Multiscale Modeling of Charge Transfer Processes in Organic Semiconductors

The relationship between molecular structure and macroscopic charge mobility plays an important role in the design of organic semiconductors. In this respect, the molecular packing is the starting point that governs the electron coupling, energetic landscapes, and electron polarization (EP) energies of the charge carriers. The molecular packing is strongly dependent on the intermolecular interaction potentials. During charge transfer (CT) processes, the intermolecular potentials are related to electron state changes in which the charged molecule moves from one site to another site. Thus, traditional force fields cannot express these electron processes. To this end, state-specific polarizable force fields (SS-PFFs) derived from quantum mechanics were developed to describe the intermolecular interactions between the neutral molecules and charged molecules. The influence of the condensed phase on the EP energies and reorganization energies of CT reactions in organic solids can be explicitly discussed using SS-PFFs. The molecular descriptors of the electrostatic potentials are used to relate the condensed-phase effects and molecular structure. In this way, we can obtain a basic physical picture to guide the design of organic semiconducting molecular materials.