EP1649731A1

EP1649731A1 - Organic electroluminescent element

Info

Publication number: EP1649731A1
Application number: EP04741151A
Authority: EP
Inventors: Aurelie Falcou; Frank Meyer; Amir Parham; Heinrich Becker
Original assignee: Merck Patent GmbH; Covion Organic Semiconductors GmbH
Current assignee: Merck Patent GmbH
Priority date: 2003-07-21
Filing date: 2004-07-20
Publication date: 2006-04-26
Also published as: KR101175808B1; JP2006528836A; JP4865551B2; WO2005011334A1; US20060159951A1; KR20060061798A; US7862904B2

Abstract

The invention relates to the improvement of phosphorescent organic electroluminescent devices, whereby materials of formula (1) are used for the hole blocking layer.

Description

description

Organic electroluminescent element

Organic and organometallic compounds are used as functional materials in a number of applications that can be broadly attributed to the electronics industry. The market for organic electroluminescent devices (for a general description of the structure, see US Pat. No. 4,539,507 and US Pat. No. 5,151,629) and their individual components, organic light-emitting diodes (OLEDs), has already taken place, as have car radios with an "organic display" from Pioneer or use a digital camera from Kodak. Other such products are about to be launched. Nevertheless, significant improvements are still necessary to make these displays a real competitor to the currently dominant liquid crystal displays (LCD) or to surpass them.

A development that has emerged in recent years is the use of organometallic complexes which show phosphorescence instead of fluorescence (M.A. Baldo et al., Appl. Phys. Lett. 1999, 75, 4-6). For theoretical spin-statistical reasons, using organometallic compounds as

Phosphorescence emitters allow up to four times the energy and power efficiency. In order to improve phosphorescent OLEDs, it is not only important to develop the organometallic compounds themselves, but above all to develop other components that are specifically required for this purpose, such as matrix or hole blocking materials.

An organic electroluminescent device usually consists of several layers which are applied to one another by means of vacuum methods or different printing techniques. For phosphorescent organic electroluminescent devices, these layers are in detail:

1. Carrier plate = substrate (usually glass or plastic film);

2. Transparent anode (usually indium tin oxide, ITO);

3. Hole injection layer (HIL): z. B. based on copper phthalocyanine (CuPc) or conductive polymers; 4. Hole Transport Layer (HTL): usually based on triarylamine derivatives; 5. Emission Layer (s) (Emission Layer = EML): in phosphorescent devices usually made of a matrix material, e.g. B. 4,4'-bis (carbazol-9-yl) - biphenyl (CBP) with a phosphorescent dye, e.g. B. tris (phenylpyridyl) iridium (lr (PPy) ₃ ) or tris (2-benzothiophenylpyridyl) iridium (lr (BTP) ₃ ), is doped;

6.Hole blocking layer (HBL): usually from BCP (2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline = bathocuproin) or bis (2-methyl-8-hydroxyquinolinato) - (4- phenylphenolato) aluminum (III) (BAIq);

7. Electron Transport Layer (ETL): mostly based on aluminum tris-8-hydroxyquinolinate (AIQ ₃ );

8. Electron Injection Layer (EIL, also called insulator layer = ISL): thin layer of a material with a high dielectric constant, such as. B. LiF, Li ₂ O, BaF ₂ , MgO, NaF;

9. Cathode: usually metals, metal combinations or metal alloys with a low work function, e.g. B. Ca, Ba, Mg, Al, In, Mg / Ag, but also organic-inorganic hybrid cathodes. Depending on the device structure, several of these layers can coincide, or each of these layers need not necessarily be present. It is also possible to use thin insulator layers or dielectric layers between two of the active layers.

However, there are still significant problems that are urgent

Needs improvement to enable high quality full color applications:

1. So v. a. the operational lifespan of OLEDs is still too short, so that only simple applications have so far been commercially possible.

2. The short lifespan poses a problem: Especially for full color applications, it is particularly bad if the individual colors age at different speeds, as is currently the case. This means that there is a significant shift in the white point before the end of the service life (which is usually defined by a drop to 50% of the initial brightness). H. the color fidelity of the display is worse.

3. The aging processes go i. d. Usually accompanied by an increase in voltage. This effect makes voltage-driven organic electroluminescent devices difficult or impossible. In this case, however, a current-driven control is more complex and expensive.

4. The operating voltage required is quite high, especially in the case of efficient phosphorescent OLEDs, and must therefore be reduced in order to improve the power efficiency. 5. The efficiency, in particular the power efficiency (measured in Im / W), of phosphorescent OLEDs is acceptable, but improvements are still desired here as well. 6. The structure of the OLEDs is complex and technologically complex due to the large number of organic layers; a reduction in the number of layers is desirable for production in order to reduce the number of production steps, thereby simplifying the technology and increasing production reliability. The reasons mentioned above make improvements in the production of OLEDs necessary.

With phosphorescent OLEDs, a hole blocking layer (HBL) is usually used following the emitter layer in order to increase the efficiency and service life. These device structures are usually optimized according to the criterion of maximum efficiency. BCP (bathocuproin) is often used as the hole blocking material, which achieves very good efficiencies (e.g. BDF O'Brien et al., Appl. Phys. Lett. 1999, 74, 442), but with the decisive disadvantage that the Lifetime of the OLEDs is very low here. T. Tsutsui et al. (Japanese J. Appl. Phys. 1999, 38, L1502) cite the low stability of BCP as the reason for this, so that these devices cannot be used in high-quality displays. Another hole blocking material is bis (2-methyl-8-hydroxyquinolinato) - (4-phenylphenolato) aluminum (III) (BAIq). This significantly improved the stability and lifespan of the devices, but with the disadvantage that the quantum efficiency of the devices with BAIq is significantly (approx. 40%) lower than with BCP (T. Watanabe et al., Proc. SPIE 2001, 4105, 175). Kwong et al. (Appl. Phys. Lett. 2002, 81, 162) thus achieved lifetimes of - 10000 h at 100 cd / m ² with tris (phenylpyridyl) iridium (III) as emitter. However, this device only showed an efficiency of 19 cd / A, which is far behind the state of the art. Thus, BAIq enables good lifetimes, but overall it is not a satisfactory hole blocking material because the efficiency achieved is too low.

From this description it is clear that the hole blocking materials used to date lead to unsatisfactory results. There is therefore still a need for hole blocking materials which lead to good efficiencies in OLEDs, but at the same time also have a long service life. It has now surprisingly been found that OLEDs, the specific - listed below - Contain spirobifluorene derivatives as hole blocking materials, have significant improvements over the prior art. With these hole blocking materials, it is possible to obtain high efficiencies and good lifetimes at the same time, which is not possible with materials according to the prior art. It was also found that an electron transport layer does not necessarily have to be used with the new hole blocking materials, which is also a technological advantage.

The use of simple oligophenylenes (1,3,5-tris (4-biphenylyl) benzene and derivatives thereof) as hole-blocking material in phosphorescent OLEDs has already been described in the literature (e.g. BK Okumoto et al., Chem. Mater. 2003, 15, 699). However, the glass transition temperatures of these connections are low, sometimes well below 100 ° C, which prevents the use of this connection class in display applications. In addition, no peak efficiencies are achieved with this device configuration, so that it can be seen that this hole blocking material is obviously not suitable for the production of high-quality devices.

EP 00676461 describes the use of spirobifluorene oligophenylene derivatives and other spirobifluorene derivatives in the emitting layer or in a charge transport or injection layer in a fluorescent OLED. However, this document does not show how these compounds could be used to advantage in phosphorescent OLEDs.

The invention relates to organic electroluminescent devices containing an anode, a cathode and at least one emission layer containing at least one matrix material which is doped with at least one phosphorescent emitter, characterized in that at least one hole-blocking layer is introduced between the emission layer and the cathode, the at least one contains a compound of the formula (1),

(Formula 1) where for the symbols and indices used: Aryl is the same or different in each occurrence, an aromatic or heteroaromatic ring system with 1 to 40 aromatic C atoms, which can be substituted by one or more radicals R;

Each occurrence of R is the same or different H, F, Cl, Br, I, NO ₂ , CN or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 40 C atoms, one or more non-adjacent CH ₂ - Groups by -R ¹ C = CR ¹ -, -C - £ -, Si (R ¹ ) ₂ , Ge (R ¹ ) ₂ , Sn (R ¹ ) ₂₎ -O-, -S- or -NR ¹ - can be replaced and one or more H atoms can be replaced by F or an aromatic group R ¹ , where two or more substituents R or R with aryl can span another mono- or polycyclic, aliphatic or aromatic ring system;

Each time R ¹ is the same or different, H or an aliphatic or aromatic hydrocarbon radical having 1 to 20 C atoms, two or more substituents R ¹ or R ¹ with R and / or aryl also being another mono- or polycyclic, aliphatic or can span aromatic ring system; n is the same or different at each occurrence 1, 2, 3 or 4; m is the same or different at each occurrence 0, 1, 2, 3 or 4; o is the same or different at each occurrence 0, 1, 2 or 3; p is the same or different at each occurrence 0, 1, 2, 3 or 4; with the proviso that the sum n + o = 4 and the sum m + p = 4 per ring, further with the proviso that the hole blocking material is not identical to the matrix material, and with the further proviso that aryl does not contain diazine,

Contains triazine or tetrazine group.

The aryl substituent can be used at any point with the spirobifluorene

Basic structure to be linked.

An aromatic or heteroaromatic ring system in the sense of this invention is to be understood as a system which does not necessarily only contain simple aromatic or heteroaromatic groups, but which can also contain oligo- and polycyclic systems and condensed aromatic units and in which also several aromatic or heteroaromatic groups can be interrupted by a short non-aromatic unit, such as sp ³ -hybridized C, O, N, etc. Thus, for example, systems such as 9,9'-spirobifluorene, 9,9-diarylfluorene, triarylamine, diphenyl ether, etc. should also be understood as aromatic systems. The OLED can also contain further layers, such as, for example, hole injection layer, hole transport layer, electron injection layer and / or electron transport layer. An insulator layer between two of the active layers can also be useful. However, it should be pointed out that all of these layers do not necessarily have to be present. So good results are still obtained if, for. B. no hole injection layer and / or no hole transport layer and / or no electron transport layer and / or no electron injection layer can be used. It has thus been found that OLEDs according to the invention which contain a hole blocking layer of the formula (1) continue to provide comparably good efficiencies and lifetimes with reduced operating voltage if no electron injection and electron transport layers are used.

The hole blocking layer according to the invention preferably contains at least 50% of compounds of the formula (1), particularly preferably at least 80%, very particularly preferably consists only of compounds of the formula (1).

Organic electroluminescent devices are preferred in which for

Compounds according to formula (1) apply: aryl is the same or different in each occurrence, an aromatic or heteroaromatic ring system with 1 to 20 aromatic carbon atoms, which can be substituted by one or more radicals R;

Each occurrence of R is the same or different H, F, Cl, NO ₂ , CN, N (R ¹ ) ₂ or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 20 C atoms, one or more not being adjacent CH ₂ groups by -R ¹ C = CR ¹ -, -C --C-, Si (R ¹ ) ₂ , Ge (R ¹ ) ₂ , Sn (R ¹ ) ₂ , -O-, -S- or -NR ¹ - can be replaced and wherein one or more H atoms can be replaced by F or an aromatic group R ¹ , where two or more substituents R can span another mono- or polycyclic, aliphatic or aromatic ring system;

R ¹ is as defined above; n is the same or different at each occurrence 1 or 2; m is the same or different at each occurrence 0, 1 or 2; o is the same or different at each occurrence 2 or 3; p is the same or different at each occurrence 2, 3 or 4; the aryl substituent is preferably linked via the positions

2 and / or 4, or, if available, also via positions 5, 7, 2 ', 4', 5 'and / or T. Organic electroluminescent devices are particularly preferred in which the following applies to compounds of the formula (1):

Aryl is the same or different in each occurrence, is composed of phenyl and / or pyridine groups, contains a total of 5 to 18 aromatic C atoms and can be substituted by one or more radicals R;

Each occurrence of R is the same or different H, F, NO ₂ , CN or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 10 C atoms, one or more non-adjacent CH ₂ groups being represented by -R ¹ C = CR ¹ -, -C - C-, Si (R ¹ ) ₂ , Ge (R ¹ ) ₂ , Sn (R ¹ ) ₂ , -O-, -S- or -NR ¹ - can be replaced and wherein one or more H atoms can be replaced by F or an aromatic group R ¹ , where two or more substituents R can span another mono- or polycyclic, aliphatic or aromatic ring system;

R ¹ is as defined above; n is 1 on each occurrence; m is the same or different at each occurrence 0 or; o is 3 for each occurrence; p is the same or different at each occurrence 3 or 4; the aryl substituent and the substituents R which are not equal to H are preferably linked via position 2 or also via positions 7, 2 'and / or T.

Compounds according to formula (1) very particularly preferably contain a total of two aryl substituents which are linked to the spirobifluorene unit either via positions 2 and 7 or via positions 2 and 2 ', or they contain a total of four aryl substituents which via the Positions 2, 2 ', 7 and 7' are linked to the spirobifluorene unit.

The glass transition temperature of the compounds of the formula (1) is preferably> 100 ° C, particularly preferably> 120 ° C, very particularly preferably> 140 ° C. It has been shown that the glass transition temperature of oligoarylene compounds which contain at least one spirobifluorene unit are usually in this range, while the glass transition temperature of simple oligophenylenes is often significantly lower. Without wishing to be bound by any particular theory, this may be caused by the sterically demanding molecular structure. This justifies the preference of these materials over simple oligophenylenes according to the prior art. It has been shown that the best results (in terms of efficiency and service life) are achieved if the layer thickness of the hole blocking layer is 1 to 50 nm, preferably 5 to 30 nm.

Furthermore, it has been shown that particularly good results, in particular with regard to the operating voltage and the power efficiency, are obtained if no electron transport layer (ETL) is introduced between the hole blocking layer and the cathode or the electron injection layer. An inventive one is also preferred

Electroluminescent device which does not contain an electron transport layer and in which the hole blocking layer is directly adjacent to the electron injection layer or the cathode. This is a surprising result, since the same device structure with BCP as hole blocking material without ETL delivers significantly shorter lifetimes.

The present invention is illustrated by the following examples of hole blocking materials according to formula (1), without wishing to restrict them thereto. The person skilled in the art can produce further electroluminescent devices according to the invention with similar hole blocking materials from the description and the examples given without inventive step.

Example 1 Example 2 Example 3

Example 4 Example 5 Example 6

Example 7 Example 8 Example 9

The matrix for the phosphorescent emitter is preferably selected from the classes of carbazoles, e.g. B. according to WO 00/057676, EP 01/202358 and WO 02/074015, the ketones and imines, e.g. B. according to the unpublished application DE 10317556.3, the phosphine oxides, the phosphine sulfides, the phosphine selenides, the phosphazenes, the sulfones, the sulfoxides, for. B. according to the unpublished application DE 10330761.3, the silanes, the polypodal metal complexes, for. B. according to the unpublished application DE 103,10887.4, or the oligophenylenes based on spirobifluorenes, for. B. according to EP 676461 and WO 99/40051; ketones, phosphine oxides, sulfoxides and sulfones are particularly preferred.

The phosphorescent emitter is preferably a compound which has at least one element with an atomic number greater than 36 and less than 84. The phosphorescent emitter particularly preferably contains at least one element with an atomic number greater than 56 and less than 80, very particularly preferably molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold and / or europium, e.g. B. according to WO 98/01011, US 02/0034656, US 03/0022019, WO 00/70655, WO 01/41512, WO 02/02714, WO 02/15645, EP 1191613, EP 1191612, EP 1191614, WO 03 / 040257 and WO 03/084972.

One or more layers are preferably coated in the organic electroluminescent device using a sublimation process. The low molecular weight materials are evaporated in vacuum sublimation systems at a pressure <10 ^"5 mbar, preferably <10 ^{" 6} mbar, particularly preferably <10 ^"7 mbar.

One or more layers are likewise preferably coated in the organic electroluminescent device using the OVPD process (Organic Vapor Phase Deposition) or with the aid of carrier gas sublimation. The low molecular weight materials are applied at a pressure between 10 ^"5 mbar and 1 bar.

Also preferred are one or more layers in the organic electroluminescent device with a printing process, such as. As flexo printing or offset printing, but preferably LITI (Light Induced Thermal Imaging, thermal transfer printing) or InkJet printing (inkjet printing), coated.

The emitting devices described above now have the following surprising advantages over the prior art:

1. The efficiency of corresponding devices is higher compared to systems according to the prior art, which contain BAIq as HBL.

2. The lifespan of corresponding devices is longer compared to systems that contain BCP as HBL. This results in devices whose service life and efficiency are comparable to the best values according to the prior art and in which not only one of the two properties gives good results, as is the case with BAIq or BCP.

3. The operating voltages are lower in devices according to the invention than in devices according to the prior art. 4. The layer structure can be simplified because a separate electron transport layer does not necessarily have to be used. This is a surprising result, since the same device structure with BCP instead of compounds according to formula (1) without a separate electron transport layer delivers significantly poorer lifetimes and efficiencies. 5. If no separate electron transport layer is used, there is a further advantage: the operating voltages are much lower here; this increases the performance efficiency considerably. This is a surprising result, since the same device structure with BAIq instead of compounds according to formula (1) results in a hardly reduced operating voltage.

6. The production effort is also reduced without the use of a separate electron transport layer. This is a considerable technological advantage in the production process, since the conventional method of manufacture requires a separate vapor deposition device for each organic layer.

Details of the information given here can be found in the examples described below.

In the present application text and in the following examples, organic light-emitting diodes and the corresponding displays are aimed at. Despite this limitation of the description, it is possible for the person skilled in the art without further inventive intervention to also apply the corresponding design according to the invention to other, related devices, for. B. for organic solar cells (O-SCs), organic transistors, organic integrated circuits, organic photoreceptors or organic laser diodes (O-lasers), to name just a few other applications. These are also the subject of the present application.

Examples:

Unless stated otherwise, the following syntheses were carried out under an inert gas atmosphere in dried solvents. The starting materials (2-biphenylboronic acid, 4-biphenylboronic acid, tripotassium phosphate, palladium acetate, tris-o-tolylphosphine) were obtained from Aldrich or Lancaster. 2.2 ', 7.7'- tetrabromo-9.9 ^! Spirobifluorene was prepared according to WO 9842655 and 2,7-dibromo-2 ', 7'-di-fe / τ-butyl-9, 9' -spirobifluorene was prepared according to WO 02/077060.

Example 1: Synthesis of 2,7-bis (4-biphenyl-1-yl) -2 ', ^{7'-di-tert-butyl-spiro-9,9'} - bifluorene (HB 1) A degassed suspension of 73.3 g (125 mmol) 2,7-dibromo-2 ', 7'-di-te / t-butyl-9,9'-spirobifluorene, 69.3 g (350 mmol) 4-biphenylboronic acid and 111.5 g (525 mmol) tripotassium phosphate in one Mixture of 700 mL toluene, 100 mL dioxane and 500 mL water was mixed with 2.28 g (7.5 mmol) tris-o-tolylphosphine and then 281 mg (1.25 mmol) of palladium (II) acetate were added. This suspension was heated under reflux for 16 h. The precipitate which precipitated after cooling to room temperature was filtered off, dissolved in 1000 ml of dichloromethane and then filtered through a short column of silica gel. The filtrate was evaporated to dryness, then recrystallized six times from 400 mL dioxane each time and sublimed after a purity of> 99.9% (HPLC) in a high vacuum. The yield with a purity of> 99.9% (HPLC) was 70.8 g (96 mmol), corresponding to 77.3% of theory. T _g = 174 ° C. ¹ H-NMR (CDCI ₃ ): [ppm] = 7.97 (m, 2H), 7.76 (m, 2H), 7.70 (m, 2H), 7.60-7.51 (m, 12H), 7.42 (m, 6H), 7.33 (m, 2H), 7.01 (s, 2H), 6.77 (s, 2H), 1.17 (s, 18H).

Example 2: Synthesis of 2-2S7,7'-tetrakis (2-biphenyl-1-yl) spiro-9.9 ^' bifluorene (HBM2) A degassed suspension from 158.0 g (80 mmol) 2,2', 7, 7'-tetrabromo-9.9 '~ spirobifluorene, 75.1 g (379 mmol) 2-biphenylboronic acid and 142.7 g (672 mmol) tripotassium phosphate in a mixture of 400 mL toluene, 50 mL dioxane and 300 mL water was mixed with 2.19 g (7.2 mmol) of tris-o-tolylphosphine and then mixed with 270 mg (1.2 mmol) of palladium (II) acetate. This suspension was heated under reflux for 16 h. The one that failed after cooling to room temperature

The precipitate was filtered off, dissolved in 1000 ml of dichloromethane and then filtered through a short column of silica gel. The filtrate was evaporated to dryness, then recrystallized four times from 300 mL DMF and sublimed after a purity of> 99.9% (HPLC) in a high vacuum. The yield with a purity of> 99.9% (HPLC) was 52.0 g (56 mmol), corresponding to 70.4% of theory. T _g = 133 ° C.

¹ H NMR (CDCI ₃ ): [ppm] = 7.45 (m, 4H), 7.35-7.29 (m, 16H), 7.00-6.96 (m, 20H), 6.93-6.88 (m, 4H), 6.55 (d , 4H).

Example 3: Device structure

The OLEDs were produced using a general process which was adapted to the particular circumstances in each individual case (e.g. layer thickness variation to optimize efficiency or color). For the production of the devices according to the invention, a compound of the formula (1) was used as the hole blocking layer and the electron transport layer was optionally omitted. Electroluminescent devices according to the invention can be represented as described for example in DE10330761.3. The following examples show the results of various OLEDs, both with hole blocking materials according to formula (1) and with BCP and BAIq as comparison materials. The basic structure, the materials used and layer thicknesses (except for the HBLs) were identical for better comparability. Phosphorescent OLEDs with the following structure were produced in accordance with the above-mentioned general procedure: PEDOT (HIL) 60 nm (spun on from water; obtained as Baytron P from HC Starck; poly (3,4-ethylenedioxy-2,5-thiophene)) NaphDATA ( HTL) 20 nm (evaporated; obtained from SynTec; 4,4 ', 4 "tris (N-1-naphthyl-N-phenylamino) -triphenylamine)

S-TAD (HTL) 20 nm (evaporated; produced according to WO 99/12888; 2.2 ^, 7.7 ^, - tetrakis (diphenylamino) -spirobifluorene) (EML) 30 nm (evaporated); 10% IrPPy in bis (9,9'-spirobifluoren-2-yl) ketone as matrix material (HBL) materials and layer thicknesses: see examples in Table 1

AIQ ₃ (ETL) not available in all devices (see Table 1); if available: evaporated (obtained from SynTec; Tris (8-hydroxyquinolinato) aluminum (III)) Ba-Al (cathode) 3 nm Ba, then 150 nm AI.

These OLEDs, which have not yet been optimized, have been characterized as standard; the electroluminescence spectra, the efficiency (measured in cd / A), the power efficiency (measured in Im / W) depending on the brightness and the service life were determined. The lifetime is defined as the time after which the initial brightness of the OLED has dropped by half at a constant current density of 10 mA / cm ² .

Table 1 summarizes the results of the OLEDs according to the invention and of some comparative examples (with BCP and BAIq) (Examples 4 and 5). Only the hole blocking layer and the electron conductor layer (composition and layer thickness) are listed in the table. The other layers correspond to the structure mentioned above.

The abbreviations used above or in Table 1 correspond to the following compounds: Ir (PPy) ₃ bis (9,9'-spirobifluoren-2-yl) ketone

HBM1

HB 2

BAlq BCP

Examples 4 and 5: Comparison of hole blocking materials according to the invention (HBM1, HBM2) and comparison materials (BAIq and BCP) according to the prior art

electroluminescence:

The OLEDs all show green emission with the CIE color coordinates (0.39; 0.57) resulting from the dopant Ir (PPy) ₃ (Table 1, Examples 4 and 5).

Efficiency as a function of brightness:

For OLEDs produced with HBM1, the best efficiency (see FIG. 1 (A) and table 1, example 4a) of 33.3 cd / A and the best power efficiency (see FIG. 2 (A) and table 1, example 4a) are obtained ) from 23.8 Im / W. A similarly good efficiency of 31.6 cd / A and power efficiency of 21.7 Im / W can be achieved with HBM2 (Table 1, Example 4b). In the comparative examples, either the efficiency (FIG. 1 (■) and table 1, example 4c) and / or the power efficiency (FIG. 2 (■) and table 1, examples 4c and 4d) is significantly poorer. BAIq (example 4c) only achieved 27.3 cd / A or 18.8 Im / W and BCP (example 4d) reached 32.6 cd / A, but only a power efficiency of 18.2 Im / W. A similarly good behavior is obtained for OLEDs without AIQ ₃ as ETL and with HBM2 as a hole blocking layer, as can be seen from Table 1, Example 5. With HBM2 you get an efficiency of 31.0 cd / A, with BAIq only 24.8 cd / A and with BCP even only 16.7 cd / A. The power efficiency with HBM2 is 18.1 Im / W, in contrast with BAIq only 14.7 Im / W and with BCP only 8.7 Im / W.

Lifetime comparison:

Table 1 shows that HBM1 (Example 4a) with 910 h at 10 mA / cm ^{2 has} the best lifetime, followed by HBM2 with 650 h. OLEDs without AIQ ₃ as ETL all have a shorter lifespan, with HBM2 (example 5a) performing best at 580 h. The lifespan is usually the time after which only 50% of the initial luminance is reached. From the measured lifetimes, lifetimes can now be calculated for an initial brightness of 400 cd / m ² . In the case of HBM1 (example 4a), a service life of over 60,000 h is obtained and with HBM2 (example 5a) over 40,000 h, which is significantly higher than the 10,000 h required for display applications.

Table 1

In summary, it can be said that phosphorescent OLEDs which contain hole blocking materials according to formula (1) have high efficiencies with long lifetimes and low operating voltages, as can easily be seen from the examples in Table 1.

Claims

claims

1. Organic electroluminescent device containing an anode, a cathode and at least one emission layer containing at least one matrix material which is doped with at least one phosphorescent emitter, characterized in that at least one hole blocking layer is introduced between the emission layer and the cathode, the at least one connection according to formula (1) contains

(Formula 1) the following applies to the symbols and indices used: aryl is the same or different in each occurrence, an aromatic or heteroaromatic ring system with 1 to 40 aromatic C atoms, which can be substituted by one or more radicals R; Each occurrence of R is the same or different H, F, Cl, Br, I, NO ₂ , CN or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 40 C atoms, one or more non-adjacent CH ₂ - Groups by -R ¹ C = CR ¹ -, -C = C-, Si (R ¹ ) ₂ , Ge (R ¹ ) ₂ , Sn (R ¹ ) 2, -O-, -S- or -NR ¹ - can be replaced and one or more H atoms can be replaced by F or an aromatic group R ¹ , where two or more substituents R or R with aryl can span another mono- or polycyclic, aliphatic or aromatic ring system; Each time R ¹ is the same or different, H or an aliphatic or aromatic hydrocarbon radical having 1 to 20 C atoms, two or more substituents R ¹ or R ¹ with R and / or aryl also being another mono- or polycyclic, can span aliphatic or aromatic ring system; n is the same or different at each occurrence 1, 2, 3 or 4; m is the same or different at each occurrence 0, 1, 2, 3 or 4; o is the same or different at each occurrence 0, 1, 2 or 3; p is the same or different at each occurrence 0, 1, 2, 3 or 4; with the proviso that the sum n + o = 4 and the sum m + p = 4, with the proviso that the hole blocking material is not identical to the matrix material, and with the further proviso that aryl contains no diazine, triazine or contains tetrazine group.

2. Organic electroluminescent device according to claim 1, characterized in that a hole injection layer and / or a hole transport layer and / or an electron injection layer and / or an electron transport layer and optionally further layers are present.

3. Organic electroluminescent device according to claim 1 and / or 2, characterized in that the hole blocking layer contains at least 50% compounds according to formula (1).

4. Organic electroluminescent device according to claim 3, characterized in that the hole blocking layer consists only of compounds according to formula (1).

5. Organic electroluminescent device according to one or more of claims 1 to 4, characterized in that for compounds according to formula (1) applies: aryl is the same or different with each occurrence an aromatic or heteroaromatic ring system with 1 to 20 aromatic carbon atoms, the can be substituted by one or more radicals R; Each occurrence of R is the same or different H, F, Cl, NO ₂ , CN, N (R ¹ ) ₂ or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 20 C atoms, one or more not being adjacent CH ₂ groups by -R ¹ C = CR ¹ -, -C - C-, Si (R ¹ ) ₂ , Ge (R) ₂ , Sn (R) ₂ , -O-, -S- or -NR ¹ - can be replaced and one or more H atoms can be replaced by F or an aromatic group R ¹ , where two or more substituents R can span another mono- or polycyclic, aliphatic or aromatic ring system; R ¹ is as defined in claim 1; n is the same or different at each occurrence 1 or 2; m is the same or different at each occurrence 0, 1 or 2; o is the same or different at each occurrence 2 or 3; p is the same or different at each occurrence 2, 3 or 4; the aryl substituent is linked via positions 2 and / or 4, or, if present, also via positions 5, -7, 2 ', 4', 5 'and / or 7'.

6. Organic electroluminescent device according to claim 5, characterized in that the following applies to compounds according to formula (1): aryl is the same or different with each occurrence, is composed of phenyl and / or pyridine groups, contains a total of 5 to 18 aromatic carbon atoms and can be substituted by one or more non-aromatic radicals R; Each occurrence of R is the same or different H, F, NO ₂ , CN or a straight-chain, branched or cyclic alkyl or alkoxy group with 1 to 10 C atoms, one or more non-adjacent CH ₂ groups being represented by -R ¹ C = CR ¹ -, -C - C-, Si (R ¹ ) ₂ , Ge (R ¹ ) ₂ , Sn (R ¹ ) ₂ , -O-, -S- or -NR ¹ - can be replaced and wherein one or more H atoms can be replaced by F or an aromatic group R ¹ , it being possible for two or more substituents R to span another mono- or polycyclic, aliphatic or aromatic ring system; R ¹ is as defined in claim 1; n is 1 on each occurrence; m is the same or different at each occurrence 0 or 1; o is 3 for each occurrence; p is the same or different at each occurrence 3 or 4; the aryl substituent and the substituents R, which are not equal to H, are linked via position 2 or also via positions 7, 2 'and / or 7'.

7. Organic electroluminescent device according to one or more of claims 1 to 6, characterized in that the compounds according to formula (1) contain a total of two aryl substituents, either via positions 2 and 7 or via positions 2 and 2 'with the Spirobifluorene unit are linked, or that they contain a total of four aryl substituents which are linked to the spirobifluorene unit via positions 2, 2 ', 7 and 7'.

8. Organic electroluminescent device according to one or more of claims 1 to 7, characterized in that the glass transition temperature of the compounds according to formula (1) is> 100 ° C.

9. Organic electroluminescent device according to one or more of claims 1 to 7, characterized in that the glass transition temperature of the compounds according to formula (1)> 140 ° C.

10. Organic electroluminescent device according to one or more of claims 1 to 9, characterized in that the layer thickness of the hole blocking layer is 1 to 50 nm.

11. Organic electroluminescent device according to one or more of claims 1 to 10, characterized in that the hole blocking layer directly adjoins the cathode or the electron injection layer without using an electron transport layer.

12. Organic electroluminescent device according to one or more of claims 1 to 11, characterized in that the matrix material is selected from the classes of carbazoles, ketones and imines, phosphine oxides, phosphine sulfides, phosphine selenides, phosphazenes, sulfones, sulfoxides , the silanes, the polypodal metal complexes or the oligophenylenes based on spirobifluorenes.

13. Organic electroluminescent device according to one or more of claims 1 to 12, characterized in that the phosphorescent emitter has at least one element of the atomic number greater than 36 and less than 84.

14. Organic electroluminescent device according to claim 13, characterized in that the phosphorescent emitter contains at least one element from the group of molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium.

15. Organic electroluminescent device according to one or more of claims 1 to 14, characterized in that one or more layers are coated with a sublimation process.

16. Organic electroluminescent device according to one or more of claims 1 to 14, characterized in that one or more layers are coated with the OVPD process (Organic Vapor Phase Deposition) or with the aid of carrier gas sublimation.

17. Organic electroluminescent device according to one or more of claims 1 to 14, characterized in that one or more layers are coated with a printing process.

18. Use of the design of the electronic devices according to one or more of claims 1 to 17 for organic transistors, organic integrated circuits, organic solar cells, organic laser diodes or organic photoreceptors.