JP2004273163A - Organic el element, manufacturing method thereof, and organic el panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element for prolonging the life by enhancing light-emitting efficiency. <P>SOLUTION: In the organic EL element 101, electrons are injected into a light-emitting layer 140 from a metallic electrode 170 through an electron transport layer 160 and an electron transfer control layer 150 by applying a DC voltage between a transparent electrode (anode) 120 and a metallic electrode (cathode) 170, the electrons are coupled with positive holes in the light-emitting layer 140 to excite fluorescent molecules within the light-emitting layer 140 and a light-emitting phenomenon is caused. At this time, an amount of the electrons injected from the transport layer 160 to the light-emitting layer 140 is suppressed by the control layer 150 formed in a manner that the minimum vacant level is lower than that of the transport layer 160 and the thickness is made extremely thin, and only electrons for contributing to light-emitting are injected from the transport layer 160 into the light-emitting layer 140. As the result, the light-emitting efficiency is improved and the life of the EL element can be prolonged by suppressing consumption power. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic electroluminescent device (organic electroluminescence device: hereinafter, referred to as an “organic EL device”), a method of manufacturing the same, and an organic EL panel, and particularly to an organic EL device capable of improving luminous efficiency and a method of manufacturing the same. The present invention relates to a method and an organic EL panel.
[0002]
[Prior art]
An organic EL panel using an organic EL element using electroluminescence as a light emitting element has been receiving attention. The organic EL panel is a self-luminous type flat panel that does not require a backlight, and can realize a display with a wide viewing angle and high visibility. Further, since only necessary pixels need to emit light, power consumption can be reduced as compared with a backlight type display such as a liquid crystal display. In addition, the response performance can be made high enough to cope with a high-definition high-speed video signal expected to be put to practical use in the future.
An organic EL element used in an organic EL panel has, for example, an anode (anode layer) formed by a transparent electrode film, an organic layer as a light emitting layer, and a cathode (cathode layer) formed by a metal electrode film, for example. Formed. That is, it has a structure in which an organic material is sandwiched between electrodes (anode and cathode) from above and below. Then, by applying a voltage to the organic layer from the upper and lower electrode layers, holes are injected from the anode layer and electrons are injected from the cathode layer into the organic layer, and the holes and electrons are recombined in the organic layer to emit light. Occurs.
[0003]
In such an organic EL element, there is a problem that the life is insufficient as compared with the conventional art. In an organic EL device that applies a voltage to the device for light emission, if the power consumption is large, the inside of the device generates heat, material deterioration is promoted, and the life is shortened. Therefore, there is a need for an element that emits light with high luminance with low power consumption.
Therefore, for example, a structure has been proposed in which an electron blocking layer is inserted between the light emitting layer and the hole transport layer to prevent the transfer of electrons from the light emitting layer to the hole transport layer (for example, Patent Document 1). In addition, a method has been proposed in which a hole blocking layer is formed between a light emitting layer and an electron transport layer to increase luminous efficiency (for example, see Patent Document 2).
[0004]
[Patent Document 1]
JP-A-2002-175887
[Patent Document 2]
JP 2000-306676 A
[0005]
[Problems to be solved by the invention]
However, in the above-described method of inserting the electron block layer, it is necessary to form the electron block layer using a material having energy higher than the lowest empty level of the light emitting layer corresponding to the light emitting material. That is, when different light emitting materials are used due to different light emission colors, it is necessary to change the material of the inserted electron block layer. Therefore, when this method is applied to a display panel that emits light in full color, it is necessary to change the material of the electron block layer in accordance with the element of each color, which causes a problem that the process steps are long and complicated.
Further, in any of the methods, the life of the organic EL element cannot be said to be sufficient yet, and an organic EL element which emits light with higher luminous efficiency, suppresses power consumption, and thereby has a sufficiently long life is desired. .
[0006]
The present invention has been made in view of such problems, and an object of the present invention is to increase the luminous efficiency without significantly complicating the process steps, to reduce the power consumption and extend the life of the organic compound. An object of the present invention is to provide an EL element and a manufacturing method thereof.
Another object of the present invention is to provide an organic EL panel which can perform full color display, has high luminous efficiency, consumes little power, and has a long life.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an organic EL device of the present invention comprises:
An organic EL device in which at least one organic layer including a light-emitting layer is formed between electrode layers each formed of a transparent electrode,
An electron transfer control layer for suppressing the flow of electrons to the light emitting layer is formed between the electrode layers.
[0008]
According to such a configuration, the flow of surplus electrons that do not contribute to light emission to the light emitting layer is suppressed by the electron transfer control layer. Therefore, only effective electrons contributing to light emission are injected into the light emitting layer, and the current flowing through the element is efficiently provided for light emission, and the light emission efficiency is improved. As a result, power consumption can be reduced with the same light emission amount, and the element life can be prolonged.
[0009]
Preferably, in the organic EL device of the present invention, an electron transport layer is formed between the electrode layer serving as a cathode and the light emitting layer, and the electron transfer control layer is formed of the electron transport layer and the light emitting layer. The energy level of the lowest vacancy of the electron transfer control layer is lower than the energy level of the lowest vacancy of the electron transport layer.
More preferably, the difference between the energy levels of the lowest vacancies of the electron transfer control layer and the electron transport layer is more than 0 eV and 1 eV or less.
[0010]
According to such a configuration, the amount of electrons moving from the electron transport layer toward the light emitting layer due to the internal electric field is controlled by the electron transfer control layer interposed therebetween. Therefore, the amount of electrons injected into the light emitting layer is appropriately controlled. Further, in this configuration, the amount of electron transfer is controlled based on the difference in the lowest empty level between the electron transport layer and the electron transfer control layer. Therefore, the amount of injected electrons can be controlled without depending on the material of the light emitting layer, and the electron transfer control layer can be formed with a common material that does not depend on the type of the organic EL element.
[0011]
As a preferred example, the organic EL device of the present invention has a plurality of the light emitting layers, and the electron transfer control layer is formed on each of the light emitting layers on the side of the electrode layer as the cathode.
As a preferred example, the thickness of the electron transfer control layer is 0.1 to 20 nm.
As a preferred example, the electron transfer control layer is formed of α-NPD (α-naphthylphenyldiamine), TPD (N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1 ′). -Biphenyl 4,4'-diamine), m-TPD (N ', N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine ), 1-TNATA (4,4 ', 4 "-tris (1-naphthylphenylphenylamino) triphenylamine), p-PMTDATA (4,4', 4" -tris [biphenyl-4-yl- (3 -Methylphenyl (phenyl) amino) triphenylamine], TFATA (4,4 ′, 4 ″ -tris [9,9-dimethyl-2-fluorenyl (phenyl) amino] triphenylamine), TCA A (4,4 ', 4 "-tris (carbazol-9-yl) triphenylamine), p-DPA-TDAB (1,3,5-tris (diphenylamino) benzene), MTDAPB (1,3,5 -Tris {4-methylphenyl (phenyl) amino] phenyl} benzene), p-BPD (N, N'-di (biphenyl-4-yl) -N, N'-diphenyl- [1,1'-biphenyl) -4,4'-diamine), PFFA (N, N'-bis (9,9-dimethyl-2-fluorenyl) -N, N'-diphenyl-9,9-dimethylfluorene-2,7-diamine) or FFD (N, N, N ', N'-tetrakis (9,9-dimethyl-2-fluorenyl)-[1,1'-biphenyl] -4,4'-diamine).
[0012]
Further, in the method for manufacturing an organic EL device of the present invention, at least one of the electrode layers formed of a transparent electrode includes at least one organic layer including a light emitting layer and an electron transfer control layer for suppressing electron flow. In this case, the electrode layer, the organic layer, and the electron transfer control layer are formed.
[0013]
In addition, the organic EL panel of the present invention has an organic EL panel in which at least one is formed of a transparent electrode, and at least one organic layer including a light emitting layer and an electron transfer control layer for suppressing the flow of electrons are formed between electrode layers. In this configuration, a plurality of EL elements are arranged on a base.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to FIGS.
FIG. 1 is a partial cross-sectional view showing the structure of an organic EL device according to a first embodiment of the present invention, FIG. 2 is a flowchart showing a manufacturing process of the organic EL device, and FIG. FIG. 3B is a schematic view showing the energy of each layer of the organic EL element, FIG. 3B is a schematic view showing the energy of each layer of a conventional green organic EL element for comparison, and FIG. 4 is a green organic EL according to Example 1. FIG. 5 is a diagram showing the luminous efficiency with respect to the current flowing through the device, FIG. 5 is a diagram showing the luminous efficiency with respect to the applied voltage of the green organic EL device according to the first embodiment, and FIG. FIG. 6B is a schematic diagram showing the energy of each layer of the EL element, FIG. 6B is a schematic diagram showing the energy of each layer of a conventional blue organic EL element for comparison, and FIG. Schematic diagram showing the energy of each layer of the organic EL element, 7 (B) is a schematic view showing the energy of each layer of the conventional red organic EL element for comparison, FIG. 8 is a partial cross-sectional view showing the structure of the organic EL element according to the second embodiment of the present invention, and FIG. FIG. 7 is a partial cross-sectional view illustrating a structure of an organic EL device according to a third embodiment of the present invention.
[0015]
First embodiment
An organic EL device according to a first embodiment of the present invention will be described with reference to FIGS.
The organic EL element 101 according to the first embodiment has a laminated structure shown in FIG. That is, the organic EL element 101 includes an ITO (Indium Tin Oxide) transparent electrode 120, first and second hole transport layers 131 and 132, a light emitting layer 140, and an electron transfer control layer 150 on a transparent substrate 110. , The electron transport layer 160 and the metal electrode 170 are sequentially laminated.
[0016]
The ITO transparent electrode 120 is an anode, and is formed, for example, by forming an ITO film by a sputtering method. The thickness of the ITO transparent electrode 120 is preferably 10 to 1000 nm, and is 200 nm in the present embodiment.
The first hole transport layer 131 and the second hole transport layer 132 are layers that transport holes (holes) to the light emitting layer 140. The first hole transport layer 131 is formed by forming a thin film of m-TDATA by a vacuum evaporation method. The thickness of the first hole transport layer 131 is preferably 10 to 500 nm, and is 100 nm in the present embodiment. Further, the second hole transport layer 132 is a thin film of α-NPD, and is also formed by a vacuum evaporation method. The thickness of the second hole transport layer 132 is preferably 1 to 100 nm, and is 25 nm in the present embodiment.
[0017]
The light emitting layer 140 is a thin film layer of a light emitting material, and is formed by forming a light emitting material by a vacuum evaporation method. The light emitting material forming the light emitting layer 140 is selected according to the light emission color of the organic EL element 101. For example, when forming an organic EL element that emits green light, for example, when forming an element that emits blue light using Alq3 (tris (8-hydroxyquinoline) aluminum: tris (8-quinolinolato) aluminum complex) as a light emitting material. Is a light emitting material such as Zn (oxz)₂Is used. When an element that emits red light is formed, for example, a material in which Alq3 is doped with a red fluorescent dye called DCM1 is used as a light-emitting material. The thickness of the light emitting layer 140 is preferably 10 to 100 nm, and is 25 nm in the present embodiment.
[0018]
The electron transfer control layer 150 is a layer for controlling the amount of electrons injected into the light emitting layer 140. The electron transfer control layer 150 is formed by depositing a material having a lowest unoccupied molecular orbital (LUMO) energy lower than the lowest unoccupied energy of the electron transport layer 160 to an extremely thin predetermined thickness. It controls the amount of electrons transferred to the light emitting layer 140 by this.
The difference in the lowest vacancy between the electron transfer control layer 150 and the electron transport layer 160 is preferably greater than 0 eV and 1 eV or less, and such a material may be selected as the material for the electron transfer control layer 150. Specifically, as the electron transfer control layer, α-NPD, TPD, m-TPD, 1-TNATA, p-PMTDATA, TFATA, TCATA, p-DPA-TDAB, MTDAPB, p-BPD, PFFA or FFD It is preferable to use a material such as In the present embodiment, α-NPD which is a hole transporting material is used as the electron transfer control layer 150.
[0019]
Further, the thickness of the electron transfer control layer 150 is determined to be an appropriate value so that an appropriate amount of electrons is injected into the light emitting layer 140 by the electron transfer control layer 150. Generally, the thickness of the electron transfer control layer 150 is preferably from 0.1 to 20 nm, more preferably from 0.1 to 20 nm. In the present embodiment, it is 1 nm.
If the electron transfer control layer 150 is too thin, the curing is small. If the electron transfer control layer 150 is too thick, the injection amount of electrons into the light emitting layer 140 decreases, and the light emission amount in the light emitting layer 140 decreases. It tends to shift to the movement control layer 150 side, and tends to deteriorate the light emission characteristics. Therefore, it is preferable that the thickness of the electron transfer control layer 150 be determined to be an appropriate value based on the difference in the lowest empty level between the electron transfer control layer 150 and the electron transport layer 160. That is, if the difference between the lowest vacancies between the electron transfer control layer 150 and the electron transport layer 160 is small, the thickness of the electron transfer control layer 150 is large, and if the difference is large, the thickness of the electron transfer control layer 150 is small. Is preferred.
[0020]
The electron transport layer 160 transports electrons to the light emitting layer 140 via the electron transfer control layer 150, and is formed by forming a thin film of Alq3 by a vacuum evaporation method. The thickness of the electron transport layer 160 is preferably 1 to 100 nm, and in this embodiment, 25 nm.
The metal electrode 170 is a cathode and is formed by depositing Al by a vacuum evaporation method. The thickness of the Al electrode 170 may be arbitrary, but is preferably 10 nm or more, and is 200 nm in the present embodiment.
[0021]
In the organic EL element 101 having such a structure, holes are generated from the transparent electrode 120 by applying a DC voltage between the transparent electrode (anode) 120 and the Al electrode (cathode) 170. The light is injected into the light emitting layer 140 through the hole transport layers 131 and 132. In addition, electrons are injected from the metal electrode 170 into the light emitting layer 140 via the electron transport layer 160 and the electron transfer control layer 150. As a result, the injected holes and electrons are combined in the light-emitting layer 140, thereby exciting the fluorescent molecules in the light-emitting layer 140 and causing a light emission phenomenon.
At this time, the amount of electrons injected into the light emitting layer 140 is controlled by the electron transfer control layer 150. That is, the amount of electrons injected from the electron transport layer 160 into the light emitting layer 140 is suppressed, and the movement of electrons that do not contribute to light emission in the light emitting layer 140 is prevented.
[0022]
In the conventional organic EL element, when an excess electron is injected into the light emitting layer than electrons consumed by recombination with holes in the light emitting layer, the surplus electrons are converted into holes by an internal electric field generated by a driving voltage. Move to transport layer. As a result, electrons more than necessary for light emission are injected, and as a result, the luminous efficiency is reduced. In the organic EL element 101 of the present embodiment, as described above, only electrons that contribute to light emission due to the action of the electron transfer control layer 150 are injected from the electron transport layer 160 into the light emitting layer 140. Bring improvement. As a result, power consumption can be reduced, and the life of the element can be prolonged.
[0023]
At this time, the material of the electron transfer control layer 150 is selected such that the lowest empty level is lower than that of the material of the electron transport layer 160. That is, it does not depend on the material of the light emitting layer 140. Therefore, regardless of the material of the light emitting layer 140, in other words, the same material is used as the electron transfer control layer 150 for different types of organic EL elements 101 having different emission colors such as green, blue, and red. Can be. For this reason, it is possible to prevent the process steps from becoming complicated as compared with the case where the material of the electron transfer control layer 150 must be selected according to the material of the light emitting layer 140.
[0024]
The organic EL panel according to the present invention is such an organic EL element 101, and is formed by arranging organic EL elements that emit red, green, and blue in a predetermined pattern in a two-dimensional matrix. You. It is clear that the luminous efficiency of each organic EL element constituting the panel is improved, the power consumption is reduced, and the life is prolonged, so that the luminous efficiency is improved as a whole, the power consumption is suppressed, and the life is prolonged. is there.
[0025]
Next, a manufacturing process of the organic EL element 101 will be described with reference to FIG.
First, an ITO film is formed on the transparent substrate 110 by a sputtering method to form an ITO transparent electrode 120 (Step S201).
Next, an m-TDATA film is formed on the ITO transparent electrode 120 by a vacuum evaporation method to form a first hole transport layer 131 (Step S202).
Next, an α-NPD film is formed on the first hole transport layer 131 by a vacuum evaporation method to form a second hole transport layer 132 (Step S203).
Next, a thin film of a light emitting material is formed on the second hole transport layer 132 by a vacuum evaporation method to form the light emitting layer 140 (Step S204).
Next, a thin film of α-NPD is formed on the light emitting layer 140 by a vacuum evaporation method to form the electron transfer control layer 150 (Step S205).
Next, a thin film of Alq3 is formed on the electron transfer control layer 150 by a vacuum evaporation method to form the electron transport layer 160 (Step S206).
Then, a metal electrode 170 is formed by depositing Al on the electron transfer control layer 150 by a vacuum evaporation method (step S207).
[0026]
Second embodiment
An organic EL device according to a second embodiment of the present invention will be described with reference to FIG.
The organic EL element 102 of the second embodiment is an organic EL element in which the light emission extraction surface is not the substrate 110 side as in the first embodiment but the film formation surface side.
As shown in FIG. 8, the organic EL element 102 includes a metal electrode 172, an electron transport layer 160, an electron transfer control layer 150, a light emitting layer 140, a second hole transport layer 132, and a first hole transport on a substrate 112. It has a structure in which a layer 131 and a transparent electrode 120 are stacked.
The substrate 112 does not need to be transparent because it is not a light extraction surface.
The metal electrode 171 is formed by forming a metal having a low work function, for example, a mixed material of magnesium (Mg) and silver (Ag) into a thin film of, for example, about 5 nm by a vacuum evaporation method or the like.
[0027]
Other configurations are the same as those of the first embodiment described above, and the operation of the organic EL element 102 having such a configuration is also the same as that of the first embodiment. That is, even in such a configuration, the amount of electrons injected from the electron transport layer 160 to the light emitting layer 140 is controlled by the action of the electron transfer control layer 150, so that the luminous efficiency can be improved. In addition, power consumption can be suppressed and the life of the element can be prolonged.
As described above, even in an organic EL device in which the film formation surface side is a light extraction surface, the electron transfer control layer 150 can be interposed between the electron transport layer 160 and the light emitting layer 140. It may be implemented in such a form.
[0028]
Third embodiment
An organic EL device according to a third embodiment of the present invention will be described with reference to FIG.
The organic EL element 103 according to the third embodiment is an organic EL element having a plurality of light emitting layers.
As shown in FIG. 9, an organic EL element 103 includes, on a transparent substrate 110, an ITO transparent electrode 120, a first hole transport layer 131, a second hole transport layer 132, a first light emitting layer 141, and a first light emitting layer 141. It has a structure in which an electron transfer control layer 151, a second light emitting layer 142, a second electron transfer control layer 152, an electron transport layer 160, and a metal electrode 170 are sequentially stacked.
That is, the organic EL element 102 has a structure in which the two light emitting layers 141 and 142 are provided, and the electron transfer control layers 151 and 152 are arranged on the cathode side of each of the two light emitting layers 141 and 142.
[0029]
In an organic EL device having a plurality of light-emitting layers, an electron transfer control layer may be provided for each light-emitting layer as described above. For each electron transfer control layer, by selecting a material having a lower minimum empty level than the material on the cathode side, it is possible to appropriately control and control the amount of electrons injected into the corresponding light emitting layer. Luminous efficiency can be improved. In addition, power consumption can be suppressed and the life of the element can be prolonged.
Thus, even in an organic EL device having a plurality of light emitting layers, an electron transfer control layer can be interposed for each light emitting layer, and the present invention may be embodied in such a form.
[0030]
Note that the present invention is not limited to the above-described embodiment, and may be variously modified within the scope of the present invention.
The organic EL element of each embodiment described above is not applied only to a display panel. The present invention may be applied to an arbitrary device such as a lighting device as a backlight such as a liquid crystal device.
[0031]
【Example】
Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.
[0032]
Example 1
Using Alq3 as the light emitting material of the light emitting layer 140, the organic EL element 101 emitting green light was formed. That is, in the configuration shown in FIG. 1, an Alq3 layer having a thickness of 25 nm was disposed as the light emitting layer 140 between the second hole transport layer 132 and the electron transfer control layer 150.
Note that the energy of each layer of the organic EL element in this case is as shown in FIG. That is, the lowest empty level (LUMO) is 2.6 eV between the electron transporting layer (Alq3 layer) and the light emitting layer also having the lowest empty level of 2.6 eV (Alq3 layer). .3 eV electron transfer control layer (α-NPD layer). In addition, a conventional green organic EL element having no electron transfer control layer has a configuration in which an electron transport layer and a light emitting layer (both Alq 3 layers) are arranged adjacent to each other, as shown in FIG. .
[0033]
Luminous efficiencies with respect to current flowing through the green organic EL element and a conventional green organic EL element not provided with an electron transfer control layer for comparison were determined. FIG. 4 shows the results. In FIG. 4, the horizontal axis represents the current density obtained by dividing the current flowing through the organic EL element by the area of the element, and the vertical axis represents the luminous efficiency represented by the amount of emitted light per current flowing through the organic EL element. As shown in FIG. 4, when the same current flows, the organic EL device according to the present invention having the electron transfer control layer (α-NPD layer) is better than the conventional organic EL device having no electron transfer control layer. The light emission luminance was higher than the device, and the light emission efficiency was improved.
[0034]
FIG. 5 shows the results of the luminous efficiencies of the green organic EL device and the conventional green organic EL device not provided with the electron transfer control layer for comparison with respect to the applied voltage. In FIG. 5, the horizontal axis represents the voltage applied to the organic EL element, and the vertical axis represents the luminous efficiency indicated by the amount of emitted light per current flowing through the organic EL element. As shown in FIG. 5, when the same voltage is applied, the organic EL device according to the present invention having the electron transfer control layer (α-NPD layer) is better than the conventional organic EL device having no electron transfer control layer. The luminous efficiency was improved as compared with the device. In this case, the luminance hardly changed between the two, and the current flowing in the organic EL element was smaller in the organic EL element having the electron transfer control layer, so that the luminous efficiency was improved.
In any case, it was confirmed that the luminous efficiency was improved by inserting the α-NPD layer as the electron transfer control layer.
[0035]
Example 2
Zn (oxz) as a light emitting material of the light emitting layer 140₂Was used to form an organic EL device emitting blue light. That is, in the configuration shown in FIG. 1, between the second hole transport layer 132 and the electron transfer control layer 150, a 25 nm-thick Zn (oxz)₂The layer was arranged as a light emitting layer 140.
Note that the energy of each layer of the organic EL element in this case is as shown in FIG. That is, the electron transport layer (Alq3 layer) having the lowest empty level (LUMO) of 2.6 eV and the light emitting layer (Zn (oxz)) also having the lowest empty level of 2.91 eV.₂In this configuration, an electron transfer control layer (α-NPD layer) having a minimum empty level of 2.3 eV is disposed between the electron transfer control layer and the layer.
[0036]
For the blue organic EL element and the conventional blue organic EL element not provided with the electron transfer control layer for comparison, the luminous efficiency with respect to the current flowing through the organic EL element and the luminous efficiency with respect to the applied voltage were determined. Was. As a result, although not shown, the same results as those of the green organic EL elements shown in FIGS. 4 and 5 were obtained. That is, in any case, it was confirmed that the luminous efficiency was improved by inserting the α-NPD layer as the electron transfer control layer.
[0037]
Example 3
As a light emitting material of the light emitting layer 140, an organic EL element emitting red light was formed using a material in which Alq3 was doped with a red fluorescent dye called DCM1. That is, in the configuration shown in FIG. 1, a layer of a red light-emitting material having a thickness of 25 nm was disposed between the second hole transport layer 132 and the electron transfer control layer 150 as the light-emitting layer 140.
In this case, the energy of each layer of the organic EL element is in the state shown in FIG. That is, the energy state of the light-emitting layer 140 is a state in which the main material has both characteristics of Alq3 having the lowest empty level of 2.6 eV and DCM1 having the lowest empty level of 2.08 eV. An electron transfer control layer (α-NPD layer) having a minimum empty level of 2.3 eV is disposed between the light emitting layer and an electron transport layer (Alq3 layer) having a minimum empty level (LUMO) of 2.6 eV. The configuration is as follows.
[0038]
For the red organic EL element and the conventional red organic EL element not provided with the electron transfer control layer for comparison, the luminous efficiency with respect to the current flowing through the organic EL element and the luminous efficiency with respect to the applied voltage were determined. Was. As a result, although not shown, the same results as those of the green organic EL elements shown in FIGS. 4 and 5 were obtained. That is, in any case, it was confirmed that the luminous efficiency was improved by inserting the α-NPD layer as the electron transfer control layer.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an organic EL device having an increased luminous efficiency, reduced power consumption, and a longer life, without significantly complicating the process steps, and a method for manufacturing the same.
Further, it is possible to provide an organic EL panel which can perform full color display, has high luminous efficiency, suppresses power consumption, and has a long life.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view illustrating a structure of an organic EL device according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a manufacturing process of the organic EL device shown in FIG.
FIG. 3 is a diagram showing an energy state of each layer of a green organic EL element according to Example 1 of the organic EL element shown in FIG. 1, and FIG. 3 (A) shows the green organic EL element; FIG. 3B is a schematic diagram showing the energy of each layer of a conventional green organic EL element for comparison.
FIG. 4 is a diagram showing luminous efficiency with respect to a current flowing through the green organic EL device shown in FIG. 3;
FIG. 5 is a diagram showing luminous efficiency with respect to an applied voltage of the green organic EL element shown in FIG. 3;
6 is a diagram showing the energy state of each layer of the blue organic EL device according to Example 2 of the organic EL device shown in FIG. 1, and FIG. 6 (A) is the blue organic EL device; FIG. 6B is a schematic diagram showing the energy of each layer of a conventional blue organic EL element for comparison.
FIG. 7 is a diagram showing the energy state of each layer of the red organic EL element according to Example 1 of the organic EL element shown in FIG. 1, and FIG. 7 (A) is the red organic EL element; FIG. 7B is a schematic diagram showing the energy of each layer of a conventional red organic EL element for comparison.
FIG. 8 is a partial cross-sectional view illustrating a structure of an organic EL device according to a second embodiment of the present invention.
FIG. 9 is a partial cross-sectional view illustrating a structure of an organic EL device according to a third embodiment of the present invention.
[Explanation of symbols]
101, 102, 103: Organic EL element, 110, 111: Substrate, 120: Transparent electrode, 131, 132: Hole transport layer, 140, 141, 142: Light emitting layer, 150, 151, 152: Electron transfer control layer, 160 ... Electron transport layer, 170,171 ... Metal electrode

Claims (11)

An organic EL device in which at least one organic layer including a light-emitting layer is formed between electrode layers each formed of a transparent electrode,
An organic EL device, wherein an electron transfer control layer for suppressing the flow of electrons to the light emitting layer is formed between the electrode layers. An electron transport layer is formed between the electrode layer as a cathode and the light emitting layer,
The electron transfer control layer is formed between the electron transport layer and the light emitting layer,
The organic EL device according to claim 1, wherein an energy level of a lowest vacancy of the electron transfer control layer is lower than an energy level of a lowest vacancy of the electron transport layer. 3. The organic EL device according to claim 2, wherein a difference between energy levels of a lowest vacancy of the electron transfer control layer and the electron transport layer is greater than 0 eV and 1 eV or less. 4. 4. The organic EL device according to claim 2, comprising a plurality of the light emitting layers, wherein the electron transfer control layer is formed on each of the light emitting layers on the side of the electrode layer. The organic EL device according to claim 1, wherein a thickness of the electron transfer control layer is 0.1 to 20 nm. The electron transfer control layer is any one of α-NPD, TPD, m-TPD, 1-TNATA, p-PMTDATA, TFATA, TCATA, p-DPA-TDAB, MTDAPB, p-BPD, PFFA or FFD. Item 6. The organic EL device according to any one of Items 1 to 5. The electrode layer, the organic layer and the organic layer including at least one organic layer including a light emitting layer and an electron transfer control layer for suppressing the flow of electrons are disposed between at least one of the electrode layers formed by the transparent electrodes. A method for manufacturing an organic EL device, comprising forming the electron transfer control layer. Forming an electron transport layer that supplies electrons to the light emitting layer between the electrode layer as a cathode and the light emitting layer,
The electron transfer control layer is disposed between the electron transport layer and the light emitting layer, and the energy level of the lowest empty level of the electron transfer control layer is higher than the energy level of the lowest empty level of the electron transport layer. 8. The method according to claim 7, wherein the organic EL device is formed so as to be lower. 9. The method according to claim 8, wherein a plurality of the light emitting layers are formed, and the electron transfer control layer is formed on each of the light emitting layers on the side of the electrode layer as the cathode. The organic EL device according to claim 7, wherein the electron transfer control layer is formed with a thickness of 0.1 to 20 nm. A plurality of organic EL elements in which at least one organic layer including a light emitting layer and an electron transfer control layer for suppressing electron flow are formed between electrode layers each having at least one formed of a transparent electrode, are arranged on a substrate. Organic EL panel.

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