Phonon-driven exciton dissociation at donor - Acceptor polymer heterojunctions: direct versus bridge-mediated vibronic coupling pathways

Hiroyuki Tamura, John G.S. Ramon, Eric R. Bittner, Irene Burghardt

    研究成果: Article査読

    35 被引用数 (Scopus)

    抄録

    We present a molecular-level, quantum dynamical analysis of phonon-driven exciton dissociation at polymer heterojunctions, using a linear vibronic coupling model parametrized for 3 electronic states and 24 vibrational modes. Quantum dynamical simulations were carried out using the multiconfiguration time-dependent Hartree method. In this study, which significantly extends the two-state model of Tamura et al. (Tamura, H.; Bittner, E. R.; Burghardt, I. J. Chem. Phys. 2007, 126, 021103), we focus on the role of bridge states, which can mediate the decay of the photogenerated exciton and possibly interfere with the direct transition toward an interfacial charge-separated state. Both the direct and bridge-mediated pathways are found to depend critically on the dynamical interplay of high-frequency C=C stretch modes and low-frequency ring-torsional modes. The dynamical mechanism is interpreted in terms of a hierarchical electron - phonon model, leading to the identification of generalized reaction coordinates for the nonadiabatic process. Variation of the vibronic coupling model parameters in a realistic range provides evidence that the direct exciton decay pathway is not dynamically robust, and bridge-mediated pathways can become dominant. The ultrafast, coherent dynamics is of pronounced nonequilibrium character and cannot be modeled by conventional kinetic equations. The predicted femtosecond to picosecond decay times are consistent with time-resolved spectroscopic observations.

    本文言語English
    ページ(範囲)495-506
    ページ数12
    ジャーナルJournal of Physical Chemistry B
    112
    2
    DOI
    出版ステータスPublished - 2008 1月 17

    ASJC Scopus subject areas

    • 物理化学および理論化学
    • 表面、皮膜および薄膜
    • 材料化学

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