非共轭聚合物磷光主体材料和延迟荧光材料的理论研究

发布时间：2018-11-15 18:07

【摘要】：有机电致发光器件因在平板显示和固态照明等领域具有巨大的应用潜力,而备受学术界关注。传统的荧光材料内量子效率只能达到25%,而以重金属为基础的磷光材料可以同时捕获单重态激子和三重态激子,实现100%的内量子效率。对于磷光发光器件的发光层来说,拥有比磷光客体材料高的三重态能是对主体材料的基本要求,同时它还应兼具平衡电子空穴注入和快速传输激子的能力,来降低能力损失。当前,提高器件效率和合成色纯度较高的蓝色磷光主体材料是这个领域亟待解决的问题。此外,刚兴起的热活化延迟荧光材料,同样可以捕获单重态激子和三重态激子,而使其内量子产率达到100%。寻找具有较小单重态-三重态能量差的材料,以及探索内部电子和能量的转化机制,是该领域在当前的研究中心。当前,人们在研究磷光材料和延迟荧光材料上投入了大量的精力,有力的推动了电致发光器件的发展。本文采用密度泛函理论和含时密度泛函理论研究了系列非共轭聚合物磷光主体材料和D-A-D结构类型的延迟荧光发光材料,详细讨论了这些物质作为磷光主体材料和延迟荧光发光材料时的潜在性能,同时构建主客体模型,研究主客体之间的能量和电子转移机制。我们希望这些工作能够为主体材料和延迟荧光材料的设计研究发挥出应有的贡献。本论文将从下五个部分进行讨论：第一部分,介绍有机电致发光材料的研究现状、器件构成以及工作原理,阐述磷光主体材料以及延迟荧光材料的基本要求、分子结构及其设计原理。同时对电致发光材料的发展前景进行了展望,并指出本文的研究意义。第二部分,详细的介绍本文研究所使用的相关计算理论——分子轨道理论、密度泛函理论、含时密度泛函理论、其他的重要分析方法(例如,自然成键轨道分析、Marcus电荷转移理论等)以及发光理论。第三部分,介绍利用密度泛函理论和含时密度泛函理论方法对以聚苯乙烯为基础的一系列非共轭聚合物的主体分子性能展开研究。结果表明非共轭聚合物能够有效地阻止三重态激子的离域,使主体材料拥有一个较高的三重态能,同时通过引入合适的取代基(咔唑、吡咯、三苯胺等)使相关主体材料兼具好的电荷空穴传输能力。另外,结构分析结果表明,三重态和基态之间的结构变化,即三重态结构的平面化,是造成聚苯乙烯衍生物三重态能下降的本质原因。在主客体能量、主体发射光谱和客体吸收光谱以及主客体堆积模型的研究中表明,对位咔唑取代的poly(4-vinytriphenylamine)具有较小的单三态能量差,能够更好的和发光体匹配,即拥有更好的主体材料性能。第四部分,利用密度泛函和含时密度泛函以及其它相关理论对咔唑连接C/Si衍生物进行了详细的主体性能研究。通过咔唑直接连接C/Si衍生物以及它们中间引入苯环作为桥体的这两个系列分子结构的研究表明前一系列分子具有较高的三线态能、较强的分子轨道相互作用和较小的单三态能量差,这是由于三重态激子更容易分布在具有较大平面的区域,主客体之间存在有效的Forster和Dexter能量转移。通过C和Si的比较发现,Si更容易阻止三线态激子的离域。对于后一系列分子,我们在咔唑上引入甲基和叔丁基进行了进一步的研究,结果表明HOMO和LUMO之间出现好的分裂,表现出良好的轨道相互作用和较小的单-三态能量差。结合本体系的研究可以得出,咔唑基团直接连接Si原子系列更具备作为主体材料的潜能。第五部分,采用密度泛函理论和含时密度泛函理论研究了以D-A-D结构为基础的热活化延迟荧光材料。通过供体(9,9-dimethyl-9,10-dihydroacridine)和受体(2,5-phenyl-5,10-dihydrophenazine)采用邻、间、对的不同连接形式设计出一系列分子,预测它们作为延迟荧光材料的性能。结果表明供受体相邻原子之间的相互作用对单重态-三重态能量差有很大的影响。通过对激发态能量以及自然跃迁轨道方面分析表明供受体之间用C-N键相连的分子与主体分子可形成分子间的单重态-单重态、单重态-三重态和三重态-三重态的能量转移方式。
[Abstract]:The organic electroluminescent device has great application potential in the fields of flat panel display and solid state lighting, and has attracted the attention of the academic community. The quantum efficiency of the conventional fluorescent material can only reach 25%, while the phosphorescent material based on the heavy metal can simultaneously capture both the single-heavy-state exciton and the triplet exciton to realize the internal quantum efficiency of 100%. For the light-emitting layer of the phosphorescent light-emitting device, the triplet energy having a higher triplet energy than the phosphorescent guest material can be a basic requirement for the host material, and at the same time it should have the ability to balance the electron-hole injection and the fast-transmission exciton to reduce the power loss. At present, the blue phosphorescent host material with high device efficiency and high synthesis color purity is a problem to be solved in this field. In addition, the newly-developed heat-activated delayed fluorescent material can also capture a single-heavy-state exciton and a triplet exciton to achieve a quantum yield of 100%. The search for materials with a smaller single-to-triplet energy difference, as well as a mechanism to explore the internal electron and energy, is the current research center in this field. At present, a lot of energy is put into the research of the phosphorescent material and the delayed fluorescent material, and the development of the electroluminescent device is strongly promoted. In this paper, a series of non-copolymeric phosphorescent host materials and D-A-D structure types of delayed fluorescent light-emitting materials are studied by using the density functional theory and the time-density functional theory, and the potential properties of these materials as the phosphorescent host material and the delayed fluorescent light-emitting material are discussed in detail. At the same time, the main object model is constructed, and the energy and the electron transfer mechanism between the subject and the object are studied. We hope that these work will have a due contribution to the design study of the bulk material and the delayed fluorescent material. This paper will discuss the following five parts: the first part, the research status of the organic electroluminescent material, the structure of the device and the working principle, the basic requirements, the molecular structure and the design principle of the phosphorescent host material and the delayed fluorescent material. At the same time, the development prospect of the electroluminescent material is prospected, and the significance of this paper is also pointed out. In the second part, the relevant calculation theory _ molecular orbital theory, the density functional theory, the time-density functional theory, other important analytical methods (e.g., the natural-bond-track analysis, the Marcus charge transfer theory, etc.) used by the Institute and the light-emitting theory are introduced in detail. In the third part, the main molecular properties of a series of non-copolymeric polymers based on polystyrene are studied by using the density functional theory and the time-density functional theory. The results show that the non-copolymeric polymer can effectively prevent the off-domain of the triplet exciton, so that the host material has a higher triplet energy, and at the same time, the relevant host material has good charge hole transport capacity by the introduction of a suitable substituent (e.g., triphenyl, triphenylamine, triphenylamine, etc.). In addition, the structural analysis shows that the change of the structure between the triplet state and the ground state, that is, the planarization of the triplet structure, is the essential cause of the degradation of the triplet state of the polystyrene derivative. In the study of the main object energy, the main body emission spectrum and the object absorption spectrum and the main object stacking model, the poly (4-vinyttrium), which is substituted by the contraposition, has a small single tri-state energy difference, and can be better matched with the luminous body, that is, the performance of the main body material is better. In the fourth part, the C/ Si derivatives are studied in detail by using the density functional and the time-time-density functional and other relevant theories. The study on the molecular structure of the two series of molecules which are directly connected to the C/ Si derivative and the intermediate introduced benzene ring as the bridge body shows that the former series of molecules have a high triplet energy, a stronger molecular orbital interaction and a smaller single tristate energy difference, This is because the triplet exciton is more easily distributed in the region with the larger plane, and there is an effective Forster and Dexter energy transfer between the main objects. By comparison of C and Si, Si is more likely to block off-domain of triplet exciton. For the latter series of molecules, we conducted a further study on the introduction of methyl and tert-butyl into the molecular sieve. The results show that a good break between the HOMO and the LUMO shows good orbital interaction and a small single-state energy difference. According to the study of this system, the direct connection of the Si atom series to the Si atom series is the potential of the main material. In the fifth part, the thermal activation delayed fluorescent material based on D-A-D structure is studied by the density functional theory and the time-density functional theory. A series of molecules were designed by means of a donor (9, 9-dimetyl-9, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-dihydro-5, 10-di@@ The results show that the interaction between the adjacent atoms of the receptor has a great effect on the single-state-triplet energy difference. By analyzing the energy of the excited state and the natural transition orbit, it is shown that the molecule and the host molecule which are connected by the C-N bond between the acceptor and the acceptor can form the energy transfer mode between the single-state, the single-state, the singlet-triplet state and the triplet-triplet state between the molecules.
【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN383.1

【共引文献】