Nonlocal Electron–Phonon Coupling in Prototypical Molecular Semiconductors from First Principles

Abstract

A substantial amount of evidence indicates a relevant role played by the nonlocal electron-phonon couplings in the mechanism of charge transport in organic semiconductors. In this work, we compute the nonlocal electron-phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained from ab initio methods. We do not make the rigid molecular approximation allowing a mixing of intra- and intermolecular modes, and we use a supercell approach to sample the momentum space. Indeed, we find that some low-frequency intramolecular modes are mixed with the rigid-molecule translations and rotations in the modes with the strongest electron-phonon coupling. To rationalize the results we propose a convenient decomposition of the delocalized lattice modes into molecular-based modes.

Computationally aided design of a high-performance organic semiconductor: the development of a universal crystal engineering core

“…single-point calculation) representation, and that non-local electron-phonon couplings could play an important role in these systems. 62,63 Device performance of computationally selected derivatives Using the information gleaned from the electronic structure calculations, compounds 3b-b and 3b-h were selected and evaluated for their performance in organic eld-effect transistors. Details on device fabrication can be found in the ESI.…”

Electronic Structure, Electron-Phonon Coupling, and Charge Transport in Crystalline Rubrene Under Mechanical Strain

“…Harmonic lattice dynamics calculations were then performed on the unstrained and strained structures to determine the normal modes and the corresponding frequencies according to established procedures based on the numerical evaluation of the Hessian matrix. [34][35][36] Available inelastic neutron scattering data for deuterated naphthalene 37 and theoretical calculations [38][39][40] have shown that the low-frequency (below 200 cm −1 ) phonon modes of molecular crystals feature a pronounced wave vector dependence. The effect of such phonon dispersion on e-ph coupling and on energetic disorder has been addressed only very recently.…”

Impact of Low‐Frequency Vibrations on Charge Transport in High‐Mobility Organic Semiconductors

“…Similarly, DFTB calculations performed in ref. yielded high percentage of the intramolecular motion in the LF vibrational modes of rubrene.…”

“…The main technical challenge in DFT calculations of lattice phonons is relatively large size of the unit cell. As a result, the phonon dispersions have been accurately calculated only recently and only for small π‐conjugated molecules …”

“…Supercell solid‐state DFT calculations of the electron–phonon interaction performed for naphthalene, pentacene and rubrene yielded that acoustic vibrations below 50 cm −1 result in considerable contribution to L , which can be comparable or even exceed the impact of optical vibrations. In ref.…”