Tungsten Oxide Electrochromic Thin Film

Electrochromic film materials include various organic and inorganic compounds, of which the most studied is tungsten oxide, the main methods of preparation include vacuum thermal evaporation, electron beam evaporation, sputtering, vapor deposition, electrodeposition and sol - gel method. Electrochromic film a certain temperature heat treatment can improve their adhesion and cycle life, but the high temperature heat treatment tends to affect the magnitude of the response time and color film. General physical preparation methods require high temperature heat treatment, such as electron beam evaporation method needs a heat treatment 500e, 350e thermal evaporation requiredRF sputtering need 200 ~ 300e. These methods are often due to expensive equipment, technical complexity and demanding process conditions and subject to certain restrictions; the chemical preparation of the sol - gel method is a simple equipment, low temperature deposition uniformity and easy preparation method for preparing a large area, but usually 100e need more heat. Alkoxide method as required 250e of heat treatment, ion exchange need 150e, halogenated oxidation need 120e. 

80e heat treatment method has been reported, and in a soft deformable polyethylene terephthalate (PET) Preparation of the electrochromic thin film on the substrate so as to cover any irregularities in the surface shape of the object, but the film thus prepared The cycle life of only dozens of times, can not meet the actual needs. Sodium tungstate as raw material, ion exchange acid solution, ethanol, and polyvinyl alcohol (PVA) as an additive, by sol - gel prepared by the superior performance of the tungsten oxide electrochromic films. This film just 75e of the heat treatment temperature, the driving voltage of -1 ~ + 1V, fully colored and fade time of only a few seconds, coloring in aqueous solution - fading cycles up to 600 times, the color can be kept after coloring number of days.

The resulting film is colorless and transparent, colored blue after uniform color. At 300 ~ 900nm wavelength, variation in the film of the colored state and the faded state transmittance. When fading state, the transmittance in the visible and near-infrared region are more than 93%, but in the near-ultraviolet region due to the absorption of the matrix glass, so that a decrease in transmittance. When the colored state, in the region of 600nm or more has a good absorption, transmittance of 21% or less, which is displayed with its appearance coincides blue. Transmittance in the colored state of 600nm or less significantly increased, but the colored state and the faded state at 500nm transmittance difference also more than 50%. Test results show that the film color changed significantly, having good light controllability.