【作者】 陈曦；

【导师】 张红星；

【作者基本信息】 吉林大学 ， 物理化学， 2016， 博士

【摘要】 在过去的几十年中,有机π共轭小分子半导体材料广泛应用在有机电子器件中,如有机光生伏打电池、有机发光二级管、有机场效应晶体管以及各种类型传感器。有机材料具有成本低,轻便柔韧,易合成易加工,应用范围广等优势,受到人们极大的关注。目前的有机半导体材料还有很多不足之处,如载流子迁移率大大低于无机半导体材料,促使人们进一步对有机材料的电子过程问题的深入研究,包括不同材料所具有不同载流子的传输机制等。由于有机材料的结构决定着有机材料的光电性质,因此本论文研究了几种不同分子体系的电子结构等性质,以及分子间弱相互作用对分子堆积构型和材料的载流子传输的影响。目的是从微观角度认识材料结构与性质的关系,揭示材料的结构本质,从而为设计和预测新型有机半导体材料提供基本思路和理论依据。本论文一共分为五章。第一章为绪论,简要介绍了有机电子材料的优势和应用,概述了有机载流子传输材料以及载流子传输机理,说明了理论研究对有机半导体材料发展的意义。第二章为理论基础与计算方法,包括几个量子力学的基本原理和主要的量子化学计算方法。第三章到第五章是对不同体系中的分子结构与光电性质关系进行系统地研究和讨论。具体研究内容介绍如下:1.理论研究双吲哚并咔唑异构体的电子结构和光电性质我们用密度泛函理论(DFT)和含时密度泛函理论(TDDFT),对比分析了23个双吲哚并咔唑异构体的几何构型、前线分子轨道、电离势、亲和势、重组能、吸收和荧光发射光谱。双吲哚并咔唑异构体的差别表现在两个吡咯环的N原子连接在两者之间的苯环的位置关系。对于分子的设计和功能材料的改进来说,研究不同连接方式对异构体光电性质的影响是至关重要的。尤其是1mm、2mp和3pp的空间结构相似,因氮原子位置不同,其光电性质有很大差别,三者分别有利于电子传输、电荷平衡和空穴传输,并且3pp更容易被加工成为蓝光发光材料。2.理论研究基于二苯乙烯基苯D-A复合物的分子堆积相互作用对电子结构和电荷传输性质的影响我们研究了五个基于二苯乙烯基苯单体分子的几何结构和电子结构,以及它们作为混合堆积D-A电荷转移晶体体系时的分子对构型与分子间弱相互作用,前线分子轨道和电荷转移积分的关系。对于有机混合堆积给受体材料,电荷传输有利方向与堆积方向是一致的,这样在堆积方向上的分子堆积构型主要决定了电荷传输性质。我们发现由取代基的吸电子和给电子效应导致的分子间静电相互作用对分子间π堆积起主要作用,直接影响D-A共结晶复合物的分子堆积排布。D1-A1电荷转移复合物已经在实验中证明了是很好的双极性材料,而通过计算预测D2-A2和D2-A2’电荷转移复合物能够作为n型有机半导体材料,并且它们也可以通过改变晶体生成条件成为与D1-A1复合物类似的双极性材料。3.Corannulene(碗烯)和Sumanene(葵烯)衍生物的取代基对分子聚集和电荷传输性质的影响——双体模型的理论研究我们理论研究了曲面分子碗烯和葵烯衍生物在电子结构、分子间相互作用和电荷传输性质方面的取代基效应,这有助于未来设计并制备碗烯和葵烯衍生物作为新型有机半导体材料。计算结果表明:S系列比C系列结晶时更容易形成规则的柱形堆积。C系列的双体最优构型更容易受到取代基的影响。所有构型下的C系列,电子迁移率明显大于空穴迁移率;顺式双体比反式双体更有利于电荷传输。研究发现,重叠构型的纯碗烯本质上具有较强的电荷传输性质。引入吸电子取代基后的碗烯可以使晶体构型调整成规则的柱形堆积,从而有效增大了实际载流子迁移率。总体而言,C系列更利于电子传输;S系列中苯基位取代利于空穴传输,而苄基位取代更利于电子传输或双极传输。更多还原

【Abstract】 In the past decades, organic charge-transporting materials with π-conjugated molecules are widely studied and used as the components of organic electronic devices such as organic photovoltaic cells, organic light-emitting diodes, organic field-effect transistors and various types of sensors. Organic materials have significant advantages such as low cost, light weight, easy processability, mechanical flexibility and large-area production, which have received intense research attention. Currently, they still have many limitations, for example, the carrier mobility in organic materials is much lower than that in inorganic ones. These prompt us to study intensively on the electronic processes in organic materials, including different carrier transport mechanism in different materials. Because the photoelectrical properties are determined by the construction of organic materials, we studied the properties of several molecules composing different systems in the thesis, such as electronic structure and the impact of intermolecular weak interaction on the molecular packing and carrier transport. It is our purpose to understand the relationship between structure and property and to reveal the nature of these materials, thus our findings would provide essential ideas and theoretical foundation for design and prediction of novel organic semiconductor materials.The thesis is divided into five chapters. Chapter 1 is an instruction, and we briefly introduced the advantage and application of organic electronic materials, explained the organic charge transport materials and carrier transport mechanism, and showed the significance of theoretical study on the development of organic semiconductor materials. Chapter 2 is the theoretical foundation and calculation method, including several quantum mechanical principles and primary method of quantum chemistry calculations. From chapter 3 to chapter 6, we systematically investigated and discussed the relationship between molecular structures and photoelectrical properties for different molecular systems. The specific research content of this thesis is as follows:1. Theoretical study on the electronic structures and properties of diindolocarbazole isomersThe comparative analysis of the optimized geometries, electronic properties, frontier molecular orbitals, ionization potentials, electron affinities, reorganization energies, and absorption and emission spectra for 23 diindolecarbazole isomers was performed by DFT, TD-DFT methods. The configuration of these isomers is different in the linked position of N atoms in pyrrole sections on both sides of the benzene. To study the impact of different linkage patterns on the photoelectric properties of the isomers is very crucial for the molecular design and performance improvement of new functional materials. It is notable that the configuration of 1mm, 2mp, and 3pp are similar, their primary difference is the different orientation of the N atoms, but it turns out diverse in their electronic and optical properties. That is, 1mm, 2mp and 3pp favor the electron transport, balance charge transport, and the hole transport, respectively in according to this work. Otherwise, 3pp could be easily modulated as blue light emitting materials.2. The impact of molecular stacking interactions on the electronic structure and charge transport properties in distyrylbenzene(DSB-) based D–A complexes: a theoretical studyWe investigated the geometric and electronic structures of five monomers based distyrylbenzene, as well as their intermolecular interaction energies, frontier molecular orbitals and charge transfer properties of three D–A models influenced by the configuration of molecular pairs. With respect to the mixed stacked D–A charge transfer(CT) crystals, the favored charge transport direction coincides with the stacking direction, thus the intermolecular orientation of the stacking direction basically determines the charge transport properties. The intermolecular electrostatic interactions caused by electron-withdrawing/ electron-donating effect of substituents play a major role in π-stacking, which directly influence on molecular stacking arrangements of D–A crystals. The CT complexes of D1–A1 have been demonstrated as good ambipolar materials; while the complexes of D2–A2 and D2–A2’ should act as n-type organic semiconductor materials by the calculations in this work. Moreover, they could also act as good ambipolar materials similar to D1–A1 complexes by tuning the crystal growth conditions.3. The impact of substituents in corannulene and sumanene derivatives on the molecular assemblings and charge transport properties—a theoretical study with a dimer modelWe have theoretically investigated the substituent effect on the structures, intermolecular interactions and charge transport properties of a series of curved corannulene and sumanene derivatives. Our findings would facilitate the future design and preparation of these corannulenes and sumanenes derivatives as novel organic semiconductor materials. The results show that: the S-series should possess regular columnar stacking more easily than C-series as the crystal forms. The C-series dimers are more sensitive to the introduced substituents. The values of electron mobility are significantly larger than the hole mobility for all the configurations of the C-series; moreover, compared with the anti-type configuration, the syn-type configuration should benefit the charge transport. It is notable from our theoretical study that, the pristine corannulene dimer with eclipsed configuration has the nature of superior charge transport properties. With introduction of the electron-withdrawing substituents in pristine corannulene, the crystal structure can be tuned to ordered columnar stacking, which effectively increase the actual carrier mobility. On the whole, the C-series has superior electron transport properties; the phenyl substituted S-series show the potential of hole transport, while the benzyl substituted ones should be more beneficial to the electron or ambipolar transport.更多还原