Display device, display module, and electronic appliance

Abstract

To provide a display device with a long lifetime.SOLUTION: A display device includes a first light-emitting device and a second light-emitting device. The first light-emitting device includes a first electrode and a common electrode. The second light-emitting device includes a second electrode and the common electrode. The first light-emitting device includes a first light-emitting layer and an electron transport layer in the order from the side of the electrode functioning as an anode among the first electrode and the common electrode. The second light-emitting device includes a second light-emitting layer between the second electrode and the common electrode. The first light-emitting layer includes a first organic compound emitting light with a first color. The second light-emitting layer includes a second organic compound emitting light with a second color. The electron transport layer includes a third organic compound and a first substance. The third organic compound is an electron transport material. The first substance is a metal, a metal salt, a metal oxide, or an organic metal salt. The electron transport layer includes a first region and a second region in which the concentration of the first substance is different.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One embodiment of the present invention relates to a display device, a display module, and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention include a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, an electronic device, a lighting device, an input device (e.g., a touch sensor), an input / output device (e.g., a touch panel), a driving method thereof, or a manufacturing method thereof. [Background technology]

[0003] In recent years, display devices are expected to be used in a variety of applications. For example, applications of large display devices include home television devices (also called televisions or television receivers), digital signage, and public information displays (PIDs). In addition, smartphones and tablet devices equipped with touch panels are being developed as mobile information terminals.

[0004] As a display device, for example, a light-emitting device having a light-emitting device (also called a light-emitting element) has been developed. A light-emitting device (also called an EL device or an EL element) utilizing the electroluminescence (hereinafter referred to as EL) phenomenon has features such as being easily thin and lightweight, being capable of responding quickly to an input signal, and being capable of being driven by a low-voltage direct current power supply, and its application to a display device is being considered. For example, Patent Document 1 discloses a flexible light-emitting device to which an organic EL device (also called an organic EL element) is applied. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-197522 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of one embodiment of the present invention is to provide a display device with a long lifetime.An object of one embodiment of the present invention is to provide a display device with high reliability.An object of one embodiment of the present invention is to provide a large-sized display device.An object of one embodiment of the present invention is to provide a display device with high productivity.An object of one embodiment of the present invention is to provide a display device with high display quality.

[0007] Note that the description of these problems does not preclude the existence of other problems. One embodiment of the present invention does not necessarily have to solve all of these problems. Problems other than these can be extracted from the description of the specification, drawings, and claims. [Means for solving the problem]

[0008] One embodiment of the present invention is a display device having a first light-emitting device and a second light-emitting device. The first light-emitting device has a first electrode and a common electrode. The second light-emitting device has a first light-emitting layer and an electron transport layer, in this order from the electrode side of the first electrode and the common electrode that functions as an anode. The second light-emitting device has a second light-emitting layer between the second electrode and the common electrode. The first light-emitting layer has a first organic compound that emits light of a first color. The second light-emitting layer has a second organic compound that emits light of a second color. The electron transport layer has a third organic compound and a first substance. The third organic compound is an electron transport material. The first substance is a metal, a metal salt, a metal oxide, or an organometallic salt. The electron transport layer has a first region and a second region. The first region and the second region have different concentrations of the first substance.

[0009] When the first region is located closer to the first light-emitting layer than the second region, the first region preferably has a higher concentration of the first substance than the second region.

[0010] The second light-emitting device preferably has layers in common with the first light-emitting device between the second electrode and the common electrode.

[0011] The third organic compound has a HOMO level of −6.0 eV or higher and an electron mobility of 1×10 at a square root of an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more 5×10 -5 cm 2 It is preferable that the value is equal to or less than / Vs.

[0012] The second light-emitting layer preferably further contains a fourth organic compound and a fifth organic compound. The fourth organic compound and the fifth organic compound are preferably a combination that forms an exciplex.

[0013] The first light-emitting device preferably further includes a hole injection layer. The hole injection layer is preferably in contact with the electrode that functions as an anode out of the first electrode and the common electrode. The hole injection layer preferably includes a first compound and a second compound. The first compound preferably has an electron-accepting property toward the second compound. The HOMO level of the second compound is preferably -5.7 eV or more and -5.4 eV or less.

[0014] The first light-emitting device preferably further comprises a first hole transport layer. The first hole transport layer is preferably located between the hole injection layer and the first light-emitting layer. The first hole transport layer preferably comprises a third compound. The HOMO level of the third compound is preferably equal to or lower than the HOMO level of the second compound. The difference between the HOMO level of the third compound and the HOMO level of the second compound is preferably within 0.2 eV. Each of the second compound and the third compound preferably comprises at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.

[0015] The first light-emitting device preferably further comprises a second hole transport layer. The second hole transport layer is preferably located between the first hole transport layer and the first light-emitting layer. The second hole transport layer preferably comprises a fourth compound. The HOMO level of the fourth compound is preferably lower than the HOMO level of the third compound. The second compound, the third compound, and the fourth compound each preferably have at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.

[0016] The first organic compound is preferably a fluorescent emitting material.

[0017] The first color is preferably blue, and the second color is preferably red or green.

[0018] The first substance is preferably an organometallic complex having an alkali metal or alkaline earth metal.

[0019] The first substance is preferably an organometallic complex having a nitrogen- and oxygen-containing ligand and an alkali metal or alkaline earth metal.

[0020] The first substance is preferably an organometallic complex having a quinolinol ligand and an alkali metal or alkaline earth metal.

[0021] One embodiment of the present invention is a display module having a display device of any of the above configurations, and having a connector such as a flexible printed circuit (hereinafter referred to as FPC) or a TCP (Tape Carrier Package) attached, or a display module having an integrated circuit (IC) mounted by a COG (Chip On Glass) method or a COF (Chip On Film) method, etc.

[0022] One embodiment of the present invention is an electronic device including the above-described display module and at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button. Effect of the Invention

[0023] According to one embodiment of the present invention, a display device with a long lifetime can be provided. According to one embodiment of the present invention, a display device with high reliability can be provided. According to one embodiment of the present invention, a large-sized display device can be provided. According to one embodiment of the present invention, a display device with high productivity can be provided. According to one embodiment of the present invention, a display device with high display quality can be provided.

[0024] Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all of these effects. Effects other than these can be extracted from the description in the specification, drawings, and claims. [Brief description of the drawings]

[0025] [Figure 1] 1A and 1B are cross-sectional views showing an example of a display device. [Diagram 2] 2A and 2B are cross-sectional views showing an example of a display device. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of a display device. [Figure 4] 4A to 4C are cross-sectional views showing an example of a light-emitting device. [Diagram 5]5A to 5C are conceptual diagrams for explaining a light emission model of a light emitting device, and Fig. 5D is a diagram for explaining normalized luminance of a light emitting device over time. [Figure 6] 6A to 6D are diagrams illustrating the concentration of the first substance in the electron transport layer. [Figure 7] FIG. 7 is a perspective view showing an example of a display device. [Figure 8] 8A and 8B are cross-sectional views showing an example of a display device. [Figure 9] 9A is a cross-sectional view illustrating an example of a display device, and FIG 9B is a cross-sectional view illustrating an example of a transistor. [Figure 10] Fig. 10A is a block diagram showing an example of a pixel, and Fig. 10B is a circuit diagram showing an example of a pixel circuit. [Figure 11] Fig. 11A is a diagram for explaining the classification of IGZO crystal structures. Fig. 11B is a diagram for explaining the XRD spectrum of a quartz glass substrate. Fig. 11C is a diagram for explaining the XRD spectrum of a crystalline IGZO film. Fig. 11D is a diagram for explaining the micro-electron beam diffraction pattern of a quartz glass substrate. Fig. 11E is a diagram for explaining the micro-electron beam diffraction pattern of a crystalline IGZO film. [Figure 12] 12A and 12B are diagrams showing an example of an electronic device. [Figure 13] 13A to 13C are diagrams showing an example of an electronic device. [Figure 14] 14A and 14B are diagrams showing an example of an electronic device. [Figure 15] 15A to 15D are diagrams showing an example of an electronic device. [Figure 16] 16A to 16D are diagrams showing an example of an electronic device. [Figure 17] 17A to 17F are diagrams showing an example of an electronic device. [Figure 18] 18A shows the structure of an electron-only device, and FIG 18B shows the structure of an example light-emitting device. [Figure 19]FIG. 19 shows the current density-voltage characteristics of an electron-only device. [Figure 20] FIG. 20 is a diagram showing the frequency characteristics of the calculated capacitance C of ZADN:Liq (1:1) at a DC power supply of 7.0 V. [Figure 21] FIG. 21 is a diagram showing the frequency characteristics of −ΔB of ZADN:Liq(1:1) at a DC voltage of 7.0 V. [Figure 22] FIG. 22 is a diagram showing the electric field strength dependence of electron mobility in each organic compound. [Figure 23] FIG. 23 is a graph showing luminance-current density characteristics. [Figure 24] FIG. 24 is a diagram showing luminance-voltage characteristics. [Diagram 25] FIG. 25 is a graph showing current efficiency-luminance characteristics. [Figure 26] FIG. 26 is a diagram showing current density-voltage characteristics. [Figure 27] FIG. 27 is a diagram showing an emission spectrum. [Figure 28] FIG. 28 is a diagram showing luminance-current density characteristics. [Figure 29] FIG. 29 is a diagram showing luminance-voltage characteristics. [Diagram 30] FIG. 30 is a graph showing current efficiency-luminance characteristics. [Diagram 31] FIG. 31 is a graph showing current density-voltage characteristics. [Diagram 32] FIG. 32 is a diagram showing an emission spectrum. [Diagram 33] FIG. 33 is a graph showing luminance-current density characteristics. [Diagram 34] FIG. 34 is a diagram showing luminance-voltage characteristics. [Diagram 35] FIG. 35 is a graph showing current efficiency-luminance characteristics. [Diagram 36] FIG. 36 is a diagram showing current density-voltage characteristics. [Figure 37] FIG. 37 is a diagram showing an emission spectrum. [Figure 38]FIG. 38 is a diagram showing the results of the reliability test. [Figure 39] FIG. 39 is a diagram showing the results of the reliability test. [Diagram 40] FIG. 40 is a diagram showing the results of the reliability test. [Diagram 41] FIG. 41 is a diagram showing the results of the reliability test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The embodiments 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 easily understood by those skilled in the art that the modes and details of the present invention can be modified in various ways 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.

[0027] In the configuration of the invention described below, the same parts or parts having similar functions are denoted by the same reference numerals in different drawings, and the repeated explanations are omitted. In addition, when referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be used.

[0028] In addition, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosed invention is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0029] In addition, the words "film" and "layer" can be interchanged depending on the case or situation. For example, the term "conductive layer" can be changed to the term "conductive film". Or, for example, the term "insulating film" can be changed to the term "insulating layer".

[0030] In this specification and the like, unless otherwise specified, even when describing a configuration having a plurality of elements (light-emitting devices, light-emitting layers, etc.), when describing matters common to each element, the alphabet will be omitted. For example, when describing matters common to light-emitting layer 193R and light-emitting layer 193G, etc., the light-emitting layer may be written as 193.

[0031] (Embodiment 1) In this embodiment, a display device according to one embodiment of the present invention will be described with reference to FIGS.

[0032] The display device of this embodiment mode has a light-emitting device in a display portion and can display an image on the display portion.

[0033] As the light-emitting device, it is preferable to use an EL device such as an OLED (Organic Light Emitting Diode) or a QLED (Quantum-dot Light Emitting Diode). Examples of the light-emitting substance that the EL device has include a substance that emits fluorescence (fluorescent substance), a substance that emits phosphorescence (phosphorescent substance), an inorganic compound (such as a quantum dot material), and a substance that exhibits thermally activated delayed fluorescence (thermally activated delayed fluorescence (TADF) material).

[0034] The color-coded method is applied to the coloring method of the display device of this embodiment. When the color-coded method is used for a small display device, it is preferable because the alignment accuracy of the metal mask can be improved and the color-coded yield can be increased. In addition, since the resolution can be relatively low for a large display device, it is advantageous to adopt a light-emitting device using the color-coded method.

[0035] The light-emitting devices of the subpixels of each color have different light-emitting layers. The light-emitting layers of the light-emitting devices are preferably separated from each other. In addition, when the resolution of the display device is high, the light-emitting layers of the light-emitting devices may overlap each other.

[0036] The display device of this embodiment may be of any of a top emission type that emits light in the direction opposite to the substrate on which the light emitting device is formed, a bottom emission type that emits light toward the substrate on which the light emitting device is formed, and a dual emission type that emits light on both sides.

[0037] It is preferable to adopt a micro-optical resonator (microcavity) structure for the light-emitting device. Specifically, in order to adjust the optical distance between a pair of electrodes, it is preferable to paint another layer (e.g., a hole transport layer) in addition to the light-emitting layer in the EL layer for each color of light-emitting device, and to make the other layers common to the light-emitting devices of each color. This simplifies the process, enables efficient extraction of light, and realizes a display device capable of displaying a wide color gamut.

[0038] The display device of the present embodiment has a light-emitting device configured to allow holes to be easily injected into the light-emitting layer, but not to allow electrons to be easily injected into the light-emitting layer. By allowing holes to be easily injected from the anode side, and by suppressing the amount of electrons injected from the cathode side into the light-emitting layer, the light-emitting layer can be prevented from becoming in an electron-excess state. As electrons are injected into the light-emitting layer over time, the brightness increases, and this increase in brightness can offset initial deterioration. By using a light-emitting device in which initial deterioration is suppressed and which has a very long operating life, the life of the display device can be extended and the reliability can be increased. The configuration of the light-emitting device will be described later with reference to Figs. 4 to 6.

[0039] First, configuration examples of a display device are shown in Figures 1 to 3. In the display devices shown in Figures 1 to 3, the configuration of the light-emitting device exemplified in Figures 4 to 6 is applied to at least one light-emitting device.

[0040] [Display device 10A] FIG. 1A shows a cross-sectional view of a display device 10A.

[0041] The display device 10A has a light emitting device 190R that emits red light 21R, a light emitting device 190G that emits green light 21G, and a light emitting device 190B that emits blue light 21B.

[0042] The light-emitting device 190R includes a pixel electrode 191, an optical adjustment layer 199R, a buffer layer 192R, a light-emitting layer 193R, a buffer layer 194R, and a common electrode 115. The light-emitting layer 193R includes an organic compound that emits red light.

[0043] The light-emitting device 190G includes a pixel electrode 191, an optical adjustment layer 199G, a buffer layer 192G, a light-emitting layer 193G, a buffer layer 194G, and a common electrode 115. The light-emitting layer 193G includes an organic compound that emits green light.

[0044] The light-emitting device 190B includes a pixel electrode 191, an optical adjustment layer 199B, a buffer layer 192B, a light-emitting layer 193B, a buffer layer 194B, and a common electrode 115. The light-emitting layer 193B includes an organic compound that emits blue light.

[0045] In this specification and the like, an organic compound that emits blue light may be referred to as a first organic compound, and an organic compound that emits red light or an organic compound that emits green light may be referred to as a second organic compound.

[0046] At least one of the light emitting devices 190R, 190G, and 190B has the configuration of the light emitting device illustrated in FIGS.

[0047] In this embodiment, a case will be described as an example in which the pixel electrode 191 functions as an anode and the common electrode 115 functions as a cathode.

[0048] Pixel electrode 191, optical adjustment layer 199R, optical adjustment layer 199G, optical adjustment layer 199B, buffer layer 192R, buffer layer 192G, buffer layer 192B, emitting layer 193R, emitting layer 193G, emitting layer 193B, buffer layer 194R, buffer layer 194G, buffer layer 194B, and common electrode 115 may each have a single layer structure or a laminated structure.

[0049] The pixel electrodes 191 are located on the insulating layer 214. Ends of the pixel electrodes 191 are covered with partition walls 216. The pixel electrodes 191 are electrically insulated from each other by the partition walls 216 (also referred to as being electrically separated).

[0050] An organic insulating film is suitable for the partition wall 216. Materials that can be used for the organic insulating film include acrylic resin, polyimide resin, epoxy resin, polyamide resin, polyimideamide resin, siloxane resin, benzocyclobutene resin, phenol resin, and precursors of these resins.

[0051] The buffer layer 192 is located on the pixel electrode 191. The light-emitting layer 193 overlaps with the pixel electrode 191 through the buffer layer 192. The buffer layer 194 is located on the light-emitting layer 193. The light-emitting layer 193 overlaps with the common electrode 115 through the buffer layer 194. The buffer layer 192 can have one or both of a hole injection layer and a hole transport layer. The buffer layer 194 can have one or both of an electron injection layer and an electron transport layer.

[0052] The common electrode 115 is a layer that is shared by the light emitting devices 190 of each color.

[0053] The display device 10A has a light emitting device 190, a transistor 42, and the like between a pair of substrates (substrate 151 and substrate 152).

[0054] In the light-emitting device 190, the buffer layer 192, the light-emitting layer 193, and the buffer layer 194, which are located between the pixel electrode 191 and the common electrode 115, can also be called EL layers. The pixel electrode 191 preferably has a function of reflecting visible light. The common electrode 115 has a function of transmitting visible light.

[0055] It is preferable that a microcavity structure is applied to the light-emitting device of the display device of this embodiment. Therefore, it is preferable that one of a pair of electrodes of the light-emitting device has an electrode (semi-transmissive / semi-reflective electrode) that is transparent and reflective to visible light, and the other has an electrode (reflective electrode) that is reflective to visible light. When the light-emitting device has a microcavity structure, the light emitted from the light-emitting layer can be resonated between both electrodes, and the light emitted from the light-emitting device can be strengthened.

[0056] The semi-transmitting / semi-reflective electrode may have a laminated structure of a reflective electrode and an electrode that is transparent to visible light (also called a transparent electrode). In this specification, the reflective electrode, which functions as a part of the semi-transmitting / semi-reflective electrode, may be referred to as a pixel electrode or a common electrode, and the transparent electrode may be referred to as an optical adjustment layer, but the transparent electrode (optical adjustment layer) may also function as a pixel electrode or a common electrode.

[0057] The light transmittance of the transparent electrode is 40% or more. For example, it is preferable to use electrodes in which the transmittance of both visible light (light with a wavelength of 400 nm or more and less than 750 nm) and near-infrared light (light with a wavelength of 750 nm or more and 1300 nm or less) is 40% or more. The reflectance of each of the semi-transparent / semi-reflective electrodes for visible light and near-infrared light is 10% or more and 95% or less, preferably 30% or more and 80% or less. The reflectance of the reflective electrode for visible light and near-infrared light is 40% or more and 100% or less, preferably 70% or more and 100% or less. The resistivity of these electrodes is 1×10 -2 Ωcm or less is preferable.

[0058] In this embodiment, an example is shown in which the optical adjustment layer 199 is provided on the pixel electrode 191, but the optical adjustment layer 199 does not have to be provided. For example, the buffer layer 192 or the buffer layer 194 may function as an optical adjustment layer. By varying the film thickness of the buffer layer 192 or the buffer layer 194, it is possible to intensify and extract light of a specific color in each light-emitting device. Note that when the semi-transmissive / semi-reflective electrode has a laminated structure of a reflective electrode and a transparent electrode, the optical distance between a pair of electrodes refers to the optical distance between a pair of reflective electrodes.

[0059] The light emitting device 190 has a function of emitting visible light. Specifically, the light emitting device 190 is an electroluminescent device that emits light to the substrate 152 side by applying a voltage between a pixel electrode 191 and a common electrode 115.

[0060] The pixel electrode 191 is electrically connected to the source or drain of the transistor 42 through an opening provided in the insulating layer 214. The transistor 42 has a function of controlling the driving of the light-emitting device 190.

[0061] Each of the light-emitting devices 190 is preferably covered with a protective layer 195. In Fig. 1A, the protective layer 195 is provided on and in contact with the common electrode 115. By providing the protective layer 195, it is possible to prevent impurities such as water from entering the light-emitting device 190, and to improve the reliability of the light-emitting device 190. In addition, the protective layer 195 and the substrate 152 are bonded together by the adhesive layer 142.

[0062] The light-shielding layer BM may be made of a material that blocks light emitted from the light-emitting device. The light-shielding layer BM preferably absorbs visible light. For example, the light-shielding layer BM may be made of a black matrix using a metal material or a resin material containing a pigment (such as carbon black) or a dye. The light-shielding layer BM may have a laminated structure of a red color filter, a green color filter, and a blue color filter.

[0063] The light-emitting layer 193R preferably contains a phosphorescent material as an organic compound that emits red light. The light-emitting layer 193G preferably contains a phosphorescent material as an organic compound that emits green light. In addition, in the light-emitting device 190R, an exciplex is preferably formed in the light-emitting layer 193R by applying a voltage between the pixel electrode 191 and the common electrode 115. Similarly, in the light-emitting device 190G, an exciplex is preferably formed in the light-emitting layer 193G by applying a voltage between the pixel electrode 191 and the common electrode 115. With such a configuration, the light-emitting efficiency of each of the light-emitting device 190R and the light-emitting device 190G can be increased.

[0064] For example, each of the light-emitting layers 193R and 193G preferably has two kinds of organic compounds in addition to a light-emitting material. The two kinds of organic compounds are preferably substances that form an exciplex. It can also be said that the two kinds of organic compounds are a combination that forms an exciplex. In each of the light-emitting layers 193R and 193G, the two kinds of organic compounds can be called a host material and an assist material, or a first host material and a second host material. Alternatively, it can be said that the host material in each of the light-emitting layers 193R and 193G is a mixed material of two kinds of organic compounds. Each of the two kinds of organic compounds in the light-emitting layer 193R may be the same material as each of the two kinds of organic compounds in the light-emitting layer 193G, or may be a different material.

[0065] In this specification and the like, the two kinds of organic compounds may be referred to as a fourth organic compound and a fifth organic compound. The structure of the light-emitting layer capable of forming an exciplex will be described later.

[0066] The light-emitting layer 193B preferably contains a fluorescent material as an organic compound that emits blue light.

[0067] [Display device 10B] 1B shows a cross-sectional view of a display device 10B. In the following description of the display device, the description of the same configuration as the display device described above may be omitted.

[0068] Display device 10B differs from display device 10A in that red light-emitting device 190R and green light-emitting device 190G have common layers 182 and 184.

[0069] At least two of the light emitting devices of red, green, and blue colors, 190R, 190G, and 190B, preferably have one or more layers that are used in common (common layers), which allows the display device to be manufactured with fewer manufacturing steps.

[0070] FIG. 1B shows an example in which light-emitting device 190R and light-emitting device 190G have common layer 182 and common layer 184, but a display device according to one embodiment of the present invention may have a configuration in which light-emitting device 190R and light-emitting device 190G have only common layer 182 or only common layer 184.

[0071] The common layer 182 is located between the pixel electrode 191 and the light-emitting layer 193R, and between the pixel electrode 191 and the light-emitting layer 193G.

[0072] The common layer 184 is located between the light-emitting layer 193R and the common electrode 115, and between the light-emitting layer 193G and the common electrode 115.

[0073] Each of the common layer 182 and the common layer 184 may have a single-layer structure or a laminated structure.

[0074] As the common layer 182, for example, one or both of a hole injection layer and a hole transport layer can be formed.

[0075] As the common layer 184, for example, one or both of an electron injection layer and an electron transport layer can be formed.

[0076] The light-emitting device 190R and the light-emitting device 190G may have a buffer layer at least in one of between the pixel electrode 191 and the common layer 182, between the common layer 182 and the light-emitting layer, between the light-emitting layer and the common layer 184, and between the common layer 184 and the common electrode 115. As the buffer layer, for example, at least one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer can be formed.

[0077] For example, it is preferable that the light emitting device 190B has the configuration of the light emitting device exemplified in Figures 4 to 6. Alternatively, the light emitting device 190R and the light emitting device 190G may both have the configuration of the light emitting device exemplified in Figures 4 to 6.

[0078] 4 to 6 is applied to either the light-emitting device 190R or the light-emitting device 190G, and the light-emitting device 190B, it is preferable that either the light-emitting device 190R or the light-emitting device 190G, and the light-emitting device 190B have a common layer 182 and a common layer 184. In this case, it is preferable that the configuration of the common layer 182 and the common layer 184 is the configuration of the light-emitting device illustrated in FIG. 4 to FIG.

[0079] [Display device 10C] FIG. 2A shows a cross-sectional view of the display device 10C.

[0080] Display device 10C differs from display device 10A in that red light-emitting device 190R, green light-emitting device 190G, and blue light-emitting device 190B have common layers 112 and 114.

[0081] It is preferable that the red light emitting device 190R, the green light emitting device 190G, and the blue light emitting device 190B have one or more layers that are used in common (common layers), which allows the display device to be manufactured with fewer manufacturing steps.

[0082] Although FIG. 2A shows an example in which the light-emitting devices of each color have the common layer 112 and the common layer 114, the display device of one embodiment of the present invention may have a configuration in which the light-emitting devices of each color have only the common layer 112 or only the common layer 114.

[0083] The common layer 112 is located between the pixel electrode 191 and the light-emitting layers of each color.

[0084] The common layer 114 is located between the light emitting layers of each color and the common electrode 115 .

[0085] Each of the common layer 112 and the common layer 114 may have a single-layer structure or a laminated structure.

[0086] As the common layer 112, for example, one or both of a hole injection layer and a hole transport layer can be formed.

[0087] As the common layer 114, for example, one or both of an electron injection layer and an electron transport layer can be formed.

[0088] Each light-emitting device may have a buffer layer at least in one of the following locations: between the pixel electrode 191 and the common layer 112, between the common layer 112 and the light-emitting layer, between the light-emitting layer and the common layer 114, and between the common layer 114 and the common electrode 115. As the buffer layer, for example, at least one of a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer may be formed.

[0089] [Display device 10D] FIG. 2B shows a cross-sectional view of display device 10D.

[0090] The display device 10D differs from the display device 10C in that it does not have the substrate 151 and the substrate 152, but has the substrate 153, the substrate 154, the adhesive layer 155, and the insulating layer 212.

[0091] The substrate 153 and the insulating layer 212 are bonded together by an adhesive layer 155. The substrate 154 and the protective layer 195 are bonded together by an adhesive layer 142.

[0092] The display device 10D is fabricated by transferring the insulating layer 212, the transistor 42, the light-emitting devices of each color, and the like, which are formed on a fabrication substrate, onto the substrate 153. The substrates 153 and 154 each preferably have flexibility. This can increase the flexibility of the display device 10D. For example, the substrates 153 and 154 each preferably use a resin.

[0093] The substrates 153 and 154 may each be made of polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), polyacrylonitrile resin, acrylic resin, polyimide resin, polymethyl methacrylate resin, polycarbonate (PC) resin, polyethersulfone (PES) resin, polyamide resin (nylon, aramid, etc.), polysiloxane resin, cycloolefin resin, polystyrene resin, polyamideimide resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, polypropylene resin, polytetrafluoroethylene (PTFE) resin, ABS resin, cellulose nanofiber, etc. One or both of the substrates 153 and 154 may be made of glass having a thickness sufficient to provide flexibility.

[0094] A film having high optical isotropy may be used for the substrate of the display device of this embodiment. Examples of the film having high optical isotropy include a triacetyl cellulose (TAC, also called cellulose triacetate) film, a cycloolefin polymer (COP) film, a cycloolefin copolymer (COC) film, and an acrylic film.

[0095] [Display device 10E] FIG. 3 shows a cross-sectional view of the display device 10E.

[0096] The display device 10E differs from the display device 10C in that it is a bottom emission type.

[0097] The pixel electrode 191 has a function of transmitting visible light. It is preferable that the common electrode 115 has a function of reflecting visible light.

[0098] The transistor 42 is preferably provided at a position that does not overlap with the light emitting region of the light emitting device.

[0099] In the display device 10E, an example is shown in which the substrate 152 is provided on the protective layer 195 via the adhesive layer 142, but the adhesive layer 142 and the substrate 152 do not necessarily have to be provided.

[0100] [Light Emitting Device] 4A to 4C show an example of a light-emitting device that can be used in the display device of the present embodiment.

[0101] The light-emitting device shown in Fig. 4A has an anode 101, an EL layer 103, and a cathode 102. The EL layer 103 has, from the anode 101 side, a hole injection layer 121, a hole transport layer 122, a light-emitting layer 123, an electron transport layer 124, and an electron injection layer 125. Although not shown in Figs. 4A to 4C, the light-emitting device may have an optical adjustment layer.

[0102] The anode 101, the cathode 102, the hole injection layer 121, the hole transport layer 122, the light emitting layer 123, the electron transport layer 124, and the electron injection layer 125 may each have a single layer structure or a laminated structure.

[0103] The hole transport layer 122 of the light emitting device shown in FIGS. 4B and 4C has a two-layer structure including a hole transport layer 122a on the hole injection layer 121 side and a hole transport layer 122b on the light emitting layer 123 side.

[0104] The electron transport layer 124 of the light emitting device shown in FIG. 4C has a two-layer structure including an electron transport layer 124a on the light emitting layer 123 side and an electron transport layer 124b on the electron injection layer 125 side.

[0105] Materials that can be used in light-emitting devices are described below.

[0106] <Electrode> As a material for forming a pair of electrodes of a light-emitting device, metals, alloys, electrically conductive compounds, and mixtures thereof can be appropriately used. Specifically, In-Sn oxide (also called ITO), In-Si-Sn oxide (also called ITSO), In-Zn oxide, and In-W-Zn oxide can be mentioned. In addition, metals such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), and neodymium (Nd), and alloys containing these in appropriate combinations can also be used. In addition, elements belonging to Group 1 or 2 of the periodic table not exemplified above (e.g., lithium (Li), cesium (Cs), calcium (Ca), strontium (Sr)), rare earth metals such as europium (Eu) and ytterbium (Yb), alloys containing appropriate combinations of these, graphene, etc. can be used.

[0107] When a light-emitting device having a microcavity structure is to be fabricated, a reflective electrode and a semi-transmissive / semi-reflective electrode are used. Therefore, a single or multiple desired conductive materials can be used to form a single layer or a multilayer structure. The electrodes can be fabricated by sputtering or vacuum deposition.

[0108] <Hole injection layer> The hole injection layer 121 preferably comprises a first compound and a second compound.

[0109] The first compound is an electron-accepting material (acceptor material) and has electron-accepting properties toward the second compound.

[0110] The second compound is a hole transporting material that has a higher ability to transport holes than electrons.

[0111] The highest occupied molecular orbital level (HOMO level) of the second compound is preferably relatively low (deep). Specifically, the HOMO level of the second compound is preferably -5.7 eV or more and -5.4 eV or less. The relatively low HOMO level of the second compound is preferable because it facilitates the injection of holes into the hole transport layer 122.

[0112] As the first compound, an organic compound having an electron-withdrawing group (particularly a halogen group such as a fluoro group or a cyano group) can be used.

[0113] As the first compound, for example, an organic acceptor such as a quinodimethane derivative, a chloranil derivative, or a hexaazatriphenylene derivative can be used. Specifically, 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-TCNNQ), 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile, etc. can be mentioned. In particular, compounds in which an electron-withdrawing group is bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, are preferred because they are thermally stable. Radialene derivatives [3] having an electron-withdrawing group (especially a halogen group such as a fluoro group or a cyano group) are preferred because they have a very high electron-accepting property. Examples of radialene derivatives [3] having an electron-withdrawing group include α,α',α''-1,2,3-cyclopropane triylidene tris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α',α''-1,2,3-cyclopropane triylidene tris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], and α,α',α''-1,2,3-cyclopropane triylidene tris[2,3,4,5,6-pentafluorobenzeneacetonitrile].

[0114] The second compound preferably has a hole transporting skeleton, and the hole transporting skeleton is preferably a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, or an anthracene skeleton, which does not make the HOMO level of the hole transporting material too high (shallow).

[0115] The second compound preferably has at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton. The hole transporting 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.

[0116] It is preferable that the second compound has an N,N-bis(4-biphenyl)amino group, since a light-emitting device having a long life can be produced.

[0117] Examples of the second compound 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-8-yl-4''-phenyltriphenylamine (abbreviation: BnfBB1BP), 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: 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 (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''-phenyltriphenylamine (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 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-(1,1'-biphenyl-2-yl)-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)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3'-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 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-naphthalene-4-yl)phenylamine (abbreviation: PCBBi1BP), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl)-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]spiro-9,9'-bifluoren-2-amine (abbreviation: PCBASF), N-(1,1'-biphenyl) -4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine (abbreviation: PCBBiF), 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-fluoren-9-yl)triphenylamine (abbreviation: FLPAPA), etc.

[0118] <Hole transport layer> The hole transport layer 122 is a layer that transports the holes injected by the hole injection layer 121 to the light emitting layer 123 .

[0119] The hole transport layer 122 preferably comprises a third compound.

[0120] The third compound is a hole transporting material. As the hole transporting material, the hole transporting material that can be used for the second compound can be used.

[0121] The HOMO level of the third compound is preferably equal to or lower than the HOMO level of the second compound, and the difference between the HOMO levels of the third compound and the second compound is preferably within 0.2 eV.

[0122] Each of the second compound and the third compound preferably has at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.

[0123] It is preferable that the second compound and the third compound have the same hole transporting skeleton (particularly, a dibenzofuran skeleton) since this facilitates the injection of holes.

[0124] It is more preferable that the second compound and the third compound are the same, since this allows smooth hole injection.

[0125] When the hole transport layer 122 has a laminated structure, each layer constituting the hole transport layer 122 is a layer that transports holes to the light emitting layer 123 .

[0126] The hole transport layer 122a in FIGS. 4B and 4C may have a similar structure to the hole transport layer 122 in FIG. 4A.

[0127] It is preferable that the hole transport layer 122b in FIG. 4B and FIG. 4C (that is, the layer of the hole transport layer 122 located closest to the light emitting layer 123) has a function as an electron blocking layer.

[0128] The hole transport layer 122b preferably comprises a fourth compound.

[0129] The fourth compound is a hole transporting material. As the hole transporting material, the hole transporting material that can be used for the second compound can be used.

[0130] The HOMO level of the fourth compound is preferably lower than the HOMO level of the third compound, and the difference between the HOMO levels of the fourth compound and the third compound is preferably within 0.2 eV.

[0131] Each of the second compound, the third compound, and the fourth compound preferably has at least one of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton.

[0132] It is preferable that the second compound, the third compound, and the fourth compound have the same hole transporting skeleton (particularly a dibenzofuran skeleton) because this facilitates the injection of holes.

[0133] When the hole transport materials used in the hole injection layer 121, the hole transport layer 122a, and the hole transport layer 122b have the above-mentioned relationship, holes can be smoothly injected into each layer, and an increase in the driving voltage and a deficiency of holes in the light-emitting layer 123 can be prevented.

[0134] <Light-emitting layer> The light-emitting layer is a layer containing a light-emitting substance. The light-emitting layer can have one or more types of light-emitting substances. As the light-emitting substance, a substance that emits light of a color such as blue, purple, blue-purple, green, yellow-green, yellow, orange, or red is appropriately used. In addition, a substance that emits near-infrared light can also be used as the light-emitting substance.

[0135] The light-emitting layer may contain one or more organic compounds (host materials, assist materials, etc.) in addition to the light-emitting substance (guest material). As the one or more organic compounds, one or both of the hole-transporting material and the electron-transporting material described in this embodiment can be used. As the one or more organic compounds, a bipolar material may be used.

[0136] The light-emitting substance that can be used in the light-emitting layer is not particularly limited, and a light-emitting substance that converts singlet excitation energy into light emission in the visible light region or near-infrared light region, or a light-emitting substance that converts triplet excitation energy into light emission in the visible light region or near-infrared light region can be used.

[0137] Examples of luminescent substances that convert singlet excitation energy into luminescence include fluorescent luminescent substances, such as pyrene derivatives, anthracene derivatives, triphenylene derivatives, fluorene derivatives, carbazole derivatives, dibenzothiophene derivatives, dibenzofuran derivatives, dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridine derivatives, pyrimidine derivatives, phenanthrene derivatives, naphthalene derivatives, etc. Pyrene derivatives are particularly preferred because of their high luminescence quantum yield. Specific examples of pyrene derivatives include N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N'-diphenyl-N,N'-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(dibenzofuran-2-yl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6FrAPrn), N,N'-bis(dibenzothiophene-2-yl)-N, N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6ThAPrn), N,N'-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine] (abbreviation: 1,6BnfAPrn), N,N'-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-02), N,N'-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine] (abbreviation: 1,6BnfAPrn-03), etc. In particular, condensed aromatic diamine compounds such as pyrenediamine compounds, such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03, are preferred because they have high hole trapping properties, excellent luminous efficiency, and excellent reliability.

[0138] Other examples include 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'-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), 4-(10-phenyl-9-anthryl)-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), 4-[4-(10-phenyl-9-anthryl)phenyl]-4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine 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:2PCAPPA), N-[4-(9,10-diphenyl [N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b']bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), and the like can be used.

[0139] Examples of luminescent materials that convert triplet excitation energy into luminescence include phosphorescent luminescent materials and thermally activated delayed fluorescence (TADF) materials that exhibit thermally activated delayed fluorescence.

[0140] Examples of phosphorescent substances include organometallic complexes (particularly iridium complexes) having a 4H-triazole skeleton, a 1H-triazole skeleton, an imidazole skeleton, a pyrimidine skeleton, a pyrazine skeleton, or a pyridine skeleton; organometallic complexes (particularly iridium complexes) having a phenylpyridine derivative having an electron-withdrawing group as a ligand; platinum complexes; and rare earth metal complexes.

[0141] Examples of phosphorescent substances that exhibit blue or green light and have an emission spectrum with a peak wavelength of 450 nm or more and 570 nm or less include the following substances.

[0142] For example, tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]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 organometallic complexes having a 4H-triazole skeleton, such as tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), tris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: Ir(iPr5btz)3]), organometallic complexes with a 1H-triazole skeleton, such as fac-tris[1-(2,6-diisopropylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]) and tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Prptz1-Me)3]); organometallic complexes with an imidazole skeleton, such as tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), 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(CF3ppy)2(pic)]), bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2’] Examples include organometallic complexes with phenylpyridine derivatives having electron-withdrawing groups as ligands, such as iridium(III) acetylacetonate (abbreviation: FIr(acac)).

[0143] Examples of phosphorescent substances that exhibit green or yellow light and have an emission spectrum with a peak wavelength of 495 nm or more and 590 nm or less include the following substances.

[0144] For example, 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)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-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-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III) (abbreviation: [Ir(dmppm-dmp)2(acac)]), and (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]). iridium complexes with a pyrazine skeleton, such as (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinate)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]) and (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinate)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]); tris(2-phenylpyrazinate-N,C 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’ Organometallic iridium complexes with pyridine skeletons such as iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), [2-(4-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(4dppy)]), bis[2-(2-pyridinyl-κN)phenyl-κC][2-(4-methyl-5-phenyl-2-pyridinyl-κN)phenyl-κC], and bis(2,4-diphenyl-1,3-oxazolato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(dpo)2(acac)]), bis{2-[4'-(perfluorophenyl)phenyl]pyridinato-N,C 2’}Iridium(III) acetylacetonate (abbreviation: [Ir(p-PF-ph)2(acac)]), bis(2-phenylbenzothiazolato-N,C 2’ ) iridium(III) acetylacetonate (abbreviation: [Ir(bt)2(acac)]), as well as rare earth metal complexes such as tris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation: [Tb(acac)3(Phen)]).

[0145] Examples of phosphorescent substances that exhibit yellow or red light and have an emission spectrum with a peak wavelength of 570 nm or more and 750 nm or less include the following substances.

[0146] For example, (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(d1npm)2(dpm)]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) Organometallic complexes with pyrimidine skeletons 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)]), and bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κN)phenyl-κC). 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-P)2(dibm)]), bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ 2 O,O')iridium(III) (abbreviation: [Ir(dmdppr-dmCP)2(dpm)]), (acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C 2’ ]Iridium(III) (abbreviation: [Ir(mpq)2(acac)]), (acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C 2’)iridium(III) (abbreviation: [Ir(dpq)2(acac)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), bis{4,6-dimethyl-2-[5-(5-cyano-2-methylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ 2 Organometallic complexes with pyrazine skeletons such as iridium(III) (abbreviation: [Ir(dmdppr-m5CP)2(dpm)]) and tris(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C 2’ ) Iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]), bis[4,6-dimethyl-2-(2-quinolinyl-κN)phenyl-κC](2,4-pentanedionato-κ 2 Examples of such complexes include organometallic complexes with a pyridine skeleton, such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: [PtOEP]), and rare earth metal complexes, such as tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]) and tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]).

[0147] As the organic compound (host material, assist material, etc.) used in the light-emitting layer, one or more substances having an energy gap larger than the energy gap of the light-emitting substance can be selected and used.

[0148] As the organic compound used in combination with the fluorescent substance, it is preferable to use an organic compound having a high energy level in the singlet excited state and a low energy level in the triplet excited state.

[0149] Although some of the examples overlap with the above specific examples, specific examples of organic compounds are shown below from the viewpoint of preferable combinations with luminescent substances (fluorescent substances, phosphorescent substances).

[0150] Examples of organic compounds that can be used in combination with a fluorescent substance include condensed polycyclic aromatic compounds such as anthracene derivatives, tetracene derivatives, phenanthrene derivatives, pyrene derivatives, chrysene derivatives, and dibenzo[g,p]chrysene derivatives.

[0151] Specific examples of organic compounds (host materials) used in combination with fluorescent substances include 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: DPCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN), 9,10-diphenylanthracene (abbreviation: DPAnth), N,N-diphenyl-9-[4-(10-phenyl- 9-Anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine (abbreviation: DPhPA), YGAPA, PCAPA, N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine (abbreviation: PCAPBA), N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchryse N,N,N',N',N'',N'',N''',N'''-Octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), 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), 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 9,9'-bianthryl (abbreviation: BANT), 9,9'-(stilbene-3,3'-diyl)diphenanthrene (abbreviation: DPNS), 9,9'-(stilbene-4,4'-diyl)diphenanthrene (abbreviation: DPNS2), 1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), 5,12-diphenyltetracene, 5,12-bis(biphenyl-2-yl)tetracene, 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), etc.

[0152] As the organic compound to be used in combination with the phosphorescent substance, an organic compound having a triplet excitation energy larger than the triplet excitation energy (energy difference between the ground state and the triplet excited state) of the light-emitting substance may be selected.

[0153] When multiple organic compounds (e.g., a first host material and a second host material (or assist material)) are used in combination with a light-emitting substance to form an exciplex, it is preferable to use these multiple organic compounds in combination with a phosphorescent light-emitting substance (particularly an organometallic complex).

[0154] With this structure, light emission using ExTET (Exciplex-Triplet Energy Transfer), which is an energy transfer from an exciplex to a light-emitting substance, can be efficiently obtained. As a combination of a plurality of organic compounds, it is preferable to use a compound that easily forms an exciplex, and it is particularly preferable to combine a compound that easily receives holes (hole transporting material) with a compound that easily receives electrons (electron transporting material). By selecting a combination that forms an exciplex that exhibits light emission that overlaps with the wavelength of the lowest energy absorption band of the light-emitting substance, energy transfer becomes smooth, and light emission can be efficiently obtained. As specific examples of the hole transporting material and the electron transporting material, the materials shown in this embodiment can be used. With this structure, high efficiency, low voltage operation, and long life of the light-emitting device can be simultaneously achieved.

[0155] As a combination of materials that form an exciplex, it is preferable that the HOMO level of the hole transporting material is equal to or higher than the HOMO level of the electron transporting material. It is preferable that the LUMO level (lowest unoccupied molecular orbital level) of the hole transporting material is equal to or higher than the LUMO level of the electron transporting material. 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) measurement.

[0156] The formation of an exciplex can be confirmed, for example, by comparing the emission spectrum of a hole transport material, the emission spectrum of an electron transport material, and the emission spectrum of a mixed film obtained by mixing these materials, and observing the phenomenon that the emission spectrum of the mixed film shifts to a longer wavelength side than the emission spectrum of each material (or has a new peak on the longer wavelength side). Alternatively, it can be confirmed by comparing the transient photoluminescence (PL) of a hole transport material, the transient PL of an electron transport material, and the transient PL of a mixed film obtained by mixing these materials, and observing the difference in transient response, such as the transient PL lifetime of the mixed film having a longer lifetime component than the transient PL lifetime of each material, or the proportion of delayed components becoming larger. In addition, the above-mentioned transient PL may be read as transient electroluminescence (EL). In other words, the formation of an exciplex can also be confirmed by comparing the transient EL of a hole transport material, the transient EL of an electron transport material, and the transient EL of a mixed film obtained by mixing these materials, and observing the difference in transient response.

[0157] Examples of organic compounds that can be used in combination with phosphorescent substances include aromatic amines (compounds having an aromatic amine skeleton), carbazole derivatives (compounds having a carbazole skeleton), dibenzothiophene derivatives (thiophene derivatives), dibenzofuran derivatives (furan derivatives), zinc- or aluminum-based metal complexes, oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, pyrimidine derivatives, triazine derivatives, pyridine derivatives, bipyridine derivatives, and phenanthroline derivatives.

[0158] Specific examples of organic compounds having a high hole transporting property, such as aromatic amines, carbazole derivatives, dibenzothiophene derivatives, and dibenzofuran derivatives, include the following substances.

[0159] Examples of the carbazole derivative include bicarbazole derivatives (for example, 3,3'-bicarbazole derivatives) and aromatic amines having a carbazolyl group.

[0160] Specific examples of bicarbazole derivatives (e.g., 3,3'-bicarbazole derivatives) include 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), 9,9'-bis(1,1'-biphenyl-4-yl)-3,3'-bi-9H-carbazole, 9,9'-bis(1,1'-biphenyl-3-yl)-3,3'-bi-9H-carbazole, 9-(1,1'-biphenyl-3-yl)-9'-(1,1'-biphenyl-4-yl)-9H,9'H-3,3'-bicarbazole (abbreviation: mBPCCBP), and 9-(2-naphthyl)-9'-phenyl-9H,9'H-3,3'-bicarbazole (abbreviation: βNCCP).

[0161] Specific examples of aromatic amines having a carbazolyl group include PCBA1BP, N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine (abbreviation: PCBiF), PCBBiF, PCBBi1BP, PCBANB, PCBNBB, 4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP), N,N'-bis(9-phenylcarbazol-3-yl)-N,N'-diphenylbenzene-1,3-diamine (abbreviation: P CA2B), N,N',N''-triphenyl-N,N',N''-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine (abbreviation: PCA3B), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), PCBASF, 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), PCBASF, 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzDPA2), 3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole N-(1-naphthyl)amino)-9-phenylcarbazole (abbreviation: PCzTPN2), 2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: PCASF), N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation: YGA1BP), N,N'-bis[4-(carbazol-9-yl)phenyl]-N,N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4',4''-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA) and the like.

[0162] In addition to the above, examples of carbazole derivatives include 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), PCPN, 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), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), CzPA, and the like.

[0163] Specific examples of thiophene derivatives (compounds having a thiophene skeleton) and furan derivatives (compounds having a furan skeleton) include compounds having a thiophene skeleton such as 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-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 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II).

[0164] Specific examples of aromatic amines include 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD), 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), BPAFLP, mBPAFLP, N-(9,9-dimethyl-9H-fluorene -2-yl)-N-{9,9-dimethyl-2-[N'-phenyl-N'-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine (abbreviation: DFLADFL), N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine (abbreviation: DPNF), 2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9'-bifluorene (abbreviation: DPASF), 4,4',4''-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation: 1'-TNATA), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: m-MTDATA), N,N'-di(p-to Examples of such amines include 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).

[0165] As organic compounds with high hole-transporting properties, polymer compounds such as poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide] (abbreviation: PTPDMA), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (abbreviation: Poly-TPD) can also be used.

[0166] Specific examples of zinc- or aluminum-based metal complexes, which are organic compounds with high electron transport properties, include metal complexes having a quinoline skeleton or a benzoquinoline skeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation: Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation: Znq).

[0167] In addition, metal complexes having oxazole or thiazole ligands, such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO) and bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ), can also be used.

[0168] Specific examples of organic compounds with high electron transport properties, such as oxadiazole derivatives, triazole derivatives, benzimidazole derivatives, quinoxaline derivatives, dibenzoquinoxaline derivatives, and phenanthroline derivatives, include 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazole] -2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), 2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), 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), 4,4'-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), bathophenanthroline (abbreviation: Bphen), bathocuproine (abbreviation: BCP), 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBphen), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3'-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 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).

[0169] Specific examples of heterocyclic compounds having a diazine skeleton, a triazine skeleton, and a pyridine skeleton, which are organic compounds with high electron transport properties, include 4,6-bis[3-(phenanthren-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: 4,6mDBTP2Pm-II), and 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II). 4,6mCzP2Pm), 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 mFBPTzn), 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- Examples of such compounds include 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), 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy), and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB).

[0170] As organic compounds with high electron transport properties, polymer compounds such as poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)] (abbreviation: PF-Py), and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) can also be used.

[0171] A TADF material is a material that has a small difference between the S1 level (energy level of the singlet excited state) and the T1 level (energy level of the triplet excited state), and has the function of converting energy from triplet excitation energy to singlet excitation energy by reverse intersystem crossing. Therefore, triplet excitation energy can be upconverted to singlet excitation energy by a small amount of thermal energy (reverse intersystem crossing), and the singlet excited state can be efficiently generated. In addition, triplet excitation energy can be converted into light emission. Conditions for efficiently obtaining thermally activated delayed fluorescence include an energy difference between the S1 level and the T1 level of 0 eV or more and 0.2 eV or less, preferably 0 eV or more and 0.1 eV or less. In addition, delayed fluorescence in a TADF material refers to light emission that has a spectrum similar to that of normal fluorescence, but has a significantly long life. The life is about 10 -6 seconds or more, preferably 10 -3 More than seconds.

[0172] Excitplexes, which form excited states with two types of substances, have an extremely small difference between the S1 and T1 levels and function as TADF materials that can convert triplet excitation energy into singlet excitation energy.

[0173] As an index of the T1 level, a phosphorescence spectrum observed at low temperatures (for example, 77 K to 10 K) may be used. For a TADF material, when a tangent is drawn at the base of the short wavelength side of the fluorescence spectrum, and the energy of the wavelength of the extrapolated line is taken as the S1 level, and a tangent is drawn at the base of the short wavelength side of the phosphorescence spectrum, and the energy of the wavelength of the extrapolated line is taken 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.

[0174] The TADF material may be used as a guest material or as a host material.

[0175] Examples of TADF materials include fullerene and its derivatives, acridine derivatives such as proflavine, eosin, etc. Also included are metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), etc. Examples of metal-containing porphyrins include protoporphyrin-tin fluoride complex (abbreviation: SnF2(Proto IX)), mesoporphyrin-tin fluoride complex (abbreviation: SnF2(Meso IX)), hematoporphyrin-tin fluoride complex (abbreviation: SnF2(Hemato IX)), coproporphyrin tetramethyl ester-tin fluoride complex (abbreviation: SnF2(Copro III-4Me)), octaethylporphyrin-tin fluoride complex (abbreviation: SnF2(OEP)), etioporphyrin-tin fluoride complex (abbreviation: SnF2(Etio I)), and octaethylporphyrin-platinum chloride complex (abbreviation: PtCl2OEP).

[0176] Other examples include 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), PCCzPTzn, 2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 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), and bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DM AC-DPS), 10-phenyl-10H,10'H-spiro[acridine-9,9'-anthracene]-10'-one (abbreviation: ACRSA), 4-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl)benzofuro[3,2-d]pyrimidine (abbreviation: 4PCCzBfpm), 4-[4-(9'-phenyl-3,3'-bi-9H-carbazol-9-yl Heterocyclic compounds having a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, such as 4PCCzPBfpm (abbreviation), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9'-phenyl-2,3'-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), can be used. The heterocyclic compounds have a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring, and therefore have high electron transport and hole transport properties, which is preferable. Instead of the π-electron deficient heteroaromatic ring, an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used. Also, instead of the π-electron deficient heteroaromatic ring, a π-electron deficient skeleton can be used. Similarly, instead of the π-electron rich heteroaromatic ring, a π-electron rich skeleton can be used.

[0177] Among skeletons having a π-electron-deficient heteroaromatic ring, a pyridine skeleton, a diazine skeleton (pyrimidine skeleton, pyrazine skeleton, pyridazine skeleton), and a triazine skeleton are preferred because they are stable and have good reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferred because they have high electron-accepting properties and good reliability.

[0178] Among the skeletons having a π-electron-rich heteroaromatic ring, it is preferable to have at least one of the acridine skeleton, the phenoxazine skeleton, the phenothiazine skeleton, the furan skeleton, the thiophene skeleton, and the pyrrole skeleton, since they are stable and have good reliability. In particular, it is preferable to have a dibenzofuran skeleton, a dibenzothiophene skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton.

[0179] In addition, a substance in which a π-electron-rich heteroaromatic ring and a π-electron-deficient heteroaromatic ring are directly bonded to each other is particularly preferable because the donor property of the π-electron-rich heteroaromatic ring and the acceptor property of the π-electron-deficient heteroaromatic ring are both strong, and the energy difference between the singlet excited state and the triplet excited state is small.

[0180] Examples of the π-electron-rich skeleton include an aromatic amine skeleton, a phenazine skeleton, etc. Examples of the π-electron-deficient skeleton 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 or a heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, etc.

[0181] When a TADF material is used as a light-emitting substance, it can be used in combination with other organic compounds. In particular, it can be combined with the above-mentioned host materials (hole transporting materials, electron transporting materials). When a TADF material is used, it is preferable that the S1 level of the host material is higher than the S1 level of the TADF material. In addition, it is preferable that the T1 level of the host material is higher than the T1 level of the TADF material.

[0182] Also, a TADF material may be used as a host material, and a fluorescent material may be used as a guest material. When a TADF material is used as a host material, triplet excitation energy generated in the TADF material is converted to singlet excitation energy by reverse intersystem crossing, and the energy is further transferred to the light-emitting material, thereby improving the light-emitting efficiency of the light-emitting device. At this time, the TADF material functions as an energy donor, and the light-emitting material functions as an energy acceptor. Therefore, using a TADF material as a host material is very effective when using a fluorescent material as a guest material. At this time, in order to obtain high light-emitting efficiency, the S1 level of the TADF material is preferably higher than the S1 level of the fluorescent material. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent material. Therefore, the T1 level of the TADF material is preferably higher than the T1 level of the fluorescent material.

[0183] 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, because this allows for smooth transfer of excitation energy from the TADF material to the fluorescent material, resulting in efficient emission.

[0184] In addition, in order to efficiently generate singlet excitation energy from triplet excitation energy by reverse intersystem crossing, it is preferable that carrier recombination occurs in the TADF material. In addition, it is preferable that the triplet excitation energy generated in the TADF material does not transfer to the triplet excitation energy of the fluorescent material. For this purpose, it is preferable that the fluorescent material has a protective group around the luminophore (skeleton causing light emission) of the fluorescent material. As the protective group, a substituent having no π bond is preferable, and a saturated hydrocarbon is preferable, specifically, an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms are mentioned, and it is more preferable that there are a plurality of protective groups. Since a substituent having no π bond has poor function of transporting carriers, the distance between the TADF material and the luminophore of the fluorescent material can be increased without affecting carrier transport or carrier recombination. Here, the luminophore refers to an atomic group (skeleton) causing 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 condensed aromatic ring or a condensed heteroaromatic ring. Examples of the condensed aromatic ring or the condensed 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 they have a high fluorescence quantum yield.

[0185] <Electron transport layer> The electron transport layer 124 is a layer that transports the electrons injected from the cathode 102 to the light emitting layer 123 .

[0186] The electron transport layer 124 includes a third organic compound and the first substance.

[0187] The third organic compound is an electron transporting material that has a higher ability to transport electrons than holes.

[0188] The third organic compound preferably has a highest occupied molecular orbital level (HOMO level) of −6.0 eV or higher.

[0189] The third organic compound has an electron mobility of 1×10 at an electric field strength [V / cm] of 600. -7 cm 2 / Vs or more 1×10 -5 cm 2 / Vs or less, and 1×10 -7 cm 2 / Vs or more 5×10 -5 cm 2 It is more preferable that the Vs be equal to or less than / Vs.

[0190] It is preferable that the electron mobility of the third organic compound at a square root of the electric field strength [V / cm] of 600 is smaller than the electron mobility of the host material of the light-emitting layer 123 at a square root of the electric field strength [V / cm] of 600. By reducing the electron transportability in the electron-transport layer 124, the amount of electrons injected into the light-emitting layer 123 can be controlled, and the light-emitting layer 123 can be prevented from becoming an electron-excess state.

[0191] The third organic compound preferably has an anthracene skeleton, more preferably has an anthracene skeleton and a heterocyclic skeleton. The heterocyclic skeleton is preferably a nitrogen-containing five-membered ring skeleton. The nitrogen-containing five-membered ring skeleton is particularly preferably a nitrogen-containing five-membered ring skeleton containing two heteroatoms in the ring, such as a pyrazole ring, an imidazole ring, an oxazole ring, or a thiazole ring.

[0192] In addition, some of the electron transporting materials that can be used as the host material and the materials that can be used as the host material in combination with the fluorescent material can be used for the electron transporting layer 124 .

[0193] Examples of the third organic compound include 2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA).

[0194] In addition, as the third organic compound, an electron transporting material that can be used in the light-emitting layer, an organic compound (host material) that can be used in combination with a fluorescent light-emitting substance, and the like can be used.

[0195] The first substance is a metal, a metal salt, a metal oxide, or an organometallic salt.

[0196] The metals include alkali metals, alkaline earth metals, and rare earth metals, such as Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba.

[0197] Examples of metal salts include halides of the above metals and carbonates of the above metals, specifically LiF, NaF, KF, RbF, CsF, MgF2, CaF2, SrF2, BaF2, LiCl, NaCl, KCl, RbCl, CsCl, MgCl2, CaCl2, SrCl2, BaCl2, Li2CO3, Cs2CO3, etc.

[0198] Examples of metal oxides include oxides of the above metals, specifically Li2O, Na2O, Cs2O, MgO, CaO, etc.

[0199] The organometallic salts include, for example, organometallic complexes.

[0200] The first substance is preferably an organometallic complex having an alkali metal or alkaline earth metal.

[0201] The first substance is preferably an organometallic complex having a nitrogen- and oxygen-containing ligand and an alkali metal or alkaline earth metal.

[0202] The first substance is preferably an organometallic complex having a quinolinol ligand and an alkali metal or alkaline earth metal.

[0203] Examples of the organometallic complex include 8-(quinolinolato)lithium (abbreviation: Liq), 8-(quinolinolato)sodium (abbreviation: Naq), 8-(quinolinolato)potassium (abbreviation: Kq), (8-quinolinolato)magnesium (abbreviation: Mgq2), and (8-quinolinolato)zinc (abbreviation: Znq2).

[0204] As the first substance, Liq is particularly preferable.

[0205] 4C, the electron transport layer 124 may have an electron transport layer 124a on the light-emitting layer 123 side and an electron transport layer 124b on the cathode 102 side. The electron transport layer 124a and the electron transport layer 124b preferably have different concentration ratios of the third organic compound and the first substance. For example, the electron transport layer 124a preferably has a higher concentration of the first substance than the electron transport layer 124b.

[0206] <Electron injection layer> The electron injection layer 125 is a layer that increases the efficiency of electron injection from the cathode 102. It is preferable that the difference between the work function value of the material of the cathode 102 and the LUMO level value of the material used in the electron injection layer 125 is small (within 0.5 eV).

[0207] The electron injection layer 125 may include any of the following: lithium, cesium, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), 8-(quinolinolato)lithium (abbreviation: Liq), 2-(2-pyridyl)phenolatolithium (abbreviation: LiPP), 2-(2-pyridyl)-3-pyridinolatolithium (abbreviation: LiPPy), 4-phenyl-2-(2-pyridyl)phenolatolithium (abbreviation: LiPPP), lithium oxide (LiO x ), alkaline metals such as cesium carbonate, alkaline earth metals, or compounds thereof can be used. Rare earth metal compounds such as erbium fluoride (ErF3) can also be used. Electrides may also be used in the electron injection layer. Examples of electrides include substances in which electrons are highly concentrated in a mixed oxide of calcium and aluminum. The above-mentioned substances constituting the electron transport layer can also be used.

[0208] In addition, a composite material containing an electron transporting material and a donor material (electron donor material) may be used for the electron injection layer. Such a composite material has excellent electron injection and transport properties because electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material that is excellent in transporting the generated electrons, and specifically, for example, the above-mentioned electron transporting material (metal complex, heteroaromatic compound, etc.) can be used. As the electron donor, any substance that exhibits electron donating properties to the organic compound may be used. Specifically, alkali metals, alkaline earth metals, and rare earth metals are preferred, and examples thereof include lithium, cesium, magnesium, calcium, erbium, and ytterbium. In addition, alkali metal oxides and alkaline earth metal oxides are preferred, and examples thereof include lithium oxide, calcium oxide, and barium oxide. In addition, a Lewis base such as magnesium oxide can also be used. In addition, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can also be used.

[0209] In addition, a vacuum process such as a deposition method, or a solution process such as a spin coating method or an inkjet method can be used to manufacture the light-emitting device of one embodiment of the present invention. When a deposition method is used, a physical deposition method (PVD method) such as a sputtering method, an ion plating method, an ion beam deposition method, a molecular beam deposition method, or a vacuum deposition method, or a chemical deposition method (CVD method) can be used. In particular, the functional layers (hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer) included in the EL layer can be formed by a deposition method (vacuum deposition method, etc.), a coating method (dip coating method, die coating method, bar coating method, spin coating method, spray coating method, etc.), a printing method (inkjet method, screen (screen printing) method, offset (lithographic printing) method, flexo (relief printing) method, gravure method, microcontact method, etc.), or the like.

[0210] The materials of the functional layers constituting the light-emitting device are not limited to the above-mentioned materials. For example, the materials of the functional layers may be polymer compounds (oligomers, dendrimers, polymers, etc.), medium molecular compounds (compounds in the intermediate range between low molecular weight and high molecular weight: molecular weight 400 to 4000), inorganic compounds (quantum dot materials, etc.). As the quantum dot materials, colloidal quantum dot materials, alloy type quantum dot materials, core-shell type quantum dot materials, core type quantum dot materials, etc. may be used.

[0211] [Light-emitting model for light-emitting devices] A light emission model in a light emitting device that can be used in the display device of this embodiment will be described.

[0212] Here, a light emission model of a light emitting device will be described using the hole transport layer 122, the light emitting layer 123, and the electron transport layer 124 shown in Fig. 4A. The light emitting device is not limited to the configuration shown in Fig. 4A, and the light emission model can be applied to other configurations.

[0213] When the light-emitting layer 123 becomes in an electron excess state, as shown in FIG. 5A, a light-emitting region 123-1 is formed in a localized region in the light-emitting layer 123. In other words, the width of the light-emitting region 123-1 in the light-emitting layer 123 is narrow. Therefore, electrons (e - ) and Hall (h + ) and accelerates deterioration. Furthermore, electrons that cannot recombine in the light-emitting layer 123 pass through the light-emitting layer 123, which may reduce the lifetime or light-emitting efficiency.

[0214] On the other hand, in the light-emitting device of one embodiment of the present invention, the width of the light-emitting region 123-1 in the light-emitting layer 123 can be increased by reducing the electron-transport property in the electron-transport layer 124 (FIGS. 5B and 5C). By increasing the width of the light-emitting region 123-1, the recombination region of electrons and holes in the light-emitting layer 123 can be dispersed. Thus, a light-emitting device with a long lifetime and high light-emitting efficiency can be provided.

[0215] As shown in Fig. 5B, in the light-emitting device according to one embodiment of the present invention, the recombination region may extend to the electron transport layer 124 side in the early stage of driving. In Fig. 5B, the recombination region in the electron transport layer 124 is shown as region 124-1. Specifically, in the light-emitting device according to one embodiment of the present invention, the hole injection barrier is small in the early stage of driving and the electron transport property of the electron transport layer 124 is relatively low, so that the light-emitting region 123-1 (i.e., the recombination region) is formed throughout the light-emitting layer 123, and a recombination region may also be formed in the electron transport layer 124.

[0216] In addition, since the HOMO level of the third organic compound contained in the electron transport layer 124 is relatively high at −6.0 eV or higher, some of the holes may reach the electron transport layer 124 and recombine in the electron transport layer 124. This phenomenon may also occur when the difference in HOMO level between the host material (or assist material) contained in the light-emitting layer 123 and the third organic compound is within 0.2 eV.

[0217] As shown in FIG. 5C, in the light-emitting device according to one embodiment of the present invention, as the driving time passes, the carrier balance changes, and recombination in the electron transport layer 124 is less likely to occur. By suppressing recombination in the electron transport layer 124 while the light-emitting region 123-1 is formed over the entire light-emitting layer 123, the energy of the recombined carriers can be effectively contributed to light emission. Therefore, the luminance can be increased compared to the initial driving stage. This increase in luminance offsets the rapid decrease in luminance that occurs in the initial driving stage of the light-emitting device, that is, the so-called initial deterioration, and thus a light-emitting device with small initial deterioration and long driving life can be provided. In this specification and the like, the above-mentioned light-emitting device may be referred to as a Recombination-Site Tailoring Injection structure (ReSTI structure).

[0218] Here, the normalized luminance over time in the light-emitting device of the present embodiment and the comparative light-emitting device will be described with reference to Fig. 5D. In Fig. 5D, the thick solid line and the thick dashed line are the degradation curves of the normalized luminance of the light-emitting device of the present embodiment, and the thick dashed line is the degradation curve of the normalized luminance of the comparative light-emitting device.

[0219] 5D, the light emitting device of the present embodiment and the comparative light emitting device have different slopes of the degradation curves of normalized luminance. Specifically, the slope θ2 of the degradation curve of the light emitting device of the present embodiment is smaller than the slope θ1 of the degradation curve of the comparative light emitting device.

[0220] As shown in FIG. 5D, the light-emitting device according to one embodiment of the present invention may have a maximum value in a luminance deterioration curve obtained by a drive test under a constant current density condition (thick solid line). That is, the light-emitting device according to one embodiment of the present invention may exhibit a behavior in which the luminance increases with time. This behavior can offset the rapid deterioration at the beginning of drive (so-called initial deterioration). However, the light-emitting device according to one embodiment of the present invention is not limited to the above, and may, for example, not have a maximum value of luminance, in other words, the slope of the deterioration curve can be made small without causing an increase in luminance, as shown by the thick dashed line in FIG. 5D. Therefore, by configuring the light-emitting device to exhibit this behavior, the initial deterioration of the light-emitting device can be reduced and the drive life can be made very long.

[0221] Note that when the degradation curve having a maximum value is differentiated, there is a portion where the value is 0. Therefore, a light-emitting device having a portion where the differential of the degradation curve is 0 can be rephrased as a light-emitting device according to one embodiment of the present invention.

[0222] In the light-emitting device according to one embodiment of the present invention, the electron-transporting layer 124 preferably has a portion in which the mixture ratio (concentration) of the third organic compound and the first substance is different in the thickness direction. Specifically, it preferably has a portion in which the mixture ratio (concentration) of the electron-transporting material and the metal, metal salt, metal oxide, or organometallic salt is different.

[0223] The concentration of the first substance in the electron transport layer 124 can be estimated from the amount of atoms or molecules detected by time-of-flight secondary ion mass spectrometry (ToF-SIMS). In a portion composed of the same two types of materials but with different mixing ratios, the magnitude of the values ​​detected by ToF-SIMS analysis corresponds to the amount of the atoms or molecules of interest present. Therefore, by comparing the detected amounts of the electron transport material and the organometallic complex, the magnitude of the mixing ratio can be estimated.

[0224] The content of the first substance in the electron transport layer 124 is preferably lower on the cathode 102 side than on the anode 101 side. In other words, the electron transport layer 124 is preferably formed so that the concentration of the first substance increases from the cathode 102 side toward the anode 101 side. In other words, the electron transport layer 124 has a portion where the concentration of the third organic compound is lower on the light-emitting layer 123 side than on the portion where the concentration of the third organic compound is higher. In other words, the electron transport layer 124 has a portion where the concentration of the first substance is higher on the light-emitting layer 123 side than on the portion where the concentration of the first substance is lower.

[0225] In the electron transport layer 124, the electron mobility in the portion where the concentration of the third organic compound is high (the portion where the concentration of the first substance is low) is 1×10 -7 cm 2 / Vs or more 5×10 -5 cm 2 It is preferable that the value is equal to or less than / Vs.

[0226] For example, the content (concentration) of the first substance in the electron transport layer 124 can be configured as shown in Figures 6A to 6D. Figures 6A and 6B show a case where there is no clear boundary in the electron transport layer 124, and Figures 6C and 6D show a case where there is a clear boundary in the electron transport layer 124.

[0227] When there is no clear boundary in the electron transport layer 124, the concentrations of the third organic compound and the first substance change continuously as shown in FIG. 6A and FIG. 6B. When there is a clear boundary in the electron transport layer 124, the concentrations of the third organic compound and the first substance change stepwise as shown in FIG. 6C and FIG. 6D. When the concentrations of the third organic compound and the first substance change stepwise, it is suggested that the electron transport layer 124 is composed of multiple layers. For example, FIG. 6C shows a case where the electron transport layer 124 has a two-layer stacked structure, and FIG. 6D shows a case where the electron transport layer 124 has a three-layer stacked structure. In FIG. 6C and FIG. 6D, the dashed lines show the boundary regions of multiple layers.

[0228] The change in carrier balance in the light-emitting device according to one embodiment of the present invention is believed to be brought about by a change in the electron mobility of the electron transport layer 124 .

[0229] In the light-emitting device of one embodiment of the present invention, a concentration difference of the first substance exists inside the electron-transport layer 124. The electron-transport layer 124 has a region where the concentration of the first substance is high between a region where the concentration of the first substance is low and the light-emitting layer 123. That is, the region where the concentration of the first substance is low is located closer to the cathode 102 than the region where the concentration of the first substance is high.

[0230] The light-emitting device according to one embodiment of the present invention having the above-described structure has a very long lifetime. In particular, when the initial luminance is set to 100%, the time until the luminance reaches 95% (also referred to as LT95) can be made extremely long.

[0231] A more detailed configuration of the display device according to one embodiment of the present invention will be described below with reference to FIGS.

[0232] [Display device 100A] FIG. 7 shows a perspective view of the display device 100A, and FIG. 8A shows a cross-sectional view of the display device 100A.

[0233] The display device 100A has a configuration in which a substrate 152 and a substrate 151 are bonded together. In Fig. 7, the substrate 152 is indicated by a dashed line.

[0234] The display device 100A has a display unit 162, a circuit 164, wiring 165, etc. Fig. 7 shows an example in which an IC (integrated circuit) 173 and an FPC 172 are mounted on the display device 100A. Therefore, the configuration shown in Fig. 7 can also be said to be a display module having the display device 100A, an IC, and an FPC.

[0235] The circuit 164 can be, for example, a scanning line driver circuit.

[0236] The wiring 165 has a function of supplying signals and power to the display portion 162 and the circuit 164. The signals and power are input to the wiring 165 from the outside via the FPC 172 or from the IC 173.

[0237] 7 shows an example in which an IC 173 is provided on a substrate 151 by a chip on glass (COG) method or a chip on film (COF) method. For example, an IC having a scanning line driving circuit or a signal line driving circuit can be used as the IC 173. Note that the display device 100A and the display module may be configured without an IC. Also, the IC may be mounted on an FPC by a COF method or the like.

[0238] FIG. 8A shows an example of a cross section of display device 100A, in which a part of a region including FPC 172, a part of circuit 164, a part of display unit 162, and a part of a region including an end portion are cut away.

[0239] A display device 100A shown in FIG. 8A includes a transistor 201, a transistor 205, a light emitting device 190R, a light emitting device 190G, and a light emitting device 190B between a substrate 151 and a substrate 152. The display device 100A shown in FIG.

[0240] The protective layer 195 and the substrate 152 are bonded via an adhesive layer 142. A solid sealing structure, a hollow sealing structure, or the like can be applied to seal the light emitting device 190. In FIG. 8A, a space 143 surrounded by the substrate 152, the adhesive layer 142, and the substrate 151 is filled with an inert gas (such as nitrogen or argon), and a hollow sealing structure is applied. The adhesive layer 142 may be provided overlapping the light emitting device 190. In addition, the space 143 surrounded by the substrate 152, the adhesive layer 142, and the substrate 151 may be filled with a resin different from the adhesive layer 142.

[0241] The light-emitting device 190R has a layered structure in which the pixel electrode 191, the optical adjustment layer 199R, the common layer 112, the light-emitting layer 193R, the common layer 114, and the common electrode 115 are layered in this order from the insulating layer 214 side. Similarly, the light-emitting device 190G has a layered structure in which the pixel electrode 191, the optical adjustment layer 199G, the common layer 112, the light-emitting layer 193G, the common layer 114, and the common electrode 115 are layered in this order from the insulating layer 214 side. The light-emitting device 190B has a layered structure in which the pixel electrode 191, the optical adjustment layer 199B, the common layer 112, the light-emitting layer 193B, the common layer 114, and the common electrode 115 are layered in this order from the insulating layer 214 side.

[0242] The pixel electrode 191 is connected to a conductive layer 222 b of the transistor 205 through an opening provided in the insulating layer 214 .

[0243] The edge of the pixel electrode 191 is covered with a partition wall 216. The pixel electrode 191 includes a material that reflects visible light, and the common electrode 115 includes a material that transmits visible light.

[0244] Light emitted from the light emitting device 190 is emitted towards the substrate 152. The substrate 152 is preferably made of a material that is highly transparent to visible light.

[0245] Both the transistor 201 and the transistor 205 are formed over a substrate 151. These transistors can be manufactured using the same material and through the same process.

[0246] An insulating layer 211, an insulating layer 213, an insulating layer 215, and an insulating layer 214 are provided over the substrate 151 in this order. A part of the insulating layer 211 functions as a gate insulating layer for each transistor. A part of the insulating layer 213 functions as a gate insulating layer for each transistor. The insulating layer 215 is provided to cover the transistors. The insulating layer 214 is provided to cover the transistors and functions as a planarizing layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited, and each may be a single layer or two or more layers.

[0247] It is preferable that at least one of the insulating layers covering the transistors is made of a material that is difficult for impurities such as water and hydrogen to diffuse into. This allows the insulating layer to function as a barrier layer. With this structure, it is possible to effectively prevent impurities from diffusing into the transistors from the outside, thereby improving the reliability of the display device.

[0248] It is preferable to use an inorganic insulating film for each of the insulating layers 211, 213, and 215. As the inorganic insulating film, for example, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, an aluminum nitride film, or the like can be used. In addition, a hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. In addition, two or more of the above insulating films may be stacked.

[0249] Here, the organic insulating film often has a lower barrier property than the inorganic insulating film. Therefore, it is preferable that the organic insulating film has an opening near the end of the display device 100A. This makes it possible to suppress impurities from entering through the organic insulating film from the end of the display device 100A. Alternatively, the organic insulating film may be formed so that the end of the organic insulating film is located inside the end of the display device 100A, so that the organic insulating film is not exposed at the end of the display device 100A.

[0250] An organic insulating film is suitable for the insulating layer 214 that functions as a planarizing layer. Materials that can be used for the organic insulating film include acrylic resin, polyimide resin, epoxy resin, polyamide resin, polyimideamide resin, siloxane resin, benzocyclobutene resin, phenol resin, and precursors of these resins.

[0251] 8A, an opening is formed in insulating layer 214. This makes it possible to prevent impurities from entering display unit 162 from the outside through insulating layer 214, even when an organic insulating film is used for insulating layer 214. This makes it possible to improve the reliability of display device 100A.

[0252] The transistor 201 and the transistor 205 each have a conductive layer 221 functioning as a gate, an insulating layer 211 functioning as a gate insulating layer, a conductive layer 222a and a conductive layer 222b functioning as a source and a drain, a semiconductor layer 231, an insulating layer 213 functioning as a gate insulating layer, and a conductive layer 223 functioning as a gate. Here, the same hatched pattern is applied to a plurality of layers obtained by processing the same conductive film. The insulating layer 211 is located between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is located between the conductive layer 223 and the semiconductor layer 231.

[0253] The structure of the transistor included in the light-emitting device of this embodiment is not particularly limited. For example, a planar transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. In addition, either a top-gate type or a bottom-gate type transistor structure may be used. Alternatively, gates may be provided above and below a semiconductor layer in which a channel is formed.

[0254] The transistor 201 and the transistor 205 have a structure in which a semiconductor layer in which a channel is formed is sandwiched between two gates. The two gates may be connected and the same signal may be supplied to drive the transistor. Alternatively, the threshold voltage of the transistor may be controlled by supplying a potential for controlling the threshold voltage to one of the two gates and a potential for driving to the other.

[0255] The crystallinity of a semiconductor material used in 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 partially having a crystalline region) may be used. The use of a crystalline semiconductor is preferable because it can suppress deterioration of transistor characteristics.

[0256] The semiconductor layer of the transistor preferably contains metal oxide (also referred to as an oxide semiconductor). That is, the display device of this embodiment preferably contains a transistor in which a channel formation region is formed using metal oxide (hereinafter, referred to as an OS transistor). Alternatively, the semiconductor layer of the transistor may contain silicon. Examples of silicon include amorphous silicon, crystalline silicon (low-temperature polysilicon, single crystal silicon, and the like).

[0257] The semiconductor layer preferably contains, for example, indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc. In particular, M is preferably one or more selected from aluminum, gallium, yttrium, and tin.

[0258] In particular, it is preferable to use an oxide containing indium (In), gallium (Ga), and zinc (Zn) (also referred to as IGZO) as the semiconductor layer.

[0259] When the semiconductor layer is an In-M-Zn oxide, the atomic ratio of In in the In-M-Zn oxide is preferably equal to or greater than the atomic ratio of M. Examples of atomic ratios of metal elements in such In-M-Zn oxides include In:M:Zn=1:1:1 or a composition thereabout, In:M:Zn=1:1:1.2 or a composition thereabout, In:M:Zn=2:1:3 or a composition thereabout, In:M:Zn=3:1:2 or a composition thereabout, In:M:Zn=4:2:3 or a composition thereabout, In:M:Zn=4:2:4.1 or a composition thereabout, In:M:Zn=5:1:3 or a composition thereabout, In:M:Zn=5:1:6 or a composition thereabout, In:M:Zn=5:1:7 or a composition thereabout, In:M:Zn=5:1:8 or a composition thereabout, In:M:Zn=6:1:6 or a composition thereabout, In:M:Zn=5:2:5 or a composition thereabout, etc. The term "nearby composition" includes a range of ±30% of the desired atomic ratio.

[0260] For example, when describing a composition with an atomic ratio of In:Ga:Zn=4:2:3 or thereabout, it includes the case where, when the atomic ratio of In is 4, the atomic ratio of Ga is 1 or more and 3 or less, and the atomic ratio of Zn is 2 or more and 4 or less. Furthermore, when describing a composition with an atomic ratio of In:Ga:Zn=5:1:6 or thereabout, it includes the case where, when the atomic ratio of In is 5, the atomic ratio of Ga is more than 0.1 and 2 or less, and the atomic ratio of Zn is 5 or more and 7 or less. Furthermore, when describing a composition with an atomic ratio of In:Ga:Zn=1:1:1 or thereabout, it includes the case where, when the atomic ratio of In is 1, the atomic ratio of Ga is more than 0.1 and 2 or less, and the atomic ratio of Zn is more than 0.1 and 2 or less.

[0261] The transistors included in the circuit 164 and the transistors included in the display portion 162 may have the same structure or different structures. The transistors included in the circuit 164 may all have the same structure or may have two or more types. Similarly, the transistors included in the display portion 162 may all have the same structure or may have two or more types.

[0262] A connection portion 204 is provided in an area of ​​the substrate 151 where the substrate 152 does not overlap. In the connection portion 204, the wiring 165 is electrically connected to the FPC 172 via a conductive layer 166 and a connection layer 242. The conductive layer 166 is an example of a laminated structure of a conductive film obtained by processing the same conductive film as the pixel electrode 191 and a conductive film obtained by processing the same conductive film as the optical adjustment layer. On the upper surface of the connection portion 204, the conductive layer 166 is exposed. This allows the connection portion 204 and the FPC 172 to be electrically connected via the connection layer 242.

[0263] It is preferable to provide a light-shielding layer BM on the surface of the substrate 152 facing the substrate 151. In addition, various optical members can be arranged on the outside of the substrate 152. Examples of the optical members include a polarizing plate, a retardation plate, a light diffusion layer (such as a diffusion film), an anti-reflection layer, and a light collecting film. In addition, an antistatic film that suppresses adhesion of dust, a water-repellent film that makes it difficult for dirt to adhere, a hard coat film that suppresses the occurrence of scratches due to use, an impact absorbing layer, etc. may be arranged on the outside of the substrate 152.

[0264] By providing the protective layer 195 covering the light emitting device 190, it is possible to prevent impurities such as water from entering the light emitting device 190, and thus the reliability of the light emitting device 190 can be improved.

[0265] In a region 228 near the end of the display device 100A, it is preferable that the insulating layer 215 and the protective layer 195 contact each other through the opening in the insulating layer 214. In particular, it is preferable that the inorganic insulating film of the insulating layer 215 and the inorganic insulating film of the protective layer 195 contact each other. This makes it possible to prevent impurities from entering the display unit 162 from the outside through the organic insulating film. Therefore, it is possible to improve the reliability of the display device 100A.

[0266] 8B shows an example of a three-layer structure of protective layer 195. In Fig. 8B, protective layer 195 has an inorganic insulating layer 195a on common electrode 115, an organic insulating layer 195b on inorganic insulating layer 195a, and an inorganic insulating layer 195c on organic insulating layer 195b.

[0267] The end of the inorganic insulating layer 195a and the end of the inorganic insulating layer 195c extend outward beyond the end of the organic insulating layer 195b and are in contact with each other. The inorganic insulating layer 195a is in contact with the insulating layer 215 (inorganic insulating layer) through an opening in the insulating layer 214 (organic insulating layer). This allows the insulating layer 215 and the protective layer 195 to surround the light emitting device 190, thereby improving the reliability of the light emitting device 190.

[0268] In this way, the protective layer 195 may have a laminated structure of an organic insulating film and an inorganic insulating film. In this case, it is preferable that the end of the inorganic insulating film extends further outward than the end of the organic insulating film.

[0269] The substrate 151 and the substrate 152 can each be made of glass, quartz, ceramic, sapphire, resin, etc. When the substrate 151 and the substrate 152 are made of a flexible material, the flexibility of the display device can be increased.

[0270] As the adhesive layer, various curing adhesives such as a photo-curing adhesive such as an ultraviolet curing adhesive, a reaction curing adhesive, a heat curing adhesive, and an anaerobic adhesive can be used. Examples of such adhesives include epoxy resin, acrylic resin, silicone resin, phenolic resin, polyimide resin, imide resin, PVC (polyvinyl chloride) resin, PVB (polyvinyl butyral) resin, and EVA (ethylene vinyl acetate) resin. In particular, a material with low moisture permeability such as epoxy resin is preferable. A two-liquid mixed resin may also be used. An adhesive sheet or the like may also be used.

[0271] The connection layer 242 may be made of an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like.

[0272] The light emitting device 190 may be of a top emission type, a bottom emission type, a dual emission type, etc. A conductive film that transmits visible light is used for the electrode on the side from which light is extracted. It is preferable to use a conductive film that reflects visible light for the electrode on the side from which light is not extracted.

[0273] The light-emitting device 190 has at least a light-emitting layer 193. The light-emitting device 190 may further have a layer containing a substance with high hole injection properties, a substance with high hole transport properties, a hole blocking material, a substance with high electron transport properties, a substance with high electron injection properties, or a bipolar substance (a substance with high electron transport properties and hole transport properties) as a layer other than the light-emitting layer 193. For example, the common layer 112 preferably has one or both of a hole injection layer and a hole transport layer. For example, the common layer 114 preferably has one or both of an electron transport layer and an electron injection layer.

[0274] The preferred configuration of the light emitting device 190 is as described above (FIGS. 4 to 6).

[0275] Either a low molecular weight compound or a high molecular weight compound may be used for the common layer 112, the light emitting layer 193, and the common layer 114, and may contain an inorganic compound. The layers constituting the common layer 112, the light emitting layer 193, and the common layer 114 can be formed by a deposition method (including a vacuum deposition method), a transfer method, a printing method, an inkjet method, a coating method, or the like.

[0276] The light-emitting layer 193 is a layer containing a light-emitting substance. The light-emitting layer 193 can contain one or more types of light-emitting substances. As the light-emitting substance, a substance that emits light of a color such as blue, purple, blue-purple, green, yellow-green, yellow, orange, or red is appropriately used.

[0277] Materials that can be used for the gate, source, and drain of a transistor as well as conductive layers such as various wirings and electrodes that constitute a display device include metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten, as well as alloys containing such metals as main components, etc. Films containing these materials can be used as a single layer or a laminated structure.

[0278] As the conductive material having light transmitting properties, conductive oxides such as indium oxide, indium tin oxide, indium zinc oxide, zinc oxide, zinc oxide containing gallium, or graphene can be used. Alternatively, metal materials such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, and titanium, or alloy materials containing the metal materials can be used. Alternatively, nitrides of the metal materials (for example, titanium nitride) may be used. Note that when using metal materials or alloy materials (or their nitrides), it is preferable to make them thin enough to have light transmitting properties. Also, a laminated film of the above materials can be used as the conductive layer. For example, it is preferable to use a laminated film of an alloy of silver and magnesium and indium tin oxide, because the conductivity can be increased. These can also be used for conductive layers such as various wirings and electrodes constituting a display device, and conductive layers (conductive layers functioning as pixel electrodes or common electrodes) of a light-emitting device.

[0279] Examples of insulating materials that can be used for each insulating layer include resins such as acrylic resin and epoxy resin, and inorganic insulating materials such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminum oxide.

[0280] [Display device 100B] 9A shows a cross-sectional view of the display device 100B. The perspective view of the display device 100B is similar to that of the display device 100A (FIG. 7). FIG. 9A shows an example of a cross-section of the display device 100B when a part of a region including the FPC 172, a part of the circuit 164, and a part of the display unit 162 are cut. FIG. 9A shows an example of a cross-section of the display unit 162 when a region including the light emitting device 190G that emits green light and the light emitting device 190B that emits blue light is cut.

[0281] A display device 100B shown in FIG. 9A includes a transistor 202, a transistor 210, a light emitting device 190G, and a light emitting device 190B between a substrate 153 and a substrate 154. The display device 100B shown in FIG.

[0282] The substrate 154 and the protective layer 195 are bonded to each other via an adhesive layer 142. The adhesive layer 142 is provided so as to overlap the light emitting device 190G and the light emitting device 190B, and a solid sealing structure is applied to the display device 100B.

[0283] The substrate 153 and the insulating layer 212 are bonded together by an adhesive layer 155 .

[0284] The display device 100B is manufactured by first bonding a manufacturing substrate provided with the insulating layer 212, the transistors, the light-emitting devices, etc., to a substrate 154 provided with a light-shielding layer BM with an adhesive layer 142. The manufacturing substrate is then peeled off and a substrate 153 is attached to the exposed surface, so that each component formed on the manufacturing substrate is transferred to the substrate 153. It is preferable that the substrate 153 and the substrate 154 each have flexibility. This can increase the flexibility of the display device 100B.

[0285] The insulating layer 212 can be formed using any of the inorganic insulating films that can be used for the insulating layers 211, 213, and 215, respectively.

[0286] The light-emitting device 190G has a layered structure in which the pixel electrode 191, the common layer 112, the light-emitting layer 193G, the common layer 114, and the common electrode 115 are layered in this order from the insulating layer 214 side. Similarly, the light-emitting device 190B has a layered structure in which the pixel electrode 191, the common layer 112, the light-emitting layer 193B, the common layer 114, and the common electrode 115 are layered in this order from the insulating layer 214 side.

[0287] The pixel electrode 191 is connected to a conductive layer 222b of the transistor 210 through an opening provided in the insulating layer 214. The conductive layer 222b is connected to a low-resistance region 231n through openings provided in the insulating layers 215 and 225. The transistor 210 has a function of controlling driving of the light-emitting device 190.

[0288] The edge of the pixel electrode 191 is covered with a partition wall 216. The pixel electrode 191 includes a material that reflects visible light, and the common electrode 115 includes a material that transmits visible light.

[0289] Light emitted from light emitting device 190G and light emitting device 190B is emitted toward substrate 154. Substrate 154 is preferably made of a material that is highly transparent to visible light.

[0290] The pixel electrodes 191 of each light-emitting device can be manufactured using the same material and in the same process. The common layer 112, the common layer 114, and the common electrode 115 are used in common between the light-emitting device 190G and the light-emitting device 190B. The light-emitting devices of each color can have a common configuration except for the configuration of the light-emitting layer 193.

[0291] A connection portion 204 is provided in an area of ​​the substrate 153 where the substrate 154 does not overlap. In the connection portion 204, the wiring 165 is electrically connected to the FPC 172 via a conductive layer 166 and a connection layer 242. The conductive layer 166 can be obtained by processing the same conductive film as the pixel electrode 191. This allows the connection portion 204 and the FPC 172 to be electrically connected to each other via the connection layer 242.

[0292] The transistor 202 and the transistor 210 each include a conductive layer 221 functioning as a gate, an insulating layer 211 functioning as a gate insulating layer, a semiconductor layer having a channel formation region 231i and a pair of low-resistance regions 231n, a conductive layer 222a connected to one of the pair of low-resistance regions 231n, a conductive layer 222b connected to the other of the pair of low-resistance regions 231n, an insulating layer 225 functioning as a gate insulating layer, a conductive layer 223 functioning as a gate, and an insulating layer 215 covering the conductive layer 223. The insulating layer 211 is located between the conductive layer 221 and the channel formation region 231i. The insulating layer 225 is located between the conductive layer 223 and the channel formation region 231i.

[0293] The conductive layer 222a and the conductive layer 222b are each connected to the low-resistance region 231n through an opening provided in the insulating layer 215. One of the conductive layer 222a and the conductive layer 222b functions as a source, and the other functions as a drain.

[0294] 9A shows an example in which the insulating layer 225 covers the top surface and side surfaces of the semiconductor layer. The conductive layer 222a and the conductive layer 222b are connected to the low resistance region 231n through openings provided in the insulating layer 225 and the insulating layer 215, respectively.

[0295] On the other hand, in FIG. 9B, the insulating layer 225 overlaps with the channel formation region 231i of the semiconductor layer 231, but does not overlap with the low-resistance region 231n. For example, the insulating layer 225 is processed using the conductive layer 223 as a mask, so that the structure shown in FIG. 9B can be manufactured. In FIG. 9B, the insulating layer 215 is provided to cover the insulating layer 225 and the conductive layer 223, and the conductive layer 222a and the conductive layer 222b are each connected to the low-resistance region 231n through an opening in the insulating layer 215. Furthermore, an insulating layer 218 may be provided to cover the transistor.

[0296] As described above, by using a light emitting device in which initial deterioration is suppressed and which has a very long operating life, the reliability of the light emitting apparatus can be improved.

[0297] This embodiment mode can be combined with other embodiment modes as appropriate. In addition, in the case where a plurality of configuration examples are shown in one embodiment mode in this specification, the configuration examples can be combined as appropriate.

[0298] (Embodiment 2) In this embodiment, a display device of one embodiment of the present invention will be described with reference to FIGS.

[0299] A block diagram of a pixel is shown in Fig. 10A. The pixel shown in Fig. 10A has a memory in addition to a switching transistor (Switching Tr), a driving transistor (Driving Tr), and a light-emitting device (OLED).

[0300] The memory is supplied with data Data_W. By supplying the data Data_W to the pixel in addition to the display data Data, the current flowing through the light emitting device increases, and the display device can express high luminance.

[0301] When a light-emitting device included in the display device of one embodiment of the present invention is driven based on the display data Data and the data Data_W, the light-emitting device can emit light with high luminance.

[0302] FIG. 10B shows a specific circuit diagram of the pixel circuit.

[0303] The pixel shown in FIG. 10B includes a transistor M1, a transistor M2, a transistor M3, a transistor M4, a capacitance Cs, a capacitance Cw, and a light-emitting device EL.

[0304] One of the source or drain of the transistor M1 is electrically connected to one electrode of the capacitance Cw. The other electrode of the capacitance Cw is electrically connected to one of the source or drain of the transistor M4. One of the source or drain of the transistor M4 is electrically connected to the gate of the transistor M2. The gate of the transistor M2 is electrically connected to one electrode of the capacitance Cs. The other electrode of the capacitance Cs is electrically connected to one of the source or drain of the transistor M2. One of the source or drain of the transistor M2 is electrically connected to one of the source or drain of the transistor M3. One of the source or drain of the transistor M3 is electrically connected to one electrode of the light-emitting device EL. Each transistor shown in FIG. 10B has a backgate electrically connected to the gate, but the connection of the backgate is not limited to this. In addition, the transistor does not need to have a backgate.

[0305] Here, a node NM is defined as a node to which the other electrode of the capacitance Cw, one of the source or drain of the transistor M4, the gate of the transistor M2, and one electrode of the capacitance Cs are connected, and a node NA is defined as a node to which the other electrode of the capacitance Cs, one of the source or drain of the transistor M2, one of the source or drain of the transistor M3, and one electrode of the light-emitting device EL are connected.

[0306] The gate of the transistor M1 is electrically connected to the wiring G1. The gate of the transistor M3 is electrically connected to the wiring G1. The gate of the transistor M4 is electrically connected to the wiring G2. The other of the source and the drain of the transistor M1 is electrically connected to the wiring DATA. The other of the source and the drain of the transistor M3 is electrically connected to the wiring V0. The other of the source and the drain of the transistor M4 is electrically connected to the wiring DATA_W.

[0307] The other of the source and drain of the transistor M2 is electrically connected to a wiring ANODE (high potential side). The other electrode of the light emitting device EL is electrically connected to a wiring CATHODE (low potential side).

[0308] The wiring G1 and the wiring G2 can function as signal lines for controlling the operation of the transistors. The wiring DATA can function as a signal line for supplying an image signal to the pixel. The wiring DATA_W can function as a signal line for writing data to the memory circuit MEM. The wiring DATA_W can function as a signal line for supplying a correction signal to the pixel. The wiring V0 can function as a monitor line for acquiring the electrical characteristics of the transistor M4. In addition, the writing of the image signal can be stabilized by supplying a specific potential from the wiring V0 to the other electrode of the capacitance Cs via the transistor M3.

[0309] The transistor M2, the transistor M4, and the capacitor Cw constitute a memory circuit MEM. The node NM is a memory node, and a signal supplied to the wiring DATA_W can be written to the node NM by turning on the transistor M4. By using a transistor with an extremely low off-state current as the transistor M4, the potential of the node NM can be held for a long time.

[0310] For example, a transistor using a metal oxide for a channel formation region (OS transistor) can be used as the transistor M4. This allows the off-state current of the transistor M4 to be extremely low, and the potential of the node NM can be held for a long time. In this case, it is preferable to use OS transistors for other transistors included in the pixel. For a specific example of a metal oxide, see Embodiment 1.

[0311] OS transistors have a large energy gap and therefore exhibit extremely low off-state current. In addition, OS transistors have characteristics different from transistors that have silicon in the channel formation region (hereinafter referred to as silicon transistors), such as no impact ionization, no avalanche breakdown, and no short channel effect, and can form highly reliable circuits.

[0312] A Si transistor may be used for the transistor M4. In this case, it is preferable to use Si transistors for the other transistors constituting the pixel.

[0313] Examples of Si transistors include a transistor having amorphous silicon, a transistor having crystalline silicon (typically, low-temperature polysilicon), and a transistor having single crystal silicon.

[0314] Furthermore, one pixel may include both an OS transistor and a Si transistor.

[0315] In the pixel, a signal written to the node NM is capacitively coupled with an image signal supplied from the wiring DATA, and can be output to the node NA. Note that the transistor M1 can have a function of selecting the pixel.

[0316] That is, if a desired correction signal is stored in the node NM, the correction signal can be added to the supplied image signal. Note that the correction signal may be attenuated by elements on the transmission path, so it is preferable to generate the correction signal taking such attenuation into consideration.

[0317] By using image signals and correction signals to make the light-emitting device emit light, the current flowing through the light-emitting device can be increased, resulting in high brightness. A voltage equal to or higher than the output voltage of the source driver can be applied as the gate voltage of the drive transistor, reducing the power consumption of the source driver.

[0318] This embodiment mode can be combined with other embodiment modes as appropriate.

[0319] (Embodiment 3) In this embodiment, a metal oxide (also referred to as an oxide semiconductor) which can be used for the OS transistor described in the above embodiment will be described.

[0320] The metal oxide preferably contains at least indium or zinc. In particular, it is preferable that the metal oxide contains indium and zinc. In addition to these, it is preferable that the metal oxide contains aluminum, gallium, yttrium, tin, etc. Furthermore, the metal oxide may contain one or more elements selected from boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, cobalt, etc.

[0321] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 11A. Fig. 11A is a diagram for explaining classification of crystal structures of oxide semiconductors, typically IGZO (metal oxide containing In, Ga, and Zn).

[0322] As shown in FIG. 11A, oxide semiconductors are broadly classified into "Amorphous", "Crystalline", and "Crystal". "Amorphous" includes completely amorphous. "Crystalline" includes c-axis-aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC). "Crystalline" excludes single crystal, poly crystal, and completely amorphous. "Crystal" includes single crystal and poly crystal.

[0323] The structure in the bold frame shown in Fig. 11A is an intermediate state between "Amorphous" and "Crystal" and belongs to a new boundary region (New crystalline phase). In other words, this structure is completely different from the energetically unstable "Amorphous" and "Crystal".

[0324] The crystal structure of the film or substrate can be evaluated using X-ray diffraction (XRD) spectrum. Here, XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of a quartz glass substrate and an IGZO (also called crystalline IGZO) film having a crystal structure classified as "Crystalline" is shown in FIG. 11B and FIG. 11C, respectively. The GIXD method is also called the thin film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by the GIXD measurement shown in FIG. 11B and FIG. 11C will be simply referred to as XRD spectrum. FIG. 11B shows the XRD spectrum of the quartz glass substrate, and FIG. 11C shows the XRD spectrum of the crystalline IGZO film. The composition of the crystalline IGZO film shown in FIG. 11C is in the vicinity of In:Ga:Zn=4:2:3 [atomic ratio]. The thickness of the crystalline IGZO film shown in FIG. 11C is 500 nm.

[0325] As shown by the arrows in FIG. 11B, the peak shape of the XRD spectrum is almost symmetrical for the quartz glass substrate. On the other hand, as shown by the arrows in FIG. 11C, the peak shape of the XRD spectrum for the crystalline IGZO film is asymmetrical. The asymmetrical peak shape of the XRD spectrum clearly indicates the presence of crystals in the film or substrate. In other words, if the peak shape of the XRD spectrum is not symmetrical, the film or substrate cannot be said to be in an amorphous state. Note that FIG. 11C clearly indicates the crystal phase (IGZO crystal phase) at or near 2θ=31°. It is presumed that the asymmetrical peak shape in the XRD spectrum is due to the diffraction peak of the crystal phase (microcrystals).

[0326] Specifically, it is speculated that interference of X-rays scattered by atoms contained in IGZO contributes to the peak at or near 2θ=34°. It is also speculated that minute crystals contribute to the peak at or near 2θ=31°. In the XRD spectrum of the crystalline IGZO film shown in Figure 11C, the peak width on the low-angle side at or near 2θ=34° is broad. This suggests that minute crystals resulting from the peak at or near 2θ=31° are present in the crystalline IGZO film.

[0327] The crystal structure of the film or substrate can be evaluated by the diffraction pattern (also called the nanobeam electron diffraction pattern) observed by nanobeam electron diffraction (NBED). The diffraction patterns of the quartz glass substrate and the IGZO film formed at room temperature are shown in Fig. 11D and Fig. 11E, respectively. Fig. 11D shows the diffraction pattern of the quartz glass substrate, and Fig. 11E shows the diffraction pattern of the IGZO film. The IGZO film shown in Fig. 11E is formed by sputtering using an oxide target with an In:Ga:Zn=1:1:1 [atomic ratio]. In the nanobeam electron diffraction method, electron diffraction is performed with a probe diameter of 1 nm.

[0328] As shown in Figure 11D, a halo is observed in the diffraction pattern of the quartz glass substrate, confirming that the quartz glass is in an amorphous state. Furthermore, as shown in Figure 11E, a spot-like pattern is observed in the diffraction pattern of the IGZO film formed at room temperature, rather than a halo. For this reason, it is presumed that the IGZO film formed at room temperature is in an intermediate state that is neither crystalline nor amorphous, and therefore it cannot be concluded that it is in an amorphous state.

[0329] <<Structure of oxide semiconductor>> In addition, when focusing on the crystal structure, oxide semiconductors may be classified differently from that shown in FIG. 11A. For example, oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. In addition, non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, pseudo-amorphous-like oxide semiconductors (a-like OS), amorphous oxide semiconductors, and the like.

[0330] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0331] [CAAC-OS] CAAC-OS is an oxide semiconductor having a plurality of crystalline regions, each of which has a c-axis aligned in a specific direction. The specific direction is the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. The crystalline region is a region having periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, the crystalline region is also a region with a uniform lattice arrangement. CAAC-OS has a region in which a plurality of crystalline regions are connected in the ab-plane direction, and the region may have distortion. The distortion refers to a portion in which the direction of the lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement in the region in which the plurality of crystalline regions are connected. In other words, CAAC-OS is an oxide semiconductor having a c-axis aligned and no clear orientation in the ab-plane direction.

[0332] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be about several tens of nm.

[0333] In addition, in an In-M-Zn oxide (wherein element M is one or more elements selected from aluminum, gallium, yttrium, tin, titanium, etc.), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter, In layer) and a layer containing element M, zinc (Zn), and oxygen (hereinafter, (M, Zn) layer) are stacked. Note that indium and element M are mutually substituted. Thus, the (M, Zn) layer may contain indium. Also, the In layer may contain element M. Note that the In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution transmission electron microscope (TEM) image, for example.

[0334] When the CAAC-OS film is subjected to structural analysis using, for example, an XRD device, a peak indicating c-axis orientation is detected at or near 2θ=31° in out-of-plane XRD measurement using θ / 2θ scan. Note that the position of the peak indicating c-axis orientation (2θ value) may vary depending on the type and composition of the metal elements constituting the CAAC-OS.

[0335] For example, a plurality of bright points (spots) are observed in the electron diffraction pattern of the CAAC-OS film, and the two spots are observed at positions symmetrical to each other with respect to the spot of the incident electron beam that has passed through the sample (also called the direct spot).

[0336] When the crystal region is observed from the specific direction, the lattice arrangement in the crystal region is based on a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be a non-regular hexagon. The above distortion may have a pentagonal or heptagonal lattice arrangement. In addition, no clear grain boundary can be confirmed in the CAAC-OS even in the vicinity of the distortion. That is, it is found that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is considered to be because the CAAC-OS can tolerate distortion due to the fact that the arrangement of oxygen atoms is not dense in the ab-plane direction and the bond distance between atoms changes due to the substitution of metal atoms.

[0337] A crystal structure in which clear grain boundaries are observed is called a polycrystal. The grain boundaries are likely to become recombination centers and capture carriers, causing a decrease in the on-current of a transistor and a decrease in field effect mobility. Therefore, CAAC-OS in which clear grain boundaries are not observed is one of the crystalline oxides having a crystal structure suitable for a semiconductor layer of a transistor. In order to form a CAAC-OS, a structure containing Zn is preferable. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the occurrence of grain boundaries more than In oxide.

[0338] The CAAC-OS is an oxide semiconductor with high crystallinity and no clear crystal grain boundaries. Therefore, it can be said that the CAAC-OS is less susceptible to a decrease in electron mobility due to crystal grain boundaries. In addition, since the crystallinity of an oxide semiconductor can be decreased by the inclusion of impurities or the generation of defects, the CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, the physical properties of an oxide semiconductor having the CAAC-OS are stable. Therefore, an oxide semiconductor having the CAAC-OS is resistant to heat and has high reliability. In addition, the CAAC-OS is stable against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, the use of the CAAC-OS in an OS transistor can increase the degree of freedom in the manufacturing process.

[0339] [nc-OS] The nc-OS has periodic atomic arrangement in a minute region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has minute crystals. Note that the size of the minute crystals is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore the minute crystals are also called nanocrystals. In addition, the nc-OS does not show regularity in crystal orientation between different nanocrystals. Therefore, no orientation is seen in the entire film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor. For example, when a structure analysis is performed on an nc-OS film using an XRD device, no peak indicating crystallinity is detected in out-of-plane XRD measurement using θ / 2θ scan. In addition, when an nc-OS film is subjected to electron diffraction (also called selected area electron diffraction) using an electron beam with a probe diameter larger than that of nanocrystals (for example, 50 nm or more), a diffraction pattern like a halo pattern is observed. On the other hand, when electron diffraction (also called nanobeam electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter (e.g., 1 nm to 30 nm) that is close to the size of a nanocrystal or smaller than the nanocrystal, an electron diffraction pattern in which multiple spots are observed within a ring-shaped region centered on the direct spot may be obtained.

[0340] [a-like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a void or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS. Moreover, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and CAAC-OS.

[0341] <<Oxide semiconductor structure>> Next, the above-mentioned CAC-OS will be described in detail, with reference to its material composition.

[0342] [CAC-OS] CAC-OS is, for example, a material configuration in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. In the following, a state in which one or more metal elements are unevenly distributed in a metal oxide and the regions having the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0343] Furthermore, CAC-OS is a composite metal oxide in which the material is separated into a first region and a second region, forming a mosaic structure, and the first region is distributed throughout the film (hereinafter, also referred to as a cloud structure). In other words, CAC-OS is a composite metal oxide in which the first region and the second region are mixed together.

[0344] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are represented as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. Also, the second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. Also, the second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0345] Specifically, the first region is a region mainly composed of indium oxide, indium zinc oxide, etc., and the second region is a region mainly composed of gallium oxide, gallium zinc oxide, etc. In other words, the first region can be rephrased as a region mainly composed of In, and the second region can be rephrased as a region mainly composed of Ga.

[0346] In addition, there are cases where a clear boundary between the first region and the second region cannot be observed.

[0347] In addition, the CAC-OS in In-Ga-Zn oxide refers to a structure in which some regions mainly composed of Ga and some regions mainly composed of In are arranged randomly in a mosaic pattern in a material structure containing In, Ga, Zn, and O. Therefore, it is presumed that the CAC-OS has a structure in which metal elements are distributed non-uniformly.

[0348] CAC-OS can be formed, for example, by a sputtering method under conditions where the substrate is not intentionally heated. When CAC-OS is formed by a sputtering method, any one or more selected from an inert gas (typically argon), oxygen gas, and nitrogen gas may be used as a deposition gas. The lower the flow rate ratio of oxygen gas to the total flow rate of deposition gas during deposition, the more preferable it is. For example, the flow rate ratio of oxygen gas to the total flow rate of deposition gas during deposition is preferably 0% or more and less than 30%, and more preferably 0% or more and 10% or less.

[0349] Furthermore, for example, in the case of a CAC-OS of an In-Ga-Zn oxide, EDX mapping obtained using EDX (Energy Dispersive X-ray spectroscopy) can confirm that the CAC-OS has a structure in which a region mainly composed of In (first region) and a region mainly composed of Ga (second region) are unevenly distributed and mixed.

[0350] Here, the first region is a region with higher conductivity than the second region. In other words, the first region exhibits conductivity as a metal oxide when carriers flow through the first region. Therefore, the first region is distributed in a cloud-like shape in the metal oxide, thereby realizing a high field-effect mobility (μ).

[0351] On the other hand, the second region has higher insulating properties than the first region, that is, the second region is distributed in the metal oxide, thereby making it possible to suppress leakage current.

[0352] Therefore, when CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act in a complementary manner, giving the CAC-OS a switching function (On / Off function). In other words, CAC-OS has a conductive function in part of the material and an insulating function in part of the material, and the material as a whole functions as a semiconductor. By separating the conductive function from the insulating function, it is possible to maximize both functions. Therefore, by using CAC-OS in a transistor, it is possible to achieve a high on-current (I on ), high field effect mobility (μ), and good switching operation can be achieved.

[0353] In addition, a transistor using CAC-OS has high reliability, making it ideal for various semiconductor devices such as display devices.

[0354] Oxide semiconductors have a variety of structures and each structure has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0355] <Transistor Having Oxide Semiconductor> Next, the case where the oxide semiconductor is used for a transistor will be described.

[0356] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0357] For the transistor, an oxide semiconductor having a low carrier concentration is preferably used. For example, the carrier concentration of the oxide semiconductor is 1×10 17 cm -3 Less than or equal to 1×10 15 cm -3 Less than 1×10, more preferably 13 cm -3 Less than or equal to 1×10 11 cm -3 Less than 1×10, more preferably 10 cm -3 Less than 1 x 10 -9 cm -3 The above is the case. Note that in order to reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, an oxide semiconductor having a low impurity concentration and a low density of defect states is referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may be referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor.

[0358] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states might also be low.

[0359] In addition, charges trapped in the trap states of an oxide semiconductor take a long time to disappear and may behave as if they are fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0360] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in a nearby film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0361] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0362] When an oxide semiconductor contains silicon or carbon, which is one of the group 14 elements, defect levels are formed in the oxide semiconductor. For this reason, the concentrations of silicon or carbon in the oxide semiconductor and those near the interface with the oxide semiconductor (concentrations obtained by secondary ion mass spectrometry (SIMS)) are calculated as 2×10 18 atoms / cm 3 Less than or equal to 2×10 17 atoms / cm 3 The following applies.

[0363] In addition, when an oxide semiconductor contains an alkali metal or an alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal is likely to have normally-on characteristics. For this reason, when the concentration of an alkali metal or an alkaline earth metal in an oxide semiconductor obtained by SIMS is 1×10 18 atoms / cm 3 Less than or equal to 2×10 16 atoms / cm 3 To the following:

[0364] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor is likely to have normally-on characteristics. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in an oxide semiconductor obtained by SIMS is set to 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3Less than 5×10, more preferably 17 atoms / cm 3 To the following:

[0365] Furthermore, hydrogen contained in an oxide semiconductor reacts with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. In addition, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce hydrogen in the oxide semiconductor as much as possible. Specifically, when the hydrogen concentration in an oxide semiconductor measured by SIMS is 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Make it less than.

[0366] When an oxide semiconductor in which impurities are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0367] This embodiment mode can be combined with other embodiment modes as appropriate.

[0368] (Embodiment 4) In this embodiment, electronic devices of one embodiment of the present invention will be described with reference to FIGS.

[0369] The electronic devices of this embodiment have a long lifetime and high reliability because they include the display device of one embodiment of the present invention in their display portions. In addition, by using the display device of one embodiment of the present invention in their display portions, the electronic devices can have a long lifetime and a large screen.

[0370] The display unit of the electronic device of this embodiment can display images having a resolution of, for example, full high definition, 4K2K, 8K4K, 16K8K, or higher. The screen size of the display unit can be 20 inches or more diagonally, 30 inches or more diagonally, 50 inches or more diagonally, 60 inches or more diagonally, or 70 inches or more diagonally.

[0371] Examples of electronic devices include electronic devices with relatively large screens such as television sets, desktop or notebook personal computers, computer monitors, digital signage, large game machines such as pachinko machines, as well as digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, and audio playback devices.

[0372] The electronic device of the present embodiment can be installed along the curved surface of the inner or outer wall of a house or building, or the interior or exterior of an automobile.

[0373] The electronic device of this embodiment may have an antenna. By receiving a signal through the antenna, images, information, and the like can be displayed on a display unit. In addition, when the electronic device has an antenna and a secondary battery, the antenna may be used for contactless power transmission.

[0374] The electronic device of this embodiment may have a sensor (including a function to measure force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays).

[0375] The electronic device of the present embodiment can have various functions, such as a function of displaying various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function of displaying a calendar, date, time, etc., a function of executing various software (programs), a wireless communication function, a function of reading out a program or data recorded on a recording medium, etc.

[0376] The electronic device 6500 shown in FIG. 12A is a portable information terminal that can be used as a smartphone.

[0377] The electronic device 6500 includes a housing 6501, a display portion 6502, a power button 6503, a button 6504, a speaker 6505, a microphone 6506, a camera 6507, and a light source 6508. The display portion 6502 has a touch panel function.

[0378] The display device of one embodiment of the present invention can be applied to the display portion 6502.

[0379] FIG. 12B is a schematic cross-sectional view including the end portion of the housing 6501 on the microphone 6506 side.

[0380] A light-transmitting protective member 6510 is provided on the display surface side of the housing 6501, and a display panel 6511, optical members 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, etc. are arranged in the space surrounded by the housing 6501 and the protective member 6510.

[0381] A display panel 6511, an optical member 6512, and a touch sensor panel 6513 are fixed to the protective member 6510 by an adhesive layer (not shown).

[0382] In an area outside the display unit 6502, a part of the display panel 6511 is folded back, and the folded back part is connected to an FPC 6515. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on a printed circuit board 6517.

[0383] The flexible display device of one embodiment of the present invention can be applied to the display panel 6511. Therefore, an extremely lightweight electronic device can be realized. In addition, since the display panel 6511 is extremely thin, a large-capacity battery 6518 can be mounted thereon while keeping the thickness of the electronic device small. In addition, by folding back a part of the display panel 6511 and arranging a connection portion with the FPC 6515 on the back side of the pixel portion, an electronic device with a narrow frame can be realized.

[0384] 13 to 15 show an example of an electronic device that has a flexible display device and can be folded into a small size.

[0385] The electronic device shown in FIGS. 13 and 14 has a folding mechanism and can be folded in half so that the display surfaces face each other.

[0386] The electronic device shown in FIG. 15 has a tri-folding mechanism, and has a region that can be folded so that the display surfaces face each other, and a region that can be folded so that the surface opposite the display surface faces each other.

[0387] 13 to 15, even if the electronic device has a display device with a relatively large aspect ratio such as 16:9, 18:9, or 21:9, the electronic device can be folded up small by providing a fold in the minor axis direction, thereby improving the portability of the electronic device. In addition, when the electronic device is folded up small, the power consumption can be significantly reduced by hiding the display area that cannot be seen.

[0388] Fig. 13A is a diagram showing the electronic device 800A folded to its minimum size (in two). Fig. 13B is a diagram showing the electronic device 800B folded to its minimum size (in two). Fig. 13C is a diagram showing the electronic device 800A or the electronic device 800B unfolded.

[0389] Each of the electronic device 800A and the electronic device 800B includes a flexible display panel 801a, a housing 802a, a housing 802b, and a hinge 803.

[0390] A seamless flexible display panel can be used as the display panel 801a. The display device of one embodiment of the present invention can be used as the display panel 801a.

[0391] In the unfolded state of the electronic device 800A or the electronic device 800B, the display panel 801a has a first region 811a overlapping with the housing 802a, a second region 811b overlapping with the hinge 803, and a third region 811c overlapping with the housing 802b. These three regions are preferably included in the display region of the display panel 801a. In the state shown in FIG. 13A and FIG. 13B, the first region 811a and the third region 811c overlap each other. When the electronic device 800A and the electronic device 800B are folded as shown in FIG. 13A and FIG. 13B, the second region 811b is bent so that the display surfaces of the first region 811a and the third region 811c face each other.

[0392] The housing 802 a is connected to the housing 802 b via a hinge 803 .

[0393] At least a portion of the display panel 801a may be fixed to the housing 802a At least a portion of the display panel 801a may be fixed to the housing 802b.

[0394] The electronic device 800B further includes a display panel 801b.

[0395] In electronic device 800B, display panel 801a and display panel 801b overlap each other with housing 802a interposed therebetween. The display surface of display panel 801a and the display surface of display panel 801b face in opposite directions. Housing 802a may have display panel 801a fixed to a first surface and display panel 801b fixed to a second surface opposite to the first surface.

[0396] The display device of one embodiment of the present invention can be used for one or both of a display panel 801a and a display panel 801b included in the electronic device 800B.

[0397] When electronic device 800B is folded, the user can see the display on display panel 801b, and when electronic device 800B is unfolded, the user can see the display on display panel 801a.

[0398] Fig. 14A is a diagram showing the electronic device 800C folded to its minimum size (folded in half), and Fig. 14B is a diagram showing the electronic device 800C unfolded.

[0399] The electronic device 800C includes a flexible display panel 801, a housing 802a, a housing 802b, and a hinge 803.

[0400] A seamless flexible display panel can be used as the display panel 801. The display panel 801 can be a display device according to one embodiment of the present invention.

[0401] In the unfolded state of the electronic device 800C, the display panel 801 has a first region 811a and a second region 811b that overlap each other via the housing 802a, a third region 811c that is located between the first region 811a and the second region 811b and has a curved surface, a fourth region 811d that overlaps with the hinge 803, and a fifth region 811e that overlaps with the housing 802b. These five regions are preferably included in the display region of the display panel 801. In the state shown in FIG. 14A, the first region 811a, the second region 811b, and the fifth region 811e overlap each other. In the state shown in FIG. 14A, the user can visually recognize the display of the first region 811a and the third region 811c. In the state shown in FIG. 14B, the user can visually recognize displays in the second area 811b, the fourth area 811d, and the fifth area 811e (and further the third area 811c).

[0402] In the state shown in Fig. 14A, the display surfaces of the first region 811a and the fifth region 811e face the same direction, and the display surface of the second region 811b faces the opposite direction. When the electronic device 800C is folded as shown in Fig. 14A, the display surfaces of the second region 811b and the fifth region 811e face each other.

[0403] The housing 802 a is connected to the housing 802 b via a hinge 803 .

[0404] At least a portion of the display panel 801 may be fixed to the housing 802a. The display panel 801 is provided along three consecutive surfaces of the housing 802a (a first surface, a second surface facing the first surface, and a third surface (side surface) between the first surface and the second surface). A first region 811a of the display panel 801 may be fixed to the first surface. A second region 811b of the display panel may be fixed to the second surface. A third region 811c of the display panel 801 may be fixed to the third surface.

[0405] At least a portion of the display panel 801a may be fixed to the housing 802b. The fifth region 811e of the display panel 801 may be fixed to the housing 802b.

[0406] Fig. 15A is a diagram showing the electronic device 800D folded to its minimum size (in three). Fig. 15B is a diagram showing the electronic device 800D unfolded. Fig. 15C is a diagram showing the electronic device 800E folded to its minimum size (in three). Fig. 15D is a diagram showing the electronic device 800E unfolded.

[0407] Each of the electronic device 800D and the electronic device 800E includes a flexible display panel 801, a housing 802a, a housing 802b, a housing 802c, a hinge 803a, and a hinge 803b.

[0408] A seamless flexible display panel can be used as the display panel 801. The display panel 801 can be a display device according to one embodiment of the present invention.

[0409] In the state where the electronic device 800D or the electronic device 800E is unfolded, the display panel 801 has a first region 811a overlapping with the housing 802a, a second region 811b overlapping with the hinge 803a, a third region 811c overlapping with the housing 802b, a fourth region 811d overlapping with the hinge 803b, and a fifth region 811e overlapping with the housing 802c. These five regions are preferably included in the display region of the display panel 801. In the state shown in FIG. 15A and FIG. 15C, the first region 811a, the third region 811c, and the fifth region 811e overlap each other. In the state shown in FIG. 15A and FIG. 15C, the user can view the display in the first region 811a and the second region 811b. In the state shown in FIG. 15B and FIG. 15D, the user can view the display in all five regions.

[0410] When electronic device 800D and electronic device 800E are folded as shown in Figures 15A and 15C, second region 811b is bent so that the surfaces facing the display surfaces of first region 811a and third region 811c face each other.

[0411] When electronic device 800D and electronic device 800E are folded as shown in FIGS. 15A and 15C, fourth region 811d is bent so that the display surfaces of third region 811c and fifth region 811e face each other.

[0412] Housing 802a is connected to housing 802b via hinge 803a. Housing 802b is connected to housing 802c via hinge 803b.

[0413] At least a portion of the display panel 801 may be fixed to the housing 802a. At least a portion of the display panel 801 may be fixed to the housing 802b. At least a portion of the display panel 801 may be fixed to the housing 802c.

[0414] In each of electronic devices 800A to 800D, one of the multiple housings is thicker than the others. In electronic devices 800A to 800C, housing 802b is thicker than housing 802a. In electronic device 800D, housing 802c is thicker than housings 802a and 802b.

[0415] A relatively large battery 827 can be accommodated inside the thick housing, allowing the electronic device to operate for a long period of time. In addition, by accommodating a relatively heavy battery 827 inside the thick housing, the center of gravity of the electronic device can be located inside the thick housing even in the unfolded state. Having a housing that is thicker than the other housings and having the center of gravity inside the thick housing can improve the ease of holding the electronic device when unfolded flat.

[0416] A lithium ion battery capable of increasing the capacity is preferably used as the battery 827. The battery 827 is preferably provided with a protection circuit 828.

[0417] The electronic device 800E has a battery 827 built in the housing 802a. The electronic device 800E has an easy-to-grip grip section 806 at the end of the housing 802a, and the battery 827 can be built in the grip section 806. Since the center of gravity of the electronic device 800E is located in the grip section 806 in which the heavy battery 827 is built, the electronic device 800E can be easily held. Furthermore, as shown in FIG. 15D, when the electronic device 800E is unfolded flat, the grip section 806 serves as a leg, allowing the electronic device to be used in a stable form even on a desk. Furthermore, since the display surface is inclined, visibility can be improved.

[0418] The deformation of the electronic device of this embodiment may be performed manually, or may be performed using electrical power or mechanical power such as a spring.

[0419] It is preferable that electronic devices 800A to 800E are easy to operate regardless of left-handedness. It is preferable that electronic devices 800A to 800E are each capable of displaying images in an orientation that is easy for the user to view.

[0420] This operation is performed, for example, by detecting the inclination of the electronic device using a sensor (such as an acceleration sensor or gyro sensor) that the electronic device has, and determining the display orientation of the image from that inclination. The sensor can also detect the shaking of the electronic device from changes in inclination. Since shaking varies from person to person, the shaking information can be learned by artificial intelligence (AI) to identify the user. This function can also be used for personal authentication.

[0421] It is preferable that the electronic devices 800A to 800E have antennas in their housings. In this embodiment, an example is shown in which the antennas 825 and 826 are provided in the housing 802a, but the number of antennas and the positions at which the antennas are provided are not limited to this. The antenna 825 is an antenna for fourth generation mobile communication system (4G) communication, and the antenna 826 is an antenna for fifth generation mobile communication system (5G) communication.

[0422] Providing both the antenna 825 and the antenna 826 in the housing 802a facilitates good communication. In particular, the electronic devices 800B to 800E are often used (placed, held, etc.) in such a way that the display is easily viewable even when folded. Therefore, the housing 802a is often oriented in a direction that allows easy reception of radio waves, making it easier to receive radio waves.

[0423] 16A shows an example of a television device. In a television device 7100, a display unit 7000 is incorporated in a housing 7101. Here, the housing 7101 is supported by a stand 7103.

[0424] The display device of one embodiment of the present invention can be applied to the display portion 7000.

[0425] 16A can be operated using an operation switch provided on the housing 7101 or a separate remote control 7111. Alternatively, a touch sensor may be provided on the display unit 7000, and the television unit 7100 may be operated by touching the display unit 7000 with a finger or the like. The remote control 7111 may have a display unit that displays information output from the remote control 7111. Using an operation key or a touch panel provided on the remote control 7111, it is possible to operate the channel and the volume, and to operate the video displayed on the display unit 7000.

[0426] The television device 7100 includes a receiver and a modem. The receiver can receive general television broadcasts. By connecting to a wired or wireless communication network via the modem, one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers) information communication can be performed.

[0427] 16B shows an example of a laptop personal computer 7200. The laptop personal computer 7200 includes a housing 7211, a keyboard 7212, a pointing device 7213, an external connection port 7214, and the like. A display unit 7000 is incorporated in the housing 7211.

[0428] The display device of one embodiment of the present invention can be applied to the display portion 7000.

[0429] 16C and 16D show an example of digital signage.

[0430] 16C includes a housing 7301, a display unit 7000, and a speaker 7303. The digital signage 7300 may further include an LED lamp, an operation key (including a power switch or an operation switch), a connection terminal, various sensors, a microphone, and the like.

[0431] 16D shows a digital signage 7400 attached to a cylindrical pole 7401. The digital signage 7400 has a display unit 7000 provided along the curved surface of the pole 7401.

[0432] 16C and 16D, the display device of one embodiment of the present invention can be applied to the display portion 7000.

[0433] The larger the display unit 7000, the more information can be provided at one time. Also, the larger the display unit 7000, the more easily it catches people's attention, which can increase the advertising effect of, for example, advertisements.

[0434] Applying a touch panel to the display unit 7000 is preferable because it not only displays images or videos on the display unit 7000 but also allows the user to intuitively operate it. Furthermore, when used for providing information such as route information or traffic information, usability can be improved by intuitive operation.

[0435] 16C and 16D, it is preferable that the digital signage 7300 or the digital signage 7400 can be linked to an information terminal 7311 or an information terminal 7411 such as a smartphone carried by a user via wireless communication. For example, advertising information displayed on the display unit 7000 can be displayed on the screen of the information terminal 7311 or the information terminal 7411. Furthermore, the display on the display unit 7000 can be switched by operating the information terminal 7311 or the information terminal 7411.

[0436] In addition, a game can be executed on the digital signage 7300 or the digital signage 7400 using the screen of the information terminal 7311 or the information terminal 7411 as an operation means (controller). This allows an unspecified number of users to participate in and enjoy the game at the same time.

[0437] The electronic device shown in Figures 17A to 17F has a housing 9000, a display unit 9001, a speaker 9003, operation keys 9005 (including a power switch or an operation switch), a connection terminal 9006, a sensor 9007 (including a function to measure force, displacement, position, speed, 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 rays), a microphone 9008, etc.

[0438] The electronic device shown in Fig. 17A to Fig. 17F has various functions. For example, it can have a function of displaying various information (still images, videos, text images, etc.) on the display unit, a touch panel function, a function of displaying a calendar, date or time, a function of controlling processing by various software (programs), a wireless communication function, a function of reading and processing a program or data recorded on a recording medium, etc. The functions of the electronic device are not limited to these, and it can have various functions. The electronic device may have multiple display units. In addition, the electronic device may have a camera or the like to capture still images and videos and store them on a recording medium (external or built-in to the camera), a function of displaying the captured images on the display unit, etc.

[0439] The electronic device shown in FIGS. 17A to 17F will be described in detail below.

[0440] FIG. 17A is a perspective view showing a mobile information terminal 9101. The mobile information terminal 9101 can be used as, for example, a smartphone. The mobile information terminal 9101 may be provided with a speaker 9003, a connection terminal 9006, a sensor 9007, and the like. The mobile information terminal 9101 can display text and image information on a plurality of surfaces. FIG. 17A shows an example in which three icons 9050 are displayed. Information 9051 shown in a dashed rectangle can also be displayed on another surface of the display unit 9001. Examples of the information 9051 include notifications of incoming e-mail, SNS, and phone calls, titles of e-mail and SNS, sender names, date and time, time, remaining battery level, and antenna reception strength. Alternatively, the icon 9050 or the like may be displayed at the position where the information 9051 is displayed.

[0441] 17B is a perspective view showing a mobile information terminal 9102. The mobile information terminal 9102 has a function of displaying information on three or more sides of the display unit 9001. Here, an example is shown in which information 9052, information 9053, and information 9054 are displayed on different sides. For example, a user can check information 9053 displayed in a position that can be observed from above the mobile information terminal 9102 while the mobile information terminal 9102 is stored in a breast pocket of clothes. The user can check the display without taking the mobile information terminal 9102 out of the pocket and decide, for example, whether or not to answer a call.

[0442] FIG. 17C is a perspective view showing a wristwatch-type mobile information terminal 9200. The mobile information terminal 9200 can be used as, for example, a smart watch. The display surface of the display unit 9001 is curved, and display can be performed along the curved display surface. The mobile information terminal 9200 can also perform hands-free conversation by communicating with, for example, a headset capable of wireless communication. The mobile information terminal 9200 can also perform data transmission and charging with another information terminal through a connection terminal 9006. Note that charging may be performed by wireless power supply.

[0443] 17D to 17F are perspective views showing a foldable mobile information terminal 9201. FIG. 17D is a perspective view of the mobile information terminal 9201 in an unfolded state, FIG. 17F is a perspective view of the mobile information terminal 9201 in a folded state, and FIG. 17E is a perspective view of a state in the middle of changing from one of FIG. 17D and FIG. 17F to the other. The mobile information terminal 9201 has excellent portability in a folded state, and has excellent viewability of the display due to a seamless wide display area in an unfolded state. A display unit 9001 of the mobile information terminal 9201 is supported by three housings 9000 connected by a hinge 9055. For example, the display unit 9001 can be bent with a curvature radius of 0.1 mm or more and 150 mm or less.

[0444] This embodiment mode can be combined with other embodiment modes as appropriate.

[0445] <Reference example> In this reference example, a method for calculating the HOMO level, the LUMO level, and the electron mobility of an organic compound in a display device of one embodiment of the present invention will be described.

[0446] The HOMO level and the LUMO level can be calculated based on cyclic voltammetry (CV) measurements.

[0447] In this reference example, an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A or 600C) was used as the measuring device. The solution for CV measurement was prepared by dissolving tetra-n-butylammonium perchlorate (n-Bu4NClO4) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number: T0836) as a supporting electrolyte to a concentration of 100 mmol / L in dehydrated dimethylformamide (DMF) (manufactured by Aldrich Co., Ltd., 99.8%, catalog number: 22705-6) and further dissolving the measurement target to a concentration of 2 mmol / L. A platinum electrode (PTE platinum electrode, BAS Co., Ltd.) was used as the working electrode, a platinum electrode (Pt counter electrode (5 cm) for VC-3, BAS Co., Ltd.) was used as the auxiliary electrode, and an Ag / Ag+ electrode (RE7 non-aqueous solvent reference electrode, BAS Co., Ltd.) was used as the reference electrode. Measurements were performed at room temperature (20-25°C). The scan rate during CV measurements was standardized to 0.1 V / sec, and the oxidation potential Ea [V] and reduction potential Ec [V] relative to the reference electrode were measured. Ea was the midpoint potential of the oxidation-reduction wave, and Ec was the midpoint potential of the reduction-oxidation wave. Here, since the potential energy of the reference electrode used in this reference example with respect to the vacuum level is known to be −4.94 eV, the HOMO level and LUMO level can be calculated from the formulas HOMO level [eV] = −4.94-Ea and LUMO level [eV] = −4.94-Ec, respectively.

[0448] The electron mobility can be measured by impedance spectroscopy (IS method).

[0449] Measurements of carrier mobility in EL materials have long been known, including the time-of-flight (TOF) method and the method of calculating it from the IV characteristics of space-charge-limited current (SCLC) (SCLC method). The TOF method requires samples with a significantly thicker film thickness than actual organic EL devices. The SCLC method has the disadvantage of not being able to obtain the electric field strength dependence of carrier mobility. The IS method requires a thin organic film thickness of about several hundred nm for measurement, making it possible to form a film with a relatively small amount of EL material, and is characterized by being able to measure mobility with a film thickness close to that of actual organic EL devices, and also being able to obtain the electric field strength dependence of carrier mobility.

[0450] In the IS method, a minute sine wave voltage signal (V=V0[exp(jωt)]) is applied to the EL device, and the impedance (Z=V / I) of the EL device is calculated from the phase difference between the current amplitude of the response current signal (I=I0exp[j(ωt+φ)]) and the input signal. By applying a voltage varying from high frequency to low frequency to the EL device, it is possible to separate and measure the components with various relaxation times that contribute to the impedance.

[0451] Here, admittance Y (=1 / Z), which is the reciprocal of impedance, can be expressed by conductance G and susceptance B as shown in the following equation (1).

[0452]

number

[0453] Furthermore, the following equations (2) and (3) can be calculated using a single charge injection model. Here, g (equation (4)) is the differential conductance. In the equations, C is the capacitance, θ is ωT, which is the travel angle, and ω is the angular frequency. T is the travel time. The current equation, Poisson's equation, and current continuity equation are used in the analysis, and the existence of diffusion current and trap levels is ignored.

[0454]

number

[0455] The -ΔB method is a method for calculating mobility from the frequency characteristics of capacitance, and the ωΔG method is a method for calculating mobility from the frequency characteristics of conductance.

[0456] In practice, first, an electron-only device is made of the material for which the electron mobility is to be determined. An electron-only device is a device designed so that only electrons flow as carriers. In this specification, a method for calculating the mobility from the frequency characteristics of the capacitance (-ΔB method) is explained.

[0457] The structure of the electron-only device prepared for the measurement is shown in FIG. 18A, and the specific configuration is shown in Table 1. The electron-only device prepared in this reference example has a first layer 910, a second layer 911, and a third layer 912 between a first electrode 901 (anode) and a second electrode 902 (cathode). A material for which the electron mobility is to be determined may be used as the material of the second layer 911. In this reference example, the electron mobility was measured for a co-evaporated film of 2-{4-[9,10-di(naphthalene-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN) and 8-(quinolinolato)lithium (abbreviation: Liq) in a 1:1 (weight ratio). In this reference example, the electron mobility was also measured for 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA) and 2-[3'-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II).

[0458] [Table 1]

[0459] FIG. 19 shows the current density-voltage characteristics of an electron-only device fabricated using a co-evaporated film of ZADN and Liq as the second layer 911.

[0460] The impedance measurement was performed under the conditions of an AC voltage of 70 mV and a frequency of 1 Hz to 3 MHz while applying a DC voltage in the range of 5.0 V to 9.0 V. The capacitance was calculated from the admittance (the above-mentioned formula (1)), which is the reciprocal of the impedance obtained here. The frequency characteristic of the calculated capacitance C at an applied voltage of 7.0 V is shown in Figure 20.

[0461] The frequency characteristic of capacitance C is obtained because the space charge caused by the carriers injected by the minute voltage signal cannot completely follow the minute AC voltage, and a phase difference occurs in the current. Here, the transit time of the carriers in the film is defined as the time T for the injected carriers to reach the opposing electrode, and is expressed by the following formula (5).

[0462]

number

[0463] The negative susceptance change (-ΔB) corresponds to the capacitance change -ΔC multiplied by the angular frequency ω (-ωΔC). The lowest frequency peak frequency f' max (=ω max From equation (3), the relationship between the distance (km) from the center of gravity (P) to the travel time T can be derived as shown in equation (6).

[0464]

number

[0465] The frequency characteristic of -ΔB calculated from the above measurement (i.e., when the DC voltage is 7.0 V) is shown in Figure 21. The lowest frequency peak frequency f' obtained from Figure 21 max is indicated by an arrow in the figure.

[0466] f' obtained from the above measurements and analysis maxFrom this, the transit time T can be calculated (equation (6)), and from the above equation (5), the electron mobility at a voltage of 7.0 V in this case can be calculated. By performing similar measurements at DC voltages in the range of 5.0 V to 9.0 V, the electron mobility at each voltage (electric field strength) can be calculated, and the electric field strength dependence of the mobility can also be measured.

[0467] The electric field strength dependence of the electron mobility of each organic compound finally obtained by the above calculation method is shown in FIG. 22. From the figure, it can be seen that the square root of the electric field strength [V / cm] is 600 [V / cm]. 1 / 2 The electron mobility values ​​at this time are shown in Table 2. In Fig. 22, the squares show the results for cgDBCzPA, the triangles show the results for 2mDBTBPDBq-II, and the diamonds show the results for the co-evaporated film of ZADN and Liq.

[0468] [Table 2]

[0469] In this way, it is possible to calculate the electron mobility. For details on the measurement method, please refer to Takayuki Okachi et al., "Japanese Journal of Applied Physics," Vol. 47, No. 12, 2008, pp. 8965-8972. EXAMPLES

[0470] In this example, a light-emitting device that can be used for a display device of one embodiment of the present invention was manufactured and evaluated, and the results are described.

[0471] In this example, a device R1 emitting red light, a device G1 emitting green light, and a device B1 emitting blue light were fabricated as light-emitting devices, and the results of their evaluation will be described. The structures of the devices used in this example are shown in FIG. 18B, and the specific configurations are shown in Table 3. The chemical formulas of the materials used in this example are shown below.

[0472] [Table 3]

[0473] [ka]

[0474] [ka]

[0475] <Creating light-emitting devices> As shown in FIG. 18B, the devices R1, G1, and B1 fabricated in this embodiment have a structure in which a first electrode 130 is formed on a substrate (not shown), a hole injection layer 131, a hole transport layer 132a, a hole transport layer 132b, a light-emitting layer 133, an electron transport layer 134, and an electron injection layer 135 are sequentially stacked on the first electrode 130, and a second electrode 140 is formed on the electron injection layer 135. Each device further has a buffer layer 136 on the second electrode 140. The buffer layer 136 has a function of reducing the loss of light energy due to surface plasmons in the second electrode 140 (semi-transmissive / semi-reflective electrode). As the buffer layer 136, various organic films that can be used in light-emitting devices can be adopted.

[0476] First, a first electrode 130 was formed on the substrate. The electrode area was 4 mm 2 (2 mm×2 mm). A glass substrate was used as the substrate. The first electrode 130 was formed by forming a film of an alloy of silver (Ag), palladium (Pd), and copper (Cu) (Ag-Pd-Cu (APC)) by a sputtering method, and forming a film of indium tin oxide containing silicon oxide (ITSO) by a sputtering method. In the device R1, the APC was formed to a film thickness of 100 nm, and the ITSO was formed to a film thickness of 110 nm. In the devices G1 and B1, the APC was formed to a film thickness of 100 nm, and the ITSO was formed to a film thickness of 85 nm. In this embodiment, the first electrode 130 functions as an anode.

[0477] As a pretreatment, 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. -4 The substrate was introduced into a vacuum deposition apparatus whose inside had been reduced in pressure to about Pa, and vacuum baking was carried out at 170° C. for 30 minutes in a heating chamber in the vacuum deposition apparatus, and then the substrate was allowed to cool for about 30 minutes.

[0478] Next, a hole injection layer 131 was formed on the first electrode 130. The hole injection layer 131 was formed by evaporating the solution in a vacuum deposition apparatus for 10 -4 After reducing the pressure to 10 Pa, N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf) and ALD-MP001Q (Bunseki Kobo Co., Ltd., material serial number: 1S20180314) were co-evaporated to a weight ratio of 1:0.05 (=BBABnf:ALD-MP001Q) and a film thickness of 10 nm. ALD-MP001Q has electron accepting properties for BBABnf.

[0479] Next, a hole transport layer 132a was formed on the hole injection layer 131. The hole transport layer 132a was formed by vapor deposition of BBABnf. The hole transport layer 132a was formed to a thickness of 30 nm in device R1, 10 nm in device G1, and 25 nm in device B1.

[0480] Next, the hole transport layer 132b was formed on the hole transport layer 132a.

[0481] The hole transport layer 132b of device R1 was formed by vapor deposition of N-(1,1'-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) to a thickness of 50 nm.

[0482] The hole transport layer 132b of the device G1 was formed by vapor deposition of 4,4'-diphenyl-4''-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP) to a thickness of 50 nm.

[0483] The hole transport layer 132b of the device B1 was formed by vapor deposition of 3,3'-(naphthalene-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation: PCzN2) to a thickness of 10 nm.

[0484] Next, the light-emitting layer 133 was formed on the hole-transporting layer 132b.

[0485] The light-emitting layer 133 of the device R1 was formed by co-evaporation of 9-[(3'-dibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1',2':4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-bis(9,9-dimethyl-9H-fluoren-2-yl)amine (abbreviation: PCBFF), and ALD-MG018Q (Bunseki Kobo Co., Ltd., material serial number: 1S20161025) in a weight ratio of 0.7:0.3:0.05 (=9mDBtBPNfpr:PCBFF:ALD-MG018Q) and a film thickness of 60 nm. ALD-MG018Q is a red light-emitting material.

[0486] The light-emitting layer 133 of the device G1 was composed of 8-(1,1′-biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 9-(2-naphthyl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: βNCCP), and [2-d3-methyl-(2-pyridinyl- The film was formed by co-evaporation of 8BP-4mDBtPBfpm:βNCCP:[Ir(ppy)2(mbfpypy-d3)] with a weight ratio of 0.6:0.4:0.1 (=8BP-4mDBtPBfpm:βNCCP:[Ir(ppy)2(mbfpypy-d3)]) and a thickness of 50 nm. [Ir(ppy)2(mbfpypy-d3)] is a green luminescent material.

[0487] The light-emitting layer 133 of the device B1 was formed by co-evaporation of 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth) 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) in a weight ratio of 1:0.015 (=αN-βNPAnth:3,10PCA2Nbf(IV)-02) to a thickness of 25 nm. 3,10PCA2Nbf(IV)-02 is a blue light-emitting material.

[0488] Next, the electron transport layer 134 was formed on the light emitting layer 133. The electron transport layer 134 in the light emitting device of this example has a laminated structure of two layers having different mixture ratios of 2-{4-[9,10-di(naphthalene-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole (abbreviation: ZADN) and 8-quinolinolato-lithium (abbreviation: Liq). The electron transport layer 134 has a lower Liq content on the cathode (second electrode 140) side than on the anode (first electrode 130) side.

[0489] Specifically, the electron transport layer 134 in Device R1 and Device G1 was formed by co-evaporating ZADN and Liq at a weight ratio of 0.7:1 (=ZADN:Liq) to a thickness of 10 nm, and then co-evaporating ZADN and Liq at a weight ratio of 1:1 (=ZADN:Liq) to a thickness of 25 nm. The electron transport layer 134 in Device B1 was formed by co-evaporating ZADN and Liq at a weight ratio of 0.3:1 (=ZADN:Liq) to a thickness of 15 nm, and then co-evaporating ZADN and Liq at a weight ratio of 1:0.3 (=ZADN:Liq) to a thickness of 15 nm.

[0490] Next, the electron injection layer 135 was formed on the electron transport layer 134. The electron injection layer 135 was formed by vapor deposition using Liq so as to have a film thickness of 1 nm.

[0491] Next, the second electrode 140 was formed on the electron injection layer 135. The second electrode 140 was formed by co-evaporation of silver (Ag) and magnesium (Mg) so that the volume ratio was 1:0.1 (=Ag:Mg) and the film thickness was 15 nm. In this example, the second electrode 140 functions as a cathode.

[0492] Then, a buffer layer 136 was formed on the second electrode 140. The buffer layer 136 was formed by vapor deposition using 4,4',4''-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II) to a thickness of 80 nm.

[0493] Through the above steps, a light-emitting device was formed on the substrate, comprising an EL layer sandwiched between a pair of electrodes. Note that, in the deposition steps in the above-mentioned manufacturing method, deposition by resistance heating was used for all of the deposition steps.

[0494] The light-emitting device fabricated as described above is sealed with another substrate (not shown). When sealing using another substrate (not shown), another substrate (not shown) coated with an adhesive that is hardened by ultraviolet light is fixed onto the substrate in a glove box with a nitrogen atmosphere, and the substrates are bonded together so that the adhesive adheres to the periphery of the light-emitting device formed on the substrate. During sealing, 365 nm ultraviolet light is applied at 6 J / cm. 2 The adhesive was solidified by irradiation and then stabilized by heat treatment at 80°C for 1 hour.

[0495] <Operation characteristics of light-emitting devices> The operating characteristics of Device R1, Device G1, and Device B1 were measured at room temperature (an atmosphere maintained at 25° C.).

[0496] 23 to 27 show the characteristics of device R1. FIG. 23 shows the luminance-current density characteristics of device R1. FIG. 24 shows the luminance-voltage characteristics of device R1. FIG. 25 shows the current efficiency-luminance characteristics of device R1. FIG. 26 shows the current density-voltage characteristics of device R1. FIG. 27 shows the current efficiency-luminance characteristics of device R1 when 5 mA / cm 2 FIG. 13 is a graph showing an emission spectrum when a current is passed at a current density of 1000 nm.

[0497] 28 to 32 show the characteristics of device G1. FIG. 28 shows the luminance-current density characteristics of device G1. FIG. 29 shows the luminance-voltage characteristics of device G1. FIG. 30 shows the current efficiency-luminance characteristics of device G1. FIG. 31 shows the current density-voltage characteristics of device G1. FIG. 32 shows the current efficiency-luminance characteristics of device G1 when 5 mA / cm 2 FIG. 13 is a graph showing an emission spectrum when a current is passed at a current density of 1000 nm.

[0498] 33 to 37 show the characteristics of device B1. FIG. 33 shows the luminance-current density characteristics of device B1. FIG. 34 shows the luminance-voltage characteristics of device B1. FIG. 35 shows the current efficiency-luminance characteristics of device B1. FIG. 36 shows the current density-voltage characteristics of device B1. FIG. 37 shows the current density-voltage characteristics of device B1 when 14.7 mA / cm 2 FIG. 13 is a graph showing an emission spectrum when a current is passed at a current density of 1000 nm.

[0499] Table 4 shows 1000cd / m 2 The main initial characteristic values ​​of each light-emitting device in the vicinity are shown.

[0500] [Table 4]

[0501] As shown in Table 4, devices R1, G1, and B1 each exhibited emission with high color purity and were found to be highly efficient.

[0502] As shown in Fig. 27, device R1 exhibited an emission spectrum having a maximum peak at about 610 nm. As shown in Fig. 32, device G1 exhibited an emission spectrum having a maximum peak at about 521 nm. As shown in Fig. 37, device B1 exhibited an emission spectrum having a maximum peak at about 459 nm.

[0503] <Reliability characteristics of light-emitting devices> Next, a reliability test was carried out on each light-emitting device. The results of the reliability test are shown in Fig. 38 to Fig. 40. In Fig. 38 to Fig. 40, the vertical axis indicates normalized luminance (%) when the initial luminance is taken as 100%, and the horizontal axis indicates the driving time (h). Note that the reliability test was carried out at a current density of 75 mA / cm2 for device R1. 2 and the current density was set to 50 mA / cm for devices G1 and B1. 2 and each light-emitting device was driven.

[0504] From Fig. 38, it was found that the normalized luminance of Device R1 after 1080 hours was 84%, from Fig. 39, it was found that the normalized luminance of Device G1 after 23 hours was 96%, and from Fig. 40, it was found that the normalized luminance of Device B1 after 530 hours was 95%.

[0505] It was found that each of the devices R1, G1, and B1 exhibited behavior with small initial degradation.

[0506] As described above, in this embodiment, by applying the ReSTI structure, it was possible to fabricate a light-emitting device having a long operating life in any of light-emitting devices that emit red, green, and blue light. In addition, in this embodiment, by applying the ReSTI structure, it was possible to fabricate a light-emitting device having a long operating life in both fluorescent and phosphorescent light.

[0507] The three light-emitting devices manufactured in this embodiment have light-emitting layers containing different materials. On the other hand, the three light-emitting devices have layers using the same material, and further have layers using the same material and having the same thickness. Therefore, it was suggested that in manufacturing a display device according to one embodiment of the present invention, a common layer is provided for the three-color light-emitting devices, and a light-emitting device with a long operating lifetime can be manufactured with fewer manufacturing steps. EXAMPLES

[0508] In this example, a light-emitting device that can be used for a display device of one embodiment of the present invention was manufactured and evaluated, and the results are described.

[0509] In this example, a device R2 emitting red light, a device G2 emitting green light, and a device B2 emitting blue light were fabricated as light-emitting devices, and the results of their evaluation are described. The structures of the devices used in this example are shown in FIG. 18B, and the specific configurations are shown in Table 5.

[0510] For the method of manufacturing the light-emitting device of this embodiment, refer to Example 1. The chemical formulae of the materials used in this embodiment are shown below. Note that the chemical formulae of materials already shown are omitted.

[0511] [Table 5]

[0512] [ka]

[0513] As shown in Table 5, the electron transport layer 134 in the light-emitting device of this example has a two-layer structure with different mixture ratios of ZADN and Liq. Specifically, the electron transport layer 134 in the light-emitting device of this example has a lower Liq content on the cathode (second electrode 140) side than on the anode (first electrode 130) side.

[0514] The light-emitting layer 133 of the device G3 was formed by co-evaporation of 8BP-4mDBtPBfpm, βNCCP, and [2-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy)]) in a weight ratio of 0.6:0.4:0.1 (=8BP-4mDBtPBfpm:βNCCP:[Ir(ppy)2(mbfpypy)]) to a thickness of 50 nm.

[0515] In this embodiment, the emission colors of device R2 emitting red light, device G2 emitting green light, and device B2 emitting blue light were each fabricated to have the same chromaticity as the sub-pixels of a commercially available display device (smartphone) that uses an organic EL device.

[0516] <Reliability characteristics of light-emitting devices> A reliability test was carried out on each light-emitting device. The results of the reliability test are shown in Figure 41. In Figure 41, the vertical axis represents normalized luminance (%) when the initial luminance is taken as 100%, and the horizontal axis represents driving time (h).

[0517] In this example, a reliability test was performed by making the device R2 that emits red light, the device G2 that emits green light, and the device B2 that emits blue light emit light at the same luminance and chromaticity as the light-emitting device (organic EL device) in the subpixel of the commercially available display device (smartphone). In the commercially available display device, when each color is emitted in a single color with the brightness set to a gradation of 255 / 255 (100% brightness), the luminance is 108 cd / m for red (R). 2 , green (G) is 354cd / m 2 , blue (B) is 32.9cd / m 2 The aperture ratio of the subpixels of the commercially available display device was 4.5% for red, 4.3% for green, and 6.8% for blue. The aperture ratio and the luminance of each of the RGB in the display device give the luminance of each of the subpixels (RGB). Finally, the luminance when driving the devices R2, G2, and B2 can be determined by assuming that the transmittance including the circular polarizer is 40% (dividing the luminance of each of the subpixels (RGB) by 0.4). In the commercially available display device, a color filter and a circular polarizer are provided in each subpixel, and the chromaticity and luminance of each organic EL device were measured through these. In the light-emitting device of this embodiment, a color filter that transmits each color is placed on each light-emitting device, and the chromaticity and luminance of each light-emitting device were measured through the color filter.

[0518] Table 6 shows the driving conditions for the reliability test of each light-emitting device. That is, devices R2, G2, and B2 each had an initial luminance of 6580 cd / m 2 , 200000cd / m 2 , and 1450 cd / m 2 The constant current drive was performed under the following conditions.

[0519] [Table 6]

[0520] As shown in FIG. 41, the LT95 (the time it takes for the luminance to decrease to 95% of the initial luminance) of device R2 was more than 3000 hours, the LT95 of device G2 was 480 hours, and the LT95 of device B2 was 1640 hours.

[0521] Generally, among red, green, and blue light-emitting devices, the blue light-emitting device tends to have the shortest operating life. However, in the light-emitting device of this embodiment, the blue light-emitting device had the longest operating life after the red light-emitting device. In this embodiment, a fluorescent light-emitting layer and a ReSTI structure are applied to the light-emitting device that emits blue light. It is believed that this suppresses the initial deterioration of the light-emitting device that emits blue light and makes it possible to greatly extend the operating life.

[0522] In addition, if you want to make the emission lifespan the same for RGB, you can change the required brightness by changing the aperture ratio of the subpixels of each color, so you can adjust the emission lifespan. In that case, you can expect the effect of suppressing initial deterioration, so it can be said that it is possible to create a long-life light-emitting device for each color. Since the blue fluorescent device that uses the ReSTI structure has a very long lifespan, in the case of an OLED display, the aperture ratio of the blue subpixel can be made smaller than before. In addition, since the red phosphorescent device using the ReSTI structure and ExTET also has a very long lifespan, the aperture ratio of the red subpixel can be made the smallest among RGB. And, by making the aperture ratio of the green subpixel the largest among RGB, you can extend the overall lifespan while maintaining the balance of the white display. The fact that the aperture ratios of the blue and red subpixels can be made small is also advantageous for increasing the resolution of the Pentile type display device.

[0523] As described above, in this embodiment, by applying the ReSTI structure, it was possible to fabricate a light-emitting device having a long operating life in any of light-emitting devices that emit red, green, and blue light. In addition, in this embodiment, by applying the ReSTI structure, it was possible to fabricate a light-emitting device having a long operating life in both fluorescent and phosphorescent light.

[0524] The three light-emitting devices manufactured in this embodiment have light-emitting layers containing different materials. On the other hand, the three light-emitting devices have layers using the same material, and further have layers using the same material and having the same thickness. Therefore, it was suggested that in manufacturing a display device according to one embodiment of the present invention, a common layer is provided for the three-color light-emitting devices, and a light-emitting device with a long operating lifetime can be manufactured with fewer manufacturing steps.

[0525] <Reference example 2> In this Reference Example, a method for synthesizing 8-(1,1'-biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm) used in Examples 1 and 2 will be described.

[0526] [ka]

[0527] 1.37 g of 8-chloro-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine, 0.657 g of 4-biphenylboronic acid, 1.91 g of tripotassium phosphate, 30 mL of diethylene glycol dimethyl ether (diglyme), and 0.662 g of t-butanol were placed in a three-neck flask, and the flask was degassed by stirring under reduced pressure and replaced with nitrogen.

[0528] The mixture was heated to 60°C, 23.3 mg of palladium (II) acetate and 66.4 mg of di(1-adamantyl)-n-butylphosphine were added, and the mixture was stirred at 120°C for 27 hours. Water was added to the reaction solution, and the mixture was filtered by suction, and the resulting residue was washed with water, ethanol, and toluene. The residue was dissolved in hot toluene and passed through a filter aid filled with Celite, alumina, and Celite in that order. The resulting solution was concentrated, dried, and recrystallized with toluene to obtain the target white solid in an amount of 1.28 g and a yield of 74%.

[0529] 1.26 g of this white solid was purified by train sublimation. In the sublimation purification, the solid was heated at 310°C under a pressure of 2.56 Pa and argon gas at a flow rate of 10 mL / min. After the sublimation purification, 1.01 g of the target pale yellow solid was obtained with a recovery rate of 80%. The synthesis scheme is shown in formula (a-1).

[0530] [ka]

[0531] The pale yellow solid obtained in the above reaction was analyzed by nuclear magnetic resonance spectroscopy ( 1 The results of the analysis by H-NMR are shown below. From these results, it was found that 8BP-4mDBtPBfpm was obtained.

[0532] 1 H-NMR.δ(CDCl3):7.39(t,1H), 7.47-7.53(m,4H), 7.63-7.67(m,2H), 7.68(d,2H), 7.75(d,2H), 7.79-7.83(m,4H ), 7.87(d,1H), 7.98(d,1H), 8.02(d,1H), 8.23-8.26(m,2H), 8.57(s,1H), 8.73(d,1H), 9.05(s,1H), 9.34(s,1H). [Explanation of symbols]

[0533] Data: display data, Data_W: data, DATA: wiring, DATA_W: wiring, G1: wiring, G2: wiring, M1: transistor, M2: transistor, M3: transistor, M4: transistor, 10A: display device, 10B: display device, 10C: display device, 10D: display device, 10E: display device, 21B: light, 21G: light, 21R: light, 42: transistor, 100A: display device, 100B: display device, 101: anode, 102: cathode, 103: EL layer, 112: common layer, 114: common layer, 115: common electrode, 121: hole injection layer, 122: hole transport transport layer, 122a: hole transport layer, 122b: hole transport layer, 123: light emitting layer, 123-1: light emitting region, 124: electron transport layer, 124-1: region, 124a: electron transport layer, 124b: electron transport layer, 125: electron injection layer, 130: first electrode, 131: hole injection layer, 132a: hole transport layer, 132b: hole transport layer, 133: light emitting layer, 134: electron transport layer, 135: electron injection layer, 136: buffer layer, 140: second electrode, 142: adhesive layer, 143: space, 151: substrate, 152: substrate, 153: substrate, 154: substrate, 155: adhesive layer, 162: display unit, 164: circuit 165: wiring, 166: conductive layer, 172: FPC, 173: IC, 182: common layer, 184: common layer, 190: light emitting device, 190B: light emitting device, 190G: light emitting device, 190R: light emitting device, 191: pixel electrode, 192: buffer layer, 192B: buffer layer, 192G: buffer layer, 192R: buffer layer, 193: light emitting layer, 193B: light emitting layer, 193G: light emitting layer, 193R: light emitting layer, 194: buffer layer, 194B: buffer layer, 194G: buffer layer, 194R: buffer layer, 195: protective layer, 195a: inorganic insulating layer, 195b: Organic insulating layer, 195c: inorganic insulating layer, 199: optical adjustment layer, 199B: optical adjustment layer, 199G: optical adjustment layer, 199R: optical adjustment layer, 201: transistor, 202: transistor, 204: connection portion, 205: transistor, 210: transistor, 211: insulating layer, 212: insulating layer, 213: insulating layer, 214: insulating layer, 215: insulating layer, 216: partition wall, 218: insulating layer, 221: conductive layer, 222a: conductive layer, 222b: conductive layer, 223: conductive layer, 225: insulating layer, 228: region, 231: semiconductor layer, 231i: channel formation region, 231n: low resistance region,242: connection layer, 800A: electronic device, 800B: electronic device, 800C: electronic device, 800D: electronic device, 800E: electronic device, 801: display panel, 801a: display panel, 801b: display panel, 802a: housing, 802b: housing, 802c: housing, 803: hinge, 803a: hinge, 803b: hinge, 806: grip portion, 811a: first region, 811b: second region, 811c: third region, 811d: fourth region, 811e: fifth region, 8 25: antenna, 826: antenna, 827: battery, 828: protection circuit, 901: first electrode, 902: second electrode, 910: first layer, 911: second layer, 912: third layer, 6500: electronic device, 6501: housing, 6502: display unit, 6503: power button, 6504: button, 6505: speaker, 6506: microphone, 6507: camera, 6508: light source, 6510: protection member, 6511: display panel, 6512: optical member, 6513: touch sensor Sub-panel, 6515: FPC, 6516: IC, 6517: printed circuit board, 6518: battery, 7000: display unit, 7100: television device, 7101: housing, 7103: stand, 7111: remote control device, 7200: notebook personal computer, 7211: housing, 7212: keyboard, 7213: pointing device, 7214: external connection port, 7300: digital signage, 7301: housing, 7303: speaker, 7311: Information terminal, 7400: digital signage, 7401: pillar, 7411: information terminal, 9000: housing, 9001: display unit, 9003: speaker, 9005: operation key, 9006: connection terminal, 9007: sensor, 9008: microphone, 9050: icon, 9051: information, 9052: information, 9053: information, 9054: information, 9055: hinge, 9101: portable information terminal, 9102: portable information terminal, 9200: portable information terminal, 9201: portable information terminal,

Claims

1. a first light emitting device and a second light emitting device; the first light emitting device has a first electrode and a common electrode; the second light emitting device has a second electrode and the common electrode; the first light-emitting device has a first hole injection layer, a first hole transport layer, a second hole transport layer, a first light-emitting layer, and a first electron transport layer between the first electrode and the common electrode; the second light-emitting device has a second hole injection layer, a third hole transport layer, a fourth hole transport layer, and a second light-emitting layer between the second electrode and the common electrode; the second hole transport layer is in contact with the first light emitting layer, the fourth hole transport layer is in contact with the second light emitting layer; the first light-emitting layer comprises a first organic compound that emits light of a first color; the second light-emitting layer comprises a second organic compound that emits light of a second color; the first hole injection layer and the second hole injection layer have a first compound and a second compound; the HOMO level of the second compound is −5.7 eV or more and −5.4 eV or less; the first compound has an electron accepting property for the second compound, the first hole transport layer and the third hole transport layer have a third compound; a difference between a HOMO level of the third compound and a HOMO level of the second compound is within 0.2 eV; a compound contained in the second hole transport layer and a compound contained in the fourth hole transport layer are different compounds, the first electron transport layer includes a third organic compound and a first substance; the third organic compound has a heterocyclic skeleton, the first substance is a metal, a metal salt, a metal oxide, or an organometallic salt; the first electron transport layer has a first region and a second region; A display device, wherein the first region and the second region have mutually different concentrations of the first substance.

2. In claim 1, The display device, wherein the HOMO level of the third compound is equal to or lower than the HOMO level of the second compound.

3. In claim 1 or 2, a HOMO level of a fourth compound contained in the second hole transport layer is lower than a HOMO level of the third compound.

4. In any one of claims 1 to 3, a HOMO level of a fifth compound contained in the fourth hole transport layer is lower than a HOMO level of the third compound.

5. In any one of claims 1 to 4, The display device, wherein the second compound and the third compound are the same compound.

6. In any one of claims 1 to 5, the first region is located closer to the first light-emitting layer than the second region, A display device, wherein the first region has a higher concentration of the first substance than the second region.

7. In any one of claims 1 to 6, the second light-emitting device having a second electron transport layer; The second electron transport layer has the same compound as the first electron transport layer.

8. In any one of claims 1 to 7, The third organic compound has a HOMO level of −6.0 eV or higher.

9. In any one of claims 1 to 8, the second light-emitting layer includes a fourth organic compound and a fifth organic compound; The display device, wherein the fourth organic compound and the fifth organic compound are a combination that forms an exciplex.

10. In any one of claims 1 to 9, The display device, wherein the first organic compound is a fluorescent material.

11. In any one of claims 1 to 10, the first color is blue; The display device, wherein the second color is red or green.

12. In any one of claims 1 to 11, The display device, wherein the first substance is an organometallic complex having an alkali metal or an alkaline earth metal.

13. A display module comprising a display device according to any one of claims 1 to 12 and a connector or an integrated circuit.

14. A display module according to claim 13; An electronic device having at least one of an antenna, a battery, a housing, a camera, a speaker, a microphone, and an operation button.

Images