Anisotropic Dielectric Screened Range-Separated Hybrid Density Functional Theory Calculations of Charge Transfer States across an Anthracene-TCNQ Donor-Acceptor Interface.

Abstract

A density functional theory framework is developed to study electronic excited states affected by an anisotropic dielectric environment. In particular, an anisotropic dielectric screened range-separated hybrid (SRSH[r]) functional is defined and combined with an anisotropic polarizable continuum model (PCM) implemented through a generalized Poisson equation solver. We develop the SRSH-PCM(r) approach and use it to quantify the effect of anisotropy on an excited charge transfer (CT) state energy. In particular, the dielectric interface effect on the CT state within a donor-acceptor molecular complex of antrancene and tetracyanoquinodimethane is studied. The donor-acceptor complex and the dielectric interface are used to represent the interface between thin films consisting of these materials. We report the effect of such a dielectric interface on the energy of a CT and follow its dependence on the donor-acceptor distance. We also benchmark the anisotropy-affected energy by comparing to homogeneous dielectric calculated energies. Due to the planar interface, the anisotropic energies are expected to to match with those obtained based on isotropic calculations of the larger dielectric constant at large enough distances. The approach is applicable, in general, to more complicated dielectric constant distributions as expected to be found in actual interfaces of such thin films or in other systems, for example, for CT processes within photosystems.