Electrochromic Display Devices Research Articles

Multicolor Electrochromic Display and Patterned Device Based on Hollow-SiO2-Supported WO3 Photonic Crystals.

Electrochromic photonic crystals (PCs) have been intensively studied in the field of display, sensors, and intelligent materials due to their tunable brilliant structural colors. The mostly studied electrochromic PCs are based on the tunable lattice parameter after electrifying; namely, the electrochromic process is caused by the structural change of PCs. Besides the lattice parameter, the refractive index is another key factor to determine the structural color of PCs. Here, a kind of hollow-SiO2-supported WO3 (H-SiO2/WO3) PCs is designed, where the refractive index of the WO3 portion is changeable under charging. Benefiting from the support effect and tunable thickness of H-SiO2, large-area PC samples with good surface morphology and bright multicolor output are prepared. The reflection peaks of these composite PCs can shift by 30-90 nm, and their corresponding colors changed obviously after the voltage was applied. After being pixelated by laser-marking, the H-SiO2/WO3 PCs can dynamically display different numeric and alphabetic patterns in an electric-driven writing and erasing process. Not only does this composite PC structure broaden the color change range of WO3-based materials but also avoids the structural change in the electrochromic process. This work provides more possibilities for electrochromic PCs in the field of color-changing pattern displays.

Triarylamine-based polyamide containing adamantane group as Fe3+ probe and electrochromic smart devices

A new triarylamine-based polyamide was synthesized from 1,4-cyclohexanedicarboxylic acid and diamine monomer containing adamantane group (PA-CA), which exhibits high fluorescence quantum up to 46.1% and excellent electrochromic behaviors. The photoluminescence of PA-CA was quenched by coordination and internal filtration effect to realize Fe3+ response. Neutral colorless PA-CA film was converted to the oxidized blue in the electrochemical oxidation process and the maximum transmittance reached 80%, and the transmittance still exceeded 55% after 10,000 s. A Sandwich structure electrochromic device with PA-CA as the active layer was constructed with a simple strategy and different contents were displayed through patterned customization. Electrofluorochromic performance was regulated and decoding information was customized by applying voltage changes of the light and dark for PA-CA film. The applications of multifunctional integrated PA-CA responding to stimulus have broad prospects in the field of Fe3+ fluorescence sensors, photodetectors and multicolor electrochromic display devices.

High Electrochromic Performance of Perylene Bisimide/ZnO Hybrid Films: An Efficient, Energy-Saving, and Green Route.

The composite or hybrid of organic and inorganic materials is one of the common ways to improve the properties of photoelectric functional materials. Perylene bisimide (PBI) derivatives, as large π-conjugated organic small molecules, are a class of photoelectric functional materials with excellent performance. However, there were few reports on PBIs in the electrochromic field due to the difficulty of film-forming caused by their generally poor solubility. Here, water-soluble PBI derivatives (PDI-COOH and PCl-COOH) were synthesized. The hybrid films (ZnO@PDI-COOH/PCl-COOH) formed by the coordination bond and π-π stacking were prepared via a simple solution immersion method. Fourier transform infrared spectrometry and X-ray diffraction as well as scanning electron microscopy, and energy-dispersive spectrometry results further confirmed the formation of hybrid films. At the same time, electrochemical and spectroelectrochemical analyses revealed that the films have reversible redox activity and cathodic electrochromic properties, which can change from orange-red to purple. The ZnO@PDI-COOH hybrid film formed by coordination bonds exhibits fast switching times (1.7 s colored time and 2.6 s bleached time), good stability (retain 92.41% contrast after 2400 cycles), a low driving voltage (-0.6-0 V), and a high coloration efficiency (276.14 cm2/C). The corresponding electrochromic devices also have good electrochromic properties. On this basis, a large-area (100 mm × 100 mm) electrochromic display device with fine patterning was fabricated by using the hybrid film, and the device shows excellent reversible electrochromic performance. This idea of constructing organic-inorganic hybrid materials with coordination bonds provides an effective, energy-saving, and green method, which is expected to promote the large-scale and fine production of electrochromic materials.

Ligand Induced Low Operation Voltage Ru-Based Metallo-Supramolecular Polymer as Energy Saving Electrochromic Display Device

Ligand Induced Low Operation Voltage Ru-Based Metallo-Supramolecular Polymer as Energy Saving Electrochromic Display Device

All-in-one display device with multicolor states derived from NBU-3 MOF/monoalkylated viologen hybrid ionogel material

Recently, metal-organic frameworks (MOFs) have gained considerable attention for electrochromic (EC) applications owing to their improved electrochemical performance and superior processing ability. As a class of well-recognized organic EC materials, viologens are desirable and they are major active EC components for most of the marketed EC devices due to their structural versatility and property tunability. Over the past two decades, extensive efforts have been made to design and synthesize different types of viologen-based materials with enhanced EC properties. Herein, we report fabrication of MOFs and 1-hexyl-[4,4′-bipyridin]-1-ium bis (trifluoromethane sulfonyl) imide [MHV][TFSI] based all-in-one hybrid ionogel as an electrochromic device (ECD). The fabricated ECD showed reversible multicolor property with stability over 2000 cycles. Initially, the ECD showed light yellow color, and subsequently, it changed to light green, blue, and maroon color accordingly. The fabricated ECD displayed fast coloration time(tc), and bleaching times(tb) of 4.35 s and 7.72 s, respectively, along with a coloration efficiency of 99.14 cm2/C. The performance enhancement mechanisms are also concisely discussed in the present work. This work introduces the novel way to fabricate MOF based electrochromic ionogel (ECIG) ECDs and paves the way to the advancement of electrochromic ionogel-based display devices.

Investigations on Structural, Optical Properties, Electrical Properties and Electrochemical Stability Window of the Reduced Graphene Oxides Incorporated Blend Polymer Nanocomposite Films.

The incorporation of reduced Graphene oxides (rGO) as a nanofiller in the blend polymer nanocomposite (BPNC) based on Polyvinylpyrrolidone (PVP)-Polyvinylalcohol (PVA) and sodium bicarbonate (NaHCO₃) are presented. The blend polymer electrolytes films are prepared by the standard solution cast technique, and it is characterized to investigate the structural, morphological, thermal, optical and electrochemical property. The X-ray diffraction confirms the formation of polymer nanocomposite and is agreed with FESEM analysis. The FTIR confirms the presence of various interactions between the polymer, salt and rGO, and indicates the composite formation. The DSC examines the thermal property of the blend polymer nanocomposite electrolytes system. The bandgap energy has been obtained from the UV-spectroscopy and examines the direct and indirect gap, both offer the decreases bandgap with the addition of a higher concentration of rGO as nanofillers. The highest value of ionic conductivity of the film is obtained ~1.39×10-6 S cm-1 at 15 wt.% of rGO content in polymer blend nanocomposite (BPNC) films. For these BPNC films, the electrochemical stability window (ESW) is ~4.0 V at 25 wt.% of rGO content and ionic transport number (tion) is ~0.98, for 10 wt.% of rGO content at the room temperature. These highly stable blend polymer nanocomposite electrolyte films offer the excellent properties for utilized as a separator for solid-state devices e.g., battery, supercapacitors, electrochromic display devices and other electrochemical energy storage/ conversion devices respectively.

Synthesis and Characterization of Conducting Polymer

In recent technology, considerable attention was given to the fabrication of light weight rechargeable batteries, electro chromic display devices, microelectronics, sensor and molecule design etc. As one of the most important conducting polymers, polyaniline because of its chemical stability and relatively high conductivity and its derivatives have been extensively studied in different fields of science, because of the demand for high performance materials in advanced technologies. However, the common uses of polyaniline are restricted, due to its poor process ability and low solubility. Various techniques were given for synthesis of conducting polymer. In the current studies, polyaniline (PANI) and its composites with semiconductor was prepared chemical oxidation method in the presence of different bronsted acids from aqueous solutions. The effect of thermal treatment on electrical conductivity (DC), of the pure PANI, PANI+10%, 15% and 20% MnSO4 conducting polymers were investigated. It is found that conductivity of PANI enhancing due to stretching polymeric chain cause due to interaction with MnSO4.

Paper] Designed Electrochromic Display Devices with Ru(II)-Based Metallo-Supramolecular Polymer For Experience-Based Exhibits at Ehime Prefectural Science Museum

Paper] Designed Electrochromic Display Devices with Ru(II)-Based Metallo-Supramolecular Polymer For Experience-Based Exhibits at Ehime Prefectural Science Museum

Investigation of TiO2 thin films as a cathodic material for electrochromic display devices

Titanium dioxide is a preferred material in many fields of applications and is also used as one of best electrochromic display (ECD) candidates due to its chemical stability. Electrochromic devices are innovative, low-cost and low energy consumption for using as displays. In this work, electrochromic, morphological, structural, and some optical properties of tandem structures were comprehensively investigated. The mean thicknesses of the samples were measured as 86 and 120 nm on ITO- and FTO-coated glass substrates, respectively. The chronoamperometry test was performed to determine some electrochromic properties of the ECD. It was observed that the amounts of ions intercalated/de-intercalated from the coated TiO2 layer were almost equal to each other. According to the chronocoulometric analysis, the superior reversibility and coloration efficiency of the assembled ECD were found to be 83% and 26 cm2/C, respectively, onto ITO substrates. Higher reversibility is revealed in thinner films, which is consistent with the obtained thickness results. In a similar manner, highest coloration efficiency obtained for our ECD has demonstrated good contact between the TiO2-deposited layer and the ITO-coated glass substrate. Also, the highest porosity was reached by taking the highest coloration efficiency value into account. Moreover, coloration efficiencies and ΔT ratios are changed due to the interlayer transparent conductive oxide layers. Raman spectroscopy measurement reveals the anatase phase of TiO2 films on both substrates. Another important finding is related to the defect structures of the TiO2 phase. TiO2, TiO3 and TiO4 mixed phases show the lower coloration efficiency according to the TiO2 phase, for the first time. TiO3 and TiO4 phases were grown by using the FTO-coated glass substrate. Comparing results with reports has shown that our investigated design and technology for ECD applications are good candidates for such applications.

Recent advances in the applications of substituted polyanilines and their blends and composites

Conducting polymers remain as a key invention to the researchers in the last 3 decades. Among them, polyaniline serves as a potential candidate with feasible strategies to solve the current problems. Polyaniline is known for its extraordinary features such as ease of synthesis, low cost, considerable electrical conductivity, rich chemistry and strengthened biocompatibility. The scientific world has now diverged to the area of substituted polyanilines in the recent past owing to the efficient solubility, processability and extended applications in different fields. This review highlights the application aspects of the derivatives of polyanilines and their blends and composites in recent years. The wide application potentials of substituted polyanilines and their blends and composites in diverse fields such as in sensors, electrochromic display devices, solar cells, supercapacitors, batteries, semiconductors and anticorrosion materials, and in a variety of biological applications, have been highlighted. This review would bring new insights into polymer researchers to unravel novel applications.

Effect of pulsed magnetron sputtering process for the deposition of thin layers of nickel and nickel oxide

Abstract Magnetron sputtered nickel and nickel oxide films have been studied for various applications. We may find, among others, these films in electrochromic display devices, in resistive type gas sensors, as metal electrodes in electronic devices, in solar thermal absorbers. Pure nickel films deposited using PVD technique possess good corrosion and wear resistant properties. Magnetron sputtering has several advantages in film deposition (in comparison to other methods) such as relatively low heating temperature of the deposited substrate during sputtering process, high energy of sputtered atoms (about 10 eV) at the substrate, which influences positively the films adhesion. From application point of view, the most valuable feature of these films is the possibility of scaling target dimensions, which makes feasible the deposition on a several square meter surfaces. The improvement of magnetron sputtering devices design may influence positively the optimization of the deposition technology and its efficiency. The thin nickel and nickel oxide films were prepared by pulsed magnetron sputtering using original type WMK magnetron device. Ni (99.9 %) has been used as a sputtering target of 100 mm in diameter and different thicknesses (3 mm, 5 mm, and 6 mm). The distance between the substrate and target was the same in all experiments and equal to 120 mm. Argon and oxygen gases were introduced during the reactive process through needle gas valves at a total pressure of 0.4 Pa. The sputtering power, sputtering pressure and oxygen partial pressure have been used as technological knobs for deposition processes. The helpful tool for controlling the pulsed magnetron sputtering process was the original parameter of supply (so called circulating power). Results from our experiments showed that the deposition of Ni films is possible even from targets of 6 mm thickness. Deposition rate increased proportionally with the sputtering power. The aim of this work is to use the acquired expertise to develop an efficient technology of thin nickel oxide layers for electrochromic systems.

Stabilizing benzyl viologen radical cation by cucurbit[7]uril rotaxanation

A dumbbell-like molecule 3 consisting of one benzyl viologen unit and two end stoppers was synthesized and transformed into a [2]rotaxane R3 by slipping a CB[7] ring over the isophthalic acid stopper onto the viologen group. The 1H NMR, ESR and UV–Vis measurements indicated that R3 kept stable under the chemical reduction with excess Na2S2O4 while 3 would decompose. The CV curve of R3 showed a more negative reduction potential (ΔE = −0.30 V) when compared with 3, resulting from the CB[7] encapsulation. R3 underwent reversible electrochemical redox processes while the redox peaks of 3 disappeared gradually after thirty electrochemical redox cycles. Such a stabilization strategy by CB[7] rotaxanation provides potential applications in viologen-based electrochromic display devices.

The synthesis of a rigid conjugated viologen and its cucurbituril pseudorotaxanes

A linear viologen (bis[4-(4-pyridinyl)phenyl] viologen, BPPV) characterized by a fully-conjugated structure was synthesized through Zinke reaction. BPPV consists of a unique linear sexiaryl structure and is apt to be encapsulated by cucurbit[n]uril (CB[n], n = 6 or 7) in aqueous solution, forming a [2]pseudorotaxane (BPPV⊂CB[6]) with CB[6] in a central-included mode and a final [3]pseudorotaxane (BPPV⊂2CB[7]) with CB[7] in a side-included manner. The reduction potentials became higher for BPPV⊂2CB[7], and the highest for BPPV⊂CB[6] when compared with BPPV. BPPV, BPPV⊂CB[6] and BPPV⊂2CB[7] all underwent reversible one-electron redox reaction in aqueous solution, accompanied by obvious color changes, showing a good prospect in the fabrication of electrochromic display devices.

Investigation of mechanical bending instability in flexible low-temperature-processed electrochromic display devices

In this study, polyethylene naphthalate (PEN) was investigated as a flexible substrate because, compared with polyethylene terephthalate, it achieves a lower root mean square roughness and transmittance, which is favorable for reducing leakage from the bottom of flexible substrates. A flexible device structure composed of tungsten oxide/indium-doped tin oxide/PEN was used in an electrochromic (EC) test. The experimental results show that the flexible EC display device achieved a high transmittance difference of >40% and color efficiency of 70.2cm2/C at 560nm. The transmittance difference was degraded in the visible range after 200cycles of continuous bending. Furthermore, compared with flat fresh devices, the WO3 device exhibited poor retention properties in a colored state after being subjected to longer bending cycles.

ChemInform Abstract: Stimuli‐Responsive Metallo‐Supramolecular Polymer Films: Design, Synthesis and Device Fabrication

AbstractReview: 83 refs.

Operation mechanism investigation of electrochromic display devices using tungsten oxides based on solid-state metal–oxide–metal capacitor structures

In this work, we investigate the electrochromic effect of WO3 electrochromic display device and operation mechanism based on a solid-state TaN/WO3/ITO metal–oxide–metal capacitor. The electrochromic switching mechanism correlated with the oxygen vacancy concentration was proposed and well-predicted. The experimental results reveal that electrochromic device using electrodeposited WO3 without post annealing exhibits the much better coloration and bleach process than those of annealed sample. The cycling test of WO3 metal–oxide–metal capacitor also demonstrates that the degradations of current/voltage distributions are mainly originated from randomly distributed connected paths consisting of oxygen vacancies. Thus, oxygen vacancies formed during WO3 electrodeposition process or post film annealing need to be well controlled.

Synthesis, Characterization and Electrochemical Investigation of Phthalocyanine Compounds Bearing Fluorine Functionality

Peripherally substituted symmetrical phthalocyanine derivatives have the potential to use in a wide range of high technology applications, such as in catalysis, in photodynamic therapy, in electrochromic display devices, and as a molecular electronics, or magnetic devices. Phthalocyanines possess an extended π-conjugated electron system which permits π stacking between planar macrocycles. Adding substituents to the periphery of the macrocycles increases their solubility since these substituents increase the distance between the stacked phthalocyanines and enable their solvation. The phthalocyanine complexes are also electrochemically precious complexes due to their excellent electrochemical behaviors. It is well known that the different functionalities changes the features of the MPc complexes, thus electrochemical properties of these complexes should be investigated for possible applications. [1-3]We present here the syntheses of tetra-substituted fluorine containing biphenyl-malonic ester groups bearing phthalocyanine derivatives with different central metal atoms and investigation of their electrochemical behaviors. All synthesized novel phthalocyanine compounds have been characterized by using their elemental analyses, FT-IR, UV-Vis, 1H NMR, 13C NMR and mass spectroscopic methods. The electrochemical activity of phthalocyanine derivatives were also evaluated from the current–voltage curves obtained by cyclic and differential pulse voltammetric methods. REFERENCES 1- A. Koca, Y. Arslanoğlu, E. J Electroanal Chem, 616 (2008), pp. 107–116 2- N.B. Mckeown, B. Dunn, J.W. Goodby, A.R. West (Eds.), Phthalocyanine materials: synthesis, structure and function, Cambridge University Press, Cambridge (1998) 3- H.S. Nalwa, J.S. Shirk, C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: properties and applications, VCH Publishers Inc, New York (1996), pp. 79–181.

Preparation and characterization of pure and KBr doped polymer blend (PVC/PEO) electrolyte thin films

A potassium ion conducting polymer blend electrolyte based on polyvinyl chloride (PVC) and polyethylene oxide (PEO) complexed with KBr was prepared using solution cast technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD data revealed that the amorphous domains of polymer blend matrix increased with increase of KBr salt concentration. The complexation of the salt with the polymer blend was confirmed by FT-IR studies. Electrical conductivity of the films was measured with impedance analyzer in the frequency range of 100Hz to 1MHz and in the temperature range of 303–363K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. UV–VIS absorption spectra in wavelength region of 200–600nm were used to evaluate the optical properties like direct band gap, indirect band gap and absorption edge. The optical band gaps decreased with increasing of K+ ion concentration. This suggests that, KBr is a good dopant to improve the electrical properties of PVC+PEO polymer blend electrolytes. Studies on the electrical and optical properties of polymer blend electrolyte have attracted much attention in view of their application in electronic and optical devices like electro-chromic display devices, fuel cells, gas sensors and solid state batteries. The thermal properties of these films were investigated with differential scanning calorimetry (DSC). The variation in film morphology is examined by scanning electron microscopy examination (SEM).

Preparation of Nano-Polycrystalline WO<SUB>3</SUB> Thin Films and Their Solid-State Electrochromic Display Devices

In this paper, nano-polycrystalline WO3 thin films with the thickness in the range of 100-200 nm have been uniformly prepared on the designed regions of ITO (indium tin oxide) glass substrates by thermal evaporation deposition. Their crystal structures, surface morphologies and uniformities are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. The solid-state electrochromic display (ECD) devices based on these nano-polycrystalline WO3 thin films have been also fabricated and have demonstrated to have better performance than normal thin films, including shorter response time, higher contrast, and furthermore, higher stability to keep the colored state without power consumption. These results demonstrate nano-polycrystalline WO3 thin films can be applied to improve the performance of ECD devices, especially suitable to static display.

ChemInform Abstract: Electrochromic Conjugated Polyheterocycles and Derivatives—Highlights from the Last Decade Towards Realization of Long Lived Aspirations

AbstractReview: 167 refs.