Search

• Effects of under-layered carbon quantum dot thin film. • Highly smooth and dense fluorine-doped tin oxide film morphology. • Acceleration of fluorine-doping and oxygen vacancy concentration. • Transparent conducting electrode effects on electrochromic performances. Morphology and chemical bonding states, including surface roughness, film density, F-doping, and oxygen vacancy (V O) concentration directly affect the electrical and optical properties of fluorine-doped tin oxide (FTO) films. In this study, morphology and chemical bonding states of FTO films are engineered simultaneously by introducing a carbon quantum dot (CQD) thin film as an interface layer during ultrasonic spray pyrolysis deposition. The abundant oxygen-containing surface functional groups and large surface free energy of the CQD thin film promoted (200) oriented crystal growth and accelerated nucleation of FTO, resulting in smooth and dense FTO film morphology. The abundant carboxyl surface functional groups on the CQDs generate active F− species that are effectively doped into SnO 2. Formic acid, formed by dissociation of the carboxyl group, can serve as a strong reducing agent for extracting oxygen atoms from the SnO 2 lattice, thereby increasing the V O concentration. The accelerated F-doping and V O concentration result in the generation of additional free electrons. The effects of the optimized CQD on the morphological and chemical structures of FTO films are demonstrated by their superior electrical (sheet resistance of ∼5.7 Ω/□) and optical properties (visible transmittance of ∼85.9 %) compared with bare FTO. Moreover, CQD/FTO used as transparent conducting electrodes in electrochromic (EC) application exhibited improved EC performances, including fast switching speeds (5.3 s and 2.3 s for bleaching and coloration, respectively) and high coloration efficiency (81.1 cm2/C) compared to that of bare FTO. [ABSTRACT FROM AUTHOR]

• A V 2 O 5 /graphene (VO-G) film is prepared by a facile electrodeposition method. • The VO-G film shows high lithium storage activity and good cyclability. • The VO-G film shows superior electrochromic performance with three colors. • Superior performance is due to wrinkled morphology, more V4+, and graphene residue. A V 2 O 5 film is prepared by an electrochemical deposition method with the assistance of graphene oxide (GO). The surface morphology and microstructure of the film are characterized by scanning electron microscope, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy measurements. The results demonstrate that the prepared film is mainly composed of orthorhombic α -V 2 O 5 with a small amount of tetragonal β -V 2 O 5 ; the V 2 O 5 film has a wrinkled surface morphology and contains a certain low valance V4+ and a trace amount of graphene oxide residue. The V 2 O 5 film exhibits good lithium storage activity and excellent cycling stability (with a capacity retention rate of 93.6% after 500 cycles at 0.5 mA cm−2). During lithium intercalation and de-intercalation processes, the color of the V 2 O 5 film changes reversibly from yellow to green, and finally blue, with a fast response time (6∼9 s) and high coloration efficiency (19.77 cm2 C−1). In addition, the electrochromic device assembled with the V 2 O 5 film as the electrochromic layer, NiHCF as the ion storage layer, and 1 M LiClO 4 /propylene carbonate solution as the electrolyte also exhibits excellent cycling stability, suggesting the significant potential of this V 2 O 5 film for electrochromic and energy storage applications. [ABSTRACT FROM AUTHOR]

• Thermal annealing (TA) temperature influences the morphology of the electrochromic films. • The effective overpotential can be correlated to thermal annealing (TA) temperature. • TA temperature greatly affects the electrochromic device (ECD) performances. • The optimized ECD exhibits an excellent optical memory capability. The preparation process plays a significant role in manipulating the morphology of organic electrochromic polymer (ECP) films, thus improving the stability of the prepared devices. In this work, the influence of thermal annealing (TA) temperatures on ECP films has been systematically investigated. The relationship between the TA temperature and the effective overpotential was determined. It was found that the TA temperature is critical for achieving the desired morphology of ECP film. At the optimized TA temperature of 180 °C, electrochromic devices (ECDs) with excellent reversibility were obtained. The response speed of the solid-state device with optimized TA temperature was more than two times faster than the unoptimized one. The coloring efficiency was also significantly enhanced, reaching the value of 374 cm2/C. Notably, the ECD based on the optimal TA temperature also showed surprisingly excellent stability, maintaining its bleaching state for almost two weeks with only a slight deterioration in the visible state. [ABSTRACT FROM AUTHOR]

• Prussian green (PG) films were fabricated by a facile hydrothermal method. • The amount of HCl and hydrothermal temperatures significantly affect the PG films. • The PG device could exhibit four typical colors: green, yellow, blue and colorless. Only utilizing hydrochloric acid and potassium ferricyanide as reaction reagents, Prussian Green (PG) films were facilely fabricated on fluorine doped tin dioxide glasses by a hydrothermal method. The amount of hydrochloric acid and the temperatures of hydrothermal treatment significantly affect the component and color of as-prepared films. The optimal preparation conditions are 0.5-1 mL of hydrochloric acid and hydrothermal temperature of 100-120 °C. The hydrochloric acid plays the role of both as a reducing agent and providing acidic conditions. The PG devices based on as-prepared PG films firstly exhibited typical four-colors electrochromic properties: yellow, green, blue and colorless states, respectively, under different power supplies, which exhibit its potential application in nonemission display field. [ABSTRACT FROM AUTHOR]

This work presents a study on the thin films of WO 3 deposited on a flexible substrate as a possible application in a flexible electrochromic device. The films were prepared by the sol-gel method and deposited by a dip-coating technique on indium tin oxide/poly(ethylene terephthalate) (ITO/PET) and densified at 100 °C for 1 h. The films of WO 3 were subjected to electrochemical, optical, structural, and morphological characterizations that pointed out the film, deposited with a withdrawal of 60 mm min−1, which showed the charge density in the insertion process of 32.86 mC cm−2. This film also presented the electrochemical stability during 200 cycles. The transmittance variation (ΔT 555 nm) between colored and bleached states was 42.6% and the coloration efficiency (η) was 14.91 cm2 C−1. The X-ray diffraction (XRD) confirmed the amorphous structure of the films and the atomic force microscopy (AFM) the root mean-squared (RMS) roughness of 4.15 nm. All the results indicate that this film may be used as an active layer in a flexible electrochromic device. • Thin films of WO3 were synthesized on flexible substrate by the sol-gel method. • The best value of the charge density was 32.86 mC cm−2. • WO3 showed ΔT555 nm = 42.6% between colored and bleached states. • X-ray diffraction, XRD, confirmed amorphous structure of WO 3 on flexible substrate. • The microscopies revealed a regular and homogeneous surface of the films. [ABSTRACT FROM AUTHOR]

• Cobalt (Co) doping improves the electrochromic properties of the films. • Nickel (Ni)-Co-oxide films exhibit high transparency in the visible region. • Ni-Co-oxide films with high coloring efficiency and response time. This paper fabricates novel electrochromic films through the sol-gel spin coating of nickel (Ni) and tunable cobalt (Co) atoms. The particle size, band gap, conductivity, and response time of the electrochromic films were improved by accurately adjusting the doping ratio of Co atoms from cobalt acetate. According to the results of scanning electron microscope and X-ray diffraction, the particles size of the Ni-Co oxide film decreased from 9 nm to 25 nm, with the increase in Co content. The reduction of the band gap enhanced the film conductivity, resulting in better electrochromic properties. The electrochemical and optical measurements show the excellence of the film in switching time and coloring efficiency: thanks to incorporating Co atoms, the switching time was shortened from 15.2 s to 10.2 s, and the coloring efficiency was increased from 35.57 to 42.5 cm2 C−1. Overall, the proposed film has a promising future for electrochromic applications. [ABSTRACT FROM AUTHOR]

Abstract The development of an uncomplicated process for the preparation of tungsten oxide (WO 3) nanorods (NRs) using hydrothermal method is still underway. Thus, this study demonstrated the growth of WO 3 NRs on indium tin oxide (ITO) coated glass substrates in aqueous solution using single synthesis step hydrothermally. The surface area and size of the NRs which should be tunable for electrochromic (EC) applications were controlled by adjusting the concentration of surfactants such as propylene glycol (PG). The synthesized NRs were illustrated using crystal structure study, surface morphology, chemical analysis, and the measure of the luminance of a color. The results manifested that increasing the PG content increased the size of the crystallite with a nanoparticle-like morphology on the ITO substrate, indicating the direct deposition of a stable WO 3 thin film. In addition, the synthesized WO 3 NRs exhibited fast switching speed and high contrast ratio implying superior EC properties for smart window application. Furthermore, an EC device with the dimensions of 2 × 4 cm2 was assembled using the synthesized WO 3 NRs with the ITO/WO 3 /Lithium perchlorate-propylene carbonate-poly(methyl methacrylate)-acetonitrile/nickel oxide/ITO configuration. The device had an average optical modulation in the visible region, a fast EC response time (1.2 s for coloration and 1.5 s for decoloration), excellent coloration efficiency (243 cm2 C−1) and a superior EC stability (over 20,000 color/decolor cycles). Highlights • The one step deposition of WO 3 by hydrothermal method is described. • Propylene glycol employed to improve hexagonal structure of WO 3 thin films. • Electrochromic device assembled with configuration ITO/WO 3 /LiClO 4 -PC-PMMA-ACN/NiO/ITO. • Electrochromic stability of ECD enhanced using hydrothermally grown WO 3 nanorods. [ABSTRACT FROM AUTHOR]

Abstract Zirconium dioxide (ZrO 2) thin films were deposited onto glass substrates, indium tin oxide (ITO) coated glass substrates and nickel oxide (NiO) / ITO / glass structures by reactive radio frequency (RF) magnetron sputtering using a zirconium target at room temperature. The deposition power was held at 75 W and the influence of deposition pressure and film thickness on the properties of the ZrO 2 films were investigated. Optical, electrochemical and electrochemical impedance spectroscopy measurements of the ZrO 2 films were performed and the electrochromic behavior of a half-cell structure of ZrO 2 / NiO / ITO / glass was investigated in a wide spectral range. The amount of inserted/extracted charges into/from each film during bleaching/coloring process were investigated in detail. The highest coloration efficiency (24.3 cm2/C) and optical modulation (42.8%) at a wavelength of 550 nm were found for a ZrO 2 / NiO / ITO / glass structure having a ZrO 2 film with a thickness of 100 nm, deposited at 4.00 Pa. Finally, a unique design of an all solid-state electrochromic device with a configuration of ITO / NiO / wet lithiated ZrO 2 / dry lithiated tungsten oxide (WO 3) / ITO / glass was fabricated. The optical modulation of the device was 53% at 550 nm for the applied potentials of ±3 V. Highlights • Optical and electrochromic (EC) behavior of ZrO 2 were studied. • The EC behavior of a half-cell structure of ZrO 2 /NiO/ITO/glass was investigated. • An uniquely designed all-solid-state EC device was fabricated. • The large optical modulation was found to be 53% with the applied voltages of ±3 V. • The ZrO 2 film was used as Li+ ion conducting layer in the EC device. [ABSTRACT FROM AUTHOR]

Thin films of WO 3 :H (~450 nm) were prepared on indium tin oxide (ITO) coated glass by reactive direct current magnetron sputtering at room temperature. The visible transmittance of the original state, and the X-ray photoelectron spectroscopy analysis of WO 3 :H films prove that H + ions have been introduced into the structure of WO 3 . Based on the optimized parameters of WO 3 :H thin film, the Glass/ITO/WO 3 :H/Ta 2 O 5 /NiO x /ITO electrochromic devices (ECDs) are prepared monolithically by magnetron sputtering. Different applied voltages of 1.0, 2.0 and 3.0 V were applied to the ECD for investigating its influence on the ECD's optical contrast and cycle life. Though the ECD can get a higher contrast about 42% at 550 nm under 3.0 V voltage, however, it will be destructed quickly. When the operating voltage is 2.0 V, the ECD has a stable cycle performance with the optical contrast of >30%. [ABSTRACT FROM AUTHOR]

All solid-state electrochromic devices were fabricated using radio-frequency magnetron sputtering. The electrochromic layers employed in the all solid-state device were subjected to lithiation insertion to improve performance of the device. Two structures, one with dry, and one with both wet and dry lithiation processes were used for intercalation of lithium atoms into the electrochromic layers. The main device configuration was as follows: indium tin oxide (ITO)/NiO/Ta 2 O 5 /dry lithiated WO 3 /ITO/glass. Dry lithiation was performed by exposing the WO 3 layer in vacuum to Li vapor atoms obtained by radio-frequency (RF) magnetron sputtering of LiNbO 3 at room temperature. An additional, wet lithiation, step was performed on one structure by electrochemical cycling in a solution containing lithium ions, leading to Li + insertion into the Ta 2 O 5 layer used as an ion-conducting layer. The optical modulation of the device containing only dry lithiated WO 3 was found to be 34.8% at 550 nm for applied potentials of ±4 V. With wet lithiation additionally applied to the ion-conducting layer (Ta 2 O 5 ), the optical modulation of the device increased to 71.7% at 550 nm for applied potentials of ±4 V. [ABSTRACT FROM AUTHOR]

Galvanostaticaly electrodeposited polyaniline thin films were used as both potentiometric and optical pH chemical sensor. The galvanostatic deposition parameters were: deposited charge from 150 to 600 mC cm −2 , current density from 0.5 to 1.0 mA cm −2 and deposition time from 150 to 1200 s. The electrodeposited polyaniline thin films in these conditions presented passivation charge 150 ± 12 mC cm −2 . The variation of the deposition parameters led to the production of thin films with distinct properties and characteristics. Basically, they presented two distinct oxidation states. The set of films produced using a current density of 0.5 mA cm −2 showed the best performances for both sensors, reaching a sensitivity of 81 ± 1 mV pH −1 and 30 ± 3 pH −1 for the potentiometric and optical pH chemical sensor, respectively. This set of films presented the best performances because they had a partially oxidized structure, the emeraldine base, which has the largest protonation potential and reaches a high electrical conductivity. The understanding of the mechanisms involved in pH detection is discussed based on the structure-property relationship established by the characterization of the PANI thin films together with the polymer's electrochemical and optical mechanism of sensitivity to pH variation. [ABSTRACT FROM AUTHOR]

Contemporary architecture is characterized by large glazings, which are able to accomplish good indoors–outdoors contact and daylighting. However, glazings, encompassing windows and glass facades, are challenging with regard to energy efficiency and often lead to excessive solar energy ingress and to large thermal losses, which must be balanced by energy-demanding cooling or heating. Cooling, especially, has grown strongly in importance during recent years. Emerging technologies utilizing thermochromics and electrochromics allow control of the inflow of visible light and solar energy and thereby produce better energy efficiency than traditional glazings employing static solutions. Thermochromic thin films, based on vanadium dioxide, let through less solar energy at high temperature than at low temperature, whereas electrochromic devices include thin films—usually based on tungsten oxide and nickel oxide—that can change their transmittance of solar energy and visible light upon the application of a voltage. It is important that electrochromics, and to some degree thermochromics, can enhance indoor comfort and lead to better living and working conditions. The present brief review covers a number of recent advances in thermochromics and electrochromics with a view to applications in energy-efficient buildings. [ABSTRACT FROM AUTHOR]

• Electrochromic properties of sputtered films from WO 3 and W targets were investigated. • Films were produced using different power sources of DC, pulsed DC, RF generators. • Change in transmittance was observed regardless of sputtering power and target type. • Films under DC power using W target exhibited optimal electrochromic properties. The structure, morphology, and electrochromic properties of sputtered-WO 3 thin films from ceramic and metallic targets were investigated. The films were produced using different types of power sources, namely, direct current (DC), pulsed DC, and radio frequency (RF) generators. Highly transparent as-deposited WO 3 thin films grown at room temperature using each target changed to dark blue upon introduction of an electric field in electrolyte regardless of types of sputtering power. WO 3 films obtained by sputtering the ceramic target using a pulsed DC power exhibited a large transmittance difference of 97.5% and high coloration efficiency of 55.2 cm2/C compared to the films using DC and RF powers, these films had higher response speeds and stable transmittance modulation after long-term cycle tests. WO 3 thin films produced by sputtering a metallic tungsten target showed enhanced electrochromic performance when grown under DC power and a coloration efficiency of 69.1 cm2/C due to their porous microstructure. This article presents methods for the fabrication of low-cost and large-scale oxide electronic devices for various applications, such as electrochromic displays, that can be applied for mass production. [ABSTRACT FROM AUTHOR]

• In 2 O 3 :Sn electrodes were employed in flexible all-thin-film electrochromic devices (ATF-ECDs). • The thickness of In 2 O 3 :Sn electrodes plays a great role in device performance. • The flexible ATF-ECD with a 125 nm thick In 2 O 3 :Sn performed the best performances. In this study, tin doped indium oxide (In 2 O 3 :Sn, ITO) thin films with a thickness range of 65-563 nm were prepared on polyethylene terephthalate substrates by radio frequency magnetron sputtering. Various material properties including the electrical properties, optical properties, morphologies, grain structures and bending properties were systematically investigated. All ITO thin films were employed as transparent conductive electrodes in the flexible all-thin-film electrochromic devices (ATF-ECDs). The flexible ATF-ECD with an 125 nm thick ITO electrode have achieved a high optical modulation of 64.2% at 600 nm, relatively fast electrochromic response speeds (1.2 s at bleaching step and 17 s at coloring step, respectively) and relatively high coloration efficiencies (181 cm2/C at bleaching step and 165 cm2/C at coloring step, respectively), which is regarded to be the optimal device in terms of comprehensively electrochromic performances and manufacturing cost. [ABSTRACT FROM AUTHOR]

Hybrid film comprised tungsten oxide and poly (3,4-ethylenedioxythiophene):polystyrene sulphonate (WO 3 –PEDOT:PSS) was developed by applying one-step inkjet printing from an office inkjet printer. The WO 3 nanoparticles were synthesized from commercial crystalline WO 3 powder through a wet ball-milling process, which is a simple, environmentally friendly, and cost-effective method of using water as a green solvent and low-energy milling. The WO 3 –PEDOT:PSS inkjet ink was prepared by dispersing the as-milled WO 3 and PEDOT:PSS in n-propanol and deionized water. The inkjet-printed WO 3 –PEDOT:PSS thin films show marked improvements of cathodic electrochromism over WO 3 films: the transmittance change of 20% at 550 nm (visible region) and 35% at 900 nm (infrared region) along with the response time of 5.67/0.30 s in their colored/bleached state, and the electrochromic coloration efficiency of 27.86 cm 2 /C at 550 nm and 69.64 cm 2 /C at 900 nm. [ABSTRACT FROM AUTHOR]

Electroactive poly(2,5-Bis(9-methyl-9 H-carbazol-3-yl)-1,3,4-oxadiazole) (PolyBCO) film was synthesized to form a highly stable conducting polymer with excellent electrochromic properties. The polymer was characterized by cyclic voltammetry, UV–Vis-NIR spectroscopy and colorimetry. Spectroelectrochemistry analysis demonstrated that the polymer can undergo both p-type and n-type doping processes. The polymer has four accessible color states. Further kinetic studies demonstrated that the polymer revealed high contrast ratio (75%), fast response time (0.9 s), excellent stability and color persistence. A dual-polymer electrochromic device was constructed in sandwich configuration where PolyBCO was used as the anodically coloring material. The device switches between a transmissive light gray state and a blue-colored state with a fast response time and high stability. [ABSTRACT FROM AUTHOR]

We report the deposition of tungsten oxide (WO 3 ) thin films on fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO) glass substrates by using a room-temperature deposition system based on low-vacuum air-spray for the fabrication of inorganic electrochromic windows. The structure of the WO 3 films was characterized using X-ray diffraction, and the surface morphology and film thickness were investigated using scanning electron microscopy and atomic force microscopy. The color of the prepared WO 3 films changed from slight yellow to dark blue under applied voltages, demonstrating electrochromism. The WO 3 film coated FTO glass exhibited a large electrochromic contrast of up to 50% at a wavelength of 800 nm. The electrochemical properties of the films were examined using cyclic voltammetry and chronocoulometry. [ABSTRACT FROM AUTHOR]

• WO 3 :Al films (0.7–4.3 at%) were prepared by RF Magnetron Sputtering. • W ions exist in the 6+ valence. • Al doping did not adversely affect the transparency of WO 3 films. • 1.5% Al doped WO 3 sample showed the highest optical modulation of 44%. Effect of Al doping on the structural, optic, and electrochromic properties of tungsten trioxide (WO 3) thin films was investigated through X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, optic transmittance, spectral ellipsometry, cyclic voltammetry and chronoamperometry measurements. Undoped and 0.7–4.3% Al doped WO 3 films were grown by radio frequency magnetron sputtering. All of the WO 3 :Al films investigated grew in amorphous phase. The thicknesses of the films varied between 113 and 124 nm. X-ray photoelectron spectroscopy analysis indicated that tungsten atoms exist as W6+ in both undoped and Al doped WO 3 films. The optical transmittance of WO 3 films is not affected by the Al doping. Their transparency in the visible range is around 90% while the transmittance in the near infrared region seems to slightly increase (around 5%) with increasing Al doping. The optical band gap energies increase with Al doping concentrations exceeding 1.5%. Variation of the coloration / bleaching times and coloration efficiency of the WO 3 films with Al doping was analyzed. The highest optical modulation of 44% was obtained for 1.5% Al doped WO 3 film at 630 nm. [ABSTRACT FROM AUTHOR]

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 70.2 cm 2 /C at 560 nm. The transmittance difference was degraded in the visible range after 200 cycles of continuous bending. Furthermore, compared with flat fresh devices, the WO 3 device exhibited poor retention properties in a colored state after being subjected to longer bending cycles. [ABSTRACT FROM AUTHOR]

This work proposes a simple and inexpensive method for the deposition of WO 3 films with electrochromic and photocatalytic properties. It consists of preparing a precursor solution of WO 3 powder in H 2 O 2 , allowing the precursor to age for a period of 1 to 2 months and then spraying it on an appropriate substrate. Changes in the crystallinity of the WO 3 particles within the precursor were observed during aging. They were taken advantage of for the preparation of homogeneous WO 3 films of optical quality. The films thus prepared are amorphous, stable, with good adherence on the substrate. They exhibit favorable electrochromic properties, such as a high Li ion diffusion coefficient (of about 5 × 10 − 10 cm 2 /s) and reversible coloration with efficiencies of 132 cm 2 /C at 389 nm, 48.9 cm 2 /C at 534 nm and 52.4 cm 2 /C at 800 nm. These films were also used as photo-anodes for the photocatalytic degradation of methylene blue (MB) in a NaOH aqueous solution with promising results. Effective degradation of MB was observed with the lowest half-life time of 55 min recorded for a NaOH concentration of 0.8 M. [ABSTRACT FROM AUTHOR]

• The electrochromic devices are fabricated using all spray-coating methods. • The compositions and configuration are optimized for multi-layer structure. • The electrochromic devices exhibit low redox potentials and reversible color switchings. • The current approach demonstrates a proof-of-concept for electrochromic paint. Here we present the fully spray-coated electrochromic devices (ECDs) containing octa-viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS). By adopting various compositions and layer configurations, transmissive and reflective ECDs were fabricated by spray-coating on polyester and polycarbonate, respectively, substrates. As an electrode, the mixture of silver nanowires and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used in the presence of divinyl sulfone. The electrical conductivity and figure-of-merit values of the electrodes were estimated depending on the compositions. The ion gel containing OHV-POSS with ionic liquid was prepared for an electrochromic layer. An electrolyte layer containing lithium salt and a curable polymer matrix was inserted between the electrochromic and electrode layers to minimize solvent infiltration. The spray-coated plastic ECDs exhibited a low redox potential of -1.5 V and reversible color changes. The devices maintained the switching times are less than 10 s and the cyclic stability for up to 90,000 s. Using all spray-coating methods, we demonstrate a proof-of-concept for electrochromic paint. With the current achievements, it would be possible to avoid the restriction imposed on the substrate and the resulting device structure. Various device structures can be constructed as the current approach does not require an upper substrate, which is further extended to diverse solid surfaces that exhibit on-demand color-changing capabilities. [ABSTRACT FROM AUTHOR]

Abstract: Tungsten oxide–titania composite thin films with different W/Ti atomic ratios were prepared and characterized in this study. Surface morphology, composition and structure of the composite thin films were investigated by scanning electron microscope with an energy dispersive spectrometer, X-ray diffraction and atomic force microscope analyses. Electrochromic properties including transmittance modulation ability, coloration efficiency and coloring/bleaching response time of these thin films were examined using cyclic voltammetry and double-potential-step experiment with in-situ ultraviolet–visible spectroscopy measurement. The presence of titania in the composite thin film could inhibit the crystal growth of tungsten oxide, which enhances the transmittance modulation ability and coloration efficiency but prolongs the coloring/bleaching response time of the composite thin film. The tungsten oxide–titania composite thin film (WTi-30) with a W/Ti atomic ratio of 78/22 exhibited better transmittance modulation ability (57.5%) and coloration efficiency (49.2cm2/C) than a pristine tungsten trioxide thin film (53.6%, 36.2cm2/C). [Copyright &y& Elsevier]

Abstract: The effect of oxygen plasma on the electrochromic characteristics of electrochromic devices that utilize Prussian blue electrodes is investigated. Prussian blue working electrodes were electrodeposited on fluorine-doped tin oxide films that were grown on glass substrates by electron cyclotron resonance-metal organic chemical vapor deposition. An indium tin oxide coated glass was employed as the counter electrode that served as an ion storage layer. The goal of the oxygen plasma treatment is to increase the oxygen functional groups on the surface of the Prussian blue electrode leading to the enhancement of the oxidation reaction and eventually the increase in coloration efficiency. Improvement of electrochromic properties, such as optical density and response time, was also observed following plasma treatment. [Copyright &y& Elsevier]

Abstract: In this study, WO3 films for electrochromic devices were deposited on a Sn-doped In2O3 substrate by hollow-cathode gas-flow sputtering using a pair of facing W metal targets. The sputtering power for all depositions was fixed at 1000W (3.9W/cm2). The deposited WO3 films were amorphous in structure. Static deposition rates were achieved to be higher by two orders of magnitude than those for conventional dc magnetron sputtering, as well as to be the comparable colouration efficiency. [Copyright &y& Elsevier]

Abstract: An investigation is conducted into fast synthesis of electrochromic organomolybdenum oxide (MoOxCy) thin films onto 40Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates via atmospheric pressure plasma jet. A precursor [molybdenum carbonyl, Mo(CO)6] vapor, carried by argon gas, is injected into air plasma torch to synthesize MoOxCy films for offering extraordinary electrochromic performance. Only low driving voltages from −1V to 1V are needed to offer reversible Li+ ion intercalation and deintercalation in a 1M LiClO4-propylene carbonate electrolyte. Light modulation with transmittance variation of up to 61%, optical density change of 0.54 and coloration efficiency of 37.5cm2/C at a wavelength of 550nm after 200cycles of cyclic voltammetry switching measurements is achieved. [Copyright &y& Elsevier]

Abstract: A donor–acceptor type monomer 4,7-dicarbazol-9-yl-2,1,3-benzothiadiazole (CBTD) was synthesized by modified Ullmann coupling reaction and its corresponding polymer (PCBTD) was obtained via electrochemical polymerization. Characterizations of the resulting polymer PCBTD were performed by cyclic voltammetry, UV–vis spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy. The polymer displayed multiple colors changed from yellow to yellowish green, green, and turquoise blue with the applied potential. The UV–vis spectra depicted that polymer film have two absorption bands as expected for this type of donor–acceptor polymer, at 320 and 467nm, which attributed to the π–π* transition and intrachain charge transfer transition, respectively. Further, electrochemical and optical band gaps were obtained by using their oxidation and reduction onset potentials and absorption edges, respectively. The optical contrasts of the PCBTD film were found to be 28.1% at 420nm and 49.9% at 800nm in the visible region. The dual type electrochromic device constructed utilizing PCBTD and poly(3,4-ethylenedioxythiophene) showed a maximum contrast (ΔT %) of 49.4% at 620nm with response time of 0.6s and exhibited high coloration efficiency (1728cm2 C−1) and good stability. These properties make the polymer a suitable material for electrochromic applications. [Copyright &y& Elsevier]

Abstract: We have investigated the electrochromic properties of amorphous granular tungsten oxide (WO3+δ) thin films with over-stoichiometric oxygen content (δ), using LiClO4 with propylene carbonate as an electrolyte. Different optical and electrochromic characteristics are observed with increasing δ. All the devices are electrochemically stable for more than 5000 color/bleach cycles without apparent degradation, and they have a faster response to coloration than to bleaching. WO3+δ films with an optimized δ value show an optical modulation of 86% at a wavelength of 630nm and the highest coloration efficiency ever reported of ~213cm2/C. The δ-dependent coloration mechanism is discussed using the site saturation model. It is proposed that WO3+δ films with the optimal δ value have favorable thickness and stoichiometry for the generation of Li+W+5 states. [Copyright &y& Elsevier]

Abstract: The electrochromic (EC) properties of tungsten oxide (WO3), such as coloration efficiency, cyclic durability and reversibility strongly depend on the structural and morphological properties, which are influenced by the deposition method and parameters. This paper presents the steps for optimizing the deposition parameters (substrate temperature, air flow pressure and precursor solution molarity) for improving the optical and electrical properties of WO3 thin films for EC applications. WO3 thin films were deposited by spray pyrolysis using tungsten hexachloride (WCl6) dissolved in ethanol as precursor solution. The EC properties of optimized films were tested in two different electrolytes (H2SO4 1M and acetic acid/sodium acetate buffer with pH=4) and changes in structure, composition and morphology of the films after coloration/bleaching cycles were discussed. The deposition temperature, carrier gas pressure and solution molarity were optimized at 250°C, 120kPa and 0.14M respectively. Under these condition a dense, uniform film, with homogenous distribution of particles, good adhesion to the substrate, low roughness (9.02nm), high transparency (>70% in the 500–1100nm range) and conductivity was obtained. Transmission modulation is higher for the sample cycled in H2SO4 1M (64% at 630nm) compared to that cycled in the buffer (21% at 630nm), whereas opposite results were obtained for coloration efficiencies 28cm2 C−1 (at 630nm) and 35cm2 C−1 (at 630nm), respectively. Changes in surface chemistry and morphology of the optimized sample were observed after cycling in H2SO4. [Copyright &y& Elsevier]

Abstract: Inorganic-solid-state electrolyte tantalum oxide thin films were deposited by reactive DC magnetron sputtering to improve the leakage and deterioration of traditional liquid electrolytes in electrochromic devices. O2 at 1–20sccm flow rates was used to deposit the tantalum oxide films with various compositions and microstructures. The results indicate that the tantalum oxide thin films were amorphous, near-stoichiometric, porous with a loose fibrous structure, and highly transparent. The maximum charge capacity was obtained at an oxygen flow rate of 3sccm and 50W. The transmission change of the Ta2O5 film deposited on a WO3/ITO/glass substrate between colored and bleached states at a wavelength of 550nm was 56.7%. The all-solid-state electrochromic device was fabricated as a multilayer structure of glass/ITO/WO3/Ta2O5/NiOx/ITO/glass. The optical transmittance difference of the device increased with increasing applied voltage. The maximum change was 66.5% at an applied voltage of ±5V. [Copyright &y& Elsevier]

Abstract: Electropolymerization of 3,5-bis(4-bromophenyl)dithieno[3,2-b;2′,3′-d]thiophene, having a mild electron-withdrawing bromine atom attached to the para position of the two phenyl groups of dithienothiophene, was performed, utilizing a potentiodynamic method. The resultant homopolymer was characterized by cyclic volyammetry, fourier transform infrared and ultraviolet–visible spectroscopy. Spectroelectrochemical and electrochromic properties were investigated and a device was constructed with polyethylenedioxythiophene to understand the characteristics in detail, which had the potential range of 0.0–2.0V for operating the device between green and blue colors. It had a good optical contrast of 18% with a switching time of less than a second. Moreover, open circuit memory and stability of the device were investigated. [Copyright &y& Elsevier]

Abstract: Electrochromic switchable mirrors consisting of a multilayer of Mg4Ni/Pd/Al/Ta2O5/HXWO3/indium tin oxide on a glass substrate degrade when subjected to changes in humidity and temperature. Polyvinyl chloride was applied as a seal layer to such a device in an attempt to improve its durability. The optical switching properties of the device were investigated through an accelerated degradation test conducted at a constant temperature of 30°C and a relative humidity of 80%. Although the device with a seal layer was thicker, it showed superior optical switching properties with a transmittance as high as 54% in the transparent state due to interference at the multilayer. Furthermore, the device with a seal layer exhibited higher durability after 35days in an accelerated degradation environment, as well as higher switching durability. [Copyright &y& Elsevier]

Abstract: Electrochromic organomolybdenum oxide (MoOxCy) films are deposited onto 60Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates by low temperature plasma-enhanced chemical vapor deposition (PECVD) using a precursor of molybdenum carbonyl vapor, which is carried by argon gas, mixed with oxygen gas and synthesized by radio frequency power at room temperature (23°C). The MoO x C y films with modified surface morphology and compositions of varying oxygen contents are proven to offer noteworthy electrochromic performance. Porous surface of the MoO x C y film (398nm thick) provides Li+ ion diffusion coefficient value of 1.7×10−10 cm2/s for Li+ de-intercalation at a potential scan rate of 2mV/s. High x/y value at high surface composition of oxygen to carbon in the MoO x C y film offers light modulation with transmittance variation of up to 63% and coloration efficiency of 36cm2/C at a wavelength of 800nm for 200 cycles of Li+ intercalation and de-intercalation. PECVD-synthesized MoO x C y thin films show promising electrochromic properties for applications in flexible electrochromic devices. [Copyright &y& Elsevier]

Abstract: In depositing nitrogen doped tungsten oxide thin films by using reactive DC-pulsed magnetron sputtering process, nitrous oxide gas (N2O) was employed instead of nitrogen (N2) as the nitrogen dopant source. The nitrogen doping effect on the structural and electrochromic properties of WO3 thin films was investigated. X-ray diffraction (XRD) results show that the films are amorphous. Morphological images reveal that the films are characterized by a hybrid structure comprising nanoparticles embedded in amorphous matrix and open channels between the agglomerated nanoparticles, which promotes rapid charge transport through the film. Increasing the nitrogen doping concentration is found to decrease the nanoparticle size and the band gap energy. The electrochromic properties were studied using cyclic voltammetric and spectroeletrochemical techniques. The film with N content of ~5at.% exhibits higher optical modulation and coloration efficiency as well as faster ion transport kinetics. The results reveal that electrochromic and lithium ion transport properties are moderately enhanced relative to the un-doped tungsten oxide thin films by appropriate content of dopant, due to the effects of nitrogen doping. [Copyright &y& Elsevier]

Abstract: Large-scale electrochromic devices were manufactured using vacuum vapour phase polymerised (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT). Homogeneous 3,4-ethylenedioxythiophene (EDOT) and water vapour distribution within the large 115L VPP chamber is paramount for the reproducible synthesis of high conductivity PEDOT thin films. Obtaining these conditions, however, was not trivial. The issue was resolved by synthesising PEDOT under vacuum, however, this altered the dynamics of the polymerisation process. As a result, surfactant addition, monomer and water vapour distribution, monomer and chamber temperature, and polymerisation times were all systematically investigated. Controlling these parameters has resulted in PEDOT with conductivity exceeding 1100S·cm−1, with a best of 1485S·cm−1, and electrochromic devices with an optical switch of Δ%Tx≥50%. The resulting high conductivity and optical range are due to long undisrupted PEDOT polymer chains coupled with low levels of oligomers within the matrix. [Copyright &y& Elsevier]

Abstract: An electrochromic (EC) switchable mirror glass can change between a reflective state and a transparent state with voltage application. The conventional device has a multilayer of Mg4Ni/Pd/Al/Ta2O5/WO3/indium-tin oxide on a transparent substrate. A palladium thin film was used as the proton injection layer. For practical use, we attempted to reduce the amount of palladium thin film from the viewpoints of the reduction in total fabrication cost and the efficient use of resources. The thickness of the film was related to the optical switching properties of the device. Although the device with a 1-nm-thick palladium film showed a high transmittance of 63% in the transparent state, its low switching durability was not suitable for practical application. Moreover, we were able to adapt a palladium-based alloy (Pd0.8Ag0.2) which is a well-known hydrogen permeation membrane as the proton injection layer to reduce the amount of palladium thin film. As a result, we found that a 4-nm-thick Pd–Ag thin film has good adaptability to the EC switchable mirror. [Copyright &y& Elsevier]

Abstract: An investigation was conducted on the electrochromic properties of plasma sputtered-nickel–vanadium oxide thin films on 40Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates. Metallic Ni0.93V0.07 target, sputtered by radio frequency power with argon gases and reacted with oxygen gases at room temperature (23°C), was proven to provide extraordinary electrochromic performance. Cyclic voltammetry switching measurements found that only low driving voltages from −1V to 1V were needed to provide reversible Li+ ion intercalation and deintercalation. The light modulation with up to 52% of transmittance variation, optical density change of 0.446 and color efficiency of 63.8cm2/C at a wavelength of 550nm was obtained for 200cycles of Li+ intercalation and deintercalation in a 1M LiClO4-propylene carbonate electrolyte. [Copyright &y& Elsevier]

Abstract: Hexagonal tungsten bronze (HTB) nanocrystal and TiO2 nanoparticles were assembled into thin films by layer-by-layer self-assembly method. HTB nanocrystals were synthesized by hydrothermal route at 155°C. UV–Vis spectra showed that the HTB/TiO2 films exhibit a linear increase in film thickness with assembly exposure steps. The electrochromic property of the film was carefully investigated. Cyclic voltammetry indicated that the redox peak was around −0.5V. The electrochromic contrast, coloration efficiency, switching speed, stability and optical memory were carefully investigated. The films vary from white to blue and finally dark brown. The electrochromic contrast is 63.9% at 633nm. The coloration efficiency of the films is relatively high. The response time is less than 3s. [Copyright &y& Elsevier]

Abstract: We prepared an all-solid-state reflectance-type electrochromic device (ECD), consisting of the following five layers: Al/WO3/Ta2O5/Ir x Sn1 − x O2/ITO. Using RF ion plating, we prepared a film containing dispersed iridium oxide in a tin oxide matrix; this film acts as the counter electrode in the all-solid-state ECD. Protons were used as coloration ions in the ECD. The size of the ECD was 150cm2, and the reflectance changed between more than 60% from 15%. The coloration and bleaching response times were less than a few seconds. We analyze the optical characteristics of the ECD, and report the results of a consecutive drive test and a high-temperature heat resistance test. [Copyright &y& Elsevier]

Abstract: Chromogenic materials allow the transmittance of visible light and solar energy to be varied under the action of an external stimulus. This paper first discusses buildings related energy savings that can be accomplished by chromogenic technologies, and their beneficial effects on comfort issues. We then summarize recent work on thermochromic VO2-based thin films with particular attention to multi-layers of VO2 and TiO2 and to new VO2:Mg films for which the doping gives significantly lowered absorption of visible light. The final part covers electrochromic materials and devices with foci on coloration efficiency and on durability issues for foil-type constructions based on films of WO3 and NiO. [Copyright &y& Elsevier]

Abstract: Using a vacuum dry process, we constructed an all-solid-state transmittance-type electrochromic (EC) device consisting of five thin layers: ITO/IrOx/Ta2O5/WO3/ITO. We measured the optical and electrochemical properties of the EC device. By using Ta2O5 film as a proton conducting solid electrolyte, the device exhibited a fast response speed of 0.2s and stable coloration characteristics. With an AC impedance method, we determined the properties of the device under varying temperature and environmental conditions. In the solid electrolyte (Ta2O5), the ion resistance controlled the response speed; the ionic conductivity and activation energy were 3×10−6 S/cm and 0.31eV, respectively. [Copyright &y& Elsevier]

Abstract: Electrochromic performance of WOxCy films deposited onto 60Ω/□ flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates by low temperature plasma-enhanced chemical vapor deposition (PECVD) was investigated. It was proven that extraordinary electrochromic performance was provided when the precursor [tungsten carbonyl, W(CO)6; TC] vapor, carried by argon gas, was mixed with air gas and synthesized by radio frequency (r.f.) power at room temperature (23°C). Cyclic voltammetry switching measurements found that only low driving voltages from −1V to 1V were needed to provide reversible Li+ ion intercalation and de-intercalation. The light modulation with up to 63.6% of transmittance variation at a wavelength of 650nm was obtained for 150cycles of Li+ intercalation and de-intercalation in a 0.1M LiClO4-PC (propylene carbonate) electrolyte. [Copyright &y& Elsevier]

Abstract: Transparent conductors based on Au films, with thicknesses in the 2.6< d <9.8 nm range, were made by DC magnetron sputtering onto glass. The films went from an “island” structure at low thicknesses to a uniform structure at d >8 nm, as seen from electron microscopy, electrical resistance, and spectrophotometric transmittance and reflectance. Optical data for uniform films were given a consistent interpretation within the Drude model. Optimized TiO2/Au/TiO2 films, with a luminous transmittance of 80%, were found to have good electrochemical durability and may be useful for applications in electrochromic devices. [Copyright &y& Elsevier]

Abstract: Recently reported studies have shown some optical limitations of dual electrochromic systems. Among all the possible combinations between two materials in a dual system, the maximum contrast available was lower than that obtainable by one of the constituent materials by itself. In this study, we mathematically prove that this is a valid result for any electrochromic system constituted by materials that obey the Beer–Lambert law. [Copyright &y& Elsevier]

Abstract: Electrochromic ultrathin films composed of the polyoxometalate cluster K10[P2W17O61]·17H2O (P2W17), polyallylamine hydrochloride (PAH) and Neutral Red (NR) were fabricated on quartz, silicon wafer and indium–tin oxide substrates by the layer-by-layer self-assembly method. The multilayer [P2W17/PAH/P2W17/NR]n films were characterized by UV–vis spectroscopy, scanning electron microscopy, cyclic voltammetry and chronoamperometry and in-situ spectral electrochemical measurements, which exhibited suitable response time, high optical contrast and low operation potential. The monolacunary polyoxometalate-based electrochromic film displays adjustable colors and undergoes transitions from deep pink to light purple, then to dark purple-blue over the potential range from +0.2 V to −1.0 V. Furthermore, two types of data storage using optical changes of the [P2W17/PAH/P2W17/NR]35 film are proposed. The results provide valuable information for exploring applications in tunable-color electrochromic devices and data-storage devices. [Copyright &y& Elsevier]

Abstract: Crystalline WO3 nanoparticles are employed in the development of flexible electrochromic (EC) devices. The nanoparticles are synthesized at high-density with a hot-wire chemical vapor deposition process where the hot filament provides the source of the tungsten metal. Polyethylene terephthalate coated with indium tin oxide is employed as a transparent flexible substrate. A simple electrophoresis technique is employed to deposit the WO3 nanoparticles on the polymer, resulting in a uniform thin film. The EC performance is optimized for WO3 particles that were baked at ~300 °C for 2 h prior to electrode fabrication. The transmittance is modulated between ~94% and ~28% without degradation for 100 cycles. [Copyright &y& Elsevier]

Abstract: Molybdenum-doped vanadium pentoxide (Mo-doped V2O5) thin films with doping levels of 3–10 mol% were prepared by dip-coating technique from a stable Mo-doped V2O5 sol synthesized by sol–gel and hydrothermal reaction. The Mo-doped V2O5 films had a layered V2O5 matrix structure along c-axis orientation with Mo6+ as substitutes. Values of the inserted and extracted charge density of 21.4 and 21.3 mC·cm−2 and the transmittance variation (ΔT at 640 nm) between anodic (+1.0 V) and cathodic (−1.0 V) colored states of 41% were observed for the films with 5 mol% Mo6+ doping. Above this dopant concentration, the charge capacity and ΔT decreased. The enhancement of the electrochemical and electrochromic properties of the films is related to changes in the electronic properties of V2O5 films due to the creation of energy levels in the band gap of V2O5 by the Mo doping, accompanied by the reduction of the forbidden-band width and the increase of the conductivity. [Copyright &y& Elsevier]

Abstract: Proof-of-principle gas-reservoir MnNiMg electrochromic mirror devices have been investigated. In contrast to conventional electrochromic approaches, hydrogen is stored (at low concentration) in the gas volume between glass panes of the insulated glass units (IGUs). The elimination of a solid state ion storage layer simplifies the layer stack, enhances overall transmission, and reduces cost. The cyclic switching properties were demonstrated and system durability improved with the incorporation a thin Zr barrier layer between the MnNiMg layer and the Pd catalyst. Addition of 9% silver to the palladium catalyst further improved system durability. About 100 full cycles have been demonstrated before devices slow considerably. Degradation of device performance appears to be related to Pd catalyst mobility, rather than delamination or metal layer oxidation issues originally presumed likely to present significant challenges. [Copyright &y& Elsevier]

• Electrochromic (EC) Ni(OH) 2 /In 2 O 3 -rods composite porous film was designed and constructed. • Stability of Ni(OH) 2 film was obviously improved by the introduction of In 2 O 3 rod array layer. • Improvement in film/substrate connection and EC performance was discussed and explained. • Effect of EC cycling on the microstructure and performance of composite film was analyzed. In this paper, a Ni(OH) 2 /In 2 O 3 -rod composite film with a porous structure was prepared by hydrothermal and solvothermal techniques using fluorine-doped tin oxide conductive glass as a substrate to improve the film/substrate connection and the cycle stability of the Ni(OH) 2 film. A blank Ni(OH) 2 film was also prepared for comparison purposes. The morphology, microstructure, and components of the films were characterized through X-ray photoelectron spectroscope, scanning electron microscope, and X-ray diffractometer. The electrochromic performance of the films including transmittance, cyclic voltammetry, cycle stability, electrochemical impedance, and switch speed was examined. The energy level positions and band gaps of the fluorine-doped tin oxide conductive glass and In 2 O 3 layers were calculated based on their Mott–Schottky plots and ultraviolet-visible diffuse reflectance spectra. The results show that the In 2 O 3 rods are approximately perpendicular to the substrate. The introduction of the In 2 O 3 rod array transition layer enhanced the film/substrate connection in addition to providing favorable conditions for the nucleation and growth of Ni(OH) 2 , resulting in the improved Ni(OH) 2 stability and porous structure as well as electrochromic performance. The mechanism of the improvement is explained in this paper. [ABSTRACT FROM AUTHOR]

Abstract: The conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic) acid (PEDOT–PSS) thin-films was increased by up to 900 times with the addition of linear-diols. Three series of linear-diols were investigated. It is proposed that three mechanisms contribute to improved conductivity; conformational changes in the polymer from coil to expanded, spatial separation of PEDOT–PSS grains and charge screening. The variation in conductivity with temperature indicates that diols affect both intra- and inter-chain charge transports. Electrochromic devices were constructed using standard and enhanced conductivity PEDOT–PSS. Switching times from bleached to darkened states were reduced while darkened to bleached states remained unaltered. Total percent transmission change (%ΔTx) remained constant indicating that enhanced conductivity PEDOT–PSS improves switching but does not lead to additional electrochromic redox sites being accessed. [Copyright &y& Elsevier]

Abstract: Poly(9-fluorenecarboxylic acid) (PFCA) was synthesized by electrochemical oxidation of 9-fluorenecarboxylic acid (FCA) using a mixture of nitromethane and boron trifluoride diethyl etherate as the solvent and tetrabutylammonium tetrafluoroborate as the supporting electrolyte. An insoluble and conducting brownish-orange film was deposited on the electrode surface, both during repetitive cycling and constant potential electrolysis at 1.15 V. Characterization of the polymer film has been carried out using Fourier Transform Infrared spectroscopy technique and thermal behavior was studied via thermal gravimetric analysis. Structural analysis showed that the polymerization of FCA occurred at 2,7-position. Spectroelectrochemical behavior of the polymer film on indium tin oxide working electrode was studied by recording the electronic absorption spectra, in-situ, in monomer-free electrolytic solution at different potentials and it is found that the PFCA film can be reversibly cycled between 0.0 V and 1.2 V. Furthermore, a dual type electrochromic device based on PFCA was constructed and its spectroelectrochemical properties were investigated. The electrochromic device exhibits color change from transparent to dark blue with a good open circuit memory. [Copyright &y& Elsevier]