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Photoinduced electron transfer processes in dye-semiconductor systems with different spacer groups
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10.1063/1.4746768
/content/aip/journal/jcp/137/22/10.1063/1.4746768
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/22/10.1063/1.4746768

Figures

Image of FIG. 1.
FIG. 1.

The three dye-semiconductor complexes investigated: (a) PeCOOH-(TiO2)60, (b) PeCH=CHCOOH-(TiO2)60, and (c) PeCH2CH2COOH-(TiO2)60.

Image of FIG. 2.
FIG. 2.

Energy-level schemes of the investigated dye-semiconductor complexes: (a) PeCOOH, (b) PeCH=CHCOOH, and (c) PeCH2CH2COOH adsorbed at the (TiO2)60 substrate. From left to right in each subfigure: energy levels of the donor orbitals (obtained from the partitioning procedure) which are localized in the adsorbate, energy levels of the overall complex, and energy levels of the acceptor orbitals (obtained from the partitioning procedure) which are localized in the semiconductor substrate. The selected donor state |ψ d ⟩ as well as the correlations among some energy levels relevant for the ET reaction are indicated.

Image of FIG. 3.
FIG. 3.

Selected localized adsorbate orbitals (as obtained from the partitioning procedure) of the investigated systems (a) PeCOOH-(TiO2)60, (c) PeCH=CHCOOH-(TiO2)60, and (e) PeCH2CH2COOH-(TiO2)60 that are associated with the HOMO of corresponding isolated dye molecules (b) PeCOOH, (d) PeCH=CHCOOH, and (f) PeCH2CH2COOH.

Image of FIG. 4.
FIG. 4.

Selected localized adsorbate orbitals (as obtained from the partitioning procedure) of the investigated systems (a) PeCOOH-(TiO2)60, (c) PeCH=CHCOOH-(TiO2)60, and (e) PeCH2CH2COOH-(TiO2)60 that are associated with the LUMO of corresponding isolated dye molecules (b) PeCOOH, (d) PeCH=CHCOOH, and (f) PeCH2CH2COOH.

Image of FIG. 5.
FIG. 5.

Modulus of donor-acceptor electronic coupling matrix elements V dk (discrete lines) and the decay-width function (continuous line) of (a) PeCOOH-(TiO2)60, (b) PeCH=CHCOOH-(TiO2)60, and (c) PeCH2CH2COOH-(TiO2)60. For each system, the red vertical line indicates the energy of the donor state ɛ d .

Image of FIG. 6.
FIG. 6.

Population dynamics of the donor state after photoexcitation in the investigated systems PeCOOH-TiO2 (black lines), PeCH=CHCOOH-TiO2 (red lines), and PeCH2CH2COOH-TiO2 (blue lines). Shown are results obtained for the finite (TiO2)60 cluster (thick lines) and for the model of an infinite TiO2 surface (thin lines). All results are obtained for a purely electronic model, i.e., neglecting electronic-vibrational coupling.

Image of FIG. 7.
FIG. 7.

Reorganization energies of the intramolecular modes of PeCH2CH2COOH associated with (a) the transition from the ground to the electronically excited state and (b) the ET transition.

Image of FIG. 8.
FIG. 8.

Absorption spectrum of PeCH2CH2COOH-TiO2.

Image of FIG. 9.
FIG. 9.

Vibrational normal modes that are associated with the vibronic structures in the simulated absorption spectrum (Figure 8). The frequencies of the modes are (a) 305 cm−1, (b) 360 cm−1, (c) 1325 cm−1, (d) 1389 cm−1, and (e) 1602 cm−1.

Image of FIG. 10.
FIG. 10.

Population dynamics of the donor state after photoexcitation in PeCH2CH2COOH-TiO2. Shown are results obtained for (a) a finite (TiO2)60 nanocluster and (b) for a model of an extended TiO2 substrate. Both results with vibronic coupling (solid lines) and without vibronic coupling (dashed lines) are depicted.

Image of FIG. 11.
FIG. 11.

Population dynamics of the donor state after photoexcitation in model systems for PeCH2CH2COOH-TiO2 with increased electronic-vibrational coupling in comparison with the dynamics of the original, first-principles-based model (thin solid lines). The models are defined in Table III. Shown are (a) results, where reorganization energies with respect to excitation, ionization, and ET for all modes are scaled by a factor of 2 (model I, thick dashed line) and 4 (model II, thick solid line), respectively, and (b) results, where the excitation reorganization energy (model III, thick solid line) and the ionization reorganization energy (model IV, thick dashed line) for all modes are scaled by a factor of 4, respectively. All results are obtained for an extended TiO2 substrate.

Tables

Generic image for table
Table I.

Characteristic times of the electron injection processes in the investigated systems. The definition of the different time scales is given in the text. All data are given in fs.

Generic image for table
Table II.

Classification of vibronic structures in the absorption spectrum of PeCH2CH2COOH-TiO2 (Figure 8). Listed are the approximate energy difference between each vibronic structure and the 0 → 0 transition, the frequencies of the corresponding vibrational modes as well as their reorganization energies with respect to excitation, ionization and ET, respectively. All data are given in cm−1.

Generic image for table
Table III.

Total reorganization energies with respect to excitation (), ionization (), and ET () of the first-principles-based model as well as the models considered in Figure 11, where the reorganization energies were increased by scaling factors. All data are given in eV.

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/content/aip/journal/jcp/137/22/10.1063/1.4746768
2012-08-23
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photoinduced electron transfer processes in dye-semiconductor systems with different spacer groups
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/22/10.1063/1.4746768
10.1063/1.4746768
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