Low Cost Process for Tungsten Oxide Electrochromic Film

When applied voltage to materials, the reversible color change of materials is called electrochromic. Electrochromic materials include organic materials and inorganic materials. Inorganic materials have attracted much attention because of their good cyclic stability. Tungsten trioxide is the representative of inorganic materials.

How to fabricate large area porous electrochromic films by simple and inexpensive process is an urgent problem in the process of engineering. For this reason, some researchers have proposed a preparation method of electrochromic film with molybdenum doped tungsten oxide nanostructure by screen printing. The prepared film has porous structure and is conducive to the insertion and removal of electrolyte ions in the electrochromic process. It has the advantages of short response time and fast discoloration speed. The process is as follows:

1.Dissolve 5 g tungstic acid in 60 mL 30% hydrogen peroxide, heat the oil bath to 95 ℃, stir to get the clarification solution, add 1.44 g molybdenum oxide, 70 mL ethylene glycol and 70 mL deionized water to the clarification solution, heat the oil bath to 120 ℃, condense and reflux for 10 hours, then get nano tungsten oxide sol, and then dissociate with 10 000 rpm. When the heart rotates for 20 minutes, the supernatant is dumped and the precipitates are washed with ionic water and ethanol respectively.

2. Ethyl cellulose is dissolved in ethanol at room temperature, the mass ratio of ethyl cellulose to ethanol is 1:10, stirred to obtain a clear and transparent sol, 15 g of the obtained sol is added and 12 g of terpineol and 3 g of molybdenum are added. The tungsten oxide nanosol is rotated at 90 ℃ to evaporate the organic solvent to prepare a molybdenum doped tungsten oxide nanopaste;

2.Using detergent, deionized water, acetone and ethanol respectively for 15 minutes, drying in oven at 70 ℃, surface active treatment of ITO or FTO conductive glass with plasma instrument was carried out. The working power was 200 W and the time was 5 min. The change order of oxygen pressure was 120 Pa and 40 Pa. Pa, 90Pa, 68Pa. The Molybdenum-doped tungsten oxide nano-slurry prepared above was uniformly adhered to ITO or FTO conductive glass by scraping method. Then it was heat treated by muffle furnace. The temperature of muffle furnace was 450 ℃ and the holding time was 2h. The electrochromic properties of Molybdenum-doped tungsten oxide nanostructure were obtained by natural cooling. The film thickness is 50nm.

Molybdenum-doped tungsten oxide nanostructured electrochromic thin films prepared by screen printing are based on Molybdenum-doped tungsten oxide nanosol prepared by condensation reflux method. It is a simple and convenient method to prepare large-area electrochromic layer. After heat treatment, Molybdenum-doped tungsten oxide thin films will produce porous due to the volatilization of organic matter. Microstructure is conducive to the implantation and removal of ions in the process of discoloration. The preparation of Molybdenum-doped tungsten oxide thin films by screen printing is conducive to solving the key problems encountered in the industrialization of electrochromic smart windows, greatly reducing the production cost of enterprises, and is expected to be popularized in the engineering of electrochromic smart windows.

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