JP3748110B1 - LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE USING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element having a low driving voltage and having a longer lifetime than a conventional light emitting element and a method for manufacturing the light emitting element.
A light-emitting element of the present invention has a plurality of layers between a pair of electrodes, and at least one of the plurality of layers includes a compound selected from an oxide semiconductor and a metal oxide. It is a layer containing a compound having a high hole transporting property. By using the light-emitting element having such a structure, crystallization of a layer including one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property can be suppressed. In addition, as a result of the suppression of crystallization, the light emitting element has a long lifetime.
[Selection] Figure 1

Description

  The present invention relates to a light-emitting element having a structure in which a plurality of layers are sandwiched between a pair of electrodes, and more particularly to a structure of a layer that can be used as at least one of the plurality of layers.

  A light-emitting device using light emitted from an electroluminescence element (light-emitting element) has attracted attention as a display or illumination device.

  As a light-emitting element used in a light-emitting device, one having a structure in which a layer containing a light-emitting compound is sandwiched between a pair of electrodes is well known.

  In such a light-emitting element, one electrode functions as an anode and the other electrode functions as a cathode, and holes injected from the anode side and electrons injected from the cathode side are recombined to be in an excited state. It forms a molecule and emits light when it returns to the ground state.

  By the way, display devices to be incorporated into various information processing devices that have been rapidly developed in recent years have a particularly high demand for low power consumption. In order to achieve this, attempts have been made to reduce the driving voltage of light-emitting elements. Yes. In view of commercialization, it is important not only to lower the driving voltage but also to extend the life of the light emitting element, and the development of light emitting elements to achieve this is underway.

  For example, in Patent Document 1, a low driving voltage of a light emitting element is achieved by using a metal oxide having a high work function such as molybdenum oxide for an anode. In addition, the effect of extending the life is also obtained.

However, in particular, regarding the extension of the lifetime, it cannot be said that the means disclosed in Patent Document 1 alone is sufficient, and it is necessary to develop a technology for achieving a longer lifetime.
JP-A-9-63771

  It is an object of the present invention to provide a light-emitting element that has a low driving voltage and can have a longer lifetime than a conventional light-emitting element and a method for manufacturing the light-emitting element.

  The light-emitting element of the present invention has a plurality of layers between a pair of electrodes, and at least one of the plurality of layers has one compound selected from an oxide semiconductor and a metal oxide and a hole transport property. It is characterized by being a layer containing a high compound.

  Note that the plurality of layers are configured by combining layers made of a substance having a high carrier-injecting property, a substance having a high carrier-transporting property, or the like so that a light-emitting region is formed away from the electrode.

  By using the light-emitting element having such a structure, crystallization of a layer including one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property can be suppressed. In addition, as a result of the suppression of crystallization, the light emitting element has a long lifetime.

  Specific examples of the oxide semiconductor and the metal oxide include molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), and the like. In addition, indium tin oxide (ITO), zinc oxide (ZnO), and tin oxide (SnO) can be used. However, it is not limited to those shown here, and other substances may be used.

  Examples of the compound having a high hole-transport property 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) (ie, benzene ring-nitrogen) And a compound having a bond of However, it is not limited to those shown here, and other substances may be used.

  The light-emitting element of the present invention has a plurality of layers between a pair of electrodes, and at least one of the plurality of layers has a hole-transporting property with one compound selected from an oxide semiconductor and a metal oxide. It is characterized by being a layer containing a high compound and a compound having a large steric hindrance.

  In addition, the plurality of layers are configured by combining layers made of a substance having a high carrier-injecting property or a substance having a high carrier-transporting property so that a light-emitting region is formed away from the electrode, as described above. Is.

  As described above, by forming a light-emitting element having a structure containing a compound having a large steric hindrance in a layer containing one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property, Crystallization of the layer can be further suppressed. In addition, as a result of the suppression of crystallization, the light emitting element has a longer lifetime.

  Note that the oxide semiconductor, the metal oxide, and the compound having a high hole-transport property are the same as those described above.

  As a compound having a large steric hindrance (that is, having a structure having a spatial extension unlike a planar structure), 5,6,11,12-tetraphenyltetracene (abbreviation: rubrene) is preferable. However, other than this, hexabenylbenzene, diphenylanthracene, t-butylperylene, 9,10-di (phenyl) anthracene, coumarin 545T, or the like may be used. In addition, dendrimers and the like are also effective.

  According to the present invention, aggregation of an oxide semiconductor or a metal oxide can be suppressed, and crystallization of a layer containing the oxide semiconductor or metal oxide can be suppressed. In addition, by suppressing crystallization, generation of a leakage current due to crystallization is suppressed, and a light-emitting element having a long lifetime can be obtained.

  The light-emitting element of the present invention has a plurality of layers between one electrode. The plurality of layers have a high carrier injection property and carrier transport so that a light emitting region is formed at a position away from the electrode, that is, a carrier (carrier) is recombined at a position away from the electrode. The layers are formed by combining layers made of highly specific materials.

  One embodiment of the light-emitting element of the present invention is described below with reference to FIG.

  In this embodiment mode, the light-emitting element 210 is provided over a substrate 201 for supporting the light-emitting element 210, and includes a first electrode 202, a first layer 203 sequentially stacked on the first electrode 202, and a second layer. The layer 204, the third layer 205, the fourth layer 206, and the second electrode 207 provided thereon. Note that in this embodiment mode, the first electrode 202 functions as an anode, and the second electrode 207 functions as a cathode.

  As the substrate 201, for example, glass or plastic can be used. Note that other materials may be used as long as the light-emitting element functions as a support in the manufacturing process.

  The first electrode 202 is preferably formed of a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a high work function (work function of 4.0 eV or more). Specifically, indium tin oxide (ITO), indium tin oxide containing silicon, IZO (Indium Zinc Oxide) in which 2 to 20% zinc oxide (ZnO) is mixed with indium oxide. , Gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd) Alternatively, a nitride of metal (TiN) or the like can be used.

The first layer 203 is a layer including one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property. Specific examples of the oxide semiconductor and the metal oxide include molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), and the like. In addition, indium tin oxide (ITO) or zinc oxide (ZnO) can be used. However, it is not limited to those shown here, and other substances may be used. Examples of the compound having a high hole-transport property 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), 4,4 ′, 4 ″ -tris (N, N-diphenyl-amino) -triphenylamine (abbreviation: Aromatic amine systems such as TDATA), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine (abbreviation: MTDATA) (ie, benzene ring— A compound having a nitrogen bond) can be used. The substances mentioned here are mainly substances having a hole mobility of 10 ⁻⁶ cm ² / Vs or higher. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used.

  The first layer 203 having the above structure is a layer having a high hole injection property. In the first layer 203, aggregation of the oxide semiconductor or the metal oxide is suppressed by a substance having a high hole-transport property included in the layer. That is, crystallization of the first layer 203 is suppressed. Note that the first layer 203 is not limited to a single layer as described above, and may have a structure in which, for example, a semiconductor and a compound having a high hole-transport property are included and two or more layers having different mixing ratios are stacked. .

  The first layer 203 has a larger steric hindrance in addition to one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property (that is, different from a planar structure). It may have a compound (having a structure having a spatial extension). As the compound having a large steric hindrance, 5,6,11,12-tetraphenyltetracene (abbreviation: rubrene) is preferable. However, other than these, hexaphenylbenzene, diphenylanthracene, t-butylperylene, 9,10-di (phenyl) anthracene, coumarin 545T, and the like can also be used. In addition, dendrimers are also effective. In this manner, by mixing a substance having a structure having a large steric hindrance, that is, a structure having a spatial extension unlike a planar structure, crystallization of molybdenum oxide can be further suppressed.

The second layer 204 is a layer made of a substance having a high hole transporting property, for example, an aromatic amine-based compound (that is, having a benzene ring-nitrogen bond) such as α-NPD, TPD, TDATA, or MTDATA. . The substances mentioned here are mainly substances having a hole mobility of 10 ⁻⁶ cm ² / Vs or higher. Note that other than these substances, any substance that has a property of transporting more holes than electrons may be used. Note that the second layer 204 is not limited to a single layer, and may be a stack of two or more layers including any of the above substances.

The third layer 205 is a layer containing a substance having a high light-emitting property. For example, a highly luminescent substance such as N, N′-dimethylquinacridone (abbreviation: DMQd) or 2H-chromen-2-one (abbreviation: coumarin) and tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ) or 9 , 10-di (2-naphthyl) anthracene (abbreviation: DNA), and the like, are freely combined with a material having high carrier transportability and good film-forming properties (that is, difficult to crystallize). However, since Alq ₃ and DNA are substances having high light-emitting properties, a structure in which these substances are used alone may be used as the third layer 205.

The fourth layer 206 is formed using a substance having a high electron transporting property, for example, tris (8-quinolinolato) aluminum (abbreviation: Alq ₃ ), tris (5-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), etc., having a quinoline skeleton or a benzoquinoline skeleton It is a layer made of a metal complex or the like. In addition, bis [2- (2-hydroxyphenyl) -benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), bis [2- (2-hydroxyphenyl) -benzothiazolate] zinc (abbreviation: Zn ( Metal complexes having an oxazole or thiazole ligand such as BTZ) ₂ ) 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 also be used. The substances mentioned here are mainly substances having an electron mobility of 10 ⁻⁶ cm ² / Vs or higher. Note that any substance other than the above substances may be used for the fourth layer 206 as long as it has a property of transporting more electrons than holes. The fourth layer 206 is not limited to a single layer, and two or more layers including any of the above substances may be stacked.

  As a material for forming the second electrode 207, a metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a low work function (a work function of 3.8 eV or less) can be used. Specific examples of such a cathode material include elements belonging to Group 1 or Group 2 of the periodic table of elements, that is, alkali metals such as lithium (Li) and cesium (Cs), and magnesium (Mg), calcium (Ca), Examples thereof include alkaline earth metals such as strontium (Sr) and alloys containing them (Mg: Ag, Al: Li). However, by providing a layer having a function of accelerating electron injection between the second electrode 207 and the light-emitting layer by stacking with the second electrode, regardless of the work function, Al, Ag, Various conductive materials such as ITO and ITO containing silicon can be used for the second electrode 207.

Note that as a layer having a function of promoting electron injection, an alkali metal or alkaline earth metal compound such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF ₂ ), or the like is used. Can do. In addition, a layer made of a substance having an electron transporting property containing an alkali metal or an alkaline earth metal, for example, a layer containing magnesium (Mg) in Alq ₃ can be used.

  Further, the first layer 203, the second layer 204, the third layer 205, and the fourth layer 206 may be formed by a method other than the above evaporation method. For example, an ink jet method or a spin coating method may be used. Moreover, you may form using the different film-forming method for each electrode or each layer.

  The light-emitting element of the present invention having the above structure is a third layer that contains a highly light-emitting substance because a current flows due to a potential difference generated between the first electrode 202 and the second electrode 207. In the layer 205, holes and electrons recombine to emit light. That is, a light emitting region is formed in the third layer 205. However, it is not necessary that all of the third layer 205 functions as a light emitting region. For example, the light emitting region is formed only on the second layer 204 side or the fourth layer 206 side of the third layer 205. It may be anything.

  Light emission is extracted outside through one or both of the first electrode 202 and the second electrode 207. Therefore, one or both of the first electrode 202 and the second electrode 207 is formed of a light-transmitting substance. In the case where only the first electrode 202 is formed using a light-transmitting substance, light emission is extracted from the substrate side through the first electrode 202 as illustrated in FIG. In the case where only the second electrode 207 is formed using a light-transmitting substance, light emission is extracted from the side opposite to the substrate through the second electrode 207 as illustrated in FIG. In the case where both the first electrode 202 and the second electrode 207 are made of a light-transmitting substance, light is emitted from the first electrode 202 and the second electrode 207 as shown in FIG. And is taken out from both the substrate side and the opposite side of the substrate.

  Note that the structure of the layers provided between the first electrode 202 and the second electrode 207 is not limited to the above. A structure in which holes and electrons are recombined at a site away from the first electrode 202 and the second electrode 207 so that quenching caused by the proximity of the light emitting region and the metal is suppressed. And a layer including one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property (and may include a compound having a large steric hindrance). Any other than the above may be used. In other words, the layered structure of the layers is not particularly limited, and a substance having a high electron transporting property or a substance having a high hole transporting property, a substance having a high electron injecting property, a substance having a high hole injecting property, or a bipolar property (electron and hole) A layer composed of a substance having a high transportability of a material) is freely combined with a layer including one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole transportability. That's fine. Further, for example, a carrier recombination site may be controlled by providing a layer made of an extremely thin silicon oxide film or the like. For example, a configuration as shown in FIG. However, the layer structure is not limited to these.

  A light-emitting element illustrated in FIG. 3 includes a first layer 503 made of a substance having a high electron-transport property, a second layer 504 containing a substance having a high light-emitting property, and a hole transport over the first electrode 502 functioning as a cathode. A third layer 505 made of a highly conductive material, a fourth layer 506 containing one compound selected from an oxide semiconductor and a metal oxide and a compound having a high hole-transport property, and a first layer functioning as an anode Two electrodes 507 are sequentially stacked. Reference numeral 501 denotes a substrate.

  In this embodiment mode, a light-emitting element is manufactured over a substrate made of glass, plastic, or the like. A passive light-emitting device can be manufactured by manufacturing a plurality of such light-emitting elements over one substrate. In addition to a substrate made of glass, plastic, or the like, a light emitting element may be manufactured on a thin film transistor (TFT) array substrate, for example. Thus, an active matrix light-emitting device in which driving of the light-emitting element is controlled by the TFT can be manufactured. Note that the structure of the TFT is not particularly limited. A staggered TFT or an inverted staggered TFT may be used. Also, the driving circuit formed on the TFT array substrate may be composed of N-type and P-type TFTs, or may be composed of only one of N-type and P-type.

  As described above, in a light-emitting element having a layer containing one compound selected from an oxide semiconductor and a metal oxide and a substance having a high hole-transport property, crystallization of the layer can be suppressed. . Therefore, generation of a leakage current due to crystallization of the layer is suppressed, and a light-emitting element with a long lifetime can be obtained. In addition, in a light-emitting element having a layer containing a substance having a large steric hindrance in addition to one compound selected from an oxide semiconductor and a metal oxide and a substance having a high hole-transport property, crystals of the layer further include A light-emitting element that is suppressed and has a longer lifetime can be obtained.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described.

  A first electrode is formed by depositing indium tin oxide (ITO) over a glass substrate. Next, the glass substrate on which ITO is formed is processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, molybdenum oxide and α-NPD, which is a substance having a high hole-transport property, were co-evaporated to form a first layer over the first electrode. The weight ratio of molybdenum oxide and α-NPD was 0.245 (molybdenum oxide): 1 (α-NPD). The film thickness was 130 nm. Here, co-evaporation refers to a vapor deposition method in which raw materials are vaporized from a plurality of vapor deposition sources provided in one processing chamber, the vaporized raw materials are mixed in a gas phase state, and deposited on an object to be processed.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.002. The film thickness was 37.5 nm.

Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm.

Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm.

  Next, aluminum was formed and vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

  Element characteristics of the light-emitting element manufactured as described above are shown in FIGS.

FIG. 4 is a graph showing luminance-voltage characteristics of the light-emitting element manufactured in this example. In FIG. 4, the horizontal axis represents the applied voltage (V), and the vertical axis represents the emission luminance (cd / m ² ). 4 that the drive voltage (the voltage at which light emission of 1 cd / m ² or more starts) is about 2.5V.

FIG. 1 shows measurement results obtained by measuring changes over time in light emission luminance of the light-emitting elements manufactured in this example. In FIG. 1, the horizontal axis represents elapsed time (hour), and the vertical axis represents emission luminance. The light emission luminance is expressed as a relative value with respect to the initial luminance when the initial luminance is 100. Note that the change in the light emission luminance over time was measured by a method in which a current having a constant current density was continuously supplied to the light emitting element, and the luminance of the light emitting element was measured every arbitrary time. As the current density, a value when the initial luminance is 1000 cd / m ² was used. As can be seen from FIG. 1, in the light emitting device of this example, the light emission luminance after 100 hours elapsed is about 18% lower than the initial luminance and is 82.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described.

  A first electrode is formed by depositing indium tin oxide (ITO) over a glass substrate. Next, the glass substrate on which ITO is formed is processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, molybdenum oxide, α-NPD, which is a substance having a high hole-transport property, and rubrene, which is a substance having a high steric hindrance, were co-evaporated to form a first layer over the first electrode. Note that the weight ratio of molybdenum oxide, α-NPD, and rubrene was 0.245 (molybdenum oxide): 1 (α-NPD): 0.018 (rubrene). The film thickness was 130 nm.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.002. The film thickness was 37.5 nm.

Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm.

Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm.

  Next, aluminum was vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

  Element characteristics of the light-emitting element manufactured as described above are shown in FIGS. The measurement method and the like are the same as those shown in Example 1.

4 that the drive voltage (the voltage at which light emission of 1 cd / m ² or more starts) is about 2.5V.

  In addition, it can be seen from FIG. 1 that in the light emitting device of this example, the light emission luminance (relative value) after 100 hours is about 92%, which is about 8% lower than the initial luminance.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described.

  A first electrode is formed by depositing indium tin oxide (ITO) over a glass substrate. Next, the glass substrate on which ITO is formed is processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, 4,4-bis (N- (4- (N, N-di-m-tolylamino) phenyl) -N-phenylamino) biphenyl (abbreviation: a substance having a high hole-transport property with molybdenum oxide) DNTPD) and rubrene, which is a substance having a high steric hindrance, were co-evaporated to form a first layer on the first electrode. The weight ratio of molybdenum oxide, DNTPD, and rubrene was set to 0.5 (molybdenum oxide): 1 (DNTPD): 0.05 (rubrene). The film thickness was set to 120 nm.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio of Alq ₃ and coumarin 6 was set to 1: 0.003. The film thickness was 37.5 nm.

Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm.

Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm.

  Next, aluminum was vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

The element characteristics of the light-emitting element manufactured as described above are shown in FIGS. The measurement method and the like are the same as those shown in Example 1. In FIG. 8, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m ² ). In FIG. 9, the horizontal axis represents time (hour), and the vertical axis represents emission luminance (relative value).

From FIG. 8, it can be seen that the drive voltage (the voltage at which light emission of 1 cd / m ² or more starts is used as the drive voltage) is about 2.4V.

  In addition, it can be seen from FIG. 9 that in the light emitting element of this example, the light emission luminance after 100 hours elapsed is about 7% lower than the initial luminance and is 93.

(Comparative Example 1)
As a comparative example for the light-emitting element of the present invention, a method for manufacturing a light-emitting element in which the second layer is made of only molybdenum oxide and the characteristics of the light-emitting element will be described.

    A first electrode is formed by depositing indium tin oxide (ITO) over a glass substrate. Next, the glass substrate on which ITO is formed is processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, molybdenum oxide was evaporated to form a first layer on the first electrode. The film thickness was set to 100 nm.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was set to 60 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.002. The film thickness was 37.5 nm.

Next, Alq _{3 was} deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm.

Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm.

  Next, aluminum was vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

  Element characteristics of the light-emitting element manufactured as described above are shown in FIGS. The measurement method and the like are the same as those shown in Example 1.

4 that the drive voltage (the voltage at which light emission of 1 cd / m ² or more starts) is about 2.5V.

  Further, it can be seen from FIG. 1 that in the light emitting device of this comparative example, the light emission luminance after 100 hours has rapidly decreased and no light is emitted. This is presumably because the second layer was crystallized and a leak current was generated.

  From the above, it can be seen that the light-emitting elements shown in Example 1 and Example 2 emit light at a driving voltage comparable to that shown in the comparative example. That is, it can be seen that the light-emitting element of the present invention has a low driving voltage as well as a light-emitting element having a layer formed only of a molybdenum oxide film. It can be seen that the light-emitting element as shown in Example 1 or Example 2 has a long lifetime. Moreover, this is considered to be because the crystallization of the compound was suppressed by mixing with a compound having a high hole transport property such as α-NPD or a compound having a large steric hindrance such as rubrene.

  In this embodiment, a structure of an active matrix light-emitting device having the light-emitting element of the present invention will be described.

  In FIG. 5, on a substrate 90, a driving transistor 91 and a light emitting element 92 of the present invention are provided. A driving transistor 91 for driving the light emitting element is electrically connected to the light emitting element 92 of the present invention. Here, the light-emitting element has a light-emitting layer between the electrode 93 and the electrode 94, and part of the layer includes molybdenum oxide, a substance having a high hole-transport property, and a substance having a large steric hindrance. Have Further, the light emitting elements 92 are separated by the partition wall layer 95.

  In the light-emitting element of the present invention, the electrode functioning as an anode is on the lower side (the side where the driving transistor is provided for the light-emitting element), and the electrode functioning as the cathode is on the upper side (the driving transistor is provided for the light-emitting element). Or an electrode functioning as a cathode on the lower side and an electrode functioning as an anode on the upper side.

  In the former case, the driving transistor 91 is a P-channel type, and in the latter case, the driving transistor 91 is an N-channel type. However, the structure of the driving transistor 91 may be a staggered type or an inverted staggered type. The driving transistor 91 may be either a crystalline semiconductor layer or an amorphous transistor. A semi-amorphous material may be used.

The semi-amorphous semiconductor is as follows. A semiconductor having an intermediate structure between amorphous and crystalline (including single crystal and polycrystal) and having a third state that is stable in terms of free energy, has a short-range order, and has a lattice distortion. It contains a crystalline region. Further, at least a part of the region in the film contains crystal grains of 0.5 to 20 nm. The Raman spectrum is shifted to the lower wavenumber side than 520 cm ⁻¹ . In X-ray diffraction, diffraction peaks of (111) and (220) that are derived from the Si crystal lattice are observed. At least 1 atomic% or more of hydrogen or halogen is contained as a neutralizing agent for dangling bonds. It is also called a so-called microcrystalline semiconductor (microcrystal semiconductor). A silicide gas is formed by glow discharge decomposition (plasma CVD). As the silicide gas, SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiF ₄ or the like can be used. This silicide gas may be diluted with H ₂ , or H ₂ and one or more kinds of rare gas elements selected from He, Ar, Kr, and Ne. The dilution rate is in the range of 2 to 1000 times. The pressure is generally in the range of 0.1 Pa to 133 Pa, and the power supply frequency is 1 MHz to 120 MHz, preferably 13 MHz to 60 MHz. The substrate heating temperature may be 300 ° C. or less, preferably 100 to 250 ° C. 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. Note that the mobility of a TFT (thin film transistor) using a semi-amorphous semiconductor is approximately 1 to 10 m ² / Vsec.

  One or both of the electrode functioning as the anode and the electrode functioning as the cathode are formed using a light-transmitting substance.

  For example, in the case where the electrode functioning as the anode is on the lower side and only the electrode functioning as the anode is formed of a light-transmitting substance, a driving transistor is provided as illustrated in FIG. Emits light from the side. In the case where the electrode functioning as the cathode is on the lower side and only the electrode functioning as the cathode is formed of a light-transmitting substance, as shown in FIG. Light is emitted from the provided side. In the case where the electrode functioning as the anode is on the lower side and only the electrode functioning as the cathode is formed of a light-transmitting substance, a driving transistor is provided as shown in FIG. Light is emitted from the opposite side (ie, the upper side). In the case where the electrode functioning as the cathode is on the lower side and only the electrode functioning as the anode is formed of a light-transmitting substance, as shown in FIG. Light is emitted from the side opposite to the provided side. Further, in the case where both the electrode functioning as the anode and the electrode functioning as the cathode are formed of a light-transmitting substance, even if any electrode is on the upper side or the lower side, FIG. Emits light from both sides as shown.

  Note that the light-emitting element may be a single-color light-emitting element or may emit a plurality of colors such as red (R), green (G), and blue (B). Each light emitting element is preferably separated by a partition layer, and the partition layer may be formed of any one or both of an inorganic material and an organic material. For example, a silicon oxide film may be used, and a material having a skeleton structure formed of a bond of acrylic, polyimide, siloxane (silicon (Si) and oxygen (O) and containing at least hydrogen as a substituent is used. Any material such as a substance having at least one of fluorine, an alkyl group, and an aromatic hydrocarbon) may be used. In addition, it is preferable that a partition layer is a shape where a curvature radius changes continuously in an edge part.

  Since the light-emitting element of the present invention has a long lifetime, a light-emitting device to which the present invention is applied can be displayed or illuminated for a long time.

  A light-emitting device having a light-emitting element of the present invention as shown in Example 4 is mounted on various electronic devices after mounting an external input terminal or the like.

  Such an electronic device to which the present invention is applied can display a good image for a long time. This is because the light-emitting element of the present invention has a long lifetime.

  In this example, a light-emitting device having the light-emitting element of the present invention and an electronic device mounted with the light-emitting device will be described with reference to FIGS.

  FIG. 6 is a top view of a light-emitting device having the light-emitting element of the present invention. However, what is shown in FIG. 7 is an example, and the structure of the light-emitting device is not limited to this.

  In FIG. 6, 401 indicated by a dotted line is a drive circuit portion (source side drive circuit), 402 is a pixel portion, and 403 is a drive circuit portion (gate side drive circuit). Reference numeral 404 denotes a sealing substrate, and reference numeral 405 denotes a portion where a sealing material is applied.

  Note that a source side driver circuit 401 and a gate side driver are received by receiving a video signal, a clock signal, a start signal, a reset signal, and the like from an FPC (flexible printed circuit) 409 serving as an external input terminal through a wiring provided on the element substrate 410. A signal is input to the circuit 403. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting device in this embodiment includes not only the light-emitting device body but also a state in which an FPC or PWB is attached thereto.

  FIG. 7 shows an embodiment of an electronic device in which the light emitting device as shown in FIG. 6 is mounted.

  FIG. 7 illustrates a laptop personal computer manufactured by applying the present invention, which includes a main body 5501, a housing 5502, a display portion 5503, a keyboard 5504, and the like. A display device can be completed by incorporating a light-emitting device having the light-emitting element of the present invention into a personal computer.

  Note that in this embodiment, a laptop personal computer is described; however, in addition to this, a light emitting device having the light emitting element of the present invention is mounted on a mobile phone, a television receiver, a car navigation system, or a lighting device. It doesn't matter.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described. In this example, four light-emitting elements, the light-emitting element (1), the light-emitting element (2), the light-emitting element (3), and the light-emitting element (4) with different thicknesses of the first layer were manufactured.

  A first electrode was formed by depositing indium tin oxide containing silicon oxide over a glass substrate. Next, the glass substrate on which the first electrode was formed was processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, molybdenum oxide, rubrene, and DNTPD were co-evaporated to form a first layer on the first electrode. The weight ratio of molybdenum oxide, rubrene, and DNTPD was 0.67 (molybdenum oxide): 1 (DNTPD): 0.02 (rubrene). Here, in the light emitting element (1), the thickness of the first layer was set to 40 nm. In the light emitting element (2), the thickness of the first layer was set to 80 nm. In the light emitting element (3), the thickness of the first layer was set to 120 nm. In the light emitting element (4), the thickness of the first layer was set to 160 nm.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.005. The film thickness was 37.5 nm.

Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm.

  Next, lithium fluoride (LiF) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm.

  Next, aluminum was formed and vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

  The element characteristics of the light emitting element manufactured as described above are shown in FIGS.

FIG. 10 is a graph showing luminance-voltage characteristics of the light-emitting element manufactured in this example. In FIG. 10, the horizontal axis represents applied voltage (V), and the vertical axis represents light emission luminance (cd / m ² ). The mark ● represents the characteristics of the light emitting element (1), the mark ○ represents the characteristics of the light emitting element (2), the mark ■ represents the characteristics of the light emitting element (3), and the mark □ represents the characteristics of the light emitting element (4). From FIG. 10, the driving voltage (the voltage at which light emission of 1 cd / m ² or more starts is used as the driving voltage) is about 2.5 V for any of the light emitting elements, regardless of the thickness of the first layer. It turns out that it is equivalent. That is, in the light emitting element to which the present invention is applied, a driving voltage depending on the thickness of the first layer is hardly observed. Therefore, by applying the present invention, when producing a light emitting element that uses the electrode as a reflection surface of the emitted light, the optical path length through which the light passes is adjusted by changing the thickness of the first layer, It becomes easy to improve the external extraction efficiency of light emission.

FIG. 11 shows measurement results obtained by measuring changes over time in light emission luminance of the light-emitting elements manufactured in this example. In FIG. 11, the horizontal axis represents elapsed time (hour), and the vertical axis represents emission luminance. The light emission luminance is expressed as a relative value with respect to the initial luminance when the initial luminance is 100. Note that the change in the light emission luminance over time was measured by a method in which a current having a constant current density was continuously supplied to the light emitting element, and the luminance of the light emitting element was measured every arbitrary time. The current density was a value when the initial luminance was 3000 cd / m ² . From FIG. 11, in any of the light emitting elements (1), (2), (3), and (4), the light emission luminance after 100 hours is about 14% or less of the initial luminance. It can be seen that a light-emitting element to which is applied is a light-emitting element with little luminance deterioration.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described. In this embodiment, four materials of the light-emitting element, the light-emitting element (11), the light-emitting element (12), the light-emitting element (13), the light-emitting element (14), and the light-emitting element, which are different from each other, are formed from different materials. (15), a light emitting element (16), a light emitting element (17), a light emitting element (18), and a light emitting element (19) were produced.

  A first electrode of the light-emitting element (11) was formed by depositing aluminum containing several percent of silicon over a glass substrate. A first electrode of the light-emitting element (12) was formed by forming aluminum containing several percent of titanium over a glass substrate. In addition, a first electrode of the light-emitting element (13) was formed by forming a titanium film over the glass substrate. In addition, titanium nitride was formed over the glass substrate to form the first electrode of the light-emitting element (14). A tantalum film was formed on a glass substrate to form the first electrode of the light emitting element (15). In addition, tantalum nitride was formed over a glass substrate to form the first electrode of the light-emitting element (16). Further, a first electrode of the light-emitting element (17) was formed by forming a tungsten film over the glass substrate. Further, a first electrode of the light-emitting element (18) was formed by forming a chromium film on the glass substrate. In addition, molybdenum was formed over a glass substrate to form the first electrode of the light-emitting element (19).

  Next, the glass substrates on which the first electrodes were formed were each processed in a vacuum atmosphere at 150 degrees for 30 minutes.

  Next, molybdenum oxide, rubrene, and α-NPD were co-evaporated to form a first layer on the first electrode. The weight ratio of molybdenum oxide, rubrene, and α-NPD was 0.1 (molybdenum oxide): 1 (α-NPD): 0.02 (rubrene). The film thickness was set to 60 nm.

  Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.005. The film thickness was set to 40 nm.

Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was set to 20 nm.

  Next, lithium (Li) and 4,4′-bis (5-methylbenzoxazol-2-yl) stilbene (abbreviation: BzOs) are co-evaporated, and a fifth layer is formed on the fourth layer. Formed. The film thickness was set to 20 nm. The weight ratio of Li and BzOs was set to 0.02 (Li): 1 (BzOS). The film thickness was set to 20 nm.

  Next, indium tin oxide was formed, and a second electrode was formed over the fifth layer. The film thickness was set to 110 nm.

Each light-emitting element manufactured as described above is driven by applying a voltage so that the potential of the first electrode is higher than the potential of the second electrode, and light emission of 1 cd / m ² or more starts. The voltage was examined. The results are indicated by the ▪ marks in FIG. In FIG. 12, the horizontal axis represents which light-emitting element, and the vertical axis represents voltage (V).

(Comparative Example 2)
A light-emitting element, a light-emitting element (21), a light-emitting element (22), a light-emitting element (23), a light-emitting element (24), a light-emitting element (25), and a light-emitting element (26) as comparative examples for the light-emitting element described in Example 7 ), The light emitting element (27), the light emitting element (28), and the light emitting element (29) will be described.

  In the light emitting elements (21) to (29), the first layer was formed using copper phthalocyanine so as to have a thickness of 20 nm. ) To (19). Note that the first electrode of the light-emitting element (21) is made of aluminum containing several percent of silicon, and the first electrode of the light-emitting element (22) is made of aluminum containing several percent of titanium. The first electrode is made of titanium, the first electrode of the light emitting element (24) is made of titanium nitride, the first electrode of the light emitting element (25) is made of tantalum, and the first electrode of the light emitting element (26) is made. Is made of tantalum nitride, the first electrode of the light emitting element (27) is made of tungsten, the first electrode of the light emitting element (28) is made of chromium, and the first electrode of the light emitting element (29) is made of molybdenum. .

A voltage is applied to the light emitting elements (21) to (29) so that the potential of the first electrode is higher than the potential of the second electrode, and the voltage at which light emission of 1 cd / m ² or more starts is examined. It was. The result is shown by ▲ in FIG.

  From FIG. 12, in the light emitting elements (21) to (29) of the comparative examples in which the first layer is formed using copper phthalocyanine, the light emission depends on the light emitting element, that is, depending on the material forming the first electrode. It can be seen that the voltage at which is started differs greatly. On the other hand, in the light emitting elements (11) to (21) to which the present invention is applied, it can be seen that the voltage at which light emission starts hardly changes even if the material forming the first electrode is different. Thus, it can be seen that the light-emitting element of the present invention is an element which is not easily influenced by the type of material forming the electrode. Therefore, when a light-emitting element that uses an electrode as a reflection surface of emitted light is manufactured, the application of the present invention makes it easy to select an electrode having a better reflectivity.

  A method for manufacturing a light-emitting element of the present invention and characteristics of the light-emitting element will be described. In this example, light-emitting elements with different first layer thicknesses were manufactured. Then, the film thickness dependence of the driving voltage was clarified.

  As the sample, the light emitting elements (1) to (4) manufactured in Example 6 were used. That is, in the light emitting element (1), the thickness of the first layer was set to 40 nm. In the light emitting element (2), the thickness of the first layer was set to 80 nm. In the light emitting element (3), the thickness of the first layer was set to 120 nm. In the light emitting element (4), the thickness of the first layer was set to 160 nm.

  Each light-emitting element was driven by applying a voltage so that the potential of the first electrode was higher than the potential of the second electrode. FIG. 13 shows current density versus voltage characteristics of the light-emitting elements (1) to (4). In these light emitting elements, even if the thickness of the first layer is different, the current density vs. voltage characteristics hardly change. That is, even when the thickness of the first layer formed of molybdenum oxide, rubrene, and DNTPD is increased, the drive voltage does not increase.

(Comparative Example 3)
As comparative examples for the light emitting element described in Example 8, the light emitting element (30), the light emitting element (31), the light emitting element (32), the light emitting element (33), the light emitting element (34), and the light emitting element (35) will be described. To do.

  The light emitting elements (30) to (35) have different thicknesses of the second layer. Here, the first layer was formed to have a thickness of 20 nm using copper phthalocyanine. The second layer was formed by vapor deposition of α-NPD. The film thickness is 60 nm for the light emitting element (30), 80 nm for the light emitting element (31), 100 nm for the light emitting element (32), 120 nm for the light emitting element (33), 140 nm for the light emitting element (34), and 140 nm for the light emitting element (35). The thickness was set to 160 nm.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The weight ratio between Alq ₃ and coumarin 6 was set to 1: 0.005. The film thickness was 37.5 nm. Next, Alq ₃ was vapor deposited to form a fourth layer on the third layer. The film thickness was 37.5 nm. Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm. Next, aluminum was vapor-deposited to form a second electrode on the fifth layer. The film thickness was set to 200 nm.

  Each light-emitting element was driven by applying a voltage so that the potential of the first electrode was higher than the potential of the second electrode. FIG. 14 shows current density versus voltage characteristics of the light emitting elements (30) to (35). In these light emitting elements, the driving voltage is greatly increased as the thickness of the second layer is increased. That is, when the thickness of the second layer formed of α-NPD is increased, the drive voltage increases.

(Comparative Example 4)
As a comparative example with respect to the light emitting element described in Example 8, a light emitting element (36), a light emitting element (37), and a light emitting element (38) will be described. In each of the light emitting elements (36) to (38), the first layer is formed of molybdenum oxide and the film thickness thereof is different. On the first layer, a second layer was formed using copper phthalocyanine so as to have a thickness of 20 nm. The third layer was formed to a thickness of 40 nm by vapor deposition of α-NPD.

Next, Alq ₃ and coumarin 6 were co-evaporated to form a fourth layer on the third layer. The film thickness was 37.5 nm. Next, Alq ₃ was deposited to form a fifth layer on the fourth layer. The film thickness was 37.5 nm. Next, calcium fluoride (CaF ₂ ) was deposited to form a sixth layer on the fifth layer. The film thickness was 1 nm. Next, aluminum was vapor-deposited to form a second electrode on the sixth layer. The film thickness was set to 200 nm.

  Each light-emitting element was driven by applying a voltage so that the potential of the first electrode was higher than the potential of the second electrode. FIG. 15 shows current density versus voltage characteristics of the light-emitting elements (36) to (38). In these light-emitting elements, the driving voltage increases as the thickness of the first layer formed of molybdenum oxide increases.

Table 1 shows the results of Example 8, Comparative Example 3 and Comparative Example 4 regarding the film thickness dependence of the driving voltage. The data shown in Table 1 is a driving voltage necessary to pass a current of 100 mA / cm ² through the light emitting element.

In Example 8, the driving voltage required to pass a current of 100 mA / cm ² to the light emitting elements (1) to (4) is 6.1 to 6.3V. On the other hand, in Comparative Example 3, the driving voltage required to flow a current of 100 mA / cm ² to the light emitting elements (30) to (35) is increased from 12.5V to 19.9V. In Comparative Example 4, the driving voltage necessary for flowing a current of 100 mA / cm ² to the light emitting elements (36) to (38) increases from 11.7V to 12.7V.

  The results in Table 1 show that by providing a layer in which an organic compound and an inorganic compound are mixed, the driving voltage can be lowered as compared with the case where α-NPD which is an organic compound or molybdenum oxide which is an inorganic compound is used. Show. Further, it is shown that the increase in driving voltage can be suppressed even when the film thickness is increased.

  As described above, by using the light-emitting element of the present invention, the driving voltage can be lowered and the power consumption can be reduced. Furthermore, since it is possible to increase the thickness of the light emitting element, it is possible to reduce short-circuit defects between the electrodes formed above and below.

  This embodiment shows characteristics of a QVGA active matrix light emitting device having a screen size of 2.4 inches. This active matrix light emitting device is a device in which a light emitting element is driven by a transistor as in the fourth embodiment. The configuration of the light emitting element was as follows.

  The first electrode was formed of indium tin oxide containing silicon oxide. On the first electrode, molybdenum oxide and α-NPD which is a substance having a high hole transporting property were co-evaporated to form a first layer.

  Here, the first layer formed by mixing molybdenum oxide and α-NPD has a thickness of 120 nm, the light emitting device (1), and similarly, the first layer has a thickness of 240 nm. Is referred to as a light emitting device (2).

Next, α-NPD was deposited to form a second layer on the first layer. The film thickness was 10 nm. Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The film thickness of the third layer was set to 40 nm.

Alq ₃ was deposited on the third layer to form a fourth layer. The film thickness of the fourth layer was set to 30 nm. Then, by vapor deposition of calcium fluoride (CaF _2), thereby forming a fifth layer over the fourth layer. The film thickness was 1 nm. Aluminum was vapor-deposited on the fifth layer to form a second electrode. The thickness of the second electrode was set to 200 nm.

  About the light emitting device (1) and the light emitting device (2), a dark spot pixel (a pixel that does not emit light) after conducting an initial energization and a temperature cycle test (+ 85 ° C. (4 hours) to −40 ° C. (4 hours)) for 60 hours ) Check the number.

  For the light emitting device (1), the average number of dark spot pixels was 0.7 at the beginning of energization, and the average number of dark spot pixels was 2.3 after the temperature cycle test. As for the light emitting device (2), the average number of dark spot pixels was 0.5 at the initial stage of energization, and the average number of dark spot pixels was 0.5 after the temperature cycle test. Note that the average number of dark spot pixels indicates the average value of the evaluated ▲ light emitting devices.

(Comparative Example 5)
An active matrix light-emitting device (3) in which the structure of the light-emitting element is different from that of Example 9 was manufactured.

In the light-emitting element, the first layer was formed using copper phthalocyanine so as to have a thickness of 20 nm. As the second layer, α-NPD was formed to a thickness of 40 nm. Next, Alq ₃ and coumarin 6 were co-evaporated to form a third layer on the second layer. The film thickness of the third layer was set to 40 nm. Alq ₃ was deposited on the third layer to form a fourth layer having a thickness of 40 nm. Next, calcium fluoride (CaF ₂ ) was deposited to form a fifth layer on the fourth layer. The film thickness was 1 nm. And aluminum was vapor-deposited and the 2nd electrode with a film thickness of 200 nm was formed on the 5th layer.

  For the light-emitting device (3), the number of dark spot pixels after conducting an initial energization and a temperature cycle test (+ 85 ° C. (4 hours) to −40 ° C. (4 hours)) for 60 hours was examined.

  In the light emitting device (3), the average number of dark spot missing pixels at the beginning of energization was 18. Then, after the temperature cycle test, the average number of dark spot pixels was 444, an increase of about 25 times.

  Table 2 shows the results of Example 9 and Comparative Example 5 with respect to the number of dark spots after the initial energization and the temperature cycle test (+ 85 ° C. (4 hours) to −40 ° C. (4 hours)) for 60 hours. ing.

  In the light-emitting device (1) and the light-emitting device (2) of Example 9, almost no dark spot pixels were observed from the initial energization, and they did not increase even after the temperature cycle test. On the other hand, in the light emitting device (3) of Comparative Example 5, a large number of dark spot pixels were observed at the initial stage of energization, and the result increased 25 times after the temperature cycle test. This difference can be explained as an effect obtained by increasing the thickness of the first layer formed by mixing molybdenum oxide and α-NPD.

  The results of Example 9 indicate that the number of dark spots can be significantly reduced by increasing the thickness of the light emitting element. Further, from the results of Example 8, it is clear that the driving voltage does not increase even when the light emitting element is thickened. The above results show that the present invention can provide a light-emitting device with a low driving voltage and greatly suppressed dark spot pixels.

  The characteristics of molybdenum oxide as a metal oxide, α-NPD which is an organic compound having a high hole-transport property, and a mixture of molybdenum oxide and α-NPD were examined. These films were produced by vapor deposition.

  As shown in Table 3, compared to molybdenum oxide and α-NPD, the ionization potential of the film in which both are mixed is about 0.1 to 0.2 eV smaller. That is, it can be seen that the hole injection property is improved.

  FIG. 16 shows absorption spectra of these films. In the absorption spectrum, α-NPD and molybdenum oxide do not give a characteristic peak in the visible light region. On the other hand, in the film (OMOx) in which molybdenum oxide and α-NPD are mixed, the absorption is lower than in the case of molybdenum oxide alone. Thus, light absorption loss can be reduced when the light-emitting element is formed using a layer in which α-NPD and molybdenum oxide are mixed, compared to molybdenum oxide.

  In FIG. 16, when α-NPD and molybdenum oxide are mixed, a new absorption peak appears in the vicinity of 500 nm. This is considered to be because a charge transfer complex is formed between molybdenum oxide and α-NPD. Molybdenum oxide is an acceptor and α-NPD is a donor. It has been confirmed that not only α-NPD but also amine compounds such as DNTPD function as donors.

  Further, as shown in Example 1 or Example 2, a light-emitting element including a layer containing one compound selected from metal oxides and a compound having a high hole-transport property is formed by crystallizing the layer. Is suppressed, and the lifetime of the light-emitting element can be extended. Thus, by mixing a specific inorganic material and an organic material, a synergistic effect that cannot be obtained by each single substance can be expressed.

4A and 4B illustrate a change with time in light emission luminance of the light-emitting elements of the present invention and the light-emitting elements of Comparative Examples. 4A and 4B illustrate a cross-sectional structure of a light-emitting element of the present invention. 4A and 4B illustrate a cross-sectional structure of a light-emitting element of the present invention. FIG. 9 shows luminance-voltage characteristics of the light-emitting element of the present invention and the light-emitting element of the comparative example. 3A and 3B each illustrate a cross-sectional structure of a light-emitting device having the light-emitting element of the present invention. 1 is a top view of a light emitting device having a light emitting element of the present invention. FIG. 16 is a diagram of an electronic device mounted with a light-emitting device having a light-emitting element of the present invention. FIG. 9 shows luminance-voltage characteristics of the light-emitting element of the present invention and the light-emitting element of the comparative example. 4A and 4B are diagrams illustrating a change over time in light emission luminance of the light-emitting element of the present invention. FIG. 6 shows luminance-voltage characteristics of the light-emitting element of the present invention. 4A and 4B are diagrams illustrating a change over time in light emission luminance of the light-emitting element of the present invention. The figure which plotted the voltage which light emission starts with respect to the light emitting element of this invention. FIG. 11 shows current density-voltage characteristics of the light-emitting element of the present invention. FIG. 13 shows current density-voltage characteristics of a light-emitting element of a comparative example. FIG. 13 shows current density-voltage characteristics of a light-emitting element of a comparative example. The figure which shows the absorption spectrum of a film | membrane.

Explanation of symbols

201 Substrate 202 Electrode 203 Layer 204 Layer 205 Layer 206 Layer 207 Electrode 210 Light Emitting Element 502 Electrode 503 Layer 504 Layer 505 Layer 506 Layer 507 Electrode 90 Substrate 91 Driving Transistor 92 Light Emitting Element 93 Electrode 94 Electrode 95 Bulkhead Layer 401 Source Side Driving Circuit 403 Gate side drive circuit 409 FPC (flexible printed circuit)
410 Element substrate 5501 Main body 5502 Housing 5503 Display unit 5504 Keyboard

Claims (37)

A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer includes a molybdenum oxide and an aromatic amine compound. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— Any one of (di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer contains molybdenum oxide and an aromatic amine compound, and has a thickness of 40 nm or more. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— One of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and having a thickness of 40 nm or more. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer includes a molybdenum oxide and an aromatic amine compound, and is formed by co-evaporation. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— A light-emitting device comprising any one of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and formed by co-evaporation. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer contains a molybdenum oxide and an aromatic amine compound. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— Any one of (di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer contains molybdenum oxide and an aromatic amine compound, and has a thickness of 40 nm or more. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— One of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and having a thickness of 40 nm or more. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and an aromatic amine compound, and is formed by co-evaporation. Between the first electrode and the second electrode, a layer containing a light emitting substance, a mixed layer in contact with the first electrode, a layer containing a hole transporting substance, and an electron transporting substance And a layer containing
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— A light-emitting device comprising any one of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and formed by co-evaporation. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer is formed using molybdenum trioxide and an aromatic amine compound. A layer containing a light-emitting substance and a mixed layer in contact with the first electrode between the first electrode and the second electrode;
The mixed layer comprises molybdenum trioxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— It is formed using any of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer is formed using molybdenum trioxide and an aromatic amine compound. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer comprises molybdenum trioxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— It is formed using any of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer includes a molybdenum oxide and an aromatic amine compound. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— Any one of (di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer contains molybdenum oxide and an aromatic amine compound, and has a thickness of 40 nm or more. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— One of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and having a thickness of 40 nm or more. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer includes a molybdenum oxide and an aromatic amine compound, and is formed by co-evaporation. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— A light-emitting device comprising any one of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and formed by co-evaporation. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer contains a molybdenum oxide and an aromatic amine compound. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— Any one of (di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer contains molybdenum oxide and an aromatic amine compound, and has a thickness of 40 nm or more. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— One of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and having a thickness of 40 nm or more. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and an aromatic amine compound, and is formed by co-evaporation. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer includes molybdenum oxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— A light-emitting device comprising any one of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl and formed by co-evaporation. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer is formed using molybdenum trioxide and an aromatic amine compound. A layer containing a light-emitting substance and a mixed layer between the first electrode and the second electrode;
The mixed layer comprises molybdenum trioxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— It is formed using any of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer is formed using molybdenum trioxide and an aromatic amine compound. Between the first electrode and the second electrode, a layer containing a light-emitting substance, a mixed layer provided closer to the first electrode than the layer containing the light-emitting substance, and hole transport Having a layer containing a conductive substance and a layer containing an electron transporting substance,
The layer containing the hole transporting substance is provided between the mixed layer and the layer containing the light emitting substance,
The layer containing the electron transporting substance is provided between the second electrode and the layer containing the light emitting substance,
The mixed layer comprises molybdenum trioxide and 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl or 4,4-bis (N- (4- (N, N— It is formed using any of di-m-tolylamino) phenyl) -N-phenylamino) biphenyl.   The aromatic amine compound is 4,4′-bis [N- (1-naphthyl) -N-phenyl-amino] -biphenyl, 4,4-bis (N- (4- (N, N-di-m). -Tolylamino) phenyl) -N-phenylamino) biphenyl, 4,4′-bis [N- (3-methylphenyl) -N-phenyl-amino] -biphenyl, 4,4 ′, 4 ′ ′-tris (N , N-diphenyl-amino) -triphenylamine, 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenyl-amino] -triphenylamine Claim 1, Claim 3, Claim 5, Claim 7, Claim 9, Claim 11, Claim 13, Claim 15, Claim 19, Claim 21, Claim 23, Claim 25, Claim 27, Claim 29, Claim 31 Any light-emitting device according to an item. The first electrode is made of indium tin oxide, aluminum containing silicon, aluminum containing titanium, titanium, titanium nitride, tantalum, tantalum nitride, tungsten, chromium, molybdenum, indium tin oxide containing silicon, 2 to 20% 34. The light emitting device according to claim 1 , wherein the light emitting device is made of any one of indium oxide containing zinc oxide, gold, platinum, nickel, iron, cobalt, copper, and palladium. The mixed layer is one selected from 5,6,11,12-tetraphenyltetracene, hexabenenylbenzene, diphenylanthracene, t-butylperylene, 9,10-di (phenyl) anthracene, and coumarin 545T. The light emitting device according to any one of claims 1 to 34 , comprising a compound. The light emitting device according to any one of claims 1 to 34 , wherein the mixed layer includes a dendrimer. An electronic device comprising the light emitting device according to any one of claims 1 to 36 .

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