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In this study, results on the effect of technological parameters of the nickel(II)‐oxide thin‐film deposition process, obtained through chemical vapor deposition in an argon–oxygen environment using bis‐(ethylcyclopentadienyl)‐nickel (EtCp)2Ni, on their electrochromic properties, are presented. It is shown that the films lose ability to electrochromic coloring in alkaline environments as their thickness increases up to 170 nm. The introduction of small ozone additions of 0.1 vol% O3 into the gas phase leads to a decrease in the NiO films deposition rate, the formation of a rougher layer with an average grain size up to 71.4 nm, capable of coloring in light brown. Additional cathodic treatment of NiO films at a potential of −0.8 V for 30 s in alkaline environments containing fullerene C60(OH)24 leads to the modification of the surface layer and the formation of NiO–C carbon‐containing nanocomposite coatings with enhanced contrast and the ability to retain the colored state after polarization is turned off, i.e., possessing optical memory properties. Using NiO–C nanocomposite and indium–tin–oxide films, which have opposite coloring mechanisms, in the structure of an electrochromic device allows for an increase in the grade of glass darkening, significantly reducing energy consumption, improving operational characteristics, and life span. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with reversible redox units and a conjugated molecular skeleton possess novel photoelectrochemical properties. In this work, tris(4-aminophenyl)amine and 4,4-biphenyldiformaldehyde were chosen to synthesize TABP-COF electrochromic film with triphenylamine (TPA) active unit by a solvothermal method in a Teflon-lined reactor. The growth process and reaction time optimization of the TABP-COF were studied. TABP-COF shows a self-assembly growth process from an array of nanosheets to nanospheres. Owing to the redox characteristics of TPA, the TABP-COF film exhibits reversible electrochromic behavior. With a solvothermal reaction time of 72 h, the TABP-COF-3 film exhibits the best electrochromic properties, including contrast of 0.483 and response time of 7.3 s/13.6 s. Considering the abundance of redox-active units that can be chosen, COF materials with different redox units and color changes can be designed for a variety of applications in the field of electrochromic materials. [ABSTRACT FROM AUTHOR]

Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy. [ABSTRACT FROM AUTHOR]

Electrochromism (EC) is a color control technique for providing visual information, in which vanadium pentoxide (V2O5) is a promising material for electrochromic applications due to its excellent ionic intercalation/deintercalation properties and cathodic/anodic color-changing properties. However, its poor cycling stability and color change response rate limit its practical application. Metal–organic frameworks (MOFs) combine the rigidity and flexibility of inorganic–organic materials and can meet the requirements of EC materials such as cycle stability, electrical conductivity, and stress-interference resistance. We report here a strategy to modify V2O5 with Cu-MOF. Cu-doped V2O5 and carbon skeleton (Cu2V2O7@C) composites were prepared for electrochromism. In this scheme, Cu doping can facilitate lithium ion migration by broadening and stabilizing the structure of V2O5, and the distribution of the carbon skeleton can broaden the contact of the active material with the electrolyte and improve the electron conduction. Combining these merits, it exhibits excellent long-term cycle stability (the capacity retention rate reaches 91.78% after 2000 cycles), the light transmission modulation is greatly improved compared with V2O5 (ΔT = 69%, doubled), and the response time is reduced by 30.43%. This study provides a new perspective for improving the light modulation ability and long-term use stability of vanadium oxide EC materials and promotes the development of MOF materials in the field of electrochromism. [ABSTRACT FROM AUTHOR]

The development of electrochromic (EC) materials has paved the way for a wide range of devices, such as smart windows, color displays, optical filters, wearable camouflages, among others. However, the advancement of electrochromism faces a significant hurdle due to its poor stability and limited color options. This lack of stability is primarily attributed to the substantial alteration in the dielectric properties of EC materials during cycling. Consequently, the design of advanced plasmonic materials is a key strategy to achieve a stable EC device. In this review, we provide an overview of the current state-of-the-art designs of plasmonic-based EC materials and devices. We discuss their working principles, techniques for structure/morphology engineering, doping methods, and crystal phase design. Furthermore, we explore the integration of plasmonic materials with other EC materials to create advanced EC devices. Finally, we outline the challenges that need to be addressed and present an outlook on the development of high-performance EC devices.

We performed an electrochromic investigation to optimize the composition of reactive magnetron-sputtered mixed layers of zinc oxide and tin oxide (ZnO-SnO2). Deposition experiments were conducted as a combinatorial material synthesis approach. The binary system for the samples of SnO2-ZnO represented the full composition range. The coloration efficiency (CE) was determined for the mixed oxide films with the simultaneous measurement of layer transmittance, in a conventional three-electrode configuration, and an electric current was applied by using organic propylene carbonate electrolyte cells. The optical parameters and composition were measured and mapped by using spectroscopic ellipsometry (SE). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) measurements were carried out to check the SE results, for (TiO2-SnO2). Pure metal targets were placed separately from each other, and the indium–tin-oxide (ITO)-covered glass samples and Si-probes on a glass holder were moved under the two separated targets (Zn and Sn) in a reactive argon–oxygen (Ar-O2) gas mixture. This combinatorial process ensured that all the compositions (from 0 to 100%) were achieved in the same sputtering chamber after one sputtering preparation cycle. The CE data evaluated from the electro-optical measurements plotted against the composition displayed a characteristic maximum at around 29% ZnO. The accuracy of our combinatorial approach was 5%.

Conductive polymer-based electrochromic fabrics show promising applications in new intelligent displays, flexible smart wearables, and military camouflage, thanks to their flexibility, light weight, high degree of controllability, and wide range of color change. However, despite these advantages, electrochromic textiles that rely on conductive polymers face several limitations, such as discomfort during use, instability in structure, and issues with the continuous production technology of electrochromic fibers. These factors hinder their further development. To address these limitations and promote the industrialization of conductive polymer-based electrochromic fabrics, this paper provides a comprehensive analysis that covers various aspects of electrochromic devices, including device structure, color-change mechanisms, electrochromic materials, application of electrochromic textiles, and the advantages and disadvantages of commonly used conductive polymers in electrochromic fabrics. By exploring these aspects, a better understanding of the structure and performance of conductive polymer-based electrochromic fabrics can be achieved, leading to a more effective promotion of their industrialization. Moreover, progress in the research of conductive polymer-based electrochromic fabrics is systematically reviewed from the structural design perspective, both domestically and internationally. Finally, the challenges that conductive polymer-based electrochromic fabrics currently face are discussed, and their future development trends are presented. [ABSTRACT FROM AUTHOR]

Most redox systems generally cannot avoid the involvement of open‐shell species upon generating multiply charged species, which often reduces reversibility in multi‐color electrochromic systems. In this study, we newly synthesized octakis(aminophenyl)‐substituted pentacenebisquinodimethane (BQD) derivatives and their hybrids with alkoxyphenyl analogues. Thanks to apparent two‐electron transfer accompanied by double dramatic changes in the structure of the arylated quinodimethane skeleton, the dicationic and tetracationic states were generated and isolated quantitatively because of the negligible steady‐state concentration of intermediary open‐shell species such as monocation or trication radicals. When two electrophores with different donating abilities are attached to the BQD skeleton, a dicationic state with a different color can be isolated in addition to the neutral and tetracationic states. For these tetracations, an interchromophore interaction induces a red‐shift of the NIR absorptions, thus realizing tricolor UV/Vis/NIR electrochromic behavior involving only closed‐shell states. [ABSTRACT FROM AUTHOR]

Layered optoelectronic devices are manufactured using multistep procedures that require high precision in the spatial positioning of individual materials. Current technology uses costly and tedious procedures and instrumentation. In this work instead, we propose an approach which exploits the fundamental properties of the substrate to direct the growth of the next layer, here controlled by an electrochemical potential. We have electrochemically synthesized and characterized a series of polymeric materials that are most commonly used in the field. The films produced show gradient monomer ratios embedded in the polymeric film as a function of the distance from the working electrode. Under the optimized conditions, reproducible construction of simple electronic elements, e. g., rectifying diodes, is achieved. We argue that the sequential in situ method leads to gradient composition of polymer chains and the film resulting in the rectification of electric current. We discuss how this system can open new avenues in advanced optoelectronic applications, such as organic light‐emitting diodes (OLEDs) or field‐effect transistors (OFETs). [ABSTRACT FROM AUTHOR]

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Thin films of mixed MoO3 and WO3 were obtained using reactive magnetron sputtering onto ITO-covered glass, and the optimal composition was determined for the best electrochromic (EC) properties. A combinatorial material synthesis approach was applied throughout the deposition experiments, and the samples represented the full composition range of the binary MoO3/WO3 system. The electrochromic characteristics of the mixed oxide films were determined with simultaneous measurement of layer transmittance and applied electric current through the using organic propylene carbonate electrolyte cells in a conventional three-electrode configuration. Coloration efficiency data evaluated from the primary data plotted against the composition displayed a characteristic maximum at around 60% MoO3. Our combinatorial approach allows the localization of the maximum at 5% accuracy.

Solid state ionics is one of the key research topics of the Institute of Solid State Physics, University of Latvia since its establishment. The research direction included topics ranging from electrochromic phenomena in transition metal oxides through gas sensors and electronic nose to materials for rechargeable battery electrodes and materials for hydrogen energy. By the late 1980s, the institute had become one of the biggest and most prolific solid state ionic centres in the USSR and Eastern Europe and continues to maintain its position among the regional leaders in the field. Regular regional conferences and workshops were organized and some of the published works can be ranked among the pioneering works in the world of science. This extensive historical review summarizes information on the development of solid state ionics, actual research and achievements from establishment of the institute to the present day. Currently many collaborations are ongoing with partners across Europe and beyond in research ranging from battery materials and smart windows for zero energy buildings to hydrogen production, maintaining and growing its strength as key national, regional, and international centre of research excellence in solid state ionics. [ABSTRACT FROM AUTHOR]

We determined the optimal composition of reactive magnetron-sputtered mixed layers of Titanium oxide and Tin oxide (TiO2-SnO2) for electrochromic purposes. We determined and mapped the composition and optical parameters using Spectroscopic Ellipsometry (SE). Ti and Sn targets were put separately from each other, and the Si-wafers on a glass substrate (30 cm × 30 cm) were moved under the two separated targets (Ti and Sn) in a reactive Argon-Oxygen (Ar-O2) gas mixture. Different optical models, such as the Bruggeman Effective Medium Approximation (BEMA) or the 2-Tauc–Lorentz multiple oscillator model (2T–L), were used to obtain the thickness and composition maps of the sample. Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) has been used to check the SE results. The performance of diverse optical models has been compared. We show that in the case of molecular-level mixed layers, 2T–L is better than EMA. The electrochromic effectiveness (the change of light absorption for the same electric charge) of mixed metal oxides (TiO2-SnO2) that are deposited by reactive sputtering has been mapped too. [ABSTRACT FROM AUTHOR]

The novel monomer, 4‐(2‐(4‐(bis(4‐(thiophen‐2‐yl)phenyl)amino)phenyl)‐5‐(thiophen‐2‐yl)thieno[3,2‐b]thiophen‐3‐yl)benzonitrile, is synthesized by applying Suzuki coupling reaction and electropolymerized directly onto indium tin oxide coated glass electrode surface to obtain a conjugated microporous polymer of [Th3CNTT–TPA] (P[Th3CNTT–TPA]). The morphology and structure of the polymer film are characterized by atomic force microscopy, Fourier transform infrared, and UV–visible spectroscopies. Electrochemical properties are studied using cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge–discharge, and chronoamperometric measurements. Its gravimetric capacity and capacitance values are measured to be 65 and 235 F g−1 at a current density of 3 A g−1, respectively. It shows high energy and power densities of 65 and 32.5 kWh kg−1, respectively, and exhibits high coloration efficiency of 513 C−1 cm2 in visible region, switching between yellow and grey colors. Three different electrochromic–supercapacitor devices, that is, one symmetrical (energy storage device (ESD)1) and two asymmetrical, using poly(3,4‐ethylendioxythiophen) (ESD2) and poly(3,4‐propylenedioxypyrrole) (ESD3) as counter electrodes, are fabricated. The asymmetrical device, ESD3, demonstrats better capacity and stability. Regarding the cyclic stability and electrochromic‐energy‐storage properties, P[Th3CNTT–TPA] can be considered as a good candidate for multifunctional applications. [ABSTRACT FROM AUTHOR]

Inorganic metal oxide electrochromic materials have good application prospects for energy‐saving windows in buildings and smart display applications. Therefore, the development of electrochromic films with good cycling stabilities, fast color‐change response times, and high coloring efficiencies has attracted considerable attention. In this study, nanoflake Li‐doped NiO electrochromic films were prepared using a hydrothermal method, and the films exhibited superior electrochromic performances in the LiOH electrolyte. Li+ ions doping increased the ion transmission rates of the NiO films, and effectively promoted the transportation of ions from the electrolyte into NiO films. Meanwhile, the nanoflake microstructure caused the NiO films to have larger specific surface areas, providing more active sites for electrochemical reactions. It was determined that the NiO‐Li20% film exhibited an ultra‐fast response in the LiOH electrolyte (coloring and bleaching times reached 3 and 1.5 s, respectively). Additionally, the coloration efficiency was 62.1 cm2 C−1, and good cycling stability was maintained beyond 1500 cycles. Finally, the simulation calculation results showed that Li doping weakened the adsorption strengths of the NiO films to OH−, which reduced the generation and decomposition of NiOOH and helped to improve the cycling stabilities of the films. Therefore, the research presented in this article provides a strategy for designing electrochromic materials in the future. [ABSTRACT FROM AUTHOR]

This review describes the various applications of graphene derivative (GO/rGO) with the tungsten oxide nanocomposite such as supercapacitor, electrochromism, photocatalysis and energy sensing. This review article also presents the properties of tungsten oxide with the graphene derivatives and their classification on basis of transition metals, metal oxides, nonmetals, sulfide, and polymers. Graphene oxide is a wonder material that has the potential to impart extraordinary properties into several hybrid materials, resulting in distinctive application in enormous domains. The impressive application and properties of the graphene derivatives have been discussed in this review article. The transition metal oxides (TMOs) have gained considerable research attention due to their unique physicochemical characteristics. Among TMOs, tungsten oxide (WO3) is a versatile material with excellent properties, diverse applications, stability, and low fabrication cost. The enhanced property of tungsten oxide by incorporation of graphene derivatives is also discussed in this review. The main focus of this review article is to summarize the 5-year applications of GO/rGO-based tungsten oxide nanocomposite in energy storage (super capacitors and batteries), gas sensor devices, electrochromism, and photocatalyst. This review article will also provide the research gap and can excite new ideas for further improvement of GO/rGO-based tungsten oxide nanocomposite. [ABSTRACT FROM AUTHOR]

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N′-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4′-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4′-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV–Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials. [ABSTRACT FROM AUTHOR]

The consumption of energy by buildings accounts for 30% of the total amount of social primary energy used, and approximately 30%∼50% of this is lost through windows. To promote energy conservation, the green development of buildings, and revolutionarily upgrade energy production and consumption, developing energy-efficient windows while preserving architectural aesthetics is necessary. Electrochromic smart windows (ESWs) can control the amount of solar energy transmitted into buildings based on personal preference or weather conditions, thereby reducing the amount of energy consumed by buildings for lighting and cooling. The optical transmittance of ESWs is changed by applying different voltages, and they maintain their state without the input of energy. Metal oxides are considered among the most promising electrochromic films for use in ESWs because of their relatively good physical and chemical stabilities. After nearly half a century of development, the practical application of metal oxide-based ESWs is nearly realized. This review presents an evaluation of the performance of ESWs and summarizes five strategies that can be used to enhance the electrochromic properties of metal oxides. These include controlling the oxygen vacancy concentration, doping aliovalent ions, controlling the morphology, selecting the optimal electrolyte, and controlling crystallinity. This review also investigates the development of metal-oxide-based ESWs.

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]

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]

We performed an electrochromic investigation to optimize the composition of reactive magnetron-sputtered mixed layers of zinc oxide and tin oxide (ZnO-SnO 2 ). Deposition experiments were conducted as a combinatorial material synthesis approach. The binary system for the samples of SnO 2 -ZnO represented the full composition range. The coloration efficiency (CE) was determined for the mixed oxide films with the simultaneous measurement of layer transmittance, in a conventional three-electrode configuration, and an electric current was applied by using organic propylene carbonate electrolyte cells. The optical parameters and composition were measured and mapped by using spectroscopic ellipsometry (SE). Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) measurements were carried out to check the SE results, for (TiO 2 -SnO 2 ). Pure metal targets were placed separately from each other, and the indium-tin-oxide (ITO)-covered glass samples and Si-probes on a glass holder were moved under the two separated targets (Zn and Sn) in a reactive argon-oxygen (Ar-O 2 ) gas mixture. This combinatorial process ensured that all the compositions (from 0 to 100%) were achieved in the same sputtering chamber after one sputtering preparation cycle. The CE data evaluated from the electro-optical measurements plotted against the composition displayed a characteristic maximum at around 29% ZnO. The accuracy of our combinatorial approach was 5%.

We determined the optimal composition of reactive magnetron-sputtered mixed layers of Titanium oxide and Tin oxide (TiO2-SnO2) for electrochromic purposes. We determined and mapped the composition and optical parameters using Spectroscopic Ellipsometry (SE). Ti and Sn targets were put separately from each other, and the Si-wafers on a glass substrate (30 cm × 30 cm) were moved under the two separated targets (Ti and Sn) in a reactive Argon-Oxygen (Ar-O2) gas mixture. Different optical models, such as the Bruggeman Effective Medium Approximation (BEMA) or the 2-Tauc–Lorentz multiple oscillator model (2T–L), were used to obtain the thickness and composition maps of the sample. Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) has been used to check the SE results. The performance of diverse optical models has been compared. We show that in the case of molecular-level mixed layers, 2T–L is better than EMA. The electrochromic effectiveness (the change of light absorption for the same electric charge) of mixed metal oxides (TiO2-SnO2) that are deposited by reactive sputtering has been mapped too.

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]

Depending on adjusting substrate temperature during film depositing, a series of NiOx films has been prepared by magnetron sputtering. The electrochromic (EC) advantage of NiOx films modified by substrate temperature is verified. Moderate heating substrate can improve surface charge transfer (from ≈30 to ≈40 mC cm−2) and energy storage capacity (45% increment) without damaging other performance effectively. Considering the different electrochemical mechanisms in varied electrolytes, the EC performance of NiOx films in two electrolytes is discussed. In KOH electrolyte, NiOx films at 300 °C substrates show prominent optical modulation (≈81%) and high charge capacity (≈40 mC cm−2). 300 °C heating compensates for the shortage of poor stability and tedious activation. In LiClO4‐PC electrolyte, NiOx films can undergo long‐term cycles compared with aqueous conditions, the coloration efficiency keeps high level (≈80 cm2 C−2) which means small charge quantities can drive a wide transmittance range. The cyclic discrepancy in two electrolytes can be ascribed to diverse reacted modes between electrolyte ions and NiOx films. In aqueous KOH electrolyte, EC process and activated state strongly relies on Ni2+ distribution on films surface, while NiOx experiences two phases oxidation to get thorough coloration in PC‐Li based electrolyte. [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]

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N′-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4′-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4′-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV–Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials.

Electrochromic (EC) materials that change color with voltage have been widely studied for use in dynamic windows. However, colorless-to-colorful switching with high contrast ratio is generically unattainable, especially for colorless-to-black electrochromic materials with an ultrahigh contrast ratio over the entire visible region. In this work, we developed Nb1.33C MXene-based dynamic windows with colorless-to-black switching of up to 75% reversible change in transmittance from 300 to 1,500 nm. By exploring the electrochromic effects of different electrolytes through in situ optical changes and electrochemical quartz crystal microbalance (EQCM), it is found that electrochromic behavior is greatly influenced by the extent of reversible Li+ insertion/deinsertion between the two-dimensional Nb1.33C MXene nanosheets. In addition, a colorless-to-black EC device based on Nb1.33C with an overall integrated contrast ratio over 80% was successfully constructed by a solution-processable spin coating method. This work enables a simple route to fabricate MXene-based high-performance electrochromic smart windows, which is important for further expanding the application of MXenes to optoelectronic and photonic applications. [ABSTRACT FROM AUTHOR]

Reducing energy consumption is one of the major concerns in modern building design and construction because buildings account for ≈40% of the total energy consumption in modern society. Among various technologies for saving energy, electrochromic smart windows are considered as a highly promising one. Except for the application in saving energy, electrochromism has also attracted extensive attention in many other fields, such as, anti‐glare rearview mirrors, displays, military camouflage, flexible wearable fabric, etc. However, there are still many challenges needed to be solved, such as, the response rate and durability of electrochromic materials (ECMs). The transmission rate of ions in ECMs determines the response rate of the whole electrochromic device. Besides, the embedding depth and total amount of ions directly affect the contrast, durability, and coloration efficiency of ECMs. It is crucial to select suitable electrolyte ions to obtain high‐efficiency ECMs. Here, the challenges in ECMs based on ions insertion/extraction are presented, which are focused on advanced nanostructured ECMs' design and electrochromic devices' practical application. Recent advances in ECMs are presented to discuss the important questions, which are especially focused on the connection between suitable ions and advanced nanostructural ECMs. Finally, a perspective for next‐generation electrochromic devices is presented. [ABSTRACT FROM AUTHOR]

Bipolar electrode-based (BPE-based) electrochromic devices have garnered increasing attention in the past decade. These BPE-based electrochromic devices have been used for analytical health monitoring, point-ofcare (POC) diagnostics, and chemical sensing. In this review, we highlight recent progress made regarding BPE-based electrochromic devices constructed for these analytical applications. Various, available electrochromic materials are summarized in the first section, after which the different device types (e. g., paper-based and selfpowered) are discussed. Biological- and chemical-based analytical demonstrations of these devices are then reviewed. Finally, we conclude this review with a perspective on the future developments of BPE-based electrochromic devices in analytical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochromism (EC) is a unique property of certain materials that undergo an electrochemical-induced change in colouration. During the last decades, electrochromic materials (ECMs) have been applied in a variety of technologies ranging from smart windows to information displays and energy storage devices. More recently, ECMs have attracted the attention of the (bio)sensing community thanks to their ability to combine the sensitivity of electrochemical methods with the intuitive readout of optical sensors. Although still a nascent technology, EC-based sensors are on the rise with several targets (e.g. cancer biomarkers, bacteria, metabolites and pesticides), which have already been detected by (bio)sensors using ECMs as transducers. In this review, we provide the reader with all the information to understand EC and its use in the development of EC-based biosensors. [ABSTRACT FROM AUTHOR]

Metal–organic framework (MOF) is a promising electrochromic material due to its high specific surface area and tunable pore size, which can benefit the fast transportation of ion/charge. Here, a simple solvothermal deposition method for fabrication of Ni-MOF 74 electrochromic films on ITO is developed. It is found that the reaction temperature has played an important role in the morphology and electrochromic performance of as-prepared Ni-MOF 74 film. The film prepared at the optimized temperature exhibits the best electrochromic performance with a rapid switching speed (the coloration/bleaching time = 24.5/23.5 s). In addition, the optimized film displays a high optical contrast of 44.4% at 550 nm and can be stably switched for 650 cycles with < 21.5% contrast attenuation. The electrochromism of Ni-MOF 74 can be attributed to the oxidized and reduced states of 2,5-dihydroxyterephthalic acid ligands. This simple method can be broaden to fabricate other metal-based MOF films for electrochromic applications. [ABSTRACT FROM AUTHOR]

Smart materials have an important role in modern applications. They have contributed to improving various applications in several fields. One of the areas most affected by the improvement of smart materials is nanostructures. These materials are created by basic techniques, such as arrangement manipulation. Significant efforts have been made to enhance smart materials so that they resemble natural materials in terms of accuracy, design, and utility. Here, a review of the latest research on smart materials that can alter the electrical properties of nanostructures is presented. The main objective of this review is to introduce the role of smart materials in controlling the electrical performance of nanostructures. Furthermore, this review proposes an analysis of the integration and cooperation of previous research, such as the use of a piezoelectric motor in the design of structural magnetic nanodevices to control these devices. Piezoelectric actuators can also be used to develop a new method for controlling PV modulators for fabricating a single-wall nanotube. This new proposal could alter the properties of many nanoscale systems serving several medical and engineering fields. Moreover, this review proposes a novel methodology for nanocoating by introducing an antireflective coating with multiple layers. This method can effectively enhance the functions of the nanoscale coating. [ABSTRACT FROM AUTHOR]

The embedding of photonic crystals within stimuli‐responsive hydrogels has attracted tremendous interest because it provides new applications such as optical switches, displays, and sensors. However, the production of electrically tunable photonic hydrogels with a wide range of color tunability, fast electrical response, and high stability for repeated use is still challenging. Here, electrically tunable photonic hydrogels are fabricated using ultrahigh‐water‐content polyelectrolyte layered hydrogels composed of thousands of bilayer domain structures. The layered hydrogel exhibits versatile color tunability by applying an electric field parallel or perpendicular to the direction of the gel layers. The hydrogel exhibits homogeneous color tuning when a perpendicular electric field is applied, while it shows a large rainbow‐like electric‐optic response in the visible to near‐infrared region when a parallel electric field is applied. Additionally, by a simple method using patterned electrodes, a reflective display showing the designed characters is demonstrated and maintained for hours underwater without an external source of energy. Moreover, the electrically induced optical patterns can be erased, and the responsive photonic hydrogel shows excellent stability for repeated use. We anticipate that this study will provide the foundation for the development of responsive photonic hydrogels with new and large electro‐optical effects for future chromatic applications. [ABSTRACT FROM AUTHOR]

In comparison with traditional inorganic electrochromic materials, organic polymers offer advantages such as fast switching speed, flexibility, lightweightness, low cost and nontoxicity, solution‐processability, and color tunability. Herein, a series of hyper‐branched copolymers are synthesized from triphenylamine and 3,4‐ethylenedioxythiophene with different feed ratios via iron(III) chloride (FeCl3)‐mediated oxidative polymerization. The resultant organic‐soluble polymers are easily processable and their corresponding electrochromic devices are found to be stable with limited degradation upon 2500 cycles. In addition to their facile synthesis to achieve solution‐processable polymers, studies also show that the polymers exhibit multielectrochromic properties and give rise to five colored states upon oxidative‐doping by applying an external voltage between 0 and 2.0 V, providing an interesting example of polymers with unique electrochromic switching among up to five colors, from yellow at the neutral state, to pale green, pale purple, orange, and finally gray. [ABSTRACT FROM AUTHOR]

Electrochromic (EC) device reversibly changes color and optical state by applying electric potential. EC materials shows color change due to redox process and electron transfer across various states under influence of electric field. EC devices are categorized based on various classes of EC materials inorganic metal oxide and polyoxometalates (POMs), metal complexes, hybrid materials, metal plasmonics–metal/alloy and organic molecules/conjugated polymers. EC materials and its viability for device application are presented herein considering various performance parameter indices. The performance of EC devices is monitored by its switching time between transparent‐bleached state to colored state and vice versa, cycling stability, coloration efficiency, applied voltage, electro‐optical properties, electrochemical stability and breakdown potentials of EC materials and electrolytes. Recent advances in the area of EC devices and materials, its operation mechanism in various categories of EC materials along with existing challenges and recommendations to improve performances and reliability are summarized. [ABSTRACT FROM AUTHOR]

Prussian blue (PB) is an electrochromic material, which can be used as a signal transducer in the formation of optical urea biosensors. The previous researches in electrochromic properties of PB demonstrated the optical PB response to ammonium ions, which occurs when ammonium ions are interacting with PB layer at a constant 0.2 V vs Ag|AgCl|KClsat potential. In this work PB optical dependence on ammonium ions concentration was applied in the formation of electrochromic urea biosensor. Biosensor was formed by modifying the optically transparent indium tin oxide (ITO) coated glass electrode (glass/ITO) with Prussian blue layer and immobilizing urease (glass/ITO/PB‐urease). Calibration curve showed the linear dependency (R2=0.995) between the change of maximal absorbance (ΔA) and urea concentration in concentration range varying from 3 mM to 30 mM. The highest sensitivity (4 ΔA M−1) of glass/ITO/PB‐urease biosensor is in the concentration range from 7 mM to 30 mM. It was determined that working principle of the glass/ITO/PB‐urease biosensor is not related to pH changes occurring during enzymatic hydrolysis of urea. [ABSTRACT FROM AUTHOR]

In this work, the electrochromic (EC) application of the hybrid fibers based on bis‐thiomethylcyclohexanone derivatives is evaluated. For this purpose, two new bis‐thiomethylcyclohexanone derivatives, 2,6‐bis(phenyl(phenylthio)methyl)cyclohexanone (PPTMC) and 2,6‐bis((2,6‐dichlorophenyl)(phenylthio)methyl)cyclohexanone (CPPTMC), were synthesized by thio‐Michael addition and characterized by spectroscopic methods and X‐ray diffraction. The hybrid fibers based on bis‐thiomethylcyclohexanone and poly(methyl methacrylate) (PMMA) were successfully prepared with electrospinning. The surface morphology and elemental compositions of these hybrid fibers were investigated by scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS). The electrochemical, optical and electrochromic behaviors of indium tin oxide (ITO) glass substrates coated with those fibers were evaluated using spectrophotometry techniques. Moreover, the electrochromic devices (ECDs) based on PPTMC‐PMMA and CPPTMC‐PMMA hybrid fibers showed reversible color change from the transparent state to light brown by switching from +3.0 to −3.0 V. The calculated coloration efficiency of the hybrid fibers based on PPTMC‐PMMA was found to be 207.27 cm2/C whereas a higher coloration efficiency was obtained for the hybrid fibers based on CPPTMC‐PMMA (273.31 cm2/C). Our results show that hybrid fibers based on PPTMC‐PMMA and CPPTMC‐PMMA are potential materials for optical and electrochromic applications. [ABSTRACT FROM AUTHOR]

The experimental analysis of the main figures of merit of an innovative electrochromic (EC) prototype, based on low cost gel-polymer electrolytes, is at the basis of the numerical simulation exposed hereafter, aiming at the assessment of energy and visual comfort benefits deriving from building integration of smart windows in a multi-storey office building. The effectiveness of the dynamic modulation of glazing properties to improve energy efficiency and users' comfort was tested comparing the EC windows with a typical law-compliant static commercial glazing system and with a clear windows. To better understand the performances of the proposed EC film, six different locations – ranging from Seville to Helsinki – were selected throughout the European continent to conduct energy and daylighting analyses on three different exposures (east, south, west). The results obtained show reductions of summer cooling and winter heating as well in all the locations considered. Eventually, the effect of electrochromic switching of transmittance on the indoor visual comfort, is considered using a well-established metric: Useful Daylight Illuminance; with regards to daylight analyses, a significant reduction of hours in which excessive illuminance occurs was observed in all the locations considered, confirming that properly controlled EC devices improve both energy efficiency and visual comfort. [ABSTRACT FROM AUTHOR]

The fusion of monodentate or multidentate ditopic organic moieties with transition metal ions leads to the development of novel metallopolymers through complexation reactions. The properties of these metallopolymers can be easily tuned by appropriately substituting functional groups in the organic backbone or by introducing a new metal ion as the inorganic component, which resulted in a wide variation of electrical, magnetic, and optical properties in the newly developed functional materials. As a result, these metallopolymers are being designed and developed with remarkable potential in several fields, such as memory devices, stimuli-responsive materials, luminescence materials, self-healing, supercapacitors as well as biomedicine, and further potential applications are still emerging. In this review, we highlighted the recent advancement and astounding applications of functional metallopolymers. [Display omitted] • Electrochemically active metallopolymers reviewed as smart functional materials. • These metallopolymers react to specific stimuli and chemical analytes. • Metallopolymers' molecular structure has been also reviewed. • Recent advancements in several application areas have been addressed. • Various applications of hydrogel of metallopolymers have also been discussed. [ABSTRACT FROM AUTHOR]

A series of non-noble transition metal complexes were synthesized by coordinating Fe2+, Co2+, and Ni2+ with ligands having a parent structure of 4,7-diphenyl-1,10-phenanthroline (L 1 and L 2) and dipyrido[3,2-a:2′,3′-c]phenazine (L 3 –L 5), and their photophysical, electrochemical, and electrochromic properties were studied. Both transition metal ions and ligands produce more or less influence on these properties. Electrochromic properties such as color, optical contrast, response time, coloration efficiency and switching stabilities can be tuned by selecting proper metal ions, parent structure of ligands, and substituent groups. Theory calculation results indicate that electrons flow from the metallic center to the ligands. The UV–vis spectra of all five Fe(II) complexes showed a broad and strong MLCT band at ca. 530 nm. The UV–vis spectra of Fe(II), Co(II) and Ni(II) complexes with L 2 ligand showed a strong LC (π–π*) band at ca. 325 nm. Electrochromic process caused a change in the intensity of LC and MLCT absorption. The ligands produced little effect on the bleached and colored states of Fe(II) complexes, all of them showed a bleached state of red and a colored state of purple-red probably due to the reversible Fe(II)/Fe(III) transition. Both Co(II) and Ni(II) complexes showed a bleached state of pale yellow, however, the ligands produced significant effect on their colored states probably due to the partially electron density displacement between the metal ions and the ligands. When the parent structure of ligand is 4,7-diphenyl-1,10-phenanthroline, electron-donating substituent such as –OCH 3 is beneficial to electrochromic properties, and Fe(II) complexes have higher optical contrast and coloration efficiency compared to Co(II) and Ni(II) complexes. When the parent structure of ligand is dipyrido[3,2-a:2′,3′-c]phenazine, –CN substituent markedly enhances the optical contrast and coloration efficiency of Fe(II), Co(II) and Ni(II) complexes. [Display omitted] • Electrochromic behavior of transition metal complexes is reported. • Both metal ion and ligands affect the electrochromic properties. • Fe(II) complexes have same bleached and colored states due to Fe2+/Fe3+ transition. • -CN substituent on DPPZ markedly enhances their electrochromic performance. [ABSTRACT FROM AUTHOR]

Exactly 50 years ago, the first article on electrochromism was published. Today electrochromic materials are highly popular in various devices. Interest in nanostructured electrochromic and nanocomposite organic/inorganic nanostructured electrochromic materials has increased in the last decade. These materials can enhance the electrochemical and electrochromic properties of devices related to them. This article describes electrochromic materials, proposes their classification and systematization for organic inorganic and nanostructured electrochromic materials, identifies their advantages and shortcomings, analyzes current tendencies in the development of nanomaterials used in electrochromic coatings (films) and their practical use in various optical devices for protection from light radiation, in particular, their use as light filters and light modulators for optoelectronic devices, as well as methods for their preparation. The modern technologies of “Smart Windows”, which are based on chromogenic materials and liquid crystals, are analyzed, and their advantages and disadvantages are also given. Various types of chromogenic materials are presented, examples of which include photochromic, thermochromic and gasochromic materials, as well as the main physical effects affecting changes in their optical properties. Additionally, this study describes electrochromic technologies based on WO3 films prepared by different methods, such as electrochemical deposition, magnetron sputtering, spray pyrolysis, sol–gel, etc. An example of an electrochromic “Smart Window” based on WO3 is shown in the article. A modern analysis of electrochromic devices based on nanostructured materials used in various applications is presented. The paper discusses the causes of internal and external size effects in the process of modifying WO3 electrochromic films using nanomaterials, in particular, GO/rGO nanomaterials.

The power of isoreticular chemistry has been widely exploited to engineer metal-organic frameworks (MOFs) with fascinating molecular sieving and storage properties but is underexplored for designing MOFs with tunable optoelectronic properties. Herein, three dipyrazole-terminated XDIs (X = PM (pyromellitic), N (naphthalene), or P (perylene); DI = diimide) with different lengths and electronic properties are prepared and employed as linkers for the construction of an isoreticular series of Zn-XDI MOFs with distinct electrochromism. The MOFs are grown on fluorine-doped tin oxide (FTO) as high-quality crystalline thin films and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Due to the constituting electronically isolated XDI linkers, each member of the isoreticular thin film series exhibits two reversible one-electron redox events, each at a distinct electrochemical potential. The orientation of the MOFs as thin films as well as their isoreticular nature results in identical cation-coupled electron hopping transport rates in all three materials, as demonstrated by comparable apparent electron diffusion coefficients, D e app . Upon electrochemical reduction to either the [XDI] •- or [XDI] 2- state, each MOF undergoes characteristic changes in its optical properties as a function of linker length and redox state of the linker. Operando spectroelectrochemistry measurements reveal that Zn-PDI@FTO (PDI = perylene diimide) thin films exhibit a record high coloration efficiency of 941 cm 2 C -1 at 746 nm, which is attributed to the maximized Faradaic transformations at each electronically isolated PDI unit. The electrochromic response of the thin film is retained to more than 99% over 100 reduction-oxidation cycles, demonstrating the applicability of the presented materials.