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Spatial Separation of Molecular Conformers and Clusters

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Rectifying effect in polar conjugated molecular junctions: a first-principles study.

Jing Huang¹, Qunxiang Li, Zhenyu Li

¹Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China.

Journal of Nanoscience and Nanotechnology

|May 16, 2009

Summary

This study investigates electronic transport in polar conjugated molecules, revealing that increasing molecular length enhances current-voltage asymmetry. Asymmetric coupling further boosts this rectifying effect in molecular junctions.

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Area of Science:

Condensed Matter Physics
Materials Science
Molecular Electronics

Background:

Understanding charge transport in molecular systems is crucial for developing novel electronic devices.
Polar conjugated molecules offer unique electronic properties due to their charge distribution and extended pi-systems.
Molecular length and electrode coupling significantly influence charge transport characteristics.

Purpose of the Study:

To investigate the electronic transport properties of polar conjugated molecules with varying lengths.
To analyze the origin of asymmetric current-voltage (I-V) behavior in molecular junctions.
To explore methods for enhancing the rectifying effect in molecular electronic devices.

Main Methods:

Utilizing a fully self-consistent non-equilibrium Green's function (NEGF) method.
Employing density functional theory (DFT) for electronic structure calculations.
Simulating charge transport through molecular junctions with gold electrodes.

Main Results:

The current-voltage (I-V) curves exhibit a clear asymmetric feature that intensifies with increasing molecular length.
This asymmetry arises from bias-dependent shifts in molecular energy levels and spatial variations in tunneling wave functions.
Introducing asymmetric electrode coupling was shown to further enhance the observed rectifying effect.

Conclusions:

Molecular length is a key factor in controlling the rectification properties of polar conjugated molecules.
The interplay between energy level shifts and wave function asymmetry dictates the observed electronic transport behavior.
Asymmetric coupling provides a viable strategy for optimizing molecular rectifiers.