In this Letter, the electron injection in TiO2 films sensitized with six fluorene sensitizers is studied by femtosecond time resolved fluorescence spectroscopy using nanocrystalline Al2O3 films as reference. The sensitizers are dipolar organic molecules with the fluorene group utilized as a conjugated bridge. The electron injection efficiency is correlated to the structure, conjugation length and excited state potential of the sensitizers. One of the sensitizers has been studied using different amounts of cheno-deoxy cholic acid as co-adsorbent. In order to correlate the efficiency of electron injection with the device performance, quasi solid-state solar cells have been fabricated and characterized. (C) 2013 Elsevier B. V. All rights reserved.