Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China.
Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Jan 5;224:117434. doi: 10.1016/j.saa.2019.117434. Epub 2019 Jul 29.
Molecular motion plays an important role in the reverse intersystem crossing of thermally activated delayed fluorescence (TADF) materials, since the conformation varies as the molecule vibrates, leading to potential changes in the energies of excited states. Although many theoretical simulations have researched the relationship between the excited states and the molecular conformations, there are still few experimental results showing the energy level difference between different long-lived excited states. Herein, a novel method for measuring spectrally resolved luminescence lifetimes is proposed to detect the energy splitting of the long-lived excited states of a classical TADF molecule, BTZ-DMAC. A set of the time-gated luminescence spectra with different delay times were captured by a spectrograph equipped on an auto-phase-locked system, and then used for lifetime analysis at each wavelength. Unlike traditional measurement techniques, the proposed novel method does not require ultrafast laser, high-speed detector and any phase matching circuitry, thus significantly reducing the cost. This method revealed a definite energy gap between the two excited states of BTZ-DMAC with different lifetimes, indicating different conformations caused by molecular vibration. This low-cost method could be also used to detect many other luminescence materials for investigating the detail mechanisms of multiple excited states.
分子运动在热激活延迟荧光（TADF）材料的反向系间窜越中起着重要作用，因为随着分子振动，构象会发生变化，从而导致激发态能量的潜在变化。尽管许多理论模拟已经研究了激发态和分子构象之间的关系，但仍很少有实验结果显示不同长寿命激发态之间的能级差。在此，提出了一种新的用于测量光谱分辨发光寿命的方法，以检测经典 TADF 分子 BTZ-DMAC 的长寿命激发态的能量分裂。通过配备在自动锁定系统上的光谱仪捕获一组具有不同延迟时间的时间门控发光光谱，然后在每个波长处进行寿命分析。与传统的测量技术不同，所提出的新方法不需要超快激光、高速探测器和任何相位匹配电路，因此大大降低了成本。该方法揭示了 BTZ-DMAC 的两个具有不同寿命的激发态之间存在明确的能量间隙，表明分子振动导致了不同的构象。这种低成本的方法也可以用于检测许多其他发光材料，以研究多激发态的详细机制。
