Electrochromic Thin Films Research Articles

铜掺杂氧化镍电致变色薄膜的制备及性能

铜掺杂氧化镍电致变色薄膜的制备及性能

High-Contrast Electrochromic Thin Films via Layer-by-Layer Assembly of Starlike and Sulfonated Polyaniline

In this Article, we report the layer-by-layer (LbL) assembly and electrochromic properties of polyaniline-tethered cubic polyhedral oligomeric silsesquioxane (POSS-PANI)/sulfonated polyaniline (SPANI) multilayer thin films. The interaction between POSS-PANI and SPANI is characterized using X-ray photoelectron spectroscopy (XPS), ultraviolet−visible-near-infrared spectroscopy, and four-point probe conductivity. We show that the inclusion of SPANI during LbL assembly effectively dopes the underlying POSS-PANI layer and extends the conjugation length, as evidenced by probing the surface layers with XPS. We also demonstrate that the POSS-PANI/SPANI multilayer films have more electroactive units, lower band gap energies, and higher electrical conductivity values compared to those of POSS-PANI/poly(2-acrylamido-methane-2-propanesulfonic acid) (PAMPS) and spin-coated SPANI films. Under constant applied potentials, a 50 bilayer film of POSS-PANI/SPANI, (POSS-PANI/SPANI)50, shows significant enhancement in optical...

Electrochromic Thin Films from a Redox Active Diarylethene by Electrochemical Polymerization

A diarylethene substituted with 3,4-(propane-1,3-diyldioxy)thiophene (ProDOT) was synthesized to induce electrochemical deposition of diarylethenes. The ProDOT substituted diarylethene (BTFPP) showed reversible photochromism from colorless to purple upon exposure to a UV light and bleached to colorless by a visibly light. The oxidation potential of the new ProDOT substituted diarylethene was lower than that of the unsubstituted diarylethenes due to the electroactive ProDOT unit. Under an electrochemical condition, the solution of BTFPP gave soluble polymers but deposited insoluble film on a working electrode coated with a PEDOT layer. This result indicates that the PEDOT nano layer (68 nm thick) function as a seeding layer to induce polymerization and electrodeposition of BTFPP. Furthermore electro-copolymerization using a mixture of BTFPP and EDOT afforded electrodeposition of the copolymers on the PEDOT seeding layer. An electrochromic electrode was successfully fabricated by depositing the photochromic BTFPP on an ITO glass, which shows a reversible electrochromic change from violet to sky blue.

ChemInform Abstract: Characterization of Electrochromic Nickel Oxide Thin Films Prepared by Anodic Deposition.

Nickel oxide (NiOx) thin films have been prepared on transparent conducting indium tin oxide (ITO) substrates by anodic deposition from a nickel ammine complex solution. Electrochromic (EC) behaviour of these films was observed in a borate buffer solution at pH 10 in the potential range 0–1 V vs. Ag/AgCl; an as-prepared film (PF) was cathodically reduced to a colourless form (RF) and oxidized to a brown form (OF) by anodic polarization. Characterization of these films by low-angle incident X-ray diffraction and X-ray photoelectron spectroscopy with argon-ion (Ar+) etching revealed that the EC properties are based on the electrolytic transformation of the NiOx structure between β-NiOOH and β-Ni(OH)2, i.e. involving the redox reaction Ni3++ e ⇄ Ni2+.

ChemInform Abstract: Improvement in Electrochromic Stability of Electrodeposited Nickel Hydroxide Thin Film.

The electrochromic nickel hydroxide thin film was anodically deposited from an aqueous solution. The effect of solution temperature, postheat-treatment temperature, and addition of cadmium on the electrochromic behavior (color/bleach durability cycle, response time, and coloration efficiency of the nickel hydroxide films in NaOH) were investigated. A significant increase in the color/bleach durability cycle from 500 (for the as-deposited film) to more than 5000 cycles (for the heat-treated film) was observed. The addition of cadmium increased the utilization of the active materials. It was found that the coloration efficiency was 40 cm{sup 2}/C and coloration and bleaching response time were 20 to 30 s and 8 to 10 s, respectively. The change in the electrochromic properties with heat-treatment temperature is discussed based on the physical and electrochemical analysis.

Multicoloured electrochromic thin films of NiO/PANI

NiO/polyaniline (PANI) thin films have been prepared by a two-step process. NiO thin films were electrodeposited from an aqueous solution of NiCl2 · 6H2O at pH 7.5 on fluorine-doped tin oxide coated glass substrates and a layer of PANI was formed on NiO thin films by chemical bath deposition. The films were characterized for their structural, optical, morphological and electrochromic properties. X-ray diffraction and Fourier-transform infrared spectroscopy indicated the formation of NiO and PANI, in which NiO is of cubic structure. Scanning electron micrographs represent porous granular NiO, which get uniformly carpeted with PANI, leading to a matty morphology of NiO/PANI samples. The electrochromic performance of NiO/PANI films has been studied using cyclic voltammetry and chronoamperometry over the −1.2 to +2.2 V (versus saturated calomel electrode (SCE)) potential window in 1M LiClO4 + propylene carbonate. The NiO/PANI films exhibit electrochromism with colour that changes from pale yellow (leucoemeraldine base at −0.7 V versus SCE) to dark green (emeraldine salt at 0.4 V versus SCE) to purple (pernigraniline at 0.8 V versus SCE) in the reduced states and dark blue (nigraniline at 0.5 V versus SCE) to dark green (emeraldine salt at 0.1 V versus SCE) to light green (photoemeraldine at −0.3 V versus SCE) in its oxidized states. These colours, though akin to pure PANI, have higher contrast, high speed of operation and high stability, owing to the properties of NiO. The colouration efficiency of the NiO/PANI film was estimated to be 85 cm2 C−1.

Electrochromic Properties of Nano-Columnar Nickel Oxide

Electrochromic properties of transition metal oxides had much attention in recent years. The electrochromic thin films can be assembly as electrochromic devices (ECDs) and then used for applications in devices such as mirrors, panels and smart windows. A kind of complementary ECD is popular in resent years. Therefore, a specific investigation on nickel oxide (NiO) electrochromic properties is completed in this study. The crystalline structure of the NiO films was analyzed using XRD (PANalytical X’Pert PRO) with Cu-Kα radiation. The atmosphere of oxygen concentration increasing has changed the NiO films crystalline from (200) to (111). The thicknesses and surface microstructures of the NiO films were investigated using a scanning electron microscope (SEM, Philips/FEI XL40 FEG). It is observed that films are relatively smooth deposited without oxygen. The characterization of the electrochromic properties was carried out in a two-electrode cell with an electrochemical analyzer (CHI 611B). The NiOx changes the transmittance of NiO films in the wavelength range of 300-1500 nm and the color of the film changes from transparent to brown. The nano-crack exhibits in the NiO film did enhance the electrochromic properties.

Fast switching electrochromism from colloidal indium tin oxide in tungstate-based thin film assemblies

Layer-by-layer assembly was used to alternately deposit tungstate anions with cationic poly(4-vinylpyridine- co-styrene) to generate electrochromic thin films that transit from transparent to dark blue in their oxidized and reduced states, respectively. Tungstate is a good electrochromic material because it is completely colorless in its deposited state, while most other electrochromic materials exhibit some type of color in the absence of an applied voltage. Despite its advantages, tungstates are plagued by long switching time (>30 s), which is common amongst ceramic electrochromics, due to lack of electrical conductivity in at least one of the two states. In an effort to decrease switching time, indium tin oxide (ITO) nanoparticles were incorporated into these tungstate-based assemblies. In the absence of ITO, these films take 30–60 s to completely switch and exhibit reduced contrast with each switch. ITO-containing films, with ITO in every other bilayer, fully switch in 14 s and do not exhibit the same drift in transmittance with repeated switching. ITO allows these films to maintain electrical conductivity in both states, which is the source of this faster, more stable switching. With further optimization, this combination of fast switching and high contrast makes these films promising for use in smart windows and flexible displays.

Layer-by-Layer Assembly of a pH-Responsive and Electrochromic Thin Film

This article summarizes an experiment on thin-film fabrication with layer-by-layer assembly that is appropriate for undergraduate laboratory courses. The purpose of this experiment is to teach students about self-assembly in the context of thin films and to expose students to the concepts of functional polymeric coatings. Students dip coat microscope slides and conductive glass with films containing polyaniline (PANi), a conducting polymer, and sulfonated polystyrene. Assembly of the film is characterized by visual inspection, UV−vis spectroscopy, and conductance measurements with a hand-held multimeter. Green-colored films with measurable conductance are apparent after two PANi layers. Subsequently, the students observe the pH-dependent optical properties of the films and also determine the electrochromic performance of the films using spectroelectrochemistry. The feasibility of this experiment has been tested by inclusion into an undergraduate-level polymer science laboratory with third- and fourth-year...

Molybdenum oxide (MoO3) thin film based electrochromic cell characterisation in 0·1M LiClO4.PC electrolyte

Electrochromic thin films of molybdenum oxide (MoO3) were prepared on transparent conducting oxide substrates, i.e. fluorine doped tin oxide coated (FTO or SnO2:F) glass substrates by electron beam evaporation technique using pure MoO3 (99.99%) pellets at various substrate temperatures (i.e. Tsub=room temperature (30°C), 100 and 200°C) under the vacuum of 1 × 10−5 mbar. The room temperature prepared films were further annealed Tanne at 200 and 300°C for about one hour in the vacuum environment. The electrochemical nature of the films was studied by the cyclic voltammetry technique using a three electrode electrochemical cell in 0·1M LiClO4.PC electrolyte. The performance of the films was also tested by making electrochromic cells. The films produced at higher substrate temperature show lesser modulation in the visible spectrum, compared with the films produced at lower temperatures. A maximum colouration efficiency of 66 cm2 C−1 was observed in the infrared region for the films prepared at room temperature.

Incorporation of a stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) in an electrochromic device

A stable organic radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), was studied. We employed TEMPO as a cathodic radical provider in propylene carbonate (PC) and poly(3,4-propylenedioxythiophene) derivatives (PProDOT-Et 2) as an anodic electrochromic (EC) thin film, which was obtained through electropolymerization. On assembling them together in a device, the electrochemical and optical performances of this hybrid electrochromic device (ECD) showed reversible cycling stability and high absorbance attenuation in the visible range. By selecting proper electrolytes (LiClO 4/PC) and controlling the deposited charge of the PProDOT-Et 2 thin film, it was possible to obtain a transmittance change (Δ T) of up to 59% at 590 nm with no noticeable degradation after operating between 0 and 0.9 V for 1000 cycles. Furthermore, an electrochemical quartz crystal microbalance (EQCM) was used to investigate ion migrations in the PProDOT-Et 2 thin film, which influenced its long-term stability.

Studies on the correlation between electrochromic colouration and the relative density of tungsten trioxide (WO3−x) thin films prepared by electron beam evaporation

The colouration efficiency in the electrochromic devices depends upon the amount of intercalating charge in the tungsten oxide (WO3−x) thin films. One of the physical properties of the film that significantly influence the intercalating charge is the film density. In this paper, the dependence of intercalated charge in WO3−x thin films on the film density is reported. The amorphous tungsten oxide thin films have been prepared by electron beam evaporation at three substrate temperatures: 300, 470 and 570 K. With increasing substrate temperature, the refractive indices of the films increase. The relative film density calculated from the refractive index using the Lorentz–Lorentz relationship increases with the substrate temperature. With increasing density of the WO3 thin films, the diffusion coefficients of protons and the amount of intercalated charge decrease. The intercalated charge in the coloured electrochromic thin films brings about a change in the surface work function of the thin film; the difference in the surface work function (between the coloured and the bleached states) is measured by the Kelvin probe. In the present investigation, an intercalating charge of 59, 48 and 39 mC cm−2 brings about a change of 0.24, 0.16 and 0.13 eV in the surface work function of the WO3 thin films.

Fabricating red–blue-switching dual polymer electrochromic devices using room temperature ionic liquid

In this work, room temperature ionic liquid (RTIL)—1-butyl-3-methyl-imidazolium hexafluorophosphate ([BMIM]PF 6)—was employed to fabricate dual polymer electrochromic devices (DPECDs). [BMIM]PF 6 was used as the electrolyte both in the electrochemical synthesis of conducting polymers (CPs) and in the fabrication of DPECDs. The electrochemically deposited poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-methylthiophene) (PMeT) were employed to serve as two complementary coloring electrochromic thin films. Through combining these two electrochromic layers, the assembled DPECDs were found to switch between deep red and deep blue, which are two primary colors for a display. By employing RTIL as electrolyte, the devices retained 65% of their optical contrast and electroactivity after 5×10 3 deep double potential steps, showing enhanced stability and durability. The DPECDs also exhibited stable electrochromic performance, with a maximum optical contrast of 26% at 665 nm, and achieved a high coloring efficiency of 460 cm 2 C –1.

Multicolor electrochromic and pH-sensitive nanocomposite thin film based on polyoxometalates and polyviologen

A multiple-colored electrochromic composite film of polyoxometalates (P 2W 18) and poly(hexyl viologen) (PXV) is fabricated by layer-by-layer (LbL) self-assembly method. The P 2W 18/PXV composite film exhibits a linear increase in film thickness with assembly processing, and undergoes a colorless to blue to violet transition over the potential range from +0.1 to −0.9 V. The optical contrast, response time and stability for the as-prepared films are carefully investigated. These results show the validation of an LbL method based intermixing strategy for the design of tunable-color electrochromic thin films. The composite film can also be used as a pH sensor because of the pH dependence of its electrochemical response.

Optical iris application of electrochromic thin films

We have successfully developed an electrochromic device (ECD) as the “optical iris” of a camera lens that could potentially control the transmittance intentionally. To realize this goal, we have applied photolithography and subsequent wet etching to fabricate the patterned complementary electrochromic systems where tungsten oxide and prussian blue were electrodeposited. At this point it is important to note that such a device could be directly attached onto a camera lens without any mechanical equipment. In this way the device will reduce power consumption and will be much smaller and thinner which results would also further the miniaturization of cameras.

Thin Solid Films and Nanomaterials for Solar Energy Conversion and Energy Saving Applications

Important new applications are possible today in the fields of energy conversion and storage by the application of thin and nanostructured solid films on surfaces. These special films, or multiple films, will be integral parts of the energy systems in the near future for the production of useful thermal and electrical energy and for energy saving applications, especially in buildings. We review the research in this direction. As we are facing the threats of insufficient energy supply and the greenhouse gas emissions from the intense use of fossil sources, we realize that the impacts as well as the future of the solar energy systems have been greatly underestimated. We review the work on solar thermal systems and energy saving applications. The efficient use of solar thermal technologies is very important for the introduction of a sizeable share of environmentally friendly renewable energy sources. New and nano structured materials along with the design and the geometry of advanced systems, capable of achieving high temperatures, as well as on integrated collection and storage systems have been proposed. Recent progress in high-vacuum technology and new materials had a remarkable effect in thin-film quality and cost. As a result new thermal absorbers have appeared along with new evaluation methods. We also present work on low-e coatings and electrochromic thin films that are very important for thermal energy savings in buildings and increase the efficiency of devices. For the photovoltaic solar energy conversion we present results on thin film solar cells and the efforts on dye sensitized nanostructured and organic solar cells.

Reactive sputtering deposition of V2O5 − z on flexible PET/ITO substrates for electrochromic devices

The reactive sputtering deposition of electrochromic thin films of V2O5−z onto flexible PET/ITO substrates using argon and oxygen at room temperature (23 °C) was investigated. Cyclic voltammetry measurements showed that only low driving voltages, between −0.6 V and +1 V, were needed to provide reversible Li+ ion insertion and extraction. XPS showed that thin film with oxygen deficiency z of 0.13 can offer promising light modulation at a wavelength of 400 nm under visible-UV spectroscopy, with up to 36.5% transmittance variation even after 200 cycles of cyclic voltammetry tests.

Electrochromic properties of V 2O 5 − z thin films sputtered onto flexible PET/ITO substrates

The electrochromic properties of V 2O 5 − z (vanadium oxide) thin films sputtered onto 60 Ω/□ flexible PET (polyethylene terephthalate)/ITO (indium tin oxide) substrates at various oxygen flow rates were investigated. The metallic vanadium (V) target, sputtered by radio frequency (r.f.) power with argon gases, and reacted with oxygen gases in room temperature (23 °C), was proven to provide extraordinary electrochromic properties. Cyclic voltammetry measurement demonstrated that only low driving voltages from − 0.6 V to 1 V were needed to provide reversible Li + ion insertion and extraction to and from a working electrode. The working electrode was part of a PET/ITO/V 2O 5 − z flexible electrochromic device (FECD) in a 0.1 M LiClO 4–PC (propylene carbonate) electrolyte with a Pt counter electrode and a saturated calomel reference electrode. Cyclic voltammetric (CV) analyses and ultraviolet (UV)–visible spectroscopy measured the electrochromic thin films of a-V 2O 5 − z sputtered onto flexible PET/ITO substrate. An oxygen flow rate of 2 sccm with an oxygen deficiency z of 0.169, an insertion coefficient x of 0.097 and x Li + inserted / x Li + extracted ratio of 0.992 can offer excellent light modulation of up to 43.3% of transmittance variance, optical density change of 0.38 and color efficiency of 102.5 cm 2/C at a wavelength of 400 nm for 200 cycles of Li + insertion and extraction.

Vapor growth of electrochromic thin films of transition metal oxides

Mixed oxide films of transition metals gain considerable much attention due to their interesting optoelectronic properties. The low temperature chemical vapor growth processing of thin films of mixed W and Mo oxides is presented. The investigation is related to optimization of films structure and the related optoelectronic properties in dependence on the chemical vapor deposition (CVD) process parameters. Their electrochromic behavior and photoelectrode properties were studied.

An EQCM study for a novel aromatic poly(amine-imide) electrochromic thin film

A new aromatic poly(amine-imide) electrochromic thin film synthesized with N, N-bis(4-aminophenyl)- N′, N′-diphenyl-1,4-phenylenediamine and 3,3′,4,4′-benzo-phenonetetra carboxylic dianhydride, abbreviated as poly(PD-BCD), was studied. The poly(PD-BCD) thin-film electrode has been characterized by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). As the polymer chain acquires positive charge during the oxidation of poly(PD-BCD) to its radical cation state or dication state, the anions would insert into the polymer matrix in order to neutralize the charge. However, when the electrodes were cycled in electrolytes containing different cations, including 0.1 M LiClO 4/acetonitrile (ACN), 0.1 M NaClO 4/ACN and 0.1 M TBAClO 4/ACN, the experimental results revealed two mechanisms for the redox reaction. A plot of mass change (Δ m) vs. accumulated charge ( Q) gave a slope, from which the electrochromic mechanism can be extracted. The slopes of Δ m– Q obtained from the CV–EQCM measurements in three electrolytes were different for the first redox stage, but the slopes were almost the same for the second redox stage. This means that, in addition to the involvement of anions, cations also play an important role in the first redox stage, however, the role of the cations is less in the second stage. Moreover, two reaction mechanisms for the two reaction stages of poly(PD-BCD) are proposed in this study.