JP4906073B2 - LIGHT EMITTING DEVICE AND ELECTRONIC DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to a light-emitting element capable of obtaining light emission from a triplet excited state, a light-emitting device using the light-emitting element, and an electronic device.

  In recent years, light-emitting elements that emit light when holes and electrons flowing between electrodes are recombined and the generated excitons return to the ground state can be used as pixels or light sources. In the development of a light emitting element, improvement in light emission efficiency is important for reducing power consumption of a light emitting device using the light emitting element as a pixel or a lighting device using the light emitting element as a light source.

  So far, it has been known to improve luminous efficiency by using phosphorescent substances. For example, Patent Document 1 discloses a light-emitting element that can emit light efficiently as a result of suppressing movement of holes to the cathode side by providing a mixed layer doped with a phosphorescent material between a cathode and an anode. Are listed.

  It is considered effective to emit light efficiently by a technique such as Patent Document 1. However, in order to implement Patent Document 1, it is necessary to deposit three kinds of materials at the same time with high accuracy, and it is considered that the manufacturing margin may be lowered. Therefore, it is required to develop a new technique for obtaining a light emitting element that emits light with high efficiency.

JP-T-2004-515895

  An object of the present invention is to provide a light-emitting element capable of efficiently emitting light from an organometallic complex. It is another object of the present invention to provide a light emitting device that can be operated efficiently.

  In the practice of the present invention, an organometallic complex represented by the following general formula (1) is used.

In the general formula (1), R ¹ and R ² each represent an electron withdrawing group. R ³ and R ⁴ each represent either hydrogen or an alkyl group having 1 to 4 carbon atoms. L is a monoanionic ligand having a beta diketone structure, a monoanionic bidentate chelate ligand having a carboxyl group, or a monoanionic bidentate chelate ligand having a phenolic hydroxyl group Represents a monoanionic ligand such as Here, the electron withdrawing group is preferably any group selected from a halogen group, a —CF ₃ group, a cyano group, and an alkoxycarbonyl group. Further, the alkyl group having 1 to 4 carbon atoms is preferably any group selected from a methyl group, an ethyl group, an isopropyl group, and a sec-butyl group. Specifically, L is preferably any monoanionic ligand selected from ligands represented by the following structural formulas (1) to (7).

  Hereinafter, the present invention will be specifically described.

According to one aspect of the present invention, a light emitting layer, a hole transport layer provided in contact with the light emitting layer, an electron transport layer provided in contact with the light emitting layer, between the first electrode and the second electrode, A light emitting device having a mixed layer provided between the electron transport layer and the second electrode.
The hole transporting material contained in the hole transporting layer is not particularly limited, but is preferably a hole transporting material having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more. It is more preferable to use a hole transporting substance having a higher excitation energy than that of the host used in and having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. The first electron transporting material contained in the electron transporting layer is not particularly limited, but is preferably an electron transporting material having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more. It is more preferable that the substance be an electron-transporting substance having an excitation energy higher than that of the host used in 113 and an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. The mixed layer includes a second electron transporting substance and a substance that exhibits an electron donating property with respect to the second electron transporting substance. The light emitting layer contains an organometallic complex represented by the general formula (1) and a host. Note that the first electron transporting substance and the second electron transporting substance may be different or the same. Further, the second electron transporting material may have an excitation energy smaller than that of the host.
Between the first electrode and the second electrode, the hole-injecting layer or the second hole-transporting substance and the second hole-transporting substance are electron-accepting. A second mixed layer containing a substance may be provided. Note that the hole transporting substance and the second hole transporting substance contained in the hole transporting layer may be different or the same. Further, the second hole transporting material may have an excitation energy smaller than that of the host. With the light-emitting element having such a structure, light can be efficiently emitted when a voltage is applied so that the potential of the first electrode is higher than the potential of the second electrode.

  One aspect of the present invention is a light-emitting device using the light-emitting element of the present invention described above as a pixel or a light source.

  One embodiment of the present invention is an electronic device in which a light-emitting device using the light-emitting element of the present invention described above as a pixel or a light source is used for a display portion.

By implementing the present invention, a light-emitting element that emits light efficiently can be obtained. This is because, according to the present invention, electrons and holes can be injected into the light emitting layer in a well-balanced manner, and the injected electrons and holes can be effectively used to emit light. .
By implementing the present invention, a light-emitting device that can be operated with high current efficiency can be obtained. This is because by using the light emitting element of the present invention with improved external quantum efficiency, light emission with high luminance can be obtained even at a low voltage.
By implementing the present invention, an electronic device that can be operated with low power consumption can be obtained. This is because a light-emitting device that can be operated with high current efficiency by using the light-emitting element of the present invention is used as display means or illumination means.

  Hereinafter, one embodiment of the present invention will be described. 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 the embodiment.

(Embodiment 1)
One mode of a light-emitting element of the present invention will be described with reference to FIG.

  FIG. 1 illustrates a light-emitting element having a light-emitting layer 113 between a first electrode 101 and a second electrode 102. A first mixed layer 115 including an electron transporting substance and a substance that exhibits an electron donating property with respect to the electron transporting substance is provided between the light-emitting layer 113 and the second electrode 102. . Further, a hole transport layer 112 is provided in contact with the light emitting layer 113 on the first electrode 101 side of the light emitting layer 113, and an electron transport layer 114 is in contact with the light emitting layer 113 on the second electrode 102 side. Is provided. Note that in the light-emitting element in FIG. 1, a hole-injection layer 111 is provided between the first electrode 101 and the hole-transport layer 112. The light emitting layer 113 contains a light emitting substance. In such a light-emitting element, when a voltage is applied to the first electrode 101 and the second electrode 102 so that the potential of the first electrode 101 is higher than the potential of the second electrode 102, the light-emitting layer 113 is used. Then, holes are injected from the first electrode 101 side, and electrons are injected from the second electrode 102 side. Then, the holes and electrons injected into the light emitting layer 113 are recombined. The light-emitting layer 113 contains a light-emitting substance, and the light-emitting substance is excited by excitation energy generated by recombination. The luminescent material in the excited state emits light when returning to the ground state.

  Hereinafter, the first electrode 101, the second electrode 102, and each layer provided between the first electrode 101 and the second electrode 102 will be specifically described.

  There is no particular limitation on the substance forming the first electrode 101, but indium tin oxide, indium tin oxide containing silicon oxide, indium oxide containing 2 to 20% zinc oxide, gold (Au), platinum (Pt ), Nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), tantalum nitride, etc. It is preferable to use a substance. However, in the case where a layer having a function of generating holes is provided instead of the hole injection layer 111, the first electrode 101 may be formed using a substance having a low work function such as aluminum or magnesium. it can.

  As a material for forming the second electrode 102, in addition to a material having a low work function such as aluminum and magnesium, indium tin oxide, indium tin oxide containing silicon oxide, and oxide containing 2 to 20% zinc oxide are used. Indium, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd ), A substance having a high work function such as tantalum nitride, or the like can also be used.

  Note that the first electrode 101 and the second electrode 102 are preferably formed so that one or both of the electrodes can transmit light emitted.

The hole injection layer 111 is a layer having a function of assisting injection of holes from the first electrode 101 to the hole transport layer 112. By providing the hole injection layer 111, the difference in ionization potential between the first electrode 101 and the hole transport layer 112 is reduced, and holes are easily injected. The hole injection layer 111 has a lower ionization potential than the substance forming the hole transport layer 112 and a higher ionization potential than the substance forming the first electrode 101, or the hole transport layer 112. The first electrode 101 is preferably formed using a substance having an energy band gradient that increases the level on the hole transport layer 112 side when a thin film having a thickness of 1 to 2 nm is provided between the first electrode 101 and the first electrode 101. . Specific examples of a substance that can be used to form the hole-injection layer 111 include phthalocyanine (abbreviation: H ₂ Pc), copper phthalocyanine (CuPC), 4,4′-bis {N- [4- (N, N-di-m-tolylamino) phenyl] -N-phenylamino} biphenyl (abbreviation: DNTPD) and other low molecular weight poly (ethylenedioxythiophene) / poly (styrenesulfonic acid) aqueous solution (PEDOT / PSS) Molecule. That is, the hole injection layer 111 can be formed by selecting a material whose ionization potential in the hole injection layer 111 is smaller than that in the hole transport layer 112.

The hole transport layer 112 is a layer having a function of transporting holes. In the light-emitting element of this embodiment mode, the hole transport layer 112 has a function of transporting holes from the hole injection layer 111 to the light-emitting layer 113. Further, in the case where the hole transport layer 112 is provided in contact with the light emitting layer 113 as in this embodiment, the hole transport layer 112 has excitation energy generated in the light emitting layer 113 from the light emitting layer 113 to other layers. It also has a function to prevent it from moving to.
There is no particular limitation on the hole-transporting material used for forming the hole-transporting layer 112, but a hole-transporting material having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more is preferably used, and light emission It is more preferable to use a hole-transporting substance that has a higher excitation energy than the host used in the layer 113 and has a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. By using a hole transporting material having a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher, an increase in driving voltage due to hole mobility can be suppressed. In addition, the excitation energy is transferred from the light-emitting layer 113 to the hole-transport layer 112 by using a hole-transporting material that has a higher excitation energy than the host and has a hole mobility of 1 × 10 ⁻⁶ cm ² / Vs or more. Can be prevented, and a decrease in light emission efficiency due to transfer of excitation energy can be reduced. Here, the hole transporting substance is a substance having a hole mobility higher than that of electrons, and is preferably a value of a ratio of hole mobility to electron mobility (= hole mobility / electron). A substance whose mobility is greater than 100.
Specific examples of the hole transporting substance include 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), 4,4′-bis [N- (3- Methylphenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 1,3,5-tris [N, N-di (m-tolyl) amino] benzene (abbreviation: m-MTDAB), 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine (abbreviation: TCTA) and the like can be given. Of these hole transporting substances, a substance having an excitation energy higher than that of a substance used as a host may be appropriately selected and used.
The thickness of the hole transport layer 112 is not particularly limited, but is preferably 5 to 30 nm. With such a thickness, another layer (a hole injection layer 111 in this embodiment, or a layer between the hole transport layer 112 and the hole injection layer 111 is further provided from the hole transport layer 112 is provided. In this case, it is possible to suppress the transfer of excitation energy to the layer.) And to suppress an increase in driving voltage due to the thickness of the hole transport layer 112.
Since the hole transport layer 112 is provided as described above, the distance between the first electrode 101 and the light-emitting layer 113 can be increased, and thus light emission is caused by the metal contained in the first electrode 101. Quenching can be prevented. In addition, since excitation energy can be prevented from moving from the light emitting layer 113 to another layer, light can be emitted with high quantum efficiency.

As described above, the light-emitting layer 113 includes a light-emitting substance (also referred to as a guest). More specifically, the light emitting substance is contained in the light emitting layer 113 in a dispersed state. In the light-emitting layer 113, a substance having an energy gap in a triplet excited state wider than that of the light-emitting substance (an energy gap is an energy gap between the LUMO level and the HOMO level) is combined with the light-emitting substance. include. A substance having an energy gap wider than that of the light-emitting substance is included as a main component of the light-emitting layer 113 at a higher concentration than the light-emitting substance of the light-emitting layer 113 and is referred to as a host. The host has a function of assisting the light emitting material to emit light.
The light-emitting element of this embodiment includes an organometallic complex represented by the following general formula (1) as a light-emitting substance. By using the organometallic complex represented by the general formula (1), the recombination efficiency of holes and electrons can be improved. In addition, the increase in non-emissive transition due to the excitation lifetime of the triplet excited state is less likely to occur, and the repetition of excitation and emission can be performed efficiently.

In the general formula (1), R ¹ and R ² each represent an electron withdrawing group. R ³ and R ⁴ each represent either hydrogen or an alkyl group having 1 to 4 carbon atoms. L is a monoanionic ligand having a beta diketone structure, a monoanionic bidentate chelate ligand having a carboxyl group, or a monoanionic bidentate chelate ligand having a phenolic hydroxyl group Represents one of the following. Here, the electron withdrawing group is preferably any group selected from a halogen group, a —CF ₃ group, a cyano group, and an alkoxycarbonyl group. In addition, the alkyl group having 1 to 4 carbon atoms is preferably any group selected from a methyl group, an ethyl group, an isopropyl group, and a sec-butyl group. Specifically, L is preferably any ligand selected from ligands represented by the following structural formulas (1) to (7).

  In addition, among the organometallic complexes represented by the general formula (1), it is preferable to use organometallic complexes represented by the structural formulas (8) to (31).

As the host, carbazole such as 4,4′-di (N-carbazolyl) biphenyl (abbreviation: CBP), 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine (abbreviation: TCTA), etc. Derivatives, compounds having an arylamine skeleton such as 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB), bis [2- (2-hydroxyphenyl) pyridinato] It is preferable to use a metal complex such as zinc (abbreviation: Znpp ₂ ) or bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: ZnBOX).

The electron transport layer 114 is a layer having a function of transporting electrons. In the light-emitting element of this embodiment mode, the electron transport layer 114 has a function of transporting electrons from the first mixed layer 115 to the light-emitting layer 113. Further, in the case where the electron transport layer 114 is provided in contact with the light emitting layer 113 as in this embodiment, the electron transport layer 114 has the excitation energy generated in the light emitting layer 113 transferred from the light emitting layer 113 to other layers. It also has a function to prevent it from occurring.
There is no particular limitation on the electron-transporting material used for forming the electron-transporting layer 114, but an electron-transporting material having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher is preferably used for the light-emitting layer 113. It is more preferable to use an electron transporting substance having an excitation mobility larger than that of the host to be used and having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher. By using an electron transporting material having an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or higher, an increase in driving voltage due to the electron mobility can be suppressed. In addition, by using an electron transporting material having an excitation energy larger than that of the host and an electron mobility of 1 × 10 ⁻⁶ cm ² / Vs or more, the excitation energy is transferred from the light emitting layer 113 to the electron transporting layer 114. This can be prevented, and a decrease in light emission efficiency due to transfer of excitation energy can be reduced. Here, the electron transporting substance is a substance having electron mobility higher than that of holes, and is preferably a value of a ratio of electron mobility to hole mobility (= electron mobility / hole mobility). Refers to a substance having a degree greater than 100.
Specific examples of the electron transporting substance include bathocuproin (abbreviation: BCP), 3- (4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole (abbreviation: TAZ), bis [2- (2-hydroxyphenyl) benzoxazolate] zinc (abbreviation: Zn (BOX) ₂ ), 1,3-bis [5- (p-tert-butylphenyl) -1,3, 4-oxadiazol-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2 , 4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), and the like. Of these electron transporting substances, those having excitation energy higher than that of the substance used as the host may be appropriately selected and used.
Further, the thickness of the electron transport layer 114 is not particularly limited, but is preferably 5 to 30 nm. By setting the thickness as described above, another layer is provided from the electron transport layer 114 (in this embodiment, the first mixed layer 115, and further layers are provided between the electron transport layer 114 and the first mixed layer 115). In this case, it is possible to suppress the transfer of excitation energy to the layer.) And to suppress an increase in driving voltage due to the thickness of the electron transport layer 114.
By providing the electron transport layer 114 as described above, the distance between the first mixed layer 115 and the light emitting layer 113 which will be described later can be increased, which is attributed to the metal contained in the first mixed layer 115. Thus, the light emission can be prevented from being quenched. In addition, since excitation energy can be prevented from moving from the light emitting layer 113 to another layer, light can be emitted with high quantum efficiency.

Each of the hole transport layer 112, the light emitting layer 113, and the electron transport layer 114 has been described above. However, the hole transport material used for forming the hole transport layer 112, the host, and the electron transport layer 114 are used. The electron transporting material preferably satisfies the following relationships (i) and (ii).
(I) The absolute value of the difference between the ionization potential of the hole transporting substance used for forming the hole transport layer 112 and the ionization potential of the host is 0.4 eV or less. (Ii) Electrons used for forming the electron transport layer 114 The absolute value of the difference between the electron affinity of the transport material and the electron affinity of the host is 0.5 eV or less. By satisfying these relationships, injection of holes from the hole transport layer 112 to the light-emitting layer 113 and the electron transport layer 114 are performed. Can be easily injected into the light emitting layer 113, and as a result, the current efficiency can be further improved.

  Here, specific examples (1) to (3) of preferable combinations of the hole transporting material used for forming the hole transporting layer 112, the host, and the electron transporting material used for forming the electron transporting layer 114. Is shown in Table 1.

  Table 2 shows the ionization potential and electron affinity of the substances described in Table 1. The ionization potential (Ip) described in Table 2 is a value based on measurement by a photoelectron spectrometer (AC-2, Riken Keiki Co., Ltd.). Further, the electron affinity (Ea) described in Table 2 is obtained from the value of the ionization potential obtained by measurement after obtaining the value of the energy gap (ΔE) of each substance based on the absorption spectrum of each substance. It is a value calculated by subtracting the value of the energy gap. In addition, when calculating | requiring the value of an energy gap based on an absorption spectrum, it converted as 1.24 micrometer = 1eV. In addition, Ip, Ea, and ΔEa of substances not listed in Table 1 are also listed in Table 2 for reference.

  The most preferable combination shown in Table 1 is the combination represented by (1). By combining as in (1), a light-emitting element having an external quantum efficiency exceeding 20% as described in Example 1 can be manufactured.

The first mixed layer 115 is a layer including an electron transporting substance and a substance that exhibits an electron donating property with respect to the electron transporting substance. As the electron transporting material included in the first mixed layer 115, a material having an excitation energy larger than that of the host is not necessarily selected.
Specific examples of the electron transporting substance that can be used for forming the first mixed layer 115 include tris (8-quinolinolato) aluminum (abbreviation :) in addition to the electron transporting substance described in the description of the electron transporting layer 114. Alq ₃ ), tris (4-methyl-8-quinolinolato) aluminum (abbreviation: Almq ₃ ), bis (10-hydroxybenzo [h] -quinolinato) beryllium (abbreviation: BeBq ₂ ), bis (2-methyl-8- In addition to metal complexes such as quinolinolato) -4-phenylphenolato-aluminum (abbreviation: BAlq), bis [2- (2-hydroxyphenyl) benzothiazolate] zinc (abbreviation: Zn (BTZ) ₂ ), 2- (4- Biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 4,4- Scan (5-methyl-benzoxazolyl-2-yl) stilbene (abbreviation: BzOs) electron transporting material or the like can also be used.
In addition, examples of substances that exhibit electron donating properties include alkali metals such as lithium, sodium, and cesium (metals of group I of the periodic table), and alkaline earth metals such as magnesium, calcium, strontium, and barium (metals of group II of the periodic table) It is preferable to use a metal such as
By providing the first mixed layer 115 as described above, more electrons can be injected from the second electrode 102 side into the light-emitting layer 113.

In the light-emitting element having the above structure, electrons and holes can be injected into the light-emitting layer 113 with a good balance. This is because a layer including an electron transporting material such as the first mixed layer 115 and a material that exhibits an electron donating property with respect to the electron transporting material is provided, whereby more electrons are emitted from the light emitting layer 113. This is because it is possible to prevent excessive holes from being injected into the light-emitting layer 113 as a result. Further, the light-emitting element having the above structure has a high ratio of electrons and holes contributing to light emission among electrons and holes injected into the light-emitting layer 113, that is, high current efficiency. This is because the use of the organometallic complex represented by the general formula (1) as a luminescent substance makes it possible to effectively use the electrons and holes injected into the luminescent layer 113 for light emission. In other words, by using the organometallic complex represented by the general formula (1) as a light-emitting substance, electrons and holes can be efficiently recombined, that is, the recombination efficiency of carriers can be improved. This is because the repetition of excitation and emission can be performed efficiently.
As described above, by implementing the present invention, current efficiency is improved, and as a result, a light-emitting element with good external quantum efficiency can be obtained.

  Note that in the light-emitting element described above, instead of the hole-injection layer 111, a second mixed layer including a hole-transporting substance and a substance that exhibits an electron-accepting property with respect to the hole-transporting substance is provided. May be. As the hole transporting material used for forming the second mixed layer, it is not always necessary to select a material having an excitation energy higher than that of the host. In forming the second mixed layer, the hole transporting substance described in the description of the hole transport layer 112 can be used. As the substance exhibiting electron accepting properties, it is preferable to use a metal oxide such as molybdenum oxide, vanadium oxide, ruthenium oxide, or rhenium oxide.

  In the light-emitting element described above, a hole transporting property different from the hole transporting material used for forming the hole transporting layer 112 is provided between the hole transporting layer 112 and the hole injecting layer 111. A hole transport layer formed using a substance may be further provided. Further, since the hole transport layer provided in this manner is not in contact with the light emitting layer 113, the hole transport layer may be formed using a hole transport material having lower excitation energy than the host. Further, between the electron transport layer 114 and the first mixed layer 115, an electron transport layer formed using an electron transport material different from the electron transport material used for forming the electron transport layer 114 is also provided. Further, it may be provided. Further, since the electron transport layer provided in this manner is not in contact with the light emitting layer 113, the electron transport layer may be formed using an electron transport material having lower excitation energy than the host.

  There is no particular limitation on the method for manufacturing the light-emitting element described above, and a method such as a sputtering method, an evaporation method, or an inkjet method can be selected as appropriate and used. In particular, a layer in which a plurality of compounds are mixed, such as the light-emitting layer 113 and the first mixed layer 115, may be formed using, for example, a co-evaporation method. 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, and vaporized compounds are deposited on an object to be processed in a mixed state.

  Alternatively, the light-emitting element described above may be manufactured in the order in which the light-emitting layers and the like are stacked in order from the first electrode 101 and the second electrode 102 is finally formed, or from the second electrode 102. The light-emitting elements described above may be manufactured in the order in which the light-emitting layers and the like are sequentially stacked and the first electrode 101 is finally formed.

(Embodiment 2)
A method for synthesizing the organometallic complex used in the practice of the present invention will be described. Note that the synthesis method is not limited to the method disclosed herein, and other synthesis methods may be applied.

  The organometallic complex of the present invention represented by any one of structural formula (8) to structural formula (31) is synthesized as represented by the following synthetic scheme (a-1) to synthetic scheme (a-3). Obtained by the method. A ligand containing an electron withdrawing group is synthesized as in the synthesis scheme (a-1). Then, the synthesized ligand containing an electron withdrawing group is mixed with iridium chloride hydrochloride hydrate and coordinated to iridium as represented by the synthesis scheme (a-2). Furthermore, as represented by the synthesis scheme (a-3), a monoanionic ligand is coordinated to iridium.

Here, in Synthesis Scheme (a-1) to Synthesis Scheme (a-3), R ⁵ and R ⁶ each represent any of a fluoro group, a —CF ₃ group, a cyano group, and an alkoxycarbonyl group. R ⁷ and R ⁸ each represent hydrogen or a methyl group. L represents acetylacetone or picolinic acid.

Note that the method for synthesizing the organometallic complex of the present invention is not limited to those represented by the synthesis scheme (a-1) to the synthesis scheme (a-3). For example, in the ligand obtained in (a-1), regarding the ligand in which both R ⁷ and R ⁸ are alkyl-substituted, first, the para-position of the phenyl group is substituted with an electron-withdrawing group. 3-Diphenyl-1,4-dihydropyrazine-5,6-dione is used as a raw material to form a dichloro body in which the 5- and 6-positions are chlorinated using POCl ₃ or the like, and the resulting dichloro body and an alkyl metal are obtained. Obtained by coupling. Further, by using a salt containing platinum such as potassium tetrachloroplatinate instead of iridium chloride hydrochloride hydrate, the organometallic complex of the present invention containing platinum as a central metal can also be obtained. Further, by using a ligand such as dimethyl malonate, salicylaldehyde, salicylideneamine, tetrapyrazolato boronate instead of acetylacetone or picolinic acid, structural formulas (2), (4) to (7 It is also possible to obtain an organometallic complex of the present invention containing a ligand represented by

(Embodiment 3)
Since the light-emitting element of the present invention can emit light efficiently, a light-emitting device that can perform display operation with high current efficiency can be obtained by using the light-emitting element of the present invention described in Embodiment Mode 1 as a pixel. it can.

  In this embodiment, a circuit configuration and a driving method of a light-emitting device having a display function will be described with reference to FIGS.

  FIG. 2 is a schematic view of a light emitting device to which the present invention is applied as viewed from above. In FIG. 2, a pixel portion 6511, a source signal line driver circuit 6512, a write gate signal line driver circuit 6513, and an erase gate signal line driver circuit 6514 are provided over a substrate 6500. The source signal line drive circuit 6512, the write gate signal line drive circuit 6513, and the erase gate signal line drive circuit 6514 are each an FPC (flexible printed circuit) 6503 which is an external input terminal via a wiring group. Connected. The source signal line driver circuit 6512, the writing gate signal line driver circuit 6513, and the erasing gate signal line driver circuit 6514 receive a video signal, a clock signal, a start signal, a reset signal, and the like from the FPC 6503, respectively. . A printed wiring board (PWB) 6504 is attached to the FPC 6503. Note that the driver circuit portion is not necessarily provided over the same substrate as the pixel portion 6511 as described above. For example, an IC chip mounted on an FPC on which a wiring pattern is formed (TCP) or the like is used. It may be used and provided outside the substrate.

  In the pixel portion 6511, a plurality of source signal lines extending in the column direction are arranged side by side in the row direction. In addition, current supply lines are arranged side by side in the row direction. In the pixel portion 6511, a plurality of gate signal lines extending in the row direction are arranged side by side in the column direction. In the pixel portion 6511, a plurality of sets of circuits including light-emitting elements are arranged.

  FIG. 3 is a diagram illustrating a circuit for operating one pixel. The circuit illustrated in FIG. 3 includes a first transistor 901, a second transistor 902, and a light emitting element 903.

  Each of the first transistor 901 and the second transistor 902 is a three-terminal element including a gate electrode, a drain region, and a source region, and has a channel region between the drain region and the source region. Here, since the source region and the drain region vary depending on the structure and operating conditions of the transistor, it is difficult to limit which is the source region or the drain region. Therefore, in this embodiment, regions functioning as a source or a drain are referred to as a first electrode of a transistor and a second electrode of the transistor, respectively.

  The gate signal line 911 and the writing gate signal line driving circuit 913 are provided so as to be electrically connected or disconnected by a switch 918. The gate signal line 911 and the erasing gate signal line driver circuit 914 are provided so as to be electrically connected or disconnected by a switch 919. The source signal line 912 is provided so as to be electrically connected to either the source signal line driver circuit 915 or the power source 916 by the switch 920. The gate of the first transistor 901 is electrically connected to the gate signal line 911. The first electrode of the first transistor is electrically connected to the source signal line 912, and the second electrode is electrically connected to the gate electrode of the second transistor 902. The first electrode of the second transistor 902 is electrically connected to the current supply line 917, and the second electrode is electrically connected to one electrode included in the light-emitting element 903. Note that the switch 918 may be included in the write gate signal line driver circuit 913. The switch 919 may also be included in the erase gate signal line driver circuit 914. Further, the switch 920 may also be included in the source signal line driver circuit 915.

  There is no particular limitation on the arrangement of transistors, light-emitting elements, and the like in the pixel portion. For example, they can be arranged as shown in the top view of FIG. In FIG. 4, the first electrode of the first transistor 1001 is connected to the source signal line 1004, and the second electrode is connected to the gate electrode of the second transistor 1002. The first electrode of the second transistor is connected to the current supply line 1005, and the second electrode is connected to the electrode 1006 of the light emitting element. Part of the gate signal line 1003 functions as a gate electrode of the first transistor 1001.

  Next, a driving method will be described. FIG. 5 is a diagram for explaining the operation of a frame over time. In FIG. 5, the horizontal direction represents the passage of time, and the vertical direction represents the number of scanning stages of the gate signal line.

  When image display is performed using the light emitting device of the present invention, the screen rewriting operation and the display operation are repeatedly performed during the display period. The number of rewrites is not particularly limited, but is preferably at least about 60 times per second so that a person viewing the image does not feel flicker. Here, a period during which one screen (one frame) is rewritten and displayed is referred to as one frame period.

As shown in FIG. 5, one frame is time-divided into four subframes 501, 502, 503, and 504 including a writing period 501a, 502a, 503a, and 504a and a holding period 501b, 502b, 503b, and 504b. . A light emitting element to which a signal for emitting light is given is in a light emitting state in the holding period. The ratio of the length of the holding period in each subframe is as follows: first subframe 501: second subframe 502: third subframe 503: fourth subframe 504 = 2 ³ : 2 ² : 2 ¹ : 2 ⁰ = 8: 4: 2: 1. As a result, 4-bit gradation can be expressed. However, the number of bits and the number of gradations are not limited to those described here. For example, eight subframes may be provided so that 8-bit gradation can be performed.

  An operation in one frame will be described. First, in the subframe 501, the write operation is performed in order from the first row to the last row. Therefore, the start time of the writing period differs depending on the row. From the row in which the writing period 501a ends, the storage period 501b is started in order. In the holding period, the light-emitting element to which a signal for emitting light is given is in a light-emitting state. Further, the processing proceeds to the next subframe 502 in order from the row in which the holding period 501b ends, and the writing operation is performed in order from the first row to the last row as in the case of the subframe 501. The operation as described above is repeated until the holding period 504b of the subframe 504 ends. When the operation in the subframe 504 is completed, the process proceeds to the next frame. Thus, the accumulated time of the light emission in each subframe is the light emission time of each light emitting element in one frame. Various display colors having different brightness and chromaticity can be formed by changing the light emission time for each light emitting element and combining them in various ways within one pixel.

  When it is desired to forcibly end the holding period in the row that has already finished writing and has shifted to the holding period before the writing up to the last row is completed as in the subframe 504, after the holding period 504b. It is preferable to provide an erasing period 504c and control to forcibly enter a non-light emitting state. Then, the row that is forcibly set to the non-light-emitting state is kept in the non-light-emitting state for a certain period (this period is referred to as a non-light-emitting period 504d). Then, as soon as the writing period 504a of the last row ends, the next (or frame) writing period starts in order from the first row. Accordingly, it is possible to prevent the writing period 504a of the subframe 504 from overlapping with the writing period of the next subframe.

  In this embodiment, the subframes 501 to 504 are arranged in order from the longest holding period. However, the subframes 501 to 504 are not necessarily arranged as in the present embodiment. For example, the subframes 501 to 504 may be arranged from the shortest holding period. Alternatively, a long holding period and a short holding period may be arranged at random. In addition, the subframe may be further divided into a plurality of frames. That is, the gate signal line may be scanned a plurality of times during the period when the same video signal is applied.

  Here, the operation of the circuit shown in FIG. 3 in the writing period and the erasing period will be described.

  First, the operation in the writing period will be described. In the writing period, the gate signal line 911 in the n-th row (n is a natural number) is electrically connected to the writing gate signal line driving circuit 913 via the switch 918 and is connected to the erasing gate signal line driving circuit 914. Is disconnected. The source signal line 912 is electrically connected to the source signal line driver circuit 915 through the switch 920. Here, a signal is input to the gate of the first transistor 901 connected to the gate signal line 911 in the n-th row (n is a natural number), and the first transistor 901 is turned on. At this time, video signals are simultaneously input to the source signal lines from the first column to the last column. Note that the video signals input from the source signal lines 912 in each column are independent from each other. A video signal input from the source signal line 912 is input to the gate electrode of the second transistor 902 through the first transistor 901 connected to each source signal line 912. At this time, the light-emitting element 903 determines whether to emit light or not according to a signal input to the second transistor 902. For example, in the case where the second transistor 902 is a p-channel transistor, the light-emitting element 903 emits light by inputting a low level signal to the gate electrode of the second transistor 902. On the other hand, in the case where the second transistor 902 is an n-channel transistor, the light-emitting element 903 emits light when a high level signal is input to the gate electrode of the second transistor 902.

  Next, the operation in the erasing period will be described. In the erasing period, the gate signal line 911 in the n-th row (n is a natural number) is electrically connected to the erasing gate signal line driving circuit 914 via the switch 919, and is connected to the writing gate signal line driving circuit 913. Not connected. The source signal line 912 is electrically connected to the power source 916 through the switch 920. Here, a signal is input to the gate of the first transistor 901 connected to the gate signal line 911 in the n-th row, and the first transistor 901 is turned on. At this time, the erase signal is simultaneously input to the source signal lines from the first column to the last column. The erase signal input from the source signal line 912 is input to the gate electrode of the second transistor 902 through the first transistor 901 connected to each source signal line. At this time, current supplied from the current supply line 917 to the light-emitting element 903 is blocked by a signal input to the second transistor 902. Then, the light emitting element 903 is forced to emit no light. For example, in the case where the second transistor 902 is a p-channel transistor, the light-emitting element 903 does not emit light when a high level signal is input to the gate electrode of the second transistor 902. On the other hand, in the case where the second transistor 902 is an n-channel transistor, the light emitting element 903 does not emit light by inputting a low level signal to the gate electrode of the second transistor 902.

  In the erasing period, for the nth row (n is a natural number), a signal for erasing is input by the operation as described above. However, as described above, the nth row may be an erasing period and the other row (mth row (m is a natural number)) may be a writing period. In such a case, it is necessary to input a signal for erasure to the n-th row and a signal for writing to the m-th row using the source signal line in the same column. It is preferable to operate as described above.

  The gate signal line 911 and the erasing gate signal line driving circuit 914 are immediately disconnected after the light emitting element 903 in the n-th row does not emit light by the operation in the erasing period described above. The switch 920 is switched to connect the source signal line 912 and the source signal line driver circuit 915. Then, the source signal line 912 and the source signal line driver circuit 915 are connected, and the gate signal line 911 and the writing gate signal line driver circuit 913 are connected. Then, a signal is selectively input from the write gate signal line driver circuit 913 to the gate signal line 911 in the m-th row, the first transistor is turned on, and the source signal line driver circuit 915 receives the first column. A signal for writing is input to the source signal lines from the first column to the last column. By this signal, the light emitting element 903 in the m-th row emits light or does not emit light.

  Immediately after the writing period for the m-th row is completed as described above, the erasing period for the (n + 1) -th row is started. For this purpose, the gate signal line 911 and the writing gate signal line drive circuit 913 are disconnected, and the switch 920 is switched to connect the source signal line 912 to the power source 916. Further, the gate signal line 911 and the writing gate signal line driving circuit 913 are disconnected, and the gate signal line 911 is connected to the erasing gate signal line driving circuit 914. A signal is selectively input from the erasing gate signal line driver circuit 914 to the gate signal line 911 in the (n + 1) th row to turn on the signal to the first transistor 901, and an erasing signal is input from the power supply 916. In this way, immediately after the erasing period of the (n + 1) th row is completed, the writing period of the (m + 1) th row is started. Thereafter, similarly, the erasing period and the writing period may be repeated until the erasing period of the last row is operated.

  In this embodiment, the mode in which the m-th writing period is provided between the n-th erasing period and the (n + 1) -th erasing period has been described. An m-th writing period may be provided between the period and the n-th erasing period.

  In this embodiment, when the non-light emission period 504d is provided as in the subframe 504, the erasing gate signal line driver circuit 914 and a certain gate signal line 911 are disconnected from each other and writing is performed. The operation of connecting the gate signal line driving circuit 913 and the other gate signal lines to the connected state is repeated. Such an operation may be performed particularly in a frame in which a non-light emitting period is not provided.

(Embodiment 4)
One mode of a light-emitting device including the light-emitting element of the present invention is described with reference to a cross-sectional view of FIG.

  In FIG. 6, a transistor 11 provided for driving the light emitting element 12 of the present invention is surrounded by a dotted line. The light-emitting element 12 is the light-emitting element of the present invention described in Embodiment Mode 1. The drain of the transistor 11 and the first electrode 13 are electrically connected by a wiring 17 penetrating the first interlayer insulating film 16 (16a, 16b, 16c). The light emitting element 12 is separated from another light emitting element provided adjacent thereto by a partition wall layer 18. The light-emitting device of the present invention having such a structure is provided over the substrate 10 in this embodiment.

  Note that the transistor 11 illustrated in FIG. 6 is a top-gate transistor in which a gate electrode is provided on the opposite side of the substrate with a semiconductor layer as a center. However, the structure of the transistor 11 is not particularly limited, and may be, for example, a bottom gate type. In the case of a bottom gate, the semiconductor layer forming a channel may be formed with a protective film (channel protection type), or the semiconductor layer forming the channel may be partially concave ( Channel etch type).

  Further, the semiconductor layer included in the transistor 11 may be either crystalline or non-crystalline. Moreover, a semi-amorphous etc. may be sufficient.

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. In order to terminate dangling bonds (dangling bonds), hydrogen or halogen is contained at least 1 atomic% or more. It is also called a so-called microcrystalline semiconductor (microcrystal semiconductor). The microcrystalline semiconductor can be formed by glow discharge decomposition (plasma CVD) of SiH ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , or SiF ₄ . These gases 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 ³ or less, and in particular, the oxygen concentration is 5 × 10 ¹⁹ / cm ³ or less, preferably 1 × 10 ¹⁹ / cm ³ or less.

  Further, specific examples of the crystalline semiconductor layer include those made of single crystal or polycrystalline silicon, silicon germanium, or the like. These may be formed by laser crystallization, or may be formed by crystallization by a solid phase growth method using nickel or the like, for example.

  Note that in the case where the semiconductor layer is formed of an amorphous material, for example, amorphous silicon, the transistor 11 and other transistors (transistors constituting a circuit for driving a light emitting element) are all configured by N-channel transistors. It is preferable that the light-emitting device have a structured circuit. Other than that, a light-emitting device having a circuit including any one of an N-channel transistor and a P-channel transistor, or a light-emitting device including a circuit including both transistors may be used.

  Further, the first interlayer insulating film 16 may be a multilayer as shown in FIGS. 6A, 6B, or 6C, or may be a single layer. Note that 16a is made of an inorganic material such as silicon oxide or silicon nitride, 16b is acrylic or siloxane (siloxane has a skeletal structure formed by a bond of silicon (Si) and oxygen (O), and a substituent is a fluoro group. Or a compound containing an organic group such as an alkyl group.) Or a substance such as silicon oxide that can be coated and formed. Further, 16c is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. As described above, the first interlayer insulating film 16 may be formed using both an inorganic material and an organic material, or may be formed of any one of an inorganic material and an organic material.

  The partition layer 18 preferably has a shape in which the radius of curvature continuously changes at the edge portion. The partition layer 18 is formed using acrylic, siloxane, resist, silicon oxide, or the like. The partition wall layer 18 may be formed of any one of an inorganic material and an organic material, or may be formed using both.

  In FIGS. 6A and 6C, only the first interlayer insulating film 16 is provided between the transistor 11 and the light emitting element 12, but as shown in FIG. 6B, the first interlayer insulating film 16 is provided. In addition to the insulating film 16 (16a, 16b), the second interlayer insulating film 19 (19a, 19b) may be provided. In the light emitting device shown in FIG. 6B, the first electrode 13 penetrates through the second interlayer insulating film 19 and is connected to the wiring 17.

  Similar to the first interlayer insulating film 16, the second interlayer insulating film 19 may be a multilayer or a single layer. 19a is made of a material such as acrylic, siloxane, or silicon oxide that can be coated. Further, 19b is made of a silicon nitride film containing argon (Ar). In addition, there is no limitation in particular about the substance which comprises each layer, You may use things other than what was described here. Moreover, you may further combine the layer which consists of substances other than these. As described above, the second interlayer insulating film 19 may be formed using both an inorganic material and an organic material, or may be formed of any one of an inorganic film and an organic film.

  In the light-emitting element 12, when both the first electrode and the second electrode are formed using a light-transmitting substance, the first electrode and the second electrode are represented by the white arrows in FIG. Light emission can be extracted from both the electrode 13 side and the second electrode 14 side. In addition, in the case where only the second electrode 14 is formed using a light-transmitting substance, light emission is extracted only from the second electrode 14 side as represented by a white arrow in FIG. 6B. be able to. In this case, it is preferable that the first electrode 13 is made of a material having a high reflectivity, or a film (reflective film) made of a material having a high reflectivity is provided below the first electrode 13. In addition, in the case where only the first electrode 13 is formed using a light-transmitting substance, light emission is extracted only from the first electrode 13 side as represented by a white arrow in FIG. be able to. In this case, it is preferable that the second electrode 14 is made of a highly reflective material, or a reflective film is provided above the second electrode 14.

  In addition, the light emitting element 12 may be one in which the layer 15 is stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is higher than the potential of the first electrode 13. Alternatively, the layer 15 may be stacked so as to operate when a voltage is applied so that the potential of the second electrode 14 is lower than the potential of the first electrode 13. In the former case, the transistor 11 is an N-channel transistor, and in the latter case, the transistor 11 is a P-channel transistor.

  As described above, in this embodiment mode, an active light-emitting device that controls driving of a light-emitting element using a transistor has been described. In addition to this, a light-emitting element is driven without particularly providing a driving element such as a transistor. A passive light emitting device may be used. FIG. 7 is a perspective view of a passive light emitting device manufactured by applying the present invention. 7 includes the light-emitting element of the present invention having a structure in which a layer 955 including a light-emitting layer and the like is provided between an electrode 952 and an electrode 956 over a substrate 951. An end portion of the electrode 952 is covered with an insulating layer 953. A partition layer 954 is provided over the insulating layer 953. The side wall of the partition wall layer 954 has an inclination such that the distance between one side wall and the other side wall becomes narrower as it approaches the substrate surface. That is, the cross section in the short side direction of the partition wall layer 954 has a trapezoidal shape, and the bottom side (the side facing the insulating layer 953 in the same direction as the surface direction of the insulating layer 953) is the top side (the surface of the insulating layer 953). The direction is the same as the direction and is shorter than the side not in contact with the insulating layer 953. In this manner, by providing the partition layer 954, defects in the light-emitting element due to static electricity or the like can be prevented. A passive light emitting device can also be driven with low power consumption by including the light emitting element of the present invention that operates at a low driving voltage.

(Embodiment 5)
Since a light-emitting device using the light-emitting element of the present invention as a pixel or a light source can be operated with high current efficiency, an electronic device that can be operated with low power consumption can be obtained by using such a light-emitting device for a display portion. It is done.

  One embodiment of an electronic device mounted with a light emitting device to which the present invention is applied is shown in FIG.

  FIG. 8A illustrates a computer manufactured by applying the present invention, which includes a main body 5521, a housing 5522, a display portion 5523, a keyboard 5524, and the like. Low power consumption by incorporating a light-emitting device using the light-emitting element of the present invention as a pixel as described in Embodiment 1 (for example, a light-emitting device including a structure as described in Embodiments 3 and 4) as a display portion. You can complete a computer that can run on In addition, a computer can be completed even when a light-emitting device using the light-emitting element of the present invention as a light source is incorporated as a backlight. Specifically, as illustrated in FIG. 9, a lighting device in which a liquid crystal device 5512 and a light-emitting device 5513 are fitted in a housing 5511 and a housing 5514 may be incorporated as a display portion. In FIG. 9, an external input terminal 5515 is attached to the liquid crystal device 5512, and an external input terminal 5516 is attached to the light emitting device 5513.

  FIG. 8B illustrates a telephone manufactured by applying the present invention. The main body 5552 includes a display portion 5551, an audio output portion 5554, an audio input portion 5555, operation switches 5556 and 5557, an antenna 5553, and the like. ing. By incorporating a light-emitting device having the light-emitting element of the present invention as a display portion, a telephone that can be driven with low power consumption can be completed.

  FIG. 8C illustrates a television set manufactured by applying the present invention, which includes a display portion 5531, a housing 5532, a speaker 5533, and the like. By incorporating a light-emitting device having the light-emitting element of the present invention as a display portion, a television receiver that can be operated with low power consumption can be completed.

  As described above, the light-emitting device of the present invention is very suitable for use as a display portion of various electronic devices. Note that the electronic device is not limited to that described in this embodiment, and may be another electronic device such as a navigation device.

  In this example, two light-emitting elements, a light-emitting element (1) manufactured using TAZ as an electron transporting substance and a light-emitting element (2) manufactured using BCP as an electron transporting substance, are used with reference to FIGS. I will explain. These light emitting elements are formed using different electron transporting materials, but the other structures are the same. The light emitting element (1) corresponds to the combination of (1) in Table 1, and the light emitting element (2) corresponds to the combination of (2) in Table 1.

  First, the first electrode 201 was formed over the substrate 200 by sputtering using indium tin oxide containing silicon oxide. The thickness of the first electrode 201 was set to 110 nm.

  Next, the first layer 211 was formed to have a thickness of 40 nm on the first electrode 201 by vapor deposition using DNTPD. The first layer 211 thus formed functions as a hole injection layer.

  Next, the second layer 212 was formed to a thickness of 20 nm on the first layer 211 by evaporation using TCTA. The second layer 212 functions as a hole transport layer.

Next, a third layer 213 containing CBP and Ir (Fdppr-Me) ₂ acac represented by the structural formula (16) is formed on the second layer 212 so as to have a thickness of 30 nm. It formed by the co-evaporation method. The weight ratio of CBP to Ir (Fdppr-Me) ₂ acac was 1: 0.05 (= CBP: Ir (Fdppr-Me) ₂ acac). As a result, Ir (Fdppr-Me) ₂ acac is dispersed in a layer made of CBP. The third layer 213 functions as a light emitting layer, and Ir (Fdppr-Me) acac functions as a light emitting substance.

  Next, in the light-emitting element (1), the fourth layer 214 was formed to a thickness of 20 nm on the third layer 213 by vapor deposition using TAZ. In the light emitting element (2), the fourth layer 214 made of BCP was formed to a thickness of 20 nm on the third layer 213 by vapor deposition. Each of the fourth layers 214 functions as an electron transport layer.

  Next, in the light-emitting element (1), a fifth layer 215 containing TAZ and lithium was formed to a thickness of 30 nm on the fourth layer 214 by a co-evaporation method. The weight ratio of TAZ and lithium was 1: 0.01 (= TAZ: lithium). In the light-emitting element (2), the fifth layer 215 containing BCP and lithium was formed on the fourth layer 214 so as to have a thickness of 30 nm. The weight ratio of BCP to lithium was 1: 0.01 (= BCP: lithium).

  Next, the second electrode 202 was formed by evaporation on the fifth layer 215 using aluminum. The thickness of the second electrode 202 was set to 200 nm.

The light emitting elements (1) and (2) were produced as described above. Note that in the light emitting elements (1) and (2), the first electrode 201 and the second electrode 202 are formed so that the area of each light emission surface is 4 mm ² .

  A voltage is applied to the light-emitting elements (1) and (2) manufactured as described above so that the potential of the first electrode 201 is higher than the potential of the second electrode 202, whereby the light-emitting element (1). Next, the characteristics obtained when (2) is caused to emit light will be described.

11 plots the voltage-luminance characteristics, FIG. 12 plots the voltage-current characteristics, FIG. 13 plots the current density-luminance characteristics, and FIG. 14 plots the brightness-current efficiency characteristics. In FIG. 11, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m ² ). In FIG. 12, the horizontal axis represents voltage (V), and the vertical axis represents current (mA). In FIG. 13, the horizontal axis represents current density (mA / cm ² ), and the vertical axis represents luminance (cd / m ² ). In FIG. 14, the horizontal axis represents luminance (cd / m ² ) and the vertical axis represents current efficiency (cd / A). In FIGS. 11 to 14, the plots represented by ● are for the light emitting element (1), and the plots represented by ○ are for the light emitting element (2). 15A shows an emission spectrum obtained when a current of 1 mA was passed through the light-emitting element (1), and FIG. 15B was obtained when a current of 1 mA was passed through the light-emitting element (2). It is a figure shown about the obtained emission spectrum. 15A and 15B, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit).

11-14, it turns out that both the light emitting elements (1) and (2) emit light efficiently. In particular, it can be seen that the light-emitting element (1) is a light-emitting element with extremely excellent current efficiency. 15A and 15B show that yellow light emission derived from Ir (Fdppr-Me) ₂ acac is obtained in any of the light-emitting elements (1) and (2). 16 is a graph plotting the external quantum efficiencies of the light emitting elements (1) and (2) based on the current density-luminance characteristics shown in FIG. 13 and the emission spectrum shown in FIG. In FIG. 16, the horizontal axis represents luminance (cd / m ² ) and the vertical axis represents external quantum efficiency (%). A plot represented by ● is a plot for the light emitting element (1), and a plot represented by ○ is a plot for the light emitting element (2). FIG. 16 shows that the external quantum efficiency is good for both of the light-emitting elements (1) and (2). In particular, regarding the light emitting element (1), the external quantum efficiency sometimes exceeds 20%, which indicates that the light emitting element is very excellent.

  In this example, an example of the light-emitting element of the present invention using the organometallic complex represented by the following structural formula (32), which is one of the organometallic complexes represented by the general formula (1), will be described. . Note that the light-emitting element of this example is the same as the light-emitting element described in Example 1 in that five layers are provided between the first electrode and the second electrode. The embodiment will also be described with reference to FIG. 10 used in the description of the first embodiment.

  First, the first electrode 201 was formed over the substrate 200 by sputtering using indium tin oxide containing silicon oxide. The thickness of the first electrode 201 was set to 110 nm.

  Next, NPB and molybdenum trioxide were co-evaporated on the first electrode 201, whereby the first layer 211 was formed to a thickness of 40 nm. The deposition rates of NPB and molybdenum trioxide were adjusted so that the mixing ratio of NPB and molybdenum trioxide was NPB: molybdenum trioxide = 4: 1 in terms of mass ratio. The first layer 211 formed in this manner is a mixed layer containing NPB that is a hole-transporting substance and molybdenum oxide that is one of metal oxides that exhibit an electron-accepting property with respect to the hole-transporting substance. And has a function of generating holes.

  Next, the second layer 212 was formed to a thickness of 20 nm on the first layer 211 by evaporation using TCTA. The second layer 212 functions as a hole transport layer.

Next, a third layer 213 containing CBP and Ir (Fdppr-iPr) ₂ (pic) represented by the structural formula (32) is formed on the second layer 212 so as to have a thickness of 30 nm. And formed by a co-evaporation method. The weight ratio of CBP to Ir (Fdppr-iPr) ₂ (pic) was 1: 0.05 (= CBP: Ir (Fdppr-iPr) ₂ (pic)). As a result, Ir (Fdppr-iPr) ₂ (pic) is in a state of being dispersed in a layer containing CBP as a main component. The third layer 213 functions as a light-emitting layer, and Ir (Fdppr-iPr) ₂ (pic) functions as a light-emitting substance.

  Next, a fourth layer 214 having a thickness of 20 nm was formed on the third layer 213 by TAZ using a vapor deposition method. The fourth layer 214 functions as an electron transport layer.

  Next, a fifth layer 215 containing TAZ and lithium was formed over the fourth layer 214 so as to have a thickness of 30 nm. The weight ratio of TAZ and lithium was 1: 0.01 (= TAZ: lithium).

  Next, the second electrode 202 was formed by evaporation on the fifth layer 215 using aluminum. The thickness of the second electrode 202 was set to 200 nm.

As described above, the light-emitting element of this example was manufactured. Note that in this light-emitting element, the first electrode 201 and the second electrode 202 are formed so that the area of the light emission surface is 4 mm ² .

  The characteristics obtained when a voltage is applied to the light-emitting element manufactured as described above so that the potential of the first electrode 201 is higher than the potential of the second electrode 202 and the light-emitting element emits light. Will be described next.

FIG. 17 is a plot of voltage-luminance characteristics, FIG. 18 is a plot of voltage-current characteristics, FIG. 19 is a plot of current density-luminance characteristics, and FIG. 20 is a plot of luminance-current efficiency characteristics. In FIG. 17, the horizontal axis represents voltage (V) and the vertical axis represents luminance (cd / m ² ). In FIG. 18, the horizontal axis represents voltage (V), and the vertical axis represents current (mA). In FIG. 19, the horizontal axis represents current density (mA / cm ² ), and the vertical axis represents luminance (cd / m ² ). In FIG. 20, the horizontal axis represents luminance (cd / m ² ) and the vertical axis represents current efficiency (cd / A). FIG. 21 is a graph showing an emission spectrum obtained when a current of 1 mA is passed through the light-emitting element. In FIG. 21, the horizontal axis represents wavelength (nm) and the vertical axis represents emission intensity (arbitrary unit).

FIG. 21 shows that the light-emitting element emits green-yellow light derived from Ir (Fdppr-iPr) ₂ (pic). FIG. 22 is a graph plotting the external quantum efficiency of the light-emitting element based on the current density-luminance characteristics shown in FIG. 19 and the emission spectrum shown in FIG. In FIG. 22, the horizontal axis represents luminance (cd / m ² ) and the vertical axis represents external quantum efficiency (%). FIG. 22 shows that the light-emitting element has good external quantum efficiency. The maximum value of the external quantum efficiency is about 20%, which indicates that the light emitting element emits light very efficiently.

(Synthesis Example 1)
Ir (Fdppr-Me) ₂ acac, which is one of the organometallic complexes represented by the general formula (1), is used in the implementation of Example 1 and is the organometallic complex represented by the structural formula (16). A synthesis method will be described.

Synthesis Method of Organometallic Complex of the Present Invention Represented by Structural Formula (16) (name: (acetylacetonato) bis [2,3-bis (4-fluorophenyl) -5-methylpyrazinato] iridium (III)) explain.
[Step 1: Synthesis of Ligand (abbreviation: HFdppr-Me)]
First, using ethanol as a solvent, 5.31 g of 4,4′-difluorobenzyl [manufactured by Tokyo Chemical Industry] and 1.60 g of 1,2-diaminopropane [manufactured by Kanto Chemical] were mixed and then refluxed for 3 hours. The refluxed mixed solution was concentrated by an evaporator, washed with ethanol and recrystallized to obtain 2,3-bis (4-fluorophenyl) -5-methyl-5,6-dihydropyrazine (light yellow powder, collected). 86%).
Next, using ethanol as a solvent, 5.29 g of 2,3-bis (4-fluorophenyl) -5-methyl-5,6-dihydropyrazine obtained above and 6.04 g of iron (III) chloride were mixed. The mixture was gently heated and stirred for 3 hours. After the reaction, the solid obtained by adding water was purified with a column using dichloromethane as a developing solvent to obtain the ligand 2,3-bis (4-fluorophenyl) -5-methylpyrazine (HFdppr-Me). (Milky white powder, yield 72%).
A synthesis scheme (b-1) relating to the synthesis of Step 1 is shown below.

[Step 2: Synthesis of Binuclear Complex (abbreviation: [Ir (Fdppr-Me) ₂ Cl] ₂ )]
Next, using a mixed liquid of 30 ml of 2-ethoxyethanol and 10 ml of water as a solvent, 3.75 g of the ligand HFdppr-Me obtained above, iridium chloride hydrochloride hydrate (III) (IrCl ₃ .HCl. 1.59 g of H ₂ O) [Sigma-Aldrich] was mixed and refluxed for 16 hours under a nitrogen atmosphere to obtain a binuclear complex [Ir (Fdppr-Me) ₂ Cl] ₂ (red brown powder, yield) 87%).
A synthesis scheme (b-2) relating to the synthesis of Step 2 is shown below.

[Step 3: Synthesis of Organometallic Complex of the Present Invention (abbreviation: [Ir (Fdppr-Me) ₂ (acac)])]
Furthermore, using 30 ml of 2-ethoxyethanol as a solvent, 1.91 g of [Ir (Fdppr-Me) ₂ Cl] ₂ obtained above, 0.37 ml of acetylacetone (Hacac), and 1.28 g of sodium carbonate were mixed. The mixture was refluxed for 16 hours under a nitrogen atmosphere to obtain a yellow-orange powder (yield 34%).
A synthesis scheme (b-3) relating to the synthesis of Step 3 is shown below.

When the obtained yellow-orange powder was analyzed by nuclear magnetic resonance spectroscopy ( ¹ H-NMR), the following results were obtained, and Ir (Fdppr-Me) ₂ (acac) represented by the structural formula (16) was obtained. )

¹ H-NMR. δ (CDCl ₃ ): 8.27 (s, 2H), 7.66 (dd, 4H), 7.22 (m, 4H), 6.78 (dd, 2H), 6.26 (td, 2H) , 5.92 (dd, 2H), 5.31 (s, 1H), 2.70 (s, 6H), 1.89 (s, 6H)

Moreover, when the decomposition temperature _Td of the obtained organometallic complex Ir (Fdppr-Me) ₂ (acac) of the present invention was measured by a differential thermothermal gravimetric simultaneous measurement apparatus (TG / DTA 320 type, manufactured by Seiko Electronics Co., Ltd.). , T _d = 291 ° C., showing good heat resistance.

Next, it melt | dissolved in the dichloromethane solution of Ir (Fdppr-Me) ₂ (acac), and measured the emission spectrum (FS920 made from a fluorophotometer Hamamatsu Photonics Co., Ltd.). As a result, it was found that the emission spectrum of Ir (Fdppr-Me) ₂ (acac) was yellow emission having a peak at 564 nm.

(Synthesis Example 2)
Ir (Fdppr-iPr) ₂ (pic), which is one of the organometallic complexes represented by the general formula (1), is used in the implementation of Example 1, and is the organometallic complex represented by the structural formula (32). ) Will be described.

[Step 1: Synthesis of Ligand (abbreviation: HFdppr-iPr)]
First, 5.36 g of 4,4′-difluorobenzyl (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1.31 g of anhydrous ethylenediamine [manufactured by Tokyo Chemical Industry Co., Ltd.] are mixed in 150 mL of dehydrated ethanol, The mixture was refluxed for 3 hours under a nitrogen atmosphere. The reaction solution was allowed to cool to room temperature, 1.60 g of acetone and 1.47 g of potassium hydroxide were added, and the solution was refluxed for 6 hours under a nitrogen atmosphere. After the reaction, water was added to the reaction solution, and the organic layer was extracted with ethyl acetate. The organic layer obtained by extraction was dried over sodium sulfate and filtered, and then the solvent of the filtrate was distilled off. By purifying the obtained residue by silica gel column chromatography using dichloromethane as a developing solvent, 4.00 g of 2,3-bis (4-fluorophenyl) -5-isopropylpyrazine (HFdppr-iPr) which is a ligand. (Light yellow oil, yield 59%) was obtained. A synthesis scheme (c-1) relating to the synthesis of Step 1 is shown below.

[Step 2: Synthesis of a binuclear complex (abbreviation: [Ir (Fdppr-iPr) ₂ Cl] ₂ )]
Next, in a mixed solvent obtained by mixing 30 mL of 2-ethoxyethanol and 10 mL of water, 4.00 g of the ligand HFdppr-iPr obtained in Step 1 above, iridium (III) chloride hydrate (IrCl _3. 1.61 g of H ₂ O) [manufactured by Sigma-Aldrich] was mixed, and the mixture was refluxed for 19 hours under a nitrogen atmosphere to obtain a binuclear complex [Ir (Fdppr-iPr) ₂ Cl] ₂ ( Orange powder, yield 72%). A synthesis scheme (c-2) relating to the synthesis of Step 2 is shown below.

[Step 3: Synthesis of Organometallic Complex of the Present Invention (abbreviation: Ir (Fdppr-iPr) ₂ (pic))]
Furthermore, 1.61 g of the binuclear complex [Ir (Fdppr-iPr) ₂ Cl] ₂ obtained in Step 2 above and 0.94 g of picolinic acid were mixed with 25 mL of dichloromethane, and the mixture was mixed under a nitrogen atmosphere for 18 hours. A reflux color powder was obtained by refluxing (yield 90%). A synthesis scheme (c-3) relating to the synthesis of Step 3 is shown below.

When the obtained bright yellow powder was analyzed by nuclear magnetic resonance spectroscopy ( ¹ H-NMR), the following results were obtained, which is one of the organometallic complexes of the present invention and represented by the structural formula (32). It was found that Ir (Fdppr-iPr) ₂ (pic).

¹ H-NMR. δ (CDCl ₃ ): 1.15 (d, 6H), 1.32 (t, 6H), 2.93 (quin, 1H), 3.16 (quin, 1H), 5.82 (dd, 1H) , 6.07 (dd, 1H), 6.31 (td, 1H), 6.38 (td, 1H), 6.85 (dd, 1H), 6.92 (dd, 1H), 7.11- 7.32 (m, 5H), 7.53 (m, 1H), 7.59-7.69 (m, 4H), 7.80 (d, 1H), 8.05 (td, 1H), 8 .43 (d, 1H), 8.60 (s, 1H).

In addition, the decomposition temperature _Td of the obtained organometallic complex Ir (Fdppr-iPr) ₂ (pic) of the present invention was determined by TG / DTA (TG / DTA 320 type, manufactured by Seiko Electronics Co., Ltd.). When measured, it was found that T _d = 348 ° C. and good heat resistance was exhibited.

Next, it melt | dissolved in the dichloromethane solution of Ir (Fdppr-iPr) ₂ (pic), and measured the emission spectrum (FS920 by the fluorimeter Hamamatsu Photonics Co., Ltd.). As a result, it was found that the emission spectrum of Ir (Fdppr-iPr) ₂ (pic) was yellow emission having a peak at 559 nm.

4A and 4B illustrate one embodiment of a light-emitting element of the present invention. FIG. 6 is a top view illustrating one embodiment of a light-emitting device of the present invention. 4A and 4B each illustrate one embodiment of a circuit for driving pixels provided in a light-emitting device of the present invention. 4A and 4B illustrate one embodiment of a pixel portion included in a light-emitting device of the present invention. 4 is a frame diagram illustrating a driving method for driving pixels included in the light-emitting device of the present invention. FIG. 3A and 3B each illustrate one embodiment of a cross section of a light-emitting device of the present invention. 4A and 4B illustrate one embodiment of a light-emitting device of the present invention. 6A and 6B illustrate one embodiment of an electronic device to which the present invention is applied. 6A and 6B illustrate one embodiment of an electronic device to which the present invention is applied. 4A and 4B illustrate a light-emitting element manufactured in Example 1. FIG. FIG. 6 shows voltage-luminance characteristics of the light-emitting element manufactured in Example 1. FIG. 5 shows voltage-current characteristics of the light-emitting element manufactured in Example 1. FIG. 6 shows current density-luminance characteristics of the light-emitting element manufactured in Example 1. FIG. 11 shows luminance-current efficiency characteristics of the light-emitting element manufactured in Example 1. 2 shows an emission spectrum of the light-emitting element manufactured in Example 1. FIG. 9 shows luminance vs. external quantum efficiency of the light-emitting element manufactured in Example 1. FIG. 11 shows voltage-luminance characteristics of the light-emitting element manufactured in Example 2. FIG. 6 shows voltage-current characteristics of the light-emitting element manufactured in Example 2. FIG. 6 shows current density-luminance characteristics of the light-emitting element manufactured in Example 2. FIG. 11 shows luminance-current efficiency characteristics of the light-emitting element manufactured in Example 2. 4 shows an emission spectrum of the light-emitting element manufactured in Example 2. FIG. 11 shows luminance vs. external quantum efficiency of the light-emitting element manufactured in Example 2.

Explanation of symbols

10 substrate 11 transistor 12 light emitting element 12 light emitting element 13 first electrode 14 second electrode 15 layer 16 interlayer insulating film 17 wiring 18 partition wall layer 19 interlayer insulating film 101 first electrode 102 second electrode 111 hole injection layer 112 hole transport layer 113 light emitting layer 114 electron transport layer 115 first mixed layer 200 substrate 201 first electrode 202 second electrode 211 first layer 212 second layer 213 third layer 214 fourth layer 215 Fifth layer 501 Subframe 502 Subframe 503 Subframe 504 Subframe 901 Transistor 902 Transistor 903 Light emitting element 911 Gate signal line 912 Source signal line 913 Write gate signal line drive circuit 914 Erase gate signal line drive circuit 915 Source signal line drive circuit 916 Power supply 917 Current supply line 918 Switch 19 switch 920 switch 951 substrate 952 electrode 953 insulating layer 954 partition layer 955 layer 956 electrode 1001 transistor 1002 transistor 1003 gate signal line 1004 source signal line 1005 current supply line 1006 electrode 501a writing period 501b holding period 502a writing period 502b holding period 503a writing Period 503b Holding period 504a Writing period 504b Holding period 504b Holding period 504c Erasing period 504d Non-light emitting period 5511 Case 5512 Liquid crystal device 5513 Light emitting device 5514 Case 5515 External input terminal 5516 External input terminal 5521 Body 5522 Case 5523 Display portion 5524 Keyboard 5531 Display portion 5532 Housing 5533 Speaker 5551 Display portion 5552 Body 5553 Antenna 5554 Audio output unit 5555 Audio input unit 5556 Operation switch 6500 Substrate 6503 FPC
6504 Printed Wiring Board (PWB)
6511 Pixel portion 6512 Source signal line drive circuit 6513 Write gate signal line drive circuit 6514 Erase gate signal line drive circuit

Claims (9)

Between the first electrode and the second electrode, a light emitting layer, a hole transport layer provided in contact with the light emitting layer, an electron transport layer provided in contact with the light emitting layer, and the electron transport A mixed layer provided between the layer and the second electrode,
The hole transport layer contains a hole transport material,
The electron transport layer includes a first electron transport material,
The light emitting layer includes an organometallic complex represented by the general formula (1) and a host,
The light-emitting device, wherein the mixed layer includes a second electron transporting substance and an alkali metal or an alkaline earth metal.

(In the formula, R ¹ and R ² each represent any group selected from a halogen group, —CF ₃ group, cyano group, and alkoxycarbonyl group . Also, R ³ and R ⁴ are respectively It represents either hydrogen or an alkyl group having 1 to 4 carbon atoms, L represents a monoanionic ligand.) Between the first electrode and the second electrode, a light emitting layer, a hole transport layer provided in contact with the light emitting layer, an electron transport layer provided in contact with the light emitting layer, and the holes A hole injection layer provided between a transport layer and the first electrode, and a mixed layer provided between the electron transport layer and the second electrode,
The hole transport layer contains a hole transport material,
The electron transport layer includes a first electron transport material,
The light emitting layer includes an organometallic complex represented by the general formula (1) and a host,
The light-emitting device, wherein the mixed layer includes a second electron transporting substance and an alkali metal or an alkaline earth metal.

(Wherein R ¹ , R ² Are each a halogen group, -CF ₃ It represents any group selected from a group, a cyano group, and an alkoxycarbonyl group. R ³ , R ⁴ Each represents either hydrogen or an alkyl group having 1 to 4 carbon atoms. L represents a monoanionic ligand. ) The monoanionic ligand in the organometallic complex represented by the general formula (1) is a ligand represented by any one of the structural formulas (1) to (7). The light-emitting device according to claim 1 , wherein the light-emitting device is a light-emitting device.
A light emitting layer, a hole transport layer provided in contact with the light emitting layer, an electron transport layer provided in contact with the light emitting layer, and the electron transport layer between the first electrode and the second electrode And a mixed layer provided between the second electrode and the second electrode,
The hole transport layer contains a hole transport material,
The electron transport layer includes a first electron transport material,
The light emitting layer includes (acetylacetonato) bis [2,3-bis (4-fluorophenyl) -5-methylpyrazinato] iridium (III) and a host,
The mixed layer, a second electron transporting material, light emitting device according to claim including that an alkali metal or alkaline earth metal. The hole transport material has a higher excitation energy than the host,
5. The light-emitting device according to claim 1, wherein the first electron transporting substance has excitation energy larger than that of the host. The hole transporting material state, and are the absolute value of 0.4eV or less of the difference between the ionization potential of the host,
The first electron transporting substance is claimed in any one of claims 1 to 5 the absolute value of the difference between the electron affinity of the host, wherein the following der Turkey 0.5eV Light-emitting device. The hole transporting substance includes 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, 4,4′-bis [N- (3-methylphenyl) -N-phenylamino. ] Selected from biphenyl, 1,3,5-tris [N, N-di (m-tolyl) amino] benzene, and 4,4 ′, 4 ″ -tris (N-carbazolyl) triphenylamine Or a single substance
The first electron transporting substance includes bathocuproine, 3- (4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl) -1,2,4-triazole, bis [2- (2- Hydroxyphenyl) benzoxazolate] zinc, 1,3-bis [5- (p-tert-butylphenyl) -1,3,4-oxadiazol-2-yl] benzene, 3- (4-tert- It is any one substance selected from butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4-triazole and bathophenanthroline. The light emitting device according to any one of claims 1 to 6. The host is 4,4′-di (N-carbazolyl) biphenyl, 4,4 ′, 4 ″ -tri (N-carbazolyl) triphenylamine, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, bis [2- (2-hydroxyphenyl) pyridinato] zinc, and bis [2- (2-hydroxyphenyl) benzoxazolate] zinc The light emitting device according to claim 1, wherein the light emitting device is provided.   An electronic apparatus including the light emitting device according to claim 1.