Porphyrin dyes for TiO2 sensitization

Abstract

A series of six new free base porphyrins were synthesized for use as photosensitizers in TiO 2 dye-sensitized photo-electrochemical cells. The porphyrin sensitizers are attached to the TiO 2 photoelectrode by phosphonic or carboxylic acid anchoring groups. These anchoring groups were placed on different substitution positions on the porphyrin moiety. The new dyes were fully characterized by absorption and emission spectroscopies, electrochemistry and photo-electrochemical spectroscopy. The photo-electrochemical performances of the sensitizers are discussed and compared to the known 5,10,15,20-tetra(4-carboxyphenyl)porphyrin sensitizer. In this study, we show that the nature of the anchoring group (phosphonic or carboxylic acids) has little impact on the photo-electrochemical performance of the cell. However, the substitution position of the anchoring group on the porphyrin strongly influences the monochromatic photon-to-electron conversion efficiency of the resulting cell. The results indicate that the electronic coupling of this type of dye with the d-band of the semiconductor is one of the key parameters in the design of efficient sensitizers.

Effect of the anchoring group in porphyrin sensitizers: phosphonate versus carboxylate linkages

“…Odobel and coworkers have prepared a series of porphyrins sensitizers (28)(29)(30)(31)(32) where the phosphonic group was the anchoring entity (Scheme 8).…”

Survey of Synthetic Routes towards Phosphorus Substituted Porphyrins

“…[23] This synthesis based on the classical condensation of pyrrole with the corresponding aldehyde under Adler conditions has been then described by Odobel and coworkers to form porphyrin (Scheme 6). [24] The meso-tetraarylporphyrins 10 have been prepared by condensation of pyrrole with the para-and meta-phosphoryl substituted benzaldehydes, while the trans-porphyrin A 2 B 2 11 was obtained through the MacDonald [2+2] condensation of 5-phenyl-dipyrromethane with the functionalized benzaldehyde (Scheme 7). [24] It has to be noted that the functionalized benzaldehydes were prepared by Hirao's reaction.…”

“…[24] The meso-tetraarylporphyrins 10 have been prepared by condensation of pyrrole with the para-and meta-phosphoryl substituted benzaldehydes, while the trans-porphyrin A 2 B 2 11 was obtained through the MacDonald [2+2] condensation of 5-phenyl-dipyrromethane with the functionalized benzaldehyde (Scheme 7). [24] It has to be noted that the functionalized benzaldehydes were prepared by Hirao's reaction. Protection of the aldehyde group is needed to obtain the target precursors under these conditions in good yields.…”

The Basic Research on the Dye-Sensitized Solar Cells (DSSC)

“…Several metal complexes and organic dyes have been synthesized and used as sensitizers including porphyrins [10], platinum complex [11] and others. Ru-based complexes sensitizers have been widely used because they have better efficiency and high durability.…”