Flexible Composite Electrochromic Device with Long-Term Bistability Based on a Viologen Derivative and Prussian Blue

Abstract

Viologen and Prussian blue (PB) exhibit good electrochromic properties, but certain limitations still exist. To improve the electrochromic properties of viologen, a viologen derivative 1,1′-bis(4-(bromomethyl)benzyl)-[4,4′-bipyridine]-1,1′-diium hexafluorophosphate (BBDV) was synthesized, and its electrochromic properties were investigated. Additionally, a flexible composite electrochromic device (FC-ECD) was prepared by using BBDV and PB as active materials. The structure of the FC-ECD was PET-ITO/gel electrolyte−BBDV/ PB/PET-ITO. The applied voltage required for the FC-ECD was found to be lower than that of the ECD based on BBDV(FBBDV-ECD). Compared to FBBDV-ECD, FC-ECD exhibited a higher optical contrast (71.42%) and cyclic stability (89.51%). The FC-ECD exhibited multicolor changes under different applied voltages (ranging from −2.0 to +1.6 V). Especially, the color of the FC-ECD remained stable for 14 h after the removal of the applied voltage.

Multifunctional Applications of D−π–A-Type Poly Schiff Bases for Electrochromic, Electrofluorochromic Materials, and Organic Cathodes for Aqueous Zinc Ion Batteries

“…The interest of researchers in investigating multifunctional conductive polymers was piqued by the rapid advancement of smart-technology methodologies. − Conductive polymer materials, such as electrode materials, electrochromic (EC) materials, electrofluorochromic (EFC) materials and devices, , energy-saving smart windows, − electromagnetic shielding materials, sensing materials, − and light-emitting diodes, − have been among the most discussed materials for the past few years due to their numerous practical applications.…”

Influence of Cross-Link Density on Electrochromic Properties of Conjugated Polymer

“…Electrochromism indicates the optical absorption properties of materials could vary reversibly between different potentials, leading to the apparent color varying reversibly under low energy consumption. , The features endow electrochromic materials with wide applications in smart glass of buildings and automobiles, camouflage materials, multifunctional electronics, etc. − The reported electrochromic materials include organic materials (polymer and small organic molecule), − inorganic materials (WO 3 , TiO 2 , NiO, etc. ), − and organic/inorganic composites. , Conjugated polymer as an organic electrochromic material exhibits many unique advantages relative to others, such as good flexibility, lightweight, rich color, fast respond time, etc. − A series of high-performance conjugated polymers as electrochromic materials were reported, such as black-transparent polymers, , multicolored polymers, , near-infrared polymers, , etc. It must be pointed out that many reported conjugated polymers often exhibit good performance only at one electrochromic parameter, which is adverse to their commercial application.…”

Electrochromism and Bistable Electrochromic Devices of Five-Membered-Heterocycle Bridged Viologen Polymers

“…ECMs are crucial components of ECDs which can be categorized into two main classes based on their chemical compositions: inorganic materials and organic materials . Prussian blue and transition metal oxides are the typical representatives of inorganic materials. − Organic materials primarily encompass organic small molecules with distinct conjugation and conductive polymers. − Among them, viologen materials, which are favored for their facile structural modifications, straightforward synthesis, elevated optical contrast, and excellent stability in oxidation–reduction processes, have been extensively and comprehensively investigated. ,− The introduction of additional redox centers into viologens enables the creation of extended viologen derivatives with stable radical formation, offering a fresh avenue for developing viologen-functionalized ECDs. − The adjustable conjugation length of chromophores also endows extended viologen derivatives with bright colors. Simultaneously, the extension of π-conjugation broadens the absorption range into the near-infrared (NIR) region, prompting researchers to explore its potential applications in thermal insulation materials. , Thiophene and its derivatives are incorporated between the two pyridine moieties of viologen molecules in order to augment conjugation interactions, thereby effectively stabilizing radicals within the highly delocalized extended conjugation framework …”