Light emitting apparatus, display apparatus, and electronic instrument

Abstract

Provided is a light emitting apparatus comprising a light emitting device A and a light emitting device B. The light emitting device A has a first electrode A, a second electrode A, a light emission layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light emission layer A, and a second layer A sandwiched between the first layer A and the light emission layer A. The light emitting device B has a first electrode B, a second electrode B, a light emission layer B sandwiched between the first electrode B and the second electrode B, a first layer B sandwiched between the first electrode B and the light emission layer B, a second layer B positioned between the first layer B and the light emission layer B, and a third layer B sandwiched between the first electrode B and the light emission layer B. The light emission layer A has a light emitting substance A. The light emission layer B has a light emitting substance B. The light emission peak wavelength of the light emitting substance A is shorter than the light emission peak wavelength of the light emitting substance B. The first layer A and the first layer B, and the second layer A and the second layer B respectively include the same material. The ordinary light refractive index of the first layer A at the light emission peak wavelength of the light emitting substance A is lower than the ordinary light refractive index of the second layer A. The ordinary light refractive index of the first layer B at the light emission peak wavelength of the light emitting substance B is lower than the ordinary light refractive index of the second layer B. The third layer B is positioned between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light emission layer B.

Description

Light-emitting device, display device and electronic device

[0001] One embodiment of the present invention relates to an organic compound, a light-emitting element, a light-emitting device, a display module, a lighting module, a display device, a light-emitting device, an electronic device, a lighting device, and an electronic device. Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, an imaging device, a driving method thereof, or a manufacturing method thereof.

[0002] Light-emitting devices (organic EL devices) that utilize electroluminescence (EL) using organic compounds are becoming increasingly practical. The basic structure of these light-emitting devices is a pair of electrodes sandwiching an organic compound layer (EL layer) containing a light-emitting material. By applying a voltage to this device, carriers are injected, and the recombination energy of the carriers is utilized to emit light from the light-emitting material.

[0003] Since such light-emitting devices are self-luminous, when used as display pixels, they offer advantages such as higher visibility and no need for backlighting compared to liquid crystal displays, making them particularly suitable for flat panel displays. Another major advantage of displays using such light-emitting devices is that they can be fabricated to be thin and lightweight. Another feature is their extremely fast response time.

[0004] Furthermore, these light-emitting devices can have a continuous light-emitting layer formed two-dimensionally, enabling them to emit light in a planar form. This is a feature that is difficult to obtain with point light sources such as incandescent lamps or LEDs, or linear light sources such as fluorescent lamps, making them highly useful as planar light sources for lighting and other applications.

[0005] Displays and lighting devices using such light-emitting devices are suitable for a variety of electronic devices, but research and development is ongoing to find light-emitting devices with even better characteristics.

[0006] One of the problems often cited when discussing organic EL devices is their low light extraction efficiency. To improve this, a structure has been proposed in which a layer made of a low refractive index material is formed inside the EL layer (see, for example, Patent Document 1).

[0007] US Patent Application Publication No. 2020 / 0176692

[0008] An object of one embodiment of the present invention is to provide a light-emitting device with high emission efficiency, or to provide a display device and an electronic device with low power consumption.

[0009] The present invention is intended to solve any one of the above problems.

[0010] One aspect of the present invention is a light-emitting device including a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, the first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a third layer B sandwiched between the first electrode B and the light-emitting layer B, and the light-emitting layer A a light-emitting device comprising a light-emitting substance A, the light-emitting layer B comprising a light-emitting substance B, the emission peak wavelength of the light-emitting substance A being shorter than the emission peak wavelength of the light-emitting substance B, the first layer A and the first layer B, and the second layer A and the second layer B each comprise the same material, the ordinary refractive index of the first layer A at the emission peak wavelength of the light-emitting substance A is lower than the ordinary refractive index of the second layer A, the ordinary refractive index of the first layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B, and the third layer B is located either between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light-emitting layer B.

[0011] Alternatively, another aspect of the present invention includes a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, the first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a third layer B sandwiched between the first electrode B and the light-emitting layer B, the first layer A and the first layer B, and the second layer A and the second layer B, are each made of the same material; the ordinary refractive index of the first layer A at the emission peak wavelength of the luminescent substance A is lower than the ordinary refractive index of the second layer A; the ordinary refractive index of the first layer B at the emission peak wavelength of the luminescent substance B is lower than the ordinary refractive index of the second layer B; and the third layer B is located either between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the luminescent layer B.

[0012] Alternatively, another aspect of the present invention includes a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, the first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a third layer B sandwiched between the first electrode B and the light-emitting layer B, the light-emitting layer A contains a luminescent material A, the light-emitting layer B contains a luminescent material B, the emission peak wavelength of the luminescent material A is shorter than the emission peak wavelength of the luminescent material B, the first layer A and the first layer B, and the second layer A and the second layer B each have the same configuration, the ordinary refractive index of the first layer A at the emission peak wavelength of the luminescent material A is lower than the ordinary refractive index of the second layer A, the ordinary refractive index of the first layer B at the emission peak wavelength of the luminescent material B is lower than the ordinary refractive index of the second layer B, and the third layer B is located either between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light-emitting layer B.

[0013] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the first electrode B and the first layer B.

[0014] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B and the first layer B are in contact with each other, and the first layer B and the second layer B are in contact with each other.

[0015] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B by 0.15 or more.

[0016] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B.

[0017] Alternatively, another embodiment of the present invention is a light-emitting device having the above structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is equal to or lower than the ordinary refractive index of the first layer B.

[0018] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the first layer B and the second layer B.

[0019] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer B and the third layer B are in contact with each other, and the third layer B and the second layer B are in contact with each other.

[0020] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is higher than the ordinary refractive index of the first layer B by 0.15 or more.

[0021] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is higher than the ordinary refractive index of the first layer B.

[0022] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is equal to or higher than the ordinary refractive index of the second layer B.

[0023] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the second layer B and the light-emitting layer B.

[0024] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer B and the second layer B are in contact with each other, and the second layer B and the third layer B are in contact with each other.

[0025] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B by 0.15 or more.

[0026] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B.

[0027] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described structure, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting substance B is equal to or lower than the ordinary refractive index of the first layer B.

[0028] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first electrode A and the first layer A are in contact with each other.

[0029] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first electrode B is in contact with the first layer B or the third layer B.

[0030] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the first layer A at the emission peak wavelength of the light-emitting substance A is lower than the ordinary refractive index of the second layer A by 0.20 or more, and the ordinary refractive index of the first layer B at the emission peak wavelength of the light-emitting substance B is lower than the ordinary refractive index of the second layer B by 0.15 or more.

[0031] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer A and the first layer B are continuous with each other, and the second layer A and the second layer B are continuous with each other.

[0032] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the first layer A at the emission peak wavelength of the light-emitting substance A is 1.75 or less, and the ordinary refractive index of the first layer B at the emission peak wavelength of the light-emitting substance B is 1.70 or less.

[0033] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the second layer A at the emission peak wavelength of the light-emitting substance A is 1.90 or more, and the ordinary refractive index of the second layer B at the emission peak wavelength of the light-emitting substance B is 1.90 or more.

[0034] Alternatively, another aspect of the present invention is a light-emitting device including a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, a first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a second layer A sandwiched between the first electrode B and the light-emitting layer B. the light-emitting device A has a peak emission wavelength shorter than the peak emission wavelength of the light-emitting device B; the first layer A and the first layer B, and the second layer A and the second layer B each contain the same material; the ordinary refractive index of the first layer A at the peak emission wavelength of the light-emitting device A is lower than the ordinary refractive index of the second layer A; the ordinary refractive index of the first layer B at the peak emission wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B; and the third layer B is located either between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light-emitting layer B.

[0035] Alternatively, another aspect of the present invention includes a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, the first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a second layer A sandwiched between the first electrode B and the light-emitting layer B. a third layer B, wherein the peak emission wavelength of the light-emitting device A is shorter than the peak emission wavelength of the light-emitting device B; the first layer A and the first layer B, and the second layer A and the second layer B are each made of the same material; the ordinary refractive index of the first layer A at the peak emission wavelength of the light-emitting device A is lower than the ordinary refractive index of the second layer A; the ordinary refractive index of the first layer B at the peak emission wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B; and the third layer B is located either between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light-emitting layer B.

[0036] Alternatively, another aspect of the present invention is a light-emitting device including a light-emitting device A and a light-emitting device B, wherein the light-emitting device A includes a first electrode A, a second electrode A, a light-emitting layer A sandwiched between the first electrode A and the second electrode A, a first layer A sandwiched between the first electrode A and the light-emitting layer A, and a second layer A sandwiched between the first layer A and the light-emitting layer A, and the light-emitting device B includes a first electrode B, a second electrode B, a light-emitting layer B sandwiched between the first electrode B and the second electrode B, a first layer B sandwiched between the first electrode B and the light-emitting layer B, a second layer B located between the first layer B and the light-emitting layer B, and a second layer A sandwiched between the first electrode B and the light-emitting layer B. the light-emitting device A has a peak emission wavelength shorter than the peak emission wavelength of the light-emitting device B; the first layer A and the first layer B, and the second layer A and the second layer B, have the same configuration; the ordinary refractive index of the first layer A at the peak emission wavelength of the light-emitting device A is lower than the ordinary refractive index of the second layer A; the ordinary refractive index of the first layer B at the peak emission wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B; and the third layer B is located anywhere between the first electrode B and the first layer B, between the first layer B and the second layer B, or between the second layer B and the light-emitting layer B.

[0037] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the first electrode B and the first layer B.

[0038] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B and the first layer B are in contact with each other, and the first layer B and the second layer B are in contact with each other.

[0039] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the first layer B and the second layer B.

[0040] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer B and the third layer B are in contact with each other, and the third layer B and the second layer B are in contact with each other.

[0041] Another embodiment of the present invention is a light-emitting device having the above structure, in which the third layer B is located between the second layer B and the light-emitting layer B.

[0042] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer B and the second layer B are in contact with each other, and the second layer B and the third layer B are in contact with each other.

[0043] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first electrode A and the first layer A are in contact with each other.

[0044] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first electrode B is in contact with the first layer B or the third layer B.

[0045] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting device B is higher than the ordinary refractive index of the first layer B.

[0046] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting device B is higher than the ordinary refractive index of the first layer B by 0.15 or more.

[0047] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B.

[0048] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the third layer B at the emission peak wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B by 0.15 or more.

[0049] Alternatively, another aspect of the present invention is a light-emitting device having the above configuration, wherein the ordinary refractive index of the first layer A at the emission peak wavelength of the light-emitting device A is lower than the ordinary refractive index of the second layer A by 0.20 or more, and the ordinary refractive index of the first layer B at the emission peak wavelength of the light-emitting device B is lower than the ordinary refractive index of the second layer B by 0.15 or more.

[0050] Alternatively, another embodiment of the present invention is a light-emitting device having the above configuration, wherein the light-emitting device A further has a fourth layer A, which is located between the second layer A and the light-emitting layer A and is in contact with the second layer A and the light-emitting layer A; the light-emitting device B further has a fourth layer B, which is located between the second layer B or the third layer B and the light-emitting layer B and is in contact with the second layer B or the third layer B and the light-emitting layer B; and the fourth layer A and the fourth layer B contain the same material.

[0051] Alternatively, another embodiment of the present invention is a light-emitting device having the above configuration, wherein the light-emitting device A further has a fourth layer A, the fourth layer A being located between the second layer A and the light-emitting layer A and the fourth layer A being in contact with the second layer A and the light-emitting layer A; the light-emitting device B further has a fourth layer B, the fourth layer B being located between the second layer B or the third layer B and the light-emitting layer B and the fourth layer B being in contact with the second layer B or the third layer B and the light-emitting layer B; and the fourth layer A and the fourth layer B being made of the same material.

[0052] Alternatively, another embodiment of the present invention is a light-emitting device having the above-described configuration, wherein the light-emitting device A further has a fourth layer A, the fourth layer A being located between the second layer A and the light-emitting layer A and the fourth layer A being in contact with the second layer A and the light-emitting layer A; the light-emitting device B further has a fourth layer B, the fourth layer B being located between the second layer B or the third layer B and the light-emitting layer B and the fourth layer B being in contact with the second layer B or the third layer B and the light-emitting layer B; and the fourth layer A and the fourth layer B having the same configuration.

[0053] Another embodiment of the present invention is a light-emitting device having the above structure, in which the fourth layer A and the fourth layer B have a thickness of 20 nm or less.

[0054] Another embodiment of the present invention is a light-emitting device having the above structure, in which the fourth layer A and the fourth layer B are continuous with each other.

[0055] Another embodiment of the present invention is a light-emitting device having the above structure, in which the first layer A and the first layer B are continuous with each other, and the second layer A and the second layer B are continuous with each other.

[0056] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the first layer A at the emission peak wavelength of the light-emitting device A is 1.70 or less, and the ordinary refractive index of the first layer B at the emission peak wavelength of the light-emitting device B is 1.70 or less.

[0057] Alternatively, another aspect of the present invention is a light-emitting device having the above-described configuration, wherein the ordinary refractive index of the second layer A at the emission peak wavelength of the light-emitting device A is 1.90 or more, and the ordinary refractive index of the second layer B at the emission peak wavelength of the light-emitting device B is 1.90 or more.

[0058] Another embodiment of the present invention is a display device including any of the above light-emitting devices.

[0059] Another embodiment of the present invention is an electronic device including any of the above light-emitting devices, a sensor, an operation button, and a speaker or a microphone.

[0060] The term "display device" as used herein includes an image display device using a light-emitting device. The term "light-emitting device" may also include a module in which a connector, such as an anisotropic conductive film or a TCP (Tape Carrier Package), is attached to a light-emitting device, a module in which a printed wiring board is provided at the end of a TCP, or a module in which an IC (integrated circuit) is directly mounted on a light-emitting device by a COG (Chip On Glass) method.

[0061] According to one embodiment of the present invention, a light-emitting device with high emission efficiency can be provided. Alternatively, according to one embodiment of the present invention, a light-emitting device with a long lifetime can be provided. Alternatively, according to one embodiment of the present invention, any of an electronic device, a display device, and a light-emitting device with low power consumption can be provided.

[0062] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc.

[0063] 1A to 1C are schematic diagrams of a light-emitting device. 2A to 2C are schematic diagrams of a light-emitting device. 3A to 3C are schematic diagrams of a light-emitting device. 4A and 4B are top and cross-sectional views of a light-emitting device. 5 is a cross-sectional view of a light-emitting device. 6A, 6B1, 6B2, and 6C are diagrams of electronic devices. 7A, 7B, and 7C are diagrams of electronic devices. 8 is a diagram of an in-vehicle electronic device. 9A and 9B are diagrams of electronic devices. 10A, 10B, and 10C are diagrams of electronic devices. 11 shows the refractive index of dchPAF. 12 shows the refractive index of PCBBiF. 13 shows the emission spectrum used in the calculation. 14 shows the refractive indexes of DBfBB1TP, 2mDBTBPDBq-II, NBPhen, DBT3P-II, and αN-βNPAnth. 15 shows a schematic diagram of a light-emitting device. Fig. 16 is a graph showing the luminance-current density characteristics of light-emitting device 1 and comparative light-emitting device 1. Fig. 17 is a graph showing the luminance-voltage characteristics of light-emitting device 1 and comparative light-emitting device 1. Fig. 18 is a graph showing the current efficiency-luminance characteristics of light-emitting device 1 and comparative light-emitting device 1. Fig. 19 is a graph showing the current density-voltage characteristics of light-emitting device 1 and comparative light-emitting device 1. Fig. 20 is a graph showing the external quantum efficiency-luminance characteristics of light-emitting device 1 and comparative light-emitting device 1. Fig. 21 is a graph showing the emission spectra of light-emitting device 1 and comparative light-emitting device 1.

[0064] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the embodiments shown below.

[0065] When light is incident on a material with optical anisotropy, the light in the vibration plane parallel to the optical axis is called extraordinary light (ray), and the light in the vibration plane perpendicular to the optical axis is called ordinary light (ray). However, the refractive index of the material for ordinary light and the refractive index for extraordinary light may differ. In such cases, anisotropy analysis can be performed to separate the ordinary refractive index and the extraordinary refractive index and calculate each refractive index. In this specification, if the measured material has both an ordinary refractive index and an extraordinary refractive index, the ordinary refractive index will be used as the index.

[0066] (Embodiment 1) When a light-emitting device is used as a display element in a display, a single pixel needs to be provided with a plurality of sub-pixels each emitting a different light color in order to achieve full-color display. There are several methods for forming sub-pixels emitting different light colors to achieve full-color display, but in a display employing a color-by-color method, the light-emitting devices of the sub-pixels emitting different light colors contain light-emitting materials with different emission peak wavelengths. For example, when a pixel has three sub-pixels, it is preferable that the light-emitting devices of the sub-pixels contain a light-emitting material having an emission peak wavelength in the red region, a light-emitting material having an emission peak wavelength in the green region, and a light-emitting material having an emission peak wavelength in the blue region, respectively.

[0067] As disclosed in Patent Document 1, providing a low-refractive index layer in a light-emitting device can be expected to improve light extraction efficiency. This efficiency improvement effect can be effectively achieved by adjusting the film thickness of the low-refractive index layer according to the emitted light color. Furthermore, the efficiency improvement effect can be more effectively achieved by stacking the low-refractive index layer with other layers having appropriate refractive indices and film thicknesses to form a layered structure with a refractive index step.

[0068] However, if a layered structure tailored to improve the extraction efficiency of a light-emitting device emitting a certain emission color is applied to a light-emitting device emitting a different emission color, not only will the efficiency improvement not be effective, but the extraction efficiency may actually be reduced. Therefore, the above-mentioned layered structure usually needs to be tailored to have a film thickness appropriate for each emission color. However, in order to form such a layered structure tailored to each emission color, processes corresponding to the number of layers must be repeated for each emission color, which is extremely cumbersome, time-consuming, and costly.

[0069] Therefore, in a light-emitting device according to one embodiment of the present invention, a stack structure having a refractive index step with an optical path matching that of a light-emitting device included in a subpixel that emits an emission color with the shortest wavelength among a plurality of subpixels included in a pixel is shared by light-emitting devices that emit other emission colors, provided that the light-emitting devices that emit other emission colors further include an optical adjustment layer in the stack structure.

[0070] With this configuration, in the light-emitting device of one embodiment of the present invention, the stacked structure can be shared among the light-emitting devices of a plurality of emission colors, while suppressing a decrease in the light extraction efficiency and further improving the extraction efficiency of the light-emitting devices of a plurality of emission colors. Furthermore, by sharing the stacked structure among the light-emitting devices of a plurality of emission colors, the stacked structure can be formed in the light-emitting devices of a plurality of emission colors in the same process, and therefore a light-emitting device with good luminous efficiency in which the extraction efficiency of the light-emitting devices of a plurality of emission colors is improved can be provided simply, quickly, and inexpensively.

[0071] In one embodiment of the present invention, the light-emitting device with a longer wavelength only changes the thickness of one layer in the stacked structure having a refractive index step by the optical adjustment layer, and the other layers remain the layers adjusted to match the light-emitting device with a shorter wavelength. Nevertheless, one embodiment of the present invention is characterized in that not only is there no decrease in efficiency, but there is also an effect of improving efficiency.

[0072] As shown in Example 1, if a laminate structure adjusted for a short-wavelength light-emitting device is applied as is to a long-wavelength light-emitting device, the luminous efficiency will be significantly reduced (for example, if a laminate structure adjusted for a blue light-emitting device is applied as is to a green light-emitting device, the luminous efficiency (current efficiency in this case) will be dramatically reduced to 10% or less of that of a light-emitting device without a laminate structure). The fact that this adverse effect can be eliminated with just one optical adjustment layer and that an efficiency improvement effect can still be obtained is a major effect that would not normally be expected.

[0073] 1A to 1C are diagrams illustrating a light-emitting device according to one embodiment of the present invention, each of which illustrates two light-emitting devices emitting different light colors. The light-emitting device L shown on the right side emits light with a wavelength longer than that of the light-emitting device S.

[0074] The light-emitting device S includes a first electrode 101, a stacked structure 122 (a first layer 122-1 and a second layer 122-2) having a refractive index difference, a light-emitting layer 113S, and a second electrode 102, all of which are disposed on an insulating layer 100. The first layer 122-1 and the second layer 122-2 are provided in this order from the first electrode 101 side so as to be in contact with each other. The light-emitting layer 113S includes a light-emitting substance S.

[0075] The light-emitting device L has a first electrode 101, a laminated structure 122 (a first layer 122-1, a second layer 122-2, and a third layer 122-3) having a refractive index difference, a light-emitting layer 113L, and a second electrode 102 on an insulating layer 100. The first layer 122-1 and the second layer 122-2 are provided in this order from the first electrode 101 side. The light-emitting layer 113L contains a light-emitting substance L. The light-emitting substance L is a light-emitting substance whose emission peak wavelength is longer than that of the light-emitting substance S. As will be described later, the third layer 122-3 is an optical adjustment layer, and there are two patterns: an optical adjustment layer with a low refractive index and an optical adjustment layer with a high refractive index.

[0076] The third layer 122-3 may be provided between the second layer 122-2 and the light-emitting layer 113L and in contact with the second layer 122-2 (third layer 122-3a) as shown in Fig. 1A, or between the first layer 122-1 and the second layer 122-2 and in contact with the first layer 122-1 and the second layer 122-2 (third layer 122-3b) as shown in Fig. 1B, or between the first electrode 101 and the first layer 122-1 and in contact with the first layer 122-1 (third layer 122-3c) as shown in Fig. 1C. Within the stacked structure 122, the first layer 122-1 to the third layer 122-3 are stacked in contact with adjacent layers, regardless of the position of the third layer 122-3. That is, there are configurations in which the first layer 122-1, the second layer 122-2, and the third layer 122-3 are stacked in contact with each other in this order, configurations in which the first layer 122-1, the third layer 122-3, and the second layer 122-2 are stacked in contact with each other in this order, and configurations in which the third layer 122-3, the first layer 122-1, and the second layer 122-2 are stacked in contact with each other in this order.

[0077] Note that in this specification, the third layers 122-3a to 122-3c may be collectively referred to as the third layer 122-3.

[0078] The second layer 122-2 has a higher refractive index than the first layer 122-1. Specifically, the ordinary refractive index of the second layer 122-2 for light of a wavelength λ is preferably higher than the ordinary refractive index of the first layer 122-1 by 0.15 or more, and more preferably 0.20 or more. The wavelength λ is any wavelength between 450 nm and 650 nm, or the entire range.

[0079] When the light-emitting device S emits light in the blue region, the wavelength λ is preferably set to any wavelength between 455 nm and 465 nm or the entire region. In this case, the difference in ordinary refractive index is preferably 0.20 or more. Since the wavelength λ is usually used as an index of refractive index, this value may be used. In this case, the difference in ordinary refractive index is preferably 0.15 or more. The wavelength λ is set to the emission peak wavelength λ of the light-emitting substance S. Ｓ It is preferable that:

[0080] Such a laminated structure may be referred to as a Low-High (LH) structure based on the order of the refractive indexes of the first layer and the second layer.

[0081] The third layer 122-3 may be a layer having a higher ordinary refractive index for light of a certain wavelength λ than the first layer 122-1, or a layer having a lower ordinary refractive index for light of a certain wavelength λ than the second layer 122-2, where the wavelength λ is any wavelength between 450 nm and 650 nm, or the entire range.

[0082] When the third layer 122-3 is located between the second layer 122-2 and the light-emitting layer 113, or between the first electrode 101 and the first layer 122-1, i.e., when it is the third layer 122-3a or 122-3c, the ordinary refractive index of the third layer for light of a certain wavelength λ is preferably lower than the ordinary refractive index of the second layer 122-2 for light of that wavelength λ. In this case, the difference in ordinary refractive index is preferably 0.15 or more, preferably 0.20 or more. Furthermore, it is preferable that the ordinary refractive index of the third layer 122-3a and 122-3c for light of a certain wavelength λ be equal to or lower than the ordinary refractive index of the first layer 122-1 for light of that wavelength λ, as this provides a greater efficiency improvement effect.

[0083] Furthermore, when the third layer 122-3 is located between the first layer 122-1 and the second layer 122-2, i.e., when it is the third layer 122-3b, it is preferable that the ordinary refractive index of the third layer 122-3b for light of a certain wavelength λ is higher than the ordinary refractive index of the first layer 122-1 for light of that wavelength λ. In this case, it is preferable that the difference in ordinary refractive index is 0.15 or more, preferably 0.20 or more. Furthermore, it is preferable that the ordinary refractive index of the third layer 122-3b for light of a certain wavelength λ is equal to or higher than the ordinary refractive index of the second layer 122-2 for light of that wavelength λ, because this has a greater effect of improving efficiency.

[0084] When the light-emitting device L emits light in the green region, the wavelength λ is preferably any wavelength or the entire region from 520 nm to 540 nm, and when the light-emitting device L emits light in the red region, the wavelength λ is preferably any wavelength or the entire region from 610 nm to 640 nm. In these cases, the difference in ordinary refractive index is preferably 0.15 or more. The wavelength λ is the emission peak wavelength λ of the light-emitting substance L. Ｌ It is preferable that:

[0085] The refractive index of the first layer 122-1 for light of wavelength λ is preferably 1.40 or more and 1.75 or less. Furthermore, if the third layer 122-3 is a layer with a low refractive index, the refractive index of the third layer 122-3 for light of wavelength λ is preferably 1.40 or more and 1.75 or less.

[0086] More specifically, when the light-emitting device S emits light in the blue region, the first layer 122-1 emits light in any wavelength region of 455 nm to 465 nm or the entire region, preferably the peak wavelength λ of the light-emitting material S. Ｓ The refractive index of the film for ordinary light at 633 nm is preferably 1.40 or more and 1.75 or less. Alternatively, the refractive index of the film for ordinary light at 633 nm is preferably 1.40 or more and 1.70 or less.

[0087] Furthermore, when the third layer 122-3 is a layer with a low refractive index, the third layer 122-3 has an ordinary refractive index in any wavelength range of 520 nm to 540 nm or in the entire wavelength range, preferably the emission peak wavelength λ of the luminescent material L, when the light-emitting device L emits light in the green region. Ｌ In the case where the light-emitting device L emits light in the red region, the ordinary refractive index at any wavelength from 610 nm to 640 nm or the entire wavelength range is preferably 1.40 or more and 1.70 or less. Ｌ Preferably, the ordinary refractive index of the third layer 122-3 at 633 nm is 1.40 or more and 1.70 or less. Alternatively, the ordinary refractive index of the third layer 122-3 at 633 nm is 1.40 or more and 1.70 or less.

[0088] Furthermore, it is preferable that the difference in ordinary refractive index at wavelength λ between the first layer 122-1 and the third layer 122-3, if the layer has a low refractive index, is 0.10 or less.

[0089] The refractive index of the second layer 122-2 for light of wavelength λ is preferably 1.75 or more, and more preferably 1.90 or more. When the third layer 122-3 is a layer with a high refractive index, the refractive index of the third layer 122-3 for light of wavelength λ is preferably 1.75 or more, and more preferably 1.90 or more.

[0090] More specifically, when the light-emitting device S emits light in the blue region, the second layer 122-2 emits light in any wavelength region of 455 nm to 465 nm or the entire region, preferably the emission peak wavelength λ of the light-emitting material S. Ｓ The ordinary refractive index at 633 nm light, which is normally used for measuring refractive index, is preferably 1.75 to 2.40, and more preferably 1.90 to 2.40, or the ordinary refractive index at 633 nm light, which is normally used for measuring refractive index, is preferably 1.75 to 2.30, and more preferably 1.90 to 2.30.

[0091] Furthermore, when the third layer 122-3 is a layer with a high refractive index and the light-emitting device L emits light in the green region, the third layer 122-3 has an ordinary refractive index in any wavelength region of 520 nm to 540 nm or in the entire region, preferably the emission peak wavelength λ of the light-emitting material L. Ｌ In the case where the light-emitting device L emits light in the red region, the ordinary refractive index at any wavelength from 610 nm to 640 nm or the entire wavelength range, preferably the emission peak wavelength λ of the light-emitting material L, is preferably 1.75 or more and 2.30 or less, and more preferably 1.90 or more and 2.30 or less. Ｌ The ordinary refractive index of the third layer 122-3 at 633 nm is preferably 1.75 to 2.30, and more preferably 1.90 to 2.30. Alternatively, the ordinary refractive index of the third layer 122-3 at 633 nm is preferably 1.75 to 2.30, and more preferably 1.90 to 2.30.

[0092] Furthermore, the difference in ordinary refractive index at wavelength λ between the second layer 122-2 and the third layer 122-3, if the third layer 122-3 is a layer with a high refractive index, is preferably 0.10 or less.

[0093] The layered structure 122 having a refractive index difference is provided between the first electrode 101 and the light-emitting layer 113S and between the first electrode 101 and the light-emitting layer 113L. Since the first electrode 101 preferably includes an anode, the first layer 122-1, the second layer 122-2, and the third layer 122-3 are preferably layers having hole transport properties. Examples of layers having hole transport properties include a hole injection layer, a hole transport layer, and an electron blocking layer. The layered structure 122 may also function as a functional layer having other hole transport properties. The first layer 122-1 preferably functions as a hole injection layer or a hole transport layer, and the second layer 122-2 preferably functions as a hole transport layer or an electron blocking layer. The third layer 122-3 may function as any layer depending on its location.

[0094] In addition, when the ordinary light refractive indexes of the hole injection layer and the hole transport layer are approximately the same (for example, when the hole injection layer and the hole transport layer contain the same organic compound and only the hole injection layer further contains an electron acceptor material; specifically, the difference in refractive index is within 0.05), the two layers together can also be regarded as the first layer 122-1.

[0095] Furthermore, when the third layer 122-3 is located between the first electrode 101 and the first layer 122-1 as shown in FIG. 1C , i.e., when the third layer 122-3c is used as a hole injection layer, and particularly when this layer has a high refractive index, the hole injection layer is independent between the light-emitting device S and the light-emitting device L, i.e., it is not provided in the light-emitting device S and is therefore not continuous, which is a preferable configuration because it makes it possible to suppress crosstalk to adjacent light-emitting devices even in a high-resolution display device.

[0096] Among the layers constituting the stack structure 122 having a refractive index difference, the difference in HOMO level between the layer closest to the first electrode 101 and the layer closest to the second electrode 102 is preferably 0.20 eV or less, more preferably 0.10 eV or less, because hole transport is facilitated. The difference in HOMO levels between adjacent layers is preferably 0.20 eV or less, more preferably 0.1 eV or less, because hole transport is facilitated.

[0097] It is preferable that the first layer 122-1 and the third layer 122-3 (if the layer has a low refractive index) contain the same organic compound, since this facilitates hole transport and reduces the amount of material used in fabricating the light-emitting device. For the same reason, it is also preferable that the second layer 122-2 and the third layer 122-3 (if the layer has a high refractive index) contain the same organic compound.

[0098] The first electrode 101 is an electrode including a reflective electrode, and the second electrode 102 is an electrode having a property of transmitting visible light. Note that the first electrode 101 preferably includes an anode, and the second electrode 102 is preferably a cathode. Furthermore, when the first electrode 101 has a layered structure, the electrode closest to the second electrode 102 is preferably an electrode having a property of transmitting visible light and also an anode. That is, the first electrode 101 preferably has a structure in which a light-transmitting electrode functioning as an anode is layered on a reflective electrode. Furthermore, the second electrode 102 preferably has a function of transmitting visible light and reflecting visible light at the same time.

[0099] Specifically, the first electrode 101 preferably includes a reflective electrode that reflects visible light by 40% or more, preferably 70% or more. The second electrode 102 is preferably a semi-transmissive / semi-reflective electrode that has a visible light reflectance of 20% to 80%, preferably 40% to 70%. With such a structure, the light-emitting device of one embodiment of the present invention becomes a top-emission light-emitting device that emits light from the second electrode 102 side, and can have a microcavity structure by adjusting the film thickness of the EL layer.

[0100] Note that a cap layer 131 (see FIG. 3C ) may be provided on a surface of the light-emitting electrode (the second electrode 102 in this embodiment) opposite to the EL layer 103. The cap layer 131 is preferably formed using a material with a relatively high refractive index.

[0101] Specifically, the cap layer 131 preferably has an ordinary light refractive index of 1.90 to 2.40, more preferably 1.95 to 2.40, at any wavelength from 455 nm to 465 nm, preferably over the entire wavelength range. Furthermore, the cap layer preferably has an ordinary light extinction coefficient of 0 to 0.01, at any wavelength from 455 nm to 465 nm, preferably over the entire wavelength range. Alternatively, the cap layer 131 preferably has an ordinary light refractive index of 1.85 to 2.40, more preferably 1.90 to 2.40, at any wavelength from 500 nm to 650 nm, preferably over the entire wavelength range. Furthermore, the cap layer preferably has an ordinary light extinction coefficient of 0 to 0.01, at any wavelength from 500 nm to 650 nm, preferably over the entire wavelength range.

[0102] Furthermore, it is preferable to use an organic compound that can be formed by evaporation because it can be easily formed. By providing the capping layer 131, the light extraction efficiency is improved, and therefore the light emission efficiency can be further increased. In addition to the organic compounds that can be used for the second layer 122-2, the material of the capping layer 131 can also be 3-{4-(triphenylen-2-yl)phenyl}-9-(triphenylen-2-yl)-9H-carbazole (abbreviation: TpPCzTp), 3,6-bis[4-(2-naphthyl)phenyl]-9-(2-naphthyl)-9H-carbazole (abbreviation: βNP2βNC), 9-[4-(2,2'-binaphthalen-6-yl)phenyl]-3-[4-(2-naphthyl)phenyl]-9H-carbazole (abbreviation: (βN2)PCPβN), 2-{4 -[2-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2PCCzPDBq-02), 9-[4-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)phenyl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9pPCCzPNfpr), 4,8-bis[3-(triphenylen-2-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mTpP2Bfpm), and the like can be suitably used.

[0103] Here, the thickness of the first layer 122-1 and the second layer 122-2 is preferably such that light emitted from the light-emitting layer 113 in the light-emitting device S and light reflected at the interfaces of each layer and the electrodes are amplified by interference. ｔ The product of the ordinary refractive index and the film thickness at ｔ By adjusting the optical path length of the light to be an integer multiple of λ / 4, the phase of the light reflected from the front surface and the light reflected from the back surface can be matched. ｔ By setting the ratio to 60% or more and 140% or less of / 4, the interference of light can be effectively strengthened.

[0104] Here, λ in an actual light emitting device ｔ is the peak wavelength λ of light emitted from the subpixel including the light-emitting device S. ＳＤ or the emission peak wavelength λ of the luminescent material S Ｓ is equivalent to

[0105] When light is reflected by the reflective electrode of the first electrode 101, the phase change is 0.5λ. ｔ The film thickness of the first layer 122-1 may deviate from the above formula due to the influence of a phase shift that occurs when light is reflected by the reflective electrode of the first electrode 101 and the presence of a light-transmitting electrode. ｔ The product of the ordinary refractive index and the film thickness of the first layer 122-1 in ｔ In addition, if the thickness of the EL layer 103 is too thick, the driving voltage increases. ｔ The thickness of the light-transmitting electrode is preferably 5 nm to 40 nm.

[0106] The second layer 122-2 has a wavelength λ from the main light-emitting region (region with a high carrier recombination probability) in the light-emitting layer 113S to the interface between the second layer 122-2 and the first layer 122-1. ｔ The optical distance at ｔ It is preferable that the wavelength λ is in the range of 60% to 140% of / 2. ｔ The product of the ordinary refractive index and the film thickness of the second layer 122-2 in ｔ In addition, if the thickness of the EL layer 103 is too thick, the driving voltage increases. ｔ / 2. In this case, the film thickness of the light-emitting layer 113S is preferably 5 nm or more and 70 nm or less. If it is difficult to accurately determine the main light-emitting region of the light-emitting layer, the position may be set as a reference, estimated in consideration of the transport properties of the light-emitting layer. Alternatively, the light-emitting region may be assumed to be the center of the light-emitting layer.

[0107] The second layer 122-2 is λ ｔ / 4, and the electron blocking layer is formed so as to have a wavelength λ from the main light-emitting region (region with a high probability of carrier recombination) in the light-emitting layer 113S to the interface between the second layer 122-2 and the first layer 122-1. ｔ The optical distance at ｔ In another embodiment, the ratio is set to 60% or more and 140% or less of / 2.

[0108] From the above, the wavelength λ ｔ (Wavelength λ of light emitted from the sub-pixel including the light-emitting device S) ＳＤ or the emission peak wavelength λ of the luminescent material S Ｓ ) The product of the ordinary refractive index and the film thickness (nm) of the first layer 122-1 is 0.03λ ｔ More than 0.25λ ｔ The wavelength λ of the second layer 122-2 is preferably equal to or less than 1 / 2. ｔ The product of the ordinary refractive index and the film thickness at ｔ 0.60λ or more ｔ Less than or equal to 0.25λ, preferably ｔ More than 0.50λ ｔIt is preferable that the following be true:

[0109] Also, the wavelength λ ｔ (Wavelength λ of light emitted from the sub-pixel including the light-emitting device L) ＬＤ or the emission peak wavelength λ of the luminescent material L Ｌ ) the product of the ordinary refractive index and the film thickness (nm) of the third layer 122-3 is 0.15λ ｔ 0.35λ or more ｔ It is preferable that:

[0110] A hole injection layer having an ordinary refractive index of 1.75 or more may be provided between the layer structure 122 having a refractive index step and the first electrode 101. In this case, it is preferable that the hole injection layer has a thickness of 5 nm to 15 nm, preferably 5 nm to 10 nm, because it has little effect on the optical path length. In this case, it is more preferable that the film thickness of the first layer 122-1 (or the third layer 122-3) is formed accordingly thinner.

[0111] Furthermore, an electron blocking layer may be provided between the layered structure 122 having a refractive index step and the light-emitting layer 113S and the light-emitting layer 113L. In this case, the electron blocking layer is preferably 20 nm or less in thickness to minimize the effect on the optical path length, and more preferably 5 nm to 20 nm. It is more preferable to set the thickness of the second layer 122-2 by regarding the thickness of the electron blocking layer as part of the thickness of the light-emitting layer.

[0112] When the hole injection layer or electron blocking layer is formed, it is preferable that the layer is formed continuously and commonly in a plurality of light-emitting devices.

[0113] The optical distance between the interface of the reflective electrode on the EL layer 103 side and the interface of the first layer 122-1 (or the third layer 122-3c) on the reflective electrode side is 0.13λ. ｔ 〜0.38λ ｔ In addition, the optical distance between the main light-emitting region of the light-emitting layer 113S or the light-emitting layer 113L and the interface on the reflective electrode side of the first layer 122-1 (or the third layer 122-3c) is preferably 0.38λ. ｔ 〜0.63λ ｔThe optical distance between the interface of the reflective electrode on the EL layer 103 side and the interface of the second layer 122-2 (or the third layer 122-3b in the case of a layer with a high refractive index) on the reflective electrode side is preferably 0.38λ. ｔ 〜0.63λ ｔ In addition, the optical distance between the main light-emitting region of the light-emitting layer 113 and the interface on the light-emitting layer side of the second layer 122-2 (or the third layer 122-3a) is preferably 0.13λ. ｔ 〜0.38λ ｔ With such a configuration, the light reflected by the interfaces of the layers and the reflective electrode is amplified, and it is possible to obtain a light emitting device with good efficiency and good color purity.

[0114] It is preferable that the first layer 122-1 in the light-emitting device L and the first layer 122-1 in the light-emitting device S, and the second layer 122-2 in the light-emitting device L and the second layer 122-2 in the light-emitting device S each contain the same material and are made of the same material.

[0115] Furthermore, the film thicknesses of the first layer 122-1 and the second layer 122-2 in the light-emitting device L are similar to those of the first layer 122-1 and the second layer 122-2 in the light-emitting device S.

[0116] Furthermore, the compositions and thicknesses of the first layer 122-1 to the third layer 122-3 in the light-emitting device L are preferably similar to those of the first layer 122-1 and the second layer 122-2 in the light-emitting device S.

[0117] In this specification, the term "similar" means that the layers may be different to the extent that variations in film thickness and composition of the film-forming equipment are tolerated. This configuration allows the first layer 122-1 and the second layer 122-2 of the light-emitting device L and the first layer 122-1 and the second layer 122-2 of the light-emitting device S to be formed simultaneously. The first layer 122-1 and the second layer 122-2 have thicknesses that amplify the light of the light-emitting device S. While this alone may reduce the extraction efficiency of the light-emitting device L, in one embodiment of the present invention, the light-emitting device L can be made to emit light efficiently by further including the third layer 122-3, thereby improving the extraction efficiency. Thus, in one embodiment of the present invention, a light-emitting device including a light-emitting device with good luminous efficiency for any emission color can be obtained simply, quickly, and inexpensively.

[0118] Here, if the third layer 122-3 is made of the same material and has the same composition as any of the adjacent layers, the first layer 122-1 or the second layer 122-2, the boundary between the adjacent layers may be unclear, and the third layer 122-3 may appear to be a single layer. However, in this case, since layers similar to the first layer 122-1 and the second layer 122-2 in the light-emitting device S are also formed in the light-emitting device L, the position and thickness of the third layer 122-3 can be estimated.

[0119] The thickness of these layers may be determined using a commercially available organic device simulator.

[0120] The emission peak wavelength of the light-emitting substance can be determined from the photoluminescence spectrum in a solution state. Since the relative dielectric constant of the organic compound constituting the EL layer of a light-emitting device is about 3, in order to minimize the discrepancy with the emission spectrum when used in a light-emitting device, the relative dielectric constant of the solvent for putting the light-emitting substance into a solution state is preferably 1 or more and 10 or less at room temperature, more preferably 2 or more and 5 or less. Specific examples include hexane, benzene, toluene, diethyl ether, ethyl acetate, chloroform, chlorobenzene, and dichloromethane. Furthermore, a general-purpose solvent having a relative dielectric constant of 2 or more and 5 or less at room temperature, high solubility, is more preferred, such as toluene or chloroform.

[0121] The refractive index (ordinary refractive index and extraordinary refractive index) of each layer can be considered to be the refractive index of the material contained therein. For example, the refractive index of a film of material with a similar composition can be measured, and the measured value can be considered to be the refractive index of the layer. Furthermore, the HOMO level of each layer can be the HOMO level of the material mainly contained in the layer.

[0122] In addition, when determining the refractive index of a layer made of a mixed material, in addition to direct measurement, it can also be determined as a value obtained by multiplying the ordinary refractive index of a film made of each material alone by the composition ratio of each material in the layer and adding up the results. If the exact ratio cannot be determined, it is also possible to use a value obtained by dividing each ordinary refractive index by the number of composition components and adding up the results.

[0123] In a light-emitting device according to one embodiment of the present invention having the above-described structure, light emitted from a light-emitting material is reflected at the interface between layers having different refractive indices. This allows for more light to be reflected than when only a reflective electrode is used. This improves external quantum efficiency. Furthermore, the influence of surface plasmons at the reflective electrode can be reduced, thereby reducing energy loss and enabling efficient light extraction. Furthermore, the light-emitting device has a stacked structure with a common refractive index step, and the thickness of the stacked structure is adjusted so that the light emitted by each subpixel is amplified. This allows for simple, rapid, and inexpensive improvement in the emission efficiency of all emitted colors.

[0124] Both the light-emitting device S and the light-emitting device L may have an electron transport layer 114, an electron injection layer 115, or the like between the light-emitting layer 113 and the second electrode 102. The EL layer 103 may have various functional layers such as a hole injection layer, a hole transport layer, a carrier blocking layer, and an exciton blocking layer. These functional layers may be common to all light-emitting devices of all emitted colors or may be independent, but having a common functional layer simplifies the fabrication of the light-emitting device.

[0125] 2A to 2C show an example in which the above-described structure is applied to a light-emitting device having light-emitting devices for three colors, red, green, and blue. That is, each of FIGS. 2A to 2C shows a light-emitting device according to one embodiment of the present invention, which has three subpixels in one pixel. Note that the same reference numerals may be used for the same components as those in FIGS. 1 and 3, and descriptions thereof may be omitted.

[0126] 2A to 2C clearly show the reflective electrode 101-1 and the light-transmitting electrode (anode) 101-2 included in the first electrode 101. A light-emitting device is formed in the portion where the first electrode and the second electrode 102 overlap without an insulating layer 123 in between. In the figures, the light-emitting device having the blue light-emitting layer 113B is a blue light-emitting device, the light-emitting device having the green light-emitting layer 113G is a green light-emitting device, and the light-emitting device having the red light-emitting layer 113R is a red light-emitting device, and the blue light-emitting device corresponds to the light-emitting device that emits light with the shortest wavelength.

[0127] The EL layer of the blue light-emitting device includes a laminated structure 122 having a refractive index step, a blue light-emitting layer 113B, an electron transport layer 114B, and an electron injection layer 115. The film thicknesses of the first layer 122-1 and the second layer 122-2 included in the laminated structure 122 are adjusted to improve the light extraction efficiency of the blue light-emitting device. Note that the first layer 122-1, the second layer 122-2, and the electron injection layer 115 are preferably provided as a continuous layer common to other light-emitting devices.

[0128] The EL layer of the green light-emitting device includes a stacked layer structure 122 having a refractive index step, a green light-emitting layer 113G containing a green light-emitting material, an electron transport layer 114G, and an electron injection layer 115. The stacked layer structure 122 of the green light-emitting device includes a first layer 122-1, a second layer 122-2, and a third layer 122-3G (third layer 122-3Ga ( FIG. 2A ), third layer 122-3Gb ( FIG. 2B ), and third layer 122-3Gc ( FIG. 2C )). The first layer 122-1 and second layer 122-2 of the green light-emitting device have the same composition and thickness as those of the blue light-emitting device. This allows the first layer 122-1 and second layer 122-2 of the blue light-emitting device and the first layer 122-1 to third layer 122-3 of the green light-emitting device to be formed simultaneously. As described above, the green light-emitting device further includes a third layer 122-3G in the stacked structure 122. By including the third layer 122-3G, the green light-emitting device can be a green light-emitting device that exhibits good luminous efficiency while having a configuration similar to that of the first layer 122-1 and the second layer 122-2 of the blue light-emitting device.

[0129] The EL layer of the red light-emitting device includes a layered structure 122 having a refractive index step, a red light-emitting layer 113R containing a red light-emitting material, an electron transport layer 114R, and an electron injection layer 115. The layered structure 122 of the red light-emitting device includes a first layer 122-1, a second layer 122-2, and a third layer 122-3R (third layer 122-3Ra ( FIG. 2A ), third layer 122-3Rb ( FIG. 2B ), and third layer 122-3Rc ( FIG. 2C )). The first layer 122-1 and second layer 122-2 of the red light-emitting device have the same composition and thickness as those of the blue light-emitting device. This allows the first layer 122-1 and second layer 122-2 of the blue light-emitting device and the first layer 122-1 and second layer 122-2 of the red light-emitting device to be formed simultaneously. As described above, the red light-emitting device further includes a third layer 122-3R in the stacked structure 122. By including the third layer 122-3R, the red light-emitting device can exhibit good luminous efficiency while having a configuration similar to that of the first layer 122-1 and the second layer 122-2 of the blue light-emitting device.

[0130] The blue light-emitting layer 113B, the green light-emitting layer 113G, and the red light-emitting layer 113R each contain a different light-emitting material, and the third layer 122-3G and the third layer 122-3R may have the same or different thicknesses, but preferably have different thicknesses. The electron transport layer 114B, the electron transport layer 114G, and the electron transport layer 114R may have the same or different configurations. If they have the same configuration, they are shown separately for each light-emitting device in FIG. 2, but they may be formed continuously in each light-emitting device. The electron transport layer 114 may also be composed of multiple layers. In this case, one layer may be separate for each light-emitting color, and the other layers may be common.

[0131] The third layer 122-3G and the third layer 122-3R correspond to the third layer 122-3 described with reference to Figure 1 and may be a low-refractive index layer or a high-refractive index layer. By appropriately setting the film thickness according to the emitted color, it is possible to easily, quickly, and inexpensively suppress a decrease in luminous efficiency or improve luminous efficiency in each light-emitting device while having a stacked structure with a common refractive index step with the blue light-emitting device. Furthermore, by sharing this stacked structure among light-emitting devices of multiple emitted colors, it is possible to easily, quickly, and inexpensively provide a light-emitting device with good luminous efficiency in which the extraction efficiency of the light-emitting devices of multiple emitted colors is improved.

[0132] <Examples of Low-Refractive Index Materials> The first layer 122-1 and, when a low-refractive index layer is used, the third layer 122-3 are formed using a material with a relatively low refractive index. However, there is usually a trade-off between high carrier transportability and a low refractive index. This is because the carrier transportability of organic compounds is largely due to the presence of unsaturated bonds, and organic compounds with many unsaturated bonds tend to have a high refractive index. Even if a material has a low refractive index, if the carrier transportability is low, problems such as an increase in driving voltage and a decrease in luminous efficiency and reliability due to a carrier imbalance can occur, making it impossible to obtain a light-emitting device with good characteristics. Furthermore, even if a material has sufficient carrier transportability and a low refractive index, if it has an unstable structure and therefore has problems with the glass transition point (Tg) or durability, it will be impossible to obtain a light-emitting device with good reliability.

[0133] Therefore, as an organic compound that can be used for the first layer 122-1 and the third layer 122-3 when it is a low refractive index layer, it is preferable to use a monoamine compound that has a first aromatic group, a second aromatic group, and a third aromatic group, and the first aromatic group, the second aromatic group, and the third aromatic group are bonded to the same nitrogen atom.

[0134] In the monoamine compound, the ratio of carbon atoms forming bonds via sp3 hybrid orbitals to the total number of carbon atoms in the molecule is preferably 23% or more and 55% or less, and １ The monoamine compound is preferably a compound in which the integral value of a signal below 4 ppm exceeds the integral value of a signal at 4 ppm or more when the compound is measured by H-NMR.

[0135] Furthermore, it is preferable that the monoamine compound has at least one fluorene skeleton, and that one or more of the first aromatic group, the second aromatic group, and the third aromatic group are fluorene skeletons. Note that fluorenylamine has the effect of increasing the HOMO level, so when three fluorenes are bonded to the nitrogen of the monoamine compound, the HOMO level may be significantly increased. In this case, the difference with the HOMO level of the surrounding material (for example, the HOMO level of the high refractive index material of the second layer 122-2) becomes large, which may affect the driving voltage, reliability, etc. Therefore, it is more preferable that one or two of the first aromatic group, the second aromatic group, and the third aromatic group are fluorene skeletons.

[0136] Examples of the organic compound having the hole transporting property as described above include those having the following general formula (G ｈ１ 1) to (G ｈ１ 4) can be mentioned as an organic compound having a structure such as the one shown below.

[0137]

[0138] The general formula (G ｈ１ In 1), Ar １ , Ar ２ each independently represents a benzene ring or a substituent in which two or three benzene rings are bonded to each other, provided that Ar １ , Ar ２ one or both of Ar and Ar have one or more hydrocarbon groups having 1 to 12 carbon atoms in which carbon atoms form bonds only through sp3 hybrid orbitals, １ and Ar ２ The total number of carbon atoms contained in all the hydrocarbon groups bonded to Ar is 8 or more, and １ and Ar ２ The total number of carbon atoms contained in all the hydrocarbon groups bonded to either Ar or Ar is 6 or more. １ or Ar ２When a plurality of linear alkyl groups having 1 to 2 carbon atoms are bonded to the hydrocarbon group, the linear alkyl groups may be bonded to each other to form a ring. As the hydrocarbon group having 1 to 12 carbon atoms in which carbon atoms form bonds only through sp3 hybrid orbitals, alkyl groups having 3 to 8 carbon atoms and cycloalkyl groups having 6 to 12 carbon atoms are preferred. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a cyclohexyl group, a 4-methylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a decahydronaphthyl group, a cycloundecyl group, a cyclododecyl group, and the like can be used, with a t-butyl group, a cyclohexyl group, and a cyclododecyl group being particularly preferred.

[0139]

[0140] The general formula (G ｈ１ In 2), m and r each independently represent 1 or 2, and m+r is 2 or 3. Each t independently represents an integer of 0 to 4, preferably 0. ４ and R ５ each independently represents hydrogen or a hydrocarbon group having 1 to 3 carbon atoms. When m is 2, the types of substituents, the number of substituents, and the positions of bonds of the two phenylene groups may be the same or different, and when r is 2, the types of substituents, the number of substituents, and the positions of bonds of the two phenyl groups may be the same or different. When t is an integer of 2 to 4, a plurality of R ５ may be the same or different, R ５ Adjacent groups may be bonded to each other to form a ring.

[0141]

[0142] The general formula (G ｈ１ 2) and (G ｈ１In 3), n and p each independently represent 1 or 2, and n+p is 2 or 3. Each s independently represents an integer of 0 to 4, preferably 0. When s is an integer of 2 to 4, a plurality of R ４ may be the same or different. ４ represents either hydrogen or a hydrocarbon group having 1 to 3 carbon atoms. When n is 2, the types of substituents, the number of substituents, and the positions of bonds on the two phenylene groups may be the same or different, and when p is 2, the types of substituents, the number of substituents, and the positions of bonds on the two phenyl groups may be the same or different. Examples of hydrocarbon groups having 1 to 3 carbon atoms include a methyl group, an ethyl group, a propyl group, and an isopropyl group.

[0143]

[0144] The general formula (G ｈ１ 2) to (G ｈ１ 4) In R １０ ~R １４ and R ２０ ~R ２４ Each independently represents hydrogen or a hydrocarbon group having 1 to 12 carbon atoms in which carbon atoms form bonds only through sp3 hybrid orbitals. １０ ~R １４ At least three of, and R ２０ ~R ２４ Preferably, at least 3 of R are hydrogen atoms. As the hydrocarbon group having 1 to 12 carbon atoms in which carbon atoms form bonds only through sp3 hybrid orbitals, a tert-butyl group and a cyclohexyl group are preferred. １０ ~R １４ and R ２０ ~R ２４ The total number of carbon atoms contained in R is 8 or more, and １０ ~R １４ or R ２０ ~R ２４ The total number of carbon atoms contained in either one of the above is 6 or more. １０ ~R １４ and R ２０ ~R ２４Adjacent groups may be bonded to each other to form a ring.

[0145] As the hydrocarbon group having 1 to 12 carbon atoms in which carbon atoms form bonds only through sp3 hybrid orbitals, an alkyl group having 3 to 8 carbon atoms and a cycloalkyl group having 6 to 12 carbon atoms are preferred. Specifically, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a neopentyl group, a hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, a neohexyl group, a heptyl group, an octyl group, a cyclohexyl group, a 4-methylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a decahydronaphthyl group, a cycloundecyl group, a cyclododecyl group, and the like can be used, with a t-butyl group, a cyclohexyl group, and a cyclododecyl group being particularly preferred.

[0146] In addition, the above general formula (G ｈ１ 1) to (G ｈ１ In 4), each u independently represents an integer of 0 to 4, and is preferably 0. When u is an integer of 2 to 4, a plurality of R ３ may be the same or different. １ , R ２ and R ３ each independently represents an alkyl group having 1 to 4 carbon atoms; R １ and R ２ may be bonded to each other to form a ring. Examples of the hydrocarbon group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

[0147] Another preferred example of a material having hole transport properties that can be used for the first hole transport layer and the third hole transport layer is an arylamine compound having at least one aromatic group, the aromatic group having first to third benzene rings and at least three alkyl groups, where the first to third benzene rings are bonded in this order and the first benzene ring is directly bonded to the nitrogen of the amine.

[0148] The first benzene ring may further have a substituted or unsubstituted phenyl group, preferably an unsubstituted phenyl group, and the second benzene ring or the third benzene ring may have a phenyl group substituted with an alkyl group.

[0149] It should be noted that hydrogen is not directly bonded to the carbon atoms at the first and third positions of two or more of the first to third benzene rings, preferably all of the benzene rings, but is bonded to any of the first to third benzene rings, the phenyl group substituted with an alkyl group, the at least three alkyl groups, and the nitrogen of the amine.

[0150] In addition, the arylamine compound preferably further has a second aromatic group.The second aromatic group is preferably an unsubstituted monocyclic ring or a group having substituted or unsubstituted fused rings of 3 or less, and more preferably a substituted or unsubstituted fused ring of 3 or less, and the fused ring is more preferably a group having fused rings with 6 to 13 carbon atoms forming the ring, and is further preferably a group having a benzene ring, a naphthalene ring, a fluorene ring, or an acenaphthylene ring, and particularly preferably a group having a fluorene ring.In addition, the second aromatic group is preferably a dimethylfluorenyl group.

[0151] The arylamine compound preferably further comprises a third aromatic group, which is a group having one to three substituted or unsubstituted benzene rings.

[0152] The at least three alkyl groups and the alkyl group substituting the phenyl group are preferably chain alkyl groups having 2 to 5 carbon atoms. In particular, the alkyl group is preferably a branched chain alkyl group having 3 to 5 carbon atoms, and more preferably a t-butyl group.

[0153] Examples of the material having the hole transporting property as described above include the following (G ｈ２ 1) to (G ｈ２ Examples of the organic compound include those having the structure shown in 3).

[0154]

[0155] In addition, the above general formula (G ｈ２ In 1), Ar １０１ represents a substituted or unsubstituted benzene ring, or a substituent in which two or three substituted or unsubstituted benzene rings are bonded to each other.

[0156]

[0157] In addition, the above general formula (G ｈ２ In 2), x and y each independently represent 1 or 2, and x+y is 2 or 3. １０９ represents an alkyl group having 1 to 4 carbon atoms, and w represents an integer of 0 to 4. １４１ ~R １４５ each independently represents one of hydrogen, an alkyl group having 1 to 6 carbon atoms, and a cycloalkyl group having 5 to 12 carbon atoms. When w is 2 or more, multiple R １０９ may be the same or different. When x is 2, the type of substituents, the number of substituents, and the position of the bond of the two phenylene groups may be the same or different. When y is 2, the two R １４１ ~R １４５ The types and numbers of the substituents on the phenyl groups having the formula (I) may be the same or different.

[0158]

[0159] In addition, the above general formula (G ｈ２ 3) In R １０１ ~R １０５ each independently represents one of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 6 to 12 carbon atoms, and a substituted or unsubstituted phenyl group.

[0160] In addition, the above general formula (G ｈ２ 1) to (G ｈ２ 3) In R １０６ , R １０７ and R １０８ Each independently represents an alkyl group having 1 to 4 carbon atoms, and v represents an integer of 0 to 4. When v is 2 or more, a plurality of R １０８may be the same or different. １１１ ~R １１５ One of R is a substituent represented by the general formula (g1) above, and the rest each independently represent one of hydrogen, an alkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted phenyl group. １２１ ~R １２５ One of R is a substituent represented by the above general formula (g2), and the rest each independently represent one of hydrogen, an alkyl group having 1 to 6 carbon atoms, and a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms. １３１ ~R １３５ Each of R independently represents one of hydrogen, an alkyl group having 1 to 6 carbon atoms, and a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms. １１１ ~R １１５ , R １２１ ~R １２５ and R １３１ ~R １３５ At least three of R are alkyl groups having 1 to 6 carbon atoms; １１１ ~R １１５ The number of substituted or unsubstituted phenyl groups in R １２１ ~R １２５ and R １３１ ~R １３５ In R, the number of phenyl groups substituted with alkyl groups having 1 to 6 carbon atoms is 1 or less. １１２ and R １１４ , R １２２ and R １２４ , and R １３２ and R １３４ In at least two of the three combinations, at least one R is other than hydrogen.

[0161] General formula (G ｈ２ 1) to (G ｈ２In 3), when the substituted or unsubstituted benzene ring or the substituted or unsubstituted phenyl group has a substituent, the substituent can be an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 5 to 12 carbon atoms. Furthermore, as the alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group is preferred. As the alkyl group having 1 to 6 carbon atoms, a chain alkyl group having 2 or more carbon atoms is preferred, and from the viewpoint of ensuring transportability, a chain alkyl group having 5 or less carbon atoms is preferred. Furthermore, a branched chain alkyl group having 3 or more carbon atoms has a remarkable refractive index reducing effect. That is, as the alkyl group having 1 to 6 carbon atoms, a chain alkyl group having 2 to 5 carbon atoms is preferred, and a branched chain alkyl group having 3 to 5 carbon atoms is more preferred. As the alkyl group having 1 to 6 carbon atoms, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, and a pentyl group are preferred, and a tert-butyl group is particularly preferred. As the cycloalkyl group having 5 to 12 carbon atoms, a cyclohexyl group, a 4-methylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a decahydronaphthyl group, a cycloundecyl group, and a cyclododecyl group can be used, but a cycloalkyl group having 6 or more carbon atoms is preferred in order to lower the refractive index, and a cyclohexyl group and a cyclododecyl group are particularly preferred.

[0162] The organic compound having hole-transport properties as described above has an ordinary refractive index of 1.40 to 1.75 in the blue light-emitting region (455 nm to 465 nm) or an ordinary refractive index of 1.40 to 1.70 in the 633 nm wavelength range typically used for measuring refractive index, and is an organic compound with good hole-transport properties. It is also possible to obtain an organic compound with high Tg and good reliability. Since such an organic compound also has sufficient hole-transport properties, it can be suitably used as a material for the first layer 122-1.

[0163] Examples of such materials include N,N-bis(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: dchPAF), N-[(4′-cyclohexyl)-1,1′-biphenyl-4yl]-N-(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: chBichPAF), and N,N-bis(4-cyclohexylphenyl)-N-(spiro[cyclohexane-1,9′[9H]fluoren]-2′yl)amine (abbreviation: dchPAS). chF), N-[(4'-cyclohexyl)-1,1'-biphenyl-4-yl]-N-(4-cyclohexylphenyl)-N-(spiro[cyclohexane-1,9'-[9H]-fluoren]-2'-yl)-amine (abbreviation: chBichPASchF), N-(4-cyclohexylphenyl)-bis(spiro[cyclohexane-1,9'-[9H]fluoren]-2'-yl)amine (abbreviation: SchFB1chP), N-[(3',5'-ditertiarybutyl)-1,1'-biphenyl-4-yl]-N-(4-cyclohexylphenyl)- N,N-bis(3',5'-ditert-butyl-1,1'-biphenyl-4-yl)-9,9,-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBuBichPAF), N,N-bis(3',5'-ditert-butyl-1,1'-biphenyl-4-yl)-9,9,-dimethyl-9H-fluoren-2-amine (abbreviation: dmmtBuBiAF), N-(3,5-ditert-butylphenyl)-N-(3',5',-ditert-butyl-1,1'-biphenyl-4-yl)-9,9,-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBuBimmt BuPAF), N,N-bis(4-cyclohexylphenyl)-9,9-dipropyl-9H-fluoren-2-amine (abbreviation: dchPAPrF), N-[(3',5'-dicyclohexyl)-1,1'-biphenyl-4-yl]-N-(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmchBichPAF), N-(3,3",5,5"-tetra-t-butyl-1,1':3',1"-terphenyl-5'-yl)-N-(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPchPAF), N-(4-cyclododecylphenyl)-N-(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: CdoPchPAF), N-(3,3″,5,5″-tetra-t-butyl-1,1′:3′,1″-terphenyl-5′-yl)-N-phenyl-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPFA), N-(1,1′-biphenyl-4-yl)-N-(3,3″,5,5″-tetra N-(1,1'-biphenyl-2-yl)-N-(3,3",5,5"-tetra-t-butyl-1,1':3',1"-terphenyl-5'-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPFBi), N-(1,1'-biphenyl-2-yl)-N-(3,3",5,5"-tetra-t-butyl-1,1':3',1"-terphenyl-5'-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi), N-[(3,3',5'-tri-t-butyl)-1,1'-biphenyl-5-yl]-N-(4-cyclohexylphenyl)-9,9-dimethyl -9H-fluoren-2-amine (abbreviation: mmtBumBichPAF), N-(1,1'-biphenyl-2-yl)-N-[(3,3',5'-tri-t-butyl)-1,1'-biphenyl-5-yl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumBioFBi), N-(4-tert-butylphenyl)-N-(3,3",5,5"-tetra-t-butyl-1,1':3',1"-terphenyl-5'-yl)-9,9,-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPtBuPAF), N- (3,3″,5′,5″-tetra-tert-butyl-1,1′:3′,1″-terphenyl-5-yl)-N-phenyl-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPFA-02), N-(1,1′-biphenyl-4-yl)-N-(3,3″,5′,5″-tetra-tert-butyl-1,1′:3′,1″-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPFBi-02), N-(1,1′-biphenyl-2-yl)-N-(3,3″,5′,5′-tetra-tert-butyl-1,1′:3′,1″-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi-02), N-(4-cyclohexylphenyl)-N-(3,3″,5′,5″-tetra-tert-butyl-1,1′:3′,1″-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPchPAF-02), N-(1,1′-biphenyl-2-yl)-N-(3″,5′,5″-tri-tert-butyl N-(4-cyclohexylphenyl)-N-(3",5',5"-tri-tert-butyl-1,1':3',1"-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi-03), N-(4-cyclohexylphenyl)-N-(3",5',5"-tri-tert-butyl-1,1':3',1"-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPchPAF-03), N-(3",5',5"-tri-t-butyl-1,1':3',1"-terphenyl-4-yl)-N-(1,1'-biphenyl-2 N-(4-cyclohexylphenyl)-N-(3",5',5"-tri-tert-butyl-1,1':3',1"-terphenyl-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi-04), N-(4-cyclohexylphenyl)-N-(3",5',5"-tri-tert-butyl-1,1':3',1"-terphenyl-4-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPchPAF-04), N-(1,1'-biphenyl-2-yl)-N-(3,3",5"-tri-tert-butyl-1,1':4',1"-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine Preferred are N-(4-cyclohexylphenyl)-N-(3,3',5'-tri-tert-butyl-1,1':4',1'-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi-05), N-(4-cyclohexylphenyl)-N-(3,3',5'-tri-tert-butyl-1,1':4',1'-terphenyl-5-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPchPAF-05), and N-(3',5'-ditert-butyl-1,1'-biphenyl-4-yl)-N-(1,1'-biphenyl-2-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBuBioFBi).

[0164] In addition, 1,1-bis{4-[bis(4-methylphenyl)amino]phenyl}cyclohexane (abbreviation: TAPC) and the like can also be used.

[0165] <Examples of High Refractive Index Materials> The second layer 122-2 and, when the third layer 122-3 is a layer with a high refractive index, are formed using organic compounds with a relatively high refractive index. Such organic compounds are preferably compounds having a fused aromatic hydrocarbon ring or a fused heteroaromatic ring. The fused aromatic hydrocarbon ring is preferably a compound containing a naphthalene ring structure within the fused aromatic hydrocarbon ring, such as a naphthalene ring, an anthracene ring, a phenanthrene ring, or a triphenylene ring. The fused heteroaromatic ring is preferably a compound containing a carbazole ring, a dibenzofuran ring, or a dibenzothiophene ring structure. For example, benzo[b]naphtho[1,2-d]furan is preferred because it contains a dibenzofuran ring structure.

[0166] In addition, organic compounds containing one or more elements from the third period or later, organic compounds having a terphenyl skeleton, or organic compounds containing both can be suitably used. For example, a biphenyl group substituted with a naphthyl group or a phenyl group substituted with a dibenzofuranyl group can be said to contain a terphenyl skeleton. Specifically, N,N-bis[4-(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)phenyl]-4-amino-p-terphenyl (abbreviation: BnfBB1TP), 4,4′-bis[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: βNBiB1BP), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), 4-[4′-(carbazol-9-yl)biphenyl-4-yl]-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: YGTBiβNB), 5,5′-diphenyl-2,2′-di-5H-[1]benzothieno[3,2-c]carbazole (abbreviation: BisBTc), and the like can be suitably used.

[0167] <GSP> In one embodiment of the present invention, the light extraction efficiency is improved by stacking multiple hole transport layers with different refractive indices. However, at the same time, the light-emitting device has more layers than a typical light-emitting device. This increases the number of layer interfaces, which can easily generate resistance due to the interfaces and result in an increase in driving voltage.

[0168] Typically, in the hole transport region of an organic semiconductor device, holes must be sequentially injected into layers made of organic compounds with different HOMO levels between the active layer and the light-emitting layer to allow for hole exchange with the electrode. Naturally, if the difference in HOMO levels between layers is too large, the driving voltage will increase. Therefore, the difference in HOMO levels is mitigated by placing a layer made of an organic compound with a HOMO level between the electrode and the active layer (light-emitting layer). However, even if the difference in HOMO levels between layers is not that large, the driving voltage can sometimes increase significantly depending on the combination of organic compounds used. Until now, there have been no guidelines for avoiding this problem, and it has been dismissed as a matter of compatibility between materials.

[0169] Organic compounds include polar and nonpolar molecules. Polar molecules have a permanent dipole moment, but when polar molecules are vapor-deposited, if the vapor-deposited film is randomly oriented, the polarity bias is canceled out and no polarization due to the polarity of the molecules occurs within the film. However, if the vapor-deposited film has molecular orientation, a giant surface potential due to the polarization bias may appear.

[0170] Giant surface potential is a phenomenon in which the surface potential of a vapor-deposited film increases in proportion to the film thickness. It can be explained as a spontaneous orientation polarization phenomenon caused by a slight bias in the film thickness direction of the permanent dipole moment of an organic compound. To treat its magnitude as a numerical value independent of film thickness, the value obtained by dividing the surface potential of the vapor-deposited film by the film thickness, i.e., the potential gradient (slope) of the surface potential of the vapor-deposited film, can be used. In this specification, the potential gradient of the surface potential of the vapor-deposited film is referred to as the GSP slope (mV / nm).

[0171] By taking the value of the GSP slope into consideration, it becomes possible to eliminate the mismatch that has conventionally been attributed to the compatibility of materials, as described above, and to easily obtain an organic semiconductor device with good characteristics.

[0172] In one aspect of the present invention, the value obtained by subtracting the slope of the GSP of the second layer 122-2 from the slope of the GSP of the first layer 122-1 (ΔGSP １−２ ) is preferably 10 (mV / nm) or less, and more preferably 0 (mV / nm) or less.

[0173] This configuration makes it possible to easily obtain a light-emitting device having favorable characteristics such as a low driving voltage, low power consumption, or high power efficiency.

[0174] Furthermore, it is preferable that the GSP gradient of the second layer 122-2 is higher than that of the first layer 122-1. This configuration makes it easier to obtain a light-emitting device with favorable characteristics such as a low driving voltage, low power consumption, or high power efficiency.

[0175] The GSP gradient of each layer can be determined by measuring the GSP gradient of the evaporated film of the material (organic compound) that constitutes each layer.

[0176] A method for determining the slope of the GSP of an organic compound will be described.

[0177] Generally, the slope of the surface potential of a deposited film measured by a Kelvin probe plotted against the film thickness direction is discussed as the magnitude of the giant surface potential, i.e., the slope of the GSP (mV / nm). However, when two different layers are stacked, the polarization charge density (mC / m ２ ) changes in relation to the slope of the GSP, which can be used to estimate the slope of the GSP.

[0178] When organic thin films (thin film 1 and thin film 2, where thin film 1 is located on the anode side and thin film 2 is located on the cathode side) having different spontaneous polarizations are stacked and a current is passed through them, the following equation holds true:

[0179]

[0180]

[0181] In formula (1), σ ｉｆ is the polarization charge density, V ｉ is the hole injection voltage, V ｂｉ is the threshold voltage, d ２ is the thickness of thin film 2, ε ２ is the dielectric constant of the thin film 2. V ｉ , V ｂｉ can be estimated from the capacitance-voltage characteristics of the device. ｏ In this way, the V estimated from the capacitance-voltage characteristics can be calculated as ｉ , V ｂｉ and the dielectric constant ε of the thin film 2 calculated from the refractive index ２ , and the thickness d of the thin film 2 ２ Therefore, using equation (1), the polarization charge density σ ｉｆ can be obtained.

[0182] Next, in equation (2), σ ｉｆ is the polarization charge density, P ｎ is the slope of the GSP of the thin film n, ε ｎ is the dielectric constant of the thin film n. Here, from the above formula (1), the polarization charge density σ ｉｆ Therefore, by using a material with a known GSP as the thin film 2, the gradient of the GSP of the thin film 1 can be estimated.

[0183] As described above, the GSP gradient can be determined by the above method using the evaporated film of the organic compound for which the GSP gradient is to be determined as the thin film 1.

[0184] In this specification, the thin film 2 is Alq, which has a known GSP gradient of 48 (mV / nm). ３ The refractive index was measured using a spectroscopic ellipsometer (M-2000U manufactured by J.A. Woollam Japan).

[0185] In addition, it is known that the orientation of a deposited film depends on the substrate temperature during deposition, and the value of the GSP tilt may also depend on the substrate temperature during deposition. The measurements in this specification are those for films deposited at room temperature during deposition.

[0186] <Structure of Light-Emitting Device> Next, the structure and materials of a light-emitting device included in a light-emitting device of one embodiment of the present invention will be described in detail with reference to Fig. 3A . The light-emitting device included in a light-emitting device of one embodiment of the present invention includes the EL layer 103 including the light-emitting layer 113 and the stacked layer structure 122 having a refractive index step (LH structure) between a pair of electrodes, the first electrode 101 and the second electrode 102, as described above. The stacked layer structure 122 is located between the light-emitting layer 113 and the first electrode 101 and includes a first layer 122-1 and a second layer 122-2, or a first layer 122-1, a second layer 122-2, and a third layer 122-3b.

[0187] The light-emitting layer 113 contains a light-emitting substance. The first electrode 101 preferably has a laminated structure including a reflective electrode and an anode. In this case, the anode preferably has a property of transmitting visible light and is provided between the reflective electrode and the laminated structure 122 in contact with the reflective electrode.

[0188] The anode is preferably formed using a metal, alloy, conductive compound, or mixture thereof having a large work function (specifically, 4.0 eV or more). Specific examples include indium oxide-tin oxide (ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, and indium oxide containing tungsten oxide and zinc oxide (IWZO). These conductive metal oxide films are usually formed by sputtering, but may also be prepared by applying a sol-gel method. As an example of a preparation method, indium oxide-zinc oxide can be formed by sputtering using a target in which 1 to 20 wt % of zinc oxide is added to indium oxide. Indium oxide containing tungsten oxide and zinc oxide (IWZO) can also be formed by sputtering using a target containing 0.5 to 5 wt % tungsten oxide and 0.1 to 1 wt % zinc oxide relative to indium oxide. Other materials that can be used for the anode include, for example, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), and nitrides of metal materials (e.g., titanium nitride). Alternatively, graphene can be used for the anode. Note that using a composite material described below as a layer in contact with the anode (typically a hole injection layer) allows the electrode material to be selected regardless of the work function.

[0189] The EL layer 103 preferably has a laminated structure, and the laminated structure is not particularly limited except for the light-emitting layer 113 and the laminated structure 122 having a refractive index difference. The EL layer 103 may appropriately use various functional layers such as a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a carrier block layer (hole block layer, electron block layer), an exciton block layer, an intermediate layer, and a charge generation layer. The laminated structure 122 having a refractive index difference functions as a hole injection layer, a hole transport layer, an electron block layer, etc.

[0190] 3A illustrates a configuration including a hole injection layer 111, an electron transport layer 114, and an electron injection layer 115 in addition to the light-emitting layer 113 (light-emitting layer 113S, light-emitting layer 113L), a stacked structure 122 having a refractive index step (a first layer 122-1, a second layer 122-2 (and a third layer 122-3)). In addition, in FIG. 3A, the first layer 122-1 to the third layer 122-3 function as hole transport layers.

[0191] The hole injection layer 111 is provided in contact with the anode and has a function of facilitating injection of holes into the EL layer 103. The hole injection layer is made of phthalocyanine (abbreviation: H ２ Pc), copper phthalocyanine complex compounds such as copper phthalocyanine (abbreviation: CuPc), aromatic amine compounds such as 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) and 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), or polymers such as poly(3,4-ethylenedioxythiophene) / (polystyrenesulfonic acid) (abbreviation: PEDOT / PSS).

[0192] The hole injection layer may be formed of a substance having electron acceptor properties. Examples of the substance having acceptor properties include organic compounds having an electron-withdrawing group (such as a halogen group or a cyano group), such as 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCCNNQ), and 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile. In particular, compounds in which an electron-withdrawing group is bonded to a fused aromatic ring having a plurality of heteroatoms, such as HAT-CN, are thermally stable and preferred. Also, [3]radialene derivatives having an electron-withdrawing group (especially a halogen group such as a fluoro group, a cyano group, etc.) are preferred because they have very high electron-accepting properties, and specific examples thereof include α,α',α''-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile]. In addition to the organic compounds described above, the substance having acceptor properties can also be a transition metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, manganese oxide, etc. The substance having acceptor properties can extract electrons from the adjacent hole transport layer (or hole transport material) by applying a voltage between the electrodes.

[0193] The hole injection layer may be formed of a composite material containing the above-mentioned material having acceptor properties and a material having hole transport properties. As the material having hole transport properties used for the composite material, various organic compounds such as aromatic amine compounds, heteroaromatic compounds, aromatic hydrocarbons, and polymer compounds (oligomers, dendrimers, polymers, etc.) can be used. The material having hole transport properties used for the composite material can be a 1×10 −６ cm ２ / Vs or more. The material having hole transport properties used in the composite material is preferably a compound having a fused aromatic hydrocarbon ring or a π-electron-rich heteroaromatic ring. As the fused aromatic hydrocarbon ring, an anthracene ring, a naphthalene ring, or the like is preferable. Furthermore, as the π-electron-rich heteroaromatic ring, a fused aromatic ring containing at least one of a pyrrole skeleton, a furan skeleton, and a thiophene skeleton in the ring is preferable, and specifically, a carbazole ring, a dibenzothiophene ring, or a ring in which an aromatic ring or a heteroaromatic ring is further fused to the above ring is preferable.

[0194] The material having such hole-transporting properties preferably has a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton. In particular, the material may be an aromatic amine having a substituent containing a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine having a naphthalene ring, or an aromatic monoamine in which a 9-fluorenyl group is bonded to the nitrogen of the amine via an arylene group. It is preferable that the material having hole-transporting properties is a substance having an N,N-bis(4-biphenyl)amino group, since this allows the fabrication of a light-emitting device with a long lifetime. Specific examples of the material having hole transport properties as described above include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan) and 4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan). N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N-bis(4-biphenyl)benzo[b]naphtho[2,3- d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4',4''-diphenyltriphenylamine (abbreviation: abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4',4''-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4'-diphenyl-4''-(6;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4'-diphenyl-4''-(7;1'-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB-03), 4,4'-Diphenyl-4''-(7-phenyl)naphthyl-2-yltriphenylamine (abbreviation: BBAPβNB-03), 4,4'-diphenyl-4''-(6;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B), 4,4'-diphenyl-4''-(7;2'-binaphthyl-2-yl)triphenylamine (abbreviation: BBA(βN2)B-03), 4,4'-diphenyl-4''-(4;2'-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB), 4,4'-diphenyl-4''-(5;2'- binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4'-(2-naphthyl)-4''-phenyltriphenylamine (abbreviation: TPBiAβNB), 4-(3-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: mTPBiAβNBi), 4-(4-biphenylyl)-4'-[4-(2-naphthyl)phenyl]-4''-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4'-(1-naphthyl)triphenylamine nylamine (abbreviation: αNBA1BP), 4,4'-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4'-diphenyl-4''-[4'-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4'-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(1,1'-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4'-(carbazol-9-yl)biphenyl-4-yl]-4'-(2-naphthyl)-4''-phenyl triphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluorene]-2-amine (abbreviation: PCBNBSF), N,N-bis([1,1′-biphenyl]-4-yl)-9,9′-spirobi[9H-fluorene]-2-amine (abbreviation: BBASF), N,N-bis([1,1′-biphenyl]-4-yl)-9,9′-spirobi[9H-fluorene]-4-amine (abbreviation: BBASF(4)), N-(1,N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi[9H-fluorene]-4-amine (abbreviation: oFBiSF), N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4'-(9-phenylfluoren-9-yl)trimethylamine triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4'-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-4-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-3-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-2-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-2-amine, N,N-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9'-spirobi-9H-fluoren-1-amine, etc.

[0195] Other aromatic amine compounds that can be used as the material having hole transport properties include N,N'-di(p-tolyl)-N,N'-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), and 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B).

[0196] In addition, as the material having hole-transport properties in the composite material, organic compounds with a low refractive index listed as organic compounds that can be used for the first layer 122-1 and the like can also be used. When a composite material containing such an organic compound as a material having hole-transport properties in the composite material is used for the first layer 122-1, the first layer 122-1 can function as a hole-transport layer. Furthermore, when a third layer 122-3 is provided between the first electrode and the first layer 122-1 (e.g., the third layer 122-3c in FIG. 1C ) and a composite material containing the organic compound as a material having hole-transport properties used in the composite material is used for the third layer 122-3c, the third layer 122-3c can function as a hole-injection layer. In this case, the hole-injection layer 111 does not necessarily need to be formed between the stacked structure 122 and the first electrode 101.

[0197] It is more preferable that the material having hole-transporting properties used in the composite material has a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less. When the material having hole-transporting properties used in the composite material has a relatively deep HOMO level, injection of holes into the hole-transport layer becomes easy, and a light-emitting device with a long lifetime can be easily obtained. Furthermore, when the material having hole-transporting properties used in the composite material has a relatively deep HOMO level, induction of holes is appropriately suppressed, and a light-emitting device with a long lifetime can be obtained.

[0198] By forming the hole injection layer 111 or by making the first layer 122-1 or the third layer 122-3 function as a hole injection layer, the hole injection property is improved, and a light-emitting device with a low driving voltage can be obtained.

[0199] Among substances having acceptor properties, organic compounds having acceptor properties are easy to use because they can be easily vapor-deposited and formed into a film.

[0200] The hole transport layer is formed by including a material having a hole transport property. −６ cm ２ 3A , the hole transport layer is preferably the first layer 122-1 and the second layer 122-2 or the first layer 122-1 to the third layer 122-3, as described above. This configuration allows for a light-emitting device with good luminous efficiency. For example, the light-emitting device can have good external quantum efficiency, current efficiency, and / or blue index.

[0201] 3B , an electron blocking layer 130 may be provided between the stacked structure 122 and the light-emitting layer 113. The electron blocking layer preferably uses an organic compound that has a hole-transporting property and a LUMO level that is 0.25 eV or more higher than that of the host material of the light-emitting layer 113. When an organic compound that can be used for the first layer 122-1 is used as the organic compound, the third layer 122-3a can function as the electron blocking layer. When an organic compound that can be used for the second layer 122-2 or the like is used as the organic compound, the third layer 122-3a can function as the electron blocking layer.

[0202] Note that FIG. 3A shows an example in which the hole injection layer 111 and the stacked structure 122 having a refractive index step are provided between the first electrode 101 and the light-emitting layer 113. However, the stacked structure 122 may be formed in contact with the first electrode 101 without providing the hole injection layer 111, and the first layer 122-1 (or the third layer 122-3c) may function as a hole injection layer.

[0203] The light-emitting layer 113 preferably contains a light-emitting substance and a host material. The light-emitting layer 113 may also contain other materials. Alternatively, the light-emitting layer 113 may be a laminate of two layers with different compositions.

[0204] The luminescent material may be a fluorescent material, a phosphorescent material, a material exhibiting thermally activated delayed fluorescence (TADF), or any other luminescent material.

[0205] Examples of materials that can be used as the fluorescent substance in the light-emitting layer 113 include the following: In addition, fluorescent substances other than these can also be used.

[0206] 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2'-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4'-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2'-bipyridine (abbreviation: PAPP2BPy), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine )phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-bis[4-(9H-carbazol-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4'-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-( 10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N''-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N',N'-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9 -diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PAPPA), N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N',N',N'',N'',N''',N'''-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), Coumarin 30, N-(9,10-diphenyl-2-anthryl)-N,9-Diphenyl-9H-carbazole-3-amine (abbreviation: 2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,N',N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPA BPhA), 9,10-bis(1,1'-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine (abbreviation: DPhAPhA), Coumarin 545T, N,N'-diphenylquinacridone (abbreviation: DPQd), rubrene, 5,12-bis(1,1'-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT), 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6 -methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine amine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJ™), N,N'-diphenyl-N,N'-(1,6-pyren-diyl)bis[(6-phenylbenzo[b ]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), and 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02). In particular, condensed aromatic diamine compounds typified by pyrene diamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03 are preferred because they have high hole-trapping properties and excellent luminous efficiency or reliability. ,

[0207] When a phosphorescent material is used as the light-emitting material in the light-emitting layer 113, examples of materials that can be used include the following.

[0208] Tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp) ３ ]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz) ３ ]), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b) ３organometallic iridium complexes having a 4H-triazole skeleton, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp) ３ ]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me) ３ organometallic iridium complexes having a 1H-triazole skeleton, such as fac-tris[(1-2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpmi) ３ ]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me) ３ organometallic iridium complexes having an imidazole skeleton, such as bis[2-(4',6'-difluorophenyl)pyridinato-N,C ２’ ]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4',6'-difluorophenyl)pyridinato-N,C ２’ ]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3',5'-bis(trifluoromethyl)phenyl]pyridinato-N,C ２’} Iridium(III) picolinate (abbreviation: [Ir(CF ３ ppy) ２ (pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C ２’ ] Organometallic iridium complexes having a phenylpyridine derivative having an electron-withdrawing group as a ligand, such as iridium(III) acetylacetonate (abbreviation: FIracac), are examples of such compounds that exhibit blue phosphorescence and have an emission peak in the wavelength range of 450 nm to 520 nm.

[0209] Also, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) ３]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) ３ ]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm) ２ (acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm) ２ (acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm) ２ (acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm) ２ (acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm) ２ organometallic iridium complexes having a pyrimidine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me) ２ (acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr) ２ organometallic iridium complexes having a pyrazine skeleton, such as tris(2-phenylpyridinato-N,C(acac)]); ２’ ) Iridium(III) (abbreviation: [Ir(ppy) ３ ]), bis(2-phenylpyridinato-N,C ２’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(ppy) ２ (acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq) ２ (acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq) ３]), tris(2-phenylquinolinato-N,C ２’ ) Iridium(III) (abbreviation: [Ir(pq) ３ ]), bis(2-phenylquinolinato-N,C ２’ ) iridium(III) acetylacetonate (abbreviation: [Ir(pq) ２ (acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(5mppy-d3) ２ (mbfpypy-d3)), [2-(methyl-d3)-8-[4-(1-methylethyl-1-d)-2-pyridinyl-κN]benzofuro[2,3-b]pyridin-7-yl-κC]bis[5-(methyl-d3)-2-[5-(methyl-d3)-2-pyridinyl-κN]phenyl-κC]iridium(III) (abbreviation: Ir(5mtpy-d6) ２ (mbfpypy-iPr-d4)), [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy) ２ (mbfpypy-d3)), [2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy) ２ In addition to organometallic iridium complexes having a pyridine skeleton, such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac) ３ These compounds mainly exhibit green phosphorescence, with an emission peak in the wavelength range of 500 nm to 600 nm. Organometallic iridium complexes having a pyrimidine skeleton are particularly preferred because they are remarkably excellent in reliability and luminous efficiency.

[0210] Also, (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm) ２ (dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm) ２ (dpm)]), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(dpm) ２ organometallic iridium complexes having a pyrimidine skeleton, such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr) ２ (acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr) ２ (dpm)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq) ２ organometallic iridium complexes having a pyrazine skeleton, such as tris(1-phenylisoquinolinato-N,C(acac)]); ２’ ) Iridium(III) (abbreviation: [Ir(piq) ３ ]), bis(1-phenylisoquinolinato-N,C ２’ ) iridium(III) acetylacetonate (abbreviation: [Ir(piq) ２ In addition to organometallic iridium complexes having a pyridine skeleton such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (abbreviation: PtOEP), platinum complexes such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM) ３ (Phen)]), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA) ３Examples of rare earth metal complexes include iridium complexes such as iridium complexes containing pyrazine skeletons and iridium complexes containing iridium ions. These compounds exhibit red phosphorescence and have an emission peak in the wavelength range of 600 nm to 700 nm. Organometallic iridium complexes containing pyrazine skeletons exhibit red emission with good chromaticity.

[0211] In addition to the phosphorescent compounds described above, known phosphorescent compounds may be selected and used.

[0212] Examples of TADF materials that can be used include fullerene and its derivatives, acridine and its derivatives, and eosin derivatives. Other examples include metal-containing porphyrins containing magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd). Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complexes (SnF) represented by the following structural formula: ２ (Proto IX)), mesoporphyrin-tin fluoride complex (SnF ２ (Meso IX)), hematoporphyrin-tin fluoride complex (SnF ２ (Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (SnF ２ (Copro III-4Me)), octaethylporphyrin-tin fluoride complex (SnF ２ (OEP)), etioporphyrin-tin fluoride complex (SnF ２ (Etio I)), octaethylporphyrin-platinum chloride complex (PtCl ２ OEP) and the like.

[0213]

[0214] Further, 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), and Heterocyclic compounds having one or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), and 10-phenyl-10H,10′H-spiro[acridine-9,9′-anthracene]-10′-one (abbreviation: ACRSA), can also be used. The heterocyclic compound has a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring, and therefore has high electron transport and hole transport properties, and is therefore preferred. Among the skeletons having a π-electron-deficient heteroaromatic ring, pyridine skeleton, diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and triazine skeleton are preferred because they are stable and reliable. In particular, benzofuropyrimidine skeleton, benzothienopyrimidine skeleton, benzofuropyrazine skeleton, and benzothienopyrazine skeleton are preferred because they have high acceptor properties and good reliability. Furthermore, among the skeletons having a π-electron-rich heteroaromatic ring, acridine skeleton, phenoxazine skeleton, phenothiazine skeleton, furan skeleton, thiophene skeleton, and pyrrole skeleton are preferred because they are stable and reliable.The furan skeleton is preferably a dibenzofuran skeleton, and the thiophene skeleton is preferably a dibenzothiophene skeleton. The pyrrole skeleton is particularly preferably an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, or a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton. A substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded is particularly preferred because the electron-donating property of the π-electron-rich heteroaromatic ring and the electron-accepting property of the π-electron-deficient heteroaromatic ring are both enhanced, reducing the energy difference between the S1 level and the T1 level, thereby enabling efficient thermally activated delayed fluorescence. Instead of the π-electron-deficient heteroaromatic ring, an aromatic ring bonded to an electron-withdrawing group such as a cyano group may be used. The π-electron-rich skeleton may be, for example, an aromatic amine skeleton or a phenazine skeleton. Examples of usable π-electron-deficient skeletons include a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a boron-containing skeleton such as phenylborane or boranthrene, an aromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a heteroaromatic ring, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc. In this way, a π-electron-deficient skeleton and a π-electron-rich skeleton can be used in place of at least one of a π-electron-deficient heteroaromatic ring and a π-electron-rich heteroaromatic ring.

[0215]

[0216] Alternatively, a TADF material in which the singlet excited state and the triplet excited state are in thermal equilibrium may be used. Such a TADF material has a short emission lifetime (excitation lifetime), which can suppress a decrease in efficiency in the high brightness region of a light-emitting element. Specific examples include materials with the molecular structure shown below.

[0217]

[0218] The TADF material is a material that has a small difference between the S1 level and the T1 level and has the function of converting triplet excitation energy to singlet excitation energy by reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy (reverse intersystem crossing) with a small amount of thermal energy, and a singlet excited state can be efficiently generated. Furthermore, triplet excitation energy can be converted into luminescence.

[0219] Furthermore, an exciplex (also called an exciplex) that forms an excited state with two types of substances has an extremely small difference between the S1 level and the T1 level, and functions as a TADF material that can convert triplet excitation energy into singlet excitation energy.

[0220] The T1 level can be determined by using a phosphorescence spectrum observed at low temperatures (e.g., 77 K to 10 K). When a tangent line is drawn at the base of the fluorescence spectrum on the short wavelength side of the TADF material, and the energy of the wavelength of the extrapolated line is defined as the S1 level, and when a tangent line is drawn at the base of the phosphorescence spectrum on the short wavelength side of the TADF material, and the energy of the wavelength of the extrapolated line is defined as the T1 level, the difference between S1 and T1 is preferably 0.3 eV or less, and more preferably 0.2 eV or less.

[0221] When a TADF material is used as a light-emitting material, the S1 level of the host material is preferably higher than the S1 level of the TADF material, and the T1 level of the host material is preferably higher than the T1 level of the TADF material.

[0222] As the host material of the light-emitting layer, various carrier transport materials such as a material having an electron transport property and / or a material having a hole transport property, and the above-mentioned TADF material can be used.

[0223] As a material having hole transport properties, an organic compound having an amine skeleton, a π-electron-rich heteroaromatic skeleton, etc. is preferable. For example, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (abbreviation: TPD), 4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP ... mBPAFLP), 4-phenyl-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4 aromatic amine skeletons such as 4'-di(1-naphthyl)-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9'-spirobi[9H-fluorene]-2-amine (abbreviation: PCBASF). compounds having a carbazole skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), and 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II);Examples of suitable compounds include compounds having a thiophene skeleton, such as 8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III) and 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV), and compounds having a furan skeleton, such as 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) and 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II). Among the compounds listed above, compounds having an aromatic amine skeleton or a carbazole skeleton are preferred because they have good reliability, high hole transport properties, and contribute to reducing driving voltage. In addition, the organic compounds listed as examples of materials having hole transport properties in the hole transport layer can also be used.

[0224] Examples of materials having electron transport properties include bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq ２), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), or other metal complexes; and organic compounds having a π-electron-deficient heteroaromatic ring are preferred. Examples of organic compounds having a π-electron-deficient heteroaromatic ring include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazole-2 -yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: m organic compounds having an azole skeleton such as 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), bathophenanthroline (abbreviation: Bphen), and bathocupro organic compounds containing heteroaromatic rings with a pyridine skeleton, such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3-(3′-dibenzothiophen-4-yl)bi ...h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4'-(9-phenyl-9H-carbazol-3-yl)-3,1'-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophene 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[(3'-dibenzothiophen-4-yl)biphenyl-4-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9pm DBtBPNfpr), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9'-[pyrimidine-4,6-diylbis(biphenyl-3,3'-diyl)]bis(9H-carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(1,1'-biphenyl-4-yl) 4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-[3′-(dibenzothiophen-4-yl)(1,1′-biphenyl-3-yl)]naphtho[1′,2':4,5]furo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2'-binaphthalen)-6-yl]-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), 2,2'-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine phenyl} (abbreviation: 2,6(NP-PPm)2Py), 6-(1,1'-biphenyl-3-yl)-4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalen-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenyl-6-(1,1'-biphenyl-4-yl)pyrimidine (abbreviation: 6BP-4Cz2 PPm), 7-[4-(9-phenyl-9H-carbazol-2-yl)quinazolin-2-yl]-7H-dibenzo[c,g]carbazole (abbreviation: PC-cgDBCzQz), organic compounds having a diazine skeleton such as 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5 -triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)-1,1′-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn) , 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris(3′-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-(4-[1,1'-biphenyl]-4-yl-6-phenyl-1,3,5-triazin-2-yl)-11,12-dihydro-12-phenyl-indolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenylen-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl'1,3,5-triazine (abbreviation: mTpBPTzn), 9-[4-(4, Examples of suitable organic compounds include those containing heteroaromatic rings with a triazine skeleton, such as [6-diphenyl-1,3,5-triazin-2-yl]-2-dibenzothiophenyl]-2-phenyl-9H-carbazole (abbreviation: PCDBfTzn) and 2-[1,1'-biphenyl]-3-yl-4-phenyl-6-(8-[1,1':4',1''-terphenyl]-4-yl-1-dibenzofuranyl)-1,3,5-triazine (abbreviation: mBP-TPDBfTzn). Among the above, organic compounds containing heteroaromatic rings with a diazine skeleton, organic compounds containing heteroaromatic rings with a pyridine skeleton, and organic compounds containing heteroaromatic rings with a triazine skeleton are preferred due to their high reliability. In particular, organic compounds containing heteroaromatic rings with a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing heteroaromatic rings with a triazine skeleton have high electron transport properties and contribute to reduced driving voltage.

[0225] The TADF materials that can be used as the host material can be the same as those listed above. When a TADF material is used as a host material, triplet excitation energy generated in the TADF material is converted into singlet excitation energy by reverse intersystem crossing, and the energy is further transferred to a light-emitting substance, thereby improving the luminous efficiency of the light-emitting device. In this case, the TADF material functions as an energy donor, and the light-emitting substance functions as an energy acceptor.

[0226] This is very effective when the luminescent material is a fluorescent luminescent material. Furthermore, in this case, in order to obtain high luminous efficiency, it is preferable that the S1 level of the TADF material is higher than the S1 level of the fluorescent luminescent material. Furthermore, it is preferable that the T1 level of the TADF material is higher than the S1 level of the fluorescent luminescent material. Therefore, it is preferable that the T1 level of the TADF material is higher than the T1 level of the fluorescent luminescent material.

[0227] It is also preferable to use a TADF material that emits light that overlaps with the wavelength of the lowest-energy absorption band of the fluorescent material, since this allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient light emission.

[0228] Furthermore, in order to efficiently generate singlet excitation energy from triplet excitation energy through reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. To this end, it is preferable that the fluorescent material has a protecting group around the luminophore (the skeleton responsible for light emission) possessed by the fluorescent material. The protecting group is preferably a substituent without a π bond, and is preferably a saturated hydrocarbon. Specific examples include alkyl groups having 3 to 10 carbon atoms, substituted or unsubstituted cycloalkyl groups having 3 to 10 carbon atoms, and trialkylsilyl groups having 3 to 10 carbon atoms. It is even more preferable that the protecting group has multiple protecting groups. Substituents without a π bond have poor carrier transport function, so the distance between the TADF material and the luminophore of the fluorescent material can be increased without significantly affecting carrier transport or carrier recombination. Here, the luminophore refers to the atomic group (skeleton) responsible for light emission in the fluorescent material. The luminophore preferably has a skeleton having a π bond, preferably contains an aromatic ring, and preferably has a fused aromatic ring or a fused heteroaromatic ring. Examples of the fused aromatic ring or the fused heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, fluorescent substances having a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, or a naphthobisbenzofuran skeleton are preferred because of their high fluorescence quantum yield.

[0229] When a fluorescent light-emitting substance is used as the light-emitting substance, a material having an anthracene skeleton is suitable as the host material. Using a substance having an anthracene skeleton as the host material for a fluorescent light-emitting substance makes it possible to realize an emitting layer with both excellent luminous efficiency and durability. As a substance having an anthracene skeleton to be used as the host material, a substance having a diphenylanthracene skeleton, particularly a 9,10-diphenylanthracene skeleton, is preferred because it is chemically stable. Furthermore, a host material having a carbazole skeleton is preferred because it enhances hole injection and transport properties. However, a host material containing a benzocarbazole skeleton in which a benzene ring is further condensed to carbazole is more preferred because its HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter. In particular, a host material containing a dibenzocarbazole skeleton is preferred because its HOMO is shallower by about 0.1 eV than that of carbazole, making it easier for holes to enter, and it also has excellent hole transport properties and high heat resistance. Therefore, a more preferable host material is a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton (or a benzocarbazole skeleton or a dibenzocarbazole skeleton). Note that, in view of the hole injection / transport property, a benzofluorene skeleton or a dibenzofluorene skeleton may be used instead of the carbazole skeleton.Examples of such substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-(1-naphthyl)-10-(2-naphthyl)anthracene (abbreviation: α,βADN), 2-(10-phenylanthracen-9-yl)dibenzofuran, 2-(10-phenyl-9-anthracenyl)-benzo[b ] naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: βN-mβNPAnth), 1-[4-(10-[1,1′-biphenyl]-4-yl-9-anthracenyl)phenyl]-2-ethyl-1H-benzimidazole (abbreviation: EtBImPBPhA), etc. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA are preferred choices because they exhibit very good properties.

[0230] The host material may be a mixture of a plurality of substances. When a mixture of host materials is used, it is preferable to mix a material having electron transport properties with a material having hole transport properties. By mixing a material having electron transport properties with a material having hole transport properties, the transport properties of the light-emitting layer 113 can be easily adjusted, and the recombination region can also be easily controlled. The weight ratio of the content of the material having hole transport properties to the material having electron transport properties may be 1:19 to 19:1 (material having hole transport properties:material having electron transport properties).

[0231] A phosphorescent material can be used as part of the mixed material. The phosphorescent material can be used as an energy donor that provides excitation energy to a fluorescent material when the fluorescent material is used as a light-emitting material.

[0232] Furthermore, these mixed materials may form an exciplex. It is preferable to select a combination that forms an exciplex that emits light that overlaps with the wavelength of the lowest-energy absorption band of the light-emitting material, because this allows for smooth energy transfer and efficient light emission. Furthermore, using this structure is also preferable because it reduces the driving voltage.

[0233] At least one of the materials forming the exciplex may be a phosphorescent material, which allows efficient conversion of triplet excitation energy into singlet excitation energy through reverse intersystem crossing.

[0234] As a combination of materials that efficiently form an exciplex, it is preferable that the HOMO level of the material having hole transport properties is equal to or higher than the HOMO level of the material having electron transport properties. Also, it is preferable that the LUMO level of the material having hole transport properties is equal to or higher than the LUMO level of the material having electron transport properties. Note that the LUMO level and HOMO level of the material can be derived from the electrochemical properties (reduction potential and oxidation potential) of the material measured by cyclic voltammetry (CV).

[0235] The formation of exciplexes can be confirmed, for example, by comparing the emission spectra of a material having hole transport properties, a material having electron transport properties, and a mixed film obtained by mixing these materials, and observing the phenomenon in which the emission spectrum of the mixed film is shifted to longer wavelengths than the emission spectra of each material (or has a new peak on the longer wavelength side). Alternatively, the formation of exciplexes can be confirmed by comparing the transient photoluminescence (PL) of a material having hole transport properties, the transient PL of a material having electron transport properties, and a mixed film obtained by mixing these materials, and observing differences in transient response, such as the transient PL lifetime of the mixed film having a longer-lifetime component or a larger proportion of delayed components than the transient PL lifetimes of the individual materials. The above-mentioned transient PL may also be interpreted as transient electroluminescence (EL). In other words, the formation of exciplexes can also be confirmed by comparing the transient EL of a material having hole transport properties, the transient EL of a material having electron transport properties, and a mixed film obtained by mixing these materials, and observing the differences in transient response.

[0236] The electron transport layer 114 is a layer containing a substance having an electron transport property. The material having an electron transport property is a material having an electron mobility of 1×10 or less at a square root of an electric field strength [V / cm] of 600. −７ cm ２ / Vs or more, preferably 1×10 −６ cm ２ A substance having an electron mobility of 1 / Vs or more is preferred. Note that, other substances can be used as long as they have a higher electron transporting property than holes. Note that, as the organic compound, an organic compound having a π-electron-deficient heteroaromatic ring is preferred. As the organic compound having a π-electron-deficient heteroaromatic ring, for example, one or more of an organic compound including a heteroaromatic ring having a polyazole skeleton, an organic compound including a heteroaromatic ring having a pyridine skeleton, an organic compound including a heteroaromatic ring having a diazine skeleton, and an organic compound including a heteroaromatic ring having a triazine skeleton are preferred.

[0237] Specific examples of the material having an electron transport property that can be used for the electron transport layer include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-8), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-9), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-10), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-11), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-12), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-13), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene] (abbreviation: OXD-14), 1,3-bis[5-(p-tert-butyl organic compounds having an azole skeleton, such as 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II), and 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs); organic compounds containing a heteroaromatic ring having a pyridine skeleton, such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), ... (3'-dibenzothiophen-4-yl)biphenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 2-[4'-(9-phenyl-9H-carbazol-3-yl)-3,1'-biphenyl-1-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mpPCBPDBq), 2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2CzPDBq-III), 7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 7mDBTPDBq-II), and 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 6mDBTPDBq-II), 9-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), 9-[(3′- ... [1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9pmDBtBPNfpr), 4,6-bis[3-(phenanthrene-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mCzP2Pm), 9,9'-[pyrimidine-4,6-diylbis(biphenyl-3,3'-diyl)]bis(9H- carbazole) (abbreviation: 4,6mCzBP2Pm), 8-(1,1'-biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 3,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[2,3-b]pyrazine (abbreviation: 3,8mDBtP2Bfpr), 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8- [3'-(dibenzothiophen-4-yl)(1,1'-biphenyl-3-yl)]naphtho[1',2':4,5]furo[3,2-d]pyrimidine (abbreviation: 8mDBtBPNfpm), 8-[(2,2'-binaphthalen)-6-yl]-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8(βN2)-4mDBtPBfpm), 2,2'-(pyridine-2,6-diyl)bis(4-phenylbenzo[h]quinazoline) (abbreviation: 2,6(P-Bqn)2Py), 2,2'-(pyridine-2,6-diyl)bis{4-[4-(2-naphthyl)phenyl]-6-phenylpyrimidine} (abbreviation: 2,6(NP-PPm)2Py), 6-(1,1'-biphenyl-3-yl)-4-[3,5-bis(9H-carbazol-9-yl)phenyl]-2-phenylpyrimidine (abbreviation: 6mBP-4Cz2PPm), 2,6-bis(4-naphthalen-1-ylphenyl)-4-[4-(3-pyridyl)phenyl]pyrimidine (abbreviation: 2,4NP-6PyPPm), 4-[3,5-bis(9H-carbazol-9-yl)phenyl organic compounds having a diazine skeleton such as 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-[(1,1'-biphenyl)-4-yl]-4-phenyl-6-[9,9'-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-[3-[3 mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02), mPCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 2-[3'-(9,9-dimethyl-9H-fluoren-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 5-[3-(4,6-diphenyl-1,3,5-triazin-2yl)phenyl]-7,7-dimethyl-5H,7H-indeno[2,1-b]carbazole (abbreviation: mINc(II)PTzn), 2-{3-[3-(dibenzothiophen-4-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mDBtBPTzn), 2,4,6-tris(3′-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine (abbreviation: TmPPPyTz), 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn), 11-(4-[1,1′-biphenyl]-4-yl-6-phenyl-1,3,5-triazin-2-yl)-11,12-dihydro-12-phenyl and organic compounds having a triazine skeleton such as 1,1'-indolo[2,3-a]carbazole (abbreviation: BP-Icz(II)Tzn), 2-[3'-(triphenylen-2-yl)-1,1'-biphenyl-3-yl]-4,6-diphenyl'1,3,5-triazine (abbreviation: mTpBPTzn), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-dibenzothiophenyl]-2-phenyl-9H-carbazole (abbreviation: PCDBfTzn), and 2-[1,1'-biphenyl]-3-yl-4-phenyl-6-(8-[1,1':4',1''-terphenyl]-4-yl-1-dibenzofuranyl)-1,3,5-triazine (abbreviation: mBP-TPDBfTzn). Among the above, organic compounds containing a heteroaromatic ring having a diazine skeleton, organic compounds containing a heteroaromatic ring having a pyridine skeleton, and organic compounds containing a heteroaromatic ring having a triazine skeleton are preferred because of their high reliability. In particular, organic compounds containing a heteroaromatic ring having a diazine (pyrimidine or pyrazine) skeleton and organic compounds containing a heteroaromatic ring having a triazine skeleton have high electron transport properties and contribute to reducing driving voltage.

[0238] When the above organic compound having electron-transport properties is used for the electron-transport layer 114, the electron-transport layer 114 preferably further contains a metal complex of an alkali metal or an alkaline earth metal. Among these, heterocyclic compounds having a diazine skeleton, heterocyclic compounds having a triazine skeleton, and heterocyclic compounds having a pyridine skeleton are preferred from the viewpoint of operating life because they easily stabilize the energy when they form an exciplex with an organic metal complex of an alkali metal (easily lengthening the emission wavelength of the exciplex). In particular, heterocyclic compounds having a diazine skeleton or heterocyclic compounds having a triazine skeleton are suitable for stabilizing the energy of the exciplex because they have a deep LUMO level.

[0239] The alkali metal organometallic complex is preferably a sodium or lithium metal complex. Alternatively, the alkali metal organometallic complex preferably has a ligand having a quinolinol skeleton. More preferably, the alkali metal organometallic complex is a lithium complex having an 8-quinolinolato structure or a derivative thereof. As a derivative of a lithium complex having an 8-quinolinolato structure, a lithium complex having an 8-quinolinolato structure with an alkyl group is preferred, and a methyl group is particularly preferred.

[0240] Specific examples of the metal complex include 8-quinolinolato-lithium (abbreviated as Liq) and 8-hydroxyquinolinato-sodium (abbreviated as Naq). In particular, monovalent metal ion complexes, especially lithium complexes, are preferred, with Liq being more preferred. In addition, when an 8-hydroxyquinolinato structure is included, it is also preferred to use its methyl-substituted derivatives (e.g., 2-methyl-substituted, 5-methyl-substituted, or 6-methyl-substituted derivatives). In particular, the use of an alkali metal complex having an 8-quinolinolato structure with an alkyl group at the 6th position has the effect of reducing the driving voltage of a light-emitting device.

[0241] The electron transport layer 114 has an electron mobility of 1×10 when the square root of the electric field strength [V / cm] is 600. −７ cm ２ / Vs or more 5×10 −５ cm ２ / Vs or less. By reducing the electron transport property of the electron-transport layer 114, the amount of electrons injected into the light-emitting layer can be controlled, and the light-emitting layer can be prevented from becoming an electron-excess state. This structure is particularly preferable when the hole-injection layer is formed of a composite material and the HOMO level of the material having hole-transport properties in the composite material is a substance having a relatively deep HOMO level of -5.7 eV or more and -5.4 eV or less, because this structure provides a long lifetime. In this case, the HOMO level of the material having electron-transport properties is preferably -6.0 eV or more.

[0242] Between the electron transport layer 114 and the second electrode 102, an electron injection layer 115 containing lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ２ Alternatively, a layer containing an alkali metal or alkaline earth metal such as lithium (8-quinolinolato) (Liq), 8-quinolinolato-lithium (Liq), or ytterbium (Yb), or a compound or complex thereof, may be provided. The electron injection layer 115 may be a layer made of a substance having electron transport properties containing an alkali metal or alkaline earth metal or a compound thereof, or may be an electride. Examples of the electride include a mixed oxide of calcium and aluminum to which electrons are added at a high concentration.

[0243] Note that a layer containing a substance having an electron transport property (preferably an organic compound having a bipyridine skeleton) containing a fluoride of the alkali metal or alkaline earth metal at a concentration (50 wt % or more) that results in a microcrystalline state can also be used as the electron-injection layer 115. Since this layer has a low refractive index, it is possible to provide a light-emitting device with better external quantum efficiency.

[0244] The second electrode 102 is preferably a cathode. Materials that can be used to form the cathode include metals, alloys, electrically conductive compounds, and mixtures thereof with a small work function (specifically, 3.8 eV or less). Specific examples of such cathode materials include alkali metals such as lithium (Li) or cesium (Cs), elements belonging to Group 1 or Group 2 of the periodic table such as magnesium (Mg), calcium (Ca), and strontium (Sr), alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer between the second electrode 102 and the electron transport layer, various conductive materials, such as Al, Ag, ITO, and indium oxide-tin oxide containing silicon or silicon oxide, can be used as the cathode, regardless of the magnitude of the work function.

[0245] When the second electrode 102 is formed using a material that is transparent to visible light, the light-emitting device can emit light from the side of the second electrode 102. When the first electrode 101 is formed on the substrate side, the light-emitting device can be a so-called top-emission light-emitting device.

[0246] These conductive materials can be formed into films by dry methods such as vacuum deposition or sputtering, inkjet methods, spin coating methods, etc. Alternatively, they may be formed by wet methods using a sol-gel method, or by wet methods using a paste of a metal material.

[0247] The EL layer 103 may be formed by any of various methods, including dry and wet methods, such as vacuum deposition, gravure printing, offset printing, screen printing, inkjet printing, and spin coating.

[0248] Furthermore, the above-mentioned electrodes or layers may be formed using different film formation methods.

[0249] Although the application to a light-emitting device with a color-coded coating method has been described in this embodiment, one embodiment of the present invention can also be applied to a light-emitting device with a white color filter method. In this case, the light emitted from each light-emitting device may be the same, and the light-emitting substance contained in the light-emitting layer 113 may also be the same. However, a stacked structure may be formed in accordance with the wavelength of light extracted in each sub-pixel.

[0250] <Tandem Device> Next, an embodiment of a light-emitting device (also referred to as a stacked device or tandem device) having a configuration in which multiple light-emitting units are stacked will be described. This light-emitting device has multiple light-emitting layers and a charge-generating layer between a first electrode and a second electrode. The charge-generating layer is located between the light-emitting layers. The region sandwiched between the first electrode and the charge-generating layer, the region sandwiched between the charge-generating layers, and the region sandwiched between the charge-generating layer and the second electrode are each referred to as a light-emitting unit.

[0251] 15 illustrates an example of a light-emitting device according to one embodiment of the present invention having a tandem element. Both light-emitting device S and light-emitting device L include one charge generation layer 116 and two light-emitting units (a first light-emitting unit 103_1 and a second light-emitting unit 103_2) between a first electrode 101 and a second electrode 102. The first electrode 101 has a stacked structure including a reflective electrode 101-1 and a light-transmitting electrode 101-2. While this embodiment describes a light-emitting device having one charge generation layer 116 and two light-emitting units as an example, the light-emitting device may also have n (n is an integer of 2 or more) charge generation layers and n+1 light-emitting units.

[0252] The charge generation layer has a function of injecting holes into the layer in contact with the cathode side of the layer and injecting electrons into the layer in contact with the anode side of the layer when a voltage is applied between the electrodes. That is, in Figure 15, when a voltage is applied so that the potential of the first electrode 101 is higher than the potential of the second electrode 102, the charge generation layer 116 injects electrons into the first light-emitting unit and injects holes into the second light-emitting unit.

[0253] The charge generation layer 116 includes at least a P-type layer 117. The P-type layer 117 is preferably formed using a composite material listed above as a material that can be used to form the hole injection layer 111. The P-type layer 117 may also be formed by laminating a film containing a material having acceptor properties and a film containing a hole transport material. By applying a potential to the P-type layer 117, electrons are injected into the electron transport layer 114_1 and holes are injected into the hole transport layers 112S_2 and 112L_2, thereby operating the light-emitting device. Note that because the P-type layer 117 serves as a hole injection layer in the light-emitting unit on the cathode side, a hole injection layer may not be formed in the light-emitting unit on the cathode side (light-emitting unit 103_2 in FIG. 15 ).

[0254] It is preferable that the charge generating layer 116 be provided with either or both of an electron relay layer 118 and an electron injection buffer layer 119 in addition to the P-type layer 117 .

[0255] The electron relay layer 118 contains at least a substance having electron transport properties and has the function of preventing interaction between the electron injection buffer layer 119 and the P-type layer 117 and smoothly transferring electrons. The LUMO level of the substance having electron transport properties contained in the electron relay layer 118 is preferably between the LUMO level of the acceptor substance in the P-type layer 117 and the LUMO level of the substance contained in the layer of the electron transport layer 114 that is in contact with the charge generation layer 116. The specific energy level of the LUMO level of the substance having electron transport properties used in the electron relay layer 118 is −5.0 eV or higher, preferably −5.0 eV or higher and −3.0 eV or lower. Note that the substance having electron transport properties used in the electron relay layer 118 is preferably a phthalocyanine-based material or a metal complex having a metal-oxygen bond and an aromatic ligand.

[0256] The electron injection buffer layer 119 contains alkali metals, alkaline earth metals, rare earth metals, and their compounds (alkali metal compounds (lithium oxide (Li ２It is possible to use a substance with high electron injection properties, such as oxides of rare earth metals (including oxides, halides, and carbonates) such as lithium carbonate (e.g., lithium iodide), halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), or rare earth metal compounds (including oxides, halides, and carbonates).

[0257] Furthermore, when the electron injection buffer layer 119 is formed to contain a substance having an electron transport property and a donor substance, examples of the donor substance that can be used include alkali metals, alkaline earth metals, rare earth metals, and compounds thereof (alkali metal compounds (including oxides such as lithium oxide, halides, and carbonates such as lithium carbonate and cesium carbonate), alkaline earth metal compounds (including oxides, halides, and carbonates), and rare earth metal compounds (including oxides, halides, and carbonates)), as well as organic compounds such as tetrathianaphthacene (abbreviation: TTN), nickelocene, and decamethylnickelocene.

[0258] Note that the electron-injection buffer layer 119 can be formed using a substance having an electron-transporting property that can be used for the electron-injection buffer layer 119 using the same material as the material for forming the electron-transporting layer 114 described above.

[0259] When the electron injection buffer layer 119 is provided in the charge generation layer of the tandem element, the electron injection buffer layer 119 plays the role of the electron injection layer in the light-emitting unit on the anode side, and therefore, an electron injection layer does not need to be formed in the light-emitting unit on the anode side (the first light-emitting unit 103_1 in FIG. 15 ).

[0260] In this example, the light-emitting unit 103_1 of the light-emitting device S includes a light-emitting layer 113S_1 and an electron-transporting layer 114_1 in addition to the stacked layer structure 122 (a first layer 122-1 and a second layer 122-2). The light-emitting unit 103_1 is in contact with the electron-injection buffer layer 119 on the cathode side, so an electron-injection layer is not necessarily provided, but may be provided. A hole-injection layer may be provided between the stacked layer structure 122 and the light-transmitting electrode 101-2. The light-emitting layer 113S_1 contains a light-emitting substance S_1.

[0261] The light-emitting unit 103_2 of the light-emitting device S includes at least a light-emitting layer 113S_2. The light-emitting layer 113S_2 contains a light-emitting substance S_2. In FIG. 15, the light-emitting unit 103_2 includes a hole-transporting layer 112S_2, an electron-transporting layer 114S_2, an electron-injecting layer 115_2, and the like in addition to the light-emitting layer 113S_2. Because the light-emitting unit 103_2 is in contact with the P-type layer 117 on the anode side, a hole-injecting layer may not be provided.

[0262] In this example, the light-emitting unit 103_1 of the light-emitting device L includes a light-emitting layer 113L_1 and an electron-transporting layer 114_1 in addition to the stacked layer structure 122 (a first layer 122-1, a second layer 122-2, and a third layer 122-3). Because the light-emitting unit 103_1 is in contact with the electron-injection buffer layer 119 on the cathode side, an electron-injection layer may not be provided, but may be provided. Furthermore, a hole-injection layer may be provided between the stacked layer structure 122 and the light-transmitting electrode 101-2. The light-emitting layer 113L_1 contains a light-emitting substance L_1.

[0263] The light-emitting unit 103_2 of the light-emitting device L includes at least a light-emitting layer 113L_2. The light-emitting layer 113L_2 contains a light-emitting substance L_2. In FIG. 15, the light-emitting unit 103_2 includes a hole-transporting layer 112L_2, an electron-transporting layer 114L_2, an electron-injecting layer 115_2, and the like in addition to the light-emitting layer 113L_2. Because the light-emitting unit 103_2 is in contact with the P-type layer 117 on the anode side, a hole-injecting layer may not be provided.

[0264] The light-emitting material S_1 and the light-emitting material S_2 may be the same or different, but the same material is preferable because current efficiency is significantly increased. When the materials are different, light that is a combination of the emissions of the light-emitting material S_1 and the light-emitting material S_2, such as white light, can be emitted from the light-emitting device S.

[0265] In the tandem device according to one embodiment of the present invention, it is preferable that the light-emitting unit (light-emitting unit 103_1) on the electrode side having the reflective electrode is provided with a stacked structure 122 having an LH structure. In addition, the optical distance from the surface of the reflective electrode 101-1 on the second electrode 102 side to the surface of the second electrode 102 on the first electrode side is set to 1 / 200 sq. m / s. ｔ Approximately 1.5 times (1.5λ ｔ By forming the light emitting device so that the optical path length is 1.5λ, a light emitting device having very good luminous efficiency can be obtained. ｔ If it is 70% or more and 110% or less of the wavelength λ ｔ This allows for effective amplification of light.

[0266] wavelength λ ｔ is the peak wavelength λ of light emitted from the light-emitting device S, which is the subpixel including the light-emitting device S. ＳＤ In the light-emitting device L, the emission peak wavelength λ of the light emitted from the subpixel including the light-emitting device L ＬＤ is equivalent to

[0267] Or, when the luminescent material S_1 and the luminescent material S_2 are the same, the wavelength λ ｔ is the emission peak wavelength λ of the luminescent material S_1 and the luminescent material S_2 Ｓ When the luminescent material L_1 and the luminescent material L_2 are the same, the wavelength λ ｔ is the emission peak wavelength λ of the luminescent material L Ｌ is equivalent to

[0268] In addition, when the light-emitting material S_1 and the light-emitting material S_2 are different light-emitting materials and the light obtained by combining the emission spectrum of the light-emitting material S_1 and the emission spectrum of the light-emitting material S_2 has a continuous spectrum from 450 nm to 650 nm (for example, white light emission), it is preferable that the light-emitting material S_1 is the same light-emitting material as the light-emitting material L_1 and the light-emitting material S_2 is the same material as the light-emitting material L_2. ｔ is the peak wavelength λ of light emitted from the light-emitting device S, which is the subpixel including the light-emitting device S. ＳＤIn the light-emitting device L, the emission peak wavelength λ of the light emitted from the subpixel including the light-emitting device L ＬＤ 1 and 2. In this case, the light-emitting layer 113S_1 and the light-emitting layer 113L_1 are continuous layers, and the light-emitting layer 113S_2 and the light-emitting layer 113L_2 are continuous layers, which is preferable because it simplifies the manufacturing process. Any or all of the light-emitting layers may be composed of multiple layers containing different light-emitting materials. For example, the light-emitting layer 113S_2 may be composed of a stack of a layer containing a light-emitting material G that emits green light and a layer containing a light-emitting material R that emits red light. In this case, the light-emitting material S_2 is a collective term for the two materials, light-emitting material G and light-emitting material R. In this case, it is preferable that a color filter be further included.

[0269] In this way, by arranging multiple light-emitting units between a pair of electrodes and separating them with a charge-generating layer, it is possible to realize a device that can emit high-luminance light while maintaining a low current density, and that has a long life.It is also possible to realize a light-emitting device that can be driven at a low voltage and consumes little power.

[0270] This embodiment mode can be freely combined with other embodiment modes.

[0271] Embodiment 2 In this embodiment, a structure other than the light-emitting device in a light-emitting device according to one embodiment of the present invention will be described.

[0272] In this embodiment, a light-emitting device of one embodiment of the present invention will be described with reference to Fig. 4A and Fig. 4B . Fig. 4A is a top view of the light-emitting device, and Fig. 4B is a cross-sectional view taken along dashed lines A-B and C-D in Fig. 4A . This light-emitting device includes a source line driver circuit 601, a pixel portion 602, and a gate line driver circuit 603, each indicated by dotted lines, for controlling light emission from the light-emitting device. Reference numeral 604 denotes a sealing substrate, 605 denotes a sealant, and the inside surrounded by the sealant 605 forms a space 607.

[0273] The routing wiring 608 is wiring for transmitting signals input to the source line driver circuit 601 and the gate line driver circuit 603, and receives video signals, clock signals, start signals, reset signals, etc. from an FPC (flexible printed circuit) 609, which serves as an external input terminal. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to this FPC. In this specification, the light-emitting device includes not only the light-emitting device itself but also a state in which an FPC or PWB is attached to it.

[0274] Next, the cross-sectional structure will be described with reference to Fig. 4B. A driver circuit portion and a pixel portion are formed on an element substrate 610, but here, a source line driver circuit 601, which is the driver circuit portion, and one pixel in a pixel portion 602 are shown.

[0275] The element substrate 610 may be made of a substrate made of glass, quartz, organic resin, metal, alloy, semiconductor, or the like, or a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, or the like.

[0276] The structure of a transistor used in a pixel or a driver circuit is not particularly limited. For example, an inverted staggered transistor or a staggered transistor may be used. Furthermore, a top-gate transistor or a bottom-gate transistor may be used. The semiconductor material used for the transistor is not particularly limited, and examples thereof include silicon, germanium, silicon carbide, and gallium nitride. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In—Ga—Zn-based metal oxide, may be used.

[0277] The crystallinity of a semiconductor material used for a transistor is not particularly limited, and any of an amorphous semiconductor and a crystalline semiconductor (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor having a crystalline region in part) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0278] Here, it is preferable to use an oxide semiconductor for the transistors provided in the pixel or the driver circuit, as well as for semiconductor devices such as transistors used in touch sensors, which will be described later. In particular, it is preferable to use an oxide semiconductor having a wider band gap than silicon. By using an oxide semiconductor having a wider band gap than silicon, the current in the off state of the transistor can be reduced.

[0279] The oxide semiconductor preferably contains at least indium (In) or zinc (Zn), and more preferably contains an oxide represented by In-M-Zn-based oxide (M is a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).

[0280] In particular, it is preferable to use, as the semiconductor layer, an oxide semiconductor film which has a plurality of crystal parts whose c-axes are oriented perpendicular to a surface on which the semiconductor layer is formed or a top surface of the semiconductor layer and which does not have grain boundaries between adjacent crystal parts.

[0281] By using such a material for the semiconductor layer, fluctuations in electrical characteristics are suppressed, and a highly reliable transistor can be realized.

[0282] Furthermore, a transistor having the above-described semiconductor layer can retain charge stored in a capacitor through the transistor for a long period of time due to its low off-state current. By applying such a transistor to a pixel, it is possible to stop the driver circuit while maintaining the gray level of an image displayed in each display region. As a result, an electronic device with extremely low power consumption can be realized.

[0283] For example, to stabilize the characteristics of a transistor, it is preferable to provide a base film. The base film can be formed as a single layer or a stacked layer using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The base film can be formed by a sputtering method, a CVD (Chemical Vapor Deposition) method (such as a plasma CVD method, a thermal CVD method, or a MOCVD (Metal Organic CVD) method), an ALD (Atomic Layer Deposition) method, a coating method, a printing method, or the like. Note that the base film need not be provided if it is not necessary.

[0284] Note that the FET 623 represents one of the transistors formed in the source line driver circuit 601. The driver circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In addition, although this embodiment shows a driver-integrated type in which the driver circuit is formed on a substrate, this is not necessarily required, and the driver circuit may also be formed externally rather than on the substrate.

[0285] Furthermore, the pixel portion 602 is formed by a plurality of pixels including a switching FET 611, a current control FET 612, and a first electrode 613 electrically connected to the drain of the FET, but is not limited to this, and the pixel portion may be formed by combining three or more FETs and a capacitance element.

[0286] An insulator 614 is formed to cover an end portion of the first electrode 613. Here, the insulator 614 can be formed by using a positive photosensitive acrylic resin film.

[0287] Furthermore, in order to improve the coverage of the EL layer and the like to be formed later, a curved surface having a curvature is formed at the upper or lower end of the insulator 614. For example, when a positive photosensitive acrylic resin is used as the material of the insulator 614, it is preferable to provide a curved surface having a curvature radius (0.2 μm to 3 μm) only at the upper end of the insulator 614. Furthermore, either a negative photosensitive resin or a positive photosensitive resin can be used as the insulator 614.

[0288] An EL layer 616 and a second electrode 617 are formed over the first electrode 613. The first electrode 613 corresponds to the first electrode 101 in Embodiment 1, the EL layer 616 corresponds to the EL layer 103, and the second electrode 617 corresponds to the second electrode 102.

[0289] Note that a light-emitting device is formed by the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting device has the structure described in Embodiment Mode 1.

[0290] Furthermore, by bonding the sealing substrate 604 to the element substrate 610 with a sealing material 605, a structure is formed in which a light-emitting device 618 is provided in a space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 is filled with a filler, and in some cases, the space is filled with an inert gas (nitrogen, argon, etc.), or with a sealing material. A recess is formed in the sealing substrate, and by providing a desiccant therein, deterioration due to the influence of moisture can be suppressed, which is a preferable configuration.

[0291] It is preferable to use an epoxy resin or glass frit for the sealing material 605. It is also desirable that these materials are as moisture- and oxygen-impermeable as possible. In addition to a glass substrate or a quartz substrate, the sealing substrate 604 can also be made of a plastic substrate made of FRP (Fiber Reinforced Plastics), PVF (Polyvinyl Fluoride), polyester, acrylic resin, or the like.

[0292] 4A and 4B, a protective film may be provided on the second electrode 617. The protective film may be formed of an organic resin film or an inorganic insulating film. The protective film may be formed so as to cover the exposed portion of the sealing material 605. The protective film may be provided so as to cover the surfaces and side surfaces of the pair of substrates, the exposed side surfaces of the sealing layer, the insulating layer, etc.

[0293] The protective film can be made of a material that is impermeable to impurities such as water, and therefore can effectively prevent impurities such as water from diffusing from the outside to the inside.

[0294] The protective film may be made of an oxide, nitride, fluoride, sulfide, ternary compound, metal, polymer, or the like. For example, a material containing aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, indium oxide, or the like; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, gallium nitride, or the like; a nitride containing titanium and aluminum; an oxide containing titanium and aluminum; an oxide containing aluminum and zinc; a sulfide containing manganese and zinc; a sulfide containing cerium and strontium; an oxide containing erbium and aluminum; or an oxide containing yttrium and zirconium.

[0295] The protective film is preferably formed using a film formation method that provides good step coverage. One such method is atomic layer deposition (ALD). It is preferable to use a material that can be formed using the ALD method for the protective film. By using the ALD method, it is possible to form a dense protective film with reduced defects such as cracks or pinholes, or with a uniform thickness. Furthermore, it is possible to reduce damage to the workpiece when forming the protective film.

[0296] For example, by forming a protective film using the ALD method, it is possible to form a uniform protective film with few defects on a surface having a complex uneven shape or on the top, side and back surfaces of a touch panel.

[0297] In the above manner, a light-emitting device of one embodiment of the present invention can be obtained.

[0298] In the light-emitting device according to the present embodiment, light emitted by the light-emitting material is reflected at the interface between layers with different refractive indices, allowing for more light to be reflected than when only a reflective electrode is used, thereby improving external quantum efficiency. At the same time, the influence of surface plasmons at the reflective electrode can be reduced, thereby reducing energy loss and enabling efficient light extraction. Furthermore, since the device has a stacked structure with a common refractive index step and the film thickness of the stacked structure is adjusted according to the light emitted by each sub-pixel, the luminous efficiency of all emitted colors can be improved simply, quickly, and inexpensively.

[0299] 5 shows an example of a light-emitting device in which color purity is improved by providing a colored layer (color filter), etc. The illustration shows a substrate 1001, a base insulating film 1002, a gate insulating film 1003, gate electrodes 1006, 1007, and 1008, a first interlayer insulating film 1020, a second interlayer insulating film 1021, a peripheral portion 1042, a pixel portion 1040, a driver circuit portion 1041, first electrodes 1024R, 1024G, and 1024B of the light-emitting device, a partition wall 1025, an EL layer 1028, a second electrode 1029 of the light-emitting device, a sealing substrate 1031, a sealant 1032, a third interlayer insulating film 1037, and the like.

[0300] In the top-emission structure shown in FIG. 5 , sealing can be performed using a sealing substrate 1031 provided with colored layers (a red colored layer 1034R, a green colored layer 1034G, and a blue colored layer 1034B). The sealing substrate 1031 may be provided with a black matrix 1035 positioned between pixels. The colored layers (the red colored layer 1034R, the green colored layer 1034G, and the blue colored layer 1034B) or the black matrix may be covered with an overcoat layer. Note that the sealing substrate 1031 is a light-transmitting substrate.

[0301] The first electrodes 1024R, 1024G, and 1024B of the light-emitting device include reflective electrodes. The first electrodes preferably include anodes. The EL layer 1028 has the same structure as that of the EL layer 103 in the first embodiment.

[0302] A microcavity structure is suitable for use in top-emission light-emitting devices. A light-emitting device with a microcavity structure can be obtained by using one electrode including a reflective electrode and the other electrode as a semi-transparent / semi-reflective electrode. At least an EL layer is present between the reflective electrode and the semi-transparent / semi-reflective electrode, and at least a light-emitting layer that serves as a light-emitting region is present.

[0303] In the light-emitting device, the optical distance between the reflective electrode and the semi-transmissive / semi-reflective electrode can be changed by changing the thickness of the light-transmitting conductive film, the composite material described above, the carrier transport material, etc. This makes it possible to intensify light of a resonating wavelength and attenuate light of a non-resonating wavelength between the reflective electrode and the semi-transmissive / semi-reflective electrode.

[0304] The microcavity structure makes it possible to increase the light emission intensity of a specific wavelength in the front direction, thereby reducing power consumption. In the case of a light-emitting device that displays images using four sub-pixels of red, yellow, green, and blue, the yellow light emission has the effect of improving brightness, and the microcavity structure that matches the wavelength of each color can be applied to all sub-pixels, resulting in a light-emitting device with good characteristics.

[0305] In addition, since the light-emitting device of one embodiment of the present invention has a stacked structure with a refractive index difference within the EL layer, light emitted from the light-emitting material is reflected at the interface between layers with different refractive indices, and therefore, more light can be reflected than when only the reflective electrode is used, thereby improving the external quantum efficiency. At the same time, the influence of surface plasmons at the reflective electrode can be reduced, thereby reducing energy loss and enabling efficient light extraction.

[0306] The light-emitting device of one embodiment of the present invention having the above-described structure has a stacked layer structure having a common refractive index step and the thickness of the stacked layer structure is adjusted depending on the light emitted by each sub-pixel. Therefore, the light-emitting efficiency of all emission colors can be improved simply, quickly, and inexpensively.

[0307] This embodiment mode can be freely combined with other embodiment modes.

[0308] Embodiment 3 In this embodiment, an example of an electronic device including a light-emitting device according to one embodiment of the present invention will be described. The light-emitting device according to one embodiment of the present invention has high emission efficiency and low power consumption. As a result, the electronic device described in this embodiment can be an electronic device having a light-emitting portion with low power consumption.

[0309] Examples of electronic devices to which the light-emitting devices are applied include television sets (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, personal digital assistants, sound reproducing devices, large game machines such as pachinko machines, etc. Specific examples of these electronic devices are shown below.

[0310] 6A illustrates an example of a television set. The television set includes a display portion 7103 built in a housing 7101. Here, the housing 7101 is supported by a stand 7105. Images can be displayed on the display portion 7103, which is formed using the light-emitting device of one embodiment of the present invention.

[0311] The television set can be operated using an operation switch provided on the housing 7101 or a separate remote control 7110. A channel or volume can be controlled using operation keys 7109 provided on the remote control 7110, and an image displayed on the display portion 7103 can be controlled. The remote control 7110 may be provided with a display portion 7107 that displays information output from the remote control 7110. Note that the light-emitting device of one embodiment of the present invention, arranged in a matrix, can also be applied to the display portion 7107.

[0312] The television device is configured to include a receiver, a modem, etc. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via the modem, it is also possible to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0313] FIG. 6B1 illustrates a computer including a main body 7201, a housing 7202, a display portion 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like. Note that this computer is manufactured by using the light-emitting device of one embodiment of the present invention for the display portion 7203. The computer in FIG. 6B1 may have a configuration as shown in FIG. 6B2. The computer in FIG. 6B2 is provided with a display portion 7210 instead of the keyboard 7204 and the pointing device 7206. The display portion 7210 is a touch panel type, and input can be performed by operating an input display displayed on the display portion 7210 with a finger or a dedicated pen. The display portion 7210 can display not only an input display but also other images. The display portion 7203 may also be a touch panel. The two screens are connected by a hinge, which can prevent problems such as scratches or breakage of the screens during storage or transportation.

[0314] 6C illustrates an example of a mobile terminal. The mobile phone includes a display portion 7402 incorporated in a housing 7401, operation buttons 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like. Note that the mobile phone includes the display portion 7402 in which the light-emitting devices of one embodiment of the present invention are arranged in a matrix.

[0315] 6C can be configured so that information can be input by touching the display portion 7402 with a finger or the like. In this case, operations such as making a call or creating an email can be performed by touching the display portion 7402 with a finger or the like.

[0316] The screen of the display portion 7402 has three main modes. The first is a display mode mainly for displaying images, the second is an input mode mainly for inputting information such as characters, and the third is a display+input mode that combines the display mode and the input mode.

[0317] For example, when making a call or creating an email, the display portion 7402 may be set to a character input mode mainly for inputting characters, and characters displayed on the screen may be input. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display portion 7402.

[0318] In addition, by providing a detection device having a sensor that detects tilt, such as a gyro or an acceleration sensor, inside the mobile terminal, the orientation of the mobile terminal (portrait or landscape) can be determined and the screen display of the display portion 7402 can be automatically switched.

[0319] The screen mode can be switched by touching the display portion 7402 or by operating the operation buttons 7403 on the housing 7401. The screen mode can also be switched depending on the type of image displayed on the display portion 7402. For example, if the image signal to be displayed on the display portion is moving image data, the display mode is selected, and if it is text data, the input mode is selected.

[0320] In addition, in the input mode, a signal detected by an optical sensor in the display portion 7402 may be detected, and if there is no input by touch operation on the display portion 7402 for a certain period of time, the screen mode may be controlled to switch from the input mode to the display mode.

[0321] The display portion 7402 can also function as an image sensor. For example, personal authentication can be performed by touching the display portion 7402 with a palm or a finger to capture an image of a palm print, a fingerprint, or the like. Furthermore, by using a backlight that emits near-infrared light or a sensing light source that emits near-infrared light for the display portion, finger veins, palm veins, or the like can also be captured.

[0322] Note that the structure described in this embodiment mode can be used by combining the structures described in Embodiment Mode 1 and Embodiment Mode 2 as appropriate.

[0323] As described above, the light-emitting device described in Embodiments 1 and 2 has a very wide range of application and can be applied to electronic devices in a variety of fields. By using the light-emitting device described in Embodiments 1 and 2, electronic devices with low power consumption can be obtained.

[0324] FIG. 7A is a schematic diagram showing an example of a cleaning robot.

[0325] The cleaning robot 5100 has a display 5101 arranged on its top surface, multiple cameras 5102 arranged on its side, a brush 5103, and an operation button 5104. Although not shown, the cleaning robot 5100 is also provided with tires, a suction port, and the like on its bottom surface. The cleaning robot 5100 is also provided with various other sensors, such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyro sensor. The cleaning robot 5100 is also provided with wireless communication means.

[0326] The cleaning robot 5100 can move by itself, detect dust 5120, and suck up the dust from a suction port provided on the bottom surface.

[0327] The cleaning robot 5100 can also analyze the image captured by the camera 5102 to determine whether there are any obstacles such as walls, furniture, or steps. If the image analysis detects an object that may become tangled in the brush 5103, such as a wire, the cleaning robot 5100 can stop the rotation of the brush 5103.

[0328] The display 5101 can display the remaining battery level, the amount of dust that has been sucked up, etc. The path traveled by the cleaning robot 5100 may be displayed on the display 5101. The display 5101 may also be a touch panel, and an operation button 5104 may be provided on the display 5101.

[0329] The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. Images captured by the camera 5102 can be displayed on the portable electronic device 5140. This allows the owner of the cleaning robot 5100 to know the state of the room even when they are away from home. In addition, the display on the display 5101 can be confirmed on the portable electronic device such as a smartphone.

[0330] The light-emitting device of one embodiment of the present invention can be used for the display 5101 .

[0331] The robot 2100 shown in FIG. 7B includes a computing device 2110, an illuminance sensor 2101, a microphone 2102, an upper camera 2103, a speaker 2104, a display 2105, a lower camera 2106, an obstacle sensor 2107, and a movement mechanism 2108.

[0332] The microphone 2102 has a function of detecting the user's voice, environmental sounds, etc. The speaker 2104 has a function of emitting sound. The robot 2100 can communicate with the user using the microphone 2102 and the speaker 2104.

[0333] The display 2105 has a function of displaying various information. The robot 2100 can display information desired by the user on the display 2105. The display 2105 may be equipped with a touch panel. The display 2105 may also be a detachable information terminal, which can be installed in a fixed position on the robot 2100 to enable charging and data transfer.

[0334] The upper camera 2103 and the lower camera 2106 have a function of capturing images of the surroundings of the robot 2100. In addition, the obstacle sensor 2107 can detect the presence or absence of an obstacle in the moving direction when the robot 2100 moves forward using the moving mechanism 2108. The robot 2100 can recognize the surrounding environment and move safely using the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting device of one embodiment of the present invention can be used for the display 2105.

[0335] 7C is a diagram illustrating an example of a goggle-type display. The goggle-type display includes, for example, a housing 5000, a display unit 5001, a speaker 5003, an LED lamp 5004 (including a power switch or an operation switch), a connection terminal 5006, a sensor 5007 (including a function for measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared ray), a microphone 5008, a second display unit 5002, a support unit 5012, and earphones 5013.

[0336] The light-emitting device of one embodiment of the present invention can be used for the display portion 5001 and the second display portion 5002 .

[0337] The light-emitting device of one embodiment of the present invention can also be mounted on a windshield or dashboard of an automobile. Figure 8 shows an example in which the light-emitting device of one embodiment of the present invention is used on a windshield or dashboard of an automobile. Display regions 5200 to 5203 are displays provided using the light-emitting device of one embodiment of the present invention.

[0338] The display region 5200 and the display region 5201 are light-emitting devices provided on the windshield of an automobile, each incorporating a light-emitting device according to one embodiment of the present invention. The light-emitting device according to one embodiment of the present invention can be a so-called see-through light-emitting device, in which the other side can be seen through, by forming the anode and the cathode using light-transmitting electrodes. A see-through display can be installed on the windshield of an automobile without obstructing the view. When a transistor or the like is provided for driving the light-emitting device, a light-transmitting transistor such as an organic transistor made of an organic semiconductor material or a transistor using an oxide semiconductor is preferably used.

[0339] The display area 5202 is a light-emitting device provided in a pillar portion and incorporating a light-emitting device according to one embodiment of the present invention. By displaying an image from an imaging means provided on the vehicle body in the display area 5202, the view blocked by the pillar can be complemented. Similarly, the display area 5203 provided on the dashboard can complement the view blocked by the vehicle body by displaying an image from an imaging means provided on the outside of the vehicle, thereby compensating for blind spots and improving safety. By displaying an image to complement the invisible parts, safety can be confirmed more naturally and without discomfort.

[0340] The display area 5203 can also provide various other information such as navigation information, speed or RPM, and air conditioning settings. The display items or layout can be changed as needed to suit the user's preferences. This information can also be provided in the display areas 5200 to 5202. The display areas 5200 to 5203 can also be used as lighting devices.

[0341] 9A and 9B show a foldable portable information terminal 5150. The foldable portable information terminal 5150 has a housing 5151, a display area 5152, and a bending portion 5153. FIG. 9A shows the portable information terminal 5150 in an unfolded state. FIG. 9B shows the portable information terminal in a folded state. Although the portable information terminal 5150 has a large display area 5152, it is compact and highly portable when folded.

[0342] The display area 5152 can be folded in half by a bending portion 5153. The bending portion 5153 is composed of an expandable member and multiple support members, and when folding, the expandable member stretches. The bending portion 5153 is folded with a curvature radius of 2 mm or more, preferably 3 mm or more.

[0343] Note that the display region 5152 may be a touch panel (input / output device) equipped with a touch sensor (input device). The light-emitting device of one embodiment of the present invention can be used for the display region 5152.

[0344] 10A to 10C show a foldable portable information terminal 9310. Fig. 10A shows the portable information terminal 9310 in an unfolded state. Fig. 10B shows the portable information terminal 9310 in a state in the process of changing from one of an unfolded state and a folded state to the other. Fig. 10C shows the portable information terminal 9310 in a folded state. The portable information terminal 9310 has excellent portability in a folded state, and has excellent display visibility due to a seamless, wide display area in an unfolded state.

[0345] The display panel 9311 is supported by three housings 9315 connected by hinges 9313. Note that the display panel 9311 may be a touch panel (input / output device) equipped with a touch sensor (input device). Furthermore, the display panel 9311 can be reversibly transformed from an unfolded state to a folded state by bending the two housings 9315 via the hinges 9313. The light-emitting device of one embodiment of the present invention can be used for the display panel 9311.

[0346] In this example, we show the results of calculations verifying the efficiency improvement effect of the light-emitting device used in the light-emitting device of the present invention. In this example, we assumed a light-emitting device including a blue light-emitting device (light-emitting device B) with an LH structure and a green light-emitting device (light-emitting device G) that has the LH structure as a common layer, and performed verification on each light-emitting device.

[0347] In this example, calculations were performed assuming that the light-emitting device B had the structure shown in Table 1 below.

[0348]

[0349] The calculations were performed assuming that the first layer 122-1 (Low(1)) was made of a low refractive index material, N,N-bis(4-cyclohexylphenyl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: dchPAF), and the second layer 122-2 (High(2)) was made of a high refractive index material, N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF). The refractive indices of dchPAF and PCBBiF in the visible light region are shown in FIGS. 11 and 12. The first layer 122-1 and the second layer 122-2 have such a structure (LH structure), which allows the light extraction efficiency of light-emitting device B to be improved.

[0350] The reflective electrode is made of APC (an alloy film of silver (Ag), palladium (Pd), and copper (Cu)), the transparent electrode (anode) is made of ITSO (indium tin oxide containing silicon oxide), the electron blocking layer is made of N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), and the first electron transport layer is made of 2-[3-(3′-dibenzothiophene)]-4-amino-p-terphenyl (abbreviation: DBfBB1TP). The first electron transport layer was 2,9-di(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), and the cap layer was 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II).

[0351] Since the light-emitting layer is usually a mixed layer of a dopant and a host, in this example, calculations were performed using the optical properties of the host material, which is a major component. Assuming that 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) was used as the host material, calculations were performed using this value. The light emitted from the light-emitting layer was assumed to have the spectrum shown as (B) in Figure 13.

[0352] The molecular structures of the organic compounds assumed for this calculation as materials for the light-emitting device are shown below. The refractive indices of organic compounds other than dchPAF and PCBBiF in the visible light region are also shown in Figure 14. Measurements were performed using a spectroscopic ellipsometer (M-2000U manufactured by J.A. Woollam Japan). The measurement sample used was a film of approximately 50 nm thickness formed by vacuum deposition of the materials for each layer on a quartz substrate.

[0353]

[0354] For the light-emitting device B having such a configuration, the film thicknesses of the first layer 122-1, the second layer 122-2, and the second electron transport layer (portions indicated by asterisks in Table 1) were calculated so as to maximize the blue index (BI).

[0355] These three layers are intended to be common to light-emitting devices that emit different colors of light (light-emitting device B and light-emitting device G in this example). The second electron transport layer may or may not be common, but a common layer is preferred because it shortens the manufacturing process. Other layers may also be common layers.

[0356] The blue index (BI) (cd / A / y) is a value obtained by dividing the current efficiency (cd / A) by the y value in the xy chromaticity diagram of the CIE chromaticity coordinates of the light, and is one of the indices representing the luminous characteristics of blue light emission. The smaller the y value, the higher the color purity of the blue light emission tends to be. Blue light emission with high color purity can express a wide range of blue even with a small luminance component, and using blue light emission with high color purity reduces the required luminance to express blue, thereby achieving a reduction in power consumption. Therefore, the BI, which takes into account the y value, which is one of the indices of blue purity, is preferably used as a means of expressing the efficiency of blue light emission. It can be said that a light-emitting device with a higher BI has better efficiency as a blue light-emitting device used in a display.

[0357] In this embodiment, the index is set to BI because the emission color with the shortest wavelength in the pixel is blue. However, if this is not blue, calculations can be performed to maximize any index according to the desired characteristics, such as current efficiency.

[0358] The calculations were performed using an organic device simulator (semiconducting emissive thin film optics simulator: setfos; Cybernet Systems Co., Ltd.). The light-emitting region was fixed at the center of the light-emitting layer, the dopant was not oriented, and the exciton generation probability and internal quantum efficiency were each assumed to be 100%. The calculations also took into account quenching due to the Purcell effect.

[0359] By calculation, the film thickness at which the maximum BI was obtained in the light-emitting device B having the structure shown in Table 1 above was as shown in the table below.

[0360]

[0361] Next, the calculation results for BI of the light-emitting device B having such a structure were compared with the calculation results for BI of the comparative light-emitting device B. The element structure of the comparative light-emitting device B is shown in Table 3 below.

[0362]

[0363] Light-emitting device B and comparative light-emitting device B were identical in all respects except for stacked structure 122 (first layer 122-1 and second layer 122-2) and the second electron transport layer. Comparative light-emitting device B is a blue light-emitting device in which stacked structure 122 is formed entirely of PCBBiF and does not have a refractive index step (LH structure), and the film thicknesses of stacked structure 122 and the second electron transport layer are calculated to provide the maximum BI for that configuration. In other words, the light-emitting devices were compared to each other, with the film thicknesses that provide the highest BI among the structures of the common parts of the light-emitting devices.

[0364] As a result, it was found that the BI of the light-emitting device B was improved by 3% compared to the BI of the comparative light-emitting device B, to 103%.

[0365] Next, calculations were performed on a light-emitting device (light-emitting device G, a green light-emitting device in this example) that emits light of a different color from that of light-emitting device B. Light-emitting device G had the element structure shown in Table 4 below, and included a first layer 122-1, a second layer 122-2, and a second electron transport layer that were the same as those of light-emitting device B. The light emitted from the light-emitting layer of light-emitting device G was light having the spectrum indicated by (G) in FIG. 13. Light-emitting device G included a third layer 122-3 (third layer 122-3a to third layer 122-3c) at any of positions a to c in Table 4.

[0366]

[0367] In this example, the film thickness of the third layer 122-3 that maximizes the current efficiency in the configuration was calculated. The third layer 122-3 has patterns of a high refractive index layer (High(3)) and a low refractive index layer (Low(3)), so calculations were performed for six patterns of element structures, as shown in Table 5 below. The calculations were performed with PCBBiF as the high refractive index layer (High(3)) and dchPAF as the low refractive index layer (Low(3)) of the third layer 122-3.

[0368]

[0369] The results are shown in Table 6. In both Tables 5 and 6, the portions written in bold correspond to the third layer 122-3, and each cell in Table 6 shows the film thickness (nm) of the layer represented by the corresponding cell in Table 5. In Tables 5 and 6, the portions surrounded by bold frames are areas where the refractive index of the third layer 122-3 is the same as that of the adjacent layer, and are therefore optically determined to be one layer. Even if the third layer 122-3 is optically a single layer, the film thicknesses of the first layer 122-1 and second layer 122-2, which are common layers with light-emitting device B, can be determined from light-emitting device B, and therefore the film thickness of the third layer 122-3 can be calculated.

[0370]

[0371] Thereafter, the calculation results for the current efficiency of the light-emitting devices G (element structures 1 to 6) having the respective element structures to which the film thicknesses shown in Table 6 above were applied were compared with the calculation results for the current efficiency of the comparative light-emitting device G1.

[0372] The comparative light-emitting device G1 had the same configuration as the light-emitting device G except for the material and thickness of the stacked structure 122. The stacked structure 122 of the comparative light-emitting device G1 was made of PCBBiF for all three layers, resulting in no refractive index step. The thicknesses of the first layer 122-1 and the second layer 122-2 and the second electron transport layer were determined to maximize the BI of the comparative light-emitting device B. In other words, the comparative light-emitting device G1 has the same configurations as the comparative light-emitting device B, namely, the first layer 122-1, the second layer 122-2, and the second electron transport layer. Furthermore, by adjusting the thickness of the third layer 122-3, the comparative light-emitting device G1 can be said to be a light-emitting device with a configuration that maximizes the current efficiency. Therefore, the comparative light-emitting devices G1 and B can be fabricated using the first layer 122-1, the second layer 122-2, and the second electron transport layer as common layers.

[0373] That is, just as it is assumed that light-emitting device B and light-emitting device G are light-emitting devices included in a single light-emitting device, it is also assumed that comparative light-emitting device B and comparative light-emitting device G1 are light-emitting devices included in a single light-emitting device. Furthermore, because comparative light-emitting device B and comparative light-emitting device G1 do not have a refractive index step or a low refractive index layer, they can also be said to be light-emitting devices with a conventional configuration.

[0375] The element structure of the comparative light-emitting device G1 is shown in Table 7.

[0376]

[0377] The results of comparing current efficiencies are shown in Table 8. Table 8 also shows the results of comparing BI between light-emitting device B and comparative light-emitting device B.

[0378]

[0379] Table 8 shows that in the light-emitting device of one embodiment of the present invention, the current efficiency of both the blue and green light-emitting devices is the same or improved while the light-emitting devices share part of the stacked structure having a refractive index step. In particular, in element structure 6, the current efficiency of light-emitting device G is significantly increased to 115% of that of comparative light-emitting device G1.

[0380] Furthermore, by sharing this stacked structure among light-emitting devices of multiple emission colors, it has become possible to easily, quickly, and inexpensively fabricate a light-emitting device with improved extraction efficiency and good luminous efficiency in the light-emitting devices of multiple emission colors.

[0381] The current efficiency of comparative light-emitting device G2, which has a different configuration from that of comparative light-emitting device G1, was compared with that of comparative light-emitting device G1. Comparative light-emitting device G2 has a configuration similar to that of light-emitting device G except that it does not have third layer 122-3.

[0382] The element structure of the comparative light-emitting device G2 is shown in Table 9.

[0383]

[0384] As a result of the comparison, the current efficiency of the comparative light-emitting device G2 was 8.7% of that of the comparative light-emitting device G1, and it was confirmed that the current efficiency of a light-emitting device that has only the stack structure 122 (first layer 122-1 and second layer 122-2) that is combined to improve the BI of the light-emitting device B and does not have the third layer 122-3 is significantly reduced. In light of this, when the improvement in the current efficiency of the light-emitting device G (Table 8) in the light-emitting device of one embodiment of the present invention that has the third layer 122-3 is examined, it can be said that an efficiency improvement of 11.5 to 13.2 times was obtained simply by adding one third layer 122-3.

[0385] As described above, in the light-emitting device of one embodiment of the present invention, a stacked structure (LH structure) tailored to improve the extraction efficiency of one emission color is shared by light-emitting devices of multiple emission colors, while a decrease in emission efficiency is suppressed and the efficiency of the light-emitting devices of multiple emission colors can be improved. Furthermore, by sharing the stacked structure among light-emitting devices of multiple emission colors, it is not necessary to fabricate separate stacked structures for each emission color. Therefore, a light-emitting device with good emission efficiency in which the extraction efficiency of the light-emitting devices of multiple emission colors is improved can be provided simply, quickly, and inexpensively.

[0386] Reference Example 1 In this reference example, a light-emitting device in which the tilt of the GSP is taken into consideration will be described in detail. The structural formulas of representative organic compounds used in this reference example are shown below.

[0387]

[0388] (Method of Fabricating Light-Emitting Device 1) First, a film of indium tin oxide containing silicon oxide (ITSO) was formed on a glass substrate by sputtering to form a first electrode 101 as an anode. The film thickness was 55 nm, and the electrode area was 2 mm × 2 mm.

[0389] Next, as a pretreatment for forming a light-emitting device on the substrate, the surface of the substrate was washed with water, baked at 200° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.

[0390] Then, 10 −４ The substrate was introduced into a vacuum deposition apparatus whose internal pressure had been reduced to about Pa, and was subjected to vacuum baking at 170° C. for 30 minutes in a heating chamber within the vacuum deposition apparatus, after which the substrate was allowed to cool for about 30 minutes.

[0391] Next, the substrate on which the first electrode 101 was formed was fixed to a substrate holder provided in a vacuum evaporation apparatus so that the surface on which the first electrode 101 was formed faced downward. N-(3",5',5"-tri-t-butyl-1,1':3',1"-terphenyl-4-yl)-N-(1,1'-biphenyl-2-yl)-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumTPoFBi-04) represented by the above structural formula (i) and an electron acceptor material (OCHD-003) having a molecular weight of 672 and containing fluorine were co-deposited on the first electrode 101 to a thickness of 10 nm by an evaporation method using resistance heating so as to give a weight ratio of 1:0.1 (=mmtBumTPoFBi-04:OCHD-003), thereby forming a hole-injection layer 111.

[0392] Next, mmtBumTPoFBi-04 was evaporated on the hole injection layer 111 to a thickness of 100 nm to form a first hole transport layer, and then N-[4-(9H-carbazol-9-yl)phenyl]-N-[4-(4-dibenzofuranyl)phenyl]-[1,1':4',1''-terphenyl]-4-amine (abbreviation: YGTPDBfB) represented by the above structural formula (ii) was deposited to a thickness of 10 nm to form a hole transport layer 112.

[0393] Furthermore, on the hole-transport layer 112, 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan (abbreviation: Bnf(II)PhA) represented by the above structural formula (iii) and 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02) represented by the above structural formula (iv) were co-deposited at a weight ratio of 1:0.015 (=Bnf(II)PhA:3,10PCA2Nbf(IV)-02) to a film thickness of 25 nm, thereby forming a light-emitting layer 113.

[0394] Next, a hole-blocking layer was formed on the light-emitting layer 113 by depositing a film of 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)-1,1′-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn) represented by the above structural formula (v) to a thickness of 10 nm.

[0395] Thereafter, 2-[3-(2,6-dimethyl-3-pyridinyl)-5-(9-phenanthrenyl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mPn-mDMePyPTzn) represented by the above structural formula (vi) and 8-quinolinolato-lithium (abbreviation: Liq) represented by the above structural formula (vii) were co-deposited at a weight ratio of 1:1 (=mPn-mDMePyPTzn:Liq) to a film thickness of 15 nm, thereby forming an electron transport layer 114.

[0396] After forming the electron transport layer 114, Liq was evaporated to a thickness of 1 nm to form the electron injection layer 115, and finally aluminum was evaporated to a thickness of 200 nm to form the second electrode 102, thereby producing the light-emitting device 1.

[0397] (Method for producing comparative light-emitting device 1) Comparative light-emitting device 1 was produced in the same manner as light-emitting device 1, except that mmtBumTPoFBi-04 in light-emitting device 1 was changed to N-(1,1′-biphenyl-2-yl)-N-[(3,3′,5′-tri-t-butyl)-1,1′-biphenyl-5-yl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: mmtBumBioFBi) represented by the above structural formula (viii).

[0398] The device structures of the above light-emitting device 1 and comparative light-emitting device 1 are summarized in the table below.

[0399]

[0400] The above-mentioned light-emitting device 1 and comparative light-emitting device 1 were sealed with glass substrates in a nitrogen atmosphere glove box to prevent exposure to the atmosphere (a sealant was applied around the elements, and UV treatment was performed during sealing, followed by heat treatment at 80°C for 1 hour), and then the initial characteristics of these light-emitting devices were measured. Note that no special measures were taken to improve extraction efficiency for the glass substrates on which the light-emitting devices were fabricated.

[0401] The luminance-current density characteristics of light-emitting device 1 and comparative light-emitting device 1 are shown in Fig. 16, their luminance-voltage characteristics in Fig. 17, their current efficiency-luminance characteristics in Fig. 18, their current density-voltage characteristics in Fig. 19, their external quantum efficiency-luminance characteristics in Fig. 20, and their emission spectra in Fig. 21. ２ The main characteristics in the vicinity are shown in Table 11. The luminance, CIE chromaticity, and emission spectrum were measured using a spectroradiometer (UR-UL1R, manufactured by Topcon Corporation) at room temperature. The external quantum efficiency was calculated using the measured luminance and emission spectrum, assuming that the light distribution characteristics were Lambertian.

[0402]

[0403] 16 to 21 and Table 11, it was found that the light-emitting device 1 is a light-emitting device having excellent characteristics, such as a good driving voltage and luminous efficiency, compared to the comparative light-emitting device 1.

[0404] The table below summarizes the GSP (mV / nm) of the vapor-deposited film of the organic compound having hole transport properties used in the hole transport layer for each light-emitting device. The table also shows the value (ΔGSP) obtained by subtracting the GSP (GSP2) of the organic compound having hole transport properties (HTM2) used in the hole transport layer (second hole transport layer) formed later from the GSP (GSP1) of the organic compound having hole transport properties (HTM1) used in the hole transport layer (first hole transport layer) formed earlier.

[0405]

[0406] Thus, the large ΔGSP of Comparative Light-Emitting Device 1 is thought to be the reason for the poor hole injection from the first hole transport layer to the second hole transport layer, resulting in an increase in driving voltage. On the other hand, it was found that a light-emitting device with a small ΔGSP is a light-emitting device with good characteristics, such as a small driving voltage.

[0407] 100: insulating layer, 101: first electrode, 101-1: reflective electrode, 101-2: light-transmitting electrode (anode), 102: second electrode, 103: EL layer, 111: hole injection layer, 113: light-emitting layer, 113L: light-emitting layer, 113L_1: light-emitting layer, 113L_2: light-emitting layer, 113S_1: light-emitting layer, 113S_2: light-emitting layer, 113S: light-emitting layer, 113R: light-emitting layer, 1 13G: light-emitting layer, 113B: light-emitting layer, 114: electron transport layer, 114_1: electron transport layer, 114L_2: electron transport layer, 114S_2: electron transport layer, 114R: electron transport layer, 114G: electron transport layer, 114B: electron transport layer, 115: electron injection layer, 115-2: electron injection layer, 122: stacked structure, 122-1: first layer, 122-2: second layer, 122-3: third layer, 122-3a: third layer, 122-3b: third layer, 122-3c: third layer, 122-3c: third layer, 122-3Ga: third layer, 122-3Gb: third layer, 122-3Gc: third layer, 122-3Ra: third layer, 122-3Rb: third layer, 122-3Rc: third layer, 123: insulating layer, 130 Electron blocking layer, 601: source line driving circuit, 602: pixel portion, 603: gate line driving circuit, 604: sealing substrate, 605: sealing material, 607: space, 608: wiring, 609: FPC (flexible printed circuit), 610: element substrate, 611: switching FET, 612: current control FET, 613: first electrode, 614: insulator, 616: EL layer, 617: second electrode, 618: light emitting device, 1001 substrate, 1002 base insulating film, 1003 gate insulating film, 1006 gate electrode, 1007 gate electrode, 1008 gate electrode, 1020 first interlayer insulating film, 1021 second interlayer insulating film, 1024W first electrode, 1024R first electrode, 1024G first electrode, 1024B first electrode, 1025 Partition wall, 1028 EL layer, 1029 second electrode, 1031 sealing substrate, 1032 sealing material, 1034R red colored layer, 1034G green colored layer, 1034B blue colored layer, 1035 black matrix, 1037 third interlayer insulating film, 1040 pixel portion, 1041 driver circuit portion, 1042 peripheral portion, 2100: robot, 2110: computing device, 2101: illuminance sensor, 2102: microphone, 2103: upper camera, 2104: speaker,2105: display, 2106: lower camera, 2107: obstacle sensor, 2108: movement mechanism, 5000: housing, 5001: display unit, 5002: second display unit, 5003: speaker, 5004: LED lamp, 5006: connection terminal, 5007: sensor, 5008: microphone, 5012: support unit, 5013: earphone, 5100: cleaning robot, 5101: display, 5102: camera, 5103: brush, 5104: operation button, 5150: mobile information terminal, 5151: housing, 5152: display area, 5153: bending portion, 5120: dust, 5200: display area, 520 1: display area, 5202: display area, 5203: display area, 7101: housing, 7103: display unit, 7105: stand, 7107: display unit, 7109: operation keys, 7110: remote control, 7201: main body, 7202: housing, 7203: display unit, 7204: keyboard, 7205: external connection port, 7206: pointing device, 7210: display unit, 7401: housing, 7402: display unit, 7403: operation buttons, 7404: external connection port, 7405: speaker, 7406: microphone, 9310: mobile information terminal, 9311: display panel, 9313: hinge, 9315: housing,

Claims

1. a first light emitting device; and a second light-emitting device; the first light-emitting device comprises a first electrode, a second electrode, a first light-emitting layer sandwiched between the first electrode and the second electrode, a first layer sandwiched between the first electrode and the first light-emitting layer, and a second layer sandwiched between the first layer and the first light-emitting layer; the second light-emitting device has a third electrode, a fourth electrode, a second light-emitting layer sandwiched between the third electrode and the fourth electrode, a third layer sandwiched between the third electrode and the second light-emitting layer, a fourth layer located between the third layer and the second light-emitting layer, and a fifth layer sandwiched between the third electrode and the second light-emitting layer; the first light-emitting layer comprises a first light-emitting material; the second light-emitting layer comprises a second light-emitting material; an emission peak wavelength of the first luminescent material is shorter than an emission peak wavelength of the second luminescent material; the first layer and the third layer, and the second layer and the fourth layer each contain the same material; an ordinary refractive index of the first layer at an emission peak wavelength of the first luminescent material is lower than an ordinary refractive index of the second layer; an ordinary refractive index of the third layer at an emission peak wavelength of the second light-emitting substance is lower than an ordinary refractive index of the fourth layer; A light-emitting device, wherein the fifth layer is located either between the third electrode and the third layer, between the third layer and the fourth layer, or between the fourth layer and the second light-emitting layer.

2. a first light emitting device; and a second light-emitting device; the first light-emitting device comprises a first electrode, a second electrode, a first light-emitting layer sandwiched between the first electrode and the second electrode, a first layer sandwiched between the first electrode and the first light-emitting layer, and a second layer sandwiched between the first layer and the first light-emitting layer; the second light-emitting device has a third electrode, a fourth electrode, a second light-emitting layer sandwiched between the third electrode and the fourth electrode, a third layer sandwiched between the third electrode and the second light-emitting layer, a fourth layer located between the third layer and the second light-emitting layer, and a fifth layer sandwiched between the third electrode and the second light-emitting layer; the first light-emitting layer comprises a first light-emitting material; the second light-emitting layer comprises a second light-emitting material; an emission peak wavelength of the first luminescent material is shorter than an emission peak wavelength of the second luminescent material; the first layer and the third layer, and the second layer and the fourth layer are each made of the same material; an ordinary refractive index of the first layer at an emission peak wavelength of the first luminescent material is lower than an ordinary refractive index of the second layer; an ordinary refractive index of the third layer at an emission peak wavelength of the second light-emitting substance is lower than an ordinary refractive index of the fourth layer; A light-emitting device, wherein the fifth layer is located either between the third electrode and the third layer, between the third layer and the fourth layer, or between the fourth layer and the second light-emitting layer.

3. a first light emitting device; and a second light-emitting device; the first light-emitting device comprises a first electrode, a second electrode, a first light-emitting layer sandwiched between the first electrode and the second electrode, a first layer sandwiched between the first electrode and the first light-emitting layer, and a second layer sandwiched between the first layer and the first light-emitting layer; the second light-emitting device has a third electrode, a fourth electrode, a second light-emitting layer sandwiched between the third electrode and the fourth electrode, a third layer sandwiched between the third electrode and the second light-emitting layer, a fourth layer located between the third layer and the second light-emitting layer, and a fifth layer sandwiched between the third electrode and the second light-emitting layer; the first light-emitting layer comprises a first light-emitting material; the second light-emitting layer comprises a second light-emitting material; an emission peak wavelength of the first luminescent material is shorter than an emission peak wavelength of the second luminescent material; the first layer and the third layer, and the second layer and the fourth layer each have the same configuration; an ordinary refractive index of the first layer at an emission peak wavelength of the first luminescent material is lower than an ordinary refractive index of the second layer; an ordinary refractive index of the third layer at an emission peak wavelength of the second light-emitting substance is lower than an ordinary refractive index of the fourth layer; A light-emitting device, wherein the fifth layer is located either between the third electrode and the third layer, between the third layer and the fourth layer, or between the fourth layer and the second light-emitting layer.

4. In any one of claims 1 to 3, The light-emitting device, wherein the fifth layer is located between the third electrode and the third layer.

5. In claim 4, A light emitting device in which the fifth layer and the third layer, and the third layer and the fourth layer are in contact with each other.

6. In any one of claims 1 to 3, The light emitting device, wherein the fifth layer is located between the third layer and the fourth layer.

7. In claim 6, A light emitting device in which the third layer and the fifth layer, and the third layer and the fourth layer are in contact with each other.

8. In any one of claims 1 to 3, The light-emitting device, wherein the fifth layer is located between the fourth layer and the second light-emitting layer.

9. In claim 8, The light emitting device wherein the third layer and the fourth layer, and the fourth layer and the fifth layer are in contact with each other.

10. A display device comprising the light-emitting device according to claim 1 .

11. 4. An electronic device comprising: the light-emitting device according to claim 1; a sensor; an operation button; and a speaker or a microphone.