The efficiency of electron injection from excited N719 dye to nanocrystalline TiO2 films was studied in films with several different dye loads by means of time-resolved microwave conductivity measurements. High-efficiency electron injection was observed in all films. The adsorption data could be fitted to the Langmuir-type isotherm, and the absorption spectra of N719 adsorbed on the TiO2 films did not vary with dye loading. These findings suggest that no dye aggregation occurred on the films even at full coverage condition. (C) 2011 Elsevier B.V. All rights reserved.