network with a sheet resistance of 9 Ω/sq, a visible transmittance of 91.7%, and a haze factor of 3.7% was deposited for a spray time of only 3 min for the 100 cm 2 area. The trade-off sheet resistance/haze factor showed similar and even better results than the ones published in the literature for smaller substrate area coverage by using other methods of deposition.

The construction of a ZnO/SnO2 heterostructure is considered in the literature as an efficient strategy to improve photocatalytic properties of ZnO due to an electron/hole delocalisation process. This study is dedicated to an investigation of the photocatalytic performance of ZnO/SnO2 heterostructures directly synthesized in macroporous glass fibres membranes. Hydrothermal ZnO nanorods have been functionalized with SnO2 using an atomic layer deposition (ALD) process. The coverage rate of SnO2 on ZnO nanorods was precisely tailored by controlling the number of ALD cycles. We highlight here the tight control of the photocatalytic properties of the ZnO/SnO2 structure according to the coverage rate of SnO2 on the ZnO nanorods. We show that the highest degradation of methylene blue is obtained when a 40% coverage rate of SnO2 is reached. Interestingly, we also demonstrate that a higher coverage rate leads to a full passivation of the photocatalyst. In addition, we highlight that 40% coverage rate of SnO2 onto ZnO is sufficient for getting a protective layer, leading to a more stable photocatalyst in reuse.