Charge-Transfer Dynamics Control by Manipulating Dielectric Constants with Hyperbolic Metamaterial Structures as Solvent Analogues
Charge transfer (CT) is essential to numerous fields including biology, physics and chemistry. Here, we demonstrate that multi-layered hyperbolic metamaterial (HMM) substrates alter CT dynamics. With triphenylene:perylene diimide dyad supramolecular self-assemblies, we show that both charge separation and recombination characteristic times are increased by factors of 2.5 and 1.6, respectively, resulting in longer-lived CT states. We successfully rationalise the experimental data by introducing dipole image interactions in Marcus theory to tune the driving force. The number of metal-dielectric pairs induces a non-local effect near the HMM structure formalised in the dielectric permittivity, and is presented as a solid analogue to local solvent polarizability effects. The model and PH3T:PCBM data show the phenomenon generality and that molecular and substrate engineering offer a wide range of kinetic tailoring opportunities. This work opens the path toward novel artificial substrates designed to control CT dynamics with potential applications in fields including optoelectronics and chemistry.