HK1109780A - Polythiophene formulations for improving organic light emitting diodes - Google Patents

Description

Polythiophene formulations for improving organic light-emitting diodes

The invention relates to formulations comprising polythiophenes and other polymers, to the use thereof and to electroluminescent arrangements comprising hole-injection layers comprising the above formulations.

An electroluminescent device (EL device) is characterized in that it emits light under a current flow when a voltage is applied. Such devices have been known for a long time under the name "light emitting diodes" (LEDs). The emission of light is generated by the recombination of positive charges (holes) and negative charges (electrons) and the emission of light.

LEDs customary in the art are all predominantly made of inorganic semiconductor materials. EL devices constructed primarily of organic materials, however, have been known for several years.

These organic EL devices typically include one or more layers of organic charge transport compounds.

The main layer structure of the EL device is, for example, as follows:

1 support, substrate

2-base electrode

3 hole-injecting layer

4 electron-blocking layer

5 light-emitting layer

6 hole-blocking layer

7 electron-injecting layer

8 Top electrode

9 contact

10 housing, package

This structure represents the most detailed situation and can be simplified by omitting individual layers, so that one layer assumes several functions. In the simplest case, an EL device comprises two electrodes between which are organic layers that perform all the functions-including light emission.

In practice, however, it has been found that electron-and/or hole-injection layers are particularly advantageous in electroluminescent structures in order to increase the luminous density.

It is known from EP-A-686662 to use specific mixtures of conductive organic polymers, such as poly (3, 4-ethylenedioxythiophene), and, for example, polyhydroxyl compounds or lactams as electrodes for electroluminescent displays. However, in practice it has been found that these electrodes do not have sufficient conductivity, particularly for large screen displays. On the other hand, the conductivity is for small displays (light emitting area < 1 cm)²) Is sufficient.

It is known from DE-A-19627071 to use polymeric organic conductors, for example poly (3, 4-ethylenedioxythiophene), as hole-injecting layers. This shows that the light emission density of the electroluminescent display can be significantly increased compared to a structure without the polymer organic interlayer. By reducing the particle size of the poly (3, 4-alkylenedioxythiophene) dispersions, the conductivity can be adjusted in a controlled manner. It is therefore possible to prevent electrical interference (cross-talk) of adjacent address lines, particularly in passive matrix displays (EP- ｃA-1227529).

EPA1564251 further reports that the lifetime of these displays can be increased by using specific polymer anions.

However, although controllable adjustment by particle size is possible, for certain applications, such as, for example, for passive matrix displays, the hole-injection layer of known materials is still too electrically conductive, or the production of the display is not sufficiently economical due to the increased expense of previously decreasing particle size.

Therefore, there continues to be a need for producing EL devices having, in addition to a high emission density (emission intensity) and a long lifetime, a lower hole-injecting layer conductivity than known EL devices. For example, it has the advantageous effect of reducing crosstalk in passive matrix displays without having to use raw materials having particularly small particle sizes.

It is therefore an object of the present invention to find and provide suitable formulations for the production of such EL devices. It is a further object to produce improved EL devices from these materials.

It has now surprisingly been found that hitherto unknown formulations comprising specific, optionally substituted polythiophenes and other polymers are outstandingly suitable for producing hole-injection layers for EL devices, and that such hole-injection layers are capable of preventing the occurrence of crosstalk without requiring particularly small particle sizes.

Accordingly, the present invention provides a formulation comprising

A) At least one polythiophene comprising a repeating unit of the general formula (I-a) and/or (I-b)

Wherein

A represents optionally substituted C₁-C₅Alkylene, preferably optionally substituted ethylene or propylene, particularly preferably 1, 2-ethylene,

y independently of one another represents O or S,

r represents a linear or branched C₁-C₁₈Alkyl, preferably straight or branched C₁-C₁₄Alkyl, particularly preferably methyl or ethyl, C₅-C₁₂-cycloalkyl, C₆-C₁₄-aryl, C₇-C₁₈-aralkyl group, C₁-C₄-a hydroxyalkyl group or a hydroxyl group,

x represents an integer from 0 to 8, preferably 0, 1 or 2, particularly preferably 0 or 1 and

in the case where a plurality of groups R are bonded to A, these substituents may be the same or different,

wherein, in the case where Y represents O in the general formula (I-a), the polythiophene further contains a repeating unit of the general formula (I-a) in which Y represents S, or contains a repeating unit of the general formula (I-b)

B) At least one SO-containing₃ ^-M⁺Or COO^-M⁺Polymers of radicals in which M⁺Represents H⁺、Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺Or NH4⁺Preferably H⁺、Na⁺Or K⁺And is and

C) at least one SO-containing₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers of radicals in which M⁺Represents H⁺、Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺Or NH4⁺Preferably H⁺、Na⁺Or K⁺。

The general formula (I) is to be understood as meaning that the substituents R can be bonded x times to the alkylene radical A.

In the context of the present application, a formulation (composition) is any mixture of components a), B) and C) as a solid, solution or dispersion. Besides polythiophene a), it is also possible to use other known conductive polymers, in particular optionally substituted polyanilines, polypyrroles or polythiophenes, such as, for example, homopolythiophenes having recurring units of the general formula (I-a) in which Y represents O. Such a homopolythiophene having a recurring unit of the formula (I-a)) wherein Y represents O is preferably poly (3, 4 ethylenedioxythiophene). These different electrically conductive polymers can be used in any desired mixtures with polythiophene a).

Unless otherwise specifically indicated, herein and below substitutions will be understood to mean substitutions by groups selected from the following series:

alkyl, preferably C₁-C₂₀Alkyl, cycloalkyl, preferably C₃-C₂₀-cycloalkyl, arylOr preferably C₆-C₁₄Aryl, halogen, preferably Cl, Br, I, ether, thioether, disulfide, sulfoxide, sulfone, amino, aldehyde, ketone, carboxylate, cyano, alkylsilane and alkoxysilane groups, and carboxamide groups.

In a preferred embodiment of the preparations according to the invention, at least one polythiophene comprising recurring units of the general formulae (I-a) and (I-b) is a polythiophene comprising recurring units of the general formulae (I-aa) and/or (I-bb)

Wherein

R, Y and x have the meanings mentioned above.

In a very particularly preferred formulation according to the above, x represents 0 or 1. In the case where x is 1, R particularly preferably represents methyl or hydroxymethyl.

In a further preferred embodiment of the preparations according to the invention, at least one polythiophene A) comprising recurring units of the general formula (I-a) or (I-b) is a polythiophene comprising recurring units of the general formula (I-aa-1) and/or (I-aa-2) and/or (I-bb-1)

In the context of the present invention, the prefix poly-will be understood as meaning that the polymer or polythiophene contains more than one identical or different repeating unit. The polythiophenes contain in total n recurring units of the general formulae (I-a) and/or (I-b), where n can be an integer from 2 to 2,000, preferably from 2 to 100. The recurring units of the general formula (I-a) and/or (I-b) in the polythiophenes may be identical or different in each case. Preferred polythiophenes are polythiophenes which in each case contain identical recurring units of the general formula (I-a) in which Y represents S, polythiophenes which in each case contain identical recurring units of the general formula (I-b) in which Y represents S and copolymers which contain recurring units of the general formula (I-a) in which Y represents O and S or copolymers which contain recurring units of the general formulae (I-a) and (I-b). Particular preference is given to homopolythiophenes having recurring units of the formula (I-aa) in which Y represents S or having recurring units of the formula (I-bb), particular preference to homopolythiophenes having recurring units of the formula (I-aa-2) or (I-bb-1). Further particularly preferred polythiophenes are those having recurring units of the formulae (I-aa) in which Y represents O and S or those having recurring units of the formulae (I-aa) and (I-bb), particularly preferably those having recurring units of the formulae (I-aa-1) and (I-aa-2) or those having recurring units of the formulae (I-aa-1) and (I-bb-1) or those having recurring units of the formulae (I-aa-2) and (I-bb-1).

In the context of the present invention, a repeating unit will be understood to mean a unit of the general formula (I-a), (I-b), (I-aa), (I-bb), (I-aa-1), (I-aa-2) or (I-bb-1), hereinafter summarized as a repeating unit of the general formula (I), irrespective of whether the polythiophene comprises one or more of the above-mentioned repeating units. That is to say, if the polythiophene comprises it only once, the units of the general formula (I) can also be understood as repeating units.

The preparations according to the invention may also be those which, in addition to at least one polythiophene A) described above comprising recurring units of the general formula (I), also comprise electrically conductive polymers, such as polyaniline, polypyrrole or other polythiophenes, in the mixture. In a preferred embodiment, the preparations according to the invention can comprise, in addition to the abovementioned polythiophenes A) comprising recurring units of the general formula (I), in mixtures, also (3, 4-ethylenedioxythiophene) as further polythiophene.

In each case, the polythiophenes preferably bear H at the end groups.

The polythiophenes A) contain a total of n recurring units of the formula (I), where n is preferably an integer from 2 to 1,000. Preferably 3 to 100, particularly preferably 4 to 15.

C₁-C₅Alkylene A is, in particular, methylene, ethylene, n-propylene, n-butyleneOr n-pentylene. C₁-C₁₈Alkyl represents, in particular, straight-chain or branched C₁-C₁₈-alkenyl radicals, such as methyl, ethyl, n-or i-propyl, n-, i-, s-or t-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1-dimethylpropyl, 1, 2-dimethylpropyl, 2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, C₅-C₁₂Cycloalkyl represents C₅-C₁₂Cycloalkyl radicals, such as, for example, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclodecyl, C₆-C₁₄Aryl represents C₆-C₁₄Aryl radicals, e.g. phenyl or naphthyl, C₇-C₁₈Aralkyl for C₇-C₁₈Aralkyl radicals, e.g. benzyl, and C₇-C₁₈Alkyl represents C₇-C₁₈Alkylaryl groups, such as o-, m-, p-tolyl, 2, 3-, 2, 4, 2, 5-, 2, 6-, 3, 4-, 3, 5-xylyl or mesityl. The foregoing list is illustrative of the present invention and is not to be construed as a complete list.

In EP-A440957, Blanchard, Philippe; cappon, Alexandre; levilain, Eric; nicolas, Yohann; frere, Pierre; roncali, Jean, Organic Letters (2002), 4(4), 607-; sesbandri, Venkatara-manan; the preparation of polythiophenes A) comprising recurring units of the formula (I) is described in principle in Sotzing, Gregory A., synthetic metals (2005), 152(1-3), 177-180).

The polymerization of the corresponding monomeric starting compounds is carried out in a suitable solvent in the presence of a suitable oxidizing agent. Examples of suitable oxidizing agents are iron (III) salts, in particular FeCl₃And Iron (III) salts of aromatic and aliphatic sulfonic acids, H₂O₂、K₂Cr₂O₇、K₂S₂O₈、Na₂S₂O₈、KMnO₄Alkali metal perborates and alkali metal or ammonium persulfates or mixtures of these oxidizing agents. Further suitable oxidizing agents are described, for example, in the Handbook of conductive Polymers (Skotheim, edited by t.a.), Marcel Dekker: new York, 1986, volume 1, 46-57. A particularly preferred oxidizing agent is FeCl₃、Na₂S₂O₈And K₂S₂O₈Or mixtures thereof. The polymerization is preferably carried out at a reaction temperature of from-20 to 100 ℃. Particularly preferred is a reaction temperature of 20 to 100 ℃. The reaction solution is then treated, if desired, with at least one ion exchanger.

Suitable solvents for the above-mentioned reactions are, for example, polar solvents, such as water, alcohols, such as methanol, ethanol, 2-propanol, n-butanol, diacetone alcohol, ethylene glycol, glycerol or mixtures thereof. Aliphatic ketones, such as acetone and methyl ethyl ketone, aliphatic nitriles, such as acetonitrile, aliphatic amides and cyclic amides, such as N, N-dimethylacetamide, N-Dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (NMP), ethers, such as Tetrahydrofuran (THF), and sulfoxides, such as dimethyl sulfoxide (DMSO), or mixtures thereof with one another or with the abovementioned solvents, are also suitable.

Corresponding monomer compounds for preparing polythiophenes A) which contain recurring units of the formula (I) are known. They can be prepared, for example, by reacting alkali metal salts of 3, 4-dihydroxythiophene-2, 5-dicarboxylic acid esters with the corresponding alkylene dihalides, followed by decarboxylation of the free 3, 4- (alkylenedioxy) thiophene-2, 5-dicarboxylic acids (see, for example, Tetrahedron (Tetrahedron)1967, 23, 2437-and J.Am.Chem.Soc.1945, 67, 2217-2218), by ether exchange of 3, 4-dialkoxythiophene and 2-mercapto-ethanol (Blanchard, Philippe; Cappon, Alexander; Levilain, Eric; Nicolas, Yohann; Frere, Piene; Roncali, JeanOrganic Letters (2002), 4(4), 607-609) or, in the case of thieno (3, 4-b) thiophenes, according to L.ndsma, Braksrud.1990.20. Commun.75.

The polythiophenes obtained are very readily soluble or dispersible in polar solvents or solvent mixtures.

The preparations according to the invention comprise, in addition to at least one partially or perfluorinated polymer C), at least one SO-containing polymer₃ ^-M⁺Or COO^-M⁺Further polymers B) of radicals. Containing SO₃ ^-M⁺Or COO-M⁺Suitable polymers B) of the radicals are preferably those which do not contain a completely conjugated main chain and are abbreviated below as non-conjugated. Containing SO₃ ^-MM⁺Or COO^-M⁺Examples which may be mentioned of suitable polymers B) of radicals are polycarboxylic acids, such as polyacrylic acid, polymethacrylic acid or polymaleic acid, or polysulfonic acids, such as polystyrenesulfonic acid and polyvinylsulfonic acid. Also, copolymers of vinyl carboxylic and vinyl sulfonic acids with other polymerizable monomers, such as acrylates and styrene, are possible. Particularly suitable are polystyrenesulfonic acid, poly- (styrenesulfonic acid-co-maleic acid) or poly- (vinylsulfonic acid). Very particularly suitable formulations are characterized in that they comprise polystyrenesulfonic acid (PSS) as at least one SO-containing₃ ^-M⁺Or COO^-M⁺Polymers B) of radicals.

These polymers B) are preferably soluble or dispersible in polar solvents, such as water, alcohols, such as methanol, ethanol, 2-propanol, N-butanol, diacetone alcohol, ethylene glycol, glycerol, aliphatic ketones, such as acetone and methyl ethyl ketone, aliphatic nitriles, such as acetonitrile, aliphatic and cyclic amides, such as N, N-dimethylacetamide, N-Dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (NMP), ethers, such as Tetrahydrofuran (THF), and sulfoxides, such as dimethyl sulfoxide (DMSO), or mixtures comprising the abovementioned solvents, preferably in water, alcohols, such as methanol, ethanol, 2-propanol, N-propanol and N-butanol, or mixtures thereof.

As mentioned aboveSuitable formulations are characterized in that they comprise at least one SO-containing₃ ^-M⁺Or COO^-M⁺Partially or perfluorinated polymers C) of radicals, for example those containing repeating units of the formulae (II-a) and (II-b)

Wherein Rf represents a group having at least one, preferably 1 to 30 repeating units of formula (II-c)

Such perfluorinated polymers are, for example, commercially available under the trade name Nafion^_Under the trade name Liquion^_The polymer of (1).

In a particularly preferred embodiment, the novel formulation comprises Nafion^_(copolymers of tetrafluoroethylene and a trifluorovinyl ether of poly (hexafluoropropylene oxide) mono (tetrafluoroethylene sulfonic acid) ether) as at least one SO-containing₃ ^-M⁺Or COO^-M⁺Polymer C) of the group.

Particularly preferred formulations comprise polystyrenesulfonic acid (PSS) as containing SO₃ ^-M⁺Or COO^-M⁺Polymers of radicals B) and Nafion^_(copolymers of tetrafluoroethylene and trifluoroethylene ether of poly (hexafluoropropylene oxide) mono (tetrafluoroethylene sulfonate) as containing SO)₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers C) of the groups.

The molecular weight of the poly-acid is preferably 1,000-2,000,000, particularly preferably 2,000-500,000. Poly-acids or their alkali metal salts are commercially available, for example polystyrenesulfonic acids and polyacrylic acids, or can be prepared by known methods (see, for example, Houben Weyl, Methoden der organischen Chemie, vol. E20Makromolekulare Stoffe, second part, (1987), pages 1141 onwards).

Wherein polythiophene A) (if appropriate together with additional conductive polymers contained therein) is reacted with a compound containing SO₃ ^-M⁺Or COO^-M⁺Formulations having a weight ratio of the radical polymers B) of from 1 to 2 (1: 2) to 1 to 25 (1: 25), preferably from 1 to 2 (1: 2) to 1 to 20 (1: 20), are very particularly preferred.

Wherein polythiophene A) (if appropriate together with additional conductive polymers contained therein) is reacted with a compound containing SO₃ ^-M⁺Or COO^-M⁺Formulations having a weight ratio of the partially or perfluorinated polymers C) of the radicals from 1: 1 to 1: 50 (1: 50), preferably from 1: 2 (1: 2) to 1: 30 (1: 30), are furthermore very particularly preferred.

The polythiophene A0 and the sulfur-containing compound₃ ^-M⁺Or COO^-M⁺Polymers B) and polythiophenes A) of radicals with SO₃ ^-M⁺Or COO^-M⁺All desired combinations of the two weight ratios of the partially or perfluorinated polymers C) of the radicals can be achieved in the preferred formulations and are therefore to be considered as disclosed therein.

The novel formulations may further additionally comprise at least one polar diluent D) (polar solvent). In the context of the present invention, a polar diluent D) (polar solvent) will be understood as having 16MPa^1/2And above, preferably 19MPa^1/2And diluents of the above solubility parameter delta. The solubility parameter is usually measured at standard temperature (20 ℃). For the measurement and calculation of the solubility parameters, see J.Brandrup et al Polymer handbook (Polymer handbook), 4 th edition, 1999, VII/675-VII/688. Solubility parameters are given in tabular form, for example in the Polymer Handbook of J.Brandrup et al (Polymer Handbook), 4 th edition, 1999, VII/688-VII/697. Preferred polar diluents D) are water, alcohols, such as methanol, ethanol,2-propanol, N-butanol, diacetone alcohol, ethylene glycol, glycerol, aliphatic ketones, such as acetone and methyl ethyl ketone, aliphatic nitriles, such as acetonitrile, aliphatic and cyclic amides, such as N, N-dimethylacetamide, N-Dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (NMP), ethers, such as Tetrahydrofuran (THF), and sulfoxides, such as dimethyl sulfoxide (DMSO), or mixtures comprising the aforementioned solvents. Particularly preferred polar diluents D) are water, alcohols or mixtures comprising the abovementioned solvents, and very particularly preferably water, methanol, ethanol, n-propanol, 2-propanol or n-butanol or mixtures comprising the abovementioned solvents. In a preferred embodiment, the novel formulations comprise a mixture of water and at least one alcohol as polar diluent D).

This new preferred formulation comprises at least one polar diluent D), preferably 99.99 to 80 wt.%, particularly preferably 99.8 to 95 wt.%, of a polar diluent D), and has a solids content of 0.01 to 20 wt.%, particularly preferably 0.2 to 5 wt.%, that is to say comprises a total of 0.01 to 20 wt.%, particularly preferably 0.2 to 5 wt.%, of polythiophene a), contains SO₃ ^-M⁺Or COO^-M⁺Polymers B) and C) of the radicals and optionally further components, such as, for example, binders, crosslinkers and/or surfactants, in dissolved and/or dispersed form.

The viscosity of the new preferred formulations containing at least one polar diluent is between the viscosity of the diluent and 200mPas, preferably < 100mPas, at 20 ℃.

To achieve the desired solids content and the desired viscosity, the desired amount of diluent can be removed from the formulation by distillation, preferably under vacuum, or by other methods, such as ultrafiltration.

Organic, polymeric binders and/or organic, low molecular weight crosslinking agents or surfactants may additionally be added to the formulations according to the invention. Corresponding adhesives are described in EP-A564911. Examples which may be mentioned here are polyvinylcarbazole as binder, silanes, e.g. Silquest^_A187(OSi specialities), or surfacesThe active agent is a crosslinking agent, and for example, a fluorosurfactant FT248 (bayer corporation).

The formulations may preferably contain small amounts of ionic impurities, for example within the limits of the ranges described in EP-A991303. The formulation preferably contains less than 1,000ppm ionic impurities.

The preparation according to the invention can be prepared in a simple manner by mixing at least one SO-containing substance₃ ^-M⁺Or COO^-M⁺The weight ratio between the polymer B) and the polythiophene A) in the weight ratios described above for the formulations according to the invention, and the mixture optionally in the form of a solution or dispersion, with at least one finished mixture containing SO₃M⁺Or COO^-M⁺Partially or perfluorinated polymers C) of groups, optionally in the form of a solution or dispersion, in the weight ratios mentioned above for the preparation according to the invention relative to the polythiophene A). The invention likewise provides a process for preparing the formulations according to the invention. For example, by including at least one SO-containing compound₃ ^-M⁺Or COO^-M⁺The finished mixture of the radical polymers B) and at least one polythiophene A) with at least one SO-containing substance₃ ^-M⁺Or COO^-M⁺Partially or perfluorinated polymers C) of the groups and optionally adding at least one diluent to the mixture, preferably completely or partially dissolving or dispersing the mixture in at least one diluent. It is also possible to add SO to the solution containing₃ ^-M⁺Or COO^-M⁺Adding at least one diluent D) to the finished mixture of the radical polymers B) and of the at least one polythiophene A), preferably completely or partially dissolving or dispersing the finished mixture in the at least one diluent D), and adding at least one additive containing SO₃ ^-M⁺Or COO^-M⁺Partially or perfluorinated polymers C) of the radicals are dissolved or dispersed in a diluent,the solution and/or dispersion is then mixed. If desired, all or part of the diluent D) can then be removed from the mixture again, for example by distillation or other methods, or the mixture can be diluted.

Surprisingly, the formulations according to the invention are outstandingly suitable for the production of hole-injecting or hole-transporting layers in EL devices, organic solar cells, organic laser diodes, organic thin-film transistors or organic field-effect transistors, for the production of electrodes or electrically conductive coatings.

The invention therefore also provides for the use of the formulations according to the invention for producing hole-injecting layers in EL arrangements, for producing electrodes or electrically conductive coatings.

These EL devices are used as display elements (displays), for example in flat screens, such as laptop computers, pagers, mobile telephones, navigation devices, car radios, vehicle dashboards, or as flat emitters, such as lamps, illumination areas, LCD displays, backlighting of signboards.

In particular, EL devices having a hole-injecting layer comprising a formulation according to the invention are distinguished by a high luminous intensity (luminous density) and a long lifetime, which, however, also have the advantage over known EL devices that expensive control of the particle size is avoided, which is no longer necessary, for example in passive matrix displays.

Crosstalk is understood by those skilled in the art to refer to electrical interference between adjacent address lines in a passive matrix display. To avoid cross talk in OLEDs, it is desirable that none of the layers used have a specific resistance of less than 1E4Ohm cm. Particularly, for the hole-injecting layer, it is required to maintain the resistivity at 1.10⁴Ohm·cm-1·10⁷Ohm cm. The upper limit of the range is determined by the need to minimize the voltage drop of the layer. The resistivity is calculated from the product of the surface resistance and the layer thickness of the conductive polymer layer. The surface resistance of the conductive polymer is measured according to DIN EN ISO3915, and the thickness of the polymer layer is measured with the aid of a pin-type profilometerThe amount of the compound is as follows.

The formulations according to the invention provide further advantages in terms of the electrical rectification ratio obtained in EL devices. This is understood by those skilled in the art to mean the ratio of forward current to reverse current at a fixed voltage. If the OLED is polarized in the forward direction, i.e., the anode, e.g., an ITO anode, is connected to the positive pole of a voltage source and the vapor-fused metal electrode is connected to the negative pole, a forward current "I +" flows. If the polarity is reversed, a reverse current "I-" flows. Since during operation of a passive matrix OLED most of the individual light emitting points (pixels) are oppositely polarized, the highest possible rectification ratio is desired in order to keep the electrical losses low. Recommended I +/I-rectification ratio > 1.10⁵。

The invention therefore also provides EL devices, in particular light-emitting diodes, comprising a hole-injecting layer containing the formulations according to the invention. Preferred EL devices comprise at least two electrodes, of which optionally at least one is applied to an optionally transparent substrate, at least one light-emitting layer located between the two electrodes and at least one hole-injecting layer located between one of the two electrodes and the light-emitting layer, characterized in that the hole-injecting layer comprises a formulation according to the invention.

In the production of many large area EL devices, such as large area electroluminescent display elements, it is advantageous if at least one current-carrying electrode is made of a transparent and electrically conductive material. Suitable examples of such transparent and electrically conductive electrode materials are

a) Metal oxides such as Indium Tin Oxide (ITO), tin oxide (NESA), doped tin oxide, doped zinc oxide, and the like,

b) translucent metal films, such as gold, platinum, silver, copper, and the like,

c) semi-transparent conductive polymers such as polythiophene, polyaniline, polypyrrole, and the like.

The electrode not made of one of the above-mentioned transparent and electrically conductive materials is preferably a metal electrode, in particular a metal cathode.

Suitable materials for the metal cathode are those materials commonly used in electro-optic structures and well known to those skilled in the art. Possible metal cathodes are preferably those of low emission power, such as magnesium, calcium or barium, or metal salts, such as LiF.

Suitable optional transparent substrates are, for example, glass, ultra-thin glass (toughened glass) or plastic, preferably plastic films.

Particularly suitable plastics for the substrate are: polycarbonates, polyesters, such as, for example, PET and PEN (polyethylene terephthalate or polyethylene naphthalate), copolycarbonates, polyacrylates, polysulfones, polyether sulfones (PES), polyimides, polyethylene, polypropylene or cyclic polyolefins or Cyclic Olefin Copolymers (COC), hydrogenated polystyrenes or hydrogenated styrene copolymers.

Suitable polymer substrates may be, for example, films, such as polyester films, PES films from Sumitomo or polycarbonate films from Bayer (Makrofol)^_)。

The light-emitting layer of the EL device according to the present invention contains at least one light-emitting material. Suitable light-emitting materials are the materials which are customary for electro-optical structures and are known to the person skilled in the art. Preferred possible luminescent materials are conjugated polymers, such as polyphenylene-vinylenes and/or polyfluorenes, for example, the polyparaphenylene-vinylene derivatives and polyfluorene derivatives described, for example, in WO-A90/13148, or light-emitting sources from the class of low-molecular-weight light-emitting sources, also known in the art as small molecules, for example aluminum complexes, such as tris (8-hydroxyquinolinato) aluminum (Alq)₃) Fluorescent dyes, e.g. quinacridones, or phosphorescent light sources, e.g. Ir (ppy)₃. Luminescent materials are described, for example, in DE-A19627071.

In such electroluminescent layer constructions (EL devices), in addition to the above-mentioned layers, further functional layers can be present, such as, for example, further charge-injecting layers, for example electron-injecting layers, charge-transporting or charge-blocking interlayers. Such layer configurations are known to those skilled in the art and are described, for example, in j.r. sheats et al, Science 273, (1996), 884. A single layer can also serve multiple functions. For example, the above-described light-emitting material may be applied to a hole-transporting interlayer between a hole-injecting layer and a light-emitting layer (see, for example, US4,539,507 and US5,150,006).

The production principle of such EL devices in general is well known to the person skilled in the art. For example, they can be produced by applying the electrodes from a solution or dispersion onto a substrate, or by vapor deposition. For example, metal oxide or semi-transparent metal thin film electrodes are preferably applied to a substrate by vapor deposition, while semi-transparent, conductive polymer electrodes are preferably applied from a solution or dispersion. If desired, the adhesion promoter may be applied by vapor deposition or from a solution or dispersion prior to application of the electrode material to the substrate. Some such substrates coated with electrode material are also commercially available (e.g. K-glass, ITO-coated glass substrates). The hole-injecting layer can then be applied to the electrode, wherein in the case of an EL arrangement according to the invention comprising a hole-injecting layer of a formulation according to the invention, the application of the hole-injecting layer to the electrode is advantageously applied from a solution or dispersion. Depending on the raw materials used, further layers are then applied to the hole-injecting layer from solution or dispersion or by vapor deposition in the order given in the introduction-it being contemplated that the individual layers may be omitted. The layer of devices is then connected and encapsulated.

The production of the cavitation-incorporation layer comprising the formulation according to the invention is carried out by known techniques. For this purpose, the formulations according to the invention are applied to an electrode, preferably a base electrode, in the form of a thin film, optionally in a solvent. Suitable solvents are the polar diluents mentioned above, preferably water, alcohols or mixtures thereof. Suitable alcohols are, for example, methanol, ethanol, n-propanol, 2-propanol and n-butanol.

The use of these solvents has the advantage that the other layers can be applied from organic solvents, for example mixtures of aromatic and aliphatic hydrocarbons, without corroding and redissolving the hole-injecting layer.

The formulations according to the invention-optionally in a solvent-may be uniformly distributed on the electrode, for example, by printing techniques such as spin coating, melt coating, knife coating, printing, curtain coating, and the like. These layers may then be dried at room temperature or at temperatures up to 300 deg.C, preferably 100 deg.C and 200 deg.C.

The formulations according to the invention-optionally in a solvent-can also be applied in structured form, preferably by techniques such as ink-jetting. Such techniques are well known to those skilled in the art and use water soluble and dispersible polythiophenes, such as 3, 4-polyethylenedioxy-thiophene: polystyrene sulfonic acid (PEDT: PSS), as described, for example, in Science (Science), volume 279, 1135, 1998 and DE-A19841804.

The formulation according to the invention-optionally in a solvent-is preferably filtered with a filter before use.

Preparations which can be purified by filtration are particularly readily obtainable, for example, if, based on one part by weight of the polythiophene comprising repeating units of the formula (I), preferably from 1 to 30 parts by weight, particularly preferably from 2 to 25 parts by weight, of the SO-containing solvent D) are used₃ ^-M⁺Or COO^-M⁺Polymers B) of clusters.

The thickness of the hole-injecting layer is, for example, 3 to 500nm, preferably 10 to 200 nm.

Examples

Example 1

Using Nafion^_Preparation of poly (ethyleneoxy thio thiophene) -PSS complexes and complexes thereof

1.06 g of PSS (molecular weight M)_W48,000) a solution of 0.47 g EOTT and 0.25 g sodium iodate in 103.7 g water was stirred at 50 c for 7 days. Then, the dark blue reaction mixture was washed with water9 g of cation and anion exchanger (Lewatit) were used in each case^_S100 and Lewatit^_MP62) was deionized for 8 hours, and then the ion exchange resin was filtered off. Ion content: sulfate radical 1ppm, Na⁺14ppm, iodide ion < 20 ppm.

The deionised preparation formed for the preparation of the mixture according to the invention is mixed as follows:

19.6 g of the above deionized formulation corresponding to 0.225 g of the PEOTT-PSS complex

12.97 g of water

12.1 g of ethanol

10.75 grams of Liquion^_1100(Naifion^_-a solution containing water from Ion Power inc., US; 2-propanol/water solution at a concentration of 5% by weight, 1,100eq.), corresponding to 0.5g of Nafion^_。

For this purpose, first, the liquid is added to Liquion^_1100 ethanol and water were injected, the mixture was stirred for 1/4 hours at 23 ℃ and after stirring the mixture for another 1/2 hours at 23 ℃, then the PEOTT-PSS complex was injected.

Monomer (b): PSS: the weight ratio of the fluoropolymer corresponds to 1: 2.3: 7.3.

Example 2

Preparation of a mixture of aggregated (3, 4-ethylenedioxythiophene)/polystyrene sulfonic acid and perfluoropolymer

Polyethylene dioxythiophene/polystyrene sulfonic acid solution (h.c. starck GmbH, Baytron)^_PH desalted) and Nafion (r)^_Solution (Liquion)^_1100, 5% strength by weight 2-propanol/water solution, 1,100eq, Ion Power Inc., US) PEDT: PSS: Nafion at 1: 2.5: 7.5^_Mixing the components in a certain ratio.

Example 3

The formulations according to the invention from example 1 were used for the production of organic light-emitting diodes (OLEDs). The OLED was produced as follows:

1. preparation of ITO-coated substrates

The ITO-coated glass (Merck Balzers AG, FL, part number 253674XO) was cut into pieces (substrates) with a size of 50 mm x 50 mm. The substrate was then rinsed in an ultrasonic bath for 15 minutes with a 3% strength aqueous solution of Mucasol. The substrate was then rinsed with distilled water and spin dried in a centrifuge. The rinsing and drying operations were repeated 10 times. Just prior to coating, the ITO-coated side was cleaned in a UV/ozone reactor (PR-100, UVP inc., cambridge, england) for 10 minutes.

2. Application of hole-injecting layer

About 10 ml of the preparation according to the invention obtained in example 1 were filtered (micropore HV, 0.45 μm). The cleaned ITO-coated substrate was placed on a spin-spray coater and the filtered solution was distributed over the ITO-coated side of the substrate. The plate was then spun at 500 rpm with the lid closed for 30 seconds to remove the supernatant. The substrate coated in this way was then dried on a hot plate at 200 ℃ for 5 minutes. The layer thickness is 50 nm (Tencor, Alphastep 500).

The conductivity was determined on the isolating layer by means of a 2.5 cm long silver electrode deposited by vapour phase of the tape cover at a distance of 0.5 mm (similar to the method of step 4). The resistivity is obtained by multiplying the surface resistance determined by the electrometer by the layer thickness.

3. Application of a light-emitting layer

5 ml of a 1% by weight concentration of the light-emitting source Green 1300 Lu MATION^TMThe xylene solution (Dow chemical) was filtered (millipore HV, 0.45 microns) and distributed over the dried hole-injecting layer. The plate was then spun at 500 rpm with the cover plate closed for 30 seconds to remove the supernatant of the light emitting source. The layer was then dried on a heat-plate at 110 ℃ for 5 minutes. The total layer thickness is 130 nm。

All further working procedures are in pure N₂Air atmosphere (inert gas cover box system, m.braun, Garching) into which the coated substrate is transferred. The coated substrate was first dried here on a hot plate for 15 minutes at 130 ℃.

4. Application of metallic cathode

And depositing a metal electrode on the light-emitting layer as a cathode. For this purpose, the substrate with the light-emitting layer was placed down on a band-shaped cover with holes having a diameter of 2.5 mm. A5 nm thick barium layer and then a 200nm thick silver layer were etched at p ═ 10^-3Vapor-deposition was continued from two vapor-deposition dishes at a pressure of Pa. The vapor deposition rate for barium was 10 a/sec and for silver was 20 a/sec. The separated metal electrode has a thickness of 4.9mm²The area of (a).

5. Characteristics of OLED

The two electrodes of the organic LED are connected (contacted) to a power supply via electrical leads. The positive electrode was connected to an ITO electrode, and the negative electrode was connected to a metal electrode by a thin and flexible gold wire. Recording OLED Current and electroluminescent intensity (with photodiode (EG)&GC 30809E)) and voltage. Then, the ratio of I to 0.32mA (8 mA/cm)²) The lifetime is determined by flowing a direct current through the device and monitoring the voltage and luminous intensity as a function of time.

Comparative example 3.1

With poly (3, 4-ethylenedioxythiophene)/polystyrene sulfonic acid and Nafion^_Production of OLEDs as hole injection layer:

the procedure is as in example 3, with the following differences in step 2:

2. application of hole injection layer

About 10 ml of the solution from example 2 were filtered (MilliporeHV, 0.45 μm). The ITO-coated substrate was then placed on a spin-spray coater and the filtered solution was distributed on the ITO-coated side of the substrate. The plate was then spun at 850 rpm with the lid closed for 30 seconds to remove the supernatant. The substrate coated in this way was then dried on a hot plate at 200 ℃ for 5 minutes. The layer thickness is 50 nm.

According to the method in step 4, the metal cathode and the layer structure obtained from example 3 were applied together to ensure comparability. The characterization was also carried out as in example 3.

Table 1: measurement results of characteristic lines of the devices obtained from example 3 and comparative example 3.1

	Specific resistivity [ Ohm cm]	Efficiency when U is 4V [ cd/A ]]	Rectification rate I +/I when U is 8V-
				OLED from example 3	＞1·106	6.7	2.2·106
OLED from comparative example 3.1	15	5.7	1.5·103

The OLEDs according to the invention, which have a hole-injecting layer with a formulation according to example 1 of the invention, have a sufficiently high resistivity for passive matrix OLEDs. In contrast, the resistivity in the comparative example is too low and may cause electrical interference (cross-talk) between adjacent address lines.

A further advantage of the OLED according to the invention resulting from example 3 is that it has a higher efficiency and a significantly more favorable rectification ratio compared to the OLED according to the comparative example.

Example 4

Poly (thieno [3, 4-b)]Thiophene)/polystyrene sulfonic acid complexes and their use with Nafion^_Preparation of the mixture of

1.25g of PSS (molecular weight M)_W460,000g/mol), 195.6 g of water and 1.44 g of a 1% strength aqueous iron (III) sulfate solution are stirred at room temperature. 285 mg of thieno [3, 4-b ] were added]Thiophene and the solution was stirred for 1 hour. 726 mg of sodium peroxodisulfate were added. After stirring for 3 hours, 215 mg of thieno [3, 4-b ] were added]Thiophene, after stirring for a further 15 minutes, 474 mg of sodium peroxodisulfate are added. After stirring for 18 hours, the mixture is freed from 10 g of cation exchanger and 6 g of anion exchanger (kewatit)^_S100 and lewatit^_MP62) was deionized for 8 hours, and then the ion exchange resin was filtered. Concentration of poly (thiophene) s in a rotary evaporatorAnd [3, 4-b ]]Thiophene)/polystyrene sulfonic acid (PTT/PSS) dispersion to half volume.

The resulting formulations were mixed as follows to prepare mixtures according to the invention:

20 g of the above deionization preparation, corresponding to 0.3 g of the PTT-PSS complex

13 g of water

12.1 g of ethanol

13.82 grams Liquion^_1100(Nafion^_-a solution containing water from Ion Power inc., US; 2-propanol/water solution at a concentration of 5% by weight, 1,100eq.), corresponding to 0.64 g of Nafion^_。

For this purpose, ethanol and water are first injected into the liquid^_1100, the mixture was stirred at 23 ℃ for one hour and after stirring the mixture at 23 ℃ for one hour, the PTT-PSS complex was injected.

Monomer (b): PSS: the weight ratio of the fluoropolymer corresponds to 1: 2.5: 7.5.

Claims (15)

1. A formulation comprising

A) At least one polythiophene comprising a repeating unit of the general formula (I-a) and/or (I-b)

Wherein

A represents optionally substituted C₁-C₅An alkylene group, preferably an optionally substituted ethylene or propylene group,

y, independently of one another, represents O or S,

r represents a linear or branched C₁-C₁₈Alkyl radical, C₅-C₁₂-cycloalkyl, C₆-C₁₄-aryl, C₇-C₁₈-aralkyl group, C₁-C₄-a hydroxyalkyl group or a hydroxyl group,

x represents an integer of 0 to 8 and

in the case where several groups R are attached to A, these substituents may be the same or different,

wherein, in the case where Y represents O in the general formula (I-a), the polythiophene further contains a repeating unit of the general formula (I-a) in which Y represents S or contains a repeating unit of the general formula (I-b)

B) At least one SO-containing₃ ^-M⁺Or COO^-M⁺Polymers of radicals in which M⁺Represents H⁺、Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺Or NH₄ ⁺Preferably H⁺、Na⁺Or K⁺And an

C) At least one SO-containing₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers of radicals in which M⁺Represents H⁺、Li⁺、Na⁺、K⁺、Rb⁺、Cs⁺Or NH₄ ⁺Preferably H⁺、Na⁺Or K⁺。

2. Preparation according to claim 1, characterized in that the at least one polythiophene comprising recurring units of the general formula (I-a) and/or (I-b) comprises recurring units of the general formula (I-aa) and/or (I + bb)

Wherein

R, Y and x have the meanings given in claim 1, and preferably x represents 0 or 1.

3. Preparation according to claim 1 or 2, characterized in that the at least one polythiophene comprising recurring units of the general formula (I-a) and/or (I-b) comprises recurring units of the general formula (I-aa-1) and/or (I-aa-2) and/or (I-bb-1)

4. Preparation according to at least one of claims 1 to 3, characterized in that the at least one polythiophene comprising recurring units of the general formula (I-a) and/or (I-b) is a polythiophene comprising in each case identical recurring units of the general formula (I-a) in which Y represents S, a polythiophene comprising in each case identical recurring units of the general formula (I-b) in which Y represents S, or a copolymer comprising recurring units of the general formula (I-a) in which Y represents O and S, or a copolymer comprising recurring units of the general formula (I-a) and (I-b).

5. Preparation according to at least one of claims 1 to 4, characterized in that the preparation comprises, in addition to at least one polythiophene comprising repeating units of the general formula (I-a) and/or (I-b), further electrically conductive polymers, such as polyaniline, polypyrrole or polythiophene, preferably poly (3, 4-ethylenedioxythiophene).

6. Preparation according to at least one of claims 1 to 5, characterized in that it comprises polystyrene sulfonic acid (PSS) as at least one SO-containing₃ ^-M⁺Or COO^-M⁺Polymers B) of radicals.

7. Preparation according to at least one of claims 1 to 6, characterized in that it comprises as at least one member a copolymer of tetrafluoroethylene and trifluorovinyl ether of poly (hexafluoropropylene oxide) mono (tetrafluorovinylsulfonic acid) etherContaining SO₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers C) of the groups.

8. Preparation according to at least one of claims 1 to 7, characterized in that it comprises at least one SO-containing₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers C) of radicals, for example polymers C) containing recurring units of the formulae (II-a) and (II-b)

Wherein R is_fRepresents a group having at least one, preferably 1 to 30 repeating units of the formula (II-c)

9. Preparation according to at least one of claims 1 to 8, characterized in that the polythiophene A) is reacted with a compound containing SO₃ ^-M⁺Or COO^-M⁺The weight ratio of the partially fluorinated or perfluorinated polymers C) of the radicals is from 1: 2 to 1: 15.

10. Preparation according to at least one of claims 1 to 9, characterized in that the polythiophene A) is admixed with SO₃ ^-M⁺Or COO^-M⁺The weight ratio of the polymers F) of the radicals is from 1: 2 to 1: 25.

11. Formulation according to at least one of claims 1 to 10, characterized in that it additionally comprises at least one polar diluent.

12. Formulation according to claim 11, characterized in that water, alcohols, in particular selected from the series consisting of methanol, ethanol, n-propanol, 2-propanol or n-butanol, or comprising at least one of the above diluents

13. A process for preparing a formulation according to at least one of claims 1 to 12, characterized in that it comprises at least one SO-containing substance₃ ^-M⁺Or COO^-M⁺Mixtures of polymers B) of radicals and at least one polythiophene A), optionally in solution or dispersion in a diluent, with at least one SO-containing substance₃ ^-M⁺Or COO^-M⁺Partially fluorinated or perfluorinated polymers C) of the radicals, optionally in solution or dispersion in a diluent.

14. Use of the formulation according to at least one of claims 1 to 12 for producing electrodes or electrically conductive coatings in the production of hole-injecting or hole-transporting layers in electroluminescent devices, organic solar cells, organic laser diodes, organic thin-film transistors or organic field-effect transistors.

15. An electroluminescent arrangement, in particular a light-emitting diode, comprising at least two electrodes, at least one light-emitting layer between the two electrodes, and at least one hole-injecting layer between one of the two electrodes and the light-emitting layer, wherein optionally at least one electrode is located on an optionally transparent substrate, characterized in that the formulation according to any of claims 1 to 12 is contained in the hole-injecting layer.