Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan.
Chemphyschem. 2013 Aug 26;14(12):2750-8. doi: 10.1002/cphc.201300362. Epub 2013 Jul 19.
A liquid-crystalline (LC) phenylterthiophene derivative, which exhibited an ordered smectic phase at room temperature, was purified by vacuum sublimation under a flow of nitrogen. During the sublimation process, thin plates with sizes of 1 mm grew on the surface of the vacuum tube. The crystals exhibited the same X-ray diffraction patterns as the ordered smectic phase of the LC state that was formed through a conventional recrystallization process by using organic solvents. Because of the removal of chemical impurities, the hole mobility in the ordered smectic phase of the vacuum-grown thin plates increased to 1.2×10(-1) cm(2) V(-1) s(-1) at room temperature, whereas that of the LC precipitates was 7×10(-2) cm(2) V(-1) s(-1). The hole mobility in the ordered smectic phase of the vacuum-sublimated sample was temperature-independent between 400 and 220 K. The electric-field dependence of the hole mobility was also very small within this temperature range. The temperature dependence of hole mobility was well-described by the Hoesterey-Letson model. The hole-transport characteristics indicate that band-like conduction affected by the localized states, rather than a charge-carrier-hopping mechanism, is a valid mechanism for hole transport in an ordered smectic phase.
一种液晶苯基噻吩衍生物，在室温下呈现有序的近晶相，通过在氮气流下的真空升华进行纯化。在升华过程中，在真空管的表面上生长出尺寸为 1 毫米的薄片。这些晶体表现出与通过使用有机溶剂进行常规重结晶过程形成的液晶状态的有序近晶相相同的 X 射线衍射图案。由于去除了化学杂质，真空生长的薄片有序近晶相中载流子迁移率在室温下增加到 1.2×10^(-1) cm^(2) V^(-1) s^(-1)，而 LC 沉淀物的载流子迁移率为 7×10^(-2) cm^(2) V^(-1) s^(-1)。在 400 到 220 K 之间，真空升华样品的有序近晶相中载流子迁移率与温度无关。在该温度范围内，载流子迁移率对电场的依赖性也很小。载流子迁移率的温度依赖性很好地符合 Hoesterey-Letson 模型。空穴传输特性表明，受局部态影响的带型传导，而不是载流子跳跃机制，是有序近晶相中空穴传输的有效机制。
