Debnath Sanchari, Ramkissoon Pria, Salzner Ulrike, Hall Christopher R, Panjwani Naitik A, Kim Woojae, Smith Trevor A, Patil Satish
Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, India.
ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Melbourne, Parkville, Australia.
Nat Commun. 2025 Mar 26;16(1):2982. doi: 10.1038/s41467-025-56987-4.
One of the key challenges in developing efficient organic light-emitting diodes (OLEDs) is overcoming the loss channel of triplet excitons. A common approach to mitigate these losses to enhance the external quantum efficiency of OLEDs is employing emitter molecules optimized for thermally activated delayed fluorescence (TADF) or triplet-triplet annihilation (TTA). However, achieving both in the solid state from the same organic chromophore poses a formidable challenge due to energetic and structural requirements needing to be met simultaneously. Here, we demonstrate TADF and TTA in donor-acceptor phthalimide derivatives by employing triphenylamine (TPA) or phenyl carbazole (PhCz) as a donor. Thin films of the TPA-substituted phthalimides doped in the poly(methyl methacrylate) matrix exhibit TADF emission from the singlet charge-transfer (CT) state. On the contrary, PhCz-substituted emitters display dominant TTA-induced delayed fluorescence in the neat film due to long-range molecular ordering that facilitates efficient triplet diffusion. The present study provides insight into how dual TADF-TTA delayed fluorescence can be realized in thin films of molecular semiconductors via rational molecular design.
开发高效有机发光二极管（OLED）的关键挑战之一是克服三重态激子的损失通道。减轻这些损失以提高OLED外部量子效率的一种常见方法是使用针对热激活延迟荧光（TADF）或三重态-三重态湮灭（TTA）进行优化的发射体分子。然而，由于需要同时满足能量和结构要求，要从同一有机发色团在固态中实现这两者是一项艰巨的挑战。在此，我们通过使用三苯胺（TPA）或苯基咔唑（PhCz）作为供体，在供体-受体邻苯二甲酰亚胺衍生物中展示了TADF和TTA。掺杂在聚甲基丙烯酸甲酯基质中的TPA取代邻苯二甲酰亚胺薄膜表现出单重态电荷转移（CT）态的TADF发射。相反，由于促进有效三重态扩散的长程分子有序排列，PhCz取代的发射体在纯薄膜中显示出占主导地位的TTA诱导延迟荧光。本研究深入探讨了如何通过合理的分子设计在分子半导体薄膜中实现双TADF-TTA延迟荧光。
