Good Electrochromic Performance Research Articles

Novel electrochromic-supercapacitor device based on P(TPACz)/WO3-PDA nanocomposite film

Organic–inorganic composites of (E)-3,5-di(9 H-carbazol-9-yl)-N-(4-(diphenylamino)benzylidene)aniline/dopamine-modified WO3 (P(TPACz)/WO3-PDA) were prepared by electrochemical polymerisation. The as-prepared P(TPACz)/WO3-PDA composites showed good electrochromic and electrochemical performance. The prominent electrochemical performance of P(TPACz)/WO3-PDA represents a high areal capacitance (32.15 mF cm−2 at 0.1 mA cm−2) and wide range of potential windows (-2.0−1.6 V). Additionally, symmetric supercapacitor devices based on P(TPACz)/WO3-PDA composite films were successfully constructed, which exhibited a high specific capacitance (13.88 mF cm−2 at 0.02 mA cm−2) and an energy density of 7.71 × 10−3 mWh cm−2 in n-doped station. The remarkable electrochromic and electrochemical performances are due to the synergy between the organic polymer and WO3-PDA. A complete large-area composite film structure with high conductivity promises fast electronic transport. This study provides a method for preparing multifunctional composite electrode materials, offering technical support for intelligent displays and energy storage technologies.

Fabrication of a hot mirror using ITO-free electrochromic films

In this study, WO3/Ag/W/WO3 (WAWW) films were deposited at room temperature on a B270 glass substrate from W and Ag targets using a radiofrequency magnetron reactive sputtering system. The influence of the thin tungsten interlayer on the electrical and optical properties of the WAWW layer structure was investigated through ellipsometry, a four-point probe and a spectrophotometer. It was determined that the thin tungsten interlayer effectively prevented the oxidation of the silver film. The WAWW film had a dielectric-metal-dielectric (DMD) layered structure with good electrical conductivity and high visible transmittance. The tungsten layer was no more than 2-nm thick. The sheet resistance and luminous transmittance of the WO3(29.5 nm)/Ag(14.2 nm)/W(2 nm)/WO3(68.6 nm) film were 4.64 Ω/sq and 65.4 %, respectively. Based on the WAWW four-layer structure, stacked WO3(29.5 nm)/Ag(14.2 nm)/W(2 nm)/WO3(68.6 nm)/Ag(16.9 nm)/W(2 nm)/WO3(30.4 nm) seven-layer structures deposited on B270 glass substrates were used for both ITO-free electrochromic and hot mirror applications. The visible (400–700 nm) and NIR (700–1200 nm) transmittance values of the bleached WAWW seven-layer structure were 71.5 % and 9.9 %, respectively. The visible transmittance of the colored WAWW seven-layer structure was 23.6 %. Finally, the bi-layer WAWW films were used to obtain an ITO-free WAWW seven-layer structure with a good electrochromic and optical performance.

Preparing and investigating the monolithically stacked flexible tandem all-thin-film electrochromic device

A flexible tandem all-thin-film electrochromic device (ATF-ECD) with a device structure of polyethylene terephthalate (PET)/tin doped indium oxide (In2O3:Sn, ITO)/tungsten oxide (WO3)/lithium tantalate (LiTaO3)/nickel oxide (NiOX)/ITO/NiOX/LiTaO3/WO3/ITO has been fabricated by all magnetron sputtering technologies, in which the bottom ATF-ECD with a superstrate-type structure and the top ATF-ECD with a substrate-type structure are physically and monolithically stacked but electrically connected in parallel. They are systematically investigated for the optical and electrochemical properties through chronoamperometry (CA) and cyclic voltammetry (CV) measurements under different test cases. Both sub-devices work well and the flexible tandem ATF-ECD has achieved a high optical modulation of 59.8% at 600 nm. The numerical simulation is carried out for the tandem ATF-ECD and the single ATF-ECDs with different device structures. The details on transmission spectra are deeply discussed. The flexible tandem ATF-ECD with good electrochromic performances under the low driving voltages provides promising applications in the future smart windows.

Porous NiMoO4 Nanosheet Films and a Device with Ultralarge Optical Modulation for Electrochromic Energy-Storage Applications.

Reducing building energy consumption, improving aesthetics, and improving occupant privacy as well as comfort by dynamically adjusting solar radiation are important application areas for electrochromic (EC) smart windows. However, the current transition metal oxides still cannot meet the requirements of neutral coloration and large optical modulation. We report NiMoO4 nanosheet films directly grown on fluorine-doped tin oxide glasses. The as-grown NiMoO4 film not only achieves neutral coloration from transparent to dark brown but also shows an ultralarge optical modulation (86.8% at 480 nm) and excellent cycling stability (99.4% retention of maximum optical modulation after 1500 cycles). Meanwhile, an EC device demonstrating good EC performance was constructed. These results will greatly promote the research and development of binary transition metal oxides for both EC and energy-storage applications, and NiMoO4 films may be an excellent candidate to replace NiO films as ion-storage layers in complementary EC devices with WO3 films as EC layers.

Rapid and low-temperature preparation of tungsten oxide electrochromic thin films by oxygen plasma treatment

Electrochromic materials have attracted considerable attention due to their ability to change color reversibly and rapidly under an external electrical stimulus, making them highly promising for use in various applications such as smart windows, displays, and optical memory devices. In particular, tungsten trioxide (WO3) thin films have shown excellent electrochromic properties, leading to their wide application in electrochromic devices. In this study, oxygen plasma treatment was used to convert WCl6 thin film to WO3 electrochromic thin film on ITO glass substrate. Surface morphology, element composition, phase, optical property, and electrochromic characteristics of WO3 film are analyzed. It has been proved that the conversion of precursor films is rapid and efficient, the mean roughness and root mean square of amorphous WO3 thin film are lower than 1.8 nm and 2.2 nm respectively, and the film exhibits good electrochromic performance parameters. The optical modulation range and coloration efficiency of the film can reach 58.5% and 80.2 cm2/C before cycle and 56.3% and 84.0 cm2/C after 100 cycles, coloration time and bleaching time are within 10 s. The method of plasma treatment avoids annealing and prepare WO3 film with good and stable performance. This method has the potential to expand to other electrochromic materials, and provides a new solution for the large area preparation and flexible application of electrochromic materials.

Novel self-assembled porous yolk-shell NiO nanospheres with excellent electrochromic performance for smart windows

With the rapid development of optoelectronics, electrochromic (EC) materials (ECMs) with the advantages of low power consumption, easy viewing, high contrast ratio, etc. have attached more and more attention from the fields of smart windows, electronic billboards, emerging wearable and portable electronics, and other next-generation displays. Nickel oxide (NiO) is a promising candidate for high-performance ECMs because of its neutral-colored states and low cost. However, NiO-based ECMs still face the problem of slow switching speed due to their low electrical conductivity and small lattice spacing. Metal-organic frameworks (MOFs) are promising candidates to fabricate hollow and porous transition metal oxides (TMOs) with high ion transport efficiency, excellent specific capacitance, and electrochemical activities. In this work, porous yolk-shell NiO nanospheres (PYS–NiO NSs) were synthesized via a solvothermal and subsequent calcination process of Ni-MOF, which exhibited outstanding EC performance. Because the large specific surface areas and hollow porous nanostructures were conducive to ionic transport, PYS-NiO NSs exhibited a fast coloring/bleaching speed (3.6/3.9 s per one coloring/bleaching cycle) and excellent cycling stability (82% of capacity retention after 3000 cycles). These superior EC properties indicated that the PYS-NiO NSs was a promising candidate for high-performance EC devices. This work provides a new and feasible strategy for the efficient preparation of TMOs ECMs with good EC performance, especially fast switching speed.

Temperature-Dependent Electrochromic Devices for Energy-Saving Dual-Mode Displays.

Electrochromic (EC) devices show promising prospects with the increasing demand for energy-efficient and sustainable technologies. Multifunctionality integration is an inevitable characteristic for EC devices to adapt to changing environments. Herein, a dual-mode temperature-dependent EC device is demonstrated for the first time. Combined with the transparent PVA/EG-ZnCl2 organohydrogel electrolyte, the devices exhibit good EC performances over a wide temperature range (-40 to 40 °C). The evolutions of ion/electron transport kinetics-related indicators with temperature are further explored and simulated to reveal the mechanism of the temperature dependence of EC devices. Significantly, the optimized tungsten oxide-based EC device shows high performances at the extremely low temperature of -40 °C with a large transmittance modulation (80.8% @660 nm) and outstanding optical memory effects (97.3% retention of the initial transmittance modulation after 32 h) without electrical energy consumption. Furthermore, with a perovskite quantum dot photoluminescence film serving as the backlight, the device can switch display modes between emissive and reflective to realize its functionality in bright or dark conditions. This work provides a broad application prospect for EC devices in diverse environments of light (bright/dark) and temperature (hot/cold).

High performance multi-color prussian blue/poly(indole-5-carboxylic acid) nanocomposites with multiple layer nanosphere structure for electrochromic supercapacitor application

A novel Prussian blue/poly(indole-5-carboxylic acid) (PB/P5ICA) nanocomposites with multiple layer nanosphere structure are successfully prepared. The structure and morphology of the prepared PB/P5ICA nanocomposites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman and X-ray photoelectron spectroscopy (XPS) techniques. Due to the synergistic effect of the electrochromic properties of PB and P5ICA, the PB/P5ICA nanocomposites have good electrochromic performance and rich color changes, which can be reversibly changed among light yellow, light green, blue, and yellow-green. In addition, PB/P5ICA also shows good capacitance performance and cycle stability. The specific capacitance value reaches up to 98.12 mF cm−2 (723.48 F g−1) at the current density of 0.2 mA cm−2, which is much higher than PB and P5ICA at the same current density. A symmetric electrochromic supercapacitor device (ESD) is fabricated based on the PB/P5ICA nanocomposite. The supercapacitive properties, color changes and cycle stability of the device are also studied. The results indicate that the device has good energy storage capacity. When the current density is 0.2 mA cm−2, the specific capacitance of the device is 36.2 mF cm−2 (321.09 F g−1). Moreover, the color of the electrode material changes obviously during the charging and discharging process of the device, which can realize the visual monitoring of the device’s energy storage state. Through long-term cyclic voltammetry (CV) and galvanostatic charge and discharge (GCD) test, the device shows good cycle stability. The research is of great significance to the preparation of multifunctional energy storage materials and the application of electronic devices.

Robust and swiftly multicolor Zn2+-electrochromic devices based on polyaniline cathode

Multifunctional electrochromic (EC) devices are very important for the current research on smart electronic devices. Herein, we report a robust and swiftly multicolor EC energy storage device design based on polyaniline (PANI) cathode. To achieve this goal, we systematically studied the EC properties of PANI in aqueous and organic Zn 2+ electrolytes for the first time. Compared with Zn 2+ aqueous electrolyte, the PANI film measured in organic Zn 2+ electrolyte delivered a fast-switching time (τ c /τ b = 2.0/2.4 s), high optical contrast (72.2%), high coloration efficiency (205 cm C −1 ), and good cycle stability (optical contrast remains 92.7% after 10,000 cycles). The excellent EC performance could be attributed to the good wettability of the interface between organic Zn 2+ electrolyte and PANI film, which supports rapid charge transfer kinetics. The PANI cathode in the organic Zn 2+ electrolyte also provided a multicolor electrochromism (light yellow, green and dark green) along with a high specific capacitance of 26.4 mAh m −2 and 72.2% spectral modulation range at a current density of 0.1 A m −2 , excellent rate capability of 86.4% capacity retention and 81.3% spectral modulation even at an 8-fold current-density increase. The laboratory prototype device also verified the EC energy storage performance of organic Zn 2+ intercalated/deintercalated PANI, confirming that they are suitable for highly robust multicolor EC energy storage applications. • The EC properties of PANI film in aqueous and organic Zn 2+ electrolytes for the first time were systematically revealed. • The PANI film delivered a fast-switching time, high optical contrast, high coloration efficiency, and excellent cycle stability (optical contrast remains 92.7% after 10,000 cycles). • The laboratory prototype device based on PANI showed a good EC performance as well as energy storage.

Electrochromic behavior of fac-tricarbonyl rhenium complexes

Tricarbonyl rhenium complex shows good electrochromic performance with a colored stage of green, rapid response and good switching stability.

Fabrication of nitrogen doped TiO2-B nanotube film with novel electrochromic performance

Doping with foreign atoms is an efficient way to enhance the electrochromic performance of the pristine single material. In this work, N-doped TiO2-B nanotube films were successfully prepared via hydrothermal approach combined with ion exchange method. The nitrogen doped TiO2-B nanotube film shows good electrochromic performance and cyclic stability. At 633 nm and −1.6 V, the optical modulation amplitude of the nitrogen doped TiO2-B film can reach 76%, which is higher than pristine TiO2-B film (64%). The coloring efficiency of the nitrogen doped samples is 35.38 cm2/C which is higher than pure TiO2-B (21.72 cm2/C). Such good performance can be ascribed to the increase of the TiO2-B electrical conductivity caused by the doping of N species.

Advanced electrochromic/electrofluorochromic poly(amic acid) toward the colorimetric/fluorometric dual-determination of glycosuria

The electrochromic/electrofluorochromic (EC/EFC) dual-functional polymers have gained intense attention owing to the unique electrochemically induced absorption and emission change simultaneously. Most of the efforts have recently been devoted to improving their EC/EFC performance. However, the practical application studies of the EC/EFC polymers are still in their infancy. Herein, we present a poly(amic acid) based material bearing high solid fluorescence-efficiency AIEgens and electroactive oligoaniline groups, featuring a good electrochromic performance with desirable optical contrast, high coloration efficiency, and outstanding durability. This occurs in tandem with electrofluorochromic behavior with ideal fluorescence contrast and moderate switching speed. By virtue of the versatile electrospinning technique, we manufactured a nanofibrous test strip base on the resultant polymer for glucose determination. The colorimetric/fluorometric dual-determination of glucose is carried out with an obvious color change from gray to dark green, along with a drastic fluorescence change from light to dark, which exhibits numerous advantages of easy operation, rapid detection, favorable selectivity, and unique repeated use feature. Furthermore, the nanofibrous test strips also provide reliable results in the glycosuria test. This strategy shows distinct promise for future sensing applications.

All-solid-state electrochromic devices based on the LiAlSiO4 electrolyte

Herein, LiAlSiO4 was used as electrolyte material for all-solid-state electrochromic devices for the first time, and an electrochromic device (ECD) with the structure of glass/ITO/NiO/Ta2O5/LiAlSiO4/Ta2O5/WO3/ITO was prepared by magnetron sputtering method. Since LiAlSiO4 electrolyte exhibits high transparency and good ionic conductivity, the ECD shows good electrochromic performance including: large optical transmittance modulations (50.8% at 586 nm, 64.1% at 1000 nm), good stability (optical modulation is still maintained at 81.4% (586 nm) and 89.0% (1000 nm) of initial state after 1000 cycles) and high coloration efficiency (60.3 cm2 C−1 at 586 nm, 150.6 cm2 C−1 at 1000 nm). Considering the low cost and abundance of Al and Si, LiAlSiO4 may be acknowledged as a sustainable electrolyte for future high-performance ECDs.

Highly oriented lamellar polyaniline with short-range disorder for enhanced electrochromic performance

• Highly oriented lamellar PANI with in-plane short-range disorder was prepared. • Every PANI layer serves as an independent electrochromic film for ion transmission. • This structure simultaneously improves ion diffusion capability and reaction area. • pTSA-PANI displays high contrast ratio, coloration efficiency and fast response. Conjugated organic polymers (COP) are fundamental for the future development of electrochromic devices. Despite the progress of composite materials, the electrochromic performance of pristine COP is still limited by dense three-dimensional (3D) structure. This work reports the fabrication of high optical contrast polyaniline (PANI) films with fast switching speed by electrochemical polymerization. Benefitting from the stereo-structure and size of p-toluenesulfonic acid (pTSA), highly oriented lamellar polyaniline with nanoscale large inter-layer spacing and a disordered in-plane structure is obtained. These structural factors simultaneously improve ion diffusion capability and optimise reaction area, resulting in a high optical contrast of above 70% at a wavelength of 720 nm, a fast response time (0.8 s for coloring and 4.2 s for bleaching), and remarkable coloration efficiency (328.5 cm 2 C −1 ). In addition, the pTSA-PANI quasi-solid-state electrochromic device displayed good electrochromic performance with optical contrast of 82%, suggesting an inherent suitability for use in electrochromic fields. Furthermore, the synthetic method developed here represents a new and simple technique to modulate photoelectronic properties.

Electropolymerizations and electrochromic performances of tetrathiafulvalene-σ-thiophenes

Three tetrathiafulvalene (TTF)-functionalized thiophene (Th) monomers with different σ bridges were synthesized. The UV–Vis spectra and CV implied that the weak intramolecular charge transfer effects existed in these monomers. They could be electropolymerized into the polythiophenes with TTF unit as pendant group during the CV and CA processes, while the electropolymerization of non-TTF-substituted thiophenes failed under the same conditions. The electropolymerized P (TTF-σ-Th) exhibited good electrochromic performances, especially in P (TTF-Th-3), due to the thiophene backbone activated by the TTF group. Novel Tetrathiafulvalene-σ-Thiophenes monomers were successfully electropolymerized with good electrochromic performance due to the activation effect of TTF pendent.

Visible and infrared electrochromism of bis(2-(2-(2-hydroxyethoxy)ethoxy)ethyl) viologen with sodium carboxymethyl chitosan-based hydrogel electrolytes

Electrochromic devices (ECDs) which able to absorb the solar spectrum of visible (400–780 nm) and infrared (780–2000 nm) have attracted considerable attention due to the light control and energy-saving properties. In this paper, a electrochromic derived derivative of viologens, bis (2-(2-(2-hydroxyethoxy)ethoxy)ethyl) viologen bromide (HEV2+2Br−) was successfully synthesized and added to novel environmentally benign hydrogel electrolytes containg deionized water, sodium carboxymethyl chitosan and vitamin C (as electron mediators for the first time) as an electrochromic chromophore. The electrochromic devices on the basic of electrochromic materials (HEV2+2Br−) and hydrogel electrolytes underwent reversible switching between colorlessness and deep purple hues upon the potential ranges from 0 V to −1.2 V. Spectroelectrochemical studies demonstrated that HEV-based gel devices showed exceptional electrochromic behaviors with low driving voltage of −0.80 V, satisfactory optical contrast (unambiguously exceeded 64.13%) and high coloration efficiency (up to 243 cm2/C at 520 nm and 119 cm2/C at 865 nm) in the visible and infrared radiation. In consideration of their good electrochromic performance and environmentally friendly properties of benign hydrogel electrolytes containing HEV, the HEV-based gel devices have brilliant potentialities as candidates for related electrochromic applications for energy-efficient architecture.

Low band gap donor-acceptor-donor compounds containing carbazole and naphthalene diimide units: Synthesis, electropolymerization and spectroelectrochemical behaviour

A new DπAπD compound consisting of naphthalene diimide core-functionalized with 1,4-phenylene-functionalized carbazole, namely 2,6-bis[4-(9H-carbazol-9-yl)phenyl]-N,N’-bis(2-ethylhexyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (CNDI) was synthesized. Its redox properties (reduction and oxidation potentials, electron affinities (EA) and ionization potentials (IP)) were compared with those of 4,7-bis(4-(9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole (CBTD) – a specially synthesized reference compound containing identical Dπ- units and significantly weaker acceptor (benzothiadiazole). It was demonstrated that the acceptor strength, determined as the index of the spatial extent of the charge transfer, DCTP, only weakly influenced the molecule oxidation potential and by consequence its ionization potential. To the contrary, strong effect of charge transfer, expressed by DCTP, was found for the reduction potential of CNDI and CBTD, showing significantly higher reduction potential of the former leading to much higher |EA|. CNDI could be electrochemically polymerized yielding a low band gap polymer (Eg = 1.63 eV) of ambipolar character, exhibiting low ionization potential (IP = 5.48 eV) and high electron affinity (|EA| = 3.85 eV). In its cyclic voltammograms polyCNDI shows five redox states, namely neutral, first and second reduction and first and second oxidation ones. As revealed by detailed studies of electrochromic parameters only three redox states (neutral, first reduction and first oxidation) demonstrate good electrochromic performance.

An Efficient Electrochromic Supercapacitor Based on Solution-Processable Nanoporous Poly{tris[4-(3,4-ethylenedioxythiophene)phenyl]amine}.

A new green synthetic route to tris[4-(3,4-ethylenedioxythiophene)phenyl]amine (TEPA) monomer has been developed and the molecular structure of TEPA has been determined by using single-crystal XRD. Solution-processable nanoporous poly{tris[4-(3,4-ethylenedioxythiophene)phenyl]amine} (PTEPA) is prepared by a chemical oxidative polymerization in a microemulsion. Based on the distorted structure of TEPA in the solid state, it is proposed that dendritic PTEPA has a distorted 3 D conformation with multiple twisted channels and pores that are narrowed and blocked by bifurcation and distortion of PTEPA, which is consistent with the observed hierarchical pore structure. As a cathode material, PTEPA exhibits a discharge capacity of 89.5 mAh g-1 in the initial cycle with a highly sloping two-stage discharge curve and relatively stable cycling performance. Beyond its excellent energy storage properties, PTEPA also shows relatively good electrochromic performance. Furthermore, an efficient all-solid-state electrochromic supercapacitor (ECSC) with good electrochromic performance and high energy storage capacity (13.3 mF cm-2 ) is assembled from PTEPA and nanoporous graphene films. During charge-discharge processes, the color of the ECSC changes between yellow-green and steel blue. Thus, the energy storage level of the ECSC can be monitored by the corresponding color changes. The fabricated ECSC may have practical applications, for example, in self-powered electrochromic smart windows.

High-performance and ultraflexible PEDOT/silver nanowires/graphene films for electrochromic applications.

We fabricate a kind of flexible electrochromic (EC) film by spraying the mixed dispersion of silver nanowires (AgNWs) and poly (3, 4-ethylenedioxythiophene) (PEDOT) on the graphene (GR) electrode. AgNWs are embedded in the PEDOT nanoparticles, forming an interlaced conductive network and double electron transport channels; therefore, the disadvantages of poor conductive GR electrodes have been remedied effectively. The subsequent GR-based PEDOT/AgNWs composite films have revealed remarkable optical contrast (63%), high coloration efficiency (${182.8}\;{{\rm cm}^{2}}\;{{\rm C}^{ - 1}}$182.8cm2C-1), and good cycle stability (keeping the optical contrast about 60% after switching cycles of 16,000 s). In addition, the GR-based composite films can keep good EC performance after 2000 cycles of bending tests, while those of the ITO/PET-based composite films decrease dramatically. The ultraflexible GR-based PEDOT/AgNWs composite films with excellent EC properties present an opportunity for fabricating large-area flexible EC devices.

Synthesis of oriented core/shell hexagonal tungsten oxide/amorphous titanium dioxide nanorod arrays and its electrochromic-pseudocapacitive properties

In this work, well-aligned core/shell hexagonal tungsten oxide/amorphous titanium dioxide nanorod arrays (denoted as core/shell WTNRAs) were synthesized on FTO substrates by a hydrothermal-spin coating approach and has been proved to have enhanced electrochromic-pseudocapacitive properties compared with initial WO3 nanorod arrays (h-WNRAs). The influence of spin-coated amorphous TiO2 (a-TiO2) layer on the microstructure, electrochromic (EC) and pseudocapacitive (PC) properties of the core/shell WTNRAs was intensively investigated. With the suitable a-TiO2 shell, the core/shell WTNRAs presented good EC performance including larger optical modulation (682 nm, 78%), faster response (coloring time 15 s, bleaching time 12 s), higher coloration efficiency (800 nm, 122.3 cm2·C−1) and good cyclic stability. In the meantime, the core/shell structures achieved excellent PC properties such as higher charge storage capacity (426.8 F·g−1 at 1 A·g−1), good charge-discharge cycle efficiency (81%) and rate performance. The mechanism of improving the bifunctional properties was also discussed. Furthermore, the energy storage stages of the material could be visually monitored by rapid and reversible colour changes at different current densities.