Mońka Michał, Pander Piotr, Grzywacz Daria, Sikorski Artur, Rogowski Radosław, Bojarski Piotr, Monkman Andrew P, Serdiuk Illia E
Faculty of Mathematics, Physics and Informatics, University of Gdańsk, Wita Stwosza 57, 80-308 Gdańsk, Poland.
Faculty of Chemistry, Silesian University of Technology, M. Strzody 9, 44-100 Gliwice, Poland.
ACS Appl Mater Interfaces. 2025 Feb 12;17(6):9635-9645. doi: 10.1021/acsami.4c21674. Epub 2025 Jan 31.
The approaches to design and control intermolecular interactions for a selective enhancement of specific process(es) are of high interest in technologies using molecular materials. Here, we describe how π-π stacking enables control over the heavy-atom effect and spin-orbit coupling (SOC) through dimerization of an organic emitter in solid media. π-π interactions in a red thermally activated delayed fluorescence (TADF) emitter afford specific types of dimers. In its brominated derivative , the vicinity of the Br atom and the electronic density of the dimer involved in a spin-flip transition afford up to 200-fold increase of the SOC, in the most favorable case, attributed to the external heavy-atom effect (EHAE) of the halogen atom. The presence of such dimers in the films of provides enhancement of reverse intersystem crossing, and thus, TADF occurs mostly within a few microseconds, up to 20 times faster than in . For this reason, organic light-emitting diodes using as an emitter and an assistant dopant show a decreased efficiency roll-off by a factor of 4 and 1.5, respectively. The crucial aspects of the intermolecular electronic interactions between a chromophore system and an HA together with the particularly favorable dimer geometry not only help to understand the nature of the EHAE but also provide guidelines for the molecular design of emitters for all-organic light-emitting devices with enhanced stability.
在使用分子材料的技术中，通过设计和控制分子间相互作用来选择性增强特定过程的方法备受关注。在此，我们描述了π-π堆积如何通过固体介质中有机发光体的二聚化来控制重原子效应和自旋轨道耦合（SOC）。红色热激活延迟荧光（TADF）发光体中的π-π相互作用产生特定类型的二聚体。在其溴化衍生物中，溴原子附近以及参与自旋翻转跃迁的二聚体的电子密度，在最有利的情况下，由于卤原子的外部重原子效应（EHAE），使SOC增加了200倍。在薄膜中存在这种二聚体可增强反向系间窜越，因此，TADF大多在几微秒内发生，比在……中快20倍。因此，使用……作为发光体和辅助掺杂剂的有机发光二极管的效率滚降分别降低了4倍和1.5倍。发色团系统与重原子之间分子间电子相互作用的关键方面以及特别有利的二聚体几何结构，不仅有助于理解EHAE的本质，还为具有增强稳定性的全有机发光器件的发光体分子设计提供了指导。
