Search Results (196)

In order to improve the electrochromic properties of NiO_x films, Mg ions were introduced into NiO_x films using the sol–gel method and the spin-coating method. The introduction of Mg ions leads to the loose structure of the compact NiO_x film, which can provide more channels for the transport of OH⁻. In addition, the introduction of Mg ions increases the oxygen vacancies and oxygen interstitial defects in the NiO_x film, which effectively increases the reactive sites and improves the charge transfer efficiency at the interface between the NiO_x film and the electrolyte. The electrochemical results further show that the film electrode (NiO_x-Mg2) has the largest charge storage capacity when the Mg doping concentration is 10%. Compared with the undoped NiO_x film, the doping of Mg improves the transmittance modulation (ΔT) performance of the NiO_x film (ΔT up to 55.8%) and shortens the response time (2.39 s/0.63 s for coloring/bleaching). In general, Mg doping is an effective method for improving the electrochromic properties of NiO_x films. Full article

Perylenediimides are an interesting group of compounds that are finding more and more applications. However, the synthetic route of obtaining and modifying them is usually very complicated, costly, and time-consuming. Therefore, the conducted research aimed to develop new, greener, electrochemical methods of obtaining unknown perylenediimides (containing 2-ethylhexyl at the nitrogen atom). For the products obtained in this way, optical and electrochemical studies were conducted and compared with DFT results (i.e., energy gaps and HOMO and LUMO levels). Asa result of optical studies, different emission wavelengths of two isomers originating from the same excitation wavelength were observed. Electrochemical studies also confirmed significant differences in properties between the obtained isomers. Spectroelectrochemical measurements were also performed; they revealed the electrochromic properties of the obtained isomers in the visible and near-infrared range. Considering all the properties (optical and (spectro)electrochemical), the obtained compounds have a high potential for use in optoelectronic devices. Moreover, unprecedented pi-expansion of cis-DBPDI via 1,2-bis(p-bromophenyl)acetylene Diels–Alder cycloaddition into the bay region was also realized successfully. Summing up, electrosynthesis and further pi-expansion via cycloaddition offer a sea of opportunities for obtaining nanographenes. Full article

A series of water-soluble molecules based on 8-isopropyl-2-methyl-5-nitroquinoline and 1,10-phenanthroline core were designed by introducing a π-conjugated bridge, vinyl unit –CH=CH–. We present the selective conversion of methyl groups located on the C2 and C9 positions in the constitution of selected quinoline or 1,10-phenanthroline derivatives, respectively, into vinyl (or styryl) products by applying Perkin condensation. The two groups of ligands differ in the presence of one or two arms. The structure of the molecule ((1E,1′E)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl))bis(benzene-4,1,3-triyl) tetraacetate was determined by single-crystal X-ray diffraction measurements. The X-ray, NMR, and DFT computational studies indicate the influence of rotation (rotamers) on the physical properties of studied styryl molecules. The results show that the styryl molecules with the vinyl unit –CH=CH– exhibit significant static and dynamic hyperpolarizabilities. Quantum chemical calculations using density functional theory and B3LYP/6-311++G(d,p) with Grimme’s dispersion correction approach predict the existence and relative stability of different spatial cis(Z)- and trans(E)-conformers of styryl derivatives of quinoline and 1,10-phenanthroline, which exhibit different electronic distribution and conjugation within the molecular skeleton, dipole moments, and steric interactions, leading to variations in their photophysical behavior and various applications. Our studies indicate that the rotation and isomerization of aryl groups can significantly influence the electronic and optical properties of π-conjugated systems, such as vinyl units (–CH=CH–). The rotation of aryl groups around the single bond that connects them to the vinyl unit can lead to changes in the effective π-conjugation between the aryl group and the rest of the π-conjugated system. The rotation and isomerization of aryl groups in π-conjugated systems significantly impact their electronic and optical properties. These changes can modify the efficiency of π-conjugation, affecting charge transfer processes, absorption properties, light emission, and electrical conductivity. In designing optoelectronic materials, such as organic dyes, organic semiconductors, or electrochromic materials, controlling the rotation and isomerization of aryl groups can be crucial for optimizing their functionality. Full article

Electrochromic devices have garnered significant interest owing to their promising applications in smart multifunctional electrochromic energy storage systems (EESDs) and their emerging next-generation electronic technologies. Tungsten oxide (WO₃), possessing both electrochromic and pseudocapacitive characteristics, offers great potential for developing multifunctional devices with enhanced performance. However, achieving an efficient and straightforward synthesis of WO₃ electrochromic films, while simultaneously ensuring high coloration efficiency and energy storage capability, remains a significant challenge. In this work, a low-temperature hydrothermal approach is employed to directly grow hexagonal-phase WO₃ films on FTO substrates. This process utilizes sorbitol to promote nucleation and rubidium sulfate to regulate crystal growth, enabling a one-step in situ fabrication strategy. To complement the high-performance WO₃ cathode, a composite PB/SnO₂ film was designed as the anode, offering improved electrochromic properties and enhanced stability. The assembled EESD exhibited fast bleaching/coloration response and a high coloration efficiency of 101.2 cm² C⁻¹. Furthermore, it exhibited a clear and reversible change in optical properties, shifting from a transparent state to a deep blue color, with a transmittance modulation reaching 81.47%. Full article

Electrochromic supercapacitors (ECSCs), which visually indicate their operating status through color changes, have attracted considerable attention in the field of wearable electronics. The conductive polymer polyaniline (PANI) shows great potential for integrated intelligent devices by combining bi-functional electrochromic spectral modulation and energy storage capabilities. In this work, a microsphere-like structured PANI-based composite film was fabricated on a porous Au/nylon 66 electrode via a one-step electrochemical copolymerization process, using 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt (PTSA) as both the dopant and cross-linking agent for the PANI backbone, serving as the ECSC electrode. Compared to the pristine PANI electrode, the PANI-PTSA composite film exhibits lower intrinsic resistance and higher electrical conductivity, delivering a higher specific capacitance of 310.0 F g⁻¹@1 A g⁻¹ and an areal capacitance of 340.0 mF cm⁻²@1 mA cm⁻², respectively. The dopant facilitates enhanced electrochemical performance by promoting charge transport within the PANI polymer network. Meanwhile, as a counter anion to the PANI backbone, PTSA regulates the growth of PANI chains and acts as a morphological controller. Furthermore, a symmetric ECSC based on the PANI-PTSA_8:1 electrode was assembled, and its electrochemical properties were thoroughly investigated. The device demonstrated a high specific capacitance of 169.2 mF cm⁻² at 1 mA cm⁻², a notable energy density of 23.5 μWh cm⁻² at a power density of 0.5 mW cm⁻², and excellent cycling stability with 79% capacitance retention after 3000 cycles at a current density of 5 mA cm⁻², alongside remarkable mechanical flexibility. Additionally, the working status of the ECSCs can be directly monitored through reversible color changes from yellow-green to deep blue during charge–discharge processes. Full article

This study was conducted at SPINLab. The full-scale experiments were performed using two experimental spaces of identical specifications to investigate the effects of electrochromic film (OG + EC_ON or OG + EC_OFF) on indoor environment and air conditioning electricity consumption in buildings with different orientations (East and West). The electricity-saving effects are more pronounced on the building’s west-facing side than on its east-facing side. For the east-facing side, the average electricity savings for OG + EC_ON and OG + EC_OFF were 4.5%, and 5.1%, respectively. For the west-facing side, the average electricity savings increased to 9.2% and 9.4% for OG + EC_ON and OG + EC_OFF. The research results on thermal comfort indicate (PMV) that applying electrochromic film (OG + EC_ON or OG + EC_OFF) significantly improved indoor thermal comfort compared to using clear glass (OG) alone. The visual comfort analysis results indicate that the opaque (OG + EC_OFF) and transparent (OG + EC_ON) states of electrochromic film could reduce daylight glare probability (DGP) values. However, due to the light-scattering properties of the liquid crystal droplets, the OG + EC_OFF and OG + EC_ON states of the electrochromic film increased DGP values in 26.5% and 41.5% of the cases, respectively, when sunlight directly entered the interior. Full article

This study is dedicated to the design of multiple redox-active oligonuclear manganese complexes supported with a bis(tetradentate) ligand (TPDP = 1,3-bis(bis(2-pyridinylmethyl)amino)-2-propanol) for high-contrast electrochromism based on the reversible redox process between Mn(II) (colorless) and Mn(III) (dark brown). Pentanuclear Mn₅ complex 1 (colorless) was synthesized via a one-pot reaction of Mn²⁺ and TPDP, while tetranuclear Mn₄ complex 2 (brown) was obtained through aerial oxidation of complex 1. Mn₅ complex 1 features a central MnCl₆ unit connected to two Mn₂(μ-TPDP) fragments through μ₃-Cl⁻ and μ-Cl⁻, whereas Mn₄ complex 2 adopts a symmetric tetranuclear structure with two mixed-valence Mn₂^II,III(μ-TPDP)(μ-Cl) fragments that are further linked by μ-oxo. Electrochemical studies revealed multi-step reversible redox properties for both complexes, attributed to Mn^II/Mn^III processes with significant electronic coupling (ΔE_1/2 = 0.27–0.37 V) between Mn centers. Spectroelectrochemical analysis revealed dynamic optical modulation through the tunable d-d transition and ligand-to-metal charge transfer (LMCT) state through reversible multiple redox processes based on Mn(II) ⇆ Mn(III) interconversion. The fabricated electrochromic device (ECD) exhibited reversible and high optical contrast between the colored state (dark brown) and the bleaching state (colorless). The results highlight the potential of polynuclear manganese complexes as high-contrast electrochromic materials for next-generation smart windows and adaptive optical technologies. Full article

Viologens, i.e., quaternary 4,4′-bipyridinum salts, are a well-known class of functional organic compounds that have attracted in the past few decades a great deal of attention for their peculiar chemical and electrochemical properties and have therefore found numerous applications ranging from herbicides to electrochromic devices. In this paper, the synthesis and characterization of a novel viologen derivative are described. In the reported compound, the pyridinium nitrogen atoms have been quaternarized with the benzyl group and an additional unsaturated moiety, namely a 9,10-diethynylanthracene core, has been inserted between the charged pyridinium rings to extend the conjugation. Characterization by means of absorbance and diffuse reflectance UV–visible spectroscopy suggested intriguing optical and electronic properties, making this extended viologen a potential candidate for different optoelectronic applications. Full article

Three new amide-preformed triphenylamine-diamine monomers, namely 4,4′-bis(p-aminobenzamido)triphenylamine (4), 4,4′-bis(p-aminobenzamido)-4″-methoxytriphenylamine (MeO-4), and 4,4′-bis(p-aminobenzamido)-4″-tert-butyltriphenylamine (t-Bu-4), were synthesized and subsequently used to produce three series of electroactive aromatic poly(amide-imide)s (PAIs) via two-step polycondensation reactions with commercially available tetracarboxylic dianhydrides. Strong and flexible PAI films could be obtained by solution casting of the poly(amic acid) films followed by thermal imidization or direct solution casting from the organosoluble PAI samples. The PAIs had high glass-transition temperatures of 296–355 °C and showed no significant decomposition below 500 °C. The PAIs based on diamines MeO-4 and t-Bu-4 showed high electrochemical redox stability and strong color changes upon oxidation. For the PAIs derived from diamine 4, the TPA radical cation formed in situ during the electro-oxidative process could dimerize to a tetraphenylbenzidine structure, resulting in an additional oxidation state and color change. These PAIs exhibited increased solubility, lowered oxidation potentials, and enhanced redox stability compared to their polyimide analogs. Full article

Aqueous zinc-ion batteries (AZIBs) have attracted interest for their low cost and environmental friendliness. Two bipolar organic materials with different degrees of conjugation, pPMQT and pNTQT, were rationally designed and synthesized as cathode candidates for AZIBs based on 4,4′-diaminotriphenylamine (TPA), 2,7-diaminoanthraquinone (AQ), and two anhydrides. This molecular design features an increased conjugation and electron cloud density, thereby improving charge transport kinetics, specific capacity, and cycling stability. In comparison with pPMQ and pNTQ (n-type), pPMQT and pNTQT demonstrate better electrochemical characteristics. In this work, pNTQT shows outstanding performance. It exhibits an initial capacity of 349.79 mAh g⁻¹ at 0.1 A g⁻¹ and retains a specific capacity of 190.25 mAh g⁻¹ (87.6%) after 5000 cycles at 5 A g⁻¹. In comparison, pNTQ demonstrates a specific capacity of only 207.55 mAh g⁻¹ at 0.1 A g⁻¹, and after 5000 cycles at 5 A g⁻¹, its capacity retention rate is only 81.2%. At the same time, both pPMQT and pNTQT polymer films demonstrate attractive electrochromic (EC) properties, displaying reversible color transitions from yellow to dark blue in the UV–visible spectrum. This work lays the foundation for the further development of triphenylamine-based polyimide materials for application in AZIBs and electrochromism. Full article

Electrochromic materials have a wide range of energy-effective applications, such as in mirrors, smart windows, automobile sunroofs, and display devices. The electrochromic behavior of mixed metal oxides is focused on in this review. Extra heat absorbed by buildings is one of the major problems in our modern era, so electrochromic films have been used as components of smart windows to reduce heat absorption through glass windows. Transition metal (W, V, Ti, Mo, and Ni) oxides are considered popular electrochromic materials for this purpose. Smart windows consist of electrochromic material layers (such as metal oxide layers) and solid electrolytes sandwiched between transparent conductive layers. Few publications have studied the use of mixtures of different metal oxides as electrochromic materials. This study focuses on the results of investigations of such multicomponent materials, such as the effects on the electrochromic properties of mixed metal oxides and how they contrast with pure metal oxides. Reviewing these papers, we found WO₃- and MoO₃-based mixtures to be the most promising, especially the magnetron-sputtered, amorphous WO₃(40%)–MoO₃(60%) composition, which had 200–300 cm²/C coloration efficiency. The mixed oxide materials reported in this review have room for development (and even commercialization) in the oxide-based electrochromic device market. Full article

We report the successful synthesis of amorphous titanium-engineered tungsten oxide (WTi) films via a facile and cost-effective electrodeposition method. Unlike conventional high-temperature or vacuum-based techniques, our approach enables a scalable, all-solution process, ensuring efficiency and sustainability. X-ray diffraction (XRD) confirmed the amorphous nature of all films, a key factor in enhancing ion diffusion for superior electrochromic (EC) performance. Field-emission scanning electron microscopy (FESEM) revealed that an optimized nanoparticle network facilitates rapid charge transport and ion intercalation, while uncontrolled nucleation and grain growth hinder EC efficiency. By precisely tuning the Ti concentration, the optimized 3 at% WTi-3 film achieved outstanding EC properties, including an impressive optical modulation of 85% at 600 nm, exceptional reversibility of 95.61%, and a high coloration efficiency of 51.55 cm²/C. This study underscores the pivotal role of amorphous engineering and dopant concentrations in advancing high-performance EC materials, paving the way for next-generation smart windows and energy-efficient displays. Our findings highlight a transformative strategy for low-cost, high-efficiency EC devices, demonstrating unprecedented performance through precision-engineered material design. Full article

The integration of various transition metal oxides into tungsten oxide (WO₃) has been widely investigated to enhance its electrochromic (EC) performance. This approach aims to address the inherent limitations of individual metal oxides, such as poor durability, inadequate color neutrality, and restricted coloring efficiency and optical properties. The use of mixed metal oxides has emerged as a promising strategy, enabling a synergistic effect that optimizes EC performance and expands the material’s functional capabilities. In this study, we compare single-layer WO₃ films with bilayer WO₃/cobalt oxide (CoO) (denoted as W@C) composite films, focusing on their structural, morphological, and electrochromic properties. Both films were fabricated using the electrodeposition technique, with a consistent number of deposition cycles. Field emission scanning electron microscopy (FESEM) analysis revealed that the WO₃ film presented a tightly packed arrangement of nanogranules. In contrast, the bilayer W@C composite thin film exhibited a highly interconnected and porous granular structure, with morphology evolving into larger spherical aggregates. The optimized bilayer W@C composite demonstrated exceptional electrochromic performance, achieving an optical modulation of 85.0% at 600 nm and a significantly improved coloration efficiency of 96.07 cm²/C. Stability tests confirmed its remarkable durability, showing only a 1.05% decrease in optical contrast after 5000 s of operation. Additionally, a prototype electrochromic device based on the W@C film demonstrated an optical modulation of 52.13% and outstanding long-term stability, with minimal degradation in performance. Full article

Niobium oxide (Nb₂O₅) is a compelling preference for electrochromic (EC) applications due to its remarkable optical modulation, chemical resilience, and efficient charge accommodation. This study attentively explores the influence of reaction temperature on the structural, morphological, and EC characteristics of Nb₂O₅ thin films synthesized via a hydrothermal approach. Reaction temperatures spanning 140 °C to 200 °C were optimized to unravel their pivotal role in dictating material properties and device performance. Field-emission scanning electron microscopy elucidates significant morphological transformations, transitioning from agglomerated, cracked structures at lower temperatures to well-defined, porous architectures at optimal conditions, followed by a re-compaction of the surface at elevated temperatures. Electrochemical analysis established a strong correlation between thermal-induced structural refinements and enhanced EC performance metrics. The optimized N-180 thin films exhibit enhanced charge injection dynamics, improved coloration efficiency of 81.33 cm²/C, and superior optical modulation of 74.13% at 600 nm. The device fabricated with the most favorable film demonstrated significant optical contrast and long-term stability, reinforcing its practical viability for smart window and energy-efficient applications. This study pioneers a comprehensive understanding of the thermal modulation of Nb₂O₅ thin films, providing new insights into the interplay between reaction temperature and material functionality. Full article

Electrochromic fabrics (ECFs) can be applied to wearable displays and military camouflage clothing, and they have great potential in developing wearable products. Current ECFs are often bulky, involve complicated processes, and have high production costs. In this study, we report a novel strategy for preparing electrochromic fabrics that require only a three-layer structure: cotton fabric as the substrate, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the electrochromic layer and the electrodes, and an ion-conducting film (ICF) bonded to the fabric by hot pressing. Compared with conventional ECFs, this method does not require the extra preparation of electrode layers on the fabric, as these layers affect the color-changing effect. Hot pressing eliminates the need for a complex sealing process and is more suitable for fabrics with poor wicking effects, which increases the method’s applicability. Cotton fabrics offer the value of biodegradability and are more environmentally friendly. Meanwhile, unlike carbon cloth, the fabric’s color does not interfere with the electrochromic effect. The ICF is non-liquid and can maintain the dryness of the fabric. Additionally, the ICF provides high-temperature protection up to 150 °C. The ECFs exhibit exceptional thinness at 161 µm and a lightweight construction with a 0.03 g/cm² weight. Furthermore, the ECFs exhibit a relatively long sustain time of 115 min without voltage, demonstrating impressive performance. Improved peel strength to 7.11 N is achieved through an improved hot-pressing process. The development strategy for ECFs can also be applied to other electrochromic substances, potentially advancing intelligent applications such as wearable fabrics and military camouflage while promoting rapid progress in electrochromic fabrics. Full article