ANOMALOUS TRANSIT-TIME DISPERSION IN AMORPHOUS SOLIDS
ANOMALOUS TRANSIT-TIME DISPERSION IN AMORPHOUS SOLIDS
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DOI：
10.1103/physrevb.12.2455
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发表时间：
1975-01-01
影响因子：
3.7
通讯作者：
MONTROLL, EW
中科院分区：
文献类型：
--
作者：
SCHER, H;MONTROLL, EW
对越来越多的无机和有机非晶态材料的瞬时光电流I(T)的测量显示出反常的输运性质。I(T)的长尾表示载流子传输时间的离散。然而，I(T)对电场和样品厚度的形状不变性(对于这里考虑的材料类别被指定为普适性)与传统的统计扩展概念，即高斯载波分组是不相容的。我们建立了I(T)的随机输运模型，该模型描述了在样品表面存在依赖于场的空间偏置和吸收势垒的情况下，载体包执行随时间变化的随机游动的动力学。随机游走的时间依赖性由跳跃时间分布Ψ(T)控制。利用无序系统中跳跃的Ψ(T)特征生成的分组[例如，Ψ(T)∼t−(1+α)，0<；α<；1]被示出以许多反常的非高斯属性传播。与这个包相关的计算的I(T)不仅符合普适性，而且可以定量地解释各种实验。该理论提出的新的数据分析方法使人们可以直接提取渡越时间，即使是对于没有特征的电流轨迹。特别是，我们将分析无机(−As 2 Se 3)和有机(三硝基荧酮-聚乙烯基咔唑)体系。我们的函数Ψ(T)与第一原理计算有关。需要强调的是，这些Ψ(T)S刻画了一种非马尔科夫输运过程的实现。此外，该理论还表明了迁移率概念在这种弥散类型的输运中的局限性。
Measurements of the transient photocurrent I (t) in an increasing number of inorganic and organic amorphous materials display anomalous transport properties. The long tail of I (t) indicates a dispersion of carrier transit times. However, the shape invariance of I (t) to electric field and sample thickness (designated as universality for the classes of materials here considered) is incompatible with traditional concepts of statistical spreading, ie, a Gaussian carrier packet. We have developed a stochastic transport model for I (t) which describes the dynamics of a carrier packet executing a time-dependent random walk in the presence of a field-dependent spatial bias and an absorbing barrier at the sample surface. The time dependence of the random walk is governed by hopping time distribution Ψ (t). A packet, generated with a Ψ (t) characteristic of hopping in a disordered system [eg, Ψ (t)∼ t−(1+ α), 0< α< 1], is shown to propagate with a number of anomalous non-Gaussian properties. The calculated I (t) associated with this packet not only obeys the property of universality but can account quantitatively for a large variety of experiments. The new method of data analysis advanced by the theory allows one to directly extract the transit time even for a featureless current trace. In particular, we shall analyze both an inorganic (a− As 2 Se 3) and an organic (trinitrofluorenone-polyvinylcarbazole) system. Our function Ψ (t) is related to a first-principles calculation. It is to be emphasized that these Ψ (t)'s characterize a realization of a non-Markoffian transport process. Moreover, the theory shows the limitations of the concept of a mobility in this dispersive type of transport.