Doped tungsten oxide electrochromic film can be prepared by an ion exchange method and a spin coating method. Specifically, PEO, MoWO3 doped tungstic acid sol can be prepared by ion exchange method in sol-gel technique. Then, the film is prepared by spin coating on conductive glass (ITO/glass) and conductive polyester film (ITO/PET) respectively. After heat treatment at different temperatures, organic-inorganic multi-doped nanocomposite electrochromic film can be obtained.
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Wherein, some experts have studied the effect of the addition of MoO3 on the stability of tungstic acid sol. Experts have found that under the same conditions, the tungstic acid sol without doping with MoO3 is extremely unstable, and condensation occurs in a short time (about half an hour), so that the unstable sol is not suitable for electrochromic film preparation. While the doping of MoO3 can greatly improve the stability of the tungstic acid sol. This is because MoO3 and WO3 have similarities in structure, so when doping with tungstic acid with MoO3, Mo6+ can replace part of W6+ to form stable charged polytungstic acid colloidal particles, which are adsorbed with [MoO4]^2-ion. It is precisely because of the stable double-layer structure of colloidal particles that the moderate doping of MoO3 can greatly improve the stability of tungstic acid sol. But at the same time, we also found that when the doping amount of MoO3 reaches a certain level, the stability of tungstic acid sol is reduced, which is mainly due to the excessive doping of molybdenum destroying its stable structure.
