Electrochromic Nickel Tungsten Oxide Synthesis

Nickel tungsten oxide has been proved to be able to be used as an anode or ion storage layer in electrochromic devices. Nickel exists in nickel-tungsten oxide thin films in the form of positive bivalent and positive trivalent. Increasing the content of positive trivalent nickel ion is beneficial to improving the discoloration range and ion storage capacity of the thin films, thereby improving the performance of electrochromic devices.

In order to improve the electrochromic properties of the materials, the primary technical problem to be solved is to increase the content of positive trivalent nickel ions in the nickel-tungsten oxide films, which is more suitable for practical use. Therefore, some researchers have adopted magnetron sputtering to achieve this goal. The process is as follows:

1)Select nickel-tungsten alloy target and place it in the magnetron sputtering chamber, the molar percentage of nickel in target is 80%; place the substrate on the rotating table of the magnetron sputtering chamber; vacuum the magnetron sputtering chamber by 2.0 *10-4 Pa, inject argon gas to 2 Pa, adjust the power density by 2.22/cm², start-up sputtering, adjust the vacuum of the magnetron sputtering chamber by 0.4 Pa, clean up the nickel-tungsten alloy target. The time was 10 minutes.

2)Oxygen is injected into the magnetron sputtering chamber, the working pressure is adjusted to 0.4 Pa, and the power is applied to pre-sputter for 10 minutes. Among them, the volume content of oxygen in the magnetron sputtering chamber is 50%.

3)Remove the baffle, deposit nickel-tungsten oxide film on the base by magnetron sputtering, stop ventilation after the end, and obtain the nickel-tungsten oxide film. The vacuum is 0.4Pa, the power density is 2.2W/cm², and the coating time is 50min. The content data of positive trivalent nickel ion can be obtained by comparing the peak area with the peak plot of X-ray photoelectron spectroscopy. Among them, the molar ratio of positive trivalent nickel ion to nickel element is 72%.

The above process can increase the content of positive trivalent nickel ions in nickel-tungsten oxide thin films by adjusting the oxygen percentage and working pressure, thus improving the discoloration range and ion storage capacity of the films. Moreover, the method of preparing nickel-tungsten oxide thin films by magnetron sputtering is simple, the film thickness can be accurately controlled, and it is easy to realize large-scale industrial production and improve economic benefits.

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