Browsing by Author "del Valle, M. A."

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    New Polymers Based on 2,6-di(thiophen-2-yl) aniline and 2,2 '-(thiophen-2,5-diyl) dianiline Monomers. Preparation, Characterization and Thermal, Optical, Electronic and Photovoltaic Properties
    (ESG, 2012) Jessop, I. A.; Zamora, P. P.; Diaz, F. R.; del Valle, M. A.; Leiva, A.; Cattin, L.; Makha, M.; Bernede, J. C.
    A new series of polymers, chemically and electrochemically obtained from monomers containing aniline and thiophene moieties, has been prepared. The purpose is to use them as electron donor layers in the fabrication of dual-layer organic solar cells. Both the monomers and the polymers were characterized using techniques such as NMR, FT-IR, cyclic voltammetry, etc. It was found that polymer growth occurred only through aniline unit(s) and not through thiophene unit(s), as might also be expected. Optical and electronic studies revealed that the products displayed properties suitable for use in photovoltaic devices. However, prepared prototypes yields ranged just between 10(-2) and 10(-3).
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    Nucleation and growth mechanisms during electropolymerization of substituted 3-alkylthiophenes
    (ELSEVIER, 2008) Soto, J. P.; Diaz, F. R.; del Valle, M. A.; Velez, J. H.; East, G. A.
    In the present work the electrochemical study of compounds based on 3-((omega-bromoalkyloxy) methyl) thiophene, varying the length of the alkyl chain between 6 and 12 carbon atoms, is reported. Electropolymerization of the monomers was achieved by potentiodynamic (cyclic voltammetry, CV) and potentiostatic (constant potential) techniques. Voltammograms obtained by CV show that all monomers can be electrochemically oxidized at potentials about 1800 mV to synthesize the respective polymer. Besides, the potential shifts to more anodic potentials on successive scans, increasing thus the resistivity of the material. Nucleation and growth mechanism (NGM) of electropolymerization was investigated by a potentiostatic technique (j-t). Deconvolution of the current-time transient data fitted with a theoretical model suggests that at short times the instantaneous nucleation with two-dimensional growth (IN2D) contribution prevails, followed by an instantaneous nucleation with three-dimensional growth controlled by the charge transfer (IN3Dct) contribution and, finally at longer times, the instantaneous nucleation with three-dimensional growth controlled by diffusion (IN3Ddif) contribution becomes important. The predominance of each contribution to the NGM depends on the monomer being electropolymerized, and the electrolysis time. The morphology predicted from these NGMs fully correlates with that determined by SEM. (C) 2007 Elsevier B.V. All rights reserved.
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    ZnO thin films fabricated by chemical bath deposition, used as buffer layer in organic solar cells
    (ELSEVIER SCIENCE BV, 2009) Lare, Y.; Godoy, A.; Cattin, L.; Jondo, K.; Abachi, T.; Diaz, F. R.; Morsli, M.; Napo, K.; del Valle, M. A.; Bernede, J. C.
    ZnO thin films synthetized by chemical bath deposition are used as buffer layer between the anode and the organic electron donor in organic solar cells. Films deposited from zinc nitrate solutions are annealed in room air at 300 degrees C for half an hour. The X-ray diffraction and microanalysis studies show that ZnO polycrystalline thin films are obtained. The solar cells used are based on the couple copper phthalocyanine as electron donor and (N, N-diheptyl-3,4,9,10-perylenetetracarboxylicdiimide-PTCDI-C7) as electron acceptor. It is shown that the presence of the ZnO buffer layer improves the energy conversion efficiency of the cells. Such improvement could be attributed to a better energy level alignment at the anode/electron donor interface. The anode roughness induced by the ZnO buffer layer can also transform the planar interface organic electron donor/electron acceptor into roughen topography. This increases the interface area, where carrier separation takes place, which improves solar cells performances. (C) 2009 Elsevier B. V. All rights reserved.