RESUMEN
A new approach for developing solid-state dye-sensitised solar cells (DSSCs) on glass/ITO and plastic substrates (PEN/ITO) is presented in this manuscript. A two step electrodeposition technique has been employed to realize the ZnO photoelectrodes. First a ZnO thin film is deposited on the ITO substrate and subsequently on this buffer layer 650 nm long ZnO nanowires are grown. The different nanostructured electrodes are crystallized and show a transparency close to 80% in the visible spectral range. The electrodes are then sensitized with a new purely organic dye, whose synthesis is presented here, which reveals a wide absorption spectrum and a high molar extinction coefficient. Finally, the sensitized electrodes were employed for the fabrication of liquid and solid-state DSSCs, using, respectively, a liquid iodine/iodide electrolyte and the spiro-OMeTAD hole transporter. These devices represent the first solid-state DSSCs fabricated using electrodeposited zinc oxide nanowires. Their power conversion efficiency is still limited, respectively, 0.18% and 0.03% under standard AM 1.5G sunlight (100 mW cm(-2)), nevertheless, these results prove the interest in this low-temperature deposition method for the realization of nanostructured electrodes on rigid and flexible substrates, and open up new perspectives for the development of solid state DSSCs on plastic substrates.
RESUMEN
A structural phase transition is shown around 400 K for the thermoelectric lamellar misfit cobalt oxide [Ca2CoO3][CoO2]1.62. This transition is related to a rearrangement of the central [CoO] layer of the [Ca2CoO3] slab of this structure, characterized by a commensurate intrinsic modulation q2 = 2/3a*-1/3c*. The partial residual disorder related to split Co and O atomic sites along the misfit b direction disappears and one can describe this layer with its triple chains as a modulated configuration with a regular and not distorted periodicity along b. This phase transition is associated with small changes observed in the transport and magnetic properties as a function of temperature.
RESUMEN
The structure of the thermoelectric lamellar misfit cobalt oxide [Ca(2)CoO(3)][CoO(2)](1.62) was refined again using single-crystal X-ray diffraction data. A new commensurate intrinsic modulation was observed involving a modulation vector orthogonal to the misfit direction ((2/3),0,-(1/3)). The five-dimensional superspace group is C2/m(1delta0)(alpha0gamma)gm and the structure was solved using a commensurate approximation. A new model is given involving an occupation modulation of the split sites of the [CoO] layer. This [CoO] layer can be described by triple chains running along b. The residual disorder along b can then be explained by the assumption of a local ordering with two types of clusters: CoO(2) and Co(5)O(4). A powder neutron diffraction experiment confirmed the ordering evidenced by the single-crystal X-ray diffraction study, but was not sufficient by itself to deal with this double modulated scheme. The new intrinsic modulation is destroyed by partial metal substitutions in the [CoO] layer. The structural modifications of this layer directly influence the physical properties which are related to the electronic structure of the [CoO(2)] layers.
RESUMEN
The structure of the thermoelectric lamellar misfit cobalt oxide [Bi0.84CaO2]2[CoO2]1.69 has been refined using single crystal X-ray diffraction data. Using the four dimensional superspace formalism for aperiodic structures, the superspace group is confirmed P2/m(0delta1/2) (a1 = 4.9069(4), b1 = 4.7135(7), b2 = 2.8256(4), c1 = 14.668(5) A, beta1 = 93.32(1) degrees). The modulated displacements and site occupancies have been refined and are both compatible with the misfit character of the structure, and with a longitudinal modulation of the Bi-O layers of the structure. This modulation is similar to the corresponding one in the related Sr phase [Bi0.87SrO2]2[CoO2]1.82, but now oriented in the orthogonal direction. Because its incommensurate wavelength is locked with the aperiodicity of the misfit structure, it is possible to distinguish between the modulation parameters induced by the accommodation of both subsystems and those related to the longitudinal modulation of the Bi-O layers. In this original structure, two independent aperiodic phenomena coexist in an single crystallographic direction. A particular attention has been paid to the structural configuration of the CoO2 layer, in relation with other similar phases. The thermoelectric properties are probably directly related to the specific distortion of the compressed layer, but the different measured values for the Seebeck coefficient cannot be related to a significant modification of the CoO6 octahedra.
RESUMEN
A new aluminum fluoride, Al(2)F(8).2NC(5)H(6).C(6)H(3)(CO(2)H)(3), was synthesized under mild hydrothermal conditions (200 degrees C, 3 days) in the presence of 1,3,5-benzenetricarboxylic acid (btc) in pyridine/HF (pyr/HF) solvent. Its structure is characterized with single-crystal XRD analysis and high-resolution solid-state NMR. The inorganic framework consists of the corner- and edge-shared connections of AlF(6) octahedra. They are linked via a common edge and form a bioctahedral motif which is trans-connected through the corner-shared fluorine. It results in the formation of an original infinite double file of AlF(6) octahedra running along the a axis. A high-power decoupled MAS (27)Al{(19)F} Hahn echo NMR spectrum allowed us to distinguish the two crystallographic hexacoordinated Al sites. Four unresolved (19)F NMR signals are observed in the MAS spectra to account for the eight crystallographic fluorine atoms. Half of the terminal fluorine sites interact via strong hydrogen bonds with the ammonium groups of the pyridine moieties. The resulting mixed pyridine-fluoroaluminate chains are intercalated by the btc molecules which are hydrogen-bonded to the remaining free terminal fluoride anions through the protonated carboxylic acid function. The (1)H nuclei of both organic molecules are observed in the protonated form.