WO2006085615A1

WO2006085615A1 - Self-luminous device and self-luminous panel

Info

Publication number: WO2006085615A1
Application number: PCT/JP2006/302357
Authority: WO
Inventors: Yoshinori Fukuda; Masanobu Akagi
Original assignee: Tohoku Pioneer Corporation
Priority date: 2005-02-10
Filing date: 2006-02-10
Publication date: 2006-08-17

Abstract

Disclosed is a self-luminous device (100) comprising an electrode pair (101) having an anode (101a) and a cathode (101b) arranged opposite to the anode (101a), a light-emitting layer (104) arranged between the electrode pair (101), a doped layer (102) arranged between the light-emitting layer (104) and the anode (101a) and doped with an electron-accepting material, and a buffer layer (103) arranged between the doped layer (102) and the light-emitting layer (104) and having a film thickness larger than that of the doped layer (102). Since the doped layer (102) is doped with an electron-accepting material, a display panel can be improved in luminance decrease and display defect.

Description

Specification

Self-luminous element and self-luminous panel

Technical field

The present invention relates to a self light emitting element and a self light emitting panel.

Background art

[0002] Conventionally, there has been a self-luminous element in which a light emitting layer is provided between a pair of electrodes and light is emitted by recombination of holes and electrons in the light emitting layer when a voltage is applied between the electrodes. . Such a self-luminous element is used for a self-luminous panel that performs display or illumination and various information displays. Examples of such a self-luminous element include an organic EL (Electro Luminescence) element in which a light emitting layer is formed of an organic compound.

[0003] Organic EL elements exhibit diode characteristics when the organic layer is correctly interposed between the electrodes. However, if scratches, protrusions, foreign matters, etc. exist on the support substrate, the film is formed in a state where the electrodes and the organic layer are disturbed. In the organic layer formed in a disordered state, there is a portion where the thickness of the layer is locally thin. Insulation resistance is low in areas where the layer is thin. Similarly, if a conductive foreign substance adheres to the substrate, the film is formed in a state where the electrodes and the organic layer are disturbed, and a part having a low insulation resistance is generated locally.

[0004] The insulation resistance of the organic EL element is low, and the part does not exhibit diode characteristics. In addition, the insulation resistance in the organic EL element is low, and a short circuit between the electrodes may occur or the so-called leakage current may be generated due to low impedance. The occurrence of leakage current causes element destruction and drive failure.

[0005] Conventionally, as countermeasures, the lower electrode is made as smooth as possible, or foreign substances adhering to the substrate are removed. Another measure is to prevent short-circuits by covering discontinuous structures on the substrate with an insulating film. Furthermore, when forming an organic material, the substrate is rotated to make it easier to cover the abnormally shaped part, and when the upper electrode is formed, the substrate is kept stationary so that the abnormally shaped part is not covered. Technologies that prevent shorts between electrodes have also been proposed. In addition, by thickening the organic layer, there is a technology that sufficiently covers the leakage current sources such as scratches, protrusions, and foreign objects. However, since the organic layer generally has a low carrier density and a resistivity of 1 × 10 ¹⁰ Ω′cm or more in general, the thicker film increases the resistance between the electrodes, and the drive voltage There was a problem of increasing the price.

[0007] Here, in the self-light emitting element, there are various conventional techniques for lowering the driving voltage at the time of light emission. For example, there is a technology that increases the carrier density of an organic layer (hole injection layer, etc.) by doping an electron-accepting substance into an organic layer (hole injection layer, etc.) in contact with the anode, for example. (For example, see Patent Documents 1 and 2 below;). With this technology, the hole injection barrier from the anode to the organic layer (hole injection layer, etc.) is reduced, or the energy required for hole injection is reduced by using the injection mechanism as tunnel injection, and the driving voltage is reduced. Can be reduced.

[0008] In addition, a drive layer is provided by including a doped layer doped with an electron-accepting substance and a buffer layer not containing the electron-accepting substance, and making the thickness of the doped layer larger than the thickness of the buffer layer. there is a technique so as to lower Do (e.g., see below Patent Document 3.) ₀

Patent Document 1: Japanese Patent Application Laid-Open No. 11 251067

Patent Document 2: Japanese Patent Laid-Open No. 2003-217862

Patent Document 3: Japanese Translation of Special Publication 2004-537149

Disclosure of the invention

Problems to be solved by the invention

However, in the conventional techniques described in Patent Documents 1 and 2 described above, an organic layer doped with an electron-accepting substance (such as a hole injection layer) uses holes as conductive carriers. p-type conductor. For this reason, hole injection from the anode to the organic layer (hole injection layer, etc.) can be facilitated, but the electron blocking performance deteriorates due to the increase in conductivity, and electrons injected from the cathode pass through the light emitting layer. Conducted through the doped organic layer (hole injection layer, etc.) and anode.

As a result, recombination of electrons and holes occurs in a region other than the light emitting layer, and the recombination energy is not effectively converted into light emission energy, or the electrons reach the counter electrode as they are and are recombined. There is a problem that the current does not contribute and the current efficiency of the self-luminous panel is lowered. In other words, there is a problem that wasteful power consumption becomes significant. I

[0012] Further, in the technique described in Patent Document 3 described above, a thick film can be formed without increasing the driving voltage, but when a reverse noise voltage is applied by inserting a doped conductive layer, There was a problem that the leakage current (hereinafter referred to as “leakage current in the film thickness direction”) increased. In particular, in a so-called passive drive type organic EL panel that applies a reverse noise voltage to an organic EL element that does not emit light during driving, all leakage currents generated by the application of the reverse bias voltage become reactive currents. As a result, there is a problem that power is wasted.

[0013] Also, with the technique described in Patent Document 3 described above, the film thickness can be increased without increasing the driving voltage, but because of the doped conductive layer, it is orthogonal to the stacking direction of each layer in the organic EL element. Since conductivity remains in the direction (hereinafter simply referred to as the lateral direction), there is a problem in that a lateral leakage current occurs between the so-called separated electrodes. In the case of a self-light-emitting panel in which a plurality of self-light-emitting elements are arranged on a single substrate, such leakage current causes the periphery of the self-light-emitting element (pixel) to be driven to emit light. In addition, the self-light-emitting element (pixel) adjacent to the self-light-emitting element to be driven may emit light. As a result, there has been a problem that display defects (pixel blurring emission) occur, for example, the edges of the display image become unclear.

[0014] When a part of the organic EL element has a light emitting defect due to a film formation defect or the like, if the part causing a defect such as a light emitting defect is a part of the element, it is suitable for this organic EL element. By applying a reverse bias voltage of a large magnitude, local current flows only in the defective part and only a small reverse bias current flows in the normal part.

[0015] By short-circuiting the defective light emitting portion locally and instantaneously, it can be repaired so that the defective portion is physically destroyed by the heat generation or discharge of the minute portion and the local current does not flow between the electrodes. Thus, the light emitting state of the element can be within a favorable range (repaired). This repair can improve the yield in manufacturing the self-luminous panel. However, if the above-described leakage current is generated, there is a problem that the current cannot be transferred to the light emitting failure portion in the organic EL element, and the repair cannot be performed. [0016] An object of the present invention is to deal with such a problem. In other words, the present invention sufficiently recombines electrons and holes in the light emitting layer to prevent a decrease in brightness of the self light emitting panel, and prevents a lateral leakage current of each layer in the self light emitting element, Suppressing invalid current and bleeding of light emission, preventing display failure due to short-circuit between electrodes of self-luminous panel, improving reverse bias withstand voltage when applying reverse bias of self-luminous element, reverse of self-luminous element The purpose is to not use up unnecessary power of the self-luminous panel by improving the bias characteristics, and to improve the manufacturing yield of the self-luminous panel by improving the reverse bias characteristics of the self-luminous elements.

Means for solving the problem

[0017] As described in Patent Document 3 described above, the inventor has found that there is a doped layer of about lOnm that can be made thicker by using a thicker doped layer and a thinner buffer layer. It was verified that the driving voltage force of the organic EL element (self-emitting element) was constant regardless of the thickness of the S buffer layer.

[0018] A self-luminous element according to the invention of claim 1 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, and the light emitting layer. A dimension between the doped layer, which is provided between the lower electrode and doped with an electron-accepting substance, and between the doped layer and the light-emitting layer, along the opposing direction of the electrode pair ( And a buffer layer having a larger thickness than the thickness of the doped layer.

[0019] A self-luminous element according to the invention of claim 2 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, the light emitting layer, Provided between the upper electrode and a doped layer doped with an electron-accepting substance; provided between the doped layer and the light-emitting layer; A large buffer layer.

[0020] A self-luminous element according to the invention of claim 7 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, the light emitting layer, Provided between the lower electrode and a doped layer doped with an electron donating substance; and between the doped layer and the light emitting layer, and the film thickness is greater than the film thickness of the doped layer. Also And a large buffer layer.

[0021] The self-light-emitting element according to the invention of claim 8 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light-emitting layer provided between the electrode pair, the light-emitting layer, Provided between the upper electrode and a doped layer doped with an electron donating substance; and between the doped layer and the light emitting layer, the film thickness is greater than the film thickness of the doped layer. A large buffer layer.

A self-luminous panel according to the invention of claim 14 includes an electrode pair comprising a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, the light emitting layer, Provided between the lower electrode and a doped layer doped with an electron-accepting substance or an electron-donating substance, and provided between the doped layer and the light-emitting layer. A plurality of self-luminous elements including a buffer layer larger than the thickness of the doped layer are provided on the substrate.

[0023] The self-luminous panel according to the invention of claim 15 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, the light emitting layer, Provided between the upper electrode and a doped layer doped with an electron-accepting substance or an electron-donating substance, and provided between the doped layer and the light-emitting layer. A plurality of self-luminous elements including a buffer layer larger than the thickness of the doped layer are provided on the substrate.

[0024] The self-light-emitting panel according to the invention of claim 16 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light-emitting layer provided between the electrode pair, the light-emitting layer, and the A doped layer provided between the lower electrode and doped with an electron donating substance; and provided between the doped layer and the light emitting layer, wherein the film thickness is greater than the film thickness of the doped layer. A plurality of self-luminous elements each including a large buffer layer are provided on a substrate.

[0025] The self-luminous panel according to the invention of claim 17 includes an electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, the light emitting layer, and the A doped layer provided between the upper electrode and doped with an electron donating substance; and provided between the doped layer and the light emitting layer, wherein the film thickness is equal to the film thickness of the doped layer. A plurality of self-luminous elements each having a larger buffer layer are provided on the substrate.

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing an example of the structure of an organic EL element in the first embodiment.

FIG. 2 is a cross-sectional view showing an example of the structure of the organic EL element in the second embodiment.

FIG. 3 is a cross-sectional view showing an example of the structure of an organic EL element according to a third embodiment.

FIG. 4 is a cross-sectional view showing an example of the structure of a conventional organic EL element.

FIG. 5 is an explanatory diagram showing the behavior of a carrier when a reverse bias voltage is applied to a conventional organic EL element.

FIG. 6 is an explanatory diagram showing the behavior of carriers when a reverse bias is applied to the organic EL element according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the behavior of carriers when a reverse bias voltage is applied to a conventional organic EL element.

FIG. 8 is an explanatory diagram showing the behavior of carriers when a reverse bias is applied to the organic EL element according to the embodiment of the present invention.

FIG. 9 is a cross-sectional view showing an example of a self-luminous panel in the fourth embodiment.

FIG. 10 is a cross-sectional view showing an example of a self-luminous panel provided with a conventional organic EL element.

FIG. 11 is a plan view showing the arrangement of organic EL elements in a self-luminous panel.

FIG. 12 is a graph showing the relationship between the film thickness of the doped layer and the buffer layer and the drive voltage.

[FIG. 13] FIG. 13 is an explanatory diagram (part 1) for explaining the effect of thickening the buffer layer.

[FIG. 14] FIG. 14 is an explanatory diagram (part 2) for explaining the effect of thickening the buffer layer. FIG. 15 is a schematic diagram showing the structures of three types of organic EL elements having different configurations.

FIG. 16 is a graph showing diode characteristics when a forward bias voltage is applied to an organic EL element and then a reverse bias voltage is applied.

FIG. 17 is a cross-sectional view illustrating the structure of an organic EL element according to a fifth embodiment.

FIG. 18 is an explanatory diagram showing an organic EL element according to a sixth embodiment.

FIG. 19 is a longitudinal side view showing a multi-photon device according to a seventh embodiment.

FIG. 20 is a schematic diagram showing the operation of a conventional charge generation layer.

FIG. 21 is a schematic diagram showing the operation of the charge generation layer in the embodiment of the present invention.

FIG. 22 is a schematic diagram showing a relationship between energy levels of intermediate electrodes in the embodiment of the present invention.

FIG. 23 is a longitudinal side view showing a multi-photon device according to an embodiment of the present invention.

FIG. 24 is a longitudinal sectional side view showing a multi-photon device according to another embodiment of the present invention.

Explanation of symbols

100 organic EL elements

101 electrode pair

102 doped layer

103 Noffer layer

104 Light-emitting layer

105 Charge transport layer

200 organic EL elements

201 electrode pair

202 Hole injection layer (dope layer)

203 Electronic block layer (buffer layer) 204 Light-emitting layer

205 Electron injection transport layer

300 OLED device

301 Hole injection transport layer

302 Hole blocking layer (buffer layer)

303 Electron injection layer (dope layer)

900 Self-luminous panel

1700 OLED device

1701 Hole injection layer

1702 Hole transport layer

1703 Noffer layer

1900 Manolet ophton element

1910 Organic EL device

1920 Organic EL device

2300 Mano rephon phone element

2400 Multi photon element

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Preferred embodiments of a self-light-emitting element and a self-light-emitting panel according to the present invention will be described below in detail with reference to the accompanying drawings. In each embodiment described below, an example in which an organic EL element is used as a self-luminous element will be described. That is, in this embodiment, a self-luminous element is realized by an organic EL element!

[0029] (First embodiment)

FIG. 1 is a cross-sectional view showing an example of the structure of the organic EL element in the first embodiment. First, an example of the structure of the organic EL element in the first embodiment will be described with reference to FIG. As shown in FIG. 1, an organic EL element 100 in the present embodiment includes an electrode pair 101, a doped layer 102, a buffer layer 103, a light emitting layer 104, and a charge transport layer 105.

The organic EL element 100 is formed on the substrate 106. The substrate 106 is, for example, glass Thus, it is formed of a transparent and insulating material. The substrate 106 is not limited to being formed of a transparent material. For example, various substrates 106 such as an active drive TFT substrate and a substrate provided with a color filter can be used as appropriate in accordance with the driving method of a self-luminous panel (not shown) using the organic EL element 100. .

Next, each configuration provided in the organic EL element 100 will be described. First, the electrode pair 101 will be described. The electrode pair 101 includes an anode 101a and an anode 101b facing the anode 101a. In the electrode pair 101 shown in FIG. 1, the anode 101 a is provided on the substrate 106. In this case, the lower electrode is realized by the anode 101a, and the upper electrode is realized by the cathode 101b.

Note that the electrode pair 101 may be provided on the cathode 101b force substrate 106, for example. In this case, the lower electrode is realized by the cathode 101b and the upper electrode is realized by the anode 101a. In any case, a layer for the purpose of improving adhesion, preventing alkali elution, or smoothing may be provided between the substrate 106 and the lower electrode.

[0033] The organic EL element 100 has a structure in which the respective components are sequentially laminated in the order of the substrate 106, the anode 101a, the doped layer 102, the buffer layer 103, the light emitting layer 104, the charge transport layer 105, and the cathode 101b. .

Next, the doped layer 102 will be described. The doped layer 102 is provided between the light emitting layer 104 and the anode 101a. The doped layer 102 is a charge transport layer formed mainly of an organic material and having a high charge (electron or hole) density. The doped layer 102 is formed by doping a material having a charge transporting property with an electron accepting substance (acceptor). Here, the material having a charge transporting property is a hole transporting material having a high hole transporting function. The electron-accepting substance doped in the hole transporting material generates electrons in the doped layer 102 by receiving electrons in the doped layer 102.

In the first embodiment, the force exemplified for the doped layer 102 including the hole transporting material as the charge transporting material and the electron accepting material is not limited to this. . The doped layer 102 may be formed by doping an electron-donating substance (donor) with a material having a charge transporting property. In this case, the material having a charge transporting property is an electron transporting material having a high electron transporting function. Electron donation doped in electron transport materials The conductive material generates electrons in the doped layer 102 by donating electrons in the doped layer 102.

[0036] In the doped layer 102, the material having a charge transporting property is, for example, the same material as the material forming the notch layer 103. In the doped layer 102, the material having a charge transporting property may be a material different from the material forming the notch layer 103, for example.

[0037] Although not shown, an adhesion layer for improving the adhesion of the dopant layer 102 to the anode 101a or a surface modification layer for improving carrier injection is provided between the anode 101a and the doped layer 102. Alternatively, a layer for the purpose of stabilizing the organic EL element 100 may be further provided.

Next, the buffer layer 103 will be described. The buffer layer 103 is provided between the doped layer 102 and the light emitting layer 104. The noffer layer 103 blocks charges (electrons or holes), and charges injected from each electrode (anode 101a or cathode 101b) (having opposite characteristics to the blocked charges) as the light emitting layer 104. It has the function of injecting and transporting.

Buffer layer 103 has a dimension (hereinafter referred to as a film thickness) along the facing direction of electrode pair 101 (the direction of arrow A in FIG. 1) so as to be larger than the film thickness of doped layer 102. Is provided. The nother layer 103 may be formed of the same material as that forming the doped layer 102, or may be formed of a material different from the material forming the doped layer 102. The buffer layer 103 is formed mainly of an organic material.

[0040] The buffer layer 103 of the first embodiment has a hole transport function of transporting holes conducted from the doped layer 102 to the light emitting layer 104, and electrons that move from the light emitting layer 104 to the doped layer 102. Electronic block function to block. The details of the electronic block function will be described later.

[0041] In the organic EL element 100, all the layers including the buffer layer 103 are the first reflections that reflect the light emitted from the light emitting layer 104 on the surface of the layer on the light emitting layer 104. The light is provided in such a film thickness that causes optical interference such that light is emitted from the light emitting layer 104, transmitted through the buffer layer 103, and reflected by the surface on the doped layer 102 side. In addition, of the light emitted from the light-emitting layer 104, the film thickness is adjusted so that optical interference is generated such that the light emitted in the opposing direction of the electrode pair 101 and multiple-reflected at the interface between the layers is intensified. It doesn't matter. Next, the light emitting layer 104 will be described. The light emitting layer 104 is provided between the electrode pair 101. More specifically, the light emitting layer 104 of the first embodiment is provided between the notch layer 103 and the charge transport layer 105. The light emitting layer 104 of the first embodiment is formed of an organic compound.

[0043] Next, the charge transport layer 105 will be described. The charge transport layer 105 is provided between the light emitting layer 104 and the cathode 101b. In the first embodiment, the charge transport layer 105 is described as an electron transport layer. The charge transport layer 105 is formed mainly of an organic material. The charge transport property in the charge transport layer 105 may be manifested by doping this organic material with an electron donating substance (donor). A hole blocking layer (not shown) having a low hole transporting property may be inserted between the charge transport layer 105 and the light emitting layer 104. Further, the charge transport layer 105 may be omitted.

When a forward bias voltage is applied to the electrode pair 101 in the organic EL element 100 shown in FIG. 1, electrons injected into the charge transport layer 105 from the cathode 101b move to the light emitting layer 104, and from the cathode 101a. The holes injected into the doped layer 102 move to the light emitting layer 104. The electrons and holes that have moved to the light emitting layer 104 are recombined inside the light emitting layer 104. This recombination energy excites the light emitting molecules in the light emitting layer 104. In the organic EL element 100, electoric luminescence is generated by emitting light when the excited luminescent molecule returns to the ground state.

[0045] (Second embodiment)

FIG. 2 is a cross-sectional view showing an example of the structure of the organic EL element according to the second embodiment. Next, an example of the structure of the organic EL element in the second embodiment will be described with reference to FIG. Note that the same components as those in the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

[0046] The organic EL element 200 of the second embodiment includes a substrate 106, an electrode pair 201, a hole injection layer,

(Dope layer) 202, electron block layer (buffer layer) 203, light emitting layer 204, and electron injecting and transporting layer 205 are provided. The thickness of the electron block layer (buffer layer) 203 is larger than that of the hole injection layer (dope layer) 202.

[0047] First, the electrode pair 201 will be described. The electrode pair 201 includes an anode 201a and the anode 2 A cathode 201b facing Ola is provided. In the electrode pair 201 shown in FIG. 2, the anode 201 a is provided on the force substrate 106. The anode 201a may be provided directly on the substrate 106, or may be formed after an alkali barrier film, an adhesion improving film, an optical adjustment film, or the like (not shown) is formed on the substrate 106. Well ...

[0048] In the second embodiment, the lower electrode is realized by the anode 201a, and the upper electrode is realized by the cathode 201b. Hereinafter, the anode 201a will be described as “lower electrode (anode) 201a” and the cathode 201b will be described as “upper electrode (cathode) 201b”.

[0049] In the second embodiment, the force for explaining the case where the lower electrode is realized by the anode 201a and the upper electrode is realized by the cathode 201b is not limited to this. The upper electrode may be realized by the anode 201a and the lower electrode may be realized by the cathode 201b.

[0050] The organic EL element 200 includes a substrate 106, a lower electrode (anode) 201a, a hole injection layer 202, an electron block layer 203, a light emitting layer 204, an electron injection transport layer 205, and an upper electrode (cathode) 201b in this order. Each structure is sequentially stacked. Hereinafter, each component included in the organic EL element 200 will be described in detail. Note that the description of the same parts as those described in the first embodiment will be omitted as appropriate.

[0051] Next, the lower electrode (anode) 20 la will be described. As a material for forming the lower electrode (anode) 20 la, for example, a conductive oxide such as tin oxide, indium oxide, and indium tin oxide (ITO), or aluminum, copper, gold, silver, chromium, and the like are used. Metals, inorganic conductive materials such as copper iodide and copper sulfide, and the like can be used. The material for forming the lower electrode (anode) 201a is not limited to these materials.

Next, the upper electrode (cathode) 201b will be described. As a material for forming the upper electrode (cathode) 201b, for example, a simple substance such as aluminum, copper, silver, or gold, an alloy such as magnesium and silver, lithium and silver, or a conductive oxide such as indium tin oxide (ITO) is used. Can be used.

Next, the hole injection layer 202 and the electron injection / transport layer 205 will be described. For the hole injecting layer 202 and the electron injecting and transporting layer 205, conventionally used materials (regardless of polymer materials, low molecular weight materials, organic materials, and inorganic materials) can be appropriately selected. Second In the embodiment, the hole injection layer 202 realizes a doped layer provided between the light emitting layer 204 and the lower electrode (anode) 2 Ola and doped with an electron accepting substance.

Next, the light emitting layer 204 will be described. As a material for forming the light emitting layer 204, a conventionally used material (regardless of a polymer material, a low molecular material, an organic material, or an inorganic material) can be appropriately selected. In the luminescent material, there are light emission (fluorescence) when returning from the singlet excited state to the ground state and light emission (phosphorescence) when returning from the triplet excited state to the ground state. In the second embodiment, It can be used in the organic EL element 200 using either light emission.

Next, the electronic block layer 203 will be described. The electron blocking layer 203 is provided between the lower electrode (anode) 201 a and the light emitting layer 204. In the second embodiment, for example, for the purpose of improving the hole injection efficiency, an example in which a hole injection layer 202 is provided between the lower electrode (anode) 201a and the electron block layer 203 will be described. The power explained is not limited to this. The electron blocking layer 203 may be in direct contact with the lower electrode (anode) 201a.

Here, the function of the electronic block layer 203 will be described. When a voltage is applied in the forward direction with respect to the electrode pair 201, in the organic EL element 200, a force of electrons on the upper electrode (cathode) 201 b side also flows toward the lower electrode (anode) 201 a side. The electron blocking layer 203 suppresses the transmission of the electron force reaching the lower electrode (anode) 201a side that has reached the surface on the upper electrode (cathode) 201b side of the two interfaces in the electron blocking layer 203. As a result, electrons are effectively confined on the lower electrode (anode) 201a side of the light emitting layer 204.

[0057] Further, when the electron blocking layer 203 has hole transporting performance, electrons efficiently injected from the lower electrode (anode) 201a are transported to the light emitting layer 204 via the electron blocking layer 203. can do. In this case, holes efficiently transported to the light-emitting layer 204 through the electron blocking layer 203 and efficiently injected from the upper electrode (cathode) 201b and transported through the electron injecting and transporting layer 205 are then transferred to the electron blocking layer. The electrons blocked in 203 can be effectively recombined inside the light emitting layer 204. The recombination energy in this recombination Therefore, the light emitting molecules in the light emitting layer 204 are excited and luminescence is obtained. In other words, efficient recombination can be obtained by effective recombination within the light emitting layer 204.

On the other hand, when a voltage is applied to the electron blocking layer 203 in the reverse direction, the organic EL element 200 has a lower electrode (electron force forcibly injected from the lower electrode (anode) 201a ( Anode) Electron flows from the 20 la side to the upper electrode (cathode) 201b side. The electron blocking layer 203 suppresses transmission of the electron force reaching the upper electrode (cathode) 201b side, which has reached the surface of the lower electrode (anode) 201a side, out of the two interfaces in the electron blocking layer 203.

Next, materials for forming the electron block layer 203 will be described. In general, a material having a high electron block performance has a low positive / negative carrier density, but as a material for forming the electron block layer 203, a material having an electron block property and a hole transport performance is preferable. Specifically, for example, it is preferable to use a-NPD (see JP-A-2003-272860).

Next, materials for forming the hole injection layer 202 will be described. The hole injection layer 202 is formed mainly of an organic material. The hole injection layer 202 is preferably made of a material having the highest occupied orbital (HOMO) level close to the work function of the lower electrode (anode) 201a and having hole transport performance. When the HOMO level is larger than the work function of the lower electrode (anode) 201a, hole injection from the lower electrode (anode) 201a becomes ohmic, and smooth carrier injection without rectification becomes possible.

[0061] When the HOMO level is smaller than the work function of the lower electrode (anode) 201a, thermal diffusion hole injection is performed that exceeds the energy barrier at the injection interface. In this case, the voltage required for the holes to exceed the energy barrier is required, and smooth hole injection is obtained because of the depletion layer generated on the hole injection layer 202 side of the injection interface. Electrode (anode) 20 la material is particularly selected.

[0062] Another injection form is tunnel injection. Tunnel injection is particularly effective when the hole carrier density of the hole injection layer 202 is high. During tunnel injection, the band at the interface with the lower electrode (anode) 201a is abruptly distorted, and holes are trapped through a distorted thin barrier. Inject the tunnel. In tunnel injection, since it is not necessary to consider the energy barrier between the lower electrode (anode) 201a and the hole injection layer 202, many materials can be selected as a material for forming the lower electrode (anode) 201a. As a result, the efficiency of hole injection can be increased.

[0063] As a material for forming the hole injection layer 202, in order to increase the hole carrier density of the hole injection layer 202, an electron-accepting substance (acceptor) is doped into a material having hole transport performance. It may be a made material. Hereinafter, the description will be made on the assumption that the hole carrier density of the hole injection layer 202 is particularly high.

[0064] In the hole injection layer 202 doped with an electron-accepting substance (acceptor), a material having a hole carrier transporting performance transports holes relatively compared to electron transport. It is a material with high performance. In general, it is said that the hole transport layer has better performance as it is easier to transport holes that are difficult to transport electrons.

The electron accepting substance (acceptor) generates holes in the hole injection layer 202 by receiving electrons in the hole injection layer 202. The hole injection layer 202 includes, for example, the same material as that for forming the electron block layer 203 and an electron accepting material (acceptor). The hole injection layer 202 may include a material having hole transport performance different from the material forming the electron blocking layer 203 and an electron accepting material (acceptor).

[0066] Examples of the electron-accepting substance doped in the hole injection layer 202 include Lewis acid compounds, metal oxides, metal halides, fullerenes, and the like. Further, the force described above for the lower electrode (anode) 201a and the hole injection layer 202 is exactly the same for the upper electrode (cathode) 201b and the electron injection / transport layer 205, and can be explained only with different signs. .

Next, materials for forming the upper electrode (cathode) 201b and the electron injection / transport layer (which may be an electron injection layer or an electron transport layer) 205 will be described. Examples of the material for forming the upper electrode (cathode) 201b and the electron injecting and transporting layer 205 include a material having an electron transporting property as an electron injecting material, and an electron donating substance (a Examples of the ceptor include alkali metals, alkaline earth metals, rare earth metals, alkali metal compounds, alkaline earth metal compounds, and rare earth compounds.

[0068] Specific examples of the Lewis acid compound include, for example, ferric chloride, ferric bromide, and Yowi 2nd. Iron, Aluminum chloride, Aluminum bromide, Aluminum iodide, Aluminum chloride, Gallium bromide, Gallium iodide, Indium chloride, Indium bromide, Indium iodide, Antimony pentachloride, Arsenic pentafluoride , Inorganic compounds such as boron trifluoride, DDQ (disananodichloroquinone), TNF (tri-trofluorenone), TCNQ (tetracyanoquinodimethane), F4—TC NQ (tetrafluoroacetate tetracyanoquinodimethane, etc. Is mentioned.

[0069] Specific examples of metal oxides and metal halides include, for example, V 2 O 3

twenty five

Dium) or Re 2 O (rhenium oxide), MoO, WO, etc. Alkali metal, Al

2 7 3 3

Potassium earth metals, rare earth metals and their compounds include Li, Cs, Mg, Ca, Eu, LiF, Li 0,

2

Examples include CsF, NaCl, KC1, and MgF.

2

[0070] Examples of the electron-accepting substance (acceptor) include an organic substance having fluorine as a substituent and an organic substance having a cyano group as a substituent. The electron accepting substance (acceptor) is not limited to these materials described above.

[0071] When an electron transporting material such as tris (8-hydroxyquinolinol) aluminum is used for the electron injecting and transporting layer 205, an electron donating property may be obtained by doping with an electron donating substance such as fullerene or carbon nanotube. The substance (donor) itself may be used for the electron injecting and transporting layer 205. As a material for forming the hole injection layer 202, the electron injection transport layer 205, and the electron block layer 203, various known compounds generally used in the manufacture of the organic EL element 200 are appropriately used. Can be used.

[Third Embodiment]

FIG. 3 is a cross-sectional view showing an example of the structure of the organic EL element according to the third embodiment. Next, an example of the structure of the organic EL element in the third embodiment will be described with reference to FIG. Note that the same components as those in the first and second embodiments described above are denoted by the same reference numerals, and description thereof is omitted.

[0073] The organic EL device 300 in the third embodiment includes a substrate 106, an electrode pair 201, a hole injecting and transporting layer 301, a light emitting layer 204, a hole blocking layer (buffer layer) 302, an electron An injection layer (dope layer) 303. The hole blocking layer (buffer layer) 302 is thicker than the electron injection layer (dope layer) 303.

[0074] The organic EL element 300 includes a substrate 106, a lower electrode (anode) 201a, a hole injecting and transporting layer 301, The light emitting layer 204, the hole blocking layer 302, the electron injecting layer 303, and the upper electrode (cathode) 201b are sequentially stacked. Below, each structure with which the organic EL element 300 is provided is demonstrated in detail. Note that the description of the same parts as those described in the first and second embodiments is omitted as appropriate.

[0075] The organic EL element 300 of the third embodiment is configured so that the upper electrode (cathode) 201b and the electron injection layer 303 are the lower electrode (anode) 201a in the organic EL element 200 shown in FIG. It has a structure in which the positive and negative signs of the hole injection layer 202 and the carrier are reversed. That is, the thickness of the hole blocking layer (buffer layer) 302 is larger than that of the electron injection layer (dope layer) 303. The organic EL device 300 shown in FIG. 3 has exactly the same mechanism as the organic EL device 200 shown in FIG. 2, and carriers are injected and transported by forward and reverse bias voltages.

[0076] The hole blocking layer 302 included in the organic EL element 300 is desirably formed of a material capable of suppressing the passage of holes and efficiently transporting electrons. When a forward bias voltage is applied to the organic EL element 300, the hole blocking layer 302 efficiently transports electrons injected from the upper electrode (cathode) 201b to the light emitting layer 204, and also lower electrode (anode). ) The holes injected from 201a are blocked on the surface of the hole blocking layer 302 on the light emitting layer 204 side. Thus, positive and negative carrier recombination can be effectively performed in the light emitting layer 204.

[0077] The hole blocking layer 302 is forcibly injected from the upper electrode (cathode) 201b when a reverse bias voltage (hereinafter referred to as "reverse bias voltage") is applied to the organic EL element 300. The formed holes are prevented from transmitting to the lower electrode (anode) 201a side. As a result, the leakage current when a reverse bias voltage is applied can be reduced.

[0078] The electron injection layer 303 of the third embodiment is formed mainly of an organic material or an inorganic material. In order to have a higher electron carrier density, the electron injecting layer 303 may be doped with an electron donating substance (donor) in a material having a charge transporting property. At this time, the material having a charge transporting property is an electron transporting material having a relatively high performance of transporting electrons compared to the performance of transporting holes, and has an electron transporting performance. The electron donating substance generates electrons in the electron injection layer 303 by emitting electrons in the electron injection layer 303. Make it. When the carrier density is high, tunnel injection is the same as in the case of hole injection.

[0079] The electron injection layer 303 includes, for example, the same material as that for forming the hole blocking layer 302, and an electron donating substance (donor). The electron injection layer 303 may include, for example, a charge transporting material different from the material forming the hole blocking layer 302 and an electron donating substance (donor).

[0080] As a material for forming the hole blocking layer 302, a material having a hole blocking property is preferable. Materials that have hole blocking properties and high electron transport performance include, for example, BCP (2, 9 dimethyl 4, 7 diphenyl 1, 10 phenolic phosphorus), BAlq (l, 1, bisphenol 4-olatobis (2-methyl-8 quinolinolato-Nl, 08)), BPhen (4,7-diphenenole 1, 10 phenanthrene).

[0081] (Difference between the organic EL device of the embodiment and the conventional organic EL device (Part 1))

The difference (part 1) between the organic EL element of the embodiment and the conventional organic EL element is described below. First, the structural difference between the organic EL element of the embodiment and the conventional organic EL element will be described. Here, as the organic EL element of the embodiment of the present invention, the organic EL element 100 of the first embodiment shown in FIG. 1 described above (or the organic EL element of the second embodiment shown in FIG. 2). This will be described using the element 200).

[0082] (Conventional organic EL device structure)

FIG. 4 is a cross-sectional view showing an example of the structure of a conventional organic EL element. A conventional organic EL element will be described below with reference to FIG. Note that, in the conventional organic EL element 400 shown in FIG. 4, the same parts as those of the organic EL elements 100, 200, and 300 in the above-described embodiments are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 4, a conventional organic EL element 400 includes an electrode pair 101, a doped layer 102, a buffer layer 103, a light emitting layer 104, and a charge transport layer 105. The electrode pair 101 includes an anode 101a that is a lower electrode and a cathode 101b that is an upper electrode. The organic EL element 400 has a structure in which the respective components are sequentially laminated in the order of the substrate 106, the anode 101a, the doped layer 102, the buffer layer 103, the light emitting layer 104, the charge transport layer 105, and the cathode 101b.

[0084] The thickness of the doped layer 102 in the conventional organic EL device 400 is equal to the thickness of the buffer layer 103. It is also big. In the conventional organic EL element 400, when conducting in the doped layer 102, the conductive carrier is a hole, and a hole-derived current is generated regardless of the direction of the bias voltage. That is, the doped layer 102 loses rectification and behaves ohmic.

[0085] (Difference in behavior (part 1))

FIG. 5 is an explanatory view showing the behavior of carriers when a reverse bias voltage is applied to the organic EL element 400 of the conventional form. FIG. 6 is an explanatory diagram showing the behavior of carriers when a reverse bias is applied to the organic EL element 100 according to the embodiment of the present invention. Hereinafter, the difference in behavior when a reverse bias voltage is applied to the conventional organic EL element 400 and the organic EL element 100 will be described with reference to FIGS. 5 and 6. FIG.

FIG. 5 and FIG. 6 schematically show in which layer many carriers are accumulated when reverse noise voltage is applied to the conventional organic EL element 400 and the organic EL element 100. Yes. Normally, when the organic EL elements 400 and 100 emit light, a positive voltage is applied to the anode 101a side, and a negative voltage is applied to the cathode 101b side (in this embodiment, a noisy voltage applied in such a direction is applied). This will be described as a forward bias voltage.)

Apart from this, the reverse noise voltage is a voltage in a direction opposite to the direction of the voltage applied when the organic EL elements 400 and 100 emit light. The reverse noise may apply a negative voltage to the original anode 101a side and a positive voltage to the original negative electrode 101b side, for example, because of the advantage of improving the performance of the organic EL elements 400 and 100. It is considered that carriers accumulated in the organic EL elements 400 and 100 can be eliminated by applying reverse noise.

[0088] As a specific application example of applying the reverse bias voltage, for example, in a self-luminous panel (not shown) in which a plurality of organic EL elements 400, 100 are formed on the substrate 106, the organic EL element 400 , 100 is line-sequentially driven along the scanning line direction. In this case, the forward noise voltage is applied only to the organic EL elements 400 and 100 existing on the selected scanning line, and the reverse bias voltage is applied to the organic EL elements 400 and 100 existing on the other non-selected scanning lines. Is applied. This enables display without crosstalk.

[0089] Further, by applying a reverse bias voltage, a defective light emitting portion is repaired, so-called auto You can repair yourself. Since self-repair is a known technique, the description thereof is omitted.

As shown in FIG. 5 and FIG. 6, the organic EL elements 400 and 100 according to the conventional and the embodiments of the present invention are both “lower electrode Z hole injection layer Z electron blocking layer Z light emission. It has an element structure of “layer Z electron injection transport layer Z upper electrode” (reference numeral omitted). The difference in configuration between the organic EL element 400 having the conventional configuration and the organic EL element 100 according to the present embodiment is the thickness of the buffer layer (electronic block layer) 103.

[0091] As described above, in the conventional organic EL element 400, the doped layer (hole injection layer) 102 is thicker than the buffer layer (electron block layer) 103 having the electron blocking function. On the other hand, in the organic EL device 100 according to the embodiment of the present invention, the buffer layer (electron block layer) 103 is much thicker than the doped layer (hole injection layer) 102.

[0092] This prevents the electron force light-emitting layer 104 injected from the cathode 101b side into the light-emitting layer 104 from moving to the buffer layer 103 side. Carrier recombination within layer 104 can be effectively performed.

[0093] Here, normally, when the thickness of the high-resistivity buffer layer (electronic block layer) 103 is increased, there is a concern that the drive voltage increases as the resistance increases. Then, it is found that the carrier accumulation at the injection interface disappears, and the increase in voltage is small even when the buffer layer (electron block layer) 103 is made thicker.

That is, according to the organic EL elements 100, 200, and 300 according to the embodiment of the present invention, recombination of carriers in the light emitting layers 104 and 204 is effectively performed while suppressing an increase in driving voltage. Therefore, the organic EL elements 100, 200, and 300 can emit light efficiently.

[0095] In the organic EL devices 100 and 400 shown in Figs. 5 and 6, the lower electrode (anode) 101a is formed of ITO, and the doped layer (hole injection layer) 102 is 4F-TC on α-NPD. It is formed by adding NQ as an electron accepting substance (acceptor), and the buffer layer (electron blocking layer) 103 is formed by α-NPD so that the film thickness becomes X nm. Further, a buffer layer such as CuPc can be used between ITO and the doped layer (hole injection layer) 102. In this case, it is considered that tunnel injection occurs at the interface between the buffer layer (electron block layer) 103 and the doped layer (hole injection layer) 102. [0096] (Difference in behavior (Part 2))

Next, the difference (No. 2) between the organic EL element of the embodiment of the present invention and the conventional organic EL element will be described with reference to FIGS. Here, the organic EL element according to the third embodiment shown in FIG. 3 will be described as the organic EL element according to the embodiment of the present invention.

[0097] (Conventional organic EL device structure)

FIG. 7 is an explanatory diagram showing carrier behavior when a reverse bias voltage is applied to a conventional organic EL element. Hereinafter, a conventional organic EL element will be described with reference to FIG. In the conventional organic EL element 700 shown in FIG. 7, the same parts as those of the organic EL elements 100, 200, and 300 in the above-described embodiments are denoted by the same reference numerals, and the description thereof is omitted.

A conventional organic EL element 700 includes a substrate 106, electrode pairs 201 a and 201 b, a hole injection / transport layer 301, a light emitting layer 204, a hole blocking layer 302, and an electron injection layer 303. A conventional organic EL device 700 includes a substrate 106, a lower electrode (anode) 201a, a hole injection transport layer 301, a light emitting layer 204, a hole blocking layer 302, an electron injection layer 303, and an upper electrode (cathode) 201b. In this order, each structure is sequentially stacked. In the conventional organic EL element 700, the thickness of the electron injection layer (dope layer) 303 is larger than the thickness of the hole blocking layer (buffer layer) 302.

FIG. 8 is an explanatory view showing the behavior of carriers when a reverse bias is applied to the organic EL element 300 according to the embodiment of the present invention. Hereinafter, differences in behavior when a reverse bias voltage is applied to the conventional organic EL element 700 and the organic EL element 300 according to the embodiment of the present invention will be described with reference to FIG. 7 and FIG. .

[0100] FIGS. 7 and 8 schematically show in which layer a large amount of carriers are accumulated when a reverse noise voltage is applied to the conventional organic EL element 700 and the organic EL element 300. Yes. As can be seen from FIG. 7 and FIG. 8, the organic EL elements 700 and 300 of the configuration of the conventional and the present embodiment are both “lower electrode Z hole injection transport layer Z light emitting layer Z hole block layer”. It has an element structure of “Z electron injection layer Z upper electrode” (reference numeral omitted). The difference in configuration between the organic EL element 700 having the conventional configuration and the organic EL element 300 according to the present embodiment is the thickness of the hole blocking layer 302. [0101] The organic EL element 700 having a conventional configuration has a thickness relationship between the doped electron injection layer 303 and the hole blocking layer 302 that are thicker than the doped electron injection layer 303. 303 is thicker than the hole blocking layer 302. In contrast, in the organic EL element 300 of the present embodiment, the hole blocking layer 302 is much thicker than the electron injection layer 303.

[0102] Thereby, electrons injected from the upper electrode 201b are efficiently injected into the light emitting layer 204 side by the electron injection layer 303, and holes injected from the lower electrode (anode) 201a are transmitted through the light emitting layer 204. As a result, it is possible to effectively recombine carriers in the light emitting layer 204 as described above.

That is, according to the organic EL elements 100, 200, and 300 of the embodiment of the present invention, recombination of carriers in the light emitting layers 104 and 204 is effectively performed while suppressing an increase in driving voltage. Therefore, the organic EL elements 100, 200, and 300 can emit light efficiently.

[Fourth embodiment]

FIG. 9 is a cross-sectional view showing an example of a self-luminous panel in the fourth embodiment. Next, a self-luminous panel according to a fourth embodiment will be described with reference to FIG. A self-luminous panel 900 according to the fourth embodiment has a configuration in which a plurality of organic EL elements 100 shown in FIG.

[0105] The self-light-emitting panel 900 may be a passive-drive self-light-emitting panel that displays display data because the data lines formed by the plurality of anodes 101a and the scanning lines formed by the plurality of cathodes 101b are orthogonal to each other. An active drive type self-luminous panel having a configuration in which 101a and a drive transistor are connected may be used.

[0106] In the self-luminous panel 900, the voltage applied to the anode 101a of each organic EL element 100 is controlled for each organic EL element 100, thereby controlling the emission Z non-emission in units of 100 of the organic EL elements. Can do. Since the technique for individually controlling the light emission Z non-light emission of each organic EL element 100 arranged in a matrix is a known technique, the description thereof is omitted. In FIG. 9, reference numeral 901 denotes an insulating member that insulates the anodes 101a.

FIG. 10 is a cross-sectional view showing an example of a self-luminous panel including the conventional organic EL element 400. The following is a description of a self-luminous panel 1000 having a conventional organic EL element 400 and a fourth embodiment. Differences from the self-luminous panel 900 in the state will be described. In the self-luminous panel 1000 having the conventional organic EL element 400, for example, when the organic EL element A emits light and the organic EL element B is extinguished, an anode corresponding to the organic EL element A (hereinafter, positive electrode is used as necessary). A) 101a and V between anode 101a and cathode 101b (V> 0, where V is the threshold voltage)

A A A

Apply a voltage that generates a larger potential difference ヽ).

[0108] The anode corresponding to the organic EL element B (hereinafter referred to as anode B if necessary) 101a has the same potential as the negative electrode 101b (ie, V = 0) or a forward bias voltage equal to or lower than the threshold voltage. ,is there

B

Alternatively, a reverse bias voltage of V (V <0) is applied to the cathode 101b. At this time, the anode

B B

The potential difference between A and anode B is V -V.

A B

[0109] Originally, only the organic EL element A emits light by controlling the voltage applied to the anode A and the anode B in this way. However, when doped layer 102 is conductive, anode A and anode B are electrically connected through doped layer 102, and the resistance between anode A and anode B and the lateral direction according to V-V Leakage current occurs, and organic EL element A and organic EL element

A B

The light is emitted between the child B and the organic EL element B.

FIG. 11 is a plan view showing the arrangement of the organic EL elements 100 or 400 in the self-luminous panel 900 or 1000. FIG. The leakage current that leaks from the adjacent organic EL element A to the organic EL element B will be described with reference to FIG. 11 and FIG. 10 described above. First, when the resistance between the anode A and the anode B is R [Ω], the resistance R is expressed by the following equation (1).

AB AB

[0111] [Equation 1]

R _AB? [Ω]… (

t x l

However,

P: Resistivity of doped layer [Q.cm]

d: Distance between adjacent organic EL elements [cm] t: Thickness of doped layer [cm]

I: Length of organic EL element [cm] [0112] The current flowing from anode A to anode B (leakage current) I [A] is calculated using the following equation (1):

AB

It is expressed by equation (2).

[0113] [Equation 2]

X_AB

ΑΒ

P d

: VAB '1

d P

= ^ (σ) [A] ~ (2)

a

However,

V _AB: Potential difference between anodes A and B [V]

B: Dove layer conductivity [Sm]

[0114] From equation (2), the amount of current leaking from the organic EL element A to the adjacent organic EL element B is proportional to the film thickness t of the doped layer 102 and the conductivity σ of the doped layer 102. I understand. The conductivity σ is expressed as the reciprocal of the resistivity ρ. In other words, from equation (2), in order to suppress the occurrence of leakage current to the adjacent organic EL element Α, the conductivity in the cadmium doped layer 102 is reduced. It is necessary to take measures to keep the rate σ low.

[0115] When the leakage current I [Α] is expressed by the above equation (2), the brightness in the organic EL device Β

ΑΒ

The degree L is expressed by the following equation (3).

Β

[0116] [Equation 3]

4 VAB t

= 10 "x a

P d-w

=

A (t .bi) cd / m

However,

a: Current luminance efficiency of organic EL elements [ _G d / A]

S _B: Area of organic EL element B [cm ² ]

w: Width of organic EL element [cm]

A = 10 ⁴ x (constant)

[0117] In the equation (3), 10 ⁴ is the area conversion coefficient of the cm unit system force to the m unit system. In the equation (3), the relationship between the conductivity σ and the resistivity p in the doped layer 102 is lZ / o [Ω ′ cm] = σ [S Zcm]. S is a unit of conductance expressed as the reciprocal of electrical resistance [Ω].

[0118] Also from equation (3), in order to keep the luminance L in the organic EL element Β low, the film of the doped layer 102

Β

It can be seen that it is necessary to take measures to reduce the electrical conductivity σ in the force-doped layer 102 that reduces the thickness t. F4—Changes in conductivity σ when TCNQ is doped into VOPc are described, for example, in FIG. 1 (a) in Applied Physics Letters, Volume 73, No. 22, 3202 (1998), M. Pfeiffer et al. .

[0119] By the way, for example, to obtain a p-type organic semiconductor layer, providing the doped layer 102 doped with an electron-accepting substance in the organic EL element 100 agrees with increasing σ in the equation (3). It is. In other words, in the self-luminous panel 1000 including the conventional organic EL element 400 in which the thickness of the doped layer 102 is larger than that of the nofer layer 103, It can be said that the luminance of EL element B tends to increase.

[0120] Also, by doping the electron-accepting substance to improve the hole injection rate from the anode 101a, the electron blocking performance in the doped layer 102 is lowered, and the luminance in the organic EL element A is lowered. Resulting in.

[0121] In contrast, in the organic EL device 100 of the first embodiment, the doped layer 102 doped with the electron-accepting substance and the low electron transport property and the hole transport property, but the carrier density is low. A low buffer layer 103 and a low resistivity (for example, about IX 10 ⁵ Ω 'cm) and a higher resistivity than the thickness of the doped layer 102 ^ (1 Χ 1Ο ¹⁰ Ω · cm or more) Since the film thickness of the layer 103 is larger, the inflow of electrons from the light emitting layer 104 to the doped layer 102 is prevented to improve the hole injection efficiency to the light emitting layer 104, and the lateral direction to the adjacent pixels The generation of leakage current can be prevented.

[0122] This makes it possible to achieve both reduction in drive voltage and prevention of reduction in luminance in the organic EL element A. In addition, by preventing the occurrence of leakage current from the organic EL element A and preventing pixel bleeding in the organic EL element A, it is possible to avoid display defects in the self-luminous panel 1000 and perform a clear display. Can do.

[0123] The organic EL device 100 of the first embodiment can be manufactured using various known techniques. For example, the doped layer 102, the nofer layer 103, or the light emitting layer 104 can be formed by using a resistance heating vacuum film forming method. That is, the organic EL element 100 of the present embodiment can be manufactured without any particular change compared to the conventional method for manufacturing an organic EL element. Since a conventional method for manufacturing an organic EL element is a known technique, a description thereof will be omitted.

[0124] (Relationship between film thickness of doped layer and buffer layer and driving voltage)

FIG. 12 is a graph showing the relationship between the film thickness of the doped layer and the buffer layer and the driving voltage. Next, the relationship between the film thickness of the doped layer and the buffer layer and the drive voltage will be described. Here, the organic EL element 100 described in the first embodiment will be described as an example.

[0125] Like the organic EL element 100 according to the first embodiment described above, the first effect obtained by thickening the nofer layer 103 is between the electrodes (between the anode 101a and the cathode 101b). Short Is to prevent. Here, FIG. 13 and FIG. 14 are explanatory views (No. 1) and (No. 2) for explaining the effect of thickening the notfer layer 103. FIG.

[0126] In the organic EL device 100 in which the buffer layer 103 is formed by vacuum evaporation, the foreign matter 1301 exists on the substrate 106 as shown in FIG. 13, or the rate of change is extremely uneven as shown in FIG. When the portion 1401 is present, a thin portion of the deposited organic layer 103 is generated. In such a thin portion, the thickness resistance of the notfer layer 103 is lowered. In this case, when a voltage is applied between the electrodes (between 101a and 101b), the portion where the breakdown voltage is locally reduced breaks down and a short circuit occurs.

[0127] When the noffer layer 103 is made sufficiently thick, the pressure resistance of the weakest part is improved, and the short-circuit failure rate can be reduced. Since a general organic material has a high resistivity, when a thick film is formed as it is, a driving voltage increases. Patent Document 3 described above describes that the conductive doped layer is thickened to prevent voltage increase due to thickening of the doped layer.

[0128] However, increasing the thickness of the conductive film leads to a decrease in lateral insulation as described above. As a result of the experiment, the inventor has found that the drive voltage does not change even when the thickness of the low-conductivity hole transport layer is increased by inserting a highly conductive doped layer of about 10 nm.

[0129] [Table 1]

table 1

Table 1 shows driving voltages of the self-luminous panel 900 using the organic EL element 100 when the film thicknesses of the doped layer 102 and the buffer layer 103 are divided into a plurality of stages. As shown in Table 1, unless the doped layer 102 is present (X = Onm), if the doped layer 102 has a constant thickness, the thickness of the notched layer 103 is divided into multiple stages. However, there is no significant change in the driving voltage. From Table 1, it can also be seen that in the absence of the doped layer 102 (X = Onm), a change in the thickness of the buffer layer 103 causes a change in drive voltage.

[0131] Thus, according to the self-luminous panel 900 using the organic EL element 100 of the first embodiment, the drive voltage is not increased while the conductivity is kept low, and the short circuit between the electrodes is generated. The rate can be reduced.

[0132] The second effect of thickening the noffer layer 103 is that optical interference can be used effectively. In general, the total thickness of the organic EL element 100 is about a fraction of the wavelength of visible light. Light emission from the light emitting layer 104 in the organic EL element 100 is caused by interference between reflected light and radiated light from the interfaces of the anode 101a and the cathode 101b formed of a conductive oxide or metal, the substrate 106, and each of the stacked layers. As a result, the luminous efficiency changes greatly.

[0133] In an element structure in which one electrode constituting the electrode pair 101 is transparent or translucent and the other electrode has high reflectivity, the reflectance of the reflecting surface holding the light emitting layer 104 is unbalanced. Works as a weak micro-optical resonator. Strictly speaking, if the interference analysis of a multilayer stack is carried out when the light source is inherent in the stack, then.

[0134] When a portion where both electrodes have a high reflectivity or a high reflection factor is explicitly provided in the element, a strong (high Q) optical resonator is formed, and the light emitting point in the resonator is reduced. Regardless of the position, a specific wavelength can be enhanced. The resonance condition in this case is roughly expressed by the following equation (4).

[0135] [Equation 4]

2ηά = λ (νη-Φ / 2π), m is a positive integer ■■■ (4)

However,

n: Refractive index of the layer through which light passes

d: Total thickness of the layer through which light passes

Φ: Total phase change at the reflecting surface where light is reflected

[0136] The optical interference can be adjusted by adjusting the film thickness of a conductive layer such as a transparent electrode. The influence on the driving voltage is small. When the entire surface of the display panel emits light with the same color, the optical interference can be optimized by the thickness of the transparent electrode. On the other hand, when multiple colors exist on the same display panel, the film thickness that optimizes optical interference differs for each emission color. Changing the film thickness of the transparent electrode for each part on the same substrate is not desirable because it increases the number of processes. Therefore, it is necessary to perform optical adjustment with the film thickness of the element portion formed for each emission color.

[0137] From equation (4), in order to achieve optical optimization, when increasing the film thickness of a general organic EL element, the resistance in the organic EL element increases as the film thickness increases. It can be seen that increases. As the resistance increases, the drive voltage increases and the power emission efficiency of the organic EL element decreases. Thus, it is difficult for conventional organic EL devices to achieve both an increase in film thickness for optical optimization and a decrease in drive voltage.

Here, FIG. 15 is a schematic diagram showing the structures of three types of organic EL elements having different configurations. In FIG. 15, (a) and (b) exemplify the structure of a conventional organic EL element, and (c) shows the structure of the organic EL element 100 in the first embodiment. The organic EL element 1510 shown in (a) is different from the organic EL element 100 in that it does not have the doped layer 102. The organic EL element 1520 shown in (b) is different from the organic EL element 100 in that the organic EL element 1520 has a nofer layer 103.

[0139] [Table 2]

Table 2

(Horse-ku dynamic current off .sma / cm ²⁾ Table 2, the driving voltage at a current density of each layer of film thickness and a constant of each organic EL element 1510, 1520, 100 shown in FIG. 15 shows a light emission amount . As shown in Table 2, in the organic EL element 100 according to the first embodiment, the buffer layer 103 has a film thickness in the range of 5 to 100 nm. It can be seen that there is no significant change in the drive voltage even when the change is made. That is, according to the organic EL element 100 of the first embodiment, the drive voltage is not increased even when the thickness of the buffer layer 103 is adjusted in order to improve the light emission efficiency. Furthermore, the emission spectrum can be adjusted by adjusting the interference spectrum.

As described above, the organic EL device 100 according to the first embodiment includes the doped layer 102 doped with the electron-accepting material and the buffer layer 103 not doped with the electron-accepting material. Therefore, the doped layer 102 is doped with an electron-accepting substance to reduce the driving voltage, and by adjusting the film thickness of the buffer layer 103, the luminous efficiency can be improved. By making the film 103 thick, it is possible to obtain a display with little short-circuit failure between electrodes while maintaining the driving voltage.

[0142] Thus, unlike the self-luminous panel 1000 including the conventional organic EL element 400, a display defect such as an edge of a display image becoming unclear due to the occurrence of a leakage current does not occur.

[0143] Here, the effects of the first organic EL element 100 have been described by way of example, but the present invention is not limited to this. Even if the electron blocking layer 203 in the organic EL device 200 of the second embodiment or the hole blocking layer 302 in the organic EL device 300 of the third embodiment is thickened, the same effect is obtained. Obtainable.

[0144] (Diode characteristics of organic EL elements)

FIG. 16 is a graph showing diode characteristics when a forward bias voltage is applied to an organic EL element and then a reverse bias voltage is applied. Next, the diode characteristics when a forward bias voltage is applied to the organic EL element and then a reverse bias voltage is applied will be described with reference to FIG. Here, the organic EL element 200 of the second embodiment and the conventional organic EL element 700 shown in FIG. 7 will be described as an example.

Here, the light emitting layer 204 in the organic EL device 200 of the second embodiment and the conventional organic EL device 700 is formed of Alq, the electron injection transport layer 205 is formed of LiF, and the upper electrode ( The case where the cathode 201b is formed of A1 will be described. For each of these organic EL devices 200 and 700, a forward bias voltage was applied and then a reverse bias voltage was applied, and the diode characteristics at that time were examined. Figure 16 shows that Results are shown.

As can be seen from FIG. 16, in the range where the film thickness X of the electron block layer 203 is X = 5 to 50 nm, the reverse bias withstand voltage is very bad, which is about IV. In contrast, when the film thickness is increased to lOOnm as in the case of the organic EL element 200 of the second embodiment, the reverse bias withstand voltage is improved and recovered to about −5V.

In the second embodiment, an organic EL device having a structure including a doped hole injection layer 202 and an electron blocking layer 203 between a lower electrode (anode) 201a and a light emitting layer 204 Forces shown for leakage current suppression effect for 200 In addition, an organic EL device with a structure including an electron injection layer and a hole blocking layer doped between 20 lb of the upper electrode (cathode) and the light emitting layer 204 (see FIG. 18) The same effect can be expected for the leakage current suppression effect for

As described above, according to the second embodiment, by providing the doped hole injection layer 202 between the lower electrode (anode) 201a and the light emitting layer 204, the driving voltage is reduced. Can be achieved. Further, according to the second embodiment, the electron blocking layer (buffer layer) 203 is provided thickly between the doped hole injection layer 202 and the light emitting layer 204, so that the drive voltage does not increase. A distance between the doped hole injection layer 202 and the light emitting layer 204 can be secured.

As a result, the drive voltage is lowered, and the reverse bias withstand voltage due to the provision of the electron blocking layer 203 thicker than the hole injection layer 202 between the lower electrode (anode) 201a and the light emitting layer 204 is reduced. The decrease can be suppressed. That is, since it is possible to prevent the occurrence of a leakage current when a reverse bias voltage is applied, it is possible to reduce the power consumption when driving the organic EL element 200 and the self-luminous panel using the organic EL element 200.

[0150] The organic EL element 200 of the second embodiment has been described as an example, but the same applies to the organic EL element 100 of the first embodiment. According to the first embodiment, the drive voltage can be lowered by providing the doped layer 102 between the anode 1 Ola and the light emitting layer 104. Further, according to the first embodiment, by providing the buffer layer 103 thick between the doped layer 102 and the light emitting layer 104, the doped layer 102 and the light emitting layer 104 can be connected without increasing the driving voltage. A distance can be secured. [0151] Similarly, according to the third embodiment, by providing the doped electron injection layer 303 between the upper electrode (cathode) 201b and the light emitting layer 204, the driving voltage is lowered and the drain voltage is reduced. The distance between the doped electron injection layer 303 and the light emitting layer 204 is secured by the hole blocking layer 302, so that the doped electron injection layer 303 is formed between the upper electrode (cathode) 201 b and the light emitting layer 204. It is possible to suppress a decrease in the reverse noise breakdown voltage due to the provision.

[0152] As a result, the drive voltage can be lowered and the occurrence of leakage current when a reverse bias voltage is applied can be prevented, so that self-light emission using the organic EL element 300 and the organic EL element 300 is possible. It is possible to reduce power consumption when driving the panel.

[0153] Also, according to the first embodiment, the buffer layer 103 has a charge blocking function to block the charge moving from the light emitting layer 104 to the doped layer 102 side, so that the doped layer 102 is provided. It is possible to suppress a decrease in electronic block performance due to an increase in conductivity, and to prevent carriers injected from the cathode 101b or the anode 101a from passing through the light emitting layer 104 and recombining in a region other than the light emitting layer 104. As a result, the generation of leakage current that does not contribute to light emission can be prevented, and current efficiency can be improved.

Similarly, according to the second or third embodiment, the electron blocking layer 203 and the hole blocking layer 302 have a high carrier density layer force and a carrier that blocks the movement of the opposite carrier to the light emitting layer 204. In order to provide blocking performance, the provision of the doped hole injection layer 202 and the doped electron injection layer 303 suppresses the deterioration of the electron blocking performance due to the increase in conductivity, and the upper electrode (cathode) 201b or lower It is possible to prevent the carrier injected from the electrode (anode) 201 a from passing through the light emitting layer 204 and recombining in a region other than the light emitting layer 204. As a result, it is possible to prevent leakage current that does not contribute to light emission and improve current efficiency.

[0155] According to the second or third embodiment, an electrode is provided between at least one of the light emitting layer 204 and the upper electrode (cathode) 201b and between the light emitting layer 204 and the lower electrode (anode) 201a. In order to provide a blocking layer that blocks the movement of charge carriers that move according to the voltage applied to the pair 201 to the light-emitting layer 204, the charge was injected from the upper electrode (cathode) 201b or the lower electrode (anode) 201a. Carriers can be prevented from passing through the light emitting layer 204 and recombining in a region other than the light emitting layer 204. This prevents the occurrence of leakage current that does not contribute to light emission, The current efficiency can be improved.

[0156] Also, according to the first embodiment, in the organic EL element 100, the film thicknesses of all the layers are radiated in the opposing direction of the electrode pair 101 out of the light emitted from the light emitting layer 104. Luminous efficiency can be further improved because the optical interference is adjusted so that the light that is multiply reflected at the laminated interface is intensified.

[0157] As described above, by preventing the occurrence of leakage current without contributing to light emission, it is possible to reliably repair a defective light emission location by applying a strong voltage to the organic EL element. Thereby, it is possible to improve the yield when manufacturing the self-luminous panel.

[0158] Further, the power to be omitted from the illustration. The organic EL elements 200 and 300 are self-luminous panels (see FIG. 9) in which a plurality of such organic EL elements 200 and 300 are arranged on the substrate 106. A self-luminous panel can be obtained. As for the structure and manufacturing method of the self-luminous panel, conventional techniques can be used except that the organic EL elements 200 and 300 of the second or third embodiment are used. Is omitted.

[0159] (Fifth embodiment)

FIG. 17 is a cross-sectional view illustrating the structure of an organic EL element according to the fifth embodiment. The organic EL element in the fifth embodiment will be described below with reference to FIG. An organic EL element 1700 according to the fifth embodiment includes a hole injection layer 1701, a hole transport layer 1702, and a buffer layer 1703 between the anode 101a and the light emitting layer 104 in the organic EL element 100 shown in FIG. It has a 3HTL structure.

According to the organic EL element 1700, the doped layer 102 in FIG. 1 is realized by the hole injection layer 1701 and the hole transport layer 1702. According to the organic EL element 1700, the buffer layer 103 in FIG.

[0161] In the fifth embodiment, the force is such that the anode 101a is provided on the substrate 106, and the respective layers are sequentially stacked on the anode 101a. For example, a cathode may be provided on the substrate 106, and each layer may be sequentially stacked on the cathode. In this case, the lower electrode is realized by the cathode and the upper electrode is realized by the anode.

In this case, the layers stacked on the cathode are stacked in the order opposite to the stacking order of the layers shown in FIG. Also, the explanation so far is about hole injection from the anode, hole transport from the anode. The same is true for electron injection from the cathode, electron transport, and hole blocking.

[0163] The substrate 106 used in the fifth embodiment may be a substrate in which the anode 101a is preliminarily formed, a substrate on which an anode is formed after an alkali barrier film is formed, an active driving TFT, A substrate and a substrate provided with a color filter can be used as appropriate. The substrate 106 need not be transparent.

[0164] Regarding the organic EL element 1700 of the fifth embodiment, after forming the organic EL element 1700 on the substrate 106, the organic EL element 1700 is sealed to prevent deterioration of the organic EL element 1700. To do. As the form of sealing, there are various forms such as a conventionally known sealing form, solid sealing form, and film sealing form.

[0165] Sealing-type sealing is a sealing method in which the organic EL element 1700 is sealed by bonding the sealing substrate and the substrate 106 using a sealing adhesive. For hermetic sealing, glass substrates such as soda glass, lead glass, and hard glass, plastic substrates such as polyethylene, polypropylene, polyethylene terephthalate, and polymethyl methacrylate, metal substrates such as aluminum and stainless steel, etc. A sealing substrate that has strength such as a material is used.

[0166] Solid sealing refers to "resin layer Z barrier layer", "resin layer Z barrier layer Z resin layer", "resin layer Z barrier layer Z resin layer Z barrier layer" In this sealing method, the organic EL element 1700 is sealed by sequentially laminating a resin layer and a barrier layer. Here, the NOR layer is a layer that prevents permeation of moisture and the like.

[0167] The resin layer is formed of a resin material such as a photo-polymerizable resin, a photo-thion polymerizable resin, a photo-curable resin, a thermo-plastic resin, or a thermosetting resin. The radical photopolymerizable resin is a resin mainly composed of various acrylates such as polyester acrylate, polyether acrylate, epoxy acrylate, and polyurethane acrylate. Light power thione-polymerized resin is a resin mainly composed of resin such as epoxy and butyl ether. The photo-curing resin is a resin such as thiol-added resin.

[0168] Thermoplastic resins and thermosetting resins are polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate, polyurethane, acrylic resin, polyacryl-tolyl. , Polybulasseta Resins such as rubber, polyamide, polyimide, diacryl phthalate resin, cellulosic plastic, poly (vinyl acetate), polyvinyl chloride, polysalt vinylidene, and two or more of these resins It is a resin such as a copolymer. The barrier layer is formed of a ceramic material such as glass or a metal material such as stainless steel or aluminum.

[0169] Film sealing is a sealing method in which the organic EL element 1700 is sealed by sequentially laminating a planarization layer and a barrier layer formed of a filmable material. In film sealing, the planarizing layer is composed of an inorganic material such as lithium fluoride, a filmable resin material such as an acrylate-containing monomer or oligomer accompanying a polymerization reaction, or the like. The barrier layer is made of a metal such as aluminum or a material such as an inorganic material such as silicon nitride, silicon oxide, or silicon nitride oxide. The barrier layer is a layer that prevents penetration of moisture and the like.

[0170] (Sixth embodiment)

FIG. 18 is an explanatory diagram showing an organic EL element according to the sixth embodiment. Next, an organic EL element according to a sixth embodiment will be described with reference to FIG. An organic EL device 1800 shown in FIG. 18 includes an electron block layer (buffer layer) 203 and a hole injection layer 202 on the lower electrode (anode) 201a side of the light emitting layer 204, and is more than the light emitting layer 204. A hole blocking layer (buffer layer) 302 and an electron injection layer 303 are provided on the upper electrode (cathode) 201b side.

[0171] By adopting such an organic EL element 1800, the effects exhibited by the organic EL elements 200 and 300 shown in FIGS. 2 and 3 described above can be realized by a single organic EL element 1800. it can.

[0172] (Seventh embodiment)

FIG. 19 is a longitudinal side view showing the multi-photon device according to the seventh embodiment. The seventh embodiment will be described below with reference to FIG. 2, 3, and 18, the organic EL elements 200, 300, and 1800 having a single light emitting layer 204 have been described. However, the present invention is not limited to this, and as shown in FIG. Equipped with an organic EL device (hereinafter referred to as “multiphoton device”) 1900!

[0173] The multiphoton element 1900 is an organic EL element having a structure including a plurality of light-emitting layers 204 in a single element. In principle, the multiphoton element 1900 is composed of a plurality of organic EL elements 1910 and 1920 having a single light-emitting layer 204, and the organic EL elements 1910 and 1920. The layers are stacked along the stacking direction of the layers and connected in series.

In multiphoton element 1900, intermediate electrode 1901 including a charge generation layer (see FIG. 21) is interposed between stacked organic EL elements 1910 and 1920. Thus, when a voltage is applied to the multiphoton element 1900, holes can be injected from the intermediate electrode 1901 to the organic EL element 1910 and electrons can be injected to the organic EL element 1920. In other words, the multiphoton device 1900 can improve the emission quantum efficiency by the amount of carriers generated inside the device.

[0175] The intermediate electrode 1901 is configured as follows. The lower electrode (anode) 201a is the anode. In the case of a general organic EL element, the intermediate electrode 1901 is thinly provided with a normal cathode on the organic EL element 1920 side, and charge is generated on the organic EL element 1910 side on this thin cathode. Stack layers. Furthermore, the hole transport layer (hole injection layer (dope layer) 202 and electron block layer (buffer layer) 203) of the organic EL element 1910 is laminated, and then the light emitting layer 204 and the like are laminated to form a multiphoton element. . The charge generation layer is usually used as a film made of an electron-accepting material (acceptor) or doped with an electron-accepting material (acceptor) in a hole transporting material.

[0176] (Operation of charge generation layer)

FIG. 20 is a schematic diagram showing the operation of a conventional charge generation layer. FIG. 21 is a schematic diagram showing the operation of the charge generation layer in the embodiment of the present invention. The operation of the conventional charge generation layer and the charge generation layer according to the embodiment of the present invention will be described below with reference to FIGS. 20 and 21. FIG.

As shown in FIGS. 20 and 21, the intermediate electrode 1901 includes a charge generation layer 2001 and a cathode 2002. As shown in FIG. 20, the role of the charge generation layer 2001 is described as generating positive and negative charges in the charge generation layer 2001 and distributing them to the organic EL element 1910 and the organic EL element 1920.

However, according to the results of experiments and discussions, the role of the charge generation layer 2001 is from the upper surface of the cathode 2002 disposed in the organic EL element 1920 due to the distortion of the energy band due to the high carrier density that is not the generation of charges. It can be said that the hole injection by tunnel injection is effectively generated. FIG. 22 is a schematic diagram showing the relationship between the energy levels of intermediate electrode 1901 in the embodiment of the present invention. Hereinafter, the relationship between the energy levels of the intermediate electrode 1901 in the embodiment of the present invention will be described with reference to FIG. In FIG. 22, a multiphoton intermediate electrode portion will be described as an example of intermediate electrode 1901 in the embodiment of the present invention.

[0180] In FIG. 22, the energy band at the junction interface between the charge generation layer 2001 having a high hole density and the cathode 2002 is locally distorted, and the holes are not normally injected due to an energy barrier. It is shown that it is effectively injected from the cathode 2002 into the charge generation layer 2001. According to this model, it is the negative electrode 2002 of the organic EL element 1920 that truly generates a charge. For this reason, the charge generation layer 2001 will be hereinafter referred to as a high carrier density layer as appropriate.

[0181] As the charge generation layer (high carrier density layer) 2001, for example, ITO which can be generally used as an anode of an organic EL element can be used. In this case, the cathode 2002 of the organic EL element 1920 and the ITO are in ohmic contact with each other, and two pairs of anode and cathode are connected in series.

[0182] By the way, ITO has high conductivity and is defined as a light-emitting area, and the part also emits light, so it cannot be used for a normal light-emitting panel. However, as described above, the p-type or n-type charge generation layer (high carrier density layer) 2001 and the charge generation layer (high carrier density layer) are formed on the intermediate electrode 1901 portion of the multiphoton element 1900. An electrode capable of injecting carriers corresponding to 2001 is required.

[0183] Charge generation layer (high carrier density layer) When the conductivity of 2001 is high, the leakage current when the reverse bias voltage is applied as described above, or effective carrier confinement when the forward bias voltage is applied. In order to improve the luminous efficiency due to the above, a carrier block layer is preferably provided as appropriate.

FIG. 23 is a longitudinal side view showing the multi-photon device according to the embodiment of the present invention.

A multiphoton element according to an embodiment of the present invention will be described below with reference to FIG. Note that the same components as those described in the above-described embodiments are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 23, the multiphoton element 2300 according to the embodiment of the present invention includes a lower Between the electrode (anode) 201a and the light emitting layer 204 closest to the lower electrode, a hole injection layer (dope layer) 202 which is a high carrier density layer and an electron block layer (buffer layer) which is a low carrier density layer ) 203.

[0186] Similarly, the multiphoton element 2300 includes an electron injection layer (dope layer) 303, which is a high carrier density layer, between the upper electrode (cathode) 201b and the light emitting layer 204 closest to the upper electrode (cathode) 20 lb. And a hole blocking layer (buffer layer) 302 which is a low carrier density layer.

[0187] As described above, when a plurality of light-emitting layers are sandwiched between the electron block layer 203 and the hole block layer 302, when a forward voltage is applied, carriers penetrate to the counter electrode or light emission occurs. Recombination in layers other than layer 204 can be prevented. In addition, when a reverse bias voltage is applied, the interval between the charges that are blocked and accumulated at the interface can be widened.

Thus, a highly durable multiphoton element 2300 can be obtained. In particular, in the multiphoton element 2300, the accumulated charge distance can be increased by increasing the thickness of the electron blocking layer 203 and the hole blocking layer 302.

[0189] Furthermore, by providing the electron blocking layer 203 and the hole blocking layer 302 inside the two light emitting layers 204, carrier confinement in the light emitting layer 204 functions effectively, and the light emission quantum efficiency is improved. be able to.

FIG. 24 is a vertical side view showing a multi-photon device according to another embodiment of the present invention. A multiphoton element according to another embodiment of the present invention will be described below with reference to FIG. A multi-photon device 2400 according to another embodiment of the present invention has a configuration in which three organic EL devices each including a single light emitting layer 204 are stacked along the voltage application direction. The multiphoton element 2400 of the present embodiment also has basically the same configuration as the multiphoton element 2300 in which two organic EL elements each having a single light-emitting layer 204 are stacked along the voltage application direction. ing.

The multiphoton element 2400 of this embodiment includes a hole injection layer (dope layer) 202 that is a high carrier density layer between a lower electrode (anode) 201a and a light emitting layer 204. In the multiphoton element 2400, an electron injection layer (dope layer) 303 which is a high carrier density layer and a hole blocking layer (buffer) which is a low carrier density layer are provided between the light emitting layer 204 and the light emitting layer 204. Layer) 302, a cathode 2002, a charge generation layer (high carrier density layer) 2001, and an electron block layer (buffer layer) 203 are provided.

[0192] As described above, this organic EL device has a plurality of light emitting layers 204 along the direction of the electrode pair 201! In 2300 and 2400, a layer for blocking the corresponding carrier is provided between the lower electrode (anode) 201a and the upper electrode (cathode) 201b and the light emitting layer 204 closest to the electrodes 201a and 201b. By providing the high carrier density layer 2001, the electron injection layer (dope layer) 303, and the hole injection layer (dope layer) 202, the decrease in carrier block performance, which is a concern, is suppressed. It is possible to improve the leakage current characteristics when the bias voltage is applied.

Example

[0193] Next, the organic EL device in the examples will be described. The structure of the organic EL element in the example is the same as that of the organic EL element 100 described in the first embodiment. For this reason, the same parts as those of the organic EL element 100 in the first embodiment are denoted by the same reference numerals, and illustration and description thereof are omitted. Here, the material for forming each layer will be specifically described.

[0194] The electrode (anode 101a) is provided on a transparent and insulating substrate such as glass. The electrode (anode 101a) may be a conductive oxide such as tin oxide, indium oxide, or indium tin oxide (ITO), or a metal such as gold, silver, or chromium, or an inorganic conductive material such as copper iodide or copper sulfide. A sex substance can be used. The material for forming the electrode (anode 101a) is not limited to these.

[0195] As the electron-accepting substance doped in the doped layer 102, Lewis acid compound, metal oxide, metal halide, alkali metal, alkaline earth metal, rare earth metal, alkali metal compound, alkali Examples include earth metal compounds and rare earth compounds. Lewis acid compounds include ferric chloride, ferric bromide, ferric iodide, aluminum chloride, aluminum bromide, aluminum iodide, gallium chloride, gallium bromide, gallium iodide, Inorganic compounds such as indium chloride, indium bromide, indium iodide, antimony pentachloride, arsenic pentafluoride, boron trifluoride, DDQ (disyanodichloroquinone), TNF (tri-trofluorenone), TCNQ ( Tetracyanoquinodimethane), F4—TCNQ (Tetrafluorotetrasia) Nokinodimethane, etc.

[0196] Specific examples of metal oxides and metal halides include, for example, V 2 O (vanadium pentoxide

2 5 Dimu) or Re 2 O (Rhenium oxide), MoO, WO, etc. Alkali metal, Al

2 7 3 3

2

Examples include CsF, NaCl, KC1, and MgF.

2

[0197] Further, as an electron-accepting substance, there are an organic substance having fluorine as a substituent and an organic substance having a cyano group as a substituent, and the material is not limited to these materials. Can also be used. On the other hand, when an electron transporting material such as tris (8-hydroxyquinolinol) aluminum is used for the doped layer 102, an electron donating substance such as fullerene or carbon nanotube may be doped.

[0198] In addition, as materials for forming the doped layer 102 and the buffer layer 103, various known compounds generally used in the manufacture of organic EL elements can be used as appropriate. For the light-emitting layer 104 and the charge transport layer 105, various known materials for forming the light-emitting layer 104 and the charge transport layer 105 can be used.

[0199] The electrode (cathode 101b) may be made of a simple substance such as aluminum, copper, silver, or gold, or an alloy such as magnesium and silver, lithium and silver, or a conductive oxide such as indium tin oxide (ITO). I'll do it.

[0200] (Specific example)

Next, specific examples of the organic EL element 100 and the self-luminous panel 900 using the organic EL element 100 will be described. In this specific example, a self-luminous panel 900 using the organic EL element 100 and the organic EL element 100 created based on the following procedure will be described. Although illustration is omitted, when manufacturing the organic EL element 100 of this specific example and the self-luminous panel 900 using the organic EL element 100, first, lOnm ITO was formed on a glass substrate by a sputtering method. .

[0201] Next, a photoresist AZ6112 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was patterned on the ITO film with a width of 2 mm. The resist-patterned substrate was immersed in a mixed solution of ferric chloride aqueous solution and hydrochloric acid. As a result, the portion of the ITO film not covered with the resist was etched. The etched glass substrate was immersed in acetone. As a result, the cash register The stripe was removed and the ITO electrode stripe pattern with a width of 2 mm was formed.

[0202] The glass substrate on which the ITO electrode stripe pattern is formed is washed with a surfactant. Thereafter, UV ozone cleaning was performed for 10 minutes using a UV ozone stripper UV-1 manufactured by Samco International Laboratory. The glass substrate that had been subjected to UV ozone cleaning was put into a vacuum chamber. The degree of vacuum is 1 X 10- ⁶ Τοπ in vacuum chamber: upon reaching, by the resistance heating evaporation, deposition CuPc the at deposition rate per second 0. 5 nm to a thickness of 25nm as the hole injection layer did.

[0203] Next, αNPD doped with an electron accepting substance (acceptor) was deposited as a doped layer 102 at a deposition rate of 0.5 nm per second in the same manner as described above. During film formation, the material used for film formation was heated and evaporated in a vacuum atmosphere (resistance heating vacuum film formation). At this time, 4F-TCNQ, which is a molecule of the electron-accepting substance, was also heated and evaporated at the same time, and a mixed film was formed so that the film formation rate ratio of a-NPD and F4-TCNQ was 10: 1. Similarly, samples with different film thicknesses of x = 10, 50, lOOnm were prepared, where the film thickness was xnm.

[0204] Subsequently, a resistance heating vacuum film formation was performed at a film formation rate of 0.5 nm per second in the same manner as described above, using only NPD. If the film thickness at this time is ynm, samples with three different film thicknesses of y = 10, 50, lOOnm were manufactured. By forming the organic EL element as described above, a plurality of types of samples were obtained by combining the film thickness X and the film thickness y.

[0205] Next, in each of the above-mentioned plural types of samples, Alq is used as the light emitting layer 104 at 0.5 nm per second.

Three

Resistance heating vacuum film formation was performed until the film thickness reached 60 nm at a film formation speed of. LiF on Alq

Three

As an electron injection additive, resistance heating vacuum film formation was performed until a thickness of 0.5 nm was reached at a film formation rate of 0.0 Olnm per second. The thus produced light emitting layer 104 and the charge transport layer 105 is formed so as to cover the stripe ITO film already made form, it was consistently deposited in a high vacuum of 1 X 10- ⁶ Torr .

[0206] On the charge transport layer 105, a shadow mask for a cathode was applied in a vacuum, and aluminum was formed into a resistance heating vacuum film to a thickness of lOOnm at a speed of lnm per second. At this time, the aluminum film was formed into a 2 mm wide stripe in a direction perpendicular to the ITO film stripe. . In the self-luminous panel 900 thus produced, the size of the organic EL element 100 determined by the intersection of the anode 101a formed of the ITO film and the cathode 101b formed of aluminum is 2 mm X 2 mm.

[0207] (Comparative example)

Next, an organic EL element as a comparative example for the above-described specific example will be described. Although illustration is omitted, the organic EL element as a comparative example is the same as the specific example except for the step of forming the doped layer 102 doped with the electron-accepting substance in the organic EL element described as the specific example. Manufactured. In the process of forming the doped layer 102, x = 0 nm, y = 10, 50, and lOOnm.

[0208] For each sample of the specific example and the comparative example manufactured in this way, the relationship between the applied voltage necessary to pass a current of 7.5 mA / cm 2 and the thickness y of the buffer layer 103 was examined. It was. As a result, in the comparative example, the drive voltage increased at a predetermined rate depending on the thickness of the buffer layer 103. In contrast, in the specific example in which the doped layer 102 doped with the electron-accepting substance was provided, the driving voltage did not increase due to the thickness of the notch layer 103 (see FIG. 12 and the table in the above embodiment). 1).

[0209] Note that regarding the increase in drive voltage according to the thickness of the buffer layer 103, even when a mixed layer of αNPD and F4 — TCNQ is formed directly on the anode 101a, it is formed via CuPc. It was confirmed that the same effect appeared when the film was formed. That is, in the specific example in which the doped layer 102 doped with the electron accepting substance was provided, an increase in driving voltage due to the difference in the thickness of the buffer layer 103 was not confirmed. As long as the mixing ratio of α-NPD and F4-TCNQ is allocated in the range of 100: 5 to L00: 50! /, The drive voltage due to the difference in the thickness of the buffer layer 103 It was confirmed that there was no increase.

[0210] (Comparative example)

Next, an organic EL device as another comparative example for the above-described specific example will be described. As a comparative example to the specific example described above, an organic EL element exactly the same as the specific example described above was manufactured except that the film thickness of the low carrier density layer was set to 5, 20, and 50 ηm. As a result, when the diode characteristics of these elements were measured, the reverse bias withstand voltage was about IV, which was very low.

Claims

The scope of the claims

[1] an electrode pair comprising a lower electrode and an upper electrode facing the lower electrode;

A light emitting layer provided between the electrode pair;

A doped layer provided between the light emitting layer and the lower electrode and doped with an electron accepting substance;

A buffer layer provided between the doped layer and the light emitting layer and having a dimension along the opposing direction of the electrode pair (hereinafter referred to as a film thickness) greater than the film thickness of the doped layer;

A self-luminous element comprising:

[2] an electrode pair comprising a lower electrode and an upper electrode facing the lower electrode;

A light emitting layer provided between the electrode pair;

A doped layer provided between the light emitting layer and the upper electrode and doped with an electron accepting substance;

A buffer layer provided between the doped layer and the light emitting layer, the film thickness being larger than the film thickness of the doped layer;

A self-luminous element comprising:

[3] The self-luminous element according to [1] or [2], wherein the buffer layer has a charge blocking function for blocking charges moving from the light emitting layer to the doped layer side.

[4] The buffer layer includes first reflected light that is reflected on a surface of a layer on which the light emitted from the light emitting layer is stacked, and light that is emitted from the light emitting layer and passes through the buffer layer. 4. The self-luminous element according to claim 3, wherein the self-luminous element is provided with a film thickness that causes optical interference that strengthens the second reflected light reflected by the surface on the doped layer side.

[5] The self-luminous element according to [1] or [2], wherein the doped layer includes the same material as that for forming the buffer layer and the electron accepting substance.

6. The self-luminous element according to claim 1, wherein the doped layer includes a material different from a material forming the buffer layer and the electron-accepting substance.

[7] an electrode pair comprising a lower electrode and an upper electrode facing the lower electrode;

A light emitting layer provided between the electrode pair;

Provided between the light emitting layer and the lower electrode and doped with an electron donating substance A doped layer;

A self-luminous element comprising:

[8] an electrode pair comprising a lower electrode and an upper electrode facing the lower electrode;

A light emitting layer provided between the electrode pair;

A doped layer provided between the light emitting layer and the upper electrode and doped with an electron donating substance;

A self-luminous element comprising:

[9] The self-luminous element according to [7] or [8], wherein the buffer layer has a charge blocking function for blocking charges moving from the light emitting layer to the doped layer side.

[10] The buffer layer includes first reflected light that is reflected on a surface of the layer on which the light emitted from the light emitting layer is stacked, and light that is emitted from the light emitting layer and passes through the buffer layer. 10. The self-luminous element according to claim 9, wherein the self-luminous element is provided with a film thickness that causes optical interference that strengthens the second reflected light reflected by the surface on the doped layer side.

[11] The self-luminous element according to [7] or [8], wherein the doped layer includes the same material as the material forming the buffer layer and the electron donating substance.

[12] The self-luminous element according to [7] or [8], wherein the doped layer includes a material different from a material forming the buffer layer and the electron donating substance.

13. The self-luminous element according to claim 1, 2, 7 or 8, wherein the self-luminous element is an organic EL element.

[14] An electrode pair including a lower electrode and an upper electrode facing the lower electrode, a light emitting layer provided between the electrode pair, and an electron pair provided between the light emitting layer and the lower electrode, A doped layer doped with an acceptor substance or an electron-donating substance, a buffer layer provided between the doped layer and the light emitting layer, wherein the film thickness is larger than the film thickness of the doped layer; A self-light-emitting panel comprising a plurality of self-light-emitting elements provided on a substrate Le.

An electrode pair including a lower electrode and an upper electrode facing the lower electrode; a light emitting layer provided between the electrode pair; and an electron accepting property provided between the light emitting layer and the upper electrode. A doped layer doped with a substance or an electron-donating substance, and a buffer layer provided between the doped layer and the light emitting layer, wherein the film thickness is larger than the film thickness of the doped layer. A self-luminous panel comprising a plurality of light-emitting elements disposed on a substrate.