Department of Mechanical Engineering, University of California, 201D Gilman Hall, Berkeley, California 94720-1462, USA.
ACS Nano. 2011 Nov 22;5(11):9256-63. doi: 10.1021/nn203520v. Epub 2011 Oct 31.
The transport properties of a junction consisting of small donor-acceptor molecules bound to Au electrodes are studied and understood in terms of its hybrid donor-acceptor-electrode interfaces. A newly synthesized donor-acceptor molecule consisting of a bithiophene donor and a naphthalenediimide acceptor separated by a conjugated phenylacetylene bridge and a nonconjugated end group shows rectification in the reverse polarization, behavior opposite to that observed in mesoscopic p-n junctions. Solution-based spectroscopic measurements demonstrate that the molecule retains many of its original constituent properties, suggesting a weak hybridization between the wave functions of the donor and acceptor moieties, even in the presence of a conjugated bridge. Differential conductance measurements for biases as high as 1.5 V are reported and indicate a large asymmetry in the orbital contributions to transport arising from disproportionate electronic coupling at anode-donor and acceptor-cathode interfaces. A semi-empirical single Lorentzian coherent transport model, developed from experimental data and density functional theory based calculations, is found to explain the inverse rectification.
研究了由结合在 Au 电极上的小分子给体-受体组成的结的输运性质，并根据其杂化给体-受体-电极界面来理解。一种新合成的给体-受体分子由一个双噻吩给体和一个萘二酰亚胺受体组成，由共轭的苯乙炔桥和非共轭的端基隔开，在反向极化中表现出整流，行为与介观 p-n 结观察到的相反。基于溶液的光谱测量表明，该分子保留了其许多原始组成性质，表明即使在存在共轭桥的情况下，供体和受体部分的波函数之间也存在弱杂化。报道了高达 1.5 V 的偏置的微分电导测量结果，并表明来自阳极-供体和受体-阴极界面的不成比例电子耦合的轨道贡献在输运中存在很大的不对称性。从实验数据和基于密度泛函理论的计算中开发的半经验单洛伦兹相干输运模型被发现可以解释反向整流。
