Charge-Transfer Dynamics and Nonlocal Dielectric Permittivities Tuned with Metamaterial Structures as Solvent Analogues

TL;DR

This paper demonstrates that multi-layered hyperbolic metamaterial substrates can significantly modify charge transfer dynamics in molecular systems, acting as solvent analogues through nonlocal dielectric effects, with implications for optoelectronic and chemical applications.

Contribution

It introduces a novel approach to tuning charge transfer dynamics using metamaterial structures, linking nonlocal dielectric permittivities to substrate engineering.

Findings

Longer-lived charge transfer states observed with HMM substrates

Charge separation and recombination times increased by factors of 2.4 and 1.7

Modeling with image dipole interactions explains experimental results

Abstract

Charge transfer (CT) is a fundamental and ubiquitous mechanism in biology, physics and chemistry. Here, we evidence that CT dynamics can be altered by multi-layered hyperbolic metamaterial (HMM) substrates. Taking triphenylene:perylene diimide dyad supramolecular self-assemblies as a model system, we reveal longer-lived CT states in presence of HMM structures with both charge separation and recombination characteristic times increased by factors of 2.4 and 1.7, i.e. relative variations of 140 and 73 %, respectively. To rationalise these experimental results in terms of driving force, we successfully introduce image dipole interactions in Marcus theory. The non-local effect herein demonstrated is directly linked to the number of metal-dielectric pairs, can be formalised in the dielectric permittivity, and is presented as a solid analogue to local solvent polarizability effects. This model and extra PH3T:PC60BM results show the generality of this non-local phenomenon and that a wide range of kinetic tailoring opportunities can arise from substrate engineering. This work paves the way toward the design of artificial substrates to control CT dynamics of interest for applications in optoelectronics and chemistry.