Despite the design and proposal of several new structural motifs as thermally activated delayed fluorescent (TADF) emitters for organic light-emitting device (OLED) applications, the nature of their interaction with the host matrix in the emissive layer of the device and their influence on observed photophysical outputs remain unclear. To address this issue, we present, for the first time, the use of up to four regioisomers bearing a donor–acceptor–donor electronic structure based on the desymmetrized naphthalene benzimidazole scaffold, equipped with various electron-donating units and possessing distinguished conformational lability. Quantum chemical calculations allow us to identify the most favorable conformations adopted by the electron-rich groups across the entire pool of regioisomers. These conformations were then compared with conformational changes caused by the interaction of the emitter with the Zeonex and 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) matrices, and the correlation with observed photophysics was monitored by UV–vis absorption and steady-state photoluminescence spectra, combined with time-resolved spectroscopic techniques. Importantly, a CBP matrix was found to have a significant impact on the conformational change of regioisomers, leading to unique TADF emission mechanisms that encompass dual emission and inversion of the singlet–triplet excited-state energies and result in the enhancement of TADF efficiency. As a proof of concept, regioisomers with optimal donor positions were utilized to fabricate an OLED, revealing, with the best-performing dye, an external quantum emission of 11.6%, accompanied by remarkable luminance (28,000 cd/m²). These observations lay the groundwork for a better understanding of the role of the host matrix. In the long term, this new knowledge can lead to predicting the influence of the host matrix and adopting the structure of the emitter in a way that allows the development of highly efficient and efficient OLEDs.

中文翻译：

---

区域异构与构象：分子设计对有机发光器件发射器发射途径的影响

尽管设计和提出了几种新的结构图案作为有机发光器件（OLED）应用的热激活延迟荧光（TADF）发射器，但它们与器件发射层中的主体基质相互作用的性质及其对观察到的光物理输出仍不清楚。为了解决这个问题，我们首次提出使用多达四种带有供体-受体-供体电子结构的区域异构体，其基于去对称的萘苯并咪唑支架，配备有各种电子供体单元并具有显着的构象不稳定性。量子化学计算使我们能够确定整个区域异构体库中富电子基团采用的最有利的构象。然后将这些构象与发射体与 Zeonex 和 4,4'-双( N-咔唑基)-1,1'-联苯 (CBP) 基质相互作用引起的构象变化进行比较，并监测与观察到的光物理学的相关性通过紫外可见吸收和稳态光致发光光谱，结合时间分辨光谱技术。重要的是，CBP 矩阵被发现对区域异构体的构象变化有显着影响，从而产生独特的 TADF 发射机制，包括双发射和单线态-三线态激发态能量的反转，并导致 TADF 效率的提高。作为概念验证，利用具有最佳供体位置的区域异构体来制造 OLED，使用性能最佳的染料显示出 11.6% 的外部量子发射，并伴有显着的亮度 (28,000 cd/m ² )。这些观察结果为更好地理解宿主基质的作用奠定了基础。从长远来看，这一新知识可以预测主基质的影响并采用发射器的结构，从而开发出高效且高效的 OLED。