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Marcus Theory and Long-Range Activationless Transport in Molecular Junctions
Sylvain Pitié1, Yannick J Dappe2, François Maurel1
1Université Paris Cité, ITODYS, CNRS UMR 7086, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France.
Electronic transport in molecular junctions (MJs) is polaron-driven and activationless for oligo(bisthienylbenzene) systems. This contrasts with conjugated oligonaphthalenefluoreneimine wires, revealing new insights into long-range charge transport.
Area of Science:
- Molecular Electronics
- Condensed Matter Physics
- Supramolecular Chemistry
Background:
- Modeling intrachain transport in molecular junctions (MJs) longer than 5 nm traditionally relies on Marcus theory.
- Understanding charge transport mechanisms in conjugated molecular wires is crucial for developing advanced electronic devices.
Purpose of the Study:
- To investigate the mechanism of intrachain electronic transport in oligo(bisthienylbenzene)-based MJs.
- To compare transport characteristics between oligo(bisthienylbenzene) and conjugated oligonaphthalenefluoreneimine systems.
- To propose a new perspective on long-range activationless transport in MJs.
Main Methods:
- Theoretical modeling of intrachain transport using Marcus theory.
- Calculation of polaron localization, reorganization energies (λ), and electronic coupling parameters (H_ab).
- Analysis of activation energy (ΔG*) for charge transport in different molecular junction systems.
Main Results:
- In oligo(bisthienylbenzene) MJs, polarons localized on three monomers (approx. 4 nm) exhibit hopping and tunneling.
- These systems show high reorganization energies (λ ≈ 400-600 meV) and electronic coupling (H_ab ≈ λ/2), leading to near-zero activation energy for transport.
- Conjugated oligonaphthalenefluoreneimine wires exhibit lower electronic coupling (H_ab << λ/2), predicting significant activation energies (≈115 meV).
Conclusions:
- Intrachain transport in specific MJs can be activationless due to polaron dynamics and strong electronic coupling.
- The findings challenge the conventional understanding of transport solely within the tunneling regime for long molecular wires.
- This study offers a new framework for explaining long-range activationless transport in molecular electronic systems.
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