Exfoliated Clay Nanoplatelets as Gelator and Oxidizing Agent for Ionic Liquid Electrolyte to Enhance Photovoltaic Performance of Dye-Sensitized Solar Cells

摘要

Exfoliated montmorillonite (exMMT) nanoplatelets are a two-dimensional electrolyte carrying ～1.78 dissociable monovalent cations per nanometer square. They were fabricated through soap-free emulsion polymerization of poly(methyl methacrylate) in the presence of MMT. Because the dissociated exMMTs are anionic, they were not only capable of gelatinizing 1-methyl-3-propylimidazolium iodide (MPII) ionic liquid-based electrolyte, but also increased the power conversion efficiency of resulting dye-sensitized solar cell (DSSC) from 6 to 7.77%. Recently, we investigated the ionic conductive mechanism of exMMT-gelled MPII ionic liquid-based electrolyte and found that the exMMTs acted like an oxidizing agent for iodide ions (I~-). As exMMTs were mixed with MPII, I~- ions readily oxidized to I_3~- and even to I_5~- ions by losing the electrons. Consequently, the ionic conductivity was significantly increased due to the fact that I~-, I_3~-, and I_5~- tended to form redox couples that transported faster by way of the Grothus/exchange reaction process.