JP4343653B2 - Organic light emitting device having metal borate or metal organic boride - Google Patents

Description

  The present invention relates to a charge injection type light emitting device, and more particularly to an organic charge injection type light emitting device using a metal borate or a metal boron compound.

  Organic electroluminescence elements (organic EL elements) are actively developed.

  Patent Documents 1 and 2 disclose a configuration in which an organic layer having a metal functioning as a donor (electron donating) dopant is provided in contact with a cathode. The metal used as the donor (electron donating) dopant includes alkali metals, alkaline earth metals, transition metals including rare earths, and the like. Since these are doped with a simple metal, they are poor in chemical stability, adsorbing a very small amount of moisture in the deposition chamber, and decomposing the organic material to be co-deposited.

  Further, in Patent Document 3, alkali metal, alkaline earth metal, rare earth metal metal oxide or metal salt is used as a dopant, but the deposition temperature of these metal oxide or metal salt as compared with the organic compound as a host. Therefore, when co-depositing organic compounds and these, the organic compound that becomes the host is decomposed by the radiant heat of the metal, or the organic compounds adhering to the deposition chamber and their decomposition products are again deposited. As a result, there is a risk of reducing the service life.

Furthermore, Patent Document 4 and Patent Document 5 disclose a mixed layer of an electron-transporting organic compound and an organometallic complex, but a metal whose cathode electrode can reduce the complex metal ion of the mixed layer to a metal in a vacuum, That is, it is limited to Al, Zr, Ti, Sc, and Si, and cannot be used for transparent electrodes such as Ag, Au, ITO, and IZO.
JP-A-10-270171 US Pat. No. 6,013,384 JP-A-10-270172 JP 2000-182774 A US Pat. No. 6,396,209

  Therefore, the object of the present invention is high chemical stability, easy control of the film composition, and even when co-deposited, the dopant deposition temperature is the same as that of the organic compound, and the organic compound is relatively damaged. It is an object to provide an organic light-emitting device having an extremely high efficiency and high-luminance light output, and an extremely durable organic light-emitting device.

The organic light-emitting device of the present invention comprises a pair of electrodes ing an anode and a cathode, the organic light emitting element and the ing from at least one layer of an organic compound is sandwiched between a pair of electrodes, the cathode is made of Ag, the between layers consisting of cathode and the organic compound, see containing a metal borate salt or metal organic boron compound, possess an electronic note sintering bed in contact with the cathode, the metal of the metal borate salt or the metal organic boron compound Is made of an alkali metal or an alkaline earth metal . The organic light-emitting device according to the present invention includes a pair of electrodes composed of an anode and a cathode, and an organic light-emitting device composed of at least one organic compound sandwiched between the pair of electrodes, wherein the cathode is made of ITO or IZO. A metal boronate or a metal organic boron compound between the cathode and the organic compound layer, and an electron injection layer in contact with the cathode, wherein the metal borate or the metal organic boron compound metal Is made of an alkali metal or an alkaline earth metal. The organic light-emitting device of the present invention is a light-emitting device comprising a pair of electrodes comprising an anode and a cathode and at least one organic compound sandwiched between the pair of electrodes, wherein the cathode comprises IZO, And an organic injection layer in contact with the cathode, wherein the metal of the metal borate or the metal organic boron compound is an alkali. It consists of a metal or an alkaline earth metal.

  According to the organic light emitting device of the present invention, by using a metal borate or a metal organic boride as an electron injecting material, the chemical stability is high, the film composition is easily controlled, and the deposition temperature is an organic compound. As a result, an electron injection material that can hardly damage an organic compound at the same level is provided, and an organic light emitting device that exhibits extremely high efficiency, high luminance light output, and extremely good durability has been obtained.

  Hereinafter, the details of the organic light emitting device of the present invention will be described.

  The organic light emitting device of the present invention is characterized in that a metal borate or a metal organic boron compound is used for the electron injection layer. Further, the metal of the metal borate or the metal organic borate is characterized by comprising an alkali metal or an alkaline earth metal. Although it does not specifically limit as a metal borate or a metal organoboron compound, For example, lithium tetraborate, sodium tetraborate, potassium tetraborate, rubidium tetraborate, cesium tetraborate, calcium tetraborate, tetraborate Strontium acid, barium tetraborate, lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate, rubidium tetrafluoroborate, cesium tetrafluoroborate, lithium tetraphenylborate, sodium tetraphenylborate, Examples thereof include potassium tetraphenylborate, rubidium tetraphenylborate, and hydrate or anhydrous cesium tetraphenylborate. Further, compounds in which a substituent is added to the phenyl group of tetraphenylboric acid, such as fluorine-substituted lithium tetrakis-4-fluorophenylborate, sodium tetrakis-4-fluorophenylborate (common name: caribol), tetrakis-4 -Potassium fluorophenylborate, rubidium tetrakis-4-fluorophenylborate, cesium tetrakis-4-fluorophenylborate, lithium-substituted tetrakis-4-chlorophenylborate, sodium tetrakis-4-chlorophenylborate, tetrakis Potassium 4-chlorophenylborate, rubidium tetrakis-4-chlorophenylborate, cesium tetrakis-4-chlorophenylborate, or lithium tetrakis-p-tolylborate substituted with methyl Lakis-p-tolylborate sodium, tetrakis-p-tolylborate potassium, tetrakis-p-tolylborate rubidium, tetrakis-p-tolylborate cesium, lithium tetrakis-4-fluoromethylphenylborate substituted with a trifluoromethyl group, Sodium tetrakis-4-fluoromethylphenylborate, potassium tetrakis-4-fluoromethylphenylborate, rubidium tetrakis-4-fluoromethylphenylborate, cesium tetrakis-4-fluoromethylphenylborate, and tetrakis-2-thienylborate Lithium oxide, sodium tetrakis-2-thienylborate, potassium tetrakis-2-thienylborate, rubidium tetrakis-2-thienylborate, cesium tetrakis-2-thienylborate, It is possible to use lithium trakis-1-imidazolylborate, sodium tetrakis-1-imidazolylborate, potassium tetrakis-1-imidazolylborate, rubidium tetrakis-1-imidazolylborate, cesium tetrakis-1-imidazolylborate, and the like. .

  By using tetraboric acid, tetrafluoroboric acid, tetraphenylboric acid and its derivatives, etc., it is chemically stable and relatively easy to resist than using a single metal, or an oxide, halide, or nitride. In addition, the vapor deposition temperature of tetraboric acid and the like can be deposited at a temperature equivalent to that of an organic compound of about 300 ° C. to 400 ° C. in the case of co-deposition with an organic compound. In addition, the present invention has been achieved because vapor deposition with very little damage to organic compounds has become possible. In general, an organic light-emitting device is preferred to be anhydrous rather than hydrated because it dislikes moisture, but even if it is hydrated, only water of crystallization comes off first in the stage of the heating process during vapor deposition. Vapor deposition can be performed as a Japanese product.

  The electron injection layer in the present invention can be selected and used as a single layer of a metal borate or a metal organic boron compound or a mixed layer of these materials and an electron transporting organic material. In the present invention, it can be said that the electron injecting and transporting layer contains a metal borate or a metal organic boron compound in the sense that it may be a single layer.

  Further, another layer may be provided between the cathode and the organic compound layer. This other layer may be an organic layer, an inorganic layer, or an organic / inorganic mixed layer. More specifically, a LiF layer may be used. In addition, electron injection is further improved by providing such another layer. And even if this other layer is provided, it can be said that the cathode and the organic compound layer are in substantial electrical contact.

  Although the thickness in the case of using a metal borate or a metal organic boron compound as a single layer as the electron injection layer in the present invention is not particularly limited, it is preferably 1 to 1000 mm. If it is less than 1 mm, sufficient electron injectability cannot be obtained, and if it exceeds 1000 mm, carrier movement is lost.

  Even when used in the mixed layer, the thickness is not particularly limited, but is preferably 1 to 3000 mm. If it is less than 1 mm, the amount of injected metal molecules present in the vicinity of the electrode interface is small, so that the injectability is not improved, and if it exceeds 3000 mm, the entire organic film becomes too thick, leading to an increase in driving voltage. .

  The doping amount of the metal borate in the mixed layer is not particularly limited, but is desirably 1 to 99% by weight. In particular, if it is less than 1% by weight, the doping effect is small because the concentration of the dopant is too low.

  The electron injecting layer may be formed by any thin film forming method, for example, vapor deposition or sputtering.

  The organic compound that can be used in the mixed layer is not particularly limited as long as it is an organic compound that can be used as a light-emitting layer and an electron transport layer.For example, naphthalene, anthracene, tetracene, pyrene, chrysene, coronene, naphthacene, phenanthrene, and the like. Fused polycyclic hydrocarbon compounds and derivatives thereof, condensed heterocyclic compounds such as acridine, quinoline, quinoxaline and derivatives thereof, or perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, oxadiazole, fluorene, fluorescein, Diphenylbutadiene, tetraphenylbutadiene, bisbenzoxazoline, bisstyryl, pyrazine, cyclopentadienoxin, aminoquinoline, imine, diphenylethylene, vinylanthracene, Examples of aminocarbazole, pyran, thiopyran, polymethine, merocyanine, quinacridone, rubrene and their derivatives, and nitrogen-containing organic bases include phenanthroline, bathophenanthroline, phenanthridine, pyridine, bipyridine, terpyridine and their derivatives, tris (8- (Quinolinolato) metal complexes such as aluminum.

  In particular, in the case of a mixed layer of an organic material containing a nitrogen-containing organic base and the metal borate or metal boron compound of the present invention, a very good electron injection effect can be obtained.

  Such an organic light emitting device can be used as a pixel of a display. The pixels in the effective display area of the display have pixels for each color such as red, blue, and green. The light-emitting element of the present invention can be applied to organic light-emitting elements corresponding to pixels of each color. Of course, the organic light-emitting element of the present invention may be used for a pixel of a monochrome display.

  Moreover, you may use the organic light emitting element of this invention for the organic light emitting element array which has a some organic light emitting element. In order to cause a plurality of organic light emitting elements to emit light, it is preferable to arrange a switching element in each organic light emitting element. In this case, light emission and non-light emission can be controlled for each organic light emitting element. The switching element is preferably a thin film transistor. Two-dimensional image display is possible by arranging such organic light-emitting elements having thin film transistors in a two-dimensional manner. Moreover, although the structure which takes out light from the board | substrate of the side in which the thin-film transistor is arrange | positioned is good, it can apply preferably also to the organic light emitting element of the structure which takes out light from the other side. In that case, it is preferable to dispose the transparent electrode on the opposite side of the substrate, and a cathode may be used as the transparent electrode.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  1 to 6 show configuration examples of the organic light emitting device of the present invention.

  FIG. 1 is a cross-sectional view showing an example of the organic light emitting device of the present invention. FIG. 1 shows a structure in which an anode 2, a light emitting layer 3, an electron injection layer 4 and a cathode 5 are sequentially provided on a substrate 1. In this case, the luminescent material used here has a single hole transport ability, electron transport ability and luminescent performance by itself, or a mixture of compounds having the respective characteristics. Useful.

  FIG. 2 is a cross-sectional view showing another example of the organic light emitting device of the present invention. FIG. 2 shows a configuration in which an anode 2, a hole transport layer 6, an electron transport layer 7, an electron injection layer 4 and a cathode 5 are sequentially provided on a substrate 1. In this case, the light emitting material is either a hole transporting property or an electron transporting property, or a material having both functions is used for each layer, and it is combined with a simple hole transporting material or an electron transporting material having no light emitting property. This is useful when used. In this case, the light emitting layer 3 is composed of either the hole transport layer 6 or the electron transport layer 7.

  FIG. 3 is a cross-sectional view showing another example of the organic light emitting device of the present invention. FIG. 3 shows a structure in which an anode 2, a hole transport layer 6, a light emitting layer 3, an electron transport layer 7, an electron injection layer 4 and a cathode 5 are sequentially provided on a substrate 1. This is a function that separates the functions of carrier transport and light emission, and is used in combination with compounds having hole transport properties, electron transport properties, and light emission properties in a timely manner, and the degree of freedom of material selection is greatly increased. Since various compounds having different emission wavelengths can be used, the emission hue can be diversified. Further, it is possible to effectively confine each carrier or exciton in the central light emitting layer 3 to improve the light emission efficiency.

  FIG. 4 is a cross-sectional view showing another example of the organic light emitting device of the present invention. FIG. 4 shows a structure in which a hole injection layer 8 is inserted on the anode 2 side with respect to FIG. 3, and is effective in improving the adhesion between the anode 2 and the hole transport layer 6 or improving the hole injection property. It is effective.

  FIG. 5 is a cross-sectional view showing another example of the organic light emitting device of the present invention. FIG. 5 shows a structure in which a layer (hole blocking layer 9) that prevents holes or excitons (excitons) from passing to the cathode 5 side is inserted between the light emitting layer 3 and the electron transport layer 7. . By using a compound having a very high ionization potential as the hole blocking layer 9, the structure is effective in improving the light emission efficiency.

  FIG. 6 is a combination of the configurations of FIG. 4 and FIG.

  However, FIG. 1 to FIG. 6 are very basic device configurations, and the configuration of the organic light emitting device using the compound of the present invention is not limited thereto. For example, various layer configurations such as providing an insulating layer at the interface between the electrode and the organic layer, providing an adhesive layer or an interference layer, and the hole transport layer including two layers having different ionization potentials can be employed.

  The present invention relates to a light emitting layer or a light emitting region having various configurations described above, and can be implemented with any configuration. As other components, known low molecular weight hole transport compounds, light emitting materials, electron transport compounds, polymer materials, and the like can be used as necessary.

  The cathode material generally has a small work function, and can be used as a single metal or a plurality of alloys such as lithium, sodium, potassium, calcium, magnesium, aluminum, and indium. Further, the cathode may have a single layer structure or a multilayer structure. In Japanese Unexamined Patent Publication No. 2000-182774 and US Pat. No. 6,396,209, a metal having a reducing property as a cathode material, that is, aluminum, zirconium, titanium, yttrium, scandium, silicon, or the like is used, and metal ions that are constituent materials of an electron injection layer are used. Although it is described that the electron injection barrier is reduced by reducing and liberating the metal in vacuum and further reducing the organic compound with this free metal, the driving voltage is reduced. When a boron compound is used for the electron injection layer, the electron injection property can be improved even when a non-reducing metal is used as the cathode electrode. Furthermore, since the work function of the material used for the cathode is not limited, the cathode electrode material can be selected from a wide range of materials, such as gold, silver, platinum, nickel, palladium, cobalt, selenium, vanadium, lead, tin, In addition to chromium and other metals having a relatively high work function and alloys thereof, in addition to visible light using metal oxides such as indium tin oxide (ITO), indium zinc oxide (IZO), and zinc oxide aluminum (AZO, IXO) The transparent cathode electrode preferably has a transmittance of 70% or more in the visible light region, that is, in the wavelength region of 400 to 700 nm.

  On the other hand, the anode material preferably has a work function as large as possible, for example, gold, silver, platinum, nickel, palladium, cobalt, selenium, vanadium, lead, tin, chromium, or other simple metals or alloys thereof, tin oxide Metal oxides such as zinc oxide, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), and IXO can be used. In addition, conductive polymers such as polyaniline, polypyrrole, polythiophene, and polyphenylene sulfide can also be used. These electrode materials may be used alone or in combination.

  When the cathode electrode is transparent and light is extracted from the cathode side, the anode is preferably an electrode having high reflectivity in the visible light region. Either a chromium (Cr) electrode or a silver (Ag) electrode or any of these It is preferable that the electrode is made of an alloy containing the above, and the reflectance is desirably 70% or more in a wavelength region of 400 nm to 700 nm. In particular, an Ag—Ru—Au alloy (commonly known as ARA) or an Ag—Ru—Cu alloy having a reflectance of 85% or more is particularly preferable because of good light extraction efficiency.

  Although it does not specifically limit as a board | substrate used by this invention, Transparent substrates, such as opaque board | substrates, such as a metal board | substrate and a ceramic board | substrate, glass, quartz, a plastic sheet, are used. It is also possible to control the color light by using a color filter film, a fluorescent color conversion filter film, a dielectric reflection film, or the like on the substrate.

  Note that a protective layer or a sealing layer can be provided on the prepared element for the purpose of preventing contact with oxygen or moisture. Examples of protective layers include diamond thin films, inorganic material films such as metal oxides and metal nitrides, polymer films such as fluororesins, polyparaxylene, polyethylene, silicone resins, and polystyrene resins, and photocurable resins. Can be mentioned. Further, it is possible to cover glass, a gas impermeable film, a metal, etc., and to package the element itself with an appropriate sealing resin.

(Example)
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

( Reference Example 1)
An indium tin oxide (ITO) film formed by sputtering on a glass substrate to a thickness of 1200 mm was used as a transparent conductive support substrate. This was ultrasonically washed successively with acetone and isopropyl alcohol (IPA), boiled and washed with IPA, and dried. Further, UV / ozone cleaning was performed.

  On this substrate, first, α-NPD (the following formula [1]) is 400Å as a hole transport material, and then tris (8-quinolinolato) aluminum (hereinafter referred to as Alq3) is used as a light emitting layer (the following formula [2] )) Was sequentially vacuum-deposited with 200% of a compound doped with 1% of coumarin 6 (the following formula [3]). Further, a bathophenanthroline-based compound represented by the formula [4] was vacuum-deposited for 400 mm as an electron transport layer.

  Next, 5 μm of sodium tetraborate was formed as an electron injection layer by vacuum deposition, and then 1500 μm of Al was formed by vacuum deposition to produce an organic EL device.

The degree of vacuum at the time of vapor deposition was 2 × 10 ⁻⁴ Pa, the film formation rate of the organic layer was 1 、 / s, and the cathode was 10 Å / s.

  Sodium tetraborate was easily deposited and a stable thin film was obtained.

When the ITO electrode of the device thus obtained was used as the positive electrode and the Al electrode as the negative electrode and was driven at 20 mA / cm ^2, it showed a voltage of 4.4 V and green light emission of about 1750 cd / m ² was obtained. The luminous efficiency was 6.1 lm / W, and the external quantum efficiency was 2.5%.

  Further, when the device was driven at a constant current of 100 mA / cm 2 and a relationship between the attenuation change of the initial luminance and the elapsed time was examined, the time required for the initial luminance to be halved was about 600 hours.

(Comparative Example 1)
A device having the same configuration as that of Reference Example 1 was prepared except that an Al electrode was directly laminated on the compound [4] layer without an electron injection layer.

When this element was driven at 20 mA / cm ² with the ITO electrode as the positive electrode and the Al electrode as the negative electrode, it showed a voltage of 13.2 V, green light emission of about 270 cd / m ² was obtained, and the luminous efficiency was 0.3 lm. / W, the external quantum efficiency was 0.4%.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was less than 1 hour.

As described above, when Reference Example 1 and Comparative Example 1 are compared, Example 1 using the metal borate according to the present invention can be driven at a lower voltage than Comparative Example 1 without the electron injection layer, has higher luminous efficiency, and has a higher electron efficiency. The effect as a layer was very large.

  Furthermore, deterioration due to continuous driving of the element was remarkably improved by sodium tetraborate.

( Reference Example 2)
On the transparent conductive support substrate with ITO used in Reference Example 1, 400 μg of α-NPD represented by the formula [1] is used as the hole transport material, and then Alq3 represented by the formula [2] is used as the light emitting layer. In addition, 200% of a compound doped with 1% of coumarin 6 represented by the formula [3] was further vacuum-deposited with 200% of a bathophenanthroline compound represented by the formula [4] as an electron transport layer. Next, as an electron injection layer, a bathophenanthroline compound of the formula [4] and potassium tetraborate anhydrate were co-deposited so as to have a molar ratio of approximately 1: 2, and a thickness of 150 mm was formed. Subsequently, 1500 liters of Al was formed by a vacuum evaporation method, and an organic EL element was produced.

When the obtained device was driven at 20 mA / cm ² in the same manner as in Reference Example 1, a voltage of 4.2 V was obtained, green light emission of about 1780 cd / m ² was obtained, luminous efficiency was 6.6 lm / W, external The quantum efficiency was 2.6%.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 550 hours.

  In this example, potassium tetraborate and an electron-transporting organic compound were co-evaporated to form an electron injection layer, but the electron injection property was significantly improved and device deterioration was greatly improved as compared with Comparative Example 1 without the injection layer. It was improved.

(Example 1 )
In the same configuration as in Reference Example 2, Ag was used for the cathode electrode instead of Al . When the obtained device was driven at 20 mA / cm ² , a voltage of 4.4 V was exhibited, green light emission of about 1720 cd / m ² was obtained, the light emission efficiency was 6.1 lm / W, and the external quantum efficiency was 2.5. %, And the same characteristics as the Al electrode were obtained.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 500 hours.

  When the metal borate of the present invention is used and co-evaporated with an electron injection material, even if a non-reducing metal is used for the cathode electrode, the electron injection property is improved. You can choose.

( Reference Example 3 )
Instead of lithium tetraborate, 20 g of rubidium tetraphenylborate was deposited on the electron injection layer of the device used in Reference Example 1, and then 1500 g of Al was formed to produce an organic EL device.

  The rubidium tetraphenylborate was easy to deposit and a stable thin film was obtained.

When the obtained device was driven at 20 mA / cm ² , a voltage of 4.0 V was exhibited, green light emission of about 1600 cd / m ² was obtained, the light emission efficiency was 6.3 lm / W, and the external quantum efficiency was 2.3. %Met.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 550 hours.

(Example 2 )
In the same configuration as in Reference Example 3 , an Ag electrode was provided by a vacuum deposition method instead of the Al electrode. When the obtained device was driven at 20 mA / cm ^2, it showed a voltage of 5.7 V, green light emission of about 1620 cd / m ² was obtained, the light emission efficiency was 4.5 lm / W, and the external quantum efficiency was 2.3. %Met.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 500 hours.

(Comparative Example 2)
A device having the same configuration as that of Reference Example 1 was prepared except that lithium fluoride (LiF) was used as an electron injection layer and 5 mm was used instead of Al as a cathode electrode. When driven at 20 mA / cm ^2, it showed 8.5 V, green light emission of about 540 cd / m ² was obtained, the light emission efficiency was 1.0 lm / W, and the external quantum efficiency was 0.8%.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was less than 10 hours.

This comparative example shows that even when an electron injection layer such as lithium fluoride is provided, when a non-reducible metal is used for the cathode electrode, the electron injection property is not improved. On the other hand, in Example 2 , there was no significant decrease in the electron injection effect compared with Reference Example 3, and there was clearly an electron injection effect compared with Comparative Example 1 without the electron injection layer.

( Reference Example 4 )
In the same configuration as in Reference Example 2, as the electron injection layer, bathophenanthroline represented by Formula [4] and sodium tetraphenylborate were co-deposited so that the molar ratio was approximately 2: 1. Subsequently, 1500 liters of Al was formed by a vacuum deposition method, and an element was produced.

  Sodium tetraphenylborate was easily deposited, and a stable co-deposited thin film was obtained.

When the device thus obtained was driven at 20 mA / cm ² in the same manner as in Reference Example 1, a voltage of 3.9 V was obtained, green light emission of about 1810 cd / m ² was obtained, and the light emission efficiency was 7.3 lm. / W, the external quantum efficiency was 2.6%.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 600 hours.

  By adding sodium tetraphenylborate as the electron injection layer, the light emission characteristics were remarkably improved as compared with Comparative Example 2 without the electron injection layer.

(Example 3 )
In the same configuration as in Reference Example 4 , Ag was used for the cathode electrode instead of Al . When the obtained device was driven at 20 mA / cm ² , a voltage of 4.1 V was exhibited, green light emission of about 1600 cd / m ² was obtained, the light emission efficiency was 6.1 lm / W, and the external quantum efficiency was 2.3. %, And the same characteristics as the Al electrode were obtained.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was 550 hours.

( Reference Example 5 )
In the same configuration as in Reference Example 4 , Au was used for the cathode electrode instead of Al . When the obtained device was driven at 20 mA / cm ² , a voltage of 4.1 V was exhibited, green light emission of about 1350 cd / m ² was obtained, the light emission efficiency was 5.2 lm / W, and the external quantum efficiency was 2.0. %Met.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 550 hours.

  The Au electrode is slightly inferior to the element using the Al or Ag electrode in terms of the brightness / light emission efficiency of the element and the external quantum efficiency because the reflectance of light at the cathode is smaller than that of the Al or Ag electrode. The current characteristics were almost the same among the three.

  Thus, even when a non-reducible metal was used for the cathode electrode, the electron injection property was improved, and excellent electron injection property was exhibited regardless of the cathode material.

(Example 4 )
This embodiment is applied to a light emitting element using chromium (Cr) functioning as a reflective electrode for the anode and indium tin oxide (ITO) functioning as a transparent light extraction electrode for the cathode, that is, a top emission type element. An example is shown.

  Chromium (Cr) was deposited on the substrate by DC sputtering to a thickness of 2000 mm to obtain an anode electrode. Argon gas was used as the sputtering gas, the pressure was 0.2 Pa, and the DC output was 300 W. Thereafter, the substrate was UV / ozone cleaned and then transferred to a vapor deposition machine. Subsequently, copper phthalocyanine (the following formula [5]) was vapor-deposited as a hole injecting material on chromium (Cr) serving as the anode electrode. Hereinafter, α-NPD represented by the formula [1] was formed in a thickness of 500 mm as a transport layer under the same conditions as in Example 1, and a coumarin represented by the formula [3] was formed thereon as a light emitting layer. 6 (1.0 wt%) and an Alq3 co-deposited film represented by the formula [2] were formed to a thickness of 300 mm. Next, 200 liters of bathophenanthroline represented by the formula [4] was formed as an electron transport layer, and the deposition rate was adjusted so that bathophenanthroline and potassium tetraphenylborate were mixed in a ratio of 9: 1. The electron injecting material was deposited to a thickness of 300 mm by adjustment.

  Subsequently, the substrate on which the organic compound layer was formed in this way was moved to a DC sputtering apparatus [manufactured by Osaka Vacuum Co., Ltd.], and 2000 mm of indium tin oxide (ITO) was formed on the organic compound layer by sputtering. A transparent light emitting cathode electrode was obtained. A mixed gas of argon and oxygen (volume ratio: argon: oxygen = 200: 1) was used as the sputtering gas, the pressure was 0.3 Pa, and the DC output was 40 W.

  In this way, a top emission type light emitting device having a reflective anode electrode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an organic compound layer and a transparent cathode electrode on a substrate was obtained. .

When the obtained device was driven at 20 mA / cm ^2, it showed a voltage of 6.3 V, green light emission of about 2250 cd / m ² was obtained, the light emission efficiency was 5.6 lm / W, and the external quantum efficiency was 3.3. %Met.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 500 hours.

(Example 5 )
In Example 4, was 400Å deposited bathophenanthroline shown in Formula [4] as an electron transport layer, the same as in Example 4 except that further deposited potassium tetraphenylborate to a thickness of 30Å as an electron injection layer A top-emission element with a configuration was created.

When the obtained device was driven at 20 mA / cm ^2, it showed a voltage of 7.5 V, green light emission of about 1900 cd / m ² was obtained, the light emission efficiency was 4.0 lm / W, and the external quantum efficiency was 2.8. %Met.

When the element was driven at a constant current under the conditions of Reference Example 1, the time required for the initial luminance to be halved was about 550 hours.

(Example 6 )
The present invention shows an application example to an element using a polymer material.

  Chromium (Cr) was deposited on the substrate by DC sputtering to a thickness of 2000 mm to obtain an anode electrode. Argon gas was used as the sputtering gas, the pressure was 0.2 Pa, and the DC output was 300 W. Then, after UV / ozone cleaning of the substrate, Poly (3,4-ethylenedithiothiophene) / poly (styresulfonate) (hereinafter referred to as PEDOT / PSS) as a polymer hole transport layer on chromium (Cr) as an anode electrode The solution was formed to a thickness of 550 Å by spin coating. The spin coating conditions were 1000 rpm for 3 minutes, the drying conditions were 150 ° C. for 1 hour, and the pressure was reduced to −760 mmHg. Next, on the surface on which PEDOT / PSS is formed, poly (2-methoxy, 5- (2′-ethyl-hexoxy) -1, -phenylene-vinylene) (hereinafter, MEH-PPV) is used as a polymer electron transport layer and a light-emitting layer. The solution was added dropwise, spin-coated under the condition of 2000 rpm / 1 minute, and then dried and laminated at 120 ° C. for 30 minutes while reducing the pressure to −760 mmHg. The thickness of the obtained MEH-PPV film was 1200 mm. Next, the substrate was transferred to a vapor deposition machine, and potassium tetraphenylborate was deposited as an electron injection layer on the MEH-PPV layer to a thickness of 30 mm. Further, this substrate was moved to a DC sputtering apparatus [manufactured by Osaka Vacuum Co., Ltd.] and 2000 mm of indium tin oxide (ITO) was formed on the electron injection layer by sputtering under the conditions of Example 9 to obtain a transparent light emitting cathode electrode. Got. As described above, a top emission type light emitting device in which a reflective anode electrode, a polymer hole transport layer, a polymer electron transport / light emitting layer, an electron injection layer, and a transparent cathode electrode were provided on a substrate was obtained. .

When this element was driven at 20 mA / cm ^2, it showed a voltage of 6.8 V, reddish-orange light emission of about 480 cd / m ² was obtained, the light emission efficiency was 1.1 lm / W, and the external quantum efficiency was 2.4%. Met. When this element was driven at a constant current under the conditions of Reference Example 1, it took about 200 hours to reduce the initial luminance by half.

  The electron injecting material of the present invention has shown sufficient electron injecting property even in a polymer organic light emitting device. Further, in this example, the layer of the electron injection material of the present invention was formed by vapor deposition, but the electron injection material of the present invention was dissolved and dispersed in advance in a polymer electron transport material to form a film. In addition, a structure that doubles as an electron injection layer can also be employed.

It is sectional drawing which shows an example of the organic light emitting element in this invention. It is sectional drawing which shows the other example of the organic light emitting element in this invention. It is sectional drawing which shows the other example of the organic light emitting element in this invention. It is sectional drawing which shows the other example of the organic light emitting element in this invention. It is sectional drawing which shows the other example of the organic light emitting element in this invention. It is sectional drawing which shows the other example of the organic light emitting element in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Light emitting layer 4 Electron injection layer 5 Cathode 6 Hole transport layer 7 Electron transport layer 8 Hole injection layer 9 Hole / exciton blocking layer

Claims (11)

A pair of electrodes ing an anode and a cathode, in the pair of electrodes between the organic light emitting device ing from at least one layer of an organic compound is sandwiched, layer of the cathode is made of Ag, comprising the organic compound and the cathode between, seen containing a metal borate salt or metal organic boron compound, possess an electronic note sintering bed in contact with the cathode, the metal of the metal borate salt or the metal organic boron compound, an alkali metal or alkaline earth An organic light emitting device comprising a metal . In an organic light emitting device composed of a pair of electrodes composed of an anode and a cathode and at least one organic compound sandwiched between the pair of electrodes, the cathode is composed of ITO, and between the cathode and the layer composed of the organic compound to include a metal borate salt or metal organic boron compound, an electron injection layer in contact with the cathode, the metal of the metal borate salt or the metal organic boron compound, be made of alkali metal or alkaline earth metal organic light emitting element characterized. In an organic light emitting device composed of a pair of electrodes composed of an anode and a cathode and at least one organic compound sandwiched between the pair of electrodes, the cathode is composed of IZO, and between the layer composed of the cathode and the organic compound And an electron injection layer in contact with the cathode, wherein the metal of the metal borate or the metal organic boron compound is made of an alkali metal or an alkaline earth metal. organic light emitting element characterized. The organic light-emitting device according to any one of claims 1 to 3, wherein the electronic note sintering bed is a unitary thin the metal borate salt or the metal organic boron compound. The organic light-emitting device according to any one of claims 1 to 3, wherein the electron injection layer is a mixed layer of the metal borate salt or the metal organic boron compound and an organic material. 6. The organic light emitting device according to claim 5 , wherein the mixed layer comprises a nitrogen-containing organic base and the metal borate or the nitrogen-containing organic base and the metal organic borate . The organic light-emitting device according to claim 6, wherein the nitrogen-containing organic base is bathophenanthroline . The organic light emitting device according to claim 1 , wherein the metal borate or the metal organic boron compound is potassium tetraborate, rubidium tetraphenylborate, or sodium tetraphenylborate . 4. The organic light-emitting device according to claim 2, wherein the metal borate or the metal organic boron compound is potassium tetraphenylborate . The organic light emitting element according to any one of claims 1 to 9, wherein the anode is an electrode having a function of reflecting light. The organic light emitting element according to claim 10, wherein the anode is an electrode including Ag.

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