Organic electroluminescent element with carrier injection control electrode

Abstract

The organic electroluminescent element of the present invention comprises: a first electrode; a third electrode having a region opposite to the first electrode; a first insulating layer between the first electrode and the third electrode; a second insulating layer between the first insulating layer and the third electrode; an electron transport layer between the first insulating layer and the third electrode; a light-emitting layer between the electron transport layer and the third electrode, comprising an organic electroluminescent material; and a second electrode disposed between the first insulating layer and the second insulating layer and electrically connected to the electron transport layer. The second insulating layer has an opening, and the opening has an overlapping region where the third electrode, the light-emitting layer, the electron transport layer, the first insulating layer, and the first electrode overlap, and the second electrode is disposed outside the overlapping region.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority based on Japanese patent application No. 2018-162568 filed on August 31, 2018, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] One embodiment of the present invention relates to an element structure of an organic electroluminescent element (hereinafter also referred to as an "organic EL element") using an organic electroluminescent material. One embodiment of the invention disclosed in this specification relates to an organic electroluminescent element having an electrode for controlling the amount of carriers injected into a light-emitting layer. Background Art

[0004] An organic EL element has a pair of electrodes called an anode and a cathode, and has a structure in which a light-emitting layer is arranged between the pair of electrodes. Although an organic EL element has a two-terminal type element as a basic structure, a three-terminal type organic EL element having a third electrode added thereto is also disclosed.

[0005] For example, an organic EL element is disclosed, which is provided with an anode, a layer formed of an organic electroluminescent material called a light-emitting material layer, a cathode, and an auxiliary electrode arranged opposite to the cathode and the light-emitting material layer via an insulating layer (for example, refer to JP-A-2002-343578). In addition, a light-emitting transistor is disclosed, which has a structure in which a hole injection layer, a carrier dispersion layer, a hole transport layer, and a light-emitting layer are stacked from the anode side between the anode and the cathode, and an auxiliary electrode is arranged opposite to the anode via an insulating film (for example, refer to International Publication No. 2007 / 043697).

[0006] In addition, an organic light-emitting transistor element is disclosed, which is composed of: an auxiliary electrode, an insulating film arranged on the auxiliary electrode, a first electrode arranged on the insulating film with a given size, a charge injection inhibition layer on the first electrode, a charge injection layer arranged on the insulating film without the first electrode, a light-emitting layer arranged on the charge injection inhibition layer and the charge injection layer or on the charge injection layer, and a second electrode arranged on the light-emitting layer (for example, refer to JP Patent Gazette No. 2007-149922 and JP Patent Gazette No. 2007-157871). Summary of the invention

[0007] An organic electroluminescent element according to one embodiment of the present invention comprises: a first electrode; a third electrode having a region opposite to the first electrode; a first insulating layer between the first electrode and the third electrode; a second insulating layer between the first insulating layer and the third electrode; an electron transport layer between the first insulating layer and the third electrode; a light-emitting layer between the electron transport layer and the third electrode, comprising an organic electroluminescent material; and a second electrode disposed between the first insulating layer and the second insulating layer and electrically connected to the electron transport layer. The second insulating layer has an opening, and the opening has an overlapping region where the third electrode, the light-emitting layer, the electron transport layer, the first insulating layer, and the first electrode overlap, and the second electrode is disposed outside the overlapping region.

[0008] In one embodiment of the present invention, the electron transport layer constituting the organic electroluminescent element is preferably formed of a light-transmitting metal oxide, for example, an n-type oxide semiconductor.

[0009] Effects of the Invention

[0010] According to one embodiment of the present invention, in an organic electroluminescent element, by providing a third electrode overlapping with an electron transport layer through an insulating layer, the amount of carriers injected into the light-emitting layer can be controlled. According to one embodiment of the present invention, since the electron transport layer of the organic electroluminescent element is formed of an oxide semiconductor, the transport characteristics of the carriers can be improved to obtain uniform light emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0012] Figure 2 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0013] Figure 3 is a diagram for explaining the operation of an organic EL element according to one embodiment of the present invention;

[0014] Figure 4 is a diagram for explaining the operation of an organic EL element according to one embodiment of the present invention;

[0015] Figure 5 is a diagram for explaining the operation of an organic EL element according to one embodiment of the present invention;

[0016] Figure 6 A graph showing an example of the operating characteristics of an organic EL element according to an embodiment of the present invention;

[0017] 7A to 7CA diagram illustrating a method for manufacturing an organic EL element according to one embodiment of the present invention;

[0018] Fig. 8A and Figure 8B A diagram illustrating a method for manufacturing an organic EL element according to one embodiment of the present invention;

[0019] Fig.9A and Fig. 9B A diagram illustrating a method for manufacturing an organic EL element according to one embodiment of the present invention;

[0020] Fig.10 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0021] Fig.11 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0022] Fig.12 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0023] Fig.13 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0024] Fig.14 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0025] Fig.15 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0026] Fig.16 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0027] Fig.17 is a cross-sectional view showing the structure of an organic EL element according to one embodiment of the present invention;

[0028] Fig.18 is a diagram showing an example of an equivalent circuit of a pixel in a display device including an organic EL element according to an embodiment of the present invention;

[0029] Fig.19 is a diagram showing an example of an equivalent circuit of a pixel in a display device including an organic EL element according to an embodiment of the present invention;

[0030] Fig. 20 is a plan view showing the structure of a pixel in a display device using an organic EL element according to an embodiment of the present invention;

[0031] Fig.21A and Fig.21B It is a cross-sectional view showing the structure of a pixel in a display device using the organic EL element according to one embodiment of the present invention. DETAILED DESCRIPTION

[0032] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention includes a variety of different forms and should not be limited to the following embodiments. In order to make the description clearer, the drawings attached to this specification sometimes show schematic representations of the width, thickness, shape, etc. of each part compared with the actual form, but this is only an example and does not necessarily limit the content of the present invention. In addition, in the present invention, when a specific element recorded in a certain figure is the same as or corresponds to a specific element recorded in another figure, it is marked with the same symbol (or a, b, etc. are marked after the number recorded as the symbol), and repeated descriptions are appropriately omitted. Furthermore, the words "1st" and "2nd" marked on each element are convenient marks for distinguishing each element, and there is no further meaning unless otherwise specified.

[0033] In this specification, when a certain component or region is located "on (or below)" another component or region, unless otherwise specified, this includes not only the case where it is located directly above (or directly below) another component or region, but also the case where it is located above (or below) another component or region. In other words, it also includes the case where another component is included between the above (or below) another component or region and the certain component or region.

[0034] First Embodiment

[0035] 1. Structure of organic EL element

[0036] The structure of the organic EL element is classified based on the emission direction of light: a bottom emission type that allows light to pass through the substrate and emit light to the side opposite to the substrate, and a top emission type that allows light to emit to the side opposite to the substrate. The structure of the organic EL element is also classified based on the stacking order in the manufacturing process: a positive stacking structure in which the anode, hole transport layer, light-emitting layer, electron transport layer, and cathode are stacked in the order from the substrate side, and a reverse stacking structure in which the anode, hole transport layer, light-emitting layer, electron transport layer, and cathode are stacked in the reverse order. The organic EL element involved in this embodiment is classified as a reverse stacking structure and can be applied to both the bottom emission type and the top emission type.

[0037] Incidentally, the organic EL element disclosed in JP-2002-343578 has a problem that the amount of electrons injected from the cathode is basically determined by the potential difference between the anode and the cathode, and the bias voltage applied from the auxiliary electrode has almost no effect on the carrier injection, because the electron mobility in the luminescent material layer is low and the resistance is high. Therefore, the injection of electrons into the luminescent material layer is concentrated only near the cathode, and the bias voltage applied to the auxiliary electrode has no effect on the amount of electrons injected.

[0038] The light-emitting transistor described in the specification of International Publication No. 2007 / 043697 has the problem that the amount of carriers (electrons, holes) of different polarities injected into the light-emitting layer cannot be independently controlled even with an external circuit because the auxiliary electrode controls the light-emitting / non-light-emitting state. Furthermore, the light-emitting transistor described in JP Patent Publication No. 2002-343578 has the problem that the position of the region where electrons and holes recombine in the light-emitting layer, i.e., the light-emitting region, cannot be controlled. In addition, the organic light-emitting transistor elements described in JP Patent Publication No. 2007-149922 and JP Patent Publication No. 2007-157871 have the problem that the display panel cannot be made larger and higher-definition because the carrier (electron) mobility of the electron transport layer formed of organic materials is low.

[0039] However, as described in detail below, an organic EL element according to an embodiment of the present invention includes a configuration that can overcome these problems.

[0040] 1-1. Bottom-emission organic EL element

[0041] Figure 1 A cross-sectional structure of an organic EL element 200 a according to one embodiment of the present invention is shown. Figure 1 The organic EL element 200a shown is a bottom emission type and has a reverse stacking structure. That is, the organic EL element 200a has a structure in which a first electrode 102, a first insulating layer 104, an electron transport layer 106 (a first electron transport layer 106a, a second electron transport layer 106b), a light-emitting layer 112, and a third electrode 118 are stacked from the substrate 100 side.

[0042] Figure 1 The structure further includes a hole transport layer 114 and a hole injection layer 116 between the light emitting layer 112 and the third electrode 118. The organic EL element 200a may omit one of the hole injection layer 116 and the hole transport layer 114, or may replace the hole injection layer with a hole injection layer having both hole injection and hole transport functions. Figure 1Although not shown, a hole blocking layer may be disposed between the electron injection layer 110 and the light-emitting layer 112 , and an electron blocking layer may be disposed between the light-emitting layer 112 and the hole transport layer 114 .

[0043] Figure 1 In the organic EL element 200a shown, the first electrode 102, the first insulating layer 104, the electron transport layer 106 (the first electron transport layer 106a, the second electron transport layer 106b), the electron injection layer 110, the light-emitting layer 112, and the third electrode 118 are arranged to overlap in the longitudinal direction. On the other hand, the second electrode 108 is arranged outside the region where these layers overlap (overlapping region) and is configured to be electrically connected to the first electron transport layer 106a. The second electrode 108 is arranged in a manner that contacts at least a portion of the first electron transport layer 106a. For example, the second electrode 108 can be arranged in a manner that surrounds the first electron transport layer 106a. In this specification, the expression "these layers" may include electrodes. For example, in this paragraph, "these layers" include the first electrode 102, the first insulating layer 104, and the third electrode 118.

[0044] exist Figure 1 In the embodiment, the third electrode 118 is an electrode that has the function of injecting holes into the hole injection layer 116 and is also called an "anode". The second electrode 108 is an electrode that has the function of injecting electrons into the electron transport layer 106 and is also called a "cathode". The first electrode 102 has the function of controlling the amount of carriers (electrons) injected into the light-emitting layer 112 and is also called a "carrier injection amount control electrode".

[0045] In the organic EL element 200a, the electron transport layer 106 is represented by two separate layers, namely the first electron transport layer 106a and the second electron transport layer 106b. The details of the electron transport layer 106 will be described below. The first electron transport layer 106a and the second electron transport layer 106b have a common function of transporting electrons injected from the second electrode 108 to the light-emitting layer 112. On the other hand, the first electron transport layer 106a in contact with the second electrode 108 and the second electron transport layer 106b arranged on the side close to the light-emitting layer 112 have different electron concentrations and electron mobilities. For example, the carrier concentration (electron concentration) of the second electron transport layer 106b is preferably relatively lower than the carrier concentration (electron concentration) of the first electron transport layer 106a to prevent carrier deactivation.

[0046] In the organic EL element 200 a , the second electron transport layer 106 b may be omitted. In addition, the first electron transport layer 106 a and the second electron transport layer 106 b may be regarded as one layer in terms of their common function of transporting electrons injected from the second electrode 108 to the light-emitting layer 112 .

[0047] The organic EL element 200a may also include a second insulating layer 120 disposed between the first electron transport layer 106a and the second electron transport layer 106b. The second insulating layer 120 covers the peripheral portion of the first electron transport layer 106a and has an opening 124a that exposes the upper surface. The first electron transport layer 106a and the second electron transport layer 106b are in contact with each other at the opening 124a of the second insulating layer 120. In the region where the opening 124a is disposed, the first electron transport layer 106a, the second electron transport layer 106b, the electron injection layer 110, the light-emitting layer 112, and the third electrode 118 are stacked. The region where these layers are stacked becomes the light-emitting region of the organic EL element 200a. In other words, the light-emitting region of the organic EL element 200a is defined by the opening 124a of the second insulating layer 120.

[0048] The second electrode 108 is sandwiched between the first insulating layer 104 and the second insulating layer 120. Since the second electrode 108 is sandwiched between the first insulating layer 104 and the second insulating layer 120, it is arranged at a position not exposed from the opening 124a. The second electrode 108 is provided in a manner overlapping the third electrode 118 via the insulating layer. Since the end of the second electrode 108 is not exposed in the opening 124a of the second insulating layer 120, it is configured in a manner that no electric field concentration is generated between the third electrode 118 and the second electrode 108 in the light emitting region. The organic EL element 200a is provided with an offset region 126 so as not to expose the second electrode 108 in the opening 124a of the second insulating layer 120. The offset region 126 is a region from the end of the opening 124a to the end of the second electrode 108, and corresponds to a region where the first electron transport layer 106a is sandwiched between the first insulating layer 104 and the second insulating layer 120. Regarding the length of the offset region 126, for the purpose of preventing electric field concentration, if the total film thickness of the electron transport layer 106, the electron injection layer 110, the light-emitting layer 112, the hole transport layer 114, the hole injection layer 116, etc. is set to 100nm~1000nm, then the length is set to be more than 10 times the total film thickness, preferably about 1μm~20μm, for example 2μm~5μm.

[0049] As described above, in the organic EL element 200a involved in this embodiment, the second electrode 108 is sandwiched between the first insulating layer 104 and the second insulating layer 120, and the end of the second electrode 108 is arranged on the outside of the opening 124a of the second insulating layer 120, thereby improving the withstand voltage of the organic EL element 200a and improving the uniformity of the luminous intensity in the luminous area.

[0050] Figure 1 1 shows a mode in which the third insulating layer 122 is provided on the second insulating layer 120. By providing the third insulating layer 122 on the second insulating layer 120, the distance between the third electrode 118 and the second electrode 108 can be increased, and the parasitic capacitance can be reduced.

[0051] The third insulating layer 122 is provided with an opening 124b, which is the same width as or wider than the opening 124a provided on the second insulating layer 120. By widening the width of the opening 124b of the third insulating layer 122 relative to the width of the opening 124a of the second insulating layer 120, a stepped step can be formed. In addition, the side of the second insulating layer 120 in the opening 124a and the side of the third insulating layer 122 in the opening 124b are preferably inclined in an upwardly open manner. By such a cross-sectional shape of the opening 124a and the opening 124b, the steepness of the step can be alleviated. Thus, when the second electron transport layer 106b, the light-emitting layer 112, and the third electrode 118 are provided overlapping with the opening 124a and the opening 124b, each layer can be formed along the step portion. In other words, it is possible to prevent cracks, that is, so-called step fractures, from being formed in the second electron transport layer 106 b , the light emitting layer 112 , the third electrode 118 , and the like.

[0052] The first electrode 102 is arranged so as to overlap with the opening 124a of the second insulating layer 120, and is arranged so as to overlap with the first electron transport layer 106a via the first insulating layer 104. The first electrode 102 is insulated from the first electron transport layer 106a by the first insulating layer 104. Although there is no transfer of carriers between the first electrode 102 and the first electron transport layer 106a, if a voltage is applied to the first electrode 102, the first electron transport layer 106a is affected by the electric field generated thereby.

[0053] The first electron transport layer 106a is acted upon by the electric field formed by the first electrode 102. The amount of carriers (electrons) transmitted from the electron transport layer 106 (first electron transport layer 106a, second electron transport layer 106b) to the light-emitting layer 112 can be controlled by the electric field strength of the first electrode 102. If the voltage applied to the first electrode 102 increases, the electric field acting on the electron transport layer 106 (first electron transport layer 106a, second electron transport layer 106b) will also increase. The electric field generated by applying a positive voltage to the first electrode 102 plays a role in pulling carriers (electrons) from the second electrode 108 into the first electron transport layer 106a, so the amount of carriers (electrons) transmitted to the light-emitting layer 112 can be increased. That is, the amount of carriers (electrons) transmitted from the first electron transport layer 106a to the light-emitting layer 112 can be controlled by the magnitude of the voltage applied to the first electrode 102. In other words, by controlling the voltage applied to the first electrode 102 , it is possible to adjust the balance (carrier balance) between the amount of electrons injected from the second electrode 108 and the amount of holes injected from the third electrode 118 .

[0054] The first electrode 102 is preferably configured so as to overlap with the offset region 126 of the first electron transport layer 106a. With this configuration, the first electrode 102 can cause an electric field to act on the offset region 126. If a positive voltage is applied to the first electrode 102, carriers (electrons) can be induced in the first electron transport layer 106a forming the offset region 126, thereby preventing the resistance of the offset region 126 from increasing. If the length of the offset region 126 is about 1 μm to 5 μm, electrons can be prevented from flowing from the second electrode 108 into the first electron transport layer 106a when the first electrode 102 is connected to the ground potential.

[0055] because Figure 1 The organic EL element 200a shown is a bottom emission type, so the first electrode 102 has light transmittance. For example, the first electrode 102 is formed of a transparent conductive film. On the other hand, the third electrode 118 has a light reflecting surface for reflecting the light emitted from the light emitting layer 112. In order to inject holes into the hole injection layer 116, the third electrode 118 is preferably formed of a material with a large work function. The third electrode 118 is formed of a transparent conductive film such as indium tin oxide (ITO). The light reflecting surface of the third electrode 118 can be formed by laminating a metal film such as aluminum on the transparent conductive film.

[0056] As described below, the electron transport layer 106 (the first electron transport layer 106a, the second electron transport layer 106b) is formed of a light-transmitting oxide semiconductor. The light-transmitting oxide semiconductor is an inorganic material and an oxide, so it is thermally stable. The organic EL element 200a forms the electron transport layer 106 with an oxide semiconductor, so that even if it is a reverse stacking structure, it can achieve a stable structure without characteristic degradation.

[0057] 1-2. Top emission organic EL element

[0058] Figure 2 2 shows a top emission type organic EL element 200b. The top emission type organic EL element 200b is different from the top emission type organic EL element 200b in that the third electrode 118 and the first electrode 102 are structured differently. Figure 1 The bottom emission type organic EL element 200a shown has the same structure. In the case where the organic EL element 200b is a top emission type, the first electrode 102 is formed of a metal film to form a light reflecting surface, and the third electrode 118 is formed of a transparent conductive film to transmit light emitted from the light emitting layer 112. Since the second electrode 108 is arranged outside the light emitting region, there is no need to particularly change the structure and constituent materials.

[0059] Since the first electrode 102 is formed of a metal film, it has a function as a light reflecting plate in the organic EL element 200b. Since the electron transport layer 106 (the first electron transport layer 106a, the second electron transport layer 106b) is formed of a light-transmitting oxide semiconductor film, it is possible to prevent the attenuation of light reflected by the first electrode 102, and to improve the light extraction efficiency (external quantum efficiency).

[0060] The top emission type organic EL element 200b and the bottom emission type organic EL element 200a differ only in the configuration of the third electrode 118 and the first electrode 102. That is, the organic EL elements involved in this embodiment have a reverse stacking structure as a common point, and can realize both the bottom emission type and the top emission type by slightly changing. In addition, in this specification, the organic EL element 200a and the organic EL element 200b are sometimes collectively referred to as "organic EL element 200".

[0061] Figure 1 The bottom emission type organic EL element 200a and Figure 2The top emission type organic EL element 200b shown has the following structure: at least the electron transport layer 106, the electron injection layer 110, the light emitting layer 112, and the third electrode 118 are stacked in the vertical direction, and the first electrode 102 is provided in a manner adjacent to the electron transport layer 106 via the first insulating layer 104, and the second electrode 108 is arranged outside the electron transport layer 106. The organic EL element 200 can control the amount of carriers (electrons) transmitted from the electron transport layer 106 to the light emitting layer 112 by controlling the potential of the first electrode 102 independently of the third electrode 118 and the second electrode 108. In addition, the organic EL element 200 can realize two structures of bottom emission type and top emission type by appropriately selecting the materials of the first electrode 102 and the third electrode 118.

[0062] 2. Components of organic EL elements

[0063] 2-1. First electrode (carrier injection amount control electrode)

[0064] The first electrode 102 is formed using a metal material, a conductive metal oxide material, a metal nitride material, or a metal oxynitride material. The metal material is formed of a metal material such as aluminum (Al), silver (Ag), titanium (Ti), molybdenum (Mo), tantalum (Ta), or an alloy material containing these metals. As the metal oxide material, for example, indium tin oxide (In2O3·SnO2: ITO), indium zinc oxide (In2O3·ZnO: IZO), tin oxide (SnO2), and zinc oxide (ZnO) can be used. Furthermore, as the metal oxide material, niobium (Nb)-doped titanium oxide (TiO x As the metal nitride material, titanium nitride (TiN x ), zirconium nitride (ZrN x ) etc. As the metal nitride oxide material, titanium oxynitride (TiO x N y ), Tantalum Oxynitride (TaO x N y ), zirconium oxynitride (ZrO x N y ), Hafnium Oxynitride (HfO x N y ) etc. A trace amount of metal elements that improve conductivity may also be added to these metal oxide materials, metal nitride materials, and metal oxynitride materials. For example, titanium oxide (TiO x :Ta).

[0065] The material forming the first electrode 102 can also be appropriately selected depending on whether the organic EL element 200 is a top emission type or a bottom emission type. In the case of the bottom emission type, the first electrode 102 is formed of a metal oxide material, a metal nitride material, or a metal nitride oxide material that is conductive and light-transmitting. As a result, the organic EL element 200a can make the light emitted by the light-emitting layer 112 pass through the first electrode 102 and emit. On the other hand, in the case of the top emission type, the first electrode 102 is formed of a metal material with a high reflectivity for visible light. The organic EL element 200b can make the light emitted by the light-emitting layer 112 reflect and emit from the third electrode 118 by forming the first electrode 102 of a metal material.

[0066] 2-2. First insulation layer, second insulation layer, third insulation layer

[0067] The first insulating layer 104, the second insulating layer 120, and the third insulating layer 122 are formed using an inorganic insulating material. As the inorganic insulating material, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc. can be selected. The first insulating layer 104, the second insulating layer 120, and the third insulating layer 122 are formed using a plasma CVD (Chemical Vapor Deposition) method, a sputtering method, etc. The first insulating layer 104 is formed with a film thickness of 50nm to 700nm, preferably 100nm to 400nm. By setting the film thickness of the first insulating layer 104 to the above range, the electric field generated by the first electrode 102 can act on the electron transport layer 106, and even when the bias voltage is increased, the tunneling current caused by the tunneling effect can be prevented from flowing from the first electrode 102 to the electron transport layer 106. The thickness of the second insulating layer 120 and the third insulating layer 122 is not particularly limited, and they are formed to have a thickness of, for example, 100 nm to 1000 nm.

[0068] By using such insulating materials, the first insulating layer 104, the second insulating layer 120, and the third insulating layer 122 can have both insulating properties and transparency. Therefore, it can be applied to both the bottom emission type organic EL element 200a and the top emission type organic EL element 200b. The first insulating layer 104 can insulate the first electrode 102 and the electron transport layer 106, and the first electrode 102 and the second electrode 108.

[0069] In addition, the third insulating layer 122 may also be made of an organic insulating material such as polyimide, acrylic resin, or epoxy resin. Since the third insulating layer 122 is formed of an organic insulating material, it is easy to control the cross-sectional shape of the opening 124b. The opening of the third insulating layer 122 is preferably tapered, and by using a photosensitive organic insulating material, the cross-sectional shape of the opening 124b can be formed into a tapered shape. In the case where the third insulating layer 122 is made to function as a planarizing film, the film thickness may be increased to about 2 μm to 5 μm.

[0070] 2-3. Electron transport layer

[0071] The electron transport layer 106 is preferably formed of a material with high electron mobility in order to transport the carriers (electrons) injected from the second electrode 108 to the surface of the light-emitting region of the organic EL element 200. In addition, in the case of a bottom emission type, the electron transport layer 106 is preferably formed of a material having good visible light transmittance because it is arranged closer to the light-emitting side than the light-emitting layer. In addition, in order to make the carrier concentration between the first electron transport layer 106a and the second electron transport layer 106b different, it is preferably formed of a material that is easy to control the carrier concentration.

[0072] In this embodiment, the electron transport layer 106 (the first electron transport layer 106a, the second electron transport layer 106b) uses a metal oxide material. As the metal oxide material, it is preferred to use an oxide semiconductor material with a band gap of 2.8 eV or more, preferably 3.0 eV or more and high electron mobility. This oxide semiconductor material also has semiconductor properties when a thin film is formed, is transparent to visible light, and has n-type conductivity.

[0073] As oxide semiconductor materials used in the electron transport layer 106, quaternary oxide materials, ternary oxide materials, binary oxide materials, and monovalent oxide materials can be exemplified. The metal oxide materials exemplified here have a band gap of 2.8 eV or more, exhibit n-type conductivity, and can control the donor concentration through oxygen vacancies, etc., so they are classified as oxide semiconductors.

[0074] As quaternary oxide materials, In2O3-Ga2O3-SnO2-ZnO oxide materials can be used. As ternary oxide materials, In2O3-Ga2O3-ZnO oxide materials, In2O3-SnO2-ZnO oxide materials, In2O3-Al2O3-ZnO oxide materials, Ga2O3-SnO2-ZnO oxide materials, Ga2O3-Al2O3-ZnO oxide materials, SnO2-Al2O3-ZnO oxide materials can be used. As binary oxide materials, In2O3-Ga2O3-SnO2-ZnO oxide materials can be used. 3-ZnO series oxide materials, SnO2-ZnO series oxide materials, Al2O3-ZnO series oxide materials, Ga2O3-SnO2 series oxide materials, Ga2O3-ZnO series oxide materials, Ga2O3-MgO series oxide materials, MgO-ZnO series oxide materials, SnO2-MgO series oxide materials, In2O3-MgO series oxide materials. As monometallic oxide materials, In2O3 series metal oxide materials, Ga2O3 series metal oxide materials, SnO2 series metal oxide materials, ZnO series metal oxide materials, etc. can be used.

[0075] In addition, the metal oxide material may include silicon (Si), nickel (Ni), tungsten (W), hafnium (Hf), and titanium (Ti). In addition, for example, the In-Ga-Zn-O series oxide material shown above is a metal oxide material containing at least In, Ga, and Zn, and its composition ratio is not particularly limited. In addition, if other expressions are used, the first electron transport layer 106a and the second electron transport layer 106b can use the chemical formula InMO3(ZnO) m (m>0) represented by a thin film. Here, M represents one or more metal elements selected from Ga, Al, Mg, Ti, Ta, W, Hf and Si. In addition, the above-mentioned quaternary oxide materials, ternary oxide materials, binary oxide materials, and monocyclic oxide materials are not limited to materials in which the oxides contained are stoichiometric compositions, but may also be composed of oxide materials with deviated stoichiometric compositions. In addition, the oxide semiconductor layer serving as the electron transport layer 106 may have an amorphous phase, may have crystallinity, and may also be a mixture of an amorphous phase and a crystalline phase.

[0076] The first electron transport layer 106a and the second electron transport layer 106b are preferably formed of oxide semiconductor materials of different compositions. For example, the first electron transport layer 106a is preferably formed of a tin (Sn)-based oxide semiconductor (InGaSnO x 、InWSnO x 、InSiSnO xThe second electron transport layer 106b is preferably made of a zinc (Zn)-based oxide semiconductor (ZnSiO x 、ZnMgO x 、ZnGaO x In other words, the first electron transport layer 106a is preferably a metal oxide containing tin oxide and indium oxide, and at least one selected from gallium oxide, tungsten oxide, aluminum oxide and silicon oxide, and the second electron transport layer 106b is preferably a metal oxide containing zinc oxide, and at least one selected from silicon oxide, magnesium oxide, aluminum oxide and gallium oxide.

[0077] By selecting oxide semiconductor materials of different compositions like this, the band gaps of the first electron transport layer 106a and the second electron transport layer 106b can be optimized. For example, the band gap of the second electron transport layer 106b can be enlarged relative to the band gap of the first electron transport layer 106a. Specifically, the band gap of the first electron transport layer 106a can be set to be above 3.0 eV, and the band gap of the second electron transport layer 106b can be set to be above the band gap of the first electron transport layer 106a. The band gap of the second electron transport layer 106b is preferably set to be above 3.4 eV. By setting the band gap of the second electron transport layer 106b to be above 3.4 eV, the absorption of blue light can be reduced and reliability can be improved.

[0078] In addition, as the electron transport layer 106 (the first electron transport layer 106a and the second electron transport layer 106b), indium tin oxide (In2O3·SnO2: ITO), indium zinc oxide (In2O3·ZnO: IZO), tin oxide (SnO2), titanium oxide (TiO x ) etc. In addition, the electron transport layer 106 may be made of a metal nitride material or a metal oxide nitride material. As the metal nitride material, gallium nitride (GaN), aluminum nitride-gallium (GaAlN x ) etc. As the metal nitride oxide material, titanium oxynitride (TiO x N y ), Tantalum Oxynitride (TaO x N y ), zirconium oxynitride (ZrO x N y ), Hafnium Oxynitride (HfO x N y ) etc. A trace amount of metal elements that improve conductivity can be added to these metal oxide materials, metal nitride materials, and metal oxynitride materials. For example, niobium-doped titanium oxide (TiO x : Nb). In order to make the band gap of these metal compounds at least 2.8 eV or more, it is sufficient to adjust the oxygen content or the nitrogen content.

[0079] The first electron transport layer 106a and the second electron transport layer 106b formed of an oxide semiconductor material can be formed by sputtering, vacuum evaporation, coating, etc. Preferably, the first electron transport layer 106a has a film thickness of 10nm to 200nm, and the second electron transport layer 106b is formed with a film thickness of 50nm to 500nm.

[0080] Preferably, the carrier concentration of the first electron transport layer 106a is 10 times or more, preferably 100 times or more higher than the carrier concentration of the second electron transport layer 106b. For example, preferably, the carrier concentration (electron concentration) of the first electron transport layer 106a is 10 14 / cm 3 ~10 19 / cm 3 In the range of 10 11 / cm 3 ~10 17 / cm 3 Within the range of, the difference in carrier concentration between the two is more than 1 order of magnitude as described above, preferably more than 2 orders of magnitude.

[0081] In addition, preferably, the electron mobility of the second electron transport layer 106b is 1 / 5 to 1 / 10 of the electron mobility of the first electron transport layer 106a. For example, the electron mobility of the first electron transport layer 106a is preferably 1 cm 2 / V·sec~50cm 2 / V·sec, and the electron mobility of the second electron transport layer 106b is preferably 0.01 cm 2 / V·sec~10cm 2 / V·sec.

[0082] The first electron transport layer 106a can achieve low resistance by having the carrier concentration and electron mobility as described above. By having such physical properties, the first electron transport layer 106a can make the in-plane distribution of electrons injected from the second electrode 108 uniform. In other words, the carriers (electrons) injected from the peripheral portion of the first electron transport layer 106a by the second electrode 108 can be transmitted toward the central direction, so that the electron concentration in the light-emitting area becomes uniform. Thus, the luminous intensity of the organic EL element 200 can be made uniform within the surface. In addition, by using the first electron transport layer 106a with relatively high conductivity, the carriers (electrons) injected from the second electrode 108 can be transmitted to the area where the electric field of the first electrode 102 acts.

[0083] The second electron transport layer 106b and the light emitting layer 112 are arranged close to each other. 20 / cm 3 If the carrier concentration (electron concentration) of the second electron transport layer 106b is 10 11 / cm 3 By making the carrier concentration and electron mobility of the first electron transport layer 106a and the second electron transport layer 106b different in this way, the luminous efficiency of the organic EL element 200 can be improved and the luminous intensity can be made uniform in the plane.

[0084] 2-4. Second electrode (cathode)

[0085] As the cathode material of organic EL element, materials such as aluminum-lithium alloy (AlLi) and magnesium-silver alloy (MgAg) were used in the past. However, these materials are easily degraded by the influence of oxygen and moisture in the atmosphere and are difficult to handle. In addition, these materials are metals or alkali metals, and in order to have light transmittance, they must be made into thin films or semi-transparent films. However, if the cathode is thin-filmed, the problem of sheet resistance becoming higher will occur. Since the resistance of the electrode plays a role as a series resistance component in the organic EL element, the thin-filming of the cathode becomes a factor in improving the driving voltage and increasing power consumption. Furthermore, it also becomes the cause of the unevenness of the luminous intensity (brightness) in the surface of the light-emitting area of ​​the organic EL element.

[0086] In the organic EL element 200 according to this embodiment, the second electrode 108 and the first electron transport layer 106a are formed of a metal oxide material. In other words, the second electrode 108 is formed of an oxide semiconductor film. For example, the second electrode 108 is formed by reducing the resistance of the peripheral portion of the oxide semiconductor layer forming the first electron transport layer 106a. The carrier concentration of the second electrode 108 is preferably 10 20 / cm 3 ~10 21 / cm 3 The second electrode 108 has such a carrier concentration, so that the resistance can be reduced and the series resistance loss can be suppressed. Thus, the power consumption of the organic EL element 200 can be reduced and the current efficiency can be improved.

[0087] The second electrode 108 can be formed by reducing the resistance of a portion of the first electron transport layer 106a. Specifically, the resistance can be reduced by increasing the oxygen vacancies in a portion of the oxide semiconductor layer (corresponding to the region of the second electrode 108) (by increasing donor defects). Local heating treatment is effective for selectively increasing oxygen vacancies in a portion of the oxide semiconductor layer. Specifically, by irradiating a portion of the oxide semiconductor layer with a laser, an area with increased oxygen vacancies can be formed. Since the oxide semiconductor layer has a wide band gap, the light source used to irradiate the laser is preferably capable of oscillating a short-wavelength laser. For example, KrF excimer lasers (wavelength 248nm), XeCl excimer lasers (wavelength 308nm), XeF excimer lasers (wavelength 351nm), etc. can be used as laser light sources. In addition, when a solid laser such as a YAG laser is used as a light source, it is sufficient to irradiate the oxide semiconductor layer with the third harmonic of the oscillation wavelength.

[0088] By increasing oxygen vacancies (donor defects) in a portion of the first electron transport layer 106a to form the second electrode 108, it is possible to form a state where the second electrode 108 and the first electron transport layer 106a are joined (a state where the continuity of the lattice is maintained). With this structure, it is possible to prevent a barrier (energy barrier) that hinders electron injection from being formed at the interface between the second electrode 108 and the first electron transport layer 106a. Thus, it is possible to prevent the series resistance of the organic EL element 200 from increasing and prevent the driving voltage from increasing. In addition, it is possible to reduce the power consumption of the organic EL element 200.

[0089] in addition, Figure 1 Although not shown, the second electrode 108 can also be formed as a layer separate from the first electron transport layer 106a using a metal material such as aluminum (Al), molybdenum (Mo), and copper (Cu). In this case, since the second electrode 108 is arranged outside the overlapping region of the third electrode 118, the light-emitting layer 112, and the electron transport layer 106 (that is, since it is arranged outside the light-emitting region), there is no need to reduce the film thickness, and low resistance can be achieved.

[0090] 2-5. Electron injection layer

[0091] In an organic EL element, an electron injection layer is used to reduce the energy barrier for injecting electrons from a cathode into an electron transport material. The organic EL element 200 according to this embodiment preferably has an electron injection layer 110 so that electrons can be easily injected from an electron transport layer 106 formed of an oxide semiconductor into a light-emitting layer 112. The electron injection layer 110 is provided between the electron transport layer 106 and the light-emitting layer 112.

[0092] The electron injection layer 110 is preferably formed of a material with a small work function in order to inject electrons into the light-emitting layer 112 formed by the organic electroluminescent material. The electron injection layer 110 is composed of calcium (Ca) oxide and aluminum (Al) oxide. As the electron injection layer 110, for example, C12A7 (12CaO·7Al2O3) electron crystal is preferably used. The C12A7 electron crystal has semiconductor properties and can be controlled between high resistance and low resistance. The work function is also the same as that of alkali metals, which is 2.4eV to 3.2eV, so it can be well used as the electron injection layer 110.

[0093] The electron injection layer 110 formed by the C12A7 electron crystal is made by sputtering with a polycrystal of the C12A7 electron compound as a target. Since the C12A7 electron crystal has semiconductor properties, the film thickness of the electron injection layer 110 can be set to a range of 1nm to 100nm. In addition, the C12A7 electron crystal preferably has a molar ratio of Ca:Al in the range of 13:13 to 11:16. The electron injection layer 110 using the C12A7 electron crystal can be formed using a sputtering method. The electron injection layer 110 formed by the C12A7 electron crystal is preferably amorphous, but may also have crystallinity.

[0094] Since C12A7 electron crystal is stable in the atmosphere, it has the advantage of being easier to handle than alkali metal compounds such as lithium fluoride (LiF), lithium oxide (Li2O), sodium chloride (NaCl), and potassium chloride (KCl) that have been used as electron injection layers in the past. As a result, in the manufacturing process of the organic EL element 200, it is not necessary to operate in dry air or inert gas, and the restrictions on manufacturing conditions are relaxed.

[0095] In addition, since the C12A7 electron crystal has a large ionization potential, it can be used as a hole blocking layer by being arranged on the opposite side of the hole transport layer 114 through the light-emitting layer 112. That is, by providing the electron injection layer 110 formed of the C12A7 electron crystal between the electron transport layer 106 and the light-emitting layer 112, it is possible to suppress the holes injected into the light-emitting layer 112 from penetrating to the second electrode 108 side, thereby improving the light emission efficiency. x Zn y O, such as Mg 0.3 Zn 0.7 O) can also be used as an electron injection layer because of its small work function of 3.1 eV and high stability in the atmosphere.

[0096] 2-6. Luminescent layer

[0097] The light-emitting layer 112 is formed using an organic electroluminescent material. As the organic electroluminescent material, for example, a fluorescent compound material that emits fluorescence, a phosphorescent compound material that emits phosphorescence, or a thermally activated delayed fluorescence (TADF) material can be used.

[0098] For example, as a blue-based light-emitting material, N,N'-bis[4-(9H-carbazole-9-yl)phenyl]-N,N'-diphenylstilbene-4,4'-diamine (YGA2S), 4-(9H-carbazole-9-yl)-4'-(10-phenyl-9-anthryl)triphenylamine (YGAPA), etc. can be used. As a green-based light-emitting material, N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazole-3-amine (2PCAPA), N-[9,10-bis(1,1'-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazole-3-amine (2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N',N'-triphenyl-1,4-phenylenediamine (2 As the red luminescent material, N,N,N',N'-tetrakis(4-methylphenyl)tetracene-5,11-diamine (p-mPhTD), 7,13-diphenyl-N,N,N',N'-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (p-mPhAFD), etc. can be used. In addition, bis[2-(2'-benzo[4,5-α]thienyl)pyrido-N,C 3 '] Phosphorescent materials such as iridium(III) acetylacetonate (Ir(btp)2(acac)).

[0099] In addition, various well-known materials such as quantum dots (QD) can be used as the light-emitting layer 112. The light-emitting layer 112 can be produced by evaporation, transfer, spin coating, spray coating, printing (inkjet printing, gravure printing), etc. The film thickness of the light-emitting layer 112 can be appropriately selected, for example, set in the range of 10nm to 100nm.

[0100] In addition, Figure 1 and Figure 2In the example shown in FIG. 1 , the light-emitting layer 112 is separated into each organic EL element. However, when a plurality of organic EL elements are arranged on the same plane, the light-emitting layer 112 may be continuously provided across the plurality of light-emitting elements. 2-7. Hole Transport Layer

[0101] The hole transport layer 114 is formed using a material having a hole transport property. For example, the hole transport layer 114 may be an arylamine compound, an amine compound containing a carbazole group, an amine compound containing a fluorene derivative, or the like. The hole transport layer 114 can use organic materials such as 4,4'-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD), N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), 2-TNATA, 4,4',4"-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (MTDATA), 4,4'-N,N'-dicarbazolebiphenyl (CBP), 4,4'-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (DFLDPBi), 4,4'-bis[N-(spiro-9,9'-bifluorene-2-yl)-N-phenylamino]biphenyl (BSPB), spiro-NPD, spiro-TPD, spiro-TAD, TNB, etc.

[0102] The hole transport layer 114 is formed by a common film forming method such as vacuum deposition method, coating method, etc. The hole transport layer 114 is formed to have a film thickness of 10 nm to 500 nm.

[0103] 2-8. Hole injection layer

[0104] The hole injection layer 116 contains a substance with high hole injection properties for the organic layer. As a substance with high hole injection properties, metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, tungsten oxide, and manganese oxide can be used. In addition, phthalocyanine (H2Pc), copper (II) phthalocyanine (abbreviated as: CuPc), vanadium phthalocyanine (VOPc), 4,4',4"-tris(N,N-diphenylamino)triphenylamine (TDATA), 4,4',4"-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA), 4,4'-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB), 4,4'-bis(N-{4-[N'-(3-methylphenyl)-N'-phenylamino]phenyl}-N-phenylamino)biphenyl (DNTPD), 1,3,5-tri[ Organic compounds such as N-(4-diphenylaminophenyl)-N-phenylamino]benzene (DPA3B), 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (PCzPCN1), and 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HAT-CN).

[0105] The hole injection layer 116 is formed by a common film forming method such as vacuum deposition method, coating method, etc. The hole injection layer 116 is formed to have a film thickness of 1 nm to 100 nm.

[0106] 2-9. Third electrode (anode)

[0107] The third electrode 118 is made of a metal, alloy, or conductive compound having a large work function (specifically, 4.0 eV or more). The third electrode 118 uses, for example, indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide containing tungsten oxide and zinc oxide (IWZO), etc. The third electrode 118 using these conductive metal oxide materials is produced by vacuum evaporation or sputtering.

[0108] Like reference Figure 1 As described above, in the case of the bottom emission type organic EL element 200a, the third electrode 118 is located behind the light emitting surface, and therefore preferably has a light reflecting surface. In this case, the third electrode 118 preferably has a metal film stacked on a transparent conductive film. Figure 2 As described above, in the case of the top emission type organic EL element 200 b , the third electrode 118 can be formed using the above-mentioned transparent conductive film.

[0109] 3. Operation of organic EL elements

[0110] Reference Figure 3 , Figure 4 ,and Figure 5 The operation of the organic EL element according to this embodiment will be described. The organic EL element 200 shown in this section is a schematic structure.

[0111] 3-1. Luminous and non-luminous actions

[0112] Figure 3 The structure of the organic EL element 200 according to this embodiment is schematically shown. Figure 3 The structure of the organic EL element 200 includes a second electrode 108 , an electron transport layer 106 , an electron injection layer 110 , a light emitting layer 112 , a hole transport layer 114 , a hole injection layer 116 , a third electrode 118 , a first insulating layer 104 , and a first electrode 102 .

[0113] The organic EL element 200 is a type of light emitting diode, and emits light when a forward current flows between the third electrode (anode) 118 and the second electrode (cathode) 108 . Figure 3 The following form is shown: a third power source 128c is connected between the third electrode 118 and the ground (earth), a second power source 128b is connected between the second electrode 108 and the ground (earth), a second switch 130b is connected in series between the first electrode 102 and the first power source 128a, and a first switch 130a is connected between the first electrode 102 and the ground (earth). In addition, the first switch 130a and the second switch 130b are included in the switch 130. Figure 3 This shows a state in which the first switch 130 a and the second switch 130 b of the switches 130 are turned off and no bias is applied to the first electrode 102 .

[0114] Right now, Figure 3 The first switch 130a for controlling the conduction state between the first electrode 102 and the ground (earth) is turned off, and the second switch 130b for controlling the connection between the first electrode 102 and the first power supply 128a is turned off. In this state, the organic EL element 200 is biased in the forward direction, so as long as the bias voltage is equal to or higher than the emission start voltage, holes are injected from the third electrode 118 and electrons are injected from the second electrode 108. The organic EL element 200 applies a positive voltage between the third electrode 118 and the second electrode 108 through the third power supply 128c. The light emission intensity can be controlled by the magnitude of the forward current flowing to the organic EL element 200.

[0115] However, in a structure where the electron transport layer 106 and the third electrode 118 are arranged opposite to each other with the light-emitting layer 112 interposed therebetween on the first insulating layer 104, and the second electrode 108 is connected to the peripheral portion of the first electron transport layer 106a, uniform light emission cannot be obtained in the light-emitting region (the region where the electron transport layer 106, the electron injection layer 110, the light-emitting layer 112, and the third electrode 118 overlap). At this time, the electric field generated between the third electrode 118 and the second electrode 108 is not uniformly distributed in the light-emitting region, and the electric field is concentrated at the ends of the third electrode 118 and the second electrode 108. When both the first switch 130a and the second switch 130b are disconnected, the carriers (electrons) injected from the second electrode 108 are not uniformly distributed in the plane of the first electron transport layer 106a, and uniform light emission cannot be obtained in the plane of the light-emitting region.

[0116] Figure 3 In the embodiment, since the first switch 130a and the second switch 130b are disconnected, no voltage is applied to the first electrode 102 from the second power supply 128b. The carriers (electrons) injected from the second electrode 108 into the first electron transport layer 106a are not affected by the first electrode 102, so they do not diffuse to the central area of ​​the first electron transport layer 106a. That is, since the voltage is not applied to the first electrode 102, the carriers (electrons) injected into the peripheral portion of the first electron transport layer 106a do not drift, and therefore do not diffuse to the central area of ​​the first electron transport layer 106a. Therefore, in Figure 3 In the bias state shown, the organic EL element 200 emits light dimly in the center of the light-emitting region and brightly in the peripheral portion.

[0117] Figure 4 This shows that in the switch 130, the first switch 130a is turned on, and the potential of the first electrode 102 becomes the ground potential. In this state, there are no carriers (electrons) in the first electron transport layer 106a, and the first electron transport layer 106a is in an insulating state. As a result, no current flows in the organic EL element 200, and it becomes a non-luminescent state (non-luminescent state).

[0118] like Figure 5As shown, if a forward bias is applied between the third electrode 118 and the second electrode 108 of the organic EL element 200, and the second switch 130b is turned on, the electric field formed by the first electrode 102 acts on the first electron transport layer 106a. Since a positive voltage is applied to the first electrode 102, the carriers (electrons) injected from the second electrode 108 into the first electron transport layer 106a drift toward the central area of ​​the first electron transport layer 106a. As a result, the carriers (electrons) are transmitted from the peripheral portion of the first electron transport layer 106a to the central area of ​​the first electron transport layer 106a. The electric field generated by the first electrode 102 to which a positive voltage is applied plays a role in diffusing the carriers (electrons) injected from the second electrode 108 into the surface of the first electron transport layer 106a.

[0119] Since the organic EL element 200 is forward biased, the carriers (electrons) transferred to the central region of the first electron transport layer 106a migrate from the first electron transport layer 106a to the light-emitting layer 112. The carriers (holes) injected from the third electrode 118 and the carriers (electrons) injected from the second electrode 108 are recombined in the light-emitting layer 112 to generate excitons, and when the excited excitons transition to the ground state, photons are released and observed as light emission.

[0120] exist Figure 5 In the bias state shown, the amount of carriers (electrons) injected into the first electron transport layer 106a can be controlled by the voltage of the second electrode 108. By increasing the voltage of the second electrode 108, the amount of carriers (electrons) injected into the first electron transport layer 106a can be increased. The amount of carriers (electrons) injected from the first electron transport layer 106a to the light-emitting layer 112 can be controlled by the voltage of the first electrode 102. By increasing the voltage of the first electrode 102, a large amount of carriers (electrons) injected from the second electrode 108 can be pulled into the central area of ​​the first electron transport layer 106a, thereby increasing the amount of carriers injected into the light-emitting layer 112.

[0121] In order for the light-emitting layer 112 to emit light roughly uniformly over the entire surface, it is preferred that the electrons flowing to the second electron transport layer 106b form a space charge limited current. Therefore, the second electron transport layer 106b is preferably in an amorphous state, a nano-sized microcrystalline state, or a mixed state thereof. The first electron transport layer 106a is preferably a film containing nano-sized microcrystals and having a high density.

[0122] As described above, the organic EL element 200 according to the present embodiment includes the first electrode 102 in addition to the third electrode 118 and the second electrode 108, and thus can control the concentration of carriers injected into the light-emitting layer 112. Figure 5Although the example in which the first electrode 102 is arranged on the second electrode 108 side is shown, the first electrode 102 may be arranged on the third electrode 118 side instead. In addition to the first electrode 102, a fourth electrode for controlling the injection amount of carriers (holes) may be arranged on the third electrode 118 side.

[0123] 3-2. Control of carrier balance

[0124] In order to emit light, an organic EL element must inject holes from the anode and electrons from the cathode. In addition, in order to improve the current efficiency (luminous efficiency) of an organic EL element, a balance must be achieved so that the amount of holes transmitted from the anode to the light-emitting layer and the amount of electrons transmitted from the cathode to the light-emitting layer are consistent (hereinafter also referred to as "carrier balance"). Organic EL elements can improve current efficiency by achieving carrier balance.

[0125] However, the existing organic EL elements have a problem of losing carrier balance and reducing luminous efficiency because the electron mobility is low relative to the hole mobility of the light-emitting layer. In addition, if the organic EL element loses carrier balance and the number of holes in the light-emitting layer is excessive, there is the following problem: the holes accumulate at the interface between the light-emitting layer and the electron transport layer, which becomes a factor that promotes the deterioration of current efficiency (luminous efficiency). Therefore, people try to adjust the material or film thickness of the hole transport layer and the electron transport layer to achieve a balance between the holes and electrons injected into the light-emitting layer. However, there is the following problem: even if the element structure of the organic EL element itself is adjusted, it is impossible to track the time-dependent changes or temperature changes in the luminous characteristics.

[0126] In this regard, the organic EL element 200 involved in one embodiment of the present invention controls the carrier balance by the first electrode 102. That is, by controlling the amount of carriers (electrons) transferred to the light-emitting layer 112 by using the first electrode 102 provided on the electron transport layer 106 side, the carrier balance can be controlled. That is, the amount of electrons transferred from the second electrode 108 to the light-emitting layer 112 is increased by using the first electrode 102 in such a manner that the amount of electrons transferred from the second electrode 108 to the light-emitting layer 112 is not insufficient relative to the amount of holes transferred from the third electrode 118 to the light-emitting layer 112, thereby controlling the number of holes and electrons in the light-emitting layer 112 to be equal. In other words, the organic EL element 200 involved in this embodiment increases the electron current by using the first electrode 102 in such a manner that the electron current flowing from the second electrode 108 to the light-emitting layer 112 becomes equal to the hole current flowing from the third electrode 118 to the light-emitting layer 112, thereby maintaining the carrier balance in the light-emitting layer 112 constant.

[0127] Figure 6The graph schematically shows the relationship between the current (Ie) flowing between the third electrode 118 and the second electrode 108 when the voltage (Vac) applied between the third electrode 118 and the second electrode 108 of the organic EL element 200 is set constant and the voltage (Vg) applied to the first electrode 102 is changed. Figure 6 As shown in FIG. 1 , when the voltage (Vg) applied to the first electrode 102 is 0V, the electron current (Ie) is small, and the entire surface of the organic EL element 200 cannot be observed to emit light. If the voltage of the first electrode 102 is gradually increased from this state, the carriers (electrons) injected from the second electrode 108 into the first electron transport layer 106a become the electron current (Ie), and flow from the first electron transport layer 106a to the light-emitting layer 112. At this time, the electron current (Ie) increases exponentially like the forward current of a diode ( Figure 6 "I region" shown).

[0128] If the voltage (Vg) applied to the first electrode 102 is further increased, the increase in the electron current (Ie) relative to the change in the voltage (Vg) tends to be saturated, and the gradient of the curve of the Ie vs. Vg characteristic becomes gentle ( Figure 6 If the magnitude of the voltage (Vg) applied to the first electrode 102 in the "II region" is changed between the first voltage (Vg1) and the second voltage (Vg2), the electron current (Ie) will change between the first current (Ie1) and the second current (Ie2). The region where the voltage (Vg) of the first electrode 102 changes within the range from the first voltage (Vg1) to the second voltage (Vg2) is a region where the electron current (Ie) does not change sharply, and becomes a region where the light emission intensity of the organic EL element 200 gradually saturates.

[0129] The change in electron current (Ie) means that the amount of holes and electrons injected into the light-emitting layer 112 increases or decreases. If the voltage (Vg) of the first electrode 102 is changed between the first voltage (Vg1) and the second voltage (Vg2), the amount of electrons injected into the light-emitting layer 112 will change. That is, by changing the voltage (Vg) of the first electrode 102, the carrier balance of electrons and holes in the light-emitting layer 112 can be controlled. If the amount of electrons injected into the light-emitting layer 112 is changed, the center position of the region where electrons and holes recombine (the position of the light-emitting region in the thickness direction of the light-emitting layer 112) can be shifted. For example, when the first electrode 102 is at the first voltage (Vg1), the electron current is relatively smaller than the hole current, and the position of the light-emitting region in the light-emitting layer 112 becomes the cathode side ( Figure 6 On the other hand, when the first electrode 102 is at the second voltage (Vg2), the electron current is relatively larger than the hole current, and the position of the light-emitting region in the light-emitting layer 112 is toward the anode side ( Figure 6 "B" side shown) offset.

[0130] In this way, the organic EL element 200 can control the position of the light-emitting region in the light-emitting layer 112 in the thickness direction by the voltage of the first electrode 102. For example, if the voltage of the first electrode 102 is changed between the first voltage (Vg1) and the second voltage (Vg2), the position of the light-emitting region in the light-emitting layer 112 can be changed between the cathode side A and the anode side B. By controlling the voltage of the first electrode 102, the light-emitting layer 112 can be used as a light-emitting region as a whole. In this way, the entire area of ​​the light-emitting layer 112 can be used as a light-emitting region, so that the life time of brightness degradation (for example, the time for the initial brightness to drop to 70%) can be extended. By changing the voltage of the first electrode 102 between the first voltage (Vg1) and the second voltage (Vg2), the position of the light-emitting region in the light-emitting layer 112 can be changed between the cathode side A and the anode side B. Figure 6 The intensity of the luminance can be controlled by varying between Vg1 and Vg2 as shown, by the potential difference (voltage) between the second electrode 108 and the third electrode 118 .

[0131] As such, the organic EL element involved in this embodiment forms an electron transport layer by an oxide semiconductor layer, and a first electrode for controlling the amount of carrier injection is arranged opposite to the electron transport layer via an insulating layer, so that the first electrode and the third electrode 118 as an anode are arranged opposite to each other, thereby controlling the amount of electrons injected into the light-emitting layer. The organic EL element involved in this embodiment can control the carrier balance of electrons and holes in the light-emitting layer through the action of the first electrode for controlling the amount of carrier injection. As a result, the current efficiency of the organic EL element can be improved and the life time can be extended.

[0132] In the structure of the existing organic EL element, the light-emitting layer does not degrade uniformly in the thickness direction as a whole. Since the light-emitting layer degrades unevenly, it is difficult to suppress the brightness degradation and the life of the organic EL element cannot be extended. However, the organic EL element 200 involved in one embodiment of the present invention can use the light-emitting layer 112 as a light-emitting area by controlling the voltage of the first electrode 102, thereby making the light-emitting layer 112 uniformly degraded in the thickness direction as a whole, thereby extending the life of the light-emitting layer 112 against brightness degradation. Therefore, even if the thickness of the light-emitting layer 112 is increased from the previous thickness (for example, 30nm) to 1.5 to 3.0 times, that is, 45nm to 90nm, the entire area in the thickness direction of the light-emitting layer 112 can emit light, thereby further extending the life of the organic EL element 200.

[0133] 4. Method for manufacturing organic EL element

[0134] Reference Figure 7A to Figure 7C , Fig. 8A and Figure 8B ,as well as Fig.9A and Fig. 9BAn example of a method for producing an organic EL element according to an embodiment of the present invention is described below. Figure 1 A method for manufacturing the bottom emission type organic EL element 200a shown in FIG.

[0135] Fig. 7A 1 shows a step of forming a first electrode 102, a first insulating layer 104, and an electron transport layer 106 on a substrate 100. As the substrate 100, for example, a transparent insulating substrate is used. As the transparent insulating substrate, an alkali-free glass substrate, a quartz substrate, such as aluminosilicate glass, aluminoborosilicate glass, etc. are used. In addition, as the transparent insulating substrate, a resin substrate such as polyimide, acrylic resin, epoxy resin, etc. can be used.

[0136] The first electrode 102 is formed of a transparent conductive film such as indium tin oxide (ITO) or indium zinc oxide (IZO). The transparent conductive film is formed with a thickness of 30 nm to 200 nm using a sputtering method. The first electrode 102 is formed by forming a resist mask using a photolithography process and etching the transparent conductive film formed on the first surface of the substrate 100. The first electrode 102 is preferably formed so that the end face is tapered in a cross-sectional view.

[0137] The first insulating layer 104 is formed of an inorganic insulating film such as a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film. The inorganic insulating film is formed using a plasma CVD (Chemical Vapor Deposition) method or a sputtering method. The first insulating layer 104 is formed to have a thickness of about 100 nm to 500 nm. The first insulating layer 104 is formed in a manner of burying the first electrode 102. At this time, by forming the end face of the first electrode 102 in a tapered shape, the first electrode 102 including the step portion can be reliably covered.

[0138] The first electron transport layer 106a is formed using an oxide semiconductor material. The first electron transport layer 106a is formed by sputtering a target formed by sintering a metal oxide. The oxide semiconductor film 107 formed on the first insulating layer 104 by sputtering is formed in a manner that overlaps with the first electrode 102 and the peripheral portion is arranged outside the first electrode 102. The oxide semiconductor film 107 formed by sputtering is formed with a thickness of 20nm to 200nm, for example, 30nm to 50nm.

[0139] The first electron transport layer 106a is formed of a metal oxide material, and as described above, preferably, a tin (Sn)-based oxide semiconductor (InGaSnO) that does not contain zinc (Zn), magnesium (Mg), etc. x 、InWSnO x 、InSiSnO x) is formed. In addition, in a tin (Sn)-based oxide semiconductor, as long as it contains 10atm% or more of tin (Sn), even if zinc (Zn) is contained, the composition change of zinc (Zn) will become small, so it does not completely deny the presence of zinc (Zn).

[0140] Figure 7B Indicates the step of forming the second electrode 108. The second electrode 108 is formed using a portion of the oxide semiconductor film that forms the first electron transport layer 106a. Specifically, in the oxide semiconductor film that forms the first electron transport layer 106a, the second electrode 108 is formed by reducing the resistance of the region corresponding to the second electrode 108. The oxide semiconductor film can achieve low resistance by forming oxygen vacancies. The oxygen vacancies of the oxide semiconductor film can be formed by laser irradiation treatment, plasma treatment, etc. Laser irradiation treatment is a treatment that generates oxygen vacancies by irradiating the oxide semiconductor film with laser. The oxide semiconductor film is heated by irradiating the laser, generating defects such as oxygen vacancies. The oxygen vacancies of the oxide semiconductor become donor defects, so the conductivity can be improved.

[0141] Fig. 8A Indicates a form in which laser treatment or plasma treatment is performed from the film surface side where the first electron transport layer 106a is formed. At this time, the mask layer 109 is used to cover the area corresponding to the first electron transport layer 106a in order not to generate oxygen vacancies. The mask layer 109 is formed using an organic resin material such as a photoresist, or an inorganic insulating material such as silicon oxide. Through this treatment, oxygen vacancies are generated in the area exposed from the mask layer 109. In the case of laser irradiation, a KrF excimer laser (wavelength 248nm), a XeCl excimer laser (wavelength 308nm), a XeF excimer laser (wavelength 351nm), etc. are used as laser light sources. In addition, in the case of plasma treatment, a plasma treatment device capable of generating hydrogen glow discharge plasma is used. By irradiating the oxide semiconductor film with hydrogen plasma, a reduction reaction can be performed to generate oxygen vacancies. In addition, oxygen vacancies can also be generated in the oxide semiconductor film by plasma treatment using rare gases such as helium (He), neon (Ne), and argon (Ar), ion implantation treatment of nitrogen ions, or plasma doping treatment.

[0142] Figure 8BIndicates the form of forming a low resistance region in the oxide semiconductor film by irradiating laser from the substrate 100 side. The laser emitted from an ultraviolet laser light source such as a KrF excimer laser (wavelength 248nm), a XeCl excimer laser (wavelength 308nm), or a XeF excimer laser (wavelength 351nm) does not penetrate the area where the first electrode 102 is formed, and irradiates the oxide semiconductor film in the area outside it. In the case of irradiating ultraviolet laser from the substrate 100 side, the first electrode 102 can be used as a mask (light shielding film) for the laser. Thus, the second electrode 108 is formed in self-alignment with respect to the first electrode 102. That is, if the laser is irradiated from the back side of the substrate 100, the end of the second electrode 108 and the end of the first electrode 102 can be formed to be roughly consistent.

[0143] Through Fig. 8A and Figure 8B As shown, by reducing the resistance of a portion of the oxide semiconductor film 107 forming the first electron transport layer 106a, the second electrode 108 can be formed without forming a new thin film. In addition, laser treatment and plasma treatment can be performed at room temperature, so the process can be simplified.

[0144] Figure 7C Indicates the step of forming the second insulating layer 120 and the third insulating layer 122 on the first electron transport layer 106a and the second electrode 108. The second insulating layer 120 and the third insulating layer 122 are formed using an inorganic insulating material in the same manner as the first insulating layer 104. In addition, the third insulating layer 122 can also be formed of an organic insulating material such as polyimide, acrylic resin, epoxy resin, etc. The second insulating layer 120 and the third insulating layer 122 are formed with a thickness of 100nm to 5000nm. For example, in the case of a planarization process, the third insulating layer 122 is preferably formed with a thickness of 2000nm to 5000nm.

[0145] Fig.9A The figure shows the steps of forming the opening 124b in the third insulating layer 122 and the opening 124a in the second insulating layer 120. The opening 124b and the opening 124a can be formed by continuously etching the third insulating layer 122 and the second insulating layer 120. In addition, the third insulating layer 122 and the second insulating layer 120 can be etched separately so that the opening width of the opening 124b is different from the opening width of the opening 124a. When the third insulating layer 122 is formed of a photosensitive organic resin material, the opening 124b can be formed by exposing using a photomask and developing. In either case, in order to form the organic EL element 200a, the opening 124b and the opening 124a are preferably processed so that the inner wall surface becomes tapered.

[0146] Fig. 9B 106b and the electron injection layer 110 are formed. The second electron transport layer 106b is formed using a metal oxide material, and as described above, is preferably a zinc (Zn)-based oxide semiconductor (ZnSiO x 、ZnGeO x 、ZnMgO x MgGaO x 、ZnGaO x That is, the second electron transport layer 106b preferably contains zinc oxide and at least one selected from silicon oxide, germanium oxide, magnesium oxide and gallium oxide. The second electron transport layer 106b can be formed by a sputtering method using a sputtering target sintered with a metal oxide, an atomic layer deposition (ALD) method, or a mist CVD (Mist Chemical Vapor Deposition) method.

[0147] The electron injection layer 110 is formed, for example, using a C12A7 electron crystal. The electron injection layer 110 can be formed by sputtering using a sputtering target of the C12A7 electron crystal. As a sputtering gas, at least one gas selected from the group consisting of He (helium), Ne (neon), N2 (nitrogen), Ar (argon), NO (nitrogen monoxide), Kr (krypton), and Xe (xenon) can be used.

[0148] In addition, magnesium zinc oxide (Mg x Zn y O) as the electron injection layer 110. For example, Mg 0.3 Zn 0.7 O has a relatively small work function of 3.1 eV and is stable in the atmosphere, and can be used as the electron injection layer 110 .

[0149] Since the second electron transport layer 106b and the electron injection layer 110 are both sputtered, they can be continuously formed in a vacuum. The second electron transport layer 106b and the electron injection layer 110 are formed in a manner that covers the opening 124a and the opening 124b. The second electron transport layer 106b is formed in a manner that contacts the first electron transport layer 106a at the bottom surface of the opening 124a, and further contacts the second insulating layer 120 and the third insulating layer 122.

[0150] Thereafter, the light emitting layer 112, the hole transport layer 114, the hole injection layer 116, and the third electrode 118 are formed to produce Figure 1 The organic EL element 200a shown in FIG. 1 is formed by using a vacuum evaporation method or a printing method. Figure 1As shown, the light-emitting layer 112 can be formed independently of each organic EL element, or can be formed continuously across multiple organic EL elements formed on the same plane. The hole transport layer and the hole injection layer are formed using a vacuum evaporation method or a coating method. Since the organic EL element 200a is a bottom emission type, the third electrode 118 is formed by sputtering a metal film such as aluminum (Al) stacked on a transparent conductive film such as indium tin oxide (ITO).

[0151] As described above, according to this embodiment, the organic EL element 200 can be formed by stacking thin films. The organic EL element 200 involved in this embodiment is a reverse stacking structure in which thin films are stacked from the cathode side, and the electron transport layer 106 and the electron injection layer 110 are formed of metal oxides, thereby having a structure that is not easily damaged during the manufacturing process. In addition, by forming the second electrode 108 and the electron transport layer 106 in the same layer without using an alkali metal, the burden of the manufacturing process is reduced, and the element can be made into a chemically stable structure.

[0152] Second Embodiment

[0153] In this embodiment, an organic EL element having a cathode structure different from that of the organic EL element described in Embodiment 1 is described. In the following description, portions different from those of Embodiment 1 are described, and description of common portions is omitted.

[0154] Fig.10 : represents the cross-sectional structure of the organic EL element 202a involved in the present embodiment. In the organic EL element 202a, the first electron transport layer 106a is arranged to be wider than the first electrode 102. At least a portion of the outer end of the first electron transport layer 106a is arranged outside the first electrode 102. Thus, the first electron transport layer 106a includes a region overlapping with the first electrode 102 across the first insulating layer 104, and further includes a region outside the region that does not overlap with the first electrode 102. The second electrode 108b is arranged on the surface of the first electron transport layer 106a that is opposite to the first insulating layer 104 side. The second electrode 108b is arranged in the region where the first electron transport layer 106a does not overlap with the first electrode 102, that is, the region between the end of the first electron transport layer 106a and the end of the first electrode 102.

[0155] The first electron transport layer 106a is formed using a metal oxide material, a metal nitride material, or a metal oxynitride material in the same manner as in the first embodiment. The first electron transport layer 106a is preferably formed of an oxide semiconductor material. The second electrode 108b is formed using a conductive material that makes ohmic contact with the first electron transport layer 106a. As the conductive material, for example, a metal material, a metal oxide material, a metal nitride material, or a metal oxynitride material can be used.

[0156] As a metal material forming the second electrode 108b, a metal material with high oxygen affinity, such as titanium (Ti), molybdenum (Mo), tungsten (W), tantalum (Ta), and cobalt (Co), can be used. For example, the second electrode 108b can be formed by titanium (Ti) and arranged in contact with the first electron transport layer 106a formed by an oxide semiconductor. At this time, titanium (Ti) with high oxygen affinity has the effect of depriving oxygen from the oxide semiconductor and generating oxygen vacancies in the oxide semiconductor. If the oxide semiconductor is deprived of oxygen, a donor energy level is formed and the resistance is reduced. As a result, the second electrode 108b and the first electron transport layer 106a can form an ohmic contact.

[0157] As the metal oxide material forming the second electrode 108b, indium tin oxide (In2O3·SnO2: ITO), indium zinc oxide (In2O3·ZnO: IZO), tin oxide (SnO2), titanium oxide (TiO x ) etc. As the metal nitride material, titanium nitride (TiN x ), zirconium nitride (ZrN x ) etc. As the metal nitride oxide material, titanium oxynitride (TiO x N y ), Tantalum Oxynitride (TaO x N y ), zirconium oxynitride (ZrO x N y ), Hafnium Oxynitride (HfO x N y ) etc. A trace amount of metal elements that improve conductivity may also be added to these metal oxide materials, metal nitride materials, and metal oxynitride materials. For example, niobium-doped titanium oxide (TiO x :Nb). By using such metal oxide materials, metal nitride materials, and metal oxynitride materials, an ohmic contact can be formed with the first electron transport layer 106a formed of the metal oxide material. x ), tungsten silicide (WSi x ), zirconium silicide (ZrSi x ) can also be used as the second electrode 108b.

[0158] The organic EL element 202a can increase the contact area by providing the second electrode 108b in contact with the surface of the first electron transport layer 106a. Thus, the organic EL element 202a can reduce the series resistance component and reduce the driving voltage. In addition, the organic EL element 202a can reduce the current density flowing into the second electrode 108b.

[0159] The second electrode 108b is preferably disposed in a manner surrounding the periphery of the first electron transport layer 106a. By configuring the second electrode 108b in this manner, the length from the central region of the first electron transport layer 106a to the second electrode 108b can be uniform over the entire periphery. However, the organic EL element 200a involved in one embodiment of the present invention is not limited to such a configuration, and the second electrode 108b only needs to be disposed in a partial region of the periphery of the first electron transport layer 106a. For example, Fig.11 As shown in FIG. 1 , the second electrode 108b may also be provided in a part of the peripheral region of the first electron transport layer 106a. As long as the resistance value of the first electron transport layer 106a is small (as long as the carrier concentration (electron concentration) is high), the second electrode 108b may be provided in a part of the peripheral region of the first electron transport layer 106a. Fig.11 As shown in FIG. 1 , the second electrode 108 b is provided so as to be in contact with a portion of the first electron transport layer 106 a .

[0160] Fig.12 FIG. 2 shows a cross-sectional structure of an organic EL element 202b according to this embodiment. In the organic EL element 202b, the second electrode 108b is provided in contact with the first insulating layer 104, and the first electron transport layer 106a is provided to cover the second electrode 108b. Fig.10 The organic EL element 202a shown in the figure is different. By providing the second electrode 108b in contact with the first insulating layer 104, the selectivity during etching can be improved, and the cathode patterning can be easily performed. In addition, in this specification, the organic EL element 202a and the organic EL element 202b are sometimes collectively referred to as "organic EL element 202".

[0161] The organic EL element 202b can increase the contact area by placing the upper surface of the second electrode 108b in contact with the first electron transport layer 106a. As a result, the organic EL element 202b can reduce the series resistance component and reduce the driving voltage. In addition, the organic EL element 202b can reduce the current density flowing into the second electrode 108b. Furthermore, the organic EL element 202b can make the area with fewer surface defects of the first electron transport layer 106a contact the second electrode 108b by first forming the second electrode 108b. In addition, Fig.12 The configuration of the second electrode 108b shown in FIG. Fig.11 As described above, it is provided so as to be in contact with a part of the peripheral portion of the first electron transport layer 106 a .

[0162] The organic EL element 202 according to the present embodiment is the same as that of the first embodiment except that the configurations of the second electrode 108 b and the first electron transport layer 106 a are different, and can exhibit the same operational effects.

[0163] Third Embodiment

[0164] This embodiment shows an organic EL element having a different cathode and electron transport layer configuration from the organic EL element shown in Embodiment 1. In the following description, the parts different from the first embodiment are described, and the description of the common parts is omitted.

[0165] Fig.13 : represents the cross-sectional structure of the organic EL element 204 involved in this embodiment. The difference of the organic EL element 204 is that the electron transport layer 106 (the first electron transport layer 106a, the second electron transport layer 106b) is not provided with an insulating layer between the electron transport layer 106a and the electron transport layer 106b, but is provided in a stacked manner on the first insulating layer 104. The first electron transport layer 106a and the second electron transport layer 106b are provided in a stacked manner. The second electron transport layer 106b is provided on the lower side of the second insulating layer 120 and is exposed from the opening 124 of the second insulating layer 120. The second electron transport layer 106b is in contact with the electron injection layer 110 at the opening 124.

[0166] The first electron transport layer 106a and the second electron transport layer 106b are preferably formed of different compositions. As in the first embodiment, the first electron transport layer 106a is preferably formed of a tin (Sn)-based oxide semiconductor (InGaSnO x 、InWSnO x 、InSiSnO x The second electron transport layer 106b is preferably made of a zinc (Zn)-based oxide semiconductor (ZnSiO x 、ZnMgO x 、ZnGaO x etc.) are formed.

[0167] Through Fig.13 As shown, the first electron transport layer 106a and the second electron transport layer 106b are stacked without providing an insulating layer between the electron transport layer 106a and the electron transport layer 106b, which can simplify the manufacturing process. The first electron transport layer 106a and the second electron transport layer 106b can be formed continuously when the film is formed by sputtering. In addition, the first electron transport layer 106a and the second electron transport layer 106b can be patterned simultaneously in the photolithography process.

[0168] The second electrode 108 is formed by reducing the resistance of the first electron transport layer 106a and the second electron transport layer 106b. Although not shown in the figure, the second electrode 108 may also be formed as shown in FIG. Fig.10 As described above, it is formed using a metal material, a metal nitride material, a metal oxide material, or a metal oxynitride material.

[0169] According to the organic EL element 204 of this embodiment, by stacking the first electron transport layer 106a and the second electron transport layer 106b without sandwiching an insulating layer therebetween, the structure and manufacturing process of the element can be simplified. The organic EL element 204 is the same as the first embodiment except that the first electron transport layer 106a and the second electron transport layer 106b and the second electrode 108 are different in structure, and can exert the same effect.

[0170] Fourth Embodiment

[0171] This embodiment shows an organic EL element having a second electron transport layer 106b and an electron injection layer 110 having different configurations from those of the organic EL element shown in Embodiment 1. In the following description, portions different from those of Embodiment 1 are described, and description of common portions is omitted.

[0172] Fig.14 1 shows a cross-sectional structure of an organic EL element 206 according to this embodiment. The organic EL element 206 is different from the organic EL element 200 shown in the first embodiment in that the second electron transport layer 106b and the electron injection layer 110 are patterned according to the arrangement of the opening 124a of the second insulating layer 120 and the opening 124b of the third insulating layer 122.

[0173] The second electron transport layer 106b and the electron injection layer 110 are provided in a manner covering the openings 124a and 124b. The ends of the second electron transport layer 106b and the electron injection layer 110 are located on the third insulating layer 122 and are arranged further inside than the ends of the light emitting layer 112. This structure can be obtained by processing the second electron transport layer 106b and the electron injection layer 110 using a photolithography process and an etching process before forming the light emitting layer 112.

[0174] As described in the first embodiment, the carrier concentration (electron concentration) of the second electron transport layer 106b is 10 11 / cm 3 ~10 17 / cm 3 The second electron transport layer 106b having semiconductor properties is not exposed at the end of the unit element by using a structure at the end of the organic EL element 206, so that the leakage current flowing through the adjacent unit element can be reduced. In addition, by using a structure in which the second electron transport layer 106b and the electron injection layer 110 are formed smaller than the light-emitting layer 112 in a top view and are covered by the light-emitting layer 112, the hole transport layer 114 can be prevented from contacting with the second electron transport layer 106b and the electron injection layer 110.

[0175] According to this embodiment, by forming the second electron transport layer 106b and the electron injection layer 110 from an oxide semiconductor, patterning can be performed by a photolithography process, and leakage current can be prevented from flowing in the organic EL element 206. The organic EL element 206 is the same as the first embodiment except that the second electron transport layer 106b and the electron injection layer 110 have different structures, and can exert the same effects. In addition, the structures of the second electron transport layer 106b and the electron injection layer 110 shown in this embodiment can also be applied to the organic EL element 202 shown in the second embodiment.

[0176] Fifth Embodiment

[0177] This embodiment shows an organic EL element having a third insulating layer 122 having a different structure from the organic EL element shown in Embodiment 1. In the following description, portions different from the first embodiment will be described, and description of common portions will be omitted.

[0178] Fig.15 : shows a cross-sectional structure of an organic EL element 208 according to this embodiment. In the organic EL element 208, the end of the opening 124b formed by the third insulating layer 122 is arranged on the inner side than the end of the opening 124a of the second insulating layer 120, which is different from the organic EL element 200 according to the first embodiment. In this embodiment, the third insulating layer 122 is preferably formed of a photosensitivity organic resin material such as polyimide, acrylic resin, epoxy resin, etc.

[0179] By forming the third insulating layer 122 from an organic resin material, the side wall of the opening 124b can be made into an inclined surface and a curved surface. In other words, by forming the third insulating layer 122 from an organic resin material, the opening end of the opening 124b can be formed into a curved surface shape in a cross-sectional view. By making the opening end of the opening 124b have a curved surface shape, the second electron transport layer 106b, the electron injection layer 110, the light-emitting layer 112, the hole transport layer 114, and the hole injection layer 116 can be formed from the upper surface of the first electron transport layer 106a along the surface of the third insulating layer 122. That is, it is possible to prevent defects such as cracks from occurring in the organic EL element 208 due to the step difference of the opening 124b.

[0180] The opening end of the opening 124a of the second insulating layer 120 is buried in the third insulating layer 122. Therefore, the end of the opening 124a of the second insulating layer 120a does not need to be formed into a tapered shape. Even if the end of the opening 124a of the second insulating layer 120 is vertical, it will not affect the step coverage of each layer such as the second electron transport layer 106b, the electron injection layer 110, and the light emitting layer 112.

[0181] As described above, according to the present embodiment, by setting the end face of the opening 124b of the third insulating layer 122 to a curved shape and covering the end of the opening 124a of the second insulating layer 120, it is possible to prevent the second electron transport layer 106b, the electron injection layer 110, the light emitting layer 112, etc. from being broken in steps. In addition, the opening 124a of the second insulating layer 120 does not need to be etched into a tapered shape, thereby improving productivity.

[0182] You can also Fig.16 As shown, the first electron transport layer 106a and the second electron transport layer 106b are stacked in the same manner as in the third embodiment, and then the electron injection layer 110 is stacked and patterned, and then the third insulating layer 122 is provided using a photosensitive resin material. By forming the first electron transport layer 106a and the second electron transport layer 106b, and the electron injection layer 110 from an inorganic material, the third insulating layer 122 can be formed from a photosensitive resin material on these layers and an opening 124b can be provided. As a result, the structure and manufacturing process of the element can be simplified.

[0183] The organic EL element 208 is the same as the first embodiment except for the difference in the configuration of the second insulating layer 120 and the third insulating layer 122, and can exhibit the same functions and effects. The configuration of this embodiment can be implemented in combination with other embodiments as appropriate.

[0184] Sixth Embodiment

[0185] This embodiment shows an organic EL element having a so-called normal-order stacking structure and having a first electrode for controlling the amount of carrier injection. Although the stacking order of the organic EL element according to this embodiment is different from that of the organic EL element in the first embodiment, the materials forming each layer are the same.

[0186] like Fig.17 As shown, the organic EL element 210 has a structure in which a third electrode 118, a hole injection layer 116, a hole transport layer 114, a light emitting layer 112, an electron injection layer 110, an electron transport layer 106, a first insulating layer 104, and a first electrode 102 are stacked from the substrate 100 side. The peripheral portion of the third electrode 118 is covered with the second insulating layer 120, and is in contact with the hole injection layer 116 at the opening 124.

[0187] The organic EL element 210 has an opening 124 of the second insulating layer 120, and the region where the third electrode 118, the hole injection layer 116, the hole transport layer 114, the light-emitting layer 112, the electron injection layer 110, and the electron transport layer 106 overlap to form a light-emitting region. The first electrode 102 is arranged to control the amount of carriers (electrons) injected into the light-emitting layer 112 by overlapping the electron transport layer 106 via the first insulating layer 104. The second electrode 108 is provided on the electron transport layer 106, and is arranged in a region that does not overlap with the opening 124.

[0188] Fig.17 The bottom emission type structure is shown in which the third electrode 118 is formed of a transparent conductive film and the first electrode 102 is formed of a metal film. On the other hand, although not shown in the figure, the organic EL element 210 can also be made into a top emission type by forming a light reflecting surface on the third electrode 118 and forming the first electrode 102 of a transparent conductive film.

[0189] Even in the top emission type, the organic EL element 210 has a stacked structure in which the first insulating layer 104 is interposed between the second electrode 108 and the first electrode 102, and at least the second insulating layer 120 is interposed between the second electrode 108 and the third electrode 118. In addition, the end of the second electrode 108 is arranged outside the end of the opening 124 of the second insulating layer 120, and has an offset region 126.

[0190] By providing a carrier injection amount control electrode (first electrode 102) on the electron transport layer via an insulating layer as shown in this embodiment, the amount of carriers injected into the light-emitting layer can be controlled by a bias voltage in an organic EL element having a positive-sequence stacked structure. Thus, an organic EL element 210 having the same effect as the organic EL element 200 shown in the first embodiment can be obtained.

[0191] Seventh Embodiment

[0192] In this embodiment, an example of a display device (organic EL display device) in which pixels are constituted by organic EL elements according to one embodiment of the present invention will be described.

[0193] Fig.18The equivalent circuit of a pixel 300 of a display device according to an embodiment of the present invention is shown. The pixel 300 includes a selection transistor 136, a driving transistor 138, and a capacitor 140 in addition to the organic EL element 200. The gate of the selection transistor 136 is electrically connected to the scanning signal line 132, the source is electrically connected to the data signal line 134, and the drain is electrically connected to the gate of the driving transistor 138. The source of the driving transistor 138 is electrically connected to the common potential line 144, and the drain is electrically connected to the second electrode 108 of the organic EL element 200. The capacitor 140 is electrically connected between the gate of the driving transistor 138 and the common potential line 144. The first electrode 102 of the organic EL element 200 is electrically connected to the carrier injection amount control signal line 146, and the third electrode 118 is electrically connected to the power line 142.

[0194] also, Fig.18 In order to specifically represent the connection structure of the organic EL element 200, the organic EL element 200 is not represented by a circuit symbol, but is schematically represented in a manner that the configuration of the electrodes corresponds to the actual element structure. Fig.18 Although the organic EL element 200 in the first embodiment is shown in FIG. 1 , the present embodiment is not limited thereto, and the organic EL elements shown in the second to sixth embodiments can be applied.

[0195] exist Fig.18 In the equivalent circuit of the pixel 300 shown in FIG. 1 , a scanning signal is supplied to the scanning signal line 132, and a data signal (video signal) is supplied to the data signal line 134. A power supply potential (Vdd) is supplied to the power supply line 142, and a ground potential (ground potential) or a potential (Vss) lower than the power supply potential (Vdd) is applied to the common potential line 144. Figure 6 As described above, a voltage (Vg) for controlling the amount of carriers injected into the light-emitting layer 112 is applied to the carrier injection amount control signal line 146. The voltage (Vg) for controlling the amount of carriers injected may be a constant positive voltage or a constant voltage such as Figure 6 The voltage shown varies between given voltages Vg1 and Vg2.

[0196] exist Fig.18In the pixel 300 shown, when the selection transistor 136 is turned on, a voltage based on the data signal is applied to the gate of the driving transistor 138 from the data signal line 134. The capacitor 140 maintains the voltage between the source and the gate of the driving transistor 138. When the gate of the driving transistor 138 is turned on, a current flows from the power supply line 142 into the organic EL element 200 to emit light. At this time, if a voltage (Vg) for controlling the amount of carrier injection is applied to the first electrode 102, not only the luminous intensity of the organic EL element 200 can be controlled, but also the position of the region where electrons and holes in the light-emitting layer 112 recombine (in other words, the light-emitting region) can be controlled. That is, the carrier balance in the light-emitting layer 112 can be controlled.

[0197] According to the present embodiment, the pixel 300 is formed by an organic EL element provided with a carrier injection amount control electrode (first electrode 102), and a carrier injection amount control signal line is provided and connected to the carrier injection amount control electrode (first electrode 102), so that the light emission state of the organic EL element can be controlled. That is, by controlling the light emission of the organic EL element by the carrier injection amount control electrode instead of only the driving transistor, the degradation of the organic EL element can be suppressed, and the reliability of the organic EL display device can be improved.

[0198] Eighth Embodiment

[0199] In this embodiment, an example of a display device (organic EL display device) in which pixels are constituted by organic EL elements according to one embodiment of the present invention will be described.

[0200] Fig.19 An example of an equivalent circuit of a pixel 302 provided in the display device involved in the present embodiment is shown. The pixel 302 includes a selection transistor 136, a driving transistor 138, and a capacitor 140 in addition to the organic EL element 200, similarly to the seventh embodiment. The gate of the selection transistor 136 is electrically connected to the scanning signal line 132, the source is electrically connected to the data signal line 134, and the drain is electrically connected to the gate of the driving transistor 138. The source of the driving transistor 138 is electrically connected to the common potential line 144, and the drain is electrically connected to the second electrode 108 of the organic EL element 200. The capacitor 140 is electrically connected between the gate of the driving transistor 138 and the common potential line 144. The first electrode 102 of the organic EL element 200 is electrically connected to the carrier injection amount control signal line 146, and the third electrode 118 is electrically connected to the power line 142. In addition, Fig.19 The case where the selection transistor 136 and the driving transistor 138 are of a dual-gate type is shown.

[0201] Fig. 20 FIG. 2 is a top view of a pixel 302 of a display device according to this embodiment. Fig.21A Indicates along Fig. 20 The cross-sectional structure of the A1-A2 line is shown. Fig.21B Indicates along Fig. 20 In the following description, reference is made to these drawings.

[0202] The pixel 302 is provided with a selection transistor 136, a drive transistor 138, a capacitor 140, and an organic EL element 200. Fig. 20 The top view of the pixel 302 shown in the figure shows the arrangement of the first electrode 102 , the first electron transport layer 106 a , and the opening 124 which are components of the organic EL element 200 .

[0203] The driving transistor 138 is constituted by including a first oxide semiconductor layer 152a, a first gate electrode 154a, and a second gate electrode 156a. The first gate electrode 154a and the second gate electrode 156a are configured in a manner having an overlapping region with the first oxide semiconductor layer 152a interposed therebetween. The first insulating layer 104 is disposed between the first oxide semiconductor layer 152a and the substrate 100. The first gate electrode 154a is disposed between the first insulating layer 104 and the substrate 100. In addition, the second insulating layer 120 is disposed between the first oxide semiconductor layer 152a and the second gate electrode 156a. In other words, the first oxide semiconductor layer 152a is disposed between the first insulating layer 104 and the second insulating layer 120, and the first insulating layer 104, the first oxide semiconductor layer 152a, and the second insulating layer 120 are interposed between the first gate electrode 154a and the second gate electrode 156a.

[0204] In this embodiment, the driving transistor 138 has a dual-gate structure in which the first oxide semiconductor layer 152a is sandwiched by the first gate electrode 154a and the second gate electrode 156a. The driving transistor 138 forms a channel region in a region where the first oxide semiconductor layer 152a overlaps with one or both of the first gate electrode 154a and the second gate electrode 156a. In addition, the first oxide semiconductor layer 152a may be provided with a low resistance region having a lower specific resistance than the region forming the channel region in an outer region that does not overlap with the first gate electrode 154a and the second gate electrode 156a. Fig.21A The region with low specific resistance is represented as a source region 158a and a drain region 160a.

[0205] In the first oxide semiconductor layer 152a, the carrier concentration in the region serving as the channel region is preferably 1×10 14 / cm 3 ~5×10 18 / cm 3The carrier concentration of the source region 158a and the drain region 160a is preferably 1×10 19 / cm 3 ~5×10 21 / cm 3 The carrier concentration of the source region 158a and the drain region 160a can be increased, for example, by increasing the density of donor levels formed by oxygen deficiencies in the first oxide semiconductor layer 152a. The oxygen vacancies in the first oxide semiconductor layer 152a can be formed by plasma treatment using a rare gas such as helium (He) or argon (Ar), hydrogen plasma treatment, or laser irradiation.

[0206] The driving transistor 138 includes a first transparent conductive layer 148a and a second transparent conductive layer 148b disposed between the first oxide semiconductor layer 152a and the first insulating layer 104. The first transparent conductive layer 148a and the second transparent conductive layer 148b are disposed separately from each other. In addition, a conductive layer 150a is disposed between the first transparent conductive layer 148a and the first oxide semiconductor layer 152a, and a conductive layer 150b is disposed between the second transparent conductive layer 148b and the first oxide semiconductor layer 152a. The conductive layer 150a is disposed on the inner side less than the end of the first transparent conductive layer 148a, and the conductive layer 150b is disposed on the inner side less than the end of the second transparent conductive layer 148b. The first transparent conductive layer 148a and the conductive layer 150a are disposed in contact with the drain region 160a, and the second transparent conductive layer 148b and the conductive layer 150b are disposed in contact with the source region 158a.

[0207] The first gate electrode 154a and the second gate electrode 156a are arranged in an overlapping manner in a region where the first transparent conductive layer 148a and the second transparent conductive layer 148b are separated. The first transparent conductive layer 148a and the second transparent conductive layer 148b may be arranged so that a part of the region overlaps with one or both of the first gate electrode 154a and the second gate electrode 156a. By arranging at least one of the first transparent conductive layer 148a and the second transparent conductive layer 148b to overlap with one or both of the first gate electrode 154a and the second gate electrode 156a in a manner adjacent to the channel region of the first oxide semiconductor layer 152a, the drain current of the driving transistor 138 can be increased.

[0208] The source region 158a of the driving transistor 138 is electrically connected to the common potential line 144 via a contact hole provided in the first insulating layer 104. On the other hand, the drain region 160a side of the first oxide semiconductor layer 152a is provided so as to extend to the region where the organic EL element 200 is provided. That is, the first oxide semiconductor layer 152a is provided so as to overlap with the first electrode 102 via the first insulating layer 104. Furthermore, the carrier concentration of the region where the first oxide semiconductor layer 152a overlaps with the first electrode 102 is adjusted to 1×10 14 / cm 3 ~1×10 19 / cm 3 , thereby performing the function as the first electron transport layer 106a. In addition, the first oxide semiconductor layer 152a includes a region adjacent to the region that functions as the first electron transport layer 106a and functions as the second electrode 108. The region in which the first oxide semiconductor layer 152a functions as the second electrode 108 is a region continuous from the drain region 160a. By controlling the carrier concentration of the first oxide semiconductor layer 152a for each region as shown in this embodiment, a structure in which the driving transistor 138 and the organic EL element 200 are connected by an oxide semiconductor layer can be formed. As a result, the structure of the pixel 302 can be simplified.

[0209] like Fig.21B As shown, the selection transistor 136 has the same structure as the driving transistor 138. That is, the selection transistor 136 includes a second oxide semiconductor layer 152b, a first gate electrode 154b, and a second gate electrode 156b. In addition, the third transparent conductive layer 148c and the conductive layer 150c, and the fourth transparent conductive layer 148d and the conductive layer 150d are connected to the second oxide semiconductor layer 152b. The second oxide semiconductor layer 152b can also form a source region 158b and a drain region 160b as a low specific resistance region. The conductive layer 150c forms the data signal line 134.

[0210] The drain region 160b of the selection transistor 136 is electrically connected to the first gate electrode 154a of the driving transistor 138 via a contact hole provided in the first insulating layer 104. For example, the fourth transparent conductive layer 148d and the conductive layer 150d may be provided between the drain region 160b and the first gate electrode 154a. The drain region 160b of the selection transistor 136 is further electrically connected to the second gate electrode 156a of the driving transistor 138 via a contact hole provided in the second insulating layer 120. In this way, the drain region 160b provided in the second oxide semiconductor layer 152b is easily electrically connected to the gate electrode of the driving transistor 138 by being stacked with the fourth transparent conductive layer 148d and the conductive layer 150d.

[0211] The capacitor element 140 is formed in a region where the fourth transparent conductive layer 148d overlaps with the capacitor electrode 162 via the first insulating layer 104. The capacitor electrode 162 is formed so as to also serve as the common potential line 144.

[0212] In this embodiment, the oxide semiconductor layer 152 can be made of the same material as the oxide semiconductor material described in Embodiment 1. Inorganic insulating materials are used for the first insulating layer 104 and the second insulating layer 120. As the inorganic insulating material, silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, or the like is used.

[0213] In addition, as the metal oxide material for the transparent conductive layer 148, titanium oxide (TiO x ) etc. As metal nitride materials, titanium nitride (TiN x ), zirconium nitride (ZrN x ) etc. As the metal nitride oxide material, titanium oxynitride (TiO x N y ), Tantalum Oxynitride (TaO x N y ), zirconium oxynitride (ZrO x N y ), Hafnium Oxynitride (HfO x N y ) etc. In addition, trace metal elements that improve conductivity may be added to these metal oxide materials, metal nitride materials, and metal oxynitride materials. For example, niobium-doped titanium oxide (TiO x :Nb).

[0214] As the conductive layer 150, a metal material with high conductivity such as aluminum (Al) and copper (Cu) can be used. For example, the conductive layer 150c (data signal line 134) is made of aluminum alloy, copper alloy, or silver alloy. In addition, the common potential line 144 and the first gate electrode 154 formed in the same layer as the common potential line 144 are also preferably made of aluminum alloy, copper alloy, or silver alloy. The second gate electrode 156 and the scanning signal line 132 are made of metal materials such as aluminum (Al), molybdenum (Mo), tungsten (W), and zirconium (Zr). As aluminum alloys, aluminum-neodymium alloy (Al-Nd), aluminum-titanium alloy (Al-Ti), aluminum-silicon alloy (Al-Si), aluminum-neodymium-nickel alloy (Al-Nd-Ni), aluminum-carbon-nickel alloy (Al-C-Ni), copper-nickel alloy (Cu-Ni), etc. can be applied. If such a metal material is used, it has heat resistance and can reduce wiring resistance.

[0215] The organic EL element 200 has the same structure as that shown in the first embodiment. The organic EL element 200 is electrically connected to the driving transistor 138. In the organic EL element 200, the region corresponding to the second electrode 108 is formed continuously from the first oxide semiconductor layer 152a of the driving transistor 138. With this structure, it is possible to simplify the routing of wiring and improve the aperture ratio of the pixel 302 (the ratio of the region where the organic EL element actually emits light to the area occupied by one pixel). In addition, the organic EL element 200 can be replaced with the organic EL element shown in the second to sixth embodiments.

[0216] In addition, in order to increase the aperture ratio of the pixel, the electron mobility of the first electron transport layer 106a must be increased. For example, the pixel pitch in an 85-inch display panel with a resolution of 8K×4K (7680×4320 pixels) becomes about 244μm. Here, assuming a rectangular pixel, the length in the long side direction becomes about 732μm. When the time from the application of voltage to the organic EL element to the light emission is set to about 4 to 5μsec, and a region corresponding to the second electrode 108 is provided at one end of the long side direction of the rectangular pixel, if the carrier (electron) mobility of the first electron transport layer 106a is not 10cm 2 / V·sec or more, preferably 20cm 2 / V·sec or more, it is difficult for carriers (electrons) to reach the other end in the long side direction of the pixel.

[0217] Of course, if the region corresponding to the second electrode 108 is arranged so as to surround the four sides of the rectangular pixel, the carriers will drift from the four sides to the center, so the carrier (electron) mobility only needs to be 2.5 cm 2 However, in this case, the effective light emitting area per pixel is reduced, and the reduction in aperture ratio becomes a problem.

[0218] In this case, if the oxide semiconductor material is as exemplified in this embodiment, the required carrier (electron) mobility can be achieved. On the other hand, the electron transport layer formed of organic materials as described in JP-A-2007-149922 and JP-A-2007-157871 has a carrier (electron) mobility of less than 2.5 cm 2 / V·sec, so there is a problem that the display panel cannot be made larger and higher in definition.

[0219] The display device according to this embodiment uses an oxide semiconductor layer as an electron transport layer forming an organic EL element, and can manufacture the electron transport layer 106 by the same manufacturing process as elements such as a drive transistor and a selection transistor manufactured using an oxide semiconductor layer. In addition, the display device according to this embodiment provides a carrier injection amount control electrode (first electrode 102) in the organic EL element, and configures an electron transport layer with high carrier (electron) mobility with respect to the carrier injection amount control electrode (first electrode 102) via an insulating layer (first insulating layer 104), so that the light emission intensity within the pixel surface can be uniformed and processed with high definition.

[0220] (Description of the label)

[0221] 100 Substrate

[0222] 102 1st electrode

[0223] 104 1st insulation layer

[0224] 106 Electron Transport Layer

[0225] 107 Oxide semiconductor film

[0226] 108 Second electrode

[0227] 109 mask layer

[0228] 110 Electron injection layer

[0229] 112 Luminous layer

[0230] 114 Hole transport layer

[0231] 116 Hole injection layer

[0232] 118 The third electrode (anode)

[0233] 120 Second insulation layer

[0234] 122 Third insulation layer

[0235] 124 Opening

[0236] 126 Offset Area

[0237] 128 Power Supply

[0238] 130 Switch

[0239] 132 Scan signal line

[0240] 134 Data signal line

[0241] 136 Select transistor

[0242] 138 Driver transistor

[0243] 140 Capacitor Components

[0244] 142 Power cord

[0245] 144 Common potential line

[0246] 146 Carrier injection amount control signal line

[0247] 148 transparent conductive layer

[0248] 150 Conductive layer

[0249] 152 oxide semiconductor layer

[0250] 154 1st gate electrode

[0251] 156 2nd gate electrode

[0252] 158 Source region

[0253] 160 Drain region

[0254] 162 Capacitor Electrode

[0255] 200~210 Organic EL components

[0256] 300, 302 pixels

Claims

1. An organic electroluminescent element, characterized in that have: A first electrode (102); a third electrode (118) having a region facing the first electrode; a first insulating layer (104) between the first electrode and the third electrode; a second insulating layer (120) between the first insulating layer and the third electrode; an electron transport layer (106) between the first insulating layer and the third electrode; a light-emitting layer (112), which is between the electron transport layer and the third electrode and contains an organic electroluminescent material; An electron injection layer (110) between the electron transport layer and the light emitting layer; a second electrode (108), which is disposed between the first insulating layer and the second insulating layer and is electrically connected to the electron transport layer; as well as a third insulating layer (122) between the second insulating layer and the third electrode; The second insulating layer has a first opening (124a); The third insulating layer includes a second opening (124b) overlapping the first opening; The first opening and the second opening have an overlapping region where the third electrode, the light-emitting layer, the electron injection layer, the electron transport layer, the first insulating layer, and the first electrode overlap; The electron transport layer (106) includes a first electron transport layer (106a) in contact with the first insulating layer (104), and a second electron transport layer (106b) between the first electron transport layer and the electron injection layer. The carrier concentration of the first electron transport layer is higher than the carrier concentration of the second electron transport layer. The band gap of the first electron transport layer is 3.0 eV or more, and the band gap of the second electron transport layer is 3.4 eV or more, The second electrode is arranged outside the overlapping region, The first electron transport layer includes an offset region (126) between an end of the second electrode and an end of the first opening, wherein the offset region overlaps with the first electrode. The second electrode is in contact with the first electron transport layer in a region outside the overlapping region. The second electrode includes an overlapping portion overlapping with the first electrode and a non-overlapping portion not overlapping with the first electrode, and The first electron transport layer and the second electron transport layer are in contact with each other at the first opening, the first electron transport layer has a region sandwiched between the first insulating layer and the second insulating layer, and the second electron transport layer is in contact with the second insulating layer and the third insulating layer.

2. The organic electroluminescent element according to claim 1, wherein The electron mobility of the first electron transport layer (106a) is higher than the electron mobility of the second electron transport layer (106b).

3. The organic electroluminescent element according to claim 1, wherein The first electron transport layer (106a) and the second electron transport layer (106b) include an oxide semiconductor, and the second electron transport layer is thicker than the first electron transport layer.

4. The organic electroluminescent element according to claim 3, wherein The first electron transport layer (106a) is a tin (Sn)-based oxide semiconductor that does not contain magnesium (Mg), and the second electron transport layer (106b) is a zinc (Zn)-based oxide semiconductor that does not contain tin (Sn).

5. The organic electroluminescent element according to claim 3, wherein The first electron transport layer (106a) comprises tin oxide, indium oxide, and at least one selected from gallium oxide, tungsten oxide, and silicon oxide; The second electron transport layer (106b) includes zinc oxide and at least one selected from silicon oxide, magnesium oxide and gallium oxide.

6. The organic electroluminescent element according to claim 3, wherein The second electrode (108) includes an oxide semiconductor.

7. The organic electroluminescent element according to claim 1, wherein The electron injection layer is C12A7 (12CaO·7Al2O3) electron crystal.

8. The organic electroluminescent element according to claim 1, wherein The electron injection layer comprises Mg 0.3 Zn 0.7 Oxide semiconductor.

9. The organic electroluminescent element according to claim 1, wherein The first electrode (102) has light-transmitting properties, and the third electrode (118) has a light-reflecting surface.

10. The organic electroluminescent element according to claim 1, wherein The first electrode (102) has light reflectivity, and the third electrode (118) has light transmittance.

11. The organic electroluminescent element according to claim 1, wherein The offset region (126) is 1 μm to 5 μm.

12. The organic electroluminescent element according to claim 1, wherein A voltage having the same polarity as that of the third electrode (118) is applied to the first electrode (102).

13. The organic electroluminescent element according to claim 1, wherein A voltage having the same polarity as that of the second electrode (108) is applied to the first electrode (102) to emit light.

14. The organic electroluminescent element according to claim 1, wherein The light emission brightness is controlled by the voltage applied to the second electrode (108).

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