Yamanaka Noriyo, Kawano Ryuji, Kubo Wataru, Masaki Naruhiko, Kitamura Takayuki, Wada Yuji, Watanabe Masayoshi, Yanagida Shozo
Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan.
J Phys Chem B. 2007 May 10;111(18):4763-9. doi: 10.1021/jp0671446.
A novel ionic liquid crystal (ILC) system (C(12)MImI/I(2)) with a smectic A phase used as an electrolyte for a dye-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 (C(11)MImI/I(2)), 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 supported that the higher conductivity of ILC is attributed to the enhancement of the exchange reaction between iodide species. As a result of formation of the two-dimensional electron conductive pathways organized by the localized I(3)- and I- at S(A) layers, the concentration of polyiodide species exemplified by I(m)- (m = 5, 7, ...) was higher in C(12)MImI/I(2). However, as the increment of the concentration of polyiodide species is less than that of D(ex), the contribution of a two-dimensional structure of the conductive pathway through the increase of collision frequency between iodide species was proposed. Furthermore, a quasi-solid-state ionic liquid crystal DSSC was successfully fabricated by employing a low molecular gelator. Addition of the 5.0 g/L gelator to ILC improved light-to-electricity conversion efficiency through the increase of J(SC) due to the enhancement of the conductivity in C(12)MImI/I(2)-gel.
一种新型离子液晶（ILC）体系（C(12)MImI/I(2)），其具有近晶A相，用作染料敏化太阳能电池（DSSC）的电解质，与使用非液晶离子液体（C(11)MImI/I(2)）的体系相比，表现出更高的短路电流密度（J(SC)）和更高的光电转换效率，这归因于ILC具有更高的电导率。为了详细研究电解质的电荷传输特性，评估了基于交换反应的扩散系数（D(ex)）。ILC的D(ex)值较大，这表明ILC的高电导率归因于碘化物物种之间交换反应的增强。由于在S(A)层由局部的I(3)-和I-组织形成二维电子传导途径，在C(12)MImI/I(2)中以I(m)-（m = 5, 7, ...）为例的多碘化物物种的浓度更高。然而，由于多碘化物物种浓度的增加小于D(ex)的增加，因此提出了通过增加碘化物物种之间的碰撞频率来实现传导途径二维结构的贡献。此外，通过使用低分子凝胶剂成功制备了准固态离子液晶DSSC。向ILC中添加5.0 g/L的凝胶剂，由于C(12)MImI/I(2)-凝胶中电导率的提高，通过增加J(SC)提高了光电转换效率。
