SPECTRAL SENSITIZATION OF A SPRAYED ZNO THIN-FILM ELECTRODE BY A NEW SYNTHETIC DYE (2-IMIDAZOLIN-5-ONE) IN ACETONITRILE MEDIUM

A new tailor-made organic dye, namely ethoxy-p-hydroxystyryl-1-phenyl- 2-imidazolin-5-one (subsequently referred to as 2-imidazolin-5-one), h as been studied as a photosensitizer for its application in a photoele ctrochemical cell. Highly n-doped polycrystalline thin ZnO films prepa red by the spray pyrolysis method were used as photoelectrodes and hyd roquinone as the supersensitizer for such investigations. The absorpti on spectrum of the adsorbed dye on a dry ZnO electrode was found to be drastically modified compared with that of dye in solution and this h as been attributed to the strong interaction between dye and ZnO surfa ce and the formation of J-aggregates due to intermolecular hydrogen bo nding. The cyclic voltammogram of the dye at the platinum electrode ex hibited a quasi-reversible anodic peak with formal redox potential E(D /D+)(0) = 1.24 V versus SSCE. The flat band potential of the ZnO elect rode in dye containing acetonitrile solution, V-fb = -0.62 V versus SS CE, was determined from the Mott-Schottky plots. The transient techniq ue was used to monitor the response of a dye-coated ZnO electrode to m onochromatic light. The photocurrent response of a dye-coated ZnO elec trode was found to be extended well into the visible region. The incid ent photon to current conversion efficiency (IPCE) was found to be 3.4 % at the excitation wavelength (480 nm) of the dye.