Electrochromic Stability Research Articles

Highly stable Ag@Au nanowires micromesh as transparent conductive network for stretchable electrochromic modulator

The stretchable electrochromic modulator is one of the most promising energy-saving optoelectronic devices that can be integrated into smart portable and wearable electronics. A lot of focus has been on developing transparent conductive electrodes of stretchable electrochromic modulators, but they generally suffer from poor chemical stability, low photoelectric balance, and unsatisfactory deformability. To address this challenge, we first develop Ag@Au nanowires (NWs) micromesh-based stretchable transparent conductive electrodes (STCEs) using a self-assembled approach, which displays superior photoelectric performance (8.5 Ω sq-1 with a transmittance of 81.5 %), good chemical stability in harsh electrolyte environment (acidic and alkaline) as well as robust mechanical stability (bending, folding, stretching and twisting). As a demonstration, the grown WO3 on Ag@Au NWs-based STCEs can deliver good electrochromic stability even after bending over 1000 cycles and stretching to 50 %. Moreover, highly soft Zn//WO3 and polyaniline (PANI)//WO3 electrochromic modulators were assembled using flexible Ag@Au micromesh STCEs, which still retain uniform electrochromism in neutral and acidic electrolytes respectively. Definitionally, the strategy of in-situ grown Au shell on the surface of AgNWs micromesh provides an innovative solution to fabricate high-performance STCEs for the related portable smart wearable electronic devices.

Achieving ultrahigh electrochromic stability of triarylamine-based polymers by the design of five electroactive nitrogen centers

A shortage of long-term stability of electrochromic materials has been hindering their practical application. A series of novel polyamides (PAs) (4) with five electroactive nitrogen atoms within triphenylamine (TPA)-containing structures was synthesized via phosphorylation polyamidation. Polyamide 4b exhibited highly integrated electrochromic performances, including multiple color changes, high contrast of optical transmittance change, and the highest electrochromic stability (only 11.2 and 9.6 % decay of its coloration efficiency (CE) at 450 nm after 50000 and 16000 switching cycles, respectively) compared to all other triarylamine-based polymers to date. This record-high electrochromic cycling is attributed to the enhanced stability of polaron, which was studied through the electron-donating or electron-withdrawing effect of substituents and the resonance effect of electron delocalization over the electroactive nitrogen centers. Importantly, our core design of five electroactive nitrogen centers with electron-donating methoxy groups is the key factor to increase stability of polaron in the resulting polymers 4. More electroactive nitrogen centers are able to create a weaker electronic coupling due to a charge of cation radical dispersed by resonance successfully in-between the different redox states, which is evidenced clearly by the observed longer wavelength absorption in the NIR region. Our research confirms that the key to determining polaron stability is the resonance by the electrons delocalized over all the redox centers, rather than the electronic coupling between the different redox centers. And the resonance leads to increasing electrochromic stability of the polymer.

Electrochemical and impedance analysis of nickel oxide nanoflakes-based electrodes for efficient chromo supercapacitors

In response to the dynamic advancement of our growing world, there is a tenacious need for sophisticated technologies and continuous refinement of existing knowledge through rigorous scientific endeavors, all with a focus on achieving sustainable development goals for a cleaner and more prosperous future. In this context, this study involves a novel approach to the synthesis of highly porous and stable nickel oxide (NiO) nanoflakes assembled with stacked nanosheet thin films through hydrothermal methods. These films are in-detail examined for their redox-active chromo-supercapacitive properties. The hydrothermal synthesis technique yields thin films with exceptional adhesion to the electrode surface, remarkable chemical stability, and suitable porous structure. These characteristics are strategically employed to facilitate rapid ion intercalation and deintercalation processes, thereby enhancing electrochemical activity. Notably, films deposited for 6-hour reaction times deliver a higher areal capacitance of 140 mF/cm² (and capacity of 70 mC/cm2) at 0.5 mA/cm², which is higher than other electrodes and earlier reports. In-situ, optical investigations further underscore the high coloration efficiency of 44.14 cm²/C, coupled with large optical modulation of 56.5 % and enduring the electrochemical and electrochromic stability. Further research and optimization of NiO-based materials hold significant potential for the development of efficient, smart, and sustainable energy storage solutions in the evolving field of electrochromic supercapacitors to meet the demands of next-generation electronic systems.

Redox-Stable and Multicolor Electrochromic Polyamides with Four Triarylamine Cores in the Repeating Unit.

Two new triarylamine-based diamine monomers, namely, N,N'-bis(4-methoxyphenyl)-N,N'-bis(4-(4-aminophenyl-4'-methoxyphenylamino)phenyl)-p-phenylenediamine (3) and N,N'-bis(4-methoxyphenyl)-N,N'-bis(4-((4-aminophenyl-1-naphthyl)amino)phenyl)-p-phenylenediamine (7), were successfully synthesized and led to two series of electroactive polyamides by polycondensation reactions with common aromatic dicarboxylic acids. The polymers demonstrated multicolored electrochromism, high optical contrast, and remarkable enhancements in redox and electrochromic stability. Compared to other triarylamine-based polymers, the studied polyamides exhibited enhanced electrochromic stability (only 3~6% decay of its coloration efficiency at 445 nm after 14,000 switching cycles) at the first oxidation stage. The polyamides also showed strong absorption in the near-infrared region upon oxidation. Polymers with multicolored electrochromism and high redox stability can be developed by incorporation of four triarylamine cores in each repeat unit and electron-donating methoxy groups on the active sites of the triphenylamine units.

Cobalt Ion-Modified Titanium Oxide Nanorods: A Promising Approach for High-Performance Electrochromic Application

The development of novel cathodic materials with tailored nanostructures is crucial for the advancement of electrochromic devices. In this study, we synthesized cobalt-doped titanium dioxide (Ti-Co) thin films using a facile hydrothermal method to investigate the effects of cobalt doping on their structural, morphological, and electrochromic properties. Comprehensive characterization techniques, including X-ray diffraction and Raman analysis, confirmed the highly crystalline nature of the Ti-Co thin films, with specific Raman bands indicating distinct modifications due to cobalt incorporation. The TiO2 nanorods, optimally doped with cobalt (TC-3), demonstrated enhanced charge transport and mobility, significantly improving the electrochromic performance. Among the various compositions studied, the TC-3 sample exhibited superior lithium-ion accommodation, achieving an optical modulation of 73.6% and a high coloration efficiency of 81.50 cm2/C. It also demonstrated excellent electrochromic stability, maintaining performance for up to 5000 s of coloring/bleaching cycles. These results confirm the beneficial impact of cobalt doping on the structural and functional properties of the host material. Furthermore, the practical effectiveness of the TC-3 thin film was validated through the fabrication of an electrochromic device, which showed efficient coloration and bleaching capabilities. This comprehensive research enhances the understanding and functionality of Ti-Co nanorod architectures, highlighting their promising potential for advanced electrochromic applications.

Electrochromic Smart Window Based on Transition-Metal Phthalocyanine Derivatives.

Phthalocyanines have been widely investigated as electrochromic materials because of their large conjugated structure. However, they have shown limited applicability due to their complex electrochromism mechanism and low solubility in common organic solvents. Replacement of central metal ions in phthalocyanines affects their stability and is responsible for various electrochromic phenomena, such as color change. Herein, the relationship between the electron d-orbital arrangement in the outermost layer of transition metals and the electrochromic stability of phthalocyanine derivatives has been investigated. An enhanced solubility of phthalocyanines in organic solvents was obtained through the introduction of quaternary tert-butyl substitution. Electrochromic devices fabricated with transition-metal phthalocyanine derivatives showed high response speeds and good stability. The fast color-switching feature between blue/green and blue/purple makes it a promising candidate for smart windows and adaptive camouflage applications.

Bionic vine-stems structure for enhancing electrochromic cyclic stability and mechanical stability of multiband spectral regulation fiber

Wearable electrochromic (EC) devices can adjust visible-infrared spectra demonstrate promising potential for applications in display, decoration, personal thermal management, and adaptive thermal camouflage. However, existing flat layer-layer EC devices are hindered by poor air permeability, limited flexibility, and integration difficulties with fabrics, particularly in the realm of intelligent wearables. The creation of highly efficient fiber-shaped infrared (IR) modulation devices with exceptional structural and performance stability represents a significant challenge. We draw inspiration from the arboreous vine-stems structure observed in Chinese wistaria, which effectively minimizes the risk of damage to their vine and stems during harsh weather conditions. We have successfully designed a wearable high efficient multiband spectral regulation fiber (MSRF) with a bioinspired vine-stems structure using carbon fiber and polyaniline (PANI) as the active layer. The planar working electrode (Au) with PANI deposited on its surface was spirally wound around the counter electrode (carbon fiber) and separated by a gel electrolyte (PC/LiClO4), with polyolefin serving as the encapsulation layer. The distribution of electrical potential and lithium ions in the MSRF were analyzed using finite element analysis, demonstrating exceptional electrochromic stability without the length limit of the fiber. Moreover, the MSRF exhibited exceptional IR emissivity (△ε = 0.528) within the 8–14 μm range, fast response time (2.44 s) at low applied potentials (−0.8 V and 0.8 V), robust long-term cycling stability (at least 5000 cycles), and remarkable mechanical stability (at least 5000 bending cycles). The compatibility of the fiber with fabric and potential for patterning using MSRF with high length was also explored, providing new insights into the development of wearable adaptive thermal camouflage and spectral regulation fiber devices.

Hydrogen-Bonding Induced Crosslinked Polymer Network for Highly Stable Electrochromic Device and a Construction Strategy for Black-Bilayer Electrochromic Film.

This work presents a new strategy to achieve highly stable electrochromic devices and bilayer film construction. A novel solution-processable electrochromic polymer P1-Boc with quinacridone as the conjugated backbone and t-Boc as N-substituted non-conjugated solubilizing groups is designed. Thermal annealing of P1-Boc film results in the cleavage of t-Boc groups and the formation of N─H⋯O═C hydrogen-bonding crosslinked network, which changes its intrinsic solubility characteristics into a solvent-resistant P1 film. This film retains the electrochemical behavior and spectroelectrochemistry properties of the original P1-Boc film. Intriguingly, the electrochromic device based on the P1 film exhibits an ultrafast switching time (0.56/0.80 s at 523nm) and robust electrochromic stability (retaining 88.4% of the initial optical contrast after 100000 cycles). The observed cycle lifetime is one of the highest reported for all-organic electrochromic devices. In addition, a black-transparent bilayer electrochromic film P1/P2 is developed in which the use of the solvent-resistant P1 film as the bottom layer avoids interface erosion of the solution-processable polymer in a multilayer stacking.

Isoindigo-Thiophene D-A-D-Type Conjugated Polymers: Electrosynthesis and Electrochromic Performances.

Four novel isoindigo-thiophene D-A-D-type precursors are synthesized by Stille coupling and electrosynthesized to yield corresponding hybrid polymers with favorable electrochemical and electrochromic performances. Intrinsic structure-property relationships of precursors and corresponding polymers, including surface morphology, band gaps, electrochemical properties, and electrochromic behaviors, are systematically investigated. The resultant isoindigo-thiophene D-A-D-type polymer combines the merits of isoindigo and polythiophene, including the excellent stability of isoindigo-based polymers and the extraordinary electrochromic stability of polythiophene. The low onset oxidation potential of precursors ranges from 1.10 to 1.15 V vs. Ag/AgCl, contributing to the electrodeposition of high-quality polymer films. Further kinetic studies illustrate that isoindigo-thiophene D-A-D-type polymers possess favorable electrochromic performances, including high optical contrast (53%, 1000 nm), fast switching time (0.8 s), and high coloration efficiency (124 cm2 C-1). These features of isoindigo-thiophene D-A-D-type conjugated polymers could provide a possibility for rational design and application as electrochromic materials.

A new black to highly transmissive switching bilayer polymer composite films with electroactive pEA as a color buffer layer for improving electrochromic stability

AbstractTwo reported D‐A‐D monomers based on 3,4‐ethylenedioxythiophene (EDOT) were selected for electrochemical copolymerization to obtain copolymer film, named pRG. Then, a soluble polymer poly[3,4‐ethylenedioxythiophene‐alt‐3,4‐bis([2‐ethylhexyl]oxy)thiophene] (pEA) based on the EDOT derivative was screened out, which is complementary to the absorption trough of the pRG film in visible region and matched with its working potential. The bilayer composite film pRG/pEA was obtained by spinning pEA basement membrane on fluorine doped tin oxide (FTO) coated glass surface, and then in situ electrochemical polymerization of pRG film. Compared to the pRG monolayer film, the bilayer composite film shows a more saturated black color in the neutral state and significant improvement on cyclic stability (only decreased by 1.7% after 250 cycles, while pRG film decreased by 17.1%). The introduction of pEA buffer layer not only achieves the full spectral absorption of the composite film in the visible region, but also significantly improves the cyclic stability of the bilayer composite film. The assembled EC prototype device based on the pRG/pEA composite film exhibits a “black to high transmission” reversible switch. Finally, this method combining electrochemical copolymerization, spin‐coating, lamination and other methods provides a new research idea for designing and preparing black to transmissive electrochromic materials.

A feasible strategy of Prussian blue reflective electrochromic devices capable of reversible switching between sand-yellow and leaf-green

A flexible reflective-type electrochromic device based on PB films has been constructed. Based on the subtractive color-mixing theory, the demonstrated electrochromic device exhibits a unique reversible color changes from leaf-green to sand-yellow by electrochemical operation. Fast response time of 0.9 s for bleaching and 1.3 s for coloring is observed, which is faster than most reports. In addition, the device exhibits high electrochromic stability of more than 100 cycles without compromising its performance. The flexible device shows promise for a broad range of potential application in the wearable electrochromic displays and camouflage.

Electrodeposited Gold Nanostructures for the Enhancement of Electrochromic Properties of PANI-PEDOT Film Deposited on Transparent Electrode.

Conjugated polymers (CPs) are attractive materials for use in different areas; nevertheless, the enhancement of electrochromic stability and switching time is still necessary to expand the commercialization of electrochromic devices. To our best knowledge, this is the first study demonstrating the employment of electrodeposited gold nanostructures (AuNS) for the enhancement of CPs’ electrochromic properties when a transparent electrode is used as a substrate. Polyaniline–poly(3,4-ethylenedioxythiophene) (PANI-PEDOT) films were electrodeposited on a transparent indium tin oxide glass electrode, which was pre-modified by two different methods. AuNS were electrodeposited at −0.2 V constant potential for 60 s using both the 1st method (synthesis solution consisted of 3 mM HAuCl4 and 0.1 M H2SO4) and 2nd method (15 mM HAuCl4 and 1 M KNO3) resulting in an improvement of optical contrast by 3% and 22%, respectively. Additionally, when using the 1st method, the coloration efficiency was improved by 50% while the switching time was reduced by 17%. Furthermore, in both cases, the employment of AuNS resulted in an enhancement of the electrochromic stability of the CPs layer. A further selection of AuNS pre-modification conditions with the aim to control their morphology and size can be a possible stepping stone for the further improvement of CPs electrochromic properties.

Multi-color poly(3-methylthiophene) films prepared by a novel pre-nucleation electrodeposition grown method for enhancing electrochromic stability

Poly(3-methylthiophene) (PMeT) is considered a promising conductive polymer for applications in electrochromic displays due to its red to blue multi-color switch as well as low cost. However, the non-uniformity of the films caused by high electrochemical polymerization potentials during electrodeposition and the rapid electrochemical stability decay caused by weak adhesion limits its practical application. In this study, a new pre-nucleation electrodeposition method is developed to synthesize PMeT film. The nucleation grown progress is investigated by electrochemical fitting tests and scanning electron microscopy. Compared with a directly grown film, the pre-nucleation PMeT film presents excellent electrochromic EC transmittance modulation of 75% at wavelength of 1050nm, and sustains a transmittance modulation of about 91 % after 400 cycles. This was the result of enhanced uniformity and adhesion from the pre-nucleation method. The surface uniformity and roughness of PMeT films were analyzed by optical microscopy and atomic force microscopy measurements. After controlling thickness using this method, the PMeT films exhibited multiple transmittance change and red–green–blue color change.

Enhancing the electrochromic stability of Prussian blue based on TiO2 nanorod arrays

The cyclic stability and optical modulation of Prussian blue (PB) via TiO2 nanorod arrays are enhanced.

Facile Fabrication of Triphenylamine-Based Redox-Active Nanocomposites by a Sol-Gel Method: Enhanced Electrochromic Response Capability and Stability Performance.

In this research, a new design of organic-inorganic hybrid networks involving covalently bonding, novel, electron-donating triphenylamine (TPA)-containing electroactive molecules to inorganic metal oxides is successfully developed by using a facile sol-gel process. These anodically electrochromic TPA-containing materials exhibit multicolor electrochromic behaviors at various oxidation states. By introducing zirconium oxide into electrochromic materials, not only can an excellent optical transparency in the visible light region at a neutral state be achieved given the nature of the large energy bandgap, but the electrochromic switching can also be driven by a lower oxidation potential with an enhanced response capability (shorter coloring times and bleaching times). Moreover, the hybrid films show outstanding electrochemical stability and high reversibility under long-term operations owing to their good adhesion to the electrode. Consequently, the electrochromic devices derived from these novel hybrid electroactive materials reveal a huge potential for electrochromic applications.

Soluble high coloration efficiency electrochromic polymers based on (N-phenyl)carbazole, triphenylamine and 9,9-dioctyl-9H-fluorene

Here, we synthesized four kinds of monomers of 3,6-dibromo-(N-phenyl)carbazole with different substituent group, DCB, DDC, DNC and DTC, respectively, and used 4-(3-bromo-9H-carbazol-9-yl)benzaldehyde to react with triphenylamine (TPA) unit and hydrazine hydrate unit, respectively, to obtain the other two monomers, BCB-TPA and BCB-HH. Six novel polymers coded as PDCB-DF, PDDC-DF, PDNC-DF, PDCB-DTC-DF, PBCB-TPA-DF and PBCB-HH-DF, were synthesized by Suzuki reactions of 2,2'-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(1,3,2-dioxaborinane) with the six kinds of monomers and their electrochemical and spectroelectrochemical properties were investigated. The polymers showed good solubility and film-forming ability. Flexible or robust films of them could be readily obtained via solution-casting. These polymers showed the onset temperatures in the range of 300–470 °C when the 10% weight loss of polymers. The polymer films showed high coloration efficiency (CE) (196-376 cm2·C−1) and electrochromic stability. These properties illustrate that the polymers have great application prospect as electrochromic materials.

Influences on oxidation voltage and holding time on poly(3-methylthiophene) film for electrochromic stability**Project supported by the National Natural Science Foundation of China (Grant No. 51403102) and the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20140811).

In this study, we report the influences of oxidation potential and holding time on the electrochromic (EC) stability of poly(3-methylthiophene) (P3MT) film during the electrochemical reaction. The cycle stability and transmittance changes of the film were investigated by optimizing the oxidation potential, and its chemical compositions were measured by x-ray photoelectron spectra after multiple electrochemical cycles. High oxidation potentials can increase the P3MT film color contrast and decrease its cycle stability because of accelerating chemical decomposition. Moreover, the holding time with potential pulsing was analyzed by using the optical memory of P3MT at an optimized oxidation potential, which revealed the reduced voltage duration saved energy consumption by 11.6% and improved the EC cycle stability without changing in color contrast.

Prominent Electrochromism Achieved Using Aluminum Ion Insertion/Extraction in Amorphous WO3 Films

Although monovalent lithium has been successfully used as a coloring ion in electrochromic applications, it still faces the challenges of low safety, high cost, and limited reserves. Herein, we demonstrate that the amorphous WO3 films intercalated with Al3+ ions could exhibit desired wide optical modulation (∼63.0%) and high coloration efficiency (∼72.0 cm2 A–1, which is >100% higher than that with Li+ or Na+), benefiting from the three-electron redox properties of aluminum. Due to the strong electrostatic force and large atomic weight, the charge exchange processes for Al3+ ions are limited only to the near-surface region and consequently bring about enhanced electrochromic stability. Our findings provide in-depth insights into the nature of electrochromism and also open up a new route toward scalable electrochromic devices using sputtering techniques and earth-abundant materials.

Enhanced performance and stability of electrochromic device based on poly (3-methylthiophene) using 2-thiophenecarboxylic acid as interfacial modifier

In this paper, we modified the surface of Indium tin oxide (ITO) electrode with 2-thiophenecarboxylic acid (ThCA), and then prepared the poly (3-methylthiophene) (PMeT) film covalently bonded to ITO electrode (PMeT-ITO) by electrochemical polymerization. It was found that interfacial modification enhanced the adsorption force between PMeT and ITO substrate, PMeT-ITO exhibited better stability. Moreover, we successfully fabricated the electrochromic device (ECD) by using PMeT films on ITO substrate. The results of cycling tests showed that the optical contrast of ECD based on PMeT-ITO was kept almost the same after recycling 66 times. Compared with ECD based on PMeT physically adsorbed on bare ITO substrate (PD-PMeT), the ECD based on PMeT-ITO possessed good electrochromic stability in the 150 cycles. This demonstrated that the interaction between PMeT and ITO substrate became stronger by chemical bonding approach, improving the cyclic stability of ECD.

Solution layer-by-layer uniform thin film dip coating of nickel hydroxide and metal incorporated nickel hydroxide and its improved electrochromic performance

In this work, we identified the problem faced by conventional successive ionic layer adsorption and reaction (SILAR) process in producing uniform nickel hydroxide films as the homogeneous precipitation reaction in water. Subsequently we proposed a novel SILAR recipe with a modified rinsing step and successfully demonstrated, for the first time, a layer-by-layer coating of uniform nickel hydroxide thin film without surface structures or agglomerated precipitates. In addition, we explored and demonstrated the capability of the proposed SILAR process in incorporating additional element such as aluminum into the nickel hydroxide film. The aluminum incorporated nickel hydroxide film shows improved electrochromic stability evidenced by reducing the degradation in coloration efficiency from 46% to 6%. The average coloration efficient is reported as 22 cm2/C and the response time is 4.5 s for bleaching and 4 s for coloration.