Interaction between tetrasulfophthalocyanines and colloidal titanium dioxide and photoelectric behavior on sensitized microporous TiO2 electrodes

Strong interaction between sulfophthalocyanines and TiO2 occur when the former is adsorbed on the colloidal TiO2 surface. Upon excitation, electron transfer from excited singlet state of sulfophthalocyanine to the conduction band of TiO2 occurs, leading to the quenching of sulfophthalocyanine fluorescence. Sensitization of the TiO2 microporous electrode with sulfophthalocyanine extends the photoresponse of the electrode to visible and near IR region as shown by the photocurrent spectra. It is indicated that only monomeric sulfophthalocyanine plays a dominant role in the photoresponse of the electrode, while the sulfophthalocyanine aggregates give less or even no contribution to the conversion of visible light into electricity.