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Nonadiabatic Exciton and Charge Separation Dynamics at Interfaces of Zinc Phthalocyanine and Fullerene: Orientation Does Matter.
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2020-08-27 , DOI: 10.1021/acs.jpca.0c05865
Xiang-Yang Liu 1 , Zi-Wen Li 2 , Wei-Hai Fang 2 , Ganglong Cui 2
Affiliation  

Interface orientation between zinc phthalocyanine (ZnPc) and fullerene (C60) affects their interfacial charge separation dynamics; however, the underlying physical origin is still elusive. In this work, we have employed the time-dependent density functional theory (TDDFT) method to explore excited-state properties of ZnPc and C60 heterojunctions with both face-on and edge-on configurations. Spectroscopically bright absorption is from locally excited (LE) singlet excitons within ZnPc. In the face-on configuration, LE excitons are much higher in energy than charge-transfer (CT) excitons, thereby making charge separation process favorable. However, in the edge-on configuration, LE excitons are the lowest ones and CT ones are higher in energy; thus, charge separation is not efficient. Subsequently, we have carried out TDDFT-based nonadiabatic dynamics method to simulate photoinduced exciton and charge separation dynamics of ZnPc and C60 heterojunctions with both edge-on and face-on configurations. In the former, there are no exciton transfer and charge separation processes observed within 300 fs simulation time; while, in the latter, fragment-based electronic transition density matrix analysis reveals that only LE excitons |C60ZnPC*⟩ and CT excitons |C60ZnPC+⟩ are involved. The exciton transfer from |C60ZnPC*⟩ to |C60ZnPC+⟩ is completed within about 100 fs in which charge separation takes place with electron–hole distances increasing from 1.0 to 4.5 Å. This exciton transfer process is essentially in company with electron transfer from ZnPc to C60 but almost not involving hole transfer. These gained insights not only rationalize experiments but also enrich our knowledge to design donor–acceptor orientations to optimize organic photovoltaic performance.

中文翻译:

酞菁锌和富勒烯界面的非绝热激子和电荷分离动力学:方向确实很重要。

酞菁锌(ZnPc)和富勒烯(C 60)之间的界面取向会影响它们的界面电荷分离动力学。但是,潜在的物理起源仍然难以捉摸。在这项工作中,我们采用了时变密度泛函理论(TDDFT)方法来探索ZnPc和C 60的激发态性质。具有面对配置和边缘配置的异质结。光谱学上的明亮吸收来自ZnPc中的局部激发(LE)单线态激子。在面对配置中,LE激子的能量比电荷转移(CT)激子高得多,从而使电荷分离过程更有利。但是,在边缘接通结构中,LE激子的能量最低,而CT激子的能量较高。因此,电荷分离效率不高。随后,我们进行了基于TDDFT的非绝热动力学方法来模拟ZnPc和C 60的光致激子和电荷分离动力学。边缘连接和面对配置的异质结。在前者中,在300 fs仿真时间内没有观察到激子转移和电荷分离过程。而在后者中,基于片段的电子跃迁密度矩阵分析表明,仅涉及LE激子| C 60 ZnPC *⟩和CT激子| C 60 ZnPC + .。从| C 60 ZnPC *⟩到| C 60 ZnPC + exc的激子转移在大约100 fs内完成,其中电荷分离发生,电子-空穴距离从1.0增大到4.5Å。激子转移过程实质上是伴随着ZnPc到C 60的电子转移但几乎不涉及空穴转移。这些获得的见解不仅使实验合理化,而且丰富了我们的知识,以设计供体-受体取向以优化有机光伏性能。
更新日期:2020-09-18
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