WO2009000547A2

WO2009000547A2 - Electrochromic device with improved viologen adsorption and inks for making same

Info

Publication number: WO2009000547A2
Application number: PCT/EP2008/005276
Authority: WO
Inventors: Michael Ryan; David Corr; Nigel Leyland; Francois Pichot; Gavin Copeland
Original assignee: Ntera Limited
Priority date: 2007-06-27
Filing date: 2008-06-27
Publication date: 2008-12-31
Also published as: WO2009000547A3

Abstract

An electrochromic reflective display device and method for fabricating same. The device includes a plurality of patterned areas, redox chromophore moieties, electronic circuitry and a common electrode. The plurality of electrically discrete patterned areas includes a metal oxide having a surface area of at least 97 meters square per gram of metal oxide said metal oxide. At least 12 nmols of redox chromophore moieties per square centimeter area per micron of thickness of the metal oxide are absorbed to each of the patterned areas. The redox chromophore moieties in each patterned area vary color of absorbed light as the redox chromophore moieties in the patterned area transition from a first redox state to a second redox state. The electronic circuitry, coupled to each of the patterned areas, selectively transitions the redox chromophore moieties in each of the patterned areas between the first redox state and the second redox state.

Description

ELECTROCHROMIC DEVICE WITH IMPROVED VlOLOGEN ADSORPTION AND INKS FOR MAKING SAME

FIELD OF DISCLOSURE This application relates generally to nanochromic devices and methods for fabricating same.

BACKGROUND

Eleclrochromic devices comprising electrodes based on nanostructured conducting or semiconducting metal oxide films having surface-adsorbed electrochromic compounds are known in the art. Such electrodes are prepared by applying nanostructured conducting or semiconducting film to a conducting substrate and annealing at high temperatures, followed by chemisorption of the electrochromic compounds on the surface of the nanoparticles in the film. The metal oxide, however, has limited surface area which limits the adsorption of the electrochromic compounds onto the metal oxide. The present disclosure addresses these problems and provides for a nanochromic device having improved properties due to increase uptake of electrochromic compounds.

SUMMARY

The present disclosure provides for an electrochromic reflectiv e display device which includes a coloring electrode having a plurality of electrically discrete patterned areas, redox chromophore moieties, electronic circuitry and a common electrode. The plurality of electrically discrete patterned areas includes a metal oxide having a surface area of at least 97 meters square per gram of metal oxide where the metal oxide is disposed on a substrate. At least 12 nmols of redox chromophore moieties per micron of thickness of the metal oxide per square centimeter of substrate are absorbed onto each of the patterned areas The redox chromophore moieties in each patterned area varies the color of light it adsorbs as the redox chromophore moieties in the electrically discrete patterned area transition from a first redox state to a second redox state. Electronic circuitry, coupled to each of the patterned areas. provides charge to selectively transition the redox chromophore moieties in each of the patterned areas between the first redox state and the second redox state.

The disclosure further provides for a method for making an electrochromic device. A plurality of electrically discrete patterned areas of metal oxide are formed on a first substrate by printing a first ink on the first substrate. The first ink include a nanocryslalline. nanoporous metal oxide having a particle size ranging from 5 nm to 80 nm. an alcohol and a binder. The patterned areas are heated to a maximum temperature thai is less than 350⁰C.

After the heating step, redox chromophore moieties are deposited onto the substrate and are subsequently adsorbed to the metal oxide on each of the electrically discrete patterned areas. Electronic circuitry is then coupled to each of the electrically discrete patterned areas, for selectπ ely transitioning the redox chromophore moieties in each of the electrically discrete patterned areas between the first redox stale and the second redox state.

A common electrode layer is formed on a second substrate by silk screen printing a second ink on the substrate. The second ink includes a conductive metal oxide, an alcohol and a binder. A reflective layer is also formed on the second substrate by silk screen printing a reflective ink over the common electrode layer. The reflective ink includes a substantially reflective metal oxide, an alcohol and a binder. The conductive metal oxide layer and/or the reflective layer, supported on the substrate, are heated to a maximum temperature that is less than 350⁰C. The first substrate is sealed to the second substrate. Using an opening between the first and second substrates, the space between the two substrates is filled with an electrolyte.

The disclosure also provides for an ink suitable for silk screen printing a metal oxide film on a substrate. The ink comprises a nanocrystalline, nanoporous metal oxide having a particle size ranging from 5 nm to 80 nm, at least one alcohol and at least one binder. The ink has a viscosity sufficient to permit formation of the metal oxide layer on the substrate by silk screen printing. The disclosure further provides for an ink suitable for silk screen printing redox chromophore moieties on a substrate. The redox chromophore moieties include moieties which upon reduction from a first redox state to a second redox state produce one of the following colors: red. blue, green, purple. The disclosure provides for an ink suitable for silk screen printing a conductive film on a substrate. The ink comprises a conductive metal oxide having a particle size ranging from 5 to 100 micron, at least one alcohol and at least one binder. The ink has a viscosity sufficient to permit formation of the metal oxide layer on the substrate by silk screen printing. An ink suitable for silk screen printing a reflective film on a substrate is provided for in the present disclosure. The ink comprises a substantially reflective metal oxide, at least one alcohol and at least one binder, wherein the ink has a viscosity sufficient to permit formation of the metal oxide layer on the substrate In- silk screen printing.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. In the drawings:

Figure 1 illustrates an exemplary device of the present disclosure; Figures 2 A and 2B illustrate an exemplary electrode of the present disclosure:

Figure 3 illustrates a graph showing voltage versus color for a device of the present disclosure;

Figure 4 is a flow chart illustrating an exemplars' method of the present disclosure; Figure 5 illustrates the contrast ratio for inventive electrochromic reflective display devices compared Io the contrast ratio for a comparative electrochromic reflective display device, and Figure 6 illustrates the contrast ratio versus time for inventive electrochromic reflective display devices compared to the contrast ratio for a comparath e electrochromic reflective display device.

DESCRIPTION OF THE EMBODIMENTS Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The presenl disclosure prov ides for an electrochromic reflecthe display device including a coloring electrode, a common electrode, electrolyte and electronic circuitry. The coloring electrode contains a plurality of electrically discrete patterned areas each of which share the common electrode. The electronic circuitry is coupled to each of the patterned areas and the common electrode. The electrohle fills the space between the two panels of electrodes to provide a passage for charge transfer. One or more of the electrically discrete patterned areas area arranged to form an image, having high color contrast againsi a white background which is displayed by the device

With reference to Figure 1. an exemplary nanochromic display device is illustrated. The coloring electrode 1 10 includes a plurality of electrically discrete patterned areas 1 14a and 114b supported on a substrate 1 12. Each electrically discrete patterned area 114a and 1 14b functions as a "'mini-coloring electrode.'^" Between each patterned area is a line 117 of bare substrate material. The width of the line ranges from 10 to 120 microns. Each patterned area 1 14a and 1 14b has an associated layer of electrically conducting material 1 13 and a layer of elecirochromic material 1 15a and 1 15b. The layer of conducting material 1 13 is placed between the substrate 1 12 and the elecirochromic material 1 15a and 1 15b. In one embodiment, the electrochromic material includes a conducting or semiconducting metal oxide having intrinsic electrochromic properties such as WOj. MoQ? V₂O5 and N₂O₅. In another embodiment, the electrochromic material ] 15a and 1 15b includes a redox chromophore-metal oxide complex. Electronic circuitry (not shown) connects each electrically discrete patterned area to the common electrode 150. The common electrode 150 includes a substrate 152 coated with one or more layers of conducting metal oxides 154 and 156 and a reflective material 158.

Substrates 1 12 and 152 are formed from transparent glass, transparent ceramic or transparent plastic materials. Representative transparent plastic materials include Poly( ethylene lereph thai ate). Polyfethernitrile), Poly propylene. Poly (ethersulfone), Ultrahigh MW Polyethylene, Polyethylene. Poly(acrylonitrile). The substrates 112 and 152 are rendered electrically conducting by applying an electrically conducting material 1 13 and 154 to the substrate surface. For substrate 152. the electronical Iy conducting material is applied to the entire substrate surface. For substrate 1 12. the electronically conducting material 113 is applied to the entire substrate surface and then etched using standard wet- etching techniques to form the electrically discrete patterned areas 1 14a and 1 14b with lines 1 17 of bare substrate separating each patterned area 1 14a and 1 14b. In certain embodiments, the electrically conducting coating preferably comprises a doped metal oxide. In one embodiment, the electrically conducting metal oxide includes tin doped indium oxide. In another embodiment, the electrically conducting metal oxide includes fluorine doped tin oxide. In yet another embodiment, the electrically conducting metal oxide includes antimony doped tinoxide. In still another embodiment, when the intrinsic sheet resistance of substrates 1 12 or 152 is less than 10₇(K)O ohms per square, (he application of an electrically conducting coating is not required.

In one embodiment, each electrically discrete patterned area 1 14a and 1 14b includes a layer of an electrochromic material 1 15a and 1 15b comprising a redox chromophore moiety 1 18a and 1 18b physically adsorbed or chemically adsorbed to a layer of metal oxide 116. In one embodiment, the metal oxide layer 1 16 has a TiIm thickness of 0.5-10 microns. In another embodiment, the metal oxide layer 116 has a film thickness of 1-7 microns.

The layer of metal oxide 1 16 includes a nanoporous. nanocrystalline metal oxide having high surface area and a small particle size. The surface area and panicle size are measured using nitrogen adsorption by the BET method In some embodiments, the nanoporous, nanocrystalline metal oxide has a surface area of: at least 97 πrVg of the metal oxide; at least 98 nr/g of the metal oxide; at least 99 πr/g of the metal oxide; al least 100 nvVg of the metal oxide: at least 102 m²/g of the metal oxide: at least 104 m²/g of the metal oxide: at least 106 m²/g of the metal oxide: at least 108 πr/g of the metal oxide: at least 1 10 nr/g of the metal oxide: at least 1 12 nr/g of the metal oxide; at least 1 14 m²/g of (he metal oxide: at least 1 16 m²/g of the metal oxide: al least 1 18 m²/g of the metal oxide; and at least 120 m²/g of the metal oxide. In other embodiments, the nanoporous. nanocrystalline metal oxide has a surface area of: ranging from 97 m7g to 120 m7g of the metal oxide; ranging from 100 m²/g to 120 m^2/g of the metal oxide: ranging from 100 m²/g to 110 m²/g of the meial oxide: and ranging from 105 m²/g to 1 10 m²/g of the metal oxide

In one embodiment the nanoporous. nanocrystalline metal oxide has a particle size of up to 80 nanometers. In another embodiment, the nanoporous, nanocrystalline metal oxide has a particle size of up to 50 nanometers. In yet another embodiment, the nanoporous. nanocrystalline metal oxide has a particle size of up to 30 nanometers. In one embodiment. the nanoporous, nanocrystalline metal oxide has a particle size ranging from 5 to 80 nanometers. In another embodiment, the nanoporous, nanocrystalline metal oxide has a particle size ranging from 30 to 80 nanometers. In yet another embodiment, the nanoporous, nanocrystalline metal oxide has a particle size ranging from 5 to 30 nanometers.

The nanoporous. nanocryslalline metal oxide includes conducting metal oxides or semiconducting metal oxides. The nanoporous, nanocrystalline conducting melal oxide includes wide band gap metal oxides. Representative examples include one or more of the following oxides. SnO₂ doped with F₅ CL Sb_: N. P, As Nb, V and/or B; ZnO doped with AL IrL Ga, B, F, Si. Ge, Ti_: Zr or Hf; In₂Or, doped wilh Sn; CdO; Ternary oxides ZnSnO?, ZnJn₂Os, In₄Sn₃Oi₂. GaInO? or MgIn₂O₄; TiO₂ doped with F, CL Sb_r N, P, As Nb. V and/or B: Fe₂O? doped with Sb: and Fe₂O?/Sb or SnO₂/Sb systems. The nanoporous, nanocrystalline 5 conducting semiconducting metal oxide includes oxides of one or more of the following metals: titanium, zirconium, hafnium, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, silver, zinc, strontium, iron (Fe²+ or Fe"+). nickel and a perovskite of each of the proceeding metals In one embodiment, the nanoporous. nanocrystalline metal oxide includes TiO₂. In another embodiment, the nanoporous. nanocryslalline metal oxide includes

J O indinium doped tin oxide. In yet another embodiment, the nanoporous. nanocrystalline metal oxide includes ZnO.

Redox chromophore moieties 1 18a and 1 18b. are physically adsorbed or chemically adsorbed to the layer of nanoporous, nanocrystalline metal oxide 1 16, and have at least two oxidation-reduction ("redox^") states. When voltage or current is applied to the coloring

15 electrode, the redox chromophore moieties 1 18a and 1 18b are reduced transitioning the redox chromophore from a first redox state to a second redox state. The color of light adsorbed by the redox chromophore moiety varies 118a and 1 18b between the redox chromophore moiety in the first oxidation state and the redox chromophore moiety in the second oxidation slate. In one embodiment, the redox chromophore moiety is colorless in its first oxidation state and 0 is colored in its second oxidation stale.

Examples of redox chromophore moieties which, used to form the nanoporous, nanocrystalline metal oxide-redox chromophore complex, are described in one or more of the following: U S Patent No. 6.067.184, entitled 'Εlectrochromic or Photoelectrochromic Device;" U.S. 6.301,038, entitled -Εlectrochromic System:" U.S. Patent No. 6_:870_r657, 5 entitled "Electrochromic Device:^" and US Patent Application Publication No. 200601 10638, entitled "Electrochromic Compounds,^" each of which is incorporated by reference herein in its entirety. In one embodiment, a single redox chromophore moiety is adsorbed onto the nanoporous. nanocrystalline metal oxide to form a desired color upon transiϋoning to a different redox state. In another embodiment, two or more redox chromophore moieties are adsorbed onto the nanoporous. nanocrystalline metaJ oxide to form the desired color upon transitioning to a different redox state.

In one embodiment, the redox chromophore moiety includes an attachment group such as a phosphate group, a carboxylate group, a salicylate group, a catecholate group a boranic acid group, or an organosiloxane group. Representative examples include:

In another embodiment, the redox chromophore moiety includes 1.1 ^" disubstituted- 4,4^' bipyridinium salts viologen compounds wherein the 1.1 ^" disubsliluted^^-dipyridinium cation has as substituents a phosphate anchoring group on the 1 -position of the 4.4^"- dipyridinium cation and various substilucnt groups on the 1 ^"-position of the 4.4^'- dipyridinium cation. Representative examples include: l -Phosphonoethyl-I ^"-(3- phenylpropyl)-4.4^'-bipyridinium dichloride; 1 -Phosphonoethyl-] ^"-(3-phenylpropyI)-4.4^"- bipyridinium bis-hexafluorophosphale; 1 -Phosphonoethyl- 1 ^"-(2.4.6-trimethylphenyl)-4.4'- bipyridinium dichloride; 1 -Phosphonoelhyl- 1 ^"-(2.4,6-triniethylphenyl)-4,4'-bipyridinium bis- hexafluorophosphate: l -Phosphonoethyl-r-naphthyl-4,4^?-bipyridinium dichloride; 1 - Phosphonoethyl-1 ^"-(4-c\-anonaphthy])-4.4^"-bipyridinium dichloride; 1 -Phosphonoethyl- 1 ^"-(4- methvlphenyl)-4.4^'-bipyridinium dichloride; 1 -Phosphonoethyl- 1 ^~-(4-cyanophenyl)-4.4^'- bipyridinium dichloride: I -PhosphonoelhyM ^'-(4-fiuorophenyl)-4.4^;-bipyridinium dichloride: 1 -Phosphonoethyl- 1 ^'-(4-phenoxyphenyl)-4.4^:-bipγndinium dichloride: 1 -Phosphonoethyl- 1 ^'- (4-t-butylphenyl)-4,4^"-bipyridinium dichloride: 1 -Phosphonoethyl- 1 ^"-(2.6-dimethylphenyl)- 4.4^'-bipyridinium dichloride; 1 -Phosphonoethyl -1 ^'-(3.5-dimethylphenyl)-4.4^"-bipyridinium dichloride; l -Phosphonoethyl-r-(4-benzophenone)-4₅4^τ-bip\τidinium dichloride; I -

Phosphonobenzj l-] ^"-(3-phen\ lpropyJ)-4.4'-bipyridinium dichloride: l-Phosphonobenzyl-l ^"- (3-phenylpropyi)-4.4^"-bipyridtnium bis-hexafluorophosphate; 1 -Phosphonobeirøl-l ^'-

4,4^"-bip\τidinium dichloride: 1 -Phosphonobεnzyl- 1 '-(2,4-dinilrophenyl)-4.4^"-bipyτidinium bis-he\afluorophosphale: 1-Phosphonobenzyl-l '-(4-phenoxyρhenyl)-4,4^"-bipyridinium dichloride; 1

'-(4-phenoxyphenyl)-4.4^r-bipyridinium bis- hexafluorophosphate: 1-Phosphonobenz} l-1 ^'-(4-fluorophenyl)-4,4^t-bipyridinium dichloride; l -Phosphonobenz>l-r-(4-methylphenyl)-4.4'-bipyridιnium dichloride: 1-Phosphonobenz> l- 1 ^"-(2,4.6-trimethylphenyl)-4.4'-bipyridinium dichloride; 1 -Phosphonobenzyl-1 ^"-benzyl-4.4^"- bipxridinium dichloride: 1 -Phosphonobenzxi- 1 ^!-naphthyl-4,4^"-bipyridinium dichloride: 1 - PhosphonobenzΛ l-1 ^"-phenyl-4.4'-bipyridinium dichloride; 1 -Phosphonobenz\ I-I ^"-(4- cyanophenyl)-4.4^"-bipyτidinium dichloride; 1-Phosphonobenzyl-l '-(4-benzophenone)-4.4'- bipyridinium dichloride; 1 -Phosphonobenzyl-l '-(4-cyanonaphlhyl)-4.4^*-bipyridinium dichloride: 1 -Phosphonobenz> l-1 ^"-(2.6-dimethylphenyl)-4.4^"-bipyridinium dichloride; 1- Phosphonobenz\"l-r-(3.5-dimelhylphenv"l)-4,4^'-bipyridinium dichloride: and 1- Phosphonobenzyl- 1 ^"-(2.4.6-trimethylphenyl)-4.4^"-bip>τidinium bis- trifluoromelhanesulfonimide.

Olher representative redox chromophore moieties, which are used lo form the metal oxide-redox chromophore complex, include one or more of the following:

4X- wherein Rj is selected from the following:

R₂ is selected from Ci-io alkyl. N-oxide. dimethylamino. acelonitrile. benzyl and phenyl optionally mono- or di-substituted by nitro; Rj is Ci-io alk> l and R4-R7 are each independently selected from hydrogen; Ci-10 alkyl: Ci-io alkylene; aryl or substituted aryl; halogen: nitro; and an alcohol group; X is a charge balancing ion which is selected from the group consisting of chloride, bromide, iodide. BF₄.^', PFβ^", and ClOj ^' and n=l -] 0.

In yet another embodiment, the redox chromophore moiety or a mixture of redox chromophore moieties is selected so that the electrochromic metal oxide-redox chromophore complex produces a desired color, for the patterned areas, upon transitioning from a first redox stale to a second redox stale. The colors include red. blue, green, yellow, black, purple. orange, turquoise, magenta or purple. Representative examples of redox chromophore moieties which result in a blue color upon a transition in redox state include: Bis-(2- phosphonoelhyl)-4.4^'-bip\τidiniuni dichloride. 1 - Phosphonoethyl-l^"-( Ethyl)-4.4'- bipyridinium dichloride; 1- Phosphonoelhyl-r-( N-oxide)-4,4^"-bipyridinium dichloride; 1 - Phosphonoethyl 1^"-(1 -Dimethyl amino)-4.4^"-bipyridiπium dichloride: 1- Phosphonoethyl ] ^'-( Benzyl)-4,4^"-bipyridinium dichloride; 1- Phosphonoethyl 2.4-Dinitrophenyl l '(2- phosphonoelhyl)-4.4^"-bipyridinium dichloride; 1- Phosphonoethyl l ^:-( Phenyl)-4,4^"- bipyridinium dihexafluorophosphate. Representative examples of redox chromophore moieties which result in a green color upon a transition in redox state include: l.l^'-Bis- (phosphonomelhyl 4-phenyI)-4.4^'-bipyridinium dichloride: and l .l ^"-Bis-(4-carboxy-3- hydroxphenyl)-4.4^:-bipyridinium dichloride

One or more redox chromophore moieties. 118a and 1 18b. forming the electrochromic complex, are associated with each electrically discrete patterned area 1 14a and 1 14b. In one embodiment, one or more redox chromophore moieties adsorbed to each of the patterned areas at a concentration of least 12 nmols per square centimeter area per micron of thickness of the metal oxide. In another embodiment, one or more redox chromophore moieties adsorbed to each of the patterned areas at a concentration of least 20 nmols per square centimeter area per micron of thickness of the metal oxide In yet another embodiment, one or more redox chromophore moieties adsorbed to each of the patterned areas at a concentration ranging from 12 to 20 nmols per square centimeter area per micron of thickness of the metal oxide. In still yet another embodiment, one or more redox chromophore moieties adsorbed to each of the patterned areas at a concentration ranging from 12 to 18 nmols per square centimeter area per micron of thickness of the metal oxide. The redox chromophore moieties are selected to create images having a variety of color patterns displayed by the device. In one embodiment, each patterned area 114a and 114b has the same t>pe of redox chromophore moiety 1 18a and 1 18b absorbed to the nanoporous. nanocrystalline metal oxide 1 16. In another embodimait, at least two of the patterned areas 114a and 1 14b have different types of redox chromophore moieties 1 18a and 118b absorbed to the nanoporous, nanocrystalline metal oxide 1 16. In yet another embodiment, a single patterned area 1 14a and 1 14b has a mixture of different t\pes of redox chromophore moieties 1 18a and 1 18b adsorbed to the nanoporous. nanocrystalline metal oxide 1 16.

Each patterned area 1 14a and 1 14b. of the coloring electrode 110, is coupled to electronic circuitry. The circuitry provides charge to the coloring electrode to selectively transition the redox chromophore moiety, adsorbed onto the metal oxide, from a first redox state to second redox state. Figures 2A and 2B illustrate an exemplary coloring electrode of bare substrate. Figure 2A illustrates electrically discrete patterned areas 210 separated by^¬ lines 215. Electrically conductive track lines 220 ('tracks") are positioned to run from each electrically discrete patterned area 210 to the edge of the substrate 230. The redox chromophore moieties associated with the electrically discrete patterned areas 210 are charged, via the track lines 220. using a fixed or variable applied voltage or current during the "charge time^" to move charges on the patterned areas. K is important (o note thai {he coloring of the electrically discrete patterned areas 210 appears only after a threshold charge is applied to the coloring electrode 205. In one embodiment, an electrical insulator (at times referred to as varnish as it can be transparent or colored) is applied on top of the track, to electrically insolate it from the electrolyte.

The amount of charge fed by the electronic circuitry determines the density of charge on the patterned areas vvhich in turn determines the number of redox chromophore moieties which transition from the first to the second redox state. As illustrated in Figure 3. when a patterned area has the charge represented by 310, the electronic circuitry has provided sufficient charge to transition a portion of the redox chromophore moieties from the first redox slate to the second redox state. When the patterned area has charge represented by 320, the electronic circuitry has provided sufficient charge to transition substantially all of the redox chromophore moieties from the first redox state to the second redox state so the color will appear more intense. In one embodiment, at least 0.5 milli-coulombs per square centimeter of metal oxide layer is required to transition substantially all of the redox chromophore moieties in the pattered area from the first redox state to the second redox state. Referring again lo Figure L the exemplary electrochromic reflective display device also includes a shared common electrode 150. The common electrode 150 is made up of substrate 152 coated with a layer 154 of conducting metal oxide. The conducting metal oxide has a particle size ranging from 5 to 100 nm. In one embodiment, the conducting metal oxide includes indium doped tin oxide. In another embodiment, the conducting metal oxide includes antimony doped tin oxide. A layer of a nanoporous. nanocrystalHne metal oxide 156 and a layer of reflector material 158 are applied to the conducting metal oxide layer 154. The nanoporous. nanocrystalline metal oxide 156 includes a conducting metal oxide 156. In one embodiment, the nanoporous. nanocrystalline metal oxide layer 156 includes antimony-doped tin oxide. In another embodiment, the nanoporous, nanocrystalline oxide layer 156 includes phosphorous doped tin oxide. The reflector material layer 158 includes a substantially reflecti\ e metal oxide. In one embodiment, the substantially reflective metal oxide includes rulile TiCh. In another embodiment, the substantially reflective metal oxide includes zirconium oxide. In yet another embodiment, the substantially reflective metal oxide includes silica.

An electrolyte 160 fills the space between the coloring electrode 110 and the common 5 electrode 150 to provide transfer of charge. In one embodiment, the electrolyte 160 is used in a liquid form. In another embodiment, the electrolyte 160 is used in a gel form. In yet another embodiment, the electrolyte 160 is used in a solid form.

In certain embodiments, the electrolyte 160 includes at least one electrochemical]}- inert salt in solution in a solvent. Examples of suitable salts include lithium salts, such as

J 0 lithium perchlorate (LiClOa). lithium telrafluoroborate (L1BF₄). lithium iodide (Ll). lithium hexafluorophosphate (LiPKe). lithium hexafluoroarsenate (LiAsFn), lithium styrylsulfonate (LiSS), lithium inflate (LiCFjSCb). lithium methacrylate. lithium halides other than LI, such as lithium chloride (LiCl). lithium bromide (LiBr) and the like, lithium trifluoroacetate (CF.-COOLi) and combinations thereof. Of these, LiClO₄ or combinations of LiClOj and

15 LiBFa are preferred. These sources of alkali metal ions are present in the electrolyte in a concentration of about ϋ.01 M to 1 I . OM. with a concentration of about 0.05M to 0.2M being preferred.

Suitable solvents selected from water, acetonitrile, 3-hydroxypropionitriIe. melhoxypropionitrile, 3-ethoxypropionitriIe, 2-acetylbuiyrolactone, propylene carbonate, 0 ethylene carbonate, glycerine carbonate, tetramethylene sulfone. cyanoethyl sucrose.

.gamma.-butyrolactone, 2-methylglutaronitriie_: N.N'-dimethylformamide, 3-methylsuifolane, gluiaronitriJe. 3.3'-oxydiproptonitrile, methylethyl ketone, cyclopentanone, cyclohexanone. benzoyl acetone. 4-hydroxv-4-methyl-2-pentanone, acetophenone. 2-methoxyethyl ether, trielhylene glycol dimethyl ether. 4-elhenyl-l ,3-dioxalane-2-one. 1.2-butylene carbonate, 5 glycidyl ether carbonates (such as those commercially available from Texaco Chemical Company, Austin, Tex.) and combinations thereof, preferred of which include γ- butyrol acton e, propylene carbonate. 1,2-butylene carbonate, the combination of tetramethylene sulfone and propylene carbonate and the combination of L2-butylene carbonate and propylene carbonate.

An electrochromic reflective display dev ice, of the present disclosure, exhibits improved contrast ratio compared to prior art devices as illustrated in Figures 5 and 6. The electrochromic reflective device and the prior an device were prepared using l -(2- phosphonoethyl)- 1 ^■-(2.4,6-trimethylphen\'l)-4,4 'bipyridiniumbis | bis(trifluoromethylsulfony])imide as the electrochromophore. The contrast ratio is a measure of a display device, defined as the ratio of the luminance of the brightest color (white) to that of the darkest color (black) that the system is capable of producing. The contrast ratios, show in Figures 5 and 6, were measured at an applied voltage of 650 mV as described in Accurate Contrast Raiiυ Measurements Using a Cone Mask. S1D97 Digest; pg. 823-826 (1997). In one embodiment, an electrochromic reflective display device exhibits a contrast ratio of at least 3.5:1 after 10 seconds of applied voltage. In another embodiment, an electrochromic reflective display device exhibits a contrast ratio of at least 3.7: 1 after 10 seconds of applied voltage. In yet another embodiment, an electrochromic reflective display- device exhibits a contrast ratio of at least 4.0:1 after 30 seconds of applied voltage. In still yet another embodiment, an electrochromic reflective display device exhibits a-contrast ratio of at least 4.5: 1 after 180 seconds of applied voltage. In one embodiment, an electrochromic reflective display device exhibits a contrast ratio ranging from 3:5: 1 to 4.5: 1 after 10 seconds of applied voltage. In yet another embodiment an electrochromic reflective display device exhibits a contrast ratio ranging from 4.0:1 to 5.0: 1 after 30 seconds of applied voltage. In still yet another embodiment, an electrochromic reflective display device exhibits a contrast ratio ranging from 4.0: 1 to 5.5: 1 after 180 seconds of applied voltage. The coloring electrode and the common electrode, of the present disclosure, are fabricated by printing one or more of a plurality of inks, containing metal oxides and redox chromophore moieties, onlo substrates. Each of the inks has a viscosity sufficient to permit formation a layer of metal oxide on the substrate or deposit redox chromophore moieties on the metal oxide layer when using silk screen printing techniques. The viscosity ranges from 50 mPas @ Is^'1 to 2 kPas % Is^"1. The inks include one or more of the following: nanoporous. nanocrystalline metal oxide inks, electrically conductive nanoporous,. nanocrysiaHine metal oxide inks, reflective metal oxide inks and redox chromophore moiety inks.

In one embodiment, an ink suitable for silk screen printing a nanoporous. nanocrystailine metal oxide having high surface area and small particle size, is used to deposit nanoporous. nanocrystalline metal oxide onto the substrate used to support the plurality of patterned area I^"he nanoporous. nanocrystalline metal oxide ink includes a nanocrysialline, nanoporous metal oxide, suspended in an alcohol solvent and a binder. In some embodiments, the nanoporous. nanocη, stalline metal oxide has a surface area of: at least 97 m²/g of the metal oxide; at least 98 m²/g of the metal oxide: at least 99 m²/g of the metal oxide: at least 100 m²/g of the metal oxide; at least 102 m²/g of the metal oxide: at least 104 m²/g of the metal oxide: at least 106 m²/g of the metal oxide: at least 108 πr/g of the metal oxide; at least 110 m²/g of the metal oxide: at least 1 12 πrVg of the metal oxide; at least 1 14 m²/g of the metal oxide: at least 1 16 m²/g of the metal oxide; at least 1 18 m²/g of the metal oxide; and at least 120 m²/g of the metal oxide. In other embodiments, the nanoporous. nanocrystalline metal oxide has a surface area of: ranging from 97 nr/g to 120 m²/g of the metal oxide: ranging from 100 m²/g to 120 m²/g of the metal oxide: ranging from 100 m²/g to 1 K) m²/g of the metal oxide: and ranging from 105 m²/g to 1 10 m²/g of the metal oxide. In one embodiment, the nanoporous, nanocrystalline metal oxide has a particle size of up to 80 nanometers. In another embodiment, the nanoporous. nanocrystalline metal oxide has a particle size of up to 50 nanometers. In yet another embodiment, the nanoporous, nanocrystalline metal oxide has a particle size of up to 30 nanometers. In one embodiment. the nanoporous. nanocrystalline melal oxide has a particle size ranging from 5 to 80 nanometers. In another embodiment, the nanoporous. nanocrystalline metal oxide has a particle size ranging from 30 to 80 nanometers. In yet another embodiment, the nanoporous. nanocrystalline metal oxide has a particle size ranging from 5 to 30 nanometers. In another embodiment an ink suitable for silk screen printing a conductive film is used to deposit an electrically conductive metal oxide onto the substrate used to form the common electrode. The conductive metal oxide ink includes an electrically conductive metal oxide having a particle size ranging from 5 to 100 microns, at least one alcohol and at least one binder. The conducting metal oxide includes a nanoporous. nanocryslalline metal oxide. In one embodiment, melal oxide includes antimony-doped tin oxide In another embodiment, the melal oxide includes phosphorous doped tin oxide

In yet another embodiment an ink suitable for silk screen printing a reflective film is used to deposit a reflective metal oxide onto the substrate used to form the common electrode. The reflective metal oxide ink includes a substantially reflective metal oxide, at least one alcohol and at least one binder. In one embodiment, the substantially reflective metal oxide includes rutile TiO₂. In another embodiment the substantially reflective metal oxide includes indium lin oxide. In yet another embodiment, the reflective metal oxide ink includes a plurality of non-conductive beads.

The nanoporous. nanocrystalline metal oxide ink. the conducthe melal oxide ink and the reflective melal oxide ink also include at least one binder. Representative binders include compounds such as cellulose, cellulose acetale, cellulose triacetate, ethyl cellulose, hydroxypropy] cellulose, carboxymethyl cellulose, hydroxy-propyl methyl cellulose, and hydroxyethyl methyl cellulose In one embodiment, the binder includes hydrox\propyl cellulose. The nanoporous, nanocrystalline melal oxide ink. the conductive melal oxide ink and the reflectή e melal oxide ink also include at least one alcohol. Representative alcohols include terpinol. cyclohexanol. l -pentanol. ethyleneglycol. diethyleneglycol. menthoL methanol, elhanol. 1-propanol, 2-propanol.

In still another embodiment, an ink suitable for silk screen printing one or more viologens is used to deposit a layer of one or more viologen onto the substrate used to support the plurality of patterned area. The viologen ink contains terpineol. ethanol. hydroxy-propyl cellulose, poly(ethyleneglycol). γ-butyrolactone along with the one or more redox chromophore moieties.

Figure 4 illustrates an exemplary flow chart describing the construction of a nanochromic display device, in step 410, a nanoporous, nanocrystalline metal oxide ink is printed on the patterned areas of the first substrate forming a plurality of patterned areas on the substrate. The substrate, with the nanoporous. nanocrystalline metal oxide coated patterned areas, are heated to a maximum temperature that is less than 350 ⁰C. step 420. In one embodiment, the nanoporous. nanocrystalline metal oxide coated substrate is heated to a temperature ranging from 100⁰C to 300 ⁰C. In another embodiment, the nanoporous. nanocryslalline metal oxide coated substrate is heated to a temperature ranging from 20O⁰C to 300 ⁰C. In yet another embodiment, the nanoporous. nanocrystalline metal oxide coated substrate is healed to a temperature ranging from 100⁰C to 200 ⁰C. In still yet another embodiment, the nanoporous. nanocrvstalline metal oxide coaled substrate is heated to a temperature ranging from 50⁰C to 100 ⁰C. In step 430, one or more redox chromophore moieties are deposited onto the patterned areas of the heated nanoporous, nanocryslallme metal oxide substrate. The nanoporous, nanocrystalline metal oxide in the patterned areas chemically adsorb or physically adsorb the redox chromophore moieties. In one embodiment, at least one redox chromophore containing ink is deposited on each of the patterned areas. In another embodiment, at least two of the patterned areas have different types of redox chromophore moieties deposited onto each area. In yet another embodiment a mixture of different types of redox chromophore moieties are deposited onto a single patterned area.

The deposition of the redox chromophore moieties onto the patterned areas of the metal oxide substrate is performed by a variety of techniques. In one embodiment, the deposition of the redox chromophore moieties is performed by immersing the nanoporous. nanocrystalline metal oxide coated substrate into a solution of the redox chromophore moieties.

In another embodiment, the redox chromophore ink is deposited onto the nanoporous. nanocrystalline metal oxide containing substrate using printing techniques. One embodiment of the printing technique includes silk screen printing. Another embodiment of the printing technique includes ink jet printing.

Using ink printing techniques, a coloring electrode is fabricated wherein the patterned areas of nanoporous. nanocrystalline metal oxide have one or more redox chromophore moieties adsorbed thereto. This is accomplished by selecting subsets of patterned areas where each subset is designated for printing with one or more redox chromophore inks. In one example, a first subset of patterned areas is identified for printing with a first redox chromophore. A second subset of patterned areas maybe identified for priming with a second redox chromophore. The first redox chromophore generates a first color of adsorbed light when the chromophore transitions between a first redox state to a second redox state. The second redox chromophore generates a second color of adsorbed light when the second chromophore transitions between a first redox state to a second redox state. In one embodiment, the first subset of patterned areas reflects a blue color and the second subset of patterned areas reflects a green color when the redox chromophore moieties, associated with the first subset and second subset of patterned areas, are reduced to a second redox state. In this embodiment, the first redox chromophore generates a blue color of reflected light when the chromophore has been reduced to the second redox state. The second redox chromophore generates a green color of reflected light when the chromophore is reduced to the second redox state.

Once the patterned areas have been printed with the metal oxide ink and the redox chromophore ink. electronic circuitry is coupled to each of the patterned areas, in step 440. This is accomplished by attaching an electrically conducth e material along tracks leading to each of the patterned areas. The tracks, with the electrically conductive material, follow from the patterned areas to the edge of the substrate where the tracks are connected to drivers.

In step 450. a common electrode layer is formed on a second substrate by silk screen printing a conductive metal oxide ink on the substrate. In step 460. a reflective layer is formed by silk screen printing a reflective metal oxide ink over the common electrode la> er. Step 470 illustrates one embodiment wherein the second substrate coated with the common electrode layer and the reflective layer are heated to a maximum temperature of less than 350 "C. In one such embodiment, the second substrate coated with the common electrode layer and the reflective layer are healed to a maximum temperature of: ranging from 100 ⁰C to 300 ⁰C. ranging from 200 ⁰C to 300 ⁰C. ranging from 100 ⁰C to 200 ⁰C: and ranging from 50 ⁰C to 1 (K) ⁰C In another embodiment, the second substrate coated with the common electrode layer is heated to maximum temperature that is less than 350 "C. In one such embodiment, the second substrate coated with the common electrode layer is heated to a maximum temperature of- ranging from 100 ⁰C to 300 ⁰C. ranging from 200 ⁰C to 300 ⁰C; ranging from 100 ⁰C to 200 ⁰C. and ranging from 50 ⁰C to 100 ⁰C. In yet another embodiment, the second substrate, is heated to a maximum temperature of less than 350 "C after common electrode layer is formed and again after the reflective layer is formed. In one such embodiment, the second substrate is heated at a maximum temperature of. ranging from 100 ⁰C to 300 ⁰C, ranging from 200 ⁰C to 300 ⁰C: ranging from 100 ⁰C to 200 ⁰C: and ranging from 50 ⁰C to 100 ⁰C. In step 480, the first and second substrates are then sealed together while lea\ ing an opening between the two substrates. An electrolyte is then added to the void area between sealed substrates using the opening between the first and second substrates, in step 490.

Inventive Example 1

An exemplary electrochromic reflective device and its method of preparation is illustrated in the following Example.

Coloring Electrode

A metal oxide ink was prepared using TiO₂ suspended in a solvent with a binder. The TiO₂ was used as an 18 nm colloidal solution in methanol. The solvent was Terpineol as an anhydrous mixture from Sigma- Aldrich Co. The binder was elhylcellulose A redox chromophore ink was prepared containing a redox chromophore moiety, water and acetonitrile. Representative redox chromophore moieties include one or more of the folloλving; l -Phosphonoethyl-r-(3-phenylpropyl)-4.4^"-bip\τidinium dichloride. 1- Phosphonoethyl-1 ^'-(3-phenylpropyl)-4.4^"-bipyridinium bis-trifluoromethanesulfonimide. 1 - Phosphonoethyl-1 ^■-(2.4,6-trimethylphenyl)-4.4^"-bipyridinium dichloride. 1 -Phosphonoethyl- l M2.4.64rimelhylphenyl)-4,4^*-bip\τidiniurn bis-trifluoromethanesulfonimide. 1-

Phosphonoethyl-1 ^;-(4-methylphenyl)-4.4^"-bipyridinium dichioride. 1 -PhosphonoelhyI-l ^"-(4- t-butγlphenyl)-4.4'-bipyridinium dichloride. 1 -Phosphonoethv!-] ^■-(3,5-dimethylphenyl)-4.4^"- bipyridinium dichloride, and l -Phosphonobenzγl- r-phosphonoethyl-4,4^"-bipyπdiniurn dichloride. In this example. l -(2-phosphonoeth> l)-l ^"-(2.4.6-trimeth> lphenyl)- 4,4'bipyridiniumbis |bιs(tπfluoromethylsulfonyl)imide was used.

A supporting substrate in the form of glass coaled with tin doped indium oxide (ITO) was etched according to standard wet-etching techniques.

Using silk screen printing techniques, the metal oxide ink was deposited onto the ITO coaled substrate to a thickness of 0.5 to 10 micron. The melal oxide ink was deposited over the patterned areas of the ITO coated substrate to form a plurality discrete patterned areas of metal oxide on the ITO coated substrate. The TiO₂-ITO coated substrate was then heated to a temperature 31)0 ⁰C. The surface area of the calcined TiO₂ was measured using nitrogen adsorption via the BET method. The TiO₂ was removed from the ITO coated substrate for the measurements. The surface area was determined as 109 nv/g of metal oxide

The redox chromophore ink was deposited onto the calcined TiOa-ITO coated 5 substrate for adsorption by the TiO₂. The redox chromophore-TiOi-ITO coaled substrate was dried at room temperature.

Based on electrochemical measurements, the TiOi, in the patterned areas, adsorbed 14.0 nmole redox chromophore moieties per micron of thickness of the TiO_^ per square centimeter of substrate for l-(2-phosphonoethyI)-r-(2,4.6-trimethylphenyl)- K) 4,4'bipyridiniumbis |bis(trifluoromelh\ lsulfonyl)imidej with lithium bistrifluoromethane sulfonimide as electrolyte. This value is based on the measured charge consumption to color the patterned area.

Electronic circuitry was then coupled to each of the patterned areas of the redox chromophore-Tiθ₂-ITO coated substrate. 15 Common Electrode

A conducting metal oxide ink was prepared using antimony tin oxide particles suspended in a solvent with a binder. The solvent was Terpineol as an anhydrous mixture from Sigma-Aldrich Co. and ethylcellulose was the binder.

A reflective metal oxide ink was prepared using TiOi. in the rutile form, suspended in 0 terpineol with ethylcellulose as the binder.

Using silk screen printing techniques, the Sb-SnU2 ink was deposited onto the ITO coated substrate to a thickness of 1 -30 micron. The Tiθ2-rutϋe ink was then deposited onto the Sb-SnOz-ITO coated substrate.

The TiOi-Sb-SnO₂-ITO coated substrate was then heated to a temperature 300 ⁰C. 5 A spacer in the form of glass beads was placed between the coloring electrode and the common electrode. The coloring electrode and common electrode were sealed. A lithium salt electrohle was then added to fill the void between the coloring electrode and the common electrode.

Comparative Example 1

A comparative electrochromic device is described below Coloring Electrode

The metal oxide inks, the redox chromophore ink and the reflective metal oxide ink were prepared as described in the above inventive example.

Using silk screen printing techniques, the metal oxide ink was deposited onto the [TO coated substrate to a thickness of 0.5 to 10 micron. The metal oxide ink was deposited o\ er the patterned areas of the ITO coated substrate to form a plurality discrete patterned areas of metal oxide on the ITO coated substrate. J "he '11O2-JTO coated substrate was then heated to a temperature 500 ⁰C. The surface area of the calcined TiO₂ was measured using nitrogen adsorption via the BET method. The Tiθ₂ was remov ed from the ITO coated substrate for the measurements. The surface area was determined as 95.4 m'/g of metal oxide. Redox chromophore ink was deposited onto the calcined TiOrITO coated substrate for adsorption by the T1O₂. In this example. 1 -(2-phosphonoethyl)- 1 ^"-(2.4.6- tπmethylphenyl)-4.4^~bipyridinium [bis(trifluoromethylsulfonyl)imide was used. The redox chromophore-TiO_∑-lTO coated substrate was dried at room temperature.

Based on electrochemical measurements, the Tiθ₂. in the patterned areas, adsorbed at 1 1.8 nmole redox chromophore moieties per micron of thickness of the TiO? per square centimeter of substrate.

Electronic circuitry was then coupled to each of the patterned areas of the redox chromophore-Tiθ2-ITO coated substrate. Common Electrode

Using silk screen printing techniques, lhe Sb-SnO₂ ink was deposited onto the ITO coated substrate to a thickness of 1 to 30 micron. The Tiθ₂-rutile ink was then deposited onto the Sb-Snθ2-ITO coated substrate. The Tiθ₂-Sb-SnOrfTO coated substrate was then heated to a temperature 500 ⁰C.

The coloring electrode and common electrode were sealed. A lithium electrolyte was then added to Fill the void between the coloring electrode and the common electrode.

Comparison of the surface area and uptake of redox chromophore for the inventive nanochromic device and comparative device illustrates al4 % increase in T1O₂ surface area and an 18% increase in uptake of the redox chromophore ink.

Example 2

A series of five inventive electrochromic reflective display devices were prepared as described in Example 1. A series of five comparative display devices were also prepared as in Comparative Example 1. Contrast ratios were measured at 650 mV. The contrast ratio was measured as described in Accurate Contrast Ratio Measurements Using a Cone Mask. SID97 Digest; pg. 823-826 (1997). Figure 5 illustrates the contrast ratio for the five inventive devices 510 compared to the contrast ratio 520 for the five comparative devices. The contrast ratio for the inventive devices was, on average, at least 13 % higher than the contrast ratio for the comparative devices. Figure 6 illustrates the averaged contrast ratio versus lime 610 for the inventive devices and the averaged contrast ratio versus time 620 for the comparative devices. At 5 seconds, the inventive device reached a contrast ratio of approximately 3.8 versus the comparative device which reached a contrast ratio of 3.4. Even after 180 seconds, the comparative device had still not achieved the contrast ratio the inventive device had achieved at 10 seconds. The present disclosure may be embodied in other specific forms without departing from the spirit or essential attributes of the disclosure. Accordingly, reference should be made to the appended claims, rather than the foregoing specification, as indicating Hie scope of the disclosure. Although the foregoing description is directed to the embodiments of the disclosure, it is noted lhat other variations and modification will be apparent to those skilled in the art, and may be made w ithout departing from the spirit or scope of the disclosure.

Claims

What is claimed is:

1. An electrochromic reflective display device, comprising: a coloring electrode having a plurality of electrically discrete patterned areas comprising metal oxide having a surface area of at least 97 meters square per gram of metal oxide said metal oxide being disposed on a first substrate; at least 12 nmols per square centimeter area per micron of thickness of the metal oxide of one or more redox cliromophore moieties adsorbed to each of the patterned areas; wherein the redox chromophore moieties in each patterned area vary a color of absorbed light as the redox chromophore moieties in the patterned area transition from a first redox state to a second redox state; electronic circuitry, coupled to each of the patterned areas, for selectively transitioning the redox chromophore moieties in each of the patterned areas between the first redox state and the second redox slate: and a common electrode on a second substrate.

2. The device of claim 1. wherein the electronic circuitry transitions substantially all of the redox chromophore moieties in a patterned area from the first redox state to the second redox state.

3. The device of claim 2, wherein a charge consumption of at least 0.5 milli-coulombs per square centimeter of metal oxide layer is required to transition substantially all of the redox chromophere monies in the pattered area from the first redox state to the second redox state.

4. The device of claim 3, wherein the metal oxide is selected from the group of semiconducting oxides consisting of titanium, zirconium, hafnium, chromium, molybdenum,, tungsten, vanadium, niobium, tantalum, silver, zinc, strontium, iron (Fe'+ or Fe'^'+). nickel and a perovskite.

5. The device of claim 3, wherein the metal oxide is selected from (he group of metal conducting metal oxides consisting of: (a) SnCh doped with one or more of the following: F. CI. Sb. N. P. As Nb, V and B:

(b) ZnO doped with AL In_; Ga_τ B, F. Si, Ge. Ti, Zr or Hf;

(c) In₂O? doped with Sn:

(d) CdO

(e) Ternary oxides ZnSnOs- Zn₂In₂Os, In₄SmOn, GaInO.- or MgImO₄:

(f) TiO₂ doped with one or more of the following: F_: CL Sb_; N, P, As Nb, V and B; and

(g) Fe₂O? doped with Sb: and (h) Fe₂OySb or SnO₂/Sb systems.

6. The device of claim 1 , wherein the redox chromophore moieties are selected from the group consisting of:

4X" Oi IW

4X-

wherein Ri is selected from the group consisting of:

HO(CH₂Vi- HOOC(CH₂)n- (1Ia)₂B(CU₁)Ii-

^HO\ϊ Fι (CH₂)_n / (' \ > - NH-(CH₂)-

IiO

R₂ is selected from Ci-m alkyl, N-oxide. dimethylamino. acetonilrile. benzyl and phenyl optionally mono- or di-substituted by nitro; R? is Ci-io alkyl and R4-R7 are each independently selected from hydrogen: Ci-κ_> alkyl. C _MO alkylene; aryl or substituted aryl; halogen: nitro: and an alcohol group; X is a charge balancing ion which is selected from the group consisting of chloride, bromide, iodide. BF4 ^", PF_O ^". and CIO4 ^" and n=l -10.

7. The device of claim 1 , wherein at least two of the patterned areas have different types of redox chromophore moieties adsorbed thereto, each of the different types of redox chromophore moieties varying a different color of absorbed light as the redox chromophore moieties transition between the first redox state to the second redox state.

8. The device of claim 1, wherein a single patterned area has a mixture of different t>pes of redox chromophore moieties adsorbed thereto, each of the different t>pes of redox chromophore moieties varying a different color of absorbed light as the redox chromophore moieties transition between the first redox state to the second redox state.

9. A method for making an electrochromic device, comprising: forming a plurality of electrically discrete patterned areas of metal oxide on a first substrate by printing a first ink on the first substrate; the first ink comprising: a nanocrystalline. nanoporous metal oxide having a particle si/.e ranging from 5 nm to 80 nm. an alcohol and a binder; heating the patterned areas to a maximum temperature that is less than 350⁰C; after the healing, depositing redox chromophore moieties which are subsequently adsorbed to the metal oxide on each of the patterned areas; wherein the redox chromophore moieties in each patterned area vary a color of absorbed light as the redox chromophore moieties in the patterned area transition from a first redox state to a second redox state; and coupling electronic circuitry, to each of the patterned areas, for selectively transitioning the redox chromophore moieties in each of the patterned areas between the first redox state and the second redox state.

10. The method of claim 9. wherein the binder is selected from the group of consisting of cellulose, cellulose acetate, cellulose triacetate, ethyl cellulose, hydroxy-propyl cellulose, carboxymethyl cellulose, hydroxvpropyl methyl cellulose, and hydroxyethyl methyl cellulose.

1 1. The method of claim 9, wherein the depositing step comprises immersing the first substrate in a solution comprising a redox chromophore dissolved in a solvent.

12. The method of claim 9, wherein the depositing step comprises printing at least one ink including the redox chromophore moieties on the metal oxide on each of the patterned areas

13. The method of claim 9. wherein the depositing step comprises silk screen printing at least one ink including the redox chromophore moieties on the metal oxide on each of the patterned areas.

14. The method of claim 9, wherein the depositing step comprises ink jet printing at least one ink including the redox chromophore moieties on the metal oxide on each of the patterned areas.

15. The method of claim 12. wherein the at least one ink with the redox chromophore

5 moieties further comprises an alcohol, a binder and a viologen which produces a blue color upon a change from a first redox slate to a second redox state.

16. The method of claim 12. wherein the depositing step comprises:

(i) printing an ink that includes a first type of redox chromophore moieties on the metal oxide on a first subset of the patterned areas; and

] 0 (ii) printing an ink that includes a second type of the redox chromophore moieties on the metal oxide on a second sel of the patterned areas; wherein each of the first and second types of redox chromophore moieties vary a different color of absorbed light as the redox chromophore moieties transition between the first redox state to the second redox state. 15

17. The method of claim 12, wherein the depositing step comprises:

(i) silk screen printing an ink that includes a first type of redox chromophore moieties on the metal oxide on a first subset of the patterned areas: and

(ii) silk screen printing an ink that includes a second type of the redox chromophore moieties on the metal oxide on a second set of the patterned areas; 0 wherein each of the first and second types of redox chromophore moieties vary a different color of absorbed light as the redox chromophore moieties transition between the first redox state to the second redox state.

18. The method of claim 12. wherein the depositing step comprises:

(i) ink jet printing an ink that includes a first type of redox chromophore moieties on 5 the metal oxide on a first subset of the patterned areas; and (ii) ink je1 printing an ink that includes a second type of the redox chromophore moieties on the metal oxide on a second set of the patterned areas: wherein each of the first and second types of redox chromophore moieties vary a different color of absorbed light as the redox chromophore moieties transition between the 5 first redox state to the second redox state.

19. The method of claim 9, wherein the metal oxide is selected from the group of semiconducting oxides consisting of titanium, zirconium, hafhium, chromium, molybdenum, tungsten, vanadium, niobium, tantalum, silver, zinc, strontium, iron (Fe²+ or Fe^'+), nickel and a perovskite of each of the proceeding metals.

I O

20. The method of claim 9. wherein the metal oxide is selected from the group of metal conducting melal oxides consisting of:

(a) SnO₂ doped with one or more of the following: F. Cl, Sb. N. P. As Nb, V and B;

(b) ZnO doped with AL In, Ga, B_: F, Si, Ge, Ti, Zr or Hf;

(c) In₂O;, doped with Sn; 15 (d) CdO

(e) Ternary oxides ZnSnOj, Zn₂In₂Os, lotSn-Oπ, GaInO? or MgIn₂O^

(O TiO₂ doped with one or more of the following: F, Cl. Sb, N. P, As Nb.. Y and B; and

(g) Fe₂Oj doped with Sb; and 0 (h) Fe₂O₅ZSb or SnO₂ZSb systems.

21. The device of claim 9, wherein the redox chromophore moieties are selected from the group consisting of:

4X-

R;)

4X- wherein Ri is selected from the group consisting of:

HO(CH₂)/;- HOOC(CH;)«- (HO_ΛB(CH_;)»ι

R₂ is selected from Ci-io alky!. N-oxide, dimelh\ lamino, acetonitrile. benzyl and phenyl 5 optionally mono- or di-substituted by nitro: R3 is Ci-io alkyl and R₄-R7 are each independently selected from hydrogen; Ci-io alb.i; Ci.10 alkylene: ar>I or substituted aryl: halogen; nitro; and an alcohol group: X is a charge balancing ion which is selected from the group consisting of chloride, bromide., iodide. BF4.^". PF(f. and CIO4 ^" and n=l-10.

22. Tlie method of claim 9. further comprising:

I O forming a common electrode layer on a second substrate by silk screen printing a second ink on the substrate, the second ink comprising a conductive metal oxide, an alcohol and a binder; heating the second substrate with at least the common electrode layer formed thereon to a maximum temperature that is less than 350"C.

23. The method of claim 22. wherein the binder in the second ink is selected from the group of consisting of cellulose, cellulose acetate, cellulose triacetate, ethyl cellulose. hydroχ\propyl cellulose, carboxymethyl cellulose, hydroxy-propyl methyl cellulose, and hydroxvelhyl methyl cellulose.

24. The method of claim 22. further comprising sealing the first substrate to the second substrate, and filling an opening between the first and second substrates with an electrohte.

25. The method of claim 24, further comprising: forming a reflective layer by silk screen printing a reflective ink over the common electrode layer: the reflective ink comprising a substantially reflective metal oxide, an alcohol and a binder: and wherein the heating of the second substrate comprises heating the second substrate with at least the common electrode layer and the reflective layer formed thereon to a maximum temperature that is less than 35(FC.

26. ^'llrie method of claim 25, wherein the reflective ink includes a plurality of non-conductive beads that maintain a spacing of said opening after the sealing step.

27. The method of claim 9, wherein the plurality of electrical \y discrete patterned areas of metal oxide have a film thickness of 0.5 to 10 microns.

28. An ink suitable for silk screen printing a metal oxide film on a substrate, comprising: a nanocrysiailine. nanoporous metal oxide having a particle size ranging from 5 nm to 80 nm. at least one alcohol and at least one binder, wherein the ink has a viscosity sufficient to permit formation of the metal oxide layer on the substrate b> silk screen printing.

29. The ink of claim 28. wherein said at least one alcohol includes terpineol.

30. The ink of claim 29, wherein said at least one alcohol further includes methanol.

31. The ink of claim 28. wherein said at least one binder is selected from the group of consisting of cellulose, cellulose acetate, cellulose triacetate, ethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxxpropyl methyl cellulose, and hydroxyethyl methyl cellulose

32. An ink suitable for silk screen printing redox chromophore moieties on a substrate, comprising: an alcohol, a binder and a viologen which produces a blue color upon a change from a first redox state to a second redox stale.

33. An ink suitable for silk screen printing a conductive film on a substrate, comprising: a conductive metal oxide having a particle size ranging from 5 to HX) nanometers, at least one alcohol and at least one binder, wherein the ink has a \ iscosity sufficient to permit formation of the metal oxide layer on the substrate by silk screen printing.

34. The ink of claim 26, wherein said at least one alcohol includes lerpineol.

35. The ink of claim 26, wherein said at least one binder is selected from the group of consisting of cellulose, cellulose acetate, cellulose triacetate, ethyl cellulose, hydroxypropvl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose

36. An ink suitable for silk screen printing a reflective film on a substrate, comprising: a substantially reflective metal oxide, at least one alcohol and at least one binder, wherein the ink has a viscosity sufficient to permit formation of the metal oxide layer on the substrate by silk screen priming.

37. The ink of claim 29, wherein said at least one alcohol includes terpineol.

38. The ink of claim 29. wherein said at least one binder is selected from the group of consisting of cellulose, cellulose acelate, cellulose triacetate, ethyl cellulose, hydroxypropvl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methvl cellulose.

39. The ink of claim 38. wherein said substantially reflective metal oxide includes rutile TiO₂.

40. The ink of claim 38. wherein said substantially reflective metal oxide includes indium tin oxide