DE102005056180B4 - Emitter polymer, electroluminescent device and method of making the same - Google Patents

Abstract

wobei A eine Einfachbindung oder einen Benzolring, R¹ eine Emitterverbindung, R⁴ eine Elektronentransportverbindung und
R² eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl und R³ eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl
repräsentieren, und wobei
k > 10 und für jedes k jeweils
1 ≤ n ≤ 10, 1 ≤ m ≤ 3000 gilt.Emitter material characterized by

where A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound, and
R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl
represent, and where
k> 10 and for each k respectively
1 ≤ n ≤ 10, 1 ≤ m ≤ 3000.

Description

The The invention relates to an emitter polymer, an electroluminescent device and a method for producing the same, in particular the invention is a carbazole based emitter polymer for use in an org. Single-electroluminescent (so-called "single layer configuration ").

In conventional triplet emitter OLED structures, a multilayer structure is produced by thermal evaporation of organometallic materials or low molecular weight functional materials. An exemplary structure is in 1 shown. The electroluminescent device has a hole transport layer 3 , Emitter layer 4 and electron transport layer 5 existing multi-layer structure, which is arranged between the anode and cathode. The corresponding energy levels of the individual layers are in 2 , shown schematically.

• – Jede einzelne Schicht ist darauf spezialisiert, eine bestimmte Funktion zu erfüllen. Beispielsweise wird die Elektronentransportschicht nur Elektronen, jedoch keine Defektelektronen transportieren. Daher können die einzelnen Schichten so gewählt werden, dass eine Degradation aufgrund unzweckmäßiger Funktion vermieden werden kann. Eine unzweckmäßige Funktion kann in diesem Zusammenhang beispielweise bedeuten, dass eine Elektronentransportschicht ebenfalls positive Ladungsträger transportieren muss, was zu einer vorzeitigen Degradation führen kann.
• – Es ist möglich, Energiebarrieren zwischen den einzelnen Schichten zu etablieren. Daher kann in einem Mehrschichtsystem die ungewollte Abwanderung von Ladungsträgern verhindert werden. Vielmehr werden die Ladungsträger (Elektronen von der Katode und Defektelektronen von der Anode) im gewünschten Bereich zur Rekombination gezwungen. Die so realisierbare Steuerung und Anpassung der Ladungsträgerdichten führt zu einer Verbesserung der Effizienz.

The multilayer structure or the multilayer system differs in comparison with the single-layer system in the following respect:

• - Every single layer is specialized to fulfill a specific function. For example, the electron transport layer will transport only electrons, but no holes. Therefore, the individual layers can be chosen so that degradation due to improper function can be avoided. An inappropriate function in this context may mean, for example, that an electron transport layer also has to transport positive charge carriers, which can lead to premature degradation.
• - It is possible to establish energy barriers between the individual layers. Therefore, in a multi-layer system, the unwanted migration of charge carriers can be prevented. Rather, the charge carriers (electrons from the cathode and holes from the anode) are forced to recombine in the desired region. The thus feasible control and adaptation of the charge carrier densities leads to an improvement in the efficiency.

In a single-layer system, on the other hand, all functionalities (hole transport, electron transport, recombination zone and the emission of light) are integrated into a material system. One possible layer structure for a single-layer system is in 3 shown schematically. The corresponding energy levels of the individual layers are in 4 shown schematically. It is assumed that electrons move only in the electron conductor material and in the emitter layer, defect electrons move only in the hole conductor material and the emitter layer, and excited states (exitones) occur only in the emitter layer. The need for spatial separation is already over 4 can be seen in which the original energy levels of the individual multi-layer layers (electron transport layer, hole transport layer and emitter layer) have been drawn. It can already be seen from this energy diagram that the energy barriers (energy levels) can not be constructed in a simple way as in the multilayer system. Carrier losses then undesirably cause the balance of electrons and holes to be disrupted, resulting in a reduction in efficiency. In addition, the presence of electrons, holes and exitons in the light-emitting film leads to increased degradation and thus to a reduction in the lifetime. A common way to combine different functions of an OLED material, such as emitter, hole and electron transport, and conduction, is the use of so-called "blends" blends, which regularly comprise a polymer, the polymer having low molecular weight emitters and charge transport units. The polymer may also have active functions (as in the case of PVK as a film-forming material) and serve as a hole transport layer. PVK-based phosphorescent blends are known from the literature, for example from (Neher, Xang et al Appl Phys. Lett. 84 (2004) 2476). It describes green phosphorescent emitter OLEDs with an efficiency of 40 cd / A based on PVK blends. US 6,870,198 B2 describes the use of LITI (Laser Induced Thermal Imaging) for structuring phosphorescent, emitting blend materials. To improve the charge carrier mobilities, for example of PVK, beat US 6,630,254 B2 and WO 03/088271 A1 the mixing with low-molecular charge carrier transport molecules before.

WO 2004/095598 A2 describes an OLED in which the phosphorescent host (polymer) was mixed with a matrix which does not act as a charge transport material and has a bandgap of greater than 3.5 eV or which acts as an electron conductor with a band gap greater than 3.2 eV. For example, silicon-containing components or non-conjugated polyarylenes have been proposed for such materials. Despite the high efficiency of using the proposed blends, the lifetime of the OLED is greatly reduced.

One possible reason for the above-mentioned short lifetime could be the instability of the individual components of the misery. Therefore, efforts have been made to substitute the corresponding materials For example, PVK, undertaken. Thus, the prior art describes the use of alternative polymeric host materials which are intended to enable energy transfer to a phosphorescent low molecular weight emitter material. So describe US 2005/0129980 A1 . US 2005/0118521 A1 and US 2004/0258953 A1 Process for the polymerization of CBP, a low-molecular-weight host material for low-molecular-weight phosphorescent emitter materials, in order to enable wet-chemical processing of CBP-based blends.

US 2005/0073245 A1 describes the use of a semiconductive polymer as a host for a low molecular weight phosphorescent emitter. The polymer consists of segments of polyfluorene (PFO). PFO as a soluble, pourable host for phosphorescent emitters is also available in US 2004/0131881 A1 described. Carbazole-oxadiazole-based copolymers as host material for phosphorescent emitters are described in van Dijken et. al (J. Am. Chem. Soc 2004, 126, pp. 7718). Here, hole-conducting molecules (bicarbazole and electron-conducting molecules (spiro-fluorene or oxadiazole) are directly linked to each other, resulting in an efficiency of 23 cd / A for green phosphorescent OLEDs.

Another aspect is the low solubility of some functional molecules used in low molecular weight emitters, such as the green phosphorescent emitter material Ir (ppy) ₃ , which has a solubility of less than 0.3 g / L in toluene. DE 102 38 909 A1 describes the synthesis of iridium- or rhodium-based organic metal complexes, whereby the solubility of the complexes can be adjusted by a side-chain modification of heteroaryl groups.

To overcome the aforementioned disadvantages in the use of misery suggests GB 2395356 A a cross-linking of a matrix. The matrix is crosslinked after an emissive dye is previously diffused into the matrix to mechanically fix the dye.

Farther is the use of co-polymers for single-layer emitter components known. For example, Tokito el al. (Organic electronics 4 (2003) pp. 105) phosphorescent red, green and blue emitter polymers, wherein the emitter polymers and carbazole units are covalently as a side chain a polyethylene polymer chain are connected. additionally become electron-conducting low-molecular substances to the described Co-polymer added.

Holms et. al (J. Am. Chem. Soc 2004, 126, pp 7041) describes a triplet emitter, as part of a main chain consisting of a polyfluorene, was polymerized. Both disclosed in the prior art approaches to Use of co-polymers have a relatively low energy transfer to the phosphorescent emitter.

A alternative possibility for wet-chemical Applicable phosphorescent emitters is the use of dendrimers.

Dendrimers are highly branched macromolecules in which branches (dendrites) are attached to a nucleus. The use of dendrimers for OLEDs is for example in WO 02/066552 A1 and US 2005/123850 A1 described.

All the prior art removable substances for use in coating systems organic electronic luminescence devices have the disadvantage low efficiency or low life.

It is therefore an object of the present invention, an emitter material for one organic luminescence device as a single-layer system, an organic Luminescence device and a method for their preparation indicate which is both high efficiency and high Have life.

These Task is achieved by the features of the claims 1 (emitter material), 5 (electroluminescent device) and 13 (method) solved. Preferred embodiments of the invention are contained in the subclaims.

verwendet, wobei A eine Einfachbindung oder einen Benzolring, R¹ eine Emitterverbindung, R⁴ eine Elektronentransportverbindung und R² eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl und R³ eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl repräsentieren, und wobei k > 10 und für jedes k jeweils 1 ≤ n ≤ 10, 1 ≤ m ≤ 3000 gilt. Vorzugsweise weist die Emitterverbindung einen Iridiumphenylpyridinat-Komplex, einen Iridiumnapthylpyridinat-Komplex, einen Iridium(benzothienyl-pyridinat)-Komplex oder einen Metallkomplex auf. Vorzugsweise ist der Metallkomplex ein elektrophosphoreszierender Iridium- oder Platin-Komplex oder ein Metallkomplex auf Basis von Ruthenium, Rhodium, Palladium oder Osmium mit zweizähnigen Phenyl-Stickstoff- oder Phenyl-Schwefel-Liganden. Vorzugsweise ist die Elektronentransportverbindung aus der Klasse der Oligofluorene, Oxadiazole, Triazole, Benzimidazole, Chinoxaline, Triazine, Pyrimidine, Phenanthroline oder Napthalentetracarbonsäureamide ausgewählt.According to the invention, for an organic electroluminescent device, an emitter material of the chemical formula

A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl, Represent ethyl, isopropyl, t-butyl or ethylhexyl, and wherein k> 10 and for each k 1≤n≤10, 1≤m≤3000. Preferably, the emitter compound comprises an iridium phenyl pyridinate complex, an iridium naphthyl pyridinate complex, an iridium (benzothienyl pyridinate) complex or a metal complex. Preferably, the metal complex is an electrophosphorescent iridium or platinum complex or a metal complex based on ruthenium, rhodium, palladium or osmium with bidentate phenyl-nitrogen or phenyl-sulfur ligands. Preferably, the electron transport compound is selected from the class of oligofluorenes, oxadiazoles, triazoles, benzimidazoles, quinoxalines, triazines, pyrimidines, phenanthrolines or naphthalenetetracarboxamides.

aufweist, wobei A eine Einfachbindung oder einen Benzolring, R¹ eine Emitterverbindung, R⁴ eine Elektronentransportverbindung und R² eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl und R³ eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl repräsentieren, und wobei k > 10 und für jedes k jeweils 1 ≤ n ≤ 10, 1 ≤ m ≤ 3000 gilt.An electroluminescent device according to the invention has a substrate, a first electrode layer, an emitter layer and a second electrode layer, wherein the emitter layer comprises a compound of the formula:

where A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl, Represent ethyl, isopropyl, t-butyl or ethylhexyl, and wherein k> 10 and for each k 1≤n≤10, 1≤m≤3000.

Preferably, the first electrode layer is formed as an anode and the second electrode layer as a cathode. Preferably, a hole injection layer and / or a hole transport layer is arranged between anode layer and emitter layer. The hole injection layer is preferably doped and consists in a preferred embodiment of conductive organic materials such as poly (ethylenedioxythiophene) polystyrenesulfonic acid (PEDT-PSS), polyaniline and polypyrrole. Furthermore, not perma nent conductive, ie undoped, Lochinjektionsschichten based on polymeric triphenylamine and Benzidinderivaten- and fluorenyl-arenamine available.

• – Bereitstellen eines Substrats,
• – Anordnen einer ersten Elektrodenschicht auf dem Substrat,
• – Anordnen einer Emitterschicht auf der ersten Elektrodenschicht,
• – Anordnen einer zweiten Elektrodenschicht auf der Emitterschicht,

wobei als Emitterschicht eine Verbindung der Formel:

verwendet wird, und A eine Einfachbindung oder einen Benzolring, R¹ eine Emitterverbindung, R⁴ eine Elektronentransportverbindung und R² eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl und R³ eine Elektronentransportverbindung, ein Wasserstoffatom, Methyl, Ethyl, Isopropyl, t-butyl oder Ethylhexyl repräsentieren, und wobei k > 10 und für jedes k jeweils 1 ≤ n ≤ 10, 1 ≤ m ≤ 3000 gilt und die Emitterschicht (4) nasschemisch aufgebracht wird.The method for producing an electroluminescent device according to the invention comprises the following method steps:

• Providing a substrate,
• Arranging a first electrode layer on the substrate,
• Arranging an emitter layer on the first electrode layer,
• Arranging a second electrode layer on the emitter layer,

wherein as emitter layer a compound of the formula:

and A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl , Ethyl, isopropyl, t-butyl or ethylhexyl, and where k> 10 and for each k each 1 ≦ n ≦ 10, 1 ≦ m ≦ 3000 and the emitter layer ( 4 ) is applied wet-chemically.

Preferably is the emitter layer by spin coating, spray coating, ink jet printing or applied by means of laser-induced layer transfer (LITI).

The idea of the present invention thus resides in efficient recombination of holes and electrons, which is achieved by positioning both the electrons and the holes spatially close to the emitter junctions. This is achieved in particular by a spatial arrangement of hole transport groups, electron transport groups and emitter groups. The structure is organized such that the polymer backbone is not conjugated and both the electron transporting groups and the emitter groups are attached directly to the respective carbazole group. The general formula of the new emitter compound is in 5 shown schematically, in which the emitter groups (R1) and the electron transport groups (R2, R3, R4) are attached in close proximity to each other to the carbazole system. The concentration of emitter compounds is generally lower than the concentration of electron transport compounds or carbazole groups. Typical weight fractions of the emitter groups are in the range of 0.5 to 15%, calculated on the total weight. The carbazole also assumes the function of a hole conductor.

Preferred polymer materials contain as emitter group iridium (phenylpyridinate) ₂ groups, which are attached as substituent R1 via 1,3-diketo groups to the carbazole unit. This results in a green light emission. In the preferred variant, the substituent R 2 represents a methyl group. The electron transport group R 4 used is an oxadiazole unit or a quinoxaline unit. Oxadiazole or quinoxaline is also preferably used as the electron transport compound for the substituent R3. The preferred concentration of emitter units is between 1 and 15 weight percent, preferably between 1 and 10 weight percent, even more preferably between 1 and 5 weight percent, and most preferably 5 weight percent equivalent to a ratio m / n = 35 (at 15 weight percent would correspond to a ratio m / n = 11.7 and 1 weight percent would correspond to a ratio m / n = 175), the preferred molecular weight of the polymer is in the range greater than 10 ⁵ and less than 10 ⁶ . For the particularly preferred value M _w = 150,000 results with n = 1, m = 35 a repetition value k = 20.

In this context, it is known that the oxidative addition of carbazole monomers occurs via the 3,3'-position, ie, para to the nitrogen atom. This is the reactive position of the carbazole monomer, and it is obvious that blocking this position can increase the chemical stability of the carbazole group of a carbazole polymer. Therefore, by the in the general formula of 5 proposed substitution increases the stability of the carbazole polymer.

End groups of in 5 shown polymer group are groups resulting from the usual radical initiators, for. Phenyl or 2- (2-cyanopropyl). Alternatively, a cationic polymerization, for. B. under the action of Lewis acids such as boron trifluoride. In this case, one end group is hydrogen, while the end group generated by chain termination is dictated by the quencher used. In the case of methanol as a quencher is a methoxy group.

One way to synthesize an emitter-doped phenyl-carbazole monomer (with Ir (ppy) ₂ as the emitter compound) is in 6 shown schematically. One way to synthesize a corresponding monomer unit with an electron transport compound is in 7 shown schematically.

1

substratum

2

transparent anode

3

Hole transport layer / planarization layer

4

emitter layer

5

Electron transport layer

6

cathode

7

Highest occupied molecular orbital (HOMO) of the hole transport layer

8th

lowest Unoccupied molecular orbital (LUMO) of the hole transport layer

9

HOMO the emitter layer

10

LUMO the emitter layer

11

HOMO the electron transport layer

12

LUMO the electron transport layer

13

doped Hole injection layer

14

Fermi Level the hole injection layer

Claims (14)

Emitter material characterized by

A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl, ethyl, Isopropyl, t-butyl or ethylhexyl and k> 10 and for each k 1 ≤ n ≤ 10, 1 ≤ m ≤ 3000. The emitter material according to claim 1, characterized in that the emitter compound (R ¹ ) contains an iridium phenyl pyridinate complex, an iridium naphthyl pyridinate complex, an iridium (benzothienyl pyridinate) complex or a metal complex. Emitter material according to claim 2, characterized that the metal complex is an electrophosphorescent platinum complex or a metal complex based on ruthenium, rhodium, palladium or osmium with bidentate Phenyl-nitrogen, phenyl-sulfur or 1,3-diketole ligands. Emitter material according to one of the preceding claims, characterized in that the electron transport compound (R ² , R ⁴ ) is selected from the class of oligofluorenes, oxadiazoles, triazoles, benzimidazoles, quinoxalines, triazines, pyrimidines, phenanthrolines or naphthalenetetracarboxamides. Electroluminescent device with one on a substrate ( 1 ) arranged first electrode layer ( 2 ), an emitter layer ( 4 ) and a second electrode layer ( 6 characterized in that the emitter layer ( 4 ) a compound of the formula:

where A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl, Represent ethyl, isopropyl, t-butyl or ethylhexyl, and wherein k> 10 and for each k 1≤n≤10, 1≤m≤3000. A device according to claim 5, characterized in that the emitter compound (R ¹ ,) comprises an iridium phenyl pyridinate complex, an iridium naphthyl pyridinate complex, an iridium (benzothienyl pyridinate) complex, or a metal complex. Device according to claim 6, characterized in that that the metal complex is an electrophosphorescent platinum complex or a metal complex based on ruthenium, rhodium, palladium or osmium with bidentate Phenyl-nitrogen, phenyl-sulfur or 1,3-diketole ligands. Device according to one of claims 5 to 7, characterized in that the Electron transport compound (R ² , R ⁴ ) is selected from the class of oligofluorenes, oxadiazoles, triazoles, benzimidazoles, quinoxalines, phenanthrolines, triazines, pyrimidines, or naphthalenetetracarboxamides. Device according to one of claims 5 to 7, characterized in that the first electrode layer ( 2 ) as the anode and the second electrode layer ( 6 ) is designed as a cathode. Device according to claim 9, characterized in that between anode layer ( 2 ) and emitter layer ( 4 ) a hole injection layer ( 13 ) and / or a hole transport layer is arranged. Apparatus according to claim 10, characterized in that the hole injection layer ( 13 ) Poly (ethylenedioxythiophene) polystyrenesulfonic acid (PEDT: PSS), polyaniline, polypyrrole or non-permanently conductive materials based on polymeric triphenylamine, benzidine derivatives and fluorenyl-arenamine units. Method for producing an electroluminescent device, comprising the following method steps: providing a substrate ( 1 ), Arranging a first electrode layer ( 2 ) on the substrate ( 1 ), Arranging an emitter layer ( 4 ) on the first electrode layer ( 2 ), Placing a second electrode layer on the ( 6 ) Emitter layer ( 4 ), characterized in that as emitter layer ( 4 ) a compound of the formula:

where A is a single bond or a benzene ring, R ^{1 is} an emitter compound, R ^{4 is} an electron transport compound and R ^{2 is} an electron transport compound, a hydrogen atom, methyl, ethyl, isopropyl, t-butyl or ethylhexyl and R ^{3 is} an electron transport compound, a hydrogen atom, methyl , Ethyl, isopropyl, t-butyl or ethylhexyl, and where k> 10 and for each k each 1 ≦ n ≦ 10, 1 ≦ m ≦ 3000 and the emitter layer ( 4 ) is applied wet-chemically. Method according to claim 12, characterized in that the emitter layer ( 4 ) is applied by spin coating, spray coating, ink jet printing or laser induced layer transfer (LITI). Method according to one of claims 12 and 13, characterized in that between the first electrode layer ( 2 ) and the emitter layer ( 4 ) a hole injection layer ( 13 ) is arranged.