Excellent Electrochromic 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.

Exploring electrochromic performance via layered deposition of tungsten oxide on niobium oxide composite electrode

Previous studies examined the incorporation of several transition metal oxides into niobium oxide (Nb2O5) to enhance the electrochromic (EC) performance. The objective was to improve the durability, color neutrality, coloring efficiency, and optical characteristics because individual metal oxides often exhibit limits that might affect overall functioning. Therefore, an innovative approach, integrating mixed metal oxides, emerges. This novel approach addresses these challenges and unlocks new possibilities to enhance EC efficiency. This paper introduces a new method for synthesizing niobium oxide/tungsten oxide (Nb2O5/WO3) bilayer composite materials using a combination of facile hydrothermal synthesis with electrodeposition. The electrochromic, structural, morphological, and optical characteristics of Nb2O5 thin films were enhanced by conducting thorough investigations into different electrodeposition cycles of WO3. X-ray diffraction confirmed the amorphous nature of WO3 in combination with the crystalline orthorhombic Nb2O5 structure. Raman spectroscopy examined the vibrational modes and structural attributes in the Nb2O5/WO3 bilayer composite thin films. X-ray photoelectron spectroscopy was conducted to examine the chemical composition, elemental state, and surface characteristics. Field emission scanning electron microscopy was used to examine the impact of different WO3 electrodeposition cycles on the morphology of Nb2O5 thin films, revealing the formation of porous, clumped, and dense nanogranules on the film surface. EC investigations highlight the superior performance of the NW-20 thin film, showing efficient Li+ accommodation. The optimized NW-20 sample exhibits excellent EC performance, including high optical modulation (81.48 %), good reversibility (98.11 %), and high coloration efficiency (115.09 cm2/C) with long-term cycling stability. The NW-20 electrode incorporated into a device form exhibited functionality on a real-world scale, delivering remarkable EC performance with substantial optical modulation (78.1 %) and excellent cycling stability. These findings expand the potential applications of Nb2O5/WO3 bilayer composite materials for EC performance.

Integrating Electrochemically Grown Nano‐Oxide and Polymer Films for Electrochromic Device: Achieving Near‐Infrared Shielding and Four‐Digit Efficiency

Electrochemically deposited thin films yield high uniformity, a property which is quite vital to in the context of electrochromic (EC) coatings and devices. Tungsten oxide and polyaniline are two such materials that show superior EC properties individually. However, when combined into a solid‐state device structure, they yield a device where the efficiency increases multifolds. This device combination, being thoroughly characterized in the domain of EC parameters such as high switching speeds, rich color contrast, and stability, is found to be an excellent complementary EC pair. The unique property of the said device is that it can reduce the transmission of wavelengths in the near‐infrared region of the electromagnetic spectrum, providing an edge over other such combinations. In addition, a four‐digit value of coloration efficiency makes this device stand out in the family of its contemporaries. Overall, the hybrid nature of the device prompts it to be an excellent combination indicating its high performance in terms of increased endurance and heat isolation capacity.

Bifunctional D-A type conjugated polymer based on triarylamine-containing oxazole[5,4-d]oxazole/thiazolo[5,4-d]thiazole exhibiting electrofluorochromism and reversible electrochromism

Bredereck oxazole synthesis was utilized to create a series of novel D-A polymers based on the triphenylamine (TPA) derivative, 4,4′-Diformyltriphenylamine (DPA), 4,4′-((4-bromophenyl)azanediyl)dibenzaldehyde (BPA), and oxamide/dithiooxamide. The obtained novel polymers exhibited impressive solution processabilities and excellent thermal stabilities. In the entire processes of electrochemical oxidation, these polymer films exhibited excellent electrochromic (EC) performances, high optical contrasts (49.6–52.8 %), high coloration efficiencies (362–451 cm2·C−1), and excellent cycling stabilities (18.6–33.9 % decay) with a cycle time of 20 s. By applying voltage, electrofluorochromic (EFC) performance can also be adjusted. Furthermore, these polymers showed fluorescence (PL) in solvents and solvatochromic effects in absorption. The outcome was indicative of the addition of oxazole[5,4-d]oxazoles (OzOz) and thiazolo[5,4-d]thiazoles (TzTz), whose highly conjugate rigid planar structures can significantly increase molecule stabilities and minimizing volume shrinking during charge transfer. In addition, due to introducing bromine atoms, the p-π conjugations enhanced the conjugation degrees of the molecules, which facilitated the electron transfers. Experimental results show that these improvement schemes will pave a way for obtaining multi-function optoelectronic devices with long-term cyclic stabilities.

Bifunctionalized polyamides based on quinoxaline structure for durable electrochromic display and memory storage

With the aim to obtain multifunctional durable electrochromic (EC) devices, we propose an effective strategy by introducing weak electron acceptor segment with suitable bandgap and oxidation potential. A series of quinoxaline-based units polyamides (PAs) (denoted as T2BPA-CA, T2BPA-OA, T2BPA-TP, and T2BPA-SA) were prepared from a novel donor–acceptor-donor (D-A-D) type diamine with weak electron acceptor quinoxaline and connected with two methoxyl-substituted donor triphenylamine, 10,13-bis[4-aminophenyl (4-methoxyphenyl) amino]-dibenzo[a,c]phenazine, and four dicarboxylic acids, which are high soluble in various organic solvents and exhibit excellent thermostability. Furthermore, the T2BPA-SA thin film exhibits excellent EC performance with outstanding optical contrast (50 %), high coloration efficiency (230 cm2 C−1) and impressive cycle stability (optical contrast remains 80 % over 1400 cycles) in the NIR range. Meanwhile, all of these PAs are served as memristors and exhibit typical nonvolatile ternary memory, realizing an accessible threshold voltage of −0.65 V, a retention time of more than104 s and high current switch ratio (103.52:102.43:1). Overall, this work implies the great potential of these PAs in EC displays and memory storage devices.

Homogeneous and Nanogranular Prussian Blue to Enable Long-Term-Stable Electrochromic Devices.

The increasing demand for the state-of-the-art electrochromic devices has received great interest in synthesizing Prussian blue (PB) nanoparticles with a uniform diameter that exhibit excellent electrochromism, electrochemistry, and cyclability. Herein, we report the controllable synthesis of sub-100 nm PB nanoparticles via the coprecipitation method. The diameter of PB nanoparticles can be modulated by adjusting the reactant concentration, the selection of a chelator, and their purification. The self-assembled nanogranular thin films, homogeneously fabricated by using optimized PB nanoparticles with an average diameter of 50 nm as building blocks via the blade coating technique enable excellent performance with a large optical modulation of 80% and a high coloration efficiency of 417.79 cm2 C-1. It is also demonstrated by in situ and ex situ observations that the nanogranular PB thin films possess outstanding structural and electrochemical reversibility. Furthermore, such nanogranular PB thin films can enjoy the enhanced long-term cycling stability of the PB-WO3 complementary electrochromic devices having a 91.4% optical contrast retention after 16,000 consecutive cycles. This work provides a newly and industrially compatible approach to producing a complementary electrochromic device with extraordinary durability for various practical applications.

Transparent-to-Brown-Black Patterned Electrochromic Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) exhibit promising electrochromic (EC) performance owing to their porous structure, regular channel, and tunable component characteristics. However, few reports focus on MOF materials with the EC performance of a transparent to brown-black (neutral colored state) change that is more suitable for smart windows. In this work, we proposed a strategy for synthesizing MOF (named Ni-BPY) EC materials and corresponding films fabricated via a low-cost electrostatic spray deposition technique. The obtained film exhibits excellent EC performance with a neutral color change from transparent to brown-black, a large optical modulation of 70% at 430 nm, and a fast response within 10 s. Benefiting from good electrical and chemical stability, the Ni-BPY film can be cycled over 500 times. Notably, the Ni-BPY MOF film also delivers a stepwise-controlled process during the bleached state due to its porous characteristics. In addition, the unique color variation of the Ni-BPY film derives from the redox reaction of the Ni metal node between Ni2+ and Ni3+, which is verified by the in situ potential-dependent Raman and X-ray photoelectron spectroscopy (XPS) measurement. As a proof of application, the patterned Ni-BPY EC films and devices are additionally constructed to demonstrate their potential application in electronic tags and logo displays.

Niobium-Tungsten Bimetallic Oxide Electrodes with High Dual-Band Electrochromic Performance Prepared by Hydrothermal Method

Dual-band electrochromic (EC) smart windows, capable of selectively regulating visible (VIS) and near-infrared (NIR) light, are one of the most attractive candidates for significantly reducing the energy consumption of buildings. Niobium-tungsten bimetallic oxides exhibit a fast ion exchange rate and high cycle stability in the electrochemical field because of various structural chemistry in the pseudobinary system Nb2O5/WO3, showing excellent dual-band EC potential. Herein, we employ a facile hydrothermal technique to synthesize Nb18W16O93 (NWO) films with low temperature and facile procedure. The obtained NWO films exhibit impressive dual-band electrochromic performances, including high optical regulation (radiation blocking rates of 33.1% and 77.5% in the VIS and NIR band) and short coloring/bleaching time (12 s/2.6 s at 633 nm and 6.5 s/6.1 s at 1600 nm). These results demonstrate that NWO is a high-performance dual-band EC material and provide a practical strategy to synthesize the NWO electrodes with nanorod stacking architectures in a facile and low-cost way.

Bendable & twistable oxide-polymer based hybrid electrochromic device: Flexible and multi-wavelength color modulation

Flexible electrochromic (EC) technology has made huge progress in electronic industry for their applications in flexible displays, e-papers, e-curtains etc. The performance of device is the main concern while fabricating a flexible electrochromic device. In this paper, a solid state flexible electrochromic device (flex-ECD) has been demonstrated by combining the excellent EC performance of organic polymer and excellent stability of metal oxides which exhibits fast color switching and excellent stability after bending and twisting it for several times. For the fabrication of device, first Co3O4 and WO3 powders have been synthesised and utilised as dopants in the two electrochromic active materials namely polythiophene (P3HT) and ethyl viologen (EV), respectively. Due to the doping of these nanomaterials the performance of the flex-ECD has been enhanced as measured in terms of coloration efficiency, switching time and stability. Additionally, the device shows color switching in their different wavelength regions between visible and NIR. The flex-ECD shows high stability with a few seconds of switching time and high coloration efficiency of 420 cm2/C. The device was first bent and subsequently twisted for several more times. After bending, the performance has been checked, exhibiting minimal change in switching time at 515 nm and 665 nm without compromising the coloration efficiency much. The device shows excellent stability after bending and twisting moments making it a good design for future wearable electronics.

Oligo (ethylene glycol) side chain engineering: An efficient way for boosting the development of green-solvent processable electrochromic devices

As an effective strategy for improving the performance of optoelectronic polymers, oligo (ethylene glycol) (OEG) side chain engineering has been widely used in optoelectronic materials field. However, the research of its impact on electrochromic (EC) polymers started to be explored in recent years. In this work, the excellent EC properties of the star polymer PTQ-10 (poly[(thiophene)-alt-(6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline)]) were first investigated and proved. Subsequently, a series of novel PTQ-type polymers with OEG side chains (PTQ-OEGs) were successfully synthesized and studied. Compared with PTQ-10, the introduction of OEG side chains can significantly shorten the coloring time (∼82.2 %) and improve the coloration efficiency (∼37.3 %). Notably, the solubility of PTQ-OEGs is greatly enhanced in ideal green solvents (ethanol) via introducing the OEG side chains. Therefore, the EC active layers of PTQ-BTEG can be simply fabricated by its ethanol solution. Based on this feature, an all-green EC device PTQ-BTEG@ECD-3 (from material processing to device preparation) was prepared successfully, which exhibited fast coloring (6.25 s) and bleaching (0.85 s) as well as high coloration efficiency (622.57 cm2 C−1). Hence, we not only reported the relationship between OEGs and EC polymers thoroughly, but also proved the OEG engineering is a practical approach to promote the development of all-green EC devices in the near future.

88‐4: Late‐News Paper: Electrochromic Devices with Metallo‐Supramolecular Polymers

Metallo‐supramolecular polymers (MSPs) were synthesized by 1:1 complexation of metal ions with multitopic organic ligands. MSPs showed excellent electrochromic (EC) properties, which were triggered by the electrochemical redox of the metal ions. In addition, the color of MSPs was tunable by changing the combination of the metal and the ligand. EC devices (ECDs) with MSPs were successfully fabricated by the combination with an MSP layer, an electrolyte layer, and a counter material layer. In this presentation, recent progress on ECDs with MSPs will be introduced.

Dual Redox-Responsive Os/Ru-Based Alternated Heterobimetallic Supramolecular Polymer as a Multicolor Electrochromic Material for Camouflage Devices

Materials that show multicolor electrochromism, including yellow and green, are highly applicable for various smart applications including voltage-tunable multicolor electrochromic (EC) displays and camouflage devices. Although metallo-supramolecular polymers (MSPs) show excellent EC color variability with attractive EC properties, the generation of multicolor electrochromism from one MSP is still difficult. Moreover, an MSP-based multicolor EC device (ECD) that also exhibits yellow and green EC colors has not been realized to date. Herein, we report the synthesis of a dual redox-responsive heterobimetallic supramolecular polymer (PolyOsRu) as a multicolor EC material that can also be used for camouflage applications. PolyOsRu was synthesized by stepwise homoleptic complexation of Os2+ and Ru2+ ions using a 2,2′:6′,2″-terpyridine-based ligand and characterized by various analytical and spectroscopic techniques. The polymer shows broad absorption (312–671 nm) and well-separated dual redox potentials of Os2+/Os3+ (E1/2 = 0.59 V) and Ru2+/Ru3+ (E1/2 = 0.93 V) pairs. A thin film of PolyOsRu on ITO displays reversible multicolor (brown–red ↔ yellow ↔ green) electrochromism with a maximum optical contrast of ∼58%, fast EC color switching (<1 s), a good coloration efficiency of 404.39 cm2/C, and a more than 2400 EC cycling stability. Finally, the fabrication of a solid-state ECD and a prototype EC camouflage display with the polymer film is demonstrated to represent its potentiality as a multicolor EC material for display and camouflage applications.

Fast‐Switching Speed and Ultralong Lifespan Au/Prussian Blue Electrochromic Film for Iris Devices Applications

AbstractPrussian Blue (PB) is an excellent electrochromic (EC) material, possessing many praiseworthy advantages such as proper redox potential, large transmittance, environmental benignity, neutral colored state, and low cost. However, the co‐influence of weak interaction force and low electrical conductivity results in poor cyclic stability and slow switching speed. In this work, the novel Pt/Au and Au/PB films are prepared by electrodeposition to improve the EC properties of PB. The introduction of Au and Pt nanoparticles not only enhances the conductivity and inhibits polarization, but also increases the contact area and alleviates the stress and strain caused by volume expansion during ion insertion/extraction. Furthermore, the Pt/PB and Au/PB heterojunction with a strong inner electronic field promote the separation of electrons and holes and quicken charge transfer. In consideration of the better electrical conductivity, higher transmittance and strong local plasma resonance effect of Au nanoparticles, the Au/PB film shows ultrastable EC cyclic stability (96.4% after 2000), fast coloration/bleaching switching time (1.36/2.32 s), small charge transfer resistance (38.2 Ω), and high coloration efficiency (131.3 cm2 C−1). In addition, the EC iris devices are designed and assembled using Au/PB film as an EC layer to confirm the feasibility of the material in digital cameras and mobile phones.

Electrochromic Displays via the Room-Temperature Electrochemical Oxidation of Nickel.

Electrochromism refers to the persistent and reversible change in color by applying an electric field. The phenomenon involves the insertion and extraction of electrons and ions within the active material. There is a keen interest in electrochromic (EC) materials, since they exhibit a wide range of potential applications. In recent years, transition-metal oxides have been widely investigated as EC materials due to their low power requirement, high coloration efficiency, and memory effect under an open-circuit condition. Nickel oxide (NiO), a p-type wide band gap semiconductor, exhibits attractive features such as a high color contrast ratio, good chemical stability, cost-effectiveness, and good compatibility with the cathodically coloring tungsten oxide. NiO thin films have been fabricated by various methods, but these are not cost-effective, scalable, or suitable for flexible applications. With the increasing demand for flexible and soft EC devices, it is essential to find routes to fabricate NiO thin films at lower temperatures. In this work, a NiO/Ni(OH)2-based thin EC layer on fluorine-doped tin oxide-coated glass is developed via an electroless nickel (EN) deposition route, followed by room-temperature electrochemical oxidation. The deposition time is optimized to control the film thickness. The EC performance is investigated in an aqueous alkaline electrolyte (1 M KOH) by means of cyclic voltammetry, chronoamperometry, and transmittance measurements. Both the as-deposited and annealed films, after electrochemical oxidation, exhibit excellent EC properties with an optical modulation of approximately 64% (at 550 nm) and good response times of approximately 3 s (coloration) and 14 s (bleaching). A 2 × 2 display obtained by patterning the EN deposition is also demonstrated as part of this work.

P-doped carbon quantum dot graft-functionalized amorphous WO3 for stable and flexible electrochromic energy-storage devices

The intrinsic structural instability of amorphous WO3 (a-WO3) following repeated Li ion insertion/extraction and bending hinders its application in stable and flexible electrochromic (EC) energy-storage devices. To resolve this problem, developing an elaborate heterostructure of a-WO3 is essential for high-performance flexible EC energy-storage devices. Herein, a novel structure is proposed to introduce P-doped carbon quantum dots (P-CQDs) into a-WO3 through a low-temperature process to induce robust chemical linkages with a-WO3. The functional groups of P-CQDs form strong hydrogen bonds with a-WO3 in the form of quantum dot grafts, which effectively tolerate structural deformation following long, repetitive cycling electrochemical reactions and bending. Moreover, the functional groups and graphitic carbon of P-CQDs improve the Li ion wettability and electrical conductivity, respectively, thereby enhancing the electrochemical activity and kinetics. As a result of the impacts, P-CQD graft-functionalized a-WO3 (P-CQD/a-WO3) electrodes exhibit excellent EC energy-storage performances. Furthermore, a flexible EC energy-storage device fabricated with the P-CQD/a-WO3 electrode exhibits a remarkably enhanced long-term cycle stability (transmittance retention of 87.3% after 4,000 cycles) and flexibility (transmittance retention of 84.1% and specific capacitance retention of 85.3% after 500 bending cycles). Therefore, we believe that the proposed heterostructure-inducing quantum dot graft functionalization with a-WO3 is a breakthrough in the realization of high-performance flexible EC energy-storage devices.

Robust and swiftly multicolor Zn2+-electrochromic devices based on polyaniline cathode

Multifunctional electrochromic (EC) devices are very important for the current research on smart electronic devices. Herein, we report a robust and swiftly multicolor EC energy storage device design based on polyaniline (PANI) cathode. To achieve this goal, we systematically studied the EC properties of PANI in aqueous and organic Zn 2+ electrolytes for the first time. Compared with Zn 2+ aqueous electrolyte, the PANI film measured in organic Zn 2+ electrolyte delivered a fast-switching time (τ c /τ b = 2.0/2.4 s), high optical contrast (72.2%), high coloration efficiency (205 cm C −1 ), and good cycle stability (optical contrast remains 92.7% after 10,000 cycles). The excellent EC performance could be attributed to the good wettability of the interface between organic Zn 2+ electrolyte and PANI film, which supports rapid charge transfer kinetics. The PANI cathode in the organic Zn 2+ electrolyte also provided a multicolor electrochromism (light yellow, green and dark green) along with a high specific capacitance of 26.4 mAh m −2 and 72.2% spectral modulation range at a current density of 0.1 A m −2 , excellent rate capability of 86.4% capacity retention and 81.3% spectral modulation even at an 8-fold current-density increase. The laboratory prototype device also verified the EC energy storage performance of organic Zn 2+ intercalated/deintercalated PANI, confirming that they are suitable for highly robust multicolor EC energy storage applications. • The EC properties of PANI film in aqueous and organic Zn 2+ electrolytes for the first time were systematically revealed. • The PANI film delivered a fast-switching time, high optical contrast, high coloration efficiency, and excellent cycle stability (optical contrast remains 92.7% after 10,000 cycles). • The laboratory prototype device based on PANI showed a good EC performance as well as energy storage.

Novel WO3-PEDOT core–shell inverse opal films with enhanced electrochromic performance for smart windows

Electrochromic (EC) materials have been widely studied in energy-saving smart windows due to their reversible control of optical performance under electric fields. Novel tungsten oxide-poly (3, 4-ethylenedioxythiophene) (WO3-PEDOT) core–shell inverse opal (IO) films are obtained by electrochemical polymerization of PEDOT onto WO3 IO templates. The WO3 IO templates are prepared through the electrodeposition of WO3 into the voids of a polystyrene (PS) colloidal crystal, followed by calcination to remove the polystyrene microspheres. The designed microstructure and chemical composition of the WO3-PEDOT IO films are determined by SEM, XRD, XPS and Raman spectroscopy. The WO3-PEDOT IO films exhibit promising optical contrast ([Formula: see text]52% at 600 nm and [Formula: see text]77% at 1020 nm), indicating their bifunctional potentials in both visible and near infrared (NIR) region modulation. The WO3-PEDOT IO films also show excellent EC properties of much shorter response time (6.7 s for coloring and 5.8 s for bleaching) and superior cycling stability than that of the bare WO3 IO. These results suggest that the synergistic effect between the WO3 IO core and PEDOT shell may greatly increase the electrolyte accessibility to active sites and improve the interaction between the inorganic/organic interfaces to obtain enhanced EC performance.

Versatile Photo/Electricity Responsive Properties of a Coordination Polymer Based on Extended Viologen Ligands

Responsive chromogenic materials have attracted increasing interest among researchers; however, up until now, few materials have exhibited multifunctional chromogenic properties. The coordination polymers (CPs) provide intriguing platforms to design and construct multifunctional materials. Here, a multifunctional photo/electricity responsive CP named Zn−Oxv, which is based on the “extended viologen” (ExV) ligand, was synthesized. The Zn−Oxv exhibited reversible photochromism, photomodulated fluorescence, electrochromism and electrofluorochromism. Furthermore, we prepared Zn−Oxv thin films and investigated electrochromic (EC) properties of viologen−based CPs for the first time. Zn−Oxv thin films showed excellent EC performance with a rapid switching speed (both coloring and bleaching time within 1 s), high coloration efficiency (102.9 cm2/C) and transmittance change (exceeding 40%). Notably, the Zn−Oxv is by far the fastest CP EC material based on redox−active ligands ever reported, indicating that the viologen−based CPs could open up a new field of materials for EC applications. Therefore, viologen−based CPs are attractive candidates for the design of novel multi−responsive chromogenic materials and EC materials that could promise creative applications in intelligent technology, dynamic displays and smart sensors.

Unraveling the Effect of Cation Types on Electrochromic Properties of Titanium Dioxide Nanocrystals

Electrochromic (EC) devices have been regarded as promising candidates for energy-saving smart windows, next-generation displays, and wearable electronics. Monovalent ions such as H + - and Li + -based electrolytes are the benchmark insertion ions for EC devices but have serious limitations such as high cost, instability, and difficulty to handle. Seeking multivalent electrolytes is an effective alternative way to prepare high-performance EC devices; unfortunately, the related reports are currently limited to tungsten oxide EC materials. Herein, for the first time, we investigate the EC properties driven by different valence cationic (i.e., Li + , Zn 2+ , and Al 3+ ) electrolytes in the titanium dioxide system. It is found that the initial optical modulation ranges of TiO 2 nanocrystal (NC) films in Li + , Zn 2+ , and Al 3+ electrolytes are 76.8%, 77.4%, and 77.3%, respectively. After 250 cycles, the optical contrast of these films in Zn 2+ electrolyte decreased by only 2.3%, much lower than that in benchmark Li + electrolyte of 10.1% and Al 3+ electrolyte of 59.1%. Density functional theory calculation indicates that the potential barriers of Li + , Zn 2+ , and Al 3+ in TiO 2 are 0.59, 0.55, and 0.74 eV, respectively, which makes TiO 2 NCs show good EC properties in Zn 2+ electrolytes. This work unravels the effect of different valence cations on the electrochromic properties of titanium dioxide NCs, which may provide some new directions for the development of excellent EC devices with long-term stability and durability.

Effect of laser power density on the electrochromic properties of WO3 films obtained by pulsed laser deposition

Pulsed laser deposition (PLD) was used to prepare tungsten trioxide (WO3) films on ITO substrates with a varying laser power density of 4.0–5.5 W/cm2. XPS indicated that when the laser power density decreased, the peak positions of the W 4f and O 1s orbits shifted slightly to low energy due to the difference in oxygen vacancies. As the laser power density decreased, W6+ gradually replaced the lattice position of O2−, increasing oxygen vacancies in the lattice. The transmittance modulated values (ΔT) were over 44% at 830 nm, indicating strong absorption by the WO3 thin films in the near-infrared ray. The switching time of the WO3 thin films between bleached states and coloured states decreased as the laser power density increased due to the amorphous structure, morphology, and lower oxygen deficiency at a high power density. The high ΔT and very fast switching time of tb (1.09 s) and tc (6.01 s) demonstrated the excellent electrochromic (EC) properties of the WO3 films prepared by PLD.