Electronic element, organic electroluminescence element, display device, and lighting device

Abstract

To provide an electronic element that comprises a charge transport layer achieving both high conductivity and high transparency in a visible light region while containing a metal oxide.SOLUTION: An electronic element 1 comprises an anode 50, a cathode 20, a charge transport layer 30 located between the anode 50 and the cathode 20. The charge transport layer 30 contains a metal oxide, and a compound having reducibility higher than that of the metal oxide. A rate of content of the compound having the reducibility higher than that of the metal oxide is 10 pts.mass or less per 100 pts.mass of the metal oxide.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to an electronic device, and an organic electroluminescence (hereinafter, electroluminescence (field emission) may be referred to as "EL") device, a display device, and a lighting device using the same.

Background Art

[0002] In recent years, research and development of display devices and lighting devices using organic electroluminescence devices (hereinafter, may be abbreviated as "organic EL devices") that utilize light emitted when an electric field is applied to an organic substance have been actively conducted, and their spread has been rapidly progressing. Further, in recent years, for further performance improvement, development of organic-inorganic hybrid devices using inorganic substances having lower resistance than organic substances as charge transport layers has been active. Among them, in particular, development of metal oxide conductive films formed by a solution process has been active.

[0003] Generally, in an organic EL device, in order to obtain good characteristics, it is necessary to appropriately control optical interference inside the device, and for this purpose, a charge transport layer with a thick film of several tens of nm or more is required. However, except for some transparent conductive films, general metal oxides absorb light in the visible light region. Therefore, when a thick metal oxide layer is provided inside an organic EL device, the light emitted by charge recombination is absorbed by the metal oxide layer and the luminous efficiency decreases. Therefore, there is a problem that it is difficult to obtain high luminous efficiency when using a metal oxide with a thick film of several tens of nm or more. Further, this problem can be said to be a general problem in electronic devices (particularly, optical devices) such as organic solar cells as well as organic EL devices.

[0004] As a metal oxide that is colorless and transparent in the visible light region and can be used in a solution process, phosphotungstic acid (PWA) composed of phosphoric acid and tungsten trioxide is known. Although tungsten trioxide contained in the PWA has a high electrical resistance, once an electric current flows, tungsten is reduced and the electrical resistance decreases. However, when the tungsten in the PWA is reduced, there is a problem that it becomes colored blue because it enters a mixed valence state.

[0005] On the other hand, in indium tin oxide (ITO), which is well-known as a transparent conductive film formed by a dry process, the valence of the metal is controlled by changing conditions such as the oxygen partial pressure during sputtering film formation, and high transparency in the visible light region is achieved (Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, in indium tin oxide (ITO), the valence of the metal can be controlled by changing conditions such as the oxygen partial pressure during sputtering film formation. However, in a solution process, it is difficult to control the valence of the metal. Therefore, the development of an electronic device that can be formed by a solution process, includes a metal oxide, and has a charge transport layer that achieves both high conductivity and high transparency in the visible light region has become an issue.

[0008] Therefore, an object of the present invention is to solve the problems of the above prior art and provide an electronic device that includes a metal oxide and has a charge transport layer that achieves both high conductivity and high transparency in the visible light region. Another object of the present invention is to provide an organic EL device, a display device, and a lighting device using such an electronic device.

Means for Solving the Problem

[0009] The gist configuration of the present invention for solving the above problems is as follows.

[0010] The electronic device of the present invention includes an anode, a cathode, and a charge transport layer located between the anode and the cathode. In the electronic device, the charge transport layer contains a metal oxide and a compound having higher reducibility than the metal oxide, and is characterized in that the content of the compound having higher reducibility than the metal oxide is 10 parts by mass or less with respect to 100 parts by mass of the metal oxide. The electronic device of the present invention can achieve both high conductivity and high transparency in the visible light region while containing a metal oxide.

[0011] In a preferred example of the electronic device of the present invention, the metal oxide has the formula: H 3 PW 12 O 40 and is phosphotungstic acid represented by this formula. In this case, the transparency of the charge transport layer in the visible light region is further improved, and the smoothness of the charge transport layer is also improved.

[0012] In another preferred example of the electronic device of the present invention, the compound having higher reducibility than the metal oxide is at least one selected from the group consisting of molybdic acid, copper(I) iodide, and dipyrazino[2,3-f:2’,3’-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN). In this case, the transparency of the charge transport layer can be maintained at a high level.

[0013] Further, the organic electroluminescence device of the present invention includes the above electronic device and a light-emitting layer, and is characterized in that the light-emitting layer is located between the anode and the cathode. The organic electroluminescence device of the present invention has high luminous efficiency.

[0014] In addition, the display device of the present invention is characterized by including the above-described organic electroluminescence element. Such a display device of the present invention has high luminous efficiency.

[0015] In addition, the lighting device of the present invention is characterized by including the above-described organic electroluminescence element. Such a lighting device of the present invention has high luminous efficiency.

Effects of the Invention

[0016] According to the present invention, it is possible to provide an electronic device including a charge transport layer that includes a metal oxide and achieves both high conductivity and high transparency in the visible light region. In addition, according to the present invention, it is possible to provide an organic EL device, a display device, and a lighting device using such an electronic device.

Brief Description of the Drawings

[0017]

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Figure 8

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Figure 11

Figure 12

Mode for Carrying Out the Invention

[0018] Hereinafter, the electronic device, organic electroluminescence device, display device, and lighting device of the present invention will be exemplified and described in detail based on their embodiments.

[0019] <Electronic device> The electronic device of the present invention includes an anode, a cathode, and a charge transport layer located between the anode and the cathode. In the electronic device of the present invention, the charge transport layer contains a metal oxide and a compound having higher reducibility than the metal oxide, and the content of the compound having higher reducibility than the metal oxide is 10 parts by mass or less with respect to 100 parts by mass of the metal oxide.

[0020] In the electronic device of the present invention, the charge transport layer contains a metal oxide and a compound having a higher reducibility than the metal oxide. When current flows, the compound having a higher reducibility than the metal oxide is reduced, thereby suppressing the reduction of the metal oxide. By suppressing the reduction of the metal oxide, coloring of the charge transport layer can be prevented and high transparency in the visible light region can be maintained. Further, in the electronic device of the present invention, since the content of the compound having a higher reducibility than the metal oxide is small, being 10 parts by mass or less with respect to 100 parts by mass of the metal oxide, the influence on the electrical conductivity characteristics is small. Therefore, the charge transport layer of the electronic device of the present invention can achieve both high conductivity and high transparency in the visible light region while containing a metal oxide.

[0021] Here, in the present invention, the "reducibility" of the compound having a higher reducibility than the metal oxide is determined by XPS. Specifically, a compound having an action of reducing the spectral intensity on the low binding energy side after applying an electric current by adding it to the metal oxide is defined as a compound having a higher reducibility than the metal oxide. As an example, when the metal oxide is a metal oxide containing tungsten (W), the "reducibility" of the compound having a higher reducibility than the metal oxide can be evaluated by measuring the XPS spectrum of W4f.

[0022] As the compound having a higher reducibility than the metal oxide (hereinafter sometimes referred to as "coloring inhibitor"), those having less light absorption in the visible light region are preferable. The following structural formula:

Chemical formula

[0023] Next, as an example of the charge transport layer of the electronic device of the present invention, as a metal oxide, phosphotungstic acid (PWA) is included, and as a compound (anti-coloring agent) having higher reducibility than the metal oxide, dipyrazino[2,3-f:2’,3’-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), phosphomolybdic acid (PMA), or copper(I) iodide (CuI) is included. A thin film will be described in detail as an example.

[0024] FIG. 1 shows the absorption spectrum of a thin film of phosphotungstic acid (PWA), and the absorption spectra of thin films formed by adding 0.5 parts by mass, 1 part by mass, 3 parts by mass, or 10 parts by mass of HAT-CN to 100 parts by mass of PWA and containing phosphotungstic acid (PWA) and HAT-CN. Further, FIG. 2 shows the absorption spectrum of a thin film of phosphotungstic acid (PWA), and the absorption spectra of thin films formed by adding 0.5 parts by mass, 1 part by mass, 3 parts by mass, or 10 parts by mass of PMA to 100 parts by mass of PWA and containing phosphotungstic acid (PWA) and phosphomolybdic acid (PMA). Further, FIG. 3 shows the absorption spectrum of a thin film of phosphotungstic acid (PWA), and the absorption spectra of thin films formed by adding 0.5 parts by mass, 1 part by mass, or 3 parts by mass of CuI to 100 parts by mass of PWA and containing phosphotungstic acid (PWA) and CuI.

[0025] From FIGS. 1 to 3, it can be seen that when the metal oxide is phosphotungstic acid (PWA), the absorption in the visible light region does not increase even when HAT-CN, PMA, or CuI is added.

[0026] In order to suppress coloring when driving an electronic device including a charge transport layer containing phosphotungstic acid (PWA), it is required that the additive (anti-coloring agent) be more easily reduced than PWA. This ease of reduction can be evaluated by measuring the XPS spectrum of W4f as described above.

[0027] FIG. 4 is the XPS spectrum of W4f of a thin film of phosphotungstic acid (PWA). Figure 5 is the XPS spectrum of W4f of the thin film formed by adding 3 parts by mass of HAT-CN to 100 parts by mass of phosphotungstic acid (PWA). Figure 6 is the XPS spectrum of W4f of the thin film formed by adding 3 parts by mass of PMA to 100 parts by mass of phosphotungstic acid (PWA). Figure 7 is the XPS spectrum of W4f of the thin film formed by adding 3 parts by mass of CuI to 100 parts by mass of phosphotungstic acid (PWA).

[0028] It can be seen that the XPS spectrum of the PWA thin film shown in Figure 4 has a greater intensity of the shoulder on the low binding energy side compared to the XPS spectra of the thin films formed by adding HAT-CN, PMA, or CuI to PWA shown in Figures 5 to 7. Here, the portion on the low binding energy side represents the presence of tungsten with a smaller valence. Peak separation was performed, and Table 1 shows the summarized abundance ratio of the valence states of W.

[0029]

Table 1

[0030] As can be seen from Table 1, in the PWA thin film (without additive), 89.0% of the tungsten (W) has a valence of 6, and the remaining 11% has a smaller valence than that. On the other hand, in the thin film with HAT-CN added to PWA, 95.5% of the tungsten (W) has a valence of 6. In the thin film with PMA added to PWA, 93.3% of the tungsten (W) has a valence of 6. In the thin film with CuI added to PWA, 90.8% of the tungsten (W) has a valence of 6. In all cases, compared to the PWA thin film (without additive), the proportion of tungsten (W) with a higher valence is larger, indicating that it is oxidized. Therefore, it can be seen that HAT-CN, PMA, and CuI all have the ability to oxidize PWA (the ability to suppress the reduction of PWA). Also, from this, it can be seen that when PWA is reduced, instead, HAT-CN, PMA, and CuI are reduced. In the present invention, not limited to HAT-CN, PMA, and CuI, a compound having higher reducibility than a metal oxide can be added to the metal oxide as an anti-coloring agent to suppress the reduction of the metal oxide and prevent the coloring of the metal oxide.

[0031] Next, an embodiment of the electronic device of the present invention will be described in detail with reference to the drawings. FIG. 8 is a schematic cross-sectional view for explaining an example of the electronic device of the present embodiment.

[0032] In the electronic device 1 of the present embodiment shown in FIG. 8, an electrode 20 (cathode 20 in FIG. 8) serving as an anode or a cathode is provided on a substrate 10. Further, in the electronic device 1 shown in FIG. 8, a charge transport layer 30 and a functional layer 40 formed by adding an anti-coloring agent to a metal oxide are sequentially laminated on the upper layer of the electrode 20 (cathode 20 in FIG. 8), and finally, an electrode 50 (anode 50 in FIG. 2) serving as a counter electrode to the electrode 20 is laminated. Here, the functional layer 40 may or may not be present.

[0033] (Substrate 10) The substrate 10 is made of a material such as glass or resin and can be used as appropriate. As the material of the substrate 10, only one kind may be used, or two or more kinds may be used in combination. Examples of the glass material used for the substrate 10 include quartz glass and soda glass. On the other hand, examples of the resin material used for the substrate 10 include polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, polyarylate, and the like. When a resin material is used as the material of the substrate 10, an electronic device 1 having excellent flexibility can be obtained. The average thickness of the substrate 10 is not particularly limited, but is preferably 0.1 to 30 mm, and more preferably 0.1 to 10 mm.

[0034] (Electrode 20) For the electrode 20, an electrode material generally used in electronic devices can be preferably used. For example, highly conductive transparent electrodes made of ITO (indium tin oxide), IZO (indium zinc oxide), FTO (fluorine tin oxide), InSnZnO (indium zinc tin oxide, ITZO), In 3 O 3 , SnO 2 , Sb-containing SnO 2 , Al-containing ZnO, etc., or electrodes made of aluminum, silver, etc., with high reflectivity and high conductivity can be appropriately used. The average thickness of the electrode 20 (the cathode 20 in FIG. 2) is not particularly limited, but is preferably 10 to 500 nm, and more preferably 50 to 200 nm.

[0035] (Charge transport layer 30) As the material of the charge transport layer 30, a material obtained by adding a compound (anti-coloring agent) having higher reducibility than the above-described metal oxide to the metal oxide is used.

[0036] --Metal oxide-- As the metal oxide, polyoxometalate is preferable, and heteropolyoxometalate is more preferable. The heteropolyoxometalate is a compound having a structure in which heteroatoms (P 5+ , Si 4+ , Ge 4+ , Bi 3+ , etc.) are centered, and polyatoms (W 6+ , Mo 6+ , V 5+ , etc.) are coordinated to the heteroatoms via oxygen, and structures such as Keggin type and Dawson type are known.

[0037] As the polyoxometalate, acids such as phosphotungstic acid (PWA), phosphomolybdic acid (PMA), silicotungstic acid (SWA), etc., and sodium salts of these acids such as sodium salt of PWA (PWA-Na), sodium salt of PMA (PMA-Na), etc. can be used. The polyoxometalate has high solubility in a solvent and can easily form a charge transport layer with a thickness of several hundred nm by dissolving it in the solvent and applying and forming a film as an ink. The formed film preferably has a smooth surface.

[0038] As the metal oxide, the formula: H 3 PW 12 O 40 Phosphotungstic acid (PWA) represented by is preferred. Phosphotungstic acid (PWA) has particularly high solubility in a solvent, high transparency in the visible light region, and further, when phosphotungstic acid (PWA) is used for forming the charge transport layer, the smoothness of the formed film (charge transport layer) is improved. Since the smoothness of the fabricated film varies depending on the impurity concentration, it is preferable to appropriately select and use a raw material that results in a smoother film.

[0039] The content of the metal oxide in the charge transport layer 30 is preferably 90% by mass or more, more preferably 95% by mass or more, and preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less.

[0040] --Compound with higher reducibility than the metal oxide-- The compound with higher reducibility than the metal oxide is selected according to the metal oxide to be used, and it may be any compound that can accept electrons in place of the metal oxide when an electric current is passed through the electronic device. Here, the "reducibility" of the compound is determined by XPS. The compound with higher reducibility than the metal oxide suppresses the coloring due to the reduction of the metal oxide and acts as a so-called anti-coloring agent.

[0041] Examples of the compound having higher reducibility than the metal oxide include polyoxometalates such as molybdic acid, copper(I) iodide, electron-accepting organic compounds such as dipyrazino[2,3-f:2’,3’-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN), and further compounds used as materials for hole injection layers and charge-accepting layers in charge generation layers in general organic EL elements. Here, molybdic acid is a compound containing an oxoanion of molybdenum, and the molybdic acid includes polyoxometalates such as phosphomolybdic acid (PMA). In addition, when molybdic acid, copper(I) iodide, or HAT-CN is used as the compound having higher reducibility than the metal oxide, the effect of suppressing the reduction of the metal oxide is high, further suppressing the coloring of the metal oxide and maintaining the transparency of the charge transport layer at a high level.

[0042] In addition, as the compound having higher reducibility than the metal oxide, a compound having high solubility in polar solvents such as alcohols, acetonitrile, and esters in which the metal oxide dissolves is preferable. Specifically, the compound having higher reducibility than the metal oxide preferably dissolves 20 mg or more per 1 mL of the solvent.

[0043] The content of the compound (coloring inhibitor) having higher reducibility than the metal oxide is 10 parts by mass or less with respect to 100 parts by mass of the metal oxide. If the content of the compound having higher reducibility than the metal oxide is 10 parts by mass or less with respect to 100 parts by mass of the metal oxide, the influence on the electrical conductivity characteristics of the charge transport layer 30 is small, and high conductivity can be maintained. In addition, the content of a compound (anti-coloring agent) having higher reducibility than the metal oxide is preferably high as long as it does not significantly inhibit the electrical conductivity of the metal oxide. When the content of the compound (anti-coloring agent) having higher reducibility than the metal oxide is low, the effect of preventing coloring of the metal oxide is small. Specifically, the content of the compound having higher reducibility than the metal oxide is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 1 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the metal oxide. In particular, the content of the compound (anti-coloring agent) having higher reducibility than the metal oxide is preferably in the range of 1 part by mass or more and 3 parts by mass or less.

[0044] The thickness (average thickness) of the charge transport layer 30 is preferably 100 nm or more, and more preferably 120 nm or more. The upper limit of the thickness (average thickness) of the charge transport layer 30 is not particularly limited, but from the viewpoint of the balance between the effect and cost, it is preferably 1000 nm or less, and more preferably 500 nm or less. Here, the thickness (average thickness) of the charge transport layer 30 can be measured by a non-contact optical film thickness measuring device such as a spectroscopic ellipsometry method or a non-contact surface shape measuring device.

[0045] (Functional layer 40) The electronic device of the present invention may or may not have a functional layer 40. For example, in the electronic device of the present invention, as described later, the layers constituting the organic EL device can be used as the functional layer. Further, the electronic device of the present invention can also be used for diode devices, solar cell devices, etc. composed of inorganic materials other than organic EL devices.

[0046] (Electrode 50) When there is a functional layer 40, the electrode 50 is preferably one that can smoothly exchange charges with the material constituting the functional layer 40. When there is no functional layer 40, the electrode 50 is preferably one that can smoothly exchange charges with the material constituting the charge transport layer 30. For example, a metal material such as aluminum is preferable. The average thickness of the electrode 50 (the anode 50 in Fig. 2) is not particularly limited, but is preferably 10 to 500 nm, more preferably 50 to 200 nm.

[0047] (Forming method) In the electronic device 1 shown in Fig. 8, the method for forming all the layers is not particularly limited, and chemical vapor deposition (CVD) methods such as plasma CVD, thermal CVD, and laser CVD which are vapor deposition methods, dry plating methods such as vacuum evaporation, sputtering, and ion plating, spraying methods, and wet plating methods such as electrolytic plating, immersion plating, and electroless plating which are liquid phase deposition methods, sol-gel methods, MOD methods, spray pyrolysis methods, doctor blade methods using particulate dispersions, spin coating methods, inkjet methods, printing techniques such as screen printing, etc. can be used, and an appropriate method can be selected and used according to the material. These methods are preferably selected according to the characteristics of the materials of each layer, and the manufacturing methods may be different for each layer.

[0048] <Electroluminescent element> The above-described functional layer 40 can be a part of a light-emitting element such as an organic EL element or a quantum dot EL element. In a normal-structure EL element, a carrier transport mechanism in which charges are generated inside the EL element and the charge transport layer 30 receives the electrons obtained by the generation is preferable. On the other hand, in an inverted-structure EL element, it becomes a carrier transport mechanism in which electrons are injected and transported from the cathode to the charge transport layer 30 and electrons are injected into the functional layer 40. In order to facilitate electron injection from the charge transport layer 30 to the functional layer 40, it is preferable to insert a layer made of a material having a low work function between the charge transport layer 30 and the functional layer 40. Such materials are, for example, metals such as aluminum and silver, and transparent conductive films such as ITO. From the viewpoint of suppressing light absorption and electron conduction in the surface direction of the device, when using a metal, the layer made of a material having a low work function is preferably used with a thickness of 3 nm or less.

[0049] <Organic electroluminescent element> The organic electroluminescence device of the present invention includes the above-described electronic device and a light-emitting layer, and is characterized in that the light-emitting layer is located between the anode and the cathode. Since the organic electroluminescence device of the present invention includes an electronic device that achieves both the above-described high conductivity and high transparency in the visible light region, it has high luminous efficiency.

[0050] The organic EL device according to an embodiment of the present invention is a so-called inverted-structure organic EL device in which a cathode is provided on a substrate, and the above-described charge transport layer is provided on the cathode. Here, the charge transport layer contains the above-described metal oxide and a compound having higher reducibility than the metal oxide. Further, an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, an anode, etc. can be provided in this order on the upper part of the charge transport layer (opposite side to the substrate). Note that the configuration of the organic EL device of the present invention is not limited to this, and it is sufficient that at least one light-emitting layer is included between the cathode and the anode. Embodiments of the organic EL device of the present invention are not limited to this example.

[0051] <Display device> The display device of the present invention is characterized by including the above-described organic electroluminescence device. Since the display device of the present invention includes the above-described organic electroluminescence device, it has high luminous efficiency. The display device can be formed by forming the organic EL device of the present invention on an upper layer such as a TFT circuit generally used for driving an organic EL display.

[0052] <Lighting device> The lighting device of the present invention is characterized by including the above-described organic electroluminescence device. Since the lighting device of the present invention includes the above-described organic electroluminescence device, it has high luminous efficiency. The lighting device can be formed by incorporating the organic EL device of the present invention into a lighting fixture generally used for organic EL lighting.

Example

[0053] Examples are given below to explain the present invention in more detail, but the present invention is not limited to the following examples at all.

[0054] (Comparative Example 1-1 and Examples 1-1 to 1-11) The electronic element 1 of Comparative Example 1-1 and Examples 1-1 to 1-11 was manufactured as follows. The structure of the manufactured electronic element 1 is as shown in FIG. 8. However, the manufactured electronic element 1 does not have a functional layer 40.

[0055] A glass substrate with ITO having a width of 15 mm and a thickness of 150 nm was washed, followed by UV ozone treatment, and then moved into a glove box filled with nitrogen. An acetonitrile solution of phosphotungstic acid (PWA) adjusted to a predetermined concentration so as to obtain a film thickness of 173 nm (Comparative Example 1-1), and to this solution, A solution in which 0.5 part by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-1), A solution in which 1 part by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-2), A solution in which 3 parts by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-3), A solution in which 10 parts by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-4), A solution in which 0.5 part by mass of phosphomolybdic acid (PMA) was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-5), A solution in which 1 part by mass of phosphomolybdic acid (PMA) was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-6), A solution in which 3 parts by mass of phosphomolybdic acid (PMA) was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-7), A solution in which 10 parts by mass of phosphomolybdic acid (PMA) was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 1-8), A solution (Example 1-9) prepared by adding 0.5 parts by mass of copper iodide (CuI) to 100 parts by mass of phosphotungstic acid (PWA), A solution (Example 1-10) prepared by adding 1 part by mass of copper iodide (CuI) to 100 parts by mass of phosphotungstic acid (PWA), A solution (Example 1-11) prepared by adding 3 parts by mass of copper iodide (CuI) to 100 parts by mass of phosphotungstic acid (PWA) were prepared.

[0056] Each solution was dropped onto a substrate fixed on the spin table of a spin coater and spin-rotated at 5000 rpm for 180 seconds to coat and form a charge transport layer without an anti-coloring agent (Comparative Example 1-1) and a charge transport layer with an anti-coloring agent (Examples 1-1 to 1-11). At this time, the parts that were not desired to be coated were covered with a mask, and the mask was removed after coating. Next, a heat treatment was performed at 150 °C for 10 minutes under nitrogen to remove the solvent. Next, the substrate was transferred into a vacuum chamber, and an anode with a thickness of 12 nm was vapor-deposited and formed with Al having a width of 10 mm at a film formation rate of 1 to 10 Å / second. Subsequently, the substrate was taken out from the vacuum chamber into a glove box filled with nitrogen, and a glass tube coated with a UV-curable adhesive was covered over the element part and sealed by UV irradiation. The area of the fabricated element was 150 mm 2 is.

[0057] <Measurement results for verification: Evaluation of coloring> The Al film thickness of the fabricated element is as thin as 12 nm and allows a part of visible light to pass through, so the absorption spectrum can be evaluated. Also, the element area is 10 mm × 15 mm, which is sufficiently larger than the shape of the light used for general absorption spectrum measurement. First, with the ITO electrode of the element as the cathode and Al as the anode, a power supply was connected, and the absorption spectrum of the element part was measured without applying a voltage. Next, a voltage was applied to the device. The voltage was gradually increased from 0 V to allow current to flow, and it was increased up to 7 V. After holding at 7 V for 1 minute, the application of the voltage was stopped. The absorption spectrum of the device part was measured again. The differences in the absorption spectra before and after the voltage application are shown in FIGS. 9 to 12, and the differences in absorbance at 685 nm and 480 nm are shown in Tables 2 and 3.

[0058] [Table 2]

[0059] [Table 3]

[0060] From FIGS. 9 to 12, Tables 2 and 3, it can be seen that in all the devices (Examples 1-1 to 1-11) to which the anti-coloring agent was added, the coloring after driving by applying a voltage to the device was suppressed compared to the one with only PWA (Comparative Example 1-1). This is because the anti-coloring agent receives electrons instead of PWA, suppressing the reduction of tungsten in PWA.

[0061] (Comparative Example 2-1 and Examples 2-1 to 2-6) The electronic devices 1 of Comparative Example 2-1 and Examples 2-1 to 2-6 were manufactured as follows. The structure of the manufactured electronic device 1 is as shown in FIG. 8. However, the manufactured electronic device 1 does not have the functional layer 40.

[0062] A glass substrate with ITO having a width of 3 mm and a thickness of 150 nm was washed, followed by UV ozone treatment, and then moved into a glove box filled with nitrogen. An acetonitrile solution of phosphotungstic acid (PWA) adjusted to a predetermined concentration so as to obtain a film thickness of 173 nm (Comparative Example 2-1), and to this solution, A solution in which 1 part by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 2-1), and A solution in which 3 parts by mass of HAT-CN was added to 100 parts by mass of phosphotungstic acid (PWA) (Example 2-2), and A solution (Example 2-3) prepared by adding 1 part by mass of phosphomolybdic acid (PMA) to 100 parts by mass of phosphotungstic acid (PWA), A solution (Example 2-4) prepared by adding 3 parts by mass of phosphomolybdic acid (PMA) to 100 parts by mass of phosphotungstic acid (PWA), A solution (Example 2-5) prepared by adding 1 part by mass of copper iodide (CuI) to 100 parts by mass of phosphotungstic acid (PWA), A solution (Example 2-6) prepared by adding 3 parts by mass of copper iodide (CuI) to 100 parts by mass of phosphotungstic acid (PWA) were prepared.

[0063] Each solution was dropped onto a substrate fixed on the spin table of a spin coater and spin-rotated at 5000 rpm for 180 seconds to coat and form a charge transport layer without addition of an anti-coloring agent (Comparative Example 2-1) and a charge transport layer with addition of an anti-coloring agent (Examples 2-1 to 2-6). At this time, the parts that were not desired to be coated were covered with a mask, and the mask was removed after coating. Next, heat treatment was performed at 150 °C for 10 minutes under nitrogen to remove the solvent. Next, the substrate was transferred into a vacuum chamber, and an electrode with a thickness of 100 nm was vapor-deposited and formed with Al having a width of 3 mm at a film formation rate of 1 to 10 Å / second. Subsequently, the substrate was taken out from the vacuum chamber into a glove box filled with nitrogen. After attaching a desiccant to a glass tube coated with a UV curable adhesive, it was covered over the element part and sealed hollow by UV irradiation. The area of the fabricated element is 9 mm 2 is.

[0064] <Measurement results for verification: Evaluation of current density-voltage characteristics> For each element, first, the characteristics of an element having a forward structure with ITO as the anode and Al as the cathode were evaluated. The voltage was gradually increased from 0 V, and the current density-voltage characteristics were evaluated. The current density was increased to 22.2 mA / cm 2 and held at the same current density for 10 seconds. Subsequently, the second current density-voltage measurement was evaluated. The voltages at 2.5 mA / cm 2 are summarized in Table 4.

[0065] Next, using measurement points different from the above, the characteristics of an element with an inverted structure having ITO as the cathode and Al as the anode were evaluated in the same manner as above. The voltage at 2.5 mA / cm 2 is summarized in Table 4.

[0066]

Table 4

[0067] As can be seen from Table 4, the element without the addition of the anti-coloring agent (Comparative Example 2-1) was driven at 0.3 V. The elements with 1 part by mass of the anti-coloring agent added (Examples 2-1, 2-3, 2-5) all had driving voltages almost equivalent to 0.3 V. The elements with 3 parts by mass of the anti-coloring agent added (Examples 2-2, 2-4, 2-6) had slightly higher driving voltages, but the increase in the driving voltage was sufficiently small. From this, it can be understood that the addition of the anti-coloring agent can suppress coloring while suppressing the deterioration of electrical characteristics.

Industrial Applicability

[0068] The electronic element of the present invention includes a metal oxide, and has a charge transport layer that achieves both high conductivity and high transparency in the visible light region. By applying it to an organic EL element, it can be driven at a low voltage while improving the light emission efficiency. Further, by incorporating such an organic EL element into a display device or a lighting device, it becomes possible to improve the light emission efficiency of the display device or the lighting device.

Explanation of Symbols

[0069] 1: Electronic element 10: Substrate 20: Electrode (cathode) 30: Charge transport layer 40: Functional layer 50: Electrode (anode)

Claims

1. In an electronic device comprising an anode, a cathode, and a charge transport layer positioned between the anode and the cathode, the charge transport layer contains a metal oxide and a compound having a higher reducibility than the metal oxide, the content of the compound having a higher reducibility than the metal oxide is 3 parts by mass or less with respect to 100 parts by mass of the metal oxide, the metal oxide is phosphotungstic acid represented by the formula: H3PW12O40, and the electronic device is characterized by this.

2. The electronic device according to claim 1, wherein the compound having a higher reducibility than the metal oxide is at least one selected from the group consisting of molybdic acid, copper(I) iodide, and dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN).

3. An organic electroluminescence device comprising the electronic device according to claim 1 or 2 and a light-emitting layer, characterized in that the light-emitting layer is positioned between the anode and the cathode.

4. A display device comprising the organic electroluminescence device according to claim 3.

5. An illumination device comprising the organic electroluminescence device according to claim 3.

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