首都师范大学付红兵研究组报道了具有三重态禁阻效应的热激活延迟荧光，即拒绝单线态但保持稳定三重态能量。这一研究成果发表在2024年11月14日出版的国际学术期刊《德国应用化学》上。

据悉，热激活延迟荧光（TADF）分子在有机发光二极管等领域得到了广泛的研究，通常来说需要小的单重态-三重态能隙和高的辐射常数。普遍的TADF分子是通过供体-受体分子设计，这是以降低辐射常数为代价的。

本文基于三重态阻滞效应，提出了一种新的单重-三重态能隙调制方法，来构建具有高辐射常数的TADF，即三重态约束子（IB）共轭的扩展导致单重态逐渐红移，但三重态能量恒定，从而减小了从单体（IB）、单体连接剂（IB-BF2）到IB-BF2-IB二聚体的单重-三重态能隙。

自然跃迁轨道分析表明，单重态是离域的，而三重态是局域的，时间分辨电子顺磁共振谱证实了这一点。因此，单重态-三重态能隙从0.60 eV、0.46 eV减小到0.25 eV，同时保持比传统的供体-受体分子（10^6 ~ 10^7/s）更快的辐射速率（约10^8/s）。

因此，IB的荧光、IB- bf2的磷光/TADF双发射到IB- bf2 -IB的TADF发射机制受到调控。本文提出了一种新的单线态-三重态能隙调制方法，这在基础光物理和材料科学中具有重要意义。

附：英文原文

Title: Declined Singlet but Constant Triplet Energy: Thermally Activated Delayed Fluorescence with Triplet Blocking Effect

Author: Shihong Song, Fangqing Ge, Daniele Panariti, Anping Zhao, Shuhan Yu, Zhijia Wang, Hua Geng, Jianzhang Zhao, Antonio Barbon, Hongbing Fu

Issue&Volume: 2024-11-14

Abstract: Thermally activated delayed fluorescence (TADF) molecules have been widely investigated in organic light emitting diodes, etc. Small singlet-triplet energy gap and high radiative constants are desired. The prevalent TADF molecules are via donor-acceptor molecular design, which is at the expense of reducing radiative constants. Herein, we demonstrated a new singlet-triplet energy gap modulation approach to construct TADF with high radiative constant, based on triplet blocking effect, i.e., the extension of conjugation of a triplet constrainer (IB) leads to a gradually red-shifted singlet but a constant triplet energy, and therefore reduced singlet-triplet energy gap controlled from monomer (IB), monomer-linker (IB-BF2), to dimer of IB-BF2-IB. The natural transition orbital analysis indicates that singlet state is delocalized while triplet state is localized as confirmed by time resolved electron paramagnetic resonance spectroscopy. Therefore, the singlet-triplet energy gap is reduced from 0.60 eV, 0.46 eV to 0.25 eV, while keeping faster radiation rate (around 10^8/s) than that of conventional donor-acceptor molecules (10^6 ~ 10^7/s). As a result, the emission mechanisms are regulated from fluorescence for IB, phosphorescence/TADF dual emissions for IB-BF2 to TADF for IB-BF2-IB. This paper proposed a new approach of singlet-triplet energy gap modulation, which is crucial for fundamental photophysics and material science.

DOI: 10.1002/anie.202418097

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202418097