Institute of Physics, University of Brasília, Brasília, 70910-900, Brasília, Brazil.
Phys Chem Chem Phys. 2019 Jan 30;21(5):2727-2733. doi: 10.1039/c8cp06915h.
Polarons play a crucial role in the charge transport mechanism when it comes to organic molecular crystals. The features of their underlying properties - mostly the ones that directly impact the yield of the net charge mobility - are still not completely understood. Here, a two-dimensional Holstein-Peierls model is employed to numerically describe the stationary polaron properties in organic semiconductors at a molecular scale. Our computational protocol yields model parameters that accurately characterize the formation and stability of polarons in ordered and disordered oligoacene-like crystals. The results show that the interplay between the intramolecular (Holstein) and intermolecular (Peierls) electron-lattice interactions critically impacts the polaron stability. Such an interplay can produce four distinct quasi-particle solutions: free-like electrons, metastable polarons, and small and large polarons. The latter governs the charge transport in organic crystalline semiconductors. Regarding disordered lattices, the model takes into account two modes of static disorder. Interestingly, the results show that intramolecular disorder is always unfavorable to the formation of polarons whereas intermolecular disorder may favor the polaron generation in regimes below a threshold for the electronic transfer integral strength.
在有机分子晶体的电荷输运机制中，极化子起着至关重要的作用。它们潜在特性的特征——主要是直接影响净电荷迁移率的那些特征——仍未被完全理解。在这里，采用二维 Holstein-Peierls 模型在分子尺度上数值描述有机半导体中的静态极化子特性。我们的计算方案得出的模型参数准确地描述了有序和无序低聚并苯类晶体中极化子的形成和稳定性。结果表明，分子内（Holstein）和分子间（Peierls）电子-晶格相互作用的相互作用对极化子的稳定性起着至关重要的作用。这种相互作用可以产生四个不同的准粒子解：自由电子、亚稳定极化子以及小极化子和大极化子。后者控制着有机晶态半导体中的电荷输运。对于无序晶格，该模型考虑了两种静态无序模式。有趣的是，结果表明，分子内无序总是不利于极化子的形成，而分子间无序在电子转移积分强度的阈值以下的区域可能有利于极化子的产生。
