Organic light emitting device, display device, electronic device, vehicle-mounted display, and vehicle

Abstract

Disclosed are an organic light emitting device, a display device, an electronic device, a vehicle-mounted display, and a vehicle. The organic light emitting device includes: an anode and a cathode arranged facing each other; a light emitting layer arranged between the anode and the cathode; and a hole transport layer arranged between the anode and the light emitting layer, in contact with the light emitting layer. The light emitting layer includes a first host material and a second host material. A difference between a HOMO energy level of the hole transport layer and a HOMO energy level of the first host material is smaller than a difference between the HOMO energy level of the hole transport layer and a HOMO energy level of the second host material. A difference between the HOMO energy level 13H of the hole transport layer and the HOMO energy level 14aH of the first host material is 0.37 eV or less.

Description

[0001] Cross-references to related applications

[0002] This disclosure claims the benefit of Japanese Patent Application No. 2021-18159, filed on February 8, 2021, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to organic light-emitting devices, display devices, electronic devices, vehicle displays, and vehicles. Background Technology

[0004] Organic light-emitting devices, also known as organic electroluminescent (EL) devices, are used in displays and the like. An organic EL device includes an emitting layer containing an organic light-emitting material, and an anode and a cathode sandwiching the emitting layer. Furthermore, to improve the luminous efficiency of the organic EL device, a hole transport layer or hole injection layer is provided between the anode and the emitting layer, and an electron transport layer or electron injection layer is provided between the cathode and the emitting layer (see, for example, unexamined Japanese Patent Application Publication No. 2008-535266 (translation of PCT application), unexamined Japanese Patent Application Publication No. 2014-513418 (translation of PCT application), and unexamined Japanese Patent Application Publication No. 2017-022369).

[0005] It is well known that the lifespan of organic EL devices is shortened at high temperatures. Preferably, organic EL devices exposed to various environments (e.g., organic EL devices installed in vehicles) should have a longer lifespan at high temperatures.

[0006] This disclosure is made in view of the foregoing, and the purpose of this disclosure is to provide organic light-emitting devices, display devices, electronic devices, vehicle displays and vehicles with long lifespans in high-temperature environments. Summary of the Invention

[0007] To achieve the above objectives, the organic light-emitting device according to the first aspect of this disclosure includes:

[0008] The anode and cathode are arranged facing each other;

[0009] A light-emitting layer, which is arranged between the anode and the cathode; and

[0010] A hole transport layer is arranged between the anode and the light-emitting layer, and contacts the light-emitting layer;

[0011] in

[0012] The light-emitting layer comprises a first host material and a second host material.

[0013] The difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the first host material is smaller than the difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the second host material, and

[0014] The difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the first host material is equal to or less than 0.37 eV.

[0015] The display device according to the second aspect of this disclosure includes the organic light-emitting device according to the first aspect.

[0016] The vehicle-mounted display according to the third aspect of this disclosure includes the display device according to the second aspect.

[0017] The electronic device according to the fourth aspect of this disclosure includes the display device according to the second aspect.

[0018] The vehicle according to the fifth aspect of this disclosure includes the vehicle-mounted display according to the third aspect.

[0019] It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory, and are not intended to limit this disclosure.

[0020] According to this disclosure, the lifespan of organic light-emitting devices, display devices, electronic devices, vehicle displays, and vehicles can be extended in high-temperature environments. Attached Figure Description

[0021] A more complete understanding of this application can be obtained by considering the following detailed description in conjunction with the accompanying drawings, in which:

[0022] Figure 1 This is a cross-sectional view showing the structure of the organic light-emitting device according to Example 1;

[0023] Figure 2 This is an energy state diagram of the hole transport layer and the first and second host materials of the light-emitting layer of the organic light-emitting device according to Example 1;

[0024] Figure 3 This is a graph showing the relationship between the energy difference ΔE1 obtained by subtracting the HOMO level of the emitting layer from the HOMO level of the hole transport layer and the lifetime under high temperature conditions (high temperature lifetime).

[0025] Figure 4 It is a graph showing the relationship between the energy difference ΔE3 between the HOMO energy levels of the first host material and the second host material in the light-emitting layer and the lifetime under high temperature conditions (high temperature lifetime).

[0026] Figure 5It is a graph showing the relationship between the ratio of the first main material and the lifetime under high temperature conditions (high temperature lifetime);

[0027] Figure 6 This is a diagram schematically illustrating an example configuration of a display device according to Embodiment 3;

[0028] Figure 7 It is a plan view showing a portion of the display area of ​​a display device;

[0029] Figure 8 This is a diagram illustrating an example configuration of an in-vehicle display according to Embodiment 4; and

[0030] Figure 9 This is a diagram illustrating an example configuration of an electronic device according to Embodiment 5. Detailed Implementation

[0031] In the following description, an organic light-emitting device 10, a display device 20, an electronic device, an in-vehicle display 30, and a vehicle according to embodiments are described with reference to the accompanying drawings.

[0032] Example 1

[0033] like Figure 1 As shown, the organic light-emitting device 10 includes: an anode 12 disposed on a substrate 11, a hole transport layer 13 disposed on the anode 12, a light-emitting layer 14 disposed on the hole transport layer 13, an electron transport layer 15 disposed on the light-emitting layer 14, an electron injection layer 16 disposed on the electron transport layer 15, and a cathode 17 disposed on the electron injection layer 16. The organic light-emitting device 10 can be used as a monochromatic light-emitting device. Additionally, the organic light-emitting device 10 can be used as a display device with pixels having different chromaticities such as red, green, and blue, and is used in, for example, mobile products (such as smartphones or tablets), automotive displays, or similar applications.

[0034] Substrate 11 is an insulating substrate, and in one example, it is implemented as a glass substrate. Figure 1 As shown, the anode 12, hole transport layer 13, light-emitting layer 14, etc., are stacked on the substrate 11. Any substrate, such as a flexible substrate made of polyimide, polycarbonate, or the like, can be used as the substrate 11.

[0035] The anode 12 is disposed on the substrate 11, and as follows: Figure 1As shown, the cathode 17 is oriented via a hole transport layer 13, a light-emitting layer 14, an electron transport layer 15, and an electron injection layer 16. The anode 12 is connected to a power source (not shown) and supplies holes to the hole transport layer 13. A translucent and conductive material is used to form the anode 12. Examples of materials that can be used include indium tin oxide (ITO), tin oxide (SnO2), indium zinc oxide (IZO), and the like. Note that when the organic light-emitting device 10 has a top-emitting structure, light is reflected on the substrate 11 side and emitted from the cathode 17 side. In this case, an electrode obtained by arranging ITO or IZO on the surface of a reflective metal such as silver (Ag) or the like can be used as the anode 12.

[0036] A hole transport layer 13 is disposed between the anode 12 and the emitting layer 14, contacting the emitting layer 14. The hole transport layer 13 efficiently transports holes injected from the anode 12 to the emitting layer 14. Generally, the band gap of the hole transport layer 13 is larger than the band gap of the emitting layer 14. Note that the term "band gap" refers to the energy difference between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level. The HOMO level can be measured using well-known atmospheric photoelectron yield spectroscopy. The band gap of each layer can be measured using well-known ultraviolet-visible-near-infrared spectroscopy, and the LUMO level of each layer can be calculated based on the measured HOMO level and the band gap of each layer.

[0037] In this embodiment, known materials can be used to form the hole transport layer 13. For example, the hole transport layer 13 can be formed using materials such as α-NPD (name: 2,2'-dimethyl-N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine), TAPC (name: 4,4'-cyclohexyldi[N,N-di(4-methylphenyl)aniline]), TPD (name: N,N'-di(3-methylphenyl)-N,N'-diphenylbenzidine), etc. The hole transport layer 13 is not limited to a single layer and can include multiple layers.

[0038] A light-emitting layer 14 is disposed between an anode 12 and a cathode 17. In the light-emitting layer 14, holes injected from the anode 12 and electrons injected from the cathode 17 effectively recombine, and as a result of this recombination, the light-emitting layer 14 emits light. The light-emitting layer 14 comprises two types of host materials, namely a first host material and a second host material, as well as a light-emitting material.

[0039] Known materials such as fluorescent materials, thermally activated delayed fluorescence materials, and phosphorescent materials can be used as luminescent materials. Examples of luminescent materials include: stilbene derivatives, Alq3 (name: tris-(8-hydroxyquinoline)aluminum), rubrene, dimethylquinolineone, FIrpic (name: bis[2-(4,6-difluorophenyl)pyridine-C2,N](pyridinecarboxyl)iridium(III)), Ir(ppy)3 (name: tris[2-phenylpyridine-C2,N]iridium(III)), (Ppy)2Ir(acac) (name: bis[2-(2-pyridyl-N)phenyl-C](2,4-acetylacetone-O2,O4)iridium(III)), etc.

[0040] Known host materials with hole transport or electron transport properties can be used as the first host material. This also applies to the second host material.

[0041] The host material with hole transport capability is selected from pyrrole, indole, carbazole, azaindole, azacarbazole, triazole, oxazole, oxadiazole, pyrazole, imidazole, thiophene, polyaryl alkanes, pyrazoline, phenylenediamine, aromatic amines, amino-substituted chalcones, styrylanthracene, fluorogenone, hydrazone, stilbene, silazane, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethyridin, porphyrin compounds, polysilane compounds, poly(N-vinylcarbazole), aniline copolymers, thiophene oligomers, polythiophene and other conductive polymer oligomers, organosilanes, carbon films, or their derivatives.

[0042] The host materials with electron transport properties are selected from pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone, anthracene dimethyl alcohol, anthraquinone, diphenylquinone, thiopyran dioxide, carbodiimide, fluorene dimethyl ether, stilbene pyrazine, fluorinated aromatic compounds, heterocyclic tetracarboxylic anhydrides such as perylene, phthalocyanine or its derivatives (which can form fused rings with other rings), and various metal complexes, typically 8-hydroxyquinoline derivatives, metal phthalocyanines, and metal complexes using benzoxazole or benzothiazole as ligands.

[0043] Both the first and second host materials can be selected from host materials with hole transport properties, or both can be selected from host materials with electron transport properties. Alternatively, one of the first and second host materials can be selected from a host material with hole transport properties, while the other can be selected from a material with electron transport properties. In one example, the first host material is selected from a material with hole transport properties, and the second host material is selected from a material with electron transport properties. In the light-emitting layer 14, when the total weight of the first and second host materials is 100, the weight ratio of the first host material to the second host material (weight of the first host material: weight of the second host material) is from 10:90 to 90:10. In other words, in the light-emitting layer 14, the content of the first host material is from 10 wt% to 90 wt% of the total weight of the first and second host materials.

[0044] The electron transport layer 15 efficiently transports electrons injected from the electron injection layer 16 to the light-emitting layer 14. In this embodiment, known materials can be used to form the electron transport layer 15. For example, the electron transport layer 15 can be formed using Alq3, BCP (name: 3-biphenylamino-6-(4-chlorophenyl)pyridazine), thiophene derivatives, or the like. The electron transport layer 15 is not limited to a single layer and can comprise multiple layers.

[0045] The electron injection layer 16 effectively injects electrons from the cathode 17 into the electron transport layer 15. Examples of materials that can be used to form the electron injection layer 16 include lithium fluoride (LiF), ytterbium (Yb), Liq (name: 8-hydroxyquinoline-lithium), etc.

[0046] The cathode 17 is connected to a power source (not shown) and supplies electrons to the electron injection layer 16. Examples of materials that can be used to form the cathode 17 include aluminum, magnesium / silver alloys, ITO, IZO, etc.

[0047] Next, Figure 2 The energy states of the first and second host materials of the hole transport layer 13 and the light-emitting layer 14 are shown. Figure 2 In the diagram, reference numeral 13H represents the HOMO level of the hole transport layer 13, and reference numeral 13L represents the LUMO level of the hole transport layer 13. Reference numeral 14aH represents the HOMO level of the first host material of the luminescent layer 14, and reference numeral 14aL represents the LUMO level of the first host material of the luminescent layer 14. Reference numeral 14bH represents the HOMO level of the second host material of the luminescent layer 14, and reference numeral 14bL represents the LUMO level of the second host material of the luminescent layer 14.

[0048] In this embodiment, the energy states of the first and second host materials of the hole transport layer 13 and the light-emitting layer 14 have the following two particularly prominent characteristics.

[0049] First, the difference between the HOMO level 13H of the hole transport layer 13 and the HOMO level 14aH of the first host material of the emissive layer 14 is equal to or less than 0.37 eV. Note that the HOMO level 13H of the hole transport layer 13 in contact with the emissive layer 14 is higher than the HOMO level 14aH of the first host material of the emissive layer 14. (Reference) Figure 2 ΔE1 is the energy difference obtained by subtracting the HOMO energy level 14aH of the first host material of the light-emitting layer 14 from the HOMO energy level 13H of the hole transport layer 13, and ΔE1 is in the range of greater than 0 eV and equal to or less than 0.37 eV (0 eV < ΔE1 ≤ 0.37 eV). The energy difference ΔE1 is preferably in the range of greater than 0 eV and equal to or less than 0.34 eV (0 eV < ΔE1 ≤ 0.34 eV), and more preferably in the range of greater than 0 eV and equal to or less than 0.32 eV (0 eV < ΔE1 ≤ 0.32 eV).

[0050] Second, the absolute value of the difference between the HOMO energy level of the first host material and the HOMO energy level of the second host material is equal to or less than 0.3 eV. The difference between the HOMO energy level of the first host material and the HOMO energy level of the hole transport layer 13 is smaller than the difference between the HOMO energy level of the second host material and the HOMO energy level of the hole transport layer 13. In other words, the HOMO energy level of the first host material is closer to the HOMO energy level of the hole transport layer 13 than the HOMO energy level of the second host material. (Reference) Figure 2 ΔE1 is the energy difference obtained by subtracting the HOMO level 14aH of the first host material of the luminescent layer 14 from the HOMO level 13H of the hole transport layer 13, and ΔE2 is the energy difference obtained by subtracting the HOMO level 14bH of the second host material of the luminescent layer 14 from the HOMO level 13H of the hole transport layer 13. In this case, ΔE1 is less than ΔE2 (ΔE1 < ΔE2). ΔE3 is the energy difference obtained by subtracting the HOMO level 14bH of the second host material from the HOMO level 14aH of the first host material. In this case, ΔE3 is equal to or less than 0.3 eV (ΔE3 ≤ 0.3 eV).

[0051] Next, while referring to the high-temperature lifetime characteristics of the organic light-emitting device 10, a description of the advantageous effects exhibited as a result of possessing these outstanding characteristics is given.

[0052] first, Figure 3A graph showing the relationship between energy difference ΔE1 [eV] (horizontal axis) and high-temperature lifetime [h] (vertical axis) is presented. Note that in this disclosure, the term "high-temperature lifetime" refers to the energy difference ΔE1 [eV] at 85°C with a current of 10 mA / cm². 2 The time (in hours) required for the intensity of light emitted by the organic light-emitting device 10 to decrease by 20% compared to its initial intensity when continuously driven by a current density of [value missing]. The HOMO energy level can be measured using atmospheric photoelectron yield spectroscopy. Note that in [missing information] Figure 3 In this context, the energy difference (ΔE3) between the first host material and the second host material, obtained by subtracting the HOMO energy level of the second host material from the HOMO energy level of the first host material, is equal to or less than 0.3 eV.

[0053] like Figure 3 As shown, within the energy difference ΔE1 greater than 0.37 eV, the high-temperature lifetime is approximately 200 hours. However, within the energy difference ΔE1 range of 0.37 eV to 0.32 eV, the high-temperature lifetime increases as the energy difference ΔE1 decreases. When the energy difference ΔE1 is equal to or less than 0.34 eV, the high-temperature lifetime exceeds 500 hours. When the energy difference ΔE1 is equal to or less than 0.32 eV, the high-temperature lifetime exceeds 800 hours. Additionally, as... Figure 3 As shown, when the energy difference ΔE1 is less than 0 eV, that is, when the HOMO level 13H of the hole transport layer 13 in contact with the light-emitting layer 14 is less than the HOMO level 14aH of the first host material of the light-emitting layer 14, the high-temperature lifetime decreases to about 200 hours. This is predicted because when ΔE1 is equal to or less than 0 eV, the holes flowing through the hole transport layer 13 have difficulty overcoming the potential barrier of the light-emitting layer 14. Thus, the energy difference ΔE1 is preferably greater than 0 eV.

[0054] Therefore, the high-temperature lifetime can be further extended by setting the energy difference ΔE1 to be greater than 0 eV and equal to or less than 0.37 eV (0 eV < ΔE1 ≤ 0.37 eV). Preferably, the energy difference ΔE1 is set to 0 eV < ΔE1 ≤ 0.34 eV, because the high-temperature lifetime will exceed 500 hours. Particularly preferably, the energy difference ΔE1 is set to 0 eV < ΔE1 ≤ 0.32 eV, because this can further extend the high-temperature lifetime.

[0055] Next, Figure 4 A graph showing the relationship between the energy difference ΔE3[eV] (horizontal axis) obtained by subtracting the HOMO level 14bH of the second host material from the HOMO level 14aH of the first host material and the high-temperature lifetime [h] (vertical axis) is shown. Figure 4 The legend illustrates the ΔE1 value at each point. As shown in the legend, the energy difference ΔE1 at each point satisfies 0 eV < ΔE1 ≤ 0.37 eV.

[0056] like Figure 4 As shown, a high-temperature lifetime exceeding 800 hours is achieved when the energy difference ΔE3 is equal to or less than 0.3 eV. However, when the energy difference ΔE3 exceeds 0.3 eV, the high-temperature lifetime decreases with increasing energy difference ΔE3, and when the energy difference ΔE3 is 0.4 eV, the high-temperature lifetime decreases to approximately 250 hours. When ΔE3 exceeds 0.3 eV, the high-temperature lifetime also decreases even when ΔE1 is equal to or less than 0.32 eV.

[0057] Therefore, the high-temperature lifespan of the organic light-emitting device 10 can be further extended by setting the energy difference ΔE1 to be greater than 0 eV and equal to or less than 0.37 eV (0 eV < ΔE1 ≤ 0.37 eV) and by setting the energy difference ΔE3 to be equal to or less than 0.3 eV.

[0058] The organic light-emitting device 10 of this embodiment can extend its high-temperature lifespan, and in this way, the organic light-emitting device 10 can be advantageously used as an element with a short emission wavelength, especially as a green element. This is because although deeper blues and deeper greens are generally sought to broaden the color gamut in response to expanded display applications, elements with short emission wavelengths tend to have shorter lifespans.

[0059] The organic light-emitting device 10 can be manufactured by methods such as those described below.

[0060] First, a substrate 11 is prepared. Next, an anode 12, made of, for example, ITO, is formed on the surface of the substrate 11 by sputtering. Next, a hole transport layer 13 is formed on the anode 12 by, for example, vacuum deposition. Next, a light-emitting layer 14 is formed on the hole transport layer 13 by, for example, vacuum deposition. The first and second host materials of the hole transport layer 13 and the light-emitting layer 14 are selected such that the energy difference ΔE1 is greater than 0 eV and equal to or less than 0.37 eV. Furthermore, the first and second host materials of the hole transport layer 13 and the light-emitting layer 14 are selected such that the energy difference ΔE3 is equal to or less than 0.3 eV. In addition, the weight ratio of the first host material to the second host material is set to be from 10:90 to 90:10.

[0061] Next, an electron transport layer 15, an electron injection layer 16, and a cathode 17 are sequentially formed on the light-emitting layer 14 by known methods such as vacuum deposition or similar methods.

[0062] Note that this disclosure can also be applied to organic light-emitting devices comprising pixels for each light-emitting element having a different color (such as red, green, and blue). In such a case, firstly, transistors are formed on substrate 11, and an anode 12 is formed on substrate 11 by sputtering. Subsequently, a pixel defining layer is formed using an organic film. Secondly, hole transport layers 13 to cathode 17 are sequentially formed on the anode 12 in the opening region of the pixel defining layer by vacuum deposition or similar methods. Thus, an organic light-emitting device comprising pixels using each of red, green, and blue light-emitting elements can be produced.

[0063] Example 2

[0064] Next, the organic light-emitting device 10 according to Example 2 is described. Note that the organic light-emitting device 10 according to Example 2 has the same structure as the organic light-emitting device 10 according to Example 1. Figure 1 The structure shown is described below, and detailed descriptions of features common to Embodiment 1 are omitted as such.

[0065] Regarding the organic light-emitting device 10 according to Example 2, the light-emitting layer 14 includes a light-emitting material and a first host material and a second host material as in Example 1. In the light-emitting layer 14, when the total weight of the first host material and the second host material is 100, the weight ratio of the first host material to the second host material (weight of the first host material: weight of the second host material) is preferably from 20:80 to 75:25, and more preferably from 45:55 to 70:30. In other words, the content of the first host material is preferably from 20 wt% to 75 wt% of the total weight of the first host material and the second host material, and more preferably from 45 wt% to 70 wt%. Note that, as in Example 1, the HOMO level of the hole transport layer, and the HOMO level of the first host material and the HOMO level of the second host material satisfy 0 eV < ΔE1 ≤ 0.37 eV and ΔE3 ≤ 0.3 eV.

[0066] Next, while referring to the high-temperature lifetime characteristics of the organic light-emitting device 10, a description of the advantageous effects exhibited as a result of possessing these outstanding characteristics is given.

[0067] Figure 5 A graph illustrating the relationship between the percentage [%] of the first host material (horizontal axis) and the high-temperature lifetime [h] (vertical axis) is shown. The percentage [%] of the first host material is the weight (wt%) of the first host material relative to the total weight of the first host material and the second host material of the light-emitting layer 14. Figure 5As shown, when the proportion of the first main material is 20%-75%, the high-temperature life exceeds 500 hours. Furthermore, when the proportion of the first main material is 45%-70%, the high-temperature life exceeds 800 hours.

[0068] Therefore, the high-temperature lifespan of the organic light-emitting device 10 can be further extended by setting the weight ratio of the first host material to the second host material in the light-emitting layer 14 (weight of the first host material: weight of the second host material) from 20:80 to 75:25. Furthermore, the high-temperature lifespan can be further extended by setting the weight ratio of the first host material to the second host material from 45:55 to 70:30.

[0069] Example 3

[0070] Next, Embodiment 3 is described. This embodiment relates to an OLED display device (display device) 20 using the organic light-emitting device 10 according to the various embodiments described above. Figure 6 An example configuration of the display device 20 according to this embodiment is illustrated schematically.

[0071] The display device 20 includes a thin-film transistor (TFT) substrate 100, a sealing substrate 200, and a bonding agent (glass fusion bonding) 300. An organic light-emitting device 10, serving as an OLED element, is formed on the TFT substrate 100. The sealing substrate 200 is positioned opposite the TFT substrate 100. The bonding agent 300 is disposed between the TFT substrate 100 and the sealing substrate 200, bonding the TFT substrate 100 and the sealing substrate 200 together and sealing the OLED element.

[0072] Scan driver 131, transmit driver 132, protection circuit 133, and driver integrated circuit (IC) 134 are arranged around the cathode forming region 114 surrounding the display region 125 of the TFT substrate 100. These components are connected to external devices via flexible printed circuit (FPC) 135.

[0073] Scan driver 131 drives the scan lines of TFT substrate 100. Emit driver 132 drives the emission control lines to control the emission period of each sub-pixel. In one example, driver IC 134 is mounted using anisotropic conductive film (ACF).

[0074] Driver IC 134 provides power and timing signals (control signals) to scan driver 131 and transmit driver 132, and also provides data voltages corresponding to video data to the data lines. That is, driver IC 134 has display control functions.

[0075] The sealing substrate 200 is a transparent insulating substrate, and in one example it is implemented as a glass substrate. A λ / 4 delay plate and a polarizer are arranged on the light-emitting surface (front side) of the sealing substrate 200 and suppress the reflection of light entering from the outside.

[0076] Multiple subpixels are arranged in the display area 125. Figure 7 This is a plan view showing a portion of the display area 125. Figure 7 The diagram shows multiple sub-pixels arranged in a matrix. At least three sub-pixels are sub-pixels that emit light of different first to third colors. Note that in one example, the first color is blue, the second color is red, and the third color is green. Figure 7 The diagram shows a red sub-pixel (light-emitting area) 251R, a blue sub-pixel (light-emitting area) 251B, and a green sub-pixel (light-emitting area) 251G. All areas (light-emitting areas) of each sub-pixel are covered by an organic light-emitting layer of the same color. Specifically, the red sub-pixel 251R, blue sub-pixel 251B, and green sub-pixel 251G are completely covered by a red organic light-emitting layer 269R, a blue organic light-emitting layer 269B, and a green organic light-emitting layer 269G, respectively. Figure 7 In the subpixels shown, only one of each of the red, blue, and green subpixels is labeled with the attached icon. Each subpixel displays red, blue, or green. A pixel (the main pixel) consists of red, blue, and green subpixels.

[0077] In this embodiment, each of the sub-pixels is composed of an organic light-emitting device 10 according to Embodiment 1 or 2. Therefore, due to the effect of the configuration described in Embodiment 1 or 2, the high-temperature lifespan of the display device 20 can be extended.

[0078] Example 4

[0079] Next, Embodiment 4 is described. This embodiment relates to an in-vehicle display 30 using the display device 20 according to Embodiment 3. Figure 8 This is a diagram illustrating a vehicle equipped with an in-vehicle display according to this embodiment and an example of the configuration of the in-vehicle display.

[0080] like Figure 8 As shown, the vehicle-mounted display 30 is a display installed inside a motor vehicle 35, which is a vehicle. The vehicle-mounted display 30 displays various types of information. In one example, the vehicle-mounted display 30 is implemented as... Figure 8 The central information display (CID) 301, instrument display 302, and side display 303 are shown. In this embodiment, CID 301, instrument display 302, and side display 303 are displays using display device 20.

[0081] CID 301 is located in the center of the instrument panel of the vehicle 35. CID 301 displays information about the audio and navigation system and the vehicle status management system. Instrument display 302 displays the tachometer, etc. Side displays 303 are located on the left and right sides of the instrument panel and function as side mirrors by displaying camera images.

[0082] In some cases, the interior of a vehicle 35 equipped with these in-vehicle displays 30 becomes a high-temperature environment due to factors such as sunlight. Because of the use of display devices 20, including organic light-emitting devices 10, the high-temperature lifespan of the in-vehicle displays 30 can be extended. Therefore, even when exposed to high-temperature environments, the in-vehicle displays 30 can maintain excellent display quality for extended periods.

[0083] Example 5

[0084] Next, Embodiment 5 is described. This embodiment relates to an electronic device using a display device according to Embodiment 3. Figure 9 This is a perspective view of a smartphone 40 as an electronic device. Regarding the smartphone 40, a display device 20 according to Embodiment 3 is disposed within a housing 401, and a protective glass 402 is disposed on the display surface side of the display device 20. Additionally, transmitting / receiving devices, various control devices, storage devices, audio devices including speakers and microphones, a battery, and other devices requiring smartphone functions are disposed within the housing.

[0085] In some cases, smartphone 40 can be used in high-temperature environments. For example, smartphone 40 can be used outdoors. Smartphone 40 uses display device 20. As a result, the high-temperature lifespan of smartphone 40 can be extended. Therefore, even when exposed to high-temperature environments, smartphone 40 can maintain excellent display performance for a long time.

[0086] While embodiments according to this disclosure have been described above, this disclosure is not limited to these embodiments. It will be apparent to those skilled in the art that various changes, modifications, combinations, etc., are possible.

[0087] The materials used in each layer of the organic light-emitting device 10 are not limited to those described in the embodiments. Assuming the relationships 0 eV < ΔE1 ≤ 0.37 eV and ΔE3 ≤ 0.3 eV are satisfied, materials can be appropriately selected for use as the hole transport layer 13, the first host material, and the second host material. As mentioned above, the HOMO energy levels of the hole transport layer 13, the first host material, and the second host material can be measured using atmospheric photoelectron yield spectroscopy or similar methods. Using such a measurement method allows for the selection of suitable materials for each layer.

[0088] The anode 12, electron transport layer 15, electron injection layer 16, and cathode 17 are not limited to a single-layer structure and can have a stacked structure. Furthermore, the materials used for the anode 12, electron transport layer 15, electron injection layer 16, and cathode 17 are not limited to the materials described above, and any material can be selected. Note that a configuration in which the electron injection layer 16 is not formed is possible.

[0089] In Embodiment 4, an example is given in which CID 301, instrument display 302, and side display 303 are implemented as an in-vehicle display 30, but this disclosure is not limited thereto. The in-vehicle display 30 can be implemented as any display installed in a vehicle.

[0090] In Embodiment 5, an example is given in which the electronic device is implemented as a smartphone, but the present disclosure is not limited thereto, and the electronic device may be implemented as, for example, a personal computer, a personal digital assistant (PDA), a tablet terminal, a head-mounted display, a projector, a digital (video) camera, or the like.

[0091] Some exemplary embodiments have been described for illustrative purposes. While specific embodiments have been presented in the foregoing discussion, those skilled in the art will recognize that changes in form and detail may be made without departing from the broader spirit and scope of the invention. Therefore, the specification and drawings are to be regarded in an illustrative sense rather than a limiting sense. Consequently, this detailed description should not be construed in a limiting sense, and the scope of the invention is defined only by the scope of the included claims and the full scope of their authorized equivalents.

Claims

1. An organic light-emitting device, comprising: The anode and cathode are arranged facing each other; A light-emitting layer is disposed between the anode and the cathode; as well as A hole transport layer, disposed between the anode and the light-emitting layer, is in contact with the light-emitting layer. in The light-emitting layer comprises a first host material and a second host material. The difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the first host material is smaller than the difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the second host material. The difference between the HOMO energy level of the hole transport layer and the HOMO energy level of the first host material is equal to or greater than 0.05 eV and equal to or less than 0.16 eV, and The difference between the HOMO energy level of the first host material and the HOMO energy level of the second host material is equal to or less than 0.3 eV.

2. A display device, comprising: The organic light-emitting device according to claim 1.

3. A vehicle-mounted display, comprising: The display device according to claim 2.

4. An electronic device comprising: The display device according to claim 2.

5. A vehicle comprising: The vehicle display according to claim 3.

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