Dynamics of ultrafast photoinduced heterogeneous electron transfer, implications for recent solar energy conversion scenarios

Gundlach, Lars; Burfeindt, Bernd; Mahrt, J.; Willig, F.

doi:10.1016/j.cplett.2012.07.011

Cited by 12 publications

(12 citation statements)

References 31 publications

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“…The study of excitation and coherence of high-energy vibrational modes in molecular ET systems has a long tradition starting with refinements of Marcus’ classical ET theory by including vibrational quantum modes. , Ulstrup and Jortner predicted oscillatory structures in ET spectra comparable to the Franck–Condon progression in radiative transitions. Their predictions for molecular systems were partly confirmed experimentally by Miller et al , For heterogeneous systems consisting of a molecular donor interfaced with a semiconductor surface, a similar ET spectrum has been predicted by Ramakrishna et al using a fully quantum mechanical (FQM) model that includes the density of states (DOS) of the semiconductor conduction band. , The overall shape of the ET spectrum could be confirmed experimentally; , however, the coherent beating pattern that has also been predicted was not. Coherence and structural dynamics in molecular homogeneous systems as well as their influence on ET dynamics have been discussed since the advent of ultrafast lasers. , For nonadiabatic ET two cases can be distinguished (Figure (a)).…”

Section: Introductionmentioning

confidence: 64%

“…Their predictions for molecular systems were partly confirmed experimentally by Miller et al 4,5 For heterogeneous systems consisting of a molecular donor interfaced with a semiconductor surface, a similar ET spectrum has been predicted by Ramakrishna et al using a fully quantum mechanical (FQM) model that includes the density of states (DOS) of the semiconductor conduction band. 6,7 The overall shape of the ET spectrum could be confirmed experimentally; 8,9 however, the coherent beating pattern that has also been predicted was not. Coherence and structural dynamics in molecular homogeneous systems as well as their influence on ET dynamics have been discussed since the advent of ultrafast lasers.…”

Section: ■ Introductionmentioning

confidence: 75%

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Electronic–Vibrational Coupling and Electron Transfer

2019

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This Feature Article describes our recent work on implementing pump-degenerate four-wave mixing for studying electronic vibrational coupling in solid-state systems and in particular in interfacial electron transfer systems. Interfacial electron transfer (ET) reactions constitute key physical phenomena central to a variety of light-induced energy transport and conversion processes such as vision, photocatalysis, photovoltaics, energy storage, molecular electronics, etc. Heterogeneous material systems like organic/inorganic interfaces are of particular interest due to the variety of possible modifications to their properties. Although ET dynamics has been studied intensively in heterogeneous systems, many questions remain unanswered. The significance of electronic–vibrational coupling and coherence is one aspect that has yet to be fully explored. It is well-known that ET between a molecule and a semiconductor can be accompanied by vibrational excitation due to Franck–Condon overlap of the excited state and cation. The energy necessary for exciting these high-energy vibrational modes is taken from the excess energy of the transferred electron and leads to an ET spectrum. This spectrum carries information that is associated with the vibrational wavepacket that is involved in the ET process, including the coherent beating that results from periodic attempts to overcome the transition state. The dynamics of the wavepacket, and in particular its coherence time, provides insight into the strength of the coupling between electron donor and acceptor states and the adiabaticity of the process. This information is important but not readily available for interfacial ET systems comprising a large number of possible electron acceptor states because neither the rate of the reaction nor the electronic spectrum allows unambiguous assignment. These recent studies give access to vibrational wave packet dynamics triggered by ET reaction and have the potential to allow direct measurement of Huang–Rys parameters and study fundamental properties of interfacial ET like the adiabaticity and the amount of coherenceelectronic and vibrationalin the system.

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Section: Introductionmentioning

confidence: 64%

Section: ■ Introductionmentioning

confidence: 75%

Electronic–Vibrational Coupling and Electron Transfer

2019

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“…Molecular model systems that are designed to satisfy the experimental requirements as well as the computational capabilities are essential for investigating new concepts in IET. Perylene-based sensitizers have proven to be well suited for ultrafast spectroscopic investigations of IET while still being accessible to combined nonadiabatic quantum mechanics/molecular mechanics (QM/MM) simulations. ,− …”

Section: Introductionmentioning

confidence: 99%

Conformational and Binding Effects on Interfacial Electron Transfer from Dual-Linker Sensitizers

et al. 2021

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Interfacial electron transfer (IET) between novel dual-linker perylenes and TiO 2 was investigated by ultrafast spectroscopy and nonadiabatic quantum mechanics/molecular mechanics (QM/MM) simulations. The influence of the number of linkers (one vs two) and their substitution position (ortho vs peri) on IET was investigated. Perylene sensitizers derivatized with two acrylic acid linkers in the peri position, pDtBuPe-(C 2 H 2 COOH) 2 (bis-peri), and in the ortho position, oDtBuPe-(C 2 H 2 COOH) 2 (bis-ortho), were compared to their single-linker counterparts: pDtBuPeC 2 H 2 COOH (peri) and oDtBu-PeC 2 H 2 COOH (ortho). MM simulations of the bis-peri and bisortho sensitizers predicted that, in both cases, only one linker binds covalently to the {101} surface of anatase TiO 2 , while the second one binds weakly via vdW or hydrogen-bonding interactions. Results from QM/MM simulations corroborated experimental injection times for all compounds, thereby supporting single-linker binding to the surface for the dual-linker sensitizers. The study showed that, surprisingly, IET from bis-peri was significantly slower than that from peri. Theory attributes this behavior to small conformational changes caused by steric interactions. The degrees of freedom that are most strongly correlated with variations in IET times were identified by principal component analysis. Comparison between bis-ortho and ortho showed, as expected, that the dual-linker sensitizer injects faster than the single-linker variant. However, the influence of the substitution position on IET was much smaller than expected based on the difference in the static electronic structure. Finally, the strong effect of conformational changes on IET was also observed experimentally in modulations of IET due to coupling to vibrational modes, in excellent agreement with the QM/MM simulations. This study shows that small conformational changes and vibrational coupling can have a significant influence on IET even on the femtosecond time scale. The addition of linkers that differ in bonding strength and serve different functions opens up new avenues for controlling IET dynamics.

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“…The IET dynamics of a related dye molecule, (2,5-di- tert -butylperylen-9-yl)carboxylic acid (DTB-Pe-COOH), was studied in a vacuum by transient absorption (TA) spectroscopy, , and electron transfer time constants τ IET = 13 and 28 fs were measured for carboxylic acid and phosphonic acid as the respective anchor group. These studies also reported that the linear absorption of perylene in the ground and cationic states is modulated by high-energy vibrational modes.…”

Section: Introductionmentioning

confidence: 99%

Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO₂ Surfaces

et al. 2019

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We combine ultrafast transient absorption (TA) spectroscopy and nonadiabatic quantum dynamics simulations to describe the real-time unfold of vibronic effects on the photoabsorption of TiO 2 anatase sensitized with the (perylen-9-yl)carboxylate dye (Pe-COOH/TiO 2 ). The excited state is mapped in time and frequency by ultrafast broadband spectroscopy while atomistic quantum dynamics is used to simulate the self-consistent vibronic effects. The TA map shows the lifetime of the electronic population generated in the S 1 state of the dye and the rise of the absorption D 0 −D 1 of the cation. The theoretical analysis reveals that the electron transfer from perylene into TiO 2 is complete within 20 fs, in agreement with the 12 fs experimental measurement. Because of the structural relaxation produced by the photoinduced electron transfer, the optical gap decreases by 390 meV, in agreement with the D 0 −D 1 transition band. Furthermore, the reorganization energy estimated to be around 220 meV is mostly due to the energy shift of the HOMO level, since the electron transfer occurs in the wide-band limit with little dependence on reorganization energy modes. By assuming the Condon approximation and by making use of the mixed quantum/classical trajectories of the Pe-COOH/TiO 2 system, the absorption spectrum is calculated, and the broad features of the transient absorption spectrum are correlated to excited-state nuclear reorganization effects of the adsorbate dye. The reorganization energy modes are identified by the power spectrum of the velocity autocorrelation function, which shows the occurrence of nonequilibrium modes within the range 1000−1800 cm −1 as in-plane asymmetric C−C vibrations in the perylene dye. The vibrational modes with the strongest influence on the optical gap contribute to shifting the absorption spectrum up in energy by ∼2000 cm −1 . The overall agreement between theory and experiment reveals the capabilities of both methods to study vibronic effects in molecular and extended systems.

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Dynamics of ultrafast photoinduced heterogeneous electron transfer, implications for recent solar energy conversion scenarios

Cited by 12 publications

References 31 publications

Electronic–Vibrational Coupling and Electron Transfer

Electronic–Vibrational Coupling and Electron Transfer

Conformational and Binding Effects on Interfacial Electron Transfer from Dual-Linker Sensitizers

Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO₂ Surfaces

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Dynamics of ultrafast photoinduced heterogeneous electron transfer, implications for recent solar energy conversion scenarios

Cited by 12 publications

References 31 publications

Electronic–Vibrational Coupling and Electron Transfer

Electronic–Vibrational Coupling and Electron Transfer

Conformational and Binding Effects on Interfacial Electron Transfer from Dual-Linker Sensitizers

Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO2 Surfaces

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Product

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Vibronic Effects in the Ultrafast Interfacial Electron Transfer of Perylene-Sensitized TiO₂ Surfaces