EP2297381A2

EP2297381A2 - Method for manufacturing transparent conducting oxides

Info

Publication number: EP2297381A2
Application number: EP09753841A
Authority: EP
Inventors: Gero Nordmann; Norbert Wagner; Alexander Traut; Christian Bittner; Ingo MÜNSTER; Bernd Smarsly; Yude Wang; Markus Antonietti; Simone Mascotto
Original assignee: BASF SE; Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Current assignee: BASF SE; Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Priority date: 2008-05-30
Filing date: 2009-05-25
Publication date: 2011-03-23
Also published as: WO2009144186A2; US8834748B2; US20110073814A1; WO2009144186A3

Abstract

The present invention relates to a method for producing transparent conductive oxides comprising the following steps in the sequence a-b-c: (a) Reacting at least one starting compound (A) containing at least one metal or semi-metal M and optionally a dopant (D) containing at least one doping element M', wherein at least one M' is not the same as M, in the presence of a block copolymer (B) and a solvent (C), forming a composite material (K), (b) optionally applying the composite material (K) onto a substrate (S) and (c) heating the composite material (K) to a temperature of at least 350°C, characterized in that the block copolymer (B) contains at least one alkylene oxide block (AO) and at least one isobutylene block (IB). The present invention also relates to transparent conductive oxides so obtained, use thereof in electronic components, as electrode materials and as material for antistatic applications. Finally, the present invention relates to electronic components containing the transparent conductive oxides.

Description

Process for the preparation of transparent conductive oxides

description

The present invention relates to a process for the preparation of transparent conductive oxides comprising the following steps in the order a-b-c:

(a) Implementation of

- At least one starting compound (A) containing at least one metal or semimetal M

and optionally a dopant (D) containing at least one doping element M ', where at least one M' is other than M,

in the presence of a block copolymer (B) and a solvent (C) to form a composite material (K),

(b) optionally applying the composite material (K) to a substrate (S) and

(c) heating the composite material (K) to a temperature of at least 350 ^° C.,

characterized in that the block copolymer (B) contains at least one alkylene oxide block (AO) and at least one isobutylene block (IB).

Moreover, the present invention relates to the transparent conductive oxides thus obtainable, their use in electronic components, as electrode material and as material for antistatic applications. Finally, the present invention relates to electronic components containing the transparent conductive oxides.

Conductive, transparent layers are very important for applications in electronics and optoelectronics such as displays, electronic paper, solar cells, touch panels and as an electrode. To date, owing to the good electrical conductivity and the established technical realization, mainly tin-doped indium oxide (ITO) and partly also fluorine-doped SnO 2 (FTO) are used, which are usually applied to the substrates by complex application techniques (sputtering). Of great disadvantage are also the high cost of indium.

In the coating of polymeric substrates, moreover, the adhesion of the layers is critical. Layers of transparent conductive oxides deposited on substrates by chemical vapor deposition (CVD) (transparent conductive oxides, TCO) are usually very brittle and therefore dissolve very easily from thin substrates such as polymer or glass. Such produced TCO layers also have a pronounced surface roughness, which is particularly disadvantageous in components with multiple layers and in the case of layer thicknesses in the range of 100 nm or less (eg OLED).

The preparation of transparent conductive oxides (TCO) by sol-gel techniques and formation of respective layers has been proposed as a possible solution to the problems described above. The required mesoporous structure is usually generated in the prior art by templating, wherein structure-forming components such as nonionic surfactants control or influence the mesostructure.

However, it is disadvantageous in the known processes that the crystallinity, which is a prerequisite for high conductivities, must be increased by calcination at high temperature on substrates applied, for example, by dipcoating, which often leads to cracking and detachment of the films from the substrates leads.

JP 2005-060160 A describes the preparation of mesoporous films starting from metal halides by templating by means of polyoxyethylene stearyl ether and subsequent aging in a steam atmosphere below 100 ⁰ C. However, the complicated and time-consuming process and in particular the very low crystallinity and conductivity as well as the at high temperatures, insufficient stability of the mesostructure of the TCO thus obtainable.

It is known from WO 99/37705 that mesoscopically arranged oxide block copolymer composites and mesoporous metal oxide films can be obtained by using amphiphilic block copolymers in an aqueous medium which function as a structuring agent by self-assembly. The block copolymer used is alkylene oxide block copolymers and EO-PO-EO triblock copolymers. The pore sizes obtained in this way are up to 14 nm. The oxides described include, inter alia, TiO 2, ZrO 2, SiO 2, Al 2 O 3, SnO 2. Conductive transparent oxides are not mentioned. When using said alkylene oxide block copolymers, a disruption of the mesostructure during the thermal treatment can be prevented, if at all, only by elaborate temperature programs. Another disadvantage is the low crystallinity of the non-stoichiometric oxides. In addition, the process of WO 99/37705 takes place in the presence of water and, for transition metal oxides, does not lead to thin layers having a homogeneous layer thickness.

In the publication Brezesinski et al., Advanced Functional Materials 2006, 16, 1433-1440, the use of poly (ethylene-co-butylene) -block-poly (ethylene oxide) as Template (as part of the so-called EISA, evaporation-induced self-assembly) for the formation of mesostructure in the preparation of mesoporous high-crystalline thin layers of SnÜ2 described.

Fattakhova-Rohlfing et al., Advanced Materials 2006, 18, 2980-2983, describe the preparation of transparent indium-tin-oxide (ITO) by EISA in conjunction with poly (ethylene-co-butylene) -block-poly (ethylene oxide) as a structure-forming agent in one Sol-gel process. However, a disadvantage is the limited dissolution behavior of poly (ethylene-co-butylene) -block-poly (ethylene oxide), which requires the presence of high amounts of tetrahydrofuran (THF) and an incompatibility with respect to the solubility of the components of the reacting compounds, especially in complex Mixtures can lead. The methods described in the cited publications are not suitable for the production of numerous TCO, in particular of antimony-doped tin oxide. In addition, the low average pore size of the TCO thus accessible leads to a reduced stability during crystallization at high temperatures.

The use of block copolymers containing a polyethylene oxide block and an isobutylene oxide block for templating in the preparation of mesostructured silica and titania is known from Groenewolt et al., Advanced Materials 2005, 17, 1558-1162. It describes the use of PIB85-PEO79 for the preparation of mesoporous silica by a sol-gel process starting from TMOS and mesoporous TiO2 starting from TiCU. The diblock copolymer acts structurally by self-assembly. However, the publication does not disclose the preparation of transparent conductive oxides.

It was therefore an object of the present invention to provide a process which makes transparent conductive oxides (TCO), including antimony-doped tin oxide, accessible by a sol-gel process. The corresponding films of transparent conductive oxides should have a high electrical conductivity and a high homogeneity with respect to the layer thickness. The process should make transparent high-crystallinity conductive oxides available.

It was another object of the present invention to provide mesoporous transparent conductive oxides whose mesostructure has high stability even at high temperatures. Consequently, the available transparent conductive oxides should be stable during crystallization. The pore size distribution should be narrow.

Another object of the present invention was to make transparent conductive oxides accessible as thin films. In addition, the films should have a good adhesion to a substrate and a homogeneous layer thickness within the scope of customary application. tion method such as dip-coating have. The layer thickness should also be adjustable precisely in the range of about 10 nm to about 500 nm. The films thus available should show a high transparency.

The method should largely avoid a negative change in the mesostructure during crystallization. In particular, the formation of macroscopic cracks and detachment from the substrate during crystallization should be avoided.

These objects are achieved by the method according to the invention and by the transparent conductive oxides obtainable in this way.

Preferred embodiments are explained in more detail in the claims and in the following description. Combinations of preferred embodiments, in particular combinations of preferred embodiments of individual process steps, do not depart from the scope of the present invention.

The process according to the invention for the preparation of transparent conductive oxides is explained in more detail below.

Transparent conductive oxides are known in the art as a class of substances. The term "transparent conductive oxides" in the context of the present invention denotes metal oxides which may be doped and / or contain foreign atoms which satisfy the following criteria:

- Transmission at least 50% at a layer thickness of 100 nm and at a wavelength in the range of 380 nm to 780 nm according to DIN 1349-2: 1975; Electrical conductivity at least 0.1 S-cnτ ¹ according to DIN EN ISO 3915.

Preferably, the transparent conductive oxide is also mesoporous. The term mesoporous is used in the context of the present invention within the meaning of the ILJPAC definition. A mesoporous structure is characterized by a number-weighted mean pore diameter of 2 to 50 nm.

In the context of the present invention, the term "pore diameter" denotes the largest diameter through the geometric center of a pore. The number-weighted average pore diameter is determined by means of transmission electron microscopy (TEM) and subsequent image analytical evaluation using at least 500 pores of a statistically representative sample.

The number-weighted average pore size of the transparent conductive oxides obtainable according to the present invention is preferably from 10 to 45 nm, particularly preferably from 15 to 40 nm, in particular from 20 to 35 nm. The mesoporous transparent conductive oxides preferred according to the present invention may comprise both closed-cell and open-celled pores. Open cell pores are characterized in that they are able to sorb Kr in an adsorption measurement. The pores can have different geometry. In many cases, approximately spherical pores or pores with ellipsoidal shape have been found to be suitable. In particular, the number-weighted average aspect ratio of the pores according to TEM is in the range of 1 to 4. If the mesoporous transparent conductive oxides are in the form of a thin layer having a layer thickness in the range of 500 nm or less, an aspect ratio of 1.2 to 3 is preferred.

Preferably, the transparent conductive oxides of the present invention are crystalline. Crystalline in the context of the present invention means that the mass fraction of crystalline transparent conductive oxide relative to the total mass of transparent conductive oxide is at least 60%, preferably at least 70%, particularly preferably at least 80%, in particular at least 90%, determined by means of X-ray diffraction (XRD).

The crystallinity is determined in the context of the present invention by means of X-ray diffraction. Here, the crystalline part of the scattering is related to the total scattering of the sample.

Preferably, the transparent conductive oxide is selected from the group consisting of doped binary oxides and ternary oxides, wherein the ternary oxides may be doped.

Step (a)

According to the invention, according to step (a), a reaction of at least one starting compound (A) comprising at least one metal or semimetal M and optionally a dopant (D) containing at least one doping element M ', wherein at least one M' is not equal to M. The reaction takes place in the presence of a block copolymer (B) and a solvent (C) to form a composite material (K).

A composite material is a material which has both an inorganic and an organic component. In the present case, the composite material is an oxidic network or an oxidic network which still contains reactive groups from the starting compound (A) or hydroxyl groups which are linked to M, the oxidic network preferably having a mesostructure. The oxide network is in contact with the block copolymer (B) which is in the Frame of step (a) preferably as the structure, in particular the mesostructure, influencing agent, in particular acts as a template.

As starting compounds (A), it is possible in principle to use all compounds containing M which can be converted into oxidic systems by hydrolysis (sol-gel process).

Preferred starting compounds (A) are chlorides, acetates, alkoxides, alkoxy chlorides, nitrates, sulfates, bromides, and iodides of M and complexes of M with bidentate ligands. If a transition metal is used as the metal or semimetal M, its complexes with acetylacetonate or cyclooctadiene can also be used as the ligand. Preferably, the starting compound (A) used is at least one metal halide, metal alkoxide or a metal acetate.

Such starting compounds are known to the person skilled in the art. Hydrolysis and condensation form oxidic systems, which essentially consist of the corresponding metal or semimetal. The oxidic systems obtained after step (a) may also contain further groups, in particular OH groups, and also water (so-called oxide hydrates).

Preferably, the at least one metal or metalloid M is selected from Sn, Zn, In and Cd.

In a preferred embodiment, the inventive method comprises the reaction of at least one starting compound (A) containing at least one metal or semimetal M and a dopant (D) containing at least one doping element M ', wherein at least one M' is not M, in Presence of a block copolymer (B) and a solvent (C) to form a composite material (K).

In the context of the present invention, doping agent is understood as meaning an agent which leads to the doping of the conductive transparent oxide. The term doping is to be understood broadly. It comprises both a doping in the strict sense, wherein the transparent conductive oxide contains as a result of the doping of 0.1 to 100 ppm Fremdatome me, and - this is particularly preferred - the doping in the broad sense, after which the transparent conductive oxide is a mixed oxide is that which contains the component which is derived from the starting compound (A) to at least 50 wt .-%, preferably at least 70 wt .-%, in particular at least 85 wt .-%. Accordingly, it is preferable that the transparent conductive oxides of the present invention are from 0.001 to 30% by weight, preferably from 0.01 to 20% by weight, more preferably from 0.1 to

15% by weight of at least one metal M ', based on 100% by weight of all metals M and M'. Dopants for doping oxides of metals or semimetals are known in the art. The person skilled in the art will choose a suitable dopant depending on the starting compound (A) and also on the transparent conductive oxide to be prepared. It is known to the person skilled in the art that the use of dopants leads to so-called mixed oxides which, in particular in the case of binary oxides, can in many cases lead to an increase in the electrical conductivity.

Suitable doping element M 'are both metal or semimetals and nonmetals. In the context of the present invention, "doping element" is understood to be that or those elements of the doping agent (D) which are incorporated as foreign atoms in the oxide network.

If the doping element M 'is a non-metal, then the reaction in step (a) is carried out in the presence of a dopant (D) containing a doping element M' selected from F, Cl, Br or I, with F being particularly preferred.

If a dopant (D) containing a metal or semimetal is used as the doping element M ', then a doping element M' selected from Al, Ga, B, Sb, Sn, Cd, Nb, Ta and In is preferred.

If the doping element M 'is a metal or semimetal, preferred dopants (D) are chlorides, acetates, alkoxides, alkoxy chlorides, nitrates, sulfates, bromides, iodides of M' or complexes with bidentate ligands of M '. If M 'is a transition metal, it is also possible to use complexes of M' with acetylacetonate or cycloctadiene as ligand. If the doping element M 'is fluorine, then CaF 2, NaF, NH ₄ F and NR ₄ F are preferred, wherein R is an organic radical, preferably an alkyl radical having from 1 to 8 carbon atoms.

The transparent conductive oxides obtainable according to the invention are preferably selected from the group consisting of ATO (Sb-doped tin oxide), ITO (Sn-doped indium oxide, Nb- and Ta-doped Sn 2 O, F: ZnO, AhZnO, Ga: ZnO, B: ZnO, In: ZnO, F: SnO ₂ , Cd ₂ SnO ₄ , Zn ₂ SnO ₄ , MgIn ₂ O ₄ , CdSb ₂ SnO ₆ ) Y, ZnSnO ₃ , GaInO ₃ , Zn ₂ In ₂ Os, GaInO ₃ , In ₄ Sn ₃ Oi ₂ , SnO ₂ , WO ₃ , CeO ₂ , alumina, iron oxide according to the formula FeO _x where x can assume a value of 1 to 1.5 and SrTiO ₃ .

In a particularly preferred embodiment, the starting compound (A) contains tin as the metal or semimetal M and the dopant (D) contains antimony as the doping element M '. Most preferably, the transparent conductive oxide obtainable according to the invention is antimony-doped tin oxide. Block copolymer B

According to the invention, the block copolymer (B) comprises at least one alkylene oxide block (AO) and at least one isobutylene block (IB).

The individual blocks of the block copolymer (B) are linked together by means of suitable linking groups.

The linking groups can be both functional organic groups or individual atoms. Usually such linking groups are used, which lead to a linear linkage. The linking groups can also have three or more than three attachment sites, leading to star-shaped block copolymers.

In practice, the linkage usually takes place by functionalization of polyisobutylene and subsequent reaction with alkylene oxide or alkylene oxide blocks. Preferred functionalized polyisobutylenes and preferred preparation methods for the block copolymers (B) used according to the invention are described below.

The alkylene oxide blocks (AO) and the isobutylene oxide blocks (IB) may each independently be linear or also branched. Preferably, they are each linear.

The blocks (IB) and / or (AO) may be terminally arranged, i. only be connected to another block, or they may be connected to two or more other blocks. For example, blocks (IB) and (AO) may be linearly linked together in an alternating arrangement. In principle, any number of blocks can be used. As a rule, however, there are no more than 8 blocks (IB) or (AO) each. This results in the simplest case a two-block copolymer of the general formula AB. Furthermore, they may be triblock copolymers of the general formula ABA or BAB. Of course, several blocks can follow each other, for example ABAB, BABA, ABABA, BABAB or ABABAB.

Furthermore, they may be star-shaped and / or branched block copolymers or comb-like block copolymers in which in each case more than two blocks (IB) are bonded to one block (AO) or more than two blocks (AO) to one block (IB). For example, they may be block copolymers of the general formula AB _m or BA _m , where m is a natural number> 3, preferably 3 to 6 and particularly preferably 3 or 4. Of course, in the arms or It is also possible for several blocks A and B to follow one another, for example A (BA) _m or B (AB) _m .

Such block copolymers (B) are known to the person skilled in the art or can be prepared by known processes.

Preferably, the block copolymer (B) comprises at least one alkylene oxide block (AO) and at least one isobutylene block (IB), wherein the number-weighted average block length of the alkylene oxide block or blocks (AO) is from 4 to 300 monomer units and the number-weighted average block length of the isobutylene block or groups Isobutylene blocks (IB) of 5 to 300 monomer units.

Preferably, the reaction according to step (a) of the process according to the invention is carried out in the presence of at least one diblock copolymer (B) consisting of an alkylene oxide block (AO) and an isobutylene block (IB), i. the block copolymer (B) is a diblock copolymer of the general structure AO-IB.

The number-weighted mean block lengths of the alkylene oxide blocks (AO) and the isobutylene blocks (IB) in the abovementioned block copolymers (B) are, independently of one another, particularly preferably from 10 to 300 monomer units, in particular from 20 to 250 monomer units, very particularly preferably from 30 to 200 monomer units. The determination of the number-weighted mean block length (via number-average molecular weight Mn) of the isobutylene blocks (IB) and the number-average molecular weight Mn of the resulting block copolymer is carried out in each case by gel permeation chromatography (GPC) using THF as eluent against a polystyrene standard with a highly crosslinked styrene-divinylbenzene Resin as a stationary phase. The determination of the number-weighted average block length of the alkylene oxide blocks (AO) is effected therefrom by methods known to the person skilled in the art.

In a particularly preferred embodiment, the number-weighted average block length of the isobutylene blocks (IB) is from 90 to 200 monomer units and the number-weighted average block length of the alkylene oxide blocks (AO) is from 80 to 200 monomer units. Most preferably, the block copolymer (B) is a diblock copolymer of the general structure AO-IB. The person skilled in the art determines preferred number-weighted average molecular weights from the abovementioned preferred block lengths by conversion using the known molecular weight of a monomer unit.

It has proved to be advantageous if the block copolymer (B) is constructed to be non-uniform in terms of its molecular weight. Without being limited to the validity of theoretical considerations, it is believed that relatively low molecular weight block copolymer molecules are more surface-active Adjuvant act synergistically with the relatively high molecular weight block copolymer molecules, thereby assisting in the formation of the mesostructure.

It is preferred that the polydispersity index (PDI) of the block copolymer (B), which is defined as the ratio of weight average and number average molecular weight M _w / M _n , is from 1.2 to 30, more preferably from 1.5 to 25 , more preferably from 2 to 20, most preferably from 4 to 15. In particular, in the case of high average molecular weight block copolymers, it has been found advantageous to simultaneously use those having a high PDI. Accordingly, it is most preferred that the number-average block length of isobutylene (IB) blocks in the block copolymer (B) be from 90 to 200 monomer units and the number-average molecular block length of the alkylene oxide blocks (AO) be from 80 to 200 monomer units and the PDI of the block copolymer (B). from 4 to 20.

The PDI of the block copolymer (B) is determined by gel permeation chromatography (GPC) with THF as eluent against a polystyrene standard with a highly crosslinked styrene-divinylbenzene resin as the stationary phase as M _w / M _n . The determination of the polydispersity index (PDI) is described in general form, for example, in Analytiker-Taschenbuch, Vol. 4, pages 433 to 442, Berlin 1984.

The isobutylene blocks (IB) are designated as such when the repeating units of the polymer block are at least 80% by weight, preferably at least 90% by weight, of isobutene units, the end and linking groups not being counted as repeat units.

The isobutylene blocks (IB) are obtainable by polymerization of isobutene. However, the blocks may still have minor comonomers other than building blocks. Such devices can be used for fine control of the properties of the block. Noteworthy as comonomers are, in addition to 1-butene and cis- or trans-2-butene, especially isoolefins having 5 to 10 C atoms, such as 2-methyl-1-butene-1, 2

Methyl-1-pentene, 2-methyl-1-hexene, 2-ethyl-1-pentene, 2-ethyl-1-hexene and 2-propyl-1-heptene or vinylaromatics such as styrene and α-methylstyrene, Ci-C4- Alkylstyrenes such as 2-, 3- and 4-methylstyrene and 4-tert-butylstyrene. The proportion of such comonomers should not be too large. As a rule, their amount should not exceed 20% by weight, based on the amount of all the building blocks of the block. In addition to the isobutene units or comonomers, the blocks may also comprise the initiator or starter molecules or fragments thereof used for starting the polymerization. The polyisobutylenes thus prepared may be linear, branched or star-shaped. They can only have functional groups at one end of the chain or at two or more ends of the chain. Starting material for the preparation of block copolymers (B) containing isobutylene blocks (IB) are preferably functionalized polyisobutylenes. Functionalized polyisobutylenes can be prepared starting from reactive polyisobutylenes by providing these with functional groups in one-stage or multistage reactions which are known in principle to those skilled in the art. Reactive polyisobutylene is understood by the person skilled in the art to mean polyisobutylene which has a high proportion of terminal alpha-olefin end groups. The preparation of reactive polyisobutylenes is likewise known and described, for example, in detail in WO 04/9654, pages 4 to 8, and in WO 04/35635, pages 6 to 10.

Preferred embodiments of the functionalization of reactive polyisobutylene include:

i) Reaction with aromatic hydroxy compounds in the presence of an alkylation catalyst to give polyisobutylenes-alkylated aromatic

hydroxy

ii) reacting the polyisobutylene block with a peroxy compound to obtain an epoxidized polyisobutylene,

iii) reaction of the polyisobutylene block with an alkene having an electron-withdrawing double bond (enophile), in an ene reaction,

iv) Reaction of the polyisobutylene block with carbon monoxide and hydrogen in

Presence of a hydroformylation catalyst to obtain a hydroformylated polyisobutylene,

v) reacting the polyisobutylene block with a phosphorus halide or a phosphorus oxychloride to give a functionalized with phosphonic groups

polyisobutylene,

vi) reaction of the polyisobutylene block with a borane and subsequent oxidative cleavage to give a hydroxylated polyisobutylene,

vii) reaction of the polyisobutylene block with a SO 3 source, preferably acetyl sulfate or oleum, to give a polyisobutylene having terminal sulfonic acid groups,

viii) reaction of the polyisobutylene block with nitrogen oxides and subsequent hydrogenation to give a polyisobutylene having terminal amino groups. With regard to all details for carrying out the above reactions, we refer to the comments in WO 04/35635, pages 1 1 to 27.

Particular preference is given to embodiment i), with phenol being very particularly preferred as the aromatic hydroxy compound, as well as embodiment iii). In the context of iii) most preferably, maleic anhydride is used for the reaction. This results in succinic anhydride (succinic anhydride) functionalized polyisobutenes (polyisobutenyl succinic anhydride, PIBSA).

The alkylene oxide blocks (AO) are designated as such when the repeat units of the polymer block are at least 70% by weight, preferably at least 80% by weight, of alkylene oxide units, the end and linking groups not being counted as repeat units.

Alkylene oxide units are, in a manner known in principle, units of the general formula -R ¹ -O-. Here, R 1 is a divalent aliphatic hydrocarbon radical which may optionally have further substituents. Additional substituents on the radical R1 may in particular be O-containing groups, for example> C =O groups or OH groups. One

Of course, alkylene oxide block (AO) may also comprise several different oxyalkylene units.

The alkylene oxide units may in particular be - (CH 2) 2 -O-, - (CH 2) 3 -O-, - (CH ₂ ) ₄ -O-, -CH ₂ -CH (R ² ) -O-, -CH ₂ -CHOR ³ -CH ₂ -O-, where R ² is an alkyl group, in particular Ci-C ₂₄ -AlkVl or an aryl group, in particular phenyl, and R ³ is a group selected from the group of hydrogen , C ¹ -C ₂₄ -alkyl, R ¹ -C (= O) -, and R ¹ -NH-C (= O) -.

The alkylene oxide blocks (AO) may also comprise further structural units, such as, for example, ester groups, carbonate groups or amino groups. They may furthermore also comprise the initiator or starter molecules or fragments thereof used for starting the polymerization. Examples include terminal groups R ² - O-, where R ^{2 has} the meaning defined above.

The alkylene oxide blocks (AO) as main components preferably comprise ethylene oxide units - (CH ₂ ) ₂ -O- and / or propylene oxide units -CH ₂ -CH (CHs) -O, while higher alkylene oxide units, ie those with more than 3 C atoms, only are present in small amounts for fine adjustment of the properties. The blocks may be random copolymers, gradient copolymers, alternating or

Block copolymers of ethylene oxide and propylene oxide act. The amount of higher alkylene oxide units should not exceed 10% by weight, preferably 5% by weight. Preferably, these are blocks which comprise at least 50% by weight of ethylene oxide units, preferably 75% by weight and particularly preferably at least 90% by weight of ethylene oxide units. Very particular preference is given to pure polyoxyethylene blocks (AO).

The alkylene oxide blocks (AO) are obtainable in a manner known in principle, for example by polymerization of alkylene oxides and / or cyclic ethers having at least 3 C atoms and optionally further components. They can also be prepared by polycondensation of di- and / or polyalcohols, suitable initiators and optionally further monomeric components.

Examples of suitable alkylene oxides as monomers for the alkylene oxide blocks (AO) include ethylene oxide and propylene oxide and furthermore 1-butene oxide, 2,3-butene oxide, 2-methyl-1,2-propene oxide (isobutene oxide), 1-pentenoxide, 2,3-pentenoxide, 2-methyl-1, 2-butene oxide, 3-methyl-1, 2-butene oxide, 2,3-hexene oxide, 3,4-hexene oxide, 2-methyl-1, 2-pentene oxide, 2-ethyl-1, 2 butene oxide, 3-methyl-1, 2-pentenoxide, decene oxide, 4-methyl-1, 2-pentenoxide, styrene oxide or a mixture of oxides of technically available raffinate streams. Examples of cyclic ethers include in particular tetrahydrofuran. Of course, mixtures of different alkylene oxides can be used. Depending on the desired properties of the block, the person skilled in the art makes a suitable choice among the monomers or further components.

The alkylene oxide blocks (AO) may also be branched or star-shaped. Such blocks are available by using starter molecules with at least 3 arms. Examples of suitable initiators include glycerol, trimethylolpropane, pentaerythritol or ethylenediamine.

The synthesis of alkylene oxide units is known to the person skilled in the art. Details are detailed in, for example, "Polyoxyalkylenes" in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Electronic Release.

The synthesis of the block copolymers (B) used according to the invention can preferably be carried out by first preparing the alkylene oxide blocks (AO) separately and reacting them in a polymer-analogous reaction with the functionalized polyisobutenes to form block copolymers (B).

The building blocks for the isobutylene blocks (IB) and for the alkylene oxide blocks (AO) in this case have complementary functional groups, i. Groups that can react with each other to form linking groups.

The functional groups of the blocks (AO) are of course preferably OH groups, but they may also be, for example, primary or secondary Act amino groups. OH groups are particularly suitable as complementary groups for reaction with PIBSA.

In a further embodiment of the invention, the synthesis of the blocks can also be carried out by reacting polar functional group-containing polyisobutenes (i.e., blocks IB) directly with alkylene oxides to form blocks (AO).

The structure of the block copolymers used in the present invention can be influenced by selecting the kind and amount of the starting materials for the blocks (IB) and (AO) and the reaction conditions, particularly the order of addition.

The synthetic possibilities are shown below by way of example for OH groups and succinic anhydride groups (designated as S), without the invention being intended to be restricted to the use of such functional groups.

HO- [B] -OH Hydrophilic blocks containing two OH groups

[B] -OH Hydrophilic blocks containing only one OH group.

[B] - (OH) _x Hydrophilic blocks with x OH groups (x> 3)

[A] -S polyisobutene with a terminal group S

S- [A] -S polyisobutene with two terminal groups S

[A] -Sy polyisobutene with y groups S (y> 3)

The OH groups can be linked together in a manner known in principle with the succinic anhydride groups S to form ester groups. The reaction can be carried out, for example, while heating in bulk. Suitable, for example, reaction temperatures of 80 to 150 ⁰ C.

For example, triblock copolymers ABA are readily prepared by reacting one equivalent of HO- [B] -OH with two equivalents of [A] -S. This is illustrated below by way of example with complete formulas. An example is the reaction of PIBSA and a polyethylene glycol:

Here, n and m independently represent natural numbers. They are selected by the person skilled in the art in such a way that the block lengths defined at the outset for the blocks (IB) and (AO) result.

Star-shaped or branched block copolymers BA _x can be obtained by reacting [B] - (OH) _x with x equivalents [A] -S.

Block copolymers (B) used in the process according to the invention are particularly preferred:

polyisobutylene-alkylated phenol which is reacted with alkoxide, in particular ethylene oxide, - polyisobutylene having terminal amino groups, which is reacted with alkoxide, in particular ethylene oxide, and

PIBSA, which is reacted with an alkylene oxide block, in particular polyethylene oxide.

For those skilled in the art of polyisobutenes, it is clear that the obtained

Block copolymers may also have residues of starting materials depending on the conditions of preparation. In addition, they can be mixtures of different products. For example, three block copolymers of the formula ABA may also contain two-block copolymers AB as well as functionalized and unfunctionalized polyisobutene. Advantageously, these products can be used without further purification for the application. Of course, the products can also be cleaned. The person skilled in suitable cleaning methods are known.

According to the invention, in step (a) of the present invention, the reaction is carried out in the presence of a solvent (C). Preferably, as the solvent (C), at least one compound selected from the group consisting of aliphatic alcohols and aliphatic ethers is used. Particularly preferred is the solvent (C) selected from ethanol, tetrahydrofuran or a mixture of ethanol and tetrahydrofuran. Most preferably, the solvent is (C) ethanol.

In a preferred embodiment, the reaction in step (a) takes place in the absence of water or in the presence of small amounts of water, more preferably in the absence of water. In the context of the present invention, the presence of small amounts of water is understood to mean that the proportion of water in the solvent (C) is at most 5% by weight, in particular at most 1% by weight.

In a preferred embodiment, as solvent (C) at least one compound selected from the group of aliphatic alcohols, in particular

Ethanol, used.

Step (b)

In a preferred embodiment, according to step (b), the application of the composite material (K) to a substrate (S).

The transparent conductive oxide is preferably obtained in the form of a layer of the layer thickness of 10 to 500 nm on a substrate (S).

Methods for applying the composite material (K) to a substrate (S) are known to the person skilled in the art. In principle, conventional methods such as application by immersion (in particular dip-coating), application by spraying (in particular spray coating), application by evaporation of the solvent, application under rotation (in particular spin coating) and printing process into consideration. Preferably, the application is a coating.

Such methods are advantageous for the application of layers, which enable a specifically adjustable and at the same time homogeneous layer thickness in the range from 10 to 500 nm. The composite material is preferably applied by dipping, spraying, spin-coating or printing as a layer on a substrate (S).

Step (b) is preferably carried out at a point in time at which the composite material (K) obtained from the starting compound (A) is not yet completely reacted, in particular not completely crosslinked. A networked three-dimensional network is often detrimental to application to a substrate. It is advantageous to apply the composite material (K) in the presence of the solvent (C) in a still flowable state to a substrate (S).

Step (b) is preferably carried out at a temperature of 10 to 35 ° C, especially 15 to 30 ⁰ C, particularly preferably from 20 to 25 ° C.

Step (b) is preferably performed at a relative humidity of 1 to 40%, particularly preferably from 5 to 30%, most preferably from 10 to 20% at a temperature of preferably 15 to 30 ⁰ C and particularly preferably from 20 to 25 ° C performed. The humidity during step (b) can be determined, for example, with commercially available hygrometers. Preference is given to impedance and capacitive hygrometers.

A higher air humidity than the one stated above has proven disadvantageous and, after carrying out step (c), leads in particular to a lower adhesion of the transparent conductive oxide to the substrate and to the formation of larger, under Circumstances of macroscopic cracks. The term humidity refers to the atmosphere surrounding step (b) the composite material (K).

Complete or further crosslinking is then achieved by tempering in step (c).

Suitable substrates (S) are in particular those which meet the following requirements:

- Temperature stability at temperatures of up to 900 ^° C. Stability to organic solvents Oxidative stability under the conditions of steps (c) and optionally (d).

In addition, the choice of the substrate (S) is determined by the later use.

Suitable substrates are, in particular, metals, silicon wafers, glass and other polar, temperature-stable surfaces, preference being given to substrates (S) based on glass, silicon, ceramic or metals.

Step (c)

According to the invention takes place in the context of step (c), the heating of the composite material (K) to a temperature of at least 350 ⁰ C. The expert refers to the heating of a composite material to a temperature of at least 350 ⁰ C usually as calcination. Step (c) is preferably carried out in the presence of air and / or in the presence of oxygen. The calcination in the presence of oxygen leads to an advantageous and complete formation of a porous oxide network.

Preferably, the inventive method is characterized in that step (c) is carried out by tempering in at least two stages, wherein the composite material (K) in a first stage (d) from 1 to 24 hours a temperature of 80 to 200 ° C and in a further stage (c2) of 1 to 5 hours at a temperature of 350 to 900 ° C is exposed.

The person skilled in the art usually refers to step (d) as aging and step (c2) usually as calcination. These terms are used in the following for the process steps (d) and (c2), respectively, or, if the tempering is not carried out according to the above-described preferred embodiment in at least two stages, the term calcination is indicative of the application of a temperature of at least 350 ⁰ C used. Aging means that the degree of crosslinking of the oxide network is further increased and / or the number of reactive groups on the surface of the porous oxide network is reduced. Preferably, in the context of step (c1), the degree of crosslinking of the oxide network of the composite material (K) is increased.

As part of the calcination, the removal of the block copolymer (B) from the composite material (K). In addition, in the course of calcining, the formation or increase of the crystallinity of the transparent conductive oxide takes place.

The two-stage embodiment of step (c) is particularly preferred in connection with step (b), in which the application to a substrate (S) takes place.

It has been found advantageous to strictly control the increase in temperature in step (c). A slow heating is particularly important from a temperature of 200 ⁰ C of importance, since too fast occurring aging and crystallization large tensions occur in the solid, which can lead to an undesirable degradation of the mesostructure. In addition, there is a risk of large primary crystallites if the temperature is increased too fast starting at 200 ^° C.

Heating rates of 0.1 K to 20 K per minute have been found to be suitable. However, it is preferred if, starting from a temperature of 200 ^° C., the maximum temperature in step (c) is achieved by using a heating rate of at most 5 K / min. Below 200 ^° C., the heating rate is less critical. However, it is preferred to apply the above-mentioned heating rates in the temperature range of up to 200 ⁰ C.

Suitable means for controlling the temperature of the composite material (K) are known in the art and are not subject to any particular restriction, provided that they allow compliance with the above-mentioned conditions. Suitable devices are, for example, heaters with temperature control. For example, commercial high temperature, tube, annealing or muffle furnaces may be used. The temperature control is preferably carried out by means of suitable control devices that allow adjustment and control of start and target temperatures, heating rates and temperature hold times.

Step (d)

It has also proved to be advantageous, following completion of step (c), to preferentially produce the resulting test piece in the presence of an oxygen-free atmosphere consisting of nitrogen or a mixture of nitrogen and hydrogen to treat thermally. As a result, in many cases, the conductivity of the transparent conductive oxides can be further improved.

Accordingly, it is preferred to carry out after step (c) as step (d) a thermal aftertreatment of the resulting material at a temperature of 300 to 800 ⁰ C, in particular from 400 to 600 ⁰ C, with the exclusion of oxygen. The thermal aftertreatment is preferably carried out under an atmosphere of nitrogen or a mixture of nitrogen and hydrogen. The temperature can remain constant or vary within a temperature program.

The application of step (d) may be carried out by heating the fully or partially cooled material following step (c), or the already heated material is used immediately in step (d).

If step (d) is performed, it is preferable to raise the temperature according to a heating rate of at most 20 K / min, more preferably at most 15 K / min.

If a thermal post-treatment is carried out after step (d), then the duration of the thermal aftertreatment can vary over a wide period of time, which may be a few minutes or several hours. Preferably, the thermal aftertreatment according to step (d) takes place over a period of 5 minutes to 3 hours, in particular from 15 minutes to 1 hour.

use

The transparent conductive oxides obtainable according to the invention are suitable, inter alia, for applications in the field of electronics, optoelectronics, displays, touch pads, solar cells, sensors, electrode materials and components having an electrical component.

The transparent conductive oxides obtainable according to the invention are preferably used in electronic components or as electrode material or as material for antistatic applications.

The transparent conductive oxides obtainable according to the invention have high electrical conductivity, high transparency and excellent homogeneity and freedom from cracks. The adhesion to substrates is very good. The layer thickness of the transparent conductive oxides obtainable according to the invention is homogeneous. Examples

Positioning methods

5 The electrical resistance of the films was measured using a 4-point method according to DIN EN ISO 3915 using a Keithley 2000 digital multimeter. The resistivity was obtained by multiplying the resistance by the film thickness. The electrical conductivity was calculated from this by forming the reciprocal.

10

The crystallinity was determined by means of wide-angle X-ray scattering (WAXS). The measurement was carried out on a "D8 diffraction meter" from Bruker AXS GmbH, Karlsruhe (Cu-Kα radiation). The films deposited on a Si wafer were subjected to "symmetrical reflection" (Θ-2Θ geometry) using a

15 "Goebel mirror" and a Bruker AXS energy-dispersive solid phase detector (Si-based). A Soller-Spalt system was placed in front of the detector. The measurement was performed in steps of 0.05 ° between 2Θ = 5 ° -120 ° with a recording time of 1-5 seconds per measurement. The measurement provided the WAXS intensity against 2Θ.

20

The analysis of the data was performed in three stages using software (Origin®): 1.) subtraction of the constant background determined at the points with the highest and lowest 2Θ values of the WAXS curve; 2.) Multiplication of the corrected WAXS measurement data with the square of the diffraction vector s2 and the

25 the overall intensity through integration; 3.) Determination of the integral intensity of the individual Bragg reflections after separation of the signals by "substract Iine" function such that after subtraction symmetric signals were obtained and the signal foot on both sides reached an intensity of zero and formation of the sum of the integral intensities all Bragg reflexes.

30

The crystallinity (also known to those skilled in the art as the degree of crystallinity) can be determined from the integral intensity of the Bragg reflections and the total intensity of all reflections using the following formula:

φ = ^

O C Bragg amorphous

The porosity was determined by measuring the pore volume by means of ellipsometry with the UV-VIS (Variable Angle Spectroscopic EJlipsometer) Eilipsometer VASE M2000-U from Wollam, equipped with a 40 humidity control chamber (ellipsometric porosimetry). The determination of the porosity was carried out by means of the Kelvin equation, which was adjusted with regard to water adsorption has been. The data analysis was performed with the analysis software WVASE 32 (Woollam) assuming the density of Si02. After determining the layer thickness, the pore volume of the layer was determined from the resulting refractive index. Finally, the real pore volume was calculated by multiplying the value obtained for Si02 by the ratio of the densities of Si02 and the examined TCO. The density of the corresponding crystal modification of the host oxide from the database www.mindat.org was used as density for the examined TCO. The method is described in Langmuir, 21, 26, 2005, 12362-12371 by Boissiere et al. described.

The specific surface area was determined by adsorption measurement of krypton at 77K using the Quantachrome Autosorb 1-MP apparatus.

The number-average pore size and the geometric shape of the pores were determined by scanning electron microscopy and subsequent image analysis on at least 500 individual pores.

The composition was determined by means of photoelectron spectroscopy (XPS) on the ESCALAB 250 spectrometer from Thermo VG Scientific. The measure- ment was carried out at room temperature with a monochromatic Al Ka x-ray source at a power of 250 W. The pressure in the measurement chamber was adjusted to 1 x 10 ^"7 Pa. The measured spectra were decomposed by means of a square fitting method in its Gaussian components The binding energies were referenced to the main signals of the host oxides (eg C1s signal (285.0 eV) for ATO).

The layer thickness of the films was determined by SEM measurements. The film was broken in and the fractured edge analyzed.

The transparency was determined as transmission in% on quartz glass with a UV-VIS spectrometer at a layer thickness of 200 nm and at a wavelength in the range from 380 nm to 780 nm in accordance with DIN 1349-2: 1975.

example 1

The production of the TCO was carried out according to the following steps:

1.) 175 mg of an isobutylene-ethylene oxide Diblockcopolymers having a number average block length of the isobutylene block of 108 units and a number average block length of the ethylene oxide block of 100 units were dissolved in 3.0 mL of ethanol and 1 mL of THF by means of ultrasound until a homogeneous solution was obtained ,

2.) 29.6 mg of a solution of antimony (III) -ethoxide Sb (OC 2 Hs) 3 in 4 ml of ethanol added to 600 mg SnCU and stirred for one hour.

3.) The homogeneous solution of the polymer was added to the solution of the inorganic precursor.

4.) The resulting sol was stirred for 24 h. 5.) Using dip-coating, thin films were prepared on Si wafers and glass at a constant pull-out rate of 6 mm / s and a relative humidity of 15%.

6.) After application of the films they were annealed at 100 ⁰ C for 12 h. Subsequently, the sample was heated at a heating rate of 1 K / min to 200 ⁰ C and held at 200 ⁰ C for ² h. By this thermal treatment, this solidified

Network.

7.) The sample heated to 200 ^° C. was then heated at a rate of

1 ° C / min to 300 ⁰ C and further heated at a heating rate of 5 K / min to 550 ⁰ C and then cooled by opening the oven to room temperature. On the basis of this sample, the specific resistance was determined.

8.) The samples were heated after step 7) under N 2 atmosphere and post-annealed for 30 minutes at 450 ° C under N 2 atmosphere. Starting at 25 ° C, the heating rate was 10 K / min until the final temperature of 450 ° C was reached. Based on the samples obtained in step 8), the specific resistance, conductivity, crystallinity, specific surface area were determined by Kr physisorption, layer thickness and pore size.

Examples 2 and 3

The preparation was carried out analogously to Example 1, wherein the molar ratio of trivalent antimony and tetravalent tin, Sb (III) / Sn (IV), according to Table 1 was varied by instead of 29.6 mg now 59.2 mg (Example 2) or 78.8 mg (Example 3) of a solution of antimony (III) -ethoxide Sb (OC2Hs) 3 in 4 ml of ethanol was added to 600 mg of SnCU and stirred for one hour.

The samples of Examples 1-3 all had a crystallinity of more than 90%, a porosity of about 35% by volume, a specific surface area in the range of 100 m ² / g, a transmission of 93-96% and a Film thickness of about 200 nm.

The results of resistivity and conductivity measurements are summarized in Table 1. Table 1: Properties of the Sb-doped Sn2 films.

K)

4 nb = not determined

The adhesion and stability of the films according to Examples 1, 2 and 3 on the substrate was excellent and no finger abrasion was possible. The films were crack-free and had a homogeneous layer thickness.

Examples 4 and 5

Preparation of Nb- and Ta-doped Sn2

Table 2

Solutions of the amounts of Nb (OCsH ₇ ) ₅ or Ta (OCsH ₇ ) ₅ in 2 ml of ethanol given in Table 2 were added to 550 mg of SnCU and then stirred for 4 h (solution of the starting compound (A)). 120 mg of an isobutylene-ethylene oxide diblock copolymer having a number-average block length of the isobutylene block of 108 units and a number-average block length of the ethylene oxide block of 100 units were dissolved in 4 ml of ethanol (concentration: 3.66 wt.%) And sonicated until a homogeneous solution was obtained. The homogeneous solution of the polymer was mixed with the solution of the starting compound (A) and stirred for 19 hours. A transparent SoI was obtained.

By means of dip-coating, thin films were produced on Si wafers and glass substrates at a constant removal rate of the wafer of 6 mm / s and a relative humidity of 1 1-15% (20 ^° C.). After application of the film, these were added 10 h at 100 ⁰ C and after increasing the temperature to 200 ° C within 100 minutes 2 h at this temperature. The sample thus obtained was heated at a heating rate of 1 K / min to 300 ⁰ C and treated at this temperature for 2 h. It was then heated at a heating rate of 5 K / min to 550 ° C or 650 ° C and cooled by opening the oven to room temperature. Based on this sample, the resistivity was determined (corresponding to step 7). The samples were then post-annealed at 450 ⁰ C under a N2 atmosphere for 30 minutes (corresponding to step 8). Starting at 25 ° C, the heating rate was 5 K / min until the temperature of 450 ⁰ C was reached. From the samples thus obtained, the resistivity, the conductivity, the layer thickness and the pore size were determined.

The samples of Examples 4 and 5 had a specific surface area in the range of 100 m ² / g, a transmission of 91-95% and a film thickness of about 200 nm. The adhesion of the films to the substrate was excellent and there was no abrasion with fingers possible. The films were crack-free and homogeneous in layer thickness. The number-weighted mean pore size of the films after calcination was 20-25 nm parallel to the film and 10-15 nm perpendicular to the film direction.

The results of resistivity and conductivity measurements are summarized in Table 3.

Table 3: Properties of Nb- and Ta-doped Sn2 films.

Comparative Example V6

1. 04 g of decethylenoxidoctadecyl ether Ci8H37-0- (EO) io from Sigma-Aldrich Chemie GmbH (Brij 76) were dissolved in 10 g of ethanol. Subsequently, 2.66 g of SnCU and 0.15 g of SbCb were added, and the mixture was stirred for 30 minutes. The solution was filtered. For the subsequent dip-coating, both cleaned glass and cleaned Si wafers were used as the substrate. The speed of extraction was 2 mm / s.

After dip-coating, the coated plates (Si and glass) were allowed to stand for 10 h

60 ⁰ C and 20% relative humidity placed in an oven. Subsequently, the relative humidity was increased to 80% and the plates were left in the oven for a further 60 minutes at 40 ^° C. After cooling, the coated plates were allowed to stand in air for 150 hours. Subsequently, the plates were again placed in the oven for 1 h at 40 ⁰ C and 20% relative humidity.

The electrical conductivity of the resulting films was on the order of 20 megohms. The films were thus electrically insulating (non-conductive). The films were cracked and partially burst after drying from the substrate. The films were also cloudy, i. they had a low transparency. The adhesion to the substrate was insufficient. The films were not crystalline according to X-ray diffraction.

Claims

claims

1. A process for the preparation of transparent conductive oxides comprising the following steps in the order a-b-c:

(a) Implementation of

at least one starting compound (A) containing at least one metal or semimetal M

(b) optionally applying the composite material (K) to a substrate (S) and

(c) heating the composite material (K) to a temperature of at least 350 ^° C.,

characterized in that the block copolymer (B) comprises at least one alkylene oxide block (AO) and at least one isobutylene block (IB).

2. Process according to claim 1, characterized in that the block copolymer (B) comprises at least one alkylene oxide block (AO) and at least one isobutylene block (IB), wherein the number-weighted mean block length of the alkylene oxide block (AO) is from 4 to 300 monomer units and the is the number-weighted average block length of the isobutylene block (IB) of 5 to 300 monomer units.

3. Process according to claims 1 or 2, characterized in that the reaction according to step (a) is carried out in the presence of at least one Diblockcopoly- mer (B) consisting of an alkylene oxide block (AO) and a Isobutylenblock (IB).

4. Process according to claims 1 to 3, characterized in that the block copolymer (B) has a polydispersity index of 2 to 20.

5. Process according to claims 1 to 4, characterized in that the transparent conductive oxide is mesoporous.

6. The method according to claims 1 to 5, characterized in that the transparent conductive oxide is crystalline, wherein crystalline means that the mass fraction of crystalline transparent conductive oxide relative to the total mass of transparent conductive oxide at least 60%, preferably at least 70%, particularly preferably at least 80%, in particular at least 90%, determined by means of wide-angle X-ray scattering.

7. Process according to claims 1 to 6, characterized in that the starting compound (A) at least one metal or semimetal M selected from

Contains Sn, Zn, In and Cd.

8. The method according to claims 1 to 7, characterized in that the reaction in step (a) in the presence of a dopant (D) containing at least one doping element M 'is performed, wherein at least one M' is not equal to M.

9. The method according to claim 8, characterized in that the dopant (D) at least one doping element M 'selected from Al, Ga, B, Sb, Cd, Sn, In, Ta, Nb and F contains.

10. The method according to claims 1 to 9, characterized in that the starting compound (A) as metal or semimetal M contains tin and a dopant (D) containing antimony is used as the doping element M '.

1 1. A process according to claims 1 to 10, characterized in that the proportion of water in the solvent (C) is at most 1 wt .-%.

12. The method according to claims 1 to 1 1, characterized in that as solvent (C) at least one compound selected from the group of aliphatic alcohols, in particular ethanol, is used.

13. The method according to claims 1 to 12, characterized in that step (c) is carried out by tempering in at least two stages, wherein in a first stage (d) of 1 to 24 hours a temperature of 80 to 200 ⁰ C and in a further stage (c2) for 1 to 5 hours at a temperature of 400 to 900 ⁰ C is exposed.

14. The method according to claims 1 to 13, characterized in that starting from a temperature of 200 ⁰ C, the maximum temperature in step (c) by

Application of a heating rate of at most 5 K / min is achieved.

15. The method according to claims 1 to 14, characterized in that subsequent to step (c) as step (d), a thermal aftertreatment of the resulting material at a temperature of 300 to 800 ⁰ C, with the exclusion of oxygen.

16. The method according to claims 1 to 15, characterized in that the transparent conductive oxide is obtained as a layer of the layer thickness of 10 to 500 nm on a substrate (S).

17. Transparent conductive oxides obtainable according to claims 1 to 16.

18. An electronic component containing a transparent conductive oxide according to claim 17.

19. Use of the transparent conductive oxides according to claim 17 in electronic components or as electrode material or as material for antistatic applications.