Gao Yixuan, Sun Yingman, Guo Zilong, Yu Guo, Wang Yaxin, Wan Yan, Han Yandong, Yang Wensheng, Zhao Dongbing, Ma Xiaonan
Institute of Molecular Plus, Tianjin University Tianjin 300072 P. R. China
State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University Tianjin 300071 P. R. China
Chem Sci. 2024 Sep 20;15(44):18431-42. doi: 10.1039/d4sc05494f.
Delayed fluorescence (DF) is a unique emitting phenomenon of great interest for important applications in organic optoelectronics. In general, DF requires well-separated frontier orbitals, inherently corresponding to charge transfer (CT)-type emitters. However, facilitating intrinsic DF for local excited (LE)-type conjugated emitters remains very challenging. Aiming to overcome this obstacle, we demonstrate a new molecular design strategy with a DF-inactive B,N-multiple resonance (MR) emitter as a model system. Without the necessity of doping with heavy atoms, we synthesized a co-facial dimer in which an excimer-like state (S) was expected to facilitate efficient reverse intersystem crossing (RISC, T → S) and intrinsic DF. Benefiting from greatly enhanced SOC and reduced Δ , the proof-of-concept emitter Np-2CzB exhibited up to 6.5 × 10 s and intrinsic DF with >35% contribution ( / ) in dilute solution. Further investigation indicated that S state formation relies on an optimized co-facial distance ( = ∼4.7 Å), strong inter-chromophore interaction ( > 450 cm) and a rigid structure ( < 350 cm). Although our strategy was demonstrated with a B,N-MR emitter, it can be applicable to many LE-type conjugated emitters without intrinsic DF. By triggering potential DF emission, many classic emitters might play a more important role in optoelectronics.
延迟荧光（DF）是一种独特的发光现象，在有机光电子学的重要应用中备受关注。一般来说，DF需要分离良好的前沿轨道，这本质上对应于电荷转移（CT）型发射体。然而，促进局域激发（LE）型共轭发射体产生本征DF仍然极具挑战性。为了克服这一障碍，我们展示了一种新的分子设计策略，以一种无DF活性的B，N-多重共振（MR）发射体作为模型体系。无需掺杂重原子，我们合成了一种共面二聚体，其中预计类似激基缔合物的态（S）将促进有效的反向系间窜越（RISC，T→S）和本征DF。得益于显著增强的自旋-轨道耦合（SOC）和减小的Δ，概念验证发射体Np-2CzB在稀溶液中表现出高达6.5×10⁻⁶ s的寿命和本征DF，其贡献>35%（ΦDF/ΦT）。进一步研究表明，S态的形成依赖于优化的共面距离（d = ∼4.7 Å）、强发色团间相互作用（J > 450 cm⁻¹）和刚性结构（ΔE < 350 cm⁻¹）。尽管我们的策略是以B，N-MR发射体进行展示的，但它可适用于许多无本征DF的LE型共轭发射体。通过触发潜在的DF发射，许多经典发射体可能在光电子学中发挥更重要的作用。
