Fabrication of WO3/TiO2 core-shell nanowire arrays: Structure design and high electrochromic performance

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.

Preparation of a TiO2/PEDOT nanorod film with enhanced electrochromic properties

The designed growth of titanium dioxide (TiO₂)/poly(3,4-ethylenedioxythiophene) (PEDOT) nanorod arrays has been achieved by the combination of hydrothermal and electrodeposition methods. Due to the use of one-dimensional (1D) TiO₂ nanorod arrays as the template of the nanocomposites (TiO₂/PEDOT), the surface area of the active materials is enlarged and the diffusion distance of the ions is shortened. The nanorod structure also contributes to increasing the length of PEDOT conjugated chains and facilitates the transfer of electrons in the conjugated chains. Consequently, the TiO₂/PEDOT film delivers a shorter response time (∼0.5 s), higher transmittance contrast (∼55.5%) and long-cycle stability compared to the pure PEDOT film. In addition, the TiO₂/PEDOT electrode is further developed to be a smart bi-functional electrochromic device exhibiting energy storage performance. We expect that this work may lead to new designs for powerful intelligent electrochromic energy storage devices.

Review on recent progress in WO3-based electrochromic films: preparation methods and performance enhancement strategies

Transition metal oxides have drawn tremendous interest due to their unique physical and chemical properties. As one of the most promising electrochromic (EC) materials, tungsten trioxide (WO₃) has attracted great attention due to its exceptional EC characteristics. This review summarizes the background and general concept of EC devices, and key criteria for evaluation of WO₃-based EC materials. Special focus is placed on preparation techniques and performance enhancement of WO₃ EC films. Specifically, four methods - nanostructuring, regulating crystallinity, fabricating hybrid films, and preparing multilayer composite structures - have been developed to enhance the EC performance of WO₃ films. Finally, we offer some important recommendations and perspectives on potential research directions for further study.

Novel High-Performance and Low-Cost Electrochromic Prussian White Film

Prussian white (PW), due to its low cost, easy synthesis, open structure, and fast ion extraction/interaction, is introduced to the electrochromic field. The PW films were successfully grown on indium tin oxide (ITO) glass by a facial hydrothermal method. Impressively, the PW film exhibits excellent electrochemical cycling stability without obvious decay over 10 000 cycles and a high coloration efficiency of 149.3 cm² C^-1. The film also provides the large optical transmittance contrast (over 70%) in a wide wavelength range of 650-800 nm. Furthermore, the PW film shows the rapid coloration and bleaching response. These results suggest that PW is a promising practical candidate of high-performance electrochromic material.

A High-Efficiency TiO2/ZnO Nano-Film with Surface Oxygen Vacancies for Dye Degradation

Photocatalytic degradation of organic pollutants in water is a highly efficient and green approach. However, the low quantum efficiency is an intractable obstacle to lower the photocatalytic efficiency of photocatalysts. Herein, the TiO₂/ZnO heterojunction thin films combined with surface oxygen vacancies (OVs) were prepared through magnetron sputtering, which was designed to drive rapid bulk and surface separation of charge carriers. The morphology and structural and compositional properties of films were investigated via different techniques such as SEM, XRD, Raman, AFM, and XPS. It has been found that by controlling the O₂/Ar ratio, the surface morphology, thickness, chemical composition, and crystal structure can be regulated, ultimately enhancing the photocatalytic performance of the TiO₂/ZnO heterostructures. In addition, the heterojunction thin film showed improved photocatalytic properties compared with the other nano-films when the outer TiO₂ layer was prepared at an O₂/Ar ratio of 10:35. It degraded 88.0% of Rhodamine B (RhB) in 90 min and 90.8% of RhB in 120 min. This was attributed to the heterojunction interface and surface OVs, which accelerated the separation of electron–hole (e–h) pairs.