噻吩层状柱状相液晶：合成，载流子迁移速率与器件性能

Liquid crystalline (LC) semiconductor is a novel organic semiconductor and it plays an important role in organic electronics. LC semiconductors possess good solubility in common organic solvents, spontaneously alignment to ordered mesophase structures, self-healing of the structural defects, fast charge carrier mobility, low-cost device fabrication by spin-coating, drop-casting, or ink-jet printing techniques, large area flexible device on plastic substrate. Thiophene is an important heterocyclic arene, thiophene-containing organic semiconductors display high charge carrier mobility due to the S-atom orbital extension and enhanced intermolecular interaction by overlapped staking . .In order to get liquid crystalline materials with high charge carrier mobility of 10 cm2/(Vs), we will focus our research on following novel concept and ideas: by using C-H bond activation and oxidative coupling, Suzuki cross-coupling, Scholl reaction to synthesis thiophene-containing discotic LCs with highly ordered lamello-columnar mesophase for fast charge carrier mobility (charge mobility will be measured by time-of-flight, TOF technique) and good performance in electronic devices; Benzothienobenzothiophene (BTBT) derivatives substituted by electron-withdrawing perfluorobenzene for high ordered layered phase (SmE or Lam phase) and fast charge carrier mobility, and charged carriers changed from holes (p-type) to electrons (n-type), solution fabrication of organic field effect transistors (OFET), comparing the mobility value of TOF and OFET; Triphenylene-thiophene oligomers and plymers for lamello-columnar mesophase and high charge carrier mobility (TOF and OFET) and their performance in solar cells. The mesophase structures will be studied by small angel X-ray scattering (SAXS), atomic force microscopy (AFM), and 2D interface structure will be imaged by high resolution scanning tunneling microscopy (STM). The investigation of LC semiconducting molecular designing, facile synthesis, and self-organization to highly ordered mesophase, fast charge carrier mobility, and good optoelectronic device performance, which are all included in this project, are important to the development of material science and organic electronics.

液晶半导体是一类新型有机半导体材料，在有机电子学领域占有重要地位。液晶半导体化合物在有机溶剂中良好的溶解性，自组装形成有序介晶相，结构缺陷可自修复，有高的载流子迁移速率，可通过旋涂或打印等方式加工成低成本大面积柔性电子器件。噻吩是重要的杂环芳烃，并噻吩稠环芳烃硫原子轨道离域致使分子间轨道更有效重叠，分子间相互作用增强，有利于载流子分子间跃迁。为获得迁移速率大于10cm2/(Vs)的液晶材料，本项目创新性地采用碳-氢键活化/芳烃亲核取代，Suzuki和Scholl氧化环化等，构建系列噻吩盘状液晶，研究其自组装相态、电荷迁移率与器件性能；全氟苯基取代苯并噻吩并苯并噻吩及聚合物液晶相态、作为n-型半导体的电子传输性能与薄膜晶体管器件；并噻吩桥连苯并菲盘状液晶多聚体和共轭聚合物，考察其自组装相态及在场效应晶体管、太阳能电池中的应用。本项目对材料科学和有机电子学有重要学术意义与应用价值。

液晶具有晶体的部分有序性、同时具有高分子材料的可溶液加工和成膜性，是一类性能独特的有机半导体材料，在有机薄膜光电子器件中有良好的应用前景。噻吩是化学性质活泼的富电子芳烃，硫原子半径较大、有利于分子间面对面pi-pi堆积和分子间电荷载流子跃迁和传输，是有机半导体材料中不可或缺的芳环结构。本项目成功开发出新试剂四烷氧基联苯溴及其联苯硼酸酯，它们可以与商品试剂卤代芳烃或硼酸进行Suzuki-Miyaura交叉偶联反应、再串联三氯化铁Scholl氧化芳烃脱氢环化反应，一步构建多个芳烃C-C单键，高效合成了结构丰富多变的新型稠环芳烃盘状液晶。我们成功将噻吩、并二噻吩、并三噻吩，二噻吩并环戊酮、二噻吩并苯、二噻吩并醌、咔唑、芴、芴酮、萘和苝亚胺等功能单元通过上述反应、构建了多系列蝴蝶型柱相液晶和盘状液晶、二联体和三联体。这些稠环芳烃大的平面共轭分子结构有利于柱状相稳定，pi-pi堆积有序度高，相变温度宽。从吡啶出发、我们还成功合成氮杂苯并菲离子型盘状液晶；从药物中间体2-苯基苯并噻吩出发、合成构建了层状相液晶半导体。变温X-射线小角/广角散射分析结果显示，蝴蝶型和板状化合物通常都自组织形成高有序度的六方柱状相和矩形柱状相；瞬态光电流飞行时间技术TOF测试的柱相液晶和层状液晶的电荷载流子(电子和空穴)迁移速率在10-2—10-4 cm2 V-1 s-1，与无机非晶硅材料接近。新合成的多环芳烃常常显示出凝胶性，具有有机溶剂超级凝胶能力、扫描电镜SEM测试干凝胶形貌显示化合物pi-pi相互作用能力强，在溶剂中形成长纤维结构。荧光光谱测试结果显示，许多新合成的稠环芳烃具有高的荧光发光量子产率，发光颜色与芳烃共轭体系大小以及堆积模式有关。理论计算的前线轨道HOMO-LUMO能级以及优化的分子构型可以很好阐释实验测试结果。本项目发表学术论文19篇，国家发明专利20项，培养毕业研究生10人。本项目开发的四烷氧基联苯溴和联苯硼酸试剂、利用噻吩芳环活性一步构建多个C-C键的材料合成策略、化合物结构-性能关系必将对构建新有机半导体材料产生重要影响。