Donor-Acceptor Distance-Dependent Charge Transfer Dynamics Controlled by Metamaterial Structures

The capability to control charge transfer dynamics in a donor-acceptor molecule is important for efficient optoelectronic devices. Charge transfer dynamics is governed by thermodynamics of donor-acceptor charges in a given dielectric environment. Metamaterial structure has been shown to be able to control charge separation and charge recombination processes via nonlocal effect on dielectric permittivity for a fixed donor-acceptor distance organic film. Here, we report the influence of the metamaterial structure on the donor-acceptor distance dependence of the electron transfer process occurring in liquid crystalline organic semiconductor thin films. By examining the charge recombination rate in three different donor-acceptor distances, it is found that the barrier height β increases from 0.084 to 0.137 Å^-1 by 63% in the presence of metal-dielectric multilayered metamaterial structures. Based on the Marcus theory on the charge transfer process, we show that a further increase in the driving force for a larger donor-acceptor distance is mainly responsible for the barrier height increase in the presence of a multilayered metamaterial substrate when compared with a glass substrate. This study will provide a significant step forward in enabling more efficient hybrid organic-optoelectronic devices associated with the charge transfer process.