JP2007043122A - Light emitting element, light emitting device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element and a light emitting device in which power consumption is reduced furthermore and driving voltage is lowered. <P>SOLUTION: The light emitting element comprises a first electrode, a first compound layer formed on the first electrode, a second compound layer, a light emitting layer, an electron transport layer, an electron injection layer, and a second electrode. The first and second compound layers contain a metal oxide and an organic compound wherein the concentration of metal oxide in the first compound layer is set higher than that in the second compound layer thus obtaining the light emitting element having a low driving voltage. The compound layers are not limited to two layers but a multilayer structure may be employed. But the concentration of metal oxide in the compound layers increases sequentially from the light emitting layer to the first electrode side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light-emitting element having a layer containing an organic compound between a pair of electrodes, and a light-emitting device using the light-emitting element.

  In recent years, research and development of a light-emitting device having an electroluminescence element as a self-luminous light-emitting element has been advanced. In particular, a light-emitting device using a so-called organic electroluminescence element that emits light when an electric field is applied to a layer containing an organic compound has features such as a fast response speed suitable for moving image display, low-voltage driving, and low power consumption driving. Therefore, it is attracting attention as a next-generation display including a mobile phone and a personal digital assistant (PDA).

  The light-emitting element described above includes a layer containing a light-emitting substance between a pair of electrodes (anode and cathode). The light-emitting mechanism is a hole (hole) injected from the anode when a voltage is applied between the electrodes. ) And electrons injected from the cathode recombine at the luminescent center in the layer containing the luminescent material to form molecular excitons, and emit light when the molecular excitons return to the ground state. It is said that. Note that singlet excitation and triplet excitation are known as excited states, and light emission is considered to be possible through either excited state.

Recently, remarkable progress has been made in improving driving voltage. For example, by using a composite layer of a metal oxide such as vanadium pentoxide or dirhenium pentoxide and an organic compound as a hole injection layer, the organic compound layer can be formed from the anode. It is possible to lower the energy barrier at the time of hole injection into (see Patent Document 1).
JP 2005-123095 A

  By the way, a light-emitting element containing an organic substance has the potential to be driven with power consumption potentially lower than that of a liquid crystal. However, there is still much room for improvement, and further reduction in power consumption is desired. ing.

  The light emitting element described in Patent Document 1 has a hole transport layer made of only an organic compound. However, although the material used for such a hole transport layer has a certain degree of conductivity, it is difficult to say that its resistance is low.

  Therefore, an object of the present invention is to provide a light-emitting element and a light-emitting device with lower power consumption.

  In order to achieve the above object, the present invention takes the following measures.

  A light-emitting element having a pair of electrodes and a plurality of layers sandwiched between the pair of electrodes, wherein the plurality of layers are at least a light-emitting layer and between one of the pair of electrodes and the light-emitting layer. And a composite layer having a metal oxide and an organic compound.

  The composite layer has a configuration in which first regions and second regions are alternately stacked, and a metal oxide concentration in the first region is equal to or higher than a metal oxide concentration in the second region. The highest metal oxide concentration in the first region is 1 to 8 times the metal oxide concentration compared to the lowest metal oxide concentration in the second region.

  The composite layer has a configuration in which the first regions and the second regions are alternately stacked, and the metal oxide concentrations of the first region and the second region are different, and the composite layer The repetition cycle of the metal oxide concentration in is 12 nm or less.

  One embodiment of a light-emitting element of the present invention includes a first electrode, a first composite layer stacked in order on the first electrode, a second composite layer, a light-emitting layer, an electron transport layer, And the first composite layer and the second composite layer have a metal oxide and an organic compound, and the average metal oxide concentration of the first composite layer is It is characterized by being higher than the average metal oxide concentration of the second composite layer.

  In the above invention, the first composite layer and the second composite layer each have a configuration in which the first regions and the second regions are alternately stacked, and the metal oxide concentration in the first region Is greater than or equal to the metal oxide concentration in the second region, and the highest metal oxide concentration in the first region is greater than or equal to 1 times the lowest metal oxide concentration in the second region. The metal oxide concentration is twice or less.

  In the above invention, the first composite layer and the second composite layer have a configuration in which the first region and the second region are alternately stacked, and the first region and the second region are stacked. The metal oxide concentrations in the regions are different, and the repetition period of the metal oxide concentration in the first composite layer and the second composite layer is 12 nm or less.

  One embodiment of a light-emitting element of the present invention includes a first electrode, a first composite layer stacked in order on the first electrode, a second composite layer, a third composite layer, and a light-emitting layer. And the electron transport layer and the second electrode, the first composite layer, the second composite layer and the third composite layer have a metal oxide and an organic compound, An average metal oxide concentration of the first composite layer is higher than an average metal oxide concentration of the second composite layer, and an average metal oxide concentration of the second composite layer is an average of the third composite layer. It is characterized by being higher than the metal oxide concentration.

  In the above invention, the first composite layer, the second composite layer, and the third composite layer are configured such that the first regions and the second regions are alternately stacked, The metal oxide concentration in the first region is greater than or equal to the metal oxide concentration in the second region, and the highest metal oxide concentration in the first region is the lowest metal in the second region. The metal oxide concentration is 1 to 8 times the oxide concentration.

  In the above invention, the first composite layer, the second composite layer, and the third composite layer are configured such that the first regions and the second regions are alternately stacked, The metal oxide concentrations in the first region and the second region are different, and the repetition of the metal oxide concentration in the first composite layer, the second composite layer, and the third composite layer is repeated. The period is 12 nm or less.

  In the above invention, the average metal oxide concentration refers to the metal oxide concentration of the entire composite layer, and the composite layer has two regions having different metal oxide concentrations, that is, first regions and second regions alternately. It has a laminated structure.

  One embodiment of a light-emitting element of the present invention includes a first electrode, a composite layer sequentially stacked on the first electrode, a light-emitting layer, an electron transport layer, and a second electrode, The composite layer includes a metal oxide and an organic compound, and the metal oxide of the composite layer has a concentration gradient from the first electrode to the light emitting layer side.

  In the invention described above, the metal oxide concentration of the composite layer is lowest on a surface in contact with the light emitting layer.

  In the above invention, the metal oxide concentration of the composite layer is 0 wt% or more and 3 wt% or less on a surface in contact with the light emitting layer.

  In the above invention, the metal oxide may be one or more of titanium oxide, vanadium oxide, chromium oxide, zirconium oxide, niobium oxide, molybdenum oxide, hafnium oxide, tantalum oxide, tungsten oxide, and rhenium oxide. Features.

  In the above invention, the organic compound has a hole transport property.

  In the above invention, the organic compound has an arylamine skeleton or a carbazole skeleton.

  According to the present invention, a light-emitting element with improved hole transportability and low driving voltage can be provided. Further, by manufacturing a light-emitting device using the light-emitting element, a highly reliable light-emitting device with low power consumption and a long lifetime and an electric appliance including the light-emitting device can be provided.

  In particular, an element having excellent current characteristics can be manufactured by shortening the repetition period of the metal oxide concentration in the composite layer.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the structures of the present invention described below, the same reference numerals may be used in common in different drawings.

(Embodiment 1)
One mode of a light-emitting element of the present invention will be described with reference to FIG. In this embodiment mode, the light-emitting element includes a first electrode 102, a first composite layer 103a, a second composite layer 103b, a light-emitting layer 104, an electron transport layer 105, and the first electrode 102, which are sequentially stacked over the first electrode 102. An electron injection layer 106 and a second electrode 107 provided thereon are further formed. Note that in this embodiment mode, the light-emitting element is provided over the substrate 101, and the first electrode 102 functions as an anode and the second electrode 107 functions as a cathode.

  As a material used for the substrate 101, for example, quartz, glass, plastic, a flexible substrate, or the like can be used. Any other material may be used as long as it functions as a support in the manufacturing process of the light-emitting element.

  The anode material for forming the first electrode 102 is not particularly limited, but it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a high work function (work function of 4.0 eV or more). Specific examples of such an anode material include an ITO (indium tin oxide), an ITO containing silicon oxide, and a target in which 2 to 20 [wt%] zinc oxide (ZnO) is mixed with indium oxide. In addition to IZO (indium zinc oxide), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), Examples thereof include copper (Cu), palladium (Pd), and a nitride of a metal material (for example, TiN).

  The first composite layer 103a is a layer having a metal oxide and an organic compound. The metal oxide used for the first composite layer 103a is preferably a transition metal oxide. Specifically, titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, Examples include tungsten oxide, manganese oxide, and rhenium oxide. In particular, vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide are preferable because of their high electron-accepting properties. Among these, molybdenum oxide is particularly preferable because it is stable in the air and easy to handle.

  The organic compound used for the first composite layer 103a is preferably a material having excellent hole transportability. In particular, an organic material having an arylamine skeleton is preferable. For example, 4,4′-bis (N- {4- [N, N′-bis (3-methylphenyl) amino] phenyl} -N-phenylamino) Biphenyl (abbreviation: DNTPD), 4,4′-bis [N- (4-diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: DPAB), N, N′-bis (3-methylphenyl) -N , N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (abbreviation: TPD), 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation) : Α-NPD), 4,4′-bis [N- (9,9-dimethylfluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: DFLDPBi), 4,4′-bis [N- ( 4-bifu Niyl) -N-phenylamino] biphenyl (abbreviation: BBPB), 1,5-bis (diphenylamino) naphthalene (abbreviation: DPAN), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) tri Aromatic amine systems such as phenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA) (ie, A compound having a benzene ring-nitrogen bond). An organic material having a carbazole skeleton is also preferably used. For example, N- (2-naphthyl) carbazole (abbreviation: NCz), 4,4′-di (N-carbazolyl) biphenyl (abbreviation: CBP), 9, 10-bis [4- (N-carbazolyl) phenyl] anthracene (abbreviation: BCPA), 3,5-bis [4- (N-carbazolyl) phenyl] biphenyl (abbreviation: BCPPi), 1,3,5-tris [ And a compound such as 4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB). In addition, aromatic hydrocarbons such as anthracene and 9,10-diphenylanthracene (DPA), and at least one vinyl skeleton such as 4,4′-bis (2,2-diphenylvinyl) biphenyl (abbreviation: DPVBi) are included. It may be an aromatic hydrocarbon. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used.

Similarly to the first composite layer 103a, the second composite layer 103b is a layer having a metal oxide and an organic compound, and the metal oxide and the organic compound used for the second composite layer 103b are also the same as those described above. A material similar to that of the single composite layer 103a can be used. Note that the concentration of the metal oxide in the second composite layer 103b is lower than the concentration of the metal oxide in the first composite layer 103a. However, the concentration of the metal oxide contained in the second composite layer 103b is selected so that light emitted by the proximity of the light-emitting layer 104 and the metal oxide is not quenched or only a part of the quenching is suppressed. There is a need to. Note that the most preferable concentration of the metal oxide in the composite layer on the surface in contact with the light emitting layer is greater than 0 wt% and 3 wt% or less, but is not particularly limited as long as the above condition is satisfied. The concentration expressed by weight percent [wt%] can be obtained from Equation 1.

  In order to reduce the concentration of the metal oxide in the composite layer on the surface in contact with the light emitting layer, the concentration of the metal oxide contained in the second composite layer 103b has a concentration gradient in the film thickness direction. Also good. Note that the materials used as the organic compound for the first composite layer 103a and the second composite layer 103b may be the same or different.

  The first composite layer 103a and the second composite layer 103b are formed by co-evaporation using resistance heating using the above materials, co-evaporation using resistance heating deposition and electron gun deposition (EB deposition), sputtering, and resistance heating. The film may be formed by simultaneous film formation by the method. Alternatively, a film may be formed using a wet method such as a sol-gel method.

The light-emitting layer 104 is a light-emitting layer containing a substance having a high light-emitting property. There is no particular limitation on the light emitting layer, but the layer functioning as the light emitting layer is roughly divided into two modes. One is a host-guest type layer in which the luminescent material is dispersed in a material (host material) having an energy gap larger than the energy gap of the material (luminescent material or guest material) that is the emission center, and the other is luminescent. It is a layer which comprises a light emitting layer only with material. The former is preferable because concentration quenching hardly occurs. As the luminescent substance, 4-dicyanomethylene-2-methyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (abbreviation: DCJT), 4-dicyanomethylene- 2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran, periflanthene, 2,5-dicyano-1,4-bis (10-methoxy-) 1,1,7,7-tetramethyljulolidyl-9-enyl) benzene, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq) ₃ ), 9,9′-bianthryl, 9,10-diphenylanthracene (abbreviation: DPA), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA), 2,5, 8,11-tetra-t-butylperylene (abbreviation: TBP) and the like can be given. As host materials, anthracene derivatives such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA), 4,4′-bis (N-carbazolyl) biphenyl (abbreviation) : Carbazole derivatives such as CBP), tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h]- Quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp _2), bis [2- (2-hydroxyphenyl) benzoxazolato] zinc (abbreviation : ZnBOX) it is possible to use metal complexes such. In addition, as a material that can form a light-emitting layer using only a light-emitting substance, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq).

The electron transport layer 105 is preferably formed using a material capable of transporting electrons injected from the electrode functioning as a cathode into the layer containing a light-emitting substance to the light-emitting layer. Specific examples of such a material include tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (8-quinolinolato) gallium (abbreviation Gaq ₃ ), and tris (4-methyl-8-quinolinolato) aluminum (abbreviation). : Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ) and other metal complexes having a quinoline skeleton or a benzoquinoline skeleton, and bis (2-methyl-8-quinolinolato) -4 -Phenylphenolato-aluminum (abbreviation: BAlq). In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ) and other metal complexes having an oxazole-based or thiazole-based ligand can also be used as a material for forming the electron-transporting layer 105. In addition, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD) and 1,3-bis [5- (p-tert- Butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl)- 1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4-triazole (abbreviation) : P-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and inorganic substances such as titanium oxide may be used.

  The electron injection layer 106 is a layer having a function of assisting injection of electrons from the electrode functioning as a cathode into the electron transport layer 105. The electron injection layer 106 is not particularly limited, and is formed using an alkali metal or alkaline earth metal compound such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), or the like. Can be used. In addition, a layer obtained by mixing any of the above-described electron transporting materials and a substance that exhibits electron donating property with respect to any of the electron transporting materials may be used. As a substance exhibiting an electron donating property, for example, a metal having a small work function can be given. Specifically, alkali metals and alkaline earth metals are preferable, and Li, Mg, and Cs are particularly preferable. Alkali metal complexes such as lithium acetylacetonate (abbreviation: Li (acac)) and 8-quinolinolato-lithium (abbreviation: Liq) are also effective.

  As a material for forming the second electrode 107, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (a work function of 3.8 eV or less) can be used. Specific examples of such a cathode material include elements belonging to Group 1 or Group 2 of the periodic table, that is, alkali metals such as lithium (Li) and cesium (Cs), magnesium (Mg), calcium (Ca), strontium ( Alkaline earth metals such as Sr) and alloys containing them (Mg: Ag, Al: Li). Further, by using a material having an excellent electron injection function for the electron injection layer 106, the first electrode 102 such as ITO containing Al, Ag, ITO, or silicon oxide regardless of the work function. Various conductive materials including the materials mentioned as the material can be used for the second electrode 107. In addition to the electron injection layer 106, the same effect can be obtained by providing a layer having an excellent function of injecting electrons on the side of the light emitting layer 104 of the second electrode 107 and the second electrode 107. be able to.

  Note that the first electrode 102 and the second electrode 107 are formed by depositing the above-described anode material or cathode material by an evaporation method, a sputtering method, or the like, respectively. Alternatively, a droplet including a conductive material may be used by an inkjet method or the like. The light-emitting layer 104, the electron transport layer 105, and the electron injection layer 106 can be formed by an inkjet method, a spin coat method, or the like in addition to a vapor deposition method. In addition, you may form using the different film-forming method for each electrode and each layer.

  By applying voltage to the light-emitting element of the present invention having the above structure so that the potential of the first electrode 102 is higher than the potential of the second electrode 107, the light-emitting element emits light. Can do.

  Light emission is extracted outside through one or both of the first electrode 102 and the second electrode 107. Therefore, one or both of the first electrode 102 and the second electrode 107 are formed using a light-transmitting substance. In the case where only the first electrode 102 is formed using a light-transmitting substance, light emission is extracted from the substrate side through the first electrode 102 as illustrated in FIG. In the case where only the second electrode 107 is formed using a light-transmitting substance, light emission is extracted from the side opposite to the substrate through the second electrode 107 as illustrated in FIG. In the case where both the first electrode 102 and the second electrode 107 are made of a light-transmitting substance, light is emitted from the first electrode 102 and the second electrode 107 as shown in FIG. And is taken out from both the substrate side and the opposite side of the substrate.

  Since the first composite layer 103a and the second composite layer 103b including the metal oxide and the organic compound do not increase in driving voltage even when the thickness is increased, the first composite layer 103a and the second composite layer By adjusting the film thickness of 103b, optical design utilizing the microcavity effect or the light interference effect can be performed. Therefore, a high-quality light-emitting element with excellent color purity and a small color change depending on the viewing angle can be manufactured. In addition, a film thickness that prevents the first electrode 102 and the second electrode 107 from being short-circuited due to the unevenness generated during the film formation on the surface of the first electrode 102 or the minute residue remaining on the electrode surface is selected. Can do.

  In addition, since the first composite layer 103a and the second composite layer 103b in contact with the first electrode 102 have high carrier density, the hole transportability is excellent. Therefore, the drive voltage can be reduced. Further, the first electrode and the composite layer can be as close as possible to ohmic contact. Therefore, the choice of electrode material is expanded.

  Further, the first composite layer 103a and the second composite layer 103b used in the present invention can be formed by vacuum deposition. Therefore, when other layers are formed by vacuum deposition, any layer can be formed in the same vacuum apparatus. Therefore, since the light-emitting element can be manufactured without being exposed to the atmosphere until the light-emitting element is completely sealed, the process becomes easy and the yield can be improved.

  In addition, since the first composite layer 103a and the second composite layer 103b include an organic material and an inorganic material, stress generated between the electrode and the light-emitting layer can be reduced.

  It was found that the higher the concentration of the metal oxide contained in the composite layer, the lower the refractive index. In the light-emitting element of the present invention, as described above, the concentration of the metal oxide contained in the first composite layer 103a is higher than that of the second composite layer 103b. Therefore, the refractive index of the first composite layer 103a can be made larger than the refractive index of the second composite layer 103b by appropriately selecting the concentration of the metal oxide. Further, although the refractive index of the first electrode 102 is generally higher than that of the organic compound used for the light-emitting element, the second composite layer 103b and the second composite layer 103b are formed by stacking composite layers having different metal oxide concentrations. The refractive index can be increased in the order of one composite layer 103 a and the first electrode 102.

  Due to such a refractive index relationship, when light generated in the light emitting layer 104 is extracted from the first electrode 102 side, that is, when the first electrode 102 is a transparent electrode, each interface (for example, the second composite layer) 103b and the first composite layer 103a and the interface between the first composite layer 103a and the first electrode 102) can be reduced. Since the reflectance of light decreases at the interface between substances having a more equal refractive index, light generated in the light emitting layer 104 can be efficiently extracted from the light emitting element. As described above, light extraction efficiency is improved, so that a light-emitting element with low power consumption and long life can be obtained.

  In addition, by using different organic compounds for the first composite layer 103a and the second composite layer 103b, while satisfying that the metal oxide concentration in the first composite layer 103a is larger than the second composite layer 103b, The first composite layer 103a and the second composite layer 103b that can obtain the above refractive index relationship can be formed using a smaller amount of metal oxide.

  In addition, in order to extract light from the light-emitting element more efficiently, unevenness processing may be performed on the surface of the first electrode 102. In this case, the first composite layer 103a is preferably formed using a wet method such as a spin coat method in consideration of a film stacked thereover to have a high flatness.

  Note that a structure other than the above may be used as long as it includes the first composite layer 103a, the second composite layer 103b, and the light-emitting layer 104. In this embodiment mode, the first electrode 102, the first composite layer 103a, the second composite layer 103b, the light-emitting layer 104, the electron transport layer 105, the electron injection layer 106, and the second electrode are sequentially formed over the substrate 101. The electrode 107 is stacked and provided. However, the electrode 107 may be stacked on the substrate 101 opposite to the above structure.

  Thus, the layered structure of the layers is not particularly limited, and is a material having a high electron transport property, a material having a high electron injection property, a material having a high hole injection property, or a bipolar property (a material having a high electron and hole transport property). What is necessary is just to comprise the layer which consists of a substance etc. freely combining in the lamination | stacking which consists of a light emitting layer and a 1st composite layer and a 2nd composite layer.

  Further, the composite layer is not limited to the two layers of the first composite layer 103a and the second composite layer 103b. As shown in FIG. 2, the first composite layer 203a, the second composite layer 203b, and the third composite layer are used. Three layers of the layer 203c may be used. However, the concentration of the metal oxide contained in the composite layer in order from the first electrode 102 to the first composite layer 203a, the second composite layer 203b, and the third composite layer 203c is assumed to be small.

  In addition, the composite layer is not limited to two or three layers, and it is sufficient that n> 1 when the number of stacked composite layers is n. However, the concentration of the metal oxide contained in the composite layer decreases from the first electrode to the light emitting layer side. Note that the concentration of the metal oxide contained in the composite layer in contact with the light emitting layer is selected so as not to quench the light emitted by the proximity of the light emitting layer and the metal oxide, or to suppress the quenching to a small part. There is a need. The composite layer in contact with the light emitting layer may have a concentration gradient from the first electrode to the light emitting layer side. In the second embodiment, the case where the number n of composite layers is innumerable, that is, the metal oxide in the composite layer has a concentration gradient will be described.

(Embodiment 2)
One mode of a light-emitting element of the present invention will be described with reference to FIGS. Components similar to those in Embodiment 1 are denoted by common reference numerals, and detailed description thereof is omitted.

  The light-emitting element includes a first electrode 102, a composite layer 303 stacked over the first electrode 102, a light-emitting layer 104, an electron transport layer 105, an electron injection layer 106, and a first layer provided thereon. 2 electrodes 107. Note that in this embodiment, the first electrode 102 functions as an anode and the second electrode 107 functions as a cathode.

  A first electrode 102 is formed over the substrate 101. Further, a composite layer 303 is formed over the first electrode 102. The composite layer 303 is a layer including a metal oxide and an organic compound. The metal oxide used for the composite layer 303 is preferably a transition metal oxide. Specifically, titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, Examples include manganese oxide and rhenium oxide. In particular, oxides of vanadium oxide, molybdenum oxide, tungsten oxide, and rhenium oxide are preferable because of their high electron-accepting properties. Among these, molybdenum oxide is particularly preferable because it is stable in the air and easy to handle.

  The organic compound used for the composite layer 303 is preferably a material having excellent hole transport properties. In particular, an organic material having an arylamine skeleton is preferable. For example, 4,4′-bis (N- {4- [N, N′-bis (3-methylphenyl) amino] phenyl} -N-phenylamino) Biphenyl (abbreviation: DNTPD), 4,4′-bis [N- (4-diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: DPAB), N, N′-bis (3-methylphenyl) -N , N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (abbreviation: TPD), 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation) : Α-NPD), 4,4′-bis [N- (9,9-dimethylfluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: DFLDPBi), 4,4′-bis [N- ( 4-bifu Niyl) -N-phenylamino] biphenyl (abbreviation: BBPB), 1,5-bis (diphenylamino) naphthalene (abbreviation: DPAN), 4,4 ′, 4 ″ -tris (N, N-diphenylamino) tri Aromatic amine systems such as phenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA) (ie, A compound having a benzene ring-nitrogen bond). Alternatively, an organic material having a carbazole skeleton is preferably used. For example, N- (2-naphthyl) carbazole (abbreviation: NCz), 4,4′-di (N-carbazolyl) biphenyl (abbreviation: CBP), 10-bis [4- (N-carbazolyl) phenyl] anthracene (abbreviation: BCPA), 3,5-bis [4- (N-carbazolyl) phenyl] biphenyl (abbreviation: BCPPi), 1,3,5-tris [ A compound such as 4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB) can be used. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used.

  The composite layer 303 formed using the above-described material has a structure in which the concentration of the metal oxide contained in the composite layer gradually decreases from the first electrode 102 to the light emitting layer 104 side, and the concentration gradient with respect to the film thickness direction. A layer having Note that the concentration of the metal oxide in the composite layer 303 on the surface in contact with the light-emitting layer 104 is preferably 0 wt% or more and 3 wt% or less.

  Note that the composite layer 303 is formed by co-evaporation using resistance heating using the above materials, co-evaporation using resistance heating evaporation and electron gun evaporation (EB evaporation), or simultaneous film formation using sputtering and resistance heating. That's fine. However, the evaporation amount of the metal oxide needs to be reduced with time.

  Next, the light-emitting layer 104, the electron transport layer 105, the electron injection layer 106, and the second electrode 107 are formed over the composite layer 303. The electrode, the material of each layer, and the manufacturing method are the same as those in the first embodiment.

  By applying a voltage so that the potential of the first electrode 102 is higher than the potential of the second electrode 107 to the light-emitting element of the present invention having the above structure, the light-emitting element can emit light. it can.

  Light emission is extracted outside through one or both of the first electrode 102 and the second electrode 107. Therefore, one or both of the first electrode 102 and the second electrode 107 are formed using a light-transmitting substance. In the case where only the first electrode 102 is formed using a light-transmitting substance, light emission is extracted from the substrate side through the first electrode 102 as illustrated in FIG. In the case where only the second electrode 107 is formed using a light-transmitting substance, light emission is extracted from the side opposite to the substrate through the second electrode 107 as illustrated in FIG. In the case where both the first electrode 102 and the second electrode 107 are made of a light-transmitting substance, light is emitted from the first electrode 102 and the second electrode 107 as shown in FIG. 3C. And is taken out from both the substrate side and the opposite side of the substrate.

  The composite layer 303 including a metal oxide and an organic compound does not increase the driving voltage even when the film thickness is increased. Therefore, the microcavity effect and the light interference effect are utilized by adjusting the film thickness of the composite layer 303. Optical design can be performed. Therefore, a high-quality light-emitting element with excellent color purity and a small color change depending on the viewing angle can be manufactured. In addition, a film thickness that prevents the first electrode 102 and the second electrode 107 from being short-circuited by the unevenness generated on the surface of the first electrode 102 or the minute residue remaining on the electrode surface can be selected.

  In addition, since the composite layer 303 has a high carrier density, the hole transportability is excellent. Therefore, the drive voltage can be reduced. In addition, the electrode and the composite layer can be as close as possible to ohmic contact. Therefore, the choice of electrode material is expanded.

  The composite layer 303 used in the present invention can be formed by vacuum deposition. Therefore, when other layers are formed by vacuum deposition, any layer can be formed in the same vacuum apparatus. Therefore, since the light-emitting element can be manufactured without being exposed to the atmosphere until the light-emitting element is completely sealed, the process becomes easy and the yield can be improved.

  In addition, since the composite layer 303 includes an organic material and an inorganic material, stress generated between the electrode and the light-emitting layer can be reduced.

  In this embodiment, the metal oxide in the composite layer 303 has a concentration gradient, and the concentration decreases from the first electrode 102 to the light-emitting layer 104 side. Therefore, the refractive index of the composite layer 303 can be continuously changed from the light emitting layer to the first electrode side. Further, by appropriately selecting the metal oxide concentration in the composite layer 303 on the surface in contact with the first electrode 102 so as to be close to the refractive index of the first electrode, at the interface between the composite layer and the first electrode. However, the difference in refractive index can be reduced. Therefore, when light generated in the light-emitting layer 104 is extracted from the first electrode 102 side, a difference in refractive index in the composite layer 303 and at the interface between the composite layer 303 and the first electrode 102 can be reduced. Since the reflectance of light decreases at the interface between substances having a more equal refractive index, light generated in the light emitting layer 104 can be efficiently extracted from the light emitting element. As described above, light extraction efficiency is improved, so that a light-emitting element with low power consumption and long life can be obtained.

  In addition, in order to extract light from the light-emitting element more efficiently, unevenness processing may be performed on the surface of the first electrode 102. In this case, the composite layer 303 is preferably a film having high flatness in consideration of a film stacked thereover.

  Note that a structure other than the above may be used as long as it includes the composite layer 303 and the light-emitting layer 104. In this embodiment, the first electrode 102, the composite layer 303, the light-emitting layer 104, the electron transport layer 105, the electron injection layer 106, and the second electrode 107 are sequentially stacked over the substrate 101. However, a configuration in which the substrate 101 is stacked opposite to the above configuration may be employed.

  In other words, the layered structure of the layers is not particularly limited, and a substance having a high electron transport property, a substance having a high electron injection property, a substance having a high hole injection property, a substance having a bipolar property (a material having a high electron and hole transport property), and the like May be configured by freely combining with a laminate composed of the light emitting layer, the first composite layer, and the second composite layer.

  This embodiment mode can be freely combined with the structure in Embodiment Mode 1.

(Embodiment 3)
A vapor deposition apparatus used for carrying out the present invention and a method for forming a composite layer by co-vapor deposition using the vapor deposition apparatus will be described with reference to FIGS.

  In the vapor deposition apparatus used for carrying out the present invention, as shown in FIG. 4, a transfer chamber 402 is provided in addition to a treatment chamber 401 for performing a vapor deposition process on a workpiece. The object to be processed is transferred to the processing chamber 401 through the transfer chamber 402. Note that the transfer chamber 402 is provided with an arm 403 for transferring an object to be processed.

  In the processing chamber 401, as shown in FIG. 5, a holding unit for holding an object to be processed, a vapor deposition source 501a holding a metal oxide, and a vapor deposition source 501b holding an organic compound are provided. ing. In FIG. 5, the holding unit for holding the object to be processed includes a first rotating plate 502 that rotates about a shaft 503 and a plurality of second rotating plates 504 a provided on the first rotating plate 502. ˜504d. The second rotating plates 504a to 504d may rotate independently of each other about the shaft provided for each of the second rotating plates 504a to 504d, separately from the shaft 503. The objects to be processed 505a to 505d are held on the second rotating plates 504a to 504d, respectively.

  In FIG. 5, the workpiece 505a is held on the second rotating plate 504a, the workpiece 505b is held on the second rotating plate 504b, and the workpiece 505c is held on the second rotating plate 504c. The workpiece 505d is held on the second rotating plate 504d. Although not shown here, a slide type shutter is provided above each vapor deposition source.

  The composite layer is formed by heating and evaporating each material held in the vapor deposition sources 501a and 501b.

  The distance between the upper ends of the vapor deposition sources 501a and 501b and the workpieces 505a to 505d is 270 mm, the vapor deposition rate of the organic compound is 0.4 nm / s, the rotational speed of the first rotating plate 502 is 2 rpm, molybdenum oxide and DNTPD A composite layer consisting of The cross section of the object to be processed 505a, that is, the composite layer, was observed using a transmission electron microscope (TEM). The obtained TEM image is shown in FIG. Note that the weight ratio of molybdenum oxide to DNTPD in the composite layer was 0.67: 1.

  From FIG. 11, it was found that the first dark region ((a) in the drawing) and the second light region ((b) in the drawing) exist alternately. The dark first region is a region having a large average atomic weight, and the light second region is a region having a small average atomic weight. Since the metal oxide contained in the layer containing the composite material of the present invention has a larger average atomic weight than the organic compound, the dark first region in the TEM image is a region containing a large amount of metal oxide and is light in color. The second region is a region with less metal oxide. Accordingly, the dark first region in FIG. 11 is a region having a high molybdenum oxide concentration, and the light second region is a region having a low molybdenum oxide concentration.

  In the first region where the metal oxide concentration is high, the distance between the object to be processed 505a and the evaporation source 501a in which the metal oxide is held is larger than the distance between the object to be processed 505a and the evaporation source 501b in which the organic compound is held. Also formed when close. In contrast, the second region having a low metal oxide concentration is formed when the distance between the object to be processed 505a and the vapor deposition source 501b is shorter than the distance between the object to be processed 505a and the vapor deposition source 501a. Therefore, it was found that the metal oxide concentration in the composite layer differs depending on the deposition position.

  Therefore, in order to investigate the difference in metal oxide concentration caused by the deposition position, the metal oxide concentration in the composite layer at the position A closest to the deposition source 501a and the position B closest to the deposition source 501b was examined. . In addition, the schematic diagram of the vapor deposition apparatus at the time of the said examination is shown in FIG.

  The evaporation source 501a holds molybdenum trioxide for forming molybdenum oxide that is a metal oxide, and the evaporation source 501b holds DNTPD that is an organic compound. A metal oxide or an organic compound was vapor-deposited under the same conditions, and the concentration of the metal oxide in the composite layer that would be formed at positions A and B was estimated from the respective film thicknesses. The results are shown in Table 1.

As shown in Table 1, when only the vapor deposition source 501a was vapor-deposited at the position A, 65 nm of molybdenum oxide was formed on the object to be processed. On the other hand, when only the vapor deposition source 501b was vapor-deposited under the same conditions, a 60 nm DNTPD film was formed. Therefore, when the vapor deposition sources 501a and 501b were vapor-deposited simultaneously, that is, co-vapor deposition was performed, the molybdenum oxide concentration in the composite layer formed at the position A was calculated to be 52.0 [vol%]. The concentration based on the volume percent [vol%] display can be obtained by Equation 2.

  On the other hand, at position B, when only the vapor deposition source 501a was deposited, 15 nm of molybdenum oxide was formed on the object to be processed. On the other hand, when only the vapor deposition source 501b was vapor-deposited under the same conditions, a 220 nm DNTPD was formed. Therefore, when the vapor deposition sources 501a and 501b were vapor-deposited simultaneously, that is, co-vapor-deposited, the molybdenum oxide concentration in the composite layer formed at the position B was calculated to be 6.38 [vol%].

  Therefore, it was found that the high concentration region of molybdenum oxide has 8.15 times as much molybdenum oxide as the low concentration region.

  Although the above example is an extreme case, such a phenomenon can occur when the rotation speed of the first rotating plate 502 is low or the vapor deposition speed is very high. The composite layer used for the light-emitting element is preferably uniform, but it is desirable that at least the high concentration region of the metal oxide has a metal oxide concentration of 1 to 8 times that of the low concentration region. In order to satisfy such conditions, the rotation speed, vapor deposition speed, distance between the object to be processed and the vapor deposition source, distance between the vapor deposition source and the vapor deposition source, distance between the object to be processed and the rotation axis, etc. are appropriately designed for vapor deposition. Do. The high concentration region of the metal oxide in the composite layer is a region having the highest metal oxide concentration in the first region, and the low concentration region is the lowest concentration of metal oxide in the second region. It is an area.

  Moreover, the influence which the film thickness of a 1st area | region and a 2nd area | region has on a composite layer was examined. From the production of the composite layer shown in FIG. 11, the rotational speed of the first rotating plate 502 is increased to 8 rpm, and the other conditions are the same as above, the vapor deposition rate of the organic compound is 0.4 nm / s, and molybdenum oxide and DNTPD A composite layer having a weight ratio of 0.67: 1 was formed. The cross section of the object to be processed 505a, that is, the composite layer, was observed using a transmission electron microscope (TEM). The obtained TEM image is shown in FIG.

  In FIG. 12, as in FIG. 11, it was found that the first dark regions and the second light regions were alternately present. As described above, the dark first region is a region having a high molybdenum oxide concentration, and the light second region is a region having a high DNTPD concentration.

  However, while the repetition period of the first region and the second region in the composite layer, that is, the repetition period of the molybdenum oxide concentration is about 12 nm in FIG. 11, the rotational speed of the first rotating plate 502 is It was found from the FIG. 12 that the composite layer produced by increasing the thickness was about 3 nm.

  The characteristics of the composite layer shown in FIGS. 11 and 12 were examined using the following elements. In the device, ITO containing silicon oxide was formed on a substrate, and then the composite layer shown in FIG. 11 or 12 was formed thereon with a thickness of 120 nm, and aluminum was further formed with a thickness of 300 nm. A thing was used.

  The element having the composite layer (FIG. 11) obtained when the rotational speed of the first rotating plate 502 is 2 rpm is referred to as the element 1, and is obtained when the rotational speed of the first rotating plate 502 is 8 rpm. An element having the obtained composite layer (FIG. 12) was designated as element 2.

  FIG. 13 shows current density-voltage characteristics of the element 1 and the element 2. From FIG. 13, it was found that the element 2 has better current characteristics than the element 1. Therefore, it can be said that the repetition period of the molybdenum oxide concentration in the composite layer, that is, the metal oxide concentration, is preferably shorter. From the above, the repetition period of the metal oxide concentration is 12 nm or less, preferably 3 nm or less. More preferably, the composite layer has a uniform metal oxide concentration with a repetition period close to 0 nm. In order to satisfy such a condition, the film is formed by appropriately designing the rotation speed, the deposition speed, the distance between the object to be processed and the deposition source, the distance between the deposition source and the deposition source, the distance between the substrate and the rotation axis, and the like.

  Further, a plurality of metal oxide vapor deposition sources 601a may be provided as shown in FIG. Although FIG. 6 shows an example of five vapor deposition sources, two, three, four, or six or more vapor deposition sources may be provided. When such a vapor deposition apparatus is used, the vapor deposition amount can be easily controlled by opening and closing a shutter provided above the vapor deposition source. Therefore, it becomes easy to produce a composite layer having a stack of composite layers having different metal oxide concentrations and a concentration gradient without lowering the temperature of the vapor deposition source.

  The vapor deposition rates of the metal oxide and the organic compound may be the same or different depending on each material, and are appropriately selected depending on the concentration of the metal oxide to be formed. Further, the shapes of the first rotating plate 502 and the second rotating plates 504a to 504d are not particularly limited, and may be a polygon such as a quadrangle other than a circle as shown in FIGS. Note that by providing the second rotating plates 504a to 504d, in-plane variations such as the thickness of a layer formed on the object to be processed can be reduced. Note that the second rotating plates 504a to 504d are not necessarily provided.

  The configuration in the processing chamber 401 is not limited to that shown in FIGS. 5 and 6, and for example, a configuration in which the position of the vapor deposition source as shown in FIG. 7 is changed may be used.

  In FIG. 7, vapor deposition sources 701 a and 701 b are fixed, and a rotating plate 706 that rotates about a shaft 707 and a holding portion 702 for holding workpieces 705 a to 705 d are provided to face each other. The evaporation source 701a holds a metal oxide, and the evaporation source 701b holds an organic compound. When the vapor deposition source is positioned so that the vapor deposition source 701a is closer to the workpiece 705a than the vapor deposition source 701b, the concentration of the metal oxide on the workpiece 705a is higher than the concentration of the organic compound. Co-evaporation is performed so as to be higher. Further, if the rotating plate 706 rotates and the vapor deposition source 701b is positioned closer to the workpiece 705a than the vapor deposition source 701a, the concentration of the metal oxide on the workpiece 705a is larger than that of the metal oxide. Co-evaporation is performed so that the concentration of the organic compound is higher. As described above, the vapor deposition apparatus may have a configuration in which the position of the vapor deposition source with respect to the object to be processed is changed by changing the position of the vapor deposition source. That is, the vapor deposition source and the object to be processed need only be provided so that their positions change relatively.

  There are a resistance heating method that is direct heating and a radiant heat method that is indirect heating as a vapor deposition source, but it is possible to produce a composite layer by using either method. Any vapor deposition container can be used. For example, a crucible 800 shown in FIG. 8A is a vapor deposition container often used for mass production. The vapor deposition temperature of molybdenum oxide used as the metal oxide of the composite layer depends on the shape and size of the crucible, but is about 450 to 550 ° C. in vacuum, which is higher than that of organic substances. . Therefore, it is necessary to devise the material of the vapor deposition container. For the vapor deposition container, a non-metallic material such as aluminum nitride, boron nitride, silicon carbide, boron phosphide is preferable. Further, a composite material of these materials may be used. In addition, any material such as tantalum, tungsten, or alumina may be selected as appropriate in consideration of the use temperature, reactivity, and the like. The thickness of the crucible may be determined in consideration of the assumed internal volume and shape of the vapor deposition material or the thermal conductivity of the material.

  Alternatively, as shown in FIG. 8B, a crucible with a lid 801 having an opening may be used. Similarly to the crucible 800, the lid 801 is made of one or a plurality of other materials such as aluminum nitride, boron nitride, silicon carbide, boron phosphide, tantalum, tungsten, and alumina in consideration of operating temperature, reactivity, etc. What is necessary is just to select suitably.

  In addition, a point to be noted when performing metal oxide deposition is that the material is likely to be clogged at the opening. This is because the temperature of the opening at the upper part of the vapor deposition container is lower than the temperature at the lower part of the vapor deposition container. In particular, it tends to occur when the deposition rate of the metal oxide is high.

To equalize the inside of the crucible, the number of turns of the heater at the top of the crucible is increased from the bottom, and the side of the top of the crucible is coated with a material with high thermal conductivity such as silver, gold, copper, and aluminum. 8 (C), boron nitride (thermal conductivity: 60 W · m ⁻¹ · K ⁻¹ ), silicon carbide (thermal conductivity: 270 W) together with metal oxide 802 as a vapor deposition material in a crucible 800. · ^{m -1} · ^K -1), aluminum nitride (thermal conductivity: 70W · ^{m -1} · ^K -1 or more 320W · ^{m -1} · ^K -1 or less), good thermal conductivity boron phosphide like particles It is preferable to devise such as adding 803. Moreover, it is also possible to combine these ideas suitably, and it is further effective with respect to soaking | uniform-heating. In addition, by mixing the particles 803 in the vapor deposition material, there is an effect of preventing bumping of the vapor deposition material. Note that the particle size of the particles 803 is preferably 0.1 mm or more and 5 mm or less. As for the shape, a spherical shape is illustrated, but there is no particular limitation such as an oval shape, a meteorite-like ellipsoidal sphere, a rugby ball-like ellipsoidal sphere, a disc shape, a columnar shape, or a polygonal columnar shape.

  Although the crucible filled with the metal oxide has been described, the same can be said for the crucible filled with the organic compound.

  Note that this embodiment mode can be combined with Embodiment Mode 1 or 2 as appropriate.

(Embodiment 4)
In this embodiment mode, a light-emitting device having the light-emitting element of the present invention will be described with reference to FIGS. 9A is a top view illustrating the light-emitting device, and FIG. 9B is a cross-sectional view taken along the line AA ′ in FIG. 9A (a cross-sectional view cut along AA ′). Reference numeral 900 denotes a substrate, reference numeral 901 indicated by a dotted line denotes a driver circuit portion (source side driver circuit), reference numeral 902 denotes a pixel portion, and reference numeral 903 denotes a driver circuit portion (gate side driver circuit). Reference numeral 904 denotes a sealing substrate, reference numeral 905 denotes a sealing material, and the inside surrounded by the sealing material 905 is a space 906.

  Reference numeral 907 denotes a wiring for transmitting signals input to the source side driver circuit 901 and the gate side driver circuit 903, and a video signal, a clock signal, and a start signal from an FPC (flexible printed circuit) 908 serving as an external input terminal. Receive signals, reset signals, etc. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light emitting device of the present invention includes not only the light emitting device main body but also a state in which an FPC or PWB is attached thereto.

  Next, a cross-sectional structure is described with reference to FIG. A driver circuit portion and a pixel portion are formed over the substrate 900. Here, a source side driver circuit 901 which is a driver circuit portion and a pixel portion 902 are shown.

  Note that the source side driver circuit 901 is a CMOS circuit in which an n-channel TFT 923 and a p-channel TFT 924 are combined. The TFT forming the driving circuit may be formed by a known CMOS circuit, PMOS circuit, or NMOS circuit. In this embodiment mode, a driver integrated type in which a drive circuit is formed over a substrate is shown; however, this is not always necessary, and the driver circuit can be formed outside the substrate.

  The pixel portion 902 is formed by a plurality of pixels including a switching TFT 911, a current control TFT 912, and a first electrode 913 electrically connected to the drain thereof. Note that an insulator 914 is formed so as to cover an end portion of the first electrode 913. Here, a positive photosensitive acrylic resin film is used.

  In order to improve the formation of the layer 916 containing a light-emitting substance to be formed later, the upper end portion or the lower end portion of the insulator 914 is preferably formed to have a curved surface having a curvature. For example, in the case where positive photosensitive acrylic is used as a material for the insulator 914, it is preferable that only the upper end portion of the insulator 914 has a curved surface with a radius of curvature (0.2 μm to 3 μm). As the insulator 914, either a negative type that becomes insoluble in an etchant by photosensitive light or a positive type that becomes soluble in an etchant by light can be used. Furthermore, the material of the insulator 914 is not limited to an organic material, and an inorganic material can be used. For example, silicon oxide, silicon oxynitride, or the like can be used.

  A layer 916 containing a light-emitting substance and a second electrode 917 are formed over the first electrode 913 by the method described in the above embodiment mode. In the layer 916 containing a light-emitting substance, at least a light-emitting layer and a composite layer are provided between the light-emitting layer and one electrode, the other layers are not particularly limited and can be selected as appropriate. it can.

  Further, the sealing substrate 904 is attached to the substrate 900 with the sealant 905, whereby the first electrode 913 and the layer 916 containing a light-emitting substance in the space 906 surrounded by the substrate 900, the sealing substrate 904, and the sealant 905. And a second light emitting element 918 having a second electrode 917. Note that the space 906 includes a structure filled with a sealant 905 in addition to a case where the space 906 is filled with an inert gas (nitrogen, argon, or the like).

  Note that an epoxy-based resin is preferably used for the sealant 905. Moreover, it is desirable that these materials are materials that do not transmit moisture and oxygen as much as possible. In addition to a glass substrate or a quartz substrate, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), Mylar, polyester, acrylic, or the like can be used as a material used for the sealing substrate 904.

  As described above, a light-emitting device manufactured using the present invention can be obtained. Since the light-emitting device has a composite layer, it has excellent hole transportability. Therefore, the drive voltage can be reduced. In addition, by selecting the metal oxide concentration in the composite layer in consideration of the refractive index, light reflection at the film interface from the light emitting layer to the composite layer and the electrode can be reduced, and the light extraction efficiency can be improved. . Therefore, a light-emitting device with low power consumption can be obtained.

  This embodiment mode can be combined with any structure of Embodiment Modes 1 to 3 as appropriate.

  Further, the present invention is not limited to the above embodiment.

(Embodiment 5)
In this example, various electric appliances completed using a light-emitting device having the light-emitting element of the present invention will be described. Note that by applying the present invention, a light-emitting element with a low driving voltage can be provided. Therefore, in an electronic device including the light-emitting element of the present invention, low power consumption can be achieved.

  As an electric appliance manufactured using a light-emitting device formed using the present invention, a television, a video camera, a digital camera, a goggle-type display (head-mounted display), a navigation system, a sound reproduction device (car audio, audio component) Etc.), a notebook personal computer, a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), and an image playback device equipped with a recording medium [specifically, a digital video disc (DVD And the like] and the like] and the like]. Some specific examples of the electric appliance will be described with reference to FIG. The electric appliance using the light emitting device of the present invention is not limited to these specific examples.

  FIG. 10A illustrates a display device, which includes a housing 1000, a support base 1001, a display portion 1002, a speaker portion 1003, a video input terminal 1004, and the like. The display device 1002 is manufactured using a light-emitting device formed using the present invention. The display device includes all information display devices such as a personal computer, a TV broadcast reception, and an advertisement display.

  The display portion 1002 is provided with the light-emitting element of the present invention. Since the light-emitting element of the present invention includes a composite layer including a metal oxide and an organic compound between the first electrode and the light-emitting layer, the light-emitting element has excellent hole transportability. Therefore, the drive voltage can be reduced. Further, by selecting the metal oxide concentration in the composite layer in consideration of the refractive index, light reflection at the film interface from the light emitting layer to the first electrode can be reduced, and the light extraction efficiency can be improved. . Therefore, a display device with low power consumption can be obtained.

  FIG. 10B illustrates a laptop personal computer, which includes a main body 1010, a housing 1011, a display portion 1012, a keyboard 1013, an external connection port 1014, a pointing mouse 1015, and the like.

  The display portion 1012 is provided with the light-emitting element of the present invention. Since the light-emitting element of the present invention includes a composite layer including a metal oxide and an organic compound between the first electrode and the light-emitting layer, the light-emitting element has excellent hole transportability. Therefore, the drive voltage can be reduced. Further, by selecting the metal oxide concentration in the composite layer in consideration of the refractive index, light reflection at the film interface from the light emitting layer to the first electrode can be reduced, and the light extraction efficiency can be improved. . Therefore, a personal computer with low power consumption can be obtained.

  FIG. 10C illustrates a video camera, which includes a main body 1020, a display portion 1021, a housing 1022, an external connection port 1023, a remote control receiving portion 1024, an image receiving portion 1025, a battery 1026, an audio input portion 1027, operation keys 1028, an eyepiece. Part 1029 and the like.

  The display portion 1021 is provided with the light-emitting element of the present invention. Since the light-emitting element of the present invention includes a composite layer including a metal oxide and an organic compound between the first electrode and the light-emitting layer, the light-emitting element has excellent hole transportability. Therefore, the drive voltage can be reduced. Further, by selecting the metal oxide concentration in the composite layer in consideration of the refractive index, light reflection at the film interface from the light emitting layer to the first electrode can be reduced, and the light extraction efficiency can be improved. . Thus, a video camera with low power consumption can be obtained.

  FIG. 10D illustrates a mobile phone, which includes a main body 1030, a housing 1031, a display portion 1032, a sound input portion 1033, a sound output portion 1034, operation keys 1035, an external connection port 1036, an antenna 1037, and the like.

  The display portion 1032 is provided with the light-emitting element of the present invention. Since the light-emitting element of the present invention includes a composite layer including a metal oxide and an organic compound between the first electrode and the light-emitting layer, the light-emitting element has excellent hole transportability. Therefore, the drive voltage can be reduced. Further, by selecting the metal oxide concentration in the composite layer in consideration of the refractive index, light reflection at the film interface from the light emitting layer to the first electrode can be reduced, and the light extraction efficiency can be improved. . Thus, a mobile phone with low power consumption can be obtained.

  As described above, the applicable range of the present invention is extremely wide and can be used for display devices in various fields. In addition, the electronic device of this example can be combined with any of the structures in Embodiments 1 to 4 as appropriate.

4A and 4B illustrate a light-emitting element of the present invention. 4A and 4B illustrate a light-emitting element of the present invention. 4A and 4B illustrate a light-emitting element of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting element of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting element of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting element of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting element of the present invention. 4A and 4B illustrate a method for manufacturing a light-emitting element of the present invention. 4A and 4B illustrate a light-emitting device of the present invention. 4A and 4B each illustrate an electrical appliance using a light-emitting element of the present invention. The figure which shows the observation result of the transmission electron microscope of a composite layer. The figure which shows the observation result of the transmission electron microscope of a composite layer. The figure which shows the current density-voltage characteristic of a composite layer. The schematic diagram of the vapor deposition apparatus at the time of examining about the metal oxide density | concentration in a composite layer.

Explanation of symbols

101 substrate 102 first electrode 103a first composite layer 103b second composite layer 104 light emitting layer 105 electron transport layer 106 electron injection layer 107 second electrode 203a first composite layer 203b second composite layer 203c third Composite layer 303 composite layer 401 processing chamber 402 transfer chamber 403 arm 501a deposition source 501b deposition source 502 first rotating plate 503 shaft 504a second rotating plate 504b second rotating plate 504c second rotating plate 504d second Rotating plate 505a Object 505b Object 505c Object 505d Object 601a Deposition source 701a Deposition source 701b Deposition source 702 Holding part 705a Object 705b Object 705c Object 705d Object 706 Rotating plate 707 Shaft 800 Crucible 801 Lid 802 Metal oxide 803 Particle 900 Substrate 901 Drive circuit Portion 902 pixel portion 903 drive circuit portion 904 sealing substrate 905 sealing material 906 space 907 wiring 908 FPC
911 TFT for switching
912 Current control TFT
913 First electrode 914 Insulator 916 Layer containing light emitting substance 917 Second electrode 918 Light emitting element 923 n-channel TFT
924 p-channel TFT
1000 Case 1001 Support stand 1002 Display unit 1003 Speaker unit 1004 Video input terminal 1010 Main body 1011 Case 1012 Display unit 1013 Keyboard 1014 External connection port 1015 Pointing mouse 1020 Main body 1021 Display unit 1022 Case 1023 External connection port 1024 Remote control reception unit 1025 Image receiving unit 1026 Battery 1027 Audio input unit 1028 Operation key 1029 Eyepiece unit 1030 Main body 1031 Case 1032 Display unit 1033 Audio input unit 1034 Audio output unit 1035 Operation key 1036 External connection port 1037 Antenna

Claims (14)

A first electrode, a first composite layer sequentially stacked on the first electrode, a second composite layer, a light emitting layer, an electron transport layer, and a second electrode;
The first composite layer and the second composite layer have a metal oxide and an organic compound,
An average metal oxide concentration of the first composite layer is higher than an average metal oxide concentration of the second composite layer. In claim 1,
The first composite layer and the second composite layer have a configuration in which the first regions and the second regions are alternately stacked,
The metal oxide concentration in the first region is greater than or equal to the metal oxide concentration in the second region;
The highest metal oxide concentration in the first region is 1 to 8 times the metal oxide concentration compared to the lowest metal oxide concentration in the second region. . In claim 1,
The first composite layer and the second composite layer have a configuration in which the first regions and the second regions are alternately stacked,
The metal oxide concentrations of the first region and the second region are different,
The light emitting element, wherein a repetition period of the metal oxide concentration in the first composite layer and the second composite layer is 12 nm or less. A first composite layer, a second composite layer, a third composite layer, a light emitting layer, an electron transport layer, and a second composite layer sequentially stacked on the first electrode; An electrode,
The first composite layer, the second composite layer, and the third composite layer have a metal oxide and an organic compound,
The average metal oxide concentration of the first composite layer is higher than the average metal oxide concentration of the second composite layer,
The average metal oxide concentration of the second composite layer is higher than the average metal oxide concentration of the third composite layer. In claim 4,
The first composite layer, the second composite layer, and the third composite layer each have a configuration in which first regions and second regions are alternately stacked,
The metal oxide concentration in the first region is greater than or equal to the metal oxide concentration in the second region;
The highest metal oxide concentration in the first region is 1 to 8 times the metal oxide concentration compared to the lowest metal oxide concentration in the second region. . In claim 4,
The first composite layer, the second composite layer, and the third composite layer each have a configuration in which first regions and second regions are alternately stacked,
The metal oxide concentrations of the first region and the second region are different,
The light emitting element, wherein a repetition period of the metal oxide concentration in the first composite layer, the second composite layer, and the third composite layer is 12 nm or less. A first electrode, a composite layer sequentially laminated on the first electrode, a light emitting layer, an electron transport layer, and a second electrode;
The composite layer has a metal oxide and an organic compound,
The light-emitting element in which the metal oxide of the composite layer has a concentration gradient from the first electrode to the light-emitting layer side. In claim 7,
The light emitting element characterized by the metal oxide density | concentration of the said composite layer being the lowest in the surface which contact | connects the said light emitting layer. In claim 7,
The light emitting element characterized in that the metal oxide concentration of the composite layer is 0 wt% or more and 3 wt% or less on the surface in contact with the light emitting layer. In any one of Claims 1 thru | or 9,
The metal oxide is one or more of titanium oxide, vanadium oxide, chromium oxide, zirconium oxide, niobium oxide, molybdenum oxide, hafnium oxide, tantalum oxide, tungsten oxide, and rhenium oxide. element. In any one of Claims 1 thru | or 10,
The light-emitting element, wherein the organic compound has a hole transporting property. In any one of Claims 1 thru | or 11,
The organic compound has an arylamine skeleton or a carbazole skeleton.   A light-emitting device comprising the light-emitting element according to claim 1.   An electronic apparatus comprising the light emitting device according to claim 13.