Kinetics of Electron Transfer between Dye and Semiconductor Electrode

Kinetics of Electron Transfer between Dye and Semiconductor Electrode 

Since the latter virtually disappeared at low coverages, this component was ascribed to the weakly adsorbed dye molecules. 

The shorter decay (instrument limited) was attributed to the fluorescence from adsorbred molecules strongly coupled to the surface, indicating that the electron transfer rate is much faster than 40 ps. In order to get a more accurate value for the injection rate, the integrated fluorescence intensities of the fast component of the sensitized semiconductor decay curve were compared with the intensity of the oxazine on the tape reference sample [47]. This analysis yielded a quenching factor of about 10 . From this an electron injection rate of 3 X 10 s , corresponding to an electron transfer time of around 40 fs, was obtained. 

The same authors also investigated the bleaching and recovery of the ground state of the dye after a 1-ps laser excitation [47]. Since these experiments were performed under open-circuit conditions, all the electrons transferred from the excited dye into the conduction band of SnS2 had to return to the oxidized dye. The corresponding ground state recovery was found to occur within about 10 ps. Other investigations on transfer rates will be discussed in Section 10.2.7. 

The decay rate of dye molecules adsorbed at the surface is given by 

10 Electron Transfer Processes - Excited Molecules and Semiconductor Electrodes 

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