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2017



  • M. Courté, M. Alaaeddine, V. Barth, L. Tortech, et D. Fichou, « Structural and electronic properties of 2,2′,6,6′-tetraphenyl-dipyranylidene and its use as a hole-collecting interfacial layer in organic solar cells », Dyes and Pigments, vol. 141, p. 487-492, juin 2017.
    Résumé : The accumulation of positive charges at the anodic interface considerably limits the efficiency of photovoltaic solar cells based on polymer/fullerene bulk heterojunctions (BHJs). Interfacial layers (IFLs) such as PEDOT:PSS improve charge injection but have no effect on the unbalanced electron/hole transport across the BHJ. We report here the use of 2,2′,6,6′-tetraphenyl-dipyranylidene (DIPO-Ph4), a planar quinoïd compound, as an efficient anodic IFL in organic solar cells based on BHJs made of poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM). When deposited under vacuum onto a glass substrate, DIPO-Ph4 thin films are constituted of densely packed and vertically aligned crystalline needles. Current-sensing atomic force microscopy (CS-AFM) reveals a considerable increase of the hole-carrying pathways in DIPO-Ph4 thin films as compare to PEDOT:PSS, thus revealing their hole transporting/electron blocking properties. Inserting a 10 nm thick IFL of DIPO-Ph4 in combination with a 5 nm thick PEDOT:PSS between the ITO electrode and the P3HT:PCBM film leads to photocurrent densities up to 11.5 mA/cm2 under AM 1.5G and conversion efficiencies up to 4.6%, that is substantially higher than PEDOT:PSS-only devices.
    Mots-clés : Atomic force microscopy, Bulk heterojunction, E-POM, Hole collection, Interfacial layers, NASCO, Organic solar cells, POLE 1, POLE 2.
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  • M. Courté, S. G. Surya, R. Thamankar, C. Shen, V. R. Rao, S. G. Mhailsalkar, et D. Fichou, « A non-volatile resistive memory effect in 2,2′,6,6′-tetraphenyl-dipyranylidene thin films as observed in field-effect transistors and by conductive atomic force microscopy », RSC Advances, vol. 7, nᵒ 6, p. 3336-3342.
    Résumé : The charge transport properties of 2,2′,6,6′-tetraphenyldipyranylidene (DIPO-Ph4), a large planar quinoïd π-conjugated heterocycle, are investigated in field-effect transistor (FET) configuration and by conductive atomic force microscopy (c-AFM). The FET properties show a clear p-type behavior with a hole mobility up to 2 × 10−2 cm2 V−1 s−1 and on/off ratio of 104. The transfer characteristics Id/Vg present a clear hysteresis typical of a resistive memory effect. This memory effect is again observed by means of c-AFM in lateral mode using a nearby gold top-contact as the counter-electrode. The c-AFM current response recorded for variable distances d = 0.5–9.0 μm between the AFM tip and the top electrode shows a resistive switching behavior in the low-voltage 0.0–3.0 V region. Repeated “write-read-erase-read” cycles performed at low frequency reveal a non-volatile memory effect in the form of high-resistance and low-resistance states with a stable on/off ratio of 102 during cycling operation.
    Mots-clés : NASCO, POLE 2.
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  • C. Shen, X. Wang, S. Tang, M. Courté, et D. Fichou, « Phenoxazine Derivative Operates as an Efficient Surface-Grafted Molecular Relay to Enhance the Performance and Stability of CdS- and CdSe-Sensitized TiO2 Solar Cells », ChemPhysChem, p. 1302-1307.
    Résumé : We report on a new phenoxazine derivative, 10-butyl-phenoxazine-3-carboxylic acid (BPCA), that we designed to operate as a molecular relay in semiconductor-sensitized solar cells (SSCs). After BPCA surface modification and in the presence of a cobalt-bipyridyl complex acting as a redox mediator, both TiO2/CdS/BPCA and TiO2/CdSe/BPCA SSCs exhibit enhanced photovoltaic performance and stability. In particular, the power conversion efficiencies of CdS and CdSe-based solar cells are improved by 90 % and 57 %, respectively. Furthermore, after 300 s the JSC of TiO2/CdS/BPCA SSCs is stabilized at 30 % of its initial value, while in the same time CdS-based devices retain only 1 % of their initial JSC. The origin of the improvement arises from the excellent electron-donating property of BPCA and its role as a powerful molecular relay in non-polysulfide based SSCs.
    Mots-clés : cadmium, energy conversion, NASCO, POLE 2, Redox chemistry, semiconductors, sensitizers, thin films.
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  • S. Tang, C. Shen, W. Ji, J. Liu, et D. Fichou, « Template-free synthesis of hierarchical MoO2 multi-shell architectures with improved lithium storage capability », Materials Research Bulletin, vol. 91, p. 85-90.
    Résumé : A hierarchical multi-shell structure of MoO2 is synthesized through a template-free one-pot solvothermal method. The relative MoO2 electrode exhibits high reversible specific capacity of 780 mA h g−1 after 40 cycles, good stability, high capacity retention and improved rate performance in the lithium ion battery application. This material has a unique hierarchical architecture which is a combination of pure hollow structure and core-shell structure. Such a hierarchical multi-shell structure can not only amplify active mass-electrolyte contact area and minimizes lithium ion diffusion path, but also provides a unique interstitial void space to relieve the huge volume change of material. Materials with a hierarchical multi-shell structure are expected to be promising candidates in lithium ion batteries application.
    Mots-clés : A. Nanostructures, A. Oxides, B. Solvothermal, D. Electrochemical properties, NASCO, POLE 2.
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2016

  • C. Aubert, L. Tortech, V. Gandon, D. Fichou, M. Malacria, et G. Bertrand, « Use of Cobalt Complexes for Preparing an Active Layer in a Photovoltaic Cell, and Corresponding Photovoltaic Cell. », U.S. Patent US Patent N°9,263,683.
    Mots-clés : MACO, NASCO, POLE 1, POLE 2.
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  • A. Efrem, M. Courté, K. Wang, D. Fichou, et M. Wang, « Synthesis and characterization of γ-lactone-Pechmann dye based donor-acceptor conjugated polymers », Dyes and Pigments, vol. 134, p. 171-177.
    Résumé : A new acceptor moiety, γ-lactone-Pechmann dye is synthesized and used in the construction of two new conjugated D-A polymers. The optical and electrochemical characterization shows a broad absorption band extended to 1000 nm and narrow band gaps with deep LUMO energy levels. The chemical structures of the side chains appended from the donor units affect the intermolecular aggregation and the charge transport in thin-film field-effect transistors. The high degree of planarity, low bandgap, and strong electron accepting properties could make γ-lactone-Pechmann dye as a good candidate for the construction of conjugated D-A polymers.
    Mots-clés : Conjugated D-A polymers, Field-effect transistor, Lactone, Low bandgap, NASCO, Pechmann dye, POLE 2.
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  • Z. Ku, N. H. Tiep, B. Wu, T. C. Sum, D. Fichou, et H. J. Fan, « Solvent engineering for fast growth of centimetric high-quality CH3NH3PbI3 perovskite single crystals », New Journal of Chemistry, vol. 40, nᵒ 9, p. 7261-7264.
    Résumé : Centimetre-scale CH3NH3PbI3 perovskite single crystals of high structural quality are grown by a new versatile method based on the use of a binary solvent mixture at a temperature as low as 70 degrees C. The growth rate is fast enough for a millimeter scale seed crystal to grow to the centimeter scale in a few hours.
    Mots-clés : crystallization, deposition, diffusion, electron, lead iodide perovskite, NASCO, organometal halide perovskites, performance, POLE 2, room-temperature, sensitized solar-cell, v hysteresis.
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  • I. Minguez-Bacho, S. Rodriguez-Lopez, A. Climent-Font, D. Fichou, M. Vazquez, et M. Hernandez-Velez, « Variation of the refractive index by means of sulfate anion incorporation into nanoporous anodic aluminum oxide films », Microporous and Mesoporous Materials, vol. 225, p. 192-197.
    Résumé : The variation in the refractive index of nanoporous anodic aluminum oxide (AAO) films regarding the sulfur anion incorporation is studied in this work. For this purpose, different samples are grown under potentiostatic conditions at different volta

    ges and concentrations of sulfuric acid in the electrolyte. The samples are analyzed by Rutherford backscattering spectroscopy and infrared spectrometry, confirming the presence of sulfate anions and water embedded into the nanoporous MO films. The incorporation of. sulfate ions into the alumina matrix varies from 63 up to 11.7% regarding aluminum content. We have studied Fabry-Perot optical interferences by shining incident monochromatic light in specular reflectance conditions. The reflected monochromatic light waves interact in internal reflectivity generating constructive and destructive interferences known as Fabry-Perot optical interferences. An iterative method based on the equation for constructive interferences conditions in thin films and Snell equations is developed in order to calculate the refractive index of the nanoporous AAO films as a function of the wavelength. The calculated refractive indices increase when the sulfur content of the nanoporous MO films decreases. The variation of the calculated refractive index is 0.08 and remains constant in the wavelength range 400-1200 nm. (C) 2015 Elsevier Inc. All rights reserved.
    Mots-clés : Anion incorporation, electrolyte, Fabry-Perot interferences, membranes, nanohole arrays, Nanoporous anodic alumina, nanotube arrays, NASCO, optical-properties, POLE 2, porous alumina, Refractive index, templates, thin-films, transmission, volume expansion.
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  • H. Qi, J. Wolfe, D. Fichou, et Z. Chen, « Cu2O Photocathode for Low Bias Photoelectrochemical Water Splitting Enabled by NiFe-Layered Double Hydroxide Co-Catalyst », Scientific Reports, vol. 6, p. 30882.
    Résumé : Layered double hydroxides (LDHs) are bimetallic hydroxides that currently attract considerable attention as co-catalysts in photoelectrochemical (PEC) systems in view of water splitting under solar light.
    Mots-clés : NASCO, POLE 2.
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  • V. Rajeshkumar, M. Courté, D. Fichou, et M. C. Stuparu, « Synthesis and Properties of Large Polycyclic Aromatic Hydrocarbons with Planar and Non-Planar Structural Motifs », European Journal of Organic Chemistry, vol. 2016, nᵒ 36, p. 6010-6014.
    Résumé : Implementation of non-planar aromatic motifs in the molecular design of π-conjugated materials represents a paradigm shift that is interesting from a fundamental research viewpoint but remains largely underdeveloped. To further facilitate this cause, we report on the synthesis and properties of two large polycyclic aromatic compounds (38 carbon atoms). In one compound the planar π-system pyrene is linked to bowl-shaped hydrocarbon corannulene through a C=C bond, which is referred to as “corannulene–vinylpyrene”. Photochemical treatment of this compound results in annulation of both aromatic nuclei and formation of the other large fused structure with ten six-membered aromatic rings, referred to as “corannulene–benzopyrene”. Photophysical and electrochemical studies reveal that the properties of these two structurally related hybrid materials arise from an extended π-conjugation between the planar and non-planar motifs and varies depending upon their molecular structure.
    Mots-clés : Annulation, Arenes, cyclization, Fused-ring systems, NASCO, POLE 2, polycycles.
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  • V. Rajeshkumar, C. Marc, D. Fichou, et M. C. Stuparu, « Synthesis and Properties of a Buckybowl/Buckyball Dyad », Synlett, vol. 27, nᵒ 14, p. 2101-2104.
    Résumé : Thieme E-Books & E-Journals
    Mots-clés : NASCO, POLE 2.
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  • C. Shen, D. Fichou, et Q. Wang, « Interfacial Engineering for Quantum-Dot-Sensitized Solar Cells », Chemistry – An Asian Journal, vol. 11, nᵒ 8, p. 1183-1193.
    Résumé : Quantum-dot-sensitized solar cells (QDSCs) are promising solar-energy-conversion devices, as low-cost alternatives to the prevailing photovoltaic technologies. Compared with molecular dyes, nanocrystalline quantum dot (QD) light absorbers exhibit higher molar extinction coefficients and a tunable photoresponse. However, the power-conversion efficiencies (PCEs) of QDSCs are generally below 9.5 %, far behind their molecular sensitizer counterparts (up to 13 %). These low PCEs have been attributed to a large free-energy loss during sensitizer regeneration, energy loss during the charge-carrier transport and transfer processes, and inefficient charge separation at the QD/electrolyte interfaces, and various interfacial engineering strategies for enhancing the PCE and cell stability have been reported. Herein, we review recent progress in the interfacial engineering of QDSCs and discuss future prospects for the development of highly efficient and stable QDSCs.
    Mots-clés : nanostructures, NASCO, POLE 2, quantum dots, renewable resources, sensitizers, solar cells.
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2015



  • I. Mínguez-Bacho, S. Rodríguez-López, A. Climent, D. Fichou, M. Vázquez, et M. Hernández-Vélez, « Influence of Sulfur Incorporation into Nanoporous Anodic Alumina on the Volume Expansion and Self-Ordering Degree », The Journal of Physical Chemistry C, vol. 119, nᵒ 49, p. 27392-27400.
    Résumé : Self-ordering degree of anodic alumina nanopores is related to the volume expansion of the aluminum oxide. However, little is known about how the ionic species derived from electrolyte affect parameters inducing self-ordering of the nanopores. The influence of sulfur incorporation into nanoporous anodic aluminum oxide (AAO) films on volume expansion and self-ordering degree has been investigated under potentiostatic conditions (14–25 V) in different sulfuric acid electrolytes (3–20 wt %), the average current densities of each anodization being in the range of 0.1–10 mA cm–2. Rutherford backscattering spectroscopy (RBS) reveals that the incorporation of sulfur species into AAO, as well as the volume expansion factor (VEF), follows a logarithmic dependence on the average current density regardless of the applied voltage and sulfuric acid concentration. The relationship between volume expansion and the S/Al ratio is linear for each concentration of acid in the electrolyte. Furthermore, self-ordering regimes are also revealed for each acid concentration at VEF in the range of 1.50–1.66. We suggest that plasticity, enhanced by sulfur incorporation, counterbalances the high mechanical stress generated by volume expansion, thus inducing new self-ordering regimes. These new regimes are dependent not only on VEF but also on a subtle equilibrium between stress and plasticity of the nanoporous AAO films.
    Mots-clés : NASCO, POLE 2.
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  • I. Minguez-Bacho, M. Courté, H. J. Fan, et D. Fichou, « Conformal Cu2S-coated Cu2O nanostructures grown by ion exchange reaction and their photoelectrochemical properties », Nanotechnology, vol. 26, nᵒ 18, p. 185401.
    Résumé : Cuprous oxide Cu 2 O is a promising p-type semiconductor for photoelectrochemical (PEC) solar hydrogen generation because it has a suitable bandgap ( E g = 2.0–2.2 eV) and a band alignment adapted to water reduction. In addition, metallic Cu is earth-abundant thus making Cu 2 O a low-cost material. However, the reduction potential of Cu 2 O into metallic Cu (0.47 V versus RHE) is lower than that of water which induces a severe instability under irradiation in a PEC cell. Therefore, our recent efforts focused on the growth of a protective overlayer on top of Cu 2 O in order to stabilize Cu 2 O when used as a photocathode in an aqueous electrolyte. Among potential protective materials cuprous sulphide Cu 2 S is another p-type semiconductor with a 1.2 eV bandgap and an appropriate energy level alignment with Cu 2 O that would allow electrons flowing to the interface. We present here an original and simple method aimed at protecting a compact layer (CL) or nanowires (NWs) of Cu 2 O with a Cu 2 S coating. Our method is based on the ions exchange reaction (IER) of O 2− into S 2− at the surface of Cu 2 O itself in a solution-containing Na 2 S as the sulphur source. The local surface IER implies the formation of a conformal and uniform coating independently on the starting Cu 2 O morphology, CLs or NWs. As expected, coating Cu 2 O photocathodes by a conformal Cu 2 S layer improves their stability and PEC performances.
    Mots-clés : NASCO, POLE 2.
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  • I. Mínguez-Bacho, M. Courté, C. Shi, et D. Fichou, « Controlling the nanomorphology of thin conformal Cu2S overlayers grown on Cu2O compact layers and nanowires », Materials Letters, vol. 159, p. 47-50.
    Résumé : Thin conformal Cu2S overlayers are grown on Cu2O compact layers (CLs) and nanowires (NWs) by ion exchange reaction (IER). This method is based on the exchange of O2– into S2– ions at the surface of Cu2O in a solution-containing Na2S acting as the sulfur ions source. The Cu2S overlayers are grown under different experimental conditions by varying the Na2S concentration and the duration of the IER process, thus leading to different Cu2S nanomorphologies. In particular, when a concentration of 2 mM Na2S is used, hexagonal Cu2S nanocrystals are formed on the surface of both Cu2O CLs and NWs. These nanocrystals are of larger size at the ridges of the Cu2O cubes in CLs and at the tips of Cu2O in NWs. The high-quality crystal structure and composition of Cu2S are confirmed by high resolution transmission electron spectroscopy and X-ray photoluminescence spectroscopy.
    Mots-clés : Copper oxide, Copper sulfide, ion exchange reaction, nanomorphology, NASCO, Overlayer, POLE 2.
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2014


  • G. H. V. Bertrand, L. Tortech, V. Gandon, C. Aubert, et D. Fichou, « Synthesis and photovoltaic performances in solution-processed BHJs of oligothiophene-substituted organocobalt complexes [(eta(4)-C-4(nT)(4))Co(eta(5)-C5H5)] », Chemical Communications, vol. 50, nᵒ 63, p. 8663-8666.
    Résumé : We describe an efficient synthetic route toward novel organocobalt complexes [(eta(4)-C-4(nT)(4))Co(eta(5)-C5H5)] with n = 1, 2, 3 thiophene rings. Solution-processed bulk heterojunctions solar cells based on CpCoCb(3T)(4):PCBM blends achieve power conversion efficiencies of up to 2.1%.
    Mots-clés : conversion efficiency, elements, heterojunction solar-cells, MACO, molecules, NASCO, open-circuit voltage, organic semiconductors, oxidation, phthalocyanines, POLE 1, POLE 2, polymers, srtio3.
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  • G. Y. Y. Chng, X. Sun, S. J. Cho, D. Rajwar, A. C. Grimsdale, et D. Fichou, « Synthesis and 2D self-assembly at the liquid-solid interface of novel H-bonding linear pi-conjugated oligomers terminated by uracil and melamine units », New Journal of Chemistry, vol. 38, nᵒ 6, p. 2407-2413.
    Résumé : We report here on the synthesis and 2D self-assembly of novel H-bonding linear it-conjugated oligomers terminated at both ends by either two uracil moieties (compound GR1) or by two melamine groups (compounds GR2 and GR3). The bis(uracil) GR1 compound was prepared by Sonogashira coupling of an ethynyturacil with a dihalobenzene and characterized spectroscopically. The synthesis of GR2 and GR3 was performed by Suzuki coupling of the dihalogenated benzene derivatives leading to the respective bisadducts which were then converted into the target bis-melamine derivatives by treatment with dicyanodimide. Self-assembly of the GR1 derivative is investigated at the liquid/graphite interface using scanning tunneling microscopy (STM). When deposited from n-tetradecane, GR1 forms a row-like structure stabilized by multiple terminal H-bonds between neighboring molecules. Co-adsorption of two n-tetradecane molecules per unit cell is also clearly identified. In turn, when deposited from 1-phenyloctane GR1 forms a complex quasi square-shaped open structure having asymmetric sides. One possible arrangement is that four phenyloctane molecules are co-adsorbed in-between GR1 rows similar to those formed from n-tetradecane, thus forming the two other sides of the square-shaped motif. From both solvents, the row-like 2D arrangements are governed by the multiple terminal H-bonds which create long-range alignments in one direction and by the van der Waals interdigitation of the dodecyl chains of the GR1 molecules that stabilize the network in a nearly perpendicular direction.
    Mots-clés : au(111), devices, graphite, molecular modules, monolayers, NASCO, POLE 2, surfaces, symmetry, trimesic acid.
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  • M. Alaaeddine, Q. Zhu, D. Fichou, G. Izzet, J.E. Rault, N. Barrett, A. Proust, et L. Tortech, « Enhancement of photovoltaic efficiency by insertion of a polyoxometalate layer at the anode of an organic solar cell », Inorg. Chem. Frontiers, vol. 1, nᵒ 9, p. 682-688.
    Résumé : In this article the Wells–Dawson polyoxometalate K6[P2W18O62] is grown as an interfacial layer between indium tin oxide and bulk heterojunction of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The structure of the POM layers depends on the thickness and shows a highly anisotropic surface organization. The films have been characterized by atomic force microscopy and X-ray photoelectron spectroscopy (XPS) to gain insight into their macroscopic organization and better understand their electronic properties. Then, they were put at the anodic interface of a P3HT:PCBM organic solar cell and characterized on an optical bench. The photovoltaic efficiency is discussed in terms of the benefit of the polyoxometalate at the anodic interface of an organic photovoltaic cell.
    Mots-clés : E-POM, NASCO, POLE 2.
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  • E. G. Petrov, A. Marchenko, O. L. Kapitanchuk, N. Katsonis, et D. Fichou, « Conductance Mechanism in a Linear Non-Conjugated Trimethylsilyl-Acetylene Molecule: Tunneling Through Localized States », Molecular Crystals and Liquid Crystals, vol. 589, nᵒ 1, p. 3-17.
    Résumé : The conductance properties of 1,3-(trimethylsilyl)-1-tridecene-6,12-diyne, a non-conjugated trimethylsil-acetylene molecule have been investigated both experimentally and theoretically. Based on scanning tunnelling spectroscopy experiments, a discussion on the mechanisms controlling the charge transfer through this linear molecule is carried out. A specific property of the studied molecule is that it contains localized molecular orbitals. The shifts of the MOs energy levels caused by the applied voltage as well as a distant superexchange coupling between the respective localized MOs are shown to become determining in the formation of a nonlinear hole current through the molecule.
    Mots-clés : Charge transport mechanisms, conductance, current-voltage characteristics, density, devices, electron-transport, energy, junctions, localized states, monolayer, NASCO, organosilane, POLE 2, single-molecule, stm, transmission, wires.
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  • H. Qi, J. Wolfe, D. Wang, H. J. Fan, D. Fichou, et Z. Chen, « Triple-layered nanostructured WO3 photoanodes with enhanced photocurrent generation and superior stability for photoelectrochemical solar energy conversion. », Nanoscale, vol. 6, nᵒ 22, p. 13457-62.
    Résumé : Unique nanorods/nanoparticles/nanoflakes (NRs/NPs/NFs) WO3 triple-layers are grown on a metallic W foil by a simple one-step anodization method. The triple-layered structure is formed through a self-organization process, the film thickness (up to 3 mum) being controlled by the anodization time. A first layer made of an array of WO3 densely-packed vertically-aligned NRs (1.2-1.4 mum in height) grow atop the tungsten foil, followed by a second layer of small NPs (50-80 nm) and finally a third layer made of rectangular NFs (200-300 nm). When irradiated by white light in a photoelectrochemical cell these WO3 triple-layers generate a photocurrent as high as 0.9 mA cm(-2) at 1.2 V/RHE. Moreover, we show that the stability of the triple-layered WO3 photoanodes can be considerably enhanced by adding an ultrathin (10 nm) TiO2 protective overlayer.
    Mots-clés : NASCO, POLE 2.
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  • T. Salim, J. Y. Lek, B. Braeuer, D. Fichou, et Y. M. Lam, « Polymer nanofibers: preserving nanomorphology in ternary blend organic photovoltaics (vol 16, pg 23829, 2014) », Physical Chemistry Chemical Physics, vol. 16, nᵒ 47, p. 26389-26389, 2014.

2013


  • H. Bertrand, R. Guillot, M. - P. Teulade-Fichou, et D. Fichou, « Synthesis, Properties, and Remarkable 2D Self-Assembly at the Liquid/Solid Interface of a Series of Triskele-Shaped 5,11,17-Triazatrinaphthylenes (TrisK) », Chemistry-a European Journal, vol. 19, nᵒ 43, p. 14654-14664.
    Résumé : A series of 5,11,17-triazatrinaphthylene (TrisK) derivatives, large disk-like p-conjugated molecules with C-3h symmetry, has been synthesised by following an optimised synthetic pathway. The synthesis was performed by a four-step protocol based on the N-arylation of 1,3,5-tribromobenzene with appropriate anthranilate derivatives. This strategy permits the generation of either chlorinated (TrisK-Cl-OCn) or non-chlorinated (TrisK-H-OCn) alkoxy-substituted derivatives (OCnH2n+1 with n=3, 10, 12 and 16), thus providing additional versatility in the control of the structure-property relationships. The electronic properties of the various TrisK compounds have been characterised in solution by absorption and emission spectroscopies as well as cyclic voltammetry. The crystal structure of 2,8,14-propyloxy-5,11,17-triazatrinaphthylene TrisK-H-OC3 has been determined by X-ray diffraction analysis, which revealed the presence of stabilising weak intermolecular H bonds. Scanning tunnelling microscopy (STM) at the liquid/solid interface has revealed the remarkable 2D self-assembling properties of the TrisK compounds. In particular, it has shown that TrisK-H-OC12 forms three concomitant self-organised 2D phases with different row-packing arrangements. This 2D polymorphism arises from slow ordering due to the presence of three long dodecyloxy chains on the molecular backbone. Individual molecules can be imaged with spectacular intramolecular resolution, thus providing the possibility of correlating the STM features with the calculated charge density distribution.
    Mots-clés : FICHOU, NASCO, POLE 2.
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  • C. Blouzon, F. Ott, L. Tortech, D. Fichou, et J. - B. Moussy, « Anti-ferromagnetic coupling in hybrid magnetic tunnel junctions mediated by monomolecular layers of alpha-sexithiophene », Applied Physics Letters, vol. 103, nᵒ 4, p. 042417.
    Résumé : We report here on the magnetic coupling taking place between Fe3O4 and Co layers across an organic monolayer of alpha-sexithiophene (6T). The controlled growth of 6T ultrathin films on epitaxial Fe3O4 surfaces allows to prepare highly homogeneous insulating layers with thicknesses in the range 0.5-2.0 monolayers (ML). A combined study using vibrating sample magnetometry and polarized neutron reflectivity reveals that hybrid Fe3O4/6T/Co tunnel junctions show different magnetic couplings depending on the 6T thickness. In particular, magnetic coupling between Fe3O4 and Co layers separated by 1 ML of 6T is consistent with anti-ferromagnetic coupling, opening new perspectives for controlling magnetization in organic spintronic devices. (C) 2013 AIP Publishing LLC.
    Mots-clés : co/ru, FICHOU, NASCO, order, organic semiconductors, POLE 2.
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  • A. Nion, N. Katsonis, A. Marchenko, C. Aubert, et D. Fichou, « Influence of molecular length on the adsorption of linear trimethylsilylacetylene derivatives at the n-tetradecane/Au(111) interface: chemisorption vs. physisorption », New Journal of Chemistry, vol. 37, nᵒ 8, p. 2261-2265, 2013.
    Résumé : Adsorption of two trimethylsilylacetylene (TMSA) derivatives bearing linear alkyl chains of different lengths has been studied at the n-tetradecane/Au(111) interface. The lying or standing orientation of TMSA compounds on the gold surface shows that adsorption is not only controlled by the chemical reactivity of the molecules but also by their size.
    Mots-clés : au(111), COS, FICHOU, Gold, long, MACO, NASCO, organosilane, POLE 1, POLE 2, scanning-tunneling-microscopy, self-assembled monolayers, stm, surfaces.
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  • A. Pancotti, J. Wang, P. Chen, L. Tortech, C. - M. Teodorescu, E. Frantzeskakis, et N. Barrett, « X-ray photoelectron diffraction study of relaxation and rumpling of ferroelectric domains in BaTiO3(001) », Physical Review B, vol. 87, nᵒ 18, p. 184116.
    Résumé : The surface of a ferroelectric BaTiO3(001) single crystal was studied using synchrotron radiation induced x-ray photoelectron diffraction (XPD), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and low-energy electron diffraction (LEED). AFM, XPS, and LEED show that the surface is BaO terminated with a (1 x 1) reconstruction. The Ba 4d, Ti 2p, and O 1s XPD results were compared with multiple scattering simulations for out-of- (P+, P) and in-plane (P-in) polarizations using a genetic algorithm to determine atomic rumpling and interlayer relaxation. Linear combinations of the XPD simulations of the surface structure of each polarization state allow determination of the domain ordering. The best agreement with experiment is found for 55% P+, 38% P-, and 7% P-in. The rumpling is smaller at the surface than in the bulk, suggesting that both domain ordering and surface structural changes contribute to screening of the polarization.
    Mots-clés : NASCO, NSCO, POLE 2, surface.
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2012



  • G. Bertrand, L. Tortech, D. Fichou, M. Malacria, C. Aubert, et V. Gandon, « An Improved Protocol for the Synthesis of [(η4-C4R4)Co(η5-C5H5)] Complexes », Organometallics, vol. 31, nᵒ 1, p. 126-132.
    Résumé : The reaction of bulky alkynes C2R2 with (?5-C5H5)Co(CO)(dimethyl fumarate) under microwave irradiation provides complexes of the type [(?4-C4R4)Co(?5-C5H5)] in good to excellent yields. This protocol represents a significant improvement over those reported previously. In particular, the formation of insertion products such as cyclopentadienones or cyclohexadienes can be avoided. In addition, because of the exceptional stability of (?5-C5H5)Co(CO)(dimethyl fumarate), the reactions can be carried out in crude solvents. The easy access to [(?4-C4R4)Co(?5-C5H5)] complexes stimulated a study of their reactivity, notably under cross-coupling conditions.
    Mots-clés : COS, MACO, NASCO, POLE 1, POLE 2.
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  • D. Rajwar, X. Sun, S. J. Cho, A. C. Grimsdale, et D. Fichou, « Synthesis and 2D self-assembly at the liquid-solid interface of end-substituted star-shaped oligophenylenes », CrystEngComm, vol. 14, nᵒ 16, p. 5182-5187, juill. 2012.
    Résumé : We report here on the synthesis and self-assembly of four star-shaped trigonal 1,3,5-tris-(1,1-biphenyl-4-yl)-benzene (TBB) derivatives substituted by different functional groups on the terminal positions of the three arms of the molecule: COOCH3 (1), COOH (2), NH2 (3), and CN (4). Self-assembly of the tries
    Mots-clés : FICHOU, NASCO, NSCO, POLE 2.
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