Coherent Charge Transfer Exciton Formation in Regioregular P3HT: A Quantum Dynamical Study.
Coherent Charge Transfer Exciton Formation in Regioregular P3HT: A Quantum Dynamical Study.
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DOI：
10.1021/acs.jpclett.9b01105
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发表时间：
2019-05
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影响因子：
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通讯作者：
W. Popp;Matthias A. Polkehn;R. Binder;I. Burghardt
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文献类型：
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作者：
W. Popp;Matthias A. Polkehn;R. Binder;I. Burghardt
通过对包含五个堆叠四噻吩单元的聚合模型系统的电子结构和量子动力学研究，阐明了区域规则性聚（3-己基噻吩）（rrP3HT）域中电荷转移激子（CTX）的超快形成。使用通过 TDDFT 计算对 Frenkel 和 CTX 类型的 13 个电子态以及 78 个振动模式进行参数化的多态振动耦合哈密顿量，并使用多层多配置瞬态 Hartree (ML-MCTDH) 方法进行量子动力学模拟。与时间分辨光谱结果一致 [De Sio, A.;等人。纳特。交流。 2016, 7, 13742]，发现CTX在光激发后立即形成，并伴随着周期约为22 fs的持续规则振荡。这些相干特征在高维聚集体或薄膜材料中的存在似乎令人惊讶，可以追溯到 CC 拉伸型高频模式的主要振动特征。发现这些振动特征由于离域亮激子的初始生成及其随后通过内部转换松弛到极化局域激子基态而引起的集体振动响应而得到增强。
The ultrafast formation of charge transfer excitons (CTXs) in regioregular poly(3-hexyl thiophene) (rrP3HT) domains is elucidated by electronic structure and quantum dynamical studies of an aggregate model system comprising five stacked quaterthiophene units. Using a multistate vibronic coupling Hamiltonian parametrized by TDDFT calculations for 13 electronic states of Frenkel and CTX type, along with 78 vibrational modes, quantum dynamical simulations are carried out using the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method. In line with time-resolved spectroscopic results [ De Sio , A. ; et al. Nat. Commun. 2016 , 7 , 13742 ], it is found that CTX formation occurs immediately upon photoexcitation, accompanied by sustained regular oscillations with a ∼22 fs periodicity. These coherent features, whose presence may seem surprising in a high-dimensional aggregate or thin film material, can be traced back to a dominant vibronic signature of CC stretch-type high-frequency modes. These vibrational signatures are found to be enhanced due to a collective vibronic response that is prompted by the initial generation of a delocalized bright exciton and its subsequent relaxation, by internal conversion, to a polaronic local exciton ground state.