新型热激活延迟荧光OLED主体材料的设计、合成及光电性能研究

Host materials in the emitting layer of thermally activated delayed fluorescence (TADF) OLEDs are among the key functional materials which have a significant impact on the device performance. To date, most of the reported highly efficient TADF OLEDs are based on the typical and classical host materials designed for phosphorescent OLEDs. However, the host materials with high efficiency that are specifically developed for TADF OLEDs are short in terms of diversity and quantity, which to some degree hinders the development of TADF OLEDs. On the one hand, the host materials commonly used at present are faced with the problems of unbalanced carrier transport (resulting from their unipolarity), insufficient triplet energy level to host blue TADF materials, and difficulty in obtaining high efficiency through solution processing. On the other hand, the excitons of TADF molecules (bipolar characteristics) are sensitive to the host environment, which exerts higher-level requirements on the host materials. Therefore, the high-performance host materials for TADF materials are of great significance to promote the development of TADF OLEDs. In this project, carbazole unit is used as donor and pyridine/pyrimidine/triazine serve as acceptor, which are integrated into a newly proposed molecular architecture of D-σ-O-A. Reasonable molecular structure design enables the material to have high triplet energy level, bipolar transporting ability and low dipole moment of excitons, as well as excellent solution processability, which facilitate the realization of highly efficient TADF OLEDs.

热激活延迟荧光（TADF）型OLED器件的发光层主体材料是影响其性能的关键功能性材料之一。当前，TADF型OLED大多沿用早期经典的磷光主体材料，而针对TADF发光材料设计的高效主体材料种类和数量较少，不利于TADF器件的发展。一方面，当前常用的主体材料面临载流子传输不平衡（单极性）、适配蓝光TADF客体材料的高三线态能级主体较少、难以通过湿法加工工艺获得高效率等问题；另一方面，TADF分子（本身为双极性分子）激发态对主体环境敏的特性对主体材料提出了更高的要求。因此，针对TADF发光体的高性能主体材料对促进TADF型OLED的发展具有重要意义。本项目拟以咔唑为给体，以吡啶/嘧啶/三嗪为受体，提出新型的“D-σ-O-A“的主体材料结构设计；合理的分子结构设计使材料具有高三线态能级、双极性传输能力与低激发态偶适应湿法加工等优良性质，并实现高效TADF型OLED器件制备。

针对当前高效热激活延迟荧光（TADF）型有机发光二极管（OLED）主体材料研究存在的问题，如主体材料种类缺乏、载流子传输能力欠佳、难以兼具双极性传输性质与低激发态偶极矩，尤其是适用于溶液加工工艺主体材料较少的科学问题，本项目通过σ键连策略设计并合成一系列适应溶液加工的高效TADF主体材料，并对它们的光物理、电化学、热学、以及电致发光等性能以及主体-客体相互作用进行研究。通过主体材料对客体材料的发光调控实现了高效的溶液加工TADF发光器件，所制备的主体材料实现了最高29.5%的器件外量子效率。本项目为开发新型高性能的主体材料体系提供了重要的分子设计思路。