A Nanocomposite Gel Electrolyte Made by the Sol-Gel Route for a Solid-State Dye-Sensitized Photoelectrochemical and Elec
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A Nanocomposite Gel Electrolyte Made by the Sol-Gel Route for a Solid-State DyeSensitized Photoelectrochemical and Electrochromic Cells Boris Orel1, Urška Lavrenčič Štangar1, Angela Šurca Vuk1, Panagiotis Lianos2, Philippe Colomban3 1 National Institute of Chemistry, Hajdrihova 19, SI – 1000 Ljubljana, Slovenia 2 Engineering Science Department, University of Patras, 26500 Patras, Greece 3 LADIR UMR 7075 CNRS & Paris VI University, 2 Rue Henry Dunant, 94320 Thiais, France ABSTRACT This work describes the properties of an organic-inorganic hybrid gel with an incorporated I-/I3redox couple that serves as a solid electrolyte for a dye-sensitized TiO2 photoelectrochemical (DSPEC) cell with an efficiency of 4% [1]. The influence of the AcOH on the hydrolysis and condensation reactions of the gels was studied with the help of infrared spectroscopy, while the presence and the formation of the I3- species were established from the UV-visible spectra of the gels and independently evaluated from the confocal micro-resonance Raman spectra of the electrolyte encapsulated in the DSPEC during open- and short-circuit conditions. Finally, the same gel electrolyte was used for the construction of an electrochromic (EC) window without a counter electrode with intercalation properties (transmission and reflective configuration). INTRODUCTION The efficiency of dye-sensitized photoelectrochemical cells (DSPECs) based on TiO2 sensitized with ruthenium bipyridyl dye and a liquid electrolyte containing redox (I-/I3-) species has now reached10%. DSPECs are very competitive devices because they can be constructed in ambient conditions via a soft chemistry route and, as a result, they are relatively cheap. In addition, they can be made semi-transparent and used as a “photovoltaic window”, a property that silicon photovoltaic (PV) cells do not have. The PV cell’s liquid electrolytes, which act as a redox mediator in a DSPEC, create both short- and long-term sealing problems. However, a holetransporting organic material [3], such as a p-type semiconductor deposited on dye-sensitized TiO2 [4] or a thin organic polymer incorporating a redox couple [5], may substitute for the liquid electrolytes. We used sol-gel synthesis to prepare a semi-solid (or gel) electrolyte with a nanocomposite structure in which the organic phase is incorporated and fixed with SiO2 as a gelling agent. Such organically modified silicates (ormosils) and electrolytes (ormolytes) exhibit multifunctional properties combining mechanical stability with optical, electrical and iono-optical properties. In ormosils and ormolytes the inorganic phase is formed by the hydrolysis and condensation of the metal-oxide precursor, while the organic part is either simply embedded in the sol-gel host (class I) or covalently bonded to the inorganic phase (class II) [6]. Various salts and acids have been incorporated in the sol-gel host, but only recently was the class-I ormolyte (tetraethoxy silane/polyethelene oxide) with an incorporated redox species (I-/I3-) prepared [7] and used as an elec
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