JP2000048966A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain increase in electric power consumption and deterioration of display performance caused by voltage drop, and to secure high luminous efficiency. SOLUTION: In an organic EL element 1 with an organic luminescent layer containing an organic layer 30 sandwiched between a transparent electrode 10 and a counter electrode 20, the electrode 10 is composed of a laminate laminated with at least either of a semiconductor thin film and an insulator thin film and a metal thin film, carrier densities for the semiconductor thin film and the insulator thin film are made less than 1020 cm-3, their energy gap are made 2.7 eV or more and the semiconductor thin film or the insulator thin film is neighbored to the organic layer 30. Surface resistance of the transparent electrode 10 is reduced thereby, and high luminous efficiency is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter, referred to as an organic EL device), and more particularly, to a transparent electrode, a counter electrode facing the transparent electrode, and a device between the transparent electrode and the counter electrode. And an organic EL layer sandwiched between the organic EL layers, the organic layer including an organic light emitting layer containing an organic light emitting material.

[0002]

2. Description of the Related Art Organic EL devices utilizing electroluminescence have characteristics such as high visibility due to self-luminescence and excellent impact resistance because they are completely solid devices. I have. The organic EL element uses an organic compound (organic light emitting material) as a light emitting material,
Compared with an inorganic EL device using an inorganic light emitting material, the applied voltage can be greatly reduced and the size can be easily reduced.

[0003] The organic EL element is usually formed on a substrate, and in a type in which the substrate side is a light extraction surface, a transparent electrode as an anode, an organic light emitting layer made of an organic light emitting material, and a cathode as a cathode are provided on the substrate. Are sequentially laminated. In such an organic EL device, in order to improve the performance of the device, a hole injection layer is provided between the transparent electrode and the organic light emitting layer, or an electron injection layer is provided between the counter electrode and the organic light emitting layer. In this case, a plurality of organic layers are sandwiched between the transparent electrode and the counter electrode.

[0004] Such an organic EL device is being used as a surface light source. However, since devices of various luminescent colors have been developed, application to a display device is being studied. In a display device using an organic EL element, a stripe-shaped transparent electrode and a counter electrode are arranged in a matrix on a substrate, and an organic material layer including an organic light emitting layer is sandwiched between these electrodes. Pixels are two-dimensionally arranged on a plane to form an organic EL display panel, and display is performed by independently driving the organic EL elements constituting each pixel.

On the other hand, as a material of a transparent electrode constituting an organic EL element, generally, ITO (indium tin oxide) is used.
Is used. However, the sheet resistance of ITO is 1
Since it is 0Ω / □ to 20Ω / □, high-definition organic E
When applied to an L display device, this resistance may cause the transparent electrode line to have a resistance close to 10 kΩ. For this reason, a voltage drop occurs due to the resistance of the transparent electrode line, and the power consumption increases. In addition, a time constant determined by the resistance and the element capacitance increases, causing a delay in light emission response, thereby disturbing display. was there. As a method for solving such a problem, a method has been proposed in which the transparent electrode has a three-layer structure of an amorphous conductive oxide layer / a metal thin film / amorphous conductive oxide layer (WO97 / 46054). ). In this method, by using a metal thin film for the transparent electrode,
Since the sheet resistance of the entire transparent electrode can be reduced,
An increase in power consumption and a decrease in display performance can be prevented.

[0006]

However, in this method, the In ₂ oxide used for the amorphous conductive oxide layer is not used.
O ₃ —ZnO oxide and ITO (amorphous) are n-type degenerate semiconductors having metallic properties and usually have a carrier concentration of 10 ²⁰ cm ⁻³ or more. When the material layer and the organic light emitting layer are close to each other, there is a problem in that the excited state generated in the organic light emitting layer is deactivated, quenching is caused, and the luminous efficiency is reduced.

An object of the present invention is to provide an organic EL device which can suppress an increase in power consumption and a decrease in display performance due to a voltage drop and can ensure high luminous efficiency.

[0008]

The present invention comprises a transparent electrode,
An organic material comprising: a counter electrode facing the transparent electrode; and an organic material layer sandwiched between the transparent electrode and the counter electrode. The organic material layer includes an organic light emitting layer containing an organic light emitting material. In an EL element, the transparent electrode is formed of a laminate of at least one of a semiconductor thin film and an insulator thin film and a metal thin film, and the semiconductor thin film and the insulator thin film have a carrier concentration of less than 10 ²⁰ cm ⁻³ . In addition, the energy gap is 2.7 eV or more, and one of the semiconductor thin film and the insulator thin film is adjacent to the organic material layer.

In the present invention, since the transparent electrode is composed of a laminate of a semiconductor thin film or an insulator thin film and a metal thin film, even if the semiconductor thin film or the insulator thin film has a large sheet resistance, it has high conductivity. Since the sheet resistance of the entire transparent electrode can be reduced by the metal thin film, an increase in power consumption due to a voltage drop and a decrease in display performance can be suppressed. Further, since the sheet resistance of the transparent electrode can be reduced by the metal thin film, the transparent electrode can be formed using a semiconductor thin film or an insulator thin film having a relatively large sheet resistance.

[0010] Since the semiconductor thin film or the insulator thin film of the transparent electrode is adjacent to the organic material layer, the semiconductor thin film or the insulator thin film is interposed between the metal thin film and the organic light emitting layer. Since the organic light emitting layer can be separated from the organic light emitting layer, quenching in the organic light emitting layer can be prevented.
The semiconductor thin film and the insulator thin film have a carrier concentration of less than 10 ²⁰ cm ⁻³ and an energy gap of 2.
Since it is 7 eV or more, the luminous efficiency can be maintained high. That is, when the carrier concentration is 10 ²⁰ cm ⁻³ or more, the excited state in the organic material layer is deactivated and the efficiency of the device is reduced when the organic material layer is adjacent to the organic material layer. If the energy gap is less than 2.7 eV, the transfer of excitation energy from the organic material layer to the adjacent semiconductor thin film or insulator thin film occurs, and the efficiency of the device is reduced.

In order to apply an organic EL element to a light emitting device, the transparent electrode must have a sheet resistance of 0.5 Ω / □ to 100 Ω / □.
, Preferably 0.5 Ω / □ to 1
It is desirable to be in the range of 0Ω / □. That is, when the sheet resistance of the transparent electrode is less than 0.5Ω / □,
Since the thickness of the metal thin film becomes large, the transmittance becomes 10% or less, and there is a possibility that a sufficient light extraction amount cannot be secured when light is extracted through the transparent electrode. On the other hand, if the sheet resistance exceeds 10 Ω / □, the resistance may be retained and the voltage drop may occur when the transparent electrode is thinned.

In the above, the thickness of the metal thin film is 0.5
It is preferably in the range of 30 nm, more preferably in the range of 1-9 nm. That is, if the thickness of the metal thin film is less than 0.5 nm, the film may be separated into islands and sufficient conductivity may not be obtained. Further, in order to extract light emitted from the organic light emitting layer through the transparent electrode, the visible light transmittance of the metal thin film is preferably set to 50% or more. However, when the film thickness exceeds 30 nm, sufficient light transmittance is obtained. May not be. In particular, when the thickness of the metal thin film is 1
When the thickness is in the range of ９9 nm, a metal thin film having a small electric resistance and a high light transmittance can be obtained.

The metal thin film is made of Ag, Pd, Au,
It is preferable to be made of any one selected from Cu, Pt and an alloy containing these. Since these metals have a specific resistance of 10 ⁻⁵ Ωcm or less, the sheet resistance of the transparent electrode can be sufficiently reduced.

In the above, it is desirable that the semiconductor thin film and the insulator thin film are formed using any one of oxide, oxynitride, sulfide and selenide. In this way, the carrier concentration of the semiconductor thin film or the insulator thin film can be reliably reduced. In this case, the semiconductor thin film is made of any one of oxide, sulfide, and selenide, and includes Ti, In, Sn, Mg, Zn, and Al.
And it is preferable to contain any one selected from Ga. Particularly preferred examples are ZnS, ZnSe, Z
nSSe, MgSSe, etc. can be mentioned. Also,
The insulator thin film preferably contains an alkali metal or an alkaline earth metal, particularly, Mg, Ca, Ba, S
It is preferable to be composed of an oxide containing any one selected from r, Li, Na, K and Rb.

In the above, the transparent electrode is formed from the side of the organic light emitting layer from the semiconductor thin film / metal thin film / semiconductor thin film, the insulator thin film / metal thin film / insulator thin film, the semiconductor thin film / metal thin film / insulator thin film, It is desirable to use a laminated body laminated in any order of the metal thin film / semiconductor thin film. When the transparent electrode has a three-layer structure as described above, the metal thin film is stabilized, and a structural change with time is suppressed, so that heat resistance can be improved.

The thickness of the insulator thin film is 0.1 to 3
It is preferable to set the range to 0 nm. That is,
If the thickness of the insulating thin film is less than 0.1 nm, the insulating thin film may be separated into islands at the time of film formation and a continuous film may not be obtained, and a desired performance may not be exhibited.
When the insulator thin film is adjacent to the organic material layer, a high voltage of 1 × 10 ⁶ V / cm or more needs to be applied to the insulator thin film in order to inject electric charge into the organic material layer via the insulator thin film. There is. Therefore, if the film thickness exceeds 30 nm, there is a possibility that charge injection cannot be performed well.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. The organic EL device 1 according to the present invention is shown in FIG.
As shown in FIG. 1, the transparent electrode 10, a counter electrode 20 facing the transparent electrode 10, and an organic material layer 30 sandwiched between the transparent electrode 10 and the counter electrode 20 are provided. Comprises an organic light emitting layer containing an organic light emitting material. The organic EL element 1 is laminated on a substrate 2 as a support in order from a transparent electrode 10,
The substrate 2 side is a light extraction surface. In addition, organic EL
The element 1 may be covered with a sealing layer for preventing entry of moisture or oxygen. Such an organic EL element 1 can be applied to various organic EL light emitting devices such as an organic EL display panel and a surface light source.

Hereinafter, each element constituting the organic EL device will be described in detail. (1) Transparent electrode (anode) The transparent electrode is formed of a laminate of a metal thin film and at least one of a semiconductor thin film and an insulator thin film. In the organic EL device of the present invention, one of the semiconductor thin film and the insulator thin film among the thin films constituting the transparent electrode is adjacent to the organic material layer. The semiconductor thin film and the insulator thin film constituting the transparent electrode have a carrier concentration of less than 10 ²⁰ cm ⁻³ and an energy gap of 2.7 eV or more. The sheet resistance of the transparent electrode having such a multilayer structure is preferably in the range of 0.5Ω / □ to 10Ω / □.

(A) Metal thin film When a transparent electrode is composed of only a semiconductor thin film and an insulator thin film,
The sheet resistance of the transparent electrode is about 100 Ω / □, and in some cases, 10 kΩ / □ or more, and the power consumption is increased. Therefore, the transparent electrode cannot be applied to a light emitting device. In the present invention,
In order to reduce the sheet resistance of the transparent electrode, specifically, to set the sheet resistance in the range of 0.5Ω / □ to 100Ω / □, preferably in the range of 0.5Ω / □ to 10Ω / □. To increase the transmittance of visible light using metal,
In order to make it 0% or more, an ultrathin metal film is particularly used.

The thickness of such a metal thin film is 0.5 nm.
It is preferably in the range of 30 nm to 30 nm, and more preferably in the range of 1 nm to 9 nm. The metal thin film is preferably formed in a continuous thin film shape, but may be in a partially opened tidal flat shape as long as it is connected as a whole. That is, the thickness of the metal thin film is set to 0.5 nm to 3 n
When the thickness is very thin, about m, the metal does not become a continuous film at the time of film formation, but it may be formed in a partially open tidal flat, but the metal thin film is connected without being divided Then, conductivity can be secured. As a metal constituting the metal thin film, a noble metal, a metal having a specific resistance of 10 ⁻⁵ Ωcm or less, an alloy containing these, and the like can be used. Specifically, it is preferable to be composed of any one selected from Ag, Pd, Au, Cu, Pt and alloys containing them. For example, AuIn, AgPb, PdAg, Pd
AgSb and the like can be mentioned.

(B) Semiconductor Thin Film In the present invention, the semiconductor thin film has a carrier concentration of 10 ²⁰
A material having an energy gap of 2.7 eV to 9 eV, which is in the range of cm ^-3 to 10 ¹² cm ^-3 is used. Such a semiconductor thin film is preferably made of an oxide, an oxynitride, a sulfide and a selenide,
In particular, those containing any of Ti, In, Sn, Mg, Zn, Al, and Ga are preferable. Specifically, TiO ₂ ,
In ₂ O ₃ , SnO ₂ , MgO, ZnO, In ₂ O ₃ -Zn
O, Ga ₂ O ₃ , In ₂ O ₃ —Al ₂ O ₃ , In ₂ O ₃ —TiO
₂ , SnO ₂ —TiO ₂ , In ₂ O ₃ —SnO ₂ , ZnS, Z
Examples include nSe, ZnSSe, and MgSSe. Here, the semiconductor thin film includes those formed of a transparent conductive oxide such as In ₂ O ₃ —SnO ₂ ,
Since a film of a transparent conductive oxide which is usually used has a carrier concentration of 10 ²⁰ cm ⁻³ or more and cannot exert the effects of the present invention, it is necessary to form a film with a low carrier concentration. As a method for lowering the carrier concentration of the semiconductor thin film, a method of reducing the amount of Sn relative to O ₂ during film formation,
A method of increasing the amount of O ₂ relative to Sn, a method of forming a film at room temperature, a method of using sulfide or selenide, and the like can be employed.

(C) Insulator Thin Film In the present invention, the carrier concentration is 0 to 1 as the insulator thin film.
A material having a range of 0 ²⁰ cm ^-3 and an energy gap of 2.7 eV or more is used. As described above, when an insulator having an energy gap of 2.7 eV or more is used, the excited state of the organic layer is not deactivated. The thickness of this insulator thin film is 0.1 to 30 to improve the charge injection.
nm, more preferably 0.3 to
It is 10 nm, particularly preferably 0.5 to 5 nm. Mg, Ca, B
It is preferable to employ an oxide or oxynitride containing any one selected from a, Sr, Li, Na, K and Rb. Further, as the material of the insulator thin film, fluoride and chloride are also preferable.
F, BaF ₂ , CaF ₂ , MgF ₂ , NaF and the like.

(D) Layer Configuration of Transparent Electrode The layer configuration of the transparent electrode includes one of the semiconductor thin film and the insulator thin film and the metal thin film, and the semiconductor thin film or the insulator thin film is adjacent to the organic material layer. There is no particular limitation as long as they are stacked, for example, a two-layer structure in which a semiconductor thin film or an insulator thin film and a metal thin film are stacked, or a three-layer structure in which a metal thin film is sandwiched between thin films made of a semiconductor thin film or an insulator thin film And four or more layers. Among these, when the transparent electrode has a three-layer structure, the following lamination order from the organic material layer side can be given. Semiconductor thin film / metal thin film / semiconductor thin film Insulator thin film / metal thin film / insulator thin film Semiconductor thin film / metal thin film / insulator thin film Insulator thin film / metal thin film / semiconductor thin film

(2) Substrate When the substrate is used as a light extraction surface, a transparent substrate is used.
The type of the transparent substrate may be appropriately selected according to the intended use of the organic EL element, and the light emission (EL
It is preferable to use a material made of a substance having high transmittance (light of about 80% or more) with respect to light. As such a transparent substrate, a plate-like material or a film-like material made of transparent glass such as alkali glass or non-alkali glass, transparent resin, quartz, or the like can be employed. As the transparent resin, various thermoplastic resins and thermosetting resins can be adopted, for example, polyethylene terephthalate, polycarbonate, polyether sulfone, polyether ether ketone, polyvinyl fluoride, polyacrylate, polypropylene, polyethylene, amorphous Examples thereof include polyolefin and fluorine-based resin.

When a substrate made of a transparent resin is used, a moisture-proof inorganic oxide film may be formed on the surface in advance, if necessary, in order to prevent oxygen and moisture from entering the organic EL element. This moisture-proof inorganic oxide film includes, for example, silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, yttrium oxide, ytterbium oxide,
It can be formed of magnesium oxide, tantalum oxide, cerium oxide, hafnium oxide, or the like, and has a thickness of 5 to 20
What is necessary is just to form a film to about 0 nm. Such a moisture-proof inorganic oxide film may be provided on a substrate made of a material other than a transparent resin. In this case, the moisture-proof inorganic oxide film can be used as an undercoat layer for a transparent electrode. on the other hand,
When the substrate is not used as a light extraction surface, for example, in the case of a side emission type organic EL device, a substrate other than the transparent substrate described above can be used as the substrate.

(3) Organic Material Layer The organic material layer can adopt various layer structures as long as it has a layer structure including an organic light emitting layer. As an element configuration of the organic EL element corresponding to the layer configuration of the organic layer, for example, the following can be given in the order of lamination on the substrate. Anode (transparent electrode) / organic light emitting layer / cathode (counter electrode) anode anode (transparent electrode) / hole injection layer / organic light emitting layer / cathode (counter electrode) anode (transparent electrode) / organic light emitting layer / electron injection layer / Cathode (counter electrode) Anode (transparent electrode) / hole injection layer / organic light emitting layer / electron injection layer / cathode (counter electrode) In the above type of organic EL device, the organic light emitting layer corresponds to the organic material layer. The hole injection layer and the organic light emitting layer correspond to the organic material layer, the organic light emitting layer and the electron injection layer correspond to the organic material layer, and the hole injection layer, the organic light emitting layer and the electron injection layer correspond to the organic material layer. I do.

(A) Organic Light-Emitting Layer The organic light-emitting layer is usually formed of one or more kinds of organic light-emitting materials. A mixture of the organic light-emitting material and an electron injection material and / or a hole injection material, A mixture or a polymer material in which an organic light emitting material is dispersed may be used. The organic light emitting material has the function of (a) charge injection, that is, a function of injecting holes from an anode or a hole injection layer and injecting electrons from a cathode or an electron injection layer when an electric field is applied. , (B)
A transport function, that is, a function of moving injected holes and electrons by the force of an electric field, (c) a light-emitting function, that is, a function of providing a field of recombination of electrons and holes and connecting them to light emission, What is necessary is just to have three functions of these.
Here, it is not always necessary that the organic light emitting material has sufficient performance for each of these functions (a) to (c). For example, the hole injection / transport property is Some of the larger and better materials are suitable as organic light emitting materials.

Examples of the organic luminescent material include benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent whitening agents, styrylbenzene-based compounds,
-Phthaloperinone, 1,4-diphenyl-1,3-butadiene, 1,1,4,4-tetraphenyl-1,3-butadiene, naphthalimide derivative, perylene derivative, oxadiazole derivative, aldazine derivative, pyrazirine derivative, Cyclopentadiene derivatives, pyrrolopyrrole derivatives, styrylamine derivatives, coumarin compounds, International Publication WO90 / 13148 and Appl. Phys. Lett., Vol.
58, 18, P1982 (1991), a polymer compound, an aromatic dimethylidin compound, and a compound represented by the following general formula (I)

[0029]

Embedded image (RQ) ₂ —Al—OL (I) (wherein L is a carbon number 6 to 2 containing a phenyl moiety)
4 represents a hydrocarbon, OL represents a phenolate ligand, Q represents a substituted 8-quinolinolate ligand, and R represents more than two substituted 8-quinolinolate ligands bonded to an aluminum atom. Represents an 8-quinolinolate ring substituent selected to sterically hinder )

The compounds represented by the following formulas can be used. In addition, a compound in which the above-described organic light-emitting material is used as a host and the host is doped with a strong fluorescent dye from blue to green, for example, a coumarin-based or a fluorescent dye similar to the above-described host is also suitable as the organic light-emitting material. When the above compound is used as an organic light emitting material, light emission from blue to green (emission color varies depending on the type of dopant)
Can be obtained with high efficiency. Specific examples of the host which is a material of such a compound include an organic light emitting material having a distyrylarylene skeleton (particularly preferably, for example, 4,
4'-bis (2,2-diphenylvinyl) biphenyl)
Specific examples of the dopant which is a material of the compound include diphenylaminovinyl arylene (particularly preferably, for example, N, N-diphenylaminobiphenylbenzene) and 4,4′-bis [2- [4 − (N, N
-Di-p-tolyl) phenyl] vinyl] biphenyl).

As a method for forming an organic light-emitting layer using the above-mentioned organic light-emitting material, known methods such as a vapor deposition method, a spin coating method, a casting method, and an LB method can be applied. It is preferable to apply the method of (1). The organic light emitting layer is particularly preferably a molecular deposition film. Here, the molecular deposition film is a thin film formed by deposition from a material compound in a gas phase or a film formed by solidification from a material compound in a solution state or a liquid phase. The deposited film can be distinguished from a thin film (molecule cumulative film) formed by the LB method by a difference in an aggregated structure and a higher-order structure and a functional difference caused by the difference. Furthermore, the organic light-emitting layer can also be formed by dissolving a binder such as a resin and an organic light-emitting material in a solvent to form a solution, and then thinning the solution by spin coating or the like. The thickness of the organic light-emitting layer formed in this manner is not particularly limited and can be appropriately selected depending on the situation, but is usually 5 nm to 5 μm.
Is preferable.

(B) Hole Injection Layer The material of the hole injection layer (hole injection material) may be any material having a hole injection property or an electron barrier property. A material used as a hole injection material for an electrophotosensitive member can be appropriately selected and used, and has a hole mobility of 10 ⁻⁵ cm ² / V · s (electric field intensity of 10 ⁴ to 10).
⁵ V / cm) or more is preferable. The hole injection material may be either an organic substance or an inorganic substance.

Specific examples include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives,
Styryl anthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative, silazane derivative,
Polysilane, aniline copolymer, conductive polymer oligomer (especially thiophene oligomer), porphyrin compound, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidene compound which can also be used as an organic light emitting material, p And inorganic semiconductors such as p-Si and p-SiC. Of these, a porphyrin compound, an aromatic tertiary amine compound or a styrylamine compound is preferably used as the hole injecting material, and an aromatic tertiary amine compound is particularly preferably used.

The hole injection layer may have a single-layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. When the hole injection layer having a multilayer structure is formed, the layer in contact with the organic light emitting layer has a hole transporting property, and is a layer made of a compound that does not generate a non-light emitting defect even when in contact with the organic light emitting layer. (Hereinafter, this layer is referred to as a hole transport layer). The “non-luminous defect” is caused by the disappearance of the excited state due to the interaction between the organic light-emitting layer and the hole transport layer. For example, exciplex, CT (charge transfer complex), etc. is there. As a material of the hole transport layer, a compound which does not generate a non-light emitting defect even when in contact with an organic light emitting material can be appropriately selected from the above hole injection materials. The hole injection layer including such a hole transport layer is formed by thinning the above-described hole injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, and an LB method. it can. Although the thickness of the entire hole injection layer is not particularly limited, it is usually 5 nm to 5 μm.
m.

(C) Electron Injecting Layer The material of the electron injecting layer (hereinafter referred to as “electron injecting material”) only needs to have a function of transmitting electrons injected from the cathode to the organic light emitting layer. It is desirable that the affinity is higher than the electron affinity of the organic light-emitting material and lower than the work function of the cathode (the minimum when the cathode has multiple components). However, it is not preferable that the energy level difference is extremely large because a large electron injection barrier exists there. For this reason, it is preferable that the electron affinity of the electron injection material is substantially equal to the work function of the cathode or the electron affinity of the organic light emitting material. Further, the electron injection material may be any of an organic substance and an inorganic substance.

Specific examples of the electron injecting material include nitro-substituted fluorenone derivatives, anthraquinodimethane derivatives,
Diphenylquinone derivatives, thiopyran dioxide derivatives, heterocyclic tetracarboxylic anhydrides such as naphthalene perylene, carbodiimides, fluorenylidenemethane derivatives, anthrone derivatives, oxadiazole derivatives, organic light emitting layers described in JP-A-59-194393. A series of electron-transporting compounds disclosed as materials, thiazole derivatives in which an oxygen atom of an oxadiazole ring is substituted with a sulfur atom, quinoxaline derivatives having a quinoxaline ring known as an electron withdrawing group, and 8-quinolinol derivatives Metal complexes, metal-free or metal phthalocyanines or those whose terminals are substituted with an alkyl group, a sulfone group, etc., distyrylpyrazine derivatives, n
Inorganic semiconductors such as type-Si and n-type-SiC;

The electron injection layer may have a single-layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. Such an electron injection layer can be formed by thinning the above-described electron injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, and an LB method. The thickness of the electron injection layer is not particularly limited, but is usually 5 nm to 5 μm.

(4) Counter electrode (cathode) As the material of the cathode (counter electrode), a metal, an alloy, an electrically conductive compound having a low work function (for example, 4 eV or less), a mixture thereof, or the like is preferably used. Specific examples include sodium, sodium-potassium alloy, magnesium, lithium, an alloy or mixed metal of magnesium and silver, aluminum, Al / Al ₂ O ₃ , indium,
Rare earth metals such as ytterbium are exemplified. Although the film thickness of the counter electrode depends on the material, it can be appropriately selected usually within a range of 10 nm to 1 μm, and its sheet resistance is several hundred Ω /.
□ The following is preferred. Note that the magnitude of the work function used as a reference when selecting the cathode material is not limited to 4 eV.

As described above, the transparent electrode, the organic material layer, and the counter electrode can be formed by various methods. If a vacuum deposition method is used for forming each layer, a molecular deposition film can be obtained and a vacuum deposition method can be used. Since the organic EL element can be manufactured only by the method, it is advantageous in simplifying the equipment and shortening the manufacturing time.

(5) Sealing layer As a material of the sealing layer provided for preventing intrusion of moisture and oxygen, for example, a monomer mixture containing tetrafluoroethylene and at least one comonomer is copolymerized. Obtained copolymer, fluorinated copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, chloro Copolymer of trifluoroethylene and dichlorodifluoroethylene, water-absorbing substance having an absorption of 1% or more, moisture-proof substance having a water absorption of 0.1% or less, In, Sn, Pb, A
metals such as u, Cu, Ag, Al, Ti, Ni, MgO,
SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, Ca
Metal oxides such as O, BaO, Fe ₂ O ₃ , Y ₂ O ₃ and TiO ₂ , metal fluorides such as MgF ₂ , LiF, AlF ₃ and CaF ₂ , perfluoroalkane, perfluoroamine, perfluoropolyether And the like, and a dispersion of an adsorbent for adsorbing moisture and oxygen in the liquid fluorinated carbon.

In forming the sealing layer, a vacuum evaporation method,
Spin coating, sputtering, casting, MB
E (molecular beam epitaxy) method, cluster ion beam evaporation method, ion plating method, plasma polymerization method (high-frequency excitation ion plating method), reactive sputtering method, plasma CVD method, laser CVD method, thermal CV
The D method, the gas source CVD method, or the like can be appropriately applied. When the material of the sealing layer is liquid fluorinated carbon or a material in which an adsorbent for adsorbing moisture and oxygen is dispersed in the liquid fluorinated carbon, the organic EL element formed on the substrate (already used) is used. A housing material that covers the organic EL element in cooperation with the substrate is formed outside the organic EL element while forming a gap between the organic EL element and the substrate. It is preferable to fill the formed space with the above-described material for the sealing layer to form a sealing layer. As the housing material, a material made of glass or a polymer (for example, ethylene trifluoride chloride) having a small water absorption is preferably used. When a housing material is used, only the housing material may be provided without providing the above-described sealing layer, or the adsorbent that adsorbs oxygen or water in a space formed by the housing material and the substrate. Or a layer comprising the adsorbent may be dispersed.

[0042]

[Example 1] The organic EL device of Example 1 was
In the element structure of lower electrode / organic light emitting layer (organic material layer) / counter electrode, the lower electrode is a transparent electrode. That is, a glass substrate having a thickness of 1 mm (25 mm × 75 m
m), a TiO ₂ thin film having a thickness of 50 nm was formed as a semiconductor thin film. Subsequently, the substrate with the TiO ₂ film was subjected to ultrasonic cleaning with isopropyl alcohol, dried in an N ₂ (nitrogen gas) atmosphere, and then cleaned for 30 minutes using both UV (ultraviolet rays) and ozone. .

Next, the cleaned substrate with the TiO ₂ film was set in a chamber of a vapor deposition / sputter apparatus manufactured by Japan Vacuum Corporation. Then, on the TiO ₂ film, first, as a metal thin film,
Ag was sputtered to a thickness of 10 nm. Thereafter, TiO ₂ was sputtered on the Ag film as a semiconductor thin film so as to have a thickness of 50 nm, and a three-layer laminate in which an Ag film was interposed between _two TiO ₂ films was used as a transparent electrode. . TiO ₂ is a transparent material having hole conductivity.

In sputtering TiO ₂ ,
A target is a sintered body of TiO ₂ , and argon gas and oxygen gas (argon gas) /
(Oxygen gas) was introduced such that the volume ratio thereof became 2.0.
The sputtering conditions were as follows: the degree of vacuum in the chamber was 3 ×
10 ^-4 Pa, output 50W, RF frequency 13.56M
Hz and the cathode applied voltage was 400 V.

Subsequently, on the TiO ₂ film, an 8-hydroxyquinoline Al complex (Alq complex) as an organic compound having an electron transporting property was formed as an organic light emitting layer by resistance heating to a thickness of 60 nm.
Deposited to a thickness of Then, an Al: Li alloy was formed on the organic light emitting layer as a counter electrode by resistance heating to a thickness of 200 mm.
Deposited to a thickness of nm. In Example 1, the organic EL element of Example 1 was obtained by using the counter electrode as a cathode.

[Embodiment 2] In the organic EL device of Embodiment 2, the semiconductor thin film of the organic EL device of Embodiment 1 is ZnS.
This is an e-film. Note that ZnSe is yellowish and transparent, and has hole conductivity. That is,
In the second embodiment, ZnSe which is selenide is used as a material of the semiconductor thin film in the first embodiment, and a two-layer semiconductor thin film constituting a transparent electrode is formed by an evaporation method.
Specifically, ZnSe is vapor-deposited on a substrate, and the ZnSe
Ag was sputtered on the film, and ZnSe was deposited again on the Ag film. At this time, the thickness of each layer constituting the transparent electrode was 30 nm, 10 nm, and 20 nm in the order of ZnSe / Ag / ZnSe from the substrate side.

[Embodiment 3] In this embodiment 3, an oxide In-Zn film as the semiconductor thin film of the embodiment 1 is used.
An organic EL device was obtained in the same manner as in Example 1 except that the -Mg-O film was used. Note that In-Zn-Mg-O
Is a transparent material having hole conductivity. That is,
Sputtering In-Zn-Mg-O on the substrate,
An Ag film (metal thin film) was formed on this film, and In-Zn-Mg-O was again sputtered on the Ag film to form a transparent electrode. At the time of sputtering, the atomic ratio of In to Zn, In, and Mg was set in the range of 0.57 to 0.60. In addition, In, Zn
And the atomic ratio of Mg to Mg is 0.1 to 0.23.
Within the range. Other sputtering conditions are the same as in the first embodiment.

[Embodiment 4] In the present embodiment 4, an oxide of In-Zn as the semiconductor thin film of the embodiment 1 is used.
An organic EL device was obtained in the same manner as in Example 1 except that the -Yb-O film was used. Note that In-Zn-Yb-O
Is a transparent material having hole conductivity. That is,
In the first embodiment, In-Zn-Yb-O
Is sputtered to form an Ag film (metal thin film) on this film.
Was formed, and In-Zn-Yb-O was again sputtered on the Ag film to form two semiconductor thin films constituting the transparent electrode. At the time of sputtering, the atomic ratio of In to In, Zn, and Yb was in the range of 0.57 to 0.60. Also, I
The atomic ratio of Yb to n, Zn and Yb is 0.1 to
The range was 0.23. Other sputtering conditions are the same as in the first embodiment.

Fifth Embodiment In the fifth embodiment, an insulator thin film is employed in place of the two-layer semiconductor thin film in the first embodiment, and these insulator thin films are made of MgF ₂ which is a fluoride.
Was formed in the same manner as in Example 1 except that a film was formed by sputtering, and the counter electrode was made of Au. That is, in the first embodiment, MgF ₂ was sputtered on the substrate, an Ag film (metal thin film) was formed on the film, and Mg was again formed on the Ag film.
By sputtering gF ₂ , two layers of insulating thin films constituting the transparent electrode were formed. The thickness of each layer constituting the transparent electrode is MgF ₂ / Ag /
The order of MgF ₂ was 50 nm, 10 nm, and 5 nm.
Subsequently, after forming an organic light emitting layer (Alq film) on the MgF ₂ film, Au was deposited on this organic light emitting layer to form an anode.

[Embodiment 6] In the present embodiment 6, in the above-mentioned embodiment 5, the two-layered insulator thin film is made of Li
Example 5 except that the film was formed by evaporating F.
In the same manner as in the above, an organic EL device was obtained.

[Evaluation of Organic EL Element] Examples 1-4
Were evaluated for the band gap energy, specific resistance, crystal state, luminous efficiency and half-life of the device. Examples 5 and 6
For the organic EL device obtained in (1), the band gap energy of the insulating thin film, the luminous efficiency and the half life of the device were evaluated. Table 1 shows the results.

The band gap energy was measured in Examples 1 to 4 in the transmission spectrum of the oxide or selenide forming the semiconductor thin film, and in Examples 5 and 6, the transmission of the fluoride in the insulating thin film was measured. Each spectrum was measured, and the energy corresponding to the wavelength at the absorption edge of each spectrum was obtained. The crystal state of the semiconductor thin film was observed using X-ray diffraction, electron diffraction, and SEM (electron microscope). Luminous efficiency and half-life were measured by applying a voltage of 7.5 V to the organic EL element and driving the organic EL element at a constant voltage. Here, the half-life refers to the time required for the luminance to reach half the initial luminance. When the organic EL element of Example 1 was driven at a voltage of 6 V, the initial luminance was 1
00 cd / m ² , and the luminous efficiency was 0.90 lm / W.

[0053]

[Table 1]

According to Table 1, in each of the organic EL devices of Examples 1 to 6, the semiconductor thin film or the insulator thin film constituting the transparent electrode is made of a material having a carrier concentration of less than 10 ²⁰ cm ⁻³ , and has a band gap energy, that is, energy. The gap is 2.
Since it is 7 eV or more, it is understood that a device with a long life and high efficiency can be obtained.

[0055]

As described above, according to the present invention,
In an organic EL element in which an organic material layer including an organic light emitting layer is sandwiched between a transparent electrode and a counter electrode, a transparent electrode is formed by a laminate of a metal thin film and at least one of a semiconductor thin film and an insulator thin film. Therefore, the sheet resistance of the entire transparent electrode can be reduced by the highly conductive metal thin film, so that an increase in power consumption due to a voltage drop and a decrease in display performance can be suppressed. Further, since the semiconductor thin film or the insulator thin film is arranged adjacent to the organic material layer, the metal thin film and the organic light emitting layer can be separated from each other, so that quenching in the organic light emitting layer can be prevented. The semiconductor thin film and the insulator thin film have a carrier concentration of 10 ²⁰ cm.
^{Since the} energy gap is set to less than ⁻³ and the energy gap is set to 2.7 eV or more, high luminous efficiency can be secured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Organic EL element 2 Substrate 10 Transparent electrode 20 Counter electrode 30 Organic layer

Claims (10)

[Claims] 1. An organic light emitting device comprising: a transparent electrode; a counter electrode facing the transparent electrode; and an organic material layer sandwiched between the transparent electrode and the counter electrode, wherein the organic material layer contains an organic light emitting material. An organic electroluminescence device comprising a layer, wherein the transparent electrode comprises a laminate of a metal thin film and at least one of a semiconductor thin film and an insulator thin film, and the semiconductor thin film and the insulator thin film Means that the carrier concentration is 1
An organic electroluminescent device having an energy gap of less than 0 ²⁰ cm ^-3 and an energy gap of 2.7 eV or more, wherein one of the semiconductor thin film and the insulator thin film is adjacent to the organic material layer. 2. The organic electroluminescence device according to claim 1, wherein the transparent electrode has a sheet resistance of 0.5Ω / □ to 10Ω / □.
An organic electroluminescence device characterized by the following range. 3. The organic electroluminescence device according to claim 1, wherein the thickness of the metal thin film is in a range of 0.5 to 30 nm. 4. The organic electroluminescence device according to claim 3, wherein the thickness of the metal thin film is in a range of 1 to 9 nm. 5. The organic electroluminescent device according to claim 1, wherein the metal thin film is any one selected from Ag, Pd, Au, Cu, Pt and an alloy containing these. An organic electroluminescent device, comprising: 6. The organic electroluminescence device according to claim 1, wherein the semiconductor thin film and the insulator thin film are any of an oxide, an oxynitride, a sulfide, and a selenide. An organic electroluminescence device characterized by comprising: 7. The organic electroluminescence device according to claim 6, wherein the semiconductor thin film is made of any one of an oxide, a sulfide, and a selenide, and includes Ti, In, Sn, and M.
An organic electroluminescent device containing any one selected from g, Zn, Al and Ga. 8. The organic electroluminescence device according to claim 6, wherein the insulator thin film is made of Mg, Ca, Ba, Sr, Li, or N.
An organic electroluminescent device comprising an oxide containing any one selected from a, K and Rb. 9. The organic electroluminescence device according to claim 1, wherein the transparent electrode is a semiconductor thin film / metal thin film / semiconductor thin film, an insulator thin film / metal from the organic material layer side. Thin film / insulator thin film, semiconductor thin film / metal thin film / insulator thin film, insulator thin film /
An organic electroluminescence device comprising a laminate laminated in any order of a metal thin film / semiconductor thin film. 10. The organic electroluminescence device according to claim 1, wherein a thickness of said insulator thin film is in a range of 0.1 to 30 nm. Organic electroluminescent element.