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 (9H-quinolino[3,2,1-kl]phenothiazin-9-one (QPO) and 9H-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 S₁–T₁ energy gap, opening the way to high-performance organic light-emitting diodes.

由于具有高效深蓝色发射的潜力，目前对采用多种共振诱导热激活延迟荧光 (MR-TADF) 材料的有机发光体的研究引起了广泛关注。然而，成功的 TADF 的起源和机制尚不清楚，因为许多 MR-TADF 材料在溶液中没有表现出 TADF 行为，而只是作为特定的纯固体。在这里，对著名的 MR-TADF 材料 DABNA-1 以及其他新的 MR 材料（9 H -quinolino[3,2,1- kl ]phenothiazin-9-one (QPO) 和 9 H -喹啉-[3,2,1- kl]-phenothiazin-9-one 5,5-dioxide (QP3O))，对 TADF 的起源产生了新的见解。尽管材料系统可能支持 MR 的概念，但正向和反向系统间交叉的低效率禁止了 TADF，除非合适的主体材料允许激发 TADF 的类似激发复合物的主体-发射体相互作用。这种增强的 TADF 机制可以推广到在光致发光测量中缺乏 TADF 但具有热可及 S ₁ -T ₁能隙的任何荧光染料，从而为高性能有机发光二极管开辟了道路。