Influence of dye-adsorption on charge carrier kinetics in TiO2 colloidal systems

Charge carrier kinetics in TiO2 powders and films was analyzed by contactless transient photoconductance (TPC) measurements in the microwave frequency regime. The difference between the behavior of powders and films was relatively small and in both cases an extended decay behavior was observed. A decrease in decay rate of the TPC signal (due to excess electrons) upon dye-sensitization after band-to-band excitation with laser pulses at 355 nm was detected, which was attributed to a reduced recombination rate due to the trapping of excess holes by adsorbed dye molecules. Furthermore, it was found that adsorbed dye molecules are very efficient hole traps. (C) 2012 Elsevier Ltd. All rights reserved.