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Experimental evidence for sub-3-fs charge transfer from an aromatic adsorbate to a semiconductor


The ultrafast timescale of electron transfer processes is crucial to their role in many biological systems and technological devices. In dye-sensitized solar cells1,2,3,4, the electron transfer from photo-excited dye molecules to nanostructured semiconductor substrates needs to be sufficiently fast to compete effectively against loss processes and thus achieve high solar energy conversion efficiencies4. Time-resolved laser techniques indicate an upper limit of 20 to 100 femtoseconds5,6,7,8,9 for the time needed to inject an electron from a dye into a semiconductor, which corresponds to the timescale on which competing processes such as charge redistribution10,11 and intramolecular thermalization of excited states12,13,14 occur. Here we use resonant photoemission spectroscopy, which has previously been used to monitor electron transfer in simple systems with an order-of-magnitude improvement in time resolution15,16, to show that electron transfer from an aromatic adsorbate to a TiO2 semiconductor surface can occur in less than 3 fs. These results directly confirm that electronic coupling of the aromatic molecule to its substrate is sufficiently strong to suppress competing processes17.

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Figure 1: Geometry of the adsorption structure of bi-isonicotinic acid on TiO2(110).
Figure 2: Relevant processes.
Figure 3: Density-of-states for bi-isonicotinic acid on TiO2(110): experimental monolayer density-of-states, experimental clean substrate occupied density-of-states, theoretical substrate density-of-states, and XAS calculation.
Figure 4: Comparison of RPES and XAS for a bi-isonicotinic acid monolayer.


  1. Hagfeldt, A. & Grätzel, M. Molecular photovoltaics. Acc. Chem. Res. 33, 269–277 (2000)

    Article  CAS  Google Scholar 

  2. Vlček, A. Jr The life and times of excited states of organometallic and coordination compounds. Coord. Chem. Rev. 200–202, 933–977 (2000)

    Article  Google Scholar 

  3. Grätzel, M. Photoelectrochemical cells. Nature 414, 338–344 (2001)

    Article  ADS  Google Scholar 

  4. Miller, R. J. D., McLendon, G. L., Nozik, A. J., Schmickler, W. & Willig, F. Surface Electron Transfer Processes (VCH Publishers, New York, 1995)

    Google Scholar 

  5. Tachibana, Y., Moser, J. E., Grätzel, M., Klug, D. R. & Durrant, J. R. Subpicosecond interfacial charge separation in dye-sensitized nanocrystalline titanium dioxide films. J. Phys. Chem. 100, 20056–20062 (1996)

    Article  CAS  Google Scholar 

  6. Hannappel, T., Burfeindt, B., Storck, W. & Willig, F. Measurement of ultrafast photoinduced electron transfer from chemically anchored Ru-dye molecules into empty electronic states in a colloidal anatase TiO2 film. J. Phys. Chem. B 101, 6799–6802 (1997)

    Article  CAS  Google Scholar 

  7. Asbury, J. B., Hao, E., Wang, Y., Ghosh, H. N. & Lian, T. Ultrafast electron transfer dynamics from molecular adsorbates to semiconductor nanocrystalline thin films. J. Phys. Chem. B 105, 4545–4557 (2001)

    Article  CAS  Google Scholar 

  8. Heimer, T. A., Heilweil, E. J., Bignozzi, C. A. & Meyer, G. J. Electron injection, recombination, and halide oxidation dynamics at dye-sensitized metal oxide interfaces. J. Phys. Chem. A 104, 4256–4262 (2000)

    Article  CAS  Google Scholar 

  9. Benkö, G., Kallioinen, J., Korppi-Tommola, J. E. I., Yartsev, A. P. & Sundström, V. Photoinduced ultrafast dye-to semiconductor electron injection from nonthermalized and thermalized donor states. J. Am. Chem. Soc. 124, 489–493 (2002)

    Article  Google Scholar 

  10. Yeh, A. T., Shank, C. V. & McCusker, J. K. Ultrafast electron localization dynamics following photo-induced charge transfer. Science 289, 935–938 (2000)

    Article  ADS  CAS  Google Scholar 

  11. Tachibana, Y., Haque, S. A., Mercer, I. P., Durrant, J. R. & Klug, D. R. Electron injection and recombination in dye sensitized nanocrystalline titanium dioxide films: A comparison of ruthenium bipyridyl and porphyrin sensitizer dyes. J. Phys. Chem. B 104, 1198–1205 (2000)

    Article  CAS  Google Scholar 

  12. Damrauer, N. H. et al. Femtosecond dynamics of excited-state evolution in [Ru(bpy)3]2+. Science 275, 54–57 (1997)

    Article  CAS  Google Scholar 

  13. Blanchet, V., Zgierski, M. Z., Seideman, T. & Stolow, A. Discerning vibronic molecular dynamics using time-resolved photoelectron spectroscopy. Nature 401, 52–54 (1999)

    Article  ADS  CAS  Google Scholar 

  14. Willig, F., Zimmermann, C., Ramakrishna, S. & Storck, W. Ultrafast dynamics of light-induced electron injection from a molecular donor into the wide conduction band of a semiconductor as acceptor. Electrochim. Acta 45, 4565–4575 (2000)

    Article  CAS  Google Scholar 

  15. Wurth, W. & Menzel, D. Ultrafast electron dynamics at surfaces probed by resonant Auger spectroscopy. Chem. Phys. 251, 141–149 (2000)

    Article  CAS  Google Scholar 

  16. Brühwiler, P. A., Karis, O. & Mårtensson, N. Charge transfer dynamics studied using resonant core spectroscopies. Rev. Mod. Phys. 74, 703–740 (2002)

    Article  ADS  Google Scholar 

  17. Lanzafame, J. M., Palese, S., Wang, D., Miller, R. J. D. & Muenter, A. A. Ultrafast nonlinear optical studies of surface reaction dynamics: Mapping the electron trajectory. J. Phys. Chem. 98, 11020–11033 (1994)

    Article  CAS  Google Scholar 

  18. Nazeeruddin, M. K. et al. Conversion of light to electricity by cis-X2bis(2,2′-bipyridyl-4,4′-dicarboxylate)ruthenium(II) charge transfer sensitizers (X = Cl-, Br-, I-, CN-, and SCN-) on nanocrystalline TiO2 electrodes. J. Am. Chem. Soc. 115, 6382–6390 (1993)

    Article  CAS  Google Scholar 

  19. Rensmo, H. et al. XPS studies of Ru-polypyridine complexes for solar cell applications. J. Chem. Phys. 111, 2744–2750 (1999)

    Article  ADS  CAS  Google Scholar 

  20. Patthey, L. et al. Adsorption of bi-isonicotinic acid on rutile TiO2(110). J. Chem. Phys. 110, 5913–5918 (1999)

    Article  ADS  CAS  Google Scholar 

  21. Persson, P. & Lunell, S. Binding of bi-isonicotinic acid to anatase TiO2(101). Solar Energy Mater. Solar Cells 63, 139–148 (2000)

    Article  CAS  Google Scholar 

  22. Cronemeyer, D. C. Electrical and optical properties of rutile single crystals. Phys. Rev. 87, 876–886 (1952)

    Article  ADS  CAS  Google Scholar 

  23. O'Regan, B. & Grätzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737–740 (1991)

    Article  ADS  CAS  Google Scholar 

  24. Persson, P. et al. N 1s x-ray absorption study of the bonding interaction of bi-isonicotinic acid adsorbed on rutile TiO2(110). J. Chem. Phys. 112, 3945–3948 (2000)

    Article  ADS  CAS  Google Scholar 

  25. Chang, E. K., Rohlfing, M. & Louie, S. G. Excitons and optical properties of alpha-quartz. Phys. Rev. Lett. 85, 2613–2616 (2000)

    Article  ADS  CAS  Google Scholar 

  26. Sandell, A. et al. Bonding of an isolated K atom to a surface: Experiment and theory. Phys. Rev. Lett. 78, 4994–4997 (1997)

    Article  ADS  CAS  Google Scholar 

  27. Lu, H., Prieskorn, J. N. & Hupp, J. T. Fast interfacial electron transfer: Evidence for inverted region kinetic behavior. J. Am. Chem. Soc. 115, 4927–4928 (1993)

    Article  CAS  Google Scholar 

  28. Ramakrishna, S. & Willig, F. Pump-probe spectroscopy of ultrafast electron injection from the excited state of an anchored chromophere to a semiconductor surface in UHV: A theoretical model. J. Phys. Chem. B 104, 68–77 (2000)

    Article  CAS  Google Scholar 

  29. Petersson, Å., Ratner, M. & Karlsson, H. O. Injection time in the metal oxide-molecule interface calculated within the tight-binding model. J. Phys. Chem. B 104, 8498–8502 (2000)

    Article  CAS  Google Scholar 

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We are grateful for financial support to the Consortium on Clusters and Ultrafine Particles and to the ATOMICS Consortium, which are funded by Stiftelsen for Strategisk Forskning, to Göran Gustafssons Stiftelse, and to Vetenskapsrådet. We acknowledge the Swedish National Supercomputer Centre (NSC) for computer time, and the Group for Numerically-intensive Computations of the IBM Research Laboratory Zürich and the Abteilung Parrinello of MPI Stuttgart for help with the calculations.

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Correspondence to Paul A. Brühwiler.

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Schnadt, J., Brühwiler, P., Patthey, L. et al. Experimental evidence for sub-3-fs charge transfer from an aromatic adsorbate to a semiconductor. Nature 418, 620–623 (2002).

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