WO2003105539A1

WO2003105539A1 - Organic el light-emitting device and its manufacturing method

Info

Publication number: WO2003105539A1
Application number: PCT/JP2003/007065
Authority: WO
Inventors: 鈴木　健
Original assignee: 富士電機株式会社
Priority date: 2002-06-06
Filing date: 2003-06-04
Publication date: 2003-12-18
Also published as: AU2003242023A1; TW200401585A; JP2005346925A

Abstract

An organic EL light-emitting device having an anode, an organic luminance layer, and a cathode. An inorganic layer made of group-III oxide In_(1-x-y)Ga_xAl_yN is formed between the anode and the organic luminance layer, or an anode made of the group-III oxide is used. Thus an organic EL light-emitting device having an excellent hole injection characteristic, driven on a low drive voltage, and emitting light at high efficiency is provided.

Description

Description Organic EL light emitting device and method for manufacturing the same

The present invention relates to an organic EL (Electro-Metal Luminescence) light emitting device and a method for producing the same. Background art

Organic EL light-emitting elements inject holes from the anode, inject electrons from the cathode, and excite organic dyes using the energy at which these carriers recombine in the light-emitting layer to generate excitons. This is based on the principle that the light emitted when this exciton falls to the ground level is taken out.

In this technique, the recombination of holes and electrons is performed exclusively in the light-emitting layer, thereby increasing the number of excitons generated per injected carrier and improving the luminous efficiency of the organic EL light-emitting device. Attempts have been made. To address this problem, for example, Patent Document 1 described below discloses that inorganic charge barrier layers are provided on both sides of a light emitting layer. That is, the first inorganic charge barrier layer disposed on the anode side of the light-emitting layer is formed of a material that transmits holes but blocks electrons, while the second inorganic charge barrier layer disposed on the cathode side of the light-emitting layer is It is formed of a material that allows electrons to pass but blocks holes. Using these inorganic charge barrier layers, holes and electrons are retained in the light emitting layer and recombined to generate excitons. In addition, Patent Document 2 described below discloses that an inorganic hole transport layer that allows holes to pass but does not allow electrons to pass is provided on the positive electrode side of the light emitting layer. '' In addition, in order to improve the efficiency of the OLED device, And carrier injection from the cathode) is also important. Related references disclose the provision of an organic carrier (hole or electron) injection layer in contact with the anode or cathode to facilitate carrier injection into the light emitting layer. However, there is no disclosure or suggestion of using an inorganic layer for carrier injection from the electrode to the light emitting layer.

Facilitating carrier injection from the electrodes (anode and cathode) is an important factor in lowering the device drive voltage. The invention is particularly concerned with hole injection.

In order to efficiently inject holes into an organic film, two main conditions must be satisfied. One is that the energy barrier between the organic film and the anode is small, that is, the work function of the anode material is sufficiently large. Second, the carrier density of the material forming the anode is high.

Currently, the main materials used in the anode is a transparent electrode doped with Sn or Zn to I n ₂ 0 _3. A work function of about 5 eV is obtained by oxidizing this surface, but the work function of the organic film is often about 5.5 eV, and there is still an injection barrier of about 0.5 eV. Therefore, it cannot be said that it shows sufficient performance.

Assuming that the energy barrier between the organic film and the anode is constant, the higher the carrier's density of states, the easier the carrier injection. However, the state density of a conventional organic film is about 10 ¹⁸ Zcm ^3, which is considerably lower than the carrier density of metal. Therefore, in order to drive the organic EL light emitting device at a low voltage, it is necessary to compensate for the small state density of the organic film and to make the injection of the carrier easier.

[Patent Document 1]

JP 2000-315581 A [Patent Document 2]

JP 2000-268970A DISCLOSURE OF THE INVENTION

In order to solve the above problems, an organic EL light emitting device according to a first aspect of the present invention is an organic EL light emitting device including an anode, an organic light emitting layer, and a cathode, wherein the anode and the organic Inorganic having a composition of In ₍₁ - _xy ) Ga _x Al _y N (0≤χ≤ 1 and 0≤y ^ 0.5 and 0≤1—x—y≤l) between the light emitting layer It is characterized by providing a film layer.

Further, the organic EL light-emitting device according to a second aspect of the present invention comprises an anode, an organic light-emitting layer in the organic EL light-emitting device comprising a cathode, the _{_{anode, I nu- y) Ga x A}} l y It is characterized by having a composition of N (0≤x≤l and 0 y≤0.5 and 0≤1—xy≤1).

Furthermore, the manufacturing method of the third organic EL light-emitting device of an embodiment of the present invention include Injiumu the steps of providing an anode comprising Gariumu or aluminum, by nitriding the surface of the anode, I n ₍₁ _ forming an inorganic layer having a composition of _{_{_{x _ y) G a X a}}} 1 y N (0≤x≤ l and 0≤y ^ 0. 5 and 0≤ 1- x- y ^ l), the Laminating an organic light emitting layer and a cathode on the inorganic film layer. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic sectional view of an organic EL light emitting device according to a first embodiment of the present invention.

FIG. 2 is a graph showing current-voltage characteristics of the organic EL light emitting devices of Example 1 and Comparative Example 1.

FIG. 3 shows the voltages of the organic EL light emitting devices of Example 2, Example 3, and Comparative Example 1. It is a graph which shows a flowing voltage characteristic.

FIG. 4 is a graph showing current-voltage characteristics of the organic EL light emitting devices of Example 4 and Comparative Example 1. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a sectional view showing an organic EL light emitting device according to a first embodiment of the present invention. The organic EL light emitting device of the present invention has a structure in which an anode 2, an inorganic film layer 4, an organic light emitting layer 6, and a cathode 8 are laminated.

The organic EL light emitting device of the present invention is usually formed on a substrate. The position of the substrate depends on the design and may be in contact with anode 2 or in contact with cathode 8. If a structure in which light emitted from the organic light emitting layer 6 is extracted through a substrate is adopted, the substrate should have high transparency in the wavelength range of the emitted light. If the luminescence is extracted to the opposite side of the substrate, the substrate need not be transparent. As the substrate, a material such as glass, plastic (eg, polymethyl methacrylate, polyester, polyolefin), silicon, or the like can be used.

The anode 2 is made of a material having a large work function in order to efficiently inject holes. Suitable materials for the anode 2 include conductive metal oxides such as ITO, Ι Ι, and the like. Since these conductive metal oxides are transparent in the visible light region, they are suitable for extracting light emitted from the organic light emitting layer 6 from the anode side. When light emission of the organic light emitting layer 6 is extracted from the cathode side, the anode need not be transparent.

The anode of the present invention can be formed by a conventional method such as a sputtering method, an evaporation method, and a CVD method.

In the present invention, the inorganic layer 4 provided between the anode 2 and the organic light emitting layer 6, I n - form a group III nitride having a _{_{_{(1 x _ y) G a}}} x A 1 y N having the composition Is done. Here, x and y satisfy the conditions of .0≤χ ^ 1, 0≤y≤0.5, and 0≤1 -xy≤1. It is more preferable to satisfy the following conditions: 0≤x≤0.8, 0≤y≤0.2, and 0≤1—x—y≤1. Further, the group III oxide used as the inorganic film layer 4 is preferably in an amorphous state.

A group III nitride having an appropriate composition as described above exhibits a work function of about 5.6 eV which is larger than ITO or IZO. This work function is almost equal to the work function of the organic layer. Accordingly, there is no potential barrier between the inorganic film layer 4 and the organic light emitting layer 6, and holes can be smoothly injected into the organic light emitting layer 6. When a Group III oxide is used in the present invention, its work function is preferably in the range of 5 to 5.6 eV.

On the other hand, a potential barrier exists between the anode 2 formed from ITO or IZO and the inorganic film layer 4. However, the group III nitride used as the inorganic film layer in the present invention has a very large carrier density as compared with the material of the organic light emitting layer. Specifically, while the state density of the organic light emitting layer material is about 10 ¹⁸ / cm ³ , the group III nitride of the present invention has a large carrier density of about 10 ¹⁹ to 10 ²² cm ^3. It has. Therefore, when the same electric field is used, it is considered that a carrier of 10 to 10,000 times that of the conventional anode-organic light emitting layer can flow between the anode and the inorganic film layer of the present invention. It is considered that sufficient carrier flow is possible even when a weaker electric field is used.

As described above, in the configuration of the present invention, carriers (holes) can be easily moved between the anode and the inorganic film and between the inorganic film and the organic light emitting layer. As a result, driving at a low voltage becomes possible, and an organic EL light emitting element with low power consumption can be provided. The inorganic film layer of the present invention has a thickness of i to i 0 nm, preferably l to 5 nm. Have. By having a film thickness in this range, the above effect is realized, and efficient hole injection can be performed.

Furthermore, III-nitride that forms the inorganic layer of the present invention, as described above, preferably ^{^{1 0 19 ~ 1 0 22 /}} cm with a Kiyari § density of ^{^{1 0 21 ~ 1 0 22 /}} cm 3. Having such a large state density is important to facilitate the movement of holes between the anode and the inorganic film layer. Note that the carrier density can be measured by a van der Bow method after a thick film is formed.

Further, although the physical properties are correlated with the carrier density, the inorganic film layer of the present invention has a resistivity of 0.05 to 0.5 Ωcm, preferably 0.05 to 0.1 Ωcm. It has.

The inorganic film layer of the present invention can be formed by a conventional method such as a sputtering method, an evaporation method, and a CVD method. In these methods, nitrogen may be supplied as a single gas, ammonia radical, or plasma. However, it is preferably formed by nitriding the surface of an anode containing indium, gallium or aluminum having an appropriate composition. The nitriding of the anode surface can be performed by treating the anode surface with nitrogen plasma.

In the organic EL light emitting device of the present invention, the organic light emitting layer 6 includes at least an organic EL light emitting layer, and has a structure in which a hole injection layer, a hole transport layer, and a Z or electron injection layer are interposed as necessary. Have. Specifically, a layer having the following layer configuration is employed.

(1) Organic EL light-emitting layer

(2) Hole injection layer Organic EL emission layer

(3) Organic EL light emitting layer Z electron injection layer

(4) Hole injection layer / organic EL light emitting layer / electron injection layer 0307065

(5) Hole injection layer No hole transport layer / organic EL light emitting layer Electron injection layer

(6) Hole transport layer Z organic EL light emitting layer

(7) Hole transport layer / organic EL light emitting layer / "electron injection layer

(In the above, the inorganic film layer is connected to the left side, and the cathode is connected to the right side.) As a material of each of the above layers, a known material is used. For example, in an organic EL light emitting layer for obtaining blue to blue-green light emission, for example, a fluorescent brightener such as benzothiazole, benzimidazole, benzoxazole, etc., a metal chelated oxonium compound, and a styryl Benzene compounds, aromatic dimethylidin compounds and the like are preferably used.

In the present invention, it is preferable that the inorganic film layer 4 and the organic EL light emitting layer are not in direct contact with each other, and the hole injection layer and the hole or hole transport layer are interposed therebetween. This is because the inorganic film layer 4 of the present invention has a high carrier density, and may extinguish excitons generated in the organic EL light emitting layer. In order to prevent this, it is preferable to provide a hole injection layer and / or a hole transport layer having a thickness of 20 nm or more, preferably 20 to 100 nm.

The above-mentioned organic light emitting layer or each layer constituting the organic light emitting layer can be formed by a conventional method such as an evaporation method.

The cathode 8 is made of a material having a small work function, such as an alkali metal such as lithium and sodium, an alkaline earth metal such as potassium, calcium, magnesium, and stainless steel, or a fluoride thereof. Electron-injecting metals and alloys and compounds with other metals are used. The cathode made of such a material having a small work function can be laminated on a conductive metal (not shown) provided on the surface of the cathode opposite to the organic light emitting layer. Al, Ag, Mo, W, and the like can be used as the conductive metal. This conductive metal functions as an auxiliary electrode and reduces the resistance of the entire cathode. Can be lowered.

In addition, when light emission of the organic light emitting layer 6 is extracted from the cathode side, the cathode is required to have high transparency in a wavelength region of the light emission. In this case, it is possible to adopt a structure in which a material having a small work function is made extremely thin (less than 10 nm) and a transparent conductive oxide such as ITO or IΖΟ is laminated thereon. . This structure enables efficient electron injection by using these materials having a small work function, and further minimizes the decrease in transparency due to these materials by using an extremely thin film.

The cathode of the present invention can be formed by a conventional method such as a sputtering method, an evaporation method, and a CVD method.

A second embodiment of the present invention is an organic EL light-emitting device including at least an anode formed from the above-described Group III oxide, an organic light-emitting layer, and a cathode.

In this embodiment, the organic light emitting layer and the cathode have the same materials and configurations as those described in the first embodiment.

Group III oxide I n as the anode case of using _{_{_{(1 - - x y) G}}} a Χ Α 1 y N, x and y, 0≤χ≤ 1, 0≤ y≤ 0. 5 , and 0≤ 1- x—y≤l. It is more preferable to satisfy the following conditions: 0≤x≤0.8, 0≤y≤0.2, and 0≤1—X—y≤l.

The anode of the present embodiment can be formed by a conventional method such as a sputtering method, an evaporation method, and a CVD method. In these methods, nitrogen may be supplied as a single gas, ammonia radical, or plasma.

Next, examples of the present invention will be described below.

(Example 1)

Amorphous on a glass substrate I n ₂ 0 _3: Z N_〇 (molar ratio 5% Z n 0) Were laminated by a sputtering method to form a transparent electrode having a thickness of 200 nm, which was used as an anode. An anode pattern was formed on the transparent electrode by using an ordinary photo process using a mask capable of obtaining a stripe pattern having a width of 2 mm and an interval of 0.5 mm. Thereafter, the surface was cleaned using oxygen plasma at room temperature.

Next, the surface of the transparent electrode was nitrided by treatment with nitrogen plasma at room temperature to form an ultra-thin InN thin film (about 0.5 nm thick). The work function of this ultra thin InNN film was 5.6 eV.

Then, an organic light emitting layer was formed on the InN ultrathin film. As the organic light emitting layer, a four-layer structure of an inorganic film layer, a no-hole transport layer / a light emitting layer, and a Z electron injection layer was used, and these were sequentially formed. 100 nm thick copper phthalocyanine (CuPC) as an inorganic film layer, and 20 nm thick 4,4'-bis [N-1 (1-naphthyl) -1N-phenylamino] biphene as a hole transport layer. (A—NPD), 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVB i) with a thickness of 30 nm as the light emitting layer, and aluminum oxide with a thickness of 2 O nm as the electron injection layer. Squirrel (8-quinolinolate) (A1q) was used. After the formation of the organic light-emitting layer, a 0.5-nm thick LiF and a 0.5 mm-thick resistive heating method were used to obtain a stripe pattern with a width of 2 mm perpendicular to the anode stripe turn and a spacing of 0.5 mm. A1 of 200 nm was sequentially laminated to form a cathode, and an organic EL device was obtained.

In this example, since an ultra-thin InN was produced by nitriding the surface of the transparent electrode, the electrical characteristics of the InN alone could not be measured. Separately, an amorphous InN film (100 nm thick) with the same composition was prepared, and its resistivity and carrier density were measured. It was 7 × 10 ²¹ / cm ³ .

(Comparative Example 1) T / JP03 / 07065

Ten

An organic EL light emitting device was obtained in the same manner as in Example 1, except that an InN ultrathin film was not formed.

FIG. 2 is a graph comparing the current-voltage characteristics of the organic EL light emitting devices of Example 1 and Comparative Example 1. The organic EL element of Example 1, (the voltage current starts of 10- ⁶ A flows) injection voltage than that of Comparative Example 1 is decreased by about 0. 3V. It also shows better injection properties in the high voltage region.

(Example 2)

Instead of the _{I nN I n 0. 2 G a} . . ₈ N ultrathin film (thickness 1 nm), except that was formed by sputtering, to produce an organic EL device in the same manner as in Example 1. The sputtering method was carried out at room temperature by supplying ordinary effusion cells for In and Ga and supplying nitrogen as radicals. I n ₀ formed. ₂ Ga _0. ₈ N ultrathin work function was 5. 6 e V. The I n electrical characteristics of 0. ₂ G a 0. ₈ N used in this example was measured separately prepared thick film having a thickness of 100 nm. As a result, the resistivity was 0.08 Ω · cm, and the carrier density was between ³ × 10 ²² and 1 × 1◦ ²¹ / cm ³ .

(Example 3)

I n _0. ₂ G a. , I n ₀ instead of _{_{_{8 N. G a 0. 8}}} A 1. An organic EL device was fabricated in the same manner as in Example 2, except that an ultra-thin film (thickness: 1 nm) was formed by sputtering. I n ₀ formed. A _0. ₈ A 10. The work function of ultra thin film was 5. l eV.

The I n _0. Electrical properties of a 0. ₈ A 10. used in this example was measured separately prepared thick film having a thickness of 10 0 nm. As a result, the resistivity was 0.09 Ω · cm, and the carrier density was between ³ × 10 ^{22 and} 1 × 10 ²¹ Zcm ³ .

FIG. 3 shows the voltages of the organic EL light emitting devices of Example 2, Example 3, and Comparative Example 1. It is the graph which compared the flowing voltage characteristic. The injection start voltage of the organic EL light emitting devices of Examples 2 and 3 is lower than that of Comparative Example 1 by about 0.5 V. It also shows better injection properties in the high voltage region.

(Example 4)

Polycrystalline on the glass substrate G a 0. ₈ A 1 o. A ₂ N was stacked by sputtering, to form a transparent electrode having a thickness of 200 nm, and an anode. An anode pattern was formed on the transparent electrode by using an ordinary photo process using a mask capable of obtaining a stripe pattern having a width of 2 mm and an interval of 0.5 mm. The surface was then cleaned using oxygen plasma at room temperature. Next, a treatment with nitrogen plasma was performed at 300 ° C. Then, an organic light emitting layer and a cathode were formed thereon in the same manner as in Example 1 to obtain an organic EL light emitting device.

FIG. 4 is a graph comparing the current-voltage characteristics of the organic EL light emitting devices of Example 4 and Comparative Example 1. The injection start voltage of the organic EL light emitting device of Example 4 is lower than that of Comparative Example 1 by about 0.3 V. It also shows better injection properties in the high voltage region. Industrial applicability

INDUSTRIAL APPLICATION This invention can be utilized for an organic EL light emitting element and its manufacturing method.

According to the present invention, as described above, an anode and an organic light emitting layer in the organic EL light-emitting device comprising a cathode, III between the anode and the organic emission layer Zokusan compound I n ₍₁ - _x _ _y) provided G a _x a 1 inorganic layer formed from _y N, by some have to use a positive electrode which is formed from the group III oxide, very superior holes injection property (injection voltage and It is possible to provide an organic EL light-emitting element that is excellent in current amount in a high-voltage region). The organic EL light-emitting device of the present invention includes PDA, mobile phone, notebook PC, etc., which require a low voltage. It can be used for a wide range of applications.

Claims

The scope of the claims

1. an anode, an organic light-emitting layer in the organic EL light-emitting device comprising a cathode, between the anode and the organic emission _{layer, I n (! _ X _} y) Ga x A 1 y N (0 An organic EL light emitting device comprising an inorganic film layer having a composition of ≤ x ≤ l and 0 ≤ y ≤ 0.5 and 0 ≤ 1-x-y ≤ 1).

2. An organic EL light-emitting device comprising an anode, an organic light-emitting layer, and a cathode, wherein the anode is composed of I n ₍₁ — _x — _y) G a _X A 1 _y N (0≤x≤1 and 0≤ An organic EL light-emitting device having a composition of y0.5 and 0≤l-x-y ^ l).

3. indium, and as E to produce an anode containing gallium or aluminum, by nitriding the surface of the _{_{anode, I n u- x - y)}} G a x A 1 y N (0≤ x≤ 1 and Forming an inorganic film layer having a composition of 0 ≤ y 0.5 and 0 1 _ x-y ≤ 1); and laminating an organic light emitting layer and a cathode on the inorganic film layer. Characteristic method of manufacturing organic EL light emitting device.