Sensitization of TiO2 and ZnO nanocrystalline films with acriflavine

A comparison of acriflavine sensitized photoelectrochemical cells based on nanocrystalline films of TiO2 and ZnO shows that the short-circuit photocurrent of the latter system is nearly an order of magnitude larger, despite the poor injection efficiency from this dye to ZnO. The above observation and disparity in dark currents in the two systems indicate that recombination of the injected carrier with acceptors in the electrolyte is faster in the TiO2 cell sensitized with the same dye. A study of 1/f noise in the current through acriflavine and N3 dye coated nanocrystalline films of ZnO shows that that acriflavine is more strongly bonded to ZnO and not readily displaced by water molecules, which trap electrons and mediate recombination.