JP5031445B2 - LIGHT EMITTING ELEMENT, LIGHT EMITTING DEVICE, AND ELECTRONIC DEVICE - Google Patents

Description

The present invention relates to a current excitation type light emitting element. In addition, the present invention relates to a light-emitting device and an electronic device each having a light-emitting element.
More specifically, the present invention relates to a light-emitting element having excellent color purity and a long lifetime. Furthermore, the present invention relates to a light-emitting device and an electronic device having excellent color purity and a long lifetime.

  In recent years, research and development of light emitting elements using electroluminescence have been actively conducted. The basic structure of these light-emitting elements is such that a layer containing a light-emitting substance is sandwiched between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting substance can be obtained.

  Since such a light-emitting element is a self-luminous type, it has advantages such as higher pixel visibility than a liquid crystal display and the need for a backlight, and is considered suitable as a flat panel display element. In addition, it is a great advantage that such a light-emitting element can be manufactured to be thin and light. Another feature is that the response speed is very fast.

  Since these light-emitting elements can be formed in a film shape, planar light emission can be easily obtained by forming a large-area element. This is a feature that is difficult to obtain with a point light source typified by an incandescent bulb or LED, or a line light source typified by a fluorescent lamp, and therefore has a high utility value as a surface light source applicable to illumination or the like.

A light-emitting element using the electroluminescence can be roughly classified depending on whether the light-emitting substance is an organic compound or an inorganic compound, but the present invention uses an organic compound as the light-emitting substance.
In that case, by applying a voltage to the light-emitting element, electrons and holes are each injected from the pair of electrodes into the layer containing a light-emitting organic compound, and a current flows. Then, these carriers (electrons and holes) recombine, whereby the light-emitting organic compound forms an excited state, and emits light when the excited state returns to the ground state.

  Due to such a mechanism, such a light-emitting element is called a current-excitation light-emitting element. Note that the excited states formed by the organic compound can be singlet excited state or triplet excited state. Light emission from the singlet excited state is called fluorescence, and light emission from the triplet excited state is called phosphorescence. ing.

With respect to such a light emitting element, there are many problems depending on the material in improving the element characteristics, and improvement of the element structure, material development, and the like have been performed in order to overcome these problems.
For example, Patent Document 1 discloses a long-life organic EL element that has two light emitting layers and is doped with a plurality of types of fluorescent substances having different color systems to ensure color stability. However, in Patent Document 1, since multiple types of fluorescent substances having different color systems are doped, white light emission with good color stability can be obtained, but light emission with good color purity cannot be obtained.

In addition, a light-emitting element using a light-emitting organic compound can be driven at a lower voltage than a light-emitting element using a light-emitting inorganic compound, but has a problem that the lifetime of the element is short. . Therefore, further extension of the life of the light emitting element is desired.
JP 2000-68057 A

  Therefore, an object of the present invention is to provide a light-emitting element having excellent purity and a long lifetime when an organic compound is used as the light-emitting substance. It is another object to provide a light-emitting device and an electronic device that have excellent color purity and a long lifetime.

As a result of intensive studies, the present inventors have found that the problem can be solved by making the light emitting region near the center of the light emitting layer.
That is, when there is a hole transport layer and an electron transport layer between the two electrodes, the light emitting region is not the interface between the light emitting layer and the hole transport layer or the interface between the light emitting layer and the electron transport layer. We found that the problem could be solved by making it near the center.
Further, the present inventors have found that even when there is no hole transport layer and electron transport layer, the problem can be solved by setting the center of the light emitting layer, not the interface between both electrodes and the light emitting layer.
The present invention has been developed based on the above findings, and the light emitting device of the present invention has many modes.

  The first aspect includes a light emitting layer between the first electrode and the second electrode, the light emitting layer includes the first layer and the second layer, and the first layer includes the first layer. The second organic compound, the second layer has the third organic compound and the fourth organic compound, and the first layer is the second layer of the second layer. The second organic compound has an electron transporting property, the third organic compound has an electron trapping property, the fourth organic compound has an electron transporting property, and the second organic compound has an electron transporting property. The emission color of the first organic compound and the emission color of the third organic compound are the same color system, and the first electrode and the third organic compound have a higher potential than the second electrode so that the first electrode has a higher potential than the second electrode. Light emission from the first organic compound can be obtained by applying a voltage to the second electrode.

  The second aspect includes a light emitting layer between the first electrode and the second electrode, the light emitting layer includes the first layer and the second layer, and the first layer includes the first layer. The second organic compound, the second layer has the third organic compound and the fourth organic compound, and the first layer is the second layer of the second layer. The second organic compound has an electron transporting property, and the third organic compound has a lowest orbital level lower by 0.3 eV or more than the lowest orbital level of the fourth organic compound. The fourth organic compound has an electron transporting property, and the emission color of the first organic compound and the emission color of the third organic compound are the same color system, and the first electrode is more Light emission from the first organic compound can be obtained by applying a voltage to the first electrode and the second electrode so that the potential is higher than that of the second electrode. .

  The third aspect includes a light emitting layer between the first electrode and the second electrode, the light emitting layer includes the first layer and the second layer, and the first layer includes the first layer. The second organic compound, the second layer has the third organic compound and the fourth organic compound, and the first layer is the second layer of the second layer. The second organic compound has an electron transporting property, and the third organic compound has a lowest orbital level lower by 0.3 eV or more than the lowest orbital level of the fourth organic compound. The fourth organic compound has an electron transport property, and the difference between the peak value of the emission spectrum of the first organic compound and the peak value of the emission spectrum of the third organic compound is within 30 nm, By applying a voltage to the first electrode and the second electrode so that the potential of the first electrode is higher than that of the second electrode, the first organic compound It is characterized in that the light emission can be obtained.

  The fourth aspect includes an electron transport layer and a hole transport layer between the first electrode and the second electrode, and the first layer and the second layer are disposed between the electron transport layer and the hole transport layer. The first layer has a first organic compound and a second organic compound, and the second layer has a third organic compound and a fourth organic compound. And the first layer is provided on the first electrode side of the second layer, the second organic compound has an electron transporting property, and the third organic compound has an electron trapping property. The fourth organic compound has an electron transport property, and the emission color of the first organic compound and the emission color of the third organic compound are the same color system, and the first electrode is the second electrode. Light emission from the first organic compound can be obtained by applying a voltage to the first electrode and the second electrode so that the potential becomes higher than that of the first organic compound.

  The fifth aspect includes an electron transport layer and a hole transport layer between the first electrode and the second electrode, and the first layer and the second layer are disposed between the electron transport layer and the hole transport layer. The first layer has a first organic compound and a second organic compound, and the second layer has a third organic compound and a fourth organic compound. And the first layer is provided on the first electrode side of the second layer, the second organic compound has an electron transporting property, and the third organic compound is the fourth organic compound. It has a lowest unoccupied orbital level lower by 0.3 eV or more than the lowest unoccupied orbital level, the fourth organic compound has an electron transport property, and the emission color of the first organic compound and the emission color of the third organic compound are The first organic compound having the same color system and applying a voltage to the first electrode and the second electrode so that the potential of the first electrode is higher than that of the second electrode. Departure from It is characterized in that is obtained.

  The sixth aspect includes an electron transport layer and a hole transport layer between the first electrode and the second electrode, and the first layer and the second layer are disposed between the electron transport layer and the hole transport layer. The first layer has a first organic compound and a second organic compound, and the second layer has a third organic compound and a fourth organic compound. And the first layer is provided on the first electrode side of the second layer, the second organic compound has an electron transporting property, and the third organic compound is the fourth organic compound. The lowest organic orbital level is 0.3 eV or more lower than the lowest empty orbital level, the fourth organic compound has an electron transport property, the peak value of the emission spectrum of the first organic compound, and the third organic compound. The difference in the peak value of the emission spectrum of the compound is within 30 nm, and a voltage is applied to the first electrode and the second electrode so that the potential of the first electrode is higher than that of the second electrode. By pressing, it is characterized in that the light emitted from the first organic compound is obtained.

  In many of these light-emitting element embodiments, the first layer and the second layer are preferably provided in contact with each other.

The present invention also includes a light emitting device having the above-described light emitting element. The light emitting device in this specification includes an image display device, a light emitting device, a light source (including a lighting device), and the like. Also, a panel in which a light emitting element is formed, a connector, for example, a FPC (Flexible printed circuit) or TAB (Tape Automated Bonding) tape or a TCP (Tape Carrier Package) attached module, a printed wiring board on the end of the TAB tape or TCP The light emitting device also includes a module provided with a light emitting device or a module in which an IC (integrated circuit) is directly mounted on a light emitting element by a COG (Chip On Glass) method.
Further, the case where the light emitting element includes a control means for controlling the light emission is included in the light emitting device of the present invention.

  In addition, an electronic device using the light emitting element of the present invention for the display portion is also included in the category of the present invention. Furthermore, an electronic device of the present invention includes a display portion, and the display portion includes the above-described light emitting element and a control unit that controls light emission of the light emitting element.

In the light emitting device of the present invention, since the light emitting region is formed near the center of the light emitting layer, not the interface between the light emitting layer and the hole transport layer or the interface between the light emitting layer and the electron transport layer, the device is not easily deteriorated. A light-emitting element with a long lifetime can be obtained.
Even when the hole transport layer and the electron transport layer are not provided, the same effect can be obtained by setting the vicinity of the center of the light emitting layer instead of the interface between both electrodes and the light emitting layer.

In the light-emitting element of the present invention, since the emission color of the first organic compound and the emission color of the third organic compound are similar colors, not only the first organic compound but also the third organic compound emits light. However, light emission with good color purity can be obtained.
Furthermore, by applying the light-emitting element of the present invention to a light-emitting device and an electronic device, a light-emitting device and an electronic device having excellent color purity and a long lifetime can be obtained.

  Hereinafter, various embodiments of the present invention including the best mode for carrying out the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and various changes and modifications can be made 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.

(Embodiment 1)
One embodiment of a light-emitting element of the present invention is described below with reference to FIG.
The light-emitting element of the present invention has a plurality of layers between a pair of electrodes. The plurality of layers have a high carrier injecting property and a high carrier transporting property so that a light emitting region is formed at a distance from the electrode, that is, a carrier is recombined at a position away from the electrode. It is a combination of layers of materials.

  In this embodiment mode, the light-emitting element includes a first electrode 102, a second electrode 104, and an EL layer 103 provided between the first electrode 102 and the second electrode 104. Note that in this embodiment mode, the first electrode 102 functions as an anode and the second electrode 104 functions as a cathode. That is, when voltage is applied to the first electrode 102 and the second electrode 104 so that the potential of the first electrode 102 is higher than that of the second electrode 104, light emission can be obtained. A description will be given below.

  The substrate 101 is used as a support for the light emitting element. As the substrate 101, for example, glass or plastic can be used. Note that other materials may be used as long as they function as a support in the manufacturing process of the light-emitting element.

  As the first electrode 102, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a high work function (specifically, 4.0 eV or more) is preferably used. Specifically, for example, indium tin oxide (ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium zinc oxide (IZO), tungsten oxide, and oxide. Examples thereof include indium oxide containing zinc (IWZO).

  These conductive metal oxide films are usually formed by sputtering, but may be formed by applying a sol-gel method or the like. For example, indium oxide-zinc oxide (IZO) can be formed by a sputtering method using a target in which 1 to 20 wt% of zinc oxide is added to indium oxide. Indium oxide containing tungsten oxide and zinc oxide (IWZO) is formed by sputtering using a target containing 0.5 to 5 wt% tungsten oxide and 0.1 to 1 wt% zinc oxide with respect to indium oxide. can do.

  Besides these, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu) , Palladium (Pd), or a nitride of a metal material (for example, titanium nitride: TiN).

  The layer structure of the EL layer 103 is not particularly limited, and a substance having a high electron transporting property, a substance having a high hole transporting property, a substance having a high electron injecting property, a substance having a high hole injecting property, or a bipolar property ( A layer formed of a substance having a high electron and hole transport property) and the light-emitting layer described in this embodiment may be combined as appropriate. For example, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like can be appropriately combined. The materials constituting each layer are specifically shown below. In FIG. 1, as an example, a structure in which a first electrode 102, a hole transport layer 112, a light-emitting layer 111, an electron transport layer 113, and a second electrode 104 are sequentially stacked is illustrated.

A hole injection layer may be provided between the first electrode 102 and the hole transport layer 112. The hole injection layer is a layer containing a substance having a high hole injection property. Examples of the material having a high hole injection property include molybdenum oxide (MoO _x ), vanadium oxide (VO _x ), ruthenium oxide (RuO _x ), tungsten oxide (WO _x ), manganese oxide (MnO _x ), and the like. Can be used. In addition, phthalocyanine compounds such as phthalocyanine (abbreviation: H ₂ Pc) and copper phthalocyanine (abbreviation: CuPc), or poly (ethylenedioxythiophene) / poly (3,4-styrenesulfonic acid) (PEDOT / The hole injection layer can also be formed by a polymer such as PSS).

For the hole injection layer, a composite material in which an acceptor substance is contained in a substance having a high hole-transport property can be used. By using a material having an acceptor substance contained in a substance having a high hole transporting property, a material for forming an electrode can be selected regardless of the work function of the electrode. That is, not only a material with a high work function but also a material with a low work function can be used for the first electrode 102.
Note that in this specification, “composite” means not only that a plurality of materials are mixed but also a state in which charge can be transferred between the materials by mixing.

As the acceptor substance, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F ₄ -TCNQ), chloranil, and the like can be given. Moreover, a transition metal oxide can be mentioned. In addition, oxides of metals belonging to Groups 4 to 8 in the periodic table can be given. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and rhenium oxide are preferable because of their high electron accepting properties. Among these, molybdenum oxide is especially preferable because it is stable in the air, has a low hygroscopic property, and is easy to handle.

As the substance having a high hole-transport property used for the composite material, various compounds such as an aromatic amine compound, a carbazole derivative, an aromatic hydrocarbon, and a high molecular compound (oligomer, dendrimer, polymer, and the like) can be used. Specifically, a substance having a hole mobility of 10 ⁻⁶ cm ² / Vs or higher is preferable. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Hereinafter, organic compounds having high hole transportability that can be used for the composite material are specifically listed.

  For example, as an aromatic amine compound, N, N′-bis (4-methylphenyl) -N, N′-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis [N- (4 -Diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: DPAB), 4,4'-bis (N- {4- [N '-(3-methylphenyl) -N'-phenylamino] phenyl}- N-phenylamino) biphenyl (abbreviation: DNTPD), 1,3,5-tris [N- (4-diphenylaminophenyl) -N-phenylamino] benzene (abbreviation: DPA3B), and the like can be given.

  Specific examples of the carbazole derivative that can be used for the composite material include 3- [N- (9-phenylcarbazol-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA1), 3 , 6-Bis [N- (9-phenylcarbazol-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA2), 3- [N- (1-naphthyl) -N- (9- Phenylcarbazol-3-yl) amino] -9-phenylcarbazole (abbreviation: PCzPCN1) and the like.

  As other carbazole derivatives that can be used for the composite material, 4,4′-di (N-carbazolyl) biphenyl (abbreviation: CBP), 1,3,5-tris [4- (N-carbazolyl) Phenyl] benzene (abbreviation: TCPB), 9- [4- (N-carbazolyl)] phenyl-10-phenylanthracene (abbreviation: CzPA), 1,4-bis [4- (N-carbazolyl) phenyl] -2, 3,5,6-tetraphenylbenzene or the like can be used.

  Examples of aromatic hydrocarbons that can be used for the composite material include 2-tert-butyl-9,10-di (2-naphthyl) anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9. , 10-di (1-naphthyl) anthracene, 9,10-bis (3,5-diphenylphenyl) anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis (4-phenylphenyl) anthracene ( Abbreviations: t-BuDBA), 9,10-di (2-naphthyl) anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), and the like.

  Furthermore, 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis (4-methyl-1-naphthyl) anthracene (abbreviation: DMNA), 9,10-bis [2- (1-naphthyl) Phenyl] -2-tert-butyl-anthracene, 9,10-bis [2- (1-naphthyl) phenyl] anthracene, 2,3,6,7-tetramethyl-9,10-di (1-naphthyl) anthracene 2,3,6,7-tetramethyl-9,10-di (2-naphthyl) anthracene and the like.

In addition to these, 9,9′-bianthryl, 10,10′-diphenyl-9,9′-bianthryl, 10,10′-bis (2-phenylphenyl) -9,9′-bianthryl, 10,10 ′ -Bis [(2,3,4,5,6-pentaphenyl) phenyl] -9,9'-bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra (tert-butyl) perylene Etc. In addition, pentacene, coronene, and the like can also be used. Thus, it is more preferable to use an aromatic hydrocarbon having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more and having 14 to 42 carbon atoms.

The aromatic hydrocarbon that can be used for the composite material may have a vinyl skeleton. Examples of such aromatic hydrocarbon include 4,4′-bis (2,2-diphenylvinyl). ) Biphenyl (abbreviation: DPVBi), 9,10-bis [4- (2,2-diphenylvinyl) phenyl] anthracene (abbreviation: DPVPA), and the like.
Further, a high molecular compound such as poly (N-vinylcarbazole) (abbreviation: PVK) or poly (4-vinyltriphenylamine) (abbreviation: PVTPA) can also be used.

  The hole transport layer 112 is a layer containing a substance having a high hole transport property. As a substance having a high hole-transport property, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB or α-NPD), N, N′-bis ( 3-methylphenyl) -N, N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (abbreviation: TPD), 4,4 ′, 4 ″ -tris (N, N-diphenyl) Amino) triphenylamine (abbreviation: TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (abbreviation: MTDATA), 4,4′- An aromatic amine compound such as bis [N- (spiro-9,9′-bifluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: BSPB) can be used.

The substances mentioned here are mainly substances having a hole mobility of 10 ⁻⁶ cm ² / Vs or higher. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Note that the layer containing a substance having a high hole-transport property is not limited to a single layer, and two or more layers containing the above substances may be stacked.

  The light-emitting layer 111 is a layer including a substance having high light-emitting properties. In the light-emitting element of the present invention, the light-emitting layer includes a first layer 121 and a second layer 122. The first layer 121 includes a first organic compound and a second organic compound, and the second layer 122 includes a third organic compound and a fourth organic compound.

  The first organic compound included in the first layer 121 is a substance having high light-emitting properties, and various materials can be used. Specifically, as a blue light-emitting material, N, N′-bis [4- (9H-carbazol-9-yl) phenyl] -N, N′-diphenylstilbene-4,4′-diamine (abbreviation: YGA2S), 4- (9H-carbazol-9-yl) -4 ′-(10-phenyl-9-anthryl) triphenylamine (abbreviation: YGAPA), and the like.

  As green light-emitting materials, N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), N- [9,10-bis] (1,1′-biphenyl-2-yl) -2-anthryl] -N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N- (9,10-diphenyl-2-anthryl) -N, N ', N'-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N- [9,10-bis (1,1'-biphenyl-2-yl) -2-anthryl]- N, N ′, N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis (1,1′-biphenyl-2-yl) -N- [4- (9H-carbazole) 9-yl) phenyl] -N- phenyl-anthracene-2-amine (abbreviation: 2YGABPhA), N, N, 9- triphenylamine anthracene-9-amine (abbreviation: DPhAPhA), and the like.

  In addition, examples of a yellow light-emitting material include rubrene, 5,12-bis (1,1′-biphenyl-4-yl) -6,11-diphenyltetracene (abbreviation: BPT), and the like. Further, as red light-emitting materials, N, N, N ′, N′-tetrakis (4-methylphenyl) tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,13-diphenyl-N, N , N ′, N′-tetrakis (4-methylphenyl) acenaphtho [1,2-a] fluoranthene-3,10-diamine (abbreviation: p-mPhAFD) and the like.

  The second organic compound included in the first layer 121 is a substance that has a higher electron transporting property than a hole transporting property, and a substance that disperses the above-described highly light-emitting substance. Preferred is a so-called bipolar material in which the difference in mobility between holes and electrons is 10 times or less. Specifically, 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA), tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), 4,4 '-(Quinoxaline-2,3-diyl) bis (N, N-diphenylaniline) (abbreviation: TPAQn), 9,10-diphenylanthracene (abbreviation: DPAnth), N, N'-(quinoxaline-2,3- Diyldi-4,1-phenylene) bis (N-phenyl-1,1′-biphenyl-4-amine) (abbreviation: BPAPQ), 4,4 ′-(quinoxaline-2,3-diyl) bis {N- [ 4- (9H-carbazol-9-yl) phenyl] -N-phenylaniline} (abbreviation: YGAPQ), 9,10-diphenylanthracene (abbreviation: DPAnth), etc. And the like.

The third organic compound included in the second layer 122 is an organic compound having a function of trapping electrons. Therefore, the third organic compound has a lowest orbital level (LUMO level) that is 0.3 eV or more lower than the lowest unoccupied orbital level (LUMO level) of the fourth organic compound included in the second layer 122. It is preferable that it is an organic compound to have. In addition, the third organic compound may emit light. In that case, the light emission color of the first organic compound and the light emission color of the third organic compound must be similar to maintain the color purity of the light-emitting element. Is preferred.
That is, for example, when the first organic compound exhibits blue light emission such as YGA2S or YGAPA, the third organic compound is blue to blue-green such as acridone, coumarin 102, coumarin 6H, coumarin 480D, coumarin 30 and the like. Substances that exhibit luminescence are preferred.

  Further, when the first organic compound exhibits green emission such as 2PCAPA, 2PCABPhA, 2DPAPA, 2DPABPhA, 2YGABPhA, DPhAPhA, the third organic compound is N, N′-dimethylquinacridone (abbreviation: DMQd), N, N′-diphenylquinacridone (abbreviation: DPQd), 9,18-dihydrobenzo [h] benzo [7,8] quino [2,3-b] acridine-7,16-dione (abbreviation: DMNQd-1) 9,18-dimethyl-9,18-dihydrobenzo [h] benzo [7,8] quino [2,3-b] acridine-7,16-dione (abbreviation: DMNQd-2), coumarin 30, coumarin 6 Substances exhibiting blue-green to yellow-green light emission such as Coumarin 545T and Coumarin 153 are preferable.

  In addition, when the first organic compound emits yellow light such as rubrene or BPT, the third organic compound is DMQd, (2- {2- [4- (9H-carbazol-9-yl) phenyl]. ] Ethenyl} -6-methyl-4H-pyran-4-ylidene) propanedinitrile (abbreviation: DCMCz) and the like, a substance exhibiting yellow-green to yellow-orange emission is preferable.

  Furthermore, when the first organic compound exhibits red light emission such as p-mPhTD and p-mPhAFD, the third organic compound is (2- {2- [4- (dimethylamino) phenyl] ethenyl}. -6-methyl-4H-pyran-4-ylidene) propanedinitrile (abbreviation: DCM1), {2-methyl-6- [2- (2,3,6,7-tetrahydro-1H, 5H-benzo [ij ] Quinolinidin-9-yl) ethenyl] -4H-pyran-4-ylidene} propanedinitrile (abbreviation: DCM2), {2- (1,1-dimethylethyl) -6- [2- (2,3,6) , 7-tetrahydro-1,1,7,7-tetramethyl-1H, 5H-benzo [ij] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene} propanedinitrile (abbreviation: DCJTB), Na Substance having an orange to red light emission, such as Rureddo are preferred. The above-described compound is a compound having a low LUMO level among compounds used for a light-emitting element, and exhibits excellent electron trapping properties when added to a fourth organic compound described later.

  As described above, among the substances listed above, quinacridone derivatives such as DMQd, DPQd, DMNQd-1, and DMNQd-2 are preferable as the third organic compound because they are chemically stable. That is, by using the quinacridone derivative, the lifetime of the light-emitting element can be particularly prolonged. Further, since the quinacridone derivative emits green light, the element structure of the light-emitting element of the present invention is particularly effective for a green light-emitting element. Since green is the color that needs the most brightness when manufacturing a full-color display, degradation may be larger than other colors, but this can be improved by applying the present invention. be able to.

The fourth organic compound contained in the second layer 122 is a compound having an electron transporting property. That is, the substance has a higher electron transporting property than a hole transporting property. Specifically, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), bis (8-quinolinolato) zinc (II) (abbreviation: Znq ₂ ), bis (2-methyl-8-quinolinolato) (4 -Phenylphenolato) aluminum (III) (abbreviation: BAlq), bis [2- (2-benzoxazolyl) phenolato] zinc (II) (abbreviation: ZnPBO), bis [2- (2-benzothiazolyl) phenolate] And zinc (II) (abbreviation: ZnBTZ).

  Further, as described above, it is preferable that the LUMO level of the third organic compound is lower by 0.3 eV or more than the LUMO level of the fourth organic compound. Therefore, the fourth organic compound may be appropriately selected so as to satisfy such a condition according to the type of the third organic compound to be used. For example, as described later in the examples, when DPQd is used as the third organic compound, the above-described condition is satisfied by using Alq as the fourth organic compound.

  Since the emission color of the first organic compound and the emission color of the third organic compound are preferably similar colors, the peak value of the emission spectrum of the first organic compound and the emission spectrum of the third organic compound The difference from the peak value is preferably within 30 nm. By being within 30 nm, the emission color of the first organic compound and the emission color of the third organic compound are similar colors. Therefore, even when the third organic compound emits light due to a change in voltage or the like, a change in the emission color of the light-emitting element can be suppressed.

  However, the third organic compound does not necessarily emit light. For example, when the light emission efficiency of the first organic compound is higher, the concentration of the third organic compound in the second layer 122 is adjusted so that substantially only light emission of the first organic compound can be obtained. It is preferable to slightly reduce the concentration so that light emission of the third organic compound is suppressed. In this case, since the emission color of the first organic compound and the emission color of the third organic compound are similar colors (that is, having the same energy gap), the first organic compound is changed to the third organic compound. Energy transfer is not likely to occur, and high luminous efficiency is obtained.

The electron transport layer 113 is a layer containing a substance having a high electron transport property. For example, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), tris (4-methyl-8-quinolinolato) aluminum (III) (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] quinolinato) A layer formed of a metal complex having a quinoline skeleton or a benzoquinoline skeleton such as beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) (4-phenylphenolato) aluminum (III) (abbreviation: BAlq) It is.
In addition, bis [2- (2-benzoxazolyl) phenolato] zinc (II) (abbreviation: ZnPBO), bis [2- (2-benzothiazolyl) phenolato] zinc (II) (abbreviation: ZnBTZ), etc. A metal complex having an oxazole-based or thiazole-based ligand can also be used.

In addition to metal complexes, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5 -(P-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-biphenylyl) -4-phenyl-5- (4- tert-Butylphenyl) -1,2,4-triazole (abbreviation: TAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and the like can also be used. The substances mentioned here are mainly substances having an electron mobility of 10 ⁻⁶ cm ³ / Vs or higher. Note that other than the above substances, any substance that has a property of transporting more electrons than holes may be used for the electron-transport layer. Further, the electron-transporting layer is not limited to a single layer, and two or more layers including the above substances may be stacked.

Further, an electron injecting layer that is a layer containing a substance having a high electron injecting property may be provided between the electron transporting layer 113 and the second electrode 104. As the electron injection layer, an alkali metal or alkaline earth metal compound such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), or the like can be used. Furthermore, a layer made of a substance having an electron transporting property containing alkali metal or alkaline earth metal, for example, Alq containing magnesium (Mg) can be used. Note that by using an electron injection layer containing an alkali metal or an alkaline earth metal in a layer made of a substance having an electron transporting property, electron injection from the second electrode 104 is efficiently performed. More preferred.

  As a material for forming the second electrode 104, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (specifically, 3.8 eV or less is preferable) can be used. Specific examples of such a cathode material include elements belonging to Group 1 or Group 2 of the periodic table of elements, that is, alkali metals such as lithium (Li) and cesium (Cs), magnesium (Mg), calcium (Ca). , Alkaline earth metals such as strontium (Sr), alloys containing these (MgAg, AlLi), rare earth metals such as europium (Eu) and ytterbium (Yb), and alloys containing these. However, by providing an electron injection layer between the second electrode 104 and the electron transport layer, indium oxide-tin oxide containing Al, Ag, ITO, silicon, or silicon oxide regardless of the work function. Various conductive materials such as the above can be used for the second electrode 104.

  In addition, as a formation method of the EL layer 103, various methods can be used regardless of a dry method or a wet method. For example, a vacuum deposition method, an ink jet method, a spin coating method, or the like may be used. Furthermore, it may be formed using a different film forming method for each electrode or each layer.

  In the light-emitting element of the present invention having the above structure, a current flows due to a potential difference generated between the first electrode 102 and the second electrode 104, and holes and electrons are recombined in the EL layer 103. , Emit light. More specifically, the light emitting layer 111 in the EL layer 103 has a structure in which a light emitting region is formed near the interface between the first layer 121 and the first layer 121 and the second layer 122. Yes. This principle will be described below.

  FIG. 21 is an example of a band diagram of the light-emitting element of the present invention shown in FIG. In FIG. 21, holes injected from the first electrode 102 pass through the hole transport layer 112 and are injected into the first layer 121. Here, the second organic compound constituting the first layer 121 is a substance having a higher electron transport property than a hole transport property, and preferably the difference in mobility between holes and electrons is within 10 times. Therefore, the holes injected into the first layer 121 move slowly.

  Therefore, in the case of a conventional light emitting element in which the second layer 122 is not provided, the light emitting region is formed in the vicinity of the interface between the hole transport layer 112 and the first layer 121. In that case, electrons reach the hole transport layer 112 and the hole transport layer 112 may be deteriorated. In addition, when the amount of electrons that reach the hole transport layer 112 with time increases, the recombination probability decreases with time, so that the luminance deteriorates with time. As a result, the device life is shortened.

  The light-emitting element of the present invention is characterized in that a second layer 122 is further provided in the light-emitting layer 111. Electrons injected from the second electrode 104 pass through the electron transport layer 113 and are injected into the second layer 122. Here, the second layer 122 has a structure in which a third organic compound having a function of trapping electrons is added to a fourth organic compound having an electron transporting property. Therefore, the movement of the electrons injected into the second layer 122 is slow, and the electron injection into the first layer 121 is controlled.

  As a result, the light emitting region that should have been formed in the vicinity of the interface between the hole transport layer 112 and the first layer 121 in the related art is changed from the first layer 121 to the first layer 121 in the light emitting element of the present invention. And near the interface between the second layer 122 and the second layer 122. Therefore, the possibility that electrons reach the hole transport layer 112 and the hole transport layer 112 is deteriorated is reduced. In addition, regarding the holes, since the second organic compound in the first layer 121 has an electron transporting property, the possibility that the holes reach the electron transporting layer 113 and deteriorate the electron transporting layer 113 is low.

  Furthermore, in the present invention, in the second layer 122, an organic compound having a function of trapping electrons is added to an organic compound having an electron transporting property instead of simply applying a substance having a low electron mobility. The point is important. With such a configuration, it is possible not only to control the electron injection into the first layer 121 but also to prevent the controlled electron injection amount from changing with time. In addition, since the second organic compound in the first layer 121 has an electron transporting property and the first organic compound that is a light-emitting substance is added to the first layer 121, The amount of holes is also difficult to change over time. As described above, the light-emitting element of the present invention can prevent a phenomenon in which the carrier balance deteriorates with time and the recombination probability decreases in the light-emitting element, so that deterioration of luminance with time can be suppressed. Therefore, it leads to improvement of element lifetime.

  Note that in the above description, the combination of the first layer and the second layer, specifically, the combination of the second organic compound, the third organic compound, and the fourth organic compound, the time course of the light emitting element. The positive hole transport layer 112 and the electron transport layer are capable of preventing the phenomenon in which the carrier balance is deteriorated and the recombination probability is decreased, and as a result, the luminance can be prevented from being deteriorated over time. Although the case where 113 exists is described as an example, this advantage is manifested regardless of the presence or absence of the hole transport layer 112 and the electron transport layer 113, which can be naturally understood from the above description. .

  Light emission is extracted outside through one or both of the first electrode 102 and the second electrode 104. Therefore, one or both of the first electrode 102 and the second electrode 104 is a light-transmitting electrode. In the case where only the first electrode 102 is a light-transmitting electrode, 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 104 is a light-transmitting electrode, light emission is extracted from the side opposite to the substrate through the second electrode 104 as illustrated in FIG. In the case where each of the first electrode 102 and the second electrode 104 is a light-transmitting electrode, light emission passes through the first electrode 102 and the second electrode 104 as illustrated in FIG. , Taken out from both the substrate side and the opposite side of the substrate.

Note that the structure of the layers provided between the first electrode 102 and the second electrode 104 is not limited to the above. In order to prevent quenching caused by the proximity of the light emitting region and the metal, a light emitting region in which holes and electrons are recombined is provided at a site away from the first electrode 102 and the second electrode 104. As long as the light emitting layer includes the first layer 121 and the second layer 122, other than the above may be used.
In other words, there is no particular limitation on the stacked structure of the EL layer, and a substance having a high electron transporting property, a substance having a high hole transporting property, a substance having a high electron injecting property, a substance having a high hole injecting property, or a bipolar property (electron and A layer made of a substance having a high hole-transport property may be freely combined with the light-emitting layer of the present invention.

  The light-emitting element illustrated in FIG. 2 has a structure in which a second electrode 304 functioning as a cathode, an EL layer 303, and a first electrode 302 functioning as an anode are sequentially stacked over a substrate 301. The EL layer 303 includes a hole transport layer 312, a light emitting layer 311, and an electron transport layer 313, and the light emitting layer 311 includes a first layer 321 and a second layer 322. The first layer 321 is provided closer to the first electrode functioning as an anode than the second layer 322.

  In this embodiment mode, a light-emitting element is manufactured over a substrate made of glass, plastic, or the like. A passive light-emitting device can be manufactured by manufacturing a plurality of such light-emitting elements over one substrate. Alternatively, for example, a thin film transistor (TFT) may be formed over a substrate made of glass, plastic, or the like, and a light-emitting element may be formed over an electrode electrically connected to the TFT. Thus, an active matrix light-emitting device in which driving of the light-emitting element is controlled by the TFT can be manufactured.

  Note that the structure of the TFT is not particularly limited. A staggered TFT or an inverted staggered TFT may be used. Also, the driving circuit formed on the TFT substrate may be composed of N-type and P-type TFTs, or may be composed of only one of N-type TFTs and P-type TFTs. Good. Further, the crystallinity of a semiconductor film used for the TFT is not particularly limited. An amorphous semiconductor film or a crystalline semiconductor film may be used.

  In the light-emitting element of this embodiment, a light-emitting region is not formed at the interface between the light-emitting layer and the hole-transport layer or the interface between the light-emitting layer and the electron-transport layer. Is formed. Therefore, the hole transport layer and the electron transport layer are not affected by the deterioration of the hole transport layer and the electron transport layer due to the proximity of the light emitting region to the hole transport layer and the electron transport layer. In addition, a change in carrier balance with time (especially a change with time in electron injection amount) can be suppressed. Therefore, a light-emitting element that does not easily deteriorate and has a long lifetime can be obtained.

In the light-emitting element of the present invention, since the emission color of the first organic compound and the emission color of the third organic compound are similar colors, not only the first organic compound but also the third organic compound emits light. However, light emission with good color purity can be obtained.
Note that this embodiment can be combined with any of the other embodiments as appropriate.

(Embodiment 2)
In this embodiment mode, a mode of a light-emitting element having a structure in which a plurality of light-emitting units according to the present invention is stacked (hereinafter referred to as a stacked element) will be described with reference to FIG. This light-emitting element is a stacked light-emitting element having a plurality of light-emitting units between a first electrode and a second electrode. As the light-emitting unit, a structure similar to that of the EL layer 103 described in Embodiment 1 can be used. That is, the light-emitting element described in Embodiment 1 is a light-emitting element having one light-emitting unit, and in this embodiment, a light-emitting element having a plurality of light-emitting units will be described.

  In FIG. 3, a first light-emitting unit 511 and a second light-emitting unit 512 are stacked between the first electrode 501 and the second electrode 502, and the first light-emitting unit 511 and the second light-emitting unit 512 are stacked. A charge generation layer 513 is provided between the light emitting units 512. The first electrode 501 and the second electrode 502 can be similar to those in Embodiment 1. In addition, the first light-emitting unit 511 and the second light-emitting unit 512 may have the same configuration or different configurations, and the same configuration as that in Embodiment 1 can be applied.

The charge generation layer 513 includes a composite material of an organic compound and a metal oxide. This composite material of an organic compound and a metal oxide is the composite material described in Embodiment 1, and includes an organic compound and a metal oxide such as vanadium oxide, molybdenum oxide, or tungsten oxide. As the organic compound, various compounds such as an aromatic amine compound, a carbazole derivative, an aromatic hydrocarbon, and a high molecular compound (oligomer, dendrimer, polymer, etc.) can be used. As the organic compound, it is preferable to use a hole transporting organic compound having a hole mobility of 10 ⁻⁶ cm ² / Vs or more. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Since the composite material of an organic compound and a metal oxide is excellent in carrier injecting property and carrier transporting property, low voltage driving and low current driving can be realized.

  Note that the charge generation layer 513 may be formed by combining a layer including a composite material of an organic compound and a metal oxide with a layer formed using another material. For example, a layer including a composite material of an organic compound and a metal oxide may be combined with a layer including one compound selected from electron donating substances and a compound having a high electron transporting property. Alternatively, a layer including a composite material of an organic compound and a metal oxide may be combined with a transparent conductive film.

  In any case, when the voltage is applied to the first electrode 501 and the second electrode 502, the charge generation layer 513 sandwiched between the first light emitting unit 511 and the second light emitting unit 512 has one light emitting unit. Any device may be used as long as it injects electrons into the other light emitting unit and injects holes into the other light emitting unit. For example, in FIG. 3, when a voltage is applied so that the potential of the first electrode is higher than the potential of the second electrode, the charge generation layer 513 injects electrons into the first light-emitting unit 511. Any device that injects holes into the second light emitting unit 512 may be used.

  Although the light-emitting element having two light-emitting units has been described in this embodiment mode, the present invention can be similarly applied to a light-emitting element in which three or more light-emitting units are stacked. Like the light-emitting element according to the present embodiment, a plurality of light-emitting units are partitioned and arranged between a pair of electrodes by a charge generation layer, so that a long-life element in a high-luminance region can be obtained while maintaining a low current density. realizable. Further, when illumination is used as an application example, the voltage drop due to the resistance of the electrode material can be reduced, so that uniform light emission over a large area is possible. In addition, a light-emitting device that can be driven at a low voltage and has low power consumption can be realized.

Further, by making the light emission colors of the respective light emitting units different, light emission of a desired color can be obtained as the whole light emitting element. For example, in a light-emitting element having two light-emitting units, a light-emitting element that emits white light as a whole of the light-emitting element can be obtained by making the light-emitting color of the first light-emitting unit and the light-emitting color of the second light-emitting unit complementary. It is also possible to obtain. The complementary color refers to a relationship between colors that become achromatic when mixed. That is, white light emission can be obtained by mixing light obtained from substances that emit light of complementary colors. The same applies to a light-emitting element having three light-emitting units. For example, the first light-emitting unit has a red light emission color, the second light-emitting unit has a green light emission color, and the third light-emitting unit has a third light-emitting unit. When the emission color of is blue, the entire light emitting element can emit white light.
Further, this embodiment can be combined with any of the other embodiments as appropriate.

(Embodiment 3)
In this embodiment mode, a light-emitting device having the light-emitting element of the present invention will be described.
In this embodiment mode, a light-emitting device having the light-emitting element of the present invention in a pixel portion will be described with reference to FIGS. 4A is a top view illustrating the light-emitting device, and FIG. 4B is a cross-sectional view taken along lines AA ′ and BB ′ in FIG. 4A. Reference numeral 601 indicated by a dotted line denotes a driving circuit portion (source side driving circuit), 602 denotes a pixel portion, and 603 denotes a driving circuit portion (gate side driving circuit). Reference numeral 604 denotes a sealing substrate, reference numeral 605 denotes a sealing material, and the inside surrounded by the sealing material 605 is a space 607.

  Note that the routing wiring 608 is a wiring for transmitting a signal input to the source side driving circuit 601 and the gate side driving circuit 603, and a video signal, a clock signal, an FPC (flexible printed circuit) 609 serving as an external input terminal, Receives start signal, reset signal, etc. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this specification includes not only a light-emitting device body but also a state in which an FPC or a 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 element substrate 610. Here, a source-side driver circuit 601 that is a driver circuit portion and one pixel in the pixel portion 602 are illustrated.
Note that the source side driver circuit 601 is a CMOS circuit in which an N-channel TFT 623 and a P-channel TFT 624 are combined. The drive circuit may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In this embodiment mode, a driver integrated type in which a driver circuit is formed over a substrate is shown; however, this is not necessarily required, and the driver circuit can be formed outside the substrate.

  The pixel portion 602 is formed by a plurality of pixels including a switching TFT 611, a current control TFT 612, and a first electrode 613 electrically connected to the drain thereof. Note that an insulator 614 is formed so as to cover an end portion of the first electrode 613. Here, a positive photosensitive acrylic resin film is used.

  In order to improve the coverage, a curved surface having a curvature is formed at the upper end or the lower end of the insulator 614. For example, when positive photosensitive acrylic is used as a material for the insulator 614, it is preferable that only the upper end portion of the insulator 614 has a curved surface with a curvature radius (0.2 μm to 3 μm). As the insulator 614, either a negative type that becomes insoluble in an etchant by light irradiation or a positive type that becomes soluble in an etchant by light irradiation can be used.

  An EL layer 616 and a second electrode 617 are formed over the first electrode 613. Here, as a material used for the first electrode 613, various metals, alloys, electrically conductive compounds, and mixtures thereof can be used. In the case of using the first electrode as the anode, 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).

  For example, in addition to single layer films such as indium oxide-tin oxide film, indium oxide-zinc oxide film, titanium nitride film, chromium film, tungsten film, Zn film, and Pt film containing silicon, titanium nitride and aluminum are the main components. A laminated film having a three-layer structure of a titanium nitride film, a film containing aluminum as a main component, and a titanium nitride film can be used. Note that with a stacked structure, resistance as a wiring is low, good ohmic contact can be obtained, and a function as an anode can be obtained.

  The EL layer 616 is formed by various methods such as an evaporation method using an evaporation mask, an inkjet method, and a spin coating method. The EL layer 616 includes the light-emitting layer described in Embodiments 1 and 2. Further, as another material forming the EL layer 616, a low molecular compound or a high molecular compound (including an oligomer and a dendrimer) may be used. Further, as a material used for the EL layer, not only an organic compound but also an inorganic compound may be used.

  In addition, as a material used for the second electrode 617, various metals, alloys, electrically conductive compounds, and mixtures thereof can be used. In the case where the second electrode is used as a cathode, it is preferable to use a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (work function of 3.8 eV or less). For example, elements belonging to Group 1 or Group 2 of the periodic table of elements, that is, alkali metals such as lithium (Li) and cesium (Cs), and alkalis such as magnesium (Mg), calcium (Ca), and strontium (Sr) An earth metal, and an alloy (MgAg, AlLi) containing these are mentioned.

  Note that in the case where light generated in the EL layer 616 is transmitted through the second electrode 617, a thin metal film and a transparent conductive film (indium oxide-tin oxide (ITO)) are used as the second electrode 617. Alternatively, a stack of indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide (IZO), indium oxide containing tungsten oxide and zinc oxide (IWZO), or the like can be used.

  Further, the sealing substrate 604 is attached to the element substrate 610 with the sealant 605, whereby the light-emitting element 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealant 605. ing. Note that the space 607 is filled with a filler, and may be filled with a sealing material 605 in addition to an inert gas (such as nitrogen or argon).

  Further, an epoxy resin is preferably used for the sealant 605. 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 and a quartz substrate, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic, or the like can be used as a material for the sealing substrate 604.

As described above, a light-emitting device having the light-emitting element of the present invention can be obtained.
The light-emitting device includes the light-emitting element described in any of Embodiments 1 and 2. Therefore, a light-emitting device with a long lifetime can be obtained by including the light-emitting element of the present invention with a long lifetime. In addition, a light emitting device with excellent color purity can be obtained.

  As described above, in this embodiment mode, an active light-emitting device that controls driving of a light-emitting element using a transistor has been described. In addition to this, a light-emitting element is driven without particularly providing a driving element such as a transistor. A passive light emitting device may be used. FIG. 5 is a perspective view of a passive light emitting device manufactured by applying the present invention.

  In FIG. 5, an EL layer 955 is provided over the substrate 951 between the electrode 952 and the electrode 956. An end portion of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided over the insulating layer 953. The side wall of the partition wall layer 954 has an inclination such that the distance between one side wall and the other side wall becomes narrower as it approaches the substrate surface. That is, the cross section in the short side direction of the partition wall layer 954 has a trapezoidal shape, and the bottom side (the side facing the insulating layer 953 in the same direction as the surface direction of the insulating layer 953) is the top side (the surface of the insulating layer 953). The direction is the same as the direction and is shorter than the side not in contact with the insulating layer 953. In this manner, by providing the partition layer 954, defects in the light-emitting element due to static electricity or the like can be prevented. In addition, even in a passive light-emitting device, a light-emitting device with a long lifetime can be obtained by including the light-emitting element of the present invention with a long lifetime. In addition, a light emitting device with excellent color purity can be obtained.

(Embodiment 4)
In this embodiment mode, electronic devices of the present invention which include the light-emitting device described in Embodiment Mode 3 as a part thereof will be described. An electronic device of the present invention includes a display portion with a long lifetime which includes the light-emitting element described in Embodiments 1 and 2. In addition, since the light-emitting element with excellent color purity is included, a display portion with excellent color reproducibility can be obtained.

  As an electronic device manufactured using the light emitting device of the present invention, a video camera, a digital camera, a goggle type display, a navigation system, a sound reproducing device (car audio, audio component, etc.), a computer, a game device, a portable information terminal (mobile) Display device capable of playing back a recording medium such as a computer, a mobile phone, a portable game machine, or an electronic book), and a recording medium (specifically, a digital versatile disc (DVD)) and displaying the image And the like). Specific examples of these electronic devices are shown in FIGS.

  FIG. 6A illustrates a television device according to the present invention, which includes a housing 9101, a supporting base 9102, a display portion 9103, a speaker portion 9104, a video input terminal 9105, and the like. In this television device, the display portion 9103 is formed by arranging light-emitting elements similar to those described in Embodiments 1 and 2 in a matrix. The light-emitting element has a feature of long life. Since the display portion 9103 including the light-emitting elements has similar features, this television set has a feature of long life. That is, a television device that can withstand long-time use can be provided. In addition, since the light-emitting element with excellent color purity is included, a television device having a display portion with excellent color reproducibility can be obtained.

  FIG. 6B illustrates a computer according to the present invention, which includes a main body 9201, a housing 9202, a display portion 9203, a keyboard 9204, an external connection port 9205, a pointing mouse 9206, and the like. In this computer, the display portion 9203 is formed by arranging light-emitting elements similar to those described in Embodiments 1 and 2 in a matrix. The light-emitting element has a feature of long life. Since the display portion 9203 which includes the light-emitting elements has similar features, this computer has a feature that its life is long. That is, a computer that can withstand long-term use can be provided. In addition, since the light-emitting element with excellent color purity is included, a computer having a display portion with excellent color reproducibility can be obtained.

  6C illustrates a cellular phone according to the present invention, which includes a main body 9401, a housing 9402, a display portion 9403, an audio input portion 9404, an audio output portion 9405, operation keys 9406, an external connection port 9407, an antenna 9408, and the like. . In this cellular phone, the display portion 9403 is formed by arranging light-emitting elements similar to those described in Embodiments 1 and 2 in a matrix. The light-emitting element has a feature of long life. Since the display portion 9403 which includes the light-emitting elements has similar features, this mobile phone has a feature that its lifetime is long. That is, a mobile phone that can withstand long-term use can be provided. In addition, since the light-emitting element with excellent color purity is included, a mobile phone having a display portion with excellent color reproducibility can be obtained.

  6D illustrates a camera according to the present invention, which includes a main body 9501, a display portion 9502, a housing 9503, an external connection port 9504, a remote control receiving portion 9505, an image receiving portion 9506, a battery 9507, an audio input portion 9508, and operation keys 9509. , An eyepiece 9510 and the like. In this camera, the display portion 9502 includes light-emitting elements similar to those described in Embodiments 1 and 2, arranged in a matrix. The light-emitting element has a feature of long life. Since the display portion 9502 which includes the light-emitting elements has similar features, this camera has a feature that its life is long. That is, a camera that can withstand long-term use can be provided. In addition, since the light-emitting element with excellent color purity is included, a camera having a display portion with excellent color reproducibility can be obtained.

  As described above, the applicable range of the light-emitting device of the present invention is so wide that the light-emitting device can be applied to electronic devices in various fields. By using the light-emitting device of the present invention, an electronic device having a display portion with a long lifetime that can withstand long-time use can be provided. In addition, an electronic device having a display portion with excellent color reproducibility can be obtained.

The light-emitting device of the present invention can also be used as a lighting device. One mode in which the light-emitting element of the present invention is used as a lighting device will be described with reference to FIGS.
FIG. 7 illustrates an example of a liquid crystal display device using the light-emitting device of the present invention as a backlight. The liquid crystal display device illustrated in FIG. 7 includes a housing 901, a liquid crystal layer 902, a backlight 903, and a housing 904, and the liquid crystal layer 902 is connected to a driver IC 905. The backlight 903 uses the light-emitting device of the present invention, and a current is supplied from a terminal 906.

  By using the light emitting device of the present invention as a backlight of a liquid crystal display device, a backlight having a long lifetime can be obtained. Further, the light-emitting device of the present invention is a surface-emitting illumination device and can have a large area, so that the backlight can have a large area and a liquid crystal display device can have a large area. Further, since the light-emitting device of the present invention is thin and has low power consumption, the display device can be thinned and the power consumption can be reduced.

  FIG. 8 illustrates an example in which the light-emitting device to which the present invention is applied is used as a table lamp which is a lighting device. A table lamp illustrated in FIG. 8 includes a housing 2001 and a light source 2002, and the light-emitting device of the present invention is used as the light source 2002. Since the light emitting device of the present invention has a long life, the desk lamp also has a long life.

  FIG. 9 illustrates an example in which the light-emitting device to which the present invention is applied is used as an indoor lighting device 3001. Since the light-emitting device of the present invention can have a large area, it can be used as a large-area lighting device. In addition, since the light-emitting device of the present invention has a long lifetime, it can be used as a long-life lighting device. In this manner, in the room where the light-emitting device to which the present invention is applied is used as an indoor lighting device 3001, the television device 3002 according to the present invention as described with reference to FIG. Can be appreciated. In such a case, since both devices have a long life, the number of replacements of the lighting device and the television device can be reduced, and the load on the environment can be reduced.

  In this example, a light-emitting element of the present invention will be specifically described with reference to FIG. Structural formulas of organic compounds used in this example are shown below.

(Light emitting element 1)
First, indium oxide-tin oxide containing silicon oxide was formed over the glass substrate 2101 by a sputtering method, so that the first electrode 2102 was formed. The film thickness was 110 nm and the electrode area was 2 mm × 2 mm.

Next, the substrate on which the first electrode 2102 is formed is fixed to a substrate holder provided in the vacuum evaporation apparatus so that the surface on which the first electrode 2102 is formed is downward, and is approximately 10 ⁻⁴ Pa. After that, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) and molybdenum oxide (VI) are co-evaporated on the first electrode 2102. Thus, a layer 2103 containing a composite material was formed. The film thickness was 50 nm, and the weight ratio of NPB and molybdenum oxide (VI) was adjusted to 4: 1 = (NPB: molybdenum oxide). Note that the co-evaporation method is an evaporation method in which evaporation is performed simultaneously using a plurality of evaporation sources in one processing chamber.
Subsequently, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) was formed to a thickness of 10 nm by an evaporation method using resistance heating. Then, a hole transport layer 2104 was formed.

  Next, a light-emitting layer 2105 was formed over the hole-transport layer 2104. First, 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA) which is the first organic compound and the second organic compound are formed over the hole-transport layer 2104. By co-evaporating certain N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), the first light-emitting layer 2121 is formed to a thickness of 30 nm. It was formed with a film thickness. Here, the weight ratio of CzPA to 2PCAPA was adjusted to be 1: 0.05 (= CzPA: 2PCAPA).

  Further, over the first layer 2121, the fourth organic compound, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), and the third organic compound, N, N′-diphenylquinacridone (abbreviation) : DPQd) was co-evaporated to form the second layer 2122 with a thickness of 10 nm. Here, the weight ratio of Alq to DPQd was adjusted to be 1: 0.005 (= Alq: DPQd).

Subsequently, using a vapor deposition method using resistance heating, bathophenanthroline (abbreviation: BPhen) is formed to a thickness of 30 nm over the light-emitting layer 2105 to form an electron transport layer 2106, and then the electron transport layer 2106. An electron injection layer 2107 was formed by depositing lithium fluoride (LiF) to a thickness of 1 nm on the top.
Lastly, a second electrode 2108 was formed by depositing aluminum so as to have a thickness of 200 nm using a resistance heating vapor deposition method, whereby the light-emitting element 1 was manufactured.

(Comparative light emitting element 2)
First, indium oxide-tin oxide containing silicon oxide was formed over a glass substrate by a sputtering method to form a first electrode. The film thickness was 110 nm and the electrode area was 2 mm × 2 mm.

Next, the substrate on which the first electrode is formed is fixed to a substrate holder provided in the vacuum evaporation apparatus so that the surface on which the first electrode is formed is downward, and the pressure is reduced to about 10 ⁻⁴ Pa. Then, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) and molybdenum oxide (VI) are co-evaporated on the first electrode, A layer containing the composite material was formed. The film thickness was 50 nm, and the weight ratio of NPB and molybdenum oxide (VI) was adjusted to 4: 1 = (NPB: molybdenum oxide).
Then, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) was formed to a thickness of 10 nm by an evaporation method using resistance heating, A hole transport layer was formed.

  Next, a light emitting layer was formed on the hole transport layer. 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA) and N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazole- By co-evaporation with 3-amine (abbreviation: 2PCAPA), a light-emitting layer was formed with a thickness of 40 nm. Here, the weight ratio of CzPA to 2PCAPA was adjusted to be 1: 0.05 (= CzPA: 2PCAPA).

Thereafter, using a vapor deposition method using resistance heating, bathophenanthroline (abbreviation: BPhen) was formed to a thickness of 30 nm on the light emitting layer to form an electron transport layer.
On the electron transport layer, lithium fluoride (LiF) was formed to a thickness of 1 nm, thereby forming an electron injection layer.
Finally, a second electrode was formed by using a vapor deposition method using resistance heating to form a film of aluminum with a thickness of 200 nm, and a comparative light-emitting element 2 was manufactured.

FIG. 11 shows current density-luminance characteristics of the light-emitting element 1. Further, voltage-luminance characteristics are shown in FIG. Further, FIG. 13 shows luminance-current efficiency characteristics. Further, FIG. 14 shows an emission spectrum when a current of 1 mA is passed.
The light-emitting element 1 had a CIE chromaticity coordinate (x = 0.29, y = 0.62) at a luminance of 3000 cd / m ² and emitted green light. The current efficiency at a luminance of 3000 cd / m ² was 10.7 cd / A, the voltage was 5.8 V, and the current density was 29.4 mA / cm ² .

Further, regarding the light-emitting element 1, a continuous lighting test by constant current driving was performed at an initial luminance of 3000 cd / m ^2. As a result, the light-emitting element maintained a luminance of 89% of the initial luminance even after 640 hours. I found out. On the other hand, regarding the comparative light-emitting element 2, when a continuous lighting test was similarly performed with an initial luminance of 3000 cd / m ² , the luminance decreased to 76% of the initial luminance after 640 hours, which was higher than that of the light-emitting element 1. Life was short.
Therefore, it was found that by applying the present invention, a light-emitting element having a long lifetime can be obtained.

(Light emitting element 3)
In Example 2, a light-emitting element of the present invention will be specifically described with reference to FIG.
First, indium oxide-tin oxide containing silicon oxide was formed over the glass substrate 2101 by a sputtering method, so that the first electrode 2102 was formed. The film thickness was 110 nm and the electrode area was 2 mm × 2 mm.

Next, the substrate on which the first electrode 2102 is formed is fixed to a substrate holder provided in the vacuum evaporation apparatus so that the surface on which the first electrode 2102 is formed is downward, and is approximately 10 ⁻⁴ Pa. After that, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) and molybdenum oxide (VI) are co-evaporated on the first electrode 2102. Thus, a layer 2103 containing a composite material was formed. The film thickness was 50 nm, and the weight ratio of NPB and molybdenum oxide (VI) was adjusted to 4: 1 = (NPB: molybdenum oxide).
Then, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) was formed to a thickness of 10 nm by an evaporation method using resistance heating, A hole transport layer 2104 was formed.

  Next, a light-emitting layer 2105 was formed over the hole-transport layer 2104. First, 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA), which is a second organic compound, and the first organic compound are formed over the hole-transport layer 2104. By co-evaporating certain N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCAPA), the first light-emitting layer 2121 is formed to a thickness of 30 nm. It was formed with a film thickness. Here, the weight ratio of CzPA to 2PCAPA was adjusted to be 1: 0.05 (= CzPA: 2PCAPA).

  Further, over the first layer 2121, the fourth organic compound, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq), and the third organic compound, N, N′-diphenylquinacridone (abbreviation) : DPQd) was co-evaporated to form the second layer 2122 with a thickness of 10 nm. Here, the weight ratio of Alq to DPQd was adjusted to be 1: 0.005 (= Alq: DPQd).

Thereafter, Alq was deposited to a thickness of 30 nm on the light-emitting layer 2105 by an evaporation method using resistance heating, whereby an electron-transporting layer 2106 was formed.
Further, an electron injection layer 2107 was formed on the electron transport layer 2106 by depositing lithium fluoride (LiF) to a thickness of 1 nm.
Lastly, a second electrode 2108 was formed by using a vapor deposition method using resistance heating to form aluminum with a thickness of 200 nm, whereby the light-emitting element 3 was manufactured.

(Comparative light emitting element 4)
First, indium oxide-tin oxide containing silicon oxide was formed over a glass substrate by a sputtering method to form a first electrode. The film thickness was 110 nm and the electrode area was 2 mm × 2 mm.
Subsequently, the substrate on which the first electrode is formed is fixed to a substrate holder provided in the vacuum evaporation apparatus so that the surface on which the first electrode is formed is downward, and the pressure is reduced to about 10 ⁻⁴ Pa. Then, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) and molybdenum oxide (VI) are co-evaporated on the first electrode, A layer containing the composite material was formed. The film thickness was 50 nm, and the weight ratio of NPB and molybdenum oxide (VI) was adjusted to 4: 1 = (NPB: molybdenum oxide).

Next, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB) was formed to a thickness of 10 nm by an evaporation method using resistance heating. A hole transport layer was formed.
Subsequently, a light emitting layer was formed on the hole transport layer. 9- [4- (10-phenyl-9-anthryl) phenyl] -9H-carbazole (abbreviation: CzPA) and N- (9,10-diphenyl-2-anthryl) -N, 9-diphenyl-9H-carbazole- By co-evaporation with 3-amine (abbreviation: 2PCAPA), a light-emitting layer was formed with a thickness of 40 nm. Here, the weight ratio of CzPA to 2PCAPA was adjusted to be 1: 0.05 (= CzPA: 2PCAPA).

Then, using an evaporation method by resistance heating, Alq was deposited on the light emitting layer so as to have a thickness of 30 nm to form an electron transporting layer.
Furthermore, an electron injection layer was formed by depositing lithium fluoride (LiF) on the electron transport layer so as to have a thickness of 1 nm.
Finally, a second electrode was formed by depositing aluminum so as to have a thickness of 200 nm using a resistance heating vapor deposition method, and the comparative light-emitting element 4 was manufactured.

FIG. 15 shows current density-luminance characteristics of the light-emitting element 3. Further, voltage-luminance characteristics are shown in FIG. Further, FIG. 17 shows luminance-current efficiency characteristics. FIG. 18 shows an emission spectrum when a current of 1 mA is passed.
The light-emitting element 3 had a CIE chromaticity coordinate (x = 0.29, y = 0.62) at a luminance of 3000 cd / m ² and emitted green light. The current efficiency at a luminance of 3000 cd / m ² was 11.0 cd / A, the voltage was 8.0 V, and the current density was 28.3 mA / cm ² .

Further, regarding the light-emitting element 3, a continuous lighting test by constant current driving was performed at an initial luminance of 3000 cd / m ² , and 90% of the initial luminance was maintained even after 640 hours. I found out. On the other hand, the comparative light-emitting element 4 was similarly subjected to a continuous lighting test with an initial luminance of 3000 cd / m ^{2. As a} result, the luminance decreased to 88% of the initial luminance after 470 hours. Life was short.
Therefore, it was found that by applying the present invention, a light-emitting element having a long lifetime can be obtained.

  In this example, tris (8-quinolinolato) aluminum (III) (abbreviation: Alq) used for the second layer in the light-emitting element 1 and the light-emitting element 3 manufactured in Example 1 and Example 2, N, The reduction characteristics of N′-diphenylquinacridone (abbreviation: DPQd) were examined by cyclic voltammetry (CV) measurement. From the measurement, the LUMO levels of Alq and DPQd were obtained. For the measurement, an electrochemical analyzer (manufactured by BAS Co., Ltd., model number: ALS model 600A) was used.

As a solution in CV measurement, dehydrated dimethylformamide (DMF) (manufactured by Aldrich, 99.8%, catalog number: 22705-6) was used as a solvent, and tetra-n-butylammonium perchlorate (supporting electrolyte) ( n-Bu ₄ NClO ₄ ) (manufactured by Tokyo Chemical Industry Co., Ltd., catalog number; T0836) is dissolved to a concentration of 100 mmol / L, and the measurement target is further dissolved to a concentration of 1 mmol / L. did. In addition, as a working electrode, a platinum electrode (manufactured by BAS Co., Ltd., PTE platinum electrode), and as an auxiliary electrode, a platinum electrode (manufactured by BAS Inc., Pt counter electrode for VC-3 ( 5 cm)), and an Ag / Ag ⁺ electrode (manufactured by BAS Co., Ltd., RE5 non-aqueous solvent system reference electrode) was used as a reference electrode. In addition, the measurement was performed at room temperature (20-25 degreeC).

(Calculation of potential energy for the vacuum level of the reference electrode)
First, the potential energy (eV) with respect to the vacuum level of the reference electrode (Ag / Ag ⁺ electrode) used in Example 3 was calculated. That is, the Fermi level of the Ag / Ag ⁺ electrode was calculated. The redox potential of ferrocene in methanol is +0.610 [V vs. SHE] (reference: Christian R. Goldsmith et al., J. Am. Chem. Soc., Vol. 124, No. 1, 83-96, 2002). On the other hand, when the oxidation-reduction potential of ferrocene in methanol was determined using the reference electrode used in Example 3, it was +0.20 V [vs. Ag / Ag ⁺ ]. Therefore, it was found that the potential energy of the reference electrode used in Example 3 was 0.41 [eV] lower than that of the standard hydrogen electrode.

  Here, it is known that the potential energy from the vacuum level of the standard hydrogen electrode is −4.44 eV (reference: Toshihiro Onishi, Tamami Koyama, polymer EL material (Kyoritsu Shuppan), p. 64). -67). From the above, the potential energy with respect to the vacuum level of the reference electrode used in Example 3 was calculated to be −4.44−0.41 = −4.85 [eV].

(Measurement Example 1; Alq)
In this measurement example 1, the reduction reaction characteristics of Alq were examined by cyclic voltammetry (CV) measurement. The scan speed was 0.1 V / sec. The measurement results are shown in FIG. The reduction reaction characteristics were measured by scanning the potential of the working electrode with respect to the reference electrode from −0.69 V to −2.40 V and then from −2.40 V to −0.69 V.

As shown in FIG. 19, the reduction peak potential E _pc can be read as −2.20V, and the oxidation peak potential E _pa as −2.12V. Therefore, the half-wave potential (potential between E _pc and E _pa ) can be calculated as -2.16V. This means that Alq is -2.16 [V vs. Ag / Ag ⁺ ] is reduced by the electric energy, and this energy corresponds to the LUMO level. Here, as described above, since the potential energy with respect to the vacuum level of the reference electrode used in Example 3 is −4.85 [eV], the LUMO level of Alq is −4.85 − (− 2 .16) =-2.69 [eV].

(Measurement Example 2: DPQd)
In this measurement example 2, the reduction reaction characteristics of DPQd were examined by cyclic voltammetry (CV) measurement. The scan speed was 0.1 V / sec. The measurement results are shown in FIG. The reduction reaction characteristic was measured by scanning the potential of the working electrode with respect to the reference electrode from −0.40 V to −2.10 V and then from −2.10 V to −0.40 V. Further, DPQd was poor in solubility, and undissolved residue was generated even when an attempt was made to prepare a solution at a concentration of 1 mmol / L. Therefore, the supernatant was collected with the undissolved residue precipitated and used for measurement.

As shown in FIG. 20, the reduction peak potential E _pc can be read as −1.69 V, and the oxidation peak potential E _pa as −1.63 V. Therefore, the half-wave potential (potential between E _pc and E _pa ) can be calculated as −1.66V. This means that DPQd is −1.66 [V vs. Ag / Ag ⁺ ] is reduced by the electric energy, and this energy corresponds to the LUMO level. Here, as described above, since the potential energy with respect to the vacuum level of the reference electrode used in Example 3 is −4.85 [eV], the LUMO level of DPQd is −4.85 − (− 1. .66) = − 3.19 [eV].

When the LUMO levels of Alq and DPQd obtained as described above are compared, it can be seen that the LUMO level of DPQd is 0.50 [eV] lower than Alq. This means that DPQd acts as an electron trap by adding DPQd into Alq. Therefore, the device structures of Examples 1 and 2 in which DPQd is used as the third organic compound and Alq is used as the fourth organic compound in the second layer of the light emitting device of the present invention are suitable for the present invention. Structure.

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 light-emitting device of the present invention. 4A and 4B illustrate a light-emitting device of the present invention. 8A and 8B each illustrate an electronic device of the invention. 8A and 8B each illustrate an electronic device of the invention. The figure explaining the illuminating device of this invention. The figure explaining the illuminating device of this invention. 3A and 3B illustrate a light-emitting element of an example. FIG. 6 shows current density-luminance characteristics of the light-emitting element manufactured in Example 1. FIG. 6 shows voltage-luminance characteristics of the light-emitting element manufactured in Example 1. FIG. 11 shows luminance-current efficiency characteristics of the light-emitting element manufactured in Example 1. FIG. 6 shows an emission spectrum of the light-emitting element manufactured in Example 1. FIG. 6 shows current density-luminance characteristics of the light-emitting element manufactured in Example 2. FIG. 11 shows voltage-luminance characteristics of the light-emitting element manufactured in Example 2. FIG. 11 shows luminance-current efficiency characteristics of the light-emitting element manufactured in Example 2. FIG. 6 shows an emission spectrum of the light-emitting element manufactured in Example 2. The figure which shows the reduction-reaction characteristic of Alq. The figure which shows the reductive reaction characteristic of DPQd. 4A and 4B illustrate a light-emitting element of the present invention.

Explanation of symbols

101 substrate 102 first electrode 103 EL layer 104 second electrode 111 light emitting layer 112 hole transport layer 113 electron transport layer 121 first layer 122 second layer 301 substrate 302 first electrode 303 EL layer 304 second Electrode 311 Light-emitting layer 312 Hole transport layer 313 Electron transport layer 321 First layer 322 Second layer 501 First electrode 502 Second electrode 511 First light-emitting unit 512 Second light-emitting unit 513 Charge generation layer 601 Source side driving circuit 602 Pixel portion 603 Gate side driving circuit 604 Sealing substrate 605 Sealing material 607 Space 608 Lead wiring 609 FPC (flexible printed circuit)
610 Element substrate 611 TFT for switching
612 Current control TFT
613 First electrode 614 Insulator 616 EL layer 617 Second electrode 618 Light emitting element 623 N-channel TFT
624 P-channel TFT
901 Case 902 Liquid crystal layer 903 Backlight 904 Case 905 Driver IC
906 Terminal 951 Substrate 952 Electrode 953 Insulating layer 954 Partition layer 955 EL layer 956 Electrode 2001 Housing 2002 Light source 2101 Glass substrate 2102 First electrode 2103 Layer 2 containing composite material Hole transport layer 2105 Light emitting layer 2106 Electron transport layer 2107 Electron Injection layer 2108 Second electrode 2121 First light-emitting layer 2122 Second light-emitting layer 3001 Lighting device 3002 Television device 9101 Case 9102 Support base 9103 Display portion 9104 Speaker portion 9105 Video input terminal 9201 Main body 9202 Case 9203 Display portion 9204 Keyboard 9205 External connection port 9206 Pointing mouse 9401 Main body 9402 Case 9403 Display unit 9404 Audio input unit 9405 Audio output unit 9406 Operation key 9407 External connection port 9408 Antenna 95 01 Main body 9502 Display unit 9503 Case 9504 External connection port 9505 Remote control receiving unit 9506 Image receiving unit 9507 Battery 9508 Audio input unit 9509 Operation key 9510 Eyepiece unit

Claims (7)

Between the anode and cathode, has a light emitting layer,
The light emitting layer has a first layer and a second layer,
The first layer has a first organic compound and a second organic compound,
The second layer has a third organic compound and a fourth organic compound,
The first layer is in contact with the second layer and is provided between the second layer and the anode;
The first organic compound has a light-emitting property;
The second organic compound has an electron transport property,
The third organic compound has a light emitting property and an electron trapping property,
The light-emitting element, wherein the fourth organic compound has an electron transporting property. Between the anode and cathode, has a light emitting layer,
The light emitting layer has a first layer and a second layer,
The first layer has a first organic compound and a second organic compound,
The second layer has a third organic compound and a fourth organic compound,
The first layer is in contact with the second layer and is provided between the second layer and the anode;
The first organic compound has a light-emitting property;
The second organic compound has an electron transport property,
The third organic compound has a light emitting property and a lowest unoccupied orbital level lower by 0.3 eV or more than the lowest unoccupied orbital level of the fourth organic compound,
The light-emitting element, wherein the fourth organic compound has an electron transporting property. In claim 1 or claim 2,
Having a hole transport layer between the anode and the light emitting layer;
A light emitting element comprising an electron transport layer between the cathode and the light emitting layer. In any one of Claims 1 thru | or 3,
The light emitting element characterized in that the emission color of the first organic compound and the emission color of the third organic compound are the same color system. In any one of Claims 1 thru | or 4,
The difference between the peak value of the emission spectrum of the first organic compound and the peak value of the emission spectrum of the third organic compound is within 30 nm.   A light-emitting device comprising the light-emitting element according to claim 1.   An illuminating device comprising the light emitting element according to any one of claims 1 to 5.

Images