Drift of charge carriers in crystalline organic semiconductors.
Drift of charge carriers in crystalline organic semiconductors.
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DOI：
10.1063/1.4945778
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发表时间：
2016-01
期刊：
影响因子：
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通讯作者：
Jingjuan Dong;Wei Si;Changqin Wu
中科院分区：
文献类型：
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作者：
Jingjuan Dong;Wei Si;Changqin Wu
我们利用量子经典Ehrenfest动力学和瞬时退相干校正（IDC）研究了有限外电场下晶体有机半导体的直流响应。IDC是在实际空间表示中进行的，具有能量依赖的重称重因子，以考虑分子间退相干和传导发生的能量松弛。这样，载流子的扩散运动和漂移运动在一个统一的框架中得到了描述。基于对五苯的非对角线电子-声子耦合模型，我们发现由于wanner - stark局域化，漂移速度随电场增大先增大后减小，并且迁移率与电场负相关。爱因斯坦关系是涨落耗散定理的一种表现形式，在研究的宽温度区域内，在高达10(5)V/cm的电场中可以恢复。此外，我们还表明，加入退相干和能量弛豫可以解释Ehrenfest动力学计算的迁移率与全量子方法之间的巨大差异，这证明了我们的方法可以有效地收回这些缺失过程。
We investigate the direct-current response of crystalline organic semiconductors in the presence of finite external electric fields by the quantum-classical Ehrenfest dynamics complemented with instantaneous decoherence corrections (IDC). The IDC is carried out in the real-space representation with the energy-dependent reweighing factors to account for both intermolecular decoherence and energy relaxation by which conduction occurs. In this way, both the diffusion and drift motion of charge carriers are described in a unified framework. Based on an off-diagonal electron-phonon coupling model for pentacene, we find that the drift velocity initially increases with the electric field and then decreases at higher fields due to the Wannier-Stark localization, and a negative electric-field dependence of mobility is observed. The Einstein relation, which is a manifestation of the fluctuation-dissipation theorem, is found to be restored in electric fields up to ∼10(5) V/cm for a wide temperature region studied. Furthermore, we show that the incorporated decoherence and energy relaxation could explain the large discrepancy between the mobilities calculated by the Ehrenfest dynamics and the full quantum methods, which proves the effectiveness of our approach to take back these missing processes.