Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Phys Chem Chem Phys. 2019 Oct 16;21(40):22429-22439. doi: 10.1039/c9cp03308d.
In the framework of optoelectronic luminescent materials, non-radiative decay mechanisms are relevant to interpret efficiency losses. These radiationless processes are herein studied theoretically for a series of stilbenoid derivatives, including distyrylbenzene (DSB) and cyano-substituted distyrylbenzene (DCS) molecules in vacuo. Given the difficulties of excited-state reaction path determinations, a simplified computational strategy is defined based on the exploration of the potential energy surfaces (PES) along the elongation, twisting, and pyramidalization of the vinyl bonds. For such exploration, density functional theory (DFT), time-dependent (TD)DFT, and complete-active-space self-consistent field/complete-active-space second-order perturbation theory (CASSCF/CASPT2) are combined. The strategy is firstly benchmarked for ethene, styrene, and stilbene; next it is applied to DSB and representative DCS molecules. Two energy descriptors are derived from the approximated PES, the Franck-Condon energy and the energy gap at the elongated, twisted, and pyramidalized structures. These energy descriptors correlate fairly well with the non-radiative decay rates, which validates our computational strategy. Ultimately, this strategy may be applied to predict the luminescence behavior in related compounds.
在光电发光材料的框架内，非辐射衰减机制与解释效率损失有关。本文在真空条件下，从理论上研究了一系列二苯乙烯衍生物（包括二苯乙烯（DSB）和氰基取代二苯乙烯（DCS）分子）的这些无辐射过程。鉴于确定激发态反应途径的困难，定义了一种简化的计算策略，该策略基于对乙烯基键伸长、扭曲和三角化过程中势能面（PES）的探索。对于这种探索，结合了密度泛函理论（DFT）、含时（TD）DFT 和完全活性空间自洽场/完全活性空间二级微扰理论（CASSCF/CASPT2）。该策略首先用于乙烯、苯乙烯和二苯乙烯的基准测试；然后将其应用于 DSB 和代表性的 DCS 分子。从近似 PES 中得出了两个能量描述符，即 Franck-Condon 能量和伸长、扭曲和三角化结构的能量间隙。这些能量描述符与非辐射衰减率相当吻合，验证了我们的计算策略。最终，该策略可用于预测相关化合物的发光行为。
