JP-7855884-B2 - Light-emitting element

Inventors

• 豊田 和也
• 田中 健太郎

Assignees

• 東レ株式会社

Dates

Publication Date

20260511

Application Date

20220322

Claims (6)

1. A light-emitting element that emits light by electrical energy, wherein at least an organic thin film layer and a light-emitting layer are present between an anode and a cathode, and the organic thin film layer comprises an n-type charge generation layer, an electron transport layer and/or an electron injection layer, and the n-type charge generation layer, electron transport layer and/or electron injection layer contains a phenanthroline derivative represented by the following general formula (1) containing iodine , and the iodine content in the phenanthroline derivative represented by the general formula (1) is 60 ppm or more and 100,000 ppm or less . (In the above general formula (1), R2 to R7 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkylthio group, an arylthio group, or a cyano group. R1 and R8 may be the same or different and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. However, at least one of R1 and R8 is a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group.)
2. The light-emitting element according to claim 1, comprising 2-phenyl-9-[3-(9-phenyl-1,10-phenanthroline-2-yl)phenyl]-1,10-phenanthroline and/or 2-[4-(9-phenantrenyl)-1-naphthalenyl]-1,10-phenanthroline as the phenanthroline derivative represented by the general formula (1).
3. The light-emitting element according to claim 1 or claim 2, wherein the iodine content in the phenanthroline derivative represented by the general formula (1) is 60 ppm or more and 10,000 ppm or less.
4. The light-emitting element according to any one of claims 1 to 3 , wherein the organic thin film layer contains alkali metal atoms and/or rare earth metal atoms.
5. A display device including a light-emitting element according to any one of claims 1 to 4 .
6. A lighting device including a light-emitting element according to any one of claims 1 to 4 .

Description

This invention relates to a light-emitting element. Phenanthroline derivatives are useful compounds as light-emitting elements in applications such as display elements, flat panel displays, backlights, lighting, interiors, signs, billboards, electrophotographs, and optical signal generators. As an example of a light-emitting element using a phenanthroline derivative, a device has been proposed in which a light-emitting material exists between the positive and negative electrodes and emits light in response to electrical energy, characterized in that the device contains an organic phosphor having a phenanthroline skeleton (see, for example, Patent Document 1). Japanese Patent Publication No. 2001-267080 This is a schematic cross-sectional view of an example of a light-emitting element of the present invention.This is a schematic cross-sectional view of another example of the light-emitting element of the present invention.This is a schematic cross-sectional view of another example of the light-emitting element of the present invention. The present invention will be described below. The light-emitting element of the present invention emits light in response to electrical energy, and at least an organic thin film layer and a light-emitting layer exist between the anode and the cathode. The light-emitting layer is a layer that emits light due to excitation energy generated by the recombination of holes and electrons. The organic thin film layer is a layer other than the light-emitting layer that contains the phenanthroline derivative represented by the general formula (1) above. Examples of such organic thin film layers include the n-type charge generation layer, electron transport layer, and electron injection layer described later. The n-type charge generation layer is a layer that generates or separates electrons by applying a voltage and supplies electrons to adjacent layers. The electron transport layer is a layer that transports electrons injected from the cathode or the n-type charge generation layer to the light-emitting layer. The electron injection layer is a layer that assists in the injection of electrons from the cathode to the electron transport layer. The n-type charge generation layer, electron transport layer, and electron injection layer may each have a stacked structure of two or more layers. Figures 1 to 4 show examples of schematic cross-sectional views of the light-emitting element of the present invention. The light-emitting element 1 shown in Figure 1 has an organic thin film layer 6, an emissive layer 5, and a cathode 3 on the anode 2 in that order. The light-emitting element 1 shown in Figure 2 has an emissive layer 5, an organic thin film layer 6, and a cathode 3 on the anode 2 in that order. The light-emitting element 1 shown in Figure 3 has organic thin film layers 6 and emissive layers 5 alternately stacked on the anode 2, with the cathode 3 on the upper organic thin film layer 6. That is, the organic thin film layer 6 may be formed between the anode 2 and the emissive layer 5 (see Figure 1), or between the cathode 3 and the emissive layer 5 (see Figure 2). Furthermore, in the case of a tandem structure where multiple emissive layers 5 are formed, the organic thin film layer 6 may be formed between the emissive layers 5. Also, the organic thin film layer 6 may be formed between the anode 2 and the emissive layer 5, or between the cathode 3 and the emissive layer 5 (see Figure 3). Furthermore, the organic thin film layer 6 may be a layer formed by stacking multiple layers. The present invention is characterized in that the organic thin film layer contains a phenanthroline derivative represented by the following general formula (1), which contains iodine. In the general formula (1) above, R2 to R7 may be the same or different, and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, a cycloalkyl group, an alkoxy group, an aryloxy group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkylthio group, an arylthio group, or a cyano group. Among these, a hydrogen atom is preferred because it has low steric hindrance, allowing the reaction at the R1 and/or R8 positions to proceed efficiently. R1 and R8 may be the same or different, and represent a hydrogen atom, a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. However, at least one of R1 and R8 is a substituted or unsubstituted aryl group, a heteroaryl group, an alkyl group, or a cycloalkyl group. R1 and R8 are preferably substituted or unsubstituted aryl groups or substituted or unsubstituted heteroaryl groups, as this results in a higher glass transition temperature and improved heat resistance. Furthermore, the increased electron mobility allows for a further reduction in the driving voltage. A substituted or unsubstituted aryl group is more preferable, and a substituted or unsubstituted phenyl group is even more pref