KR20000067671A - Organic electroluminescent device - Google Patents

Abstract

PURPOSE: An organic electroluminescent device is provided to increase a luminescence efficiency and a lifetime, by inserting a mixture layer between an organic stack layer and an electrode. CONSTITUTION: In an organic electroluminescent device having a first electrode(22), a second electrode(24) and a plurality of organic stack layers(23), a mixture layer(26) in which an organic compound and an organic metal material are simultaneously evaporated is formed between the organic stack layer and the electrode. The organic compound has an electron transporting capability.

Description

Organic EL device

TECHNICAL FIELD The present invention relates to display elements, and more particularly to organic EL elements.

Recently, as the size of the display device increases, the demand for a flat display device having less space occupancy is increasing. As one of the flat display devices, an electroluminescent device is attracting attention.

This electroluminescent element is largely divided into inorganic electroluminescent element and organic EL element according to the material used.

In general, an inorganic electroluminescent device is a device that emits light by applying a high electric field to a light emitting part, accelerating electrons in the high electric field, and colliding with the light emitting center to thereby excite the light emitting center.

In addition, the organic EL device has an exciton generated by combining electrons and holes injected by injecting electrons and holes into a light emitting part from an electron injection electrode and a hole injection electrode, respectively, from an excited state to a ground state. It is a device that emits light when falling.

The inorganic electroluminescent device having the above operating principle requires a high voltage of 100 to 200 V as a driving voltage because a high electric field is required, while an organic EL device can be driven at a low voltage of about 5 to 20 V. Because of this, research is being actively conducted.

In addition, the organic EL element has excellent characteristics such as wide viewing angle, high speed response and high contrast, so it can be used as a pixel of a graphic display, a pixel of a television image display or a surface light source. It is thin, light, and has good color, making it suitable for next-generation flat panel displays.

Looking at the structure of the organic EL device having such a purpose, as shown in Figure 1, the first electrode 2 formed on the transparent substrate 1, and the hole injection layer (HIL) formed on the first electrode (2) : hole injecting layer (3) and hole transport layer (HTL) (4), light emitting layer (5) formed on the hole transport layer (4), and electron transport layer (ETL: electron) formed on the light emitting layer (5) A transport layer (6) and an electron injecting layer (EIL) 7 and a second electrode 8 formed on the electron injection layer 7.

Here, one or more of the hole injection layer 3, the hole transport layer 4, the electron transport layer 6, the electron injection layer 7 may be omitted.

The second electrode 8 of the organic EL device thus formed injects electrons into the light emitting layer 5 through the electron transport layer 6 or the electron injection layer 7, and the first electrode 2 is a hole injection layer ( 3) Alternatively, by injecting holes into the light emitting layer 5 through the hole transport layer 4, light is emitted by emitting energy as electron-holes are paired in the light emitting layer 5 and then disappear.

In most organic EL devices, electron injection is much more difficult than hole injection. In general, the smaller the work function of the second electrode, the easier the electron injection.

However, in general, materials having a small work function are difficult to use as electrodes because of their high reactivity.

Therefore, one or more stable metals such as Mg: Ag and Al: Li are often used in the form of alloys and used as the second electrode.

However, these alloys are less stable than aluminum and are expensive to manufacture and difficult to deposit uniformly.

When using materials with low work functions such as Mg: Ag or Al: Li as electrodes, a more serious problem is that Mg ions or Li ions diffuse into the organic film, causing cross-talk or leakage between pixels. The current often occurs.

However, the above problems can be alleviated by using the second electrode material as aluminum, but aluminum has a poor electron injecting capability, and a method of improving the problem is needed.

Therefore, in recent years, in order to improve the electron injection ability, an insulating material such as LiF, MgF ₂ , Li ₂ O between an aluminum electrode and a light emitting layer or between an aluminum electrode and an electron transport layer may be formed into a very thin (about 0.3 to 1.0 nm) ultra thin film. Examples have been reported. [IEEE Transactions on Electronic Devices, Vol. 44, No. 8, p 1245-1248 (1997)]

In this case, Li ₂ O is an insulator with a very low work function.

Alkaline metals are generally known to have a low work function and lower when oxidized.

For example, the work function of Cs is 2.1 eV, but the work function of Cs ₂ O decreases to about 1 eV.

In order to lower the electron injection barrier, various alkali metal compounds such as Li ₂ O, LiBO ₂ , NaCl, KCl, K ₂ SiO ₃ , RbCl, and Cs ₂ O have been used in the form of an insulating buffer layer.

However, despite the above improvement, the introduction of the insulating buffer layer has revealed new problems.

That is, the adhesion between the organic laminated film and aluminum was not good, and the lifetime of the device was reduced.

As a result, the adhesion between the buffer layer and the aluminum and the interface between the buffer layer and the organic layer was poor due to the difference between the materials.

SUMMARY OF THE INVENTION The present invention has been made to improve the above-mentioned conventional problems, and an object of the present invention is to insert a mixed layer of co-deposited organic compounds and organometallic materials between an organic laminate film and a second electrode, thereby emitting light emission efficiency and lifetime. It is to provide an organic EL device that can greatly increase the.

1 is a structural cross-sectional view showing a general organic EL device,

2 is a structural cross-sectional view showing an organic EL device according to the present invention.

<Explanation of symbols for main parts of drawing>

21 transparent substrate 22 first electrode

23 organic laminated film 24 second electrode

25: protective film 26: mixed layer

27: electron injection layer

In order to achieve the above object, the present invention provides an organic EL device comprising a first electrode, a second electrode and a plurality of organic laminated films, wherein an organic compound and an organic metal material are co-exposed between the organic laminated film and the second electrode. An organic EL device is characterized in that a deposited mixed layer is formed.

The organic compound is a compound having electron transport ability, preferably Alq ₃ .

In addition, the organometallic material is characterized by consisting of one or a plurality of materials of metal porphyrin (metalloporphyrine) derivatives.

The metal porphyrin derivative may have a structure of Structural Formula 1 below.

Structural Formula 1

Wherein A is -N = or -C (R) =, wherein R is a material selected from the group consisting of hydrogen, alkyl, alkoxy, aralkyl, alkaryl, aryl and heterocyclic groups;

M is a substance selected from the group consisting of elements of groups IA, IIA, IIIA, IVA, 3, 4, 5 and 6 cycles of the periodic table;

Y is an alkoxy group, a phenoxyl group, an alkylamino group, an arylamino group, an alkylphosphine group, an arylphosphine group, an alkylsulfur group, or an arylsulfur group, or a substance selected from the group consisting of elements of the VIA and VIIA groups of the periodic table. A material selected from;

N is an integer of one of 0, 1, 2; And,

B ₁ to B ₈ are hydrogen, alkyl group, aryl group, alkoxy group, aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, alkylthiol group, arylthiol group, nitroalkyl group, alkylcarbonyl group , An alkoxycarbonyl group, a phenyl group, an amino group, a cyanyl group, a naphthyl group, an alkali group, a halogen group and a heterocyclic group, or the above-mentioned B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B ₆ And at least one of B ₇ and B ₈ are each interconnected to form an unsaturated or saturated pentagonal, hexagonal or hexagonal ring.

In the compound of Formula 1, preferably, _one or more of B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B _6, and B ₇ and B ₈ are each interconnected with an unsaturated or saturated pentagram, hexagon or The members of the hexagonal ring are selected from C, N, S and O. In addition, at least one of the B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B _6, and B ₇ and B ₈ , each of which is an unsaturated or saturated pentagonal, hexagonal or heptagonal ring is an alkyl group, an aryl group, or an alkoxy group. Group, aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, nitroalkyl group, alkylcarbonyl group, alkoxycarbonyl group, phenyl group, amino group, cyanyl group, naphthyl group, alkaryl group, halogen group and heterocyclic group It may include a material selected from the group consisting of.

M of the formula 1 is preferably 2Li, 2Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Pt, Cu, 2Ag, Zn, Pd, Al, Ga, In, Si , Sn, Pb, 2H and TiO.

Y in Structural Formula 1 is preferably a material selected from the group consisting of O, F, Cl, Br, an alkoxy group (C1-10) and a phenoxyl group.

As the metal porphyrin derivative used in the organic EL device according to the present invention, it is more preferable to use a substance having a structure of the following structural formula (2) or (3).

Structural Formula 2 Structural Formula 3

Wherein A is -N = or -C (R) =, wherein R is a substance selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, an aralkyl group, an alkaryl group, an aryl group and a heterocyclic group;

M is a substance selected from the group consisting of elements of groups IA, IIA, IIIA, IVA, 3, 4, 5 and 6 cycles of the periodic table;

Y is an alkoxy group, a phenoxyl group, an alkylamino group, an arylamino group, an alkylphosphine group, an arylphosphine group, an alkylsulfur group, or an arylsulfur group, or a substance selected from the group consisting of elements of the VIA and VIIA groups of the periodic table. A material selected from;

N is an integer of one of 0, 1, 2; And,

X ₁ to X ₈ are each hydrogen, alkyl group, aryl group, alkoxy group, aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, alkylthiol group, arylthiol group, nitroalkyl group, alkylcarbonyl group , Alkoxycarbonyl group, phenyl group, amino group, cyanyl group, naphthyl group, alkaryl group, halogen group and heterocyclic group.

M of the structural formulas 2 and 3 is preferably 2Li, 2Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Pt, Cu, 2Ag, Zn, Pd, Al, Ga, In , Si, Sn, Pb, 2H and TiO.

Y of the formulas 2 and 3 is preferably a material selected from the group consisting of O, F, Cl, Br, an alkoxy group (C10 to 10) and a phenoxyl group.

As the metal porphyrin derivative used in the organic EL device according to the present invention, most preferably, at least one of materials having the structures of the following structural formulas 4 and 5 may be used.

Structural Formula 4 Structural Formula 5

In this case, M is selected from the group consisting of Co, AlCl, Cu, 2Li, Fe, Pb, Mg, SiCl ₂ , 2Na, Sn, Zn, Ni, Mn, VO, 2Ag, MnCl, SnCl ₂ and TiO.

A further object of the present invention is to provide an organic EL device characterized in that an electron injection layer made of at least one of an alkali metal, an alkaline earth metal and a compound thereof is formed between the second electrode and the mixed layer.

The electron injection layer is Li ₂ O, Li ₂ O ₂ , Rb ₂ O, Cs ₂ O, Rb ₂ O ₂ , Cs ₂ O ₂ , LiAlO ₂ , LiBO ₂ , LiCl, RbCl, NaCl, KAlO ₂ , NaWO ₄ , It may be made of any one of K ₂ SiO ₃ , Li ₂ CO, BeO, MgO, CaO, SrO, BaO, RaO, Al: Li alloy, Mg: Sr alloy and In: Li alloy. The second electrode is preferably made of Al.

The mixing ratio of both materials in the mixed layer according to the invention can be fixed or varied as a function of position. That is, the concentration of the two materials may be configured to have a concentration gradient depending on the position of each material in the mixed layer. For example, the mixing ratio of the mixed layer using Alq ₃ as the organic compound and CuPc as the organic metal compound is as follows. That is, when the concentrations of Alq ₃ and CuPc are respectively expressed as x: y, x = 1 and y = 0 may be at the contact interface with the organic laminate, and the concentration of CuPc gradually increases toward the second electrode. In addition, the concentration of Alq ₃ gradually decreases, so that the concentration of each material may be x = 0 and y = 1 at the contact interface with the second electrode or the electron transport layer. At this time, the values of x and y are linearly changed between the two interfaces. The thickness of this mixed layer is preferably changed between 0.1 nm and 50 nm.

Hereinafter, an organic EL device having the above characteristics will be described with reference to the accompanying drawings.

2 is a structural cross-sectional view showing an organic EL device according to the present invention. As shown in FIG. 2, the organic EL device includes a transparent substrate 21, a first electrode 22, and an organic laminated film (hole injection layer, hole transport layer). And a light emitting layer) 23, a laminated structure having a second electrode 24, a protective film 25 formed on the laminated structure, and an organic laminated film 23 and a second electrode 24 having a laminated structure. In order to improve electron injection and adhesion between the layers, the mixed layer 26 and the electron injection layer 27 in which the organic compound and the organic metal material are co-deposited are formed.

Here, the materials used for the mixed layer 26 and the electron injection layer 27 are as described above.

As described above, in the present invention, the light emitting efficiency of the device is formed by stacking the mixed layer 26 made of the above material between the organic layer 23 and the second electrode 24 or between the organic layer 23 and the electron injection layer 27. Greatly improve the service life.

Here, the thicknesses of the mixed layer 26 and the electron injection layer 27 may be about 0.1 nm to 50 nm and about 5 μm to 10 μm, respectively.

Next, the manufacturing method of the organic electroluminescent element which concerns on this invention is explained in full detail. However, it is a matter of course that those skilled in the art can change the conditions such as materials, numerical values, and the like used in the following manufacturing method within the limits satisfying the objects and effects of the present invention.

(1) An indium tin oxide (ITO) thin film, which is a transparent electrode, is coated on the transparent substrate by about 140 nm as a first electrode.

(2) Copper phthalocyanine (CuPc) is vacuum deposited to a thickness of about 20 nm on the first electrode as a hole injection layer.

(3) 4,4'-bis [N- (1-naphthyl) -N-phenyl-amino] biphenyl (NPD) was vacuum deposited to a thickness of about 30 nm on the hole injection layer as a hole transport layer.

(4) Vacuum depositing the light emitting layer on the hole transport layer, in the case of the green light emitting layer, 8-hydroxyquinoline aluminum (Alq ₃ ) is vacuum deposited to a thickness of about 30nm.

(5) The organic compound and the organic metal material are co-deposited in an appropriate ratio on the light emitting layer to form a mixed layer of the organic compound and the organic metal material. The preferred thickness of the mixed layer can vary depending on the material, and is suitably between about 0.1 nm and 50 nm.

The types of organic compounds and organometallic materials that can be used are as described above, and the mixing ratio of both compounds in the mixed layer is also as mentioned above.

(6) At least one of an alkali metal, an alkaline earth metal, and a compound thereof is deposited on the mixed layer to a thickness of approximately 5 to 10 kV as an electron injection layer. Preferably, the electron injection layer is Li ₂ O, Li ₂ O, Rb ₂ O, Cs ₂ O, Rb ₂ O ₂ , Cs ₂ O ₂ , LiAlO ₂ , LiBO ₂ , LiCl, RbCl, NaCl, KAlO ₂ , It may be made of any one of NaWO ₄ , K ₂ SiO ₃ , Li ₂ CO, BeO, MgO, CaO, SrO, BaO, RaO, Al: Li alloy, Mg: Sr alloy, and In: Li alloy.

(7) Al is formed to a thickness of about 200 nm on the electron injection layer as a second electrode.

(8) Preferably, a conventional encapsulation can be performed in an inert gas after applying a protective film on the second electrode.

In the case of an electron injection layer such as Li ₂ O, not only the adhesion between Alq ₃ and Al is poor, but the Li ₂ O layer having a thickness of 1 nm is not a completely uniform layer but rather has an island-like structure.

However, a mixed layer in which an organic compound such as Alq ₃ and an organic metal material such as CuPc is co-deposited, as in the organic EL device according to the present invention, is used for interfacial adhesion between an electron injection layer such as Li ₂ O, and an organic metal such as CuPc. The material is in direct contact with the Al layer through the open space in the Li ₂ O layer.

This phenomenon increases the adhesion at the interface between the organic film and the metal and increases the life of the device.

That is, copper ions in CuPc included in the mixed layer bond relatively strongly between CuPc and Al.

The organic EL device according to the present invention has the following effects.

The organic EL device of the present invention including a mixed layer in which an organic compound and an organic metal material are co-deposited greatly increases not only the brightness but also the life of the device.

Claims (18)

In an organic EL device formed by including a first electrode, a second electrode and a plurality of organic laminated films, And a mixed layer in which an organic compound and an organometallic material are co-deposited are formed between the organic laminated film and the second electrode. An organic EL device according to claim 1, wherein the organic compound has an electron transport capability. The organic EL device according to claim 2, wherein the organic compound having electron transport capability is Alq ₃ . An organic EL device according to claim 1, wherein the organometallic material is composed of one or a plurality of materials of metalloporphyrine derivatives. The method of claim 4, wherein The metal porphyrin derivative is an organic EL device characterized in that it has a structure of the following formula 1: Structural Formula 1 A is -N = or -C (R) =, wherein R is a substance selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, an aralkyl group, an alkaryl group, an aryl group and a heterocyclic group; M is a substance selected from the group consisting of elements of groups IA, IIA, IIIA, IVA, 3, 4, 5 and 6 cycles of the periodic table; Y is an alkoxy group, a phenoxyl group, an alkylamino group, an arylamino group, an alkylphosphine group, an arylphosphine group, an alkylsulfur group, or an arylsulfur group, or a substance selected from the group consisting of elements of the VIA and VIIA groups of the periodic table. A material selected from; N is an integer of one of 0, 1, 2; And, B ₁ to B ₈ are hydrogen, alkyl group, aryl group, alkoxy group, aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, alkylthiol group, arylthiol group, nitroalkyl group, alkylcarbonyl group , An alkoxycarbonyl group, a phenyl group, an amino group, a cyanyl group, a naphthyl group, an alkali group, a halogen group and a heterocyclic group, or the above-mentioned B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B ₆ And at least one of B ₇ and B ₈ are each interconnected to form an unsaturated or saturated pentagonal, hexagonal or hexagonal ring. The method of claim 5, _One or more of B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B _6, and B ₇ and B ₈ are each interconnected with an unsaturated or saturated pentagonal, hexagonal or heptagonal ring of C, N, S and An organic EL device characterized in that the element is selected from O. The method of claim 6, _One or more of B ₁ and B ₂ , B ₃ and B ₄ , B ₅ and B _6, and B ₇ and B ₈ are each an unsaturated or saturated pentagonal, hexagonal or hexagonal ring interconnected by an alkyl group, an aryl group, an alkoxy group, Aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, nitroalkyl group, alkylcarbonyl group, alkoxycarbonyl group, phenyl group, amino group, cyanyl group, naphthyl group, alkaryl group, halogen group and heterocyclic group An organic EL device, characterized in that it comprises a material selected from. The method of claim 5, M in Structural Formula 1 is 2Li, 2Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Pt, Cu, 2Ag, Zn, Pd, Al, Ga, In, Si, Sn, Pb, An organic EL device, characterized in that the material is selected from the group consisting of 2H and TiO. The method of claim 5, Y in Structural Formula 1 is an organic EL device, characterized in that the material selected from the group consisting of O, F, Cl, Br, an alkoxy group (C1-10) and a phenoxyl group. The method of claim 5, The metal porphyrin derivative is an organic EL device, characterized in that consisting of a material having a structure of Formula 2 or Formula 3 below: Structural Formula 2 Structural Formula 3 A is -N = or -C (R) =, wherein R is a substance selected from the group consisting of hydrogen, an alkyl group, an alkoxy group, an aralkyl group, an alkaryl group, an aryl group and a heterocyclic group; M is a substance selected from the group consisting of elements of groups IA, IIA, IIIA, IVA, 3, 4, 5 and 6 cycles of the periodic table; Y is an alkoxy group, a phenoxyl group, an alkylamino group, an arylamino group, an alkylphosphine group, an arylphosphine group, an alkylsulfur group, or an arylsulfur group, or a substance selected from the group consisting of elements of the VIA and VIIA groups of the periodic table. A material selected from; N is an integer of one of 0, 1, 2; And, X ₁ to X ₈ are each hydrogen, alkyl group, aryl group, alkoxy group, aryloxyalkyl group, hydroxy group, hydroxyalkyl group, aralkyl group, alkylamino group, arylamino group, alkylthiol group, arylthiol group, nitroalkyl group, alkylcarbonyl group , Alkoxycarbonyl group, phenyl group, amino group, cyanyl group, naphthyl group, alkaryl group, halogen group and heterocyclic group. The method of claim 10, M in Structural Formulas 2 and 3 is 2Li, 2Na, Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Pt, Cu, 2Ag, Zn, Pd, Al, Ga, In, Si, Sn, An organic EL device characterized in that the material is selected from the group consisting of Pb, 2H and TiO. The method of claim 10, Y in the formulas 2 and 3 is an organic EL device, characterized in that the material selected from the group consisting of O, F, Cl, Br, an alkoxy group (1 to 10 carbon atoms) and phenoxyl group. The method of claim 10, The metal porphyrin derivative is an organic EL device, characterized in that at least one of the materials having the structures of formulas 4 and 5 below: Structural Formula 4 Structural Formula 5 M is selected from the group consisting of Co, AlCl, Cu, 2Li, Fe, Pb, Mg, SiCl ₂ , 2Na, Sn, Zn, Ni, Mn, VO, 2Ag, MnCl, SnCl ₂ and TiO. The method according to any one of claims 1 to 13, And an electron injection layer formed of at least one of an alkali metal, an alkaline earth metal and a compound thereof between the mixed layer and the second electrode. The method of claim 14, wherein the electron injection layer is Li ₂ O, Li ₂ O, Rb ₂ O, Cs ₂ O, Rb ₂ O ₂ , Cs ₂ O ₂ , LiAlO ₂ , LiBO ₂ , LiCl, RbCl, NaCl, KAlO ₂ , NaWO ₄ , K ₂ SiO ₃ , Li ₂ CO, BeO, MgO, CaO, SrO, BaO, RaO, Al: Li alloy, Mg: Sr alloy and In: Li alloy device. The organic EL device according to claim 14, wherein the second electrode is made of Al. The method of claim 14, The mixing ratio in the mixing layer is fixed or varied as a function of position. The organic EL device according to claim 14, wherein the mixed layer has a thickness of 0.1 nm to 50 nm.