Photoelectrochemical cell based on thin film ZnO electrode sensitized by rhodamine B (Rh B) has been studied in acetonitrile medium using hydroquinone as supersensitizer. Redox potentials of Rh B determined cyclic voltammetrically at Pt electrode in acetonitrile, coupled with the flat-band potential of ZnO electrode (obtained from Mott-Schottky plot) have been used to determine their respective energy levels. Stable photovoltage was found to be -260 mV. Quantum efficiency of the sensitized photocurrent at 550 nm wavelength of monochromatic light was found to be 6.5%, the highest ever reported for pure ZnO electrode sensitized by Rh B. Long-term stability of ZnO electrode in the medium of investigation has been tested and quite encouraging results have been obtained.