Vibrationally Assisted Intersystem Crossing in Benchmark Thermally Activated Delayed Fluorescence Molecules
Vibrationally Assisted Intersystem Crossing in Benchmark Thermally Activated Delayed Fluorescence Molecules
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DOI：
10.1021/acs.jpclett.8b01556
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发表时间：
2018-07-19
影响因子：
5.7
通讯作者：
Greenham, Neil C.
中科院分区：
文献类型：
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作者：
Evans, Emrys W.;Olivier, Yoann;Greenham, Neil C.
有机发光器件 (OLED) 中电注入的电荷载流子经历复合事件，以 1:3 的比例形成单线态和三线态，这是实现高量子效率的基本障碍。基于热激活延迟荧光 (TADF) 的掺杂剂已成为解决 OLED 中自旋统计问题的有希望的候选者。在这些材料中，反向单重态三重态系间窜越（rISC）变得有效，从而激活弱发射三重态的发光途径。然而，尽管人们越来越一致认为扭转振动有助于这些分子中的自旋轨道耦合（SOC-）驱动的 ISC，但仍缺乏实验证据。我们使用瞬态电子自旋共振和理论来明确表明 SOC 相互作用驱动自旋转换，并且 ISC 是由基准咔唑基二氰基苯 TADF 发射体的构象波动控制的动态过程。
Electrically injected charge carriers in organic light-emitting devices (OLEDs) undergo recombination events to form singlet and triplet states in a 1:3 ratio, representing a fundamental hurdle for achieving high quantum efficiency. Dopants based on thermally activated delayed fluorescence (TADF) have emerged as promising candidates for addressing the spin statistics issue in OLEDs. In these materials, reverse singlet triplet intersystem crossing (rISC) becomes efficient, thereby activating luminescence pathways for weakly emissive triplet states. However, despite a growing consensus that torsional vibrations facilitate spin orbit-coupling (SOC-) driven ISC in these molecules, there is a shortage of experimental evidence. We use transient electron spin resonance and theory to show unambiguously that SOC interactions drive spin conversion and that ISC is a dynamic process gated by conformational fluctuations for benchmark carbazolyl dicyanobenzene TADF emitters.