title: Evaluation of Surface State Mediated Charge Recombination in Anatase and Rutile TiO2.
abstract: In nanostructured thin films, photogenerated charge carriers can access the surface more easily than in dense films and thus react more readily. However, the high surface area of these films has also been associated with enhanced recombination losses via surface states. We herein use transient absorption spectroscopy to compare the ultrafast charge carrier kinetics in dense and nanostructured TiO2films for its two most widely used polymorphs: anatase and rutile. We find that nanostructuring does not enhance recombination rates on ultrafast time scales, indicating that surface state mediated recombination is not a key loss pathway for either TiO2polymorph. Rutile shows faster, and less intensity-dependent recombination than anatase, which we assign to its higher doping density. For both polymorphs, we conclude that bulk rather than surface recombination is the primary determinant of charge carrier lifetime.
authors: Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2AZ, U.K.
authors: Michael
authors: M
authors: Sachs
authors: Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2AZ, U.K.
authors: Ernest
authors: E
authors: Pastor
authors: Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, U.K.
authors: Andreas
authors: A
authors: Kafizas
authors: Department of Chemistry, Imperial College London , South Kensington Campus, London SW7 2AZ, U.K.
authors: James R
authors: JR
authors: Durrant