Dye-Sensitized TiO2 Solar Cells Using Imidazolium-Type Ionic Liquid Crystal Systems as Effective Electrolytes

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• 作者：Noriyo Yamanaka ; Ryuji Kawano ; Wataru Kubo ; Naruhiko Masaki ; Takayuki Kitamura ; Yuji Wada ; Masayoshi Watanabe ; Shozo Yanagida
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：May 10, 2007
• 年：2007
• 卷：111
• 期：18
• 页码：4763 - 4769
• 全文大小：324K
• 年卷期：v.111,no.18(May 10, 2007)
• ISSN：1520-5207

文摘

A novel ionic liquid crystal (ILC) system (C₁₂MImI/I₂) with a smectic A phase used as an electrolyte for adye-sensitized solar cell (DSSC) showed the higher short-circuit current density (J_SC) and the higher light-to-electricity conversion efficiency than the system using the non-liquid crystalline ionic liquid (C₁₁MImI/I₂),due to the higher conductivity of ILC. To investigate charge transport properties of the electrolytes in detail,the exchange reaction-based diffusion coefficients (D_ex) were evaluated. The larger D_ex value of ILC supportedthat the higher conductivity of ILC is attributed to the enhancement of the exchange reaction between iodidespecies. As a result of formation of the two-dimensional electron conductive pathways organized by thelocalized I₃^- and I^- at S_A layers, the concentration of polyiodide species exemplified by I_m^- (m = 5, 7, ...)was higher in C₁₂MImI/I₂. However, as the increment of the concentration of polyiodide species is less thanthat of D_ex, the contribution of a two-dimensional structure of the conductive pathway through the increaseof collision frequency between iodide species was proposed. Furthermore, a quasi-solid-state ionic liquidcrystal DSSC was successfully fabricated by employing a low molecular gelator. Addition of the 5.0 g/Lgelator to ILC improved light-to-electricity conversion efficiency through the increase of J_SC due to theenhancement of the conductivity in C₁₂MImI/I₂-gel.