JP2009093982A - Organic electroluminescence device and electronic device - Google Patents

Abstract

An organic electroluminescence device having high luminous efficiency, long life, and excellent color reproducibility is provided.
An organic electroluminescence device 1 of the present invention includes a green light emitting layer 6G, a first blue light emitting layer 6B1, a second blue light emitting layer 6B2, and a red light emitting layer 6R from the anode 3 side. The first blue light emitting layer 6B1 provided on the anode 3 side includes a hole transporting material having a hole mobility larger than the electron mobility and a first blue light emitting dopant, and is provided on the cathode 8 side. The second blue light emitting layer 6B2 includes an electron transporting material having electron mobility higher than hole mobility and a second blue light emitting dopant.
[Selection] Figure 1

Description

  The present invention relates to an organic electroluminescence device and an electronic apparatus.

In recent years, development of organic electroluminescence devices in which white light emitting elements and color filters are combined has been progressing. As a white light emitting element, one in which red, green and blue light emitting layers are laminated is known. In the white light emitting element, it is important to keep a good balance of red, green and blue. Therefore, in Patent Document 1 and Non-Patent Document 1, a carrier adjustment layer having a large band gap is formed between the red light emitting layer and the blue light emitting layer (or the green light emitting layer), and the amount of electrons supplied to the red light emitting layer. The method of adjusting is described.
Japanese Patent Laid-Open No. 2005-10091 “Late-News Paper: Highly Efficient White OLEDs Using RGB Fluorescent Materials”, H. Kuma et al., SID 07 DIGEST, p.1504-1507

  Here, the carrier adjustment layer must transport carriers (electrons and holes) to both the red light emission layer and the blue light emission layer (or green light emission layer). Both streams of holes exist. Therefore, it is expected that electrons and holes are recombined inside the carrier adjustment layer. However, since the carrier adjustment layer itself does not contain a light emitting material, energy generated by recombination is not converted into light emission energy, which causes the carrier adjustment layer to deteriorate due to thermal deactivation.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an organic electroluminescence device and an electronic apparatus that have high luminous efficiency, long life, and excellent color reproducibility.

  In order to solve the above problems, the organic electroluminescence device of the present invention is an organic electroluminescence device having a light emitting layer between an anode and a cathode, and the light emitting layer is green from the anode side. A light emitting layer, a first blue light emitting layer, a second blue light emitting layer, and a red light emitting layer are laminated, and the first blue light emitting layer provided on the anode side has a hole mobility higher than an electron mobility. The second blue light-emitting layer, which includes a large hole-transporting material and a first blue light-emitting dopant and is provided on the cathode side, has an electron-transporting material in which the mobility of electrons is larger than the mobility of holes; And a second blue light emitting dopant.

  According to this configuration, electrons flowing from the cathode to the anode are accumulated at the interface between the second blue light-emitting layer and the first blue light-emitting layer by the first blue light-emitting layer containing the hole transporting material, and from the anode to the cathode. The flowing holes are accumulated at the interface between the first blue light emitting layer and the second blue light emitting layer by the second blue light emitting layer containing the electron transporting material. Therefore, an excessive carrier (electron, hole) flow to the green light emitting layer and the red light emitting layer is prevented, and an organic electroluminescence device with excellent white balance is realized. In addition, since carriers do not concentrate on one light emitting layer, the light emitting lifetimes of the red, blue, and green light emitting layers are made uniform, and an organic electroluminescence device having a long life as a whole can be provided. Furthermore, since the problem that carriers do not pass through the red light emitting layer, the blue light emitting layer, and the green light emitting layer and do not contribute to light emission is eliminated, an organic electroluminescence device with high light emission efficiency can be provided. In the present invention, the blue light-emitting layer functions as a carrier adjustment layer that adjusts the supply amount of electrons and holes. However, unlike the case of using a carrier adjustment layer that does not contain a light-emitting material as in the prior art, the loss of non-light emission is achieved. Since the activity is small, the carrier adjustment layer itself (that is, the blue light-emitting layer) is hardly deteriorated by excitons generated inside the carrier adjustment layer. Therefore, it is possible to further extend the life.

  In the present invention, the hole mobility of the hole transporting material is preferably 10 times or more larger than the electron mobility, more preferably 100 times larger. According to this configuration, the flow of electrons from the cathode to the anode can be controlled. Examples of such materials include amine materials and acene materials. Further, the electron mobility of the electron transporting material is desirably 10 times or more larger than the hole mobility, and more desirably 100 times or more larger. According to this configuration, the flow of holes from the anode to the cathode can be controlled. Examples of such a material include silole materials.

  In the present invention, the red light-emitting layer includes a host material for red and a red light-emitting dopant, the green light-emitting layer includes a host material for green and a green light-emitting dopant, and the band gap of the hole transporting material and the It is desirable that the band gap of the electron transporting material is larger than the band gap of the red host material and that of the green host material. According to this configuration, the flow of electrons from the cathode to the anode and the flow of holes from the anode to the cathode can be controlled, and the balance of red, blue, and green is improved.

  In the present invention, the red host material and the green host material are preferably made of a perylene-based material or a naphthacene material. According to this configuration, by using a perylene-based or naphthacene-based material having a relatively large energy gap, it becomes easy to transport both holes and electrons to the blue light-emitting layer.

  In the present invention, the thickness of the first blue light emitting layer is preferably 1 nm or more and 20 nm or less. According to this configuration, it is possible to prevent the green light emission luminance from decreasing more than necessary while suppressing the flow of electrons from the cathode to the anode. For example, if the thickness of the first blue light emitting layer is smaller than 1 nm, the carrier adjustment function by the first blue light emitting layer is weakened, and the flow of electrons to the green light emitting layer cannot be sufficiently suppressed. On the other hand, if the thickness of the first blue light-emitting layer exceeds 20 nm, the flow of electrons to the green light-emitting layer is extremely reduced, and the green light emission luminance is insufficient.

  Such a situation is the same for the second blue light emitting layer. When the thickness of the second blue light emitting layer is smaller than 1 nm, the carrier adjustment function by the second blue light emitting layer is weakened, and the flow of holes to the red light emitting layer cannot be sufficiently suppressed. On the other hand, when the thickness of the second blue light-emitting layer exceeds 20 nm, the flow of electrons to the red light-emitting layer is extremely reduced, and the red light emission luminance is insufficient. Therefore, the thickness of the second blue light emitting layer is desirably 1 nm or more and 20 nm or less. Thereby, it is possible to prevent the red light emission luminance from decreasing more than necessary while suppressing the flow of holes from the anode to the cathode.

  An electronic apparatus according to the present invention includes the above-described organic electroluminescence device according to the present invention. According to this configuration, it is possible to provide an electronic device with high luminous efficiency, long life, and excellent color rendering.

  Embodiments of the present invention will be described below with reference to the drawings. Such an embodiment shows one aspect of the present invention and does not limit the present invention. In the following embodiments, various shapes, combinations, and the like of the constituent members are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, number, and the like of each structure are different.

  FIG. 1 is a schematic configuration diagram of an organic electroluminescence device 1 (hereinafter, “electroluminescence” is abbreviated as “EL”) according to an embodiment of the present invention. The organic EL device 1 includes a first electrode (anode) 3, a hole injection layer 4, a hole transport layer 5, a light emitting layer 6, an electron transport layer 7, and a first electrode on a substrate body 2 made of glass, quartz, plastic, or the like. Two electrodes (cathode) 8 are provided. The hole injection layer 4, the hole transport layer 5, the light emitting layer 6, and the electron transport layer 7 are formed of an organic material, and these hole injection layer 4, hole transport layer 5, light emitting layer 6, and electron transport layer 7 are formed. Thus, the functional layer F is formed. The functional layer F is sandwiched between the first electrode 3 and the second electrode 8, and an organic EL element 9 that is a light emitting element is formed by the first electrode 3, the functional layer F, and the second electrode 8. .

  A wiring for applying a drive voltage is connected to the first electrode 3 and the second electrode 8. Holes from the first electrode 3 and electrons from the second electrode 8 are injected into the light emitting layer 6 through the wiring. The holes and electrons injected into the light emitting layer 6 move through the light emitting layer 6 and recombine. Then, excitons are generated by the energy released upon recombination, and energy is released in the form of fluorescence or phosphorescence when the excitons return to the ground state. The light emitted from the organic EL element 9 is emitted from the substrate body 2 made of a glass substrate or the like and extracted outside (bottom emission method). When the second electrode 8 is formed of a transparent conductive film such as ITO, light emitted from the organic EL element 9 can be extracted from the second electrode 8 side (top emission method). In the following description, electrons and holes injected into the light emitting layer 6 may be referred to as carriers.

  In the present embodiment, the first electrode 3 is a transparent electrode such as ITO (indium tin oxide), and the second electrode 8 is a reflective electrode such as aluminum (Al) (bottom emission method). As the second electrode 8, in addition to aluminum, silver, a silver magnesium alloy, an aluminum lithium alloy, or the like can be used. Furthermore, a layer (electron injection layer) made of lithium fluoride (LiF) or the like can be provided on the electron transport layer 7 side of the second electrode 8.

  As the hole injection layer 4, a low molecular material such as copper phthalocyanine or arylamine is used. As the hole injection layer 4, a conductive polymer such as polythiophene or polyaniline may be used. The thickness of the hole injection layer 4 is about 10 nm to 30 nm.

  As the hole transport layer 5, phenylamine derivatives such as diphenylamine and triphenylamine, aromatic amine materials, styrylarylene derivatives, and the like can be used. The film thickness of the hole transport layer 5 is about 10 nm to 50 nm.

  The light emitting layer 6 includes a green light emitting layer 6G, a first blue light emitting layer 6B1, a second blue light emitting layer 6B2, and a red light emitting layer 6R in this order from the hole transport layer 5 side. Each of the red light emitting layer 6R and the green light emitting layer 6G includes a host material and a light emitting dopant. The host material is a material that can flow both electrons and holes. In the light emitting layer that does not include the light emitting dopant, light emission from the host material is observed, but in the light emitting layer in which the light emitting dopant and the host material are used in combination, almost no light emission from the host material is observed, and the light emitting dopant mainly emits light. . The emission spectrum observed in the light emitting layer in which the host material and the light emitting dopant are used in combination is the light emission of the light emitting dopant. The light emission waveform of the light emitting layer is determined by the organic molecular skeleton.

  As a host material for the red light emitting layer 6R and the green light emitting layer 6G, a perylene-based material or a naphthacene-based material having one or more substituents can be used. By using a perylene-based or naphthacene-based material having a relatively large energy gap, holes and electrons can be easily injected into the blue light emitting layers 6B1 and 6B2. The host material for the red light emitting layer 6R and the green light emitting layer 6G may be the same material or different materials.

  The luminescent dopant may be either a fluorescent compound that emits light from singlet excitons or a phosphorescent compound that emits light from triplet excitons. Examples of fluorescent materials include perylene derivatives, oxadiazole derivatives, Anthracene derivatives, rubrene derivatives, styrylamine derivatives, coumarin derivatives and the like can be mentioned. As the phosphorescent material, an iridium metal complex, a platinum metal complex, or the like can be used. Preferably, a dibenzodiindenoperylene derivative is used as the red light-emitting material, and a coumarin derivative or a naphthacene derivative is used as the green light-emitting material. As the host material, known materials such as an aluminum complex and a beryllium complex, an anthracene (including a dimer) derivative, a carbazole derivative, and a styrylamine derivative are used.

  A first blue light emitting layer 6B1 and a second blue light emitting layer 6B2 are provided between the red light emitting layer 6R and the green light emitting layer 6G. The first blue light emitting layer 6B1 includes a hole transporting material and a first light emitting dopant (blue light emitting dopant). The hole transporting material refers to a material having a higher hole transporting property than an electron transporting property. Specifically, a material having a higher hole mobility than the electron mobility is used, and a material having a hole mobility of 10 times or more, more preferably 100 times or more higher than the electron mobility is preferable. Adopted. As such a material, an amine-based material or an acene-based material is used. The first light emitting dopant is doped in a hole transporting material as a host material. On the other hand, the second blue light emitting layer 6B2 includes an electron transporting material and a second light emitting dopant (blue light emitting dopant). An electron transporting material refers to a material having a higher electron transporting property than a hole transporting property. Specifically, a material having a higher electron mobility than the hole mobility is used, and a material having an electron mobility of 10 times or more, more preferably 100 times or more higher than the hole mobility is preferable. Adopted. As such a material, a silole material is used. The second light emitting dopant is doped in an electron transporting material as a host material.

  The first light emitting dopant and the second light emitting dopant may be the same material or different materials. As the blue light emitting material, a styryl derivative, a styrylamine derivative, a fluoranthene derivative, or the like can be used. Preferably, a distyrylamine derivative is used.

  The hole transporting material contained in the first blue light emitting layer 6B1 and the electron transporting material contained in the second blue light emitting layer 6B2 adjust the balance of electrons and holes passing through the first blue light emitting layer 6B1, and the red light emitting layer 6R, The first blue light emitting layer 6B1, the second blue light emitting layer 6B2, and the green light emitting layer 6G function as a carrier adjustment layer for averaging the light emission luminance. In order to make it easier to adjust the balance of carriers, the LUMO energy level of the hole transporting material contained in the first blue light emitting layer 6B1 is the LUMO energy level of the host material of the red light emitting layer 6R and the green light emitting layer 6G. The HOMO energy level of the hole transporting material is lower than the HOMO energy levels of the host materials of the red light emitting layer 6R and the green light emitting layer 6G. The LUMO energy level of the electron transporting material contained in the second blue light emitting layer 6B2 is lower than the LUMO energy level of the host material of the red light emitting layer 6R and the green light emitting layer 6G, and the HOMO energy of the electron transporting material. The level is higher than the HOMO energy level of the host material of the red light emitting layer 6R and the green light emitting layer 6G. By using such a material, it is possible to suppress the flow of holes from the first blue light emitting layer 6B1 to the red light emitting layer 6G, and further suppress the flow of electrons from the second blue light emitting layer 6B2 to the green light emitting layer 6G. be able to. The film thickness of the first blue light-emitting layer 61 and the second blue light-emitting layer 6B2 is 1 nm to 20 nm, and more preferably about 5 nm to 10 nm.

  An electron transport layer 7 is provided between the light emitting layer 6 and the second electrode 8. As the electron transport layer 7, 8-hydroxyquinoline or its derivative and its metal complex, triazole derivative, oxazole derivative, oxadiazole derivative, fluorenone derivative, anthraquinodimethane derivative, anthrone derivative, diphenylquinone derivative, thiopyran dioxide Derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives and the like are used. The film thickness of the electron transport layer 7 is about 20 nm to 40 nm.

  FIG. 2 shows an example of the material of the functional layer F used in this embodiment. In the figure, HIL-A is a material for forming a hole injection layer, HTL-A is a material for forming a hole transport layer, G-host1 and G-host2 are host materials for a green light emitting layer, and G-Dopant is a material for a green light emitting layer. Luminescent dopant, R-Host1 is the red light emitting layer host material, R-Dopant is the red light emitting layer light emitting dopant, B-Host1 is the first blue light emitting layer hole transport material, B-Host2 is the second blue light emitting layer B-Dopant is a light emitting dopant for a blue light emitting layer, and Alq3 (tris (8-quinolinol) aluminum) is a material for forming an electron transporting layer. In the green light emitting layer, either G-host1 or G-host2 may be used as the host material, and the host material may be formed by mixing G-host1 and G-host2 at a predetermined ratio.

  FIG. 3 is a diagram showing an energy band of the organic EL element 9. The vertical axis represents the energy level, and the horizontal axis represents the stacking direction of the organic layers. In the green light emitting layer, the first blue light emitting layer, the second blue light emitting layer, and the red light emitting layer, the solid line indicates the energy level of the host material, and the dotted line indicates the energy level of the light emitting dopant.

  In FIG. 3, electrons supplied from the cathode pass through the red light emitting layer and are supplied to the second blue light emitting layer. Since the host material of the second blue light emitting layer is formed of an electron transporting material, the electrons supplied to the red light emitting layer are easily supplied to the second blue light emitting layer. On the other hand, the electrons passing through the second blue light emitting layer are blocked by the first blue light emitting layer because the host material of the first blue light emitting layer is formed of a hole transporting material, Flow is suppressed. In addition to the fact that the host material of the first blue light emitting layer is a hole transporting material having a high hole mobility, the LUMO energy level of the host material of the host material of the second blue light emitting layer is This is because the energy level is smaller than the energy level at the interface between the second blue light-emitting layer and the first blue light-emitting layer, making it difficult for electrons to move to the first blue light-emitting layer.

  On the other hand, the holes supplied from the anode are supplied to the first blue light emitting layer through the hole injection layer, the hole transport layer, and the green light emitting layer. Since the host material of the first blue light emitting layer is formed of a hole transporting material, the holes supplied to the green light emitting layer are easily supplied to the first blue light emitting layer. On the other hand, the holes that have passed through the first blue light-emitting layer are blocked by the second blue light-emitting layer because the host material of the second blue light-emitting layer is formed of an electron transporting material, and the holes to the red light-emitting layer. Flow is suppressed. This is because the host material of the second blue light-emitting layer is an electron-transporting material having a high electron mobility, and the HOMO energy level of the host material is the HOMO energy level of the host material of the first blue light-emitting layer. This is because the holes are less likely to move to the second blue light emitting layer beyond the energy gap at the interface between the first blue light emitting layer and the second blue light emitting layer.

  As a result, many carriers accumulate at the interface between the first blue light emitting layer and the second blue light emitting layer, and the light emission luminance of the blue light emitting layer is increased. In addition, since the supply of carriers to the red light emitting layer and the green light emitting layer is suppressed, the red, blue, and green light emission luminances are made uniform, and balanced white light emission is obtained. In addition, since carriers do not concentrate on one light emitting layer, the light emitting lifetimes of the red, blue, and green light emitting layers are made uniform, and an organic EL device having a long life as a whole can be provided. Furthermore, since the problem that carriers do not pass through the red light emitting layer, the blue light emitting layer, and the green light emitting layer and do not contribute to light emission is eliminated, an organic EL device with high light emission efficiency can be provided. In this embodiment, the blue light-emitting layer functions as a carrier adjustment layer that adjusts the supply amount of electrons and holes, but unlike the case of using a carrier adjustment layer that does not include a light-emitting material as in the prior art, The carrier adjustment layer itself (that is, the blue light emitting layer) is hardly deteriorated by excitons generated inside. Therefore, it is possible to further extend the life.

  In this embodiment, the functional layer F includes the hole injection layer 4, the hole transport layer 5, the green light emitting layer 6G, the first blue light emitting layer 6B1, the second blue light emitting layer 6B2, the red light emitting layer 6R, and the electron transport layer. However, the structure of the functional layer F is not limited to this. For the organic layers other than the light emitting layer 6 (green light emitting layer 6G, first blue light emitting layer 6B1, second blue light emitting layer 6B2, red light emitting layer 6R), any one layer or two or more layers can be omitted or added. . For example, an electron injection layer is provided between the electron transport layer 7 and the second electrode 8, or any one or more of the hole injection layer 4, the hole transport layer 5 and the electron transport layer 7 is formed. It can be omitted. Further, the red light emitting layer 6R and the green light emitting layer 6G can be interchanged in the light emitting layer 6, and the red light emitting layer 6R, the first blue light emitting layer 6B1, the second blue light emitting layer 6B2, and the green light emitting layer 6G are stacked in this order. May be.

[Organic EL display device]
FIG. 4 is a schematic configuration diagram of an organic EL display device 200 which is an example of an electronic apparatus including the organic EL device of the present invention. The organic EL display device 200 is an active matrix organic EL display device that includes organic EL elements as pixels in a matrix.

  The organic EL display device 200 includes a circuit element unit 30, a pixel electrode (first electrode) 3, a functional layer F, a counter electrode (second electrode) 8, a sealing unit 32, and the like on the base 2. The circuit element unit 30 includes a thin film transistor as a circuit element. The functional layer F includes the above-described red light emitting layer, yellow light emitting layer (carrier adjustment layer), green light emitting layer, and blue light emitting layer. The functional layer F is partitioned for each pixel region by the partition layer 31.

  For example, a glass substrate is used as the substrate 2. As a substrate in the present invention, in addition to a glass substrate, various known substrates used for electro-optical devices and circuit substrates such as a silicon substrate, a quartz substrate, a ceramic substrate, a metal substrate, a plastic substrate, and a plastic film substrate are applied. The

  On the base 2, a plurality of pixel areas A as light emitting areas are arranged in a matrix, and when performing color display, for example, each color of red (Red), green (Green), and blue (Blue) Are formed in a predetermined arrangement. In each pixel region A, a pixel electrode 3 is arranged, and in the vicinity thereof, a signal line 42, a common power supply line 43, a scanning line 41, a scanning line for other pixel electrodes (not shown), and the like are arranged. The planar shape of the pixel region A can be any shape such as a circle or an oval other than the rectangle shown in the figure.

  The sealing portion 32 prevents water and oxygen from entering and prevents the counter electrode 8 and the functional layer F from being oxidized. The sealing portion 32 is provided with a sealing substrate (or sealing can) 34. The sealing substrate 34 is made of glass, metal, or the like, and is bonded to the base 2 via a sealing agent. A color filter layer 33 is provided on the surface of the sealing substrate 34 on the base 2 side. The color filter layer 33 includes red, green, and blue color material layers, and a color material layer of any one of red, blue, and green is disposed in each pixel region A. The absorption spectrum of the color material layer coincides with the wavelengths of the three primary colors (for example, blue: about 450 nm, green: about 540 nm, red: about 610 nm).

  The pixel region A holds a first thin film transistor 44 for switching in which a scanning signal is supplied to the gate electrode through the scanning line 41 and an image signal supplied from the signal line 42 through the first thin film transistor 44. The storage capacitor cap, the driving second thin film transistor 45 to which the image signal held by the storage capacitor cap is supplied to the gate electrode, and the second thin film transistor 45, and the common feed line 43. A pixel electrode 3 into which a drive current flows from the common power supply line 43 and a functional layer F sandwiched between the pixel electrode 3 and the counter electrode 8 are provided. The functional layer F includes a light emitting layer, and the organic EL element 9 that is a light emitting element includes the pixel electrode 3, the counter electrode 8, the functional layer F, and the like.

  In the pixel area A, when the scanning line 41 is driven and the first thin film transistor 44 is turned on, the potential of the signal line 42 at that time is held in the holding capacitor cap, and the second capacitance is changed according to the state of the holding capacitor cap. The conductive state of the thin film transistor 45 is determined. In addition, a current flows from the common power supply line 43 to the pixel electrode 3 through the channel of the second thin film transistor 45, and further a current flows to the counter electrode 8 through the functional layer F. The functional layer F emits light according to the amount of current at this time.

  In the organic EL display device 200, light emitted from the functional layer F to the base 2 side is transmitted through the circuit element unit 30 and the base 2 and emitted to the lower side (observer side) of the base 2 and the functional layer. The light emitted from F to the opposite side of the base 2 is reflected by the counter electrode 8, and the light passes through the circuit element portion 30 and the base 2 and is emitted to the lower side (observer side) of the base 2 (bottom). Emission type). Note that light emitted from the counter electrode can be emitted by using a transparent material as the counter electrode 8 (top emission type). In this case, ITO, Pt, Ir, Ni, or Pd can be used as the transparent material for the counter electrode.

  Here, the organic EL element 9 has the structure of the light emitting element of the present invention described above. In the functional layer F, a red light-emitting layer, a yellow light-emitting layer (carrier adjustment layer), a blue light-emitting layer, and a green light-emitting layer are sequentially laminated, and the light emission peaks of the respective light-emitting layers are arranged almost uniformly in the visible light wavelength region. ing. Therefore, white light emitted from the functional layer F has a broad emission spectrum having a substantially constant emission intensity over the entire visible light region. Therefore, by combining with a color filter that matches the wavelengths of the three primary colors, an organic EL display device having high color rendering properties and capable of bright display can be provided.

  In the present embodiment, the organic EL display device has been described as an example of the electronic apparatus. However, the white light-emitting organic EL element of the present invention is not limited to the organic EL display device, and can be applied to various devices. For example, it can be used as an illumination light source such as a backlight or a front light of a liquid crystal display device, thereby providing a liquid crystal display device with high color rendering properties.

  Next, examples of the present invention will be described. As examples 1 to 3, organic EL elements having the configuration of the present invention were produced, and as comparative examples, organic EL elements having a conventional configuration were produced. The structure of Examples 1-3 and the structure of a comparative example are as follows.

  In said table | surface, the organic EL element of Examples 1-3 is Anode (anode) / HIL (hole injection layer) / HTL (hole transport layer) / EML-G (green light emitting layer) / EML-B1 ( 10 layer structure of 1st blue light emitting layer) / EML-B2 (2nd blue light emitting layer) / EML-R (red light emitting layer) / ETL (electron transport layer) / EIL (electron injection layer) / Cathode (cathode) Yes, the organic EL element of the comparative example is Anode (anode) / HIL (hole injection layer) / HTL (hole transport layer) / EML-G (green light emitting layer) / EML-B (blue light emitting layer) / EML -R (red light emitting layer) / ETL (electron transport layer) / EIL (electron injection layer) / Cathode (cathode) 9 layer structure. The formation material of each layer is shown in FIG.

  The organic EL element of Examples 1-3 and the organic EL element of a comparative example differ in the structure of a light emitting layer. In the organic EL element of the comparative example, the blue light-emitting layer is one layer, and the host material of the blue light-emitting layer has the same hole mobility and electron mobility (the ratio of both is smaller than 10). Yes. On the other hand, in the organic EL elements of Examples 1 to 3, the blue light emitting layer has two layers, and four light emitting layers (green light emitting layer, first blue light emitting layer, second blue light emitting layer, and red light emitting layer) emit white light. Forming a layer. The host material of the first blue light-emitting layer is a hole transporting material, and the host material of the second blue light-emitting layer is different from the comparative example in that it is an electron transporting material.

  5 to 8 are emission spectra of organic EL elements of Examples 1 to 3 and a comparative example. 5 shows Example 1, FIG. 6 shows Example 2, FIG. 7 shows Example 3, and FIG. 4 shows the emission spectrum of Comparative Example. As shown in FIG. 8, in the organic EL element of the comparative example that does not have the carrier adjustment function, even if the driving voltage of the same level as that of the example is supplied, the obtained light emission luminance is about half that of the example. In addition, the red light emission luminance is very small compared to the blue and green light emission luminances. On the other hand, in the organic EL element of the example, the emission luminance is about twice as large as that of the organic EL element of the comparative example, and the balance between the red emission luminance and the blue and green emission luminance is also improved. Therefore, it can be seen that an organic EL element having a good balance of red, blue and green and an excellent white balance is obtained from the chromaticity measurement results shown in Table 1. In Table 1, it can be seen that the organic EL elements of Examples 1 to 3 have significantly improved light emission lifetimes compared to the organic EL elements of the comparative examples, and are excellent in reliability.

1 is a schematic configuration diagram of an organic EL device according to an embodiment of the present invention. It is an example of the material used for the functional layer of an organic EL apparatus. It is a band diagram of an organic EL device. It is a schematic block diagram of the organic electroluminescence display which is an example of an electronic device. 2 is an emission spectrum of the organic EL element of Example 1. 2 is an emission spectrum of the organic EL device of Example 2. 4 is an emission spectrum of the organic EL device of Example 3. It is an emission spectrum of the organic EL element of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Organic EL device, 3 ... 1st electrode (anode), 4 ... Hole injection layer, 5 ... Hole transport layer, 6 ... Light emitting layer, 6B1 ... 1st blue light emitting layer, 6B2 ... 2nd blue light emitting layer, 6G ... green light emitting layer, 6R ... red light emitting layer, 7 ... electron transport layer, 8 ... second electrode (cathode), 9 ... organic EL element, 200 ... organic EL display device (electronic device)

Claims (8)

An organic electroluminescence device having a light emitting layer between an anode and a cathode,
The light emitting layer is formed by laminating a green light emitting layer, a first blue light emitting layer, a second blue light emitting layer, and a red light emitting layer from the anode side,
The first blue light emitting layer provided on the anode side includes a hole transporting material having a hole mobility larger than an electron mobility, and a first blue light emitting dopant,
The second blue light emitting layer provided on the cathode side includes an electron transporting material in which the mobility of electrons is larger than the mobility of holes, and a second blue light emitting dopant, and the organic electroluminescence device .   The hole mobility of the hole transport material is 10 times or more larger than the electron mobility, and the electron mobility of the electron transport material is 10 times or more larger than the hole mobility. The organic electroluminescence device according to claim 1.   The organic electroluminescent device according to claim 2, wherein the hole transporting material is formed of an amine-based material or an acene-based material, and the electron transporting material is formed of a silole-based material. The red light emitting layer includes a red host material and a red light emitting dopant,
The green light emitting layer includes a green host material and a green light emitting dopant,
The band gap of the hole transport material and the band gap of the electron transport material are larger than the band gap of the red host material and the band gap of the green host material, respectively. Organic electroluminescence device.   The organic electroluminescent device according to claim 4, wherein the red host material and the green host material are made of a perylene-based material or a naphthacene material.   2. The organic electroluminescence device according to claim 1, wherein the first blue light-emitting layer and the second blue light-emitting layer have a thickness of 1 nm to 20 nm.   The organic electroluminescent device according to claim 1, wherein the first blue light-emitting dopant and the second light-emitting dopant are made of the same material.   An electronic apparatus comprising the organic electroluminescence device according to claim 1.

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