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Abstract Organic semiconductors with distinct molecular properties and large carrier mobilities are constantly developed in attempt to produce highly‐efficient electronic materials. Recently, designer molecules with unique structural modifications have been expressly developed to suppress molecular motions in the solid state that arise from low‐energy phonon modes, which uniquely limit carrier mobilities through electron–phonon coupling. However, such low‐frequency vibrational dynamics often involve complex molecular dynamics, making comprehension of the underlying electronic origins of electron–phonon coupling difficult. In this study, first a mode‐resolved picture of electron–phonon coupling in a series of materials that are specifically designed to suppress detrimental vibrational effects, is generated. From this foundation, a method is developed based on the crystalline orbital Hamiltonian population (COHP) analyses to resolve the origins—down to the single atomic‐orbital scale—of surprisingly large electron–phonon coupling constants of particular vibrations, explicitly detailing the manner in which the intermolecular wavefunction overlap is perturbed. Overall, this approach provides a comprehensive explanation into the unexpected effects of less‐commonly studied molecular vibrations, revealing new aspects of molecular design that should be considered for creating improved organic semiconducting materials.
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Side-chain torsional dynamics strongly influence charge transport in organic semiconductors
The role of low-frequency (terahertz) vibrational motions on charge carrier dynamics in organic semiconductors (OSCs) is becoming well-known, and efforts are underway to rationally design new materials to mitigate these detrimental effects. However, most efforts have focused on stabilizing the fused-ring semiconducting ‘core’, often by functionalizing with various side-groups, yet questions regarding the role of such modifications on electron–phonon couplings are still outstanding. In this work, the influence of thiophene rings σ-bonded directly to the π-conjugated cores is explored. The manner in which these groups alter low-frequency vibrational, and resulting electronic, dynamics is quantified using a theoretical approach employing fully-periodic density functional theory (DFT) simulations. Ultimately, these results showcase how the equilibrium geometry and corresponding electronic structure are directly related to detrimental electron–phonon coupling, which have important implications for the design of improved organic optoelectronic materials.
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- PAR ID:
- 10405153
- Date Published:
- Journal Name:
- Chemical Communications
- Volume:
- 58
- Issue:
- 92
- ISSN:
- 1359-7345
- Page Range / eLocation ID:
- 12803 to 12806
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D2CC04979A
