Computer simulation studies of electrolytes for dye sensitized solar cells

C. PINILLA, M. G. DEL PÓPOLO , J. KOHANOFF AND R. M. LYNDEN-BELL

Paris, France

Congreso; 17th Workshop on Quantum Solar Energy Conversion - (QUANTSOL 2005); 2005

Room temperature molten salts -- or ionic liquids - are liquids composed solely of ionic species, which, at variance with standard inorganic salts, show typically low melting points (263 K to 283 K). Modern ionic liquids are formed by large asymmetric organic cations paired with simpler and smaller inorganic anions. Ionic liquids have been recently used as redox component in the development of dye-sensitized solar cells (Gratzel cell). This cell is based on a thin film of dye-sensitized nanocrystalline TiO2 interpenetrated by the redox medium, whose role is to regenerate the dye after this has transferred an electron to the oxide. The relevance of ionic liquids, in particular those using I- as the anion, is due to the high concentration of charged centers. Experimental evidence suggests that the TiO2 porous microstructure and the charge transport mechanism in the electrolyte affect significantly the efficiency of the cell. Here, through classical computer simulations we study the behavior of the ionic liquid [mmim]+Cl- as a model electrolyte, when it is geometrically confined between two parallel planes, and also in a cylindrical pore, with neutral and charged walls. We present results for the structural properties of the liquid, and also for relevant dynamical properties such as the diffusion coefficient for each atomic species. This study is a first step in the direction of understanding the charge transport process in the redox electrolyte.