兼顾重原子和离域效应的新型热致延迟荧光材料的设计合成与发光机理研究

Thermally activated delayed fluorescence materials have attracted major interests of OLED field due to their high quantum efficiency and low cost. However, most of researchers pay their attention to the modulation of molecular stereo-structure and the conservation of energy and there is few reports about the relation between heavy atom induced spin-orbit coupling–TADF efficiency. Here, we design a series of novel TADF materials containing O, S, Se atom based on the next two aspects: Firstly, gradually changing the spin-orbit coupling constants of materials by conjugating different VI atom. Secondly, gradually changing the delocalization of materials by grafting different electron donor group. Finally, we will study the relation between spin-orbit coupling–radiative decay rate –energy gap between singlet and triplet–efficiency. The project takes account of both energy and spin conservation, which will provide a principle for the designing of new TADF materials and TADF devices.

热致延迟荧光材料因其较高的量子效率和低成本而受到有机发光显示领域的关注。已有研究更多关注电子跃迁的能量守恒，关于重原子效应所引起的自旋轨道耦合对延迟荧光材料性能影响的研究还较少。本文拟以含有第VI主族元素的HOMO/LUMO分离的热致延迟荧光材料为研究对象，材料设计沿着两条轴线进行，第一条轴线是逐步键联不同原子序数的非金属重原子（S, Se）来改变材料的自旋轨道耦合参数；第二条轴线是通过改变给体基团的轨道离域程度来改变其单重态辐射跃迁常数。通过进一步研究材料的自旋轨道耦合参数-辐射跃迁常数-电子系间跃迁常数-三重态/单重态能隙-发光效率之间的关系，得到兼顾能量守恒与自旋守恒的材料设计理念，为实现高效率、低成本OLED提供良好的材料、器件和理论基础。

本项目在执行中，两个热致延迟荧光材料（TADF）的问题——供体选择范围有限和严重的器件滚降，得到较好的克服。具体策略如下：将咔唑、吖啶，并呋喃/噻吩等供电子基团融合，开发了多种新型“融合供体”，拓宽了供电子基团的范围。选择2,4,6-三苯基-嘧啶（TPPM）或者2,4,6-三苯基三嗪（TPTrz）作为吸电子基团，设计合成了系列TADF分子。这些大的体积和刚性的“融合供体”减弱了发光分子的分子间的堆积，利于缓解浓度猝灭。此外，系统研究了融合方式和原子效应对材料性能的影响，并讨论发光材料的自旋轨道耦合参数-辐射跃迁常数-电子系间跃迁速率-三重态/单重态能隙-发光效率之间的关系，最终得到兼顾能量守恒与自旋守恒的材料设计理念。优选出的TADF发光分子的器件实现了深蓝光到橘黄光的高效率，低的效率滚降。