Mixtures of synthetic organic dyes in a photoelectrochemical cell

Spectroscopic and photoelectric properties of phthalocyanine (Pc), tetranaphtyloporphyrin (TNP) and merocyanine (Me) and their mixtures have been studied. Dyes dissolved in polyvinyl alcohol in dimethylsulfoxide were immersed in a semiconducting/metallic photoelectrochemical cell. Absorption, fluorescence and photoacoustic spectroscopies have been used as methods to follow deactivation pathways of radiative and non-radiative processes of excited states as a competitive processes to charge separation process. The dependence of photovoltage signal on excitation wavelength (photovoltage action spectrum), kinetics of photocurrent rise and decay in second time scale have been presented. Electric parameters of the photoelectrochemical cell with dyes (conductivity, capacitance) and their mixtures in the dark and upon illumination have been estimated. It was shown that all investigated dyes are able to generate photosignal but the values of photocurrent generated were dependent on the dye used in the experiment. The complexity of photoconversion process in the electrochemical cell fulfilled with the dye mixtures has been discussed. The presence of Me dye was found to improve TNP photovoltaic effect, whereas weak enhancement of photoeffects were observed in photoelectrochemical cell based on Me and Pc. This different tetraphenyloporphyrin and Pc conversion effectiveness in the presence of Me was discussed in aspects of various mechanisms of interaction between dyes. It has been indicated that dye aggregation, energy transfer, charge recombination and other processes can lead to improvement or inhibition of the photovoltaic effects and of the conversion effectiveness depending on the composition of dyes embedded in an electrochemical tell. (C) 2001 Elsevier Science B.V. All rights reserved.