Method for Forming Tungsten Oxide Films

A method is disclosed for forming a tungsten oxide film on a substrate by applying an alkyl amine tungstate compound thereon and removing at least a portion of the alkyl amine tungstate compound to form a tungsten oxide film.

In a preferred embodiment, a solution of alkyl amine tungstate compound is formed in a solvent to uniformly apply the alkyl amine tungstate compound; the solvent is removed by evaporation thereby forming a deposit; the deposit is heated for a time and at a temperature sufficient to at least partially pyrolyze the alkyl amine tungstate compound.

The alkyl amine tungstate compound desirably may be selected from the group consisting of bis (di-n-octylammonium) tetratungstate, and di (n-octadecylammonium) tetratungstate. Preferably, bis (di-n-octylammonium) tetratungstate is used.

The invention also provides tungsten oxide films which include suboxides of tungsten oxides (WO3); which have an average ratio of oxygen atoms to tungsten atoms equal to or less than 3:1; which are denser than films produced from currently known MOD precursor compounds; which have a color gradient, that is, regions of different color; and wherein the regions of color are electrochromic.

A method for forming a tungsten oxide film comprising the steps of:

a) applying onto an ITO coated substrate a solution containing an alkyl amine tungstate compound dissolved in 50:50 2-propanol:xylene solvent,

b) vaporizing said 50:50 2-propanol:xylene solvent from the applied solution to produce a deposit on said ITO coated substrate composed predominately of said alkyl amine tungstate compound, and

c) heating the deposit in the presence of an oxygen containing atmosphere for a time between about 20 and 25 minutes and at a temperature between about 450° C. and 510° C. to decompose said alkyl amine tungstate compound to produce a tungsten oxide film which in a reduced state has a transmittance between 800-1200 nm which is less than 25 percent and which in an oxidized state has a transmittance between 400-1200 nm which is greater than 80 percent.

tungsten oxide

 

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