Organic light emitting device

Abstract

The present disclosure is an organic light-emitting device having a multilayer light-emitting layer obtained by laminating at least two light-emitting layers, in which an electron injection barrier is formed and an exciton binding region is expanded by adjusting HOMO and LUMO of organic compounds constituting the two light-emitting layers, wherein the first light-emitting layer has a first organic compound, a second organic compound, and a first light-emitting material, the second light-emitting layer has a first organic compound, a third organic compound, and a second light-emitting material, and formulae [1] and [2] are satisfied. [1] S1L1-S1L2lt; 1, S1L1-S1O1; [2] LUMOO2gt; and LUMOO2, LUMOO3, where S1L1 is the S1 energy level energy of the first luminescent material, S1L2 is the S1 energy level energy of the second luminescent material, S1O1 is the S1 energy level energy of the first organic compound, LUMOO2 is the energy level of the lowest unoccupied molecular orbital of the second organic compound, and LUMOO3 is the energy level of the lowest unoccupied molecular orbital of the third organic compound.

Description

Technical Field

[0001] The present invention relates to an organic light emitting device and an apparatus comprising the organic light emitting device. Background Art

[0002] An organic light-emitting device (also called an "organic electroluminescent device" or "organic EL device") is an electronic device including a pair of electrodes and an organic compound layer disposed between the electrodes. Electrons and holes are injected from the pair of electrodes to generate excitons of a light-emitting organic compound in the organic compound layer, and when the excitons return to a ground state, the organic light-emitting device emits light.

[0003] In recent years, organic light-emitting devices have been significantly developed, and low driving voltage, various light-emitting wavelengths, high-speed response, and thinning and weight reduction of light-emitting devices have been achieved.

[0004] Regarding the improvement of the efficiency of light-emitting devices, devices using efficiency-improving materials such as phosphorescent materials and delayed fluorescent materials can be mentioned. It is known that since any material has a light-emitting mechanism through a triplet excited state, the material deteriorates due to the transition from the triplet excited state to a higher excited state. In such an organic light-emitting device using an efficiency-improving material utilizing a triplet excited state, the improvement of the durability of the device is a subject of development. Regarding this technology, it is disclosed that the improvement is achieved by stacking a light-emitting layer.

[0005] Regarding the improvement of driving life achieved by adjacent light-emitting layers, Patent Document 1 discloses an example of stacking layers containing the same light-emitting material and different host materials to form a recombination region using a barrier caused by the HOMO energy level difference and the LUMO energy level difference of the host material. Patent Document 2 records an example of mixing two hole transport materials with a common electron transport host without the injection barrier of HOMO when stacking adjacent light-emitting layers. On the other hand, Patent Document 3 discloses an example of forming different LUMO energy levels for the same hole transport material to form an electron injection barrier. Patent Documents 2 and 3 disclose that the fact that the two host materials do not form an excited singlet state during the process of forming an exciplex contributes to the extension of life. However, there is no description of the improvement of driving degradation of a stack of multicolor light-emitting layers such as a stack of a green light-emitting layer and a red light-emitting layer.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: PCT Japanese Translation Patent Publication No. 2008-509565

[0009] Patent Document 2: Japanese Patent Laid-Open No. 2017-152410

[0010] Patent Document 3: Japanese Patent Laid-Open No. 2017-183291 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In order to provide a display with higher brightness and higher reliability, an organic light-emitting device with a longer life is required. In particular, in a high-efficiency organic light-emitting device using triplet excitons of a phosphorescent material or the like, improvement in durability is a problem. The organic light-emitting devices described in Patent Documents 1 to 3 are organic light-emitting devices including stacked light-emitting layers; however, there is room for improvement in the driving life of such organic light-emitting devices including stacked light-emitting layers.

[0013] Solutions for solving problems

[0014] Therefore, an object of the present invention is to provide an organic light emitting device including stacked light emitting layers and having a good driving lifespan at high brightness.

[0015] The present invention provides an organic light-emitting device, which comprises a first electrode, a first light-emitting layer, a second light-emitting layer in contact with the first light-emitting layer, and a second electrode in sequence, wherein

[0016] The first light-emitting layer comprises a first organic compound, a second organic compound and a first light-emitting material,

[0017] The second light-emitting layer includes a first organic compound, a third organic compound, and a second light-emitting material, and

[0018] The organic light-emitting device satisfies the following formulas [1] and [2].

[0019] |S1L1-S1L2|<|S1L1-S1O1|[1]

[0020] LUMOO2>LUMOO3[2]

[0021] S1L1: S1 level energy of the first luminescent material

[0022] S1L2: S1 level energy of the second luminescent material

[0023] S1O1: S1 level energy of the first organic compound

[0024] LUMOO2: Energy level of the lowest unoccupied molecular orbital of the second organic compound

[0025] LUMOO3: The lowest unoccupied molecular orbital energy level of the third organic compound

[0026] Effects of the Invention

[0027] According to the present invention, in a light-emitting layer stack composed of at least two light-emitting layers, an electron injection barrier is formed between the light-emitting layers, thereby expanding the recombination area of ​​holes and electrons, thereby improving the durability of the light-emitting layer. Therefore, the present invention provides an organic light-emitting device having a good driving life at high brightness and an apparatus including the organic light-emitting device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] is a conceptual diagram showing the relationship between HOMO and LUMO of a light-emitting layer stack according to one embodiment of an organic light-emitting device according to the present invention.

[0029] [ Figure 2 ] is a conceptual diagram showing the relationship between HOMO and LUMO of a light-emitting layer stack according to another embodiment of the organic light-emitting device of the present invention.

[0030] [ Figure 3 ] is a conceptual diagram showing the relationship between HOMO and LUMO of a light-emitting layer stack according to another embodiment of the organic light-emitting device of the present invention.

[0031] [ Figure 4 ] is a conceptual diagram showing the relationship between HOMO and LUMO of a light-emitting layer stack according to another embodiment of the organic light-emitting device of the present invention.

[0032] [ Figure 5 ] is a schematic cross-sectional view showing an embodiment of a display device including an organic light-emitting device according to the present invention and a transistor connected to the organic light-emitting device.

[0033] [ Figure 6 ] is a schematic diagram showing an example of a display device according to an embodiment of the present invention.

[0034] [ Fig. 7A ] is a schematic diagram showing an example of an image pickup apparatus according to an embodiment of the present invention.

[0035] [ Figure 7B ] is a schematic diagram showing an example of an electronic device according to an embodiment of the present invention.

[0036] [ Fig. 8A ] is a schematic diagram showing an example of a display device according to an embodiment of the present invention.

[0037] [ Figure 8B ] is a schematic diagram showing an example of a foldable display device.

[0038] [ Fig. 9A ] is a schematic diagram showing an example of a lighting device according to an embodiment of the present invention.

[0039] [ Fig. 9B ] is a schematic diagram showing an example of a moving body including a lighting fixture for a vehicle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is an invention for providing an organic light-emitting device with a long life. In order to achieve an extension of the life of the organic light-emitting device, it is necessary to reduce the degradation of the organic materials in the device, especially the degradation of the organic materials used for the light-emitting layer. Generally, in order to extend the life of the organic light-emitting device, it is effective to expand the recombination area of ​​electrons and holes to reduce the degradation caused by the concentration of exciton generation. The concentration of exciton generation causes energy to be transferred from a molecule in an excited state to a molecule in another excited state and causes a transfer to a higher energy state. In a high energy state, if the binding energy of a single bond site in the molecular structure is exceeded, the bond breaks and a decomposition product is generated, resulting in brightness degradation. In order to avoid this situation, it is effective to disperse the generation of excitons. Among several methods of causing dispersion, it is believed that a method of dispersing the recombination points of electrons and holes by dividing the light-emitting layer to increase the number of light-emitting interfaces is effective in the present invention.

[0041] The organic light-emitting device according to the present invention includes, as a basic structure, a first electrode, a first light-emitting layer, a second light-emitting layer in contact with the first light-emitting layer, and a second electrode in sequence. That is, at least the light-emitting layer is formed by a light-emitting layer stack in which at least two light-emitting layers are stacked in contact with each other. The first light-emitting layer contains a first organic compound as a main material, a second organic compound as an auxiliary material, and a first light-emitting material as a light-emitting material. The second light-emitting layer contains a first organic compound as a main material, a third organic compound as an auxiliary material, and a second light-emitting material as a light-emitting material. The organic light-emitting device according to the present invention satisfies the following formulas [1] and [2].

[0042] |S1L1-S1L2|<|S1L1-S1O1|[1]

[0043] LUMOO2>LUMOO3[2]

[0044] S1L1: S1 level energy of the first luminescent material

[0045] S1O1: S1 level energy of the first organic compound

[0046] LUMOO2: Energy level of the lowest unoccupied molecular orbital of the second organic compound

[0047] LUMOO3: The lowest unoccupied molecular orbital energy level of the third organic compound

[0048] Since the organic light-emitting device according to the present invention satisfies formula [1], energy transfer is more likely to occur between the first light-emitting layer and the second light-emitting layer than between the host material and the light-emitting material in the first light-emitting layer. In addition, since the organic light-emitting device satisfies formula [2], an electron injection barrier from the second light-emitting layer to the first light-emitting layer is formed between the first light-emitting layer and the second light-emitting layer, and the recombination region is expanded.

[0049] In the present invention, the organic light-emitting device preferably includes a third light-emitting layer disposed on the first electrode side in contact with the first light-emitting layer, comprising a first organic compound as a main material and a third light-emitting material as a light-emitting material. The third light-emitting layer preferably further comprises a fourth organic compound as an auxiliary material. When the first light-emitting layer and the second light-emitting layer have the same light-emitting color, the third light-emitting layer has a light-emitting color different from the light-emitting colors of the first light-emitting layer and the second light-emitting layer. In the present invention, yellow light is emitted by green light emission and red light emission. Therefore, when the first light-emitting layer and the second light-emitting layer emit green light or red light, the third light-emitting layer emits red light or green light. When the first light-emitting layer and the second light-emitting layer have different light-emitting colors, the light-emitting color of the third light-emitting layer may be the same as any of the light-emitting colors.

[0050] In the present invention, it is further preferred to satisfy the following formula [3] and still further preferred to satisfy the following formula [4] because energy easily flows from the light-emitting material of the first light-emitting layer to the light-emitting material of the third light-emitting layer.

[0051] S1L3 <S1L1[3]

[0052] HOMOL3 <HOMOL1[4]

[0053] S1L3: S1 energy level energy of the third luminescent material

[0054] HOMOL1: Energy level of the highest occupied molecular orbital of the first luminescent material

[0055] HOMOL3: Energy level of the highest occupied molecular orbital of the third luminescent material

[0056] In the present invention, it is preferable to satisfy the following formula [5] because the durability of the light-emitting material is improved to thereby improve the life of the organic light-emitting device.

[0057] LUMOL3 <LUMOL1[5]

[0058] LUMOL1: Energy level of the lowest unoccupied molecular orbital of the first luminescent material

[0059] LUMOL3: Energy level of the lowest unoccupied molecular orbital of the third luminescent material

[0060] In the present invention, it is preferred that the following formulas [6] to [8] are further satisfied.

[0061] LUMOO1>LUMOO3[6]

[0062] HOMOO4>HOMOO1[7]

[0063] HOMOO4>HOMOO2[8]

[0064] LUMOO1: Energy level of the lowest unoccupied molecular orbital of the first organic compound

[0065] LUMOO3: The lowest unoccupied molecular orbital energy level of the third organic compound

[0066] HOMOO1: Energy level of the highest occupied molecular orbital of the first organic compound

[0067] HOMOO4: The energy level of the highest occupied molecular orbital of the fourth organic compound

[0068] HOMOO2: Energy level of the highest occupied molecular orbital of the second organic compound

[0069] Furthermore, in the present invention, it is preferable to satisfy at least one of the following formulae [9] and

[10] because the driving voltage of the organic light-emitting device can be reduced.

[0070] LUMOO1>LUMOO2[9]

[0071] HOMOO2>HOMOO1

[10]

[0072] LUMOO1: Energy level of the lowest unoccupied molecular orbital of the first organic compound

[0073] LUMOO2: Energy level of the lowest unoccupied molecular orbital of the second organic compound

[0074] HOMOO1: Energy level of the highest occupied molecular orbital of the first organic compound

[0075] HOMOO2: Energy level of the highest occupied molecular orbital of the second organic compound

[0076] Hereinafter, a light-emitting layer stack in which three light-emitting layers are stacked is used as an example, and reference is made to Figure 1 to Figure 4The operation of expanding the recombination area of ​​electrons and holes in the present invention and the preferred embodiment is described. The luminescent pixels used for the display mainly need light-emitting devices that present red, green and blue luminescent colors. The light-emitting device has a structure in which a light-emitting layer is formed according to the luminescent color of each luminescent pixel or a color filter is set for a device that emits white light. A generally possible structure is a structure in which blue luminescence and yellow luminescence are combined when white light is emitted.

[0077] For the purpose of expanding the color reproduction range as a display, the yellow light-emitting layer in the light-emitting layer presents yellow by emitting two colors (red and green); however, the degradation rate of red light emission and the degradation rate of green light emission are generally different. The light-emitting layer showing green light emission is more susceptible to degradation than the light-emitting layer showing red light emission because the energy level of the excitons utilized is also high. At the same time, when the above-mentioned yellow light-emitting device is used in a display or other light-emitting device, the brightness degradation time of the red light emission is different from the brightness degradation time of the green light emission, resulting in a problem of color shift during the driving of the device. In particular, for example, when an organic light-emitting device is used in a white light-emitting device in which a blue light-emitting device and a yellow light-emitting device are connected together in a series device structure, this color shift caused by the driving degradation of the organic light-emitting device showing yellow light emission becomes a problem.

[0078] The light-emitting layer stack of the present embodiment includes a third light-emitting layer, a first light-emitting layer and a second light-emitting layer, the third light-emitting layer is configured on the hole injection electrode side, and the second light-emitting layer is configured on the electron injection electrode side. Each light-emitting layer contains a red or green light-emitting material (guest). The light-emitting layer includes at least one red light-emitting layer and at least one green light-emitting layer, and each contains a first organic compound as a host material and any one of the second to fourth organic compounds as an auxiliary material. Therefore, the light-emitting layer has the following structure.

[0079] First light-emitting layer: first organic compound, second organic compound and first light-emitting material

[0080] Second light-emitting layer: first organic compound, third organic compound and second light-emitting material

[0081] The third light-emitting layer: the first organic compound, the fourth organic compound and the third light-emitting material

[0082] In this embodiment, the host is the compound with the highest mass ratio among the compounds constituting the light-emitting layer. The guest is a compound with a lower mass ratio than the host among the compounds constituting the light-emitting layer and is responsible for the main light emission. The auxiliary material is a compound with a lower mass ratio than the host among the compounds constituting the light-emitting layer and assists the light emission of the guest. The auxiliary material is also called a second host.

[0083] A feature of the present embodiment is that the first organic compound is used together as the main material of each light-emitting layer. The main material is responsible for the function as a matrix in the light-emitting layer and the charge transport. Since the first organic compound is used as the main material, the first organic compound preferably has a high glass transition temperature. In the case where the light-emitting material includes a phosphorescent material or a thermally activated delayed fluorescent material, the lowest triplet state (T1) of the first organic compound needs to be higher than the high T1 energy level of the light-emitting material included, so the band gap must be wide. The second, third and fourth organic compounds used as auxiliary materials each need to have a content of at least 10% by mass or more in the light-emitting layer, preferably about 20% to 35% by mass, so that the organic compound is used as an auxiliary for carrier transport.

[0084] Since the first organic compound is used as a host material in each of the first to third light-emitting layers, it can contribute to the reduction of the evaporation source in the evaporation chamber of the evaporation equipment during production for the formation of the light-emitting layer stack. In addition, since a layer not containing a light-emitting material is not provided between the light-emitting layers, the generated excitons can be utilized without any surplus.

[0085] Figures 1 to 4 The relationship between the HOMO and LUMO energy levels of the first organic compound and the second to fourth organic compounds in the light-emitting layer stack of this embodiment is shown. Figures 1 to 4 The relationship shown is distinguished by the second organic compound contained in the first light-emitting layer. Figures 1 to 4 In the following description, HOMO represents the energy level of the highest occupied molecular orbital, LUMO represents the energy level of the lowest unoccupied molecular orbital, O1 represents a first organic compound, O2 represents a second organic compound, O3 represents a third organic compound, O4 represents a fourth organic compound, L1 represents a first light-emitting material, L2 represents a second light-emitting material, and L3 represents a third light-emitting material.

[0086] In the present embodiment, the fourth organic compound contained in the third light-emitting layer on the hole injection electrode side assists hole transport, and the relationship between the HOMO of the first organic compound and the HOMO of the fourth organic compound is as follows.

[0087] HOMOO4>HOMOO1[7]

[0088] The third organic compound contained in the second light-emitting layer on the electron injection electrode side assists electron transport, and the relationship between the LUMO of the first organic compound and the LUMO of the third organic compound is as follows.

[0089] LUMOO1>LUMOO3[6]

[0090] Furthermore, HOMO and LUMO of the second organic compound, the third organic compound, and the fourth organic compound have the following relationship.

[0091] LUMO O2 > LUMO O3 [2]

[0092] HOMO O4 > HOMO O2 [8]

[0093] Figure 1 Shows the case where the second organic compound contained in the first light-emitting layer neither participates in hole transport nor participates in electron transport, and the relationships between the HOMO and LUMO of the first organic compound and the second organic compound are as follows.

[0094] HOMO O2 < HOMO O1 (does not assist in hole transport)

[0095] LUMO O1 < LUMO O2 (does not assist in electron transport)

[0096] In this case, the energy level difference from HOMO O4 to HOMO O1 is the hole injection barrier from the third light-emitting layer to the first light-emitting layer, and the energy level difference from LUMO O3 to LUMO O1 is the electron injection barrier from the second light-emitting layer to the first light-emitting layer.

[0097] Figure 2 Shows the case where the second organic compound contained in the first light-emitting layer does not assist in hole transport but assists in electron transport, and the relationships between the HOMO and LUMO of the first organic compound and the second organic compound are as follows.

[0098] HOMO O2 < HOMO O1 (does not assist in hole transport)

[0099] LUMO O1 > LUMO O2 (assists in electron transport) [9]

[0100] In this case, the energy level difference from HOMO O4 to HOMO O1 is the hole injection barrier from the third light-emitting layer to the second light-emitting layer, and the energy level difference from LUMO O3 to LUMO O2 is the electron injection barrier from the second light-emitting layer to the first light-emitting layer.

[0101] Figure 3 Shows the case where the second organic compound contained in the first light-emitting layer assists in hole transport and assists in electron transport, and the relationships between the HOMO and LUMO of the first organic compound and the second organic compound are as follows.

[0102] HOMO O2 > HOMO O1 (assists in hole transport)

[10]

[0103] LUMO O1 < LUMO O2 (does not assist in electron transport)

[0104] In this case, the energy level difference from HOMOO4 to HOMOO2 is a hole injection barrier from the third light emitting layer to the first light emitting layer, and the energy level difference from LUMOO3 to LUMOO1 is an electron injection barrier from the second light emitting layer to the first light emitting layer.

[0105] Figure 4 The case where the second organic compound included in the first light-emitting layer assists both hole transport and electron transport is shown, and the relationship between HOMO and LUMO of the first organic compound and the second organic compound is as follows.

[0106] HOMOO2>HOMOO1 (assisted hole transport)

[10]

[0107] LUMOO1>LUMOO2 (assisted electron transport) [9]

[0108] In this case, the energy level difference from HOMO4 to HOMO2 is a hole injection barrier from the third light emitting layer to the first light emitting layer, and the energy level difference from LUMOO3 to LUMOO2 is an electron barrier from the second light emitting layer to the first light emitting layer.

[0109] exist Figure 1 to Figure 4 In any of the cases shown, the presence of the hole and electron injection barrier to the second light-emitting layer expands the recombination region and can reduce the degradation caused by the concentration of exciton generation. According to one embodiment of the present invention, a light-emitting device can be provided, which particularly includes a long-life yellow light-emitting layer in which red and green phosphorescent materials are used for the light-emitting layer. Therefore, the organic light-emitting device that mainly exhibits yellow light emission has an extended life. In addition, an improvement can be achieved so that color shift does not occur with drive degradation.

[0110] In the light-emitting layer stack of the present embodiment, a charge injection barrier from the second light-emitting layer and the third light-emitting layer to the first light-emitting layer is formed in each layer that contains the first organic compound. In this case, when the first organic compound has a decomposition-resistant skeleton, further improvement in durability can be expected. Specifically, for the decomposition-resistant skeleton, it is important that all single bonds in conjunction with the fused polycyclic skeleton are carbon-carbon bonds with high binding energy. This is because, as shown in the examples below about binding energy, for example, when a carbon-nitrogen bond is provided as a bond between the fused polycyclic skeletons, the bond is easily broken at a higher excitation energy state generated by a certain exciton generation.

[0111] [Chemical formula 1]

[0112]

[0113] At the same time, the first organic compound is not only required to limit the energy in the light-emitting material as a host material, but also to be responsible for hole transport and electron transport. However, although the second to fourth organic compounds are each responsible for hole transport or electron transport as an auxiliary material, thereby utilizing a strong host material, a carrier barrier can be generated at the interface between the stacked light-emitting layers. Therefore, this is a more preferred form for improving the durability of the organic light-emitting device by expanding the recombination area.

[0114] Examples of luminescent materials in the present embodiment include, but are not limited to, fluorescent materials, phosphorescent materials, and thermally activated delayed fluorescent materials. Fluorescent materials are luminescent materials in which radiative transitions from an excited singlet state to a ground state occur. Relatively speaking, phosphorescent materials are materials in which radiative transitions from the lowest triplet state to a ground state occur. Thermally activated delayed fluorescent materials are materials in which radiative transitions from an excited singlet state to a ground state occur from the lowest triplet state due to thermal excitation through a reverse intersystem crossing process.

[0115] In this embodiment, the green light-emitting material refers to a light-emitting material having a peak wavelength in the range of 500nm to 560nm in the photoluminescence spectrum. The red light-emitting material refers to a light-emitting material having a peak wavelength in the range of 600nm to 650nm in the photoluminescence spectrum. The blue light-emitting material refers to a material having a peak wavelength in the range of 440nm to 480nm in the photoluminescence spectrum.

[0116] In the present embodiment, considering the luminous efficiency of the organic light-emitting device, the luminescent material is preferably a phosphorescent material or a thermally activated delayed fluorescent material. These materials have a luminescent mechanism through the lowest triplet state; therefore, if the exciton generation is concentrated, the triplet excitons (T1) with a long excitation lifetime collide with each other, and therefore, triplet-triplet annihilation is likely to occur. If this phenomenon occurs, a higher triplet excited state is generated with a certain probability. In addition, the occurrence of transient absorption of green or red light emitted by the triplet excited state molecular absorption also produces a higher triplet excited state. These lead to material degradation. In the state of high current density, the generation of excessive excitons occurs; therefore, it is believed that similar degradation may occur not only in the luminescent material, but also in the main material and the auxiliary material. Therefore, in the present embodiment, luminescent materials such as phosphorescent materials or delayed fluorescent materials are more effective, and the first luminescent material, the second luminescent material and the third luminescent material are preferably phosphorescent materials. The concentration of the luminescent material contained in the luminescent layer is preferably 0.1 mass % to 15 mass %, but this embodiment is not particularly limited.

[0117] The light-emitting layer stack according to the present embodiment may include a fourth light-emitting layer and a charge generation layer that emits blue light between the first electrode and the light-emitting layer stack or between the second electrode and the light-emitting layer stack. The charge generation layer provides a function as a tandem device: the electrons generated in the charge generation layer and the holes injected from the first electrode undergo charge recombination to generate excitons, and the holes generated in the charge generation layer and the electrons injected from the second electrode undergo charge recombination to generate excitons. Therefore, the internal quantum efficiency is doubled. In this case, the organic light-emitting device of the present embodiment can be used as a yellow light-emitting layer used as a complementary color of blue light emission for one side of the tandem device. Therefore, the tandem device structure obtained by using the light-emitting layer stack according to the present embodiment together with the blue light-emitting layer can provide a white light-emitting device. The blue light-emitting layer contains at least an organic compound used as a host material and an organic compound as a blue light-emitting material.

[0118] White light-emitting devices can be applied to displays or lighting, for example. At this time, in the case of improving the durability of the yellow light-emitting layer, especially in the case where the brightness degradation time between the green light-emitting color and the red light-emitting color is different, it is preferred that the present embodiment be applied to colors with shorter brightness degradation time. Among the blue, green and red in the case of white light emission, for example, when the brightness degradation of the green light emission is the fastest, the light emission color is easily changed from white to light yellow. This may cause the image to stick to the display. Using the organic light-emitting device of the present embodiment, there is an effect of shortening the time taken to cause the image to stick. In the case of yellow light emission caused by red light emission and green light emission of a phosphorescent material or a thermally activated delayed fluorescent material, green light emission using more energy may experience brightness degradation. Therefore, when an organic light-emitting device that emits yellow light from a red light-emitting layer and a green light-emitting layer is used and a series device is formed with a blue light-emitting device to emit white light, it is necessary to improve the brightness degradation life of green. Therefore, two of the three light-emitting layers of the present embodiment preferably contain a light-emitting material that emits green light.

[0119] This embodiment is characterized in that the recombination region is dispersed by generating an energy barrier composed of HOMO and LUMO of the first to fourth organic compounds between three adjacent light-emitting layers to prevent the concentration of excitons. It is characterized in that, in this case, the intensity of the first organic compound is utilized to produce an effect of improving the driving life of the green light-emitting color and the red light-emitting color. The combination of light-emitting colors is as follows.

[0120] [Table 1]

[0121] combination PL peak of the first luminescent material PL peak of the second luminescent material PL peak of the third luminescent material RGG red green green RRG red red green RGR red green red GRR green red red GRG green red green GGR green green red

[0122] In contrast, there are countless combinations of film thickness configurations, but the following is given as an example. The unit of the film thickness in Table 2 is nm. In an organic light-emitting device, since the film thickness is proportional to the amount of light emitted from the corresponding light-emitting layer, the film thickness is appropriately changed when a balance of light-emitting colors is required.

[0123] [Table 2]

[0124] Film thickness structure Thickness of the first light emitting layer The thickness of the second light emitting layer Thickness of the third light emitting layer Thickness-A 10 10 10 Thickness-B 5 10 15 Thickness-C 15 10 5 Thickness-D 10 5 15 Thickness-E 15 5 10

[0125] [Layer structure]

[0126] Next, each layer of the organic light-emitting device of this embodiment is described.

[0127] The layer structure of the organic light-emitting device of this embodiment is not particularly limited. For example, the structure of first electrode / hole injection layer / hole transport layer / electron blocking layer / light-emitting layer stack / hole blocking layer / electron transport layer / electron injection layer / second electrode will be described as an example.

[0128] The hole injection / transport material forming the hole injection layer or the hole transport layer is preferably a material that is convenient for injecting holes from the anode and has a high hole mobility so as to transport the injected holes to the light-emitting layer. In addition, the hole injection / transport material is preferably a material with a high glass transition temperature to reduce the degradation of film quality such as crystallization in the organic light-emitting device. Examples of low-molecular-weight or high-molecular-weight materials having such hole injection / transport properties include triarylamine derivatives, arylcarbazole derivatives, phenylenediamine derivatives, stilbene derivatives, phthalocyanine derivatives, porphyrin derivatives, poly(vinylcarbazole), poly(thiophene) and other conductive polymers. In addition, the above-mentioned hole injection / transport material is also suitable for an electron blocking layer.

[0129] Specific examples of the compound used as the hole injection / transport material are shown below; however, in the present embodiment, the hole injection / transport material is not limited to these.

[0130] [Chemical formula 2]

[0131]

[0132] Among the above hole injection / transport materials, HT16 to HT18 can be used for the layer in contact with the anode to reduce the driving voltage. HT16 is widely used in organic light-emitting devices. HT2, HT3, HT4, HT5, HT6, HT10 and HT12 can be used for the organic compound layer adjacent to HT16. Various materials can be used for a single organic compound layer.

[0133] In this embodiment, the fourth organic compound is preferably a hole transport material. The fourth organic compound is not particularly limited as long as it is an organic compound having hole transport capability. For example, among the above compounds, each of the materials other than HT16, HT17, and HT18 is preferably used as a hole transport material for the fourth organic compound in this embodiment. The second organic compound and the fourth organic compound may also be hole transport materials.

[0134] Examples of luminescent materials mainly related to the luminescent function include condensed ring compounds (such as fluorene derivatives, naphthalene derivatives, pyrene derivatives, perylene derivatives, tetracene derivatives, anthracene derivatives and rubrene), quinacridone derivatives, coumarin derivatives, stilbene derivatives, organic aluminum complexes such as tris(8-hydroxyquinoline)aluminum, iridium complexes, platinum complexes, rhenium complexes, copper complexes, europium complexes, ruthenium complexes, and polymer derivatives such as poly(phenylene vinylene) derivatives, poly(fluorene) derivatives, and poly(phenylene) derivatives.

[0135] Specific examples of compounds used as light-emitting materials are shown below, but the light-emitting materials are of course not limited thereto.

[0136] [Chemical formula 3]

[0137]

[0138] [Chemical formula 4]

[0139]

[0140] For the light-emitting material, in order to achieve a longer driving life, the single bond of the ring of the fused polycyclic structure is preferably a carbon-carbon bond identical to the first organic compound. Hydrocarbon compounds are compounds consisting only of carbon and hydrogen, and BD7, BD8, GD5 to GD9, and RD1 correspond to such compounds. These light-emitting materials are fused polycyclic compounds comprising a 5-membered ring, and have a high ionization potential and are therefore not easily oxidized. Therefore, these light-emitting materials are more preferred because they provide highly durable devices with a long life. BD7, BD8, GD5 to GD9 and RD1 correspond to such compounds.

[0141] The first organic compound contained in the light-emitting layer is preferably a compound with good durability as a main material of the light-emitting layer. In addition to aromatic hydrocarbon compounds and their derivatives, examples of such compounds include carbazole derivatives, dibenzofuran derivatives, dibenzothiophene derivatives, organic aluminum complexes such as tris(8-hydroxyquinoline)aluminum, and organic beryllium complexes.

[0142] Specific examples of the first organic compound contained in the light-emitting layer of this embodiment are shown below, but the first organic compound is of course not limited thereto.

[0143] [Chemical formula 5]

[0144]

[0145] When the main material of the light-emitting layer used as the first organic compound is a hydrocarbon compound, the light-emitting layer easily captures electrons and holes, so the effect of improving efficiency is significant, which is preferred. The hydrocarbon compound is a compound composed only of carbon and hydrogen, and EM1 to EM12 and EM15 to EM27 correspond to hydrocarbon compounds. As the main material, from the viewpoint of stability, a material having no carbon-heteroatom bond in the single bond connecting the aromatic unit in the structure is more preferred.

[0146] The electron transport material forming the electron transport layer can be freely selected from materials capable of transporting electrons injected from the cathode to the light-emitting layer, and is selected in consideration of, for example, a balance with the hole mobility of the hole injection / transport material. Examples of materials having electron transport capability include oxadiazole derivatives, oxazole derivatives, pyrazine derivatives, triazole derivatives, triazine derivatives, quinoline derivatives, quinoxaline derivatives, phenanthroline derivatives, organoaluminum complexes, and condensed ring compounds (e.g., fluorene derivatives, naphthalene derivatives, The above-mentioned electron transporting materials are also suitable for the hole blocking layer.

[0147] Specific examples of the compound used as the electron transport material are shown below; however, in the present embodiment, the electron transport material is not limited to these.

[0148] [Chemical formula 6]

[0149]

[0150] The electron injection material forming the electron injection layer can be freely selected from materials that can easily inject electrons from the cathode, and can be selected by considering, for example, the balance with the hole injection ability. As organic compounds, n-type dopants and reductive dopants are also included. Examples thereof include alkali metal compounds such as lithium fluoride, lithium complexes such as lithium quinoline, benzimidazolidine derivatives, imidazoline derivatives, fulvalene derivatives, and acridine derivatives, etc.

[0151] On the other hand, in this embodiment, as the second organic compound or the third organic compound, the above-mentioned electron transporting material is preferred as a material assisting electron transporting ability. In this case, the electron transporting compound is not limited to any of the above-mentioned compounds.

[0152] The first to fourth organic compounds used in the light-emitting layer stack of this embodiment include the following organic compounds in addition to the compounds listed above.

[0153] [Chemical formula 7]

[0154]

[0155] Taking into account their HOMO and LUMO, the above-mentioned Z-1 to Z-23 can be selected as the first organic compound to the fourth organic compound. For example, Z-1 to Z-3 are organic compounds of aromatic hydrocarbons in which a plurality of fused polycyclic skeletons are bonded together by carbon-carbon single bonds, and can be preferably used as the first organic compound. The HOMO, LUMO, and S1 of the above-mentioned Z-1 to Z-23 are as follows. Table 1 shows the numerical values ​​of the HOMO, LUMO, and S1 of the above-mentioned Z-1 to Z-23. HOMO is the ionization potential value measured by AC-3 manufactured by RIKEN KEIKI Co., Ltd. of a 50nm film of each organic compound prepared by vacuum evaporation. LUMO is a value obtained by measuring the absorption spectrum of the same film, determining the light absorption end as a band gap, and then subtracting the band gap from the ionization potential value. The light absorption end corresponds to the lowest excited singlet state of each compound. However, in the case of a phosphorescent material, since the light absorption edge corresponds to absorption from a ground state to a triplet state, the LUMO found by the same method is not strictly correct but can be used approximately.

[0156] [Table 3]

[0157] symbol HOMO LUMO S1 Z-1 -6.38 -2.92 3.46 Z-2 -6.40 -2.94 3.46 Z-3 -6.33 -3.05 3.28 Z-4 -5.49 -2.51 2.98 Z-5 -5.77 -2.63 3.14 Z-6 -5.73 -3.15 2.58 Z-7 -5.68 -2.70 2.98 Z-8 -5.76 -2.66 3.10 Z-9 -5.85 -2.71 3.14 Z-10 -6.30 -3.22 3.08 Z-11 -6.31 -3.33 2.98 Z-12 -6.43 -3.30 3.13 Z-13 -6.58 -3.30 3.28 Z-14 -6.58 -3.49 3.09 Z-15 -6.33 -3.13 3.20 Z-16 -6.60 -3.29 3.31 Z-17 -6.51 -3.26 3.25 Z-18 -6.77 -3.42 3.35 Z-19 -6.19 -3.27 2.92 Z-20 -5.85 -3.32 2.53 Z-21 -6.55 -3.42 3.13 Z-22 -6.00 -2.82 3.18 Z-23 -5.92 -3.15 2.77

[0158] The organic light-emitting device includes an anode, an organic compound layer and a cathode formed on a substrate. A protective layer, a color filter, etc. may be provided on the cathode. When the color filter is provided, a planarization layer may be provided between the color filter and the protective layer. The planarization layer may be formed of an acrylic resin, etc.

[0159] The substrate may be formed of quartz, glass, silicon wafer, resin, metal, or the like. In addition, switching devices such as transistors and wirings may be arranged on the substrate, and an insulating layer may be arranged thereon. The insulating layer may be formed of any material as long as a contact hole may be formed therein to establish electrical connection between the anode and the wirings and as long as insulation from unconnected wirings may be ensured. For example, a resin such as polyimide, silicon oxide, or silicon nitride may be used.

[0160] The material constituting the anode preferably has a work function as large as possible. Examples of materials that can be used include single metals such as gold, platinum, silver, copper, nickel, palladium, cobalt, selenium, vanadium, and tungsten; mixtures containing these metals; alloys of their combinations; and metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide. In addition, conductive polymers such as polyaniline, polypyrrole, and polythiophene can also be used.

[0161] These electrode materials may be used alone or in combination of two or more thereof. The anode may be formed of a single layer or a plurality of layers.

[0162] When the anode is used as a reflective electrode, for example, chromium, aluminum, silver, titanium, tungsten, molybdenum, an alloy thereof, or a laminate thereof may be used. When the anode is used as a transparent electrode, a transparent conductive oxide layer such as indium tin oxide (ITO) or indium zinc oxide may be used; however, the anode is not limited thereto. The electrode may be formed by using photolithography.

[0163] In contrast, the material constituting the cathode preferably has a small work function. Examples of cathode materials include alkali metals such as lithium; alkaline earth metals such as calcium; elemental metals such as aluminum, titanium, manganese, silver, lead and chromium; and mixtures containing these metals. Alloys of these elemental metals can also be used. For example, magnesium-silver, aluminum-lithium, aluminum-magnesium, silver-copper and zinc-silver can be used. Metal oxides such as indium tin oxide (ITO) can also be used. These electrode materials can be used alone or in combination of two or more thereof. The cathode can have a single-layer structure or a multilayer structure. In particular, silver is preferably used, and a silver alloy is more preferably used to reduce the aggregation of silver. The alloying ratio is not limited as long as the aggregation of silver can be reduced. For example, the ratio can be 1:1.

[0164] The cathode is not particularly limited. The cathode may be a conductive oxide layer made of ITO or the like to provide a top-type light-emitting device. Alternatively, the cathode may be a reflective electrode made of aluminum (Al) or the like to provide a bottom-type light-emitting device. The method for forming the cathode is not particularly limited; however, for example, it is more preferred to use a DC or AC sputtering method, because good film coverage is achieved and resistance is easily reduced.

[0165] After forming the cathode, a protective layer can be provided. For example, a glass member containing a hygroscopic agent is bonded to the cathode to reduce the penetration of water, etc. into the organic compound layer. Therefore, the occurrence of display defects can be reduced. In another embodiment, a passivation film composed of silicon nitride, etc. can be provided on the cathode to reduce the penetration of water, etc. into the organic compound layer. For example, after forming the cathode, the resulting substrate can be transferred to another chamber without breaking the vacuum, and a protective layer can be formed thereon by forming a silicon nitride film with a thickness of 2 μm by means of a CVD method. After film deposition by the CVD method, a protective layer can be formed by an atomic layer deposition method (ALD method).

[0166] As described above, the organic light-emitting device of this embodiment may include a fourth light-emitting layer that emits blue light and a charge generation layer located between the light-emitting layer stack and the first electrode or the second electrode. The charge generation layer is formed by forming an n / p junction by a p layer and an n layer, or by using a p-doped layer and an n-doped layer. For example, in the case of forming a p / n junction alone, an electron injection layer is preferably provided so that the electrons extracted by the p layer are further injected into the electron transport layer. Alternatively, the structure may be an n-doped layer / p-doped layer. There is no restriction on the type of combination suitable for the charge generation layer in this embodiment.

[0167] For the p-doped layer in the charge generation layer, for example, a highly electron-absorbing HAT-CN or Lewis acid (such as molybdenum oxide) and an aromatic amine compound can be mixed. HAT-CN and molybdenum oxide, etc. are n-type materials, and these materials can be used to form a stacked structure. For the n-doped layer, for example, a material with a low work function and easily doped with electrons, such as an alkali metal or an alkaline earth metal, is preferably used. Alternatively, LiF, etc. can be combined with a reducing metal film to form an electron injection layer, and an n-type layer / p-type layer structure can be formed to generate charges. In this embodiment, whether the charge is generated at the interface or pre-generated by doping is not restricted.

[0168] When the organic light-emitting device of the present embodiment is used for a tandem device including a charge generation layer, in the carrier injection performed from the first electrode or the second electrode, the carriers generated in the charge generation layer are injected. Since the light-emitting layer stack according to the present embodiment exhibits yellow light emission, in order to exhibit white light emission, it is preferred to form a tandem device with a blue light-emitting device. The white light-emitting device formed in this way can be applied to a light source for display or an illumination light source. In this case, since the organic light-emitting device according to the present invention has an improved lifespan, the brightness degradation of green light emission, in particular, is reduced, and a white light-emitting device with a long lifespan and a light color of light that undergoes little change in brightness can be provided.

[0169] A color filter may be provided for each pixel of the white light emitting device. For example, a color filter provided in consideration of the size of the pixel may be arranged on another substrate, and the substrate may be attached to the substrate having the organic light emitting device thereon. Alternatively, a color filter may be formed on a protective layer formed of silicon oxide or the like by photolithographic patterning.

[0170] The organic compound layers forming the organic light-emitting device of the present embodiment (such as the hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, and electron injection layer) are formed by the following method.

[0171] The organic compound layer forming the organic light-emitting device of the present embodiment can be formed by a dry method such as vacuum evaporation, ionized evaporation, sputtering or plasma. Instead of the dry method, a wet method can also be used, which includes dissolving the material in an appropriate solvent and then forming a layer by a known coating method (such as spin coating, dipping, casting, LB method or inkjet method).

[0172] When the layer is formed by vacuum deposition or coating using a solution, the layer is less likely to undergo crystallization and has good stability over time. When the film is formed by coating, the film may be formed in combination with an appropriate binder resin.

[0173] Examples of binder resins include, but are not limited to, polyvinyl carbazole resins, polycarbonate resins, polyester resins, ABS resins, acrylic resins, polyimide resins, phenolic resins, epoxy resins, silicone resins, and urea-formaldehyde resins. These binder resins can be used alone as homopolymers or copolymers, or can be used in combination as mixtures of two or more thereof. In addition, known additives such as plasticizers, oxidation inhibitors, and ultraviolet light absorbers can also be optionally used in combination.

[0174] [Application of organic light-emitting devices]

[0175] The organic light emitting device according to the present embodiment can be used as a component of a display device or a lighting device. In addition, the organic light emitting device is used, for example, for an exposure light source of an electrophotographic image forming device, a backlight of a liquid crystal display device, and a light emitting device including a color filter on a white light source.

[0176] The display device may be an image information processing device including an image input unit that inputs image information from an area array CCD, a line array CCD, a memory card, or the like, and an information processing unit configured to process the input information and display the input image on a display unit.

[0177] The display unit included in the camera device or inkjet printer may have a touch panel function. The touch panel function may be operated by using infrared radiation, electrostatic capacitance, a resistive film, or electromagnetic induction, and the operation method is not particularly limited. The display device may be used in a display unit of a multifunction printer.

[0178] Next, the display device according to the present embodiment will be described with reference to the drawings. Figure 5 : is a schematic cross-sectional view showing an example of a display device including an organic light-emitting device according to the present embodiment and a transistor electrically connected to the organic light-emitting device. Each transistor is an example of an active device.

[0179] Figure 5The display device 10 shown includes a substrate 11 made of glass or the like and a moisture-proof film 12 provided on the substrate and configured to protect transistors or organic compound layers. In the figure, reference numeral 13 denotes a gate electrode made of metal, reference numeral 14 denotes a gate insulating film, and reference numeral 15 denotes a semiconductor layer.

[0180] The transistors 18 each include a semiconductor layer 15, a drain electrode 16, and a source electrode 17. An insulating film 19 is disposed on top of the transistors 18. An anode 21 constituting an organic light emitting device is connected to the source electrode 17 through a contact hole 20.

[0181] The electrical connection form between the electrodes (anode and cathode) included in each organic light emitting device and the electrodes (source electrode and drain electrode) included in the corresponding transistor in the transistor is not limited to Figure 5 In other words, any form may be adopted as long as one of the anode and the cathode is electrically connected to one of the source electrode and the drain electrode of the transistor.

[0182] exist Figure 5 In the display device 10 shown, the organic compound layer 22 is shown as a single layer; however, the organic compound layer 22 includes at least the light-emitting layer stack according to the present embodiment, and may further include other organic compound layers. A first protective layer 24 and a second protective layer 25 for reducing degradation of the organic light-emitting device are arranged above the cathode 23.

[0183] exist Figure 5 In the illustrated display device 10, a transistor is used as a switching device. Alternatively, a metal-insulator-metal (MIM) device may be used as a switching device.

[0184] Figure 5 The transistor 18 used in the display device 10 shown is not limited to a transistor using a single crystal silicon wafer, but may be a thin film transistor (TFT) device having an active layer on an insulating surface of a substrate. Examples of materials for the active layer of the TFT device include single crystal silicon, non-single crystal silicon such as amorphous silicon and microcrystalline silicon, and non-single crystal oxide semiconductors such as indium zinc oxide and indium gallium zinc oxide.

[0185] Figure 5 The transistor 18 included in the display device 10 shown can be formed inside a substrate such as a Si substrate. The transistor can be a transistor formed of low-temperature polysilicon. The expression "formed inside a substrate" used herein means that the transistor is produced by processing the substrate (e.g., Si substrate) itself. In other words, having a transistor inside a substrate can also be considered as the substrate and the transistor being formed in an integrated manner.

[0186] In the organic light-emitting device according to the present embodiment, the light-emitting brightness is controlled by the transistor 18 as an example of a switching device, so that by arranging a plurality of organic light-emitting devices in a plane, images can be displayed at various light-emitting brightness levels. The switching device according to the present embodiment is not limited to a transistor, and may be an active matrix driver formed on a substrate such as a Si substrate. The expression "on the substrate" may also be referred to as "inside the substrate". Whether the transistor is formed inside or on the substrate is selected based on the size of the display unit. For example, when the size is about 0.5 inches, the transistor is preferably formed on a Si substrate.

[0187] Figure 6 1000 is a schematic diagram showing an example of a display device according to the present embodiment. The display device 1000 may include an upper cover 1001 and a lower cover 1009, and a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 arranged between the upper cover 1001 and the lower cover 1009. The touch panel 1003 and the display panel 1005 are connected to flexible printed circuits FPC 1002 and 1004, respectively. The transistor is printed on the circuit board 1007. Unless the display device is a portable device, the battery 1008 does not have to be installed, or even if the display device is a portable device, it can be installed in a different position.

[0188] The display device according to the present embodiment can be used for the display unit of an image pickup device, which includes an optical unit including a plurality of lenses and an image pickup device that receives light that has passed through the optical unit. The image pickup device may include a display unit that displays information acquired by the image pickup device. The display unit may be a display unit exposed to the outside of the image pickup device or a display unit configured in a viewfinder. The image pickup device may be a digital camera or a digital video camera. The image pickup device may also be referred to as a photoelectric conversion device.

[0189] Fig. 7A 11 is a schematic diagram showing an example of an imaging device according to the present embodiment. The imaging device 1100 may include a viewfinder 1101, a rear display 1102, an operation unit 1103, and a housing 1104. The viewfinder 1101 includes a display device according to the present embodiment. The display device may display not only the captured image, but also, for example, environmental information and imaging instructions. The environmental information may include, for example, the intensity of external light, the direction of external light, the moving speed of an object, and the possibility that an object may be hidden behind an obstacle.

[0190] Since the appropriate time to capture an image is a very short period of time, it is desirable to display information as quickly as possible. Due to the fast response speed, the display device preferably includes the organic light-emitting device of this embodiment. Compared with a liquid crystal display device, a display device using an organic light-emitting device can be more suitable for such a device requiring a high display speed.

[0191] The image pickup device 1100 includes an optical unit not shown in the figure. The optical unit includes a plurality of lenses and is configured to form an image on the image pickup device accommodated in the housing 1104. By adjusting the relative positions of the plurality of lenses, the focus can be adjusted. This operation can also be performed automatically.

[0192] The display device according to the present embodiment may include a color filter having a red portion, a green portion, and a blue portion. The red portion, the green portion, and the blue portion of the color filter may be arranged in a triangular pattern.

[0193] The display device according to this embodiment can be used as a display unit of a portable terminal. In this case, the display device can have both a display function and an operation function. Examples of portable terminals include mobile phones such as smart phones, tablet computers, and head-mounted displays.

[0194] Figure 7B 1 is a schematic diagram showing an example of an electronic device according to the present embodiment. The electronic device 1200 includes a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may include a circuit, a printed circuit board with a circuit, a battery, and a communication unit therein. The operation unit 1202 may be a button or a touch panel type response unit. The operation unit may be a biometric authentication unit configured to, for example, recognize a fingerprint and release a lock. An electronic device including a communication unit may also be referred to as a communication device.

[0195] Fig. 8A and Figure 8B are schematic diagrams each showing an example of a display device according to the present embodiment. Fig. 8A 1300 shows a display device such as a TV monitor or a PC monitor. The display device 1300 includes a support frame 1301 and a base of a display unit 1302. The display device according to the present embodiment is used in the display unit 1302. The base 1303 is not limited to Fig. 8A The form shown. The lower side of the frame 1301 can also be used as a base. The frame 1301 and the display unit 1302 can be curved. The radius of curvature can be greater than 5,000 mm and less than 6,000 mm.

[0196] Figure 8B is a schematic diagram showing another example of the display device according to the present embodiment. Figure 8BThe display device 1310 shown is configured to be foldable and is a so-called foldable display device. The display device 1310 has a first display unit 1311, a second display unit 1312, a housing 1313, and a folding point 1314. The first display unit 1311 and the second display unit 1312 each include a display device according to the present embodiment. The first display unit 1311 and the second display unit 1312 can be a single display device without a joint. The first display unit 1311 and the second display unit 1312 can be separated at a folding point. The first display unit 1311 and the second display unit 1312 can display different images, respectively. Alternatively, a single image can be displayed on a group of the first display unit 1311 and the second display unit 1312.

[0197] Fig. 9A 1400 is a schematic diagram showing an example of a lighting device according to the present embodiment. The lighting device 1400 may include a housing 1401, a light source 1402, a circuit board 1403, an optical filter 1404, and a light diffusion unit 1405. The light source includes an organic light-emitting device according to the present embodiment. The optical filter 1404 may be a filter that improves the color rendering of the light source. The light diffusion unit 1405 may effectively diffuse the light emitted from the light source and allow the light to reach a wide range, such as for lighting. The optical filter 1404 and the light diffusion unit 1405 may be configured on the light-emitting side of the lighting. The cover may be optionally configured on the outermost portion.

[0198] The lighting device is, for example, a device for lighting a room. The lighting device may emit light such as white, natural white, or any other color from blue to red. The lighting device may include a light modulation circuit configured to modulate the light. The lighting device may include an organic light emitting device according to the present invention and a power supply circuit connected to the organic light emitting device. The power supply circuit is a circuit configured to convert an AC voltage into a DC voltage. White is a color with a color temperature of 4200K, and natural white is a color with a color temperature of 5000K. The lighting device may include a color filter.

[0199] The lighting device according to the present embodiment may include a heat dissipation unit. The heat dissipation unit dissipates the heat in the device to the outside of the device. The heat dissipation unit may be formed of, for example, a metal with high specific heat or liquid organic silicon.

[0200] Fig. 9B 15 is a schematic diagram of a car as an example of a moving body according to the present embodiment. The car has a tail light as an example of a lighting fixture. The car 1500 has a tail light 1501, and the tail light can be lit when the brake is applied, for example.

[0201] The taillight 1501 includes an organic light emitting device according to the present embodiment. The taillight may include a protective member for protecting the organic light emitting device. The protective member may be made of any material having a certain degree of high strength and transparency, and is preferably made of polycarbonate, etc. Polycarbonate may be mixed with a furan dicarboxylic acid derivative or an acrylonitrile derivative.

[0202] The car 1500 may include a body 1503 and a window 1502 attached to the body 1503. The window may be a transparent display unless it is a window for checking the front and rear of the car. The transparent display includes an organic light-emitting device according to the present embodiment. In this case, components of the organic light-emitting device such as electrodes are formed by transparent members.

[0203] The mobile body according to the present embodiment may be, for example, a ship, an aircraft, or a drone. The mobile body may include a body and a lighting fixture attached to the body. The lighting fixture may emit light to indicate the position of the body. The lighting fixture includes an organic light-emitting device according to the present embodiment.

[0204] As described above, even if a device including the organic light emitting device according to the present embodiment is used for a long time, an image with good image quality can be stably displayed.

[0205] Example

[0206] An organic light-emitting device including three light-emitting layers and configured to emit yellow light through green light emission and red light emission was prepared. The layer thickness configuration used was the thickness-A in Table 2 above, the first to fourth organic compounds were selected from the exemplary compounds Z-1 to Z-23 above, and the light-emitting materials used were the exemplary compounds RD3, RD1, GD13 and GD9 above. The HOMO, LUMO and S1 of the light-emitting materials are shown in Table 4. The configurations of the light-emitting layer stacks prepared in the examples are shown in Tables 5 and 6.

[0207] [Table 4]

[0208] symbol Exemplary compound No. HOMO LUMO S1 R-1(Red) RD3 -5.53 -3.58 1.95 R-2(Red) RD1 -5.59 -3.52 2.37 G-1(green) GD13 -5.08 -2.71 2.40 G-2(Green) GD6 -5.87 -3.47 2.07

[0209]

[0210]

[0211] (Example 1)

[0212] As shown in Table 7, an organic light-emitting device having a bottom emission type structure in which an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer stack, a hole blocking layer, an electron transport layer, an electron injection layer and a cathode are sequentially formed on a substrate was prepared. The configuration of the light-emitting layer stack is No. 1 in Table 5.

[0213] First, an ITO film is formed on a glass substrate and the desired patterning process is performed to form an ITO electrode (anode). At this time, the film thickness of the ITO electrode is 100nm. The substrate on which the ITO electrode is formed in this way is used as the ITO substrate in the following steps. Next, vacuum evaporation is performed by resistance heating in a vacuum chamber to continuously form an organic compound layer and an electrode layer shown in Table 7 below on the ITO substrate. At this time, the electrode area of ​​the counter electrode (metal electrode layer, cathode) is adjusted to 3mm 2 .

[0214] [Table 7]

[0215]

[0216] The durability of the obtained organic light-emitting device was measured under constant current conditions. For the measurement equipment, specifically, a 6240B power supply manufactured by ADC Corporation was used to make 50 mA / cm 2 A current of 1.000 was passed through the device, and the change in the luminance of light emission was measured with BM7 manufactured by TOPCON CORPORATION to conduct a continuous drive test. For durability evaluation, the time taken for the luminance degradation to reach 70% (LT70) was measured. This is expressed as a relative value relative to the luminance degradation time of Comparative Example 1. A value greater than 1.0 indicates that the durability is improved.

[0217] (Examples 2 to 36 and Comparative Examples 1 to 16)

[0218] Except that the structure of the light-emitting layer stack in Table 7 was changed as shown in Table 8, the organic light-emitting devices of Examples 2 to 36 and Comparative Examples 1 to 16 were prepared in the same manner as in Example 1. It should be noted that, regardless of the position of the light-emitting color, in the case of green light emission, the light-emitting material concentration was set to 10 mass%, and in the case of red light emission, the light-emitting material concentration was set to 2 mass%. The obtained organic light-emitting devices were evaluated in the same manner as in Example 1. Table 8 shows the evaluation results.

[0219] [Table 8]

[0220]

[0221] As shown in Table 8, the comparison of Comparative Examples 1 to 16 with Examples 35 and 36 shows that the durability performance is improved in the Examples. Specifically, it was found that due to satisfying Figure 1 In the energy relationship of the light-emitting layer shown, the recombination area is dispersed to the second light-emitting layer by the hole injection barrier and the electron injection barrier, thereby avoiding the concentrated generation of excitons and improving the durability.

[0222] In Examples 1 to 14, Examples 24 to 27, and Examples 31 to 34, in addition to the improvement in durability, a decrease in driving voltage was observed compared to Examples 35 and 36. This is because, if the formula [9] is satisfied Figure 2 Or satisfying formula

[10] Figure 3 As shown, the electron injection barrier for the dispersed recombination region is reduced, whereby the injectivity is improved and the driving voltage is reduced.

[0223] In Examples 10 to 23 and Examples 28 to 30, etc., HOMO and LUMO satisfy Figure 4 The relationship shown in FIG. 34 shows that the recombination region is dispersed and the durability is improved. In addition, compared with Examples 35 and 36, in addition to the improvement in durability, the driving voltage also tends to be reduced.

[0224] As shown in Examples, it was found that the effect of improving durability is obtained by providing a hole / electron injection barrier from the second light-emitting layer to the first light-emitting layer.

[0225] Although not described as an embodiment, since the brightness degradation time of green light emission is improved, the emission color of the organic light emitting device having a combination including green light emitting materials in two layers experiences little change compared to the organic light emitting device including red light emitting materials in two layers.

[0226] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the accompanying claims are intended to disclose the scope of the present invention.

[0227] This application claims priority based on Japanese Patent Application No. 2022-102325 filed on June 27, 2022, which is incorporated herein by reference in its entirety.

[0228] Description of Reference Numerals

[0229] 18 transistors

[0230] 10, 1000, 1300, 1310 display devices

[0231] 1100 Camera Equipment

[0232] 1201, 1302, 1311, 1312 display units

[0233] 1203, 1313 housing

[0234] 1402 Light Source

[0235] 1404 Optical Filter

[0236] 1405 Light diffusion unit

Claims

1. An organic light-emitting device, comprising: a first electrode; a first light-emitting layer; a second light-emitting layer in contact with the first light-emitting layer; and a second electrode, The first light-emitting layer comprises a first organic compound, a second organic compound and a first light-emitting material, The second light-emitting layer includes the first organic compound, a third organic compound, and a second light-emitting material, and The organic light-emitting device satisfies the following formulas [1] and [2], |S1L1-S1L2|<|S1L1-S1O1|[1] LUMOO2>LUMOO3[2] S1L1: S1 energy level energy of the first luminescent material S1L2: S1 energy level energy of the second luminescent material S1O1: S1 energy level energy of the first organic compound LUMOO2: The energy level of the lowest unoccupied molecular orbital of the second organic compound LUMOO3: energy level of the lowest unoccupied molecular orbital of the third organic compound.

2. The organic light emitting device according to claim 1, further comprising a third light emitting layer disposed between the first electrode and the first light emitting layer and in contact with the first light emitting layer, in, The third light-emitting layer includes the first organic compound and a third light-emitting material, and the organic light-emitting device satisfies the following formula [3], S1L3 <S1L1[3] S1L3: S1 energy level energy of the third luminescent material.

3. The organic light-emitting device according to claim 2, wherein the organic light-emitting device satisfies the following formula [4], HOMOL3 <HOMOL1[4] HOMOL3: energy level of the highest occupied molecular orbital of the third light-emitting material HOMOL1: energy level of the highest occupied molecular orbital of the first light-emitting material.

4. The organic light-emitting device according to claim 2 or 3, wherein the organic light-emitting device satisfies the following formula [5], LUMOL3 <LUMOL1[5] LUMOL: Energy level of the lowest unoccupied molecular orbital of the third luminescent material LUMOL1: the energy level of the lowest unoccupied molecular orbital of the first luminescent material.

5. The organic light emitting device according to any one of claims 2 to 4, wherein: The third light-emitting layer further includes a fourth organic compound, and the organic light-emitting device satisfies the following formulas [6] to [8], LUMOO1>LUMOO3[6] HOMOO4>HOMOO1[7] HOMOO4>HOMOO2[8] LUMOO1: The energy level of the lowest unoccupied molecular orbital of the first organic compound LUMOO3: Energy level of the lowest unoccupied molecular orbital of the third organic compound HOMOO1: The energy level of the highest occupied molecular orbital of the first organic compound HOMOO4: Energy level of the highest occupied molecular orbital of the fourth organic compound HOMOO2: The energy level of the highest occupied molecular orbital of the second organic compound.

6. The organic light emitting device according to any one of claims 1 to 5, wherein: The organic light-emitting device satisfies at least one of the following formula [9] and the following formula [10], LUMOO1>LUMOO2[9] HOMOO2>HOMOO1[10] LUMOO1: The energy level of the lowest unoccupied molecular orbital of the first organic compound LUMOO2: The energy level of the lowest unoccupied molecular orbital of the second organic compound HOMOO1: The energy level of the highest occupied molecular orbital of the first organic compound HOMOO2: The energy level of the highest occupied molecular orbital of the second organic compound. 7 . The organic light-emitting device according to claim 1 , wherein the first organic compound is an aromatic hydrocarbon. 8 . The organic light emitting device according to claim 7 , wherein the first organic compound has a structure in which a plurality of condensed polycyclic skeletons are bonded together with carbon-carbon single bonds.

9. The organic light emitting device according to any one of claims 2 to 5, wherein: In the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer, the first organic compound is a main component.

10. The organic light emitting device according to any one of claims 2 to 5, wherein: The first light emitting material, the second light emitting material and the third light emitting material are phosphorescent materials.

11. The organic light emitting device according to any one of claims 2 to 5, wherein: One of the first luminescent material, the second luminescent material, and the third luminescent material emits green light, and the others emit red light. 12 . A display device comprising a plurality of pixels, wherein each of the plurality of pixels comprises the organic light emitting device according to claim 1 and a transistor connected to the organic light emitting device.

13. The display device according to claim 12, further comprising color filters of three colors of red, green and blue.

14. A photoelectric conversion device comprising: An optical unit including a plurality of lenses; an imaging device receiving light passing through the optical unit; and a display unit for displaying an image captured by the imaging device, Wherein, the display unit comprises the organic light-emitting device according to any one of claims 1 to 11.

15. An electronic device, comprising: A display unit comprising the organic light-emitting device according to any one of claims 1 to 11; a housing provided with the display unit; and a communication unit disposed in the housing and communicating with an external unit.

16. A lighting device, comprising: A light source comprising an organic light-emitting device according to any one of claims 1 to 11; and a light diffusion unit or an optical filter that transmits the light emitted from the light source.

17. A mobile object, comprising: A lighting fixture comprising an organic light-emitting device according to any one of claims 1 to 11; and a body provided with the lighting device.

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