Electric-Field Effects on the Internal Charge Reorganization Energies of Crystalline Organic Semiconductors.

The synergistic effects of molecular packing and external electric fields (EEFs, including axial and nonaxial fields) on the internal charge reorganization energies (λ) of typical p-type SMOS have been investigated. Combined quantum and molecular mechanics calculations show that, for all-ring-fused rigid molecules single-molecule approximation and neglect of EEFs are adequate for computing λ, while for nonrigid molecules with inter-ring carbon-carbon (IRCC) linkers, the above simplifications may cause a significant deviation from the actual λ. For nonrigid molecules, solid-state packing can prevent "bad" EEFs (Fz and Fyz) from enhancing λ (adverse to charge transfer), while it allows λ to be greatly reduced (in favor of charge transfer) if "good" EEFs (Fx, Fxy, Fxz and Fxyz) are imposed. Last, a simple strategy that can divide λ into each subring contribution for IRCC-linked molecules has been proposed.