Improvement in photoelectric conversion of a phthalocyanine-sensitized TiO2 electrode by doping with porphyrin

The effect of doping with tetrasulfonated zinc porphyrin (ZnTsPP) on photoelectric conversion of a nano-structured titanium dioxide (TiO2) electrode sensitized with tetrasulfonated gallium phthalocyanine (GaTsPc) is reported. Doping with ZnTsPP greatly enhances the photocurrent response at long wavelength (the GaTsPc Q band of 640 similar to 760 mm), with 20- and 60-fold improvement of the quantum efficiency at 680 and 700 nm, and results in an improvement of photoelectric conversion for the liquid junction solar cell based on the co-sensitized TiO, electrode, although the photocurrent response in the Soret band of ZnTsPP is markedly decreased with 8-fold drop of the quantum efficiency at 430 nm. This may be attributed to the formation of the Pc/PP heteroaggregates on the nano-structured TiO, electrode, resulting in the decreases of the concentration of GaTsPc dimers and the possible presence of a low-lying charge-transfer state. (C) 1998 Elsevier Science B.V. All rights reserved.