Characterization of dye-doped TiO2 films prepared by spray-pyrolysis

Thin films of TiO2 were prepared by spray-pyrolysis of titanium(IV)-oxy-acetylacetonate onto indium-tin-oxide glass electrodes. Depending upon the substrate temperature, morphology of the deposited TiO2 films changed from irregular aggregates at 200°C to homogeneous particles with a diameter of 50–100 nm above 400°C. Dye-doping was achieved at the substrate temperature below 260°C by dissolving phthalocyanine or rhodamine molecules into the oxy-acetylacetonate solution. Photoelectrochemical measurements indicated that anodic photocurrents at the wavelength range below 400 nm due to direct excitation of TiO2 increased by formation of homogeneous fine particles at higher temperature. The electrode doped with phthalocyanine exhibited photocurrents in its visible absorption band at 600–700 nm whereas that doped with rhodamine yielded no sensitized photocurrent.