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Coherent electron transport in poly(p-phenylene).

Yukihito Matsuura¹

¹Department of Chemical Engineering, National Institute of Technology, Nara College, 22 Yatacho, Yamato-Koriyama, Nara, 639-1080, Japan. matsuura@chem.nara-k.ac.jp.

Journal of Molecular Modeling

|June 13, 2025

Summary

Doping conductive polymers like poly(p-phenylene) enhances conductance. However, single-molecule charge transport differs from bulk behavior, revealing unique electronic properties at the molecular level.

Keywords:

Coherent electron transport Doped state Landauer approach NEGF-DFT Polyparaphenylene

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Area of Science:

Materials Science
Condensed Matter Physics
Computational Chemistry

Background:

Conductive polymers, such as poly(p-phenylene) (PPP), exhibit polarons and bipolarons in bulk materials.
The behavior of these charged states in single-molecule junctions is not well understood, despite potential deviations from bulk properties.

Purpose of the Study:

To investigate the relationship between charge state (neutral, radical cation, dication) and conductance in single oligo(p-phenylene) molecular junctions.
To compare single-molecule charge transport mechanisms with bulk polymer behavior.

Main Methods:

First-principles calculations using Density Functional Theory (DFT) for geometry optimization.
Non-Equilibrium Green's Function (NEGF)-DFT method with QuantumATK for coherent electron transport calculations across gold electrodes.
Utilized specific functionals (B3LYP, PBE) and basis sets (6-31G(d,p), DZP, SZP) for accuracy.

Main Results:

Significant conductance enhancement was observed upon doping (radical cation and dication states).
The charge transport mechanism in single oligo(p-phenylene) junctions deviates substantially from bulk expectations.
Differences in electronic properties between molecular and bulk systems were highlighted.

Conclusions:

Single-molecule junctions exhibit distinct charge transport mechanisms compared to bulk conductive polymers.
The study underscores the importance of considering molecular-level electronic properties in conjugated systems.
First-principles calculations provide valuable insights into the behavior of charged states in molecular electronics.