新型高性能稀土敏化蓝色有机发光二极管

Rare earth complexes have been regarded as the most potential electroluminescent materials due to their narrow emission and theoretically 100% quantum efficiency. Recently, many researchers devote to developing high performances organic light-emitting diodes based on rare earth complexes. However, the wide energy gaps of rare earth complexes make it difficult to balance the distribution of holes and electrons on emitter molecules. In addition, their long excited lifetimes cause often the severe triplet-triplet annihilation, thus the rapid efficiency roll-off. In this project, we aim to designing novel high performances blue organic light-emitting diodes by selecting rare earth complexes as the sensitizer. To broaden and confine the recombination zone, double light-emitting layers device structure will be firstly designed by selecting appropriate rare earth complexes, blue-emitting transition metal complexes, and host materials with matched energy levels and triplet energies. Then, to improve the device performances, the selected rare earth complexes will be doped into carriers' transport layers as carrier trapper and hopping ladder with the help of trace doping technologies. Finally, to make clear the functions of rare earth complexes, electroluminescent mechanisms of these diodes will be investigated in detail based on theoretical and experimental methods. Our investigation can combine the advantages of rare earth complexes and transition metal complexes, thus extending the application of rare earth complexes in organic light-emitting diodes.

稀土配合物因其独特的窄带发射和100%的理论量子效率，被广泛看作是最具潜力的一类有机电致发光材料。近年来，研究人员尝试各种方法开发基于稀土配合物的高性能发光二极管。然而，稀土配合物较宽的能级不利于平衡载流子的分布；另外，其较长的激发态寿命导致严重的三重态猝灭，最终加速器件效率的衰减。本项目拟选用稀土配合物作为敏化材料，将其掺杂到载流子传输层或者载流子阻挡层，设计新型稀土敏化蓝色有机发光二极管。首先，筛选能级及能量匹配的稀土配合物、蓝色过渡金属配合物及主体材料，设计双发光层器件结构拓宽并限定发光区间。进而，采用微量掺杂技术将稀土配合物引入传输层起到载流子束缚中心与跳跃阶梯的作用，提高发光二极管的性能。最后，借助理论及实验方法，探索稀土掺杂发光二极管的工作机理，阐明稀土配合物的作用。本项目的研究能够拓宽稀土配合物在有机发光二极管领域的应用范围，实现稀土配合物与过渡金属配合物的优势互补。

相较于绿色和红色有机发光材料，蓝色有机磷光材料具有较宽的带隙（~3 eV）和较长的激子寿命（~μs），从而导致蓝光OLEDs表现出较低的效率和严重的效率滚降。为了提高蓝光器件的效率、延缓效率衰减，从而提高器件工作稳定性，获得载流子平衡和实现高效激子利用是解决问题的关键。围绕“采用热稳定性能良好的稀土配合物作为新型敏化材料，借助其宽能隙和长激发态寿命，设计优化新型高性能稀土敏化蓝光OLEDs”这一研究主线及目标任务，我们设计合成了一系列稀土配合物、过渡金属配合物，并开展新型蓝光OLEDs研发。我们通过将稀土配合物掺入载流子传输层及阻挡层作为敏化材料，设计了双敏化型OLEDs。通过优化器件结构设计，筛选能级/能量匹配的发光材料、敏化材料、主体材料及辅助功能材料，我们大幅提高了器件的综合性能，重点降低器件工作电压、提高器件效率及工作稳定性。所得器件的启亮电压2.6 V、最大电流效率71.95 cd A-1、最大功率效率74.85 lm W-1、最大亮度43171 cd m-2。继而，在器件性能大幅提高的基础上研究新型敏化蓝光OLEDs的工作机理，实验数据表明：敏化剂分子的存在不仅可以有效平衡载流子分布，还能够加速主客体材料间的能量传递过程，甚至可以拓宽发光区间、延缓效率衰减。相关研究成果发表SCI论文28篇、获授权发明专利4项，培养硕士、博士毕业生11人。借助本项目的研究，我们进一步拓宽了稀土配合物在OLEDs领域的应用范围，不仅降低了器件的工艺难度、提高了器件的重复率，还为新型高性能蓝光及白光OLEDs的设计与优化提供了新的思路。