KR-102961318-B1 - LIGHT-EMITTING ELEMENT, LIGHT-EMITTING DEVICE, ELECTRONIC DEVICE, AND LIGHTING DEVICE

KR102961318B1KR 102961318 B1KR102961318 B1KR 102961318B1KR-102961318-B1

Abstract

The present invention provides a novel light-emitting element. Or, provides a light-emitting element with a good lifespan. Or, provides a light-emitting element with good luminous efficiency. The EL layer comprises a hole injection layer, a first hole transport layer, a second hole transport layer, a third hole transport layer, an emitting layer, a first electron transport layer, and a second electron transport layer in this order, the hole injection layer comprises an organic acceptor, the HOMO level of each layer is such that the second hole transport layer is deeper than the first hole transport layer, the host material is deeper than the second hole transport layer, the third hole transport layer is equal to or deeper than the host material, and the difference between the second hole transport layer and the third hole transport layer is 0.3 eV or less, the LUMO level of each layer is such that the host material is higher than the first electron transport layer and the second electron transport layer is higher than the first electron transport layer, the host material is a material comprising a condensed aromatic ring framework, and the first electron transport layer and the second electron transport layer are materials comprising a heteroaromatic ring framework. The present invention provides a emitting device.

Inventors

세오 사토시
스즈키 쓰네노리
다키타 유스케
하시모토 나오아키

Assignees

가부시키가이샤 한도오따이 에네루기 켄큐쇼

Dates

Publication Date: 20260511
Application Date: 20250701
Priority Date: 20160728

Claims (13)

As a light-emitting element, First electrode; A hole injection layer on the first electrode, comprising a first material; A light-emitting layer above the hole injection layer, comprising a host material and a light-emitting material; As a first electron transport layer on the light-emitting layer, a first electron transport layer comprising a first electron transport material, A second electron transport layer comprising a second electron transport material as a second electron transport layer on the first electron transport layer; and It includes a second electrode on the second electron transport layer, and The first material above is an organic compound containing a fluoro group, and The LUMO level of the above host material is higher than the LUMO level of the above first electron transport material, and The LUMO level of the second electron transport material is higher than the LUMO level of the first electron transport material, and The above host material has a condensed aromatic ring backbone comprising 3 to 6 rings, The above-mentioned first electron transport material has a first heteroaromatic ring framework, The above-mentioned first heteroaromatic ring backbone comprises a first ring comprising a triazine backbone or a diazine backbone, and The above second electron transport material has a second heteroaromatic ring framework, The first heteroaromatic ring framework and the second heteroaromatic ring framework are different from each other, forming a light-emitting element.
As a light-emitting element, First electrode; A hole injection layer on the first electrode, comprising a first material; A light-emitting layer above the hole injection layer, comprising a host material and a light-emitting material; As a first electron transport layer on the light-emitting layer, a first electron transport layer comprising a first electron transport material, A second electron transport layer comprising a second electron transport material as a second electron transport layer on the first electron transport layer; and It includes a second electrode on the second electron transport layer, and The first material above is an organic compound containing a fluoro group, and The LUMO level of the above host material is higher than the LUMO level of the above first electron transport material, and The LUMO level of the second electron transport material is higher than the LUMO level of the first electron transport material, and The above host material has a condensed aromatic ring backbone comprising 3 to 6 rings, The first electron transport layer is a monolayer of the first electron transport layer material, and The above-mentioned first electron transport material has a first heteroaromatic ring framework, The above-mentioned first heteroaromatic ring backbone comprises a first ring comprising a triazine backbone or a diazine backbone, and The above second electron transport material has a second heteroaromatic ring framework, The first heteroaromatic ring framework and the second heteroaromatic ring framework are different from each other, forming a light-emitting element.
In Article 1 or Article 2, The above second electron transport material is a light-emitting device having a second ring comprising a pyridine backbone or a bipyridine backbone.
In Paragraph 3, The above second electron transport material is a light-emitting element having a phenanthroline ring.
In Article 1 or Article 2, A light-emitting device wherein the first electron transport material and the second electron transport material each comprise a nitrogen-containing 6-membered heteroaromatic ring framework.
As a light-emitting element, First electrode; A hole injection layer on the first electrode, comprising a first material; A light-emitting layer above the hole injection layer, comprising a host material and a light-emitting material; As a first electron transport layer on the light-emitting layer, a first electron transport layer comprising a first electron transport material, A second electron transport layer comprising a second electron transport material as a second electron transport layer on the first electron transport layer; and It includes a second electrode on the second electron transport layer, and The first material above is an organic compound containing a fluoro group, and The LUMO level of the above host material is higher than the LUMO level of the above first electron transport material, and The LUMO level of the second electron transport material is higher than the LUMO level of the first electron transport material, and The above host material has a condensed aromatic ring backbone comprising 3 to 6 rings, The above-mentioned first electron transport material has a first heteroaromatic ring framework, The above-mentioned first heteroaromatic ring skeleton is a condensed heteroaromatic ring, and The above-mentioned condensed heteroaromatic ring comprises a nitrogen-containing six-membered heteroaromatic ring, and The above second electron transport material has a second heteroaromatic ring framework, The first heteroaromatic ring framework and the second heteroaromatic ring framework are different from each other, forming a light-emitting element.
In Article 6, A light-emitting device in which the first heteroaromatic ring backbone comprises a dibenzoquinoxaline backbone.
In any one of Articles 1, 2 and 6, The above-mentioned light-emitting material is a phosphorescent material, and A light-emitting device in which the first electron transport material has an excitation energy level greater than that of the light-emitting material.
In Article 8, A light-emitting device in which the difference in excitation energy levels caused by the excitation energy level of the first electron transport material prevents energy transfer from the exciton of the light-emitting material.
In Article 6, A hole transport layer is additionally included between the hole injection layer and the light-emitting layer, The above hole transport layer includes a hole transport material, and A light-emitting device in which the difference between the LUMO level of the first material and the HOMO level of the hole transport material is 1 eV or less.
In any one of Articles 1, 2 and 6, A light-emitting element in which the first material has a plurality of fluoro groups.
As a light-emitting device, A light-emitting element according to any one of claims 1, 2 and 6; and A light-emitting device comprising a transistor or a substrate.
As an electronic device, A light-emitting device according to claim 12; and An electronic device comprising one selected from a sensor, an operation button, a speaker, and a microphone.

Description

Light-emitting element, light-emitting device, electronic device, and lighting device One embodiment of the present invention relates to a light-emitting element, a display module, a lighting module, a display device, a light-emitting device, an electronic device, and a lighting device. Furthermore, one embodiment of the present invention is not limited to the above technical field. The technical field to which one embodiment of the invention disclosed in this specification, etc. belongs relates to an object, a method, or a method of manufacturing. Alternatively, one embodiment of the present invention relates to a process, a machine, a product, or a composition of matter. Accordingly, more specific examples of the technical field to which one embodiment of the present invention disclosed in this specification belongs include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a storage device, a memory device, an imaging device, a method of driving the same, or a method of manufacturing the same. The commercialization of light-emitting devices (organic EL devices) utilizing electroluminescence (EL) using organic compounds is underway. The basic configuration of these light-emitting devices consists of an organic compound layer (EL layer) containing a light-emitting material sandwiched between a pair of electrodes. By applying voltage to this device to inject carriers and utilizing the recombination energy of the carriers, light emission from the light-emitting material can be obtained. Since these light-emitting elements are self-emissive, when used as pixels in a display, they offer advantages such as higher visibility compared to liquid crystals and the elimination of the need for a backlight, making them suitable as flat panel display elements. Additionally, a major advantage is that displays using these light-emitting elements can be manufactured to be thin and lightweight. Furthermore, a very fast response speed is also one of their characteristics. Furthermore, since these light-emitting devices can form a continuous two-dimensional light-emitting layer, surface light emission can be achieved. Because this is a characteristic that is difficult to obtain with point light sources, such as incandescent bulbs and LEDs, or line light sources, such as fluorescent lamps, they have high utility value as surface light sources applicable to lighting and the like. As such, displays and lighting devices using light-emitting elements are suitable for various electronic devices, but research and development are underway to develop light-emitting elements with better efficiency and lifespan. Organic acceptors are used as materials for the hole injection layer to facilitate the injection of carriers into the EL layer, particularly holes. Since organic acceptors can be easily formed by deposition, they are suitable for mass production and are widely used. However, if the LUMO level of the organic acceptor and the HOMO level of the organic compound constituting the hole transport layer are far apart, it is difficult to inject holes into the EL layer. For this reason, if a material with a shallow HOMO level is used as the organic compound constituting the hole transport layer to bring the LUMO level of the organic acceptor and the HOMO level of the organic compound constituting the hole transport layer closer, the difference between the HOMO level of the host material used in the emissive layer and the HOMO level of the organic compound constituting the hole transport layer increases. Consequently, even if holes can be injected into the EL layer, there was a problem in that it became difficult to inject the host material from the hole transport layer into the emissive layer. In addition, because organic acceptors have low hole injection capabilities, there were cases where lifespan was reduced or roll-off occurred at high brightness levels. Patent Document 1 discloses a configuration in which a hole transport material having a HOMO level between the HOMO level of a first hole injection layer and the HOMO level of a host material is provided between a first hole transport layer in contact with a hole injection layer and a light-emitting layer. In addition, Patent Document 2 discloses a light-emitting device in which a long lifespan is achieved by using an electron transport layer to which a material having electron trapping properties is added. As such, while the characteristics of light-emitting devices have been significantly improved, it must be said that they are still insufficient to meet the high demands for various characteristics, including efficiency and durability. Figure 1 is a conceptual diagram of a light-emitting element. FIG. 2 is a diagram showing an example of a method for manufacturing a light-emitting element. FIG. 3 is a drawing showing an example of a manufacturing apparatus for a light-emitting element. Figure 4 is a conceptual diag