WO2019194010A1

WO2019194010A1 - Transparent conductor, method for manufacturing same, and organic device

Info

Publication number: WO2019194010A1
Application number: PCT/JP2019/012532
Authority: WO
Inventors: 新開　浩; 祥久玉川; 俊治松原; 喜彦田邊
Original assignee: Tdk株式会社
Priority date: 2018-04-06
Filing date: 2019-03-25
Publication date: 2019-10-10
Also published as: JP2021106072A

Abstract

Provided is a transparent conductor 10 for an organic device having a light emission layer, wherein: the transparent conductor 10 comprises, in the stated order, a transparent substrate 11, a first metal oxide layer 12, a metal layer 18 containing silver or a silver alloy, and a second metal oxide layer 14; and the transparent conductor 10 satisfies equation (1) or (2), where λ [nm] is the wavelength of light from the light emission layer, n is the refractivity of the second metal oxide layer 14 at λ, and d [nm] is the thickness of the second metal oxide layer 14. (Equation 1) 0 < n × d/λ ≤ 0.0008 × λ – 0.3393 (Equation 2) 0.0012 × λ – 0.3302 ≤ n × d/λ ≤ 0.0015 × λ – 0.1975 [In equations (1) and (2), d is greater than 0 and less than or equal to 210 nm.]

Description

Transparent conductor, method for producing the same, and organic device

The present disclosure relates to a transparent conductor, a manufacturing method thereof, and an organic device.

The transparent conductor is used as a transparent electrode such as a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence panel (organic EL, inorganic EL), and a solar cell. The transparent conductor is required to have high light transmittance in some applications, for example, so as not to be an obstacle to light absorption and emission (for example, Patent Document 1).

On the other hand, organic EL is a technology that utilizes the electroluminescence phenomenon of organic materials, and attempts have been made to improve the light extraction efficiency. For example, Patent Document 2 discusses optimizing the optical path length of light emitted from the light emitting layer of the organic light emitting element to the substrate side and reflected by the reflective film to increase the intensity of the emitted light. The transparent conductor of such a light-emitting element, ITO was added tin (Sn) to indium oxide _(In 2 _{O 3),} or, IZO is added zinc (Zn) to indium oxide _(In 2 _{O 3)} It is used.

International Publication No. 2012/002113 JP 2002-252087 A

The transparent conductor is required to have flexibility in each application. In the case of a conventional ITO film, it is difficult to improve flexibility because it is necessary to increase the thickness in order to ensure conductivity. Therefore, as a transparent conductor having both excellent conductivity and flexibility, a transparent conductor having a three-layer structure in which a metal layer is laminated between a pair of metal oxide layers is considered as a promising material.

However, according to the study by the present inventors, such a transparent conductor can be emitted even when the transmittance of the transparent conductor itself is maximized when an organic device is constructed by laminating the light emitting layer. It has been found that there is a phenomenon that the light extraction efficiency from the layer is lowered. Therefore, an object of one aspect of the present disclosure is to provide a transparent conductor capable of sufficiently increasing light extraction efficiency from a light emitting layer and a method for manufacturing the transparent conductor. In another aspect, this indication aims at providing an organic device provided with the above-mentioned transparent conductor.

In one aspect, the present invention is a transparent conductor for an organic device having a light emitting layer, which is a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal. The oxide layers are provided in this order, the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. ], A transparent conductor satisfying the following formula (1) or (2) is provided.
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. In addition, when the light from the light emitting layer of an organic device contains a some wavelength, what is necessary is just to satisfy | fill said Formula (1) or Formula (2) in the at least 1 wavelength among several wavelengths.

The second metal oxide layer of the transparent conductor satisfies the above formula (1) or formula (2). Thus, when the 2nd metal oxide layer satisfy | fills said Formula (1) or Formula (2), the extraction efficiency of the light light-emitted from an organic layer can be made high. This is presumably due to the fact that the phase difference between the light extracted directly from the light emitting layer and the light reflected at the boundary between the layers is uniform. The second metal oxide layer may be composed of a plurality of metal oxide films, in which case the total film thickness of the plurality of metal oxide layers (that is, the thickness d of the second metal oxide film) is expressed by the above formula. What is necessary is just to satisfy | fill (1) or Formula (2).

The second metal oxide layer forming the surface opposite to the transparent substrate may contain indium oxide as a main component. Thereby, the hole injection efficiency can be increased and the light emission efficiency can be increased. When the second metal oxide layer is composed of a plurality of metal oxide films, the metal oxide film that is in contact with the organic layer and that forms the outermost surface may contain indium oxide as a main component.

The work function of the second metal oxide layer that forms the surface opposite to the transparent substrate and is in contact with the organic layer may be 4.7 eV or more. Thereby, the internal quantum efficiency of the organic layer can be increased.

In another aspect, the present disclosure provides a transparent conductor for an organic device, which includes a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer in this order. The second metal oxide layer is manufactured so as to satisfy the following formula (1) or formula (2) based on the wavelength λ [nm] of light emitted from the light emitting layer of the organic device. Provided is a method for producing a transparent conductor, wherein at least one of a refractive index n of a second metal oxide layer at a thickness d [nm] and λ is adjusted.
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. In addition, when the light from the light emitting layer of an organic device contains a some wavelength, what is necessary is just to satisfy | fill said Formula (1) or Formula (2) in the at least 1 wavelength among several wavelengths.

In the method for producing a transparent conductor, the second metal oxide layer satisfies the above formula (1) or formula (2). Thus, by arranging the second metal oxide layer satisfying the above formula (1) or formula (2) on the light emitting layer side, the extraction efficiency of light emitted from the organic layer can be increased.

In still another aspect, the present disclosure provides an organic device including a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, a second metal oxide layer, and a light emitting layer in this order. When the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm], An organic device satisfying the following formula (1) or (2) is provided.
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. In addition, when the light from the light emitting layer of an organic device contains a some wavelength, what is necessary is just to satisfy | fill said Formula (1) or Formula (2) in the at least 1 wavelength among several wavelengths.

The second metal oxide layer of the transparent conductor of the organic device satisfies the above formula (1) or formula (2). Thus, when the 2nd metal oxide layer satisfy | fills said Formula (1) or Formula (2), the extraction efficiency of the light light-emitted from an organic layer can be made high. This is presumably due to the fact that the phase difference between the light extracted directly from the light emitting layer and the light reflected at the boundary between the layers is uniform.

In one aspect, it is possible to provide a transparent conductor capable of sufficiently increasing the light extraction efficiency from the light emitting layer and a method for manufacturing the transparent conductor. In another aspect, an organic device comprising the transparent conductor can be provided.

FIG. 1 is a cross-sectional view schematically showing one embodiment of a transparent conductor. FIG. 2 is a diagram schematically illustrating an embodiment of an organic device. FIG. 3 is a diagram schematically showing a propagation path of light from the light emitting layer. FIG. 4 is a diagram illustrating an example of a simulation result of the organic device of FIG. FIG. 5 is a graph showing the relationship between the wavelength λ of light used in the simulation and n × d / λ. FIG. 6 is a graph showing the relationship between the current value passed through the organic EL device and the luminous efficiency (EQE). FIG. 7 is a graph showing a simulation result of Experimental Example 1. FIG. 8 is a graph showing a simulation result of Experimental Example 1. FIG. 9 is a graph showing a simulation result of Experimental Example 2.

Hereinafter, embodiments of the present invention will be described below with reference to the drawings as the case may be. However, the following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. In the description, the same reference numerals are used for elements having the same structure or the same function, and redundant description is omitted in some cases. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a transparent conductor. The transparent conductor 10 has a laminated structure in which a transparent substrate 11, a first metal oxide layer 12, a metal layer 18, and a second metal oxide layer 14 are arranged in this order.

“Transparent” in this specification means that visible light is transmitted, and the light may be scattered to some extent. Regarding the degree of light scattering, the required level varies depending on the application of the transparent conductor 10. What has light scattering generally referred to as translucent is also included in the concept of “transparency” in this specification.

The transparent substrate 11 is not particularly limited, and may be a flexible transparent resin substrate. For example, the organic resin film may be an organic resin sheet. Examples of the transparent substrate 11 include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyolefin films such as polyethylene and polypropylene, polycarbonate films, acrylic films, norbornene films, polyarylate films, and polyether sulfone. A film, a diacetyl cellulose film, a polyimide, a triacetyl cellulose film, etc. are mentioned. Of these, polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are preferable. One of the above may be used alone, or two or more may be combined.

The thickness of the transparent substrate 11 is, for example, 200 μm or less from the viewpoint of further increasing the flexibility of the transparent conductor 10. The refractive index of the transparent substrate is, for example, 1.50 to 1.70 from the viewpoint of the transparent conductor 10 having excellent optical characteristics. The refractive index in this specification is a value measured under the conditions of λ = 633 nm and a temperature of 20 ° C. The transparent substrate 11 may be subjected to at least one surface treatment selected from the group consisting of corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, and ozone treatment. .

The transparent substrate 11 is not limited to a transparent resin substrate, and may be a molded product of an inorganic compound such as soda lime glass, non-alkali glass, and quartz glass. On the other hand, when the transparent substrate 11 is a transparent resin substrate, the transparent conductor 10 can be made excellent in flexibility. Thereby, the transparent conductor 10 can be used suitably as a transparent conductor for flexible organic devices.

The first metal oxide layer 12 is a transparent layer containing a metal oxide. The first metal oxide layer 12 has a function of protecting the metal layer 18. The first metal oxide layer 12 may be made of a metal oxide different from ITO (indium tin oxide). When the 1st metal oxide layer 12 does not contain ITO, corrosion of the silver alloy contained in the metal layer 18 can be suppressed.

From the viewpoint of achieving both transparency and corrosion resistance at a higher level, the first metal oxide layer 12 is composed of, for example, four components of zinc oxide, tin oxide, indium oxide and titanium oxide, or zinc oxide, indium oxide and oxide. You may contain 3 components of titanium as a main component. By including the above four components, the first metal oxide layer 12 can have sufficiently high conductivity and transparency.

Zinc oxide contained in the first metal oxide layer 12 is, for example, ZnO, and indium oxide is, for example, In ₂ O ₃ . Titanium oxide is, for example, TiO _2. Tin oxide is, for example, SnO _2. The ratio of metal atoms to oxygen atoms in each of the metal oxides may deviate from the stoichiometric ratio. Further, another oxide having a different oxidation number may be included. The first metal oxide layer 12 may contain tin oxide, but the content of tin oxide (SnO ₂ ) is small from the viewpoint of reducing the corrosion of silver or silver alloy contained in the metal layer 18. The tin oxide may not be contained.

When the first metal oxide layer 12 includes the above three components as main components, the total content of the three components is 90% by mass or more in terms of ZnO, In ₂ O ₃ and TiO ₂ , respectively. It is preferably 95% by mass or more.

The thickness of the first metal oxide layer 12 is, for example, 60 nm or less from the viewpoint of improving flexibility. On the other hand, from the viewpoint of further improving corrosion resistance and improving productivity, the thickness is, for example, 5 nm or more.

In the first metal oxide layer 12, when the three components of zinc oxide, indium oxide and titanium oxide are converted into ZnO, In ₂ O ₃ and TiO ₂ respectively, the content of ZnO with respect to the total of the three components is , 20 to 85 mol%, or 30 to 80 mol%. When converted in the same manner, the content of In ₂ O ₃ with respect to the total of the above three components may be 10 to 35 mol% or 10 to 25 mol% from the viewpoint of achieving both high conductivity and high corrosion resistance. May be.

When converted in the same manner, the content of TiO ₂ with respect to the total of the above three components is preferably 5 to 15 mol%, and preferably 7 to 13 mol% from the viewpoint of achieving both transparency and excellent corrosion resistance. More preferred.

When the first metal oxide layer 12 contains the above four components as main components, the first metal oxide layer 12 contains four components of zinc oxide, indium oxide, titanium oxide, and tin oxide, respectively, ZnO, In When converted to ₂ O ₃ , TiO _2, and SnO ₂ , the content of zinc oxide relative to the total of the four components may be 20 to 68 mol% from the viewpoint of achieving both high conductivity and excellent corrosion resistance. .

When converted in the same manner, the content of indium oxide with respect to the total of the above four components is 15 to 35 mol% from the viewpoint of improving the corrosion resistance while sufficiently reducing the surface resistance. When converted in the same manner, the content of titanium oxide with respect to the total of the above four components is 5 to 20 mol% from the viewpoint of securing visible light transmittance and increasing alkali resistance. When converted in the same manner, the content of tin oxide with respect to the total of the four components is, for example, 5 to 40 mol% from the viewpoint of achieving both high transparency and excellent corrosion resistance.

The first metal oxide layer 12 may be composed of a plurality of metal oxide films having different compositions, and some of the plurality of metal oxide films are a metal nitride film or a metal oxynitride film. There may be. In that case, the film in contact with the transparent substrate 11 may be a metal oxide film, a metal nitride film, or a metal oxynitride film containing the above four components or other components, and the film in contact with the metal layer 18 is It may be a metal oxide film containing the above three components. The metal oxide film in contact with the transparent substrate 11 may contain, for example, silicon oxide. The metal nitride film in contact with the transparent substrate 11 may contain silicon nitride. The metal oxynitride film in contact with the transparent substrate 11 may contain silicon oxynitride (Si—O—N). In the present disclosure, silicon corresponds to a metal element, and silicon oxide and silicon nitride correspond to a metal oxide and a metal nitride, respectively.

The first metal oxide layer 12 may have low conductivity or may be an insulator. In this case, the conductivity of the transparent conductor 10 may be borne by the metal layer 18 and the second metal oxide layer 14. The first metal oxide layer 12 can be manufactured by a vacuum film formation method such as a vacuum evaporation method, a sputtering method, an ion plating method, or a CVD method. Among these, the sputtering method is preferable because the film forming chamber can be downsized and the film forming speed is high. Examples of the sputtering method include DC magnetron sputtering. As the target, a metal target or a metal oxide target can be used. The first metal oxide layer 12 may be a layer that does not dissolve in the acidic etching solution.

The metal layer 18 may contain silver or a silver alloy as a main component. The metal layer 18 may be a layer that dissolves in an acidic etching solution. Thus, patterning can be easily performed. Since the metal layer 18 has high transparency and excellent conductivity, the surface resistance can be sufficiently lowered while ensuring the transmittance of the transparent conductor 10. The metal layer 18 may contain a metal element other than silver. For example, the environment resistance of the metal layer 18 is improved by containing at least one element selected from the group consisting of Cu, Nd, Pt, Pd, Bi, Sn, and Sb as a constituent element of a silver alloy or a metal simple substance. be able to. Examples of silver alloys include Ag—Pd, Ag—Cu, Ag—Pd—Cu, Ag—Nd—Cu, Ag—In—Sn, and Ag—Sn—Sb. The silver alloy preferably contains Ag as a main component and includes the above-described metals as subcomponents. The metal layer 18 may be a layer made of only metal.

The content of metals other than Ag in the silver alloy is, for example, 0.5 to 5% by mass from the viewpoint of further improving the corrosion resistance and transparency. The silver alloy preferably contains Pd as a metal other than Ag. Thereby, the corrosion resistance in a high-temperature and high-humidity environment can be further improved.

The thickness of the metal layer 18 may be, for example, 5 to 25 nm. If the thickness of the metal layer 18 becomes too small, the continuity of the metal layer 18 is impaired and the surface resistance value of the transparent conductor 10 tends to increase. On the other hand, when the thickness of the metal layer 18 becomes too large, excellent transparency tends to be impaired.

The metal layer 18 has a function of adjusting the conductivity and surface resistance of the transparent conductor 10. The metal layer 18 can be produced by a vacuum film forming method such as a vacuum deposition method, a sputtering method, an ion plating method, or a CVD method. Among these, the sputtering method is preferable because the film forming chamber can be downsized and the film forming speed is high. Examples of the sputtering method include DC magnetron sputtering. A metal target can be used as the target.

The second metal oxide layer 14 is a transparent layer containing a metal oxide. For example, when the second metal oxide layer 14 in contact with the organic layer is disposed on the organic layer side of the organic device, it has a function of facilitating the movement of holes. The second metal oxide layer 14 in contact with the organic layer may be composed of a metal oxide containing ITO. The second metal oxide layer 14 may contain ITO as a main component, or may be composed of inevitable impurities derived from ITO and impurities of raw materials. The content of ITO in the second metal oxide layer 14 is preferably 90% by mass or more, and more preferably 95% by mass or more.

The second metal oxide layer 14 may be composed of a plurality of metal oxide films having different compositions. When the second metal oxide layer 14 is composed of a plurality of metal oxide films having different compositions, the film in contact with the metal layer 18 is a metal oxide film containing a metal oxide different from ITO as a main component. The film in contact with the organic layer may be a metal oxide film containing ITO as a main component.

ITO is an oxide of indium and tin. The oxide is a composite oxide having In, Sn, and O (oxygen) as constituent elements. The second metal oxide layer 14 may contain another composite oxide.

The work function of the surface 14a opposite to the metal layer 18 side of the second metal oxide layer 14 may be 4.7 eV or more, or 5.0 eV or more. When an organic device is manufactured by providing an organic layer on the surface 14a of the second metal oxide layer 14 having such a high work function, injection of holes into the organic layer or formation of holes from the organic layer is performed. Acceptance can be done smoothly. For this reason, the performance of the organic device can be improved. The work function of the surface 14a of the second metal oxide layer 14 can be measured using a commercially available measuring device.

The work function of the surface 14a of the second metal oxide layer 14 tends to depend on the composition in the vicinity of the surface 14a. For example, when forming the second metal oxide layer 14 containing ITO or the metal oxide film in contact with the organic layer, the Sn composition containing SnO _{2 in} the target composition or In depending on the film formation conditions during sputtering The work function of the surface 14a of the second metal oxide layer 14 can be adjusted by changing the Sn and O contents.

The thickness d of the second metal oxide layer 14 may be, for example, 2 nm or more, or 5 nm or more from the viewpoint of stably increasing the work function on the surface 14a. On the other hand, the thickness d of the second metal oxide layer 14 is, for example, 100 nm or less from the viewpoint of sufficiently increasing the transparency and flexibility of the transparent conductor 10.

The thickness of each layer constituting the transparent conductor 10 can be measured by the following procedure. The transparent conductor 10 is cut by a focused ion beam device (FIB, Focused Ion Beam) to obtain a cross section. The cross section is observed using a transmission electron microscope (TEM), and the thickness of each layer is measured. The measurement is preferably performed at 10 or more arbitrarily selected positions, and the average value is obtained. As a method for obtaining the cross section, a microtome may be used as an apparatus other than the focused ion beam apparatus. As a method for measuring the thickness, a scanning electron microscope (SEM) may be used. It is also possible to measure the film thickness using a fluorescent X-ray apparatus.

The thickness of the transparent conductor 10 may be 250 μm or less, or 200 μm or less. With such a thickness, the required levels of transparency and flexibility can be sufficiently satisfied.

The compositions of the first metal oxide layer 12 and the second metal oxide layer 14 may be different from each other. By making the composition of the first metal oxide layer 12 and the composition of the second metal oxide layer 14 different, only the second metal oxide layer 14 and the metal layer 18 are subjected to acidic etching in one step. The first metal oxide layer 12 can be left by etching using a liquid.

The transparent conductor 10 having the above-described configuration is also excellent in alkali resistance. Therefore, patterning can be performed efficiently. The transparent conductor 10 can be suitably used for organic devices such as organic EL displays and organic EL lighting.

The transparent conductor 10 in FIG. 1 may include an arbitrary layer between each layer. For example, a hard coat layer may be provided between the transparent substrate 11 and the first metal oxide layer 12, or an etching resistant layer is provided between the metal layer 18 and the first metal oxide layer 12. May be. Further, a water vapor barrier layer may be provided between the transparent substrate 11 and the first metal oxide layer 12. The hard coat layers may be provided in pairs so as to sandwich the transparent substrate 11.

Since the transparent conductor 10 is excellent in conductivity, flexibility and corrosion resistance, it is suitably used as an electrode for organic devices such as organic EL displays and organic EL lighting. In this case, the first metal oxide layer 12, the metal layer 18, and the second metal oxide layer 14 function as the transparent electrode 20. The transparent electrode 20 may be an anode or a cathode.

FIG. 2 is a diagram schematically showing an embodiment of an organic device. The organic device 100 is, for example, organic EL illumination, and includes a transparent substrate 11, a transparent electrode (anode) 20, a hole injection layer 30, a hole transport layer 32, a light emitting layer 40, an electron transport layer 50, an electron injection layer 52, And the laminated body 150 which has the metal electrode (cathode) 60 in this order is provided. As the transparent substrate 11 and the transparent electrode 20 in the organic device 100, the transparent conductor 10 can be used.

The transparent conductor 10 is provided so that the surface of the second metal oxide layer 14 of the transparent electrode 20 (the surface 14 a in FIG. 1) is in contact with the hole injection layer 30. A power source 80 is connected to the transparent electrode 20 functioning as an anode and the metal electrode 60 functioning as a cathode. By applying an electric field by the power source 80, holes are injected from the transparent electrode 20 into the hole injection layer 30, and electrons are injected from the metal electrode 60 into the electron injection layer 52.

The holes injected into the hole injection layer 30 and the electrons injected into the electron injection layer 52 move through the hole transport layer 32 and the electron transport layer 50 and recombine in the light emitting layer 40, respectively. By this recombination, the organic compound in the light emitting layer 40 emits light. The light generated by the light emission passes through the hole transport layer 32, the hole injection layer 30, the transparent electrode 20, and the transparent substrate 11 and is emitted from the side surface 20 a of the organic device 100. The metal electrode 60 functions as a reflective electrode.

Organic device 100 uses transparent conductor 10 as transparent substrate 11 and transparent electrode 20. Therefore, holes can be efficiently injected into the hole injection layer 30 by increasing the work function on the surface 14 a of the second metal oxide layer 14 of the transparent electrode 20. Thereby, the light emission amount in the light emitting layer 40 of the organic device 100 can be increased with respect to the voltage applied from the power supply 80 (current flowing between both electrodes). In addition, by optimizing the thickness d of the second metal oxide layer 14 according to the emission wavelength, the light emitted from the light emitting layer 40 can be efficiently extracted from the side surface 20a, and the light emission efficiency is sufficiently high. can do. Thereby, it is possible to increase the light emission efficiency indicating how much light can be extracted with respect to the voltage (current) applied from the power supply 80.

The hole injection layer 30, the hole transport layer 32, the light emitting layer 40, the electron transport layer 50, the electron injection layer 52, and the metal electrode (cathode) 60 can be formed using ordinary materials.

The hole injection layer 30 has a function of facilitating injection of holes from the transparent electrode 20 and transporting the injected holes into the hole transport layer 32. The hole transport layer 32 has a function of injecting holes injected from the hole injection layer 30 into the light emitting layer 40. For example, the material of the hole injection layer 30 and the hole transport layer 32 includes an aromatic amine compound and an anthracene derivative.

The light emitting layer 40 has a function of transporting injected holes and electrons and a function of generating excitons by recombination of holes and electrons. Examples of the light emitting layer 40 include a two-component system in which a host material and a dopant material are combined. Host materials include 1,10-phenanthroline derivatives, organometallic complex compounds, aromatic hydrocarbon compounds such as naphthalene, anthracene, naphthacene, perylene, benzofluoranthene, naphthofluoranthene and their derivatives, and styrylamine and And tetraaryldiamine derivatives. Examples of the dopant material include benzodifluoranthene derivatives and coumarin derivatives.

The electron transport layer 50 has a function of transporting electrons injected from the electron injection layer 52 to the light emitting layer 40. The electron injection layer 52 has a function of facilitating injection of electrons from the metal electrode 60 and a function of improving adhesion with the metal electrode 60. The electron transport layer 50 and the electron injection layer may be formed using an organic material such as a compound having a trinitrofluorenone, oxadiazole or triazole structure, or an alkali metal such as lithium, lithium fluoride, Alternatively, it may be formed using an inorganic material such as lithium oxide.

As the metal electrode 60, a metal material such as aluminum, an organic metal complex, or a metal compound can be used. Each layer can be formed by a usual method such as a vacuum deposition method, an ionization deposition method, and a coating method. The thickness of each layer of the stacked body 150 constituting the organic device 100 can be set to, for example, 1/8 to 1/4 of the wavelength of light obtained in the light emitting layer 40.

FIG. 3 is a diagram schematically showing a propagation path of light from the light emitting layer 40. In the light emitting layer 40, excitons are generated and emit light. For example, as shown in FIG. 3, a part of the emitted light is totally reflected at the interface between the hole injection layer 30 and the transparent electrode 20 and at the interface between the transparent electrode 20 and the transparent substrate 11. Then, another part of the emitted light is extracted from the side surface 20a. Assuming that the light extraction efficiency is the ratio (%) of light emitted from the side surface 20a to the light emitted from the light emitting layer 40, the light emission efficiency (external quantum efficiency) of the organic device 100 is obtained by the following formula (I). be able to. From formula (I), in order to improve the light emission efficiency of the organic device 100, it is effective to increase the light extraction efficiency.
Luminous efficiency = Internal quantum efficiency x Light extraction efficiency (I)

In the present specification, the internal quantum efficiency indicates a ratio (light energy generated in the light emitting layer 40) in which the energy excited in the light emitting layer 40 by the injected power is converted into light energy.

The light extraction efficiency can be increased by suppressing total reflection at the interface of each layer. Here, the reflectance and transmittance of the laminate 150 can be optically simulated using the optical constant (n / k) and thickness of each layer. k is an extinction coefficient. As such simulation software, for example, software (trade name: SimOLED) for an organic light emitting diode manufactured by Sim4Tec can be cited.

FIG. 4 shows the transparent substrate 11, the first metal oxide layer 12, the metal layer 18, the second metal oxide layer 14, the hole injection layer 30, the hole transport layer 32, the light emitting layer 40, and the metal electrode 60. It is a figure which shows an example of the simulation result of the organic device comprised with the laminated body which has these in this order. In this simulation, the multiple interference effect inside the light emitting layer 40 and the optical characteristics of each layer other than the light emitting layer 40 are made a function of the wavelength of light generated in the light emitting layer 40 and the light propagation angle. It is a simulation of efficiency. The prerequisites for the simulation are as shown in Table 1.

FIG. 4 shows the result of simulating the relationship between the thickness d (nm) of the second metal oxide layer 14 and the light extraction efficiency at each wavelength under the above-mentioned preconditions. Based on this simulation result, the range of the thickness d of the second metal oxide layer 14 in which the light extraction efficiency of light of each wavelength is 15% can be obtained. In the simulation shown in FIG. 4, when the thickness d is in the range of 0 to 210 nm, the range in which the light extraction efficiency of light at each wavelength is 15% or more is as follows.

When λ = 450 nm, d = 45 to 95 nm, d = 160 to 210 nm
When λ = 520 nm, d = 30 nm or less, d = 70 to 170 nm
When λ = 610 nm, d = 40 nm or less, d = 120 to 210 nm

From the above results, the range of the thickness d in which the light extraction efficiency is 15% or more is extracted in order from the smaller d (first range, second range,..., Nth range). Then, the optical path length (n × d / λ) at the upper and lower limit values of d in each range is calculated. If the refractive index n of the second metal oxide layer 14 at the wavelength λ at each upper and lower limit value is as shown in Table 2, the optical path length of the upper and lower limit values of d in each range is calculated as shown in Table 2. In the light extraction efficiency curve as shown in FIG. 4, when the light extraction efficiency is 15% or less when d = 0 nm, the optical path length in the first range is 0, and from the second range, A range of thickness d in which the extraction efficiency is 15% or more is extracted in order.

FIG. 5 is a graph showing the relationship between the wavelength λ of light used in the simulation and the lower limit value and the upper limit value in each range of the optical path length shown in Table 2. FIG. 5 shows a linear regression line and a linear regression equation of the upper limit value and the lower limit value of each range where the wavelength λ [nm] is x and n × d [nm] / λ [nm] is y. Yes.

In the region between the horizontal axis (x-axis) and the dotted line and the region between the solid line and the alternate long and short dash line shown in FIG. 5, the light extraction efficiency can be increased (for example, 15% or more). This region is expressed by the following formulas (1) and (2), respectively.
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)

In the formula (1) and the formula (2), d exceeds 0 and is 210 nm or less. N at the wavelength λ is, for example, 1.8 to 2.2. In addition, when the light from the light emitting layer 40 of an organic device contains a several wavelength, what is necessary is just to satisfy | fill said Formula (1) or Formula (2) in at least 1 wavelength among several wavelengths. The wavelength of light from the light emitting layer 40 of the organic device may be, for example, 400 to 700 nm.

By adjusting at least one of the composition and thickness d of the second metal oxide layer 14 so as to satisfy the above formula (1), the ratio of light extracted from the side surface 20a, that is, the light extraction efficiency is sufficiently increased. be able to. This is because the phase difference between the light directly extracted from the light emitting layer 40 and the light reflected at the boundary of each layer is uniform, and total reflection at the interface between the transparent substrate 11 and the transparent electrode 20 is reduced. It is inferred that this is caused by

The optical path length (n × d / λ) preferably satisfies the formula (1-1) or the formula (2-1) from the viewpoint of further increasing the light extraction efficiency, and the formula (1-2) or the formula (2) -2) is more preferable. N, d, and λ in the following expressions are synonymous with the expressions (1) and (2).
0 <n × d / λ ≦ 0.0006 × λ−0.2605 (1-1)
0.0011 × λ−0.1910 ≦ n × d / λ ≦ 0.0014 × λ−0.1914 (2-1)
0 <n × d / λ ≦ 0.0004 × λ−0.1817 (1-2)
0.0012 × λ−0.2304 ≦ n × d / λ ≦ 0.0015 × λ−0.24595 (2-2)

The manufacturing method of the transparent conductor 10 according to the embodiment includes the second method so as to satisfy the above formula (1) or formula (2) based on the wavelength λ [nm] of the light emitted from the light emitting layer 40. At least one of the thickness d [nm] and the refractive index n of the metal oxide layer 14 is adjusted. Thereby, the transparent conductor 10 having high light extraction efficiency can be manufactured.

FIG. 6 is a graph showing the relationship between the current value passed through the organic EL device using Alq3 [tris (8-quinolinolato) aluminum] emitting green light in the light emitting layer 40 and the light emission efficiency (EQE). The black circles, white squares, and black triangles in FIG. 6 are plotted in the organic device 100 shown in FIG. 2 when the thickness d of the second metal oxide layer 14 is 10 nm, 100 nm, and 40 nm, respectively. The change in luminous efficiency is shown. Among these, the black triangle is a condition for maximizing the transmittance of the transparent conductor 10, and is a conventional transparent conductor whose optical path length does not satisfy the expressions (1) and (2). As shown in FIG. 6, when the second metal oxide layer 14 has a thickness d that satisfies the formula (1) or the formula (2), the luminous efficiency can be increased. Further, the luminous efficiency can be adjusted by changing the thickness d of the second metal oxide layer 14.

Although several embodiments have been described above, the present invention is not limited to the above-described embodiments. The organic device may be organic EL lighting or an organic EL display, and the structure thereof is not limited to the structure shown in FIG.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Experimental Example 1]
(Production of transparent conductor)
A transparent conductor having a laminated structure as shown in FIG. 1 was produced. The transparent conductor had a laminated structure in which a transparent substrate, a first metal oxide layer, a metal layer, and a second metal oxide layer were laminated in this order. This transparent conductor was produced as follows.

A commercially available glass substrate (manufactured by Corning, trade name: EAGLE XG, thickness: 0.7 mm) was prepared. This glass substrate was used as a transparent substrate. A first metal oxide layer, a metal layer, and a second metal oxide layer were sequentially formed on the transparent substrate by DC magnetron sputtering.

Using a target composed of three components of zinc oxide, indium oxide, and titanium oxide, the first material was formed on the transparent substrate by DC magnetron sputtering under reduced pressure (0.5 Pa) in a mixed gas atmosphere of argon gas and oxygen gas. 1 metal oxide layer (thickness: 40 nm) was formed. In the first metal oxide layer, when zinc oxide, indium oxide, and titanium oxide are converted into ZnO, In ₂ O ₃ , and TiO ₂ , respectively, the content of ZnO with respect to the total of the above three components Was 74 mol%, the content of In ₂ O ₃ was 15 mol%, and the content of TiO ₂ was 11 mol%. The refractive index of the first metal oxide layer at a wavelength of 450 nm was 2.1.

Using a target composed of a silver alloy of Ag, Pd, and Cu, a silver alloy is mainly contained on the first metal oxide layer by DC magnetron sputtering under reduced pressure (0.5 Pa) in an argon gas atmosphere. To form a metal layer (thickness: 10 nm). The mass ratio of each metal of the silver alloy was Ag: Pd: Cu = 99.0: 0.7: 0.3.

Using a target composed of ITO, a second metal oxide layer (thickness: 40 nm, thickness: 40 nm) on the metal layer by DC magnetron sputtering under reduced pressure (0.5 Pa) in a mixed gas atmosphere of argon gas and oxygen gas. ITO layer) was formed. The refractive index of the second metal oxide layer at a wavelength of 450 nm was 1.9.

(Evaluation of transparent conductor)
The total light transmittance (transmittance) of the produced transparent conductor was measured using a haze meter (trade name: NDH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.). The total light transmittance was 88%.

The surface resistance value of the produced transparent conductor was measured using a 4-terminal resistivity meter (trade name: Loresta GP, manufactured by Mitsubishi Chemical Corporation). The surface resistance value is 10 Ω / sq. Met.

The work function on the surface of the second metal oxide layer of the produced transparent conductor was measured using a photoelectron spectrometer (trade name: FAC-1 manufactured by Riken Keiki Co., Ltd.). The work function was 5.2 eV.

Using a green light emitting element with a wavelength of 520 nm, the light extraction efficiency of the produced transparent conductor was simulated. As a result, the light extraction efficiency was less than 15%.

In the case where the emission wavelength is 450 nm, 520 nm, and 610 nm, the light extraction efficiency was simulated when the thickness d of the second metal oxide layer was changed in the above-described transparent conductor. The simulation result was as shown in FIG. As shown in FIG. 7, it was confirmed that the light extraction efficiency can be increased by adjusting the thickness d of the second metal oxide layer according to the wavelength.

When the emission wavelength is 450 nm, the light extraction efficiency is 15% or less when d = 0 nm. Therefore, the second range is the minimum range of the thickness d that can increase the light extraction efficiency. Therefore, it is considered that the light extraction efficiency can be increased if the thickness d is set in a range that satisfies the above formula (2) corresponding to the second range. Therefore, when λ = 450 nm, the range of the thickness d of the second metal oxide layer that satisfies the above formula (2) was calculated. As a result, the range of d satisfying the formula (2) was about 50 nm ≦ d ≦ about 113 nm. According to FIG. 7, it was confirmed that the light extraction efficiency is approximately 12% or more in the range of the thickness d.

When the emission wavelength was 520 nm, the light extraction efficiency and transmittance when the thickness d of the second metal oxide layer was changed in the above-described transparent conductor were simulated. The simulation result was as shown in FIG. In FIG. 8, the dotted line indicates the transmittance, and the solid line indicates the light extraction efficiency at 520 nm. As shown in FIG. 8, it was confirmed that the light extraction efficiency and the transmittance are not directly proportional to each other, and the light extraction efficiency cannot be increased even if the transmittance is increased. Further, it was confirmed that if the thickness d is in a predetermined range, even if the transmittance is 60% or less, the light extraction efficiency can be 15% or more.

[Experimental example 2 (comparative example)]
Instead of the transparent conductor of Experimental Example 1, the light extraction efficiency when an ITO single layer was formed on the commercially available glass substrate used in Experimental Example 1 was determined by simulation in the same manner as in Experimental Example 1. The simulation result was as shown in FIG.

As shown in FIG. 9, in the case of an ITO single layer, it was confirmed that it hardly depends on the emission wavelength of the light extraction efficiency and the thickness of the ITO layer.

According to the present disclosure, a transparent conductor capable of sufficiently increasing the light extraction efficiency from the light emitting layer and a method for manufacturing the transparent conductor are provided. Moreover, an organic device provided with a transparent conductor is provided.

DESCRIPTION OF SYMBOLS 10 ... Transparent conductor, 11 ... Transparent base material, 12 ... 1st metal oxide layer, 14 ... 2nd metal oxide layer, 14a ... Surface, 18 ... Metal layer, 20 ... Transparent electrode, 20a ... Side surface, DESCRIPTION OF SYMBOLS 30 ... Hole injection layer, 32 ... Hole transport layer, 40 ... Light emitting layer, 50 ... Electron transport layer, 52 ... Electron injection layer, 60 ... Metal electrode, 80 ... Power supply, 100 ... Organic device, 150 ... Laminate.

Claims

A transparent conductor for an organic device having a light emitting layer,
A transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer are provided in this order,
When the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. A transparent conductor satisfying the following formula (1) or (2).
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
[In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. ]
2. The transparent conductor according to claim 1, wherein the second metal oxide layer forming a surface opposite to the transparent substrate contains indium oxide as a main component.
The transparent conductor according to claim 1 or 2, wherein a work function of the second metal oxide layer forming a surface opposite to the transparent substrate is 4.7 eV or more.
A method for producing a transparent conductor for an organic device, comprising a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, and a second metal oxide layer in this order,
Based on the wavelength λ [nm] of light emitted from the light emitting layer of the organic device, the light emitting layer side is closer to the first metal oxide layer so as to satisfy the following formula (1) or (2). A method for producing a transparent conductor, wherein at least one of a refractive index n of the second metal oxide layer at a thickness d [nm] and λ of the second metal oxide layer provided is adjusted.
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
[In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. ]
An organic device comprising a transparent substrate, a first metal oxide layer, a metal layer containing silver or a silver alloy, a second metal oxide layer, and a light emitting layer in this order,
When the wavelength of light from the light emitting layer is λ [nm], the refractive index of the second metal oxide layer at λ is n, and the thickness of the second metal oxide layer is d [nm]. An organic device satisfying the following formula (1) or (2).
0 <n × d / λ ≦ 0.0008 × λ−0.3393 (1)
0.0012 × λ−0.3302 ≦ n × d / λ ≦ 0.0015 × λ−0.1975 (2)
[In Formula (1) and Formula (2), d is more than 0 and 210 nm or less. ]