取代基对二吡咯萘啶二酮聚集体振动分辨吸收光谱和激子动力学的影响,The Journal of Physical Chemistry A

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取代基对二吡咯萘啶二酮聚集体振动分辨吸收光谱和激子动力学的影响
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2022-09-08 , DOI: 10.1021/acs.jpca.2c03907
Shishi Feng ₁ , Yi Zhao ₁ , WanZhen Liang ₁

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Dipyrrolonaphthyridinedione (DPND) 薄膜表现出有趣的光物理性质和单线态裂变 (SF) 过程。最近的一项实验工作发现，DPND骨架中的烷基取代对电子吸收光谱和SF速率的特性有显着影响。在这里，我们通过结合电子结构计算和量子动力学模拟，从理论上阐明了取代基效应对材料光学性质和激子动力学的微观机制。结果表明，烷基取代基对单分子性质的影响较小，但通过改变分子间相互作用显着改变了 DPND 聚集体的性质。带有和不带有烷基侧链的 DPND 聚集体表现出更可能的 H 型聚集体特征。在前者（DPND6）中，分子内局部激发（LE）态和分子间电荷转移（CT）态的混合程度较弱，使得低能吸收带具有主要的光吸收，而在后者（DPND）中， CT和LE态能量相近，加上它们的强相互作用，导致大量的态混合，使其两个低能吸收带具有几乎相等的振荡器强度和超过0.5 eV的宽能量间隔。激子动力学的模拟表明，由于缺乏足够的驱动力，两种聚集体中的光引发状态都不能产生自由载流子。然而，DPND 聚合中 LE 和 CT 状态之间的种群交换比 DPND6 聚合快得多，表明不同的 SF 行为，

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Substituent Effect on Vibrationally Resolved Absorption Spectra and Exciton Dynamics of Dipyrrolonaphthyridinedione Aggregates

Dipyrrolonaphthyridinedione (DPND) thin films exhibit interesting photophysical properties and singlet fission (SF) processes. A recent experimental work found that the alkyl substitution in the DPND skeleton has the remarkable influence on the characteristics of electronic absorption spectra and SF rates. Here, we theoretically elucidate the microscopic mechanism of the substituent effect on the optical properties and exciton dynamics of materials by combining the electronic structure calculations and the quantum dynamics simulations. The results show that the alkyl substituent has a minor effect on the single molecular properties but dramatically changes those of DPND aggregates via varying the intermolecular interactions. The aggregates of DPND with and without alkyl side chains exhibit the more likely characters of H-type aggregations. In the former (DPND6), the weak degree of mixing of intramolecular localized excited (LE) states and intermolecular charge transfer (CT) states makes the low-energy absorption band possess the predominant optical absorption, while in the latter (DPND), the CT and LE states are close in energy, together with their strong interaction, resulting in the substantial state-mixing, so that its two low-energy absorption bands have nearly equal oscillator strengths and a wide energy spacing of more than 0.5 eV. The simulation of exciton dynamics elucidates that the photoinitiated states in both aggregates cannot generate the free charge carrier because of the lack of enough driving forces. However, the population exchanges between LE and CT states in DPND aggregates are much faster than in DPND6 aggregates, indicating the different SF behaviors, consistent with the experimental observation.

更新日期：2022-09-08

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