通过辅助配体修饰进行高效磷光铂配合物材料设计的理论研究

发布时间：2018-03-19 13:25

本文选题：有机发光二极管　切入点：密度泛函理论　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着科学技术的不断发展和完善,有机发光二极管(OLED)在平板显示、照明技术和电子产品中发挥了重要的作用。过渡金属配合物有着诸多优良的光学性质能够作为OLED发光层的磷光材料,尤其是这些铱类和铂类配合物。这些金属配合物由于重金属的自旋轨道耦合效应可以有效地激发单重态向三重态的跃迁,促进系间窜越,极大地提高磷光量子效率。金属铱配合物中铱原子具有较大的d-轨道分裂,能够构成八面体的构型,热稳定性高。金属铂易于形成平面四方形的结构,能够连接二齿配体、三齿配体和四齿配体。配体的多样性可以极大的影响配合物的光物理和光化学性质。本文中,我们通过DFT和TDDFT理论计算的方法对四种环金属铂配合物的几何结构、电子性质、重组能和磷光性质等进行分析。此外,我们利用自旋轨道耦合效应计算辐射跃迁速率,并且进一步分析了非辐射跃迁过程。结合上述两个过程来更准确地比较四个分子的磷光量子效率。在这些配合物中,1是实验合成分子[(bzq)Pt(dpm)],以及在辅助配体上进行修饰设计出2-4分子[(bzq)Pt(ppy)、(bzq)Pt(Ncaz)和(bzq)Pt(Ndbt)]。其中,bzq代表苯并喹啉(benzo[h]quinoline),dpm代表二戊酰甲烷(dipivolylmethanoate),ppy是苯基吡啶(2-phenylpyridine),Ncaz和Ndbt分别代表氮取代的咔唑和苯并噻吩。经过理论计算得出,配合物2-4同实验分子1比较,不同的配体可有效的改变前线分子轨道的跃迁性质和能带间隙,而且提高了电子传输能力以及空穴和电子之间的平衡能力。分析配合物的磷光性质,所有的配合物都是属于蓝绿色发光材料。配合物1、2和4的发射波长相近,这与它们前线分子轨道密度类似的分布有关,磷光发射的跃迁性质是金属到配体和配体到配体(MLCT/LLCT)的电子转移。最后,我们通过计算自旋轨道耦合效应评估辐射速率常数k_r。由于配合物2和4的S_1态能够与T_3态进行有效的耦合,并且两个激发态之间的能隙最小,所以2和4的辐射跃迁速率常数会比较大。四种配合物的k_r顺序是2431。结合上述的分析,2和4由于具有更好的分子刚性和较大的辐射跃迁速率常数将有希望成为高效的磷光材料。这些结果显示合理的辅助配体修饰可以提高量子效率,降低OLED能量消耗。衷心希望我们的理论研究对设计新型的高效磷光材料提供一些指导和帮助。
[Abstract]:With the development and perfection of science and technology, organic light emitting diodes (OLED) are displayed on flat panel. Transition metal complexes have many excellent optical properties and can be used as phosphorescent materials of OLED luminescence layer. In particular, these iridium and platinum complexes, due to the spin-orbit coupling effect of heavy metals, can effectively excite the transition from single state to triplet state and promote intersystem transition. The iridium atom in the metal iridium complex has large d-orbital splitting, which can form the configuration of octahedron and has high thermal stability. The metal platinum is easy to form a planar square structure and can be connected to a didentate ligand. Tridentate ligands and tetradentate ligands. The diversity of ligands can greatly affect the photophysical and photochemical properties of the complexes. In this paper, the geometrical structure and electronic properties of the four cyclic metal platinum complexes are calculated by DFT and TDDFT theory. The recombination energy and phosphorescence properties are analyzed. In addition, the radiative transition rate is calculated by using the spin-orbit coupling effect. Furthermore, the non-radiative transition process is further analyzed. The phosphorescence quantum efficiency of four molecules is compared more accurately by combining the above two processes. In these complexes, 1 is an experimental synthetic molecule, and modified on the auxiliary ligands. 2-4 molecules were designed for the decoration [BZQUP PtPtPtncaz) and BZQ PtN Ndbt]. Where BZQ stands for benzo [h] quinoline benzo [h] quinolineine DPM for dipentylmethanoate dipentylmethanoatebuppy (Phenopyridine 2-phenylpyridine) Ncaz and Ndbt for N-substituted carbazole and benzothiophene, respectively. The theoretical calculation shows that the two molecules are phenylpyridine pyridine 2-phenylpyridine (Ncaz) and benzothiophene (benzothiophene), respectively, which are substituted by benzo [h] quinolinine, dipentylmethanoate, dipentylmethanoate, dipentylmethane, dipentylmethanoate. Compared with experimental molecule 1, complex 2-4 can effectively change the transition properties and band gap of frontier molecular orbitals with different ligands. In addition, the electron transport ability and the balance between hole and electron are improved. The phosphorescence properties of the complexes are analyzed. All the complexes are blue-green luminescent materials. The emission wavelengths of complexes 1, 2 and 4 are similar. This is related to the similar distribution of orbital density in their front-line molecules. The properties of phosphorescence transition are electron transfer from metal to ligand and ligand to ligand MLCT / LLCT. finally, By calculating the spin orbit coupling effect, we evaluate the radiation rate constant KAR.Because the S _ s _ 1 states of complexes 2 and 4 can be effectively coupled with the T _ s _ 3 states, and the energy gap between the two excited states is minimal, Therefore, the radiation transition rate constants of 2 and 4 will be larger. The KR order of the four complexes is 2431. In combination with the above analysis, due to the better molecular rigidity and larger radiative transition rate constants, it is hopeful that the two complexes will become high. These results show that reasonable auxiliary ligand modification can improve quantum efficiency. It is hoped that our theoretical research will provide some guidance and help for the design of new high efficiency phosphorescent materials.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.4

【相似文献】