DE202021002595U1 - Solid-state electrochromic device - Google Patents

Abstract

Solid state electrochromic device (10) comprising
- a transparent electrically conductive substrate (1, 2),
- A metal halide solid layer (3) which contains at least one metal halide,
- A solid layer (4) containing lithium ions, and
- A transparent, electrically conductive cover layer (5, 6).

Description

The invention relates to an electrochromic solid-state device which is configured for reversible metal deposition and thus a reversible change in optical transparency in the visible spectral range when different electrical voltages are applied. The invention also relates to technical devices of which the solid-state electrochromic device is a component. A method of manufacturing the solid-state electrochromic device is also described.

in ein blaues Produkt über. Der Vorgang ist reversibel.Electrochromic layers, which switch between an oxidized and a reduced state when an electrical voltage is applied, which changes their optical transmission, are generally known (see e.g. V. Rai et al., Adv. Eng. Mater. 2020, 22, 2000082 ). The material most frequently used for electrochromic layers is tungsten trioxide (WO ₃ ). The colorless WO ₃ goes through electrochemical reduction and simultaneous incorporation of a charge-neutralizing cation M (such as H ⁺ , Li ⁺ or K ⁺ ) according to $$\begin{array}{l}{\text{WHERE}}_3+{\text{xe}}^{-}+{\text{xM}}^{+}\to {\text{M.}}_{\text{x}}{\text{WHERE}}_3\hfill \\ \begin{array}{ll}\text{colorless}\hfill & \text{blue}\hfill \end{array}\hfill \end{array}$$

into a blue product. The process is reversible.

Other transition metal oxide compounds that show electrochromic effects and have already been used in prototypes include IrO ₂ , MnO ₂ , MoO ₃ , NiO, Nb ₂ O ₅ (see e.g. U.S. 3,704,057 ).

Furthermore, organic or inorganic / organic redox systems are known which take advantage of the fact that numerous organic molecules and conjugated polymers exhibit electrochromic behavior. Typically, organic electrochromic materials can form multiple colors under different applied voltages, which is very desirable for multicolor displays. Viologene, 1,1'-disubstituted 4,4'-bipyridinium salts are by far the most intensively investigated electrochromic materials based on small molecules (see e.g. WO2004 / 067673 , DE102008049543 ). Some long chain polymers, such as B. Polypyrroles, polythiophenes, and polyanilines have electrochromic properties by changing their n-conjugated structures. Instead of using a single class of electrochromic materials, combinations as organic-inorganic electrochromic hybrids can combine the advantages of the individual materials and thus achieve improved electrochromic properties (see e.g. DE 60200400158 ).

Although metals do not have the necessary different oxidation states that are necessary for inherent electrochromism, unconventional electrochromic devices have been developed that are based on the reversible deposition of metal nanoparticles, such as e.g. B. Ag, Bi, Cu, Pb, Ni are based on their dissolved salts, which leads to a reversible change in the optical transparency (see X. Tao et al., Adv. Optical Mater. 2021, 2001847 ).

The particular interest in these electrochromic systems is based on their very simple component architecture, consisting of a sandwich arrangement, which in its simplest form consists of two glass substrates coated with a conductive layer (e.g. ITO, AI), between which there is a solution of metal salts and conductive salts. So far, switching cycles of 2500 (Ag ⁺ / Cu ²⁺ / TBABr-DMSO), 5500 (Cu ²⁺ , Pb ²⁺ / LiClO ₄ ) or 100000 (Bi ³⁺ , Cu ²⁺ in aqueous solution) have been observed (see V. . Rai et al., Adv. Eng. Mater. 2020, 22, 2000082, Table 3).

To achieve neutral gray or black color properties, Ag-containing systems, such as those from S. Araki et al. (Adv. Mater., Vol. 24, pp. OP122-OP126, 2012) have been described. of great interest. Here, when a voltage is applied, Ag ⁺ ions are reduced to elementary Ag nanoparticles on an ITO electrode. Conversely, a charge reversal leads to the dissolution of Ag nanoparticles, whereby this process can be accelerated by the presence of redox mediators such as Cu salts. The deposition and dissolution of Ag nanoparticles is therefore reversible and thus leads to a reversible optical change. Based on the size and shape of the deposited particles, which are strongly dependent on the deposition time, the bias voltage and the chemical nature of the solvent, the transparency can be modulated over a wide range.

The electrochromic devices described so far On the basis of the reversible deposition of metals, the serious disadvantage is that the metal salts required for the redox process have so far only been used in solutions or semi-liquid gels, which makes practical use difficult or impossible, since the typical use of electrochromic systems (e.g. B. in so-called smart windows, displays) the production and sealing of large-area liquid electrolyte layers is technologically very difficult, especially when these electrochromic devices are to be applied to flexible carriers, for example for sun protection films.

The object of the invention is to provide an improved electrochromic solid-state device based on the reversible deposition of metals, with which the disadvantages of conventional techniques are avoided. With the electrochromic solid-state device, restrictions due to the use of e.g. B. liquid electrolyte solutions or semi-liquid polymer gels are avoided, a structure made of solid layers is realized, and / or improved application properties, such as a long service life, a high number of switching cycles and / or a high transparency contrast, are made possible. The object of the invention is also to provide improved technical devices which are equipped with at least one electrochromic solid-state device and with which disadvantages of conventional devices in which electrochromic solid-state devices are used are avoided.

These objects are achieved by an electrochromic solid-state device with the features of claim 1 and by technical devices that are equipped with at least one electrochromic solid-state device according to claim 1.

According to a first general aspect of the invention, the object is achieved by an electrochromic solid-state device (also referred to as an electrochromic material) which comprises a transparent electrically conductive substrate, a metal halide solid layer containing at least one metal halide, a solid layer containing lithium ions, and a comprises transparent electrically conductive cover layer. The said layers of the electrochromic material form a layer stack, the substrate and the cover layer delimiting the layer stack on two main surfaces. The layers mentioned, in particular the inner solid layers, can be individual layers or be made up of several sub-layers. The solid-state electrochromic device may comprise further layers, e.g. B. for protective functions or coloring, are provided, wherein the electrochromic solid-state device preferably consists exclusively of solid layers, d. H. is free of liquids and / or gels.

In particular, the invention creates an electrochromic solid-state device which comprises several inorganic layers deposited from the gas phase and in which, by applying different electrical voltages, a reversible deposition of metal, in particular silver, and thus a change in optical transparency in the visible spectral range is achieved.

The at least one metal halide in the metal halide solid layer is preferably suitable for achieving reversible metal deposition between the substrate and the cover layer by applying different electrical voltages, in particular direct voltages with opposite signs. The application of an electrical voltage refers to the application of electrical voltages to the substrate and the cover layer, with the metal being deposited with a first voltage and the metal deposition being reversed with a second voltage and the metal being converted into a bonded state.

According to a preferred embodiment of the invention, the metal halide solid layer contains silver chloride. Silver chloride offers particular advantages for the fabrication of the metal halide solid layer and the electrochromic properties of the solid state electrochromic device. The metal halide solid layer is particularly preferably composed of silver chloride. The thickness of the solid layer containing silver chloride or consisting of silver chloride is advantageously selected in the range from 100 nm to 300 nm.

According to further preferred embodiments of the invention, the metal halide solid layer contains LiCl (particularly preferably 5 to 20 wt%) and / or CuCl (particularly preferably 5 to 20 wt%).

The solid layer containing lithium ions preferably comprises a layer of at least one of LiCI, LiBO2, LlBO2 / LiF (3: 2), Li30Cl, LiAlIF4, LiNbO3, LIBSO (LiBO2 / Li2SO4), LIPON (lithium phosphoroxynitride), particularly preferably with a thickness in the range from 100 nm to 300 nm ,.

According to further variants of the invention, the solid layer containing lithium ions can contain CuCl (particularly preferably 5 to 20 wt%) and / or TiO ₂ (particularly preferably 5 to 20 wt%).

According to a further preferred embodiment of the invention, the electrically conductive layer comprises an ITO layer (indium tin oxide), particularly preferably with a thickness in the range from 100 nm to 200 nm, on a transparent carrier. ITO has particular advantages due to its transparency, stability and electrical conductivity. Optionally, a TiO ₂ layer, in particular with a thickness in the range from 20 nm to 50 nm, can be arranged on the ITO layer.

The transparent carrier can advantageously comprise glass or a transparent polymer material.

Another advantage of the invention is that numerous uses of the solid-state electrochromic device are available. The solid-state electrochromic device may e.g. B. be part of a light filter, a light protection device or a display device. The solid-state electrochromic device may include a window, e.g. B. from a building or a means of transport, such. B. be a ship, an airplane or a vehicle. A technical device which has at least one electrochromic solid-state device according to the invention represents an independent subject matter of the invention.

A method for producing an electrochromic solid-state device, in particular the electrochromic solid-state device according to the invention, is also described, which comprises the following steps. A transparent carrier is provided. The carrier is coated with an electrically conductive coating, e.g. B. ITO coated. The carrier is preferably coated by sputtering. A metal halide solid layer is deposited, preferably from the gas phase by thermal evaporation in a high vacuum, optionally together with CuCl or LiCl. A solid layer containing lithium ions is deposited, preferably from the gas phase by thermal evaporation in a high vacuum or by sputtering, optionally together with CuCl or TiO ₂ . Furthermore, an electrically conductive cover layer is deposited. Finally, contact is made between the substrate and the cover layer.

• 1: eine schematische Darstellung des Schichtaufbaus einer elektrochromen Festkörper-Vorrichtung gemäß bevorzugten Ausführungsformen der Erfindung.

Further advantages and details of the invention are described with reference to the accompanying drawing. It shows

• 1 : a schematic representation of the layer structure of an electrochromic solid-state device according to preferred embodiments of the invention.

According to the invention for the electrochromic solid-state device 10 which is described below with reference to 1 described layer structure provided, the use of an AgCl solid layer deposited from the gas phase as an electrochromic layer represents the essential advantage of the invention. In practical use, the solid-state electrochromic device has 10 preferably a flat shape, the shape and size of which is selected depending on the requirements of the specific application, in particular as is known from conventional electrochromic devices.

The solid-state electrochromic device 10 comprises a transparent electrically conductive substrate with a first carrier 1 , e.g. B. made of glass or a plastic film, and a first ITO layer 2 , on which an AgCl solid layer 3, optionally with CuCl and / or LiCl, is deposited and the solid layer containing lithium ions 4th (LiX), optionally with CuCl and / or TiO ₂ , carries. The solid layer 4th forms an ion conductor (ion storage layer). The end of the layer stack opposite the substrate 1, 2 is formed by a transparent, electrically conductive cover layer with a second ITO layer 5 and a second carrier 6th , e.g. B. made of glass or a plastic film. The first and second ITO layers 2 , 5 are provided with contacts (not shown) and with a DC voltage source 7th tied together.

• (S1) Leitfähige Schicht 1, 2: Planares Glas oder eine Folie wird (wenn nicht kommerzielle ITO-beschichtete Substrate verwendet werden) durch thermisches Verdampfung oder Sputtern von Indiumzinnoxid (90:10) mit einer 100 nm bis 200 nm dicken ITO-Schicht 2 beschichtet. Alternative leitfähige aufdampfbare Beschichtungen sind z.B. mit Fluor dotiertes Zinn(IV)-oxid (FTO) oder mit Aluminium dotiertes Zinkoxid (ZnO:Al). Günstig für die S1-ITO-Schicht 2 ist eine gewisse Rauigkeit der Schicht, um den Schwärzungsgrad des abgeschiedenen Silbers zu erhöhen und Spiegelungseffekte zu reduzieren. Dies kann z.B. durch höhere Schichtdicken (die Rauigkeit der ITO-Schicht 2 nimmt mit der Wurzel aus der Schichtdicke zu) erreicht werden, oder dadurch, dass auf dem ITO-Glas aus der Gasphase eine dünne 20 nm bis 50 nm dicke TiO₂-Schicht abgeschieden wird. Die TiO₂-Schicht bietet zudem den Vorteil, die Photolyse von AgCI durch UV-Licht zu verringern.
• (S2) Elektrochrome Schicht 3: Thermische Abscheidung von AgCI und CuCI aus der Gasphase im Hochvakuum ist seit langem bekannt (siehe z. B. M. Cardona, Phys.Rev. 129 (1963) ). Insbesondere durch Anwendung dieser Verfahren kann zur Herstellung der elektrochromen Schicht durch thermische Verdampfung von AgCI-Pulver bei ca. 5×10^-4Pa eine dünne AgCl-Schicht mit einer Dicke zwischen 100 nm und 300 nm auf der ITO-Schicht 2 (S1) abgeschieden werden. Schicht 3 kann eine reine AgCI-Schicht sein. Zur Verbesserung des Schaltverhaltens sind die folgenden Varianten einzeln oder in Kombination verfügbar.
  1. (i) Zumischung von maximal 20 wt-% LiCl zur AgCI-Schicht durch eine Mehrquellenverdampfung, wodurch die Dispersität des abgeschiedenen Silbers erhöht wird, und/oder
  2. (ii) Zumischung von maximal 20% wt- CuCl als Redoxmediator zur AgCI-Schicht, wodurch die Schaltgeschwindigkeit, insbesondere die Auflösung des Silbers, in der Rückreaktion beschleunigt wird.
• (S3) lonenleiter- / Ionenspeicherschicht 4: Da die elektrochemischen Schaltvorgänge stark mit der Wanderung von Ionen und Ladungsträgern verbunden sind, ist analog zur ElektrolytLösung In flüssigen Zellen eine Schicht mit ionenleitenden bzw. ionenspeichernden Eigenschaften vorgesehen. Hierzu eignen sich thermisch verdampfbare oder sputterbare Lithium-Verbindungen, in einfachstem Fall LiCI mit Schichtdicken zwischen 100 nm und 300 nm. Des Weiteren sind verdampfbare Lithium-Verbindungen mit einer hohen lonenleitfäigkeit wie LiBO2, LlBO₂/LiF (3:2), Li₃OCl, LiAlF₄ (durch thermische Verdampfung) sowie LiNbO₃, LIBSO (LiBO_2/Li₂SO₄), LIPON (Lithium-phosphoroxynitrid) (durch RF bzw. Magnetron sputtering) als ionenleitende Schicht geeignet. Man kann die Herstellung der Lithiumsalz-Schichten noch verbinden mit der zusätzlichen Zumischung des Redoxmediators CuCl und/oder der Zumischung von TiO₂, das neben seiner UV-schützenden Wirkung als Ionen-Speicher bekannt ist.
• (S4) ITO-Kontaktschicht 5: Die Fertigstellung der elektrochromen Festkörper-Vorrichtung 10 erfolgt durch Kontaktierung mit einer ITO-Schicht 5 auf einem tranparenten Träger 6.

The manufacture of the solid-state electrochromic device 10 takes place in the following way:

• (S1) Conductive layer 1, 2: Planar glass or a film is (if non-commercial ITO-coated substrates are used) by thermal evaporation or sputtering of indium tin oxide (90:10) with a 100 nm to 200 nm thick ITO layer 2 coated. Alternative conductive vapor-deposition coatings are, for example, tin (IV) oxide (FTO) doped with fluorine or zinc oxide (ZnO: Al) doped with aluminum. A certain roughness of the layer is favorable for the S1 ITO layer 2 in order to increase the degree of blackening of the deposited silver and to reduce reflective effects. This can be achieved, for example, through higher layer thicknesses (the roughness of the ITO layer 2 increases with the root of the layer thickness), or by depositing a thin 20 nm to 50 nm thick TiO ₂ layer on the ITO glass from the gas phase. The TiO ₂ layer also offers the advantage of reducing the photolysis of AgCI by UV light.
• (S2) Electrochromic layer 3: Thermal deposition of AgCI and CuCI from the gas phase in a high vacuum has been known for a long time (see e.g. M. Cardona, Phys. Rev. 129 (1963) ). In particular, by using this method, a thin AgCl layer with a thickness between 100 nm and 300 nm can be applied to the ITO layer to produce the electrochromic layer by thermal evaporation of AgCl powder at approx. 5 × 10 ^{-4 Pa} 2 (S1) are deposited. layer 3 can be a pure AgCI layer. To improve the switching behavior, the following variants are available individually or in combination.
  1. (i) Admixture of a maximum of 20 wt% LiCl to the AgCl layer by multi-source evaporation, which increases the dispersity of the deposited silver, and / or
  2. (ii) Admixture of a maximum of 20% wt-CuCl as redox mediator to the AgCl layer, whereby the switching speed, in particular the dissolution of the silver, is accelerated in the reverse reaction.
• (S3) ion conductor / ion storage layer 4th : Since the electrochemical switching processes are strongly linked to the migration of ions and charge carriers, a layer with ion-conducting or ion-storing properties is provided in liquid cells, analogous to the electrolyte solution. Thermally vaporizable or sputterable lithium compounds are suitable for this, in the simplest case LiCI with layer thicknesses between 100 nm and 300 nm. Furthermore, vaporizable lithium compounds with a high ionic conductivity such as LiBO2, LIBO ₂ / LiF (3: 2), Li _{3 are suitable} OCl, LiAlF ₄ (by thermal evaporation) as well as LiNbO ₃ , LIBSO (LiBO _{2 /} Li ₂ SO ₄ ), LIPON (lithium phosphoroxynitride) (by RF or magnetron sputtering) are suitable as ion-conducting layers. The production of the lithium salt layers can also be combined with the additional admixture of the redox mediator CuCl and / or the admixture of TiO ₂ , which, in addition to its UV-protective effect, is known as an ion store.
• (S4) ITO contact layer 5 : The completion of the solid-state electrochromic device 10 takes place by contacting an ITO layer 5 on a transparent carrier 6th .

The following is the switching action of the solid-state electrochromic device 10 described. Will the solid-state electrochromic device 10 When a voltage of at least -2.0 V is applied, one of the ITO layers acts 2 , 5 as a cathode, which leads to increasing blackening as a result of the deposition of silver: AgCl + Li ⁺ + e- ------- → Ag + LiCl A subsequent change in the voltage to at least + 1.0 V and higher leads to a reversal of the reaction and dissolution of the silver, which increases the transparency of the layers.

1. 1. Erstmalige Nutzung des Prinzips der reversiblen Abscheidung von Metallen in elektrochromen Festkörper-Vorrichtungen;
2. 2. Nutzung einer dünnen Silberchlorid-Festkörperschicht als elektrochrome Schicht;
3. 3. Verzicht auf Elektrolytlösungen und halbflüssigen Gelen, die eine erforderliche Mehrschicht-Technologie schwierig und störanfällig machen;
4. 4. Minimaler Einsatz einfacher Rohstoffe und Nutzung einer etablierten umweltfreundlichen Technologie, die Maßstabsvergrößerungen und die Nutzung unterschiedlicher, auch flexibler Substrate problemlos erlaubt.
5. 5. Ausweitung des Prinzips der reversiblen Abscheidung von Metallen zur Herstellung elektrochromer Festkörper-Vorrichtungen auch auf andere Metallabscheidungen wie Bi, Pb prinzipiell möglich.

The advantages of the electrochromic solid-state device according to the invention are as follows over the prior art:

1. 1. First use of the principle of reversible deposition of metals in solid-state electrochromic devices;
2. 2. Use of a thin solid layer of silver chloride as an electrochromic layer;
3. 3. Avoidance of electrolyte solutions and semi-liquid gels, which make the required multilayer technology difficult and prone to failure;
4. 4. Minimal use of simple raw materials and use of an established, environmentally friendly technology that allows for scaling up and the use of different, even flexible substrates without any problems.
5. 5. Extension of the principle of the reversible deposition of metals for the production of electrochromic solid-state devices to other metal depositions such as Bi, Pb is possible in principle.

The features of the invention disclosed in the above description, the drawings and the claims can be of importance both individually and in combination or sub-combination for the implementation of the invention in its various embodiments.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 3704057 [0003]
• WO 2004/067673 [0004]
• DE 102008049543 [0004]
• DE 60200400158 [0004]

Non-patent literature cited

• V. Rai et al., Adv. Eng. Mater. 2020, 22, 2000082 [0002]
• X. Tao et al., Adv. Optical Mater. 2021, 2001847 [0005]
• S. Araki et al. (Adv. Mater., Vol. 24, pp. OP122-OP126, 2012) [0007]
• M. Cardona, Phys. Rev. 129 (1963) [0025]

Claims (13)

Solid state electrochromic device (10) comprising - a transparent electrically conductive substrate (1, 2), - A metal halide solid layer (3) which contains at least one metal halide, - A solid layer (4) containing lithium ions, and - A transparent, electrically conductive cover layer (5, 6). Solid-state electrochromic device according to Claim 1 in which - the at least one metal halide in the metal halide solid layer (3) is suitable for achieving reversible metal deposition by applying electrical voltages between the substrate (1, 2) and the cover layer (5, 6). Solid-state electrochromic device according to one of the preceding claims, in which - The metal halide solid layer (3) contains silver chloride, in particular comprises a silver chloride layer with a thickness in the range from 100 nm to 300 nm. Solid-state electrochromic device according to Claim 3 , in which - the metal halide solid layer (3) contains 5 to 20 wt% LiCl. Solid-state electrochromic device according to Claim 3 or 4th , in which - the - the metal halide solid layer (3) contains 5 to 20 wt% CuCl. Electrochromic solid-state device according to one of the preceding claims, in which - the solid-state layer (4) containing lithium ions is a layer composed of at least one of LiCl, LiBO2, LlBO ₂ / LiF (3: 2), Li ₃ OCl, LiAlF ₄ , LiNbO ₃ , LIBSO (LiBO ₂ / Li ₂ SO ₄ ), LIPON (lithium phosphoroxynitride), in particular with a thickness in the range from 100 nm to 300 nm. Solid-state electrochromic device according to Claim 6 in which - the solid layer (4) containing lithium ions contains 5 to 20 wt% CuCl. Solid-state electrochromic device according to Claim 6 or 7th in which - the solid layer (4) containing lithium ions contains 5 to 20 wt% TiO ₂ . Solid-state electrochromic device according to one of the preceding claims, in which - The electrically conductive cover layer (5, 6) comprises an ITO layer (5), in particular with a thickness in the range from 100 nm to 200 nm, on a transparent carrier (6). Solid-state electrochromic device according to Claim 9 _{In which - a TiO 2} layer, in particular with a thickness in the range from 20 nm to 50 nm, is arranged on the ITO layer (5). Solid-state electrochromic device according to Claim 9 or 10 In which - the transparent carrier (6) comprises glass or a transparent polymer material. Electrochromic solid-state device according to one of the preceding claims, which is part of a light filter, a light protection device or a display device. Technical device (20) which contains at least one electrochromic solid-state device (10) according to one of the preceding claims.

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