JP4818298B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to a light-emitting element widely used as various display devices, and relates to an organic electroluminescent element having excellent color purity.

  Electroluminescent devices have been studied by many researchers for a long time because they are brighter and clearer than liquid crystal devices because of self-luminescence. As an electroluminescent element which has reached a practical level at present, there is an element using an inorganic material ZnS. However, such an inorganic electroluminescent element has not been widely used because it requires a drive voltage of 50 V or more for light emission.

  On the other hand, the organic electroluminescent element, which is an electroluminescent element using an organic material, has been far from a practical level, but in 1987, Eastman Kodak Co., Ltd. C. W. Tang) et al. Have dramatically improved their characteristics. They have a layer made of a phosphor (electron transporting light-emitting layer) that has a stable deposited film structure and can transport electrons, and a layer made of an organic substance that can transport holes (hole transporting layer). Lamination was successful in injecting holes and electrons into the phosphor to emit light. As a result, the luminous efficiency of the organic electroluminescent device was improved, and light emission of 1000 cd / m 2 or more was obtained at a voltage of 10 V or less. After that, as a result of the functional separation of the layers constituting the device, such as dividing the electron-transporting light-emitting layer into a light-emitting layer and an electron-transporting layer, light emission characteristics of 10,000 cd / m 2 or more are currently obtained.

  Such an organic electroluminescent element can change the luminescent color arbitrarily by changing the material which comprises a light emitting layer. Further, by combining blue, green and red light emitting elements, full color display is possible, and a thin and light full color display can be realized.

  However, in order to realize a higher quality display in the above-described full color display, it is indispensable to further increase the color purity of each color of blue, green, and red.

  An object of the present invention is to realize an organic electroluminescent device having improved color purity by improving the device configuration of the organic electroluminescent device.

（式中Ａｒ1は一般式（Ａ）〜（Ｄ）のいずれかである２価の基、Ａｒ2は一般式（Ｅ）〜（Ｉ）のいずれかである２価の基である。ここでｎは１から３の整数、Ｒ1、Ｒ2はそれぞれ独立に水素原子、ハロゲン原子、低級アルキル基、置換もしくは無置換のアリール基である。）

The organic electroluminescent device of the present invention is an organic electroluminescent device comprising a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. An aromatic methylidene compound having an energy gap of 2.7 eV or more is used as a main material constituting the light emitting layer, and a material having a higher charge transport property than the material constituting the light emitting layer is mixed in the light emitting layer. It is characterized by being. By using a material having a strong fluorescence intensity as a material constituting the light emitting layer and mixing a material having a strong charge transport property, an element having excellent light emission efficiency can be obtained.
The organic electroluminescent device of the present invention is an organic electroluminescent device comprising a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. An electron transport layer is disposed in contact with the light emitting layer, and the light emitting layer uses an aromatic methylidene compound represented by the following general formula (1) as a main material constituting the light emitting layer, and the electron It is characterized in that an electron transport material having an electron affinity greater than that of the material constituting the transport layer is mixed . By using a material having a strong fluorescence intensity as a material constituting the light emitting layer and mixing a material having a strong charge transport property, an element having excellent light emission efficiency can be obtained.

(In the formula, Ar1 is a divalent group of any one of the general formulas (A) to (D), and Ar2 is a divalent group of any one of the general formulas (E) to (I). Is an integer of 1 to 3, and R 1 and R 2 are each independently a hydrogen atom, a halogen atom, a lower alkyl group, or a substituted or unsubstituted aryl group.)

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. The light emitting layer is mixed with 10 mol% or less of a charge transport material. By keeping the concentration of the charge transport material to be mixed low, exchange of charges between the charge transport materials can be suppressed, and the reactive current flowing in the light emitting layer can be reduced.

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. The light-emitting layer is mixed with a charge transport material having a fluorescence wavelength at a wavelength that can be absorbed by the material mainly constituting the light-emitting layer. By using a material having a high energy transfer probability to the material constituting the light emitting layer as the charge transporting material, the charges injected into the light emitting layer can be more reliably transferred to the light emitting material.

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. The light-emitting layer is mixed with a charge transport material having an ionization potential smaller than the ionization potential of the material constituting the hole transport layer provided in contact with the light-emitting layer. By using such a charge transport material, holes can be reliably injected into the light emitting layer.

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. The light-emitting layer is mixed with a charge transport material having an electron affinity larger than that of the material constituting the electron transport layer provided in contact with the light-emitting layer. By using such a charge transport material, electrons can be reliably injected into the light emitting layer.

（式中、Ｒ₃、Ｒ₄、Ｒ₅はそれぞれ独立に水素原子、低級アルキル基、置換または無置換のアリール基、Ｒ₆、Ｒ₇はそれぞれ独立に水素原子、低級アルキル基、ハロゲン原子を表す。） The organic electroluminescent element of the present invention is characterized in that each of the above charge transport materials is represented by the following general formula (2), and a high heat resistant organic material is used as the charge transport material. Thus, a light-emitting element with higher durability can be realized.

(Wherein R ₃ , R ₄ and R ₅ are each independently a hydrogen atom, a lower alkyl group, a substituted or unsubstituted aryl group, R ₆ and R ₇ are each independently a hydrogen atom, a lower alkyl group or a halogen atom. To express.)

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. The charge transport material is mixed in a partial layer region of the light emitting layer, and the leakage current is suppressed and the current efficiency is high by providing the mixed layer only in a part of the light emitting layer. An element can be realized.

  Moreover, the organic electroluminescent element of the present invention is an organic electroluminescent element having a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode. Providing a layer region in which a hole transport material is mixed in a region of the light emitting layer in contact with the hole transport layer, and providing a layer region in which the electron transport material is mixed in a region of the light emitting layer in contact with the electron transport layer. A feature is that by providing a layer region in which a hole transport material and an electron transport material are mixed in one light emitting layer, holes and electrons can be injected into the light emitting layer in a well-balanced manner.

  As described above, the organic electroluminescent element of the present invention has a pair of electrodes composed of an anode and a cathode, and a layer composed of one or more organic substances including at least a light emitting layer therebetween, and a light emitting material as the light emitting layer In addition, since a material having a strong charge transporting property is mixed under a certain condition, an advantageous effect that an organic electroluminescence device having excellent color purity as compared with the conventional device can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of an organic electroluminescent device according to the present invention. An anode 2 is formed on a substrate 1, and a hole transport layer 3, a light emitting layer 4, an electron transport layer 5 and a cathode 6 are formed thereon.

  The substrate 1 can be used as long as it is transparent and has a smooth surface. Generally, glass and plastic are used. In addition, a substrate having an arbitrary thickness can be used as long as it can be supported at the time of element fabrication.

  The anode 2 can use indium tin oxide (ITO) as a transparent electrode or a gold thin film as a translucent electrode.

  The hole transport layer 3 and the electron transport layer 5 each constitute a charge transport layer. Each charge transport layer serves to facilitate injection of charges from the electrode and transport the injected charges to the light emitting region. As the hole transport layer 3, a material having a strong hole transport property is used. Specifically, N, N′-diphenyl-N, N′-bis (3-methylphenyl) 1,1′-biphenyl-4 is used. , 4′-diamine (TPD), 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] biphenyl (α-NPD), and other triphenylamine derivatives, thiophene derivatives, stilbene derivatives, etc. Can be used.

  As the electron transport layer 5, a material having a strong electron transport property can be used. Specifically, quinolinol metal complexes represented by phenanthroline derivatives, oxadiazole derivatives, tris (8-hydroxyquinolinol) aluminum (Alq), and the like. Etc. can be used.

  The cathode 6 needs to be able to inject electrons into the organic film, and an alkali metal, an alkaline earth metal, or a compound thereof is often used as one of the constituent materials. Specifically, lithium, magnesium, calcium, or these metals and compounds can be used in combination with other metals.

  As the light emitting layer 4, many compound groups have been studied conventionally, but basically any substance capable of injecting electrons and holes and having fluorescence and phosphorescence can be used. In addition, it has been studied to improve the efficiency of the device, extend the lifetime, and adjust the emission color by using a film in which a small amount of a dye is dispersed in a material having excellent film formability as a light emitting layer. This technique is very effective for fluorescent dyes that are easily crystallized or cause concentration quenching.

  As described above, in general, the organic electroluminescent element can change the emission color by changing the type of material used for the light emitting layer 4. By using a blue fluorescent material having a large energy gap (Eg) as a constituent material of the light emitting layer 4, it is expected to realize a blue light emitting element with high color purity. In practice, however, charge injection into a material having a large Eg is performed. It is difficult to recombine electrons and holes in a layer other than the light emitting layer, for example, an electron transport layer or a hole transport layer. Therefore, the phenomenon that the emission spectrum of the device becomes broad and the emission color becomes whitish is often observed.

  However, according to the present embodiment, light emission can be performed more efficiently by mixing a non-light emitting material having a strong charge transporting property under a certain condition with the entire light emitting layer 4 or a part of the light emitting layer 4. Charges can be injected into the layer and recombined. For example, when a mixture of an aromatic methylidene compound with originally high fluorescence intensity and a charge transport material is used as the light emitting layer, an element with high color purity can be obtained. In particular, the material represented by the general formula (1) in (Chemical Formula 5) has a large Eg, and blue light emission with high color purity can be obtained.

  Further, the concentration when mixing the charge transport material needs to be a concentration at which hopping conduction and charge recombination do not occur between the charge transport materials. The optimum concentration varies depending on the organic material used and the element configuration, but it needs to be at least 10 mol% or less.

  As a material used for the charge transport material mixed with the light emitting layer 4, it is necessary that the charge injection from the hole transport layer 3 or the electron transport layer 5 in contact with the light emitting layer 4 is easy. Further, it is desirable to use a material in which charge recombination is unlikely to occur in the mixed charge transport material, and energy is reliably transferred to the light emitting material when recombination occurs. Specifically, a light-emitting element with higher durability can be realized by using a highly heat-resistant organic material represented by the general formula (2) of (Chemical Formula 8).

  Thus, in this embodiment, an aromatic methylidene compound, which is a blue fluorescent material having a large energy gap (Eg), is used as a constituent material of the light emitting layer 4, and a material having a strong charge transporting property is used as the material. By mixing at a concentration of mol% or less, it becomes possible to inject charges into the light emitting layer and recombine more efficiently, and an element with excellent light emission efficiency can be obtained.

  In the present embodiment, an aromatic methylidene compound having a large energy gap (Eg) is used as the light-emitting layer 4, but the present invention can also be carried out using other light-emitting materials, and a charge transport material is used for the light-emitting layer. By mixing these, an element having excellent luminous efficiency can be obtained.

  Further, in the present embodiment, the case where the organic layer is composed of the three layers of the hole transport layer 3, the light emitting layer 4, and the electron transport layer 5 has been described. In the case of the case where each layer is composed of a plurality of materials, the same can be applied. It is also possible to insert a layer having a new function.

(Example)
Next, specific examples of the present invention will be described.
Example 1
As the substrate 1, an indium tin oxide film (ITO) previously formed as a transparent anode 2 on glass and patterned in the form of an electrode was used. After this substrate 1 was sufficiently cleaned, it was set in a vacuum apparatus together with the material to be deposited and evacuated to 10 −4 Pa. Thereafter, N, N′-bis [4 ′-(N, N-diphenylamino) -4-biphenylyl] -N, N′-diphenylbenzidine (TPT) was formed into a 50 nm film as the hole transport layer 3. Thereafter, a mixed film of compound (3) (fluorescence peak wavelength: 470 nm) shown in (Chemical Formula 9) and TPT was formed into a 25 nm thick light-emitting layer 4. The ratio of TPT to the compound (3) was 5 mol%. After forming 25 nm of tris (8-hydroxyquinolinol) aluminum (Alq) as the electron transport layer 5, an Al / Li mixed film having a thickness of 150 nm was formed as the cathode 6 to prepare an element. These films were formed continuously without breaking the vacuum. The film thickness was monitored with a crystal resonator. Immediately after the device was fabricated, the electrode was taken out in dry nitrogen, and then the characteristics were measured. When voltage was applied to the resulting device, uniform blue light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 470 nm, and it was found that the light emission of this device was derived from the compound (3). The CIE chromaticity coordinates were determined to be x = 0.18 and y = 0.23.

(Example 2)
As the substrate 1, the same one as in Example 1 was used in which ITO was patterned in the form of an electrode in advance to form the anode 2. After cleaning the substrate, the substrate was set in a vapor deposition apparatus and evacuated to 10-4 Pa. Thereafter, a TPT film having a thickness of 50 nm was formed as the hole transport layer 3. Thereafter, a mixed layer of compound (3) and a hole-transporting material TPT, a layer consisting only of compound (3), and a mixed layer of compound (3) and bathocuproine (manufactured by Tokyo Kasei) 10 nm each. A light emitting layer 4 was formed by forming a film. The proportions of TPT and bathocuproine relative to compound (3) were both 5 mol%. After forming 20 nm of Alq as the electron transport layer 5, an Al / Li mixed film having a thickness of 150 nm was formed as the cathode 6 to produce a device. Immediately after the device was prepared, the electrode was taken out in dry nitrogen and measured for characteristics. When voltage was applied to the resulting device, uniform blue light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 470 nm, and it was found that the emission was derived from the compound (3). The CIE chromaticity coordinates were determined to be x = 0.17 and y = 0.21.

(Comparative Example 1)
A device was produced in the same manner as in Example 1 except that a layer composed only of the compound (3) was used as the light emitting layer 4. When voltage was applied to the resulting device, light blue uniform light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 420 nm, and it was found that the light emission of this device was mainly derived from TPT used for the hole transport layer 3.

(Comparative Example 2)
A device was produced in the same manner as in Example 1 except that a layer obtained by mixing 15 mol% of TPT with the compound (3) was used as the light emitting layer 4. When voltage was applied to the resulting device, yellow-green light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 530 nm, and it was found that the light emission of this device was mainly derived from Alq used for the electron transport layer 5.

  From the results of Examples 1 and 2 and Comparative Examples 1 and 2, the compound (3), which is a material having a large energy gap and a strong fluorescence intensity, was used, and a material having a strong charge transporting property was further added to this material at a concentration of 5 mol. By mixing, an element having excellent luminous efficiency can be obtained.

(Example 3)
As a light emitting layer, a layer obtained by mixing 5 mol% of TPAC (fluorescence peak wavelength: 370 nm), which is a charge transport material shown in (Chemical Formula 11), with respect to the compound (4) (absorption peak wavelength: 360 nm) shown in (Chemical Formula 10) A device was prepared in the same manner as in Example 1 except that it was used as 4. When voltage was applied to the resulting device, blue-green uniform light emission was observed. When an emission spectrum was observed, it was found that there was a peak at 490 nm, and it was found that the light emission of this device was derived from the compound (4). The CIE chromaticity coordinates were determined to be x = 0.17 and y = 0.35.

(Comparative Example 3)
A device was produced in the same manner as in Example 1 except that a layer obtained by mixing 15 mol% of TPAC with the compound (4) was used as the light emitting layer 4. When voltage was applied to the resulting device, yellow-green light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 520 nm, and it was found that the light emission of this device was mainly derived from Alq used for the electron transport layer 5.

From the results of Example 3 and Comparative Example 3, it was confirmed that light emission from the material mainly constituting the light emitting layer can be obtained by setting the concentration of the charge transport material added to the light emitting layer 4 to an appropriate condition. .

Example 4
The device was the same as in Example 1 except that a layer in which 5 mol% of TPAC (fluorescence peak wavelength: 370 nm) represented by (Chemical Formula 11) was mixed with Compound (3) (absorption peak wavelength: 330 nm) was used as the light emitting layer 4. Was made. When voltage was applied to the resulting device, blue uniform light emission was observed. When the emission spectrum was measured, it was found that it had a peak at 470 nm, and it was found that the light emission of this device was derived from the compound (3). The CIE chromaticity coordinates were determined to be x = 0.17 and y = 0.22.

(Comparative Example 4)
A device was prepared in the same manner as in Example 1 except that a layer in which 5 mol% of the compound (5) (fluorescence peak wavelength: 500 nm) represented by (Chemical Formula 12) was mixed with the compound (3) was used as the light emitting layer 4. . When voltage was applied to the resulting device, blue-green uniform light emission was observed. When an emission spectrum was observed, it was found that there was a peak at 500 nm, and it was found that the light emission of this device was derived from the compound (5). The CIE chromaticity coordinates were determined to be x = 0.19 and y = 0.40.

(Comparative Example 5)
A device was prepared in the same manner as in Example 1 except that a layer obtained by mixing 5 mol% of the compound (5) (fluorescence peak wavelength: 500 nm) with respect to the compound (4) was used as the light emitting layer 4. When voltage was applied to the resulting device, blue-green uniform light emission was observed. When an emission spectrum was observed, it was found that there was a peak at 500 nm, and it was found that the light emission of this device was derived from the compound (5). CIE chromaticity coordinates were determined to be x = 0.19 and y = 0.42.

  Based on the results of Examples 3 and 4 and Comparative Examples 4 and 5, the light-emitting layer is formed by mixing the light-emitting layer with a charge transport material having a fluorescence wavelength at a wavelength that can be absorbed by the material mainly constituting the light-emitting layer 4. It was confirmed that light emission derived from the material to be obtained was obtained.

(Example 5)
As the substrate 1, the same one as in Example 1 was used in which ITO was patterned in the form of an electrode in advance to form the anode 2. After cleaning the substrate, the substrate was set in a vapor deposition apparatus and evacuated to 10-4 Pa. Thereafter, TPD (ionization potential 5.5 eV) was formed into a 50 nm film as the hole transport layer 3. Further, a mixed layer of compound (3) and TPT (ionization potential 5.4 eV) was formed into a light emitting layer 4 by forming a film with a thickness of 25 nm. The ratio of TPD to compound (3) was 5 mol%. After forming 25 nm of Alq as the electron transport layer 5, an Al / Li mixed film having a thickness of 150 nm was formed as the cathode 6, thereby fabricating an element. Immediately after the device was fabricated, the electrode was taken out in dry nitrogen and the characteristics were measured. When voltage was applied to the resulting device, uniform blue light emission was observed. When the emission spectrum was examined, it was found that it had a peak at 470 nm, and it was found that the emission was derived from the compound (3). The CIE chromaticity coordinates were determined to be x = 0.17 and y = 0.22.

(Example 6)
A device was prepared in the same manner as in Example 5 except that a layer in which 5 mol% of TPT was mixed with the compound (4) was used as the light emitting layer 4. When voltage was applied to the resulting device, uniform blue-green light emission was observed. When the emission spectrum was examined, it was found that it had a peak at 490 nm, and it was found that the emission was derived from the compound (4). The CIE chromaticity coordinates were determined to be x = 0.18 and y = 0.34.

(Example 7)
As the substrate 1, as in Example 1, a substrate in which ITO was previously patterned into an electrode shape to form an anode 2 was used. After cleaning the substrate, the substrate was set in a vapor deposition apparatus and evacuated to 10-4 Pa. Thereafter, a TPT film having a thickness of 50 nm was formed as the hole transport layer 3. Further, a mixed layer of compound (3) and compound (6) (electron affinity 2.8 eV) represented by (Chemical Formula 13) was formed into a light-emitting layer 4 by forming a layer of 25 nm. The ratio of compound (6) to compound (3) was 5 mol%. As the electron transport layer 5, bathocuproine (electron affinity 2.3 eV) was deposited to a thickness of 25 nm to produce a device. Immediately after the device was fabricated, the electrode was taken out in dry nitrogen and the characteristics were measured. When voltage was applied to the resulting device, uniform blue light emission was observed. When the emission spectrum was examined, it was found that it had a peak at 470 nm, and it was found that the emission was derived from the compound (3). The CIE chromaticity coordinates were determined to be x = 0.18 and y = 0.23.

(Example 8)
A device was prepared in the same manner as in Example 7 except that a layer obtained by mixing 5 mol% of the compound (6) with respect to the compound (4) was used as the light emitting layer 4. When voltage was applied to the resulting device, uniform blue-green light emission was observed. When the emission spectrum was examined, it was found that it had a peak at 490 nm, and it was found that the emission was derived from the compound (4). The CIE chromaticity coordinates were determined to be x = 0.17 and y = 0.38.

(Comparative Example 6)
A device was fabricated in the same manner as in Example 5 except that TPT was used for the hole transport layer 3 and a 5 mol% mixed film of the compound (3) and TPD was used for the light emitting layer 4. When voltage was applied to the resulting device, blue uniform light emission was observed. When the emission spectrum was examined, it was found that there were peaks at 470 nm and 420 nm, and it was found that the light emission of this element was derived from TPT constituting the compound (3) and the hole transport layer 3.

(Comparative Example 7)
A device was fabricated in the same manner as in Example 5 except that TPT was used for the hole transport layer 3 and a 5 mol% mixed film of compound (4) and TPD was used as the light emitting layer 4. When voltage was applied to the resulting device, blue uniform light emission was observed. When the emission spectrum was examined, it was found that there were peaks at 490 nm and 420 nm, and it was found that the light emission of this device was derived from the compound (4) and TPT constituting the hole transport layer 3.

(Comparative Example 8)
A device was fabricated in the same manner as in Example 7 except that the compound (6) was used for the electron transport layer 5 and a 5 mol% mixed film of compound (3) and bathocuproine was used for the light emitting layer 4. When voltage was applied to the resulting device, light blue uniform light emission was observed. When the emission spectrum was examined, it was found that the spectrum of the compound (6) overlapped with the spectrum of the compound (3), and it was found that two layers of the light emitting layer 4 and the electron transport layer 5 were emitting light. It was.

(Comparative Example 9)
A device was fabricated in the same manner as in Example 7 except that the compound (6) was used for the electron transport layer 5 and a 5 mol% mixed film of compound (4) and bathocuproine was used for the light emitting layer 4. When voltage was applied to the resulting device, light blue uniform light emission was observed. When the emission spectrum was examined, it was found that the spectrum of the compound (6) overlapped with the spectrum of the compound (4), and it was found that two layers of the light emitting layer 4 and the electron transport layer 5 were emitting light. It was.

  From the results of Examples 5 to 8 and Comparative Examples 6 to 9, by adjusting the energy diagram of the charge transport material mixed in the hole transport layer 3 or the electron transport layer 5 and the light emitting layer 4, only from the light emitting layer 4 It was confirmed that the luminescence of can be obtained.

Schematic sectional view showing the configuration of the electroluminescent element in the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Cathode

Claims (3)

A pair of electrodes consisting of an anode and a cathode;
In the organic electroluminescent device having a layer composed of one or more organic substances including at least a light emitting layer between the anode and the cathode,
An electron transport layer is disposed in contact with the light emitting layer,
In the light emitting layer, an aromatic methylidene compound represented by the following general formula (1) is used as a main material constituting the light emitting layer, and the electron affinity of the material constituting the electron transport layer is larger. An organic electroluminescent device comprising an electron transport material having an electron affinity.

(In the formula, Ar1 is a divalent group of any one of the general formulas (A) to (D), and Ar2 is a divalent group of any one of the general formulas (E) to (I). Is an integer of 1 to 3, and R 1 and R 2 are each independently a hydrogen atom, a halogen atom, a lower alkyl group, or a substituted or unsubstituted aryl group.)

The organic electroluminescent device according to claim 1, wherein the light-emitting layer is mixed with 10 mol% or less of the electron transport material.   2. The organic electroluminescent element according to claim 1, wherein a region in which the electron transport material is mixed is provided in a region of the light emitting layer in contact with the electron transport layer.

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