State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
J Chem Phys. 2012 Jun 21;136(23):234106. doi: 10.1063/1.4729310.
The dynamic disorder model for charge carrier transport in organic semiconductors has been extensively studied in recent years. Although it is successful on determining the value of bandlike mobility in the organic crystalline materials, the incoherent hopping, the typical transport characteristic in amorphous molecular semiconductors, cannot be described. In this work, the decoherence process is taken into account via a phenomenological parameter, say, decoherence time, and the projective and Monte Carlo method are applied for this model to determine the waiting time and thus the diffusion coefficient. It is obtained that the type of transport is changed from coherent to incoherent with a sufficiently short decoherence time, which indicates the essential role of decoherence time in determining the type of transport in organics. We have also discussed the spatial extent of carriers for different decoherence time, and the transition from delocalization (carrier resides in about 10 molecules) to localization is observed. Based on the experimental results of spatial extent, we estimate that the decoherence time in pentacene has the order of 1 ps. Furthermore, the dependence of diffusion coefficient on decoherence time is also investigated, and corresponding experiments are discussed.
近年来，人们对有机半导体中载流子输运的动态无序模型进行了广泛的研究。虽然该模型在确定有机晶状材料中带状迁移率的值方面是成功的，但它不能描述无定形分子半导体中典型的非相干跳跃输运特性。在这项工作中，通过一个唯象参数（即退相干时间）考虑了退相干过程，并将投影和蒙特卡罗方法应用于该模型，以确定弛豫时间，从而确定扩散系数。结果表明，当退相干时间足够短时，输运类型从相干变为非相干，这表明退相干时间在决定有机体内输运类型方面起着重要作用。我们还讨论了不同退相干时间下载流子的空间扩展，观察到从离域（载流子位于大约 10 个分子中）到局域的转变。基于空间扩展的实验结果，我们估计并五苯中的退相干时间约为 1 ps。此外，还研究了扩散系数对退相干时间的依赖性，并讨论了相应的实验。
