Spacer Conjugation and Surface Support Effects in Monolayer Electrochromic Materials

Abstract

Electrochromic (EC) materials that change their color under applied voltage are a rapidly growing segment of "smart" materials. Recent and potential applications of EC materials include "smart" windows, a range of optoelectronic, energy conversion, and indication devices that require miniaturization, easy integration, and sustainable development. This can be achieved by forming just a monolayer of EC molecules on a conductive support with a large surface area (i.e., surface-enhanced conductive support). In this study, we have developed a range of supports by screen printing two commercial indium tin oxide (ITO-30 and ITO-50) nanoparticles and synthesized fluorine-doped tin oxide (FTO) nanoparticles on ITO/glass and FTO/ glass substrates. We have discovered the influence of spacer conjugation (single, double, and triple bond) in the terpyridine-based iron complexes anchored as EC monolayers, on the properties of EC materials. Resulting materials demonstrate fast charge transfer kinetics and a significant color difference that depends on both the nature of the ligand and substrate. Solid-state EC devices (ECDs) demonstrate a noticeable optical difference in colored and bleached states (ΔOD), enhanced spectroelectrochemical stability, and exceptional coloration efficiency. Electron mobility and EC memory are heavily impacted by the substrate. Moreover, sufficient values of pseudocapacitance and the ability to power up an LED suggest potential applications of these materials in dual-function EC supercapacitors. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations have been employed to support the experimental findings in terms of geometries, electronic structure, interpretation of photospectra, charge distributions, and transfer, revealing significant variations between the ligands.

Dual Function Metallo–Organic Assemblies for Electrochromic–Hybrid Supercapacitors

“…Metallo–organic assemblies are also known to have excellent electrochromic properties. [ 11,26,33,37–43 ] Such assemblies have been used to generate electrochromic bendable devices on polyethylene terephthalate (PET) films that have a conductive indium‐tin oxide (ITO)‐coating. [ 11,26 ] Metallo–organic assemblies have also been studied by us and others for their electron‐transport properties, Boolean logic operations, organic photovoltaics, sensing, and use as antibacterial coatings.…”

Wearable Textile UHF-RFID Sensors: A Systematic Review

“…The general conductive ink is a metal-filled paste with a solid content of a certain percentage, for which the curing process under a required temperature by the screen machine is necessarily performed after the ink is pressed. Although the screen printing technique was invented in ancient China, this technique has been systematically developed in the last 20 years and is employed for the design of robust non-bendable chemical sensors [ 28 ], electrochromic materials [ 29 ], and non-bendable UHF-RFIDs [ 30 ]. However, the invention of conductive compositions for textile printing, described by Ujiie in 2006 [ 31 ] that was further developed by Cie in 2015 [ 32 ] opens the door for utilization of screen printing in flexible electronics.…”

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

“…Furthermore, the use of two different electrochromic layers would afford devices with new optical properties that cannot be obtained with monomolecular films. Several classes of electrochromic materials have been developed, ranging from transition metal oxides, polymers, and small organic molecules, to coordination complexes . For example, Hammond et al.…”