Sensitization Processes at Nanocrystalline Semiconductor Electrodes

10 Electron Transfer Processes - Excited Molecules and Semiconductor Electrodes 

This interpretation is supported by the observation that a transient absorption was detected in the near-infrared (1100 nm) [51]. The analysis of these curves yielded an 

As already mentioned above, these investigations were performed in UHV which had the advantage that side-reactions were excluded. Some other investigations have been carried out with the same dye (N3) anchored to Ti02 in ethylene carbonate/pro-pylene carbonate solutions [52]. Tachibana et al. also predicted a fast electron injection ( 15() fs) [52]. They did not measure the intraband absorption, but detected an inter- 

The ultrashort time constants of 25 fs for electron transfer, found by Hannappel et al., indicate a different reaction mechanism for the electron transfer process [53]. The electron transfer occurs more quickly than the vibrational relaxation within the dye molecule, i.e. the electron is transferred from any excitation level directly into a corresponding energy level in the conduction band. Because of this strong coupling, this electron transfer cannot be described by the simple Marcus-Gerischer model which is only valid for comparably weak interactions. 

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