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Impact of Phonon Dispersion on Nonlocal Electron–Phonon Couplings in Organic Semiconductors: The Naphthalene Crystal as a Case Study

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journal contribution
posted on 05.12.2017, 00:00 by Zeyi Tu, Yuanping Yi, Veaceslav Coropceanu, Jean-Luc Brédas
Recent studies point to the impact that the dispersion of both optical and acoustic phonons can have on the nonlocal electron–phonon couplings in organic molecular semiconductors. Here, in order to further elucidate the influence of phonon dispersion, we have calculated the phonon modes in the entire Brillouin zone of the naphthalene crystal. The results demonstrate that the overall nonlocal couplings are underestimated by calculations in which only the phonon modes derived at the Brillouin zone center are considered. Moreover, the contributions of acoustic phonons to the overall strength of nonlocal electron–phonon couplings are calculated to be quantitatively very significant for parallel-stacked dimers, as high as 40% for holes and 47% for electrons.