FLUORINATED AMINES AS SAM IN OLEDS
The present invention relates to a layer body, a process for obtaining a layer body, the layer body obtainable by this process, electronic components comprising a layer body as well as the use of a fluorinated amine.
An electro-luminescent device (EL-device) is characterised in that it gives out light under a flow of electrical current when an electrical voltage is applied. Such devices have been known for a long time under the name "light emitting diodes" (LEDs). The emission of light arises when positive charges (holes) and negative charges (electrons) recombine with the emission of light.
LEDs employed in technology are composed predominantly of inorganic semiconductor materials. For several years, however, EL-devices have been known whose fundamental constitu- ents are organic materials. These organic EL-devices (OLED = "organic light emitting diode") contain, as a rule, one or more layers of organic charge-transport compounds.
The fundamental layer composition of an EL-device is, for example, as follows: 1 carrier, substrate
2 base electrode
3 hole injection layer
4 electron blocking layer
5 emitter layer
6 hole blocking layer
7 electron injection layer
8 top electrode
9 contacts
10 encasement, encapsulation
This arrangement represents the most detailed case and can be simplified by omission of individual layers so that one layer takes on multiple functions. In the simplest case, an EL device consists of two electrodes between which there is an organic layer which performs all of the functions, including the emission of light.
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It has been shown in practice, however, that electron injection layers and/or hole injection layers in the electro luminescent assemblies are particularly advantageous for increasing the light density, in which connection electrically conductive polymers are often employed, especially in the hole injection layer. Particular technical importance in this regard has been attained, for i0 example, by dispersions of PEDOT with polyanions, such as e.g. polystyrene sulphonic acid (PSS), as disclosed in EP 0 440 957 A2. From these dispersions can be made transparent, conductive films which are suited for use as hole injection layer in OLEDs, as is described, for instance, in EP 1 227 529 A2.
15 Polymerisation of EDOT is achieved in an aqueous solution of the polyanion, and a polyelec- trolyte complex is formed. Cationic polythiophenes, which contain polymeric anions as counters ions for charge balancing, are often referred to in the technical domain as polythio- phene/polyanion complexes. Due to the polyelectrolyte properties of PEDOT as polycation and PSS as polyanion, this complex does not represent a true solution, rather more a disper-
>0 sion. To what extent polymers or parts of the polymers, in this case, are dissolved or dispersed depends on the mass ratio relating the polycation and the polyanion, on the charge density of the polymers, on the salt concentration of the environment, and on the nature of the surrounding medium (V. Kabanov, Russian Chemical Reviews 74, 2005, 3-20). The crossovers can thereby be blurred. Therefore, no distinction will be made in the following between the terms
15 "dispersed" and "dissolved". Equally little distinction will be made between "dispersion" (Dis- pergierung) and "solution" and between "dispersing agent" and "solvent". These terms will rather be used as synonyms.
In order to improve the life span of OLEDs comprising layers based on wet-processed0 PEDOT : PSS dispersions, DE-A- 10 2004 006583 and DE-A- 10 2004 01081 1 recommend dispersions which, in addition to the conductive polymer, preferably PEDOT, contain a fluori-
nated or perfluorinated polyanion. The layers produced therefrom are particularly suitable as hole injection layers in OLEDs containing at least two electrodes, of which optionally at least one is deposited onto an optionally transparent substrate, at least one emitter layer between the two electrodes, and at least one hole injection layer between one of the two electrodes and the 5 emitter layer, in such a manner that the emitter layer is in direct contact with the hole injection layer. Layers which contain fluorinated or perfluorinated polymers, however, are characterised by a high contact angle. This makes deposition of further solvent-based layers harder, because the large contact angle impedes film formation.
0 To lengthen the life span of OLEDs, DE-A-10 2009 031 677 recommends employing func- tionalised polysulphones instead of PSS as the polyanions for balancing the charge of the cati- onic polythiophenes.
The disadvantage, however, amongst others, of using hole injection layers based on wet- 5 processed PEDOT : PSS dispersions or dispersions of PEDOT and functionalised polysulphones in OLEDs, is that degradation of the organic layer can still occur, primarily at the boundary layer between the hole injection layer and the emitter layer, thus limiting the life span of the OLEDs
!0 The use of SAMs ("self assembled monolayer") for surface modification is likewise known.
Thus Lee et al. (Proceedings of SPIE, 6655, 6655 IE (2007)) describe the use of octadecyltri- chlorosilane (OTS) for the formation of a SAM layer on a layer of PEDOT : PSS and show that this surface modification results in an increase in the efficiency of the corresponding OLEDS. DE-A-10 2009 012163 discloses the use of fluorinated silanes for the surface modifi-
!5 cation of metal oxides such as, for example, ITO and their use in OLEDs.
The present invention was based on the object of overcoming the disadvantages present in the state of the art in connection with OLEDs, in particular in connection with OLEDs comprising hole injection layers comprising conductive polymers, in particular hole injection layers com- 10 prising polythiophenes and polyanions functionalised with acid groups.
The present invention was particularly based on the object of providing a layer body comprising conductive polymers, in particular conductive polymers comprising polythiophenes and polyanions functionalised with acid groups, which is, for example, suitable as the hole injection layer in an OLED and which is less susceptible to degradation as compared to the hole 5 injection layers known from the state of the art.
The present invention was also based on the object of providing a process for the production of such a layer body, which enables the production of more stable (with respect to degradation) hole injection layers, comprising conductive polymers, in particular comprising conductive 0 polymers comprising polythiophenes and polyanions functionalised with acid groups, using the simplest possible process techniques, without thereby adversely influencing the electrical properties of such layers. The process should in particular also enable the production of OLEDs with particularly longer life spans.
15 The present invention was also based on the object of providing OLEDs which are characterised by a particularly long life span, where the longer life span should, in particular, manifest itself in that the time taken for the light intensity of the OLED at a constant electrical current to halve is as long as possible.
!0 A contribution to the solution of the aforementioned objects is made by a layer body, at least comprising a first layer comprising a conductive polymer;
15 a further layer following the first layer, comprising a fluorinated amine.
Surprisingly, it was found that fluorinated amines on a surface of a conductive polymer, in particular on a surface of a conductive polymer comprising a polythiophene and a polymer functionalised with acid groups, for example on a PEDOT : PSS surface, can form a self as- S0 sembled monolayer (SAM). The fluorinated units also serve for self organisation, because they favour the proximity of further fluorine groups. It has been shown that the life span of an
OLED can be increased significantly, for example, when the PEDOT : PSS based hole injection layer in a Glass/ITO/PEDOT : PSS NPB/Alq3/LiF/cathode assembly is coated with a solution of a perfluorinated amine.
The layer body according to the invention comprises a first layer which comprises a conductive polymer. Possible conductive polymers are all those polymers which exhibit an electrical conductivity, such as, for example, conductive polymers based on optionally substituted poly- anilines, optionally substituted polypyrroles or optionally substituted polythiophenes, polymers based on optionally substituted polythiophenes being particularly preferred.
According to a particularly preferred embodiment of the layer body according to the invention, the conductive polymer in the first layer comprises preferably cationic polythiophene and a preferably anionic polymer functionalised with acid groups.
The polythiophene is preferably a polythiophene with repeating units of the general formula (I) or (II) or a combination of units of the general formulas (I) and (II), preferably a polythiophene with repeating units of the general formula (II):
(I) (Π) wherein
A stands for an optionally substituted C]-C5-alkylene radical,
R stands for a linear or branched, optionally substituted Ci-Cis-alkyl radical, an optionally substituted C5-Ci2-cycloalkyl radical, an optionally substituted C6-Ci4-aryl radical, an optionally substituted C7-Ci8-aralkyl radical, an optionally substituted C1 -C4- hydroxyalkyl radical or a hydroxyl radical,
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x stands for a whole number from 0 to 8 and in the case where multiple radicals R are connected to A, these can be identical or different.
0 The general formulas (I) and (II) are to be so understood, that x substituents R can be connected to alkylene radical A.
Particularly preferred are polythiophenes with repeating units of the general formula (II), wherein A stands for an optionally substituted C2-C3-alkylene radical and x stands for 0 or 1. L5 Especially preferred as polythiophene is poly(3,4-ethylenedioxythiophene), which is optionally substituted.
In the context of the invention, the prefix poly- is to be understood as meaning that more than one identical or different repeating units of the general formulas (I) and/or (II) are contained in
!0 the polymer or polythiophene. As well as the repeating units of the general formulas (I) and /or (II), the polythiophene can also comprise other repeating units, it being preferred that at least 50 %, particularly preferred that at lease 75 % and most preferred that at least 95 % of all repeating units of the polythiophene exhibit the general formula(s) (I) and/or (II), preferably the general formula (II). The polythiophenes contain in total n repeating units of the general for-
>5 mula(s) (I) and/or (II), preferably of the general formula (II), n being a whole number from 2 to 2000, preferably from 2 to 100. The repeating units of the general formula(s) (I) and/or (II), preferably of the general formula (II), within a polythiophene can each be identical or different. Polythiophenes with identical repeating units of the general formula (II) are preferred.
SO The polythiophenes preferably carry H on the end groups.
In the context of the invention, Ct-C5-Alkylene radicals A are preferably methylene, ethylene, n-propylene, n-butylene or n-pentylene. Ci-C|8-alkyl R preferably stand for linear or branched Ci-C]8-alkyl radicals such as methyl, ethyl, n- or iso-propyl, n-, iso-, sec- or tert-butyl, n- pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1 ,1-dimethylpropyl, 1 ,2-
5 dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl or n-octadecyl. C5-C]2-cycloalkyl radicals R stand, for example, for cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl or cyclodecyl. C5-C14-aryl radicals R stand, for example, for phenyl or naphthyl. C7-Ci8- aralkyl radicals R stand, for example, for benzyl, o-, m-, p- tolyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-,
10 3,5-xylyl or mesityl. The preceding list serves to describe the invention with the use of examples and is not to be considered as limiting.
As optional further substituents of the radical A and/or the radical R, numerous organic groups are possible, such as, for example, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halogen, ether, thi- 15 oether, disulphide, sulphoxide, sulphone, sulphonate, amino, aldehyde, ketone, carboxylic acid ester, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane and alkoxysilane groups as well as carboxylamide groups.
The polythiophenes can be neutral or cationic. In preferred embodiments they are cationic, >0 "cationic" referring only to the charges which reside on the polythiophene main chain. Depending on the substituent of the radicals R, the polythiophenes can carry positive and negative charges in the structural unit, the positive charges being on the polythiophene main chain and the negative charges, were applicable, being on the radicals R substituted with sulphonate or carbonate groups. The positive charges of the polythiophene chain can thereby be partially or >5 fully balanced by the optionally present anionic groups on the radicals R. Considered as a whole the polythiophenes can be, in these cases, cationic, neutral or even anionic. In the context of the invention, however, they will all be considered to be cationic polythiophenes, since the positive charges on the polythiophene main chain are the decisive factor. The positive charges are not represented in the formulas, since their exact number and position can not be 50 determined absolutely. However, the number of positive charges is at least 1 and at most n, n being the total number of all repeating units (identical or different) within the polythiophene.
To compensate for the positive charge of the polythiophene, the first layer also comprises a polyanion based on polymers functionalised with acid groups. Particularly suitable as polyanion are anions of polymeric carboxylic acids, such as polyacrylic acids, polymethacrylic acid 5 or polymaleic acids, or polymeric sulphonic acids, such as polystyrene sulphonic acids and polyvinylsulphonic acids. The polycarboxylic and polysulphonic acids can also be copolymers of vinylcarboxylic and vinylsulphonic acids with other polymerisable monomers, such as acrylic acid esters and styrene. It is particularly preferable for the first layer to contain an anion of a polymeric carboxylic or sulphonic acid for compensation of the positive charge of the polio ythiophene.
Particularly preferred as polyanion is the anion of the polystyrene sulphonic acid (PSS) which, where polythiophene is used, preferably poly(3,4-ethylenedioxythiophene), is preferably present bound as a complex in the form of the PEDOT : PSS complexes known from the state of
[5 the art. Such complexes are obtainable by oxidative polymerisation of the thiophene monomers, preferably 3,4-ethylenedioxythiophene, in an aqueous solution in the presence of the polystyrene sulphonic acid.
The molecular weight of the polymers functionalised with acid groups which supply the poly- !0 anions is preferably 1,000 to 2,000,000, particularly preferably 2,000 to 500,000. The polymers functionalised with acid groups or their alkali salts are commercially available, e.g. polystyrene sulphonic acids and polyacrylic acids, or can be produced by known processes (see e.g. Houben Weyl, Methoden der organischen Chemie, vol. E 20 Makromolekulare Stoffe, Part 2, (1987), p. 1141 et seq.).
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Polymers functionalised with acid groups (polyanions) and polythiophene, in particular polystyrene sulphonic acid and poly(3,4-ethylenedioxythiophene), can be present in the first layer in a weight ratio from 0.5 : 1 to 50 : 1, preferably from 1 : 1 to 30 : 1, particularly preferably from 2 : 1 to 20: 1. The weight of the electrically conductive polymers here corresponds to the 10 weight of the monomers employed for the production of the conductive polymers, assuming that complete conversion takes place during the polymerisation. According to a particular em-
bodiment of the layer body according to the invention the polystyrene sulphonic acid is present in excess by weight compared with the polythiophene, in particular poly(3,4- ethylenedioxythiophene) .
5 According to a preferred embodiment of the layer body according to the invention the first layer consists at least 40 % by weight, particularly preferably at least 55 % by weight and most preferably at least 70 % by weight, of the polythiophene and the polymer functional ised with acid groups, particularly preferably of PEDOT : PSS, the proportion in each case being relative to the total weight of the first layer.
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The layer thickness of the first layer preferably lies in a range from 1 nm to 10 μηι, particularly preferably in a range from lO nm to 500 nm and most preferably in a range from 20 nm to 200 nm. s 5 In addition to the above described first layer, the layer body according to the invention comprises a further layer following the first layer, which comprises a fluorinated amine, it being particularly preferable according to the invention if this further layer is one which forms a self assembled monolayer (SAM). A self assembled monolayer generally forms spontaneously on dipping a substrate into a fluid comprising the fluorinated amine. It is an organised layer con-
!0 sisting of amphophilic molecules, wherein one end of each molecule possesses a specific, reversible affinity for a substrate. Unlike conventional coating techniques, such as, for example, chemical gas phase deposition, SAMs exhibit a defined layer thickness, normally a layer thickness in the range from roughly 0.1 to 2 nm.
!5 The fluorinated amines can be fluorinated or perfluorinated (i.e. the hydrogen atoms in the alkyl chains of the amine can be completely or partially replaced with fluorine atoms). It is preferred, however, for at least 40 %, particularly preferably at least 55 %, and most preferably at least 70 % of the hydrogen atoms in the amine to be replaced with fluorine atoms.
10 Furthermore, the amines can be primary, secondary or tertiary amines. In this connection it is particularly preferred for the fluorinated amine to exhibit the general formula (III)
R
I
2
R' R
(III)
5 in which R1, R2 and R3 can, independently of each other, stand for a hydrogen atom, for a C]- C20-alkyl radical, preferably for a Ci-Ci5-alkyl radical, particularly preferably for a CpCio- alkyl radical, or for a fluorinated CrC^-alkyl radical, preferably for a fluorinated CrCi5-alkyl radical, particularly preferably for a fluorinated d-C10-alkyl radical, wherein at least one of the radicals R1, R2 and R3 stands for a fluorinated Ci-C20-alkyl radical, preferably for a fluori- ίθ nated Ci-Ci5-alkyl radical and particularly preferably for a fluorinated Ci-Qo-alkyl radical.
Here also, the term "fluorinated" comprises perfluorinated as well as polyfluorinated alkyl radicals.
The above named alkyl radicals and fluorinated alkyl radicals can be straight chained or 15 branched and can optionally also comprise cyclic units, straight chain alkyl radicals being particularly preferred.
Some examples of suitable fluorinated amines are polyfluorinated or perfluorinated methyla- mine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylmethyla- mine, ethyldimethylamine, diethylmethyl amine, propylamine, dipropylamine, tripropylamine, >0 butylamine, dibutylamine, tributylamine, pentylamine, dipentylamine, tripentylamine, hexyla- mine, dihexylamine, trihexyl amine, heptylamine, diheptylamine, triheptylamine, octylamine, dioctylamine, trioctylamine, nonylamine, dinonylamine, trinonylamine, decylamine, didecyl- amine, tridecylamine, undecylamine, diundecylamine, triundecylamine, dodecylamine, di- dodecylamine or tridodecylamine. In connection with these per- or polyfluorinated alkyl, dial's kyl or trialkyl amines, it is again preferred for at least 40 %, particularly preferably at least 55 % and most preferably 70 % of the hydrogen atoms in the amine to be replaced with fluorine atoms. Where only some of the hydrogen atoms are replaced with fluorine atoms, it is preferred for the remaining hydrogen atoms to be as close as possible to the nitrogen atom. Some concrete examples of fluorinated amines are perfluorotripentylamine,
3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-l-decylamine (also known as ΙΗ,ΙΗ,- 2H,2H-perfluorodecylamine) or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-l-octylamine (also known as ΙΗ,ΙΗ-perfluorooctylamine).
In the layer body according to the invention the further layer can also comprise mixtures of at least two different fluorinated amines.
A contribution to achieving the objects named at the beginning is also made by a process for the production of a layer body comprising the process steps i) the application of a conductive polymer to a substrate to obtain a first layer; ii) the application of a fluorinated amine to the first layer to obtain a further layer.
In process step i) of the process according to the invention, a conductive polymer is applied to a substrate to obtain a first layer.
All layers which can be employed in electronic components, such as, for example, in an OLED, are suitable as the substrate. Thus, in particular, the substrate can be one which is furnished with a preferably transparent base electrode, the substrate itself preferably also being transparent. Glass, PET or other transparent plastics, for example, can be employed as transparent substrate, onto which a transparent electrically conductive electrode is then introduced, such as e.g. an electrode made of indium - tin oxide (ITO), doped zinc- or tin oxide or a conductive polymer. Particularly suitable transparent plastic substrates are, for example, polycarbonates, polyesters, such as e.g. PET and PEN (polyethyleneterephthalate and polyeth- ylenenaphthalinedicarboxylate), copolycarbonates, polyacrylates, polysulphones, polyether- sulphones (PES), polyimides, polyethylene, polypropylene, cyclic polyolefins or cyclic olefin copolymers (COC), hydrated styrene polymers or hydrated styrene copolymers. Suitable polymer bases can, for example, also be films such as polyester films, PES films from the Sumitomo company or polycarbonate films from the Bayer AG company (Makrofol®). According to the invention, ITO coated glass is particularly preferred as substrate.
The conductive polymer is deposited onto such a substrate or onto the electrode layer which has been applied to such a substrate to obtain the first layer of the layer body according to the invention, particularly preferred conductive polymers here being those conductive polymers which have already been described at the outset as preferred conductive polymer in connection with the layer body according to the invention. Thus, particularly preferred according to the invention is a conductive polymer comprising a polythiophene, particularly preferably PEDOT, and a polymer functionalised with acid groups, particularly preferably PSS, the use of PEDOT : PSS complexes as conductive polymer being particularly preferable here also.
In this connection, the conductive polymer is preferably introduced to the substrate in the form of a dispersion comprising the conductive polymer and a dispersing agent, particularly preferably in the form of a dispersion comprising polythiophene, a polymer functionalised with acid groups and a dispersing agent, especially preferably in the form of a PEDOT : PSS dispersion, with at least partial subsequent removal of dispersion agent to obtain the first layer. The application of the dispersion can be carried out, for example, using known processes, e.g. by spin coating, impregnation, pouring, dripping on, spraying, misting on, knife coating, brushing or printing, for example ink-jet, screen, Intaglio, offset or tampon printing with a wet film thickness of from 0.5 μηι to 250 μιη, preferably with a wet film thickness of from 2 μηι to 50 μιη. The at least partial removal of the dispersing agent is preferably effected by drying at a temperature in a range from 20°C to 200°C, in which connection it can be advantageous to at least partially remove the supernatant dispersion prior to the drying processes, for example by spinning off.
The production of dispersions comprising a polythiophene, a polymer functionalised with acid groups and a dispersing agent is basically described in EP-A-1 122 274 or US 5,11 1,327. The polymerisation of the appropriate monomelic compounds is carried out in the presence of polymers functionalised with acid groups, with suitable oxidising agents in suitable solvents. Examples of suitable oxidising agents are Iron(III) salts, in particular FeCl3 and Iron(III) salts of aromatic and aliphatic sulphonic acids, H202, 2Cr207, 2S208, Na2S20 , KMn04, alkali perborates and alkali or ammonium persulphates or mixtures of these oxidising agents. Further
suitable oxidising agents are described, for example, in Handbook of Conducting Polymers (Ed. Skotheim, T.A.), Marcel Dekker: New York, 1986, Vol. 1, 46-57. Particularly preferred oxidising agents are FeCl3, Na2S20 and K2S208 or mixtures thereof. The polymerisation is preferably carried out at a reaction temperature of from -20 to 100°C. Particularly preferable 5 are reaction temperatures of from 20 to 100°C. The reaction solution is optionally subsequently treated with at least one ion exchanger.
Suitable solvents are e.g. polar solvents such as, for example, water, alcohols such as methanol, ethanol, 2-propanol, n-propanol, n-butanol, diacetone alcohol, ethylene glycol, glycerine 0 or mixtures of these. Also suitable are aliphatic ketones such as acetone and methylethyl ketone, aliphatic nitriles such as acetonitrile, aliphatic and cyclic amides such as N,N- dimethylacetamide, N,N-dimethylformamide (DMF) and 1 -methyl-2-pyrrolidone (NMP), ethers such as tetrahydrofuran (THF) as well as sulphoxides such as dimethylsulphoxide (DMSO) or mixture of these with each other or with those solvents previously specified.
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The dispersions preferably exhibit a solid content in a range from 0.01 to 20 % by weight, and particularly preferably in a range from 0.2 to 5 % by weight, i.e. they contain in total 0.01 to 20 % by weight, particularly preferably 0.2 to 5 % by weight of polythiophene(s), preferably PEDOT, with polymer functionalised with acid groups, preferably PSS, and optionally further Ό components, such as e.g. binding agents, cross-linking agents and/or surfactants, in dissolved and/or dispersed form.
The viscosity at 20°C of the dispersions employed for production of the first layer preferably lies between the viscosity of the dispersing agent and 200 mPas, preferably between the vis- :5 cosity of the dispersing agent and 100 mPas.
To set the desired solid content and the required viscosity the desired amount of dispersing agent can be removed from the dispersion through distillation, preferably in a vacuum or by other processes, e.g. ultra filtration.
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Moreover, organic, polymeric binding agents and/or organic low-molecular cross-linking agents or surfactants can be added to the dispersion. Appropriate binding agents are, for example, described in EP-A 564 91 1. Examples in this regard are polyvinylcarbazole, silanes, such as Silquest® A187 (Fa. OSi Specialities) or surfactants, such as the fluoro-surfactant FT 248 (Bayer AG).
In process step ii) of the process according to the invention a fluorinated amine is then introduced onto the first layer to obtain a further layer, it being particularly preferable if a SAM forms with the application of the fluorinated amine onto the first layer in process step ii).
Preferred fluorinated amines in this connection are those fluorinated amines which have already been described at the beginning as preferred fluorinated amines in connection with the layer body according to the invention The application of the fluorinated amines onto the first layer is preferably effected by dissolving the fluorinated amines in a suitable non-polar solvent, for example in an ether such as tert- butyl ether, and then coating the first layer with the solution so obtained, where the application of the solution onto the first layer can, once more, be carried out using known process, e.g. spin coating, impregnation, pouring, dripping, spraying, misting on, knife coating, brushing or printing, for example ink-jet, screen, Intaglio, offset or tampon printing. After an exposure time in a range of 1 second to 120 minutes, particularly preferably 1 to 15 minutes at a temperature in a range preferably from 10 to 60°C, particularly preferably from 20 to 30°C, an excess of fluorinated amine can be removed, for example by spinning off the supernatant solution. The process conditions for the application of the fluorinated amine onto the first layer should preferably be selected such that a SAM layer of the fluorinated amine forms on the first, conductive polymer comprising layer, preferably on the layer comprising PEDOT : PSS. The concentration of fluorinated amine in the solution employed for introducing the fluorinated amine onto the first layer preferably lies in a range from 0.1 to 20 % by weight, particularly preferably in a range from 1 to 10 % by weight, in each case in relation to the total weight of the solu- tion.
As well as the process steps i) and ii), the process according to the invention can comprise further process steps. In particular when the layer body is part of an OLED, further process steps can follow process step ii), such as, for example, iii) the application of a hole transport layer onto the layer obtained in process step ii); iv) the application of an emitter layer onto the hole transport layer; v) the application of an electron injection layer onto the emitter layer; vi) the application of a cathode layer onto the electron injection layer.
If the first layer of the layer body according to the invention, which functions as hole injection layer, or alternatively the hole transport layer, has an ability to block electron transport, then the hole injection layer or the hole transport layer can also be designated as electron blocking layer. If the electron injection layer has the ability to block hole transport, then the electron injection layer can also be designated as hole blocking layer.
Possible hole transport layers are, for example, layers comprising polyvinylcarbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane derivatives with aromatic amine in the side or main chain, pyrazoline derivatives, aryl amine derivatives, stilbene derivatives, triphenyldiamine derivatives, polyaniline or derivatives thereof, polythiophene and derivatives thereof, polyarylamine or derivatives thereof, polypyrrole or derivatives thereof, poly p- phenylenevinylene) or derivatives thereof and poly(2,5-thienylenevinylene) or derivatives thereof. Particularly preferred as hole transport layer is NPB (N,N'-bis(naphthalene-l-yl)- N,N ' -bis(phenyl)benzidine.
Suitable materials for the emitter layer are conjugated polymers such as polyphenylene- vinylenes and/or polyfluorenes, for example, the polyparaphenylenevinylene derivatives and polyfluorene derivatives described in WO-A-90/13148, or emitters from the class of low molecular emitters, also termed , mall molecules" in technical circles, such as aluminium com-
plexes, such as, for example, tris(8-hydroxyquinolinato)aluminium (Alq3), fluorescence dyes, e.g. quinacridones, or phosphorescent emitters such as, for example, Ir(ppy)3. Further suitable materials for the emitter layer are described e.g. in DE-A-196 27 071. Particularly preferred as emitter layer, according to the invention, is tris(8-hydroxyquinolinato)aluminium (Alq3).
5
Preferred as the injection layer are single Ca layers or a stack structure consisting of a Ca layer and another layer, which consists of one or more materials selected from the group LA and IIA metals of the periodic table, excluding Ca, which exhibit a work function from 1.5 to 3.0 eV, and oxides, halogenides and carbonates thereof. Examples of group IA metals of the periodic ίθ table which exhibit a work function from 1.5 to 3.0 eV, and oxides, halogenides and carbonates thereof, are lithium, lithium fluoride, sodium oxide, lithium oxide and lithium carbonate. Examples of group IIA metals of the periodic table, excluding Ca, which exhibit a work function from 1.5 to 3.0 eV, and oxides, halogenides and carbonates thereof, are strontium, magnesium oxide, magnesium fluoride, strontium fluoride, barium fluoride, strontium
[ 5 oxide and magnesium carbonate.
Particularly suitable materials for the cathode layer are transparent or translucent materials with a relatively low work function (preferably lower than 4.0 eV). Examples of this type of material are metals, such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium
10 (Cs), Be, magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), aluminium (Al), scandium (Sc), vanadium (V), Zn, yttrium (Y), indium (In), cerium (Ce), samarium (Sm), Eu, Tb and ytterbium (Yb); alloys consisting of two or more of these metals; alloys consisting of one or more of these metals and one or more metals selected from Au, Ag, Pt, Cu, manganese (Mn), titanium (Ti), cobalt (Co), nickel (Ni), wolfram (W) and tin (Sn); graphite or graphite
15 intercalation compounds; and metal oxides, such as, for example, ITO and tin oxide. Particularly preferable is the use of aluminium as the cathode layer.
The application of the further layers, in particular of the hole transport layer, of the emitter layer, of the electron injection layer and of the cathode injection layer can be carried out in a 30 manner known to a person skilled in the art, preferably through vapour coating such as is described, for instance, in WO-A-2009/0170244.
A contribution to the solution of the objects named at the outset is also made by a layer body, particularly preferably an OLED or an OPV element, which is/are obtainable by the process according to the invention.
A contribution to the solution of the objects named at the outset is also made by an electronic component, comprising a layer body according to the invention or a layer body obtainable by the process according to the invention, this component preferably being an OLED or an OPV element, particularly preferably an OLED.
Here, the layer formation of the OLED can take any form known to the person skilled in the art, preferably, however, with the hole injecting layer replaced by the layer body according to the invention wherein the further layer of fluorinated amine, preferably the further SAM layer of fluorinated amine, is present in the boundary region between the hole injecting layer and the hole transport layer or, where no separate hole transport layer is present, then in the boundary region between the hole injecting layer and the emitter layer.
The OLED according to the invention can, for example, exhibit any of the following layer structures (a) to (h):
(a) anode/
hole injection layer/
at least one emitter layer/
cathode;
(b) anode/
hole injection layer/
hole transport layer/
at least one emitter layer/
cathode;
(c) anode/
hole injection layer/ at least one emitter layer/ electron injection layer/ 5 cathode;
(d) anode/
hole injection layer/ hole transport layer/ 0 at least one emitter layer/ electron injection layer/ cathode;
(e) anode/
5 hole inj ection layer/ at least one emitter layer/ electron transport layer/ cathode;
!0 (f) anode/
hole injection layer/ hole transport layer/ at least one emitter layer / electron transport layer/
»5 cathode;
(g) anode/
hole injection layer/ at least one emitter layer/ SO electron transport layer/ electron injection layer/
cathode;
(h) anode/
hole injection layer/
5 hole transport layer/
at least one emitter layer/
electron transport layer/
electron injection layer/
cathode;
10
the hole injection layer corresponding in each case to the layer body according to the invention or the layer body obtainable by the process according to the invention and in each case arranged in a such a way, that the further layer of fluorinated amine, preferably the further SAM of fluorinated amine is facing the hole injection layer or emitter layer.
[5
The layer structures (a) to (h) can be embodied either with the anode located next to the substrate, the substrate being, for example, glass or a transparent plastic film, or with the cathode located next to the substrate.
!0 As anode layer, hole transport layer, emitter layer, electron injection layer and cathode layer, those layers already mentioned at the outset in connection with the process according to the invention as preferred anode layer, hole transport layer, emitter layer, electron injection layer and cathode layer are again preferred.
!5 The electron transport layer can consist of materials such as, for example, oxadiazol derivatives, anthraquinodimethane or derivatives thereof, benzoquinone or derivatives thereof, naphthoquinone or derivatives thereof, anthraquinone or derivatives thereof, tetracyanoan- thraquinodimethane or derivatives thereof, fluorenone derivatives, diphenyldicyanoethylene or derivatives thereof, diphenoquinone derivatives and metal complexes of 8-hydroxyquinoline or
SO derivatives thereof, polyquinoline or derivatives thereof, polyquinoxaline or derivatives thereof or polyfluorene or derivatives thereof.
Particularly preferred in this connection, according to the invention, is an OLED which is formed of the following layers: anode layer/first layer of the layer body according to the invention or of the layer body obtainable using the process according to the invention/further layer 5 of the layer body according to the invention or of the layer body obtainable according to the invention/optional hole transport layer/optional emitter layer/optional electron injection layer/cathode layer.
A contribution to the solution of the objects named at the outset is also made by the use of a 0 fluorinated amine for the improvement of the life span of electronic components which comprise layers of a conductive polymer, preferably layers comprising PEDOT : PSS complexes, the electronic component preferably being an OLED, especially preferably an OLED formed of the following layers: anode/hole injection layer/layer of the fluorinated amine, preferably SAM layer of the fluorinated amine/hole transport layer/emitter layer/electron injection lay- 5 er/cathode. The hole injection layer preferably comprises a conductive polymer, particularly preferably complexes of PEDOT : PSS. The time taken for the light intensity of the OLEDs at a constant electrical current to halve serves as a measure of the life span of the OLEDs.
Preferred fluorinated amines in this connection are similarly those fluorinated amines which !0 have already been described at the outset as preferred fluorinated amines in connection with the layer body according to the invention.
The invention will now be further illustrated by means of non-limiting examples: 5 EXAMPLES
Example 1 : SAM layer of lH,lH,2H,2H-perfluorodecylamine (according to the invention)
0.1 g 1H,1H,2H,2H perfluorodecylamine (CHEMOS GmbH, Regenstauf, $0 Deutschland) is dissolved in 10 g tert-butylmethylether. This solution,
"SAM-1", will be used for building an organic light emitting diode (OLED).
The production and characterisation of the OLED proceed as follows:
1.1 Preparation of the ITO-coated substrate
5 ITO-coated glass is cut into 50 mm χ 50 mm pieces (substrates) and structured into four parallel lines, each 2 mm wide and 5 cm long with Photoresist and an etching solution. Then the substrates are freed from the remains of the Photoresist, cleaned in an ultrasonic bath with 0.3 % Mucasol solution, rinsed with distilled water and centrifuged dry in a centrifuge. Directly before coating the ITO-coated sides are cleaned in a UV/Ozone reac-
0 tor (PR- 100, UVP Inc., Cambridge, GB) for 10 min.
1.2 Application of the hole injection layer
The aqueous dispersion, Clevios® P AI4083 (Heraeus Clevios GmbH, Leverkusen), is 5 filtered through a syringe filter (Millipore HV, 0.45 μπι). The cleaned ITO-coated substrate is placed on a spin coater (Carl Siiss, RC13) and approximately 5 ml of the filtered solution are distributed over the ITO-coated side of the substrate. Subsequently, the supernatant solution is spun off by rotating the plate at 1000 U/min over a period of 30 s. Then the thusly coated substrate is dried for 5 minutes at 200 °C on a hotplate. The layer !0 thickness is 50 nm (Tencor, Alphastep 500).
1.3 Application of the SAM-layer according to the invention
Approximately 5 ml of the solution„SAM-1" is distributed over the coated substrate !5 which is now again on the spin coater. After an exposure of approximately 3 min the supernatant solution is spun off at 3000 U/min for 30 s. The total layer thickness has not changed after this process step and remains 50 nm.
1.4 Application of the hole transport layer and the emitter layer
SO
The thusly coated substrate is transferred into a vapour deposition apparatus (Univex
350, Leybold). First, 60 nm of a hole transport layer of NPB (N,N'-bis(naphthalene-l- yl)-N,N'-bis(phenyl)benzidine) and then 50 nm of an emitter layer of A1Q3 (tris-(8- hydroxyquinoline)aluminum) (Sensient, Bitterfeld), are sequentially vapour deposited at a pressure of 10-3 Pa and at a vapour deposition rate of 1 A/sec.
5
1.5 Application of the metal cathode
Subsequently the layer system is transferred into a glove box with an N2 atmosphere and an integrated vapour deposition apparatus (Edwards) and metal electrodes are applied by
0 vapour deposition. To that end, the substrate is placed on a shadow mask with the layer system facing downwards. The shadow mask contains rectangular slits with a width of 2 mm which are orientated perpendicular to the ITO stripes. In two small gas deposition vessels at 10-3 Pa, a 0.5 nm thick LiF layer and subsequently a 200 nm thick Al layer are sequentially vapour deposited. The vapour deposition rates are 1 A/s for LiF and 10 A s
5 for Al. The surface area of the individual OLEDs is 4.0 mm2.
1.6 Characterisation of the OLED
The two electrodes of the organic LED are connected to a power supply with electric !0 leads (contacted). The positive terminal is connected to the ITO electrode, the negative terminal with the metal electrode. The OLED characteristic curves for current and electro luminescence (as detected with by a photodiode (EG&G C30809E)) are plotted as a function of the voltage. Subsequently, the life span is determined by passing a constant current of I = 3.84 mA through the device and tracking the voltage and light intensity as !5 functions of time.
Example 2: SAM Layer of perfluorotripentylamine (according to the invention)
Production of an OLED with the material„SAM-2"
(0
The procedure is as that for example 1 with the difference that in point 1.3 ap-
proximately 5 ml of the solution SAM-2 consisting of 0.1 g perfluorotripentylamine (Fluroinert FC 70, Sigma Aldrich) in 10 g tert.- butylmethyl ether is distributed onto the coated substrate which now lies, once again, on the spin coater. After an exposure time of approximately 3 min the supernatant solution is spun off at 3000 U/min for 30 s. The layer thickness of the entire coating remains unchanged after this process step and is 50 nm.
Example 3: SAM layer of dodecylamine (Comparative example)
Production of an OLED with the material„SAM-3"
The procedure is as that in example 1, with the difference that in point 1.3 approximately 5 ml of the solution SAM-3 consisting of 0.1 g dodecylamine (Sigma Aldrich) in 10 g tert.-butylmethylether is distributed onto the coated substrate which now lies, once again, on the spin coater. After an exposure time of approximately 3 min the supernatant solution is spun off at 3000 U/min for 30 s. The layer thickness of the entire coating remains unchanged after this process step and is 50 nm.
Example 4 Production of an OLED without the SAM layer according to the invention (control test)
The procedure is as that in example 1 , with the difference that the process step described in point 1.3 "Application of the SAM layer according to the invention" is absent.
Table 1 shows an evaluation of the characteristic curves as well as the life span of the OLEDs produced in example 1-4.
Table 1
The characteristic curves were evaluated at a light intensity of 1000 cd/m2 and show that the voltage is significantly lower when SAM layers SAM-1 and SAM-2 are used than in the con- trol test or with the material SAM-3.
The life span test, which is carried out at a constant current density of 3.84 mA/cm2, shows that the OLEDs with the SAM layers SAM-1 and SAM-2 according to the invention are significantly more stable than those without. The value t 2 gives the time at which half of the original light intensity (L0) is reached.