JP5084123B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light-emitting element that emits light by passing a thin film containing a light-emitting substance between electrodes, a display device using the light-emitting element, and an electronic device using the light-emitting element.

  Development of a display using a self-luminous thin-film light-emitting element that emits light when an electric current flows is being actively promoted.

  These thin-film light-emitting elements emit light when an electrode is connected to a single-layer or multi-layer thin film formed using organic, inorganic, or both, and an electric current is applied. Such thin-film light emitting devices are expected to have low power consumption, space saving, visibility, and the like, and further expansion of the market is expected in the future.

Among these, the function of the light-emitting element having a multilayer structure can be manufactured by dividing the function for each layer, so that an element that emits light more efficiently than before can be manufactured (see, for example, Non-Patent Document 1). .
C. W. Tan et al., Applied Physics Letters, Vol. 51, no. 12, 913-915 (1987)

  A thin-film light-emitting element having a multilayer structure sandwiches a light-emitting laminate composed of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and the like between a pair of electrodes, Light emission can be obtained by applying a higher voltage to one electrode than the other electrode. Among these, the hole injection layer, the hole transport layer, the electron transport layer, and the electron injection layer may include layers that are not used depending on the element structure.

  In order to form the light-emitting laminated body having the above-described configuration, a material having characteristics suitable for each is selected. However, it is necessary to select a material having characteristics suitable for each of the electrodes sandwiching the light-emitting laminated body.

  Specifically, a material having a high work function (about 4.0 eV or more) is used for an electrode that needs to be applied with a higher voltage than the other electrode, and a material having a low work function (about 3.8 eV or less) is used for the other electrode. It was necessary to choose the material.

  However, since these electrodes must be selected in consideration of film formation characteristics, film formation method, non-translucency, conductivity, and the like, the current selection range is very narrow.

  Therefore, an object of the present invention is to provide a light-emitting element or a light-emitting device that does not need to consider the work function of an electrode. It is another object of the present invention to provide a light-emitting element or a light-emitting device that can expand the selection range of electrode materials.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, A third layer, the first layer is a layer having a donor level, the second layer is a layer including a light-emitting substance or a stack including at least a layer containing a light-emitting substance, The first layer is a layer having an acceptor level, and the first layer, the second layer, the third layer, and the fourth layer are sequentially stacked, and the first electrode is in contact with the first layer. The second electrode is provided in contact with the third layer, and is generated from the second layer when the potential of the first electrode is set higher than the potential of the second electrode. It is characterized in that the holes are joined so as to be injected into the third layer.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, The third layer includes a fourth layer, the first layer and the fourth layer are layers having donor levels, and the second layer includes a layer containing a light-emitting substance or at least a light-emitting substance. The third layer is a layer having an acceptor level, and the first layer, the second layer, the third layer, and the fourth layer are sequentially stacked. The first electrode is provided in contact with the first layer, the second electrode is provided in contact with the fourth layer, and the potential of the first electrode is higher than the potential of the second electrode. When applied, the holes generated from the second layer and the electrons generated from the fourth layer are joined so as to be injected into the third layer.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, The third layer, the fourth layer, and the fifth layer are included, the first layer and the fourth layer are layers having donor levels, and the second layer includes a light-emitting substance. A third layer and a fifth layer are layers having an acceptor level, and the first layer, the second layer, the third layer, The fourth layer and the fifth layer are laminated in order, the first electrode is provided in contact with the first layer, the second electrode is provided in contact with the fifth layer, When the potential of the first electrode is set to be higher than the potential of the second electrode, holes generated from the second layer and electrons generated from the fourth layer are injected into the third layer. To join It is characterized in that is.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, A first layer having a higher electron mobility than holes and a second material capable of donating electrons to the first material. The second layer is a layer including a third substance having a higher hole mobility than electrons and a fourth substance capable of accepting electrons from the third substance, The third layer is a layer including a light-emitting substance or a layer including at least a light-emitting substance, and the first layer, the second layer, and the third layer are sequentially stacked. The second electrode is provided in contact with the first layer, the second electrode is provided in contact with the third layer, and the potential of the first electrode is When higher than the potential of the second electrode, holes generated from the second layer is characterized in that it is joined so as to be injected into the third layer.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, The first layer has a third layer and a fourth layer, and the first layer can donate electrons to the first substance having higher electron mobility than the hole and the first substance. A layer containing a second substance, wherein the second layer comprises a third substance having a higher hole mobility than electrons and a fourth substance capable of accepting electrons from the third substance. The third layer is a layer including a luminescent material or a laminate including at least a layer including a luminescent material, and the fourth layer is a fifth material having a higher electron mobility than holes. And a sixth material capable of donating electrons to the fifth material, wherein the first layer, the second layer, the third layer, and the fourth layer are in order. The first electrode is provided in contact with the first layer, the second electrode is provided in contact with the fourth layer, and the potential of the first electrode Is made higher than the potential of the second electrode, so that holes generated from the second layer and electrons generated from the fourth layer are injected into the third layer. It is characterized by that.

  One of the configurations of the light-emitting device of the present invention for solving the above-described problem is that a first layer, a second layer, and a first layer provided between the first electrode and the second electrode, A first layer having a third layer, a fourth layer, and a fifth layer, wherein the first layer has an electron mobility higher than that of holes; A layer containing a second substance that can be donated, and the second layer can accept electrons from a third substance having a higher hole mobility than electrons and the third substance. A layer containing a luminescent substance or a layered structure including at least a layer containing a luminescent substance, and the fourth layer has a mobility of electrons rather than holes. A layer containing a fifth material having a high value and a sixth material capable of donating an electron to the fifth material, and the fifth layer has a hole mobility higher than that of the electron. A seventh substance and an eighth substance capable of accepting electrons from the seventh substance, the first layer, the second layer, the third layer, and the fourth layer. And the fifth layer are laminated in order, the first electrode is provided in contact with the first layer, and the second electrode is provided in contact with the fifth layer. When the potential of the first electrode is made higher than the potential of the second electrode, holes generated from the second layer and electrons generated from the fourth layer are injected into the third layer. It is characterized by being joined as described above.

  In the light-emitting device of the present invention having the above-described structure, the work function need not be considered when selecting the material of the electrode. In addition, the selection range of the electrode material can be widened.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different modes, and those skilled in the art can easily understand that the modes and details can be variously changed without departing from the spirit and scope of the present invention. Is done. Therefore, the present invention is not construed as being limited to the description of this embodiment mode.

(Embodiment 1)
In this embodiment, the structure of the light-emitting device of the present invention will be described with reference to FIG. In the light-emitting device of the present invention, a light-emitting stacked body 104 including a light-emitting material, an acceptor level layer 105, and a donor level layer 103 are stacked in contact with each other. The first electrode 101 is provided in contact with the light-emitting stacked body 104 and the second electrode 106 is provided in contact with the layer 103 having a donor level. The light emitting stacked body 104, the layer 105 having an acceptor level, and the donor level are provided. The stack of layers 103 includes a light-emitting element having a structure sandwiched between the first electrode 101 and the second electrode 106. Although the light-emitting element is provided over an insulator 100 having a flat surface such as a substrate or an insulating film, the order of stacking from the insulator 100 having a flat surface may be stacked from the first electrode 101 (FIG. 1). (A)) may be stacked from the second electrode 106 (FIG. 1B).

  Light can be emitted from the light-emitting stack 104 by applying a voltage to the light-emitting element having the above structure so that the potential of the first electrode 101 is lower than the potential of the second electrode.

The layer 103 having a donor level includes a layer containing both an electron transporting material and an electron donating material capable of donating electrons to the electron transporting material, an N-type semiconductor layer, or an N-type semiconductor. It is formed by the layer containing. Examples of the electron transporting material include tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), and bis (10-hydroxybenzo [h ] -Quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), etc. Can be used. In addition, bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ) and other materials such as metal complexes 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-tert-butylphenyl) -4-phenyl-5- ( 4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2, 4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and the like can be used. Examples of the electron donating material that can give electrons to these electron transporting materials include alkali metals such as lithium and cesium, alkaline earth metals such as magnesium and calcium, and rare earth metals such as erbium and ytterbium. , And alloys containing these metals, metal compounds, and the like can be used, and an electron-donating material capable of electron donation is selected depending on the combination with the electron-transporting material. Further, a metal oxide typified by molybdenum oxide, zinc oxide, and titanium oxide may be included in the layer including the electron transporting material and the electron donating material. In addition, a metal compound such as a metal oxide can be used as the N-type semiconductor, and zinc oxide, zinc sulfide, zinc selenide, titanium oxide, or the like can be used.

The layer 105 having an acceptor level includes a layer containing both a hole-transporting material and an electron-accepting material capable of receiving electrons from the hole-transporting material, a P-type semiconductor layer, or a P-type layer. A layer including a semiconductor is formed. Examples of the hole transporting material include 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (abbreviation: α-NPD) and 4,4′-bis [N -(3-Methylphenyl) -N-phenyl-amino] -biphenyl (abbreviation: TPD) or 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine (abbreviation: TDATA) 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (abbreviation: MTDATA) and 4,4′-bis (N- (4- ( N, N-di-m-tolylamino) phenyl) -N-phenylamino) biphenyl (abbreviation: DNTPD) and other aromatic amine-based compounds (that is, having a benzene ring-nitrogen bond) and phthalocyanines (abbreviation: H ₂ Pc), copper Futaroshia Emissions (abbreviation: CuPc), or vanadyl phthalocyanine (abbreviation: VOPc), and the phthalocyanine compound and the like can be used. Examples of the electron-accepting material that can receive electrons from these hole-transporting materials include molybdenum oxide, vanadium oxide, 7,7,8,8, -tetracyanoquinodimethane (abbreviation). : TCNQ), 2,3-dicyanonaphthoquinone (abbreviation: DCNNQ), 2,3,5,6-tetrafluoro-7,7,8,8, -tetracyanoquinodimethane (abbreviation: F4-TCNQ), etc. An electron-accepting material capable of accepting electrons is selected depending on the combination with a hole-transporting material. As the P-type semiconductor, metal oxides such as molybdenum oxide, vanadium oxide, ruthenium oxide, cobalt oxide, nickel oxide, and copper oxide can be used.

  The light-emitting stacked body 104 is formed of a plurality of layers including at least a light-emitting layer, an electron transport layer between the light-emitting layer in the light-emitting stacked body 104 and the first electrode 101, and a layer in which the light-emitting material in the light-emitting stacked body 104 is dispersed. A hole transporting layer may be provided between the layer 105 having an acceptor level. These layers may or may not be provided, and only one of them may be provided. In addition, as the material for the hole transport layer and the electron transport layer, in accordance with the hole transport material in the layer having the acceptor level and the electron transport material in the layer having the donor level, respectively, Description is omitted. See each description. Note that the light-emitting stacked body 104 may have a single-layer structure including only a light-emitting layer.

There are roughly two types of light emitting layers in the light emitting laminate 104. One is a layer containing a light emitting material as a light emission center dispersed in a layer made of a material having an energy gap larger than that of the light emitting substance, and the other is a layer that constitutes the light emitting layer with only the light emitting material. However, the former is a preferable configuration because concentration quenching hardly occurs. As a light-emitting substance serving as a luminescent center, 4-dicyanomethylene-2-methyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (abbreviation: DCJT), 4 -Dicyanomethylene-2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran, perifrantene, 2,5-dicyano-1,4-bis ( 10-methoxy-1,1,7,7-tetramethyljulolidyl-9-enyl) benzene, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) aluminum (abbreviation: Alq _3), 9,9'-bianthryl, 9,10-diphenyl anthracene (abbreviation: DPA) and 9,10-bis (2-naphthyl) anthracene (abbreviation: DN ), 2,5,8,11-tetra -t- butyl perylene (abbreviation: TBP), and the like. As a base material for forming a layer in which the light emitting material is dispersed, an anthracene such as 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA) is used. Derivatives, carbazole derivatives such as 4,4′-bis (N-carbazolyl) biphenyl (abbreviation: CBP), tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum ( Abbreviations: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), Bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2-hydro A metal complex such as xylphenyl) benzoxazolate] zinc (abbreviation: ZnBOX) can be used. As a material that can form the light-emitting stacked body 104 using only a light-emitting substance, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA) And bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq).

The first electrode 101 is preferably formed using 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). Specific examples of the cathode material include elements belonging to Group 1 or Group 2 of the element periodicity, that is, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, and alloys containing them. In addition to (Mg: Ag, Al: Li) and compounds (LiF, CsF, CaF ₂ ), transition metals including rare earth metals can be used, but metals such as Al, Ag, ITO (including alloys) ).

  The second electrode 106 is formed of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron ( Conductivity such as Fe), cobalt (Co), copper (Cu), palladium (Pd), lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), etc. Metals or their alloys, or nitrides of metal materials (TiN), ITO (indium tin oxide), silicon-containing ITO, and indium oxide mixed with 2 to 20% zinc oxide (ZnO) It can be formed of a conductive film such as a metal oxide such as IZO (indium zinc oxide).

  In addition, when light emission is extracted from the second electrode, it may be formed of a conductive film having transparency. ITO (indium tin oxide), ITO containing silicon, and indium oxide are oxidized at 2 to 20%. In addition to a metal oxide such as IZO (indium zinc oxide) mixed with zinc (ZnO), an ultrathin metal such as Al or Ag is used. In addition, when light emission is extracted from the first electrode, a material with high reflectivity (Al, Ag, or the like) can be used.

  In the light-emitting device of the present invention in this embodiment mode, the layer 103 having the second donor level is provided in contact with the second electrode. Therefore, when a material for forming the second electrode is selected, It is not necessary to consider the work function. When selecting a material for forming the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

  In addition, regarding the material illustrated above, it is only an illustration to the last, and a practitioner can select suitably in the range which can maintain the effect of this invention.

In the light-emitting device of the present invention having the above structure, when a voltage is applied so that the potential of the second electrode 106 is higher than the potential of the first electrode 101, electrons are applied to the second electrode from the layer 103 having a donor level. Is injected. Further, holes are injected into the light-emitting stack 104 from the layer 105 having an acceptor level. Further, electrons are injected from the first electrode 101 into the light-emitting stack 104, and the electrons and holes injected in the light-emitting stack are recombined, so that light is emitted when the excited light-emitting material returns to the ground state. can get. Here, in the light-emitting device of the present invention, the second electrode 106 does not inject holes into the layer 103 having donor levels, but the layer 103 having donor levels injects electrons into the second electrode. Therefore, the work function of the second electrode 106 need not be considered. Accordingly, when selecting a material for forming the second electrode, it is not necessary to consider the work function. When selecting a material for forming the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

(Embodiment 2)
In this embodiment, the structure of the light-emitting device of the present invention will be described with reference to FIG. In the light-emitting device of the present invention, the layer 102 having the first donor level, the light-emitting stack 104, the layer 105 having the acceptor level, and the layer 103 having the second donor level are stacked in contact with each other. The first electrode 101 is provided in contact with the layer 102 having the first donor level, and the second electrode 106 is provided in contact with the layer 103 having the second donor level, and has the first donor level. The stack of the layer 102, the light-emitting stack 104, the layer 105 having an acceptor level, and the layer 103 having a second donor level has a structure sandwiched between the first electrode 101 and the second electrode 106. It has an element. In addition, the light-emitting element is stacked over an insulator 100 such as a substrate or an insulating film. The first electrode 101, the layer 102 having the first donor level, the light-emitting stacked body 104, the layer 105 having an acceptor level, and the second layer are sequentially stacked on the insulator 100 such as a substrate or an insulating film. The layer 103 having a donor level and the order of the second electrode 106 (FIG. 2A) or the order of the second electrode 106, the layer 103 having the second donor level, and the layer 105 having an acceptor level In this order, the light-emitting stacked body 104, the layer 102 having the first donor level, and the first electrode 101 are provided in this order (FIG. 2B).

  Light can be emitted from the light-emitting stack 104 by applying a voltage to the light-emitting element having the above structure so that the potential of the first electrode 101 is lower than the potential of the second electrode.

  The layer 102 having the first donor level and the layer 103 having the second donor level may be formed of different materials, but may be formed of the same material and have the donor level in Embodiment Mode 1. The layer 103 can be formed using the same material. See the description of the material forming the layer 103 having a donor level in Embodiment 1.

  The layer 105 having an acceptor level can also be formed using the same material as the layer 105 having an acceptor level in Embodiment 1. See the description of the material forming the layer 105 having an acceptor level in Embodiment 1.

  The same applies to the light-emitting stack 104 including a light-emitting material, but the electron injection layer and the electron transport layer in the light-emitting stack are provided between the layer 102 having the first donor level and the light-emitting layer. For other structures, refer to the description of the light-emitting stacked body 104 in Embodiment 1.

The first electrode 101 is preferably formed using 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). Specific examples of the cathode material include elements belonging to Group 1 or Group 2 of the element periodicity, that is, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, and alloys containing them. In addition to (Mg: Ag, Al: Li) and compounds (LiF, CsF, CaF ₂ ), transition metals including rare earth metals can be used, but metals such as Al, Ag, ITO (including alloys) ).

  The second electrode 106 is formed of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron ( Conductivity such as Fe), cobalt (Co), copper (Cu), palladium (Pd), lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), etc. Metals or their alloys, or nitrides of metal materials (TiN), ITO (indium tin oxide), silicon-containing ITO, and indium oxide mixed with 2 to 20% zinc oxide (ZnO) It can be formed of a conductive film such as a metal oxide such as IZO (indium zinc oxide).

  In addition, when light emission is extracted from the second electrode, it may be formed of a conductive film having transparency. ITO (indium tin oxide), ITO containing silicon, and indium oxide are oxidized at 2 to 20%. In addition to a metal oxide such as IZO (indium zinc oxide) mixed with zinc (ZnO), an ultrathin metal such as Al or Ag is used. In addition, when light emission is extracted from the first electrode, a material with high reflectivity (Al, Ag, or the like) can be used.

  In the light-emitting device of the present invention in this embodiment mode, the layer 103 having the second donor level is provided in contact with the second electrode. Therefore, when a material for forming the second electrode is selected, It is not necessary to consider the work function. When selecting a material for forming the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

  In addition, regarding the material illustrated above, it is only an illustration to the last, and a practitioner can select suitably in the range which can maintain the effect of this invention.

In the light-emitting device of the present invention having the above structure, when a voltage is applied so that the potential of the second electrode 106 is higher than the potential of the first electrode 101, the second layer 106 having the second donor level has a second potential. Electrons are injected into the electrode. Further, holes are injected into the light-emitting stack 104 from the layer 105 having an acceptor level. Further, electrons are injected into the light-emitting stack 104 from the layer 102 having the first donor level, and the electrons and holes injected in the light-emitting stack are recombined so that the excited light-emitting material is in the ground state. Luminescence is obtained when returning. Here, in the light emitting device of the present invention, the second electrode 106 does not inject holes into the layer 103 having the second donor level, but the layer 103 having the second donor level is the second electrode. Therefore, the work function of the second electrode 106 need not be considered. Accordingly, when selecting a material for forming the second electrode, it is not necessary to consider the work function. When selecting a material for forming the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

(Embodiment 3)
In this embodiment, the structure of the light-emitting device of the present invention will be described with reference to FIG. The light-emitting device of the present invention includes a layer 110 having a first acceptor level, a layer 102 having a first donor level, a light-emitting stack 104, a layer 105 having a second acceptor level, and a second donor level. Are stacked in contact with each other. The first electrode 101 is provided in contact with the layer 110 having the first acceptor level, and the second electrode 106 is provided in contact with the layer 103 having the second donor level, and has the first acceptor level. The stack of the layer 110, the first electron generation layer 102, the light emitting stack 104, the layer 105 having the second acceptor level, and the layer 103 having the second donor level is the first electrode. A light emitting element having a structure sandwiched between 101 and the second electrode 106 is provided. In addition, the light-emitting element is stacked over an insulator 100 such as a substrate or an insulating film. The order of stacking on the insulator 100 such as a substrate or an insulating film is the first electrode 101, the layer 110 having the first acceptor level, the layer 102 having the first donor level, the light emitting stack 104, The layer 105 having the second acceptor level, the layer 103 having the second donor level, and the second electrode 106 in this order (FIG. 3A) or the second electrode 106 and the second donor in this order. A layer 103 having a level, a layer 105 having a second acceptor level, a light-emitting stack 104, a layer 102 having a first donor level, a layer 110 having a first acceptor level, and a first electrode 101 (In FIG. 3B).

  Light can be emitted from the light-emitting stack 104 by applying a voltage to the light-emitting element having the above structure so that the potential of the first electrode 101 is lower than the potential of the second electrode.

  The layer 102 having the first donor level and the layer 103 having the second donor level may be formed of different materials, but may be formed of the same material and have the donor level in Embodiment Mode 1. The layer 103 can be formed using the same material. See the description of the material forming the layer 103 having a donor level in Embodiment 1.

  The layer 110 having the first acceptor level and the layer 105 having the second acceptor level may be formed of different materials, but may be formed of the same material and have the acceptor level in Embodiment Mode 1. The layer 105 can be formed using the same material. See the description of the material forming the layer 105 having an acceptor level in Embodiment 1.

  The same applies to the light-emitting stack 104 including a light-emitting material, but the electron injection layer and the electron transport layer in the light-emitting stack are provided between the layer 102 having the first donor level and the light-emitting layer. For other structures, refer to the description of the light-emitting stacked body 104 in Embodiment 1.

    The first electrode 101 and the second electrode 106 are made of aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo ), Iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti) ) And the like, or their alloys, or nitrides of metal materials (TiN), ITO (indium tin oxide), silicon-containing ITO, indium oxide with 2 to 20% zinc oxide ( A conductive film such as a metal oxide such as IZO (indium zinc oxide) mixed with ZnO) can be used.

  In addition, an electrode for extracting light emission may be formed of a conductive film having transparency, and ITO (indium tin oxide), ITO containing silicon, and indium oxide with 2 to 20% zinc oxide (ZnO). In addition to a mixed metal oxide such as IZO (indium zinc oxide), an ultrathin film of a metal such as Al or Ag is used. In addition, when light emission is extracted from the first electrode, a material with high reflectivity (Al, Ag, or the like) can be used.

  In the light-emitting device of the present invention in this embodiment mode, the layer 110 having the first acceptor level is provided in contact with the first electrode 101 and the layer 103 having the second donor level is the second. Therefore, when selecting a material for forming the first electrode 101 and the second electrode 106, the work function may not be taken into consideration. In addition, when materials for forming the first electrode 101 and the second electrode 106 are selected, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

  In addition, regarding the material illustrated above, it is only an illustration to the last, and a practitioner can select suitably in the range which can maintain the effect of this invention.

  In the light-emitting device of the present invention having the above structure, when a voltage is applied so that the potential of the second electrode 106 is higher than the potential of the first electrode 101, the first light-emitting device has a first level higher than that of the layer 110 having the first acceptor level. Holes are injected into the electrode 101, and electrons are injected into the second electrode from the layer 103 having the second donor level. Further, holes are injected into the light-emitting stacked body 104 from the layer 105 having the second acceptor level. Further, electrons are injected into the light-emitting stack 104 from the layer 102 having the first donor level, and the electrons and holes injected in the light-emitting stack are recombined so that the excited light-emitting material is in the ground state. Luminescence is obtained when returning. Here, in the light-emitting device of the present invention, the first electrode 101 does not inject electrons into the layer 110 having the first acceptor level, but the layer 110 having the first acceptor level is the first electrode 101. Holes are injected into the second electrode 106 and the second electrode 106 does not inject holes into the layer 103 having the second donor level, but the layer 103 having the second donor level has electrons in the second electrode. Therefore, the work functions of the first electrode 101 and the second electrode 106 need not be considered. Thus, when selecting materials for forming the first electrode 101 and the second electrode 106, the work function need not be taken into consideration. When selecting materials for forming the first electrode 101 and the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

(Embodiment 4)
Another embodiment of the present invention will be described. In this embodiment, an example in which the viewing angle characteristics of a light-emitting device are improved by appropriately adjusting the thickness of a layer having an acceptor level will be described. In this embodiment mode, the stacked structure and materials of the light-emitting element are the same as those in Embodiment Mode 1, and thus description thereof is omitted. Refer to Embodiment Modes 1 to 3.

  Light emitted from the light emitting element includes light that is emitted directly from the light emitting laminate 104 and light that is reflected once or multiple times. The directly emitted light and reflected and emitted light interfere with each other depending on the phase relationship, and the light emitted from the light emitting element is light synthesized as a result of the interference.

  Since the phase of light reflected when entering a large medium from a medium having a small refractive index is inverted, the first electrode 101 and the second electrode in the light-emitting element having the structure described in Embodiment 1 are used. Reflection at the interface between an electrode such as 106 and the layer in contact with the electrode inverts the phase of the reflected light. When the light reflected by the electrode interferes with the light emitted from the light emitting layer, the optical distance (refractive index × physical distance) between the light emitting layer and the electrode is (2m−1) λ / 4 (m Is a natural number of 1 or more, and λ is the center wavelength of light emitted from the light emitting layer), the change in spectral shape that occurs depending on the angle at which the light emission surface is viewed can be reduced and the current efficiency of the light emitting element Will also improve. The current efficiency represents how much luminance is obtained with respect to the flowed current, and the specified luminance can be obtained even with a small current as the efficiency is improved. Moreover, there is a tendency that the deterioration of the element is small.

  Since reflection is small between films with a small difference in refractive index, it can be ignored except for the reflection that occurs at the interface between the electrode and the film in contact with the electrode, so in this embodiment, only the reflection that occurs between the electrode and the film in contact with the electrode is considered. Focus on it.

  In the case of a light-emitting device that extracts light emission from the first electrode 101 side, reflection occurs at the second electrode 106. Therefore, in order to improve the current efficiency of the light emitting element in the light emitting device and reduce the change in spectral shape that occurs depending on the angle at which the light emission surface is viewed, from the position where light emission occurs to the surface of the second electrode 106. The optical distance (refractive index × physical distance) may be (2m−1) λ / 4 (m is a natural number of 1 or more, and λ is the center wavelength of light emitted from the light emitting layer).

  The light-emitting stacked body 104 may be formed of a single layer of a light-emitting layer containing a light-emitting material, but may have a plurality of structures including a layer such as an electron transport layer and a hole transport layer and a light-emitting layer. The light emitting layer may be a layer in which a light emitting material serving as a light emission center is dispersed, or may be a layer formed only of a light emitting material.

A plurality of layers made of different materials are provided from the position where the light emission occurs to the second electrode 106. In this embodiment mode, the layer 105 having an acceptor level and the layer 103 having a second donor level are included. The light-emitting stacked body 104 can also be said to be a layer located between the position where light emission occurs from the light emission position to the second electrode 106 in the film thickness. Further, when the light emitting laminate 104 is formed of a plurality of layers, different layers may be included. In such a configuration, the optical distance from the position where light emission occurs to the second electrode 106 can be obtained by summing the product of the refractive index of each film and the film thickness. -1) λ / 4 (m is a natural number of 1 or more, and λ is the center wavelength of light emitted from the light emitting layer). That is, the light emitting layer is 1, the second electrode 106 is j (j is an integer of 4 or more), and the layers existing between the layer containing the light emitting material and the second electrode 106 are sequentially numbered from the layer containing the light emitting material. , And the refractive index n with a certain number and the film thickness d as the refractive index and film thickness of the layer with the same number (ie, n ₁ , the refractive index of the layer containing the light emitting material, d _j That is, the film thickness of the second electrode 106), and the following formula (1) is satisfied.

  Since the light emitting layer has a certain thickness, and there are innumerable emission centers, the position where the light emission has occurred cannot be determined strictly. It has become.

  Here, it is necessary to adjust the film thickness in order to satisfy the above formula (1). A layer containing an organic substance as a main component has a low electron mobility, and the driving voltage increases when the thickness of the electron transporting material in which carriers are electrons and the layer having a donor level are increased. Therefore, in this embodiment mode, the above formula (1) is satisfied without largely increasing the driving voltage by adjusting the film thickness of the layer 105 having an acceptor level with relatively high conductivity in the layer mainly composed of an organic substance. It becomes possible to make it. Note that even if the layer has a donor level in which carriers are electrons, if the material that can donate electrons is contained in an electron transporting material such as lithium, the film thickness is set to satisfy the above formula. It can be used as a layer to be adjusted.

  In the case of a light-emitting element that extracts light emission from the second electrode 106 side, reflection occurs at the first electrode 101. Therefore, in order to improve the current efficiency of the light-emitting element and reduce the change in spectral shape that occurs depending on the angle at which the light emission surface is viewed, the optical distance from the position where light emission occurs to the surface of the first electrode 101 The distance (refractive index × physical distance) may be (2m−1) λ / 4 (m is a natural number of 1 or more, and λ is the center wavelength of light emitted from the light emitting layer).

  The light-emitting stacked body 104 may be formed of a single layer of a light-emitting layer containing a light-emitting material, but may have a plurality of structures including a layer such as an electron transport layer and a hole transport layer and a light-emitting layer. The light emitting layer may be a layer in which a light emitting material serving as a light emission center is dispersed, or may be a layer formed only of a light emitting material.

Now, several layers made of different materials are provided from the position where the light emission occurs to the first electrode 101. In this embodiment mode, the layer 102 has the first acceptor level. In addition, a layer containing a light-emitting material can also be said to be a layer in which half the film thickness is located between the position where light emission occurs and the first electrode 101. Further, when the light emitting layer is formed of a plurality of layers, different layers may be included. In such a configuration, the optical distance from the position where light emission occurs to the first electrode 101 can be obtained by adding the product of the refractive index of each film and the film thickness. That is, a layer containing a light emitting material is a layer existing between the layer containing the light emitting material and the first electrode 101, where 1 is the layer containing the light emitting material and j is the first electrode 101 (j is an integer of 4 or more). When the refractive index n and the film thickness d are set to the refractive index and film thickness of the layer numbered with the same number (that is, n ₁ , the refractive index of the layer containing the light emitting material) , D _j is the film thickness of the second electrode 106), and the following equation (2) is satisfied.

  In this formula, the light emitting layer has a certain thickness, and since there are innumerable emission centers, the position where light emission has occurred cannot be determined strictly. It is a formula with

  Here, it is necessary to adjust the film thickness in order to satisfy the above formula (2). In this embodiment mode, the above formula (2) is obtained without increasing the driving voltage by adjusting the film thickness of the layer 110 having the first acceptor level having a relatively high conductivity in the layer containing an organic substance as a main component. It becomes possible to satisfy. Note that in the case where the layer 110 having the first acceptor level is not provided, an electron is transported to an electron transporting material such as lithium even in a layer having a donor level in which carriers are electrons. In the case where a lot of substances that can be donated are contained, the film thickness can be adjusted by a layer having a donor level because it can be used as a layer for adjusting the film thickness in order to satisfy the above formula.

  In the case of a structure in which light is extracted from both the first electrode 101 and the second electrode 106, the above formulas (1) and (2) may be satisfied at the same time.

  When the light-emitting element has a structure as in this embodiment mode, a light-emitting device in which a change in emission spectrum depending on an angle at which a light emission extraction surface is viewed is reduced can be provided.

  This embodiment mode can be used in combination with any appropriate structure of Embodiment Modes 1 to 3.

(Embodiment 5)
In this embodiment mode, the display device of the present invention described in Embodiment Mode 1 or Embodiment Mode 2 will be described with reference to FIGS. Note that although an example in which an active matrix display device is manufactured is described in this embodiment mode, it is needless to say that the light-emitting device of the present invention can be applied to a passive matrix display device.

  First, after the first base insulating layer 51a and the second base insulating layer 51b are formed over the substrate 50, a semiconductor layer is further formed over the second base insulating layer 51b. (Fig. 4 (A))

  As a material of the substrate 50, glass, quartz, plastic (polyimide, acrylic, polyethylene terephthalate, polycarbonate, polyacrylate, polyethersulfone, or the like) can be used. These substrates may be used after being polished by CMP or the like, if necessary. In this embodiment, a glass substrate is used.

  The first base insulating layer 51a and the second base insulating layer 51b prevent an element such as an alkali metal or an alkaline earth metal in the substrate 50 that adversely affects the characteristics of the semiconductor film from diffusing into the semiconductor layer. Provided for this purpose. As a material, silicon oxide, silicon nitride, silicon oxide containing nitrogen, silicon nitride containing oxygen, or the like can be used. In this embodiment mode, the first base insulating layer 51a is formed using silicon nitride, and the second base insulating layer 51b is formed using silicon oxide. In this embodiment mode, the base insulating layer is formed of the first base insulating layer 51a and the second base insulating layer 51b. However, the base insulating layer may be formed of a single layer or a multilayer of two or more layers. It doesn't matter. In addition, it is not necessary to provide a base insulating layer as long as the diffusion of impurities from the substrate does not matter.

  A semiconductor layer formed subsequently is obtained by laser crystallization of an amorphous silicon film in this embodiment mode. An amorphous silicon film is formed to a thickness of 25 to 100 nm (preferably 30 to 60 nm) over the second base insulating layer 51b. As a manufacturing method, a known method such as a sputtering method, a low pressure CVD method or a plasma CVD method can be used. Then, hydrogen treatment is performed at 500 ° C. for 1 hour.

  Subsequently, the amorphous silicon film is crystallized using a laser irradiation apparatus to form a crystalline silicon film. In the laser crystallization of the present embodiment, an excimer laser is used, and a laser beam oscillated is processed into a linear beam spot using an optical system and irradiated to an amorphous silicon film to form a crystalline silicon film. Used as a semiconductor layer.

  Other methods for crystallization of the amorphous silicon film include a method for crystallization only by heat treatment and a method for heat treatment using a catalyst element that promotes crystallization. Examples of elements that promote crystallization include nickel, iron, palladium, tin, lead, cobalt, platinum, copper, and gold. Compared to the case where crystallization is performed only by heat treatment by using such an element, Since crystallization is performed at a low temperature for a short time, there is little damage to the glass substrate. When crystallization is performed only by heat treatment, the substrate 50 may be a quartz substrate resistant to heat.

  Subsequently, in order to control the threshold value in the semiconductor layer as required, a small amount of impurity addition, so-called channel doping is performed. In order to obtain a required threshold value, N-type or P-type impurities (phosphorus, boron, etc.) are added by an ion doping method or the like.

  After that, as shown in FIG. 4A, the semiconductor layer is patterned into a predetermined shape, and an island-shaped semiconductor layer 52 is obtained. Patterning is performed by applying a photoresist to the semiconductor layer, exposing a predetermined mask shape, baking, forming a resist mask on the semiconductor layer, and etching using the mask.

Subsequently, a gate insulating layer 53 is formed so as to cover the semiconductor layer 52. The gate insulating layer 53 is formed of an insulating layer containing silicon with a thickness of 40 to 150 nm by plasma CVD or sputtering. In this embodiment mode, silicon oxide is used.

  Next, the gate electrode 54 is formed over the gate insulating layer 53. The gate electrode 54 may be formed of an element selected from tantalum, tungsten, titanium, molybdenum, aluminum, copper, chromium, and niobium, or an alloy material or a compound material containing the element as a main component. Alternatively, a semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. Further, an AgPdCu alloy may be used.

  Further, although the gate electrode 54 is formed as a single layer in this embodiment mode, a stacked structure of two or more layers such as tungsten in the lower layer and molybdenum in the upper layer may be used. Even in the case where the gate electrode is formed as a stacked structure, the materials described in the preceding stage may be used. Moreover, the combination may be selected as appropriate. The gate electrode 54 is processed by etching using a mask using a photoresist.

  Subsequently, a high concentration impurity is added to the semiconductor layer 52 using the gate electrode 54 as a mask. Thus, the thin film transistor 70 including the semiconductor layer 52, the gate insulating layer 53, and the gate electrode 54 is formed.

  Note that there is no particular limitation on the manufacturing process of the thin film transistor, and it may be changed as appropriate so that a transistor with a desired structure can be manufactured.

  In this embodiment mode, a top-gate thin film transistor using a crystalline silicon film crystallized by laser crystallization is used; however, a bottom-gate thin film transistor using an amorphous semiconductor film is used for a pixel portion. It is also possible. As the amorphous semiconductor, not only silicon but also silicon germanium can be used. When silicon germanium is used, the concentration of germanium is preferably about 0.01 to 4.5 atomic%.

  Alternatively, a microcrystalline semiconductor film (semi-amorphous semiconductor) in which crystals of 0.5 nm to 20 nm can be observed in an amorphous semiconductor may be used. Microcrystals capable of observing 0.5 nm to 20 nm crystals are also called so-called microcrystals (μc).

Semi-amorphous silicon (also referred to as SAS) which is a semi-amorphous semiconductor can be obtained by glow discharge decomposition of a silicide gas. A typical silicide gas is SiH ₄ , and in addition, Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF _{4 and the} like can be used. The formation of the SAS can be facilitated by diluting the silicide gas with one or plural kinds of rare gas elements selected from hydrogen, hydrogen and helium, argon, krypton, and neon. It is preferable to dilute the silicide gas at a dilution ratio in the range of 10 times to 1000 times. The reaction generation of the film by glow discharge decomposition may be performed at a pressure in the range of 0.1 Pa to 133 Pa. The power for forming the glow discharge may be high frequency power of 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature is preferably 300 ° C. or less, and a substrate heating temperature of 100 to 250 ° C. is suitable.

The SAS formed in this way has a Raman spectrum shifted to a lower wavenumber than 520 cm ⁻¹ , and diffraction peaks of (111) and (220), which are considered to be derived from the Si crystal lattice in X-ray diffraction, are observed. Is done. In order to terminate dangling bonds (dangling bonds), hydrogen or halogen is contained at least 1 atomic% or more. As an impurity element in the film, impurities of atmospheric components such as oxygen, nitrogen, and carbon are desirably 1 × 10 ²⁰ cm ⁻¹ or less, and in particular, the oxygen concentration is 5 × 10 ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁹ / cm ³ or less. When the TFT is used, μ = 1 to 10 cm ² / Vsec.

  Further, this SAS may be further crystallized with a laser.

  Subsequently, an insulating film (hydrogenated film) 59 is formed of silicon nitride so as to cover the gate electrode 54 and the gate insulating layer 53. After the insulating film (hydrogenated film) 59 is formed, heating is performed at 480 ° C. for about 1 hour to activate the impurity element and hydrogenate the semiconductor layer 52.

  Subsequently, a first interlayer insulating layer 60 covering the insulating film (hydrogenated film) 59 is formed. As a material for forming the first interlayer insulating layer 60, silicon oxide, acrylic, polyimide, siloxane, an Iow-k material, or the like may be used. In this embodiment mode, the silicon oxide film is formed as the first interlayer insulating layer. (Fig. 4 (B))

  Next, a contact hole reaching the semiconductor layer 52 is opened. The contact hole can be formed by performing etching using a resist mask until the semiconductor layer 52 is exposed, and can be formed by either wet etching or dry etching. Note that etching may be performed once depending on conditions, or etching may be performed in a plurality of times. In addition, when etching is performed a plurality of times, both wet etching and dry etching may be used. (Fig. 4 (C))

Then, a conductive layer covering the contact hole and the first interlayer insulating layer 60 is formed. The conductive layer is processed into a desired shape, and the connection portion 61a, the wiring 61b, and the like are formed. Although this wiring may be a single layer of aluminum, copper, or the like, in this embodiment mode, a multilayer structure of molybdenum, aluminum, and molybdenum is used in the order of stacking. The laminated wiring may have a structure such as titanium, aluminum, titanium, titanium, titanium nitride, aluminum, or titanium. (Fig. 4 (D))

  Thereafter, a second interlayer insulating layer 63 is formed so as to cover the connection portion 61a, the wiring 61b, and the first interlayer insulating layer 60. As a material for the second interlayer insulating layer 63, a coating film of acrylic, polyimide, siloxane or the like having self-flatness can be suitably used. In this embodiment mode, siloxane is used as the second interlayer insulating layer 63. (Fig. 4 (E))

  Subsequently, an insulating layer may be formed using silicon nitride or the like over the second interlayer insulating layer 63. This is formed to prevent the second interlayer insulating layer 63 from being etched more than necessary in the subsequent etching of the pixel electrode. Therefore, when the ratio of the etching rate between the pixel electrode and the second interlayer insulating layer is large, it may not be provided. Subsequently, a contact hole that penetrates through the second interlayer insulating layer 63 and reaches the connection portion 61a is formed.

  Then, after forming the light-transmitting conductive layer so as to cover the contact hole and the second interlayer insulating layer 63 (or insulating layer), the light-transmitting conductive layer is processed to form the first light-emitting element in the thin film light-emitting element. Two electrodes 106 are formed. Here, the second electrode 106 is in electrical contact with the connecting portion 61a.

  The material of the first electrode 101 is aluminum (Al), silver (Ag), gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), strontium (Sr), titanium (Ti), etc. Metal having conductivity, or an alloy thereof, or nitride of metal material (TiN), ITO (indium tin oxide), ITO containing silicon, indium oxide with 2 to 20% zinc oxide (ZnO) It can be formed of a conductive film such as a mixed metal oxide such as indium zinc oxide (IZO).

In addition, an electrode for extracting light emission may be formed of a conductive film having transparency, and ITO (indium tin oxide), ITO containing silicon, and indium oxide with 2 to 20% zinc oxide (ZnO). In addition to a mixed metal oxide such as IZO (indium zinc oxide), an ultrathin film of a metal such as Al or Ag is used. In addition, when light emission is extracted from the first electrode, a material with high reflectivity (Al, Ag, or the like) can be used. In this embodiment mode, ITSO is used as the second electrode 106 (FIG. 5A).

  Next, an insulating layer made of an organic material or an inorganic material is formed so as to cover the second interlayer insulating layer 63 (or the insulating layer) and the second electrode 106. Subsequently, the insulating layer is processed so that part of the second electrode 106 is exposed, so that the partition wall 65 is formed. As the material of the partition wall 65, a photosensitive organic material (acrylic, polyimide, or the like) is preferably used, but it may be formed of an organic material or an inorganic material that does not have photosensitivity. Further, a black pigment or dye such as titanium black or carbon nitride may be dispersed in the material of the partition wall 65 by using a dispersing material or the like, and the partition wall 65 may be made black to be used like a black matrix. It is desirable that the end surface of the partition wall 65 facing the first electrode has a curvature and has a tapered shape in which the curvature continuously changes (FIG. 5B).

  Next, the second electrode 106 exposed from the partition wall 65 is covered, the layer 103 having the second donor level, the layer 105 having the acceptor level, the light-emitting stacked body 104, and the layer having the first donor level 102 are stacked in this order. These layers may be formed by vapor deposition.

The layer 102 having the first donor level and the layer 103 having the second donor level may be formed using different materials, but may be formed using the same material. These layers are formed of a layer containing both an electron donating material capable of donating electrons to the material, an N-type semiconductor layer, or a layer containing an N-type semiconductor. Examples of the electron transporting material include tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), and bis (10-hydroxybenzo [h ] -Quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), etc. Can be used. In addition, bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ) and other materials such as metal complexes 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-tert-butylphenyl) -4-phenyl-5- ( 4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2, 4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproin (abbreviation: BCP), and the like can be used. Examples of the electron donating material that can give electrons to these electron transporting materials include alkali metals such as lithium and cesium, alkaline earth metals such as magnesium and calcium, and rare earth metals such as erbium and ytterbium. , And alloys containing these metals, metal compounds, and the like can be used, and an electron-donating material capable of electron donation is selected depending on the combination with the electron-transporting material. Further, a metal oxide typified by molybdenum oxide, zinc oxide, and titanium oxide may be included in the layer including the electron transporting material and the electron donating material. As the N-type semiconductor, zinc oxide, zinc sulfide, zinc selenide, titanium oxide, titanium oxide, or the like can be used.

  Note that a layer containing a plurality of materials, such as a layer containing an electron transporting material and an electron donating material, can be formed by simultaneously forming each material, and co-evaporation by resistance heating evaporation , Co-evaporation method by electron beam evaporation, co-evaporation method by resistance heating evaporation and electron beam evaporation, film formation by resistance heating evaporation and sputtering, film formation by electron beam evaporation and sputtering, etc. do it. Moreover, although the said example assumes the layer containing 2 types of materials, when it contains 3 or more types of materials, it can form similarly.

The mixing ratio of the electron transporting material and the material capable of donating electrons to the electron transporting material may be about 1: 0.5 to 1: 2, preferably 1: 1. It is a layer having a donor level in this embodiment using a lithium (Li) as an electron donating material which can donate electrons to Alq _3, Alq ₃ as a material having an electron-transporting property, a weight ratio Deposition is performed by a co-evaporation method so that Alq ₃ : Li = 1: 0.01. The film thickness is 10 nm.

  The light-emitting stacked body 104 may be formed of a single layer or a plurality of layers, and an electron transporting layer between the light-emitting layer in the light-emitting stacked body 104 and the first electrode 101, and a light-emitting material in the light-emitting stacked body 104 A hole transporting layer may be provided between the layer in which is dispersed and the layer 105 having an acceptor level. These layers may or may not be provided, and only one of them may be provided. In addition, as the material for the hole transport layer and the electron transport layer, in accordance with the hole transport material in the layer having the acceptor level and the electron transport material in the layer having the donor level, respectively, Description is omitted. See each description.

There are roughly two types of light emitting layers in the light emitting laminate 104. One is a layer containing a light emitting material as a light emission center dispersed in a layer made of a material having an energy gap larger than that of the light emitting substance, and the other is a layer that constitutes the light emitting layer with only the light emitting material. However, the former is a preferable configuration because concentration quenching hardly occurs. As a light-emitting substance serving as a light emission center, for example, 4-dicyanomethylene-2-methyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran (abbreviation: DCJT) 4-dicyanomethylene-2-t-butyl-6- (1,1,7,7-tetramethyljulolidyl-9-enyl) -4H-pyran, perifrantene, 2,5-dicyano-1,4- Bis (10-methoxy-1,1,7,7-tetramethyljulolidyl-9-enyl) benzene, N, N′-dimethylquinacridone (abbreviation: DMQd), coumarin 6, coumarin 545T, tris (8-quinolinolato) ) aluminum (abbreviation: Alq _3), 9,9'-bianthryl, 9,10-diphenyl anthracene (abbreviation: DPA) and 9,10-bis (2-naphthyl) anthracene (abbreviation : DNA), 2,5,8,11-tetra-t-butylperylene (abbreviation: TBP), 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA) and the like. Can be mentioned. In addition, as a base material in forming a layer in which the light emitting material is dispersed, for example, 9,10-di (2-naphthyl) -2-tert-butylanthracene (abbreviation: t-BuDNA) Anthracene derivatives, carbazole derivatives such as 4,4′-bis (N-carbazolyl) biphenyl (abbreviation: CBP), tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (4-methyl-8-quinolinolato) Aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq ), Bis [2- (2-hydroxyphenyl) pyridinato] zinc (abbreviation: Znpp ₂ ), bis [2- (2 Metal complexes such as -hydroxyphenyl) benzoxazolate] zinc (abbreviation: ZnBOX) can be used. As a material that can form the light-emitting stacked body 104 using only a light-emitting substance, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), 9,10-bis (2-naphthyl) anthracene (abbreviation: DNA) And bis (2-methyl-8-quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq).

In this embodiment, a hole transport layer, a light-emitting layer in which a light-emitting material is dispersed, and an electron transport layer are sequentially formed as the light-emitting stacked body 104 over the layer 105 having an acceptor level. As a hole transport layer, α-NPD has a thickness of 10 nm. As a layer in which a light emitting material is dispersed, Alq ₃ and coumarin 6 have a weight ratio of 1: 0.005, a thickness of 35 nm. As an electron transport layer, Alq ₃ has a film. Vapor deposition is performed to a thickness of 10 nm.

The layer 105 having an acceptor level includes a layer containing both a hole-transporting material and an electron-accepting material capable of receiving electrons from the hole-transporting material, a P-type semiconductor layer, or a P-type layer. A layer including a semiconductor is formed. Examples of the hole transporting material include 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl (abbreviation: α-NPD) and 4,4′-bis [N -(3-Methylphenyl) -N-phenyl-amino] -biphenyl (abbreviation: TPD) or 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine (abbreviation: TDATA) 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (abbreviation: MTDATA) and 4,4′-bis (N- (4- ( N, N-di-m-tolylamino) phenyl) -N-phenylamino) biphenyl (abbreviation: DNTPD) and other aromatic amine-based compounds (that is, having a benzene ring-nitrogen bond) and phthalocyanines (abbreviation: H2Pc) ), Copper lid Russia Emissions (abbreviation: CuPc), or vanadyl phthalocyanine (abbreviation: VOPc), and the phthalocyanine compound and the like can be used. Examples of the electron-accepting material that can receive electrons from these hole-transporting materials include molybdenum oxide, vanadium oxide, 7,7,8,8, -tetracyanoquinodimethane (abbreviation). : TCNQ), 2,3-dicyanonaphthoquinone (abbreviation: DCNNQ), 2,3,5,6-tetrafluoro-7,7,8,8, -tetracyanoquinodimethane (abbreviation: F4-TCNQ), etc. An electron-accepting material capable of accepting electrons is selected depending on the combination with a hole-transporting material. As the P-type semiconductor, molybdenum oxide, vanadium oxide, ruthenium oxide, cobalt oxide, nickel oxide, copper oxide, or the like can be used. It should be noted that the materials listed here are merely examples and can be appropriately selected by the practitioner. The mixing ratio of the electron-accepting material to the hole-transporting material between the material having hole-transporting property and the material having electron-transporting property from the material having hole-transporting property may be 0.5 or more in molar ratio. , Preferably 0.5-2. In the layer having the first acceptor level and the layer having the second acceptor level in this embodiment, electrons that can accept electrons from α-NPD and α-NPD as materials having an electron transporting property Molybdenum oxide (MoO _x ) is used as a receptive material, and film formation is performed so that α-NPD: MoO _x = 4: 0.2 (corresponding to 1 in molar ratio) by weight. Note that in this embodiment mode, the thickness of the layer having the first acceptor level is 50 nm, and the layer having the second acceptor level is 20 nm.

  Note that a layer including a plurality of materials such as a layer including a hole transporting material and an electron accepting material can be formed by forming each material at the same time, and can be formed by resistance heating evaporation. Combination of the same and different methods such as vapor deposition, co-evaporation by electron beam evaporation, co-evaporation by resistance heating evaporation and electron beam evaporation, film formation by resistance heating evaporation and sputtering, film formation by electron beam evaporation and sputtering, etc. What is necessary is just to form. Moreover, although the said example assumes the layer containing 2 types of materials, when it contains 3 or more types of materials, it can form similarly.

  The light emitting element may be configured to perform color display by forming light emitting elements having different emission wavelength bands for each pixel. Typically, a light emitting element corresponding to each color of R (red), G (green), and B (blue) is formed. In this case as well, by providing a filter (colored layer) that transmits light in the emission wavelength band on the light emission side of the pixel, the color purity is improved and the pixel portion is mirrored (reflected). Prevention can be achieved. By providing the filter (colored layer), it is possible to omit a circularly polarizing plate that has been conventionally required, and it is possible to eliminate the loss of light emitted from the light emitting element. Furthermore, a change in color tone that occurs when the pixel portion (display screen) is viewed obliquely can be reduced.

  In addition, the light-emitting element can have a structure that emits monochromatic or white light. In the case of using a white light emitting material, color display can be made possible by providing a filter (colored layer) that transmits light of a specific wavelength on the light emission side of the pixel.

To form a light emitting layer that emits white light, for _{example, Alq 3, Alq 3, Alq} 3 doped with Nile Red which is partly red light emitting pigment, p-EtTAZ, by TPD (aromatic diamine) evaporation A white color can be obtained by sequentially laminating.

  Furthermore, a triplet excitation material containing a metal complex or the like may be used for the light emitting layer in addition to a singlet excitation light emitting material. For example, among red light emitting pixels, green light emitting pixels, and blue light emitting pixels, a red light emitting pixel having a relatively short luminance half time is formed of a triplet excitation light emitting material, and the other A singlet excited luminescent material is used. The triplet excited luminescent material has a feature that the light emission efficiency is good, so that less power is required to obtain the same luminance. That is, when applied to a red pixel, the amount of current flowing through the light emitting element can be reduced, so that reliability can be improved. As a reduction in power consumption, a red light-emitting pixel and a green light-emitting pixel may be formed using a triplet excitation light-emitting material, and a blue light-emitting pixel may be formed using a singlet excitation light-emitting material. By forming a green light-emitting element having high human visibility with a triplet excited light-emitting material, power consumption can be further reduced.

  Examples of triplet excited luminescent materials include those using a metal complex as a dopant, and metal complexes having a third transition series element platinum as the central metal and metal complexes having iridium as the central metal are known. Yes. The triplet excited light-emitting material is not limited to these compounds, and a compound having the above structure and having an element belonging to group 8 to 10 in the periodic table as a central metal can also be used.

  A light-emitting element formed using the above materials emits light by being forward-biased. A pixel of a display device formed using a light-emitting element can be driven by a simple matrix method or an active matrix method. In any case, each pixel emits light by applying a forward bias at a specific timing, but is in a non-light emitting state for a certain period. By applying a reverse bias during this non-light emitting time, the reliability of the light emitting element can be improved. The light emitting element has a degradation mode in which the emission intensity decreases under a constant driving condition and a degradation mode in which the non-light emitting area is enlarged in the pixel and the luminance is apparently decreased. By performing a typical drive, the progress of deterioration can be slowed and the reliability of the light emitting device can be improved.

Subsequently, the first electrode 101 that covers the light-emitting stacked body 66 is formed. Thus, a light-emitting element 93 including the first electrode 101, the light-emitting stack 66, and the second electrode 106 can be manufactured. As a cathode material used for forming the first electrode 101, 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). Specific examples of the cathode material include elements belonging to Group 1 or Group 2 of the element periodicity, that is, alkali metals such as Li and Cs, and alkaline earth metals such as Mg, Ca, and Sr, and alloys containing them. In addition to (Mg: Ag, Al: Li) and compounds (LiF, CsF, CaF ₂ ), transition metals including rare earth metals can be used, but metals such as Al, Ag, ITO (including alloys) ). In this embodiment, aluminum is used as the cathode.

  In the light-emitting element having the above structure, the layer 103 having the second donor level is provided in contact with the second electrode. Therefore, when the material for forming the second electrode is selected, There is no need to consider functions. When selecting a material for forming the second electrode, the range of material selection is widened. Thereby, a material more suitable for the structure of the light emitting device can be used.

  In the present embodiment, the electrode that is in electrical contact with the connection portion 61 a is the second electrode 106, but the electrode that is in electrical contact with the connection portion 61 a is the first electrode 101. There may be. In this case, the first electrode 101 is covered, the layer 102 having the first donor level, the light-emitting stack 104, the layer 105 having the acceptor level, and the layer 103 having the second donor level in this order. May be laminated.

Thereafter, a silicon oxide film containing nitrogen is formed as a second passivation film by a plasma CVD method. In the case of using a silicon oxide film containing nitrogen, a silicon oxynitride film manufactured from SiH ₄ , N ₂ O, NH ₃ by a plasma CVD method, or a silicon oxynitride film manufactured from SiH ₄ , N ₂ O, Alternatively, a silicon oxynitride film formed from a gas obtained by diluting SiH ₄ or N ₂ O with Ar may be formed.

Alternatively, a silicon oxynitride silicon film formed from SiH ₄ , N ₂ O, and H ₂ may be applied as the first passivation film. Needless to say, the first passivation film is not limited to a single layer structure, and another insulating layer containing silicon may be used as a single layer structure or a stacked structure. Further, a multilayer film of a carbon nitride film and a silicon nitride film, a multilayer film of styrene polymer, a silicon nitride film, or a diamond-like carbon film may be formed instead of the silicon oxide film containing nitrogen.

  Subsequently, the display portion is sealed in order to protect the light emitting element from a substance that promotes deterioration such as water. In the case where the counter substrate is used for sealing, bonding is performed with an insulating sealing material so that the external connection portion is exposed. A space between the counter substrate and the element substrate may be filled with an inert gas such as dry nitrogen, or a sealing material may be applied to the entire surface of the pixel portion to bond the counter substrate. It is preferable to use an ultraviolet curable resin or the like for the sealing material. The sealing material may contain a desiccant or particles for keeping the gap between the substrates constant. Subsequently, the display device is completed by attaching a flexible wiring board to the external connection portion.

  One example of the structure of the display device manufactured as described above will be described with reference to FIG. In addition, even if the shapes are different, parts showing similar functions are denoted by the same reference numerals, and explanations thereof are omitted. In this embodiment mode, the thin film transistor 70 having an LDD structure is connected to the light emitting element 93 through the connection portion 61a.

  FIG. 6A illustrates a structure in which the first electrode 101 is formed using a light-transmitting conductive film, and light emitted from the light-emitting stack 66 is extracted to the substrate 50 side. Reference numeral 94 denotes a counter substrate, which is fixed to the substrate 50 by using a sealing material or the like after the light emitting element 93 is formed. Filling the counter substrate 94 with the light-transmitting resin 88 or the like between the elements and sealing them can prevent the light-emitting element 93 from being deteriorated by moisture. Further, it is desirable that the resin 88 has a hygroscopic property. Furthermore, it is a more desirable mode because it is possible to further suppress the influence of moisture when a highly transparent desiccant 89 is dispersed in the resin 88.

  FIG. 6B illustrates a structure in which both the first electrode 101 and the second electrode 106 are formed using a light-transmitting conductive film, and light can be extracted to both the substrate 50 and the counter substrate 94. It has become. Further, in this configuration, by providing the polarizing plate 90 outside the substrate 50 and the counter substrate 94, it is possible to prevent the screen from being seen through, and visibility is improved. A protective film 91 may be provided outside the polarizing plate 90.

  Note that either an analog video signal or a digital video signal may be used for the display device of the present invention having a display function. When a digital video signal is used, the video signal is classified into one using a voltage and one using a current. When the light emitting element emits light, the video signal input to the pixel has a constant voltage and a constant current. When the video signal has a constant voltage, the voltage applied to the light emitting element is constant. And the current flowing through the light emitting element is constant. In addition, a video signal having a constant current includes a constant voltage applied to the light emitting element and a constant current flowing in the light emitting element. A constant voltage applied to the light emitting element is constant voltage driving, and a constant current flowing through the light emitting element is constant current driving. In constant current driving, a constant current flows regardless of the resistance change of the light emitting element. The light emitting display device and the driving method thereof according to the present invention may be any of the methods described above.

  In the display device of the present invention formed by a method as in this embodiment mode, the work function need not be taken into consideration when the material of the second electrode 106 of the light-emitting element included in the light-emitting device is selected. In addition, when a material for forming the second electrode 106 is selected, the range of material selection is widened. Accordingly, a material more suitable for the structure of the light emitting element can be used.

  This embodiment mode can be used in combination with any appropriate structure in Embodiment Modes 1 to 4.

(Embodiment 6)
In this embodiment, the appearance of a panel of a light-emitting device that corresponds to one embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a top view of a panel in which a transistor and a light-emitting element formed over a substrate are sealed with a sealing material formed between a counter substrate 4006 and FIG. 7B is a cross-sectional view of FIG. It corresponds to. The structure of the light-emitting element mounted on this panel is that the layer in contact with the electrode is a layer having a donor level, and the light-emitting stack and the layer having an acceptor level are sandwiched between layers having a donor level. It has a structure.

  A sealant 4005 is provided so as to surround the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 which are provided over the substrate 4001. A counter substrate 4006 is provided over the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004. Therefore, the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 are sealed together with the filler 4007 by the substrate 4001, the sealant 4005, and the counter substrate 4006.

  The pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004 provided over the substrate 4001 include a plurality of thin film transistors. In FIG. 7B, the thin film transistor 4008 included in the signal line driver circuit 4003 is provided. And a thin film transistor 4010 included in the pixel portion 4002.

  The light emitting element 4011 is electrically connected to the thin film transistor 4010.

  The lead wiring 4014 corresponds to a wiring for supplying a signal or a power supply voltage to the pixel portion 4002, the signal line driver circuit 4003, and the scan line driver circuit 4004. The lead wiring 4014 is connected to the connection terminal 4016 via the lead wiring 4015a and the lead wiring 4015b. The connection terminal 4016 is electrically connected to a terminal included in a flexible printed circuit (FPC) 4018 through an anisotropic conductive film 4019.

  Note that as the filler 4007, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used, and polyvinyl chloride, acrylic, polyimide, epoxy resin, silicon resin, polyvinyl butyral, Alternatively, ethylene vinylene acetate can be used.

  Note that the light-emitting device of the present invention includes in its category a panel in which a pixel portion having a light-emitting element is formed and a module in which an IC is mounted on the panel.

  In the panel and the module having the structure as in this embodiment mode, the work function need not be considered when selecting the material of the second electrode 106 of the light-emitting element included in the panel and the module. In addition, when a material for forming the second electrode 106 is selected, the range of material selection is widened. Accordingly, a material suitable for the configuration and required performance of the light-emitting element can be used, and a panel and a module with high display quality can be easily obtained.

  This embodiment mode can be combined with any suitable structure in Embodiment Modes 1 to 5.

(Embodiment 7)
As an electronic device of the present invention on which a module whose example is shown in Embodiment 6 is mounted, a video camera, a digital camera, a goggle-type display (head-mounted display), a navigation system, a sound reproduction device (car audio component, etc.) A recording medium such as a computer, a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine, electronic book, etc.), an image reproducing device (specifically Digital Versatile Disc (DVD)) equipped with a recording medium And a device having a display capable of reproducing and displaying the image). Specific examples of these electronic devices are shown in FIGS.

  FIG. 8A illustrates a light-emitting display device, such as a television receiver or a personal computer monitor. A housing 2001, a display portion 2003, a speaker portion 2004, and the like are included. The light-emitting display device of the present invention can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element included in the display portion 2003, and has high display quality. In order to increase the contrast in the pixel portion, a polarizing plate or a circular polarizing plate may be provided. For example, a film may be provided on the sealing substrate in the order of a 1 / 4λ plate, a 1 / 2λ plate, and a polarizing plate. Further, an antireflection film may be provided on the polarizing plate.

  FIG. 8B illustrates a cellular phone, which includes a main body 2101, a housing 2102, a display portion 2103, a voice input portion 2104, a voice output portion 2105, operation keys 2106, an antenna 2108, and the like. The mobile phone of the present invention can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element included in the display portion 2103, and has high display quality.

  FIG. 8C illustrates a computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The computer of the present invention can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element included in the display portion 2203, and is a computer with high display quality. Although FIG. 8C illustrates a laptop computer, the present invention can also be applied to a desktop computer in which a hard disk and a display portion are integrated.

  FIG. 8D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The mobile computer of the present invention can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element included in the display portion 2302, and is a mobile computer with high display quality.

  FIG. 8E illustrates a portable game machine which includes a housing 2401, a display portion 2402, speaker portions 2403, operation keys 2404, a recording medium insertion portion 2405, and the like. The portable game machine of the present invention can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element of the display portion 2402, and is a portable game machine with high display quality.

As described above, the applicable range of the present invention is so wide that it can be used for electronic devices in various fields.
(Embodiment 8)

  FIG. 9 shows an example of bottom emission, double side emission, and top emission. The structure whose manufacturing process is described in Embodiment Mode 2 corresponds to the structure in FIG. 9A and 9B, the first interlayer insulating layer 900 in FIG. 9C is formed of a material having self-planarity, and a wiring connected to the thin film transistor 901 and the first electrode 101 of the light-emitting element are provided. This is a configuration when formed on the same interlayer insulating layer. FIG. 9A illustrates a structure of bottom emission in which only the first electrode 101 of the light-emitting element is formed using a light-transmitting material and light is emitted toward the lower portion of the light-emitting device, and FIG. By forming a light-transmitting material such as ITSO or IZO as the second electrode 106, a light-emitting display device that emits light from both sides as shown in FIG. 9B can be obtained. . Note that although the film is non-light-transmitting when formed with a thick film such as aluminum or silver, the light-transmitting property is obtained when the film is thinned; Even if formed, double-sided light emission can be achieved.

(Embodiment 9)

  In this embodiment mode, pixel circuits and protection circuits included in the panel and module described in Embodiment Mode 6 and operations thereof will be described. Note that the cross-sectional views shown in FIGS. 4 and 5 are cross-sectional views of the driving TFT 1403 and the light emitting element 1405.

  In the pixel shown in FIG. 10A, a signal line 1410 and power supply lines 1411 and 1412 are arranged in the column direction, and a scanning line 1414 is arranged in the row direction. The pixel further includes a switching TFT 1401, a driving TFT 1403, a current control TFT 1404, a capacitor element 1402, and a light emitting element 1405.

  The pixel shown in FIG. 10C is different from the pixel shown in FIG. 10A except that the gate electrode of the driving TFT 1403 is connected to the power supply line 1412 arranged in the row direction. It is a configuration. That is, both pixels shown in FIGS. 10A and 10C show the same equivalent circuit diagram. However, in the case where the power supply line 1412 is arranged in the row direction (FIG. 10A) and in the case where the power supply line 1412 is arranged in the column direction (FIG. 10C), each power supply line has a different layer. It is formed of a conductive film. Here, attention is paid to the wiring to which the gate electrode of the driving TFT 1403 is connected, and FIGS. 10A and 10C are shown separately to show that layers for manufacturing these are different.

  10A and 10C, the driving TFT 1403 and the current control TFT 1404 are connected in series in the pixel, and the channel length L (1403) and channel width W (1403) of the driving TFT 1403 are connected. ), The channel length L (1404) and the channel width W (1404) of the current control TFT 1404 satisfy L (1403) / W (1403): L (1404) / W (1404) = 5 to 6000: 1. It is good to set to.

  Note that the driving TFT 1403 operates in a saturation region and has a role of controlling a current value flowing through the light emitting element 1405, and the current control TFT 1404 operates in a linear region and has a role of controlling supply of current to the light emitting element 1405. . Both TFTs preferably have the same conductivity type in terms of manufacturing process, and in this embodiment mode, they are formed as n-channel TFTs. The driving TFT 1403 may be a depletion type TFT as well as an enhancement type. In the present invention having the above configuration, since the current control TFT 1404 operates in a linear region, a slight change in Vgs of the current control TFT 1404 does not affect the current value of the light emitting element 1405. That is, the current value of the light emitting element 1405 can be determined by the driving TFT 1403 operating in the saturation region. With the above structure, it is possible to provide a display device in which luminance unevenness of a light-emitting element due to variation in TFT characteristics is improved and image quality is improved.

  In the pixel shown in FIGS. 10A to 10D, the switching TFT 1401 controls input of a video signal to the pixel. When the switching TFT 1401 is turned on, the video signal is input into the pixel. Then, the voltage of the video signal is held in the capacitor element 1402. Note that FIGS. 10A and 10C illustrate the structure in which the capacitor 1402 is provided; however, the present invention is not limited to this, and the capacity for holding a video signal can be covered by a gate capacity or the like. In this case, the capacitor 1402 is not necessarily provided.

  The pixel shown in FIG. 10B has the same pixel structure as that shown in FIG. 10A except that a TFT 1406 and a scanning line 1414 are added. Similarly, the pixel illustrated in FIG. 10D has the same pixel structure as that illustrated in FIG. 10C except that a TFT 1406 and a scanning line 1414 are added.

  The TFT 1406 is controlled to be turned on or off by a newly arranged scanning line 1414. When the TFT 1406 is turned on, the charge held in the capacitor element 1402 is discharged, and the current control TFT 1404 is turned off. That is, the arrangement of the TFT 1406 can forcibly create a state where no current flows through the light-emitting element 1405. Therefore, the TFT 1406 can be called an erasing TFT. 10B and 10D, the lighting period can be started at the same time as or immediately after the start of the writing period without waiting for signal writing to all pixels, so that the duty ratio is improved. It becomes possible.

  In the pixel illustrated in FIG. 10E, a signal line 1410, a power supply line 1411 are arranged in the column direction, and a scanning line 1414 is arranged in the row direction. Further, the pixel includes a switching TFT 1401, a driving TFT 1403, a capacitor element 1402, and a light emitting element 1405. The pixel illustrated in FIG. 10F has the same pixel structure as that illustrated in FIG. 7E except that a TFT 1406 and a scanning line 1415 are added. Note that the duty ratio of the structure in FIG. 10F can also be improved by the arrangement of the TFT 1406.

  As described above, various pixel circuits can be employed. In particular, in the case where a thin film transistor is formed from an amorphous semiconductor film, it is preferable to increase the semiconductor film of the driving TFT 1403. Therefore, it is preferable that the pixel circuit be a top emission type in which light from the electroluminescent layer is emitted from the sealing substrate side.

  Such an active matrix light-emitting device is considered to be advantageous because it can be driven at a low voltage because a TFT is provided in each pixel when the pixel density is increased.

  In this embodiment mode, an active matrix light-emitting device in which each pixel is provided with each TFT has been described; however, a passive matrix light-emitting device in which a TFT is provided for each column can also be formed. A passive matrix light-emitting device has a high aperture ratio because a TFT is not provided for each pixel. In the case of a light-emitting device in which light emission is emitted to both sides of an electroluminescent layer, transmittance using a passive matrix display device is increased.

  In the display device of the present invention further including the pixel circuit as described above, a material suitable for the configuration and required performance of the light emitting element can be used as the electrode of the light emitting element of the display device. A display device having characteristics can be obtained.

  Next, the case where a diode is provided as a protection circuit in the scan line and the signal line will be described using the equivalent circuit illustrated in FIG.

  In FIG. 11, switching TFTs 1401 and 1403, a capacitor element 1402, and a light emitting element 1405 are provided in the pixel portion 1500. The signal line 1410 is provided with diodes 1561 and 1562. Similarly to the switching TFT 1401 or 1403, the diodes 1561 and 1562 are manufactured based on the above embodiment mode and include a gate electrode, a semiconductor layer, a source electrode, a drain electrode, and the like. The diodes 1561 and 1562 operate as diodes by connecting a gate electrode and a drain electrode or a source electrode.

  Common potential lines 1554 and 1555 connected to the diode are formed in the same layer as the gate electrode. Therefore, in order to connect to the source electrode or the drain electrode of the diode, it is necessary to form a contact hole in the gate insulating layer.

  A diode provided in the scan line 1414 has a similar structure.

  Thus, according to the present invention, the protection diode provided in the input stage can be formed simultaneously. Note that the position where the protective diode is formed is not limited to this, and the protective diode can be provided between the driver circuit and the pixel.

The display device of the present invention having such a protective circuit can use a material suitable for the structure and required performance of the light-emitting element as an electrode of the light-emitting element of the display device. It is possible to improve the reliability of the system.

  In this example, the light-emitting element described in Embodiment 2 (FIG. 2B) is manufactured and the measurement results are shown. In this example, a light-emitting element that emits green light was manufactured.

  First, a method for manufacturing a light-emitting element in this example is described. The light-emitting element in this example is formed over a glass substrate, and ITSO is formed with a thickness of 110 nm as the first electrode in order from the glass substrate side. The ITSO was formed by sputtering. In the present invention, the shape of the first electrode is 2 mm × 2 mm. Next, as a pretreatment for forming a light emitting element on the first electrode, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, etc.), Time heat treatment was performed, and UV ozone treatment was performed for 370 seconds.

Next, a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) as a layer having a donor level is 10 nm, followed by DNTPD and molybdenum as a layer having an acceptor level. (VI) An oxide co-deposited film (formed to have a mass ratio of 4: 2) was formed to 40 nm, and α-NPD was formed to 10 nm as a hole transport layer. On these laminated films, a 40 nm thick co-deposited film of Alq ₃ and coumarin 6 (formed to have a mass ratio of 1: 0.01) was formed as a light emitting layer. Further, after depositing 10 nm of Alq ₃ as an electron transport layer, a 10 nm film of a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) is formed as a layer having a donor level. did. Finally, an aluminum film was formed at 200 nm as the second electrode to complete the device. Note that all films except the first electrode were formed by a vacuum evaporation method using resistance heating.

The results of measuring the current density-luminance characteristics, luminance-current efficiency characteristics, voltage-luminance characteristics, and voltage-current characteristics of the light-emitting element manufactured as described above are shown in FIGS. Thus, it can be seen that the light-emitting element of the present invention operates well. The CIE chromaticity coordinates at 1000 cd / m ² were (x, y) = (0.31, 0.62), indicating good green light emission.

  In this example, the light-emitting element described in Embodiment Mode 3 (FIG. 3B) is manufactured and measured. In this example, a light-emitting element that emits green light was manufactured.

  First, a method for manufacturing a light-emitting element in this example is described. The light-emitting element in this example is formed over a glass substrate, and ITSO is formed with a thickness of 110 nm as the first electrode in order from the glass substrate side. The ITSO was formed by sputtering. In the present invention, the shape of the first electrode is 2 mm × 2 mm. Next, as a pretreatment for forming a light emitting element on the first electrode, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, etc.), Time heat treatment was performed, and UV ozone treatment was performed for 370 seconds.

Next, a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) as a layer having a donor level is 10 nm, followed by DNTPD and molybdenum as a layer having an acceptor level. (VI) An oxide co-deposited film (formed to have a mass ratio of 4: 2) was formed to 40 nm, and α-NPD was formed to 10 nm as a hole transport layer. On these laminated films, a 40 nm thick co-deposited film of Alq ₃ and coumarin 6 (formed to have a mass ratio of 1: 0.01) was formed as a light emitting layer. Further, after depositing 10 nm of Alq ₃ as an electron transport layer, a 10 nm film of a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) is formed as a layer having a donor level. Subsequently, a 20 nm thick co-deposited film of DNTPD and molybdenum (VI) oxide (formed in a mass ratio of 4: 2) was formed as a layer having an acceptor level. Finally, an aluminum film was formed at 200 nm as the second electrode to complete the device. Note that all films except the first electrode were formed by a vacuum evaporation method using resistance heating.

The results of measuring the current density-luminance characteristics, luminance-current efficiency characteristics, voltage-luminance characteristics, and voltage-current characteristics of the light-emitting element manufactured as described above are shown in FIGS. Thus, it can be seen that the light-emitting element of the present invention operates well. The CIE chromaticity coordinates at 1000 cd / m ² were (x, y) = (0.31, 0.62), indicating good green light emission.

FIG. 28 is a graph showing a change in luminance when the element is driven with an initial luminance of 3000 cd / m ² and a constant current density. The graph shows the initial luminance normalized to 100. From the graph, the light-emitting element in this embodiment showed a favorable characteristic of about 270 hours until the luminance was reduced by 20% at the initial luminance of 3000 cd.

  In this example, the light-emitting element described in Embodiment Mode 3 (FIG. 3B) is manufactured and measured. In this example, a light-emitting element that emits blue light was manufactured.

  First, a method for manufacturing a light-emitting element in this example is described. The light-emitting element in this example is formed over a glass substrate, and ITSO is formed with a thickness of 110 nm as the first electrode in order from the glass substrate side. The ITSO was formed by sputtering. In the present invention, the shape of the first electrode is 2 mm × 2 mm. Next, as a pretreatment for forming a light emitting element on the first electrode, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, etc.), Time heat treatment was performed, and UV ozone treatment was performed for 370 seconds.

Next, a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) as a layer having a donor level is 10 nm, followed by DNTPD and molybdenum as a layer having an acceptor level. (VI) An oxide co-deposited film (formed to have a mass ratio of 4: 2) was formed to 40 nm, and α-NPD was formed to 10 nm as a hole transport layer. On these laminated films, t-BuDNA was formed to a thickness of 40 nm as a light emitting layer. Further, after depositing 10 nm of Alq ₃ as an electron transport layer, a 10 nm film of a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) is formed as a layer having a donor level. Subsequently, a 20 nm thick co-deposited film of DNTPD and molybdenum (VI) oxide (formed in a mass ratio of 4: 2) was formed as a layer having an acceptor level. Finally, an aluminum film was formed at 200 nm as the second electrode to complete the device. Note that all films except the first electrode were formed by a vacuum evaporation method using resistance heating.

The results of measuring the current density-luminance characteristics, luminance-current efficiency characteristics, voltage-luminance characteristics, and voltage-current characteristics of the light-emitting element manufactured as described above are shown in FIGS. Thus, it can be seen that the light-emitting element of the present invention operates well. The CIE chromaticity coordinates at 1000 cd / m ² were (x, y) = (0.16, 0.13), and showed good blue light emission.

  In this example, the light-emitting element described in Embodiment Mode 1 (FIG. 1B) is manufactured and measured. In this example, a light-emitting element that emits green light was manufactured.

  First, a method for manufacturing a light-emitting element in this example is described. The light-emitting element in this example is formed over a glass substrate, and ITSO is formed with a thickness of 110 nm as the first electrode in order from the glass substrate side. The ITSO was formed by sputtering. In the present invention, the shape of the first electrode is 2 mm × 2 mm. Next, as a pretreatment for forming a light emitting element on the first electrode, the substrate surface is washed with a porous resin (typically, PVA (polyvinyl alcohol), nylon, etc.), Time heat treatment was performed, and UV ozone treatment was performed for 370 seconds.

Next, a co-deposited film of Alq ₃ and lithium (deposited so as to have a mass ratio of 1: 0.01) as a layer having a donor level is 10 nm, followed by DNTPD and molybdenum as a layer having an acceptor level. (VI) An oxide co-deposited film (formed to have a mass ratio of 4: 2) was formed to 40 nm, and α-NPD was formed to 10 nm as a hole transport layer. On these laminated films, a 40 nm thick co-deposited film of Alq ₃ and coumarin 6 (formed to have a mass ratio of 1: 0.01) was formed as a light emitting layer. Furthermore, 40 nm of Alq ₃ was deposited as an electron transport layer. Finally, 10 nm of lithium fluoride and 200 nm of aluminum were stacked as the second electrode, thereby completing the device. Note that all films except the first electrode were formed by a vacuum evaporation method using resistance heating.

The results of measuring the current density-luminance characteristics, luminance-current efficiency characteristics, voltage-luminance characteristics, and voltage-current characteristics of the light-emitting element manufactured as described above are shown in FIGS. 24 to 27, respectively. Thus, it can be seen that the light-emitting element of the present invention operates well. The CIE chromaticity coordinates at 1000 cd / m ² were (x, y) = (0.29, 0.64), indicating good green light emission.

FIG. 29 is a graph showing a change in luminance when the element in this embodiment is driven with an initial luminance of 3000 cd / m ² and a constant current density. The graph shows the initial luminance normalized to 100. From the graph, the light emitting device in this example showed good characteristics with an initial luminance of 3000 cd / m ² until the luminance decreased by 20%, about 280 hours.

  In addition, FIG. 29 shows the characteristics of an element that has a structure almost the same as that of the element in this example as a comparative example, but does not have a layer having a donor level on the first electrode. The method for manufacturing the element of the comparative example is as follows.

Since it is the same as that of Example 4 until it produces the 1st electrode, it omits. When the first electrode was formed in the same manner as in Example 4, a 50 nm thick co-deposited film of DNTPD and molybdenum (VI) oxide (having a mass ratio of 4: 2) was formed as a layer having an acceptor level. As a hole transport layer, α-NPD was formed to a thickness of 10 nm. On these laminated films, a 40 nm thick co-deposited film of Alq ₃ and coumarin 6 (formed to have a mass ratio of 1: 0.01) was formed as a light emitting layer. Furthermore, 40 nm of Alq ₃ was deposited as an electron transport layer. Finally, 10 nm of lithium fluoride and 200 nm of aluminum were stacked as the second electrode, thereby completing the device. Note that all films except the first electrode were formed by a vacuum evaporation method using resistance heating.

When the device of the comparative example was driven at an initial luminance of 3000 cd / m ² and a constant current density, the time until the luminance was reduced by 20% was about 140 hours. The light emitting element in this example can obtain about twice as much reliability as the comparative example. This is considered to be caused by the fact that the deterioration immediately after the start of driving is suppressed by the element of the comparative example. As described above, the light-emitting element of the present invention can also reduce deterioration immediately after the start of driving.

1A and 1B illustrate a light-emitting device of the present invention (Embodiment 1). FIG. 8 illustrates a light-emitting device of the present invention (Embodiment 2). FIG. 7 illustrates a light-emitting device of the present invention (Embodiment 3). 3A and 3B illustrate a manufacturing process of a thin film light emitting element of the present invention. 3A and 3B illustrate a manufacturing process of a thin film light emitting element of the present invention. The figure which illustrated the structure of the display apparatus. 2A and 2B are a top view and a cross-sectional view of a light-emitting device of the present invention. FIG. 10 illustrates an electronic device to which the present invention is applicable. The figure which illustrated the structure of the display apparatus. FIG. 14 illustrates an example of a pixel circuit of a display device. FIG. 11 illustrates an example of a protection circuit of a display device. Current density-luminance curve of the element (green) shown in FIG. Luminance-current efficiency curve of element (green) shown in Fig. 2 (B) Voltage-luminance curve of element (green) shown in Fig. 2 (B) Voltage-current curve of the element (green) shown in Fig. 2 (B) The current density-luminance curve of the element (green) shown in FIG. Luminance-current efficiency curve of element (green) shown in Fig. 3 (B) Voltage-luminance curve of element (green) shown in Fig. 3 (B) Voltage-current curve of the element (green) shown in Fig. 3 (B) The current density-luminance curve of the element (blue) shown in FIG. Luminance-current efficiency curve of the element (blue) shown in Fig. 3 (B) Voltage-luminance curve of the element (blue) shown in Fig. 3 (B) Voltage-current curve of the element (blue) shown in Fig. 3 (B) Current density-luminance curve of element (green) shown in FIG. Luminance vs. current efficiency curve of element (green) shown in Fig. 1 (B) Voltage-luminance curve of element (green) shown in Fig. 1 (B) Voltage-current curve of element (green) shown in Fig. 1 (B) Reliability of the element shown in FIG. Reliability of the element shown in FIG.

Explanation of symbols

50 Substrate 51a Underlying insulating layer 51b Underlying insulating layer 52 Semiconductor layer 53 Gate insulating layer 54 Gate electrode 59 Insulating film (hydrogenated film)
60 Interlayer insulating layer 61a Connection portion 61b Wiring 63 Interlayer insulating layer 65 Partition 66 Light emitting laminate 70 Thin film transistor 88 Resin 89 Drying material 90 Polarizing plate 91 Protective film 93 Light emitting element 94 Counter substrate 100 Insulator 101 Electrode 102 Layer 103 Layer 104 Light emitting laminate Body 105 layer 106 electrode 110 layer 900 interlayer insulation layer 901 thin film transistor 1401 switching TFT
1402 Capacitor element 1403 Driving TFT
1404 Current control TFT
1405 Light Emitting Element 1406 TFT
1410 Signal line 1411 Power supply line 1412 Power supply line 1414 Scanning line 1415 Scanning line 1500 Pixel part 1554 Common potential line 1561 Diode 2001 Case 2003 Display part 2004 Speaker part 2101 Main body 2102 Case 2103 Display part 2104 Audio input part 2105 Audio output part 2106 Operation key 2108 Antenna 2201 Main body 2202 Case 2203 Display unit 2204 Keyboard 2205 External connection port 2206 Pointing mouse 2301 Main body 2302 Display unit 2303 Switch 2304 Operation key 2305 Infrared port 2401 Case 2402 Display unit 2403 Speaker unit 2404 Operation key 2405 Recording medium insertion Part 4001 substrate 4002 pixel part 4003 signal line driver circuit 4004 scanning line driver circuit 4005 sealant 4006 counter group Plate 4007 Filler 4008 Thin film transistor 4010 Thin film transistor 4011 Light emitting element 4014 Wiring 4016 Connection terminal 4018 Flexible printed circuit (FPC)
4019 Anisotropic conductive film 4015a Wiring 4015b Wiring

Claims (6)

Between the first electrode and the second electrode provided to face each other, the first layer, the second layer, and the third layer,
The first layer includes a first substance having a higher electron mobility than a hole mobility, and a second substance capable of donating electrons to the first substance. Yes,
The second layer includes a third substance having a higher hole mobility than an electron mobility and a fourth substance capable of accepting electrons from the third substance. Yes,
The third layer is a layer having a layer containing at least a light-emitting substance,
The first layer is provided in contact with the second electrode,
The second layer is provided in contact with the first layer,
The third layer is provided in contact with the second layer,
The first electrode is provided in contact with the third layer,
When the potential of the second electrode is higher than the potential of the first electrode, the first layer or et electron are injected into the second electrode, the second layer or RaTadashi hole the A light-emitting device which is injected into the third layer. Between the first electrode and the second electrode provided to face each other, the first layer, the second layer, the third layer, and the fourth layer,
The first layer includes a first substance having a higher electron mobility than a hole mobility, and a second substance capable of donating electrons to the first substance. Yes,
The second layer includes a third substance having a higher hole mobility than an electron mobility and a fourth substance capable of accepting electrons from the third substance. Yes,
The third layer is a layer having a layer containing at least a light-emitting substance,
The fourth layer includes a fifth substance having a higher electron mobility than a hole mobility, and a sixth substance capable of donating electrons to the fifth substance. Yes,
The first layer is provided in contact with the second electrode,
The second layer is provided in contact with the first layer,
The third layer is provided in contact with the second layer,
The fourth layer is provided in contact with the third layer,
The first electrode is provided in contact with the fourth layer,
When the potential of the second electrode is higher than the potential of the first electrode, the first layer or et electron are injected into the second electrode, the second layer or RaTadashi hole the the third is the injected into a layer, the light emitting device wherein the fourth layer or et electronic, characterized in that it is injected into the third layer. In claim 2,
The first substance and the fifth substance are the same substance,
The light-emitting device, wherein the second substance and the sixth substance are the same substance. The first layer, the second layer, the third layer, the fourth layer, and the fifth layer are provided between the first electrode and the second electrode that are provided to face each other. Have
The first layer includes a first substance having a higher electron mobility than a hole mobility, and a second substance capable of donating electrons to the first substance. Yes,
The second layer includes a third substance having a higher hole mobility than an electron mobility and a fourth substance capable of accepting electrons from the third substance. Yes,
The third layer is a layer having a layer containing at least a light-emitting substance,
The fourth layer includes a fifth substance having a higher electron mobility than a hole mobility, and a sixth substance capable of donating electrons to the fifth substance. Yes,
The fifth layer includes a seventh substance having a higher hole mobility than an electron mobility and an eighth substance capable of accepting electrons from the seventh substance. Yes,
The first layer is provided in contact with the second electrode,
The second layer is provided in contact with the first layer,
The third layer is provided in contact with the second layer,
The fourth layer is provided in contact with the third layer,
The fifth layer is provided in contact with the fourth layer,
The first electrode is provided in contact with the fifth layer,
When the potential of the second electrode is higher than the potential of the first electrode, the first layer or et electron are injected into the second electrode, the fifth layer or RaTadashi hole the is injected into the first electrode, the second layer or RaTadashi holes are injected into the third layer, and wherein the fourth layer or et electron is injected into the third layer Light-emitting device. In claim 4,
The first substance and the fifth substance are the same substance,
The second substance and the sixth substance are the same substance,
The third substance and the seventh substance are the same substance,
The light-emitting device, wherein the fourth substance and the eighth substance are the same substance. In any one of Claims 1 thru | or 5,
The third layer includes a hole transport layer, a layer containing the luminescent material, and an electron transport layer,
The hole transport layer is provided in contact with the second layer;
The layer containing the luminescent material is provided in contact with the hole transport layer,
The light-emitting device, wherein the electron transport layer is provided in contact with the layer containing the light-emitting substance.

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