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Coherent Charge Transfer Exciton Formation in Regioregular P3HT: A Quantum Dynamical Study
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2019-05-28 00:00:00 , DOI: 10.1021/acs.jpclett.9b01105
Wjatscheslaw Popp 1 , Matthias Polkehn 1 , Robert Binder 1 , Irene Burghardt 1
Affiliation  

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.

中文翻译:

区域规则P3HT的相干电荷转移激子形成:量子动力学研究。

通过对包含五个堆叠的四噻吩单元的聚集模型系统的电子结构和量子动力学研究,阐明了在区域规则的聚(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计算得到的Frenkel和CTX类型的13个电子状态的多态振动耦合哈密顿参数,以及78种振动模式,使用多层多配置时变哈特里特(ML-MCTDH)方法进行了量子动力学模拟。 。符合时间分辨光谱结果[De Sio,A。; 等。纳特 公社 20167,13742],发现CTX形成在光激发下立即发生,伴随着一个约22个飞秒周期性持续定期振荡。这些相干特征在高维聚集体或薄膜材料中的出现似乎令人惊讶,可以追溯到CC拉伸型高频模式的主要电子特征。发现这些振动信号是由于集体振动响应而增强的,该响应由初始产生的离域明亮激子及其随后通过内部转换弛豫为极化激元局部激子基态引起。
更新日期:2019-05-28
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