红绿蓝三基色及单分子宽光谱环金属铱配合物液晶发光材料的分子构筑及其性能研究

Luminescent liquid crystal materials are the promising family in the field of polarized organic light-emitting diodes (OLEDs) due to their possessing both liquid crystalline and luminescent features. However, it remains huge challenges for the high-efficiency luminescent liquid crystal materials in polarized OLEDs, such as the difficult molecular design, as well as emission quenching in the solid state and the low polarized efficiency for these luminescent liquid crystal materials. To address these issues, in this project, a series of cyclometalated iridium complexes-based luminescent liquid crystal materials with RGB (red, green and blue) and white emission will be designed and synthesized through the synergistic effect of the emission core (non-planar iridium complex), the mesogenic units (biphenyl, oxadiazole and fluorene derivatives) and the aggregation-induced emission group. The relationship between molecular structure and liquid crystal/photophysical properties will be systematically investigated by changing the structure and number of the mesogenic units, as well as the structure of the ligands. Furthermore, the molecular construction rule of the cyclometalated iridium complexes-based luminescent liquid crystal materials will be revealed. The aligned emitter and polarized OLEDs will be fabricated via thermal treatment procedures. The effect of both molecular structure and the aligned emission layer on the polarized performance in OLEDs will be studied in detail. After optimizing the device structure, high-efficiency polarized OLEDs should be achieved with RGB and white emission, respectively. Therefore, this project has significant theoretical and practical implications for promoting the development of cyclometalated iridium complexes used as the luminescent liquid crystal materials and their application in polarized OLEDs.

液晶发光材料既具有液晶性能又具有发光性能，在偏振有机电致发光器件(OLEDs)领域具有潜在的应用价值。针对偏振OLEDs中高效液晶发光材料存在的分子构筑难、在固体薄膜中易聚集导致发光淬灭及偏振发光效率低等关键科学问题，本项目拟通过非平面结构的环金属铱配合物发光中心、外围液晶基元(联苯、噁二唑及芴衍生物)和聚集诱导发光基团的协同作用，构筑高效发光的红绿蓝三基色及单分子宽光谱(白光)环金属铱配合物液晶发光材料。通过改变液晶基元的种类与数量及配体的结构，系统研究环金属铱配合物的分子结构对液晶性能和光物理性能的影响，探索环金属铱配合物液晶发光材料的分子构筑规律。通过热处理等工艺制备取向发光层及偏振器件，研究材料结构和发光层的取向对偏振器件性能的影响；优化器件结构，获得高效的偏振单色光和白光器件。项目的实施对于促进环金属铱配合物液晶发光材料的发展及其在偏振OLEDs中的应用具有重要的理论和应用价值。

液晶发光材料因具有液晶的有序性及优良的光物理性能，成为有机半导体领域的研究热点。针对液晶发光材料存在的发光效率低、分子结构-性能关系不明确等科学问题，该项目在以下几个方面展开了研究：(1) 以环金属铱配合物为发光内核，在主配体或辅助配体中引入柔性链基团，制备了系列环金属铱配合物液晶发光材料，获得了非平面型液晶磷光材料的分子构筑规律；以环金属铂配合物为发光内核，在主配体上引入手性单元，在辅助配体中引入液晶基元，合成了系列手性液晶磷光材料，揭露了手性液晶发光材料的构筑方式；以金配合物为发光内核，在外围引入不同数目的烷氧基，构筑了系列液晶磷光材料，研究了烷基链的数目及种类对材料液晶/光物理性能的影响；以热活性延迟荧光材料为发光内核，在给体单元上引入联苯类液晶基元，获得了高效的热活性延迟荧光液晶材料；此外，项目还构筑了系列红绿蓝三基色热活性延迟荧光材料，系统研究了材料的结构-性能关系；(2) 通过核磁共振氢谱、碳谱、质谱及单晶X射线衍射确证了材料的分子结构；利用差示扫描量热法、偏光显微镜及X射线衍射测试了材料的液晶行为；通过热失重分析、稳态瞬态荧光光谱及电化学测试研究了材料的光物理性能；(3) 以液晶发光材料和热活性延迟荧光材料为发光层掺杂剂，通过溶液加工法制备电致发光器件，探讨了材料的光电性能。其中基于环金属铱配合物液晶发光材料的最大外量子效率(EQE)达10%以上；环金属铂配合物的圆偏振电致发光的不对称因子高达0.06，最大EQE为11.3%；基于热活性延迟荧光液晶材料的器件最大EQE为14.9%；基于热活性延迟荧光材料的红绿蓝及白光器件的最大EQE分别达11，22，25和28%。研究成果发表高水平学术论文18篇，授权中国发明专利7件，成果转化3件；培养硕士研究生11人。该项目系统研究了液晶发光材料及热活性延迟荧光材料的结构-性能关系，对发展新型高效率电致发光材料具有重要的研究意义。