Calculating charge-carrier mobilities in disordered semiconducting polymers: Mean field and beyond
Calculating charge-carrier mobilities in disordered semiconducting polymers: Mean field and beyond
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DOI：
10.1103/physrevb.74.115204
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发表时间：
2006-09-01
影响因子：
3.7
通讯作者：
Bobbert, P. A.
中科院分区：
文献类型：
--
作者：
Cottaar, J.;Bobbert, P. A.
我们的模型电荷输运无序半导体聚合物通过跳跃的电荷在一个规则的立方晶格的网站。一个大的现场库仑排斥禁止双重占用的网站。无序是通过从高斯分布随机站点能量。最近，它被证明，该模型导致的电荷载流子迁移率的电荷载流子的密度，这是与实验观察一致的依赖。该模型方便地解决了平均场近似，其中的职业概率之间的相关性被忽略。这种近似在电荷载流子密度为零的极限下变得精确，但需要在高密度下进行检查。我们通过将晶格划分为成对的相邻站点并明确考虑每对站点之间的相关性来执行此检查。这对近似预计占最重要的修正平均场近似。我们研究了不同的温度，电荷载流子密度和电场的影响。我们证明，在参数制度相关的半导体聚合物在实际设备中使用的平均场近似计算的迁移率的修正将不超过百分之几，使这种近似可以安全地使用。
We model charge transport in disordered semiconducting polymers by hopping of charges on a regular cubic lattice of sites. A large on-site Coulomb repulsion prohibits double occupancy of the sites. Disorder is introduced by taking random site energies from a Gaussian distribution. Recently, it was demonstrated that this model leads to a dependence of the charge-carrier mobilities on the density of charge carriers that is in agreement with experimental observations. The model is conveniently solved within a mean-field approximation, in which the correlation between the occupational probabilities of different sites is neglected. This approximation becomes exact in the limit of vanishing charge-carrier densities, but needs to be checked at high densities. We perform this check by dividing the lattice in pairs of neighboring sites and taking into account the correlation between the sites within each pair explicitly. This pair approximation is expected to account for the most important corrections to the mean-field approximation. We study the effects of varying temperature, charge-carrier density, and electric field. We demonstrate that in the parameter regime relevant for semiconducting polymers used in practical devices the corrections to the mobilities calculated from the mean-field approximation will not exceed a few percent, so that this approximation can be safely used.