Explicit Method To Evaluate the External Reorganization Energy of Charge-Transfer Reactions in Oligoacene Crystals Using the State-Specific Polarizable Force Field.

The state-specific polarizable force field (SS-PFF) are parametrized for neutral and cationic oligoacenes based on QM calculations. The SS-PFF is applied to explicitly evaluate the electron-phonon interaction for localized hole-carrier charge transfer (CT) reactions in oligoacene crystals. A two-point model is proposed to estimate the total reorganization energy including internal and external contributions for hole-carrier CT reactions in oligoacene crystals. Orientation and separation dependent external reorganization energy are well described according to the potential energy surface of SS-PFF. Moreover, increasing the temperature leads to a small increase of the external reorganization energy of CT reactions.