| Abstract
| - We report a transient absorption study of the kinetics of re-reduction of ruthenium bipyridyl dye cationsadsorbed to nanocrystalline TiO2 films by iodide ions, employing a series of RuII(dcbpy)2X dyes, wheredcpby = 4,4‘-dicarboxy-2,2‘-bipyridyl and X = (NCS)2, (CN)2, DTC (diethyldithiocarbamate), and Cl2. Thedata indicate that this re-reduction (or ‘regeneration') reaction proceeds via a transient (dye+−iodide)intermediate complex formed by reaction of photogenerated dye cations with one iodide ion. The subsequentreaction of this complex with a second iodide ion, forming I2-, is shown to be the kinetically andthermodynamically limiting step in the overall regeneration reaction. The implications of this reaction schemefor the function of dye sensitized photoelectrochemical cells are discussed, considering in particular the highphotovoltaic efficiencies obtained for such devices employing such ruthenium bipyridyl senstiser dyes incombination with iodide/tri-iodide based redox electrolytes.
|
