基于超支化结构的热活化延迟荧光材料的设计及其应用研究

Thermally activated delayed fluorescence (TADF) emitters have attracted much attention for their applications in high-efficiency organic light-emitting devices (OLEDs). The major breakthrough of TADF materials is attributed to the sufficient harvesting of both first singlet state and triplet state excitons, which can achieve an internal quantum efficiency of 100% for the molecules without employing any heavy metals. In view of practical application, the development of solution processed, non-doped TADF materials is vitally important. The dendrimer and polymer TADF materials are both solution processed luminescent materials, and should be further developed in order to satisfy the practical requirements. Hyper branched materials exhibit spatial three-dimensional structures and multiple branching sites, which can take advantages of both dendrimer and polymer. In the hyper branched TADF materials, the functional TADF groups are separated by the linking groups and the exciton quenching can be avoided effectively. The emitters based on the three-dimensional hyper branched molecular structure obviously broaden the recombination zone of the excitons, which in favor of the efficiency stability of the device. The properties of the hyper branched TADF materials can be precisely adjusted through rational molecular design. Besides, the hyper branched TADF materials exhibit good solubility, high thermal stability and good film-forming ability.. In this project, the study on the design and application of hyper branched thermal activation delayed fluorescent materials is going to carry out. By rational design the hyper branched TADF materials, a series of high-efficiency emitting materials can be obtained. In addition, the relationships between molecular structure, material property and device performance are well studied, which would provide beneficial insights for the design of novel hyper branched TADF materials.

热活化延迟荧光材料无需重金属原子参与即可利用三线态激子的能量，实现100 %的内量子效率，在高性能有机电致发光器件中得到广泛应用。开发可溶液加工的、非掺杂型发光层的热活化延迟荧光材料具有重要的现实意义。树枝型延迟荧光材料和聚合物延迟荧光材料是两类重要的溶液加工型发光材料，而超支化材料具有多个支化位点和空间三维结构，兼具树枝型化合物和聚合物的结构优势。在超支化延迟荧光材料中，延迟荧光单元被联接单元分离，有效避免激子淬灭；其三维结构显著拓宽了激子复合区域，有利于器件稳定性；材料的设计多样，可调节能力强；材料的溶解性、热稳定性和成膜性良好。. 本项目对基于超支化结构的热活化延迟荧光材料及其应用展开研究。通过构建合理的超支化延迟荧光材料设计思路，获得一类高性能的超支化延迟荧光材料；系统研究分子结构、材料性质和器件性能之间的相互关系，为新型超支化延迟荧光材料的设计提供有益思路。

本项目从热活化延迟荧光材料的分子设计要求出发，通过分子设计和优化、材料合成和鉴定、性质测试及器件性能研究，构建合理的热活化延迟荧光材料设计思路，掌握分子结构、材料性质和器件性能的相互关系，获得一类高性能的热活化延迟荧光材料。在项目执行期间，完成了以下工作：（1）设计合成了一系列基于三苯基硼受体的热活化延迟荧光材料。通过在D-A型热活化延迟荧光材料加入额外的氰基增强吸电子能力，实现荧光量子产率的较大提升；多个给体单元与受体单元组成的3D-A型热活化延迟荧光材料，可以在分子内形成多个反向系间穿越通道，提高三线态激子的利用效率，与此同时，3D-A型材料较强的分子刚性显著提升其荧光量子产率；通过邻位连接的D-A-D构型热活化延迟荧光材料，可以实现高效的通过空间传递的电荷转移态，相比于D-A型材料，更多的给体可以实现更多的反向系间穿越通道，且由于D-A-D型材料天然的位阻效应，材料的刚性更强，从而赋予材料更高的荧光量子产率。通过以上材料性质与器件性能的研究，我们获得了外量子效率超过36%的蒸镀型有机电致发光器件，以及外量子效率超过17%的溶液加工型器件。这些材料均具有较强的应用价值，有望应用于有机电致器件的发放材料。（2）设计合成了以碳硼烷为受体、以环丙烯酮或环戊烯酮为受体和以苯并噻二唑为受体的荧光材料并进行了细致的研究。通过对这些材料构性关系的进一步研究，帮助我们更加清楚的了解和掌握荧光材料的设计准则和要求。具有聚集诱导发光特性和热活化延迟荧光特征的碳硼烷类荧光材料，可以实现在非掺杂薄膜条件下的深红光发射；在给体单元上引入卤素元素，可以显著增强材料的自旋轨道耦合效应，赋予材料相比更长的延迟寿命。（3）设计合成了以苯为核心，具有六取代苯基结构的空穴传输材料，基于该类材料为空穴传输层的钙钛矿太阳能器件其功率转化效率均超过16%，具有一定的应用前景。