Zhang Qing, Liu Tao, Huang Xin, Wang Kunyan, Sun Fangxiang, Wang Xin, Lv Chunyan
Department of Materials Chemistry, Huzhou University, Huzhou 313000, China.
Henan-Macquarie University Joint Centre for Biomedical Innovation, Henan Key Laboratory of Brain Targeted Bio-Nanomedicine, School of Life Sciences, Henan University, Kaifeng 475004, China.
Molecules. 2024 Sep 27;29(19):4589. doi: 10.3390/molecules29194589.
The research on boron/nitrogen (B/N)-based multiresonance thermally activated delayed fluorescence (MR-TADF) emitters has been a prominent topic due to their narrowband emission and high luminous efficiency. However, devices derived from the common types of narrowband TADF materials often experience an efficiency roll-off, which could be ascribed to their relatively slow triplet-singlet exciton interconversion. Since inserting the heavy Se atom into the B/N scheme has been a proven strategy to address the abovementioned issues, herein, extensive density functional theory (DFT) and time-dependent DFT (TD-DFT) simulations have been employed to explore the effects of the structural modification on a series of structurally modified selenium-doped derivatives. Furthermore, the two-layered ONIOM (QM/MM) model has been employed to study the pressure effects on the crystal structure and photophysical properties of the pristine CzBSe. The theoretical results found that the introduced tert-butyl units in Cz-BSeN could result in a shorter charge transfer distance and smaller reorganization energy than the parent CzBSe. In contrast to directly incorporating the -carborane () unit to CzBSe, incorporating the bridged phenyl units is important in order to achieve narrowband emissions and high luminous efficiency. The lowest three triplet excited states of CzBSe, Cz-BSeN and PhCb-BSeN all contribute to their triplet-singlet exciton conversions, resulting in a high utilization of triplet excitons. The pressure has an evident influence on the photophysical properties of the aggregated CzBSe and is favored for obtaining narrowband emissions. Our work is promised to provide a feasible strategy for designing selenium-doped derivatives with narrowband emissions and rapid triplet-singlet exciton interconversions.
基于硼/氮（B/N）的多共振热激活延迟荧光（MR-TADF）发光体的研究一直是一个备受关注的课题，因为它们具有窄带发射和高发光效率。然而，由常见类型的窄带TADF材料制成的器件常常会出现效率滚降现象，这可能归因于它们相对较慢的三重态-单重态激子相互转换。由于将重硒原子插入B/N体系已被证明是解决上述问题的一种策略，因此，本文采用了广泛的密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）模拟，来探究结构修饰对一系列结构修饰的硒掺杂衍生物的影响。此外，还采用了双层ONIOM（QM/MM）模型来研究压力对原始CzBSe晶体结构和光物理性质 的影响。理论结果发现，在Cz-BSeN中引入叔丁基单元会导致电荷转移距离比母体CzBSe更短，重组能更小。与直接将 -碳硼烷（）单元并入CzBSe相比，并入桥连苯基单元对于实现窄带发射和高发光效率很重要。CzBSe、Cz-BSeN和PhCb-BSeN的最低三个三重态激发态都有助于它们的三重态-单重态激子转换，从而实现三重态激子的高利用率。压力对聚集态CzBSe的光物理性质有明显影响，有利于获得窄带发射。我们的工作有望为设计具有窄带发射和快速三重态-单重态激子相互转换的硒掺杂衍生物提供一种可行的策略。
