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Doping and coupling strength in molecular conductors: polyacetylene as a case study
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-11-12 , DOI: 10.1039/d1cp04728k
Carlos M Bustamante 1 , Damián A Scherlis 1
Affiliation  

The doping mechanisms responsible for elevating the currents up to eleven orders of magnitude in semiconducting polymer films are today well characterized. Doping can also improve the performance of nanoscale devices or single molecule conductors, but the mechanism in this case appears to be different, with theoretical studies suggesting that the dopant affects the electronic properties of the junctions. In the present report, multiscale time-dependent DFT transport simulations help clarify the way in which n-type doping can raise the current flowing through a polymer chain connected to a pair of electrodes, with the focus on polyacetylene. In particular, our multiscale methodology offers control over the magnitude of the chemical coupling between the molecule and the electrodes, which allows us to analyze the effect of doping in low and strong coupling regimes. Interestingly, our results establish that the impact of dopants is the highest in weakly coupled devices, while their presence tends to be irrelevant in low-resistance junctions. Our calculations point out that both the equalization of the frontier orbitals with the Fermi level and a small gap between the HOMO and the LUMO must result from doping in order to observe any significant increase of the currents.

中文翻译:

分子导体中的掺杂和耦合强度:以聚乙炔为例

负责将半导体聚合物薄膜中的电流提高到 11 个数量级的掺杂机制如今已得到很好的表征。掺杂还可以提高纳米级器件或单分子导体的性能,但这种情况下的机制似乎不同,理论研究表明掺杂剂会影响结的电子特性。在本报告中,多尺度时间相关 DFT 传输模拟有助于阐明 n 型掺杂可以提高流经连接到一对电极的聚合物链的电流的方式,重点是聚乙炔。特别是,我们的多尺度方法可以控制分子和电极之间化学耦合的大小,这使我们能够分析掺杂在低耦合和强耦合状态下的影响。有趣的是,我们的结果表明掺杂剂的影响在弱耦合器件中是最高的,而它们的存在在低电阻结中往往无关紧要。我们的计算指出,为了观察到电流的任何显着增加,前沿轨道与费米能级的均衡以及 HOMO 和 LUMO 之间的小间隙都必须由掺杂引起。
更新日期:2021-11-30
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