Porphyrin-modified electrodes for solar energy conversion

Abstract

This mini review presents our recent developments in porphyrin-modified electrodes for solar energy conversion. Various porphyrins have been assembled on nanostructured semiconducting electrodes to achieve efficient photocurrent generation. First, porphyrins have been organized with fullerenes onto semiconducting electrodes to elucidate the relationship between the molecular structures, film structures, and photoelectrochemical properties of the modified electrodes. Formation of hole and electron-transporting highways in the porphyrin/fullerene composite film led to the remarkable enhancement of photocurrent generation. Second, porphyrin-modified single-walled carbon nanotubes have also been assembled onto semiconducting electrodes. The degree of chemical functionalization by the bulky porphyrins was found to have a large impact on the photoelectrochemical properties. Third, asymmetrically π-elongated porphyrins have been successfully employed in dye-sensitized solar cells to improve the cell performance as well as the light-harvesting properties. The power conversion efficiency of the fused porphyrin cell was improved by 50% compared to the reference cell using the corresponding unfused porphyrin. Finally, carboxyquinoxalino derivatives of zinc porphyrin have been further developed to extend the concept of asymmetrically π-elongated porphyrins. The maximum power conversion efficiency of 5.2% was obtained by using 5,10,15,20-tetrakis(2,4,6-trimethylphenyl)-6′-carboxyquinoxalino[2,3-b]porphyrinatozinc(II).