TW200401585A - Organic EL light-emitting device and its manufacturing method - Google Patents

Abstract

The purpose of the present invention is to provide an organic EL light-emitting device having an excellent hole injection characteristic, driven on a low drive voltage, and emitting light at high efficiency. The present invention relates to an organic EL light-emitting device comprising an anode, an organic luminance layer, and a cathode, and using charge injection, which is characterized in that: an inorganic film layer made of In (1-x-y) GaxAlyN is formed between the anode and the organic luminance layer. (0 ≤ x ≤ 1 and 0 ≤ y ≤ 0.5 and 0 ≤ 1-x-y ≤ 1).

Description

200401585 (1) 发明 Description of the invention [Technical field to which the invention belongs] The present invention relates to an organic electroluminescent device and [prior art] The organic electroluminescent device belongs to the injection of electrons from the anode through the cathode through the anode, and is used to emit light. The principle that the energy re-knotted in the layer excites the organic dye to generate an exciton, and the principle that the light emission to the base level is taken out to the outside. In terms of this technology, the recombination of electrons in the exclusive light-emitting layer generates an excitation equivalent to the injected carrier, which significantly improves the luminous efficiency of the organic electro-optic light-emitting element. In response to Japanese Patent Laid-Open No. 2000-3 1 5 5 8 1, it is disclosed that an inorganic charge barrier layer is provided. That is, the inorganic charge barrier layer disposed in the light-emitting layer is formed by using a material that blocks the holes by passing electrons. On the one hand, the second electrode disposed on the cathode side of the light-emitting layer is formed by using materials that block the holes. The charge barrier layer keeps holes and electrons in the light-emitting layer and generates excitons. Furthermore, Japanese Patent Application Laid-Open No. 20 00-Kono revealed that an inorganic hole-transporting layer through holes was provided on the anode side of the light-emitting layer. In order to improve the efficiency of the organic electro-optical excitation element and the cathode), carrier injection is also important. The organic carriers (holes or electrons) which are in contact with the anode or the cathode are involved. Holes are inserted, and holes and hairs are increased when the excitons are dropped when these carriers are combined. For example, the organic charge barrier layer formed by the first material on the anode side on both sides of the light-emitting layer uses these inorganic materials to recombine it, but -268970 is not used, but it will not be injected into the layer through the electrode (in the anode test literature). And (2) (2) 200401585 promotes carrier injection for the light emitting layer. However, the case of using the inorganic substance layer for the carrier injection of the light emitting layer by the electrode is not disclosed or revealed. [Summary of the Invention] [Questions Solved by the Invention ] It is easy to inject carriers from the electrodes (anode and cathode), and it is an important factor to reduce the driving voltage of the device. The present invention is particularly related to the injection of holes. In order to efficiently inject holes into an organic film, two items must be mainly satisfied Conditions. First, the energy barrier between the organic film and the anode must be small, that is, the working function of the anode material must be very large. The other is that the carrier density of the material forming the anode must be The main material currently used for the anode is a transparent electrode doped with tin (S n) or zinc (Zn) in I η 2 0 3. The surface is oxidized to obtain a work function of about 5 eV, but The working function of the organic film is about 5.5eV, and the injection barrier of about 0.5eV does not show sufficient performance. When the energy barrier of the organic film and the anode is constant, the state density of these carriers increases. Large carriers are easier to inject. However, the state density of the conventional organic film is about 10 8 / cm 3, which is smaller than the carrier density of metal. Therefore, in order to drive the organic light-emitting device at a low voltage, It is necessary to supplement the small state density of the organic film, and the carrier injection is easier. [Means to Solve the Problem] The organic light-emitting device of the first aspect of the present invention has at least an anode (3) 200401585 pole and organic light-emitting. A layer 'and a cathode, and an organic light-emitting device using charge injection is characterized in that between the anode and the organic light-emitting layer, I n (1 1-y) GaxAlyN (OSx 1 and 0 yS. .5 and ^ 1 - X - y ^ 1) composed of an inorganic film.

An organic light-emitting element according to a second aspect of the present invention is an organic light-emitting element having at least an anode, an organic light-emitting layer, and a cathode, and utilizing charge injection. The anode is characterized by having In (rxy) GaxAlyN (OSxS 1 and OgySO .5 and 0 = 1—x— 1). A method of manufacturing an organic light-emitting device according to a third aspect of the present invention is characterized by having at least a process of providing an anode containing indium, gallium, or aluminum, and performing a nitridation treatment on the surface of the anode to form an electrode having I n ( i-x — y > GaxAlyN (OSx $ l and 〇 $ y $ 〇_5 and OSl-x-ygl), an inorganic film layer, and an organic light emitting layer and a cathode layered on the inorganic film layer .

[Embodiment] [Embodiment of the invention] Fig. 1 is a cross-sectional view showing an organic electroluminescent device according to a first embodiment of the present invention. The organic electroluminescent device of the present invention has a structure including a laminated anode 2, an inorganic film layer 4, an organic light emitting layer 6, and a cathode 8. The organic electroluminescent element of the present invention is usually formed on a substrate. The position of the substrate is designed to be in contact with the anode 2 or the cathode 8 depending on the design. If the light emission from the organic light emitting layer 6 is obtained through a substrate

-6-(4) (4) 200401585 In the structure, the substrate should have high transparency in the wavelength region of the light emission. When the light emission is obtained from the opposite side of the substrate, the substrate need not be transparent. The substrate can be made of materials such as glass, plastic (polymethacrylic acid, polyester, polyolefin, etc.), silicon, etc. The anode 2 is used to perform the positive hole injection with high efficiency and uses a material with a large work function. Suitable materials for the anode 2 include conductive metal oxides such as ITO, IZ 0, and the like. These conductive metal oxides are transparent in the visible light region, and are suitable for the case where the organic light emitting layer 6 emits light from the anode side. When the light emission of the organic light emitting layer 6 is obtained 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, a vapor deposition method, or a CVD method. In the present invention, the inorganic film layer 4 provided between the anode 2 and the organic light-emitting layer 6 is formed of a group III nitride having a composition of ln (up GaxAlyN. In this example, X and y satisfy 0 SXS 1 and 0 are y S 0.5 and 〇 $; [— X— ygi conditions. It is better to satisfy the conditions of 0xxS0.8, 0 $ y each 0.2 and 〇 $ 1-x-y $ 1. The group III oxide used in the inorganic film layer 4 is preferably in an amorphous state. A group III nitride having an appropriate composition as described above indicates a work function of about 5.6 eV larger than that of ITO or IZO. This work function is slightly equal to The working function of the organic layer is 値. Therefore, the hole can be smoothly injected into the organic light-emitting layer 6 without relying on a potential barrier between the inorganic film layer 4 and the organic light-emitting layer 6. In the present invention, 111 is used. For group oxides, its working function is preferably in the range of 5 to 5.6 eV. 200401585 On the one hand, there are electrical barriers between the anode 2 and the inorganic film layer 4 formed by I τ 0 or IZ 0. However, in the present invention, the group 111 nitride used in the inorganic film layer has a non- A large carrier density. Specifically, 'for a state density of the organic light emitting layer material of about 1018 / cm3', the group III nitride of the present invention has a large load of about 1020 to 1022 / cm3. Therefore, when the same electric field is used, it is considered that the anode-inorganic film layer of the present invention may flow into the carrier between 1000 and 10,000 times of the conventional anode-organic light-emitting layer, and it is considered that a weaker electric field is used. There may be sufficient carrier flow. As described above in the "structure of the present invention", the carrier (electricity) can be easily carried out for both the anode-inorganic film layer and the inorganic film layer-organic light-emitting layer. Holes). As a result, it can be driven at a low voltage and can also provide an organic electro-optical light-emitting device with low power consumption. The inorganic film layer of the present invention has a film thickness of 1 to 10 nm, preferably 1 to 5 nm. A film thickness within this range can achieve the above-mentioned effects and perform efficient hole injection. The group III nitride that forms the inorganic film layer of the present invention has 1019 to 102 Q / cm3, and preferably 1021 to 102. / cm3 carrier density. As mentioned above, with such a large The state density is important to facilitate hole transfer between the anode and the inorganic film layer. Furthermore, the carrier density is made into a thick film and measured using the Vanderborg (Vander) formula. The physical properties of the carrier density, but the inorganic film layer system of the present invention has a resistivity of 0.05 to 0.5 Ω. Cm, preferably 0.05 to 0.1 Ώ. Cm. (6) (6) 200401585 The inorganic film layer of the present invention It can be formed by a conventional method such as a sputtering method, a vapor deposition method, or a cv D method. In these methods, nitrogen can be supplied as a monomer gas such as ammonia, radicals, or plasma. However, it is preferably formed by nitriding an anode surface containing indium, gallium, or aluminum having an appropriate composition. Nitriding of the anode surface A nitrogen plasma can be used to treat the anode surface. In view of the organic electro-optic light-emitting device of the present invention, the organic light-emitting layer 6 includes at least an organic electro-optic light-emitting layer, and has a structure in which a hole injection layer, a hole transfer layer, and / or an electron injection layer are interposed according to needs. Specifically, it can be formed by the following layer formation "(1) Organic electro-excitation light layer (2) Hole injection layer / Organic electro-excitation light layer (3) Organic electro-excitation light / Electron injection layer ( 4) Hole injection layer / organic electro-excitation light layer / electron injection layer (5) Hole injection layer / hole-transmission layer / organic electro-excitation light layer / electron injection layer (6) Hole-transport layer / organic electro-excitation light Layer (7) Hole transfer layer / Organic electro-excitation light layer / Electron injection layer (in the above, the left side is connected with the inorganic film layer, and the right side is connected with the cathode) The materials of the above layers are publicly known. For example, in the organic electro-excitation light layer that is to obtain blue-green light from blue, it is preferable to use a fluorescent whitening agent such as benzo_mile-based benzimidazole-based, benzoxazole-based, and a metal honey compound An oxygen key compound, a styrylbenzene-based compound, an aromatic methylene-based compound, and the like. In the present invention, the 'inorganic film layer 4 and the organic electro-optic light-emitting layer are not in direct contact with each other, and a hole injection layer and / or a hole transmission layer are preferably interposed therebetween. Because the inorganic film layer 4 of the present invention has a large carrier density, the excitons generated in the organic electro-excitation light layer may be extinct. In order to prevent this, it is preferable to provide a hole injection layer and / or a hole transfer layer having a thickness of 20 nm or more and preferably a thickness of 20 to 100 nm. The organic light emitting layer or each layer constituting the light emitting layer can be formed by a conventional method such as a vapor deposition method. The cathode 8 can be made of alkali metals such as lithium and sodium, alkaline earth metals such as potassium, calcium, magnesium, and thallium, materials with a small work function, or electron-injecting metals made of these fluorides, and other metals. Alloy or compound. The surface opposite to the organic light emitting layer of the cathode formed of these materials having a small work function may be laminated on the conductive metal. As the conductive metal, Al, Ag, Mo, W, and the like can be used. This conductive metal can function as an auxiliary electrode and reduce the resistance 値 of the entire cathode. When the light emission of the organic light-emitting layer 6 is obtained from the cathode side, the cathode is required to have high transparency in the wavelength region of the light emission. In this case, a structure having a thin working function as described above can be used to make extremely thin (less than 10 mra), and a layer of transparent conductive oxides such as ITO and I ZO can be laminated thereon. With this structure, electrons can be efficiently injected by using these materials having a small work function ', and as a very thin film', transparency can be minimized by these materials. The cathode of the present invention can be formed by a conventional method such as a sputtering method, a vapor deposition method, and a CVD method. A second embodiment of the present invention belongs to an organic light-emitting element having at least an anode, an organic light-emitting layer, and a cathode formed of the above-mentioned Group II 丨 -10- (8) 200401585 oxide. In this embodiment, the 'organic light emitting layer and the cathode have the same material and structure as those described in the first embodiment.

When the group III oxide (y) GaxAiyN is used as the anode, X and y satisfy the conditions of 0'x ^ 1, 0SyS0.5, and 1-x-y $ l each. Moreover, it is preferable to satisfy the conditions of 0Sxg0.8 and 0SyS0.2 and 0S1-x-yg1. The anode of this embodiment can be formed by a conventional method such as a sputtering method, a vapor deposition method, or a CVD method. In these methods, nitrogen can be supplied as a monomer gas, gas, radical or plasma. [Example] (Example 1)

An amorphous In2O3: ZnO (a molar ratio of ZnO is 5%) was laminated on a glass substrate by a sputtering method, and a transparent electrode having a thickness of 200 nm was formed as an anode. This transparent electrode is formed by a general microfabrication process using a mask capable of obtaining a stripe pattern with a width of 2 mm and an interval of 0.5 mm, to form an anode pattern. The surface was then washed with an oxygen plasma at room temperature. Next, the surface of the transparent electrode was nitrided 'at room temperature using a nitrogen plasma to form an ultra-thin film of InN (thickness: about 0.5 nm). The work function of the InN ultra-thin film is 5.6 eV. An organic light-emitting layer was fabricated on the InN ultra-thin film. The organic light-emitting layer has a four-layer structure using an inorganic film layer, a hole transfer layer, a light-emitting layer, and an electron injection layer. The film is formed in this order. The inorganic film layer is made of copper cyanine (C11P c) with a thickness of 100 nm, and the hole transport layer is made of 4,4-bis [N_ (1naphthyl) -N-anilino] biphenyl with a thickness of 20 nm. (《_ NPD）, the light-emitting layer is made of 4,4, a double (2,2-phenylvinyl) biphenyl (DPVB i) with a thickness of 30 nm, and the electron injection layer is made with a thickness of 20 nm. Trialuminum (8-D quinolinol ester) (Alq).

After the organic light-emitting layer is formed, a mask that can obtain a stripe pattern 2 mm wide and 0.5 mm apart from the positive father pattern of the anode stripe pattern is used, and LiF with a thickness of 0.5 nm and A1 with a thickness of 200 nm are sequentially laminated by resistance heating A cathode was formed, and an organic electroluminescent element was obtained. Furthermore, in this embodiment, the ultra-thin film InN is formed by nitriding the surface of a transparent electrode, and the electrical characteristics cannot be measured with InN alone. When an amorphous InN film (thickness: 1000 nm) 'having the same composition was manufactured and the resistivity and carrier density were measured, the results were 0.0 7 Ω · cm and 1.7xl021 / cm3, respectively.

(Comparative Example 1) An organic electroluminescent device was obtained in the same manner as in Example 1 except that a 111N ultra-thin film was not formed. Fig. 2 is a graph showing the current-voltage characteristics of the organic electro-optic light-emitting elements of Comparative Example 1 and Comparative Example 1. The organic electroluminescent device of Example 1 had an injection start voltage (a voltage at which a current of 1 o_6a began to flow) that was approximately 0.5 V lower than that of Example 1. And even the high-voltage field shows better injection. -12- (10) 200401585 (Example 2) An organic electroluminescent device was produced in the same manner as in Example 1 except that an InQ 2GaQ 8N ultra-thin film (thickness 1 nm) was formed by a sputtering method instead of 1N. This sputtering method, In and Ga, is performed using a general effusion chamber (effusion c e 11) as a supply source and based on nitrogen, and is performed at room temperature. The work function of the formed InQ2GaG8N ultra-thin film is 5.6 eV.

The electrical characteristics of I η 〇 2 G a 〇 8 N used in this example were measured by separately preparing a thick film having a thickness of 1000 nm. As a result, the resistivity was 0.8 Ω cm. The carrier density was between 3xl022 and lxl021 / cm3. (Example 3) An organic electroluminescent device was produced in the same manner as in Example 2 except that an In01GaQ8AlOiN ultra-thin film (thickness inm) was formed by a sputtering method instead of InQ 2Ga0 8N. The working function of the formed ln () lGaG 8A1G | N ultra-thin film is 5. leV.

The electrical characteristics of InO iGu 8A10, N used in this example were measured by making a thick film having a thickness of 100 nm. As a result, the resistivity was 0.99 Ω.cm 'and the carrier density was between 3xl022 and 1xl02i / cm3. Fig. 3 is a graph showing the current-voltage characteristics of the organic electroluminescent devices of Comparative Example 2, Example 3, and Comparative Example 1. In the organic electroluminescent devices of Examples 2 and 3, the implantation start voltage was decreased by about 0.5 V compared with that of Comparative Example 1. The high-voltage range also shows better injection properties. (Example 4) -13- 694 (11) (11) 200401585 A polycrystalline Ga0 sAl0 2N was laminated on a glass substrate by a sputtering method to form a transparent electrode having a thickness of 200 η m as an anode. This transparent electrode is formed into an anode pattern by a general microfabrication process using a mask capable of obtaining a stripe pattern with a width of 2 mm 'and an interval of 0.5 mm. The surface was then washed with an oxygen plasma at room temperature. Next, at 30 ° C., a process using a nitrogen plasma was performed. An organic light-emitting layer and a cathode were formed thereon by the same method as in Example 1 to obtain an organic light-emitting element. FIG. 4 is a comparative implementation Coordinate diagrams of the current-voltage characteristics of the organic electro-optic light-emitting elements of Example 4 and Comparative Example 1. The organic electro-optical-light-emitting element's injection start voltage of Example 1 was approximately 0.3 V lower than that of Comparative Example 1. Even in the high-voltage field, [Inventive effect] With the present invention, it is possible to provide the use between the anode and the organic light-emitting layer, using the I Π group oxide I η (! — X — y) G ax A 1 y N The formed inorganic film layer or the anode formed of the group I oxide obtains excellent hole injection properties (injection start voltage and current amount in a high voltage range), and obtains an excellent organic light-emitting element. Organic light-emitting devices are widely used to create PDAs, mobile phones, and notebook computers that require low voltage. [Brief Description of the Drawings] Figure 1 is a schematic cross-section of an organic light-emitting device according to the first embodiment of the present invention. Figure 2 is a graph showing the -14-(12) (12) 200401585 current-voltage characteristics of the organic light-emitting elements of Example 1 and Comparative Example 1. Figure 3 is a graph showing Example 2, Example 3, and Comparative Example Coordinate graph of current-voltage characteristics of the organic light-emitting element of Fig. 1. Fig. 4 is a graph illustrating current-voltage characteristics of the organic light-emitting element of Example 4 and Comparative Example 1. [Illustration of drawing number]

4 Inorganic film layer 6 Organic light emitting layer 8 Cathode

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Claims (1)

200401585 范围 Patent application scope 1. An organic light-emitting device, which belongs to an organic light-emitting device having at least an anode, an organic light-emitting layer, and a cathode, using charge injection, and is characterized in that: between the anode and the organic light-emitting layer An inorganic film layer composed of In (Bu ”GaxAlyN (0 $ G and 0 μg and 0 μm) is sandwiched. 2. An organic light-emitting element 'is an organic light-emitting element that has at least an anode, an organic light-emitting layer, and a cathode and uses charge injection, and is characterized in that the anode has 1η (xy) GaxAlyN (1 and 〇SyS〇.5 And 0 彡 1— χ— y $ l). 3. A method of manufacturing an organic light emitting element, comprising: providing a process for providing an anode including indium, gallium, or aluminum; The sumbox is formed by nitriding the anode surface to form an inorganic film layer consisting of In (1 ~ x-y) Ga ', AlyN (os xg 1 and 0 each y each 0, 5 and 1-X- 1). And a process of laminating an organic light emitting layer and a cathode on the inorganic film layer. -16-