Hydrogen-bonding effects on film structure and photoelectrochemical properties of porphyrin and fullerene composites on nanostructured TiO2 electrodes

Hydrogen-bonding effects on film structures and photophysical, photoelectrochemical, and photovoltaic properties have been examined in mixed films of porphyrin and fullerene composites with and without hydrogen bonding on nanostructured TiO2 electrodes. The nanostructured TiO2 electrodes modified with the mixed films of porphyrin and fullerene composites with hydrogen bonding exhibited efficient photocurrent generation compared to the reference systems without hydrogen bonding. Atomic force microscopy, infrared reflection absorption and ultraviolet-visible absorption spectroscopies, and time-resolved fluorescence lifetime and transient absorption spectroscopic measurements disclosed the relationship between the film structures and optical and photoelectrochemical properties relating to the formation of hydrogen bonding between the porphyrins and/or the C-60 moieties in the films on the electrode surface. These results show that hydrogen bonding is a potential methodology for the fabrication of donor and acceptor composites on a nanostructured TiO2 electrode, which exhibits high open circuit potential relative to that of the corresponding SnO2 electrode.