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Zirconium (Zr)-doped NiO films with different contents were successfully synthesized via the chemical spray pyrolysis technique. The structure, morphology, optical and electrochemical behaviors of these films were investigated by X-ray diffraction (XRD), Raman spectrometer, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), UV–Vis-NIR spectrophotometry, cyclic voltammetry (CV), and chronoamperometry (CA). XRD results suggested that the synthesized samples have the cubic crystal structure and a preferred orientation along the plane (111). Raman spectra further confirmed the successful incorporation of zirconium ions into the NiO films. SEM images explained that the surfaces of the doped films were composed of uniform and dense nanoparticles. EDS analysis suggested that Zr, Ni and O elements were uniformly distributed on the films. The optical results showed that the band gap decreases from 3.53 eV to 3.47 eV as the increase of zirconium doping content. The electrochemical analysis suggested that zirconium doping improved the specific capacitance of the NiO films (the NiO film with the Zr amount of 7 %, 59 F/g at 6 mV/s). In addition, the NiO film with 5 % Zr doped amount exhibited the largest Δ OD (81 %), the largest CE (60.37 cm2/C), and the fastest coloring time (t c =2.1 s) and bleaching time (t b = 2.4 s). These results showed that this film had the excellent electrochromic properties, suggesting that the optimal Zr doped amount of NiO films is 5 %. As a novel kind of electrochromic material, the Zr-doped NiO film has broad application prospects in smart windows, green buildings and energy efficient utilization fields. [ABSTRACT FROM AUTHOR]

Electrochromic materials have been widely used in various parts of life due to their advantages of energy conservation and rich colors. In this work, a series of novel viologen derivatives (tetrasubstituted thienoviologen derivatives, a – f) were designed and synthesized as electrochromic materials by decorating 4,4′,4″,4‴-(thiophene-2,3,4,5-tetrayl)tetrapyridine with different N-substituents (alkyl, benzyl and aryl). Electrochromic devices based on a – f exhibited a low working voltage of −1.4 V. The N-substituents markedly affected their electrochromic performance. The compounds with alkyl and benzyl substituents performed better than the compound with aryl substituent. Among them, compound c with benzyl substituent performed best with a high optical contrast (66 %), a high coloration efficiency (389 cm2/C), good cycling stability, and fast response time. Besides, compound c was also applicable to sodium carboxymethyl cellulose hydrogel ECD with good cycling stability and a broad absorption band (500–700 nm) in the visible region. The applications of compound c in electronic tags, functional displays and smart windows were explored, indicating it's a promising ECM with wide application prospects. [Display omitted] • Tetrasubstituted thienoviologen derivatives (a – f) were synthesized as ECMs. • N-substituent markedly affected their electrochromic behavior. • Compound c performed best in optical contrast, coloration efficiency, and stability. • Compound c was also applicable to CMC-Na hydrogel state ECDs with good performance. • Applications in electronic tags, functional displays and smart windows were explored. [ABSTRACT FROM AUTHOR]

The ionic complex of K-C dot used as an electrolyte demonstrates high electrochromic performance and stability for Prussian blue. [Display omitted] • Novel ionic complexes based on multivalent carbon dot polyanions (C dot) have been developed. • The ionic complexes based on C dot were applied as an electrolyte for the electrochromism of PB. • The K-C dot exhibited superior electrochromic properties of PB compared to commercially available KCl. • The hydrated ionic radius of the counter cations influences the electrochromic performance of PB. • Improving electrochromic performance in ECDs requires balancing two key factors: charge neutrality of PB as well as electron transfer between PB and electrode. Electrolytes are crucial in electrochemical applications such as rechargeable batteries, supercapacitors, fuel cells, and electrochromic devices (ECDs). Therefore, developing new electrolytes with high ionic conductivity, electrochemical stability, and environmental friendliness is essential for advancing next-generation electrochemical systems. Herein, we developed a novel type of ionic complexes composed of multivalent carbon dot polyanions (C dot) and equivalent alkali cations such as Li+ (Li-C dot), Na+ (Na-C dot), and K+ (K-C dot). As an electrolyte, the K-C dot demonstrated superior electrochromic behavior of Prussian blue (PB)–a promising electrochromic material for ECDs–compared to commercially available KCl. The PB thin films exhibit high coloration efficiency (η) of 103.5 cm2 C−1, good optical density (OD) of 0.90, and fast color switching time (1.5 and 2.6 s for the bleaching and coloring processes, respectively). Furthermore, the PB thin films exhibit long-term stability, retaining 97 % of the initial optical contrast (ΔT) even after 1,000 color switching cycles. The electrochromic performance of PB is influenced by counter cations such as Li+, Na+, and K+, which occupy the interstitial cavities in the lattice of PB during the electrochromic process. These results suggest that to improve the electrochromic performance of PB thin films in ECDs, it is essential to balance the migration of counter cations into and out of the lattice channels of the PB structure with the electron transfer between the PB thin film and the electrode substrate to maintain the charge neutrality of PB. We anticipate that our study will enhance the understanding of the electrochromic process in ECDs and provide new insights into the design of electrolytes for electrochemical systems. [ABSTRACT FROM AUTHOR]

Piezoelectric nanogenerators (PENGs) are becoming increasingly popular for energy generation and their use in smart electronics. In this study, a barium stannate (BaSnO 3)-doped polyvinylidene fluoride (PVDF)-based PENG has been fabricated for the first time. The β-phase of PVDF was stabilized by optimizing the doping of BaSnO 3 nanoparticles without the need for external electrical poling. The high surface area of the BaSnO 3 nanoparticles promotes the nucleation of the polar β-phase in PVDF through electrostatic interaction. A low-cost solution casting method was used to prepare flexible BaSnO 3 /PVDF nanocomposite containing 5 wt% BaSnO 3 , which was then shaped and sandwiched between copper electrodes and protected with a thin PDMS layer to create the final PENG. The fabricated PENG can generate up to ∼41 V of voltage, ∼1.51 µA of current and ∼18.1 µW/cm2 of power density when ∼15.7 kPa pressure is applied by a human finger. The PENG can also charge capacitors, power up 16 LEDs in a series connection, and power other small electronics such as wristwatches, speakers, and calculators. Additionally, the PENG can activate the electrochromic material methyl viologen, which is commonly used in smart window applications. [Display omitted] • Barium stannate (BaSnO 3) nanoparticle with ~112 m2/g surface area was synthesized by hydrothermal method. • Stabilization of the β-phase of PVDF (~94 %) was achieved by incorporating 5 wt% of BaSnO 3 nanoparticles in PVDF. • Fabrication of a high performance flexible BaSnO 3 /PVDF based piezoelectric nanogenerator (PENG) is discussed. • PENG shows a maximum output voltage of ~41 V, output current of ~1.51 μA, and power density of ~18.1 μW/cm2. • PENG can charge capacitors, power up LEDs, wristwatches, speakers, calculators, and activate electrochromic material. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal-organic coordinated hybrid polymers are unique electrochromic materials due to metal-center-assisted electrochromism. • The dimensional perspective of these hybrid polymers plays a key role in electrochromic behaviors. • Development of different dimensional (1D, 2D and 3D) metal–organic hybrid polymers are systematically summarized. • Exploring structure–property relationships to enhance electrochromic parameters of dimensional metal–organic hybrid polymers. • Future challenges and opportunities associated with electrochromic metal–organic hybrid polymers are discussed. Electrochromic devices (ECDs), which can alter their color hue by external bias, have been considered as the potential entrants for the applications in power-saving smart windows, high-performance dynamic digital displays for future generation, e-paper, wearable electronics, and electrochromic sensing technology owing to their advantages of low power utilization, eye-friendly approaches for displays, simple and adjustable redox chemistry, etc. Starting from the metal oxides to today's metal plasmonic-based electrochromic materials (ECMs), metal–organic polymers are superior due to their ease of processability, cost-effectiveness, wide and vivid color range, and other EC parameters like switching time, durability and coloration efficiency. Even if the metal–organic hybrid polymers are superior, the EC parameters like durability, color modulation, switching fastness, coloration efficiency, and EC memory must be further improved to commercialize next-generation ECDs. In recent years, with the cooperative efforts of numerous outstanding researchers in the field of metal–organic coordinated hybrid polymers, these technical bottlenecks can be solved in some portion by introducing new kinds of strategies and materials to fabricate ECDs with excellent performances. This review reports exciting state-of-the-art results regarding the structure and EC property relationship of new and unique different dimensional metallo-organic hybrid polymers for ECDs where the electrochromism is associated with the metal center redox. Meanwhile, the review also probes the EC properties of hybrid polymers and correlates them with their structures, mechanisms, features, morphologies, etc. A critical conclusion regarding this field's remaining challenges and outlook is also proposed. Expectantly, this review can stimulate more researchers to enrich the field of metal–organic coordinated polymer for ECDs to tune the performance of ECDs by improving the key EC parameters for future development. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural features and modifications of Wells-Dawson polyoxometalates. • Post-functionalization as a method for forming multifunctional materials. • Multi-level tuning of properties and resulting versatile applications. • Potential to be explored in various fields such as hybrid polymers, energy storage materials, catalysis or biology. Wells-Dawson polyoxometalates (WD POMs) are an important subgroup within the diverse family of POMs. In the last two decades, there has been remarkable progress in the structure modification and post-functionalization of WD POMs, which has unlocked their enormous potential across various domains, including energy materials, catalysis (photocatalysis, electrocatalysis), functional materials (sensors, optical materials, electrochromic materials, magnetic materials) or biology/medicine (anticancer and antibacterial activities). What makes these systems particularly captivating is their highly adaptable topological structure, combined with the versatile functionalization methods and consequently their precise design and control, which transfers into a wide range of applications. In our comprehensive review, we focus on the exploration of their intricate structural characteristics which play a pivotal role in their functional properties. Moreover, the exciting and promising applications of WD POMs across various areas of science disciplines are highlighted. Our aim is to shed light on the current state of the art, identify emerging trends, and provide insights into the potential future directions of WD POM research, which are still being expanded, especially given the rapid development and continuous progress in the design of novel WD POM subunit functionalities. By doing so, we hope to contribute to a better understanding of these remarkable materials and inspire further innovation in their utilization. [ABSTRACT FROM AUTHOR]

W 18 O 49 -PB device can realize different optical modulation modes at different voltages. [Display omitted] • A simple solvent molecular strategy is proposed to control the morphology and crystallinity of W 18 O 49. • The morphology of W 18 O 49 film changes from the porous nanowire network of methanol to the nanowire array of n-propanol. • The porous reticulate W 18 O 49 film synthesized in methanol shows excellent electrochromic properties. • W 18 O 49 film synthesized in methanol exhibits high energy storage to improve energy utilization. 18 O 49 is a promising electrochromic material with abundant oxygen vacancy and high carrier mobility. However, the electrochromism of W 18 O 49 is not satisfactory, the regulation and synthesis of high-performance W 18 O 49 have become the research hotspot. In this work, it is found that the main chain and side chain structure of solvent molecules can control the assembly and synthesis of W 18 O 49 film, so as to achieve excellent electrochemical and electrochromic properties. The porous reticular W 18 O 49 film synthesized in short-chain molecular solvent shows the excellent transmittance modulation (81.6 % at 633 nm, 77.0 % at 1050 nm), and exhibits the high energy storage of 41.7 mF cm−2 at 0.1 mA cm−2. Solvent molecular strategy provides a new way for the synthesis and regulation of W 18 O 49 electrochromic films and promotes the further development of high-performance electrochromic materials. [ABSTRACT FROM AUTHOR]

Nitrated benzothiadiazole (BT) is the promising acceptor units in constructing D-A-D electrochromic polymers, but its researches in the electrochromic field was very limited so far. In this work, four kinds of nitrated polymer precursors (Th-NO 2 -BT, EDOT-NO 2 -BT, Th-2NO 2 -BT, and EDOT-2NO 2 -BT) were synthesized by Stille coupling reaction with EDOT and thiophene units as the end groups (electron donor units) and mono-nitrated benzothiadiazole and di-nitrated benzothiadiazole as the core groups (electron acceptor units). The chemical structure and optical properties of the precursor were investigated by means of 1H NMR, UV–vis absorption and fluorescence spectra; the corresponding mono-nitrated polymer films were obtained in CH 2 Cl 2 -Bu 4 NPF 6 system by electrochemical deposition method. The optical band gap of di-nitrated polymer precursor is obviously larger than the corresponding mono-nitrated polymer precursor (both ultraviolet and fluorescence spectra are obviously blue-shifted), accompanied with the obvious increased initial oxidation potential. Due to the fluorescence quenching effect of -NO 2 group, their absolute quantum yields are all very low (0.0006–0.015). The spectroelectrochemistry and electrochromic kinetics of mono-nitrated polymer films (P(Th-NO 2 -BT) and P(EDOT-NO 2 -BT)) were studied. It was found that P(EDOT-NO 2 -BT) can show better electrochromic performance than P(Th-NO 2 -BT), with dark green in the neutral state and more obvious electrochromic performance in the near-infrared region (optical contrast: 38.4 %, coloration efficiency: 129.1 cm2/C, and fast response time: 1.4 s). This systematically study about the effects of nitro substitution effect on the properties of D-A electrochromic polymers, which will further expand the selection of the new acceptor units and the application prospect of nitrated electrochromic materials. [Display omitted] • Four nitrated D-A polymer precursors were synthesized by Stille coupling reaction. • The nitro group has the effect of fluorescence quenching and anodic shifts in oxidation potentials of the monomers. • Different nitrated benzothiadiazole units has huge effect on the monomers' photophysical properties. • P(EDOT-NO 2 -BT) have good redox activity and more obvious electrochromic performance in the near-infrared region. [ABSTRACT FROM AUTHOR]

In this work, two fluorinated D-π-A-π-D type monomers, F-EDOT and FF-EDOT, were facilely synthesized by donor-acceptor-donor method via Stille coupling reaction, with monofluorinated benzothiadiazole and difluorinated benzothiadiazole as the acceptor units and 3,4-ethylenedioxythiophene (EDOT) as the donor units. The electrochemical polymerization behavior of the fluorinated monomers, electrochemical and electrochromic properties of the corresponding fluorinated D-A polymers were compared to study the effects of different fluorine atom numbers on the optoelectronic properties of the monomers and their resultant D-A polymers. The results show that the introduction of more F atoms into the conjugated backbone increases the oxidation potential of monomers, both of them have low initial oxidation potential (0.65 V/0.70 V). As in the case of monomers, the substitution of more F atoms also leads to the decreased HOMO energy level of the polymers, thus leading to the increased band gap energy of P(FF-EDOT) (1.39 eV). This result can be attributed to the deviation of planarity and the reduced effective conjugate length. As prepared fluorinated D-A polymers also have good adhesion on the electrode surface, favorable redox activity, and outstanding redox stability (the redox activity of P(F-EDOT) remains 99 % after 1000 cycles). At the same time, the fluorinated D-A polymers also show distinguish electrochromic properties under various external potentials; both the optical contrast and coloration efficiency decreased with the increase of F atom numbers, and the corresponding response time increased. As a result, both the fluorinated D-A polymers show light green in the neutral state, P(F-EDOT) shows more obvious electrochromic performance in the near infrared region (optical contrast: 35.02 %, coloration efficiency: 159.94 cm2 C−1, and quick response time: 0.2 s), accompanied with excellent discoloration stability and optical memory effect. The study of novel fluorinated-based electrochromic materials further expands the selection of acceptor units and the application prospect of electrochromic materials. [Display omitted] • Two D-π-A-π-D type fluorinated electrochromic monomers were obtained. • F-EDOT show a lower initial oxidation potential. • The number of fluorine atoms has obvious effects on the photophysical properties of the polymer. • Smaller band gap P(F-EDOT) owned better redox activity and redox stability. • P(F-EDOT) show excellent electrochromic with a coloration efficiency of 159.54 cm2 C−1 and very short response time. [ABSTRACT FROM AUTHOR]

The triarylamine-based polyimide (NT-TPI) COF film effectively combines electrochromic and electrochemical energy-storage, resulting in a promising electrochromic energy-storage material that exhibited transparency, high optical contrast, multi-color, and large specific capacitance. [Display omitted] • Triarylamine-based polyimide COF films were grown directly on FTO glass. • NT-TPI COF film displayed transparent bleached state, ambipolar electrochromism. • NT-TPI COF film also exhibited multi-color, and high optical contrast. • NT-TPI COF film had a specific capacitance of 141.0 mAh/g. • PM-TPI and NT-TPI COF films displayed excellent charge–discharge rate performance. Electrochromic energy storage materials that possess both electrochromic and electrochemical energy-storage properties have attracted significant attention for applications in visual energy-storage, energy-efficient windows, as well as displays. To fulfill their comprehensive applications, electrochromic energy-storage materials require specific characteristics, such as transparency, ambipolarity, multi-color capabilities, and high capacitance. Here, the polyimide covalent-organic framework based on triarylamine (PM-TPI and NT-TPI) COF films were grown successfully on FTO glass through solvothermal polycondensation, and exhibited crystallization, hierarchical porous structures, and ambipolar electrochemical redox activity. Notably, NT-TPI COF film displayed transparent bleached state, ambipolar electrochromism, multi-color (transparent, orange-red, cyan, gray), and high optical contrast. Due to their large specific surface area and efficient electron/ion transport ability, the NT-TPI COF film effectively controlled visible and near-infrared light, achieving optical contrasts of 49.8 % and 70.0 % at 420 and 850 nm, respectively. Moreover, the NT-TPI COF films showed promising electrochemical energy-storage properties and excellent charge–discharge rate performance, with a specific capacitance of 141.0 mAh/g. Additionally, NT-TPI COF/WO 3 -based ambipolar eclectrochromic energy-storage devices also exhibited high optical contrast from visible to near-infrared regions, and large capacitance. In summary, the NT-TPI COF film effectively combines the electrochromic and electrochemical energy-storage capabilities, making it a promising candidate for electrochromic energy-storage materials with transparency, ambipolarity, high optical contrast, multi-color functionality, and high specific capacitance. [ABSTRACT FROM AUTHOR]

• The bipolar COF-GZU1 structure was successfully designed. • The prepared COF-GZU1 films exhibited high specific surface area, crystallinity and porosity. • The ordered porous structure facilitates electron conduction and ion mass transfer. • Great electrochromic properties and regulation. Because of the ordered and loose structure, covalent organic framework (COF) holds broad promise in the field of electrochromism, but the simple color change limits its application and development. A bipolar and polychromatic COF-GZU1 was successfully designed and prepared in this paper. The structure, electrostatic potential and orbital structure of the COF-GZU1 were predicted and calculated using density functional theory, and the calculation results confirmed the feasibility of bipolar construction strategy. XRD, SEM, BET and GIWAXS further mutually established the successful synthesis of COF-GZU1, which exhibited high specific surface area, crystallinity and porosity. Results from electrochemical impedance spectroscopy, density of states analysis, and ion diffusion coefficient measurements verified that the ordered porous structure facilitates electron conduction and ion mass transfer, leading to a significant improvement in electrochromic performance. Moreover, the COF-GZU1 film displayed excellent electrochromic performance, providing polychromatic switching with a rapid response time (7.8/14.5 s and 1.0/12.6 s for coloring/bleaching process) and high coloring efficiency (112.8 and 127.8 cm2∙C-1 at 799 and 570 nm). These results collectively demonstrate the superiority of the COF-GZU1 film and suggest that the bipolar COF design strategy could pave the way for new and high-performance polychromatic electrochromic materials. [ABSTRACT FROM AUTHOR]

• Three soluble EC materials with finely-tuned energy gaps. • FTP and FEP can switch from yellow to green series with excellent EC properties. • FEP-PEDOT showed enhanced EC performance for adaptive camouflage. • Three novel types of camouflage net ECDs were developed. • New strategy to construct intelligent adaptive camouflage nets. The potential application of electrochromic (EC) materials and devices as adaptive camouflage in diverse environments requires further investigation. In this study, we aimed to enhance the camouflage effect of electrochromic devices (ECDs) by developing innovative EC camouflage nets. Three soluble EC materials (FTP , FEP and FBP) were synthesized by incorporating phenothiazine and ProDOT with different donors through direct(hetero) arylation polymerization. Due to the fine-tuning of the energy gap, the three materials exhibit yellow, yellowish-brown and reddish-brown colors in their neutral states, respectively. Particularly, FTP and FEP can switch between different yellow-to-green with superior EC performance. Furthermore, FTP - PEDOT and FEP - PEDOT ECDs were constructed. Notably, the FEP-PEDOT ECD demonstrated enhanced EC performance, characterized by a more noticeable yellow-to-green switch, faster switching times and improved cycle stability. To meet the adaptability for multi-environmental camouflage and wearable applications, we created diverse camouflage patterns using the mask-spray technique and developed three types (" stripe " / " cross stripe " / " block ") camouflage net ECDs. This study offers a comprehensive approach for developing adaptive camouflage nets tailored to diverse real combat settings. [ABSTRACT FROM AUTHOR]

In this study, tungsten oxide and polyaniline hybrid films were deposited on the surface of stainless steel yarns by electrochemical deposition, and the electrochromic yarns with double electrochromic layer structure were formed. WO 3 acts as a protective layer and binder to connect PANI nanorods, thereby improving electrochemical stability and electrochromic performance. The electrochromic yarns present five color changes in the voltage range of −0.4 V-1.1 V, the optical modulation of 59.98 %, the response time of 0.75 s, the coloration efficiency of 74.89 cm2/C, good electrochemical cycling stability (100 cycles without significant degeneration) and washing durability. At the same time, stable electrochromic behavior is still maintained in the bending state. The device based electrochromic yarns also has reversible multi-color variation, fast reaction time, and long-term stability. What's more, the device can be embroidered or woven into the fabric and designed into patterns of different colors. More color combinations can be achieved by adjusting the voltage. Finally, the fabric based on multifunction electrochromic yarns are used to study the thermal shielding performance. It can effectively block thermal radiation. These results indicate that the electrochromic yarn has promising potential for high-performance optical and thermal regulation applications. This research provides a prospective strategy for constructing multifunctional electronic devices in wearable application. • Flexible WO 3 /PANI/stainless steel yarns were prepared by electrochemical deposition method. • Electrochromic yarns exhibit multicolor variation, fast switching speed, good cycling stability and washing durability. • Yarn based electrochromic device presents excellent electrochromic properties and long-term stability. • Multifunctional electrochromic device with optical modulation and thermal regulation is first constructed. [ABSTRACT FROM AUTHOR]

Electrochromic materials have been widely applied in smart windows due to their color conversion and adjusting indoor solar radiation abilities. The researches on electrochromic properties of tungsten bronzes with near-infrared light absorbing abilities are important to obtain multifunctional smart windows. Here, nano potassium tungsten bronze K x WO 3 with space group P 6 3 / mcm has been synthesized to study the effects of crystal structures and valence states of W ions on its electrochromic properties. By altering the composition of reaction solution in solvothermal method, the K content x of samples can be controlled together with the adjustments in sizes of hexagonal and trigonal channels in the crystal structure and valence states of W ions. The maximum optical modulation and coloration efficiency are achieved for the maximum x. The enhanced electrochromic performance mainly benefits from the synergistic size effects of hexagonal and trigonal channels. [Display omitted] • The potassium tungsten bronze K x WO 3 has been synthesized by a solvothermal method. • The crystal structure and x are controlled by varying the molar ratio of starting materials. • Changing the channel size and ionic valence state can optimize the electrochromic properties. [ABSTRACT FROM AUTHOR]

The study of electrochromic materials has far-reaching significance for the regulation of light and heat as well as the reduction of energy consumption. In this study, rGO-Co-NiO composite films were prepared by combining graphene oxide, which has excellent conductivity and stability, with Co-NiO films. The particle size, band gap, conductivity and response time of the electrochromic films were improved by precisely adjusting the component modulation amount of graphene oxide. The results show that with the incorporation of GO it is easy to form oxygen vacancies, which is conducive to ionic conduction and diffusion, in which the film with a GO doping concentration of 4 % has excellent performances in terms of response time and coloring efficiency, and the response time is reduced from 10.2 to 5.8 seconds, and it still possesses 57.25 % of the light modulation amplitude after 600 cycles, of which the attenuation rate is only 2 % for the period from 100 to 600 cycles, The coloring efficiency after 100 cycles is 48.21 cm2/C. In summary, the investigated rGO-Co-NiO composite films have a broad potential for future application in electrochromic devices. [Display omitted] • A shortcut electron transfer pathway then results in a short electrochromic time. • The uniform microcrack microstructure and the active interface is beneficial for the electrochemical kinetic processes. • The doping of the rGO can improve the coloring efficiency and good work stability. [ABSTRACT FROM AUTHOR]

In this paper, a novel electrochromic material of 1,3,4-oxadiazole-extended viologen derivative with good coplanarity and electron acceptor-electron donor-electron acceptor structure, BPYO-C 6 H 13 , was synthesized, and a polyacrylamide-sodium alginate dual network hydrogel (PAM-SA) with advantages of low cost, environmental protection, good biocompatibility, high optical transmittance (>85 %), good mechanical properties and good ionic conductivity (16.61 mS cm−1) was developed as the electrochromic hydrogel matrix for gel-state electrochromic devices based on BPYO-C 6 H 13 (PAM-SA-ECD). BPYO-C 6 H 13 showed good electrochromic properties in both solution-state electrochromic devices and gel-state electrochromic devices, and PAM-SA-ECD had a lower operating voltage (−1.4 V versus −1.7 V), a higher optical contrast (48.4 % versus 33.1 % and 22.1 %) as well as a higher coloration efficiency (348.7 cm2/C versus 234.8 and 120.7 cm2/C). Compared to PAM-SA gel-state electrochromic devices based on 1,1′-dihexyl-[4,4′-bipyridine]-1,1′-diium, BPYO-C 6 H 13 with 1,3,4-oxadiazole π-extender showed a different colored state (green versus pink) and a higher coloration efficiency (348.7 cm2/C versus 275.9 cm2/C) due to different conjugated structure. PAM-SA-ECD was applied in smart windows and solar cell-powered displays, suggesting BPYO-C 6 H 13 is promising in energy-saving fields. [Display omitted] • 1,3,4-Oxadiazole-extended viologen derivative BPYO-C 6 H 13 is synthesized. • Polyacrylamide/sodium alginate double network hydrogel (PAM-SA) is developed. • PAM-SA-ECD based on BPYO-C 6 H 13 requires a low operating voltage. • PAM-SA-ECD shows high coloration efficiency and optical contrast. • PAM-SA-ECD is applied in energy-saving fields such as solar cell-powered displays. [ABSTRACT FROM AUTHOR]

A novel type of triphenylamine derivatives, phenyl-bridged N , N , N ′, N ′-tetrasubstituted bis(2-amino-5-thiazolyl) diamine (4) and its cationic form (5) were synthesized via the Hantzsch reaction. The UV–Vis spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculation results showed that the diamine possesses excellent redox properties and a narrow optical energy gap (∼1.85 eV). As an electrochromic material, compound 4 exhibits a notable color change from colorless to blue. It maintains stable cycling performance for up to 175 cycles, even within a higher voltage range of −2.4 to 2.4 V. In addition, as a catalyst, compound 5 exhibits good substrate compatibility and an aniline conversion rate of up to 89 % during the photocatalytic reduction of nitrobenzene. These results would contribute to understand the synthesis of triphenylamine electrochromic materials and expand their applications in the field of photocatalysis. • A new type of triphenylamine derivatives phenyl-bridged N,N,N′,N′ -tetrasubstituted bis(2-amino-5-thiazolyl) diamine (4) and its cationic form (5) were synthesized through hantzsch reaction. • 4 exhibited good electrochemical stability, even at the higher voltage range of −2.4 to 2.4 V, it can still cycle stably for 175 cycles. • 5 exhibited good substrate compatibility and an aniline conversion rate of up to 89 % during the photocatalytic reduction of nitrobenzene. [ABSTRACT FROM AUTHOR]

Molecular assembly induced by metal‐terpyridine‐based coordinative interactions has become an emergent research topic due to its ease of synthesis and diverse applications. This article highlights recent significant developments in the metal‐terpyridine‐based supramolecular architectures. At first, the design aspect of the molecular building blocks has been described, followed by elaboration on how the ligand backbone plays an important role for achieving different dimensionalities of the resulting assemblies which exhibit a wide range of potential applications. After that, we discussed different synthetic approaches for constructing these assemblies, and finally, we focused on their significant developments in three specific areas, viz., electrochromic materials, catalysis and a new application in wastewater treatment. In the field of electrochromic materials, these assemblies made important advancements in various aspects like sub‐second switching time (<1 s), low switching voltage (<1 V), increased switching stability (>10000 cycles), tuning of multiple colors by using multimetallic systems, fabrication of charge storing electrochromic devices, utilizing and storing solar energy etc. Similarly, the catalysis field witnessed application of the metal‐terpyridine assemblies in C−H monohalogenation, heterogeneous Suzuki‐Miyaura coupling, photocatalysis, reduction of carbon dioxide, etc. Finally, the environmental application of these coordination assemblies includes capturing Cr(VI) from waste water efficiently with high capture capacity, good recyclability, wide pH independency etc. [ABSTRACT FROM AUTHOR]

Prussian blue (Fe4[Fe(CN)6]3, PB) has become a widely studied anodic electrochromic material due to its advantages such as large optical modulation range, fast response speed and low voltage demand. Tungsten oxide (WO3) as a cathode electrochromic materials, have various advantages, while their low color rendering efficiency and poor cycling stability limit their applications. To this end, the following solution was proposed for the first time in this study: the hydrothermal method was adopted to prepare tungsten oxide nanorods and then coat Prussian blue on the rod-shaped tungsten oxide to form an inorganic–organic core–shell structure (WO3/PB) to improve electrochromic performance. Through comparative experiments, the effects of WO3/PB core–shell structure for the electrochromic properties of films and its mechanism were explored. The Li+ diffusion coefficient of WO3/PB core–shell structure films is 35% and 720% higher than that of single WO3 and PB, respectively. At the same time, compared with the single PB and WO3 films, the electrochromic response speed of the WO3/PB film is fast, and the light transmittance after coloring is low, with good optical properties. Relevant experimental data displayed that WO3 is wrapped by PB to form a core–shell structure, which makes the film have high electrochromic properties. The reasons are the formation of electron pair donor–acceptor system in the film and the formation of double electrochromic effect. WO3/PB forms a rod-like nano core–shell structure, which increases the surface area for the reaction and facilitates the transfer of ions and electrons into and out of the film. This method of combining anodic electrochromic materials and cathodic electrochromic materials to form a core–shell structure to improve electrochromic performance provides a new direction for future electrochromic research. [ABSTRACT FROM AUTHOR]

Since the cracks or scratches that occur during use can degrade the performances and lifetime of organic film electronic devices, the development of self-healing materials holds great potential for durable and sustainable electrochromic devices. However, the simultaneous self-healing of the structures and functions of electrochromic materials still faces enormous challenges. In this study, a strategy to synthesize intrinsically self-healing electrochromic polymer composite films was introduced by integrating electrochromic poly(3,4-ethylenedioxythiophene) (PEDOT) units with thermally self-healable polyurethane (PU-DA) containing reversible Diels–Alder groups. To adjust the self-healing and electrochromic behavior, the copolymerization of 3,4-ethylenedioxythiophene (EDOT) and its hydroxymethyl derivative (EDTM) was also carried out. In terms of a good balance of morphology, self-healing and electrochromic parameters, the prepared intrinsically conductive P(EDOT-co-EDTM)/PU-DA copolymer film has excellent electrochromic properties including a visible light contrast ratio of 47.24%, a fast response time of 0.8 s, and a coloration efficiency of 324.9 cm2 C−1. The visible light contrast can be maintained above 93% after 100 cycles. Moreover, the film after breaking up can be intrinsically self-healed through thermal stimulation (no more than 130 °C), and maintains the optical contrast at 95% of the original state. [ABSTRACT FROM AUTHOR]

Electrochromism is a reversible color change triggered by the external electrical field, which can be utilized in smart windows, displays, etc. The ability to display multiple colors in a single electrochromic device is highly beneficial for the versatile applications of the electrochromic technique. Yet, achieving the ability to adopt multiple colors in one electrochromic device has proven to be a challenging task by merely using the conventional chemical structure engineering of the electrochromic materials. In this study, a thermochromic electrolyte is introduced. A multicolor electrochromic prototype device is produced by integrating the thermochromic engineered electrolyte together with electrochromic material in which both can independently contribute to the coloring of the device. This "color palette" strategy gives an additional degree of freedom and extensive flexibility to the design of multicolor electrochromic devices. It introduces a new pathway for producing multicolor electrochromic devices and removes a bottleneck imposed by conventional strategies merely depending on the electrochromic material structure engineering. Moreover, it inspires further development of electrolytes, that share the responsibility of tuning the optical properties of electrochromic devices together with the electrochromic materials, thereby accelerating and diversifying the applications of electrochromics in industry. [ABSTRACT FROM AUTHOR]

Four new multifunctional polymers (P1, P2, P3, and P4) containing EDOT units were synthesized by the Stille coupling reaction. A PL spectrum test found that the introduction of large conjugated groups led to strong fluorescence emission in all polymers. Among the electrochromic and switch properties, these polymer films exhibited reversible color changes, as well as good coloring efficiency. Electrochemical experiments found that the initial oxidation potentials of the polymers were 1.27 V, 1.67 V, 1.78 V, and 1.58 V, respectively. Among them, P3 showed a higher coloring efficiency (283.3 cm2·C−1), and P2 showed a shorter response time (tc = 2.2 s, tb = 2.8 s). These polymers all exhibited electrochromic and resistive switching storage characteristics. They have good solubility in many organic solvents. In the resistance switch memory characteristics, all polymers had obvious memristive properties, and P4 exhibited a larger switch current ratio (2527.42) and a smaller threshold voltage (0.9 V). [ABSTRACT FROM AUTHOR]

Al3+‐based electrochromic devices (ECDs) are expected to substitute Li+‐based ECDs as the next‐generation smart windows options. Compared to Li+, Al3+ possess large quantities in the earth and safety, while the smaller ionic radius and three‐electron redox mechanism can break the capacity bottleneck of inorganic electrochromic materials (ECM). However, limited by the strong electrostatic interaction between Al3+ with ECM and the lack of matching counter electrodes, the research on Al3+ is still focused on three‐electrode system without applications in ECDs. Different from conventional complementary structure, the ECM/redox/CCE (catalytic counter electrode) structure is introduced to enhance the kinetics (from 1.56 × 10−11 to 9.45 × 10−11 cm2 s−1) of the Al3+ intercalation/extraction process. Based on this structure, Al3+‐based ECDs achieve a series of excellent properties: a) almost total absorption of visible and near‐infrared waveband (T500–1500 nm ≈0%) under −1.0 V; b) ultra‐low driving voltage (53% transmittance modulation under −0.1 V); c) excellent memory effect with the presence of redox couple; d) wide range of color modulation capability (yellow, green, blue, and black); e) outstanding energy efficiency. Moreover, the possibility of Na+ as an alternative to Li+ is also verified and Na+‐based ECDs exhibit comparable electrochromic properties to Li+‐based ECDs. [ABSTRACT FROM AUTHOR]

As an electrochromic material, Co 3 O 4 has limited applications due to its low optical modulation range and short cycle life. In order to improve the electrochromic properties, a 1D/2D Co 3 O 4 /NiO composite film was prepared by simple two-step hydrothermal process and discontinuous annealing. The electrochromic properties of the composite structure are significantly improved compared with the nanostructures using two oxides alone. The effect of film structure on electrochromic properties was studied in detail. The results show that the 1D/2D Co 3 O 4 /NiO composite film have remarkable optical modulation (16–73% in the 350–800 nm range) and high Li+ diffusion rate (5.15 × 10−12 cm2/s). The improvement of electrochromic properties is mainly due to the porous structure, which increase the two active materials to leak fully in the electrolyte, thus enhancing the diffusion of ions and electrons. NiO nanosheets grow well and distribute uniformly on the surface of Co 3 O 4 nanowires, allowing the two parts to fully contact the electrolyte. Cyclic voltammetry (CV) analysis shows that the peak current of the composite film is much higher than that of the single film, indicating that the nanoarray has high electrochemical reactivity. Results of electrochemical impedance spectroscopy show that the composite film has the lower charge transfer resistance and ion diffusion resistance, which are conducive to rate capacity. This work provides a strategy for improving the electrochromic properties of cobaltosic oxide. [ABSTRACT FROM AUTHOR]

Tungsten trioxide (WO3) is mainly studied as an electrochromic material and received attention due to N-type oxide-based semiconductors. The magnetic, structural, and optical behavior of pristine WO3 and gadolinium (Gd)-doped WO3 are being investigated using density functional theory. For exchange-correlation potential energy, generalized gradient approximation (GGA+U) is used in our calculations, where U is the Hubbard potential. The estimated bandgap of pure WO3 is 2.5 eV. After the doping of Gd, some states cross the Fermi level, and WO3 acts as a degenerate semiconductor with a 2 eV bandgap. Spin-polarized calculations show that the system is antiferromagnetic in its ground state. The WO3 material is a semiconductor, as there is a bandgap of 2.5 eV between the valence and conduction bands. The Gd-doped WO3's band structure shows few states across the Fermi level, which means that the material is metal or semimetal. After the doping of Gd, WO3 becomes the degenerate semiconductor with a bandgap of 2 eV. The energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) configurations is negative, so the Gd-doped WO3 system is AFM. The pure WO3 is nonmagnetic, where the magnetic moment in the system after doping Gd is 9.5599575 μB. [ABSTRACT FROM AUTHOR]

Electrochromic materials can tune the illumination and heat exchange of a building with the environment and thereby save energy in lighting, heating, and air conditioning in a cost‐effective way, which is vital in realizing carbon neutrality. 2D frameworks such as coordination nanosheets (CONASHs) that are widely explored for a wide range of applications in energy storage and conversion can be a cluster of novel electrochromic materials. In this work, a series of transition metal benzenehexathiol (TM‐BHT) CONASHs are theoretically investigated via first‐principles simulations. During ion intercalation and deintercalation in TM‐BHTs, changes in lattice structures, lithium diffusion barriers, atomic charges, bond strength, and electronic properties are explored in‐depth. The incurred changes are then correlated with critical electrochromic properties, including the transmittance adjustment ranges in the visible light, near‐infrared, solar spectrum, and mid‐infrared. Among the various TM‐BHT systems, Cu‐BHT and Ag‐BHT are the most promising broadband electrochromic materials for optical and thermal management in the wavelength range from visible to mid‐infrared. The theoretical guidance from this work paves a new path toward electrochromic applications of CONASHs that exploit the versatility of these 2D materials. [ABSTRACT FROM AUTHOR]

A comparative analysis of electrochromic properties of composites CuWO4.WO3, Bi2WO6.WO3 and WO3 films obtained by electrochemical and chemical methods was carried out. The study into the kinetics of light transmission and spectral characteristics of electrochromic coloration revealed some differences in electrochromic processes. It found that in the WO3, Bi2WO6.WO3, CuWO4.WO3 series, lithium intercalation in the film is slowed down, which is due to diffusion limitations in the process of coloring of the Bi and Cu oxides. Spectral characteristics of light transmission Bi2WO6.WO3 and CuWO4.WO3 also differ from WO3 in that the contribution to light absorption is also made by Bi and Cu oxides, which are partially reduced by lithium in the process of their coloring. It is shown that the metal tungstates can be effective electrochromic materials with an additional absorption band in the visible region. [ABSTRACT FROM AUTHOR]

One method in terms of architectural technology used to minimize the negative impact of overheating is to design a building with double skin façade and integrating it with electrochromic glass. The purpose of this research is to reveal whether the use of a double skin façade and the application of electrochromic glass would be preferable for buildings in tropical climates, in terms of obtaining aesthetic points while not having to sacrifice thermal comfort nor committing energy waste at the same time. The data in this research is obtained with qualitative - descriptive comparative method, which is applied for room temperature measurement with a computer simulation software, based on pre-existing theories, reference standards and material specifications from existing manufacturers. The results of this study conclude that the application of double skin façade in a building does make a significant contribution to achieving thermal and lighting comfort. Both profiles of space reduction with the use of electrochromic glass in buildings in tropical climates are able to reach ideal temperatures in comparison to when ordinary glass material is applied. And third, it is proven that the double skin façade technology and applying electrochromic glass on a building can provide significant energy efficiency for long-term projects. [ABSTRACT FROM AUTHOR]

Electrochromic small molecules suffer from the difficult film processibility and serious dissolvability at their oxidation state, which greatly limit their applications in electrochromic areas. Here, well‐defined electrochemical polymer structures, pCZ‐FSQ and pCZ‐FEQ, are obtained by taking advantage of the unique electrochemical dimerization of carbazole, and low redox‐potential phenothiazine and phenoxazine groups are introduced as an electrochromic color‐changing unit with the interruption of conjugation between them via an alkyl chain linkage. The obtained polymer films pCZ‐FSQ and pCZ‐FEQ are composed of the independent dimeric carbazole and organic small molecule units. Finally, they exhibit outstanding electrochromic properties with optical contrast of more than 50%, switching time of less than 1 s, excellent stability (over 500 cycles of optical stability), and ultrahigh coloration efficiency (276 cm2 C−1 for pCZ‐FSQ, 384 cm2 C−1 for pCZ‐FEQ). This is thought to be greatly attributed to the well‐defined electrochemical polymer structures with dual electrochromic color‐changing properties of both phenothiazine/phenoxazine and dimeric carbazole. This can also provide some implications for the future in‐depth study of small molecule electrochromism and the solution to the problem of difficult processing of small molecules. [ABSTRACT FROM AUTHOR]

Electrochromism refers to the change in the reversible color of certain materials in response to an electric field to regulate light. In this paper, WO3 thin films were prepared by hydrothermal method, and then PANI was deposited on the surface of WO3 by electrodeposition method. The organic and non-electrochromic materials were combined together, and the core–shell structure of WO3/PANI was finally obtained. The electrochromic properties of core–shell composite films are significantly improved. In particular, the cyclic stability of core–shell composite films is superior to that of single material electrochromic films. At the same time, the composite film demonstrates fast electrochromic response and large ion diffusion coefficient. The Li+ diffusion coefficient of WO3 film is 4.37 × 10–10 cm2/s, and that of WO3/PANI film is 4.93 × 10–10 cm2/s, 13% higher than that of the single film. The number of electrons and ions entering the film is greatly increased, and these improvements optimize the electrochromic properties of the film. The results show that WO3/PANI core–shell structure has broad research and application prospects as electrochromic materials. [ABSTRACT FROM AUTHOR]

Under an external voltage，the optical properties（e. g. color，transmittance，etc.）of electrochromic materials can controllably and reversibly be changed，which has an important application prospects in the fields of energy conservation and emission reduction. With the continuous innovation and development of related research，the single-component electrochromic materials cannot show the expected electrochromic properties due to the limitations of their own structure and performance，and cannot be designed and regulated in their structure and performance，so it is increasingly unable to meet the needs of practical applications. Comparing with the non-composite electrochromic materials，the composite materials have obvious advantages in this aspect. Through the reasonable material design and with the coordination of each component，the core competitiveness of the composite materials is mainly represented by the electrochromic materials with excellent structure and performance can be obtained by stimulating the advantages and overcoming the disadvantages of each component. Therefore，more and more research focus on the composite electrochromic materials in recent years. At present many kinds of composite electrochromic materials have been researched，which mainly can be divided into three categories as inorganic-inorganic composite，organic-inorganic composite and organic-organic composite according to whether the composite components are inorganic or organic materials. Compared with the organic electrochromic materials，the inorganic electrochromic materials have significant advantages in material composition control，mechanical properties，optical modulation，service stability，life and other aspects. Therefore，either the single-component or the composite inorganic electrochromic materials have always been an important direction of research in this field. Hence，this paper devotes to the research status and development tendency of the inorganic-inorganic composite electrochromic materials，devices and electrolytes，including the research progress，the existing problems and the development trend. It will provide a basis for the further development and application of composite electrochromic materials. [ABSTRACT FROM AUTHOR]

The development of bistable electrochromic materials is a promising way to reduce the energy consumption of displays. However, bistable devices with ideal implementation schemes and electrochromic performance still remain challenging due to the inherent limitations of existing electrochromic materials. Herein, a theory of "hydroxyl‐acids" assisted improvement of electrochromic rate and bistability of fluorane dyes is proposed and applied to solid‐state electrochromic devices. 80% hydroxypropyl acrylate‐20% methyl methacrylate copolymer‐based electrochromic film prepared by the theory of "hydroxyl‐acids" has a higher electrochromic rate (4.1 times) and bistability (5.4 times) than traditional PMMA‐based electrochromic films in the device. In addition, the optimum device is obtained by optimizing each layer component content of the device. The novel electrochromic device has good overall performance, including coloring time (7.5 s), transmittance change (>70%), coloration efficiency (872 cm2 C‐1), bistability (50 h), and reversibility (1,000 cycles). The theory of "hydroxyl‐acids" is suitable for a variety of fluorane dyes, and polychromatic bistable electrochromic windows are developed. [ABSTRACT FROM AUTHOR]

In recent years, the research on electrochemical devices, especially the promising electrochromic material, is gradually in a wide range of application. But there is few corresponding research about specific industrial manufacturing. The paper starts from the structure of small and medium-sized intelligent factories and designs a system framework optimized by blockchain technology. It connects the electrochromic material quality control module with the product traceability module through a blockchain-based server, which not only ensures the production quality but also effectively improves the product supply chain, which is significant for the development of the electrochromic field. [ABSTRACT FROM AUTHOR]

Electrochemical switching of luminescence color between magenta and blue using two types of luminescent materials and electrochromic molecules was demonstrated based on the control of excited energy transfer through an electrochromic reaction. The magenta photoluminescence, due to the integration of red luminescence from the Eu(III) complex and blue fluorescence from the anthracene derivative, was reversibly modulated to a pure-blue luminescence color by an electrochemical redox reaction. Electrofluorochromism is induced by effective excited energy transfer from the Eu(III) complex to the electrochromic molecule under a redox reaction. [ABSTRACT FROM AUTHOR]

Previous work has reported the synthesis of donor–acceptor–donor molecules based on dibenzophenazine acceptor group, presenting thermally activated delayed fluorescent (TADF) properties and their application in the assembly of highly efficient electroluminescent devices. Herein, we focus on the characterisation of charge carrier species through UV‐Vis‐NIR spectroelectrochemical and potentiostatic EPR techniques, in addition to the investigation of electropolymerisation properties of some compounds depicted in this study. The promising electrochromic features of both small molecules and conjugated polymers led to the assembly and investigation of electrochromic devices, evidencing the materials' versatility, applied in such different approaches as electrochromic windows and electroluminescent devices. Furthermore, the assembled OLEDs provided high efficiencies, with small roll‐off, EQEs up to 20.5 % and luminance values up to 85 000 cd/m2. [ABSTRACT FROM AUTHOR]

Electrochromic pseudocapacitive transition-metal oxide materials, such as tungsten oxide, which combine fast response, high energy density, and optical effects, can play a significant role as energy storage materials. Here we investigate the electrochemical kinetics of thin films of tungsten oxide, which turn transparent to sky-blue color in the lithiated state due to the reduction of W6+ to W5+. We investigated the charge density, charge transfer, ion diffusion, and interfacial behavior upon Li+ insertion/de-insertion in WO3. The electrochromic thin film’s pseudocapacitive and electrical double layer mechanism was differentiated based on the power-law. Faradaic diffusion-controlled process dominates over the surface capacitive behavior at scan rates below 40 mV s−1 . These films exhibit an areal charge density of around 100 mC cm−2 and a capacitance of 80 mF cm−2, superior to most comparable electrochromic materials and supercapacitors. This work combines electrochromics and energy storage properties and provides a fundamental understanding of pseudocapacitive and electrochromic mechanisms in WO3. [ABSTRACT FROM AUTHOR]

Electrochromic materials carry out redox reactions and change their colors upon external bias. These materials are the primary component in constructing smart windows for energy saving in buildings or vehicles. Enhancing the electrochromic performances of the materials is crucial for their practical applications. Micropatterned poly(3,4-ethylenedioxythiophene) (mPEDOT) thin films are electrodeposited on indium tin oxide conducting glass in this study. Their electrochromic properties, including transmittance modulation ability, color-switching rates, and coloration efficiency, are investigated and compared with nonpatterned PEDOT thin films. The mPEDOT thin films exhibited faster coloring and bleaching speeds and higher coloration efficiency than the PEDOT thin films while keeping similar transmittance modulation ability. The results suggest that micropatterning an electrochromic material thin film might enhance its electrochromic performances. This research demonstrates the possibility of promoting the color-switching rate of a PEDOT thin film by micropatterning it. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide (V2O5) is one of the most popular electrochromic material for electrochromic devices due to its excellent storage capacity of lithium ions and unique properties of anodic/cathodic coloring. However, V2O5 generally has low conductivity, causing a long coloration/bleaching response time. Consequently, its practical use as a electrochromic material in practical industrial applications remains limited. In this paper, V2O5/Mxene intercalation films (VOM) were prepared by sol–gel method with spin-coating technology. The structure and morphology of the intercalation films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and other testing techniques. The optical properties of the films were characterized by ultraviolet–visible (UV–Vis) spectroscopy, and the electrochemical properties were analyzed by cyclic voltammetry (CV) and chronoamperometry (CA). The results showed that the Mxene intercalation of V2O5 xerogel widened the interplanar distance. The bleaching time of the intercalation films was 3.20 s and the coloring time was 6.20 s when the Mxene doping was 3 wt%. Meanwhile, the transmittance contrast increased from 7.70 to 49.03% at 372 nm compared with the V2O5 xerogel films. [ABSTRACT FROM AUTHOR]

In this study, a new copolymer, which is a combination of two chemical structure (9,10-di(furan-2-yl)anthracene and 3,4-ethylenedioxythiophene was synthesized via electrochemical synthesis methods in the electrolyte medium of 0.1 M TBAPF6/ACN solution. PEDOT homopolymer was also electrosynthesized for comparator experiments of the polymer formations in the same medium. The characterizations of polymers were achieved with general optical and electrochemical characterization techniques. The corresponding electrochromic copolymer shows blue and lilac color in its neutral and oxidized states, respectively. The copolymer has an optical band gap of 1.65 eV and 24% optical contrast at 500 nm with a high coloration efficiency (170 cm2/C) and a fast switching time (1.0 s). [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) demonstrate potential for application in the development of integrated smart energy devices based on bifunctional electrochromic (EC) optical modulation and electrochemical energy storage. Herein, a nanocomposite thin film composed of a vanadium-substituted Dawson-type POM, i.e., K7[P2W17VO62]·18H2O, and TiO2 nanowires were constructed via the combination of hydrothermal and layer-by-layer self-assembly methods. Through scanning electron microscopy and energy-dispersive spectroscopy characterisations, it was found that the TiO2 nanowire substrate acts as a skeleton to adsorb POM nanoparticles, thereby avoiding the aggregation or stacking of POM particles. The unique three-dimensional core−shell structures of these nanocomposites with high specific surface areas increases the number of active sites during the reaction process and shortens the ion diffusion pathway, thereby improving the electrochemical activities and electrical conductivities. Compared with pure POM thin films, the composite films showed improved EC properties with a significant optical contrast (38.32% at 580 nm), a short response time (1.65 and 1.64 s for colouring and bleaching, respectively), an excellent colouration efficiency (116.5 cm2 C−1), and satisfactory energy-storage properties (volumetric capacitance = 297.1 F cm−3 at 0.2 mA cm−2). Finally, a solid-state electrochromic energy-storage (EES) device was fabricated using the composite film as the cathode. After charging, the constructed device was able to light up a single light-emitting diode for 20 s. These results highlight the promising features of POM-based EES devices and demonstrate their potential for use in a wide range of applications, such as smart windows, military camouflage, sensors, and intelligent systems. [ABSTRACT FROM AUTHOR]

Color is a property directly discernible by our eyes, making it perceptually conspicuous. Changes in color, whether achromatic (from white to black) or chromatic (from colorless to colored or between different colors), are easily detectable by people with normal vision or through simple spectrophotometric instruments. The categorization of chromogenic systems reveals various mechanisms of chromism. Applications photochromic, thermochromic, and electrochromic materials have been extensively discussed, including their behavior, mechanisms, and limitations. In the landscape of future energy storage systems, the significance of chromisms transcends conventional boundaries, promising transformative impacts on energy efficiency, management strategies, and sustainability. Chromic materials, endowed with their dynamic color-changing attributes, emerge as catalysts for innovation across diverse applications such as batteries, supercapacitors, and smart windows. This review aspires to offer a comprehensive exposition on the intrinsic chromism phenomena within energy storage systems. Commencing with a succinct overview of chromism phenomena and their nuanced formation mechanisms, the narrative seamlessly transitions to an exhaustive scrutiny of recent strides. This exploration encompasses a thorough examination of the components, intricate structures, and diverse properties characterizing chromism phenomena. [ABSTRACT FROM AUTHOR]

Electrochemical sensors have a broad range of industrial applications due to their sensitivity, speed, and cost-effectiveness. These sensors enable the continuous monitoring and control of critical parameters in various industrial processes. For instance, they are essential in food safety, environmental monitoring, biomedical applications, and pharmaceutical production. In the food industry, electrochemical sensors facilitate the rapid and reliable detection of contaminants and pathogens in food products, thus enhancing product quality and consumer safety. An electrochemical sensor was developed with the molecularly imprinted polymer (MIP) technique to detect deltamethrin with high sensitivity and selectivity. The sensor was fabricated by electrodeposition of Co 3 O 4 on indium tin oxide (ITO), followed by electropolymerization of o -phenylenediamine with deltamethrin as a template molecule. The template molecules were then removed from the modified electrode by a methanol. The MIP-based electrochemical sensor exhibited high sensitivity and selectivity towards deltamethrin. Under the optimized conditions, the LOD values for the MIP/Co 3 O 4 /ITO electrode in the first and second linear regressions were 1.53 nM for linear range of 2.82 nM to 56.5 nM and 0.34 μM for linear range of 0.25 μM to 3.98 μM. Moreover, the LOD values for the NIP/Co 3 O 4 /ITO electrode in the first and second regressions were 2.43 nM for the linear range of 3.91 nM to 65.0 nM and 726.0 nM for the linear range of 0.023 μM to 4.5 μM. The developed electrochromic pesticide sensor, being an electrochemical-based molecularly imprinted polymer (MIP) sensor incorporating electrochromic materials, enables both target-specific pesticide detection and visual pesticide identification based on color changes dependent on pesticide concentration. Consequently, this system is more advantageous compared to electrochemical-based MIP sensors, as it provides both qualitative and quantitative determinations. The qualitative assessment aims to enhance the ease of use of the sensor, thereby increasing the potential for it to become a commercially viable product by reducing the need for instrumental devices. • Electrochromic MIP/Co 3 O 4 /ITO was designed for deltamethrin detection. • Electrochromic properties were determined both quantitatively and qualitatively. • MIP/Co 3 O 4 /ITO electrode exhibited a linear range of 2.82 nM to 56.5 nM. • The LOD and sensitivity were estimated as 1.53 nM and 13.4 μA nM−1, respectively. [ABSTRACT FROM AUTHOR]

V 2 O 5 is a promising electrochromic material for adaptive camouflage or electronic display. However, it is still challenging to enable fast response time, multicolor change and good cyclic stability. In this paper, we successfully synthesized different cation (NH 4 +, K+ and Na+) pre-inserted vanadium oxide nanobelt films (NVO, KVO and NaVO) by stirring impregnation method. All nanobelts are composed of V 3 O 8 layers with hydrated cations acting as pillars in the interlayer, exhibiting excellent electrochromic properties and remarkable multicolor changes. Among them, the NVO nanobelt films have the highest transmittance modulation (ΔT = 54 % at 510 nm and ΔT = 56 % at 950 nm), fastest response time (4.4 s for coloration time, 5.5 s for bleaching time at 422 nm and 6.8 s for coloration time and 7.7 s for bleaching time at 950 nm) and best stability (3000 cycles). Impressively, the NVO film is highly reversible between five colors: orange-red, orange, yellow, green and blue-grey, showing great breakthrough in adaptive camouflage application. [Display omitted] • Cationic pre-inserted vanadium oxide nanobelts were synthesized by stirring strategy. • The nanobelts consisted of V 3 O 8 layers with hydrated cations as interlayer columns. • NVO nanobelts film showing excellent electrochromic properties. • NVO has five reversible colors of orange-red, orange, yellow, green and blue-grey. [ABSTRACT FROM AUTHOR]

In the pursuit of high-performance electrochromic materials, in this paper, six donor-acceptor type with different gradient band gaps electrochromic conjugated polymers, named PBTz-T, PBTz-TT, PBTz-DT, PTBTO8-T, PTBTO8-TT, and PTBTO8-DT, were synthesized via direct (hetero) arylation polymerization, employing two benzothiadiazole derivatives with varying electron-accepting capabilities and three thiophene derivatives with different electron-donating capacities. The structures, optical, electrochemical, and electrochromic properties of the six polymers were investigated. As the number of fused thiophene increases, enhancing the electron-donating ability, a growth trend of electrochemical stability is observed for all polymers. Meanwhile, enhance electron-accepting capabilities of acceptors (from benzotriazole to benzothiadiazole) significantly lower the electronic band gap and improve electrochemical stability. PBTz-DT boasts a bleaching time of 0.3 s, outperforming most reported electrochromic polymers. PBTz-T, at 530 nm, exhibits exceptionally high coloration efficiency, reaching 916 cm2 C⁻1, and demonstrates higher electron utilization and lower energy consumption, making it an excellent candidate for high-performance electrochromic devices. This work compared studies the relationship of gradient band gaps of electrochromic conjugated polymers and their electrochemical and electrochromic performance, offers new insights into enhancing the electrochemical stability and synthesizing high coloration efficiency electrochromic materials. Six donor-acceptor type with different gradient band gaps electrochromic polymers were synthesized via direct (hetero) arylation polymerization, employing two benzothiadiazole derivatives with varying electron-accepting capabilities and three thiophene derivatives with different electron-donating capacities. The structures, optical, electrochemical, and electrochromic properties of the six polymers were investigated. As the number of fused thiophene increases, enhancing the electron-donating ability, a growth trend of electrochemical stability is observed for all polymers. Meanwhile, enhance electron-accepting capabilities of acceptors (from benzotriazole to benzothiadiazole) significantly lower the electronic band gap and improve electrochemical stability. PBTz-T, at 530 nm, exhibits exceptionally high coloration efficiency, reaching 916 cm2 C⁻1, and demonstrates higher electron utilization and lower energy consumption, making it an excellent candidate for high-performance electrochromic devices. This study offers new insights into enhancing the electrochemical stability and synthesizing high coloration efficiency electrochromic materials. [Display omitted] • Six electrochromic polymers were synthesized via direct (hetero) arylation polymerization. • PBTz-T exhibits high coloration efficiency of 916 cm2 C⁻1. • This work offers new insights into enhancing stability and synthesizing high coloration efficiency electrochromic polymers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solar-thermal conversion, as a novel and cost-effective method, was proposed to mitigate undesirable electrochromic performance in low-temperature conditions. • Inspired by the super black feathers of the Paradisaeidae , a multiscale hierarchical structure was purposely designed to enhance the solar-thermal conversion. • A high absorption of 87 % over the entire solar spectrum was achieved, along with rapid recovery of electrochromic performance at −20 °C within merely 8 mins. • The absorption mechanism and optical path were thoroughly elucidated using ray-tracing simulations. Solar-thermal conversion can mitigate the inadequate electrochemical performance in extreme cold environment for aqueous electrochromic devices (AEDs). However, the limited intrinsic absorptance of electrochromic materials impedes a satisfying solar-thermal conversion. Herein, bioinspired by the Paradisaeidae 's super black feathers, multiscale hierarchical structure is purposely made to compose of WO 3-x nanowires (WNWs) and silver nanowires (AgNWs), where WNWs are grown on AgNWs in different orientations (denoted as WAg). Our ray tracing simulation reveals its underlying absorption mechanism, demonstrating both an increased optical path and a concentrated energy distribution. Comparably, the WAg-AED exhibits much enhanced absorption (87.0 vs. 68.5 % across the entire solar spectrum) and a broader surface temperature change (51.2 vs. 39.7 °C within 8 min) under 1 solar illumination. This leads to a rapid recovery of electrochromic/electrochemical performance even conducted at −20 °C. Notably, upon irradiation for 12 min, the areal capacities of WAg-AED at 0.5mA cm−2 increase by 3.8 and 1.7 times, when compared to the device operating at −20 °C and room temperature, respectively. The WAg-AED establishes a close connection between the photo-thermal conversion and electrochemistry, proving a new pathway in the development of sustainable electronics. [ABSTRACT FROM AUTHOR]

Using radio frequency magnetron sputtering (RFMS), the undoped and Ti-doped vertical nanowall structured MoS 2 thin films were grown. In order to benefit from the chromic properties of the MoO 3 and inherited surface/volume ratio of the vertical nanowall structures of the MoS 2 , these films thermally oxidized to α-MoO 3 while retaining the morphology. Measurements of in-situ transmittance during the oxidation process revealed that the MoS 2 samples with a highTi content oxidized more quickly. On the other hand, the presence of Ti has led to denser nanowall formations. Optical modulation (OM) in the visible region improved with increasing Ti concentration within the coloring potential range of -0.2 to -0.45 V, which are relatively low working voltages that indicate energy efficient electrochromic materials. The highest Ti-doped MoO 3 (MTO40) and undoped (MBO) samples exhibit 52.2 % and 37.6 % OM at 700 nm (47.8 % and 25.7 %, respectively, at 550 nm) under -0.45 V applied potential. On the other hand, the coloring times for MBO, MTO20, MTO30, and MTO40 are 4.7, 4.1, 6.2, and 2.9 s, respectively, while the bleaching durations are 3.1, 1.4, 1.1, and 1.2 s for samples. These Ti-doped MoO 3 electrochemical characteristics demonstrate the suitability of the proposed technique for device applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Pursuing to develop novel polymer-based electrode materials and explore their performance in electrochromic capacitive windows (ECWs), three polyamides containing propylenedioxythiophene (ProDOT) units were synthesized. The polymers were processed into thin coatings and subjected to rigorous structural and photophysical characterization, with focus on the electrochromic response and energy storage capability. One of the polymers showed electrochromic response with ultrafast color change (0.8 s for coloring) from highly transmissive yellow to deep green, opposite to most ProDOT-based materials that exhibit bleaching trends during oxidation, which is more convenient for smart glazing. A coloration efficiency of 358 cm2 × C−1, a maximum CE decay of 2.6 % after 100 cycles, and an excellent electrochromic stability, even up to 500 cycles was achieved for this material. In three-electrode cell configuration, this polymer revealed practical energy storage properties, including a wide voltage window, a good capacitance, of 5.63 mF × cm−2, and an outstanding electrochemical cycling durability. Therefore, a prototype polyamide based-ECW device was built and its overall performance was explored. Due to the well capability of this polymer to simultaneously operate as a smart color changing and energy storage electrode, it can be considered as promising material for use in energy storage smart windows with potential applications in green-enabling technologies. • Three polyamides containing propylenedioxythiophene (ProDOT) units are synthesized. • The polymers display thermal stability up to 270 °C and CT blue/green fluorescence. • The polymers containing only ProDOT provide low capacitance and no electrochromism. • TPA- and ProDOT-based polyamide undergoes ultrafast color switch while stores energy. • An ECW is realized enabling smart monitoring of the energy level stored in the device. [ABSTRACT FROM AUTHOR]

The covalent organic frameworks (COFs) possess high designability, which provides a platform for synthesizing novel optoelectric materials, including electrochromic materials. In this work, N,N,N′,N′-tetra-(4-aminophenyl)-1,4-phenylenediamine (TPDA) with π-electron conjugate system and redox active centers was used as the main building block. The 4,4′-biphenyl diformaldehyde (BDA) and the 2,2′-thiophene-5,5′-diformaldehyde (TDA) were used as the aldehyde building units. Two imine-based COF electrochromic active materials (COF TPDA-BDA and COF TPDA-TDA) were prepared by Schiff base reaction. The test results reveal that COF TPDA-TDA has superior electrochromic properties than COF TPDA-BDA. Their contrasts are 0.46 and 0.40, and the coloring/fading times are 3.1/10.6 s and 10.9/14.3 s, respectively. The COF TPDA-TDA material possessing a bifunctional group structure was synthesized by replacing the biphenyl group with the bithiophene group with redox activity, which can enhance the optical properties and inter-layer π-π conjugation. Besides the electrochromic properties, the morphology and crystal lattice parameters are different. Therefore, it is expected to develop COFs-based electrochromic materials with rich colors, excellent performance, and wide application by introducing construction units with different redox active centers. [ABSTRACT FROM AUTHOR]

Viologens are considered among the most promising electrochromic materials for utilization in electrochromic devices (ECDs). In this regard, poly(butyl viologen) (PBV) has gained interest due to its stability, conductivity, and ease of synthesis, thus making it suitable for electrochromic applications. Regrettably, the poor adhesion of PBV thin film with substrates/electrodes deters the redox properties and long-term stability of PBV-based ECDs. To address this issue, herein, two types of surface-modified indium tin oxide (ITO) electrodes, grafted with 4-cyanophenol (P–CN-ITO) and benzyl phosphonic acid (BPO 3 -ITO), are introduced for the deployment in PBV-based ECDs. The optical contrast (ΔT, %) for substrate-modified P–CN and BPO 3 -based ECD was measured to be ∼57.0 and ∼59.5, respectively, which was remarkably higher (an improvement of ∼66 %) than that of ECD with bare ITO (∼34.3). Meanwhile, the coloration times ( τ c) of the P–CN, BPO 3, and bare ITO-based ECD were registered to be ∼1.7, ∼2.0, and ∼4.1 s, respectively, thus revealing the superiority of utilized functional groups over the unmodified substrate. The P–CN and BPO 3 -based ECD retained ∼70.2 % and ∼55.5 % of initial ΔT, respectively, after continuous switching of 10,000 cycles, thus showing high endurance and reversibility. The XPS results indicated the strong covalent bond formation between the utilized functional groups (P–CN and BPO 3) and ITO, which delivered improved electrochemical, optical, and stability behavior when deployed in ECDs. Our study suggests that P–CN and BPO 3 -based substrates can be promising for deployment as terminal electrodes in viologen-based ECDs for improved overall performance. [Display omitted] • A strategy to address poor film/electrode adhesion in PBV-based ECD is presented. • 4-cyanophenol (P–CN) and benzyl phosphonic acid (BPO 3) grafted ITOs were prepared. • XPS results indicated the strong covalent bond formation at the film/electrode. • The P–CN-ITO and BPO 3 -ITO endowed improved performance in PBV-based ECD. • ΔT increment (∼66 %) was noticed for ECDs with functionalized substrates. [ABSTRACT FROM AUTHOR]

Owing to their immense potential in the fields of display boards and signage, portable/wearable electronics, adaptive camouflage, etc., the development of electrochromic materials (ECMs) and devices (ECDs) has attracted great attention from both academia and industry. However, despite the rapid progress in this area, traditional ECMs have a number of obstacles and limitations that encourage us to look for new solutions. Here we introduce a novel, non-conventional ECD architecture that includes two different electrodes separated by an opaque membrane, which is impregnated with a lithium carbonate-based electrolyte. In contrast to a traditional ECD, in which the colors of ECMs on both electrodes define the resulting color of the device, the incorporation of an opaque membrane allows for the separation of the optical properties of each electrode. Working in the bilateral mode, where the application of −2/2 V sequentially switches both sides of the device between colored and bleached states, ECD demonstrates very good stability performing 12,000 cycles. When operating in the unilateral mode, where the application of 0/2 V results in the color switch of the working electrode (WE) only, the device shows extraordinarily high stability of 100,000 cycles on iron-based side. Follow-up cycling on the osmium-based side demonstrates successful ECD performance for another 23,000 cycles. The superior long-term durability of non-conventional asymmetric double-sided ECD makes the proposed architecture promising for future practical applications. Graphical abstracts should be submitted as a separate file in the online submission system. Image size: Please provide an image with a minimum of 531 × 1328 pixels (h × w) or proportionally more. The image should be readable at a size of 5 × 13 cm using a regular screen resolution of 96 dpi. Preferred file types: TIFF, EPS, PDF or MS Office files. [Display omitted] • Novel unique non-conventional asymmetric double-side electrochromic device architecture. • Surface-confined metal-organic monolayers on high-surface-area conductive indium tin oxide electrodes. • The immobilization of isostructural iron or osmium complexes allows for identical molecular loading on the electrode materials. • Outstanding performance in unilateral and bilateral modes of operation, ultra-long durability of 105+ electrochemical cycles. [ABSTRACT FROM AUTHOR]