Ultrafast Dynamics and Spectroscopy of Bacterial Photosynthetic Reaction Centers

As an important building block for optoelectronic applications, various chemical modifications at C9-position of fluorene have been proposed to enhance its performance by suppressing the well-known keto effect. In order to identify different substitution effects on the photophysical and charge transport properties of fluorene, we systematically study the electronic structures and photophysical behaviors of fluorene (FR) and its three dimerized counterparts, namely, 9,9 0 -spirobifluorene (SBF), 9,9 0 -bifluorenylidene (BFD), and bis(biphenyl-2-2-diyl)allene (BDA), by employing density functional theory calculations. The changes in bond length alternation indicate that the geometrical relaxations of the fluorene unit in its dimerized derivatives are smaller than FR compound. This fact was further proved by the nonradiative decay rate estimated of the first excited singlet state for each compound. Meanwhile, the vibration relaxation analyses suggest that the bridge between two fluorene fragments plays an important role in the nonradiative decay process. In addition, the injection abilities were evaluated in terms of the ionization potentials and electron affinities, and the carrier transport properties were discussed in the framework of Marcus theory. We find BFD could be a better ambipolar transport material, and BDA can be used as a high-efficient luminescent building unit with excellent hole transport property.

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“…Under the harmonic approximation, the Born-Oppenheimer internal conversion rate k ic can be given as follows [52][53][54]:…”

Section: Computational Methods and Theoretical Methodologymentioning

confidence: 99%

Toward design of high-performance optoelectronic materials: comparative theoretical studies on the photophysical and charge transport properties of fluorene-based compounds

Sun

Geng

et al. 2012

Theor Chem Acc

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“…(2.26) We remark that in the above sum we have 4 terms, i.e., the indices (m, k) are (4,5), (4,6), (5,4) or (6,4), according to Eq. (2.11).…”

Section: The Semiclassical Herman-kluk Propagatormentioning

confidence: 99%

“…Lin and Bersohn 2, 3 set the framework over forty years ago in their seminal papers. A summary of the historical development of the theory may be found in a recent review by Lin et al 4 These studies are though limited to harmonic models for the vibrations in both the ground and excited electronic states. 5 At best, anharmonicity is dealt with using perturbation theory about the harmonic limit as described, for example, in Refs.…”

Section: Introductionmentioning

confidence: 99%

On-the-fly semiclassical study of internal conversion rates of formaldehyde

Ianconescu

Tatchen

Pollak

2013

The Journal of Chemical Physics

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Internal conversion is an inherently quantum mechanical process. To date, "ab initio" computation of internal conversion rates was limited to harmonic based approximations. These are questionable since the typical transition to the ground electronic state occurs at energies which are far from the harmonic limit. It is thus of interest to study the applicability of the Semiclassical Initial Value Representation (SCIVR) approach which is in principle amenable to "on the fly" studies even with "many" degrees of freedom. In this work we apply the Herman-Kluk-SCIVR methodology to compute the internal conversion rates for formaldehyde for a variety of initial vibronic states. The SCIVR computation gives reasonable agreement with experiment, while the harmonic approximation typically gives rates that are too high.

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“…The charge transfer rate formula considering the quantum effects was derived by Jortner [37] and Lin et al [38] It starts from the general Fermi's Golden rule for the transfer rate from the initial state, jii, to the final state, jf i: Here, V fi and " hx fi are the coupling and energy difference between the final and initial state. If we write the contributions of the electronic state and the nuclear vibrational state separately, we get…”

Section: Fermi's Gold Rulementioning

confidence: 99%

Hopping Mechanism

Shuai¹,

Wang²,

Song³

2012

SpringerBriefs in Molecular Science

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In the limit of strong electron-phonon coupling and weak intermolecular electronic coupling, a charged molecule undergoes a large geometry relaxation, which eventually traps the charge. In this case, the charge transport can be viewed as an intermolecular hopping process. With the known electron transfer rates between neighboring molecules, the charge carrier mobility can be evaluated through the Einstein relation from random walk simulations. In general, the classical Marcus electron transfer theory, which works well in the high-temperature limit. For a better understanding, we incorporate the nuclear tunneling effect arising from the intramolecular high-frequency vibrations to characterize the transport behavior at room temperature. Dynamic disorder effect arising from the intermolecular low-frequency vibrations is found to be very much materials structure or space-dimension dependent, which may give rise to the phononassisted current.Keywords Hopping mechanism Á Marcus electron transfer rate Á Random walk simulation Á Temperature dependence of mobility Á Nuclear tunneling Á Dynamic disorder In Sect. 2.1, we describe the general methodology to simulate the hopping mobility using the electron transfer rate formalism. This approach is applied to different organic materials and discussed in Sects. 2.2, 2.3, 2.4. Section 2.5 investigates the nuclear tunneling effect of the intramolecular vibrations, and finally Sect. 2.7 is about the dynamic disorder effect of the intermolecular modes. For each of these improvements, application examples are presented in Sects. 2.6 and 2.8, respectively.Z. Shuai et al.,

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Ultrafast Dynamics and Spectroscopy of Bacterial Photosynthetic Reaction Centers

Cited by 117 publications

References 45 publications

Toward design of high-performance optoelectronic materials: comparative theoretical studies on the photophysical and charge transport properties of fluorene-based compounds

Toward design of high-performance optoelectronic materials: comparative theoretical studies on the photophysical and charge transport properties of fluorene-based compounds

On-the-fly semiclassical study of internal conversion rates of formaldehyde

Hopping Mechanism

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