DYE-SENSITIZING EFFECT OF TIOPC THIN-FILM ON N-TIO2(001) SURFACE

Dye-sensitization processes for the (001) surface of n-type titanium o xide (n-TiO2) single crystal coated with vacuum-deposited titanylphtha locyanine (TiOPc) were investigated by means of photoelectrochemical m easurements and X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS). The electrode of n-TiO2 coated with TiOPc exhibited two photoox idation current bands in an aqueous electrolyte including hydroquinone (H(2)Q), due to direct excitation of n-TiO2 below 420 nm and electron transfer from TiOPc to n-TiO2 under the Q-band absorption of TiOPc at 600-800 nm, respectively, The former photocurrent process due to n-Ti O2 excitation was remarkably decreased by presence of surface states, which originated from defects of oxygen induced by Ar ion bombardment of the n-TiO2 surface. The photooxidation process sensitized by the la tter was evaluated from the determined energy levels of electronic ban ds for n-TiO2 and TiOPc. The LUMO level of TiOPc was located 0.3 eV ab ove that of n-TiO2, which enabled electrons to transfer from TiOPc to n-TiO2. The excited state of TiOPc was not quenched by the surface sta tes of n-TiO2 but was efficiently transferred to n-TiO2 at the n-TiO2/ TiOPc interface.