A comprehensive study of the effect of reactive end groups on the charge carrier transport within polymerized and nonpolymerized liquid crystals
A comprehensive study of the effect of reactive end groups on the charge carrier transport within polymerized and nonpolymerized liquid crystals
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DOI：
10.1063/1.2432045
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发表时间：
2007-01-15
影响因子：
3.2
通讯作者：
McCulloch, I.
中科院分区：
文献类型：
--
作者：
Baldwin, R. J.;Kreouzis, T.;McCulloch, I.
可聚合液晶半导体，称为反应性介晶（RM），由具有通过脂肪族间隔基去耦的反应性端基的π-共辄核组成。这些可以在中间相内聚合，保持自组装形态和电荷传输特性。然后，聚合膜可用于有机电子应用，例如有机发光二极管和场效应晶体管中的电荷传输层。我们提出了一个系统的研究的影响，反应性端基的电荷传输在棒状液晶（RM）使用飞行时间技术。合成了几种不同的化合物，其中液晶（LC）介晶核心基团和官能端基都有变化。与非反应性LC中间相传输相比，反应性端基在大多数情况下影响中间相电荷传输。这表现为流动性的降低，从最好情况下的4倍到两个数量级。然而，在最好的系统研究，反应性端基的运输效果，相比非反应性中间相运输，是可以忽略不计的。聚合的反应性介晶保持长程传输，具有与它们在宽温度范围（包括室温）内聚合的相相当的迁移率。空穴和电子迁移率聚合系统中发现的探索使用Holstein小极化子模型在非绝热极限，产生相关的极化子结合能和带宽，并使用Bassler高斯无序模型，产生相关的充满活力的无序参数。(c)2007年，美国物理学会。
Polymerizable liquid crystalline semiconductors, referred to as reactive mesogens (RMs), consist of pi-conjugated cores with reactive end groups decoupled by an aliphatic spacer. These can be polymerized within the mesophase, maintaining the self-assembled morphology and charge transport characteristics. The polymerized films can then be used in organic electronic applications such as charge transport layers in organic light emitting diodes and field effect transistors. We present a systematic study of the effect of reactive end groups on charge transport in calamitic liquid crystals (RMs) using the time-of-flight technique. Several different compounds were synthesized with a variation in both the liquid crystal (LC) mesogenic core group and the functional end groups. The reactive end groups in most cases affect the mesophase charge transport compared to the nonreactive LC mesophase transport. This manifests itself as a reduction in mobility, varying from a factor of 4 in the best case to as large as two orders of magnitude. In the best systems studied, however, the reactive end group effect on the transport, compared to the nonreactive mesophase transport, is negligible. Polymerized reactive mesogens do maintain long-range transport, with comparable mobilities to those of the phase in which they were polymerized over a broad temperature range, including room temperature. The hole and electron mobilities found in polymerized systems are explored using the Holstein small polaron model in the nonadiabatic limit, yielding the relevant polaron binding energies and bandwidths, and using the Bassler Gaussian disorder model, yielding the relevant energetic disorder parameters. (c) 2007 American Institute of Physics.