JP5395447B2 - Coating liquid for forming organic / inorganic composite semiconductor material layer and organic EL device - Google Patents

Description

  The present invention relates to a coating liquid for forming an organic-inorganic composite semiconductor material layer and an organic EL element having an electron transport layer formed using the coating liquid.

Examples of the organic semiconductor element having an organic semiconductor layer or an organic-inorganic composite semiconductor layer include an organic EL element, an organic transistor, and an organic solar battery.
In an organic EL (electroluminescence) element, by applying a voltage between a cathode and an anode sandwiching an organic light emitting layer (organic electroluminescence layer), electrons and holes injected from both electrodes are organically emitted. The layers recombine, and their energy emits light by exciting the emission center.
The organic EL device using an organic compound as a light-emitting material is inferior in luminous efficiency compared to an inorganic EL device using a metal compound as a light-emitting material, but can be driven at a low voltage, and various emission colors can be obtained. In recent years, active research has been carried out.

For example, in order to obtain a higher-performance organic EL device, a device structure in which various layers that facilitate transport and injection of electrons and holes are provided between the cathode and the light-emitting layer or between the anode and the light-emitting layer. Has been proposed.
In addition, the performance of these layers has a great influence on device characteristics, so that improvement is urgently required.

  Japanese Patent Application Laid-Open No. 11-162646 (Patent Document 1) discloses an alkali metal halide or halogenated metal between a hole injection electrode (anode) and an organic layer and between an electron injection electrode (cathode) and an organic layer, respectively. An organic EL element provided with a dielectric thin film layer made of an alkaline earth metal is disclosed. However, the method of forming the dielectric thin film layer is a dry method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, or a sputtering method, and cannot be produced by a wet method such as printing that can easily form a layer. Small manufacturing merit.

  Japanese Patent Laying-Open No. 2007-141917 (Patent Document 2) discloses an organic EL element in which an organic compound layer containing a decomposition product of cesium carbonate is provided between a cathode and an organic layer. However, since the organic compound layer is formed by a resistance heating method and is exposed to a high temperature of 700 ° C. or higher during vapor deposition, there is a possibility that the underlying organic layer may be destroyed by heat. It is not preferable.

  Japanese Unexamined Patent Application Publication No. 2006-190995 (Patent Document 3) discloses an organic EL device in which an organic layer directly under a cathode contains an electron-donating metal compound. However, in the manufacturing process, the electron-donating metal compound has been improved in electron transportability by steam treatment, hydrolysis, etc., so that there is a problem that deterioration of the organic EL element due to moisture remaining in the organic layer is promoted. is there.

  JP 2007-281039 A (Patent Document 4) includes an anode, a hole injection layer, an organic light emitting layer, an electron transport layer, and a cathode, which are stacked in this order, and the electron transport layer includes a specific phosphorus compound, an alkali metal ion, There has been disclosed an organic EL device composed mainly of a material containing at least one metal ion of alkaline earth metal ions and rare earth metal ions. In this organic EL element, the organic EL element is intended to be driven at a low voltage by the interaction between a phosphate group of a specific phosphorus compound and a metal ion.

  Japanese Unexamined Patent Application Publication No. 2007-273978 (Patent Document 5) discloses an organic EL element in which the electron transport layer is a layer made of at least one matrix material that is an electron transport material and at least one doping material. However, it is a combination of materials that can be used only in the vacuum deposition method in the manufacturing process, and is not suitable as a manufacturing process for manufacturing a large-area organic EL element.

JP-A-11-162646 JP 2007-141917 A JP 2006-190995 A JP 2007-283939 A JP 2007-273978 A

  The present invention is a coating liquid that can form an organic-inorganic composite semiconductor material layer that can be driven at a low voltage by a simple method that does not require heat treatment at a high temperature that adversely affects large-scale devices and elements, using few materials. It is another object of the present invention to provide an organic EL element having an electron transport layer formed using the same.

As a result of intensive studies to solve the above problems, the inventors of the present invention have formed an organic-inorganic composite semiconductor material layer containing an organic compound (organic semiconductor material) doped with a specific metal compound and an organic solvent . The present inventors have found that the above-described problems can be solved by the coating liquid , and have completed the present invention.

  Thus, according to the present invention, the formula (1):

An organic compound represented by the formula: a metal compound capable of releasing at least one metal ion selected from alkali metal ions, alkaline earth metal ions and rare earth metal ions in a solvent; and the metal compound can be dissolved at room temperature. An organic-inorganic composite semiconductor material layer-forming coating liquid comprising an organic solvent is provided.

  Further, according to the present invention, at least a light emitting layer, an electron transport layer and a cathode are laminated in this order on the anode, and the electron transport layer uses the organic-inorganic composite semiconductor material layer forming coating solution. An organic EL device characterized by being formed by a wet method is provided.

According to the present invention, an organic-inorganic composite semiconductor material layer that can be driven at a low voltage can be formed by a simple method that does not require heat treatment at a high temperature that adversely affects large-scale devices and elements, using few materials. An organic EL device having a coating liquid and an electron transport layer formed using the coating liquid can be provided.
Further, the organic EL device of the present invention can use a metal having a high work function, such as aluminum, which has high electron transport layer efficiency and is stable as a cathode material.

It is a schematic cross section which shows an example of the organic EL element of this invention.

The coating liquid for forming an organic-inorganic composite semiconductor material layer of the present invention comprises an organic compound represented by formula (1) (hereinafter referred to as “compound 1”), an alkali metal ion, an alkaline earth metal ion, and a rare earth metal ion in a solvent. And a metal compound capable of releasing at least one metal ion selected from the above and an organic solvent capable of dissolving the metal compound at room temperature.
The coating liquid for forming an organic-inorganic composite semiconductor material layer of the present invention can be applied to layer formation of devices such as organic EL elements, organic transistors, organic solar cells, and organic semiconductor laser elements.
Hereinafter, although the aspect of an organic EL element is demonstrated, this description is an illustration and this invention is not limited by this.

Compound 1 as an organic semiconductor material contained in the coating liquid for forming an organic-inorganic composite semiconductor material layer of the present invention is 2,2 ′, 7,7′-tetrakis (diphenylphosphinyl) -9,9′-spirofluorene. It is.
Compound 1 is a known compound and can be obtained, for example, by a known method as described in International Publication No. 2005/104628 pamphlet.

The metal compound contained in the organic-inorganic composite semiconductor material layer forming coating liquid of the present invention is at least one metal selected from alkali metal ions, alkaline earth metal ions, and rare earth metal ions in a solvent (the coating liquid). It is a metal compound that can release ions.
Examples of the alkali metal ion include ions such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).
Examples of the alkaline earth metal ions include ions such as beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).
Examples of rare earth metal ions include scandium (Sc), yttrium (Y), ytterbium (Yb), samarium (Sm), and europium (Eu).

Examples of such metal compounds include inorganic acid salts such as carbonates, nitrates, and sulfates of the above metals; organic acid salts such as acetates and acetyl acetates, and halogens such as chlorides, bromides, and iodides. Metal salts such as hydrides; alkoxides such as methoxide and ethoxide; and complexes having an easily detachable ligand such as acetylacetonate.
Among these, alkali metal or alkaline earth metal halides or alkoxides are preferable.

  Specifically, cesium carbonate, cesium acetate, cesium chloride, cesium bromide, cesium iodide, cesium acetylacetonate; lithium carbonate, lithium acetate, lithium chloride, lithium bromide, lithium iodide, lithium acetylacetonate, methoxy Lithium, tert-butoxy lithium, diethoxybarium; calcium carbonate, calcium acetate, calcium chloride, calcium bromide, calcium iodide, calcium acetylacetonate; barium carbonate, barium acetate, barium chloride, barium bromide, barium iodide, Barium acetylacetonate; ytterbium carbonate, ytterbium acetate, ytterbium chloride, ytterbium acetylacetonate, and the like.

  Among these, lithium chloride, lithium iodide, cesium bromide, calcium bromide, barium bromide, barium iodide; methoxylithium, ethoxylithium, n, which are relatively stable in the atmosphere and easy to handle -Butoxylithium and tert-butoxylithium are particularly preferred.

The organic solvent capable of dissolving the metal compound at room temperature is preferably one that does not easily swell or dissolve the base layer forming the organic-inorganic composite semiconductor material layer and does not substantially contain water. Thereby, it is possible to prevent the light emitting material contained in the light emitting layer from being deteriorated, deteriorated or dissolved, and to prevent a decrease in device efficiency such as the light emitting efficiency of the organic EL element.
In view of the above points, the solvent is particularly preferably a protic polar solvent.

  Examples of the protic polar solvent include alcohols such as monohydric alcohols such as methanol, ethanol, propanol, butanol, benzyl alcohol, diethylene glycol monomethyl ether, and polyhydric alcohols such as ethylene glycol and glycerine; acetic acid, formic acid, (meta ) Carboxylic acids such as acrylic acid; Amines such as ethylenediamine and diethylamine; Amides such as formamide and N, N-dimethylformamide; Phenols such as phenol and p-butylphenol; Acetylacetone and diethyl malonate Active methylene compounds and the like. In this invention, these 1 type can be used individually or in combination of 2 or more types.

Among these, since the solubility of a metal compound is high and preparation of a coating liquid is easy, alcohols are preferable, and since water is assumed to degrade the organic EL element due to remaining, alcohols, particularly carbon number 1-7 monohydric alcohols are preferred.
Examples of monohydric alcohols having 1 to 7 carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol, 2-butanol, tert-butanol, pentanol, isopentanol, hexanol, heptanol, etc. Is mentioned.
Among these, a solvent having a relatively high boiling point is preferable for improving the film forming property, and 1-butanol, 2-butanol, and 3-methyl-1-butanol are particularly preferable.

The coating liquid for forming an organic-inorganic composite semiconductor material layer can be prepared by adding a metal compound to an organic solvent and dissolving it, and further adding Compound 1 as an organic semiconductor material.
In the case of using a mixed solvent, after dissolving the metal compound in an organic solvent in which the metal compound is more easily dissolved among the organic solvents to be used, other organic solvents are added, and the coating liquid for forming the organic / inorganic composite semiconductor material layer is prepared. It is preferable to prepare.

Although the density | concentration of the organic compound in the coating liquid for organic inorganic composite semiconductor material layer formation is not specifically limited unless it has a bad influence on a coating film or a coating process, it is preferable that it is 0.1-50 g / L, and 1-20 g. / L is particularly preferred.
Moreover, it is preferable to contain a metal compound in the ratio of 0.001-10 weight part with respect to 1 weight part of the compound 1 as an organic-semiconductor material, and it is further included in the ratio of 0.01-1 weight part. A ratio of 0.01 to 0.5 parts by weight is particularly preferable.

  The coating liquid for forming an organic-inorganic composite semiconductor material layer of the present invention may contain other additives as long as the effects of the present invention are not impaired.

The electron transport layer is applied by a known coating method, for example, by applying the organic-inorganic composite semiconductor material layer forming coating liquid of the present invention as an electron transport layer forming coating liquid on the light emitting layer of the organic EL element and drying the solvent It can be formed by a wet method.
Known coating methods include, for example, spin coating, casting, micro gravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, Examples include a flexographic printing method, an offset printing method, and an inkjet printing method.

The coating conditions may be appropriately set depending on the kind of the metal compound or solvent, the concentration of the metal compound, etc. For example, in the case of the spin coating method, the rotation speed is about 100 to 5000 rotations / minute, and the time is about 10 to 300 seconds. is there.
Drying (solvent removal) can be performed using a known apparatus such as a vacuum constant temperature dryer. The drying conditions may be such that the deposited layer does not change. For example, the temperature is about room temperature to about 200 ° C., and the time is about 0.1 to 2 hours.

In the organic EL device of the present invention, at least a light emitting layer, an electron transport layer, and a cathode are laminated in this order on the anode, and the electron transport layer uses the organic-inorganic composite semiconductor material layer forming coating solution described above. It is formed by a wet method.
The organic EL element of the present invention will be described with reference to FIG. 1, but this description is an example, and the present invention is not limited thereby.

FIG. 1 is a schematic cross-sectional view showing an example of the organic EL element of the present invention.
The organic EL element 1 is formed by laminating a transparent electrode (anode) 3, a hole injection layer 4, a light emitting layer 5, an electron transport layer 6, and a cathode 7 in this order on a substrate (glass substrate) 2. Reference numeral 8 denotes a power source for driving, and the transparent electrode (anode) 3 and the cathode 7 are connected via the power source 8.

  The substrate 2 used in the present invention is not particularly limited as long as it is a transparent electrode, a cathode, and a support for each layer and does not change when forming them. Examples of such materials include polyethylene terephthalate, polyethylene, and the like. Examples thereof include resin materials such as naphthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, and polyarylate; glass materials such as quartz glass and soda glass; and composite materials thereof.

In the organic EL element of FIG. 1, since it is the structure (bottom emission type) which takes out light from the board | substrate 2 side, the board | substrate 2 is substantially transparent (colorless transparent, colored transparent, or translucent).
On the other hand, in the case of a configuration in which light is extracted from the side opposite to the substrate 2 (top emission type), the substrate 2 may be either a transparent substrate or an opaque substrate.
Examples of the opaque substrate include a substrate made of a ceramic material such as alumina, an oxide film (insulating film) formed on the surface of a metal substrate such as stainless steel, and a substrate made of a resin material. It is done.
The thickness of the substrate is, for example, about 0.1 to 30 mm, preferably about 0.1 to 10 mm.

The transparent electrode (anode) 3 has a function of injecting holes into a hole injection layer 4 or a light emitting layer 5 described later.
As a material constituting the transparent electrode (anode), for example, indium oxide, zinc oxide, tin oxide and a composite thereof such as indium tin oxide (ITO), indium zinc oxide, etc. Examples thereof include oxides, metals such as Au (gold), Pt (platinum), Ag (silver), and Cu (copper), and organic conductors such as polyaniline, polythiophene, and derivatives thereof. Among these, ITO is preferably used. Moreover, the glass substrate with an ITO transparent electrode integrated with a board | substrate and marketed can also be used.

The transparent electrode can be formed on the substrate by a known method such as a vacuum deposition method, a sputtering method, an ion plating method, or a plating method.
The film thickness can be appropriately selected in consideration of light transmittance and electric conductivity, and is about 10 to 200 nm, preferably about 50 to 150 nm.

The cathode 7 has a function of injecting electrons into an electron transport layer 6 described later.
Examples of the material constituting the cathode 7 include materials having a low work function, for example, metal materials such as gold, silver, copper, aluminum, nickel, titanium, and tungsten, and alloys thereof. Whether the cathode is transparent or opaque may be determined according to the form of the organic EL element.

The cathode can be formed by a known method such as a vacuum deposition method, a sputtering method, or a laminating method in which a metal thin film is thermocompression bonded.
The cathode may have a laminated structure of two or more layers, and the thickness thereof is about 50 to 10,000 nm, preferably about 80 to 500 nm.

  Since the organic EL device of the present invention has an electron transport layer formed by a wet method using a specific electron transport layer forming coating liquid, a metal that is chemically stable and difficult to inject electrons into the organic layer is formed. It can be used as a cathode material, and aluminum is preferable as the cathode material from such a viewpoint.

The organic EL element of the present invention may include a hole injection layer 4.
The hole injection layer has a function of injecting holes injected from the transparent electrode (anode) 3 into the light emitting layer 4.
Examples of the material constituting the hole injection layer (hole transport material) include metal or metal-free phthalocyanine compounds such as phthalocyanine, copper phthalocyanine (CuPc), and iron phthalocyanine, polyarylamine, and fluorene-arylamine. Polymer, fluorene-bithiophene copolymer, poly (N-vinylcarbazole), polyvinylpyrene, polyvinylanthracene, polythiophene, polyalkylthiophene, polyhexylthiophene, poly (p-phenylene vinylene), polytinylene vinylene, pyrene formaldehyde resin Ethylcarbazole formaldehyde resin or a derivative thereof, and the like can be used alone or in combination of two or more.
Moreover, the said compound can also be used as a mixture with another compound. As an example, examples of the mixture containing polythiophene include poly (3,4-ethylenedioxythiophene / styrene sulfonic acid) (PEDOT / PSS).

The hole injection layer is applied by a known method, for example, a hole injection layer forming coating solution in which a hole transport material is dissolved or dispersed in a known solvent, and the solvent is dried (desolvent). Can be formed.
The thickness of the hole injection layer is about 5 to 150 nm, preferably about 10 to 80 nm.

  In the light emitting layer 5, the holes supplied (injected) from the transparent electrode (anode) 3 or the hole injection layer 4 and the electrons supplied (injected) from the electron transport layer 6 are recombined. Exciton (exciton) is generated by the released energy, and energy (fluorescence or phosphorescence) is emitted (emitted) when the exciton returns to the ground state.

As a material (light emitting material) constituting the light emitting layer 5, for example, 1,3,5-tris [(3-phenyl-6-tri-fluoromethyl) quinoxalin-2-yl] benzene (TPQ1), 1,3 , 5-[{3- (4-tert-Butylphenyl) -6-trisfluoromethyl} quinoxalin-2-yl] benzene (TPQ2), tris (8-hydroxyquinolinolate) aluminum ( Low molecular weight compounds such as Alq ₃ ), factory (2-phenylpyridine) iridium (Ir (ppy) ₃ ), oxadiazole polymers, triazole polymers, carbazole polymers, polyfluorene polymers Polymers such as polymers and polyparaphenylene vinylene polymers can be used, and one of these can be used alone or in combination of two or more.

The light emitting layer can be formed by applying a known method, for example, a light emitting layer forming coating solution in which a light emitting material is dissolved or dispersed in a known solvent, and drying (desolving) the solvent. it can.
The thickness of the light emitting layer is about 10 to 150 nm, preferably about 20 to 100 nm.

The electron transport layer 6 has a function of transporting electrons injected from the cathode 7 to the light emitting layer 5.
The electron transport layer is formed by a wet method using the coating liquid for forming the organic-inorganic composite semiconductor material layer.
The film thickness of the electron transport layer is about 0.1 to 100 nm, preferably about 5 to 50 nm.

The organic EL device of the present invention may include a sealing member (not shown) that covers the transparent electrode (anode) 3, the hole injection layer 4, the light emitting layer 5, the electron transport layer 6, the cathode 7, and the like.
The sealing member hermetically seals the electrodes and constituent layers of the organic EL element, blocks oxygen and moisture, prevents their deterioration and deterioration, and has a function of preventing deterioration of the characteristics of the organic EL element. .
As a material constituting the sealing member, for example, aluminum (Al), gold (Au), chromium (Cr), niobium (Nb), tantalum (Ta), titanium (Ti) or an alloy containing these, silicon oxide, Various resin materials are listed. When the sealing member itself has conductivity, an insulating film may be provided as necessary in order to prevent a short circuit.

  The present invention will be specifically described by the following examples and comparative examples, but these examples do not limit the scope of the present invention.

Example 1
The organic EL element 1 of FIG. 1 was produced and evaluated.
A glass substrate with indium tin oxide (ITO) transparent electrode (manufactured by Sanyo Vacuum Industry Co., Ltd., substrate: 50 mm × 50 mm × thickness 0.7 mm, electrode: line shape with film thickness 80 nm, width 3 mm) and alkaline cleaning liquid (Kanto) Chemical cleaning, product name: CLEA 635N) and ultrasonic cleaning in acetone sequentially for 5 minutes. Next, the glass substrate was cleaned by boiling in isopropyl alcohol for 5 minutes, and further UV ozone cleaned by an ultraviolet-ozone cleaner for 15 minutes.

  Next, on the transparent electrode (anode) 3 of the cleaned glass substrate 2, poly (3,4-ethylenedioxythiophene) (PEDOT) as a conductive polymer and polystyrene sulfonic acid (PSS) as a polymer electrolyte. ) Solution (polythiophene-based conductive polymer, manufactured by H.C. Starck Co., Ltd., trade name: CLEVIOS: PVP CH8000) is dropped through a 0.45 μm syringe filter and is rotated at 2000 rpm. The film was applied by spin coating under the condition of 30 seconds. Next, the obtained substrate was dried for 1 hour with a drier set at 105 ° C. to obtain a hole injection layer 4 having a thickness of 50 nm.

  Next, a solution obtained by dissolving a yellow light emitter in toluene (trade name: PDY132, manufactured by Merck Co., Ltd.) is dropped on the hole injection layer 4 through a 0.45 μm syringe filter, and is rotated at 1200 rpm. The coating was performed by a spin coat method under the condition of seconds. Next, the obtained substrate was dried for 1 hour with a drier set at a temperature of 130 ° C. to obtain a light-emitting layer 5 having a thickness of 80 nm.

Next, 3 mg of n-butoxylithium as a metal compound is dissolved in 10 mL of 1-butanol, and 2,2 ′, 7,7′-tetrakis (diphenylphosphinyl) -9,9′-spirofluorene is further dissolved as an organic compound. (Compound 1) 30 mg was added to obtain a coating solution for forming an electron transport layer.
Next, the obtained coating liquid for forming an electron transport layer was dropped on a light-emitting layer 5 through a 0.45 μm syringe filter, and was applied by spin coating at 5000 rpm for 30 seconds. Next, the obtained substrate was dried for 1 hour with a drier set at a temperature of 130 ° C. to obtain an electron transport layer 6 having a thickness of 10 nm.

Finally, aluminum was vapor-deposited on the electron transport layer 6 by a resistance heating method using a vacuum vapor deposition apparatus (manufactured by Kyushu Keiki Co., Ltd.) under conditions of a pressure of 4 × 10 ⁻⁵ Pa and a vapor deposition rate of 2 kg / sec. Then, a linear cathode 7 having a thickness of 100 nm and a width of 3 mm perpendicular to the line of the transparent electrode (anode) 2 was obtained, and the organic EL element 1 was completed.

When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. The driving voltage at a luminance of 500 cd / m ² was 3.2 V, and the current efficiency was 13.8 cd / A.
The obtained results are shown in Table 1 together with the metal compound material of the electron transport layer, the weight ratio of the organic compound to the material, and the cathode material.

(Comparative Example 1)
An organic EL element was produced in the same manner as in Example 1 except that the electron transport layer 6 was not formed, and was evaluated.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. The driving voltage at a luminance of 500 cd / m ² was 11.5 V, and the current efficiency was 0.13 cd / A.
The obtained results are shown in Table 1 together with the cathode material.

(Comparative Example 2)
The electron transport layer 6 is not formed, and a film is formed on the light emitting layer 5 by a resistance heating method using a vacuum deposition apparatus (manufactured by V-Tech Co., Ltd.) under conditions of a pressure of 4 × 10 ⁻⁵ Pa and a deposition rate of 0.2 kg / sec. Example 1 is the same as Example 1 except that 8 nm thick barium was vapor deposited and 100 nm thick aluminum was vapor deposited by resistance heating under the conditions of pressure 4 × 10 ⁻⁵ Pa and vapor deposition rate 2 Å / sec. Similarly, an organic EL element was produced and evaluated.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. The driving voltage at a luminance of 500 cd / m ² was 4.0 V, and the current efficiency was 9.8 cd / A.
The obtained results are shown in Table 1 together with the cathode material.

(Comparative Example 3)
An organic EL device was prepared in the same manner as in Example 1 except that n-butoxylithium was not doped as a metal compound in the electron transport layer 6 and evaluated.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. The driving voltage at a luminance of 500 cd / m ² was 6.4 V, and the current efficiency was 2.0 cd / A.
The obtained results are shown in Table 1 together with the cathode material.

(Comparative Example 4)
The electron transport layer 6 is not doped with n-butoxylithium as a metal compound, and a pressure of 4 × 10 ⁻⁵ Pa, a deposition rate of 0.2 Å / min is used on the electron transport layer 6 using a vacuum deposition apparatus (manufactured by V-Tech Co., Ltd.). Lithium fluoride with a film thickness of 0.6 nm is deposited by resistance heating method under the condition of seconds, and aluminum with a film thickness of 100 nm is deposited by resistance heating method under the conditions of pressure of 4 × 10 ⁻⁵ Pa and vapor deposition rate of 2 liters / second. Then, an organic EL device was produced in the same manner as in Example 1 except that the cathode 7 was obtained, and was evaluated.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. The driving voltage at a luminance of 500 cd / m ² was 3.5 V, and the current efficiency was 12.3 cd / A.
The obtained results are shown in Table 1 together with the cathode material.

(Examples 2 to 23)
As shown in Table 1, an organic EL device was prepared and evaluated in the same manner as in Example 1 except that the type of the metal compound of the electron transport layer 6 and the weight ratio of the metal compound to the compound 1 were changed. .
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. In addition, driving voltage and current efficiency at a luminance of 500 cd / m ² were measured.
The obtained results are shown in Table 1 together with the metal compound material of the electron transport layer, the weight ratio of the organic compound to the material, and the cathode material.

The following can be seen from the results in Table 1.
(1) The organic EL device (Examples 1 to 23) provided with the electron transport layer of the present invention exhibits high efficiency at a low driving voltage as compared with the organic EL device (Comparative Example 1) not provided with the electron transport layer. (2) The organic EL device (Examples 1 to 23) provided with the electron transport layer of the present invention was compared with the organic EL device (Comparative Example 2) using a barium / aluminum electrode without providing the electron transport layer. (3) The organic EL device (Examples 1 to 23) provided with the electron transport layer of the present invention is an organic EL that does not contain the inorganic group compound constituting the electron transport layer of the present invention. Compared to the device (Comparative Example 3), the effect of lowering the driving voltage is obtained. (4) The organic EL device (Examples 1 to 23) provided with the electron transport layer of the present invention is the Containing no inorganic group compound and lithium fluoride / aluminum Than organic EL device (Comparative Example 4) using an electrodeless, exhibit high efficiency equal to or lower driving voltage, it former obtained, the effect only of an aluminum electrode

(Example 24)
In 10 mL of 1-butanol, 10 mg of n-butoxylithium is dissolved as a metal compound, and 2,2 ′, 7,7′-tetrakis (diphenylphosphinyl) -9,9′-spirofluorene (compound 1) is dissolved as an organic compound. ) An organic EL device was prepared and evaluated in the same manner as in Example 1 except that 100 mg was added to obtain a coating solution for forming an electron transport layer, and an electron transport layer 6 having a film thickness of 30 nm was obtained.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. At a luminance of 500 cd / m ^2, the driving voltage was 3.8 V, the driving current was 3.9 mA / cm ² , and the current efficiency was 12.6 cd / A.

(Comparative Example 5)
As in Example 1, except that 4,4 ′, 4 ″ -tris (diphenylphosphinyl) -triphenylphosphine oxide (TPPO-Burst) was used as the organic compound in the electron transport layer 6 instead of Compound 1. Thus, an organic EL element was produced and evaluated.
When the obtained organic EL element was energized and driven, yellow light emission derived from the light emitter PDY132 of the light emitting layer 5 was obtained. At a luminance of 500 cd / m ^2, the driving voltage was 4.5 V, the driving current was 4.5 mA / cm ² , and the current efficiency was 11.5 cd / A.

  From the above results, the organic EL device (Example 24) provided with the electron transport layer of the present invention is lower than the organic EL device (Comparative Example 5) provided with an electron transport layer using a known phosphorus compound. It can be seen that the driving voltage shows high efficiency.

1 Organic EL device 2 Substrate (glass substrate)
3 Transparent electrode (anode)
4 hole injection layer 5 light emitting layer 6 electron transport layer 7 cathode 8 power supply

Claims (10)

Formula (1):
An organic compound represented by the formula: a metal compound capable of releasing at least one metal ion selected from alkali metal ions, alkaline earth metal ions and rare earth metal ions in a solvent; and the metal compound can be dissolved at room temperature. A coating liquid for forming an organic-inorganic composite semiconductor material layer, comprising an organic solvent.   Said metal compound is selected from carbonates, nitrates, sulfates, acetates, acetylacetates, halides, alkoxides and complexes of at least one metal selected from alkali metals, alkaline earth metals and rare earth metals The coating liquid for organic-inorganic composite semiconductor material layer formation of Claim 1.   The coating solution for forming an organic-inorganic composite semiconductor material layer according to claim 2, wherein the metal compound is a halide or alkoxide of an alkali metal or an alkaline earth metal.   4. The metal compound is lithium chloride, lithium iodide, cesium bromide, calcium bromide, barium bromide, barium iodide; methoxy lithium, ethoxy lithium, n-butoxy lithium or tert-butoxy lithium. Coating liquid for forming an organic-inorganic composite semiconductor material layer. The organic-inorganic composite semiconductor material layer forming coating solution contains the organic compound at a concentration of 0.1 to 50 g / L, and the metal compound is 0.001 to 10 parts by weight with respect to 1 part by weight of the organic compound. The coating liquid for organic-inorganic composite semiconductor material layer formation as described in any one of Claims 1-4 included in the ratio of these.   The said organic solvent is a protic polar solvent, The coating liquid for organic-inorganic composite semiconductor material layer formation as described in any one of Claims 1-5.   The coating liquid for forming an organic-inorganic composite semiconductor material layer according to claim 6, wherein the protic polar solvent is a monohydric alcohol having 1 to 7 carbon atoms.   The coating liquid for forming an organic-inorganic composite semiconductor material layer according to claim 7, wherein the monohydric alcohol is 1-butanol, 2-butanol or 3-methyl-1-butanol.   The light emitting layer, the electron carrying layer, and the cathode are laminated | stacked in this order on the anode, The said electron carrying layer is a coating liquid for organic-inorganic composite semiconductor material layer formation as described in any one of Claims 1-8. An organic EL element formed by a wet method using   The organic EL element according to claim 9, wherein the cathode is made of aluminum.