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

Area of Science:

• Solid State Physics
• Materials Science
• Organic Electronics

Background:

• Nonlocal electron-phonon couplings are crucial for charge transport in organic semiconductors.
• Understanding these couplings is essential for designing efficient organic electronic devices.

Purpose of the Study:

• To compute nonlocal electron-phonon couplings in rubrene and tetracene.
• To investigate the role of mixed intra- and intermolecular phonon modes.
• To develop a method for decomposing delocalized lattice modes.

Main Methods:

• Utilized ab initio methods to obtain phonon modes.
• Employed a supercell approach for momentum space sampling.
• Avoided the rigid molecular approximation to include mode mixing.

Main Results:

• Identified strong nonlocal electron-phonon couplings in rubrene and tetracene.
• Found that low-frequency intramolecular modes mix with rigid-molecule translations and rotations.
• Observed significant contributions from these mixed modes to electron-phonon coupling.

Conclusions:

• Mixed intra- and intermolecular modes play a critical role in charge transport.
• The proposed decomposition method effectively rationalizes complex lattice modes.
• This work provides fundamental insights into charge transport mechanisms in organic semiconductors.