Troisi Alessandro, Orlandi Giorgio
Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
J Phys Chem A. 2006 Mar 23;110(11):4065-70. doi: 10.1021/jp055432g.
In organic crystalline semiconductor molecular components are held together by very weak interactions and the transfer integrals between neighboring molecular orbitals are extremely sensitive to small nuclear displacements. We used a mixed quantum chemical and molecular dynamic methodology to assess the effect of nuclear dynamics on the modulation of the transfer integrals between close molecules. We have found that the fluctuations of the transfer integrals are of the same order of magnitude of their average value for pentacene and anthracene. Under these conditions the usual perturbative treatment of the electron-phonon coupling is invalid, the band description of the crystal breaks down and the charge carriers become localized. Organic crystals of pentacene and anthracene, even in the absence of defects, can be regarded as disordered media with respect to their charge transport properties. These results suggest that the dynamic electronic disorder can be the factor limiting the charge mobility in crystalline organic semiconductors.
在有机晶体半导体中，分子组件通过非常弱的相互作用结合在一起，相邻分子轨道之间的转移积分对小的核位移极其敏感。我们使用了一种混合量子化学和分子动力学的方法来评估核动力学对紧密分子间转移积分调制的影响。我们发现，对于并五苯和蒽，转移积分的波动与其平均值具有相同的数量级。在这些条件下，电子 - 声子耦合的常规微扰处理无效，晶体的能带描述失效，电荷载流子变得局域化。即使没有缺陷，就电荷传输性质而言，并五苯和蒽的有机晶体也可被视为无序介质。这些结果表明，动态电子无序可能是限制晶体有机半导体中电荷迁移率的因素。
