| Electrochromic(EC) materials have attracted a great deal of attentions over the past several decades. They can reversibly change their optical properties under an external voltage. Tungsten oxide(WO3) is one of the most studied EC materials due to its fairly good EC properties and high electrochemical stability. In this thesis, WO3 nanostructured and doped films are designed via liquid-phase fabrication technique(hydrothermal technique, electrodeposition and spray coating) to improve their EC performance. Besides, the spray coating technique can be easily scale-up in a lab, the EC properties of the large-scale EC devices(ECDs) were also systematically discussed.WO3?0.33H2 O nanosheet films were constructed using a crystal-seed-assisted hydrothermal method. Systematic investigations of the influence of seed layer and urea on the morphologies and structures of the as-synthesized films have been carried out. It was found that flower-like nanorod bundles were constructed on the substrate without seed layers. Under the assistance of seed layer, uniform films were formed and nanorod bundles were transformed into 2D nanosheets. And the existence of urea could introduce more Li+ ions into the WO3?0.33H2 O film during EC process.Nest-like WO3?0.33H2 O films were assembled directly on a FTO glass substrate via a facile self-seeded hydrothermal method. This method could eliminate the grain boundaries existing in the nanocrystalline base layer, which speeds up electron transport to the FTO glass and promotes electron transfer efficiency. Thus, the self-seeded grown film shows significantly improved EC performance, with high siwthcing time, optical modulation and coloration efficiency(CE). Compared with the crystal-seed-assisted grown film, the self-seeded grown film shows 27% higher modulation range calculated at ±0.5 V, the coloration time is reduced by 28%. The CE of the self-seeded grown film is 126.34 cm2C-1.Self-assembled WO3?2H2O nanosheets were synthesized via a solution route and high-performance 3D quasi-vertical nanosheet electrode was also prepared via electrodeposition technique. The electrode has high optical modulation of 65.9% and good cycling stability. The as-electrodeposited electrode was also used to assemble an ECD, which exhibits high coloration efficiency(52.6 cm2C-1) and fast switching times of 17 and 3.8 s during coloration and bleaching, respectively. More importantly, this method provides a new strategy to construct porous films and could be used in any conductive electrodes.Next, a novel, green and facile solution method was used to synthesize Mo doped WO3 nanoparticles(NPs), the NPs could be easily dispersed in deionization water and thus form a stable ink. Then, an in situ oxidization spray coating technique was utilized to assemble Mo doped WO3 NP films, thus the detrimental effects of oxygen vacancies on EC materials could be eliminated during the spray process. The spray coated Mo doped WO3 NP film shows 42.9% optical contrast at a low voltage, with 10 s coloring time and 7.5 s bleaching time.We produced ultrafine Mo doped WO3 nanowires(NWs) from nanocrystals by oriented attachment at low temperature and normal pressure. The NWs, with 3 nm diameter, also could be dispersed in DI water. Then, porous NP films could be obtained by spraying the NW ink on hot FTO glass, because the secondary growth of nanocrystals will break the NWs and thus porous NP films could be prepared due to the effect of NW networks. Besides, this method can be easily scale-up in a lab. We assembled a large scale ECD with 10×10 cm2, which opens up new possibilities for the replacement of vacuum sputtering, reduces the cost of large scale ECDs. |
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