吡咯并吡咯二酮/异靛蓝为受体的红光热致延迟荧光材料构筑及辐射衰减调控

热致延迟荧光通过三线态（T1）到单线态（S1）的反向系间转化（RISC）发光，为暗态T1激子低成本发光利用提供了有效途径，但有几个关键问题亟待解决: 增强RISC过程与伴随的S1辐射效率下降; 缺乏高效的红光TADF材料; 高亮度下器件效率滚降严重。本项目拟构筑吡咯并吡咯二酮和异靛蓝为受体，苯环、苯乙烯或苯乙炔基为桥连骨架的D-π-A-π-D型红光材料，通过调控与受体相连骨架的位阻强化LUMO与HOMO在桥连骨架电子云分布，增强辐射效率；调控给-受体空间分离距离控制S1与T1分裂能,，促进RISC过程。构筑Ag纳米微结构，研究其对材料激发态光动力行为的影响，然后集成到OLED器件，利用等离子共振激元加快S1辐射，破坏T1与S1平衡，促进RISC过程，降低T1浓度。项目研究将会建立新的给-受体材料体系和分子设计原则， 阐明采用分子设计和金属纳米结构对材料激发态光动力行为调控的机制。

Thermally activated delayed fluorescence (TADF) recently has become a viable alternative for harvesting both singlet and triplet state in OLEDs via effective reverse intersystem crossing (RISC) mechanism. However, several challenged issues must be addressed such as 1) difficulty to simultaneously achieves effective RISC and highly efficient fluorescent radiation, 2) deficiency of red or near-infrared TADF materials and 3) the notorious electroluminescence efficiency roll-off in increasing brightness. This project addresses these important technology challenge through developing D-π-A-π-D-type red and near-infrared TADF materials using diketopyrrolopyrrole or isoindigo as acceptor building blocks and phenyl, styrly or phenyethynyl fragment as bridge unit. The steric effect between the acceptor and bridge unit is considered to enhance the electron delocalized distribution of HOMO and LUMO in bridge unit, resulting in enhanced singlet radiation efficiency. The spatial separated distance between the acceptor and donor is used to control singlet-triplet splitting energy, resulting in improved RISC. Furthermore, the Ag nanostructures would be developed and their effects on excited state dynamics of TADF materials would be investigated. Finally, these Ag nanostructure would be incorporated into OLEDs to suppress the notorious electroluminescence efficiency roll-off by modifying the radiative decay rate of singlet, which would improve reverse intersystem crossing from triplet to singlet, decreasing the triplet concentrations. Under this grant, this project would develop a new donor-acceptor TADF material system and some rules directing future molecular design. In addition, the detailed interaction mechanism between the TADF materials and surface Plasmon resonances of the Ag nanostructures would be elucidated.