Colouration Efficiency Research Articles

Dependence of nanowire length, diameter, and concentration on the electrochromic properties of hybrid silver nanowire network/PEDOT:PSS-based devices

Mixing silver nanowires is a relevant tool to increase the overall conductivity of hybrid electrochromic systems. Herein, the addition of silver nanowires with an average diameter of 30 nm, length of 88 um, and concentration of 3.0 mg/ml lowered the sheet resistance of PEDOT:PSS films from 280 Ω/sq to 34 Ω/sq. Further characterized for their electrochromic behavior, mixing silver nanowires with PEDOT:PSS films allowed lowering the turn-on voltage from -1.5 V to -1.1 V and reducing the switching time from 7 to 3.6 seconds. Furthermore, with the addition of silver nanowires into PEDOT:PSS, an expensive ITO transparent and environmentally impactful electrode material is no longer required. Electrochromic devices based on hybrid AgNW/PEDOT:PSS films showed higher colouration efficiency, lower sheet resistance, lower turn on voltage, and faster switching times as compared to electrochromic devices made with PEDOT:PSS films only.

Nanostructure-dependent colouration efficiency of electrochromic coatings using 0D, 1D, and 2D WO3 for smart windows

Towards the development of highly efficient electrochromic coatings, the crystallinity, morphology (e.g. size and shape) of electrochromic nanomaterials, and their charge insertion capacities play a significant role. Herein, we report the structure-dependent colouration effciency in electrochromic coatings based on the use of 0D, 1D and 2D tungsten trioxide (WO3) nanostructures. A series of WO3 with different nanostructures were prepared and used as working electrodes to fabricate electrochromic devices for smart windows applications. Facile spray coating was applied on fluorine-doped tin oxide (FTO) substrate to make ∼70 ​% transparent working electrodes to investigate their charge insertion capacities, electrochromic active surface area, and colouration efficiency. Results showed that the 2D WO3 nanoflakes displayed the highest diffusion coefficient for the intercalation of 1.52 ​× ​10 −10 ​cm2/s with an increased electrochemical active surface area of 25.10 ​mF/cm2, a large modulation of optical reflectance (42.63 ​%) with 3.79 ​s shorter response time for bleaching and a greater colouration efficiency (CE) value (89.29 ​cm2/C) at 700 ​nm compared to the CE value for 1D WO3 (of 22 ​cm2/C) and 0D WO3 (8 ​cm2/C). The outcome of this study provides a new insight and valuable contribution to design an efficient electrochromic coating by controlling and optimising the nanostructures of selective electrochromic materials.

Dynamic multicolour tuning in π-conjugated polymers towards flexible electrochromic displays

Multicolour electrochromic materials have been considered as a promising alternative to achieve dynamic full-colour tuning towards next-generation electronic display technology. However, the development of electrochromics with wide colour gamut and subtle multicolour tunability still remains challenging due to inflexible energy level structures in intrinsic active materials. Herein, the electrochromic π-conjugated polymers with rich and subtle colour tunability were designed and developed based on a fine adjustment on the energy level structures. The chromatic transition covers almost full-colour gamut, and each colour scheme has a rich variety of categories stemming from versatile hues, chromas and lightnesses. Moreover, the multicolour π-conjugated polymers also demonstrate superior overall electrochromic performance, including fast switching (∼1.0 s), high colouration efficiency (160.4 cm2 C−1@550 nm) and good reversibility (over 90 % retention after 10,000 cycles). As a proof of concept, ultrathin and flexible prototype devices are developed by utilizing the multicolour π-conjugated polymers as electrochromic active layer, exhibiting a wide colour gamut and highly saturated multicolour tunability. The design principles proposed in this work may also be applicable to diverse optoelectronic applications.

Construction of TiO2/WO3/TiO2 double heterojunction films for excellent electrochromic performance

Electrochromic devices are applied extensively to camouflages, smart windows, heat insulation layers, and automobile rearview mirrors, etc. The amorphous WO3 is a very attractive electrochromic material, whereas it suffers from degradation of optical modulation and reversibility on ion exchange owing to those deep trapped ions with irreversible reaction behavior. Herein, we designed and, by using magnetron sputtering, prepared a composite film with TiO2/WO3/TiO2 double heterojunctions, which is capable of eliminating the deep trapped ions by itself under ultraviolet light (UV) assistance. The electrochromic device based on this composite film, after being recovery by short-time UV irradiation, can maintain a high transmission modulation of 94.72% after 7000 cycles of the voltammetry measurement. This feature allows the device to maintain its initial electrochromic performance after prolonged use. Moreover, the double heterojunction structure can reduce colouring time and enormously improve the colouration efficiency (CE) of electrochromic devices. Experimental research shows that when the thickness of the bottom and upper TiO2 layer of the WO3 film was 145.5 nm and 97.0 nm, respectively, the CE of electrochromic devices reached a perfectly high value (479.3 cm2/C), being much higher than that of WO3 devices (69.5 cm2/C). Functions of the TiO2/WO3/TiO2 double heterojunction in electrochromic device were investigated by combining theoretical analysis and experiment validation, and these results provide a general framework for developing and designing superior electrochromic materials and devices.

Pd-Catalysed Direct Arylation of Distyrylbenzene: Strong Dual-state Fluorescence and Electrochromism.

Distyrylbenzenes (DSBs) are well-known for their strong multicolour fluorescence. Fluorescence tuning of DSB via further functionalization/arylation, on the other hand, is uncommon. This paper reports a Pd-catalysed direct arylation approach for introducing different aryl groups onto fluorobenzene-containing DSB moiety (7) in high yields (67-72 %). The versatile methodology allows the substitution of neutral [tolyl (1)], electron-deficient [p-formyl benzene (2), p-acetyl benzene (3), p-nitrobenzene (4)] and electron-rich [carbazole (5), triphenylamine (6)] aryl groups. The electron-deficient aryls render mono-substitution, while the electron-rich counterparts promote di-substitution. The compounds (1-6) show blue, green, and yellow fluorescence in both the solution and solid states; the fluorescence quantum yields reach >98 % and the peak maxima span from 425 to 560 nm. The mono-carbazole DSB (5) exhibit white light emission (WLM) in polar solvents (acetone, DMF, CH3CN, DMSO and NMP) with very high fluorescence quantum yields (φf) of 60-80 %. For WLM, such high efficiency (φf) is somewhat uncommon. Moreover, visible-to-NIR reversible electrochromism is demonstrated by the TPA-integrated DSB (6). The colour of 6 changes from pristine light yellow to orange, and the absorption maxima shifts from 372 to 1500 nm when a positive potential of 1.0 V vs Ag/Ag+ is applied. Moreover, the system shows high colouration efficiency in the NIR region with fast switching speeds for colouration and decolouration as fast as 0.98 s and 1.05 s.

Effect of substituents of naphthalene diimide derivatives on electrochromic behaviours observed in proto-type devices

Several triphenylamine end capped to substituted central naphthalenetetracarboxylic diimide based four donor - acceptor - donor type electro-active monomers (BRTPANDI, CNTPANDI, PHTPANDI, NPYTPANDI) were designed and developed to explore the effect of substituent on the formation of electro-polymers and subsequent the chromic effect of prepared films on the conductive surface. Initially, with the help of density functional theory (DFT) studies, it was observed that HOMO was located over triphenylamine unit, responsible electro-polymerization process upon oxidation, LUMO was residing on the central naphthalene core, and all substituents were not coplanar with naphthalene moiety. Also, the band gap energy was gradually decreased with the effect of strong electron withdrawing substituents on NDI core. In three electrode configuration, reversible multiple colour changes of brown to deep blue by applying voltage 0 to 1.1 V and also brown to deep pink with the voltage change of 0 to −2 V were impressively investigated with relatively good response times, optical contrast, switching stabilities, and coloration efficiencies. Polymer made of CNTPANDI might be switched upto 1200 cycles with the optimum colouration efficiency 560 cm2/C in the anodic process and 300 cycles for the cathodic process in a three electrodes configuration. Proto type devices made of p-CNTPANDI demonstrated the electrochromism operated at a potential range of 0 to 2.2 V. Besides, the device exhibited the EC memory in open-circuit condition with 50% retention of its coloured state until 27 min. The long EC memory as well as high colouration efficiency compared to other TPA based conjugated polymers suggested the potentiality of those polymer films as a power-efficient EC material for modern display applications.

Electrochromic Properties of Sol-Gel Deposited Electrochromic TiO2 Thin Films

Electrochromic (EC) smart windows are a type of glass window that can change from transparent to darker colour shades when a small voltage is applied. Titanium dioxide (TiO2) can be utilised as an EC material for EC smart windows. Although the TiO2 sol-gel spin-coating method is commonly used, the effect of the number of TiO2 layers was not reported. Thus, this paper investigates the effect of the number of TiO2 layers. The increasing number of TiO2 film layers demonstrated a noticeable increase in the thin films ‘anodic and cathodic diffusion coefficient, particularly with 11 TiO2 layers. Additionally, the colouration and bleaching time was revealed to have a low correlation as the number of layers increased. Nonetheless, the lower number of TiO2 layers resulted in lower colouring transmittance. Comparatively, the colouration efficiency for all films did not exhibit any significant change. Hence this study on the effect of the TiO2 layering technique can open a new pathway in understanding the EC properties of TiO2-based EC devices.

Achievement of high electrochromic performance of TiO2 thin films prepared via spray pyrolysis method, influence of annealing process

In this study, an optimised TiO2 thin film was first prepared by the traditional spray pyrolysis method on SnO2:F (FTO) coated glass substrates, and then it was annealed at 450 °C in an ambient air atmosphere for different time durations of 1, 2, and 3 h. The FESEM images, XRD diffractograms, Raman and PL spectra indicate that compared to the pristine state, the annealing process has considerably affected the morphology and improved the crystallinity and stoichiometry of the layer. The electrochromic (EC) measurements revealed that the 3h annealed sample has the highest ever reported colouration efficiency of 91.54 cm2.C−1 (approximately 30 times bigger than the related reports) and low colouration and bleaching times of 0.2 and 1.1 s, respectively.

Flexibility-driven 1D-structural preference in a bis-terpyridine-Fe(ii)-metallo-supramolecular polymer possessing potential tricolor electrochromism

We report a flexible and electron-rich N-hexyldiphenylamine-based angular ditopic terpyridine ligand that contrarily affords a 1-D linear metallosupramolecular polymer, exhibiting tricolour electrochromism with decent colouration efficiency.

Effect of metal dopants on the electrochromic performance of hydrothermally-prepared tungsten oxide materials.

Electrochromic (EC) glass has the potential to significantly improve energy efficiency in buildings by controlling the amount of light and heat that the building exchanges with its exterior. However, the development of EC materials is still hindered by key challenges such as slow switching time, low coloration efficiency, short cycling lifetime, and material degradation. Metal doping is a promising technique to enhance the performance of metal oxide-based EC materials, where adding a small amount of metal into the host material can lead to lattice distortion, a variation of oxygen vacancies, and a shorter ion transfer path during the insertion and de-insertion process. In this study, we investigated the effects of niobium, gadolinium, and erbium doping on tungsten oxide using a single-step solvothermal technique. Our results demonstrate that both insertion and de-insertion current density of a doped sample can be significantly enhanced by metal elements, with an improvement of about 5, 4 and 3.5 times for niobium, gadolinium and erbium doped tungsten oxide, respectively compared to a pure tungsten oxide sample. Moreover, the colouration efficiency increased by 16, 9 and 24% when doping with niobium, gadolinium and erbium, respectively. These findings suggest that metal doping is a promising technique for improving the performance of EC materials and can pave the way for the development of more efficient EC glass for building applications.

Enhancement of the electrochemical performance of a cathodically coloured organic electrochromic material through the formation of hydrogen bonded supramolecular polymer assembly

Herein, we have developed an H-bonded network polymer architecture with improved crystallinity and photophysical properties through a supramolecular interaction between carboxylic acid-containing perylenebisimide (PBI) cross-linker and poly(4-vinyl pyridine) (P4VP) polymer chains. The H-bonded supramolecular polymers (SMPs) are thoroughly characterized using 1 H NMR, FTIR, XRD, and AFM studies. The XRD reveals higher molecular packing, long-range ordering, and better crystallinity after supramolecular assembly formation, while AFM confirms the fibril and sphere-like nanostructures in the SMP networks with decreased diameters. The long-range ordering and nanoaggregate structures in SMP benefit the network structure for better diffusion of counter ions during the redox reaction of the PBI moieties. The electrochromic (EC) measurements of the films divulge the similar reversible EC colour change of the PBI and SMP films from pristine red to deep violet along with vis-to-NIR electrochromism between the −2 V to +1 V potential sweeping along with the significant improvement of the EC parameters in SMP films compared to pristine PBI film. The colouring time (red to deep violet) is improved by 63% (5.6 s–2.2 s), while the bleaching time (deep violet to red) is speeded up by 51% (8.4 s–4.1 s) along with the increment in colouration efficiency by 50% (52.3 cm 2 /C to 78.1 cm 2 /C). Therefore, this report is very advantageous to deliver a simple and viable strategy for the enhancement of the EC parameters of organic electrochromes through the generation of ordered H-bonded polymer network formation. • Generation of H-bonded supramolecular polymer assembly (SPA) with perylene bisimide (PBI). • PBI used as cross-linker for H-bonded SPA with poly(4-vinyl pyridine). • SPA shows fast switching and improved colouration efficiency than pristine PBI. • Durable vis-to-NIR electrochromism in PBI based SPA.

Fully organic electroactive monomers for electrochromic behaviors having high coloration efficiency and long cycle stability towards flexible Solid-State electrochromic device

• Design and synthesis of three donor–acceptor-donor type monomers and electro-polymerization. • Naphthalene diimide as acceptor core and triphenylamine Derivatives as the donor moiety. • Electrochromic behaviors of the polymer films. • Enhancement of colouration efficiency. Constructing an electrochromic material with high switching stability as well as energy-saving property is really challenging with respect to the practical application which mainly depends on the lower response time, higher switching stabilities and higher colouration efficiencies. Herein, we have reported the design and synthesis of electroactive triphenylamine end capped to central pyromellitic dianhydride, naphthalenetetracarboxylic dianhydride, perylenetetracarboxylic dianhydride based three donor - acceptor - donor type monomers which are subsequently electropolymerized on conductive glass surface to have polymers which are subsequently explored by extensive cyclic voltammetry studies. Density functional theory (DFT) studies disclose that HOMO is localized solely on triphenylamine unit which accounts for the electropolymerization process upon oxidation. Besides, TD-DFT calculations unveil the responsible electronic transitions for electrochromism in the polymers. Three polymers exhibit the reversible multiple colour changes of colourless to brown to deep blue in the anodic region by applying voltage 0 to 1 to 1.2 V and also colourless to deep pink in the cathodic region (voltage window of 0 to −2 V) with attractive response times, optical contrast, switching stabilities, and coloration efficiencies. These polymers can be switched upto 10,000 cycles with the colouration efficiency 800 cm 2 /C in the anodic process and 600 cycles for the cathodic process in a three electrodes configuration. These values, to the best of our knowledge, are not reported for triphenylamine based fully organic electrochromic material till now. Finally, Solid-state devices made of three polymers have demonstrated the electrochromism operated at a potential range of 0 to 2.5 V. Among them, the large area (5 × 5 cm 2 ) of device coated with naphthalenetetracarboxylic diimide is electrochemically stable for 4000 switching cycles, suggesting its suitability as a potential electrochromic material for next-generation flexible EC display application.

Vanadium-Substituted Dawson-Type Polyoxometalate-TiO2 Nanowire Composite Film as Advanced Cathode Material for Bifunctional Electrochromic Energy-Storage Devices.

Polyoxometalates (POMs) demonstrate potential for application in the development of integrated smart energy devices based on bifunctional electrochromic (EC) optical modulation and electrochemical energy storage. Herein, a nanocomposite thin film composed of a vanadium-substituted Dawson-type POM, i.e., K7[P2W17VO62]·18H2O, and TiO2 nanowires were constructed via the combination of hydrothermal and layer-by-layer self-assembly methods. Through scanning electron microscopy and energy-dispersive spectroscopy characterisations, it was found that the TiO2 nanowire substrate acts as a skeleton to adsorb POM nanoparticles, thereby avoiding the aggregation or stacking of POM particles. The unique three-dimensional core−shell structures of these nanocomposites with high specific surface areas increases the number of active sites during the reaction process and shortens the ion diffusion pathway, thereby improving the electrochemical activities and electrical conductivities. Compared with pure POM thin films, the composite films showed improved EC properties with a significant optical contrast (38.32% at 580 nm), a short response time (1.65 and 1.64 s for colouring and bleaching, respectively), an excellent colouration efficiency (116.5 cm2 C−1), and satisfactory energy-storage properties (volumetric capacitance = 297.1 F cm−3 at 0.2 mA cm−2). Finally, a solid-state electrochromic energy-storage (EES) device was fabricated using the composite film as the cathode. After charging, the constructed device was able to light up a single light-emitting diode for 20 s. These results highlight the promising features of POM-based EES devices and demonstrate their potential for use in a wide range of applications, such as smart windows, military camouflage, sensors, and intelligent systems.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte.

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

Realisation of Solid-State Electrochromic Devices Based on Gel Electrolyte.

Background: In the last decade, there has been much interest in the area of solid polymer electrolyte (SPE) to address the issues of electrolyte leakage and evaporation in electrochromic devices (ECD). ECD is a state-of-the-art technology having the ability to change from transparent state to opaque state under the influence of a small applied voltage for energy saving applications. Methods: In this work, tungsten oxide (WO 3) films were fabricated via the sol-gel spin-coating method. Subsequently, ECDs were assembled based on SPE and liquid polymer electrolyte (LPE), respectively using indium doped tin oxide (ITO) coated glass as conducting electrodes and WO 3 films as working electrode. Results: Cyclic voltammetry (CV) results revealed reduced ionic conductivity of conducting ions in SPE based ECD (SECD) owing to increased viscosity by addition of PMMA. However, lesser time was required for the colouration process. LPE based ECD (LECD) showed higher colouration efficiency (CE) compared to its SECD counterpart. This is attributed to its larger optical modulation. Conclusions: This work presents a comparison between the performance of LECD and SECD in terms of electrochromic (EC) and optical properties. They were analysed through CV, chronoamperometry (CA) and ultraviolet-visible (UV-Vis) spectrophotometer. Furthermore, this work provides an insight on the employment of solid-state electrolytes in ECDs in view of the persistent leakage and evaporation problems in ECD implementation.

All-solid-state proton-based tandem structures for fast-switching electrochromic devices

All-solid-state electrochromic devices can be used to create smart windows that regulate the transmittance of solar radiation by applying a voltage. However, the devices suffer from a limited ion diffusion speed, which leads to slow colouration and bleaching processes. Here we report fast-switching electrochromic devices that are based on an all-solid-state tandem structure and use protons as the diffusing species. We use tungsten trioxide (WO3) as the electrochromic material, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the solid-state proton source. This structure exhibits a low contrast ratio (that is, the difference between on and off transmittance); however, we add a solid polymeric electrolyte layer on top of PEDOT:PSS, which provides sodium ions to PEDOT:PSS and pumps protons to the WO3 layer through ion exchange. The resulting electrochromic devices exhibit high contrast ratios (more than 90% at 650 nm), fast responses (colouration to 90% in 0.7 s and bleaching to 65% in 0.9 s and 90% in 7.1 s), good colouration efficiency (109 cm2 C−1 at 670 nm) and excellent cycling stability (less than 10% degradation of contrast ratio after 3,000 cycles). We also fabricate large-area (30 × 40 cm2) and flexible devices, illustrating the scaling potential of the approach.

Flexible electrochromic devices based on tungsten oxide and Prussian blue nanoparticles for automobile applications.

Smart windows, which control the amount of light entering buildings, houses, and automobiles, are promising in terms of energy conservation and their low environmental impact. Particularly, a next-generation smart window for automobiles will require high optical modulation, along with flexibility to adapt to various intelligent designs. We have previously fabricated electrochromic devices (ECDs) by wet coating glass substrates with nanoparticles (NPs), such as water-dispersive ink containing tungsten oxide (WO3), and Prussian blue (PB), and have evaluated and confirmed the various electrochromic (EC) properties, such as optical modulation, cyclic durability, and colouration efficiency, of the ECDs. However, glass substrates are heavy and difficult to adapt by deformation to meet the demand of next-generation automobiles. In this study, we aim to prepare complementary ECDs by wet coating WO3 and PB thin films on indium tin oxide (ITO)-coated flexible polyethylene terephthalate (PET) substrates. Chromaticity and haze of ECDs were investigated in detail as evaluation indexes to verify specifications for practical use in automotive applications. Repeated switching, bending, and twisting did not degrade the ECD properties, thereby demonstrating its durability and mechanical robustness. These excellent electrochromic properties of the flexible ECDs suggest that they are promising materials for application in next-generation smart windows for automobiles.

Pseudocapacitive behaviour in sol-gel derived electrochromic titania nanostructures

Nanostructured thin films are widely investigated for application in multifunctional devices thanks to their peculiar optoelectronic properties. In this work anatase TiO2 nanoparticles (average diameter 10 nm) synthesised by a green aqueous sol-gel route are exploited to fabricate optically active electrodes for pseudocapacitive-electrochromic devices. In our approach, highly transparent and homogeneous thin films having a good electronic coupling between nanoparticles are prepared. These electrodes present a spongy-like nanostructure in which the dimension of native nanoparticles is preserved, resulting in a huge surface area. Cyclic voltammetry studies reveal that there are significant contributions to the total stored charge from both intercalation capacitance and pseudocapacitance, with a remarkable 50% of the total charge deriving from this second effect. Fast and reversible colouration occurs, with an optical modulation of ∼60% in the range of 315–1660 nm, and a colouration efficiency of 25.1 cm2 C−1 at 550 nm. This combination of pseudocapacitance and electrochromism makes the sol-gel derived titania thin films promising candidates for multifunctional ‘smart windows’.

WO3/TiO2 hierarchical nanostructures for electrochromic applications

In the present work, we report the low temperature preparation of WO3/TiO2 films via a two step process by combining chemical bath deposition and nebulized spray deposition techniques. We investigate the influence of WO3 layer on the structural, compositional, morphological and electrochemical properties of TiO2 films. The deposition of WO3 nanoplates on the TiO2 layer effectively improves the current density of the TiO2 films. The electrochemical study of the annealed WO3/TiO2 films showed a colouration efficiency of 128.3 cm2 C−1, optical modulation (ΔT) of 78%, reversibility of 77.2% and with a fast response of 6 s for colouration and bleaching, and importantly, exhibited an excellent durability for 1000 cycles. This enhancement is ascribed to the interconnected nanoplate bundles which accommodate more charges, facilitate faster charge transport and in particular, the complementarity of the WO3–TiO2 layers, result in complement between each other, thus leading to efficient electrochromic performance.