Climbing up the Ladder: Intermediate Triplet States Promote the Reverse Intersystem Crossing in the Efficient TADF Emitter ACRSA,The Journal of Physical Chemistry C

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Climbing up the Ladder: Intermediate Triplet States Promote the Reverse Intersystem Crossing in the Efficient TADF Emitter ACRSA
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-09-22 00:00:00 , DOI: 10.1021/acs.jpcc.7b06187
Igor Lyskov ₁ , Christel M. Marian ₁

Affiliation

It is usually assumed that the reverse intersystem crossing (rISC) in organic TADF emitters occurs at the microsecond time scale. However, the underlying dynamics can be enhanced in the presence of low-lying nπ* states as stipulated by the El-Sayed rule. Here, we report a theoretical study of the short-time quantum dynamics of the ACRSA dye in different solvents following the electrical excitation. The wave packet propagation in multidimensional excited state potentials reveals the intersystem crossing (ISC) rate to be one or 2 orders of magnitude faster compared to the rISC process depending on the environment. Upon the molecular geometry distortions, the system rapidly converts the initial vibrational density to the valence excited-state potentials with subsequent change of spin state owing to spin–orbit interaction. We show that a local triplet ππ* state, residing on the acceptor moiety, mediates the nonradiative passage from triplet to singlet, thus increasing the quantum yield of light harvesting in OLED. This tandem interplay of vibronic and spin–orbit interactions favors the rISC to occur at the subnanosecond regime in ACRSA.

中文翻译：

爬梯子：中间三重态在有效的TADF发射器ACRSA中促进反向系统间交叉

通常假定有机TADF发射器中的反向系统间交叉（rISC）发生在微秒级的时间范围内。但是，在存在低洼nπ的情况下可以增强基本动态*表示El-Sayed规则规定的状态。在这里，我们报告了在电激发后不同溶剂中ACRSA染料的短时量子动力学的理论研究。波包在多维激发态电势中的传播表明，取决于环境，与rISC过程相比，系统间穿越（ISC）速率要快一个或两个数量级。当分子几何结构发生畸变时，系统会迅速将初始振动密度转换为化合价激发态势，随后由于自旋轨道相互作用而使自旋态发生随后的变化。我们证明了局部三元组ππ位于受体部分上的*状态介导了从三重态到单重态的非辐射通道，从而提高了OLED中光收集的量子产率。振动和自旋轨道相互作用的串联相互作用有利于rISC发生在ACRSA的亚纳秒范围内。

更新日期：2017-09-23

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