[Show abstract][Hide abstract] ABSTRACT: Lithium- and erbium-codoped zinc oxide thin films have been successfully
deposited on heated glass substrates using the spray pyrolysis
technique. This study is an investigation of the Li effect on the
enhancement of cathodoluminescent intensity on Er-monodoped ZnO films.
Crystallinity, morphology and luminescence characteristics were
investigated in detail by x-ray diffraction, scanning electron
microscopy and cathodoluminescence. The Li-Er-codoped ZnO films
show a higher intensity of blue and red emissions than the Er-monodoped
ZnO films. The behaviour of that enhancement is attributed to the
modification of the local symmetry of the Er3+ ion, which
increases the intra 4f transition of the Er3+ ion. The blue
and red emissions have an important effect to improve the capacity of
[Show abstract][Hide abstract] ABSTRACT: MoO3/Ag/MoO3(MAM) multilayer structures were deposited by vacuum evaporation on polyethylene terephthalate (PET) substrate.We demonstrate that, as in the case of glass substrate, the sheet resistance of such structures depends significantly on the Ag film deposition rate.When it is deposited between 0.2 and 0.4 nm/s, an Ag thickness of 11 nm allows achieving sheet resistance of 13 Ω/sq and an averaged transmission of 74%. A study of the influence of the PET substrate on the optimumMoO3 thicknesseswas done. A good qualitative agreement between the theoretical calculations of the variation of the optical transmittance of the MoO3/Ag/MoO3 structures is obtained. The optimum MAM structures MoO3 (17.5 nm)/Ag (11 nm)/MoO3 (35 nm) has a factor of merit FM = 4.21 10−3 (Ω/sq)−1. Proven by the scotch test the MAM structures exhibit a good adhesion to the PET substrates. The MAM structures were also submitted to bending tests. For outer bending, the samples exhibit no variation of their resistance value, while for inner bending there is a small increase of the resistance of the MAM structures. However this increasing is smaller than that exhibited by Indium Tin Oxide. When the PET/MAM structures are used as anode in organic photovoltaic cells, it is shown that the need to use thicker Ag films inside themultilayer and to cover theMAMwith Au to obtain promising Current density vs Voltage characteristics is due to the heating of the PET substrate during the deposition process.
Thin Solid Films 10/2013; 545:438-444. DOI:10.1016/j.tsf.2013.07.048 · 2.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The properties of molybdenum trioxide (20 nm)/silver (x nm)/molybdenum trioxide (35 nm) multilayer structures, deposited by simple vacuum evaporation, depend significantly on the deposition rate and on the thickness of the silver layer. If the presence of a commutation from an insulating state to a highly conductive state in these structures is usual, we show that, the thickness of the layer of Ag corresponding to the percolation of the metal paths, decreases from 8 nm to 4 nm when the Ag deposition rate increases from 0.2 nm/s to 0.4 nm/s. The transmission being optimum at 10-11 nm, the calculation of the factor of merit shows that the best structures are obtained for silver films approx. 10 nm thick deposited at a rate between 0.3 nm/s and 0.4 nm/s. When the optimal structures MoO3/Ag/MoO3 are used as anode in planar organic solar cells anode/Cul/CuPc/C-60/Alq3/Al they allow achieving power conversion efficiency of the same order of magnitude than that achieved by reference cells using ITO as anode.
Solar Energy Materials and Solar Cells 10/2013; 117:103-109. DOI:10.1016/j.solmat.2013.05.026 · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: After chemico-physical characterization of CuI thin films, the structures indium tin oxide (ITO) /CuI are systematically studied. We show that the morphology of the 3 nm thick CuI film depends on its deposition rate. To obtain smooth homogeneous CuI film, it is necessary to depose it at 0.005 nm/s. After optimization of the deposition conditions of CuI, it is shown that it behaves like a template for the organic layer. For instance, when the organic film is copper-phthalocyanine, the molecules which are usually perpendicular to the plane of the substrate lie parallel to it when deposited onto CuI. In a same way, when the electron donor is a prophyrin derivative, CuI allows to double the power conversion efficiency of the cells based on the heterojunction porphyrin/C60. When CuI is used as anode buffer layer, it increases systematically the short circuit current, the open circuit voltage, thus the efficiency of the organic solar cell. These effects are related, not only to the improvement of the band matching between the ITO and the electron donor, but also to the templating effect of the CuI. Moreover, we show that the beneficial effect of CuI is effective, not only with ITO, but also with fluorine doped tin oxide.
[Show abstract][Hide abstract] ABSTRACT: We investigate the effect of anode buffer layers (ABLs) on the performances of multi-layer heterojunction solar cells with thienylenevinylene–triphenylamine with peripheral dicyanovinylene groups (TDCV–TPA) as donor material and fullerene C60 as acceptor. The deposition of a CuI layer between the ITO anode and the electron donor significantly improves the short-circuit current density (Jsc) and fill factor (FF) but reduces the open-circuit voltage (Voc). On the other hand, a MoO3 buffer layer increases the Voc but leads to limited Jsc and FF values, thus reducing power conversion efficiency (PCE). In this context, we show that the use of a hybrid anode buffer layer MoO3/CuI leads to a considerable improvement of the cells performances and a PCE of 2.50% has been achieved. These results are discussed on the basis of the dual function of MoO3 and CuI. While both of them reduce the hole injection barrier, CuI improves the conductivity of the organic film through an improvement of molecular order while MoO3 prevents leakage current through the diode. Finally the results of a cursory study of the ageing process provide further support to this interpretation of the effects of the various buffer layers.
Solar Energy Materials and Solar Cells 03/2013; 110:107 - 114. DOI:10.1016/j.solmat.2012.12.003 · 5.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MoO3/Ag/MoO3 (MAM) multilayer structures (layers thickness 20 nm/10 nm/35 nm) are used as anode in CuPc/C60/Alq3/Al organic photovoltaic cells. The averaged transmittance (400 nm-800 nm) of these MoO3/Ag/MoO3 multilayer structures is 70% ± 2% and their sheet resistance is 3.5 ± 1.0 Ω/sq. When these multilayer structures are used as anode, the power conversion efficiency of the MoO3/Ag/MoO3/CuPc/C60/Alq3/Al cells is around 1%, this efficiency is increased of 50% when a thin CuI film (3 nm) is introduced at the interface between the anode and the organic film. This improvement is attributed to the templating effect of CuI on the CuPc molecules.
[Show abstract][Hide abstract] ABSTRACT: An oligothiophene having a donor-acceptor-donor chromophore with
hydrogen bonding groups is used as electron donor in planar
heterojunction organic photovoltaic cells. We focus on the contact
between the anode and the oligothiophene. Different anode buffer layers
(ABLs) have been used, MoO3 and CuI, alone or coupled with
MoO3. The thicknesses were 4 nm and 3 nm for MoO3
and CuI respectively. It is shown that the ABL improves the cells
performances. The best results are achieved with the couple
MoO3/CuI through an increase of the open circuit voltage and
short circuit current. The optical absorption, the surface roughness and
the organic film conductivity depend on the ABL. The conductivity of the
oligothiophene film is one order of magnitude higher when the ABL is a
CuI film. The influence of the ABL can be explained partly by the fact
that it raises the anode work function. Nevertheless, the study of the
structures ITO/ABL/oligothiophene shows that each ABL exhibits specific
advantages and disadvantages. Therefore the couple MoO3/CuI
allows summing up the advantages of both ABLs, MoO3 allows a
very good band matching and avoids too high leakage current, while CuI
allows achieving high Jsc thanks to its effect on the TTB conductivity.
The European Physical Journal Applied Physics 12/2012; 60(3):31302-. DOI:10.1051/epjap/2012120372 · 0.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: form only given. Nonlinear optical properties and photoluminescence behavior of Tin-doped indium oxide (In2O3:Sn) thin films layers were investigate in detail. On heated glass substrates, we deposited these layers at different temperatures 400°C, 450°C and 500°C and different doping agent percentage, by the so called Spray Pyrolysis Technique, the reactive chemical pulverization.
Transparent Optical Networks (ICTON), 2012 14th International Conference on; 01/2012
[Show abstract][Hide abstract] ABSTRACT: Nanocrystalline ZnO:Al thin films were deposited by reactive chemical pulverization spray pyrolysis technique on heated glass substrates at 450°C to study their crystalline structure, composition, strain, stress, roughness characteristics and nonlinear optical susceptibility as a function of Al concentration (0, 2, 3, 5at.%). The films were characterized by X-ray diffractometer (XRD), EDAX 9100 analyser, atomic force microscopy (AFM) and third harmonic generation (THG). The Al (3at.%) doped ZnO thin films exhibited the lower strain/stress than undoped films. The nonlinear properties of the ZnO:Al thin films have been found to be influenced by the films strain/stress.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we investigate NLO properties of ZnO nanostructures for optoelectronics applications. It is shown that carefully designed and fabricated nanostructured ZnO films posses some advantageous for practical use and to generate more and short wavelengths and, when combined with TiO2, produce a core–shell structure that reduces the combination rate. The limitations of ZnO-based DSCs are also discussed and several possible methods are suggested in order to expand the basic knowledge of ZnO to TiO2, motivating further improvement in the power-conversion efficiency of third harmonic generation THG.
[Show abstract][Hide abstract] ABSTRACT: form only given. (Zr -Li) codoped ZnO thin films were grown on heated glass substrates at 450°C by reactive chemical pulverization spray pyrolysis technique. The effect of lithium on the structural, morphological and the nonlinear optical properties of ZnO:Zr thin films was investigated. The X-ray diffraction patterns reveal that the ZnO:(Zr-Li) thin films are polycrystalline in nature, fitting well with a hegxagonal wurtzite structure, and showing the (002) planes as preferential growth in all deposited films. The surface morphology is dependent on the lithium concentration. A decrease, in the nonlinear response of ZnO: (Zr-Li) thin films, was observed comparing with Zr doped ZnO. The susceptibility value χ(3) of codoped films has the same order as undoped films.
[Show abstract][Hide abstract] ABSTRACT: form only given. Lithium and Erbium co-doped Zinc oxide thin films have been successfully deposited on heated glass substrates using spray pyrolysis technique. This study is an investigation of the Li effect on the enhancement of Cathodoluminescent (CL) intensity on the Er-monodoped. Crystallinity, morphology and luminescence characteristics were investigated in detail, by X-Ray Diffraction (XRD); Scanning Electron Microscopy (SEM) and Cathodoluminescent (CL). The Li-Er co-doped ZnO films show higher intensity of blue and red emissions than the Er monodoped ZnO films. The behaviour of that enhancement is attributed to the modification of the local symmetry of the Er3+ ion, which increases the intra 4f transition of Er3+ ion. Li+ ions also can reduce the OH groups in specimen, which is the other reason for enhancing the visible intensities. The blue and red emissions have an important effect to improve the capacity of data storage.
[Show abstract][Hide abstract] ABSTRACT: Aluminum doped zinc oxide (Al-doped ZnO) thin films were deposited by the spray pyrolysis technique onto the glass substrates at 450 °C using anhydrous zinc chloride (ZnCl2) and aluminum chloride (AlCl3) as sources of zinc and aluminum ions, respectively. The effect of [Al]/[Zn] ratio in the solution on the structural, optical, electrical and cathodoluminescence properties of these films were investigated. XRD study revealed that both undoped and Al-doped ZnO films were polycrystalline with hexagonal structure and exhibited (0 0 2) preferential orientation. The optical and electrical studies showed that the film deposited with the [Al]/[Zn] ratio equal to 0.05 had high transmittance (of about 80% and 95% in the visible and near infra-red regions, respectively) and minimum resistivity of 1.4×10−3 Ω cm, respectively. This resistivity value decreased with increase in temperature indicating the semiconducting nature of Al-doped ZnO films. The chemical composition analysis (EPMA) showed that this film was nearly stochiometric with a slight oxygen deficiency.
[Show abstract][Hide abstract] ABSTRACT: The compound 6-methylquinoxalin-2(1H)-one (Q-CH3) was synthesized, and its inhibiting action on the corrosion of mild steel in 1M HCl was investigated by various corrosion-monitoring techniques: electrochemical and weight-loss measurements. Results showed that this compound has fairly good inhibiting properties for steel corrosion in acidic medium, with efficiencies of around 97% at a concentration of 10 M. The protection efficiency of this inhibitor decreases slightly with the rise of temperature, and it is improved with the immersion time.