JP2019009330A - Organic el element and organic el display panel having the same - Google Patents

Abstract

To provide an organic EL element, capable of suppressing deterioration in an organic material by controlling a location of recoupling of an electron to a hole and improving a light extraction efficiency.SOLUTION: The organic EL element includes: a positive electrode; a negative electrode opposing to the positive electrode; and a luminous layer arranged between the positive electrode and the negative electrode. The luminous layer has a region containing more dielectric particles than any other region in the film thickness direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an improvement in the structure of an organic EL device, particularly a light emitting layer which is a main part thereof.

In recent years, display devices using organic EL elements are becoming widespread.
The organic EL element has a configuration in which at least a light emitting layer is sandwiched between an anode and a cathode. In many cases, the organic EL element has an electron hole for supplying electrons to the light emitting layer, with a hole transport layer for supplying holes to the light emitting layer sandwiched between the anode and the light emitting layer. The transport layer is further sandwiched between the light emitting layer and the cathode (hereinafter, the layer between the light emitting layer and the electrode, such as an electron transport layer and a hole transport layer, is referred to as a “functional layer”. ).

When a voltage is applied between the anode and the cathode, electrons are injected from the electron transport layer into the lowest unoccupied molecular orbital (LUMO) of the light emitting layer, and the highest occupied orbit of the light emitting layer from the hole transport layer. Holes are injected into (HOMO: Highest Occupied Molecular Orbital).
Further, an electric field is generated in the light emitting layer by a voltage applied between the anode and the cathode. The electrons injected into the LUMO of the light emitting layer move in the light emitting layer toward the anode under the influence of the electric field. On the other hand, the holes injected into the HOMO of the light emitting layer move in the light emitting layer toward the cathode under the influence of the electric field.

  Thus, excitons are generated when the electrons and holes relocated in the light emitting layer are recombined. When the exciton returns from the excited state to the ground state, light emission occurs (Patent Document 1).

JP-T-2004-514257 JP 2009-147276 A

  It is known that the exciton distribution in the thickness direction in the light emitting layer may have a sharp peak (hereinafter, “distribution” refers to the distribution in the thickness direction unless otherwise specified). . Conventionally, the exciton distribution is often generated near the end face of the light emitting layer near the electrode, which is a cause of promoting the deterioration of the functional layer and / or the deterioration of the light emitting layer due to the concentration of excitons at a high density. It has become.

  This invention is made | formed in view of said problem, and it aims at providing the organic EL element which controlled the exciton distribution.

  In order to achieve the above object, an organic EL device according to an aspect of the present invention includes an anode, a cathode facing the anode, and a light-emitting layer disposed between the anode and the cathode, The light emitting layer has a region containing more dielectric fine particles than other regions in the film thickness direction.

  In the organic EL device of the above aspect, in the light emitting layer, the density of electrons and / or holes is increased in the vicinity of the surface of the dielectric fine particles, whereby the region containing a large amount of dielectric fine particles is defined as the peak center of the exciton distribution. can do. Therefore, by sufficiently separating the region and the functional layer, deterioration of the functional layer can be suppressed and the light emission efficiency can be improved. Furthermore, since the position of the region containing a large amount of dielectric fine particles in the organic EL element can be controlled in the manufacturing process, the emission center can be controlled to a desired position, and the light extraction efficiency can be easily improved. .

It is sectional drawing which shows typically the structure of the organic EL element 1 which concerns on embodiment. It is a figure explaining the relationship between the position in a film thickness direction, and exciton density based on an Example and a comparative example. It is a simple schematic diagram which shows the relationship between the band diagram which concerns on an Example and a comparative example, a hole transport layer, a light emitting layer, and an electron carrying layer, and the recombination position of an electron and a hole. It is a schematic diagram which shows the movement and recombination of an electron and a hole in the 2nd area | region 172 of the light emitting layer 17 based on an Example. BRIEF DESCRIPTION OF THE DRAWINGS It is a fragmentary sectional view which shows typically a part of manufacturing process of the organic EL element which concerns on embodiment, Comprising: (a) is the state in which the TFT layer was formed on the board | substrate, (b) is on the board | substrate. (C) is a state in which a pixel electrode material is formed on the interlayer insulating layer, (d) is a state in which a hole injection layer material is formed on the pixel electrode material, e) shows a state in which a pixel electrode layer and a hole injection layer are formed. BRIEF DESCRIPTION OF THE DRAWINGS It is a fragmentary sectional view which shows typically a part of manufacturing process of the organic EL element which concerns on embodiment, Comprising: (a) is a partition material layer formed on an interlayer insulation layer, a pixel electrode, and a positive hole injection layer. (B) is a state where a partition layer is formed, (c) is a state where a hole transport layer is formed on the hole injection layer, and (d) is a light emitting layer on the hole injection layer. The state where the first region is formed is shown. BRIEF DESCRIPTION OF THE DRAWINGS It is a fragmentary sectional view which shows typically a part of manufacturing process of the organic EL element which concerns on embodiment, (a) is the state in which the 2nd area | region of the light emitting layer was formed on the 1st area | region of a light emitting layer , (B) shows a state where the third region of the light emitting layer is formed on the second region of the light emitting layer. It is a fragmentary sectional view which shows a part of manufacturing process of the organic EL element which concerns on embodiment typically, (a) is the state in which the electron carrying layer was formed on the light emitting layer and the partition layer, (b) Is a state where an electron injection layer is formed on the electron transport layer, (c) is a state where a counter electrode is formed on the electron injection layer, and (d) is a state where a sealing layer is formed on the counter electrode. Indicates. It is a flowchart which shows the manufacture process of the organic EL element which concerns on embodiment. It is a block diagram which shows the structure of the organic electroluminescent display apparatus provided with the organic electroluminescent element which concerns on embodiment.

<Background to the Aspect of the Present Disclosure>
In order to use the organic EL element as a light emitting element, it is indispensable to generate excitons that are the starting state of light emission. Therefore, conventionally, the hole injection property from the hole transport layer to the light-emitting layer and the electron injection property from the electron transport layer to the light-emitting layer are improved, and the carrier density in the light-emitting layer is improved to increase the probability of recombination of electrons and holes. Is increasing. Further, as a configuration for further improving the carrier density in the light emitting layer, the electron transport layer can be suppressed so that hole leakage from the light emitting layer to the electron transport layer and electron leakage from the light emitting layer to the hole transport layer can be suppressed. The functional layer in which the HOMO level and / or the LUMO level of the hole transport layer is adjusted is selected. This is because with such a configuration, the carrier density in the light emitting layer can be improved and the recombination probability of electrons and holes can be increased.

  On the other hand, excitons cause deterioration of the organic material forming the light emitting layer and the like. This is because not all of the exciton energy is converted into light, and part of it is converted into lattice vibration or heat of the organic material, which degrades the organic material. Moreover, it is preferable that an exciton is not produced | generated outside the light emitting layer. This is because when excitons are generated in a functional layer such as a hole transport layer or an electron transport layer, most of the energy is converted into lattice vibration and heat, and functions only as a cause of deterioration of the functional layer.

  However, in the configuration for improving the carrier density in the light emitting layer as described above, the carriers in the light emitting layer are unevenly distributed at the interface between the hole transport layer of the light emitting layer and the interface of the electron transport layer of the light emitting layer. Yes. Therefore, recombination of electrons and holes is likely to occur at the interface between the hole transport layer of the light emitting layer and the electron transport layer of the light emitting layer, which has a high carrier density, and excitons are also positively connected to the light emitting layer. It is distributed in a region centering on the interface with the hole transport layer and the interface between the light emitting layer and the electron transport layer. Therefore, the exciton density becomes extremely high in the region near the interface in the light emitting layer, and exciton generation in the functional layer easily occurs. Thereby, in the light emitting layer, the deterioration in the region near the interface is promoted, and the functional layer is further deteriorated, so that the lifetime of the organic EL element is shortened. In addition, the optical resonance to improve the light extraction efficiency by limiting the position of the peak of the exciton distribution to the interface of the light emitting layer with the hole transport layer and / or the interface of the light emitting layer with the electron transport layer. There are constraints on the design of the vessel structure. This is because, for example, when the position where the peak of the exciton distribution is at the interface with the hole transport layer of the light emitting layer, the light emitting layer is not included in the optical path between the light emitting center and the anode, and the light emission from the anode This is because the optical path length must be designed based only on the refractive index and thickness of the functional layer existing between the layers.

  Therefore, the inventor examined a technique for controlling the location of recombination of electrons and holes in the light emitting layer, and added dielectric fine particles to a specific region in the light emitting layer, so that the region in the light emitting layer The knowledge that recombination in can be promoted was obtained. As a result, the exciton density can be prevented from becoming extremely high by reducing the exciton density in the vicinity of the interface between the functional layer and the light emitting layer, and further, deterioration of the functional layer can be suppressed. Become. Furthermore, it is possible to improve the light extraction efficiency by arranging the light emission center at a desired position, and it is possible to extend the life of the organic EL element.

<Disclosure>
An organic EL element according to one embodiment of the present disclosure includes an anode, a cathode facing the anode, and a light emitting layer disposed between the anode and the cathode, and the light emitting layer is in a film thickness direction. And a region containing more dielectric fine particles than other regions.
In the organic EL device of the above aspect, the density of electrons and / or holes increases in the vicinity of the surface of the dielectric fine particles in the light emitting layer, whereby the region containing a large amount of dielectric fine particles is located at the peak center of the emission intensity distribution. It can be. Therefore, by sufficiently separating the region and the functional layer, deterioration of the functional layer can be suppressed and the light emission efficiency can be improved. Moreover, in the organic EL element of the said aspect, deterioration of a light emitting layer can be relieve | moderated by suppressing that an exciton density becomes extremely high in the interface of a light emitting layer and a functional layer. Furthermore, since the position of the region in the organic EL element can be controlled in the manufacturing process, the emission center can be controlled to a desired position, and the light extraction efficiency can be easily improved.

An organic EL display panel according to one embodiment of the present disclosure is an organic EL display panel including a plurality of the above-described organic EL elements on a substrate.
In this organic EL display panel, the same effect as described above can be obtained.
In addition, in the method for manufacturing an organic EL element according to one embodiment of the present disclosure, a substrate is prepared, a pixel electrode is formed above the substrate, and a first ink including at least an organic light emitting material is disposed above the pixel electrode. A light emitting layer is formed by applying the second ink containing the organic light emitting material and containing more dielectric fine particles than the first ink, and then the first ink, and a common electrode is formed above the light emitting layer. Form.

An organic EL element formed by this manufacturing method can provide the same effects as described above.
The organic EL element and manufacturing method of the above aspect may be as follows.
The thickness of the region may be 20% or less of the thickness of the light emitting layer.
Thereby, excitons are sufficiently concentrated in a region containing a large amount of dielectric fine particles, and excitons generated in the functional layer can be reduced. In addition, by suppressing the exciton density from becoming extremely high at the interface between the light emitting layer and the functional layer, deterioration of the light emitting layer can be alleviated. Furthermore, since the region is the emission center, the light extraction efficiency can be improved by realizing the optical resonator structure.

The particle size of the dielectric fine particles may be 1 nm or more and 30 nm or less.
Thereby, it is possible to prevent a decrease in light extraction efficiency due to light diffusion of the dielectric fine particles, and to uniformly generate a region containing a large amount of dielectric fine particles in the light emitting layer.
Moreover, the band gap of the material of the dielectric fine particles may be 3 eV or more.

Thereby, the fall of the light extraction efficiency by the light absorption of dielectric fine particles can be suppressed.
The light emitting layer includes an electron transporting material, and a difference between a conduction band lower end (CBM) of the dielectric fine particle material and a lowest empty orbital (LUMO) level in the electron transporting material is 0.1 eV or more. It is good also as.

As a result, the electron density can be improved in the vicinity of the interface between the electron transporting material and the dielectric fine particles, and in the exciton distribution, the region containing a lot of dielectric fine particles is set as the center of the peak, and the anode side of the light emitting layer The exciton density at the interface can be reduced.
The light emitting layer includes a hole transport material, and a difference between a valence band upper end (VBM) of the dielectric fine particle material and a highest occupied orbital (HOMO) level in the hole transport material is 0. It may be 1 eV or more.

As a result, the hole density can be improved in the vicinity of the interface between the hole transporting material and the dielectric fine particles, and in the exciton distribution, the region containing a large amount of dielectric fine particles is set as the center of the peak, and the emission layer The exciton density at the cathode side interface can be reduced.
The material of the dielectric fine particles may be selected from the group consisting of zinc oxide (ZnO), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), and aluminum oxide (Al ₂ O ₃ ).

Further, the surface of the dielectric fine particles may be modified with a dispersant.
The dispersant may include one or more of phosphoric acid, carboxylic acid, sulfonic acid, or salts thereof.
<Embodiment>
Hereinafter, the organic EL element according to the embodiment will be described. Note that the following description is an example for explaining the configuration, operation, and effect according to one aspect of the present invention, and is not limited to the following form except for the essential part of the present invention.

1. Configuration of Organic EL Element FIG. 1 is a partial cross-sectional view of an organic EL display panel 100 (see FIG. 10) according to Embodiment 1. The organic EL display panel 100 includes a plurality of pixels composed of organic EL elements 1 (R), 1 (G), and 1 (B) that emit three colors (red, green, and blue). FIG. 1 shows a cross section of the one pixel.

In the organic EL display panel 100, each organic EL element 1 is a so-called top emission type that emits light forward (upward in the drawing in FIG. 1).
Since the organic EL element 1 (R), the organic EL element 1 (G), and the organic EL element 1 (B) have substantially the same configuration, the organic EL element 1 will be described when not distinguished from each other.
As shown in FIG. 1, the organic EL element 1 includes a substrate 11, an interlayer insulating layer 12, a pixel electrode 13, a partition wall layer 14, a hole injection layer 15, a hole transport layer 16, a light emitting layer 17, an electron transport layer 18, The electron injection layer 19, the counter electrode 20, and the sealing layer 21 are provided.

The substrate 11, the interlayer insulating layer 12, the electron transport layer 18, the electron injection layer 19, the counter electrode 20, and the sealing layer 21 are not formed for each pixel, but are provided in the organic EL display panel 100. A plurality of organic EL elements 1 are formed in common.
<Board>
The substrate 11 includes a base material 111 that is an insulating material and a TFT (Thin Film Transistor) layer 112. In the TFT layer 112, a drive circuit is formed for each pixel. The base material 111 is, for example, a glass substrate, a quartz substrate, a silicon substrate, molybdenum sulfide, copper, zinc, aluminum, stainless steel, magnesium, iron, nickel, gold, silver or other metal substrate, gallium arsenide semiconductor substrate, plastic substrate, etc. Etc. can be adopted. As the plastic material, either a thermoplastic resin or a thermosetting resin may be used. For example, polyethylene, polypropylene, polyamide, polyimide (PI), polycarbonate, acrylic resin, polyethylene terephthalate (PET), polybutylene terephthalate, polyacetal, other fluorine resins, styrene, polyolefin, polyvinyl chloride, polyurethane, Various thermoplastic elastomers such as fluororubbers and chlorinated polyethylenes, epoxy resins, unsaturated polyesters, silicone resins, polyurethanes, etc., or copolymers, blends, polymer alloys, etc. mainly comprising these, Among them, a laminate obtained by laminating one type or two or more types can be used.

<Interlayer insulation layer>
The interlayer insulating layer 12 is formed on the substrate 11. The interlayer insulating layer 12 is made of a resin material, and is for flattening a step on the upper surface of the TFT layer 112. Examples of the resin material include a positive photosensitive material. Examples of such photosensitive materials include acrylic resins, polyimide resins, siloxane resins, and phenol resins. Further, although not shown in the cross-sectional view of FIG. 1, a contact hole is formed in the interlayer insulating layer 12 for each pixel.

<Pixel electrode>
The pixel electrode 13 includes a metal layer made of a light reflective metal material, and is formed on the interlayer insulating layer 12. The pixel electrode 13 is provided for each pixel and is electrically connected to the TFT layer 112 through a contact hole.
In the present embodiment, the pixel electrode 13 functions as an anode.

  Specific examples of the metal material having light reflectivity include Ag (silver), Al (aluminum), aluminum alloy, Mo (molybdenum), APC (silver, palladium, copper alloy), ARA (silver, rubidium, gold). Alloy), MoCr (alloy of molybdenum and chromium), MoW (alloy of molybdenum and tungsten), NiCr (alloy of nickel and chromium), and the like.

The pixel electrode 13 may be composed of a metal layer alone, but has a stacked structure in which a layer made of a metal oxide such as ITO (indium tin oxide) or IZO (indium zinc oxide) is stacked on the metal layer. Also good.
<Partition wall layer>
The partition layer 14 is formed on the hole injection layer 15 in a state where a part of the upper surface of the pixel electrode 13 and the hole injection layer 15 is exposed and a peripheral region thereof is covered. A region of the upper surface of the hole injection layer 15 that is not covered with the partition layer 14 (hereinafter referred to as “opening”) corresponds to a subpixel. That is, the partition wall layer 14 has an opening 14a provided for each subpixel.

In the present embodiment, the partition wall layer 14 is formed on the interlayer insulating layer 12 in a portion where the pixel electrode 13 is not formed. That is, in the portion where the pixel electrode 13 is not formed, the bottom surface of the partition layer 14 is in contact with the top surface of the interlayer insulating layer 12.
The partition layer 14 is made of, for example, an insulating organic material (for example, an acrylic resin, a polyimide resin, a novolac resin, a phenol resin, or the like). The partition layer 14 functions as a structure for preventing the applied ink from overflowing when the light emitting layer 17 is formed by a coating method, and when the light emitting layer 17 is formed by a vapor deposition method, the vapor deposition mask. It functions as a structure for mounting. In the present embodiment, the partition layer 14 is made of a resin material, and examples of the material of the partition layer 14 include acrylic resins, polyimide resins, siloxane resins, and phenol resins. In the present embodiment, a phenolic resin is used.

<Hole injection layer>
The hole injection layer 15 is provided on the pixel electrode 13 for the purpose of promoting injection of holes from the pixel electrode 13 to the light emitting layer 17. The hole injection layer 15 is made of, for example, an oxide such as Ag (silver), Mo (molybdenum), Cr (chromium), V (vanadium), W (tungsten), Ni (nickel), Ir (iridium), or It is a layer made of a conductive polymer material such as PEDOT (mixture of polythiophene and polystyrene sulfonic acid). Among the above, the hole injection layer 15 made of metal oxide has a function of injecting holes into the light emitting layer 17 stably or by assisting the generation of holes. Has a function. In the present embodiment, the hole injection layer 15 is made of tungsten oxide. When the hole injection layer 15 is formed of a transition metal oxide, a plurality of oxidation numbers are obtained, so that a plurality of levels can be obtained. As a result, hole injection becomes easy and contributes to a reduction in driving voltage. To do.

<Hole transport layer>
The hole transport layer 16 is formed in the opening 14a using a polymer compound having no hydrophilic group. For example, polyfluorene or a derivative thereof, or a polymer compound such as polyarylamine or a derivative thereof that does not have a hydrophilic group can be used.
The hole transport layer 16 has a function of transporting holes injected from the hole injection layer 15 to the light emitting layer 17.

<Light emitting layer>
The light emitting layer 17 is formed in the opening 14a. The light emitting layer 17 is divided into three regions in the film thickness direction, and the first region 171, the second region 172, and the third region 173 are arranged in this order from the hole transport layer 16 side. Of these, the second region 172 is a region containing dielectric fine particles. That is, the second region 172 includes an organic light emitting part 17a containing an organic light emitting material and dielectric fine particles 17b dispersed in the organic light emitting part 17a. On the other hand, the first region 171 and the third region 173 are composed of an organic light emitting unit 17a containing an organic light emitting material. The first region 171 and the third region 173 may include the dielectric fine particles 17b, but the addition amount thereof is smaller than the addition amount of the dielectric fine particles 17b in the second region 172.

  The film thickness α2 of the second region 172 is preferably 20% or less of the film thickness α1 of the entire light emitting layer 17. Thereby, excitons can be sufficiently concentrated in the second region 172 without excessively increasing the electric resistance of the light emitting layer 17, and excitons in the hole transport layer 16 and the electron transport layer 18 are reduced. be able to. At the same time, the emission intensity of the second region 172 in the light emitting layer 17 is sufficiently higher than that of the first region 171 and the third region 173. Therefore, by realizing an optical resonator structure in which the light emission center is the second region 172 between the light emitting layer 17 side interface of the pixel electrode 13 and the counter electrode 20 side, the light extraction efficiency is improved. be able to. Here, it is assumed that the film thickness of each of the first region 171, the second region 172, and the third region 173 is 35%, 15%, and 40% with respect to the entire light emitting layer 17 and the film thickness α1. The film thickness is not limited to the above example, and may be arbitrarily set within a range in which the film thickness of the second region 172 does not become too large. However, the thickness of each of the first region 171 and the third region 173 is preferably not excessively small, and is preferably greater than or equal to the thickness of the second region 172.

  The organic light emitting unit 17a has a function of emitting light of each color of R, G, and B by recombination of holes and electrons. A known material can be used as the material of the organic light emitting unit 17a. Specifically, for example, an oxinoid compound, a perylene compound, a coumarin compound, an azacoumarin compound, an oxazole compound, an oxadiazole compound, a perinone compound, a pyrrolopyrrole compound, a naphthalene described in a patent publication (JP-A-5-163488). Compound, anthracene compound, fluorene compound, fluoranthene compound, tetracene compound, pyrene compound, coronene compound, quinolone compound and azaquinolone compound, pyrazoline derivative and pyrazolone derivative, rhodamine compound, chrysene compound, phenanthrene compound, cyclopentadiene compound, stilbene compound, diphenylquinone Compound, styryl compound, butadiene compound, dicyanomethylenepyran compound, dicyanomethylenethiopyran compound, fluoresceinization Product, pyrylium compound, thiapyrylium compound, serenapyrylium compound, telluropyrylium compound, aromatic ardadiene compound, oligophenylene compound, thioxanthene compound, cyanine compound, acridine compound, metal complex of 8-hydroxyquinoline compound, metal of 2-bipyridine compound It is preferably formed of a fluorescent substance such as a complex, a Schiff salt and a group III metal complex, an oxine metal complex, or a rare earth complex.

The dielectric fine particles 17b act as a barrier against at least one of holes and electrons, thereby increasing the hole density and / or electron density in the adjacent organic light emitting portion 17a, and recombination of electrons and holes. Has a function to promote. It is preferable that the dielectric fine particles 17b are not aggregated and are uniformly dispersed in the second region 172. This is because the electron density and / or hole density in the second region 172 is made uniform, and the electrical resistance of the second region 172 increases locally by agglomeration of the dielectric fine particles 17b which are insulators. This is to deter. In order to prevent aggregation of the dielectric fine particles 17b, the surface of the dielectric fine particles 17b may be modified with a dispersant. As the dispersant, for example, a dispersant containing phosphoric acid, carboxylic acid, sulfonic acid, or salts thereof can be used. The average particle size of the dielectric fine particles 17b is preferably about 1 nm to 30 nm, and preferably has a large surface area. In order not to reduce the light extraction efficiency, the material of the dielectric fine particles 17b preferably does not absorb visible light, and is preferably a dielectric having a band gap of 3 eV or more. Furthermore, since the dielectric fine particles 17b act as a barrier against electrons, the dielectric conduction band minimum (CBM) and the LUMO level of the electron transport material contained in the organic light emitting portion 17a The difference is preferably 0.1 eV or more. Since the dielectric fine particles 17b act as a barrier against holes, the HOMO level of the hole transporting material contained in the organic light emitting portion 17a and the valence band maximum energy (VBM) of the dielectric are included. The difference from Maximum) is preferably 0.1 eV or more. Specifically, the dielectric fine particles 17b are made of zinc oxide (ZnO), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), or the like.

<Electron transport layer>
The electron transport layer 18 has a function of transporting electrons from the counter electrode 20 to the light emitting layer 17. The electron transport layer 18 is made of an organic material having a high electron transport property, and does not contain an alkali metal and an alkaline earth metal. Further, the electron transport layer 18 is formed in a thickness range of greater than 1 nm and 30 nm or less.

Examples of the organic material used for the electron transport layer 18 include π-electron low molecular weight organic materials such as an oxadiazole derivative (OXD), a triazole derivative (TAZ), and a phenanthroline derivative (BCP, Bphen).
<Electron injection layer>
The electron injection layer 19 has a function of injecting electrons supplied from the counter electrode 20 to the light emitting layer 17 side. The electron injection layer 19 is formed, for example, by doping an organic material having a high electron transport property with a doped metal selected from an alkali metal or an alkaline earth metal. In the embodiment, Ba is doped. The doping concentration of Ba is 40 wt% or less, preferably 20 wt% or less, and more preferably 15 wt% or less.

The metal corresponding to the alkali metal is lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), and the metal corresponding to the alkaline earth metal is They are calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
Examples of the organic material used for the electron injection layer 19 include π-electron low molecular weight organic materials such as an oxadiazole derivative (OXD), a triazole derivative (TAZ), and a phenanthroline derivative (BCP, Bphen).

<Counter electrode>
The counter electrode 20 is made of a light-transmitting conductive material and is formed on the electron injection layer 19. The counter electrode 20 functions as a cathode.
As a material of the counter electrode 20, for example, ITO or IZO can be used. Alternatively, a thin film of metal such as silver, a silver alloy, aluminum, or an aluminum alloy may be used as the material of the counter electrode 20.

<Sealing layer>
The sealing layer 21 has a function of suppressing exposure of organic layers such as the hole transport layer 16, the light emitting layer 17, the electron transport layer 18, and the electron injection layer 19 to moisture or air. For example, a light-transmitting material such as silicon nitride (SiN) or silicon oxynitride (SiON) is used. Further, a sealing resin layer made of a resin material such as an acrylic resin or a silicone resin may be provided over a layer formed using a material such as silicon nitride (SiN) or silicon oxynitride (SiON).

In the present embodiment, since the organic EL display panel 100 is a top emission type, the sealing layer 21 needs to be formed of a light transmissive material.
<Optical resonator structure>
In the above structure, an optical resonator structure in which the light emission center is the second region 172 may be formed between the interface of the pixel electrode 13 on the light emitting layer 17 side and the light emitting layer 17 side of the counter electrode 20.

  Specifically, the design is as follows. A part of the light emitted from the second region 172 to the counter electrode 20 side is directly emitted from the counter electrode 20. Further, the light emitted from the second region 172 to the pixel electrode 13 side is reflected by the surface of the pixel electrode 13 and travels again from the second region 172 to the counter electrode 20 side. A part of the light traveling from the second region 172 to the counter electrode 20 side is reflected at the interface between the counter electrode 20 and the electron injection layer 19, passes through the second region 172, and is reflected from the surface of the pixel electrode 13. . Therefore, the optical path length is designed so that they strengthen each other. More specifically, the optical path length that travels from the second region 172 to the pixel electrode 13 side, is reflected by the surface of the pixel electrode 13 and returns to the second region 172, proceeds from the second region 172 to the counter electrode 20 side, and reaches the counter electrode 20 side. Each of the optical path lengths reflected on the surface and returning to the second region 172 is designed to be an integral multiple of the wavelength of the emitted light.

<Others>
Although not shown in FIG. 1, a color filter or an upper substrate may be bonded onto the sealing layer 21 via a sealing resin. By bonding the upper substrate, the hole transport layer 16, the light emitting layer 17, the electron transport layer 18, and the electron injection layer 19 can be protected from moisture and air.
2. FIG. 2 is a diagram illustrating the relationship between the position in the film thickness direction and the exciton density according to the example and the comparative example. The horizontal axis in FIG. 2 indicates the film thickness direction (Z direction), and corresponds to the cross section AB in FIG. The vertical axis in FIG. 2 indicates the exciton density ρ on the logarithmic axis.

  In the light emitting layer 17 according to the example, the second region 172 includes an organic light emitting portion 17a having a higher electron transporting property than a hole transporting property, and dielectric fine particles 17b. On the other hand, the first region 171 and the third region 173 according to the embodiment include only the organic light emitting portion 17a and do not include the dielectric fine particles 17b. On the other hand, the entire area of the light emitting layer 17c according to the comparative example is the same region as the first region 171 or the third region 173. In addition, about an other than that structure, an Example and a comparative example are the same structures.

FIGS. 3A and 3B are band diagrams of the hole transport layer 16, the light emitting layer, and the electron transport layer 18 and simplified schematics showing recombination of electrons and holes, respectively, according to Examples and Comparative Examples. FIG.
In the light emitting layer according to the comparative example, as shown in the schematic diagram of FIG. 3B, the difference between the LUMO level of the electron transport layer 18 and the LUMO level of the light emitting layer 17a is small, and the LUMO level of the light emitting layer 17c. And the difference Δe1 between the LUMO level of the hole transport layer 16 and the hole transport layer 16 are designed to be large. For this reason, electrons injected into the light emitting layer 17c are unlikely to leak into the hole transport layer 16, and the density increases near the interface between the light emitting layer 17c and the hole transport layer 16. Therefore, the electron density increases near the interface between the light-emitting layer 17c and the hole transport layer 16, and recombination of electrons and holes easily occurs near the interface between the light-emitting layer 17c and the hole transport layer 16. As a result, as shown in data 301 in FIG. 2, many excitons are also distributed around the interface between the light emitting layer 17 c and the hole transport layer 16. For this reason, there arise problems that the emission center is biased to the vicinity of the interface with the hole transport layer 16 in the light emitting layer 17c, and that many excitons are also generated in the hole transport layer 16.

  On the other hand, the light emitting layer 17 according to the example is as follows. As shown in the schematic diagram of FIG. 3A, also in the light emitting layer 17 according to the example, the difference between the LUMO level of the electron transport layer 18 and the LUMO level of the organic light emitting portion 17a is small, and the organic light emitting portion 17a. The difference Δe1 between the LUMO level of the hole transport layer 16 and the LUMO level of the hole transport layer 16 is designed to be large. On the other hand, the dielectric fine particles 17b are dispersed in the second region 172 according to the embodiment, and the difference Δe between the CBM of the dielectric fine particles 17b and the LUMO level of the organic light emitting unit 17a is designed to be 0.1 eV or more. Has been. Therefore, as shown in the schematic diagram of FIG. 4A, electrons are trapped at the interface with the dielectric fine particles 17b in the organic light emitting portion 17a, thereby preventing the movement of the electrons. As a result, in the second region 172, the electron density also increases at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b. Thereby, the increase in the electron density at the interface between the first region 171 and the hole transport layer 16 can be reduced. Therefore, at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b in the second region 172, holes are recombined with the trapped electrons, and the recombination probability of the electrons and holes is increased. On the other hand, in the vicinity of the interface between the first region 171 and the hole transport layer 16, the electron density decreases, and as a result, the recombination probability of electrons and holes is smaller than that in the comparative example. As a result, the exciton distribution peak moves to the second region 172 as shown in the data 302 of FIG. Therefore, the light emission center of the light emitting layer 17 can be moved to the second region 172. In addition, since the exciton density can be prevented from becoming extremely high at the interface with the hole transport layer 16 in the first region 171, the light emitting layer 17 can be locally degraded in the vicinity of the interface. Further, deterioration of the functional layer due to excitons can be suppressed.

  In the above-described example and comparative example, the electron transport property of the organic light emitting unit 17a is higher than the hole transport property. However, the hole transport property of the organic light emitting unit 17a is higher than the electron transport property. If it does, it will be as follows. In this case, the difference between the HOMO level of the hole transport layer 16 and the HOMO level of the light emitting layer / organic light emitting portion 17a is small, and the HOMO level of the light emitting layer / organic light emitting portion 17a and the HOMO level of the electron transport layer 18 are small. The difference Δh1 is designed to be large. For this reason, holes injected into the light emitting layer / organic light emitting portion 17a are unlikely to leak into the electron transport layer 18, and the density increases near the interface between the light emitting layer / organic light emitting portion 17a and the electron transport layer 18. Therefore, when the light emitting layer does not include the dielectric fine particles 17b, recombination of electrons and holes is likely to occur near the interface between the light emitting layer 17a and the electron transport layer 18. As a result, there arise problems that the emission center is biased near the interface with the electron transport layer 18 in the light emitting layer 17a, and that many excitons are also generated in the electron transport layer 18. On the other hand, in the second region 172, as shown in the schematic diagram of FIG. 3C, the difference Δh between the VBM of the dielectric fine particles 17b and the HOMO level of the organic light emitting portion 17a is designed to be 0.1 eV or more. . Accordingly, as shown in the schematic diagram of FIG. 4B, holes are trapped at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b, thereby preventing the movement of the holes. As a result, in the second region 172, the hole density at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b also increases, and the increase in the hole density at the interface with the electron transport layer 18 in the third region 173 is reduced. Can do. Therefore, at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b in the second region 172, electrons are recombined with the trapped holes, and the recombination probability of the electrons and holes is increased. On the other hand, in the vicinity of the interface of the third region 173 with the electron transport layer 18, the hole density decreases, and as a result, the recombination probability of electrons and holes becomes smaller than that in the comparative example. As a result, the exciton distribution peak moves to the second region 172. Therefore, the light emission center of the light emitting layer 17 can be moved to the second region 172. In addition, since the exciton density can be prevented from becoming extremely high at the interface with the electron transport layer 18 in the third region 173, the light emitting layer 17 can be locally degraded in the vicinity of the interface, Degradation of the functional layer due to excitons can also be suppressed.

  In addition, when there is no remarkable difference in the electron transport property and hole transport property of the organic light emission part 17a, when the light emitting layer does not contain the dielectric fine particle 17b, the electron transport property of the organic light emission part 17a mentioned above is sufficient. There are problems both when the hole transportability is high and when the hole transportability is high compared with the electron transportability. That is, recombination of electrons and holes is likely to occur near the interface between the light emitting layer 17a and the hole transport layer 16 and near the interface between the light emitting layer 17a and the electron transport layer 18. As a result, there arise problems that the emission center is biased to both ends of the light emitting layer 17a in the film thickness direction, and excitons are generated in the hole transport layer 16 and the electron transport layer 18. On the other hand, when the light emitting layer includes the dielectric fine particles 17b, both electrons and holes are trapped at the interface between the organic light emitting portion 17a and the dielectric fine particles 17b. The recombination probability also increases.

  In addition, when the organic light emission part 17a consists of a some organic-semiconductor material, it is as follows. Focusing on the electron transport property, the material having the highest electron transport property (hereinafter referred to as “electron transport material”) among the plurality of organic semiconductor materials constituting the organic light emitting portion 17 a is the electron transport in the light emitting layer 17. Will be responsible. Therefore, it is preferable that the difference Δe between the CBM of the dielectric fine particles 17b and the LUMO level of the electron transporting material included in the organic light emitting portion 17a is 0.1 eV or more. Similarly, focusing on hole transportability, a material having the highest hole transportability (hereinafter referred to as “hole transportability material”) out of the plurality of organic semiconductor materials constituting the organic light emitting portion 17a emits light. It will be responsible for hole transport in the layer 17. Therefore, the difference Δh between the HOMO level of the hole transporting material contained in the organic light emitting portion 17a and the VBM of the dielectric fine particles 17b is preferably 0.1 eV or more. The organic light emitting unit 17a may include an electron transporting material, a hole transporting material, and an organic light emitting material, and the organic light emitting material is at least one of an electron transporting material and a hole transporting material. May function.

3. Manufacturing method of organic EL element The manufacturing method of the organic EL element 1 is demonstrated using drawing. FIGS. 5A to 5E, FIGS. 6A to 6D, FIGS. 7A to 7B, and FIGS. 8A to 8D are processes in the production of the organic EL element 1. FIG. It is a schematic cross section which shows the state in. FIG. 9 is a flowchart showing a method for manufacturing the organic EL element 1.

(1) Formation of Substrate 11 First, as shown in FIG. 5A, the TFT layer 112 is formed on the base 111 to form the substrate 11 (step S1 in FIG. 9). The TFT layer 112 can be formed by a known TFT manufacturing method.
Next, as shown in FIG. 5B, an interlayer insulating layer 12 is formed on the substrate 11 (step S2 in FIG. 9). The interlayer insulating layer 12 can be laminated by using, for example, a plasma CVD method, a sputtering method, or the like.

Next, a dry etching method is performed at a location on the source electrode of the TFT layer in the interlayer insulating layer 12 to form a contact hole. The contact hole is formed so that the surface of the source electrode is exposed at the bottom.
Next, a connection electrode layer is formed along the inner wall of the contact hole. A part of the upper portion of the connection electrode layer is disposed on the interlayer insulating layer 12. For example, a sputtering method can be used to form the connection electrode layer. After forming a metal film, patterning is performed using a photolithography method and a wet etching method.

(2) Formation of Pixel Electrode 13 and Hole Injection Layer 15 Next, as shown in FIG. 5C, a pixel electrode material layer 130 is formed on the interlayer insulating layer 12 (step S3 in FIG. 9). The pixel electrode material layer 130 can be formed using, for example, a vacuum evaporation method, a sputtering method, or the like.
Next, as shown in FIG. 5D, the hole injection material layer 150 is formed on the pixel electrode material layer 130 (step S4 in FIG. 9). The hole injection material layer 150 can be formed using, for example, a reactive sputtering method.

Then, as shown in FIG. 5E, the pixel electrode material layer 130 and the hole injection material layer 150 are patterned by etching, so that a plurality of pixel electrodes 13 and hole injection layers 15 partitioned for each subpixel are formed. Are formed (step S5 in FIG. 9).
Note that the formation method of the pixel electrode 13 and the hole injection layer 15 is not limited to the above-described method. For example, the pixel electrode material layer 130 is patterned to form the pixel electrode 13, and then the hole injection layer 15 is formed. May be.

(3) Formation of partition wall layer 14 Next, as shown in FIG. 6A, a partition wall layer resin, which is a material of the partition wall layer 14, is applied onto the hole injection layer 15 and the interlayer insulating layer 12, and the partition wall is formed. A material layer 140 is formed. For the partition wall material layer 140, a solution obtained by dissolving a phenol resin, which is a partition wall resin, in a solvent (for example, a mixed solvent of ethyl lactate and GBL) is spin-coated on the hole injection layer 15 and the interlayer insulating layer 12 or the like. It forms by apply | coating uniformly using. Then, the partition wall layer 14 is formed by performing pattern exposure and development on the partition wall material layer 140 (FIG. 6B, step S6 in FIG. 9), and the partition layer 14 is baked (step S7 in FIG. 9). Thereby, the opening part 14a used as the formation area of the light emitting layer 17 is prescribed | regulated. The partition layer 14 is baked, for example, at a temperature of 150 ° C. or higher and 210 ° C. or lower for 60 minutes.

In the step of forming the partition wall layer 14, the surface of the partition wall layer 14 may be further subjected to a surface treatment with a predetermined alkaline solution, water, an organic solvent, or the like, or a plasma treatment may be performed. This is performed for the purpose of adjusting the contact angle of the partition layer 14 with respect to the ink (solution) applied to the opening 14a, or for the purpose of imparting water repellency to the surface.
(4) Formation of Hole Transport Layer 16 Next, as shown in FIG. 6C, an ink containing an ink containing the constituent material of the hole transport layer 16 is applied to the opening 14a defined by the partition wall layer 14. The ink is ejected from the nozzle 4030 401 and applied onto the hole injection layer 15 in the opening 14a and baked (dried) to form the hole transport layer 16 (step S8 in FIG. 9).

(5) Formation of the light emitting layer 17 Next, the light emitting layer 17 is formed on the hole transport layer 16 in the opening part 14a (step S9 of FIG. 9). First, as shown in FIG. 6 (d), a first ink containing an organic light emitting material is ejected from the nozzle 4030 of the inkjet head 401, applied onto the hole transport layer 16 in the opening 14a, and dried. As a result, the first region 171 is formed. The drying here may be performed to such an extent that the ink that is the material of the second region 172 can be applied onto the first region 171. That is, it is not always necessary to include forced drying by firing or reduced pressure environment, and only natural drying may be used.

  Next, as shown in FIG. 7A, the second ink containing the dielectric fine particles 17b is ejected from the nozzle 4030 of the inkjet head 401, applied onto the first region 171 and dried to perform the second. Region 172 is formed. The second ink is generated by mixing the dielectric fine particles 17b with the first ink and sufficiently stirring. The dielectric fine particles 17b can be generated by, for example, a gas phase method such as a plasma CVD method, or a liquid phase method such as a liquid phase deposition method.

The dielectric fine particles 17b may be subjected to a surface treatment with a dispersant before being mixed with the light emitting layer ink. This is performed for the purpose of preventing the dielectric fine particles 17b from aggregating and uniformly dispersing in the ink.
Next, as shown in FIG. 7B, the first ink is ejected from the nozzle 4030 of the inkjet head 401, applied onto the second region 172, and dried to form the third region 173. Finally, baking is performed to completely dry the first region 171, the second region 172, and the third region 173, and the light emitting layer 17 is formed.

(6) Formation of Electron Transport Layer 18 Next, as shown in FIG. 8A, the electron transport layer 18 is formed on the light emitting layer 17 and the partition layer 14 (step S10 in FIG. 9). The electron transport layer 18 is formed, for example, by depositing an electron transporting organic material in common for each sub-pixel by vapor deposition.
(7) Formation of the electron injection layer 19 Next, as shown in FIG.8 (b), the electron injection layer 19 is formed on the electron carrying layer 18 (step S11 of FIG. 9). The electron injection layer 19 is formed, for example, by depositing an electron transporting organic material and a doped metal in common for each subpixel by a co-evaporation method.

(8) Formation of counter electrode 20 Next, as shown in FIG.8 (c), the counter electrode 20 is formed on the electron injection layer 19 (step S12 of FIG. 9). The counter electrode 20 is formed by forming a film of ITO, IZO, silver, aluminum or the like by a sputtering method or a vacuum evaporation method.
(9) Formation of the sealing layer 21 Next, as shown in FIG.8 (d), the sealing layer 21 is formed on the counter electrode 20 (step S13 of FIG. 9). The sealing layer 21 can be formed by depositing SiON, SiN, or the like by sputtering, CVD, or the like.

A color filter or an upper substrate may be placed on the sealing layer 21 and bonded.
5. Overall Configuration of Organic EL Display Device FIG. 10 is a schematic block diagram showing a configuration of an organic EL display device 1000 including the organic EL display panel 100. As shown in FIG. 10, the organic EL display device 1000 includes an organic EL display panel 100 and a drive control unit 200 connected thereto. The drive control unit 200 includes four drive circuits 210 to 240 and a control circuit 250.

In the actual organic EL display device 1000, the arrangement of the drive control unit 200 with respect to the organic EL display panel 100 is not limited to this.
5. Modification In the above embodiment, the cathode is the counter electrode and the top emission type organic EL display device. However, for example, the anode may be a counter electrode and the cathode may be a pixel electrode. For example, a bottom emission type organic EL display device may be used.

  Moreover, in the said embodiment, although the electron carrying layer 18, the electron injection layer 19, the hole injection layer 15, and the hole transport layer 16 were essential structures, it is not restricted to this. For example, an organic EL element that does not have the electron transport layer 18 or an organic EL element that does not have the hole transport layer 16 may be used. Further, for example, instead of the hole injection layer 15 and the hole transport layer 16, a single layer hole injection transport layer may be provided. Further, for example, an intermediate layer made of an alkali metal may be provided between the light emitting layer 17 and the electron transport layer 18.

  Moreover, the organic EL element may have components other than the above-mentioned structure. For example, a low refractive index layer is provided between the counter electrode 20 and the sealing layer 21, and an optical resonator structure is formed between the surface of the pixel electrode on the light emitting layer side and the interface between the counter electrode and the low refractive index layer. It may be formed. Or, for example, the counter electrode has a two-layer structure of a metal layer and a conductive oxide layer, and is between the surface of the pixel electrode on the light emitting layer side and the interface between the metal layer and the conductive oxide layer in the counter electrode. An optical resonator structure may be formed. In any case, the light extraction efficiency of the optical resonator can be maximized by controlling the position of the second region 172 in the light emitting layer 17.

  Moreover, in the said embodiment, although it was set as the band structure shown by Fig.3 (a) and FIG.3 (c), a band structure is not restricted to this. The dielectric fine particles 17b may hinder the transport of electrons and / or holes in the light-emitting layer 17, so that the density of electrons and / or holes in the vicinity of the interface between the organic light-emitting portion 17a and the dielectric fine particles 17b may be increased. The band structure at the interface between the light emitting layer 17 and the other layer may be different from the structure shown in FIGS. 3 (a) and 3 (c).

Moreover, it is not limited to a display device, but may be a panel type lighting device such as an organic EL lighting device.
As described above, the organic light emitting panel and the display device according to the present disclosure have been described based on the embodiments and the modifications. However, the present invention is not limited to the above embodiments and the modifications. By arbitrarily combining the components and functions in the embodiments and modifications without departing from the gist of the present invention, and forms obtained by making various modifications conceivable by those skilled in the art with respect to the above-described embodiments and modifications. Implemented forms are also included in the present invention.

  INDUSTRIAL APPLICABILITY The present invention is useful for manufacturing an organic EL element having a high luminous efficiency and a long lifetime, and an organic EL display panel and a display device including the organic EL element.

DESCRIPTION OF SYMBOLS 11 Board | substrate 12 Interlayer insulation layer 13 Pixel electrode 14 Partition layer 14a Opening part 15 Hole injection layer 16 Hole transport layer 17 Light emitting layer 171 1st area | region 172 2nd area | region (area | region)
173 3rd area | region 17a Organic light-emitting part 17b Dielectric fine particle 18 Electron transport layer 19 Electron injection layer 20 Counter electrode 21 Sealing layer 100 Organic EL display panel

Claims (11)

The anode,
A cathode facing the anode;
A light emitting layer disposed between the anode and the cathode,
The light emitting layer is an organic EL element having a region containing more dielectric fine particles than other regions in the film thickness direction. The organic EL element according to claim 1, wherein the thickness of the region is 20% or less of the thickness of the light emitting layer. The organic EL element according to claim 1 or 2, wherein the dielectric fine particles have a particle size of 1 nm or more and 30 nm or less. The organic EL element according to any one of claims 1 to 3, wherein a band gap of the material of the dielectric fine particles is 3 eV or more. The light emitting layer includes an electron transporting material,
5. The difference between the conduction band lower end (CBM) of the dielectric fine particle material and the lowest unoccupied orbital (LUMO) level in the electron transport material is 0.1 eV or more. 5. Organic EL element. The light emitting layer includes a hole transport material, and a difference between a valence band upper end (VBM) of the dielectric fine particle material and a highest occupied orbital (HOMO) level of the hole transport material is 0.1 eV or more The organic EL device according to any one of claims 1 to 5. The material of the dielectric fine particles is selected from the group consisting of zinc oxide (ZnO), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), and aluminum oxide (Al ₂ O ₃ ). 2. The organic EL element according to item 1. The organic EL element according to claim 1, wherein the surface of the dielectric fine particles is modified with a dispersant. The organic EL device according to claim 8, wherein the dispersant includes one or more of phosphoric acid, carboxylic acid, sulfonic acid, or salts thereof. An organic EL display panel comprising a plurality of organic EL elements according to any one of claims 1 to 9 on a substrate. Prepare the board
Forming a pixel electrode above the substrate;
Above the pixel electrode, a first ink containing at least an organic light emitting material, a second ink containing the organic light emitting material and containing more dielectric fine particles than the first ink, and the first ink are applied in this order. To form a light emitting layer,
A method for manufacturing an organic EL element, wherein a common electrode is formed above the light emitting layer.

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