Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons, Belgium.
J Chem Phys. 2013 Aug 14;139(6):064316. doi: 10.1063/1.4817856.
The performance of the mean field theory to account for charge transfer rate in molecular dimers and charge transport mobility in molecular stacks with small intermolecular electronic coupling and large local electron-phonon coupling (i.e., in the hopping regime) is carefully investigated against various other approaches. Using Marcus formula as a reference, it is found that mean field theory with system-bath interaction and surface hopping approaches yield fully consistent charge transfer rates in dimers. However, in contrast to the dimer case, incorporating system-bath interaction in the mean field approach results in a completely wrong temperature dependence of charge carrier mobility in larger aggregates. Although the mean field simulation starting from the relaxed geometry of a charged molecule and neglecting system-bath interaction can reproduce thermally activated transport, it is not able to characterize properly the role of additional nonlocal electron-phonon couplings. Our study reveals that the mean field theory must be used with caution when studying charge transport in the hopping regime of organic semiconductors, where the surface hopping approach is generally superior.
针对分子二聚体中的电荷转移速率和分子堆叠中的电荷输运迁移率（即在跳跃区域），我们仔细研究了平均场理论与其他各种方法相比的表现。以马库斯公式为参考，我们发现，考虑系统-溶剂相互作用和表面跳跃方法的平均场理论在二聚体中产生了完全一致的电荷转移速率。然而，与二聚体情况相反，在平均场方法中考虑系统-溶剂相互作用会导致较大聚集体中载流子迁移率的温度依赖性完全错误。尽管从带电分子的弛豫几何形状开始并忽略系统-溶剂相互作用的平均场模拟可以重现热激活输运，但它不能正确地描述额外非局部电子-声子耦合的作用。我们的研究表明，在研究有机半导体跳跃区域中的电荷输运时，必须谨慎使用平均场理论，而表面跳跃方法通常更优越。
