Tungsten oxide nanometer array electrochromic film is a WO3 nano array electrochromic film with nano cluster array morphology, which has the advantages of fast response speed, good cycle performance and large optical modulation range in the visible and infrared bands.

Yellow tungsten oxide can be used to produce electrochromic film. And the prepared thin film can be used in smart windows, including building smart windows and automotive smart windows, providing solutions for building energy efficiency. The following describes a method for preparing a yellow tungsten oxide nano array electrochromic film, comprising the following steps:

Nano tungsten trioxide can be used to prepare electrochromic film. WO3 is the most studied inorganic electrochromic material, which has the advantages of pure color, stable chemical properties and strong adhesion to the substrate. However, the conventional WO3 also has the disadvantages of slow transition speed, low coloring efficiency, single color change and short cycle life.

Tungsten trioxide film has nano-clusters, nano-trees or nanowire arrays. Among them, the tungsten trioxide nanometer array electrochromic film has the advantages of large spectral adjustment range, fast response speed and long cycle life. And such thin film can be prepared by the following method.

Amorphous tungsten trioxide thin film can form larger structural voids than crystalline tungsten trioxide film with quadrangular tunnels as amorphous WO3 has irregular network structure such as pentagonal tunnels and hexagonal tunnels in addition to quadrilateral tunnels.

Compared with the tungsten oxide film, the density of the Li doping tungsten oxide film is greatly improved. From the SEM image, it can be seen that the defects on the surface of the film are reduced and the holes are almost eliminated. Some experts used a scanning electron microscope to magnify 5.5K times and then test the surface condition of several film samples, as shown in the following figure, wherein (a) is a cross-sectional view of (d).

Li doped tungsten oxide electrochromic film can be prepared using lithium perchlorate as a lithium source by sol-gel method. Experts studied the changes in the properties of tungsten trioxide films after Li doping and discussed the doping amount.

Compared with the WO3 film, the performance of the lithium doped tungsten trioxide film is improved - the film becomes dense and smooth, the charge surface density increases, and the difference in light absorption before and after discoloration can reach 53%.

Compared with the tungsten trioxide film, the structure and color change response of the Li doping tungsten trioxide film has greatly improved.

Some experts have observed the surface morphology of Ta doping tungsten trioxide electrochromic film. The SEM micrographs are shown as below. Curve (a), (b), (c), (d), (e), (f), (g) are WO3 films which are undoped with 5% Ta, 10% Ta, 15% Ta, 25% Ta, and 35% Ta, respectively.