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 while the other being its ester analogue, were synthesized for use as photosensitizers in dye-sensitized photoelectrochemical cells (DSPEC). Only the dye with carboxylic groups is covalently attached on mesoporous TiO 2 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 TiO 2 films (in our case, synthesized through the reverse-micellar route), of the aminostilbazium bicarboxylate photosensitizer and of a I - /I 3 - /propylenecarbonate electrolyte were tested and were found to yield more than 45% maximum photon to electron conversion efficiency and 0.72% overall photovoltaic efficiency. The cells yielded a linear response within a wide range of illumination intensities.