JP2009212222A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can stabilize electron injection characteristic and improve a driving service life of a device even if its reactivity is high as a disadvantage and an alkali metal, an alkaline earth metal and its compound with superior electron injection characteristic are used as an electron injection material. <P>SOLUTION: A stable transition metal oxide is doped with at least one compound selected from an alkaline earth metal or an alkali metal as an electron injection material and/or their oxide and a halide. Thus, a stabilized electron injection layer can be made to have superior electron injection characteristic. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent device.

  An organic electroluminescent element is a light-emitting device that utilizes the electroluminescence phenomenon of a solid fluorescent material, and is partially put into practical use as a small display.

  Organic electroluminescent devices can be classified into several groups depending on the material used for the light emitting layer. One typical example is a low molecular weight organic electroluminescent device using a low molecular weight organic compound in the light emitting layer, which is mainly produced by vacuum deposition. The other is a polymer organic electroluminescent device using a polymer compound in the light emitting layer.

  The polymer organic electroluminescent device uses a solution in which the material constituting each functional layer is dissolved, so that wet methods such as a spin coating method, an ink jet method, a flood printing method, a gap coating method, a spray method, an LB method, and a printing method are used. The film can be formed by a coating method, and has attracted attention as a technology that can be expected to reduce costs and increase the area from a simple process.

  A typical polymer organic electroluminescent device is produced by laminating a plurality of functional layers such as a charge injection layer and a light emitting layer between an anode and a cathode. Below, the structure of the typical polymer organic electroluminescent element and its preparation procedure are demonstrated.

  For example, as shown in FIG. 8, PEDOT: PSS (mixture of polythiophene and polystyrene sulfonic acid: hereinafter referred to as PEDT) as a charge injection layer 123 on a glass substrate 100 on which ITO (indium tin oxide) as an anode 122 is first formed. A thin film is formed by spin coating or the like. PEDT is a material that has become a de facto standard as a charge injection layer, and functions as a hole injection layer by being disposed on the anode side.

On the PEDT layer, polyphenylene vinylene (hereinafter referred to as PPV) and a derivative thereof, or polyfluorene and a derivative thereof are formed as a light emitting layer 124 by a spin coat method or the like. An electron injection layer is formed on these light emitting layers by vacuum deposition, sputtering, or wet coating, and a metal electrode 126 is formed as a cathode using Al (aluminum), Ag (silver), or the like. Is completed. The layer having an electron injection function is a metal such as Ba (barium), Ca (calcium), Mg (magnesium), Li (lithium), Cs (cesium), or LiF (lithium fluoride), CaO (calcium oxide). Using a material having a low work function such as a fluoride or oxide of these metals or a carbonate such as CsCo ₃ , the organic material is efficiently injected into LUMO (lowest orbit). Carbon dioxide is also known to decompose during vapor deposition, and even though it is used as a vapor deposition material, the composition in the vapor deposition film is not yet fully understood, but it exists as an oxide. It is also possible to do. It is also known to use an organic matrix doped with the above materials.

  As described above, the polymer organic electroluminescent device has an excellent feature that it can be produced by a simple process, and is expected to be applied to various applications. This is a problem to be solved in that it cannot be performed and when the driving is performed for a long time, the lifetime is not sufficient.

  The decrease in the emission intensity of polymer organic electroluminescent devices, that is, the deterioration progresses in proportion to the product of the energization time and the current flowing through the device, but the details have not been clarified yet and earnest research is ongoing. It is being done.

  Various causes have been speculated about the cause of the decrease in emission intensity, but the stability of the light emitting material itself or the functional layer such as the hole injection layer and the electron injection layer to electrons and holes, side reactions from excitons, thermal It is thought to be due to a combination of various factors such as stability, stability of the interface between layers, diffusion of material by heat, oxidation of the cathode material, and the like.

  In polymer electroluminescent devices, the degradation of PEDT is considered as one of the main ones. As described above, PEDT is a mixture of two polymer substances, polystyrene sulfonic acid and polythiophene, the former being ionic and the latter having local polarity in the polymer chain. Due to the Coulomb interaction resulting from such charge anisotropy, the two are loosely coupled, thereby exhibiting excellent charge injection characteristics.

  In order for PEDT to exhibit excellent properties, close interaction between the two is indispensable. In general, however, a mixture of polymer substances tends to cause phase separation due to a subtle difference in solubility in a solvent. This is no exception for PEDT. The occurrence of phase separation means that the loose bond between the two polymers is relatively easily removed, and the PEDT is in the organic electroluminescent device, and this organic electroluminescent Possibility of instability when the device is driven, and components that did not contribute to bonding as a result of phase separation, especially ionic components, diffuse due to the electric field accompanying energization, and undesirable effects on other functional layers This indicates that there is a possibility of affecting. Thus, although PEDT has excellent charge injection characteristics, it cannot be said that it is a stable substance.

From the results of various experiments, the present inventors have responded to the concerns related to PEDT as described above by forming MoO ₃ (molybdenum trioxide) instead of PEDT between the anode and the light emitting layer. It has been proposed that good injection characteristics can be obtained (Patent Document 1).

Although the present invention has greatly improved the problems associated with the hole injection layer disposed on the anode side, a low work function metal (alkali metal or alkaline earth metal) is used for the cathode to inject electrons into the LUMO of the light emitting material. The challenge of having to remain was still left. Furthermore, these metals and their compounds easily react with oxygen and moisture, and there is a big problem that the contact with the organic material and the cathode metal cannot be taken, or the light emitting region is reduced by leaving it alone. In order to prevent this, it is necessary to perform sealing without exposure to the air after forming the cathode, and it is necessary to perform the sealing performance very strictly, resulting in an increase in cost. There is also a known problem that these alkali metals diffuse into the light emitting layer during driving.
In addition, in the patent document 2, the present inventors have described that the uniformity of light emission can be obtained by providing the molybdenum oxides between the light emitting layer and the cathode. It was insufficient.

  On the other hand, low molecular organic electroluminescent elements have a longer lifetime than devices using polymers as light emitting materials, and are being commercialized. However, as the electron injection layer, a method in which an alkali metal or alkaline earth metal halide represented by LiF or CsF, a carbonate or the like is used alone or an organic electron transport material is doped. Also in this case, as with the polymer type device, it is significantly deteriorated by exposure to the atmosphere, and trapping sites are formed by reaction and diffusion with the organic layer of the alkali metal and alkaline earth metal by continuous driving. It has been estimated that this causes a problem related to the lifetime, such as an increase in the driving voltage of the element.

JP 2005-203340 A Japanese Patent Application No. 2006-116184

In the structure of Patent Document 2, a MoO ₃ film having a thickness of about 20 nm is used on the anode, and a functional layer such as a light emitting layer is formed on the upper layer. On the electron injection side, an intermediate layer made of an alkali metal such as Ba, Ca, Mg, Li, or Cs, an alkaline earth metal, or a fluoride or oxide of these metals such as LiF or CaO is brought into contact with the organic layer. The electrode layer (cathode) made of a metal material such as Ag or Al is formed on the electron injection layer, and a laminated structure of metal composed of the intermediate layer and the electrode layer. Is used.
As described above, since a highly reactive material is used for the electron injection layer, there is a problem that it is easily oxidized and diffuses to other layers. These all contributed to the deterioration of organic electroluminescent devices. Further, these metal compounds are known to trap exciton generated in the light emitting layer, and it may be necessary to provide a buffer layer or the like for preventing this. As described above, it is necessary to use a material having a low work function for the electron injection layer, but it has high reactivity and is unstable, which leads to an increase in voltage during continuous driving and a decrease in luminance.

  The present invention has been made in view of the above circumstances, and uses an alkali metal, an alkaline earth metal and a compound thereof having an excellent electron injection property while having a defect of high reactivity as an electron injection material. An object of the present invention is to provide an element structure of an organic electroluminescent element that can stabilize injection characteristics and improve the drive life of the device.

  Accordingly, the present invention provides a stable transition metal oxide by doping at least one compound selected from an alkaline earth metal or alkali metal that is an electron injection material and / or oxides and halides thereof. In addition, the inventors have found that an electron injection layer excellent in electron injection characteristics can be configured, and have been made paying attention to this point.

  That is, the organic electroluminescent device of the present invention includes an anode and a cathode, and a plurality of functional layers formed between the anode and the cathode, and the functional layer is a light emitting element composed of at least one organic semiconductor. Between the layer having a function and the cathode and the layer having the light emitting function, at least one compound selected from an alkaline earth metal or an alkali metal and / or oxides or halides thereof is included. It has an impurity-containing transition metal oxide layer made of at least one kind of transition metal oxide.

  According to this configuration, it is unstable with respect to oxygen by doping alkali metal, alkaline earth metal and its compound, which has excellent electron injection characteristics but is unstable and has a low device driving life. The present inventors have discovered that a transition metal oxide that does not have electron injection characteristics by itself can exhibit stable and excellent electron injection characteristics, and has focused on this.

In the organic electroluminescent element, the impurity-containing transition metal oxide layer is preferably a layer in which molybdenum oxide is doped with barium or barium oxide.
According to this configuration, barium is a stable compound among the alkaline earth metals, easily enters the molybdenum oxide crystal, and easily moves in the crystal, so that the electron injection characteristics are improved. .

In the organic electroluminescent element, the impurity-containing transition metal oxide layer is preferably a layer in which molybdenum oxide is doped with lithium or lithium oxide.
According to this configuration, lithium is a highly active element, but is a stable compound among alkaline earth metals, and easily enters into the molybdenum oxide crystal and more easily moves in the crystal. As a result, the electron injection characteristics are improved.

In the organic electroluminescent device, the impurity-containing transition metal oxide layer is preferably represented by MoO _Y (Y <3) with respect to the molybdenum oxide represented by MoO ₃ .
That is, the molybdenum oxide is expressed by MoO _Y (Y <3) with respect to the molybdenum oxide expressed by MoO ₃ , and is preferably in an oxygen deficient state. It becomes closer and has higher conductivity.

  In the organic electroluminescent element, it is preferable that the impurity-containing transition metal oxide layer is formed between the layer having a light emitting function and a transition metal oxide layer.

Further, in the organic electroluminescence element, a transition metal oxide constituting the impurity-containing transition metal oxide, the transition metal oxide represented by the stoichiometric ratio M _x O _y, M _x O A transition metal oxide represented by _Y (Y <y) is desirable.
Here again, the impurity-containing transition metal oxide layer is preferably expressed as MoO _Y (Y <3) with respect to the molybdenum oxide expressed as MoO ₃ , and is preferably in an oxygen deficient state. Becomes closer to metal and has higher conductivity.
In the organic electroluminescent element, when the symbol M is a transition metal between the anode and the functional layer, the transition metal oxide represented by the stoichiometric ratio M _x O _y is M _An impurity-containing transition metal oxide layer containing a transition metal oxide represented by xO _Y (Y <y) is provided.
Here again, the impurity-containing transition metal oxide layer is preferably expressed as MoO _Y (Y <3) with respect to the molybdenum oxide expressed as MoO ₃ , and is preferably in an oxygen deficient state. Becomes closer to metal and has higher conductivity.

  Details are unknown, but in the atmosphere, alkali metals or alkaline earths are taken into the transition metal oxide matrix and the reaction with water and oxygen is inhibited by surrounding oxygen atoms. It is considered that an element structure having a stable and good injection characteristic can be obtained. Although the details are not clear, it is considered necessary for the impurity-containing transition metal oxide layer to be chemically unsaturated. Controlling this state is not known at this time, and is under investigation, but the transition metal oxide is selected from alkali metals or alkaline earth metals having a low work function and / or oxides and halides thereof. It is presumed that by doping with at least one compound, a more stable state can be achieved in the atmosphere.

  Here, the impurity-containing transition metal oxide includes at least one compound selected from alkaline earth metals or alkali metals and / or oxides or halides thereof in at least one kind of transition metal oxide. Refers to a compound.

  According to this configuration, the transition metal oxide can be stably and stably doped with an alkali metal, an alkaline earth metal, or a compound thereof, which has excellent electron injection characteristics but is unstable and has a low device driving life. An organic electroluminescent element structure having excellent electron injection characteristics can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Embodiment 1)

(Embodiment 1)
FIG. 1 illustrates a basic structure of a polymer organic electroluminescent element according to Embodiment 1 of the present invention.

  In the present embodiment, as shown in FIG. 1 which is a schematic diagram of the structure, an alkaline earth metal or alkali metal and / or oxide or halide thereof is selected between the cathode and the layer having a light emitting function. By providing an impurity-containing transition metal oxide layer comprising at least one kind of transition metal oxide containing at least one kind of compound, a stable and excellent electron injection layer is provided. It is what. That is, it constitutes a bottom emission type organic electroluminescent element, and charges (holes) are injected onto an anode 2 made of an indium tin oxide (ITO) layer formed on a translucent glass substrate 1. A molybdenum oxide thin film as a layer 3 and a polymer material as a light emitting layer 4 are sequentially laminated, and a barium-containing molybdenum oxide layer is further formed thereon as an impurity-containing transition metal oxide layer 5 as an electron injection layer 5. The cathode 6 made of an aluminum layer is sequentially laminated on the upper layer.

  That is, as shown in FIG. 1, the organic electroluminescent element of the present embodiment includes a substrate 1 made of a translucent glass material, an ITO thin film as an anode 2 formed on the substrate 1, Furthermore, a metal oxide thin film as the charge injection layer 3 formed on the upper layer, a light emitting layer 4 made of a polymer material, an impurity-containing transition metal oxide layer 5 composed of a barium-containing molybdenum oxide layer, aluminum It is comprised with the cathode 6 which consists of layers.

  When a direct current voltage or direct current is applied with the anode 2 of the organic electroluminescent element as a positive electrode and the cathode 6 as a negative electrode, the light emitting layer 4 made of a polymer film formed by a coating method has the anode 2 Then, holes are injected through the charge injection layer 3 and electrons are injected from the cathode 6. In the light emitting layer 4, the holes and electrons injected in this way are recombined, and a light emission phenomenon occurs when excitons generated along with the recombination shift from the excited state to the ground state.

According to the organic electroluminescent element of the present embodiment, since the electron injection layer is made of barium-doped molybdenum oxide (MoO ₃ ), stabilization and injection characteristics can be improved. Accordingly, it is possible to improve the light emission characteristics and extend the lifetime, and it is possible to configure a highly reliable bottom emission type organic electroluminescent element.

(Embodiment 2)
FIG. 2 illustrates a basic structure of the polymer organic electroluminescent element according to the second embodiment of the present invention.

  The difference between the present embodiment and the organic electroluminescent element of the first embodiment is that the light emitting layer 4 and the impurity as the electron injection layer of the organic electroluminescent element of the first embodiment shown in FIG. The transition metal oxide layer 7 made of molybdenum oxide having a thickness of about 5 nm is interposed between the transition metal oxide layer 5 and the contained transition metal oxide layer 5 as shown in FIG. Other parts are formed in the same manner as the organic electroluminescent element of the first embodiment.

  That is, as shown in FIG. 2, the organic electroluminescent element of the present embodiment includes a substrate 1 made of a light-transmitting glass material and indium tin oxide (as an anode 2 formed on the substrate 1). ITO) thin film, a metal oxide thin film as the charge injection layer 3 formed thereon, a light emitting layer 4 made of a polymer material, a transition metal oxide layer 7 made of molybdenum oxide, and a barium-containing oxide. An impurity-containing transition metal oxide layer 5 composed of a molybdenum layer and a cathode 6 composed of an aluminum layer.

  Also in this case, when a direct current voltage or direct current is applied with the anode 2 of the organic electroluminescent element as a positive electrode and the cathode 6 as a negative electrode, the light emitting layer 4 made of a polymer film formed by a coating method is applied. In this case, holes are injected from the anode 2 through the charge injection layer 3 and electrons are injected from the cathode 6. Here, the transition metal oxide layer 7 acts as a thin hole blocking layer. In the light emitting layer 4, the holes and electrons injected in this way are recombined, and a light emission phenomenon occurs when excitons generated along with the recombination shift from the excited state to the ground state.

  According to the organic electroluminescent element of the present embodiment, in addition to the operational effects of the first embodiment, in addition to barium-doped molybdenum oxide, a non-doped molybdenum oxide layer is stacked as an electron injection layer. Since the layer is interposed between the light emitting layer, it is more stable and has high injection characteristics. Accordingly, it is possible to improve the light emission characteristics and extend the lifetime, and it is possible to configure a highly reliable organic electroluminescent element. Here, it goes without saying that the film thickness of the non-doped molybdenum oxide layer is not limited to 5 nm and may be changed according to the characteristics required for the element.

Prior to the description of the embodiments, each element constituting the organic electroluminescent device of the present invention will be described.
(Electron injection layer)
An impurity-containing transition metal oxide layer comprising at least one transition metal oxide layer containing at least one compound selected from alkaline earth metals or alkali metals and / or oxides and halides thereof is used.
With this configuration, even if the cathode material is a highly reactive material, this impurity-containing transition metal oxide layer acts as a barrier layer, suppressing the flow of reactive substances from the cathode side and leading to deterioration of the light-emitting layer. it can. In addition, when a substance obtained by adding an impurity to a transition metal oxide such as MoO ₃ is applied to an organic electroluminescent element, charge injection is efficiently performed. Further, when used in a thin film of 1 μm or less, the influence of voltage drop is small, and an electric field applied between both electrodes is applied to the light emitting layer, and high luminance characteristics can be obtained. Impurity-containing transition metal oxides have properties such as electron injection capability, electron transport properties, and hole blocking properties, so that high functionality can be obtained with a single layer and the device configuration can be simplified. It becomes. Therefore, good electron injection can be realized and the light emitting region can be controlled. For this reason, in the past, an interlayer (intermediate layer) was interposed, and the emission region was controlled to be the interface between the emission layer and the interlayer, but there was no need to limit the emission region, and holes and electrons were injected. Molecular design for balancing is facilitated, luminous efficiency is improved, and device lifetime can be improved.

The electron injection layer of the present invention is constituted by doping an alkali metal or alkaline earth metal having a small work function. Specific examples include Ca, Ba, Li, and Cs, but are not limited thereto. In addition to these metals, oxides thereof, for example, halides such as CaO, BaO, Li ₂ O, Cs ₂ O ₃ , MgO, and LiF are also included. When these are doped into transition metal oxides, they are stabilized against air and oxygen, and it is possible to prevent instability of these compounds alone. Furthermore, since the periphery is covered with the transition metal oxide matrix, diffusion to other layers hardly occurs, and the light emission efficiency and the driving life are less adversely affected. In general, it is expected that electron emission is less likely to occur, but in the case of the present invention, as a result of various experiments, the electron emission property was good with few such side effects. Therefore, by using the element structure of the present invention, it is not necessary to arrange an electron transport layer made of an organic material or a layer made of an alkali metal having a low work function, which has been conventionally required, and a robust element can be obtained. I can do it.

The thickness of the impurity-containing transition metal oxide layer is preferably 1 nm or more and 1 μm or less.
If it exceeds 1 μm, the transmittance will be low, and it will usually be difficult to ensure, for example, 60% as the transmittance required for the display device. In consideration of the film formation time, it is preferably 500 nm or less. In the case of a thin film, even if it is not in the form of a film, if the film has an average thickness of about 1 nm, the same effect as described above can be obtained even if it is spongy. In the case of a film thinner than 1 nm, a sufficient effect as a metal oxide cannot be obtained.

Also, from the characteristics required for the device, the transmittance of the impurity-containing transition metal oxide layer is desirably 60% or more.
With this configuration, a sufficient amount of emitted light can be maintained. When the transmittance is less than 60%, there is a problem that the amount of emitted light decreases.

The impurity-containing transition metal oxide layer used as the electron injection layer in the present invention preferably has a work function of 4 to 6 eV.
With this configuration, a good ohmic contact can be formed. When the work function is less than 4 eV, the reactivity tends to be high, and it is difficult to reduce the influence of the reactive substance such as moisture or the like, which is a feature of the present invention. It may not be obtained. Moreover, although the detailed mechanism is not clear, if it exceeds 6 eV, the work function difference from the cathode becomes large, so that good light emission cannot be obtained.

In the organic electroluminescent element, the impurity-containing transition metal oxide layer preferably has a specific resistance of 1 * 10exp7Ωm or less.
With this configuration, it is possible to suppress a voltage drop caused by the transition metal oxide layer itself as a device and to emit light with high luminance.

In the organic electroluminescent element, it is desirable to use a molybdenum oxide layer as the transition metal oxide layer.
Although the molybdenum oxide layer is a metal oxide, its specific resistance is small, so that there is no voltage drop and highly reliable light emission is possible. In addition, since a good contact property can be obtained without using a reactive substance for the cathode, the cathode may have a single layer structure, and a thinner film can be achieved. In addition, since the barrier property is high and a smooth surface can be obtained, the uniformity of the light emitting layer can be obtained. Here, molybdenum oxide (MoOx) is not limited to MoO ₃ , but those having different valences are also effective.
In addition, although zinc may be classified as a typical element in recent years, it is assumed that it is included in the transition metal element of the present invention.

  In addition to molybdenum oxide, tungsten oxide, nickel oxide, vanadium oxide, titanium oxide, zinc oxide, or the like can be used for the transition metal oxide layer. Here, the oxide is not a composition defined by the stoichiometric ratio, but is preferably a compound having a different valence, that is, a compound having an oxygen defect. The oxidation number and composition can be known by XPS (X-ray photoelectron spectroscopy) analysis.

  In order to exhibit the effects of the present invention, it is necessary to dope the transition metal oxides with a compound containing an alkali metal, an alkaline earth metal, or an oxide thereof. Examples of the material used include simple metals such as barium, calcium, lithium and cesium, oxides such as barium oxide, calcium oxide, lithium oxide and cesium oxide, and halides such as lithium fluoride and calcium fluoride. It is not limited to this. In addition to oxides and halides, carbonates such as cesium carbonate are also effective, but they may become oxides during film formation processes such as vapor deposition.

In addition, when doping a transition metal oxide, its concentration depends on the thin film formation conditions, but is generally 1% to 50% by weight. Even when doping is not performed, oxygen vacancies are often caused by stoichiometry under normal deposition and sputtering conditions. When doping is performed, it is difficult to distinguish between the oxidation state of the doping element and the oxidation state of the transition metal oxide. However, in order to exert the effect of the present invention, the composition ratio of the metal and oxygen is set to oxygen. It is important to control the defect state. As the degree of oxygen vacancies increases, the metal oxide becomes closer to the metal and becomes more conductive. Since the state completely free of oxygen shows the properties of metal, the effect of the present invention cannot be obtained.
That is, an alkali metal or the like is liable to oxidize or react with water and cannot be stably driven in the air. Control of this state is not known at this time, and research is underway, but devices that use alkali metal as an electron injection layer by doping a transition metal oxide with an alkali metal having a low work function are more effective in the atmosphere. It became possible to take a stabilized state. Probably because alkali metals are taken into the transition metal oxide matrix and the reaction with water and oxygen is hindered by surrounding oxygen atoms, the details are not clear. It is considered necessary to be chemically unsaturated.

(Light emitting layer / intermediate (IL) layer)
On the hole injection layer, an organic semiconductor material is applied to form a light emitting layer. In this case, it is preferable in terms of luminous efficiency to provide an intermediate layer as a hole blocking layer between the light emitting layer and the hole injection layer. As the hole blocking layer, a polyfluorene-based polymer material having a LUMO level higher than that of the material used for the light emitting layer is used. However, the hole blocking layer is not limited to this. The light emitting layer may be of any type as long as it can be dissolved in a solvent and coated to form a thin film, including polyfluorene-based, polyphenylene vinylene-based, pendant-type, dendrimer-type, and coating-type low molecular weight types.

  In the organic electroluminescent device of the present invention, the layer having the light emitting function may be either a high molecular compound or a low molecular compound.

  In the organic electroluminescent element, the layer having the light emitting function may be a polymer compound including a fluorene ring. Here, the polymer compound containing a fluorene ring refers to a compound in which a desired group is bonded to the fluorene ring to form a polymer. Polymer compounds having various groups bonded thereto are commercially available.

  In addition, as a low molecular electroluminescent device, substrate / anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer (including doping material) / hole blocking layer / electron transport layer / electron injection layer / cathode There are various variations, for example, a top emission type that extracts light from the opposite direction of the substrate (in this case, a silver alloy or aluminum alloy with high reflectivity is used as the anode) There are a reverse structure type in which the arrangement of the anode and the cathode is reversed, a top emission type thereof, and the like, which can be applied when various compounds such as a fluorescent light emitting material and a phosphorescent light emitting material are used.

  The electron injection layer of the present invention is not limited to the above-described polymer type electroluminescent device in which the light emitting layer is made of a polymer material, but also a low molecular weight type electroluminescent device in which the light emitting layer is made of a low molecular material. It is also preferably used for nescent elements. In the case of application to a low molecular type, it is possible to replace an electron transport layer made of an organic substance. This makes it possible to remove metal layers and metal halides that are easily oxidized and are used for cathode and electron injection.

(cathode)
As the cathode, a material capable of making an ohmic contact with the electron injection layer of the present invention is preferable. Common metals such as Al, Ag, and Au, transparent conductive oxides such as ITO, and IZO are preferably used.

(Sealing)
It is preferable to seal the device of the present invention. In conventional electroluminescent devices, to ensure reliability, such as using a sealing resin with as low a moisture permeability as possible, sealing a film with a thin film layer formed on the element, and encapsulating a desiccant It was very expensive. According to the present invention, simple device sealing is necessary, but the cost can be reduced by a conventional sealing method. A simple sealing material can be widely selected from existing materials.

(Film forming method)
Further, among the functional layers constituting the organic electroluminescent device of the present invention, the film formation of the impurity-containing transition metal oxide layer and the transition metal oxide layer is not limited to the above method, but a vacuum evaporation method Desirable are dry processes such as electron beam evaporation, molecular beam epitaxy, sputtering, reactive sputtering, ion plating, laser ablation, thermal CVD, plasma CVD, and MOCVD.
Experimental results have shown that it is desirable to control the substrate temperature in such a dry process. By setting the substrate temperature to 60 to 100 ° C., it is possible to achieve an improvement in luminance and a decrease in the light emission starting voltage.
Furthermore, a continuous formation method is also effective in which the first layer is formed by co-evaporation, and then only the transition metal oxide layer is formed without containing alkali metals and alkaline earth metals.
Alternatively, the composition gradient film may be formed by co-evaporation with gradually decreasing the alkali metal and alkaline earth metal.
In addition, it is also effective to form by a co-sputtering method using a plurality of targets made of a transition metal oxide, an alkali metal, and an alkaline earth metal.
The film thickness is preferably within a range that does not impair the electron injection property, but is preferably several nm to 50 nm. Moreover, since the transmittance | permeability will become low when a metal component increases, it needs to be made thinner.
In addition, oxide nanoparticles or the like can also be applied. In this case, the sol-gel method, Langmuir-Blodgett method (LB method), layer-by-layer method, spin coating method, inkjet method, dip coating method, spray method, etc. can be selected as appropriate. Needless to say, any method can be used as long as it can be formed so as to achieve the effects of the present invention.

  When the functional layer of the present invention (light emitting layer or hole injection layer or electron injection layer formed as necessary) is formed of a polymer material, a spin coating method, a casting method, a dipping method, a bar A wet film forming method such as a coating method, a printing method using a roll, an ink jet method, or a nozzle coating method may be used. This eliminates the need for a large-scale vacuum apparatus, so that it is possible to form a film with an inexpensive facility, and it is possible to easily create an organic electroluminescent element with a large area, and also an organic electroluminescent device. Since the adhesion between each layer of the element is improved, a short circuit in the element can be suppressed, and a highly stable organic electroluminescent element can be formed.

  The glass substrate 100 is a single plate of colorless and transparent glass. Examples of the glass substrate 100 include transparent or translucent soda lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, quartz glass, and other transition metal oxide glasses, inorganic fluoride. Inorganic glass such as compound glass can be used.

(Embodiment 3)
Hereinafter, a display device using the organic electroluminescent element of the embodiment of the present invention will be described. This embodiment is an example of a top emission type polymer organic electroluminescent display device.
First, a display device using an organic electroluminescent element will be described. The display device according to the present embodiment basically has the organic electroluminescence according to the first embodiment shown in FIG. 1 in which a barium oxide-containing molybdenum oxide layer (electron injection layer) 5 is interposed on the cathode 6 side as a functional layer. An active matrix display device is formed using a light-emitting device similar to a luminescent element. 4 shows an equivalent circuit diagram of the active matrix type display device, FIG. 5 shows a layout explanatory diagram, FIG. 6 shows a sectional view, and FIG. 7 shows a top view explanatory diagram. The formed active matrix type display device is configured.

  As shown in an equivalent circuit diagram in FIG. 4 and a layout explanatory diagram of a pixel in FIG. 5, the display device 140 includes an organic electroluminescent element (electroluminescent) 110 and a switching transistor 130 that form a pixel, light detection, and the like. A plurality of driving circuits consisting of two thin film transistors (TFTs: T1, T2) consisting of current transistors 120 as elements and capacitors C are arranged vertically and horizontally, and the first TFT ( The gate electrode of T1) is connected to the scanning line 143 to give a scanning signal, and the drain electrode of the first TFT of each driving circuit arranged in the vertical direction is connected to the data line to supply a light emission signal. Has been. A driving power source (not shown) is connected to one end of the electroluminescent element (electroluminescent), and one end of the capacitor C is grounded. Reference numeral 143 denotes a scanning line, 144 denotes a signal line, 145 denotes a common power supply line, 147 denotes a scanning line driver, 148 denotes a signal line driver, and 149 denotes a common power supply line driver.

  6 is a cross-sectional view of the organic electroluminescent element (FIG. 6 is a cross-sectional view taken along the line AA of FIG. 5), and FIG. 7 is a top view of the display device, and a driving TFT (not shown). ) Formed on a glass substrate 100, an anode (Al) 112, a molybdenum oxide layer (transition metal oxide layer) 113, an organic buffer layer (charge block layer) (not shown), a light emitting layer 114 (red light emitting layer R, A green emission layer G, a blue emission layer B), a barium oxide-containing molybdenum oxide layer 115, and a cathode 116 are formed to form a top emission type organic electroluminescent element. As a structure, the anode and the charge injection layer are formed separately, the light emitting layer has an opening area defined by a protruding portion made of a silicon oxide layer as the pixel regulating layer 117, and the cathode 116 runs in a direction perpendicular to the anode. It is formed in a stripe shape. The driving TFT is formed, for example, by forming an organic semiconductor layer (polymer layer) on a glass substrate 100, covering it with a gate insulating film, forming a gate electrode thereon, and forming it on the gate insulating film. Source / drain electrodes are formed through through holes. Then, an insulating layer (flat layer) is formed by applying a polyimide film or the like thereon, and an anode (ITO) 112, a molybdenum oxide layer, an electron blocking layer, an organic semiconductor layer such as a light emitting layer, barium oxide containing It has a structure in which a molybdenum oxide layer 115 and a cathode 116 (Al ultra-thin film, ITO) are formed to form an organic electroluminescent element. In FIG. 7, although capacitors and wirings are omitted, these are also formed on the same glass substrate. A plurality of pixels composed of such TFTs and organic electroluminescent elements are formed in a matrix on the same substrate to constitute an active matrix display device.

At the time of manufacture, as shown in FIG. 5, a pixel regulating layer 117 is formed on the scanning line 143, the signal line 144, the switching TFT 130, the electrode 112 made of an aluminum pattern constituting the pixel electrode, and the like formed on the glass substrate 100. After forming, an opening is provided.
A transition metal oxide layer 113 is formed on the entire surface by vapor deposition.
Thereafter, TFB is applied as a buffer layer as required by an ink jet method. This TFB layer may be applied to the entire surface in the same manner as the transition metal oxide layer, or may be applied only to a portion corresponding to the opening.
Then, after a drying process, a polymer organic electroluminescent material corresponding to a desired color (any of RGB) is applied to a position corresponding to the opening by an ink jet method to form the light emitting layer 114.
Further, a barium oxide-containing molybdenum oxide layer 115 is formed by a co-evaporation method or the like, and finally a cathode 116 is formed in a region where the display pixel 141 is disposed.

According to this configuration, a display device that can be driven at high speed and has high reliability can be provided. Since the molybdenum oxide layer, which is an integrally formed transition metal oxide, is interposed between the light emitting layer and the anode, there is no crosstalk, and the light emitting layer is smoothed by the molybdenum oxide layer, resulting in high accuracy. The concave portion having the inner surface is controlled in size. For this reason, the light emitting layer can be reliably formed without positional deviation by the ink jet method, and the light emitting layer whose film thickness and size are controlled with high accuracy can be obtained. Further, since the molybdenum oxide layer formed integrally with the upper layer of the light emitting layer is formed, there is no spatter damage or plasma damage in the patterning process when the cathode is formed.
Therefore, the light emitting layer is formed on the uniformly formed surface, and the surface can be maintained in a smooth state. The light emitting layer is uniformly formed, there is no electric field concentration, and the electric field applied by the anode and the cathode is reduced. It is uniformly applied to the light emitting layer, and good light emission characteristics can be obtained. Further, each light emitting layer is formed uniformly, and good light emission characteristics can be obtained without variation in light emission characteristics.
Further, when the cathode 116 is formed or patterned, the light emitting layer is covered with at least the barium oxide-containing molybdenum oxide layer 116, so that it can be protected from sputter damage or plasma damage, and a highly reliable film can be formed. It becomes. Here, as shown in FIG. 6, the barium oxide-containing molybdenum oxide layer 116 and the lower molybdenum oxide layer (charge injection layer) 113 are integrally formed to be larger than the pattern of the light emitting layer 114 so as to cover the light emitting layer 114. Yes.

  Next, an example of a lighting device using a light emitting device in which a plurality of electroluminescent elements are two-dimensionally arranged will be described with reference to FIG. For the electroluminescent element 110 arranged two-dimensionally, for example, a configuration in which all the electroluminescent elements are simultaneously turned on / off can be realized very easily. However, at least one electrode (for example, a pixel electrode made of Al (see the anode 112 in FIG. 6)) is provided for each electroluminescent element unit even in such a configuration that the light is turned on / off all at once. It is desirable to have a separate configuration. This is because even if the display pixel 141 is defective due to some factor, the defect remains in the display pixel 141, so that the manufacturing yield of the entire lighting device can be improved. The lighting device having such a configuration can be applied to a general lighting fixture in a home, for example. In this case, since the lighting device can be configured to be extremely thin, it can be easily installed not only on the ceiling but also on the wall surface.

  In addition, the light emission pattern of the electroluminescent device arranged two-dimensionally can be easily controlled by supplying arbitrary data, and the electroluminescent device according to the present invention can emit light. Since the area can be configured with a size of about 40 μm square, for example, an application can be configured in which data is supplied to the lighting device and also used as a panel type display device. Of course, in this case, the display pixel 141 needs to be painted in red, green, and blue according to the position, but by using the ink jet method, it is possible to increase the number of colors very easily.

  Conventionally, when a lighting device and a display device are compared, the light emission luminance of the lighting device is larger. However, since the electroluminescent element 110 according to the present invention can have a sufficiently large area and has extremely high light emission luminance, the lighting device and the display device can be used together. In this case, the illumination device and the display device require a mechanism for adjusting the light emission luminance due to the difference in function (that is, the use mode). For this mechanism, for example, the configuration shown in the second embodiment is adopted. This can be realized by controlling the drive current to adjust the light emission luminance of each electroluminescent element. That is, when used as a lighting device, all the electroluminescent elements are driven with a larger current, and when used as a display device, the current value is small and controlled according to the gradation (i.e., in the image data). In response, each electroluminescent element may be driven. In such an application, the power source when functioning as a lighting device and the power source when functioning as a display device may be a single power source. However, for example, the dynamic range of a digital-analog converter that controls the drive current is controlled. In the case where the number of gradations when using as a display device is large, the power source (not shown) connected to the common power supply line 145 shown in FIGS. 4 and 5 is switched according to the use mode. It is desirable to use a simple configuration. Of course, even in a mode of use as a lighting device, in a mode where brightness control is necessary (that is, a lighting device having a dimming function), it is easily handled by current value control according to the gradation described above. be able to. Moreover, since the electroluminescent element of the present invention can be formed not only on the glass substrate 100 but also on a resin substrate such as PET, it can be applied as various illumination devices.

  Note that the thin film transistor may be an organic transistor. A structure in which an organic electroluminescent element is stacked on a thin film transistor or a structure in which a thin film transistor is stacked on an organic electroluminescent element is also effective.

  In addition, in order to obtain a high-quality electroluminescent display device, an electroluminescent substrate on which an organic electroluminescent element is formed and a TFT substrate on which a TFT, a capacitor, wiring, and the like are formed are electroluminescent. The electrodes on the cent substrate and the electrodes on the TFT substrate may be bonded together using a connection bank.

The transition metal oxide layer is formed so that the specific resistance in the stacking direction is about one third of the specific resistance in the plane direction. In addition, by setting the film thickness to 40 nm, which has not been considered in the past, the surface of the light emitting region can be satisfactorily reduced after the surface is smoothed and smoothed by the thick MoO ₃ layer. It is configured to regulate.

Here, a buffer layer (electronic block layer) made of TFB is interposed between the thick barium oxide-containing MoO ₃ layer as the barium oxide-containing transition metal oxide layer 115 and the anode 112 made of the Al layer. However, this buffer layer may be omitted.
Further, the barium oxide-containing transition metal oxide layer 115 may be formed on the pixel regulation layer 117.

Note that, as a modification of the third embodiment, a method of performing color separation in a color display device will be described.
In this example, RGB is separately applied using a substrate on which a thin film transistor is formed. A planarizing film was formed on the TFT substrate with an insulating organic material. On the substrate, ITO is formed as a transparent electrode by a sputtering method, and then pixel restricting layers are formed with respective thicknesses using SiN as in the third embodiment, and dry etching is performed so that a desired light emitting region is obtained.

  Then, using this TFT substrate, RGB was separately applied. A planarizing film was formed on the TFT substrate with an insulating organic material. On the substrate, ITO was formed as a transparent electrode by a sputtering method, and then a pixel regulating layer was formed with SiON in each thickness in the same manner as in Example 1, and dry etching was performed so as to obtain a desired light emitting region. . Thereafter, a bank made of polyimide was formed for each pixel column. As a result, a substrate was obtained that was divided into stripes for each column of elements in the bank. In this case, the bank has a forward tapered shape. An electroluminescent element was formed using the substrate. That is, as the hole injection layer, molybdenum oxide / tungsten instead of PEDT: PSS was formed to 50 nm in an oxygen atmosphere by co-sputtering. Molybdenum oxide / tungsten was entirely sputtered before forming the bank. This is characterized by low lateral resistance compared to PEDT and no crosstalk, so that it can be used in this way. Next, for each row divided by the bank, TFB was applied as an interlayer using a dispenser so as to have a thickness of 20 nm. After drying and baking it, using a dispenser in the same manner as the light emitting layer, inks of red light emitting material, green light emitting material, and blue light emitting material are prepared in each row divided by the bank, and the average is 80 nm. Application was performed so as to obtain a thickness. Thereafter, the molybdenum oxide and barium oxide of the present invention were deposited as an electron injection layer by a resistance heating vapor deposition apparatus. The substrate temperature was 100 ° C., and the thickness was 50 nm. Thereafter, 100 nm of aluminum was vacuum deposited as a cathode. The electron injection layer and the cathode were formed so as to cover all of the pixels.

A part of the TFT of the obtained sample was operated by an external circuit, and the light emission state and the lifetime were evaluated. A part of the TFT of the obtained sample was operated by an external circuit, and the light emission state and the lifetime were evaluated.
As a result, sufficient luminance and light emission efficiency were obtained even when operated in the atmosphere, and no significant deterioration occurred even when operated for several hours.

(Embodiment 4)
(Lighting device)

As an example of a lighting device, molybdenum oxide was sputtered to a thickness of 100 nm on a 30 cm square glass substrate provided with ITO, and then a polymer type white light emitting material was spin-coated to a thickness of 100 nm. Subsequently, 10% of lithium fluoride was co-deposited on the zinc oxide of the present invention as an electron injection layer, and then 100 nm was formed with Ag as the cathode.
When 10 V of DC was applied to the sample thus obtained, uniform light emission was obtained, and the sample was stably driven for 1 hour without generating a short circuit or a dark spot even without sealing.

Next, examples of the present invention will be described.
The structure is the same as that shown in FIG. 1, which is an example corresponding to the first embodiment, and will be described with reference to FIG.
The organic electroluminescent light emitting device of Example 1 is a glass substrate 1 designated as Corning 7029 # having a thickness of 0.71 mm, and an anode made of an ITO thin film having a thickness of 80 nm formed thereon. 2, a charge injection layer 3 made of PEDT having a thickness of 50 nm formed on the upper layer of the anode 2, and TFB which is a copolymer of polyfluorene and a triphenylamine derivative formed on the charge injection layer 3. (Poly 2,7-9,9-di-n-octylfluorene_-alt-1,4-phenylene-4-sec-butylphenylimino-1,4-phenylene) _ Poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] Poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] with a thickness of 80 nm as a material And a barium-containing oxide film having a thickness of 20 nm formed on the light-emitting layer 4. It is composed of a cathode 6 composed of a Buden layer and the thickness of 80nm layer of aluminum. The sample thus fabricated was designated as sample 103.

Here, PEDT as the charge (hole) injection layer 3 is H.264. C. CH8000 manufactured by Stark was used. PEDT was applied by spin coating and baked at 200 ° C. The thickness after baking was 60 nm. Thereafter, TFB was spin-coated as an interlayer to a thickness of 20 nm, baked at 180 ° C., and then the light emitting layer 4 was applied.
Subsequently, the materials shown in the table below were vacuum deposited as the electron injection layer 5, and Al was deposited as the cathode 6.

  The obtained sample was set to 101-105. The IV characteristics of these samples were measured, put into the atmosphere, driven at a constant current for 1 hour, and the voltage at that time was measured.

The results of the examples produced by the above method are shown in Table 1 below.

Here, a difference in driving voltage at a constant current of 100 mA / cm ² at room temperature was taken. (Voltage increase 1)
Time until each initial brightness is halved under the same conditions as above (lifetime 2)
The half lives of these organic electroluminescent light emitting devices were 10 hr, 14 hr, 50 hr, 60 hr, and 45 hr, respectively. Here, the half life was an initial luminance of 10,000 cd, and the luminance change was measured under constant current driving.

From the above, it can be seen that the initial drive voltage of the sample of the present invention is not significantly different from that of the comparative example, but the voltage increase after being driven in the atmosphere is small. This is because the deterioration in the atmosphere in the comparative example hinders the electron injection at the interface with the organic material due to the oxidation of the alkali metal, alkaline earth metal or its halide used for the electron injection layer (EIL) of the cathode. On the other hand, the sample of the present invention is protected by a stable transition metal oxide around unstable Ba and Li by being doped into a matrix of MoO ₃ , and the effect is effective for moisture in the atmosphere. It can be seen that the property of being easy to inject electrons, that is, being easily oxidized, is suppressed. It can also be seen that the electron emission capability is still maintained at a high efficiency although the efficiency is slightly lowered by doping the MoO ₃ matrix.
Here, “doped” means being contained as an impurity in the crystal lattice.

Next, Example 2 will be described. In this example, as shown in FIG. 1, the hole injection layer 3 was changed from PEDT to MoO ₃ vacuum deposition film from the organic electroluminescent element of Example 1, and was the same as Samples 101-105. 201-205 were produced. MoO ₃ was formed by resistance heating vapor deposition to a film thickness of 50 nm. The obtained sample was evaluated in the same manner as in Example 1, and data was obtained especially regarding the voltage increase during driving.
As a result, the voltage increase was about 1 V for the sample 203-205 of the present invention, which was greatly improved with respect to 2.5 V and 3 V in the case of Example 1, whereas it was as large as about 7 V for the comparative sample. There was no improvement. The same applies to the driving life.

Next, Example 3 will be described. In this example, the method for forming the electron injection layer of the organic electroluminescent element of Example 2 was changed. Further, in this embodiment, as shown in FIG. 3, the lamination direction is reversed in that the cathode 6 is formed on the glass substrate 1 side. In this embodiment, MoO ₃ was deposited to 50 nm by vacuum deposition on an ITO substrate on which an ITO thin film was formed as a cathode on the glass substrate 1. About others, it is the same as that of Example 1 and 2. A description of the overlapping parts is omitted.

Here, with respect to the sample 301, MoO ₃ was deposited by 50 nm by vacuum deposition without increasing the substrate temperature. For sample 302, the substrate temperature in the vapor deposition apparatus was set to 50 ° C., and vapor deposition was started. Sample 303 was deposited with the substrate temperature set at 100 ° C. Similarly, a sample 304 was produced in the same manner as the sample 301 except that MoO ₃ and Li ₂ O were co-evaporated. The rate of co-evaporation was MoO ₃ and Li ₂ O = 4: 1. For Samples 305-306, the substrate temperature was set similarly to Samples 302-303, and MoO ₃ and Li ₂ O were co-evaporated.

In this way, the electron injection layer 5 is formed, and a light emitting material having a polyfluorene skeleton as a light emitting material is spin-coated at 65 nm and baked at 180 ° C. to form the light emitting layer 3. 2, gold (Au) was deposited by 100 nm. About the obtained samples 301-306, the ITO thin film side was made into the cathode 6, and Au was made into the anode 2, and the voltage was applied. As a result, the higher the substrate temperature, the lower the emission start voltage and the higher the luminance. This is presumably because more defect levels were formed on the MoO ₃ valence band as the substrate temperature was higher. Then, it is considered that electrons injected from the ITO thin film (cathode) are transferred to the LUMO of the light emitting layer 4 through this defect level.

As described above, it can be seen that when the electron injection layer of the present invention is used, the value of the current flowing when a voltage is applied is greatly increased. This is clearly the effect of doping MoO ₃ with Li ₂ O, and the substrate temperature is preferably 50 ° C. or higher, more preferably 100 ° C. or higher. When the substrate temperature was 50 ° C. or higher, the current value was four times or more that at room temperature. Thus, it can be seen that the effect of co-evaporation increases as the substrate temperature increases.

  In addition, this invention is not limited to the said embodiment, You may make it interpose other functional layers, such as an electron block layer and a hole block layer, as an intermediate | middle layer. For example, in the first embodiment, an interlayer (intermediate layer) made of a polymer material may be formed between the molybdenum oxide thin film 3 as the charge (hole) injection layer and the light emitting layer 4. In this case, the above configuration is such that the charge injection layer 3 is a molybdenum oxide thin film and a polymer having an electron blocking function on an anode 2 made of an indium tin oxide (ITO) layer formed on a light-transmitting glass substrate 1. An interlayer layer, which is a material, and a polymer material as the light emitting layer 4 are sequentially laminated, and a barium-containing molybdenum oxide layer is further formed thereon as an impurity-containing transition metal oxide layer 5 as an electron injection layer 5. The cathode 6 made of an aluminum layer is sequentially laminated on the upper layer. According to this configuration, the characteristics can be further improved.

  Based on the above results, the transition metal oxide charge injection layer described in the present invention was used, and the injection layer doped with a metal or metal oxide having a lower work function was used to achieve the LUMO level of the organic material. It has been found that electrons are efficiently injected, and that a device using the injection layer operates stably in the air without using a sealing film.

  The organic electroluminescent device of the present invention can improve the electron injection characteristics and provide a long-life organic electroluminescent device in the organic electroluminescent device. The present invention can be applied not only to applications that require multicolor light emission, but also to exposure devices, printers, facsimiles, and the like that use single color light emission.

Schematic explanatory drawing which shows the structure of the organic electroluminescent element of Embodiment 1 of this invention Schematic explanatory drawing which shows the structure of the organic electroluminescent element of Embodiment 2 of this invention. Schematic explanatory drawing which shows the structure of the organic electroluminescent element of Example 3 of this invention Equivalent circuit diagram of the display device according to the third embodiment of the present invention Layout explanatory diagram of a display device according to a third embodiment of the present invention Sectional drawing of the display apparatus of Embodiment 3 of this invention Upper surface explanatory drawing of the display apparatus of Embodiment 3 of this invention. Explanatory drawing which shows the organic electroluminescent element of a prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Anode 3 Hole injection layer 4 Layer with light emission function 5 Electron injection layer 6 Cathode 7 Transition metal oxide layer 100 Glass substrate 112 Anode 113 Transition metal oxide layer 114 Light emitting layer 115 Impurity containing molybdenum oxide layer 116 Cathode 117 Pixel restriction part 118 Partition

Claims (6)

An anode and a cathode, and a plurality of functional layers formed between the anode and the cathode,
The functional layer is composed of at least one organic semiconductor layer having a light emitting function, and between the cathode and the layer having the light emitting function, an alkaline earth metal or an alkali metal and / or an oxide thereof, An organic electroluminescent device comprising an impurity-containing transition metal oxide layer comprising at least one transition metal oxide containing at least one compound selected from halides. The organic electroluminescent device according to claim 1,
The organic electroluminescent device, wherein the impurity-containing transition metal oxide layer is a layer in which molybdenum oxide is doped with barium or barium oxide. The organic electroluminescent device according to claim 2,
The organic electroluminescent element, wherein the molybdenum oxide is represented by MoO _Y (Y <3) with respect to the molybdenum oxide represented by MoO ₃ . The organic electroluminescent device according to claim 1,
The said impurity containing transition metal oxide layer is an organic electroluminescent element formed through the transition metal oxide layer between the layers which have the said light emission function. The organic electroluminescent device according to claim 1,
The transition metal oxide constituting the impurity-containing transition metal oxide is M _x O _Y (Y <y, M: transition metal) with respect to the transition metal oxide represented by the stoichiometric ratio M _x O _y. The organic electroluminescent element characterized by being a transition metal oxide represented by these. An organic electroluminescent element according to claim 5, between the anode and the functional layer, the transition metal oxide represented by the stoichiometric ratio _{M x O y, M x O} Y ( An organic electroluminescent device comprising an impurity-containing transition metal oxide layer containing a transition metal oxide represented by Y <y).

Images