Synthesis of a hemicyanine dye bearing two carboxylic groups and its use as a photosensitizer in dye-sensitized photoelectrochemical cells

Two hemicyanine (aminostilbazium) dyes, one bearing two carboxylic groups w hile the other being its ester analogue, were synthesized for use as photos ensitizers in dye-sensitized photoelectrochemical cells (DSPEC). Only the d ye with carboxylic groups is covalently attached on mesoporous TiO2 films. The ester analogue, however, is physically adsorbed and it is easily washed off by several solvents. DSPECs of the Graetzel type, made of mesoporous T iO2 films (in our case, synthesized through the reverse-micellar route), of the aminostilbazium. bicarboxylate photosensitizer and of a I-/I-3(-)/prop ylenecarbonate electrolyte were tested and were found to yield more than 45 % maximum photon to electron conversion efficiency and 0.72% overall photov oltaic efficiency. The cells yielded a linear response within a wide range of illumination intensities.