SPECTRAL SENSITIZATION OF SPRAYED N-ZNO ELECTRODE BY ROSE-BENGAL IN NONAQUEOUS PHOTOELECTROCHEMICAL CELL

Photosensitising ability of rose bengal was studied at semiconducting n-ZnO electrode in acetonitrile medium using hydroquinone as supersens itizer. In order to ascertain the exclusive effect of dye sensitizatio n on photocurrent at ZnO electrode, studies have been conducted under filtered light (lambda > 420 nm) illumination also. Energy level diagr am was constructed using redox potentials of rose bengal determined fr om cyclic voltammetric studies (reduction potential = -0.77 V and oxid ation potential = +0.93 V vs SSCE), coupled with the flat-band potenti al of ZnO electrode (V-fb = -0.60 +/- 0.02 V vs SSCE) determined throu gh i(photo)-V curve and redox potential of quinone/hydroquinone (0.45 V). The results indicated that rose bengal can act as donor as well as acceptor type dye. The quantum efficiency of dye-sensitized photocurr ent was found to be similar to 78%. Long-term stability experiments ga ve encouraging results.