JP5466024B2 - Organic electroluminescent device - Google Patents

Description

  The present invention relates to a planar light source and a display element, and relates to an organic electroluminescent element provided with an organic layer. In the following, it may be referred to as “organic EL element” or “element”.

An organic EL element is a semiconductor element that converts electrical energy into light energy. Organic EL elements can emit light at a relatively low voltage of several volts to several tens of volts, and are self-luminous and thin-film, so they have high visibility, high viewing angle, and space saving. In view of portability, it is expected to be put to practical use as a flat light source or a display element.

  However, there are still many problems with organic EL elements. For example, in order to obtain a high-brightness organic EL device, a high voltage is applied to increase the current density. However, usually, increasing the current density promotes deterioration of the organic thin film itself. There is. In order to solve this problem, it is necessary to develop an organic EL element having a low driving voltage and high luminous efficiency.

  The basic configuration of the organic EL element is a structure in which a light emitting layer containing a light emitting organic compound is sandwiched between a cathode electrode and an anode electrode. By applying a voltage to this element, electrons and holes are injected into the light emitting layer, and recombination occurs. At this time, the light-emitting organic compound forms an excited state, and light is emitted when the excited state returns to the ground state, so that the organic EL emits light.

  There are two types of excited states when an organic compound emits light: a singlet excited state and a triplet excited state. Light emitted from a singlet excited state is called fluorescence, and light emitted from a triplet excited state is called phosphorescence. . As a highly efficient element, an organic EL element using phosphorescence emission from an excited triplet has been reported (for example, Non-Patent Document 1). The upper limit of the internal quantum efficiency of fluorescence emission from excited singlet is 25%. However, when phosphorescence is used, the upper limit of internal quantum efficiency is 100%. It is considered to be four times the element.

  However, when a phosphorescent compound is used as the light emitting dopant of the light emitting layer, in order to obtain a device with high light emission efficiency, the host compound of the light emitting layer or a layer adjacent to the light emitting layer is used so that the excited triplet state does not disappear. The material used for (hole transport layer, electron transport layer) needs to have an excited triplet energy level higher than that of the phosphorescent compound. By using a compound having a high excitation triplet energy, the excitation energy of the phosphorescent compound can be confined, so that it is possible to emit light with high efficiency without reducing the light emission efficiency of the organic EL element.

  In Non-Patent Document 1, 4,4′-bis [N- (2-naphthyl) -N-phenyl-amino] biphenyl (abbreviation: α-NPD or NPB) is used for the hole transport layer. Since the effect of confining the excited triplet energy of NPD is not sufficient, there has been a problem that a sufficiently high light emission efficiency is not obtained as a device using phosphorescence emission and the driving voltage is high.

  On the other hand, as a method for reducing the drive voltage, a metal oxide having a relatively high work function, such as molybdenum oxide, is used for the anode electrode, thereby reducing the drive voltage of the device and improving the life. (For example, Patent Document 1). Furthermore, as shown in Patent Document 2, an example using a mixed layer of a metal oxide and an organic compound has been reported, and a low driving voltage is realized by using an arylcarbazole compound as an organic compound. In addition, tungsten oxide and 4,4 ′, 4 ″ -tris (N-carbazolyl) -triphenylamine (abbreviation) are intended to achieve both reduction in driving voltage and luminous efficiency of organic EL elements using phosphorescence. : TCTA) is also disclosed (for example, Non-Patent Document 2).

JP-A-9-63771 JP 2006-303470 A

Appl. Phys. Lett. 75, 4 (1999) Appl. Phys. Lett. 94, 133303 (2009)

  Both Patent Document 1 and Patent Document 2 only refer to the reduction of the driving voltage by improving the hole injection property, and it is considered that the improvement of the light emission efficiency cannot be achieved.

  In the invention of Non-Patent Document 2, in the hole injection layer, the hole transport layer, and the light emitting layer,

However, since it has an amine skeleton, it is expected that only the hole transport property is high. Therefore, in order to realize a highly efficient device using TCTA as a light emitting layer, it is necessary to mix TCTA and an electron transport material, or to provide another light emitting layer in addition to the light emitting layer using TCTA, A complicated process was required. Therefore, an object of the present invention is to provide an organic EL element that emits light with high efficiency and lower driving voltage than conventional elements.

  As a result of intensive studies to solve the above problems, the present inventor has found that an organic EL element structure that emits light with high efficiency and low driving voltage can be provided with the following configuration, and has completed the present invention.

  That is, the present invention relates to an organic electroluminescent device having at least one light emitting layer between an anode electrode and a cathode electrode, wherein the hole injection layer contains a metal oxide and an arylcarbazole compound on the anode electrode. And a hole transport layer containing an aryl carbazole compound and a light emitting layer containing an aryl carbazole compound and a phosphorescent compound are laminated in this order, and the aryl carbazole compound is represented by the following general formula (1) The present invention relates to an organic electroluminescent device comprising a group hydrocarbon and containing the same arylcarbazole compound in the hole injection layer, the hole transport layer, and the light emitting layer.

(In the formula, Ar represents an aromatic hydrocarbon having 6 to 42 carbon atoms, and R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
In a preferred embodiment, in the arylcarbazole compound, Ar in the following general formula (1) is represented by any of the aromatic hydrocarbons represented by the structural formulas (1-1) to (1-10): It is related with the said organic electroluminescent element.

(However, in the formula, R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
A preferred embodiment relates to the organic electroluminescent device, wherein the arylcarbazole compound is 4,4′-bis (N-carbazolyl) biphenyl.

In a preferred embodiment, the metal oxide contains at least one selected from molybdenum oxide (MoO _x ), ruthenium oxide (RuO _x ), tungsten oxide (WO _x ), and vanadium oxide (VO _x ). It is related with the said organic electroluminescent element characterized.

  A preferred embodiment relates to a display device including the organic electroluminescent element.

  A preferred embodiment relates to a lighting fixture including the organic electroluminescent element.

  The organic EL device of the present invention is an “organic electroluminescent device having at least one light emitting layer between an anode electrode and a cathode electrode, and contains a metal oxide and an arylcarbazole compound on the anode electrode. The hole injection layer, the hole transport layer containing the aryl carbazole compound, and the light emitting layer containing the aryl carbazole compound and the phosphorescent compound are laminated in this order, and the aryl carbazole compound is represented by the following general formula (1)

(In the formula, Ar represents an aromatic hydrocarbon having 6 to 42 carbon atoms, and R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
And the same arylcarbazole compound is contained in the hole injection layer, the hole transport layer, and the light emitting layer ''. With this configuration, the driving voltage is reduced, An organic EL element that emits light with high efficiency becomes possible.

It is a schematic sectional drawing of the organic EL element concerning 1st embodiment of this invention.

The organic EL device of the present invention has a plurality of layers between one electrode (that is, between the anode electrode and the cathode electrode). The plurality of layers has a high carrier injection property between the light emitting layer and the electrode so that a light emitting region exists at a position away from the electrode, that is, carrier recombination occurs at a position away from the electrode. It is formed by combining materials and layers made of a material having a high carrier transport property.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic cross-sectional configuration of the organic EL element according to the first embodiment. In the element shown in FIG. 1, an anode electrode 2, an organic EL layer 3, and a cathode electrode 4 are laminated on a substrate 1 in this order.

  There is no restriction | limiting in particular about the board | substrate 1 used as a support body of an organic EL element, For example, it selects suitably from a transparent substrate like glass, a silicon substrate, a flexible film substrate, a plastic substrate, etc., and is used. Among them, a transparent substrate such as glass or a transparent film substrate is preferably used from the viewpoint of transparency and workability.

Although there is no restriction | limiting in particular as the anode electrode 2 provided on the said board | substrate 1, It is formed with a metal, an alloy, an electrically conductive compound, a mixture thereof, etc. with a large work function (work function 4.0eV or more). It is preferable. It is preferable to use an anode electrode having a work function in the above range because hole injection into a hole injection layer formed thereon is considered to be enhanced. For example, in addition to metal oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), and zinc oxide (ZnO), gold ( Such as Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd) From the viewpoint of effectively extracting light generated from the light emitting layer of the organic EL element, ITO or IZO having high transparency can be more preferably used.

  The organic EL layer 3 is provided between the anode electrode 2 and the cathode electrode 4, has at least one light emitting layer, and is a layer composed of a plurality of layers mainly made of an organic compound. The organic EL layer 3 in FIG. 1 corresponds to the remaining components obtained by removing the anode electrode 2 and the cathode electrode 4 from those constituting the conventional organic EL element. The method for forming each layer constituting the organic EL layer 3 is not particularly limited, and can be formed by a method such as a spin coating method in addition to the vacuum evaporation method. At this time, each layer may be formed by the same film formation method or may be formed by different methods.

  The organic EL layer 3 is composed of a plurality of layers as described above. The plurality of layers in the present invention have at least a hole injection layer 5, a hole transport layer 6, and a light emitting layer 7 in this order. Other configurations are not particularly limited, but an electron transport layer 8 or a layer for promoting electron injection (hereinafter referred to as “electron injection layer”) or the like is appropriately provided between the light emitting layer 7 and the cathode electrode 4. It is preferable to provide it.

  As the organic EL layer 3 in the present invention, a hole injection layer 5 containing a metal oxide and an aryl carbazole compound, a hole transport layer 6 containing an aryl carbazole compound, an aryl carbazole compound and a phosphorescent compound are formed on the anode electrode 2. And a light-emitting layer 7 containing bismuth.

  Below, each layer of the organic EL layer 3 in this invention is demonstrated in detail.

  The hole injection layer 5 in the present invention is composed of a layer containing a metal oxide and an aryl carbazole compound having an aromatic hydrocarbon represented by the following general formula (1). Here, the “aryl carbazole compound having an aromatic hydrocarbon” refers to an aryl carbazole compound in which a portion other than carbazole is composed only of an aromatic hydrocarbon.

(In the formula, Ar represents an aromatic hydrocarbon having 6 to 42 carbon atoms, and R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
The arylcarbazole compound is preferably a compound in which Ar in the following general formula (1) is represented by any of the aromatic hydrocarbons represented by structural formulas (1-1) to (1-10).

(However, in the formula, R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
In the above general formula, the alkyl group is preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group, and the aryl group is preferably a phenyl group, a tolyl group, a 2-biphenylyl group, or a 4-biphenylyl group. )
As the arylcarbazole compound,

4,4′-bis (N-carbazolyl) biphenyl (abbreviation: CBP) represented by

Specific examples of the metal oxide include an oxide selected from molybdenum oxide (MoO _x ), ruthenium oxide (RuO _x ), tungsten oxide (WO _x ), vanadium oxide (VO _x ), and the like. preferable. Among these, molybdenum trioxide (MoO ₃ ) is particularly preferably used because it can be stably deposited in vacuum without changing the composition ratio.

  The hole injection layer 5 in the present invention is a layer having a function of efficiently injecting holes from the anode electrode 2 and a function of transmitting the injected holes to the next layer, that is, the hole transport layer 6. is there.

  When the hole injection layer 5 is formed of a highly conductive layer having a high hole injection property and a high conductivity because the aryl carbazole is easily radically cationized by the effect of the electron-withdrawing metal oxide. However, an increase in drive voltage can be suppressed. Therefore, since the thickness can be increased without causing an increase in driving voltage, a short circuit of an element due to dust or the like can be suppressed.

  The hole transport layer 6 in the present invention is a layer having a function of transmitting holes received from the hole injection layer 5 to the next layer, that is, the light emitting layer 7.

  The hole transport layer 6 in the present invention contains an arylcarbazole compound represented by the general formula (1). In this case, the arylcarbazole compound is preferably one in which Ar in the general formula (1) is represented by any of the aromatic hydrocarbons represented by the structural formulas (1-1) to (1-10). CBP can be particularly preferably used. The hole transport layer 6 may be composed of the aryl carbazole compound alone or may be composed of a mixture of other compounds.

  The light emitting layer 7 in the present invention contains an aryl carbazole compound represented by the general formula (1) and a phosphorescent compound. In this case, the arylcarbazole compound is preferably one in which Ar in the general formula (1) is represented by any of the aromatic hydrocarbons represented by the structural formulas (1-1) to (1-10). CBP can be particularly preferably used.

  The “phosphorescent compound” in the present invention is a compound that is confirmed to emit light from an excited triplet and has a phosphorescence quantum efficiency of 0.1% or more at 25 ° C. Among them, the phosphorescence quantum efficiency is preferably 1% or more, more preferably 10% or more.

  As the phosphorescent compound used in the present invention, known compounds can be used, preferably a complex compound containing a Group VIII metal in the periodic table of elements, more preferably an iridium compound, a platinum compound, or Since most of the osmium compounds exhibit high phosphorescence quantum efficiency, iridium compounds are most preferable.

Specific examples of the phosphorescent compound used in the present invention are shown below. For example, bis (2-benzo [b] thiophen-2-yl-pyridine) (acetylacetonato) iridium (III) (abbreviation: Ir (Btp) ₂ (acac)), tris (1-phenylisoquinoline) iridium (III ) (Abbreviation: Ir (piq) ₃ ), tris (2-phenylpyridine) iridium (III) (abbreviation: Ir (ppy) ₃ ), bis (3,5-difluoro-2- (2-pyridyl) phenyl- ( 2-carboxypyridyl) iridium (III) (abbreviation: FIrpic), bis (4 ′, 6′-difluorophenylpyridinato) tetrakis (1-pyrazolyl) borate iridium (III) (abbreviation: FIr ₆ ) and the like. However, it is not limited to these.

  The light emitting layer 7 is a layer that emits light by recombination of carriers (holes and electrons) injected from the anode electrode and the cathode electrode. This layer is composed of a dopant which is a luminescent substance and a host which is a substance that disperses the luminescent substance. As the light-emitting dopant, there are those that emit fluorescence or phosphorescence. In the present invention, a phosphorescent compound that emits phosphorescence can be used, and the arylcarbazole compound shown above can be used as the host compound.

  Moreover, when using a phosphorescent compound as a luminescent dopant, it is preferable to use the compound which shows higher excitation triplet energy than the said phosphorescent compound from the point of the luminous efficiency of an organic EL element as a host compound. In this case, the excitation energy of the phosphorescent compound can be confined, and light can be emitted with high efficiency without reducing the light emission efficiency of the organic EL element. For the same reason, the layer in contact with the light emitting layer containing the phosphorescent compound (hole transport layer or electron transport layer) is also preferably composed of a compound having a triplet energy higher than that of the phosphorescent compound.

  The aryl carbazole compounds used for the hole injection layer 5, the hole transport layer 6, and the light emitting layer 7 are the same compound. By using the same compound, the energy barrier between each of the hole injection layer 5 / hole transport layer 6 and the hole transport layer 6 / light emitting layer 7 generated when different compounds are used is eliminated, and the operation is performed with a low driving voltage. An organic EL element is obtained. At this time, as the same compound, an aryl carbazole compound having a higher excitation triplet energy than the phosphorescent compound that is a light-emitting dopant is used as a host compound, so that phosphorescence is relatively easily applied to the light-emitting layer 7 and the hole transport layer 6. The excitation energy of can be confined. As a result, an organic EL element having a low driving voltage and high luminous efficiency can be obtained. In addition, since the layer structure is simplified by using the same compound, the manufacturing process can be simplified as compared with the case where a different compound is used, and the effect of reducing the manufacturing cost can be obtained.

  In addition, as the aryl carbazole compound, by using a compound having an aromatic hydrocarbon as shown in the general formula (1), compared with a compound having an amine skeleton (such as TCTA), a light emitting layer It is considered that the recombination probability of carriers can be increased, and as a result, the light emission efficiency can be improved.

  As the arylcarbazole compound, those in which Ar in the general formula (1) is represented by any of the aromatic hydrocarbons represented by the structural formulas (1-1) to (1-10) are preferable. It is particularly preferable to use it. By using CBP having a relatively high triplet energy, phosphorescence excitation energy can be confined in the light emitting layer 7 and the hole transport layer 6. As a result, an organic EL element having a low driving voltage and high luminous efficiency can be obtained, and the manufacturing process can be further simplified.

As the electron transporting material for forming the electron transporting layer 8, a known material having a high electron transporting property can be used. For example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (5-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: A metal complex having a quinoline skeleton or a benzoquinoline skeleton such as BeBq ₂ ) or bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq) can be preferably used. In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn ( A metal complex having an oxazole-based or thiazole-based ligand such as BTZ) ₂ ) can also be used. In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5 -(P-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5 (4-Biphenylyl) -1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2 , 4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and the like can also be used. The above materials mainly have an electron mobility of 10 ⁻⁶ cm ² / Vs or higher, and are preferable from the viewpoint of reducing driving voltage. Note that other than the above substances, any substance that has a property of transporting more electrons than holes may be used. Further, the electron transport layer 8 is not limited to a single layer, and two or more layers made of the above substances may be stacked.

  As a material for forming the cathode electrode 4, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (work function of 3.8 eV or less) can be used. Specifically, elements belonging to Group I or II of the Periodic Table of Elements, that is, alkali metals such as lithium (Li) and cesium (Cs), and magnesium (Mg), calcium (Ca), strontium (Sr), etc. Examples thereof include alkaline earth metals and alloys containing them (Mg: Ag, Al: Li). It is preferable to use a work function in the above-mentioned range since it is considered that the electron injection property is enhanced. However, by laminating the electron injection layer between the cathode electrode 4 and the light emitting layer 7 so as to be adjacent to the cathode electrode 4, ITO containing Al, Ag, ITO, and silicon regardless of the work function. Various conductive materials such as these can be used as the cathode electrode 4.

As the electron injection layer, an alkali metal or alkaline earth metal compound such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), or the like can be preferably used. Further, as the electron injection layer, a layer made of a substance having an electron transporting property containing an alkali metal or an alkaline earth metal, for example, a layer containing magnesium (Mg) in Alq ₃ is preferably used. be able to.

  In the present invention, a plurality of luminescent dopants different from the phosphorescent compound used as the luminescent dopant may be added to the luminescent layer 7. Moreover, you may add a different luminescent dopant to the other layer which comprises the organic EL layer 3, for example, the electron carrying layer 8, the hole carrying layer 6, etc. FIG. By using the different luminescent dopants, a plurality of emission colors can be seen, so that a desired mixed color emission can be obtained.

  Since the organic EL element of the present invention is a self-luminous device, a backlight or the like is not necessary, and the display can be made extremely thin. In addition, it can be effectively applied to display devices and lighting fixtures from the viewpoint of energy saving with low power consumption.

  Next, a specific example of the present invention and a manufacturing procedure of an organic EL element of a comparative example with respect to these examples and evaluation results thereof will be described.

Example 1
A bottom-type evaluation element having a light emitting region of 2 mm × 2 mm was produced on an anode electrode (using ITO, film thickness 150 nm) patterned on a glass substrate.

  On the anode electrode, a mixed layer of 4,4′-bis (N-carbazolyl) biphenyl (hereinafter abbreviated as CBP) and molybdenum trioxide was used as a hole injection layer, and a film thickness of 90 nm was formed by vacuum deposition. . CBP and molybdenum trioxide of the hole injection layer were formed by a co-evaporation method so that the film thickness ratio was 9: 1.

  Next, CBP was used as the hole transport layer, and a film thickness of 20 nm (deposition rate: 0.8 nm to 1.2 nm / sec) was formed by a vacuum evaporation method.

  Next, CBP as the host material and the dopant as the light emitting layer

And tris (2-phenylpyridine) iridium (III) (hereinafter abbreviated as Ir (ppy) ₃ ), and a film thickness of 20 nm was formed by vacuum deposition. CBP and Ir (ppy) ₃ of the light emitting layer were formed by a co-evaporation method so that the film thickness ratio was 97: 3.

  Next, as an electron transport layer

The film was formed with a film thickness of 50 nm (deposition rate: 0.8 nm to 1.2 nm / sec) by vacuum evaporation using a bathocuproine (hereinafter abbreviated as BCP).

  Next, using LiF as the electron injection layer, a film having a film thickness of 1 nm (deposition rate of 0.3 to 0.5 nm / sec) is formed by vacuum deposition, and finally, Al is formed as a cathode electrode by 150 nm by vacuum deposition. It was formed with a film thickness of (deposition rate 3.0 nm to 5.0 nm / sec).

(Comparative Example 1)
In the manufacturing procedure of Example 1, as the hole injection layer

4,4′-bis [N- (2-naphthyl) -N-phenyl-amino] biphenyl (hereinafter abbreviated as α-NPD) and molybdenum trioxide (film thickness ratio 9: 1) It was. Other than that, an organic EL device was produced in exactly the same manner as Comparative Example 1.

(Comparative Example 2)
In the manufacturing procedure of Example 1, the hole injection layer was a mixed layer of α-NPD and molybdenum trioxide (film thickness ratio 9: 1), and the hole transport layer was α-NPD. Other than that, an organic EL device was produced in exactly the same manner as Comparative Example 2.

(Comparative Example 3)
In the manufacturing procedure of Example 1, the hole transport layer was α-NPD. Other than that, an organic EL element was produced in exactly the same manner as Comparative Example 3.

(Comparative Example 4)
In the production procedure of Example 1, 4,4 ′, 4 ″ -tris (N-carbazolyl) -triphenylamine (TCTA) was used instead of CBP. Other than that, an organic EL element was produced in exactly the same manner as Comparative Example 4.

The organic EL element of the present invention produced as described above and the organic EL element of the comparative example were evaluated for light emission luminance, light emission efficiency (cd / A), and drive voltage (V). Table 1 summarizes the light emission efficiency (cd / A) at a light emission luminance of 1000 cd / m ² and the driving voltage (V) at that time.

  As can be seen from Table 1, in Comparative Examples 1 to 3, CBP, which is an aryl carbazole compound, is used for the light emitting layer, and a different compound (α-NPD) other than the aryl carbazole compound is used for the hole injection layer and / or the hole transport layer. An organic EL element is used to produce a comparative example. In Comparative Example 1, the driving voltage is relatively high and the light emission efficiency is low. In Comparative Examples 2 and 3, although the drive voltage is relatively low, the light emission efficiency is also low. In addition, as in Comparative Example 4, the organic EL device manufactured using an arylcarbazole compound (TCTA) that is the same but has an amine skeleton (no hydrocarbon skeleton) has a low driving voltage. The luminous efficiency is low. On the other hand, the organic EL device of Example 1 has an aromatic hydrocarbon and uses the same aryl carbazole compound, so that it shows high luminous efficiency and operates at a low driving voltage. is there.

  As described above, a hole injection layer containing a metal oxide and an aryl carbazole compound, a hole transport layer containing an aryl carbazole compound, and a light emitting layer containing an aryl carbazole compound and a phosphorescent compound are formed on the anode electrode. In the organic EL element laminated in this order, when the aryl carbazole compound has an aromatic hydrocarbon skeleton and the same aryl carbazole compound is used for the hole injection layer, the hole transport layer, and the light emitting layer, high luminous efficiency is obtained. It can be operated with a low driving voltage.

1 Substrate 2 Anode electrode 3 Organic EL layer 4 Cathode electrode 5 Hole injection layer 6 Hole transport layer 7 Light emitting layer 8 Electron transport layer

Claims (6)

An organic electroluminescent device having at least one light emitting layer between an anode electrode and a cathode electrode,
A hole injection layer containing a metal oxide and an arylcarbazole compound on the anode electrode,
A hole transport layer containing an arylcarbazole compound;
A light emitting layer containing an arylcarbazole compound and a phosphorescent compound;
Are laminated in this order, the aryl carbazole compound has an aromatic hydrocarbon represented by the following general formula (1), and the same aryl carbazole compound is contained in the hole injection layer, the hole transport layer, and the light emitting layer. An organic electroluminescent device characterized by being included.
(In the formula, Ar represents an aromatic hydrocarbon having 6 to 42 carbon atoms, and R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.) In the arylcarbazole compound, Ar in the following general formula (1) is represented by any of the aromatic hydrocarbons represented by the structural formulas (1-1) to (1-10). The organic electroluminescent device according to 1.
(However, in the formula, R1 to R4 represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)   The organic electroluminescent device according to claim 1, wherein the aryl carbazole compound is 4,4′-bis (N-carbazolyl) biphenyl. The metal oxide contains at least one selected from molybdenum oxide (MoO _x ), ruthenium oxide (RuO _x ), tungsten oxide (WO _x ), and vanadium oxide (VO _x ). The organic electroluminescent element in any one of 1-3.   The display apparatus containing the organic electroluminescent element in any one of Claims 1-4. The lighting fixture containing the organic electroluminescent element in any one of Claims 1-5.