Optical and Electrochemical Properties of Self-Organized TiO2 Nanotube Arrays From Anodized Ti−6Al−4V Alloy

Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + β) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + β) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g−1 (34 μAh.cm−2.μm−1) at 1C rate over 50 cycles

Optical and structural properties of undoped ZnO thin films prepared by DC reactive magnetron sputtering

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Effects of oxygen flow rate on the properties of ZnO thin films prepared by DC reactive magnetron sputtering

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Microscopie à effet tunnel des surfaces de GaSe hétéroépitaxié sur Si

GaSe lamellar compound surfaces have been studied using scanning tunneling microscopy (S.T.M.). First, the experimental set-up which have been built is briefly described. S.T.M. images show that the films, deposited by molecular beam epitaxy are nice, except some localised defaults. Images exhibiting atomic resolution are also shown.Des surfaces du composé lamellaire GaSe ont été étudiées par microscopie à effet tunnel (S.T.M.). Le montage expérimental que nous avons construit est tout d'abord brièvement décrit. Les images tunnel montrent que ces couches, déposées sur des surfaces de Si(111) par épitaxie par jets moléculaires, sont de bonne qualité, avec quelques défauts localisés. Des images à la résolution atomique sont également présentées

An efficient tetrazine photoluminescent layer used for organic solar cells down shifting

International audienceThis work reports a new material used as photo luminescent layer in inverted organic solar cells. We have studied the fluorescence and the optical properties of tetrazine molecules included in the layer. The molecules are used at a small to average concentration in a matrix of polymers such as PMMA or Polystyrene, and contain an UV-absorbing moiety acting as an antenna, attached to the yellow-emitting tetrazine. It is therefore able to achieve the down conversion of otherwise useless UV photons into useful yellow photons. The results show that the performances of the inverted organic photovoltaic cells are enhanced by use the luminescent down shifting layer, especially in the UV range

Field Effect Transistors Based on Composite Films of Poly(4-vinylphenol) with ZnO Nanoparticles

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Ag nanoparticle-based efficiency enhancement in an inverted organic solar cell

Herein, we demonstrate the improvement in performance of inverted organic solar cells fabricated with an Ag-nanoparticle (Np) modified ZnO-electron transport layer. Ag NP incorporation into the ZnO layer increases light harvesting efficiency of the solar device which untimely improves Jsc of the device. As a result, power conversion efficiency (PCE) of ZnO + Ag Np buffer layer based (ITO/ZnO:Ag NP/P3HT: PCBM/MoO3/Ag) device reaches 3.02% which is 27% higher than ITO/ZnO/P3HT: PCBM/MoO3/Ag device and 55.6% higher than the electron transfer layer(ETL) free (ITO/P3HT: PCBM/MoO3/Ag) control device

Influence of substrate temperature on delafossite CuFeO2 films synthesized by reactive magnetron sputtering

International audienceDelafossite CuFeO2 films have been synthesized by reactive magnetron sputtering at different substrate temperatures from 380 up to 550 °C. The films adopt the rhombohedral structure from 380 to 550 °C. At the highest temperature, the delafossite phase partially dissociates in FCC Cu and Fe3O4 magnetite phases. In addition to the average crystallite size increase, a change of the preferential orientation in the out-of-plane direction from the [012] to [006] directions occurs between 460 and 510 °C. Modelling of the optical properties shows the presence of 2 interband transitions in the visible range. The 1st main transition at 1.5 eV is ascribed to the absorption component parallel to the c-axis whereas the 2nd transition (2.10 – 2.26 eV) is related to the absorption component in the (a, b) plane. Both evolutions with temperature of the refractive index (~ 2.5) and absorption coefficient (~ 10-3 cm-1) in the infrared suggest the formation of secondary phases. The electronic conductivity, dominated by positive charge carrier, varied from 0.01 to 10 S m-1 according to the preferential orientation and to the presence of secondary phases. A very small amount of a short-range ferromagnetic component (magnetization ~ 10 kA m-1 at 1.5 T) is clearly observed at room temperature thanks to magnetometry confirming the formation of secondary phases undetected by X-ray diffraction. In addition to depend on the film orientation, the presence of secondary phases in weak proportion alters the optical and electrical behaviours such as the transmittance in the visible range.