obtained by mixing anchoring groups like H2dcbpy (H2dcbpy = 4,4'-dicarboxy-2,2'-bipyridine)
as well as an electron donating and/or protective groups held on the second
bipyridine and a ruthenium photoactive centre (whose properties are intimately
related to surrounding ligands), opened the field of dye molecular engineering
on TiO2. Alkyl chains have been introduced and opened the generation of amphiphilic
heteroleptic ruthenium polypyridyl photosensitisers. The presence of hydrophobic
chains afforded a strong improvement in the stability of solar cells performances
emerging probably from preventing dye desorption.
In a previous
study FTIR data showed unambiguously that such heteroleptic complexes are
chemisorbed on TiO2 surface in bidentate chelation mode using two carboxylate
groups rather than forming an ester type linkage.
The nanocrystalline TiO2 (anatase) films were prepared on conducting glass
using a previously described procedure. The electrodes were heated up to 450°C
and then allowed to cool down before dipping into a dye solution for 20 hours.
The dark red coloured films were tested in photovoltaïc cells with a
redox electrolyte composed by 0.6 M butylmethylimidazolium, 50 mM iodine,
500 mM t-butylpyridine and 100 mM lithium iodide in a 1 to 1 solvent mixture