The role of host–guest interactions in organic emitters employing MR-TADF

• Published in: Nature photonics Vol. 15; no. 10; pp. 780 - 786
• Main Authors: Wu, Xiugang, Su, Bo-Kang, Chen, Deng-Gao, Liu, Denghui, Wu, Chi-Chi, Huang, Zhi-Xuan, Lin, Ta-Chun, Wu, Cheng-Ham, Zhu, Mengbing, Li, Elise Y., Hung, Wen-Yi, Zhu, Weiguo, Chou, Pi-Tai
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.10.2021; Nature Publishing Group
• Subjects: 140/125; 639/301/930/527/1819; 639/624/1020/1091; Applied and Technical Physics; Emitters; Energy; Energy gap; Engineering; Fluorescence; Laboratories; Materials science; Organic light emitting diodes; Photoluminescence; Photonics; Photons; Physics; Physics and Astronomy; Quantum Physics; Resonance
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/s41566-021-00870-3

Research into organic light emitters employing multiple resonance-induced thermally activated delayed fluorescence (MR-TADF) materials is presently attracting a great deal of attention due to the potential for efficient deep-blue emission. However, the origins and mechanisms of successful TADF are unclear, as many MR-TADF materials do not show TADF behaviour in solution, but only as particular pure solids. Here, an investigation into a well-known MR-TADF material, DABNA-1, together with other new MR materials (9 H -quinolino[3,2,1- kl ]phenothiazin-9-one (QPO) and 9 H -quinolino-[3,2,1- kl ]-phenothiazin-9-one 5,5-dioxide (QP3O)), yields new insights regarding the origin of TADF. Although a material system may support the concept of MR, inefficiency in both forward and reverse intersystem crossings forbids TADF unless a suitable host material allows an exciplex-like host–emitter interaction that boosts TADF. This boosted-TADF mechanism can be generalized to any fluorescence dye that lacks TADF in the photoluminescence measurement but has a thermally accessible S 1 –T 1 energy gap, opening the way to high-performance organic light-emitting diodes. This study reveals the importance of host–guest interactions for effective multiple-resonance thermally activated delayed fluorescence in organic light emitters.