Search

A time-dependent wavepacket diffusion method is proposed to deal with charge transport in organic crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent fluctuations which are generated from the corresponding spectral density functions. The numerical demonstrations reveal that the present approach predicts the consistent charge carrier dynamics with the rigorous quantum approaches. In addition, the diffusion coefficients obtained from the Marcus formula are well reproduced at the weak electronic coupling and high temperature limits. It is also found that the charge mobility feature of the crossover from the band-like to the hopping-type cannot be predicted from the fluctuations induced by the linear electron-phonon interactions with an Ohmic spectral density; however, it indeed appears as the electronic coupling fluctuation exponentially depends on the nuclear coordinates. Finally, it should be noted that although the present approach neglects the imaginary fluctuation, it essentially incorporates the coherent motion of the charge carrier and quantum effect of the phonon motion with a broad regime of the fluctuations for symmetric systems. Besides, the approach can easily be applied to systems having thousands of sites, which allows one to investigate charge transport in nanoscale organic crystals. [ABSTRACT FROM AUTHOR]

Low-lying singlet states and photophysical deactivation pathways of the electronically decoupled 2-(4-cyanophenyl)-N,N-dimethylaminoethane (PCN2NM) have been investigated by the density functional theory and CASSCF/CASPT2 approaches. PCN2NM in the ground state has two dominant configurations of the alkyl-twisted and alky-stretched structures with an interconversion barrier of 2.5 kcal/mol. The predicted vibrationally resolved weak absorption and fluorescence emission of 1(S1-Lb) exhibits clearly well-resolved vibronic features, whereas 1(S1-CT) state corresponding to the redshifted fluorescence has no fine structure. Due to the presence of low-energy 1(S1/S0)CI, radiationless decay of the excited PCN2NM to the ground state is facile, once the excess energy beyond the barrier is available. Present results show reasonable agreement with experimental observations available and provide a basis for understanding of the dual fluorescence of the electronically decoupled species. [ABSTRACT FROM AUTHOR]

A new non-Markovian stochastic Schrödinger equation at finite temperatures is presented to correctly describe charge carrier dynamics in organic molecular crystals. The electron-phonon interactions in both site energies and electronic couplings are incorporated by the time-dependent complex-valued random fluctuations which are generated from corresponding spectral density functions. The approach is thus easily extended to investigate coherent-to-hopping charge transfer in systems with thousands of molecular sites. The capability of present approach is demonstrated by numerical simulations of carrier dynamics in the spin-boson model and a realistic Fenna-Matthews-Olson complex. The results manifest that the non-Markovian effect and complex-valued random forces are essential to guarantee the detailed balance. In an application to a long-chain donor-acceptor system, it is also interesting to find a property of coherent-to-hopping charge transfer from temperature dependence of diffusion coefficients. [ABSTRACT FROM AUTHOR]