Light‐Triggered Release of Trapped Charges in Molecular Assemblies

Abstract

We demonstrate the mediation of charge transport and release in thin films and devices by shifting the redox properties of layers of metal complexes by light. The nanoscale surface arrangement of both photo- and electrochemically-active components is essential for the function of the thin films. Layers of well-defined ruthenium complexes on indium-tin-oxide electrodes provide electron-transport channels that allow the electrochemical addressing of layers of isostructural cobalt complexes. These cobalt complexes are electrochemically inactive when assembled directly on transparent metal-oxide electrodes. The interlayer of ruthenium complexes on such electrodes allows irreversible oxidation of the cobalt complexes. However, shifting the redox properties of the ruthenium complexes by excitation with light opens up an electron-transport channel to reduce the cobalt complexes; hence releasing the trapped positive charges.

Bifunctional Nanoscale Assemblies: Multistate Electrochromics Coupled with Charge Trapping and Release

“…Numerous studies have addressed the redox chemistry of monomolecular films; however, the properties of films consisting of two or more layers of different molecules are more complex. Such systems have been explored by Murray and others . Considering that different molecular layers differ in their redox potentials, hybrid materials with unique electron transfer properties can be designed.…”

“…Potential gradients in films perpendicular to the surface of the electrodes can either hamper or facilitate electron transfer, leading, for instance, to charge trapping or release, respectively. Such phenomena have been demonstrated with redox‐active polymers and inorganic materials . Being able to control the potential gradient in a bilayer by an external stimulus is highly desirable because it can result in the reversal of electron transfer processes.…”

“…Depending on the deposition sequence of the molecular components and the composition of the resulting metallo‐organic assemblies, materials can be formed having unidirectional or bidirectional electron transfer pathways . We have also shown how trapped charges in metallo‐organic assemblies consisting of distinct layers of ruthenium and cobalt complexes can be released using a combination of light and a potential . The main goal of this study is the demonstration and application of the coupling of charge storage–release with electrochromism in nanoscale bilayers.…”

Bifunctional Nanoscale Assemblies: Multistate Electrochromics Coupled with Charge Trapping and Release

“…Numerous studies have addressed the redox chemistry of monomolecular films; however, the properties of films consisting of two or more layers of different molecules are more complex. Such systems have been explored by Murray and others . Considering that different molecular layers differ in their redox potentials, hybrid materials with unique electron transfer properties can be designed.…”

“…Potential gradients in films perpendicular to the surface of the electrodes can either hamper or facilitate electron transfer, leading, for instance, to charge trapping or release, respectively. Such phenomena have been demonstrated with redox‐active polymers and inorganic materials . Being able to control the potential gradient in a bilayer by an external stimulus is highly desirable because it can result in the reversal of electron transfer processes.…”