A Highly Stable and Tunable Visible‐Near‐IR Electrochromic All‐in‐One Gel Device

Abstract

Energy saving is a global topic of critical importance. Electrochromic devices (ECDs) could be used to control energy flow by modulating the light absorption reversibly upon application of a small potential bias. Herein, a visible‐NIR dual‐band ECD based on the viologen analogue 4, 4′‐(thiophene‐2, 5‐diyl) bis(1‐methylpyridin‐1‐ium) diiodide (TMP) was assembled with a simple all‐in‐one configuration. The TMP‐based gel ECD possesses high dynamic contrast (81.7 % at 570 nm, 68.6 % at 835 nm, 62.8 % at 910 nm and 55.3 % at 1046 nm), excellent cyclic stability (70.6 % of ▵T at 570 nm maintained after 25000 cycles at 1.4 V), and low power consumption (15.2 mJ/cm2 to complete the coloring process, 2.5 mW/cm2 to keep color and low transmittance). Remarkably, the absorption of visible and NIR light could be selectively adjusted by varying the coloring time. For comparison, a dimethyl viologen (DMV)‐based gel ECD was fabricated, and the SAR (structure‐activity relationship) was established by cyclic voltammetry, density functional theory (DFT) calculations, and other electrochromic performance parameters.

Post-Synthetic Color Tuning of the Ultra-Effective and Highly Stable Surface-Confined Electrochromic Monolayer: Shades of Green for Camouflage Materials

“…The impact of N-quaternization on the properties of electrochromic (EC) molecules is widely studied for viologens, which are small organic electrochromes prepared by N-quaternization of the derivatives of 4,4-bipyridine. Viologen-based EC systems demonstrate promising electronic and optical properties, including desirable EC color changes as a result of the significant charge delocalization within the molecule upon N-quaternization that allows stabilizing of brightly colored cation radical species. − Notably, a simple change of the alkylating agent allows for easy and reliable color tuning of the materials. Jena and Choudhury recently utilized N-quaternization to integrate covalently linked imidazolium bromide motifs with functional tetraterpyridine iron units to create interesting EC three-dimensional (3D) assemblies with enhanced ionic diffusion and great ion-transfer efficiencies …”

Electrochemical and Solvent‐Mediated Visible‐to‐Near‐Infrared Spectroscopic Switching of Benzoselenadiazole Fluorophores

“…More importantly,itwas expected to have enhanced spectroscopic properties, including ar eversible electrochemical behavior,astrong absorption in the visible and be highly emissive. The collective spectroscopic and electrochemical properties of the benzoselenadiazole end-capped with an electroactive group would make it an ideal electrochromic materialt hat can undergo soughta fter reversible visible-to-NIR color switching with applied potential, [16] while also electrochemically modulating its emission intensity.W ithint his context, the color,e mission, emission quantum yield, along with the redox and electrochemically mediated properties of 1 are presented herein. These properties are compared to its electronically different counterparts 2 and 3 [15] for understandingt he effects of the terminal electronic groups on the spectroscopic and electrochemicalp roperties.…”

Toward Next‐Generation Smart Windows: An In‐depth Analysis of Dual‐Band Electrochromic Materials and Devices

“…These include compounds such as viologen (N,N-substituted bipyridines) and its derivatives. [67,156] Typically, they manifest electrochromic responses through charge transfer amidst varying valence states of heteroatoms (such as N, O) on the conjugated 𝜋 bond (e.g., pyridine). [64] As shown in Figure 8a,b, a novel 2,4,6-tri(pyridyl-4-propyl)−1,3,5-triazine bromide (TTPT) material with dual-band modulation capability was formed by the introduction of propyl bromide into 2,4,6-Tri(4-pyridyl)−1,3,5triazine (TPT).…”

“…Metalloporphyrins and PB are also part of this category. [62,155,156] The uniqueness of these complexes lies in their multicolor switching abilities, which are triggered through the electroredox processes of the central metal ions and the diverse ligands, with polypyridine metal complexes being the predominant ones. [165][166][167] As illustrated in Figure 8f, researchers managed to synthesize dual-redox metallo-supramolecular polymers by infusing 4,4bis(2,2:6,2-terpyridinyl)phenyl-triphenylamine as a ligand.…”

“…In addition, to further enhance the cycle life of dual‐band electrochromic materials, a viologen derivative (4, 4′‐(thiophene‐2,5‐diyl)‐bis(1‐methylpyridin‐1‐ium) diiodide (TMP)) with “acceptor–donor–acceptor” structure was synthesized by introducing a thiophene unit between two pyridines. [ 27,156 ] Benefiting from the formation of intramolecular hydrogen bonds and the enhanced stability of electron deficient radicals by donor units, the electrode exhibited a cycling life of over 25 000. [ 156 ] (2)Conductive polymers: …”