JP2009043612A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element excelling in luminous efficiency and life. <P>SOLUTION: This organic EL element is provided with: an intermediate layer formed of a metal oxide containing an alkaline metal or an alkaline earth metal; and first and second organic luminescent element units arranged to sandwich the intermediate layer therebetween, and electrically serially jointed to each other through the intermediate layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic EL element.

  In recent years, as a display device that replaces a liquid crystal display device, for example, a self-luminous display device using organic electroluminescence (hereinafter, organic EL) is expected. In the organic EL element, an organic molecule constituting the organic EL layer emits light by passing a current through the organic EL layer sandwiched between the anode and the cathode. An organic EL display device using an organic EL element is self-luminous, and thus is excellent in terms of reduction in thickness, weight, and power consumption. In addition, organic EL display devices using organic EL elements have a wide viewing angle, and thus attract much attention as candidates for next-generation flat panel displays. Actually, the practical use is expanding as a sub-display of portable music devices and mobile phones by taking advantage of its thinness and wide viewing angle.

In recent years, the organic EL display device has an organic structure in which a plurality of organic light-emitting element units are electrically connected in series via an intermediate layer in order to increase luminance without changing the drive current, that is, to improve efficiency. EL devices are being researched and developed. Here, the intermediate layer injects electrons into the light emitting unit arranged on the electron transport layer side while applying voltage, while injecting holes into the light emitting unit arranged on the hole transport layer side. It is a layer that plays a role. The intermediate layer is configured using, for example, a metal oxide such as vanadium oxide (V ₂ O ₅ ) or rhenium oxide (Re ₂ O ₇ ). It is disclosed in Document 1, Patent Document 2, and the like.
JP 2006-173550 A JP 2006-210155 A

  In the organic EL device having the above-described configuration, the intermediate layer can easily inject holes into the hole transport layer, but it is difficult to inject electrons into the electron transport layer. On the other hand, it is conventionally known that it is effective to provide the electron injection layer on the electron transport layer side of the charge light emitting layer in the light emitting unit in order to increase the electron injection efficiency from the intermediate layer to the electron transport layer. . As such an electron injection layer, for example, a mixed layer of bathocuproine (BCP) and metal cesium (Cs) or a mixed layer of (8-quinolinolato) lithium complex (Alq3) and metal magnesium (Mg) is used. .

  However, the organic EL element having the above-described configuration has a problem that the lifetime of the element is reduced by the reaction of the metal in the electron transport layer with the organic material provided in the light emitting unit.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an organic EL element having excellent luminous efficiency and lifetime.

  An organic EL device according to the present invention is provided so as to sandwich an intermediate layer composed of a metal oxide containing an alkali metal or an alkaline earth metal, and electrically interposed through the intermediate layer. And a first organic light emitting element unit and a second organic light emitting element unit joined in series.

  According to such a configuration, the intermediate layer made of a metal oxide including an alkali metal or an alkaline earth metal provided between the first and second organic light emitting element units is formed of a conventional organic substance and an alkali metal or Compared with a layer in which an alkaline earth metal is mixed, or an alkali metal or alkaline earth metal alone, it exists very stably. For this reason, the luminous efficiency and lifetime of the device are improved.

  In the organic EL device according to the present invention, the metal oxide may contain at least one of vanadium oxide, rhenium oxide, indium tin oxide, molybdenum oxide, iron oxide, and zinc oxide. Good.

  According to such a configuration, since the metal oxide contains at least one of vanadium oxide, rhenium oxide, indium tin oxide, molybdenum oxide, iron oxide, and zinc oxide, an alkali metal Alternatively, it can be mixed well with alkaline earth metals to produce a stable intermediate layer.

  Furthermore, in the organic EL device according to the present invention, the alkali metal and the alkaline earth metal may be contained in the metal oxide as a simple substance, chloride, fluoride, or oxide, respectively.

  According to such a configuration, since the alkali metal and the alkaline earth metal are contained in the metal oxide as a simple substance, chloride, fluoride, or oxide, respectively, a more stable intermediate layer can be produced. The luminous efficiency and lifetime of the device are better.

  In the organic EL device according to the present invention, the film thickness ratio of the film formed by the portion of the intermediate layer containing alkali metal or alkaline earth metal to the entire intermediate layer may be 50% or less.

  According to such a configuration, since the film thickness ratio of the portion of the intermediate layer containing the alkali metal or alkaline earth metal to the entire intermediate layer is 50% or less, the electron transport property of the intermediate layer is good. Can be kept in. Therefore, the luminous efficiency and lifetime of the device are improved.

  Further, in the organic EL device according to the present invention, an electron transport layer is provided on one of the first and second organic light emitting device units so as to face the intermediate layer, and the alkali metal or alkaline earth of the intermediate layer is provided. The metal may be contained in a portion of the intermediate layer facing the electron transport layer.

  According to such a configuration, since the alkali metal or alkaline earth metal of the intermediate layer is included in the portion of the intermediate layer facing the electron transport layer, the electron injection barrier of the device is reduced. Therefore, a more stable intermediate layer can be produced, and the light emission efficiency and lifetime of the element are improved.

  In the organic EL device according to the present invention, an electron transport layer is provided on one of the first and second organic light emitting device units so as to face the intermediate layer, and the alkali metal or alkaline earth of the intermediate layer is provided. The metal may be contained so that the concentration in the intermediate layer gradually decreases from the side of the intermediate layer facing the electron transport layer toward the opposite side.

  According to such a configuration, the concentration of the alkali metal or alkaline earth metal in the intermediate layer gradually decreases from the side facing the electron transport layer of the intermediate layer toward the opposite side. Therefore, the electron injection barrier of the device is reduced. Therefore, a more stable intermediate layer can be produced, and the light emission efficiency and lifetime of the element are improved.

  The organic EL device according to the present invention is provided so as to sandwich an intermediate layer composed of a metal oxide layer and a metal oxide layer containing an alkali metal or an alkaline earth metal, and the intermediate layer. And a first organic light emitting element unit and a second organic light emitting element unit electrically connected in series via an intermediate layer.

  According to such a configuration, since the intermediate layer is composed of a metal oxide layer and a metal oxide layer containing an alkali metal or an alkaline earth metal, it is more than a single layer. A stable intermediate layer can be produced, and the light emission efficiency and lifetime of the device are improved.

  An organic EL device according to the present invention includes an intermediate layer composed of a metal oxide layer containing an alkali metal or an alkaline earth metal, a metal oxide layer containing a p-type dopant, and an intermediate layer. And a first organic light emitting element unit and a second organic light emitting element unit which are provided so as to be sandwiched and are electrically connected in series via an intermediate layer.

  According to such a configuration, since the intermediate layer includes a metal oxide layer containing a p-type dopant in addition to a metal oxide layer containing an alkali metal or an alkaline earth metal, the hole transport property of the device・ Electron transportability is improved. Therefore, the light emission efficiency of the device becomes better.

  In the organic EL device according to the present invention, the p-type dopant may be at least one of organic compounds having a phthalocyanine skeleton, a p-quinone skeleton, an o-quinone skeleton, or a quinodimethane skeleton. .

  According to such a structure, since the p-type dopant is at least one of organic compounds having a phthalocyanine skeleton, a p-quinone skeleton, an o-quinone skeleton, or a quinodimethane skeleton, Improved transportability and electron transportability. Therefore, the light emission efficiency of the device becomes better.

  Furthermore, in the organic EL device according to the present invention, the p-type dopant may be an oxide of a transition metal.

  According to such a configuration, since the p-type dopant is an oxide of a transition metal, the hole transport property / electron transport property of the device is further enhanced. Therefore, the light emission efficiency of the device becomes better.

  In the organic EL device according to the present invention, the intermediate layer includes a metal oxide layer containing an alkali metal or an alkaline earth metal and a metal oxide layer containing a p-type dopant, respectively. The film thickness ratio may be 50% or less.

  According to such a configuration, the metal oxide layer containing the alkali metal or the alkaline earth metal in the intermediate layer and the metal oxide layer containing the p-type dopant are each in a film thickness ratio with respect to the entire intermediate layer. Therefore, the electron transport property of the intermediate layer can be kept good. Therefore, the luminous efficiency and lifetime of the device are improved.

  In the organic EL device according to the present invention, one of the first and second organic light emitting device units is provided with an electron transport layer so as to face the intermediate layer, and the other is opposed to the intermediate layer. A hole transport layer is provided, a metal oxide layer containing an alkali metal or an alkaline earth metal is provided so as to face the electron transport layer, and a metal oxide layer containing a p-type dopant is provided. It may be provided so as to face the hole transport layer.

  According to such a configuration, the metal oxide layer containing an alkali metal or alkaline earth metal is provided so as to face the electron transport layer, and the metal oxide layer containing a p-type dopant is transported by holes. Since it is provided so as to face the layer, the hole transport property and electron transport property of the element are further enhanced. Therefore, the light emission efficiency of the device becomes better.

  Further, in the organic EL device according to the present invention, the alkali metal or alkaline earth metal is contained in a portion facing the electron transport layer in the metal oxide layer containing the alkali metal or alkaline earth metal, and is a p-type dopant. May be contained in a portion facing the hole transport layer in the metal oxide layer containing the p-type dopant.

  According to such a configuration, the alkali metal or alkaline earth metal is contained in the portion facing the electron transport layer in the metal oxide layer containing the alkali metal or alkaline earth metal, and the p-type dopant is p Since it is contained in the portion facing the hole transport layer in the metal oxide layer containing the type dopant, the hole transport property and electron transport property of the device are further enhanced. Therefore, the light emission efficiency of the device becomes better.

  Further, in the organic EL device according to the present invention, as the alkali metal or alkaline earth metal moves from the side facing the electron transport layer of the metal oxide layer containing the alkali metal or alkaline earth metal to the opposite side. The p-type dopant is contained so that the concentration in the metal oxide layer gradually decreases, and the p-type dopant is included in the metal oxide layer containing the p-type dopant from the side opposite to the hole transport layer. It may be included so that the concentration in the metal oxide layer gradually decreases as it goes to.

  According to such a configuration, the alkali metal or alkaline earth metal gradually increases from the side facing the electron transport layer of the metal oxide layer containing the alkali metal or alkaline earth metal toward the opposite side. As the concentration of the metal oxide in the layer is decreased, the p-type dopant moves from the side opposite to the hole transport layer of the metal oxide layer containing the p-type dopant toward the opposite side. Since the metal oxide layer is gradually included in the metal oxide layer, the electron injection barrier and the hole transport barrier of the device are reduced. Therefore, a more stable intermediate layer can be produced, and the light emission efficiency and lifetime of the element are improved.

  Furthermore, the organic EL device according to the present invention includes a metal oxide layer and an electron transport layer containing an alkali metal or an alkaline earth metal, and a metal oxide layer and a hole transport layer containing a p-type dopant. Between the metal oxide layer containing an alkali metal or an alkaline earth metal and the metal oxide layer containing a p-type dopant. You may provide the buffer layer comprised.

  According to such a configuration, between the metal oxide layer and the electron transport layer containing an alkali metal or an alkaline earth metal, and between the metal oxide layer and the hole transport layer containing a p-type dopant. Between the metal oxide layer containing an alkali metal or an alkaline earth metal and the metal oxide layer containing a p-type dopant, and at least one of them. Since the buffer layer is provided, the reaction between the metal and the organic material that occurs between the upper and lower layers of the buffer layer can be satisfactorily suppressed. For this reason, the luminous efficiency and lifetime of the element become better.

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element excellent in luminous efficiency and lifetime can be provided.

  Hereinafter, although embodiment of this invention is described in detail, this invention is not limited to these.

(Embodiment)
The organic EL element includes a substrate on which a plurality of pixel regions are arranged in a matrix.

  A plurality of thin film transistors (TFTs), signal lines, and a planarization layer are formed on the substrate, and a first electrode (anode or cathode) is formed on the planarization layer. Accordingly, the substrate constitutes an active matrix substrate.

  The substrate may not be an active matrix substrate. For example, a passive matrix substrate in which a plurality of signal lines and first electrodes are formed on the substrate may be configured.

  On the first electrode of each pixel region, an intermediate layer provided in each of the plurality of pixel regions is provided so as to sandwich the intermediate layer, and electrically connected in series via the intermediate layer. 1 and a second organic light emitting element unit are provided.

  An active element portion such as a TFT on the active matrix substrate and the intermediate layer and the first and second organic light emitting element units are separated by an interlayer insulating film having a function of a planarizing layer. The active element portion is connected to the upper first electrode through a contact conductor that fills the contact hole through a contact hole formed in the interlayer insulating film. At this time, it is also possible to use the first electrode of the organic EL as the connecting conductor.

  A semiconductor layer composed of an amorphous silicon thin film or a polycrystalline film is used for the TFT of the active element portion. The TFT may be a top gate type or a bottom gate type.

  The interlayer insulating film having a function as a planarizing layer may have a single layer structure or a multilayer structure. A silicon nitride film as a protective film for a TFT or the like and a laminated film of a resin or the like mainly functioning as a planarizing layer are preferably used. In order to make the interlayer insulating film function as a planarizing layer, resin layers such as acrylic, epoxy, and polyimide, and liquid glass materials such as SOG (Spin on Glass) are preferably used. It is not limited to these. The planarizing layer preferably has a film thickness of at least 2 μm. The method for reducing the unevenness of the planarizing layer to 100 nm or less according to the present invention can be realized by increasing the thickness of the planarizing layer or polishing the surface of the planarizing layer, but is not limited thereto. .

  Next, the laminated structure of the organic EL element according to the embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional view of the organic EL element 10. The organic EL element 10 includes an anode 11, a first organic light emitting element unit 12, an intermediate layer 13, a second organic light emitting element unit 14, and a cathode 15 that are formed in this order on a substrate (not shown). .

  The first and second organic light emitting element units 12 and 14 are each composed of a laminated structure of various functional material layers using a low molecular material or a polymer material. Specifically, the following configurations (1) to (4) are exemplified.

(1) Hole transport layer / organic light emitting layer / electron transport layer (2) Hole injection layer / hole transport layer / organic light emitting layer / electron transport layer (3) Hole injection layer / hole transport layer / organic light emission Layer / Electron Transport Layer / Electron Injection Layer (4) Hole Transport Layer / Organic Light-Emitting Layer / Electron Transport Layer / Electron Injection Layer Here, the organic light-emitting layer may have a single layer or a multilayer structure. Further, a layer obtained by doping a base material with a dopant may be used.

  The organic light emitting layer can be formed by a known method. For example, the low molecular organic light emitting layer can be formed by a vacuum deposition method. In addition, the polymer organic light emitting layer is formed by using a coating liquid for forming an organic light emitting layer, a spin coating method, a doctor blade method, a discharge coating method, a spray coating method, an ink jet method, a letterpress printing method, an intaglio printing method, a screen printing method. It is possible to form a film by a wet process such as a micro gravure coating method.

  Hereinafter, an organic EL using a low molecular organic light emitting layer will be described as an example. However, the present invention is not limited to this, and a high molecular organic light emitting layer may of course be used.

  As a luminescent material, the well-known luminescent material for organic LED elements can be used. Such a light emitting material is classified into a low molecular light emitting material, a precursor of a low molecular light emitting material, and the like. Although these specific compounds are illustrated below, this invention is not limited to these.

Examples of the low molecular light-emitting material include poly (2-decyloxy-1,4-phenylene) (DO-PPP), poly [2,5-bis- [2- (N, N, N-triethylammonium) ethoxy]- 1,4-Phenyl-Alto 1,4-Phenyllene] dibromide (PPP-NEt ³⁺ ), poly [2- (2′-ethylhexyloxy) -5-methoxy-1,4-phenylene vinylene] (MEH-PPV) Etc.

Examples of the precursor of the polymer light emitting material include a poly (P-phenylene vinylene) precursor (Pre-PPV), a poly (P-naphthalene vinylene) precursor (Pre-PNV), and the like. In addition, each of the electron transport layer (collectively, charge transport layer) may have a single layer structure or a multilayer structure.

  The charge transport layer can be formed by a known method in the same manner as the light emitting layer material.

  A known material can be used as the charge transport material. Although these specific compounds are shown below, this invention is not limited to this.

  Examples of hole transport materials include porphyrin compounds, N, N′-bis- (3-methylphenyl) -N, N′-bis- (phenyl) -benzidine (TPD), N, N′-di (naphthalene) -1-yl) -N, N'-diphenyl-benzidine (NPD) and other aromatic tertiary amine compounds, hydrazone compounds, quinacridone compounds, low molecular weight materials such as stilamine compounds, polyaniline, 3,4-polyethylenedioxy Polymer materials such as thiophene / polystyrene sulfonate (PEDOT / PSS), poly (triphenylamine derivatives), polyvinylcarbazole (PVCz), poly (P-phenylene vinylene) precursor, poly (P-naphthalene vinylene) precursor And high molecular material precursors.

  Examples of the electron transport material include low-molecular materials such as oxadiazole derivatives, triazole derivatives, benzoquinone derivatives, naphthoquinone derivatives, and fluorene derivatives, and polymer materials such as poly [oxadiazole].

  A known electrode material can be used for each of the anode 11 and the cathode 15. Further, a film such as a carrier injection layer can be inserted at the interface between the anode 11 and the cathode 15 and the first and second organic light emitting element units 12 and 14 as necessary.

The anode 11, large metal work function material (Au, Ni, Pt, etc.) or conductive metal oxides (ITO, IZO, ZnO, SnO 2 , etc.) be used as a laminated film of a single layer or a plurality of materials it can. In addition, an oxide having a thickness that does not greatly hinder the conductivity (for example, about 1 nm) on the anode 11 may be stacked on the side in contact with the first and second organic light emitting element units 12 and 14. . For example, by providing a thin oxide layer such as SnO ₂ , the coating property of the organic light emitting material coating solution or the carrier transporting material coating solution can be further improved.

As the electrode material used as the cathode 15, Ca, Ce, Cs, Rb, Sr, Ba, Mg, Li, etc. having a low work function of 4.0 eV or less can be used. For the light emitting layer, Ca and Ba are preferably used. The cathode 15 is made of a relatively scientifically stable metal such as Ni, Os, Pt, Pd, Al, Au, Rh, Ag, etc., in order to suppress the deterioration of the above-mentioned low work function electrode due to oxygen, water, etc. An alloy or a laminated structure is preferably used. Further, in the top emission type organic EL, it is necessary to form the cathode 15 thin in order to provide translucency. Therefore, in order to ensure sufficient conductivity as an electrode, a conductive metal oxide such as ITO, IZO, ZnO, or SnO ₂ can be formed as a transparent electrode layer on a light-transmitting metal layer. The transparent electrode layer may be a single layer or a laminated film of a plurality of materials.

  The intermediate layer 13 is made of a metal oxide containing an alkali metal or an alkaline earth metal. The metal oxide of the intermediate layer 13 includes at least one of vanadium oxide, rhenium oxide, indium tin oxide, molybdenum oxide, iron oxide, and zinc oxide. The alkali metal and the alkaline earth metal are contained in the metal oxide as a simple substance, chloride, fluoride, or oxide, respectively. The intermediate layer 13 is formed so that the film thickness ratio of the film formed by the portion containing the alkali metal or alkaline earth metal to the entire intermediate layer 13 is 50% or less.

  Further, the intermediate layer of the organic EL element according to the embodiment of the present invention is not limited to that shown in FIG. 1, and may be, for example, as shown in FIGS.

  The intermediate layer 23 of the organic EL element 20 shown in FIG. 2 is made of a metal oxide, and an alkali metal is formed on a portion of the metal oxide facing the electron transport layer provided in the first organic light emitting element unit 12. Or an alkaline earth metal is contained. That is, the intermediate layer 23 is composed of a metal oxide-only layer 22 and a layer 21 in which the metal oxide contains an alkali metal or an alkaline earth metal.

  The intermediate layer 33 of the organic EL element 30 shown in FIG. 3 gradually increases the alkali metal in the intermediate layer 33 from the side facing the electron transport layer provided in the first organic light emitting element unit 12 toward the opposite side. Alternatively, the alkaline earth metal concentration is low, that is, a concentration gradient is provided.

  The intermediate layer 43 of the organic EL element 40 shown in FIG. 4 includes a metal oxide layer 41 containing an alkali metal or an alkaline earth metal and a metal oxide layer 42 containing a p-type dopant. Yes.

  A metal oxide layer 41 containing an alkali metal or an alkaline earth metal is provided so as to face the electron transport layer of the first organic light emitting device unit 12, and a metal oxide layer 42 containing a p-type dopant is provided in the first layer. Two organic light emitting element units 14 are provided so as to face the hole transport layer.

  The p-type dopant is composed of at least one of organic compounds having a phthalocyanine skeleton, a p-quinone skeleton, an o-quinone skeleton, or a quinodimethane skeleton. The p-type dopant may be composed of a transition metal oxide. Further, the metal oxide layer 41 containing an alkali metal or an alkaline earth metal and the metal oxide layer 42 containing a p-type dopant each have a film thickness ratio of 50% or less with respect to the entire intermediate layer 43. It may be formed as follows.

  The alkali metal or alkaline earth metal may be contained in a portion of the metal oxide layer 41 containing the alkali metal or alkaline earth metal that faces the electron transport layer. The p-type dopant may be contained in a portion of the metal oxide layer 42 containing the p-type dopant that faces the hole transport layer.

  The intermediate layer 53 of the organic EL element 50 shown in FIG. 5 is opposite from the side where the alkali metal or alkaline earth metal faces the electron transport layer of the metal oxide layer 51 containing the alkali metal or alkaline earth metal. It is contained so that the concentration in the metal oxide layer gradually decreases toward the side. The concentration of the p-type dopant gradually decreases in the metal oxide layer from the side facing the hole transport layer of the metal oxide layer 52 containing the p-type dopant toward the opposite side. Included. That is, a concentration gradient of alkali metal, alkaline earth metal, or p-type dopant is formed in each metal oxide layer 51, 52, respectively.

  The intermediate layer 63 of the organic EL element 60 shown in FIG. 6 includes a metal oxide layer between a metal oxide layer 61 containing an alkali metal or an alkaline earth metal and a metal oxide layer 62 containing a p-type dopant. A buffer layer 64 composed only of objects is provided. The buffer layer 64 is not limited to this, and is provided between the metal oxide layer 61 containing alkali metal or alkaline earth metal and the electron transport layer of the first organic light emitting element unit 12 in the intermediate layer 63. It may be done. The buffer layer 64 may be provided between the metal oxide layer 62 containing a p-type dopant and the hole transport layer of the second organic light emitting element unit 14. Furthermore, it may be provided between a plurality of layers arbitrarily selected from the above configuration.

  In the organic EL elements 10 to 60 in the above embodiment, the laminated pattern of the first organic light emitting element unit 12, the intermediate layers 13 to 63, and the second organic light emitting element unit 14 may be repeated any number of times. Specifically, on the upper side or the lower side (or both sides) of the first and second organic light emitting element units 12 and 14 provided via the intermediate layers 13 to 63, the third ( Or the 3rd and 4th) organic light emitting element unit may be provided, and the lamination pattern more than that may be provided.

  Next, Example 1 of the organic EL element of the present invention will be described in detail with reference to the drawings.

(Configuration of organic EL element)
FIG. 7 shows a cross-sectional view of the organic EL element 70 according to Example 1 of the present invention. In the organic EL element 70, an ITO glass substrate (not shown), an anode 71, a first organic light emitting element unit 72, an intermediate layer 73, a second organic light emitting element unit 74, and a cathode 75 are laminated in this order.

(Manufacture of organic EL element 70)
First, an ITO glass substrate (not shown) is prepared. The substrate is not limited to the ITO glass substrate. For example, in a top emission type organic EL element, the substrate does not need translucency in order to extract light from the side opposite to the substrate. For this reason, a semiconductor substrate such as a silicon wafer may be used.

  Next, a silicon semiconductor film was formed on the ITO glass substrate by plasma CVD, and a crystallization process was performed to form a polycrystalline silicon semiconductor film.

  Subsequently, the polycrystalline silicon thin film was etched to form a plurality of island patterns.

  Next, a gate insulating film and a gate electrode layer were sequentially formed on the plurality of island patterns, and patterning was performed by an etching process.

  Subsequently, a plurality of TFTs are formed by forming a source region and a drain region on each island of the island-shaped polycrystalline silicon semiconductor film by doping, and further, an interlayer insulating film having a function as a planarizing layer is formed. did. The interlayer insulating film of this embodiment is formed by stacking a silicon nitride film formed by a plasma CVD method and an acrylic resin layer formed by a spin coater.

  For the production of the interlayer insulating film, first, after forming a silicon nitride film, a contact hole communicating with the source region and / or drain region was formed by etching together with the gate insulating film. Thereafter, a source wiring was formed, an acrylic resin layer was further formed, and then a contact hole communicating with the drain region was formed at the same position as the contact hole of the drain region drilled in the gate insulating film and the silicon nitride film. The function as the flattening layer is realized by an acrylic resin layer. The acrylic resin layer was formed with a thickness of 8 μm so that the size of the irregularities on the surface was 100 nm or less. As a result, the size of the irregularities on the surface of the acrylic resin layer, which is the planarizing layer, was 48 nm at the maximum. The size of the irregularities on the surface of the acrylic resin layer, which is a flattening layer, was measured using a stylus type step gauge.

Next, an anode 71 was formed on the substrate on which the planarization layer was formed so as to be connected to the drain electrode of the TFT through a through hole provided in the planarization layer. Ni was used for the anode 71 and the film thickness was 150 nm. Next, a cover was formed so as to surround the pixel electrode for each pixel with a SiO ₂ insulating film so as to cover the edge portion of the anode 71. The opening surrounded by the partition wall obtained in this manner was 50 × 50 μm.

Subsequently, α-NPD was formed on the anode 71 as a first hole transport layer 72a by a vacuum deposition method so as to have a film thickness of 30 nm (deposition rate: 1 Å / sec). Further, CBP as the host and Ir (ppy) ₃ as the dopant are shared so as to have a film thickness of 30 nm (CBP: vapor deposition rate 1 Å / sec, Ir (ppy) ₃ : vapor deposition rate 0.1 Å / sec). The light emitting layer 72b was formed by vapor deposition.

Next, BCP is formed as a buffer layer 72c with a film thickness of 10 nm (deposition rate 1 Å / sec), and then Alq ₃ is formed as an electron transport layer 72d with a thickness of 40 nm (deposition rate 1 Å / sec). The 1st organic light emitting element unit 72 was formed.

Subsequently, the intermediate layer 73 is formed on the first organic light emitting element unit 72 by co-evaporation with molybdenum oxide (MoO ₃ ) and Ca at 20 nm (MoO ₃ : deposition rate 1 Å / sec, Ca: deposition rate 0.1 Å / sec). Formed.

  Next, the second organic light emitting element unit 74 was formed on the intermediate layer 73 in the same procedure as the formation of the first organic light emitting element unit 72 on the anode 71. Here, the plurality of layers (74a to 74d) constituting the second organic light emitting element unit 74 in FIG. 7 correspond to the plurality of layers (72a to 72d) constituting the first organic light emitting element unit 72, respectively. is there.

  Subsequently, LiF is formed as the electron injection layer 76 with a film thickness of 0.5 nm by a vacuum evaporation method (deposition rate 1 Å / sec), and an Al film (cathode 75) is formed as the cathode 75 with a film thickness of 500 nm. Thus, an organic EL element 70 was produced.

Comparative example

  Next, as a comparative example, an organic EL element 80 having the configuration shown in FIG. 8 was produced. Here, the organic EL element 80 is characterized in that an alkali metal or the like is not contained in the metal oxide of the intermediate layer 83 as compared with the organic EL element 70 of the first embodiment. In the organic EL element 80, a carrier injection layer 86 is formed on the side facing the intermediate layer of the first organic light emitting element unit. Since the other constituent elements are the same as those in the first embodiment, the same reference numerals are given.

In the production of the organic EL element 80, Alq3 was formed with a film thickness of 40 nm (deposition rate 1 Å / sec) in the same manner as in Example 1 in order to increase the electron injection capability when forming the electron transport layer 72d on the anode 71 side. Thereafter, Alq3 and metallic calcium (Ca) were formed by co-evaporation so as to have a film thickness of 10 nm (Alq3: vapor deposition rate 1 Å / sec, Li: vapor deposition rate 0.5 Å / sec). Thereafter, molybdenum oxide (MoO ₃ ) was formed with a film thickness of 20 nm (deposition rate: 1 Å / sec) by a vacuum evaporation method to form an intermediate layer 83 of the organic EL element 80.
(Evaluation result 1)

The light emitting efficiency and device lifetime of the organic EL devices 70 and 80 produced in Example 1 and the comparative example were compared and evaluated. As for the luminous efficiency, there was almost no difference between Example 1 and Comparative Example (Example 1: 62 cd / A, Comparative Example 1: 64 cd / A). However, regarding the device lifetime, it was confirmed that the organic EL device 70 of Example 1 was significantly extended (Example 1: 8000 hours, Comparative Example: 1200 hours at 2000 cd / m ² ).

  From this result, since the metal present in the electron transport layer easily reacts with the organic material, the lifetime of the multiphoton (tandem) element including a plurality of organic light emitting element units was not good. Thus, it has been found that if a metal oxide and a metal are present, the reaction between them is suppressed, so that the lifetime of the device is improved.

  The organic material of the organic light-emitting element unit is likely to be negatively localized on the oxygen atom, sulfur atom, or halogen atom when a bond of carbon atom or silicon atom and oxygen atom, sulfur atom, or halogen atom exists. . And the site | part localized to the metal plus coordinate to the site | part localized to the minus. For this reason, the bond between the carbon atom or silicon atom and the oxygen atom, sulfur atom or halogen atom is weakened, and the organic material and the metal are likely to react. On the other hand, when a metal oxide and a metal are combined, oxygen atoms in the metal oxide are not localized as negatively as organic materials. For this reason, the reactivity of a metal oxide and a metal becomes low compared with the reactivity of an organic material and a metal. Although the reactivity between the metal oxide and the metal is low, the electron injection property can be enhanced by doping the metal at a relatively high concentration (10 to 40%).

  Next, the organic EL element 90 according to Example 2 will be described in detail with reference to the drawings.

  FIG. 9 is a cross-sectional view of an organic EL element 90 according to the second embodiment. The organic EL element 90 according to Example 2 is different from the organic EL element 70 according to Example 1 only in the configuration of the intermediate layers 73 and 93.

The intermediate layer 93 of the organic EL element 90 according to Example 2 is a reaction between Alq3 of the electron transport layer 72d in the first organic light emitting element unit 72 on the anode 71 side and the metal in the intermediate layer 93, and further on the cathode 75 side. 2 The organic light-emitting element unit 74 is configured to suppress the reaction between α-NPD and metal. Specifically, the intermediate layer 93 is formed by forming the first organic light emitting element unit 72 on the anode 71 side, and then forming a MoO ₃ layer 97 with a thickness of 1 nm, and then a MoO ₃ and Ca layer 98. Was formed by co-evaporation with a film thickness of 20 nm (MoO ₃ : evaporation rate 1 Å / sec, Ca: evaporation rate 0.1 Å / sec). Thereafter, a MoO ₃ layer 97 having a thickness of 1 nm was formed. The anode 71, the first and second organic light emitting element units 72 and 74, and the cathode 75 other than the intermediate layer 93 were formed in the same procedure as in Example 1.

  Next, the organic EL element 100 according to Example 3 will be described in detail with reference to the drawings.

  FIG. 10 is a cross-sectional view of the organic EL element 100 according to the third embodiment. The organic EL element 100 according to Example 3 is different from the organic EL element 70 according to Example 1 only in the configuration of the intermediate layers 73 and 103.

In Example 3, after forming the first organic light emitting element unit 72 on the anode 71 side, the MoO ₃ layer 107 was formed to a thickness of 1 nm, and then the MoO ₃ and Ca layer 108 was co-evaporated. The film was formed with a film thickness of 10 nm (MoO ₃ : deposition rate 1 Å / sec, Ca: deposition rate 0.1 Å / sec). Subsequently, a layer 107 of MoO ₃ is further formed to a thickness of 1 nm, and then a layer 109 of MoO ₃ and F ₄ TCNQ is co-evaporated to 10 nm (MoO ₃ : evaporation rate 1 Å / sec, F ₄ TCNQ: evaporation). The film thickness was 0.1 mm / sec). Finally, the MoO ₃ layer 107 was formed to a thickness of 1 nm, and the intermediate layer 103 was produced. The anode 71, the first and second organic light emitting element units 72 and 74, and the cathode 75 other than the intermediate layer 103 were formed in the same procedure as in Example 1.
(Evaluation result 2)

  With respect to the organic EL elements 70, 90, and 100 produced in Examples 1 to 3, the driving voltage, the light emission efficiency, and the element lifetime were comparatively evaluated.

  The driving voltage was 6.4 V for the organic EL element 70 of Example 1 and 6.5 V for the organic EL element 90 of Example 2, and both were substantially equal. On the other hand, the organic EL element 100 of Example 3 was 6.2 V, which was lower than those of Examples 1 and 2.

  There was almost no difference in luminous efficiency between the organic EL element 70 of Example 1 and the organic EL element 90 of Example 2 (Example 1: 62 cd / A, Example 2: 64 cd / A). However, the light emission efficiency of the organic EL element 100 of Example 3 was slightly lower than that of Examples 1 and 2 (58 cd / A).

There was almost no difference in element lifetime between the organic EL element 70 of Example 1 and the organic EL element 90 of Example 2. On the other hand, it was confirmed that the lifetime of the organic EL element 100 of Example 3 was significantly longer than that of Examples 1 and 2 (Example 1: 8000 hours, Example 2: 9000 hours, Example 3: 13000 hours at 2000 cd / m ² ).

  From the above results, it was confirmed that by preventing the metal present in the intermediate layer from approaching the adjacent organic material, the reaction between the metal and the organic material can be suppressed, and the lifetime of the element can be increased (Examples 1 to 3). 3 and comparison with comparative example). In addition, by arranging the intermediate layer so that the electron injecting property is increased near the anode and the hole injecting property is increased near the cathode, the intermediate layer can be driven at a lower voltage to obtain a device with high luminous efficiency. (Comparison between Examples 1 and 2 and Example 3) The mechanism that can suppress the reaction between the metal and the organic material by preventing the metal present in the intermediate layer from approaching the adjacent organic material is the same as that described in the evaluation result 1.

  Next, the organic EL element 110 according to Example 4 will be described in detail with reference to the drawings.

  FIG. 11 is a cross-sectional view of the organic EL element 110 according to the fourth embodiment. The organic EL element 110 according to the fourth embodiment is different from the organic EL element 70 according to the first embodiment only in the configuration of the intermediate layers 73 and 113.

In Example 4, after the first organic light emitting element unit 72 on the anode 71 side was formed, the MoO ₃ layer 117 was formed to a thickness of 1 nm. Then, MoO ₃ and 10nm by co-evaporation layer 118 of Ca was formed to have a thickness of (MoO _3:: deposition rate 1 Å / sec, Ca from the deposition rate of 0.20Å / sec 0.05Å / sec). At that time, while the deposition rate of Ca was changed, the deposition rate of MoO ₃ was kept constant and a concentration gradient was provided. Thereafter, a layer 117 of MoO ₃ was formed with a thickness of 1 nm. Subsequently, a layer 119 of MoO ₃ and F ₄ TCNQ was formed by co-evaporation with a film thickness of 10 nm (MoO ₃ : deposition rate 1 Å / sec, F ₄ TCNQ: deposition rate 0.20 ０．２ / sec to 005 Å / sec). . At this time, the deposition rate of F ₄ TCNQ was changed, while the deposition rate of MoO ₃ was constant and a gradient was provided. Finally, the MoO ₃ layer 117 was formed to a thickness of 1 nm, and the intermediate layer 113 was produced. The anode 71, the first and second organic light emitting element units 72 and 74, and the cathode 75 other than the intermediate layer 113 were formed in the same procedure as in Example 1.

The concentration gradient can be easily formed even by using a method in which a deposition source such as in-line deposition is fixed and the substrate is transported.
(Evaluation result 3)

  The drive voltage, light emission efficiency, and element lifetime of the organic EL elements 100 and 110 produced in Example 3 and Example 4 were compared and evaluated. Compared with the organic EL element 100 produced in Example 3, the organic EL element 110 produced in Example 4 had an element lifetime of 50% longer and the luminous efficiency was equivalent.

  It was found that providing the concentration gradient reduces the electron and hole injection barrier and makes it electrochemically stable. This is because changing the doping concentration changes the work function, which facilitates the injection or movement of electrons and holes at each point. Further, it is desirable that the concentration gradient is uniform from the work function of adjacent layers. This is because the barrier for electron and hole movement is minimized. (Reference: K. Okamoto et al. J. Am. Chem. Soc. 2003, 125, 7014.)

  Next, an organic EL element according to Example 5 will be described.

  The organic EL element according to Example 5 and the organic EL element 90 according to Example 2 differ only in the configuration of the intermediate layer 93.

As an intermediate layer of the organic EL element according to Example 5, first, an anode 71 and a first organic light emitting element unit 72 similar to those of the organic EL element 90 according to Example 2 were formed. Subsequently, a layer of MoO ₃ is formed with a thickness of 1 nm, and further, a layer of MoO ₃ and Ca is formed by co-evaporation to 20 nm (MoO ₃ : deposition rate 1 Å / sec, Ca: deposition rate 0.5 Å / sec). The film thickness was formed. Next, a MoO ₃ layer was formed to a thickness of 1 nm. Further, the second organic light emitting element unit 74 and the cathode 75 were formed in the same procedure as in Example 2.
(Evaluation result 4)

The drive voltage, light emission efficiency, and element lifetime of the organic EL elements produced in Example 2 and Example 5 were comparatively evaluated. In Example 5, 50% Ca was doped with respect to MoO ₃ in a relative film thickness ratio (20% in Example 2). With respect to the organic EL element 90 of Example 2, the organic EL element produced in Example 5 has a result that the element lifetime is shortened by 10%.

As a result, the device life was shortened from about 50% or more of the metal doped with respect to MoO ₃ . That is, it is considered that the active life point at which Ca reacts with the surroundings increases and the electron transport property is lowered after the reaction, so that the device lifetime is shortened as a whole.

  Next, an organic EL element according to Example 6 will be described.

  The organic EL element according to Example 6 and the organic EL element 100 according to Example 3 have the same constituent elements, and only the configuration of the intermediate layer 103 is different.

In the production of the intermediate layer 103 of the organic EL element 100 according to Example 3, the intermediate layer of the organic EL element according to Example 6 is MoO ₃ : the vapor deposition rate of 1 Å / sec as MoO ₃ and F ₄ TCNQ. , _F 4 TCNQ: the deposition rate 0.5 Å / sec, was formed to have a thickness of 10 nm.
(Evaluation result 5)

The drive voltage, light emission efficiency, and element lifetime of the organic EL elements produced in Example 3 and Example 6 were comparatively evaluated. In Example 6, 50% F ₄ TCNQ in terms of relative film thickness ratio was doped with respect to MoO ₃ (20% in Example 3). The organic EL element produced in Example 6 was 10% shorter than the organic EL element 100 produced in Example 3.

Since the result that the device life is shortened from about 50% or more doping of metal with respect to MoO ₃ is obtained, the number of active sites where Ca reacts with the surroundings increases, and the electron transport property decreases after the reaction. It is thought that the device life as a whole was shortened.

  As described above, the present invention relates to an organic EL element.

FIG. 1 is a cross-sectional view of an organic EL element 10 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the organic EL element 20 according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of the organic EL element 30 according to the embodiment of the present invention. FIG. 4 is a cross-sectional view of the organic EL element 40 according to the embodiment of the present invention. FIG. 5 is a cross-sectional view of an organic EL element 50 according to an embodiment of the present invention. FIG. 6 is a cross-sectional view of an organic EL element 60 according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of the organic EL element 70 according to Example 1 of the present invention. FIG. 8 is a cross-sectional view of an organic EL element 80 according to a comparative example. FIG. 9 is a cross-sectional view of an organic EL element 90 according to Example 2 of the present invention. FIG. 10 is a cross-sectional view of an organic EL element 100 according to Example 3 of the present invention. FIG. 11 is a cross-sectional view of an organic EL element 110 according to Example 4 of the present invention.

Explanation of symbols

10, 20, 30, 40, 50, 60, 70, 90, 100, 110 Organic EL elements 11, 71 Anode 12, 72 First organic light emitting element units 13, 23, 33, 43, 53, 63, 73, 93 , 103, 113 Intermediate layer 14, 74 Second organic light emitting element unit 15, 75 Cathode 21, 41, 51, 61 Metal oxide layer 22 containing alkali metal or alkaline earth metal 22 Metal oxide only layer 42, 52, 62 Metal oxide layer containing p-type dopant 64 Buffer layer 72a Hole transport layer 72b Light emitting layer 72c Buffer layer 72d Electron transport layer 76 Electron injection layer 86 Carrier injection layer 97, 107, 117 MoO ₃ layer 98 , 108, 118 MoO ₃ and Ca layer 109, 119 MoO ₃ and F ₄ TCNQ layer

Claims (17)

An intermediate layer composed of a metal oxide containing an alkali metal or an alkaline earth metal;
First and second organic light-emitting element units that are provided so as to sandwich the intermediate layer and are electrically connected in series via the intermediate layer;
An organic EL device comprising: The organic EL device according to claim 1,
The metal oxide is an organic EL element including at least one of vanadium oxide, rhenium oxide, indium tin oxide, molybdenum oxide, iron oxide, and zinc oxide. The organic EL device according to claim 1,
The organic EL element in which the alkali metal and the alkaline earth metal are contained in the metal oxide as a simple substance, chloride, fluoride, or oxide, respectively. The organic EL device according to claim 1,
The organic EL element whose film thickness ratio with respect to the whole said intermediate | middle layer of the film | membrane which the part containing the alkali metal or alkaline-earth metal of the said intermediate layer comprises is 50% or less. The organic EL device according to claim 1,
One of the first and second organic light emitting element units is provided with an electron transport layer so as to face the intermediate layer,
The organic EL element in which the alkali metal or alkaline earth metal of the intermediate layer is contained in a portion of the intermediate layer facing the electron transport layer. The organic EL device according to claim 1,
One of the first and second organic light emitting element units is provided with an electron transport layer so as to face the intermediate layer,
The alkali metal or alkaline earth metal of the intermediate layer is included so that the concentration in the intermediate layer gradually decreases from the side of the intermediate layer facing the electron transport layer toward the opposite side. Organic EL element. An intermediate layer composed of a metal oxide layer, a metal oxide layer containing an alkali metal or an alkaline earth metal, and
First and second organic light-emitting element units that are provided so as to sandwich the intermediate layer and are electrically connected in series via the intermediate layer;
An organic EL device comprising: An intermediate layer composed of a metal oxide layer containing an alkali metal or an alkaline earth metal, and a metal oxide layer containing a p-type dopant;
First and second organic light-emitting element units that are provided so as to sandwich the intermediate layer and are electrically connected in series via the intermediate layer;
An organic EL device comprising: In the organic EL device according to claim 8,
The said metal oxide is an organic EL element containing at least any one of vanadium oxide, rhenium oxide, indium tin oxide, molybdenum oxide, iron oxide, and zinc oxide. In the organic EL device according to claim 8,
The organic EL device, wherein the p-type dopant is at least one of organic compounds having a phthalocyanine skeleton, a p-quinone skeleton, an o-quinone skeleton, or a quinodimethane skeleton. In the organic EL device according to claim 8,
The organic EL device in which the p-type dopant is an oxide of a transition metal. In the organic EL device according to claim 8,
The organic EL element in which the alkali metal and the alkaline earth metal are contained in the metal oxide as a simple substance, chloride, fluoride, or oxide, respectively. In the organic EL device according to claim 8,
The thickness ratio of the metal oxide layer containing the alkali metal or alkaline earth metal and the metal oxide layer containing the p-type dopant in the intermediate layer is 50% or less with respect to the entire intermediate layer. Organic EL element. In the organic EL device according to claim 8,
One of the first and second organic light emitting element units is provided with an electron transport layer so as to face the intermediate layer, and the other is provided with a hole transport layer so as to face the intermediate layer. And
A layer of a metal oxide containing the alkali metal or alkaline earth metal is provided to face the electron transport layer;
The organic EL element provided so that the metal oxide layer containing the said p-type dopant might oppose the said positive hole transport layer. In the organic EL element according to claim 14,
The alkali metal or alkaline earth metal is contained in a portion facing the electron transport layer in the metal oxide layer containing the alkali metal or alkaline earth metal,
The said p-type dopant is an organic EL element contained in the part facing the said hole transport layer in the layer of the metal oxide containing this p-type dopant. In the organic EL element according to claim 14,
The alkali metal or alkaline earth metal gradually moves from the side facing the electron transport layer to the opposite side of the metal oxide layer containing the alkali metal or alkaline earth metal. Contained so that the concentration in the layer is low,
The concentration of the p-type dopant gradually decreases in the metal oxide layer from the side facing the hole transport layer to the opposite side of the metal oxide layer containing the p-type dopant. The organic EL element contained so that it may become. In the organic EL element according to claim 14,
Between the metal oxide layer containing the alkali metal or alkaline earth metal and the electron transport layer;
Between the metal oxide layer containing the p-type dopant and the hole transport layer;
Between the metal oxide layer containing the alkali metal or alkaline earth metal and the metal oxide layer containing the p-type dopant;
An organic EL device comprising a buffer layer composed only of a metal oxide between at least one of the above.

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