TW201437300A - Formulations comprising washed silver nanowires and PEDOT - Google Patents

Abstract

The present invention relates to a process for the preparation of a composition which comprises a solvent A, silver nanowires and a conductive polymer, comprising the process steps: (i) the reduction of silver salts by means of a polyol serving as a solvent and reducing agent in the presence of a non-conductive polymer and subsequent precipitation of the silver nanowires thereby formed to obtain silver nanowires, on the surface of which at least some of the non-conductive polymer is adsorbed; (ii) the at least partial removal of the non-conductive polymer adsorbed on the surface of the silver nanowires to obtain purified silver nanowires; (iii) the bringing into contact of the purified silver nanowires with a solvent A and a conductive polymer. The present invention also relates to the compositions obtainable by this process, a composition which comprises a solvent, silver nanowires and a conductive polymer, a process for the production of an electrically conductive layer, the electrically conductive layer obtainable by this and the use of the compositions according to the invention.

Description

Formulation comprising washed silver nanowires and PEDOT

The present invention relates to a method for preparing a composition comprising a solvent, a silver nanowire and a conductive polymer, and the composition obtainable by the method comprises a solvent, a silver nanowire and a conductive polymer composition. The method of producing a conductive layer, the conductive layer obtainable by this method, and the use of the composition according to the present invention.

The economic importance of conductive polymers is increasing because polymers have advantages over metals in terms of processability, weight, and targeted property adjustment by chemical modification. Examples of known π-conjugated polymers are polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene and poly(p-phenylene-vinylene). The conductive polymer layer is used in various industrial applications, for example as a polymeric counter electrode in a capacitor or for penetrating an electroplated electronic circuit board. The preparation of the conductive polymer is carried out chemically or electrochemically by oxidation from a monomer precursor such as optionally substituted thiophene, pyrrole and aniline and optionally oligo derivatives thereof. In particular, chemical oxidative polymerization is widely used because it is easily industrially implemented in a liquid medium or on a different substrate.

A particularly important polythiophene for industrial use is poly(3,4-ethylenedioxythiophene) (PEDOT or PEDT), which is described, for example, in EP 0 339 340 A2, and by 3,4-extension It is prepared by chemical polymerization of oxythiophene (EDOT or EDT) and it has extremely high conductivity in the oxidized form. A summary of many poly(3,4-alkylenedioxythiophene) derivatives, in particular poly(3,4-ethylenedioxythiophene) derivatives, and their monomer units, synthesis and use by L. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik and JR Reynolds, Adv. Mater. 12, (2000) pp. 481-494. Dispersions of PEDOT and polyanions such as polystyrenesulfonic acid (PSS) as disclosed in EP 0 440 957 A2 have the specific industrial importance (PEDOT/PSS dispersion) that has been obtained. A transparent conductive film which has been found for many uses can be produced from such a dispersion, for example, as a hole injection layer in an organic light emitting diode (OLED) or as an intermediate layer in an organic photovoltaic element (OPV element). Due to the polyelectrolyte properties of PEDOT as a polycation and PSS as a polyanion, the PEDOT/PSS composition is not a true solution but is actually a dispersion. The extent to which the polymer or polymer is partially dissolved or dispersed in this case depends on the weight ratio of polycation to polyanion, the charge density of the polymer, the salt concentration of the environment, and the nature of the surrounding medium (V. Kabanov, Russian Chemical Reviews 74, 2005, 3-20). In this case, the transitional form can be a fluid. Therefore, there is no difference between the following terms " dispersed " and " dissolved ". Similarly, there is almost no difference between " dispersing " and " dissolving " or between " dispersing agent " and " solvent ". Rather, these terms are equally used hereinafter.

OLED and OPV components typically comprise a layer of indium tin oxide (ITO) as the conductive substrate layer. However, attempts are currently being made to dispense with the use of ITO because ITO is inflexible compared to conductive polymer layers, for example. However, the disadvantages of the PEDOT/PSS-containing dispersions known from the prior art are that the conductivity of the layers is too low to be used not only as a hole injection layer in an OLED or as a ITO in a standard construction of a P3HT:PCBM solar cell. An intermediate layer between the coated substrate and the semiconductor layer, and cannot be used as a substitute for the underlying ITO layer. In order for the layer comprising the conductive polymer to displace the ITO layer in the OLED and OPV elements, it must have a particularly high electrical conductivity (or low surface resistance) while having a high transmittance.

Alternative materials that can be used as an alternative to ITO, such as metal nanowires, have been known from the prior art. The manufacture of metal nanowires by the polyol method, and in particular the manufacture of silver nanowires, is known (for example, DE-A-10 2010 017706, US 7,585,349 or WO-A-2008/073143). The polyol here serves as a reducing agent for the solvent and a silver salt, preferably silver nitrate, such as a dispersing agent for polyvinylpyrrolidone (PVP) and a source of halide ions. The mixture of components is selected so that the particular growth of the line along the preferred crystal axis occurs. An anisotropic conductive strip having an aspect ratio of at least 10:1 to 1,000:1 is formed by this means.

By applying the nanowires to the substrate, a conductive film having a low surface resistance (SR) and a high electrical conductivity and a transparency of >80% can be obtained when the percolation threshold is exceeded. These conductive films can be applied to glass and especially flexible substrates and exhibit a constant electrical conductivity even after bending. By suitable structuring, such transparent electrodes can be used, inter alia, as ITO replacements in electronic devices such as LCD or plasma screens, touch screens, and organic light emitting diodes.

The silver nanowires can be applied in the form of a dispersion, for example by spin coating, spraying or by "embossing". However, if the silver nanowire is treated with a dispersion without a film former, the silver nanowire exhibits only poor adhesion to the surface and, due to loose bonding, often only improperly contacts and exhibits relatively high Surface resistance. This makes it necessary to press the layers in order to increase the conductivity and/or to cover it with another layer (for example a layer of TiO ₂ sol/gel) (Yang et al. ACS Nano 2011, 5, 9, 877-9, 882). Furthermore, a coating having a conductive material, in particular a conductive polymer, is proposed in the patent document, as described, for example, in WO-A-2011/041232 or WO-A-2008/131304. Imprinting of dried silver nanowires to pre-manufactured PEDOT/PSS layers is also known (Peumans et al. Adv. Mater. 2011, 23, 2905-2910).

However, the above described method for applying a conductive layer comprising a silver nanowire to a substrate is relatively technically involved. However, the simple application of a conductive layer by means of a simple coating method is desirable for use on an industrial scale. US-A-2012/0104374 describes the combination of a silver nanowire suspension with a neutral to alkaline PEDOT/PSS material and coating by spin coating using such formulations. However, the application does not contain an indication of the quality of the silver nanowires used to prepare the mixture with the conductive polymer. US-A-2012/0104374 does not give information on the purity of the silver nanowires used therein, and in detail does not give information on the amount of non-conductive polymers due to the silver nanowires. The method of manufacture is conventionally adsorbed on the surface of the silver nanowire.

The present invention is based on the object of overcoming the disadvantages associated with the use of such compositions to make conductive layers suitable for use as ITO substitutes resulting from prior art compositions comprising silver nanowires.

In particular, the present invention is based on the object of providing a composition comprising a silver nanowire which is characterized in a simple manner on a commercial scale by low surface resistance and at the same time high transmittance and is therefore suitable for use A conductive layer of ITO, an OPV component, or an ITO replacement material in a touch screen. In this case, the composition should be distinguished in detail by a particularly advantageous storage stability.

The invention is furthermore based on the object of providing a method by means of which a composition comprising silver nanowires and which is advantageous can be produced in a simple and reproducible manner.

The contribution to the above object is achieved by a method of preparing a composition (preferably a dispersion) comprising a solvent A, a silver nanowire and a conductive polymer, the method comprising the following method steps: (i) In the presence of a non-conductive polymer, the silver salt is reduced by means of a polyol as a solvent and a reducing agent, and then the silver nanowire thus formed is precipitated to obtain a silver nanowire, and at least some of the non-conductive polymer is adsorbed in the silver mine. (ii) at least partially removing the non-conductive polymer adsorbed on the surface of the silver nanowire to obtain a purified silver nanowire; (iii) purifying the purified silver nanowire with solvent A and Conductive polymer contact.

Surprisingly, it has been found that a composition comprising a conductive polymer and having been prepared from a silver nanowire which has been first purified by a washing method is more remarkable than a composition which has been prepared using an unwashed silver nanowire. Improved storage stability is distinguished.

In step (i) of the process of the process of the invention, the silver salt is first reduced in the presence of a non-conductive polymer by means of a polyol acting as a solvent and a reducing agent, and then the silver nanowire formed by this procedure is precipitated. The basic principle of the manufacture of such a silver nanowire is well known from the prior art, for example from DE-A-10 2010 017706. Process step (i) may thus comprise, for example, the following partial steps: (ia) supplying a reaction mixture comprising a polyol, a non-conductive polymer adsorbed on the surface of the silver, a chemical reagent forming a halide ion and/or forming a pseudohalogen a chemical reagent for ions and a chemical reagent for forming a redox pair (selected from the group consisting of bromine, iodine, copper, vanadium, and mixtures thereof); (ib) adding a certain amount of silver salt such that the concentration of silver in the reaction mixture is a reaction mixture The total weight is at least 0.5 wt.%; (ic) the silver salt is reduced over the duration of the reaction at a temperature of the reaction mixture of at least 75 ° C; (id) the silver nanowire is separated from the reaction mixture.

In this regard, as in DE-A-10 2010 017706, it should be noted that the reaction mixture components "chemical reagents for forming halide ions and/or chemical reagents for forming pseudohalides" and "chemical reagents for forming redox couples (selected from bromine The definitions of "groups of iodine, copper, vanadium and their mixtures" overlap. The chemical reagent bromine and iodine which form a redox pair are halogen, and the halogen (in the form of a salt thereof) is simultaneously a "salt of a halide ion" and a chemical reagent forming a redox pair (selected from a group consisting of bromine and iodine) "."

Preferred as a polyol, as a non-conductive polymer adsorbed on the surface of silver (referred to as "organic chemical agent adsorbed on a silver surface" in DE-A-10 2010 017706), as a halide ion and/or a chemical reagent for halide ions, a chemical reagent for forming a redox couple (selected from the group consisting of bromine, iodine, copper, vanadium, and mixtures thereof) and a compound thereof as a silver salt are already in DE-A-10 2010 017706 Mentioned as preferred compounds.

Preferred polyols are therefore selected from the group consisting of 1,2-ethanediol, 1,2-propane Alcohol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1, 6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, triethanolamine, trimethylolamine methane, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol and at the reaction temperature It is a liquid polyethylene glycol such as polyethylene glycol 300. Very preferred polyols are selected from the group consisting of glycerin, ethylene glycol, tetraethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol And the group consisting of 2,3-butanediol, using ethylene glycol and glycerin is the best.

The non-conductive polymer adsorbed onto the surface of the silver is required to form the desired linear morphology in the polyol process. In principle, all of the compounds mentioned under the heading " Organic Protecting Agent (OPA) " on pages 19 to 27 (paragraphs [0095] to [0116]) of WO-A-2009/128973 can be used as non- Conductive polymers. However, the preferred non-conductive polymer adsorbed on the surface of the silver is at a weight average molecular weight (preferably as determined by gel permeation chromatography) of at least 100,000 g/mol, more preferably at least 250,000 g/mol and most preferably at least 500,000 g/mol of non-conductive polymer. In this regard, it is highly preferred that the non-conductive polymer be selected from the group consisting of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and mixtures of different grades (molecular weights) of such polymers and copolymers. Suitable comonomers are, for example, N-vinylimidazole, vinyl acetate and ethylene caprolactam. However, polyvinylpyrrolidone having a molecular weight of at least 100,000 g/mol, more preferably at least 250,000 g/mol and most preferably at least 500,000 g/mol is preferably used as the non-conductive polymer.

The chemical agent forming the halide ion is preferably a salt of a halide ion, and particularly preferably NaCl, NaBr, NaI, KCl, KBr, KI or a mixture of at least two thereof, or elemental bromine, elemental iodine or a mixture of at least two thereof The chemical agent forming the pseudohalide ion is preferably a salt of a pseudohalide ion, and particularly preferably NaSCN, KSCN or a mixture thereof.

The chemical reagent for forming the redox couple is preferably elemental copper, elemental vanadium, copper oxide, vanadium oxide, copper hydroxide, vanadium hydroxide, copper sulfate, vanadium sulfate, copper nitrate, vanadium nitrate, vanadium trichloride or the like. a mixture. The chemical reagent forming the halide ion and the chemical reagent forming the redox couple are preferably present in the reaction mixture provided in process step (ia). however, These chemical agents (or at least one of such chemical agents) may also be added only after subsequent addition, for example, to the silver salt in process step (ib) or after the addition of the silver salt in process step (ib).

With regard to the presence of other possible additives in the reaction mixture provided in process step (ia) and the relative amounts of the specific components present in the mixture, reference is made to the teachings of DE-A-10 2010 017706, the disclosure of which is hereby incorporated by reference. The composition of the disclosure about the manufacture of silver nanowires.

In method step (ib), an amount of silver salt is subsequently added such that the concentration of silver in the reaction mixture is at least 0.5 wt.%, based on the total weight of the reaction mixture, and the silver salt may, for example, be at least 75 ° C, particularly preferably at least 100 ° C. The reaction mixture is added at the temperature. AgNO ₃ is preferred as the silver salt and is added to the reactants in solution or directly as a solid. Suitable solvents for the silver salt are, in particular, the polyols used in the reaction, i.e. preferably ethylene glycol and/or glycerol. The addition can be carried out simultaneously, in multiple portions or continuously over a relatively long period of time. The silver salt is added at the reaction temperature. The silver salt is mathematically equivalent to a silver concentration of at least 0.5 wt.% in the reaction mixture. In a preferred embodiment of the silver nanowire manufacturing process, the silver is present at a concentration of at least 0.75 wt.%, more preferably at least 1.0 wt.%, most preferably at least 1.5 wt.%.

In process step (ic), the silver salt is subsequently reduced, preferably at a temperature of at least 75 ° C, particularly preferably at least 100 ° C and more preferably at least 120 ° C for the entire reaction period. As described in DE-A-10 2010 017706, the formation of silver nanowires can be easily visually monitored when performing this method.

When the reaction has ended, the reaction mixture can be allowed to cool. A reaction mixture comprising silver nanowires having at least some non-conductive polymer adsorbed on the surface is obtained. The silver nanowire may then be precipitated in another part of the step (id), for example after diluting the reaction mixture by adding a suitable solvent such as acetone, tetrahydrofuran or ethyl acetate or after adding a chemical reagent to the modified electrical double layer. The reaction mixture was isolated from this. The silver nanowires precipitated in this manner can then be separated from the liquid phase by methods known to those skilled in the art, such as by centrifugation, filtration or by decantation.

Preferably, the silver nanowire is characterized by a length of from 1 μm to 200 μm, 50 The diameter of nm to 1,300 nm and the aspect ratio (length: diameter) of at least 5:1, extremely preferably an aspect ratio in the range of 10:1 to 1,000:1.

In step (ii) of the method of the invention, the non-conductive polymer adsorbed on the surface of the silver nanowire is at least partially removed to obtain a purified silver nanowire. In particular, it is preferred in this aspect to remove the non-conductive polymer adsorbed on the surface of the silver nanowire to a certain extent in method step (ii) such that the weight ratio present after the end of method step (i) Initially, silver: the weight ratio of the adsorbed non-conductive polymer is increased by at least 2 times, particularly preferably by at least 5 times and optimally by at least 10 times.

At least partial removal of the non-conductive polymer adsorbed onto the surface of the silver nanowire is preferably carried out by washing the silver nanowire obtained in step (i) of the method (i) with a solvent B which is at least partially soluble in the non-conductive polymer. In this respect, it has proven to be particularly advantageous if process step (ii) comprises the following partial steps: (iia) suspending the silver nanowire obtained in process step (i) on a non-conductive material adsorbed on the surface of the silver nanowire The polymer is at least partially soluble in solvent B; (iib) the suspended silver nanowires are separated.

If polyvinylpyrrolidone is used as the non-conductive polymer, the possible solvent B used in the method step (iia) and which is at least partially soluble in the non-conductive polymer adsorbed on the surface of the silver nanowire is water or alcohol in detail ( Such as methanol or ethanol) or a mixture thereof. In this aspect, it is further preferred that the silver nanowire is suspended in the range of from 15 ° C to 100 ° C, particularly preferably from 20 ° C to 50 ° C for from 1 minute to 5 hours, particularly preferably for 5 minutes. Minutes to 60 minutes. Further preferably, the composition obtained in the method step (id) after the silver nanowire is suspended in the silver nanowire obtained in the step (i) of the method, preferably after the silver nanowire has been separated. The amount of the solvent B is from 1 g to 100 g, particularly preferably from 2.5 g to 25 g.

The separation of the suspended silver nanowires in method step (iib) is preferably carried out again by methods known to those skilled in the art, especially preferably by centrifugation.

It has also been demonstrated by means of the washings described by the partial steps (iia) and (iib) It is advantageous to successively purify the silver nanowires several times, but particularly preferably twice, three times, four times or five times, and it has been found that the amount of non-conductive polymer adsorbed on the surface of the silver nanowire can be washed with The number of steps increases and continues to decrease.

It is also conceivable that the continuous washing of the silver nanowire obtained in the method step (i) in contact with the solvent B which is at least partially soluble in the non-conductive polymer adsorbed on the surface of the silver nanowire is also conceivable. This can be done, for example, by dialysis.

In this respect, it is especially preferred if the polyvinylpyrrolidone is used as a non-conductive polymer, the purified silver nanowire obtained in method step (ii) has a nitrogen content of less than 7 wt.%, particularly preferably less than 2.5. Wt.% and optimally less than 1 wt.%, in each case based on the total weight of the dried residue of the purified silver nanowire.

In step (iii) of the process of the invention, the purified silver nanowire is subsequently contacted with solvent A and a conductive polymer, but is particularly preferably contacted with a dispersion comprising solvent A and a conductive polymer.

In this case, polythiophene is particularly preferred as the conductive polymer, and in particular, the polythiophene has the following formula:

Wherein A represents optionally substituted C ₁ -C ₅ alkylene, and R represents a linear or branched chain optionally substituted C ₁ -C ₁₈ alkyl, optionally substituted C ₅ -C ₁₂ naphthenic Substituted, optionally substituted C ₆ -C ₁₄ aryl, optionally substituted C ₇ -C ₁₈ aralkyl, optionally substituted C ₁ -C ₄ hydroxyalkyl or hydroxy, 0 to 8 The group R can be bonded to A and, in the case of more than one group, can be the same or different.

Preferably, the polythiophene carries H on the terminal group in each case.

In the case of the present invention, C ₁ -C ₅ alkylene A is preferably methylene, ethyl, n-propyl, n-butyl or pentyl. C ₁ -C ₁₈ alkyl R preferably denotes a straight or branched C ₁ -C ₁₈ alkyl group such as methyl, ethyl, n-propyl or isopropyl, n-butyl, isobutyl, second butyl Or a tributyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1 , 2-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-decyl, n-decyl, n-undecyl, N-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl, C ₅ -C ₁₂ cycloalkyl R represents, for example, cyclopentyl, cyclohexyl, cycloheptane a group, a cyclooctyl group, a cyclodecyl group or a cyclodecyl group, a C ₅ -C ₁₄ aryl group R represents, for example, a phenyl or naphthyl group, and a C ₇ -C ₁₈ aralkyl group R represents, for example, a benzyl group, an o-tolyl group, M-tolyl, p-tolyl, 2,3-xylyl, 2,4-dimethylphenyl, 2,5-xylyl, 2,6-dimethylphenyl, 3,4-xylyl, 3, 5-dimethylphenyl or mesityl group. The foregoing list is intended to illustrate the invention by way of example and is not considered as a

In the context of the present invention, a plurality of organic groups may be optionally used as the group A and/or other substituents of the group R, such as alkyl, cycloalkyl, aryl, aralkyl, alkoxy, Halo, ether, thioether, disulfide, fluorenylene, fluorenyl, sulfonate, amine, aldehyde, ketone, carboxylate, carboxylic acid, carbonate, formic acid Ester group, cyano group, alkyl decyl group and alkoxy fluorenyl group and formamidine group.

A represents a C ₂ -C ₃ alkylene group-substituted polythiophene which is optionally substituted. Poly(3,4-extended ethylenedioxythiophene) is extremely preferred as the polythiophene.

Polythiophenes can be neutral or cationic. In particular preferred examples, which are cationic, "cationic (Cationic)" refers only to the charges on the polythiophene main chain. Depending on the substituent on the group R, the polythiophene may have a positive and negative charge in the structural unit, a positive charge on the polythiophene backbone and a negative charge as the case may be via a sulfonate group or a carboxylate group. Substituted on the group R. In this case, the positive charge of the polythiophene backbone can be partially or completely eliminated by the anionic groups which are optionally present on the group R. In summary, in these cases, the polythiophene can be cationic, neutral or even anionic. However, in the context of the present invention, they are all considered cationic polythiophenes because the positive charge on the polythiophene backbone is the determining factor. The positive charge is not shown in the equation because its exact number and position cannot be completely determined. However, the number of positive charges is at least 1 and at most n, where n is the total number of all repeating units (same or different) in the polythiophene.

In order to counteract the positive charge of the polythiophene, the electrically conductive polymer further comprises a polyanion which is preferably based on a polymer functionalized with an acid group. Anions of polymeric carboxylic acids such as polyacrylic acid, polymethacrylic acid or polymaleic acid or polymeric sulfonic acids such as polystyrenesulfonic acid and polyvinylsulfonic acid are described in detail as polyanions. These polycarboxylic acids and polysulfonic acids may also be copolymers of ethylene carboxylic acid and vinyl sulfonic acid with other polymerizable monomers such as acrylates and styrene. Possible addition of polyanionic colloid-forming perfluorinated polyanion, which may be for example commercially available under the trademark Nafion ^®. The molecular weight of the polymer functionalized with an acid group and supplied with a polyanion is preferably from 1,000 to 2,000,000, particularly preferably from 2,000 to 500,000. Acid-functionalized polymers or alkali metal salts thereof are commercially available, such as polystyrenesulfonic acid and polyacrylic acid, or can be prepared by known methods (see, for example, Houben Weyl, Methoden der organischen Chemie, E 20 Volume Makromolekulare Stoffe, Part 2, (1987), pp. 1141 and later).

The polymer functionalized with an acid group (polyanion) and polythiophene (in detail, polystyrenesulfonic acid and poly(3,4-ethylenedioxythiophene)) may be preferably 0.5:1 to 50:1. A weight ratio of from 1:1 to 30:1, particularly preferably from 2:1 to 20:1, is present in the conductive polymer used in process step (iii). The weight of the conductive polymer here corresponds to the weight of the monomer used in the preparation of the conductive polymer, assuming complete conversion occurs during the polymerization.

Preferably, the conductive polymer used in method step (iii) comprises a complex of polythiophene and a polyanion, and is most preferably a PEDOT/PSS composite. The complexes can be obtained by polymerizing a thiophene monomer, preferably 3,4-ethylenedioxythiophene, in an oxidized form in the presence of a polyanion, preferably polystyrenesulfonic acid, in an aqueous solution. .

Preferred solvents A are water, aliphatic alcohols (such as methanol, ethanol, isopropanol and n-butanol), aliphatic ketones (such as acetone and methyl ethyl ketone), aliphatic carboxylic esters (such as ethyl acetate and Butyl acetate), aromatic hydrocarbons (such as toluene and xylene), aliphatic hydrocarbons (such as hexane, heptane and cyclohexane), chlorinated hydrocarbons (such as dichloromethane and dichloroethane), aliphatic nitriles (such as acetonitrile), aliphatic hydrazine and hydrazine (such as dimethyl hydrazine and cyclobutyl hydrazine), aliphatic carboxylic acid amide (such as methyl acetamide and dimethylformamide) or aliphatic and aromatic Group ethers (such as diethyl ether and anisole), using water as the solvent A, are particularly preferred in the case where the PEDOT/PSS composite is used as the conductive polymer. A mixture of water or water and the above organic solvent can also be used as the solvent A.

According to a particularly preferred embodiment of the process of the invention, the purified silver nanowire obtained in process step (ii) is complexed with a polythiophene and a polyanion in process step (iii) (especially preferred) It is a PEDOT/PSS composite) mixed as a conductive polymer and water as an aqueous dispersion of solvent A. For this the PEDOT / PSS dispersion liquid can be obtained, for example, under the trade name Clevios ^TM commercially. The solids content of such dispersions is conventionally in the range of from 0.1 wt.% to 10 wt.%, particularly preferably from 1 wt.% to 5 wt.%. However, it is also conceivable to prepare a conductive polymer in the presence of purified silver nanowires, wherein the polymerizable precursor of the conductive polymer (for example, in poly(3,4-ethylenedioxythiophene) as a conductive polymerization) 3,4-Exoethylenedioxythiophene in the presence of a polymer is polymerized in the presence of a purified silver nanowire and in the presence of a polyanion such as polystyrenesulfonic acid.

According to the present invention, it is further preferred that the purified silver nanowire obtained in the method step (ii) is in a relative amount to the conductive polymer used in the method step (iii) such that the composition is silver: a conductive polymer. The weight ratio is in the range of 10:1 to 1:10, particularly preferably in the range of 5:1 to 1:5 and most preferably in the range of 2:1 to 1:2. When the above composite of polythiophene and polyanion is used as the conductive polymer, the relative amount specified above means the weight ratio of silver: the total amount of polythiophene and polyanion.

In addition to solvent A, silver nanowires and conductive polymers, by the method of the invention The available compositions may optionally contain other additives such as additives to increase conductivity, antioxidants, adhesion promoters, acids or bases for pH adjustment, binders, crosslinkers, surfactants or familiar techniques Other additives are known as additives to PEDOT/PSS dispersions. These additives may be added in principle to the purified silver nanowires used in process step (iii), and the dispersion used in process step (iii) comprises a conductive polymer or the process obtained in process step (iii) a mixture of two components.

A surfactant is understood to mean an amphiphilic material having a hydrophilic head group and a hydrophobic portion. The hydrophilic group can be ionic or nonionic in nature. Due to the molecular structure and tendency to accumulate at the interface, this species reduces interfacial tension and produces improved wetting characteristics. Suitable surfactants are in particular anionic surfactants, such as alkyl benzene sulfonic acid and salts, paraffin sulfonates, alcohol sulfonates, ether sulfonates, sulfosuccinates, phosphates, alkyl ethers. a carboxylic acid or a carboxylic acid ester; a cationic surfactant such as a quaternary alkyl ammonium salt; a nonionic surfactant such as a linear alcohol ethoxylate, an oxy alcohol ethoxylate, an alkyl phenol ethoxylate Or an alkyl polyglucoside.

Conductivity additives for polythiophenes that can be used are polyalkylene glycols (specifically polyethylene glycol or polypropylene glycol, polyglycerol or mixtures thereof), polyols (such as propylene glycol and ethylene glycol), and arbium (such as Amidoxime), carboxylic acid amide (such as methyl acetamide, dimethyl acetamide, dimethylformamide), N-methylpyrrolidone, N-cyclohexyl pyrrolidone, ionic Liquid or sugars such as sorbitol are highly preferred using high boiling solvents such as DMSO or ethylene glycol. The addition of 2 wt.% to 5 wt.% of these additives to the PEDOT/PSS aqueous dispersion caused a significant increase in conductivity at the time of film formation.

Antioxidants are agents that prevent oxidative degradation of materials. Oxidative degradation of materials is often promoted by UV light. In the case where polythiophene is used as the conductive polymer, an aromatic polyhydroxy compound has proven to be suitable. Particularly preferred antioxidants according to the present invention are gallic acid and propyl gallate because of their inhibitory effect in the conductive layer produced by the composition. In a month, in The value can be kept below 60 Ω/□ under the same storage conditions as the unprotected layer. The amount of gallic acid or propyl gallate used in the method of the present invention is preferably in the range of 0.001 wt.% to 5 wt.%, particularly preferably in the range of 0.005 wt.% to 1 wt.% and most preferably 0.01. In the range of wt.% to 0.2 wt.%, in each case, based on the total weight of the composition obtained by the process of the present invention.

Possible adhesion promoters are in particular organofunctional decanes and their hydrolysis products, such as 3-glycidoxypropyltrialkoxydecane, 3-aminopropyl-triethoxydecane, 3-mercaptopropyl Trimethoxy decane, 3-methacryloxypropyl-trimethoxy decane, vinyl trimethoxy decane or octyl triethoxy decane, and the crosslinking agent which can be used is a melamine compound, which is masked Isocyanate, functional decane (eg tetraethoxy decane), alkoxy decane hydrolysate (eg based on tetraethoxy decane), epoxy decane (such as 3-glycidoxypropyl trialkoxy decane) ), epoxide or oxetane.

Suitable binders are polyalkylene glycol, polyvinyl acetate, polycarbonate, polyvinyl butyrate, polyacrylate, polymethacrylate, polystyrene, polyacrylonitrile, polyvinyl chloride, polybutylene Alkene, polyisoprene, polyester, polyoxyl and pyrrole/acrylate, vinyl acetate/acrylate and ethylene/vinyl acetate copolymers, which are soluble in organic solvents.

Preferred bases for adjusting the pH are, in addition to ammonia, alkali metal hydroxides and alkaline earth metal hydroxides, more particularly amines, particularly preferably primary, secondary or tertiary amines, wherein the alkyl group is selected from the group consisting of A group consisting of methyl-, ethyl-, n-propyl- or isopropyl-. An example of a suitable amine is dimethylaminoethanol.

According to the present invention, it is further preferred to determine the pH of the composition in the range of 2 to 7, and more preferably in the range of 4 to 6.

To achieve the above object, it also contributes to a composition comprising a solvent, a silver nanowire and a conductive polymer, preferably a dispersion, which composition is obtainable by the method of the present invention. Preferably, the composition is characterized in that if SR _{t = 0 is} the surface resistance (in [Ω / □]) of the conductive layer produced by the composition at time t ₀ , and SR _{t = 30 days} is the same composition the conductive layer was produced in a closed vessel dismiss light in the 30 days of storage at the time t _{30 days,} the surface resistivity (in [Ω / □] units), then at _{25 ℃: SR t = 0 /} SR t = 30 _day 0.75.

Particularly preferably, SR _{t = 0} / SR _{t = 30 days} 0.9, better 0.95 and best 0.99.

To achieve the above object, a contribution is also made by a composition comprising a solvent A, a silver nanowire, and a conductive polymer, preferably a dispersion, wherein if SR _{t = 0} is a conductive layer produced by the composition n Surface resistance at time t ₀ (in [Ω/□]), and SR _{t = 30 days} for the same composition, the conductive layer is stored in a closed container for screen light removal at 25 ° C for 30 days at time t ₃₀ The surface resistance of the _day (in [Ω/□]), then: SR _t=0 /SR _{t=30 days} 0.75.

Particularly preferably, SR _{t = 0} / SR _{t = 30 days} 0.9, better 0.95 and best 0.99.

In this case, preferred solvent A, silver nanowire, and conductive polymer are the preferred solvents A, silver nanowires, and conductive solvents of the conductive polymers described above in connection with the method of the present invention, Silver nanowires and conductive polymers. In addition to solvent A, silver nanowires, and conductive polymers, the dispersions of the present invention may also contain other additives, and such additives which have been described above as preferred additives associated with the process of the present invention are preferred.

Preferably, the composition of the present invention (preferably the dispersion of the present invention, such as the composition obtainable by the method of the present invention) is characterized in that the composition is less than 1.5 g, particularly preferably less than 1.0 g per gram of silver, More preferably, the non-conductive polymer less than 0.85 g and most preferably less than 0.1 g is adsorbed on the surface of the silver nanowire. The polymers of the preferred non-conductive polymers which have been described above as being associated with the process of the invention are preferred in this case as non-conductive polymers. Therefore, according to the present invention, it is especially preferred that the composition has less than 1.5 g, particularly preferably less than 1.0 g, more preferably less than 0.85 g and most preferably less than 0.1 g of polyvinylpyrrolidone per gram of silver adsorbed on the silver nanowire. On the surface.

In connection with the composition of the present invention, it is further preferred that the nitrogen content of the silver nanowire in the composition (measured in the dry residue) is less than 7 wt.%, particularly preferably less than 4 wt.%, and most preferably less than 1 wt.%, based on the total weight of the dry residue of the silver nanowire in each case. The nitrogen content (measured in the dry residue of the total composition) is preferably less than 1 wt.% and particularly preferably less than 0.5 wt.%, in each case based on the total weight of the dry residue of the composition.

The composition of the present invention is further preferably characterized in that it contains a certain relative amount of silver nanowires and a conductive polymer such that the weight ratio of silver:conductive polymer in the dispersion is in the range of 10:1 to 1:10, especially Preferably in the range of 5:1 to 1:5 and optimally in the range of 2:1 to 1:2.

The pH of the dispersion of the present invention is preferably in the range of 2 to 7, particularly preferably in the range of 4 to 6.

To achieve the above object, a contribution is also made by a method of producing a conductive layer, the method comprising the steps of: I) supplying a substrate; II) applying the composition obtainable by the method of the invention or the composition of the invention Substrate; III) at least partially removing solvent A from the composition to obtain a conductive layer on the substrate.

In method step I), a substrate is first provided, the nature of which depends on the intended use of the composition obtainable by the process of the invention or the composition of the invention. When a composition is used, for example, to produce a solid electrolyte layer in a capacitor, the substrate may be, for example, a porous anode body provided with a dielectric layer. If a dispersion is used, for example, to create a hole injection layer in an OLED, the substrate can be, for example, a transparent electrode such as ITO. Possible substrates are furthermore detailed as films, particularly preferably polymeric films, very preferably polymeric films of thermoplastic polymers, or glass sheets.

In method step II), the composition obtainable by the process of the invention or the composition of the invention is then applied to the substrate, which may be carried out by known methods, for example by spin coating, dipping, pouring, dripping Falling, spraying, atomizing, knife coating, brushing or printing (for example by inkjet printing, screen printing, gravure printing, lithography or mobile printing), the wet film thickness is for example The wet film thickness is preferably from 2 μm to 50 μm from 0.5 μm to 250 μm.

In method step III), at least some of the solvent A is subsequently removed from the composition to obtain a conductive layer on the substrate, preferably removed by drying at a temperature ranging from 20 ° C to 200 ° C. The substrate of the object is carried out.

To achieve the above object, the conductive layer obtained by the above method is also contributed.

In order to achieve the above object, the conductive layer in the OLED, the OPV element, and the touch screen is also produced by using the composition obtainable by the method of the present invention or the composition of the present invention for shielding electromagnetic radiation (" EMI shielding "). Used for sensors or for generating IR reflective layers to contribute. However, it is highly preferred to use the composition obtainable by the method of the present invention or the composition of the present invention as an ITO substitute in an OLED, an OPV element or a touch screen.

The invention is now explained in more detail by means of test methods and non-limiting examples.

Test method

Determination of surface resistance

The surface resistance (SR) of the coating was measured by means of a 4-point measurement and stated in units of Ω/□.

Determination of transmittance

The transmittance of the coated substrate was measured on a 2-channel spectrometer (Lambda 900, PerkinElmer). In order to eliminate the interference of the scattered light here, the sample is measured in a photometer sphere (Ulbricht sphere), whereby the scattered light and the transmitted light are detected by the photodetector. Transmittance is therefore understood to mean the absorption of the 1-coating and substrate.

First, the transmittance of the pure substrate was measured. A Melinex 506 film having a thickness of 175 μm was used as the substrate. Thereafter, the coated substrate is measured.

In the visible range (ie 320nm to 780nm) in steps of 5nm Record the transmission spectrum.

The standard color value Y of the sample is calculated from the spectrum based on a 10° observer angle and a light pattern D65 according to DIN 5033. The internal transmittance is calculated from the ratio of the standard color value (Y) of the coated substrate to the standard color value (Y ₀ ) of the uncoated substrate: the internal transmittance is equivalent to Y/Y ₀ × 100 in percentage. For the sake of simplicity, only the transmittance is referred to hereinafter.

Determination of superior value

For better comparability of coating results, transmittance and surface resistance (FOM) are used, such as have been proposed by Gordon (RG Gordon, MRS Bulletin August 1996, pages 52-57). This figure of merit is generated by:

Determination of turbidity

The haze value was determined using a Haze-gard plus of BYK Gardner (Geretsried).

CHN analysis

A dry residue for determining the nitrogen content in the silver nanowire was obtained by drying 2 g of the silver nanowire at 100 ° C for 14 hours in a vacuum (< 50 mbar).

The elemental content determination was performed at Currenta Ltd. and OGH as a commissioned analysis. Measurements were performed on a LECO TruSpec instrument (LECO, St. Joseph, USA) and the carbon and hydrogen contents were determined using an IR measurement unit. Nitrogen determination was performed by means of a heat conduction detector.

Example

Example 1: Synthesis of Silver Nanowires (According to the Invention)

Ethylene glycol (193 g, technical grade 98%, Applichem Darmstadt) was initially introduced into the round bottom flask and heated and, under heat, polyvinylpyrrolidone (4.5 g, Luvitec K90, BASF, Ludwigshafen) was introduced. Subsequently a solution of silver nitrate (4.5 g, 63.5% metal substrate, Johnson Matthev, Enfield) in ethylene glycol (20.5 g) and vanadium chloride (9 mg, 99%, A solution of Merck, Darmstadt) in ethylene glycol (2.5 g) and heating the mixture to 120 °C. The longitudinal growth of the nanowires was monitored under a microscope, and after the end of the growth, the reaction was stopped by pouring the hot reaction mixture into a water bath. Thereby, the mixture 1 was obtained.

Example 2: Precipitation-silver nanowire (according to the invention)

To 50 g of the mixture 1 of Example 1, 130 ml of acetone was added while stirring. The beginning of the settlement is indicated by the presence of larger aggregates. The mixture was left for 30 minutes. The supernatant layer solution was discarded, and 3.5 g of a slurry-like precipitate (mixture 2) was obtained.

Example 3: Silver Nanowire - First Washing Step (According to the Invention)

5 g of the acetone-wet precipitate of Example 2 (mixture 2) was suspended in 20 g of water, and the suspension was homogenized by shaking. The homogenous mixture was centrifuged at 2,500 rpm for 20 minutes. The supernatant layer was removed and discarded, and the sediment was filled with water to 5 g, and the mixture was homogenized by shaking (mixture 3).

Example 4: Silver nanowire - second washing step (according to the invention)

5 g of the suspension of Example 3 was suspended in 20 g of water and the suspension was homogenized by shaking. The homogenous mixture was centrifuged at 2,500 rpm for 20 minutes. The supernatant layer was removed and discarded, and the sediment was filled with water to 5 g, and the mixture was homogenized by shaking (mixture 4).

Example 5: Silver nanowire - third washing step (according to the invention)

5 g of the suspension of Example 4 was suspended in 20 g of water and the suspension was homogenized by shaking. The homogenous mixture was centrifuged at 2,500 rpm for 20 minutes. The supernatant layer was removed and discarded, and the sediment was filled with water to 5 g, and the mixture was homogenized by shaking (mixture 5).

Example 6: CHN determination

In each case, a 2 g portion of the silver nanowire suspension of the mixture 2-5 was dried in vacuum at 100 ° C for 14 hours. The ingredients of the dried residue were determined by means of CHN analysis and the results are summarized in Table 1.

Table 1 clearly shows that the content of the nitrogen-containing component can be significantly reduced by washing with water.

Example 7: Formulation of silver nanowire + Clevios PH 1000 (according to the invention)

0.83 g of the mixture 3 of Example 3 (8.1% Ag content by weight, 67 mg silver) and 7.64 g of water, 7.85 g of Clevios PH 1000 (86 mg PEDOT/PSS, Heraeus Precious Metals, Leverkusen) and 0.755 g of dimethyl hydrazine were analyzed. (DMSO, ACS reagent, Sigma Aldrich, Munich) mixed. In the final step, 50 μl of Triton X 100 (Sigma-Aldrich, Munich) was added to the formulation. The formulation was applied to Melinex 506 film (Pütz Co., Ltd. + Folien KG, Taunusstein) using a spiral doctor blade of Erichsen (Erichsen K Hand Coater 620), thereby obtaining wet film thicknesses of 4, 6 and 12 μm. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 2.

Example 8: Silver Nanowires Washed twice - Formulation of Clevios PH 1000 (according to the invention)

1.12 g of the mixture 4 of Example 4 (6.0% Ag content by weight, 67 mg silver) was mixed with 7.35 g water, 7.85 g Clevios PH 1000 (86 mg PEDOT/PSS) and 0.755 g DMSO. In the final step, 50 μl of Triton X 100 was added to the formulation. The formulation was applied to Melinex 506 film using a Erichsen spiral doctor blade, thereby obtaining wet film thicknesses of 4, 6 and 12 μm. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 2.

Example 9: Washing 3 times of silver nanowires - formulation of Clevios PH 1000 (according to the invention)

0.96 g of the mixture 5 of Example 5 (7.0% Ag content by weight, 67 mg silver) was mixed with 7.51 g of water, 7.85 g of Clevios PH 1000 (86 mg PEDOT/PSS) and 0.755 g of DMSO. In the final step, 50 μl of Triton X 100 was added to the formulation. The formulation was applied to Melinex 506 film using a Erichsen spiral doctor blade, thereby obtaining wet film thicknesses of 4, 6 and 12 μm. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 2.

Example 10: Formulation without high boiling point material, 0.4% silver nanowire

2.48 g of the mixture 5 of Example 5 (2.7% Ag content by weight, 67 mg silver) was mixed with 7.51 g of water and 7.85 g of Clevios PH 1000 (86 mg PEDOT/PSS). In the final step, 50 μl of Triton X 100 was added to the formulation. The formulation was applied to Melinex 506 film using a Erichsen spiral doctor blade, thereby obtaining wet film thicknesses of 4, 6 and 12 μm. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 3.

Example 11: Formulation without conductivity additive, 0.6% silver nanowire

3.70 g of the mixture 5 of Example 5 (SAR 232-4) (2.7% Ag content by weight, 100 mg silver) was mixed with 5.55 g of water and 7.85 g of Clevios PH 1000 (86 mg PEDOT/PSS). In the final step, 50 μl of Triton X 100 was added to the formulation. The formulation was applied to Melinex 506 film using a Erichsen spiral doctor blade, thereby obtaining wet film thicknesses of 4, 6 and 12 μm. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 4.

Example 12: Storage stability of the formulation of Example 9.

After 30 days of storage, the formulation obtained in Example 9 was applied to the Melinex 506 membrane using a 6 μm spiral scraper from Erichsen. The coating was dried at 120 ° C for 5 minutes.

Example 13: Formulation of Mixture 2 (0.6% Silver Content)

0.999 g of the mixture 2 of Example 2 (10% Ag content by weight, 100 mg silver) was mixed with 7.5 g of water, 7.85 g of Clevios PH 1000 (86 mg PEDOT/PSS) and 0.755 g of DMSO. In the final step, 50 μl of Triton X 100 was added to the formulation. The formulation was applied to Melinex 506 membrane using a spiral scraper from Erichsen, thereby obtaining 12 μm Wet film thickness. The coating was dried at 120 ° C for 5 minutes. The measurement results of the coating are summarized in Table 6.

Example 14: Storage stability of the formulation of Example 13

After 4 days of storage, the formulation obtained in Example 13 was applied to the Melinex 506 membrane using a 12 μm spiral doctor blade from Erichsen. The coating was dried at 120 ° C for 5 minutes.

Example 15: CHN analysis of dry residues of the formulation.

In a vacuum drying oven, 5 g of the formulation of Example 9 was dried at 100 ° C for 1 night and the samples were investigated by means of CHN analysis.

Claims (26)

A method for preparing a composition comprising a solvent A, a silver nanowire, and a conductive polymer, the method comprising the steps of: (i) in the presence of a non-conductive polymer, by means of a polyol as a solvent and a reducing agent Reducing the silver salt, and then precipitating the silver nanowire thus formed to obtain a silver nanowire, at least some of which are adsorbed on the surface of the silver nanowire; (ii) at least partially removing the silver The non-conductive polymer adsorbed on the surface of the nanowire to obtain a purified silver nanowire; (iii) contacting the purified silver nanowire with solvent A and a conductive polymer. The method of claim 1, wherein the non-conductive polymer used in the method step (i) has a weight average molecular weight of at least 100,000 g/mol. The method of claim 1 or 2, wherein the non-conductive polymer is polyvinylpyrrolidone. The method of any of the preceding claims, wherein the at least partially removing the non-conductive polymer adsorbed on the surface of the silver nanowires is at least partially used in method step (ii) by using the non-conductive polymer The soluble solvent B is washed by the silver nanowire obtained in the step (i). The method of claim 3, wherein the solvent B used for the washing is water. The method of claim 3, wherein the nitrogen content of the purified silver nanowires obtained in the method step (ii) is based on the total weight of the dried residues of the purified silver nanowires. It is less than 7 wt.%. The method of any of the preceding claims, wherein the conductive polymer used in method step (iii) comprises polythiophene. The method of claim 7, wherein the method used in method step (iii) The electropolymer comprises a complex of polythiophene and polyanion. The method of claim 8, wherein the conductive polymer used in method step (iii) comprises a PEDOT/PSS composite. The method of any one of the preceding claims, wherein in the method step (iii), the purified silver nanowire obtained in the method step (ii) and the aqueous composition comprising the PEDOT/PSS complex mixing. The method of any one of the preceding claims, wherein in the method step (iii), the purified silver nanowires obtained in the method step (ii) and the conductive polymer are used in a relative amount The weight ratio of silver:conductive polymer in the composition is in the range of 10:1 to 1:10. A composition comprising a solvent A, a silver nanowire, and a conductive polymer, which is obtainable by the method of any one of claims 1 to 11. The composition of claim 12, wherein if SR _{t = 0 is} the surface resistance (in [Ω / □]) of the conductive layer produced by the composition at time t ₀ and SR _{t = 30 days} the conductive layer of the same composition stored at 25 arising deg.] C in a sealed vessel for 30 days dismiss light at time t _{30 days} of surface resistivity (in [Ω / □] units), then: SR _{t = 0} / SR _{t =30 days} 0.75. A composition comprising a solvent A, a silver nanowire, and a conductive polymer, wherein SR _{t = 0} is a surface resistance (in [Ω/□]) of the conductive layer produced by the composition at time t ₀ and SR _{t=30 days} is the surface resistance (in [Ω/□]) of the conductive layer produced by the same composition in a sealed container with screen light at 25 ° C for 30 days and at time t _{30 days} , then: SR _t=0 /SR _{t=30 days} 0.75. The composition of any one of clauses 12 to 14, wherein less than 1.5 g of non-conductive polymer per gram of silver is adsorbed on the surface of the silver nanowires in the composition. The composition of any one of the 12th to 15th of the patent application, wherein the non-conductive The electropolymer is polyvinylpyrrolidone. The composition of claim 16, wherein the composition has a nitrogen content of less than 1 wt.%, based on the total weight of the dry residue of the composition. The composition of any one of clauses 12 to 17, wherein the conductive polymer in the composition comprises polythiophene. The composition of claim 18, wherein the conductive polymer in the composition comprises a complex of polythiophene and a polyanion. The composition of claim 19, wherein the conductive polymer in the dispersion comprises a PEDOT/PSS composite. The composition of any one of clauses 12 to 20, wherein the composition comprises the silver nanowires and the conductive polymer in a relative amount such that the composition is silver: a conductive polymer The weight ratio is in the range of 10:1 to 1:10. The composition of any one of clauses 12 to 21, wherein the pH of the composition is in the range of 2 to 7. A method for producing a conductive layer, the method comprising the steps of: I) supplying a substrate; II) applying a composition according to any one of claims 12 to 22 to the substrate; The composition at least partially removes solvent A to obtain a conductive layer on the substrate. A conductive layer obtainable by the method of claim 23 of the patent application. The use of a composition according to any one of claims 12 to 22 for producing an OLED, an OPV element, a conductive layer in a touch screen for shielding electromagnetic radiation (" EMI shielding ") Used in sensors or for generating IR reflective layers. A use of a composition according to any one of claims 12 to 22 for use as an ITO substitute in an OLED, an OPV element or a touch screen.