Completely solid electrochromic device, electrochromic bilayer for said device, and method for producing said device

Abstract

An all-solid electrochromic device with controlled infrared reflection or emission is provided, in particular of electro-controllable type, comprising a stack successively comprising from a back face (3) as far as a front face (1) exposed to infrared radiation (2): a substrate (4) made of an electron-conducting material, or a substrate made of a non-electron-conducting material coated with a layer made of an electron-conducting material, forming a first electrode; a layer made of a first proton storage electrochromic material (5); a layer of a proton-conducting and electron-insulating electrolyte (6); a bilayer comprising a layer of a non-electrochromic, sub-stoichiometric tungsten oxide WO.sub.3-y forming a second electrode; said tungsten oxide WO.sub.3-y layer being arranged underneath a layer with variable infrared reflection of a second electrochromic material with variable proton intercalation rate, chosen from among crystallized tungsten oxide H.sub.xWO.sub.3-c and hydrated crystallized tungsten oxide H.sub.xWO.sub.3.nH.sub.20-c; a protective layer (10) transparent to infrared radiation.

Claims

1. A method of thermally protecting an object, comprising protectively associating with the object to be protected an all-solid electrochromic device with controlled infrared reflection or emission, said device comprising a stack, said stack successively comprising from a back face towards a front face exposed to infrared radiation: a) a substrate made of an electron-conducting material, or a substrate made of a non-electron-conducting material coated with a layer made of an electron-conducting material, said substrate made of an electron-conducting material or said layer made of an electron-conducting material forming a first electrode; b) a layer made of a first proton storage electrochromic material; c) a layer of a proton-conducting and electron-insulating electrolyte; d) a bilayer comprising a layer of a non-electrochromic, sub-stoichiometric tungsten oxide, WO.sub.3-y, where y is comprised between 0.2 and 1, optically absorbent in the infrared, electron-conducting, porous, forming a second electrode; said layer of tungsten oxide WO.sub.3-y being arranged underneath a layer with variable infrared reflection, of a second electrochromic material with variable proton intercalation rate, chosen from among crystallized tungsten oxide H.sub.xWO.sub.3-c where x is comprised between 0 and 1, and hydrated crystallized tungsten oxide H.sub.xWO.sub.3.nH.sub.2O-c where x is comprised between 0 and 1 and n is an integer of 1 to 2; and e) a protective layer transparent to infrared radiation, made of an inorganic material.

2. The method according to claim 1, wherein the object is a satellite.

3. The method according to claim 1, wherein said substrate is made of an electron-conducting material chosen from among materials having mechanical and chemical resistance to stresses of the external medium and chemically compatible with proton-operation.

4. The method according to claim 3, wherein said electron-conducting material is chosen from among materials chemically compatible with the first proton storage electrochromic material.

5. The method according to claim 3, wherein said electron-conducting material is chosen from among metals.

6. The method according to claim 5, wherein said electron conducting material is chosen from among aluminum, platinum, chromium and the alloys thereof.

7. The method according to claim 1, wherein said substrate is made of a non-electron-conducting material chosen from among materials having mechanical and chemical resistance to stresses of the external medium and chemically compatible with proton-operation.

8. The method according to claim 7, wherein said non-electron-conducting material is chosen from among materials chemically compatible with the first proton storage electrochromic material.

9. The method according to claim 7, wherein said non-electron-conducting material is chosen from among glasses and organic polymers having mechanical and chemical resistance.

10. The method according to claim 9, wherein the non-electron-conducting material is polyethylene terephthalate (PET).

11. The method according to claim 1, wherein the layer made of an electron-conducting material is made of an electron-conducting material chosen from among materials having mechanical and chemical resistance against stresses of the external medium, and chemically compatible with proton operation.

12. The method according to claim 11, wherein said electron-conducting material is chosen from among materials chemically compatible with the first proton storage electrochromic material.

13. The method according to claim 11, wherein said electron-conducting material is chosen from among metals and electron-conducting metal oxides.

14. The method according to claim 13, wherein said metals are aluminum, platinum, chromium, and alloys of aluminium, platinum and chromium, and said electron-conducting metal oxides are indium tin oxide and fluorine-doped tin oxide.

15. The method according to claim 1, wherein the first proton storage electrochromic material is chosen from among proton storage electrochromic materials chemically compatible with proton-operation.

16. The method according to claim 15, where said first proton storage electrochromic material is chosen from among materials chemically compatible with the proton-conducting and electron-insulating electrolyte.

17. The method according to claim 15, wherein the first proton storage electrochromic material is chosen from among hydrated metal oxides, and mixtures of two or more of said oxides.

18. The method according to claim 17, wherein said hydrated metal oxides are amorphous.

19. The method according to claim 17, wherein the first proton storage electrochromic material is hydrated tungsten oxide H.sub.xWO.sub.3.nH.sub.2O where x is comprised between 0 and 1 and n is an integer of 1 to 2.

20. The method according to claim 1, wherein the proton-conducting and electron-insulating electrolyte is chosen from among proton-conducting and electron-insulating electrolytes chemically compatible with proton-operation.

21. The method according to claim 20, wherein the proton-conducting and electron-insulating electrolyte is chosen from among proton-conducting and electron-insulating electrolytes chemically compatible with/against crystallized tungsten oxide H.sub.xWO.sub.3-c (protonated tungsten oxide) or hydrated crystallized tungsten oxide H.sub.xWO.sub.3.nH.sub.2O-c.

22. The method according to claim 20, wherein the proton-conducting and electron-insulating electrolyte is chosen from hydrated metal oxides.

23. The method according to claim 22, wherein said hydrated metal oxides are amorphous.

24. The method according to claim 23, wherein said metal oxides are amorphous hydrated tantalum oxide Ta.sub.2O.sub.5, amorphous hydrated zirconium oxide and mixtures of two or more of said oxides.

25. The method according to claim 1, wherein the protective layer transparent to infrared radiation is made of a material chosen from among materials chemically compatible with crystallized tungsten oxide H.sub.xWO.sub.3-c or hydrated crystallized tungsten oxide H.sub.xWO.sub.3.nH.sub.2O-c.

26. The method according to claim 25, wherein the protective layer transparent to infrared radiation is made of a material chosen from cerium oxide CeO.sub.2, yttrium oxide Y.sub.2O.sub.3, silica SiO.sub.2 and mixtures of two or more of said metal or metalloid oxides.

27. The method according to claim 1, wherein the substrate has a thickness of 0.175 mm to 1 mm.

28. The method according to claim 1, wherein the layer made of an electron-conducting material coating the substrate made of a non-electron-conducting material has a thickness of 50 to 150 nm.

29. The method according to claim 1, wherein the layer of a first proton storage electrochromic material has a thickness of 0.2 to 1 m.

30. The method according to claim 1, wherein the layer made of a proton-conducting and electron-insulating electrolyte has a thickness of 0.2 to 1 m.

31. The method according to claim 1, wherein the layer made of tungsten oxide WO.sub.3-y has a thickness of 0.2 to 0.5 m.

32. The method according to claim 1, wherein the layer of a second electrochromic material has a thickness of 0.2 to 1 m.

33. The method according to claim 1, wherein the protective layer transparent to infrared radiation has a thickness of 0.1 to 1 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of the device of the invention.

(2) FIG. 2 is a graph representing the resistivity (in 10.sup.2 Ohm.cm) of the WO.sub.3-y sub-layer as a function of the oxygen flow rate (in sccm) fed into the chamber of the magnetron cathode sputtering apparatus during the deposit of this layer using this technique.

(3) FIG. 3 is a graph illustrating electrochemical monitoring of the active material H.sub.xWO.sub.3-c, between 0.2 V (x=0) and 0.8 V (x=0.5) compared with a reference electrode of SCE type in 0.1 M H.sub.3PO.sub.4 medium.

(4) The Y-axis gives the plotting of the coefficient of total reflection R.sub.T in the infrared range of the active part of the H.sub.xWO.sub.3-c (320 nm)/WO.sub.3-y (400 nm)/glass stack, and the X-axis indicates the wavelength (in m) of the infrared radiation.

(5) The curves A, B, C, D, E, F, G respectively correspond to x values of 0; 0.05; 0.1; 0.2; 0.25; 0.35 and 0.5.

(6) FIG. 4 is a graph giving the average of the total reflection coefficient R.sub.T produced by the active part of the H.sub.xWO.sub.3-c (320 nm)/WO.sub.3-y (400 nm)/glass stack in bands II (curve A) and III (curve B) as a function of the intercalation rate x in H.sub.xWO.sub.3-c.

(7) FIG. 5 is a graph illustrating the electrochemical monitoring of the active material H.sub.xWO.sub.3-c between 0.2 V (x=0) and 0.8 V (x=0.5) compared with a reference electrode of SCE type in 0.1 M H.sub.3PO.sub.4 medium.

(8) The Y-axis gives the plotting of the total reflection coefficient R.sub.T in the infrared region of the active part of the H.sub.xWO.sub.3-c (560 nm)/WO.sub.3-y (400 nm)/glass stack, and the X-axis indicates the wavelength (in m) of the infrared radiation.

(9) The curves A, B, C, D, E, F respectively correspond to x values of 0; 0.1; 0.2; 0.3; 0.4 and 0.5.

(10) FIG. 6 is a graph giving the average of the total reflection coefficient R.sub.T produced by the active part of the H.sub.xWO.sub.3-c (560 nm)/WO.sub.3-y (400 nm)/glass stack in bands II (curve A) and III (curve B) as a function of the intercalation rate x in H.sub.xWO.sub.3-c.

(11) FIG. 7 is a graph illustrating the electrochemical monitoring of the active material H.sub.xWO.sub.3-c between 0.2 V (x=0) and 0.8 V (x=0.5) compared with a reference electrode of SCE type in 0.1 M H.sub.3PO.sub.4 medium.

(12) The Y-axis gives the plotting of the total reflection coefficient R.sub.T in the infrared region of the active part of the H.sub.xWO.sub.3-c (730 nm)/WO.sub.3-y (400 nm)/glass stack and the X-axis indicates the wavelength (in m) of the infrared radiation.

(13) The curves A, B, C, D, E, F respectively correspond to x values of 0; 0.1; 0.2; 0.3; 0.4 and 0.5.

(14) FIG. 8 is a graph giving the average of the total reflection coefficient R.sub.T produced by the active part of the H.sub.xWO.sub.3-c (730 nm)/WO.sub.3-y (400 nm)/glass stack in bands II (curve A) and III (curve B) as a function of the intercalation rate x in H.sub.xWO.sub.3-c.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(15) FIG. 1 shows a device of the invention comprising the specific bilayer of the invention.

(16) This device comprises a front face 1 exposed to infrared radiation 2 and a back face 3 which is not directly exposed to infrared radiation.

(17) The device of the invention first comprises a substrate or support 4 which essentially acts as metal support for the device.

(18) The substrate or support 4 generally does not have infrared transparency.

(19) The substrate or support is generally made of a lightweight material.

(20) This substrate or support 4 may be made of a material chosen from among metals, glasses such as microscope slide glass, and organic polymers having sufficient rigidity such as poly(ethylene terephthalate) or PET.

(21) The metals which may constitute the substrate or support 4 may be chosen for example from among aluminium, platinum, chromium and alloys thereof.

(22) If the substrate or support 4 is made of a material which is not electron-conducting such as glass or PET, then a layer made of an electron-conducting material is deposited on the substrate or more exactly on the top surface thereof.

(23) This layer made of an electron-conducting material acts as electrode connected to the power supply of the device.

(24) This electron-conducting material is generally chosen from among electron-conducting metals and metal oxides.

(25) Metals which may constitute the layer made of an electron-conducting material may be chosen from among the metals already cited above which may constitute the substrate or support.

(26) Electron-conducting metal oxides are well known to the man skilled in the art.

(27) Examples of such conductive oxides are Indium Tin Oxide or ITO, Fluorine-doped Tin Oxide SnO.sub.2 or FTO.

(28) The electron-conducting material of said layer, in particular if it is an electron-conducting metal oxide, is generally chosen from among those materials which can be deposited as a thin layer using a PVD method such as cathode sputtering, laser ablation or evaporation, and preferably from among materials which can be deposited as a thin layer by cathode sputtering.

(29) If the substrate or support is made of a material which is electron-conducting such as a metal, then it is not necessary for a layer made of an electron-conducting material to be deposited on the substrate.

(30) The support or substrate 4 which can then be qualified as a single-piece substrate in this case acts both as mechanical support for the device already indicated above and as electrode connected to the power supply of the device.

(31) In FIG. 1 it is this embodiment without a layer made of an electron-conducting material on the substrate, which is illustrated.

(32) It is important that the material which constitutes the layer made of an electron-conducting material if said layer is present, or the electron-conducting material which constitutes the substrate when said layer is not present, is chemically compatible with the material of the layer of a first proton storage electrochromic material 5 deposited on the substrate or on the layer made of an electron-conducting material.

(33) The material which constitutes the layer made of an electron-conducting material, or the electron-conducting material which constitutes the substrate will therefore be chosen so that it is chemically compatible with a protonated medium such as a hydrated metal oxide.

(34) The substrate 4 generally has a thickness of 0.175 to 1 mm.

(35) The substrate 3 is generally in the form of a sheet of a lightweight material.

(36) For example the thickness of the substrate 4 is generally about 1 mm for a glass substrate and about 175 m for a substrate made of a polymer, e.g. a substrate made of PET.

(37) The optional layer made of an electron-conducting material generally has a thickness of 50 to 150 nm.

(38) On the substrate or the layer made of an electronic-conducting material there is arranged a layer made of a first proton storage electrochromic material 5. This layer may also be called a proton-reservoir counter electrode.

(39) The first proton storage electrochromic material may be chosen from among all electrochromic hydrated metal oxides and the mixtures of two or more of these oxides.

(40) Examples of such oxides are hydrated tungsten oxide H.sub.xWO.sub.3.nH.sub.2O where x is between 0 and 1 (0 and 1 inclusive) and n is an integer from 1 to 2, e.g. n=1.

(41) The choice of this latter oxide similar to that of the bilayer has the advantage of further simplifying the method for preparing the device of the invention by reducing the number of targets, precursors used.

(42) The first proton storage electrochromic material is generally chosen from among materials which can be deposited in a thin layer using a PVD method such as cathode sputtering, laser ablation or evaporation, and preferably from among materials which can be deposited in a thin layer by cathode sputtering.

(43) The first proton storage electrochromic material is chosen so that it is chemically compatible with the proton-conducting electrolyte deposited on the layer of first electrochromic material.

(44) The layer made of a first proton storage electrochromic material 5 generally has a thickness of 0.2 to 1 m, preferably 0.4 to 1 m.

(45) On the layer made of a first proton storage electrochromic material 5 there is deposited a proton-conducting and electron-insulating electrolyte layer 6.

(46) This proton-conducting electrolyte may be chosen from among all hydrated metal oxides, preferably amorphous, and mixtures of two or more of these oxides.

(47) Indeed, amorphous oxides are much better proton conductors.

(48) Examples of such oxides are amorphous, hydrated tantalum oxide Ta.sub.2O.sub.5 and amorphous, hydrated zirconium oxide.

(49) The proton-conducting and electron-insulating electrolyte layer 6 generally has a thickness of 0.2 to 1 m, preferably of 0.4 to 1 m.

(50) On the proton-conducting electrolyte layer 6 the bilayer is arranged which may also be called a bilayer electrode or composite electrode 7 according to the invention.

(51) First, on the proton-conducting electrolyte layer, is arranged a tungsten oxide layer WO.sub.3-y with y between 0.2 and 1, that is sub-stoichiometric, non-electrochromic, optically absorbent in the infrared 8, forming a second electron-conducting electrode connected to the power supply of the device.

(52) This tungsten oxide layer is chemically compatible with its surrounding materials, namely with the proton-conducting electrolyte of the underlying layer 6 and with the crystallized, optionally hydrated, tungsten oxide H.sub.xWO.sub.3-c or H.sub.xWO.sub.3.nH.sub.2O-c of the layer immediately above 9 in the stack of layers of the device.

(53) This layer 8 of a tungsten oxide WO.sub.3-y is generally a porous layer, of submicron pore size, e.g. from 10 to 100 nm.

(54) The role of this layer 8 of tungsten oxide WO.sub.3-y is threefold.

(55) This role is to provide the system with an optical absorbing background whilst allowing diffusion of the protons and supplying electrons in the active material H.sub.xWO.sub.3-c or H.sub.xWO.sub.3.nH.sub.2O-c.

(56) The layer 8 made of tungsten oxide WO.sub.3-y generally has a thickness of 0.2 to 0.5 m, preferably from 0.4 to 0.5 m.

(57) The thickness of the layer 8 of tungsten oxide WO.sub.3-y must generally be 500 nm or less so that it is permeable to the protons. On the other hand, this thickness must generally be more than 200 nm to constitute an absorbent background making it possible to decouple the optical function of the front face of the device, essentially consisting of the bilayer 7, from the electrochemical function imparted by the remainder of the stack underneath the tungsten oxide WO.sub.3-y layer 8.

(58) On the layer 8 of tungsten oxide WO.sub.3-y there is arranged a layer 9 made of a second electrochromic material chosen from among crystallized tungsten oxide H.sub.xWO.sub.3-c where x is between 0 and 1 and hydrated crystallized tungsten oxide H.sub.xWO.sub.3.nH.sub.2O-c where x is between 0 and 1 and n is between 1 and 2.

(59) This layer 9 made of a second electrochromic material is generally a porous layer of submicron porosity, e.g. from 10 to 100 nm.

(60) This layer 9 made of a second electrochromic material has variable IR reflection.

(61) In this layer, the active material is a crystallized tungsten oxide represented by the formula H.sub.xWO.sub.3-c which may be hydrated to improve the performance thereof, and essentially the proton conductivity thereof.

(62) This hydrated crystallized tungsten oxide is represented by the formula H.sub.xWO.sub.3.nH.sub.2O-c.

(63) In these formulas x, which represents the intercalation rate of the active material H.sub.xWO.sub.3-c or H.sub.xWO.sub.3.nH.sub.2O-c is variable and is generally comprised between 0 and 1 (0 and 1 inclusive) whilst n is generally comprised between 1 and 2 (1 and 2 inclusive).

(64) The optical response of the device very closely follows the variations of x, with possible modulation to within 0.05, on account of the capacity of the inorganic layers to maintain their proton level also called the memory effect.

(65) In other words, the optical properties, the optical response of the active, electrochromic, reflective, crystallized and/or hydrated tungsten oxide layer 9 of formula H.sub.xWO.sub.3-c or WO.sub.3.nH.sub.2O-c can easily be modulated as a function of the proton intercalation rate (defined by x) which itself is variable as a function of the applied voltage.

(66) Therefore, by modifying this voltage, it is possible to act at will on the optical properties of the device. For example, for an applied voltage of 0.2 V, x=0, and for an applied voltage of 0.8 V, x=0.5.

(67) It is to be noted that the tungsten oxide WO.sub.3 which constitutes the active part of the stack of the device according to the invention is a material capable of working with lithium ions and/or with protons.

(68) According to the invention, it is chosen to cause the tungsten oxide WO.sub.3 to function with protons rather than with Li+ ions for kinetic-related reasons.

(69) Since all-solid devices such as the device of the invention are slower than flexible devices, it is preferable to work with a second protonic electrochromic material, with an inorganic proton electrolyte e.g. of hydrated tantalum oxide type Ta.sub.2O.sub.5, and finally with an inorganic counter-electrode that is also a proton counter-electrode.

(70) The layer made of a second active electrochromic material 9 generally has a thickness of 0.2 to 1 m, preferably of 0.3 to 0.8 m.

(71) The optical properties of the device are adaptable in the mid-infrared with the thickness of the active material H.sub.xWO.sub.3-c or H.sub.xWO.sub.3.nH.sub.2O-c, in particular in bands II (3-5 m) and III (8-12 m) of transparency of the atmosphere.

(72) For example, a narrow thickness (e.g. about 300 nm) of active material 9 will give in a privileged way, modulation of total reflection in band II, whilst a large thickness (e.g. about 700 to 800 nm) of active material will give in a privileged way, modulation of total reflection in band III.

(73) To summarize, the optical properties, the optical contrast, of the device of the invention can be modulated in the infrared, in particular in the mid-infrared, by varying x and the thickness of the active material H.sub.xWO.sub.3-c or H.sub.xWO.sub.3.nH.sub.2O-c.

(74) On the layer made of a second active electrochromic material 9 there is arranged a layer 10 to protect the stack, transparent to infrared radiations and preferably having sun radiation reflection.

(75) This layer 10 could also be called an encapsulation layer.

(76) This layer 10 is effectively deposited during a final step on the stack assembly described above to maintain the ion content (protons) inside the device and thereby to act as encapsulating material.

(77) By transparency to infrared radiations is generally meant that this layer 10 is transparent to infrared radiations of wavelengths comprised between 1.5 m and 20 m, preferably between 3 m and 12 m.

(78) By low refractive index is generally meant that this layer 10 has a refractive index of between 1 and 2.

(79) This layer 10 is generally made of a non-toxic inorganic material.

(80) Preferably, this layer 10 is made of a material chosen from among metal and metalloid oxides, and mixtures of two or more of these metal oxides and metalloid oxides.

(81) This or these, preferably amorphous, metal or metalloid oxides are preferably chosen from among oxides which can easily be deposited by PVD from an oxide or metal target such as cerium oxide CeO.sub.2, yttrium oxide Y.sub.2O.sub.3, or SiO.sub.2.

(82) The stack protective layer 10 generally has a thickness of 0.1 to 1 m, preferably from 0.4 to 1 m.

(83) The device of the invention further comprises means 11, 12 for setting up a variable voltage between the electrodes, for example a voltage varying between +3 Volts and 3 Volts.

(84) The device of the invention is prepared following the above-described method.

(85) The apparatus used to implement the method of the invention for preparing the device of the invention may be a frame for Physical Vapour Deposition (PVD) comprising: a vacuum chamber having a volume of 0.1 m.sup.3 for example, in which the initial prevailing pressure is about 5 10.sup.7 mbar for example, the maximum pumping rate to obtain the vacuum in the chamber being 900 L/s with a chamber initially filled with nitrogen; no more than 6 cathodes having a diameter of 3 inches (or 76 mm), or else 2 cathodes having a diameter of 6 inches (or 152 mm) and 2 cathodes with a diameter of 3 inches (or 76 mm); each deposit is performed by magnetron cathode sputtering from a metal target of Ir, Ta, W or Ce for example, with an applied power of 1 to 2 W/cm.sup.2, preferably in pulsed DC mode, for example at 50 kHz for 2 s to obtain high depositing speeds, e.g. of 60 to 100 nm/minute for industrialization of the method qualified as reactive.

(86) To oxidize and/or hydrate the materials in thin layers, the plasma gas consists of a mixture of argon (with hydrogen) and oxygen, injected into the chamber at flow rates respectively of 70 sccm and 9 to 20 sccm for example.

(87) It is to be noted that according to one of the advantageous characteristics of the invention, the bilayer can be prepared using a PVD method e.g. by reactive magnetron cathode sputtering from a single target of tungsten, notably with a controlled oxygen content within the depositing chamber. In this case, in which only one tungsten target is used, a sub-stoichiometric oxide WO.sub.3-y is obtained.

(88) The oxygen content of WO.sub.3-y determined by the value of y between 0.1 (namely for a flow rate of 9.9 sccm for example) and 0.5 (namely for a flow rate of 9 sccm for example) may be fully controlled by controlling the parameters of cathode sputtering, e.g. power of 400 W applied to a tungsten target of 6-inches diameter; cathode voltage of between 500 and 520 Volts; high plasma-forming gas pressure of between 2 and 2.3 10.sup.2 mbar to obtain a porous layer.

(89) The oxygen content of WO.sub.3-y may particularly be controlled by the level of oxygen in the depositing chamber whose flow rate is finely controlled, for example to within plus or minus 0.1 sccm, via optical regulation of the tungsten atoms level content in the depositing plasma. For this purpose, a photodiode is used provided with a 400 nm filter which is the wavelength of one of the main lines of W.

(90) The crystallized active material H.sub.xWO.sub.3-c is obtained with an oxygen flow rate generally set at 20 sccm by the flow-meter.

(91) The deposition parameters may be the following for example: a power density applied to the tungsten target of 2 W/cm.sup.2; a cathode voltage of 520 Volts; a plasma forming gas, e.g. a mixture of argon and oxygen, pressure of 2.5 10.sup.2 mbar.

(92) In addition, the substrate is generally heated to 350 C., with a slight ion-assistance to improve crystallization during deposition.

(93) This ion assistance may consist for example of bombardment by AR.sup.+ ions at 80 W in RF mode.

(94) WO.sub.3-y may also be prepared by co-sputtering a metal tungsten W target and a second target of stoichiometric tungsten oxide WO.sub.3.

(95) The mixing proportion of the W and WO.sub.3 materials is then adjusted by acting on the power density, in RF mode under argon, applied to their respective targets, between 1 and 2 W/cm.sup.2 at low deposition speed, e.g. 10 to 20 nm/min, to obtain a homogeneous composition.

(96) In this manner a matrix of stoichiometric WO.sub.3 is obtained in which metal W atoms are implanted capable of percolating, with a W content generally of at least 10%.

(97) This material can be qualified as a Cermet; it effectively has the characteristic properties of Cermets, in particular with a variation in conductivity typical of Cermets corresponding to the electronic percolation threshold (see Example 1).

(98) It is to be noted that crystallized H.sub.xWO.sub.3-c may also be deposited with a WO.sub.3 target in non-reactive RF mode under argon, but with a much slower deposition rate than with the reactive method using a metallic W target.

(99) The deposition rate is generally about 12 nm/min in RF mode instead of about 60 nm/min in DC mode.

(100) The inorganic, robust device of the invention of simplified design and which can operate in particular in the mid-infrared finds especially application in the thermal protection of satellites.

(101) For example patches for satellites can be used, composed of several all-solid electrochromic devices according to the invention, to replace mechanical flaps which consume much energy.

(102) The invention will now be described with reference to the following Examples given as non-limiting illustrations.

EXAMPLES

Example 1

(103) This Example illustrates control over the electronic properties of the sub-layer made of WO.sub.3-y, and in particular its resistivity by controlling the flow rate of oxygen into the chamber of the magnetron cathode sputtering frame during the depositing of this sub-layer.

(104) This WO.sub.3-y sub-layer is a fundamental element of the device and of the bilayer (bilayer, composite electrode) according to the invention.

(105) Depositing of WO.sub.3-y is preferably performed using the magnetron cathode sputtering technique in reactive pulsed DC mode using a physical vapour deposition (PVD) frame.

(106) A power of 400 W is applied to a tungsten target of 6-inch diameter.

(107) The voltage of the cathode is between 500 and 520 Volts, and the pressure of the plasma forming gas consisting of a mixture of argon and oxygen is between 2 and 2.3 10.sup.2 mbar.

(108) This method advantageously produces porous thin layers, when a high working pressure is applied, and with rapid growth e.g. of about 100 nm/min.

(109) FIG. 2 shows that the electronic properties of the WO.sub.3-y sub-layer can effectively be controlled by means of the flow rate of oxygen fed into the chamber of the frame during the deposition of this layer by magnetron cathode sputtering. In FIG. 2 it can be seen that the WO.sub.3-y material has a resistivity of between 0.5 and 5 10.sup.2 .Math.cm when the flow rate of oxygen fed into the chamber regulated by optical emission of the tungsten atoms varies from 9.0 to 9.9 sccm (standard cubic centimeter per minute) with an argon flow rate of 70 sccm.

(110) It is apparent that the electronic properties of WO.sub.3-y are highly sensitive to the flow rate of oxygen above a threshold value of 9.8 sccm.

(111) FIG. 2 shows a transition threshold of electronic properties at 9.8 sccm (y=0.25) corresponding to maximum optical absorption (CERMET principle).

(112) As a result, to ensure the reproducibility of the optical properties of the absorbent WO.sub.3-y sub-layer, use is made in following Example 2 of a thin layer of WO.sub.3-y (y=0.5) close to the optimal CERMET and prepared with 9 sccm of O.sub.2.

Example 2

(113) In this Example, it is shown that modulation of total reflection in the infrared range is effectively obtained on the front face of the all-solid device of the invention.

(114) More specifically, it is illustrated in this Example that optical modulation in the infrared (focused in bands II and III of the IR region) is obtained in an aqueous liquid medium, namely a slightly acid electrolyte comprising 0.1 M H.sub.3PO.sub.4 with stacks consisting of a H.sub.xWO.sub.3/WO.sub.3-y bilayer on a glass substrate.

(115) It is recalled that band II of the infrared range extends between the wavelengths of 3 and 5 m, and that band III of the infrared range extends between wavelengths 8 and 12 m.

(116) Said stack which constitutes the front face of the device of the invention can be considered as representing the functioning of a proton all-solid device according to the invention since the layers located underneath the WO.sub.3-y layer do not or only scarcely contribute to the optical properties of the device of the invention.

(117) As already specified above, in the stacks used in this example a thin layer of WO.sub.3-y, close to the optimal CERMET, is used, and prepared with 9 sccm of O.sub.2.

(118) The thickness of the WO.sub.3-y material must be less than 500 nm so that it is permeable to the protons.

(119) On the other hand, it must be thicker than 200 nm to form an absorbent background (R.sub.surface<200 ohm/sq) thereby decoupling the optical function of the H.sub.xWO.sub.3/WO.sub.3-y front face from the electrochemical function imparted by the remainder of the stack.

(120) In this Example, the thickness of the WO.sub.3-y layer (y=0.5) was therefore fixed at 400 nm.

(121) The active H.sub.xWO.sub.3-c layer is deposited in the same magnetron cathode sputtering chamber as the WO.sub.3-y layer, without opening the chamber, using the same tungsten target with reactive pulsed DC deposition mode, characterized by heating and ion assistance to promote the crystallization of WO.sub.3, and by a high working pressure namely a pressure P(Ar+O.sub.2)=2.5 10.sup.2 mbar for example imparting sufficient porosity to the material for its reactivity with the intercalation of the protons (represented by the intercalation rate x in H.sub.xWO.sub.3).

(122) In the initially deposited active layer x=0.

(123) Three stacks with layers of H.sub.wWO.sub.3-c of respective thickness 320 nm, 560 nm and 730 nm on a layer of WO.sub.3-y (y=0.5) of 400 nm, on a glass substrate consisting of a microscope slide of 1 mm thickness, were examined.

(124) Reversible modulation of total reflection optical response in the infrared was ensured by varying the intercalation rate x which corresponds to the level of protons in the active material H.sub.xWO.sub.3-c.

(125) The value of x was caused to vary from 0 to 0.5. a) Stack H.sub.xWO.sub.3-c (320 nm)/WO.sub.3-y (400 nm)/glass.

(126) With this stack, as can be seen in Table 1 and FIGS. 3 and 4, modulation of total reflection is obtained in a privileged way in band II on account of the narrow thickness of the layer of active material.

(127) TABLE-US-00001 TABLE 1 R R (II) (III) X (*) (*) 0.50 0.51 0.55 0.35 0.49 0.48 0.25 0.46 0.41 0.20 0.40 0.35 0.10 0.27 0.37 0.05 0.18 0.42 0 0.07 0.49 (*) R(II) and R(III) respectively represent the average of the total reflection coefficients R.sub.T produced by the active part of the stack in bands (II) and (III) of the infrared range.

(128) This stack, representing the device of the invention is very active in band II (R II=51%-7% i.e. 44%) and almost inactive in band III (R III=55%-49% i.e. 6%) when x varies from 0 to 0.5.

(129) The global response times to obtain maximum contrast in band II are shorter than one minute for a surface area of 1 cm.sup.2.

(130) With a complete stack according to the invention, which would then comprise a solid electrolyte limiting kinetics, it could be thought that the global response times would be several minutes unless the range of variation of x values is reduced to 0.1 to 0.5 (since H.sub.xWO.sub.3-c is conductive irrespective of x) with attenuated optical contrast.

(131) Therefore, by limiting modulation between 0 V (x=0.1) and 0.8 V (x=0.5), the contrasts become more balanced between bands II and III, i.e. R II=24% and R III=18% (see Table 1). b) Stack of H.sub.xWO.sub.3-c (560 nm)/WO.sub.3-y (400 nm)/glass

(132) With this stack, as can be seen in Table 2 and FIGS. 5 and 6, a good compromise is obtained between modulation of total reflection in band II and modulation of total reflection in band III due to the intermediate thickness of the active material.

(133) TABLE-US-00002 TABLE 2 R R (II) (III) X (*) (*) 0.5 0.48 0.59 0.4 0.43 0.50 0.3 0.40 0.42 0.2 0.34 0.29 0.1 0.27 0.27 0 0.22 0.32 (*) R(II) and R(III) respectively represent the average of the total reflection coefficients R.sub.T produced by the active part of the stack in bands (II) and (III) of the infrared range.

(134) This stack, representing the device of the invention, is active in band II (R II=26%) and in band III (R III=27%) when x varies from 0 to 0.5. c) Stack of H.sub.xWO.sub.3-c (730 nm)/WO.sub.3-y (400 nm)/glass.

(135) With this stack, as can be seen in Table 3 and FIGS. 7 and 8, modulation of total reflection is obtained in a privileged way in band III on account of the large thickness of the layer of active material.

(136) TABLE-US-00003 TABLE 3 R R (II) (III) X (*) (*) 0.5 0.48 0.58 0.4 0.44 0.52 0.3 0.37 0.39 0.2 0.29 0.25 0.1 0.24 0.21 0 0.22 0.22 (*) R(II) and R(III) respectively represent the average of the total reflection coefficients R.sub.T produced by the active part of the stack in bands (II) and (III) of the infrared range.

(137) This stack, representing the device of the invention, is active in band II (R II=26%) and more active in band III (R III=36%) when x varies from 0 to 0.5.