Photosensitized growth of TiO2 nanoparticles improved the charge transfer dynamics of a bichromophoric dye

Nanostructured TiO2 particles utilized in dye-sensitized solar cells (DSSCs) provide a large surface area, which facilitates the adsorption of sensitizing dye and charge recombination due to the high density of surface traps. In this article, a modified surface of TiO2 nanoparticles was successfully synthesized in the presence of (1-hydroxycyclohexyl)(phenyl)methanone (HCPM) as a sensitizer to control formation in a toluene/ethanol medium via a photolytic process. A particle-size analysis showed that the oxides which had fully oxidized to TiO2 were 20∼35 nm in diameter. The structure of the TiO2 particles being of an amorphous nature and the nearly defect-free distributions of Ti4+ and O2- energy levels imply that the grain boundaries and surface trap sites were effectively suppressed. TiO2 particles were subsequently blended with the bichromophoric dye, AMIP, to study fluorescence decay dynamics between AMIP/TiO2 interfaces. Fluorescence lifetime measurements gave the rate constant for the charge-transfer process from the excited singlet of AMIP to the conduction band of TiO2 as 1.2×109 s−l. When PL quenching measured as the TiO2 contents of these composites reached a 2.5 wt% level, the maximum enhanced charge-transfer dynamics occurred. Structural properties and photophysical behaviors of composites of AMIP bound to TiO2 were extensively demonstrated.