Nonlinear Charge Carriers in Polyacetylene
Nonlinear Charge Carriers in Polyacetylene
复制标题
聚乙炔中的非线性电荷载流子
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
W. Utz
中科院分区：
文献类型：
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作者：
W. Förner;W. Utz
摘要共轭有机聚合物本质上是半导体，但掺杂后导电，光激发后光导。 在低掺杂制度，他们通常表现出导电没有相关的自旋输运。因此，在这种情况下，假设非线性准粒子作为电荷载流子，例如具有简并基态的材料中的带电孤子，例如反式聚乙炔或过苯胺。在与非简并基态的材料的情况下，情况往往是不太清楚，但它是假设带电极化子或双极化子的电荷载流子在them.We提出了一个理论模型，用于描述这种准粒子的动力学也产生信息，他们的流动性，他们的性质和稳定性，以及他们的光谱特性。该模型基于包含电子-电子相互作用的π电子汉密尔顿。在原型材料聚乙炔的基础上，演示了如何借助相关从头算或密度泛函计算将这样的模型参数化并应用。我们讨论了一些详细的原始材料的动力学，以及掺杂和电子激发多烯链。这些动力学的帮助下，假设聚乙炔的导电机制的情况下。此外，我们计算的光学光谱的带电孤子和激发链的动力学是在公平的协议与实验。本文还研究了中性孤子的热迁移率，并进一步将该模型推广到聚乙炔以外的聚合物中。这样的修改可以产生有关的非线性准粒子的性质在电荷输运过程中的问题没有完全解决的情况下，信息。这是顺式聚乙炔的情况下，最近的文献表明，双极化子应该是不稳定的。然而，我们可以证明，带电极化子和双极化子在材料中是稳定的，双极化子比带电极化子更受欢迎。由于该模型可以扩展到其他聚合物，也可以扩展到尚未合成的化学结构，经过进一步发展，它也可以获得预测能力。
Abstract Conjugated organic polymers are intrinsically semiconductors but become conducting upon doping and photoconducting after optical excitation. In the low doping regime they show usually conduction without an associated spin transport. Thus as charge carriers in this regime nonlinear quasiparticles are assumed, such as charged solitons in materials with a degenerate ground state like e.g. trans-polyacetylene or pernigraniline. In the case of materials with a non-degenerate ground state the situation is often less clear but it is assumed that charged polarons or bipolarons are the charge carriers in them.We present a theoretical model for the description of the dynamics of such quasiparticles which yields also information on their mobility, their nature and stability, as well as their spectral properties. The model is based on a π-electron Hamiltonian including electron-electron interactions. On the basis of the prototype material polyacetylene it is demonstrated how such a model can be parametrized with the help of correlated ab initio or density functional calculations and applied. We discuss in some detail the dynamics of the pristine material, as well as of doped and of electronically excited polyene chains. With the help of these dynamics a scenario for the conduction mechanism assumed for polyacetylene is given. Further we calculate optical spectra from the dynamics for charged solitons and for excited chains which are in fair agreement with experiments. The thermal mobility of neutral solitons is also studied.Further we show how the model can be extended for applications to polymers different from polyacetylene. Such modifications could yield informations about the nature of nonlinear quasiparticles involved in the process of charge transport in cases where the question is not completely solved. This is the case in cis-polyacetylene where recent literature suggests that bipolarons should be instable. However, we could show that both charged polarons and bipolarons are stable in the material with bipolarons favored over charged polarons.Due to the fact that the model can be extended to other polymers, also to chemical stuctures not yet synthesized, it could gain also predictive power after further development.