Minimizing the dark current at the dye-sensitized TiO2 electrode

The dark current is one of the major factors limiting the performance of the dye-sensitized nanocrystalline TiO2 photovoltaic cell. It arises from the reduction of I-3(-) at the dye-sensitized TiO2 photoanode. The effects of a number of parameters on the magnitude of the dark current at electrophoretically-deposited electrodes are reported. Propylene carbonate, ethylene carbonate, acetonitrile and mixtures of these were all tested as solvents for the redox couple. With the exception of acetonitrile, which produced a slightly greater dark current, there was little variation in the dark current across the range of solvents tested. Propylene carbonate and ethylene carbonate produced significantly greater photocurrents than acetonitrile. Deoxygenation caused higher dark currents at potentials more reducing than -0.7 V but had little effect on the photocurrent, Oxygenation had no effect on the dark current but did cause a drop in the photocurrent. Degussa P25 TiO2 was the best photocatalyst. Pretreatment of the electrodes with 4-tert-butylpyridine had little effect on the dark current. (C) 1998 Elsevier Science B.V. All rights reserved.