Tungsten Oxide Films Research Articles

Bridging to Commercialization: Record-Breaking of Ultra-Large and Superior Cyclic Stability Tungsten Oxide Electrochromic Smart Window.

Electrochromic smart windows (ESWs) can significantly reduce energy consumption in buildings, but their cost-effective, large-scale production remains a challenge. In this study, the instability of black phosphorus is leveraged to induce the growth of the tungsten oxide film through its decomposition process, inspired by the 2D material-assisted in situ growth (TAIG) method. This approach results in the preparation of large-scale, high-performance WO3-x·nH2O (n<2) films. Characterization techniques and DFT calculations confirm efficient regulation ofstructural water and oxygen vacancies during TAIG preparation. The WO3-x·nH2O films exhibit excellent electrochromic (EC) properties, including high transmittance modulation (74.2%@1100nm), fast switching time (tc=5.5s, tb=3.8s), high coloration efficiency (124.7cm2C-1), and superior cyclic stability (transmittance modulation retained 94.7% after 20000 cycles). Ultra-largeWO3-x·nH2O film are prepared via a simple immersion process, and fabricated into a large-area ESW under facile laboratory conditions, demonstrating the economic and practical feasibility of this approach in industrial-scale production. Operated by the intelligent control circuit, the ESWexhibits remarkable EC properties and cyclic stability This research represents a milestone in improving the performance and industrial-scale production of ESWs, bridging the gap to the commercialization of EC technology.

Advanced Dual‐Band Smart Windows: Inorganic All‐Solid‐State Electrochromic Devices for Selective Visible and Near‐Infrared Modulation

AbstractDual‐band electrochromic smart windows (DESWs), capable of actively and selectively modulate visible (VIS) light and near‐infrared (NIR) heat, have emerged as a practical technology for enhancing user comfort and reducing building energy consumption. However, the design and development of DESWs remain a significant challenge due to the difficulty in obtaining suitable materials and high‐durability electrolytes. Here, the first all‐solid‐state DESW based on an orthorhombic oxygen‐deficient tungsten oxide (o‐WO3‐x) film is presented. Benefiting from the synergistic effects of the efficient oxygen‐vacancy‐enhanced charge transfer process and the secure transfer pathway enabled by the orthorhombic crystal structure, the o‐WO3‐x film showcases remarkable dual‐band electrochromic properties, including selective modulation of VIS light and NIR heat, large optical modulation (89.1%), rapid response time (tb/tc = 6.8/17.9 s), high coloration efficiency (155.92 cm2 C−1), and ultrastable cyclic performance (8000 cycles) even in acidic aqueous electrolyte. Furthermore, the all‐solid‐state DESWs incorporating o‐WO3‐x deliver a significant and stable dual‐band electrochromic response with excellent thermal regulation and energy‐saving capabilities. These findings underscore the considerable potential of o‐WO3‐x films and their all‐solid‐state smart windows in decreasing building energy consumption.

Simulation and deposition of Tungsten oxide (WO3) films using DC sputtering towards UV photodetector for high responsivity

Tungsten trioxide (WO3) detects UV radiation with great sensitivity while disregarding visible light, and it also has excellent electron mobility, allowing for efficient charge transport and fast response times. This work aims to develop a highly sensitive UV photodetector using WO3 material by optimizing the deposition parameter partial oxygen pressure (PaO2) and annealing the samples at various temperatures to determine the best PaO2 and annealing temperature that results in an improvement in the UV photodetector's sensitivity. The material WO3 was coated on glass substrates using DC magnetron sputtering while altering the PaO2 as 6 × 10−2 Pa, 4 × 10−2 -2 Pa, and 2 × 10−2 Pa, and then each as-deposited sample from varied PaO2 was annealed at temperatures ranging from 100°C to 400°C. When the sample's responses were compared, it was observed that the sample deposited at PaO2 2 × 10−2 Pa and annealed at 400 °C exhibited good photodetection capabilities, as evidenced by several characterization techniques such as SEM, XRD, and IV characterization. The work was subsequently carried out by evaluating the sample deposited at PaO2 2 × 10−2 Pa and annealed at 700 °C, which produced a good result for UV photodetection with the device's responsivity of 1e+4 A/W.

High-performance electrochromic devices composed of niobium tungsten oxide films

Electrochromic technology plays a pivotal role in various industries, offering significant benefits in energy efficiency and sustainability. By efficiently modulating sunlight, it reduces dependence on traditional climate control systems, thus decreasing overall energy consumption. Among electrochromic materials, tungsten oxide (WO3) is highly favored for its outstanding stability and superior optical modulation amplitude. However, the escalating demands of commercial applications necessitate enhancements in electrochromic performance, achievable through doping or composite designs. This study investigates the electrochromic characteristics of novel niobium tungsten oxide (Nb18W16O93) thin films, employing a gel electrolyte and examining their structural, optical, and electrochemical attributes. Compared to pure WO3, the Nb18W16O93-based electrochromic device exhibited a significant optical modulation of 55.1% in the visible spectrum and 31.3% in the near-infrared region. The gel-based device not only provides safety benefits over liquid electrolytes by mitigating leakage risks but also features rapid switching response times, with a coloration duration of 3.9 s and a bleaching interval of 3.6 s. Moreover, the device showcases exceptional long-term stability, retaining a ΔT of nearly 72% after 10,000 cycles.

Multifunctional electrochromic yarns for variable optical and thermal regulation

In this study, tungsten oxide and polyaniline hybrid films were deposited on the surface of stainless steel yarns by electrochemical deposition, and the electrochromic yarns with double electrochromic layer structure were formed. WO3 acts as a protective layer and binder to connect PANI nanorods, thereby improving electrochemical stability and electrochromic performance. The electrochromic yarns present five color changes in the voltage range of −0.4 V-1.1 V, the optical modulation of 59.98 %, the response time of 0.75 s, the coloration efficiency of 74.89 cm2/C, good electrochemical cycling stability (100 cycles without significant degeneration) and washing durability. At the same time, stable electrochromic behavior is still maintained in the bending state. The device based electrochromic yarns also has reversible multi-color variation, fast reaction time, and long-term stability. What's more, the device can be embroidered or woven into the fabric and designed into patterns of different colors. More color combinations can be achieved by adjusting the voltage. Finally, the fabric based on multifunction electrochromic yarns are used to study the thermal shielding performance. It can effectively block thermal radiation. These results indicate that the electrochromic yarn has promising potential for high-performance optical and thermal regulation applications. This research provides a prospective strategy for constructing multifunctional electronic devices in wearable application.

Binder-enhanced reversible photochromic films by tungsten oxide hybrid composites for advanced applications

In this study, we developed binder-enhanced reversible photochromic tungsten oxide (WO3) films for advanced applications. Expanding on previous research, we used tungsten oxide hybrid composites as the base material and incorporated various binders, specifically polyethylene glycol (PEG), polysorbate 80 (PS 80), and carboxymethyl cellulose (CMC), to evaluate their effects on reversible photochromic reactions. Our experiments demonstrated that the inclusion of CMC significantly improved the photochromic properties and exhibited the fastest reversible reactions when compared to PEG and polysorbate 80. This enhancement is attributed to the high density of hydroxyl groups and the network structure of CMC, which facilitate efficient proton transfer and oxygen permeability, both crucial for the reoxidation process in WO3. Density functional theory (DFT) calculations supported these findings by indicating that CMC has a suitable bandgap and electron mobility, which enhance charge injection and transport. Additionally, the fabricated films showed consistent and stable performance under both heat treatment and natural ambient conditions. These results underscore the potential of CMC as an effective binder for developing high-performance, reversible photochromic films suitable for applications in smart windows, displays, and optoelectronic devices.

Amorphous Hydrated Tungsten Oxides with Enhanced Pseudocapacitive Contribution for Aqueous Zinc‐Ion Electrochromic Energy Storage

AbstractTungsten oxides suffer from sluggish ion diffusion kinetics, limited ion storage capacity, and inadequate stability within the aqueous zinc ion electrolyte, thereby constraining their applicability in electrochromic energy storage devices (EESDs). Here, the amorphous hydrated tungsten oxide films with large optical modulation, fast response speed, large capacity, and high cycling stability are reported, enabled by tuning the contents of structural water and adjusting the pH value of aqueous zinc ion electrolyte. The enhancement of the electrochromic and ion storage performance is mainly due to the introduction of structural water which triggers pseudocapacitive behavior dominated by surface redox reaction, resulting in high electrochemical activity and fast electrochemical kinetics. Meanwhile, the relatively low pH value ensures the chemical stability of the hydrated tungsten oxide film, in synergy with surface redox that avoids ion trapping, leading to extraordinary cycling stability of up to 13000 cycles, marking the state‐of‐the‐art stability for tungsten oxide‐based materials in aqueous electrolyte. Based on the hydrated tungsten oxide films, high‐capacity and stable large‐size EESDs are constructed with the capability of visually monitoring energy status, recovering energy, and regulating light. This work provides a simple yet effective strategy for enhancing the performance of tungsten oxide‐based aqueous zinc ion EESDs.

The preparation of low-cost tungsten oxide films by solution-coating technique and NIR annealing for high-performance complementary electrochromic devices

Electrochromic devices can adjust their transparency by applying an electrical voltage and serve as intelligent window systems for managing incoming sunlight. In this study, we employed an environmentally friendly, large-area solution coating method to form tungsten oxide (WO3) thin films for the fabrication of electrochromic devices. We applied a WO3 precursor solution, with water as the primary solvent, onto ITO glass through blade coating and utilized near-infrared (NIR) light annealing for drying in order to rapidly optimize the film characteristics. The resulting WO3 film, combined with an ion storage layer – either sputtered NiO or blade-coated Prussian Blue (PB) - and injected with a UV-curable electrolyte, resulted in a complementary electrochromic device that exhibited good performance characteristics. For the device with NiO as the ion storage layer, the optical transmittance modulation (ΔT) can achieve 50 % at a wavelength of 680 nm, maintaining a ΔT of 45 % after 3000 coloration-bleaching cycles. For the device with PB as the ion storage layer, the ΔT achieved 64 % at 630 nm, maintaining a ΔT of 60 % after 3000 coloration-bleaching cycles. Therefore, we believe this WO3 solution coating technique combined with rapid NIR annealing technology holds promise as a low-cost and efficient method for the future production of electrochromic devices.

(Digital Presentation) The Influence of Particle Size on Electrophotocatalytic Properties of Tungsten Trioxide Photoanodes

The need for advanced wastewater treatment technologies has been highlighted owing to the widespread contamination of water sources with toxic and persistent organic chemicals. Thin films of tungsten (VI) oxide (WO3) were prepared by spin-coating and meyer rod coating nanoparticulate dispersions following a top-down approach through ball milling. The morphological properties of the layers were investigated by profilometry. The results showed that the surface area increased with the increase in milling time and for 96 hours sample it showed a nine-fold increase compared to commercial tungsten (VI) oxide powder. The electron microscopic images provided insight into the change in particle size and layer texture which comply with the morphological changes observed by profilometry. The influence of the particle size on the charge generation efficiency was investigated using photoanodes prepared from the studied suspensions. Two distinct formulations of different particle sizes were mixed in variable ratios, and we showed that multimodal coatings exhibit larger photocurrents than monomodal coatings. The main contribution of this work can be found in the economically inexpensive method of preparing thin films WO3.

Influence of Particle Size on Electrophotocatalytic Properties of Tungsten Trioxide Photoanodes

The need for advanced wastewater treatment technologies has been highlighted by the widespread contamination of water sources with toxic and persistent organic chemicals. In this work, thin films of tungsten (VI) oxide (WO3) were prepared by spin-coating and Meyer rod coating nanoparticulate dispersions following a top-down approach through ball milling. The morphological properties of the layers were investigated by profilometry. The results showed that the surface area increased with an increase in milling time for the milled mixture, and, for the sample milled for 96 h, it showed a nine-fold increase compared to the commercial tungsten (VI) oxide powder. The electron microscopic images provided insight into the change in particle size and layer texture which comply with the morphological changes observed by profilometry. The influence of the particle size on the charge generation efficiency was investigated using photoanodes prepared from the studied suspensions. Two distinct formulations of different particle sizes were mixed in variable ratios, and we showed that multimodal coatings exhibit larger photocurrents than monomodal coatings. The main contribution of this work can be found in the economically inexpensive method of preparing thin films WO3.

Amplifying Photochromic Response in Tungsten Oxide Films with Titanium Oxide and Polyvinylpyrrolidone.

Tungsten oxide (WO3) is known for its photochromic properties, making it useful for smart windows, displays, and sensors. However, its small bandgap leads to rapid recombination of electron-hole pairs, resulting in poor photochromic performance. This study aims to enhance the photochromic properties of WO3 by synthesizing hexagonal tungsten oxide via hydrothermal synthesis, which increases surface area and internal hydrates. Titanium oxide (TiO2) was adsorbed onto the tungsten oxide to inject additional charges and reduce electron-hole recombination. Additionally, polyvinylpyrrolidone (PVP) was used to improve dispersion in organic solvents, allowing for the fabrication of high-quality films using the doctor blade method. Characterization confirmed the enhanced surface area, crystal structure, and dispersion stability. Reflectance and transmittance measurements demonstrated significant improvements in photochromic properties due to the composite structure. These findings suggest that the introduction of TiO2 and PVP to tungsten oxide effectively enhances its photochromic performance, broadening its applicability in various advanced photochromic applications.

In situ carbothermal reduction of oxygen vacancies in monoclinic WO3-x film for dual-band electrochromic windows

Dual-band electrochromic windows have emerged as a promising approach to reduce building energy consumption. However, developing facile and effective method for preparing single-component dual-band electrochromic material remains a challenge. Herein, an in situ carbothermal reduction strategy was utilized to fabricate monoclinic oxygen-deficient tungsten oxide (WO3-x) for high-performance dual-band electrochromism. Polyvinylpyrrolidone (PVP–K90) underwent transformation into amorphous carbon at high temperature, serving as the reducing agent embedded in the tungsten oxide film, and in situ inducing the formation of oxygen vacancies during annealing treatment. Lastly, the amorphous carbon was gasified without weakening the transmittance of WO3-x film. The content of oxygen vacancies in WO3-x could be modulated by controlling the added amount of PVP-K90. The intrinsic generation of oxygen vacancies not only obtained a strong local surface plasmon resonance (LSPR) absorption in near-infrared (NIR) range, but also improved lithium ion (Li+) diffusion in WO3-x film. The WO3-x electrochromic film exhibited excellent dual-band electrochromic performance in optical modulation, switching time, coloring efficiency, bistability, and cycle stability. Furthermore, the WO3-x film was applied to electrochromic window to verify its available regulation in solar illumination and heat, indicating that the designed modification strategy has potential for developing a single-component dual-band electrochromic window with outstanding performance.

Effect of Si addition on epitaxial growth and gas sensing properties of tungsten oxide films

Effect of Si addition on epitaxial growth and gas sensing properties of tungsten oxide films

In-situ fabrication of tungsten oxide film pH micro-sensor and its application on the pH monitoring of Fe-Cu galvanic corrosion

Localized and interface pH values are important parameters for studying the corrosion progress and complex interface reactions. Although commercial glass pH sensors have been widely used to measure solution pH value due to their advantages of long stability and high sensitivity, they were unable to determine the interface and microregion pH value for their difficulty in miniaturization. In this work, an all-solid-state pH micro-sensor with strong adhesion strength was in-situ fabricated on diameter 15 μm tungsten ultramicroelectrode (UME) using constant current anodizing. The pH micro-sensor showed good linear response (R2 = 0.999), excellent sensitivity (with a slope of −53.8 mV/pH), quick response (<0.1 s), long lifetime (>44 days) and great anti-interference ability to most of the ions in marine (selectivity coefficients pKij > 7), such as SO42−, Cl−, NO3−, K+, Mg2+ and Fe2+. Then, the pH micro-sensor, combined with the potentiometric mode of SECM, was further employed to explore the localized pH value distribution during the galvanic corrosion of Fe-Cu couple in 0.1 M NaCl solution. To further verify the anti-interference ability of pH micro-sensor, potentiometric SECM experiment was also conducted in artificial seawater. Results showed that both acidic sites and alkalizing sites appeared on the Fe surface, while homogeneous alkalization took place overall Cu surface. This was consistent with the SVET results that anodic and cathodic areas existed simultaneously on Fe surface. Thus, it could be concluded that local corrosion occurred on Fe surface and only part of the Fe surface acted as the anodic even under galvanic effect. However, Cu acted as cathode with the homogeneously distributing cathodic current on the whole surface during the galvanic corrosion.

Effect of cerium oxide nanorods growth time on the electrochromic properties of WO3/CeO2 hybrid films

In this study, the cerium oxide nanorods (CeO2) were grown on fluorine-doped tin oxide (FTO) glass substrates by using a hydrothermal process at growth times of 4hrs, 6hrs and 12hrs and annealed at temperature 3500C. The grown samples were characterized by using Scanning electron spectroscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis spectrometer. Tungsten oxide (WO3) film was deposited, on these hydrothermally grown nanorods (NRs), by using the DC sputtering process to develop WO3/CeO2 hybrid films. From the SEM and XRD analysis, CeO2 nanorods were observed at different growth times, and crystalline structures were observed respectively. The optical transmittance decreases with the increase in synthesis time, mainly due to the increase in nanorods' thickness. The diffusion coefficient of 11.24 × 10−11 cm2/s and the cathodic peak current of −10.1 mA was observed for 12-h WO3/CeO2 films and the coloration efficiency of 12 cm2/C was observed for 4-h WO3/CeO2 hybrid film.

Improving Properties of Tungsten Oxide Films by Gamma Ray Irradiation

The deposition process and investigation of the physical properties of tungsten trioxide (WO3) thin films before and after gamma irradiation are presented in this paper. The WO3 thin films were deposited, using the pulse laser deposition technique, on glass substrates at laser energies of 600mJ and 800mJ. After deposition, the samples were gamma irradiated with Co60. The structural and optical properties of polycrystalline WO3 thin films are presented and discussed before and after 5kGy gamma irradiation at the two laser energies. X-ray diffraction spectra revealed that all the films consisted of WO3 crystallized in the triclinic form; the dislocation density and lattice strain increased with the absorbed dosage of gamma irradiation. The optical constants, the average diameter and the surface roughness of the WO3 films were calculated before and after gamma irradiation and for the two laser energies. It was found that the WO3 thin films conductivity increased by γ-irradiated and with the increase of the laser energy.

Tungsten Oxide Thin Films for Electrochromic Applications: Pulse Width‐Controlled Deposition by High‐Power Impulse Magnetron Sputtering

Tungsten oxide (WO3) thin films have been of prime interest among electrochromic materials because of their chemical stability, strong adherence to various substrates, and high coloration efficiency. High‐power impulse magnetron sputtering (HiPIMS) holds great potential in fabricating durable WO3‐based electrochromic layers. However, the tungsten target–plasma interactions in reactive‐HiPIMS deposition of WO3 and their role in modulating the electrochromic function of the resulting WO3 coatings are yet to be understood. Herein, by controlling the HiPIMS pulse length, the stoichiometry of tungsten oxide structures can be tuned to optimize the transparency and electrochromic function of the coatings. X‐ray photoelectron spectroscopy data shows that at pulse lengths shorter than 85 μs, the concentration of suboxide compounds is less than that of tungsten trioxide, while for pulse lengths longer than 100 μs, this balance is reversed. The average optical transparency of the coatings in the range of visible light is higher than 80%. The optical transmittance modulation (ΔT) of 38.1, 36.2, and 34.3% and coloration efficiency of 41.3, 38.4, and 35.9 cm2 C−1 are measured for the WOx samples deposited at pulse lengths of 70, 85, and 100 μs, respectively. Tuning the HiPIMS pulse characteristics is a simple strategy to deposit tungsten oxide films with tuned electrochromic properties for an array of applications, from smart windows to wearable displays.

Memory-Enabled Quantum-Dot Light-Emitting Diodes.

Quantum-dot light-emitting diodes (QLEDs) with memory capability can provide multifunctional integration properties in on-chip and intelligent electronic applications. Herein, memory properties are achieved by inserting a tungsten oxide (WOx) film between the ZnO electron-transporting layer and cathode. Pentavalent tungsten ions (W5+) in this nonstoichiometric WOx film can be oxidized to W6+ by storing holes, inducing significant electrons in the adjacent ZnO layer. Hole storage in the WOx layer suppresses electron injection into the quantum dot emissive layer, hence reducing electroluminescence intensity on the onset stage of the QLEDs. This operation-history correlation for the electroluminescence intensity means a memory behavior for the QLEDs. Furthermore, the power efficiency of the devices is greatly improved after inserting the WOx layer due to electrical field-dependent self-adaptive electron injection into the quantum dots (QDs). We anticipate this type of QLEDs have potential applications in on-chip integration applications, such as the optical computing field and storage.

The Counterbalancing Role of Oxygen Vacancy between the Electrochromic Properties and the Trapping Effect Passivation for Amorphous Tungsten Oxide Films

Defect engineering of electrode materials is considered highly effective in regulating their performance, among which oxygen vacancies play a vital role. Thereupon, comprehensively understanding effects of oxygen vacancy in electrochemical processes of transition metal oxides stays hot and controversial, representatively for amorphous tungsten oxide films and their electrochromic (EC) behaviors. Upon long‐term cycling, amorphous tungsten oxide suffers from the universal trapping effect governed by the intrinsic host microstructure and transport kinetics of the inserted ions, implying that manipulating oxygen vacancies could be a potential solution to the ion‐trapping problem. Hence, systematic work is urgent for not only tackling the trapping effect but also understanding the effect of oxygen vacancies on EC behaviors. Herein, the concentration of oxygen vacancies in the amorphous tungsten oxide films is modulated over a wide range. In combination with comprehensive experiments and first‐principles calculations, the presence of oxygen vacancy is detrimental to the EC properties, but it greatly attenuates the trapping effect. Excellent cyclic stability is achieved with a 100% optical modulation rate and charge capacity retention after 5000 cyclic voltammetry cycles. This study elucidates understanding of oxygen vacancy engineering in transition metal oxides, particularly regarding trapping effect passivation.

(Invited) Application of Metal Oxide Active Supports for Enhancement of Electrocatalytic Reduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of catalytic sites (metal and metal oxide nanostructures, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential deposition) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and functionalize metal (e.g. copper) nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal (e.g. Cu, Fe, Ag) centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of the above mentioned catalytic metal nanocenters thus affecting their chemisorptive and catalytic properties. Metal oxide cocatalysts can generate –OH groups at low potentials that induce proton mobility at the photo(electro)chemical interface.Our research interests concern development of systems for the electrocatalytic reduction of carbon dioxide not only in neutral but also in acid media. For example, nanosized Cu or Fe catalytic centers immobilized within ultra-thin films of tungsten oxide or mixed ZrO2-WO3 films have been considered and demonstrated to exhibit synergism during CO2-reduction. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide (CO) type intermediates leading to their protonation or hydrogenation. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities relative to the competitive hydrogen evolution. Among other important issues is the ability of certain metal oxides (e.g., WO3) to affect hydrogen via intra-structural sorption of hydrogen molecules or atoms.