Control of growth and charge transport properties of quaterthiophene thin films via hexyl chain substitutions
Control of growth and charge transport properties of quaterthiophene thin films via hexyl chain substitutions
复制标题
通过己基链取代控制四噻吩薄膜的生长和电荷传输特性
DOI：
10.1016/j.orgel.2003.12.006
复制
发表时间：
2004
影响因子：
3.2
通讯作者：
V. Safarov
中科院分区：
文献类型：
--
作者：
J. Ackermann;C. Videlot;P. Dumas;A. E. Kassmi;R. Guglielmetti;V. Safarov
研究了四噻吩基有机薄膜在Si：H（100）和SiO2衬底上的生长机理。重点研究了链端己基取代对有机薄膜生长过程和电子输运性质的影响。对于基于四噻吩（4 T）和α，ω-己基-四噻吩（DH 4 T）的薄膜，获得了高度结晶的薄膜。虽然未取代的4 T显示出典型的岛状生长，但在DH 4 T基薄膜的情况下发现了几乎完美的层与层生长。可以证明，生长模式的变化与分子结构直接相关，即与4 T核上己基链取代的存在直接相关，并且导致在相同蒸发条件下在DH 4 T膜的情况下晶粒尺寸增加一个数量级。基于这两种分子的薄膜的电荷传输特性的表征揭示了DH 4 T分子的一个数量级更高的迁移率。通过使用一个简单的多晶材料中的电荷输运模型，可以证明迁移率对晶粒尺寸的线性依赖性，与分子取代无关。结果强调了薄膜形态控制的重要性，并给出了一个令人印象深刻的例子，这种控制的情况下，己基端取代的quaterthiophene。
Growth mechanism of quaterthiophene based organic thin films deposited by high vacuum deposition on Si:H(100) and SiO2substrates have been investigated. Especially the influence of hexyl chain end-substitutions on the growth process and the electronic transport properties of organic thin films were studied in details. Highly crystalline films were obtained for both quaterthiophene (4T) and α,ω-hexyl-quaterthiophene (DH4T) based thin films. While unsubstituted 4T shows a typical island growth, an almost perfect layer-to-layer growth was found in the case of DH4T based films. It could be demonstrated that the change in the growth mode is directly related to the molecule structure, i.e. to the presence of hexyl chain substitutions on the 4T core, and leads to an increase of the grain size of one order of magnitude under the same evaporation conditions in the case of DH4T films. The characterization of the charge transport properties of thin films based on both molecules reveals one order of magnitude higher mobilities for the DH4T molecules. By using a simple model for charge transport in polycrystalline materials a linear dependence of the mobility on the grain size, independently from the molecule substitution, could be demonstrated. The results underline the importance of the control of the film morphology and give an impressive example of such a control in the case of hexyl end-substitutions of quaterthiophene.