Quantum Simulations of Charge Separation at a Model Donor-Acceptor Interface: Role of Delocalization and Local Packing
Quantum Simulations of Charge Separation at a Model Donor-Acceptor Interface: Role of Delocalization and Local Packing
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DOI：
10.1155/2018/6834908
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发表时间：
2016-12
影响因子：
1.5
通讯作者：
Allen Kelley;E. Bittner
中科院分区：
文献类型：
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作者：
Allen Kelley;E. Bittner
基于有机聚合物的光伏系统为捕光应用提供了一种可行的替代标准固态器件。在这项研究中，我们研究了模型有机光伏（OPV）异质结组成的聚亚苯基乙烯（PPV）低聚物和α-苯基C61-丁酸甲酯（PCBM）的混合物的电子动力学。我们的方法对待经典的分子动力学的原子内的一个Ekefest平均场治疗的单激发态跨越一个子集的供体和受体分子附近的相边界的共混物。我们的研究结果表明，界面电子态的调制C=C键拉伸运动，这样的运动诱导附近的激发态之间避免交叉，从而促进从本地激子配置的离域电荷分离配置的超快时间尺度上的过渡。模型界面的最低几个激发态快速混合，允许低频C-C面外扭转来调制势能面，使得系统可以在低于100 fs的时间尺度上对分子间电荷转移和电荷分离的电子构型进行采样。我们的模拟支持一个新兴的图片中的OPV系统，界面电子状态可以迅速衰减到电荷分离和电流产生状态，通过耦合到振动自由度的载流子生成。
Organic Polymer-based photovoltaic systems offer a viable alternative to more standard solid-state devices for light-harvesting applications. In this study, we investigate the electronic dynamics of a model organic photovoltaic (OPV) heterojunction consisting of polyphenylene vinylene (PPV) oligomers and a -phenyl C61-butyric acid methyl ester (PCBM) blend. Our approach treats the classical molecular dynamics of the atoms within an Ehrenfest mean-field treatment of the - singly excited states spanning a subset of donor and acceptor molecules near the phase boundary of the blend. Our results indicate that interfacial electronic states are modulated by C=C bond stretching motions and that such motions induce avoided crossings between nearby excited states thereby facilitating transitions from localized excitonic configurations to delocalized charge-separated configurations on an ultrafast time-scale. The lowest few excited states of the model interface rapidly mix allowing low frequency C-C out-of-plane torsions to modulate the potential energy surface such that the system can sample both intermolecular charge-transfer and charge-separated electronic configurations on sub-100 fs time scales. Our simulations support an emerging picture of carrier generation in OPV systems in which interfacial electronic states can rapidly decay into charge-separated and current producing states via coupling to vibronic degrees of freedom.