Transient luminescence studies of electron injection in dye sensitised nanocrystalline TiO2 films

We employ fluorescence upconversion spectroscopy to monitor the dynamics of electron injection in tetracarboxyphenyl zinc porphyin (ZnTCPP) sensitised nanocrystalline TiO2 films. A good agreement is found between these measurements and previous studies of electron injection employing transient absorption spectroscopy. In both case, nonexponential kinetics are observed, with electron injection occurring on timescales ranging from < 150 to 100 ps. A simple model, based upon inhomogeneity in electron injection energetics and an exponentially increasing density of acceptor states in the metal oxide, is shown to be good agreement with the observed nonexponential injection kinetics. (C) 2001 Elsevier Science B.V. All rights reserved.