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    A New Donor-Acceptor Double-Cable Carbazole Polymer with Perylene Bisimide Pendant Group: Synthesis, Electrochemical, and Photovoltaic Properties
    (John Wiley & Sons Inc, 2009) Koyuncu, Sermet; Zafer, Ceylan; Koyuncu, Fatma Baycan; Aydin, Banu; Can, Mustafa; Sefer, Emre; Ozdemir, Eyup
    We report here electrochemical synthesis of novel soluble donor-acceptor (D-A) polymer with suitably functionalized perylenetetracarboxylic diimide dye derivative covalently linked to carbazole moiety (Cbz-PDI). The band gap, E, was measured using UV-Vis spectroscopy and compared with that obtained by cyclic voltammetry (CV). Efficient intramolecular electron transfer from carbazole-donor to perynediimide-acceptor leads to remarkable fluorescence quenching of the perylene core. Furthermore, spectroelectrochemical property and surface morphology of the polymer film were investigated. Characteristic monoanion and dianion radical bands on the UV-Vis absorption spectra attributed to the electrochemical reduction of the neutral polymer were observed. During the reduction process, red color of the film turned into blue and violet, respectively. Finally, the photovoltaic performance of the D-A double-cable polymer was checked and nearly 0.1% electrical conversion efficiency is obtained under simulated AM 1.5 solar light with 100 mW/cm(2) radiation power. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6280-6291, 2009
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    Öğe
    Quantification of the Effects of Recombination and Injection in the Performance of Dye-Sensitized Solar Cells Based on N-Substituted Carbazole Dyes
    (Amer Chemical Soc, 2010) Barea, Eva M.; Zafer, Ceylan; Gultekin, Burak; Aydin, Banu; Koyuncu, Sermet; Icli, Siddik; Fabregat Santiago, Francisco
    Two new sensitizers for dye sensitized solar cells have been designed consisting of thiophene units asymmetrically functionalized by N-aryl carbazole. The di(tert-butyl) carbazole moieties acts as an electron donor group, the thiophene chain as a bridge group, and the cyanoacrylic acid as an anchoring and electron acceptor group. An increase of the conjugation length produces two main effects: first, it leads to a red-shift of the optical absorption of the dyes, resulting in an improved overlap of the absorption with the solar spectrum. Second, the oxidation potential decreases. The photovoltaic performance of this set of dyes as sensitizers in mesoporous TiO2 solar cells was investigated using electrolytes containing the iodide/triiodide redox couple. The dye with the best absorption characteristics showed the highest photocurrent but lower open circuit voltage due to more losses by recombination. A trend between structure (molecule dyes size) and recombination is demostrated using an analysis procedure based on beta-recombination model that combines impedance spectroscopy and density current-voltage data.