Patent Application
20230250119
One embodiment of the present invention relates to an organic compound, a light-emitting device, a display device, an electronic device, a light-emitting apparatus, a lighting device, or a semiconductor device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. One embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specific examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a light-emitting apparatus, a power storage device, a memory device, a method for driving any of them, and a method for manufacturing any of them.
A heteroleptic iridium compound to be used as a light-emitting body and a light-emitting device including the compound are known (see Patent Document 1), for example.
An object of one embodiment of the present invention is to provide a novel organic compound that is highly convenient, useful, or reliable. Another object is to provide a novel light-emitting device that is highly convenient, useful, or reliable. Another object is to provide a novel display device that is highly convenient, useful, or reliable. Another object is to provide a novel electronic device that is highly convenient, useful, or reliable. Another object is to provide a novel light-emitting apparatus that is highly convenient, useful, or reliable. Another object is to provide a novel lighting device that is highly convenient, useful, or reliable. Another object is to provide a novel organic compound, a novel light-emitting device, a novel display device, a novel electronic device, a novel light-emitting apparatus, a novel lighting device, or a novel semiconductor device.
Note that the description of these objects does not preclude the existence of other objects. In one embodiment of the present invention, there is no need to achieve all these objects. Other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
(1) One embodiment of the present invention is an organic compound represented by General Formula (G0).
Note that in General Formula (G0), R101 to R111 each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms, n is 1 or 2, and L represents a ligand represented by General Formula (L0).
Note that in General Formula (L0), R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
(2) Another embodiment of the present invention is an organic compound represented by General Formula (G1-1).
Note that in General Formula (G1-1), n is 1 or 2, and L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
(3) Another embodiment of the present invention is an organic compound represented by General Formula (G1-2).
Note that in General Formula (G1-2), n is 1 or 2, and L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
(4) Another embodiment of the present invention is the organic compound in which one or more hydrogen atoms of the alkyl group in the ligand L are substituted by deuterium.
(5) Another embodiment of the present invention is the organic compound in which the ligand L is represented by Structural Formula (L1-1).
(6) Another embodiment of the present invention is the organic compound in which the ligand L is represented by Structural Formula (L1-2).
Therefore, a deuterated alkyl group is introduced into a carbon atom having a high spin density in a triplet excited state, and the stability of the compound in an excited state can be improved. In addition, the deuterated alkyl group is introduced into a carbon atom at which the lowest unoccupied molecular orbital (LUMO) concentrates, and the stability of the compound in a state where the LUMO receives electrons, i.e., a reduction state can be improved. A phenyl group is introduced into a carbon atom adjacent to the carbon atom at which the LUMO concentrates, and the LUMO can be widened. Moreover, the LUMO is stabilized and the stability of the compound in a reduction state can be improved. The deuterated alkyl group can exhibit a steric hindrance effect against the phenyl group. The rotation of the phenyl group can be suppressed and the thermophysical property, e.g., the sublimation property of the compound can be improved. The vibration of the compound can be suppressed and thermal deactivation from the excited state can be suppressed. High emission efficiency can be achieved. A ligand is selected so that a heteroleptic structure is formed, and the shape of an emission spectrum can be adjusted. The shape of the emission spectrum can be adjusted so that light emitted from the compound includes light with a short wavelength as compared with light emitted from a homoleptic compound. The thermophysical property, e.g., the sublimation property of the compound can be improved. As a result, a novel organic compound that is highly convenient, useful, or reliable can be provided.
(7) Another embodiment of the present invention is a light-emitting device including a first electrode, a second electrode, and a first unit.
The first unit is located between the first electrode and the second electrode, and includes the above-described organic compound.
Therefore, the first unit includes the organic compound of one embodiment of the present invention. The first unit can easily receive holes. Since the LUMO is widened in the organic compound of one embodiment of the present invention, the first unit can easily receive electrons. In addition, the driving voltage of a light-emitting device can be reduced. Light emitted from the organic compound of one embodiment of the present invention includes light with a wavelength shorter than 500 nm and the emission spectrum of the organic compound covers a wavelength shorter than 500 nm, so that when the organic compound is used with a fluorescent material (e.g., a green fluorescent material) having an absorption spectrum partly overlapping with the emission spectrum, energy can be efficiently transferred to the fluorescent material. Moreover, the light-emitting device can exhibit a broad emission spectrum. A phenomenon in which the luminance of the light-emitting device decreases in use can be suppressed. The reliability of the light-emitting device can be increased. As a result, a novel light-emitting device that is highly convenient, useful, or reliable can be provided.
(8) Another embodiment of the present invention is a display device including a first light-emitting device and a second light-emitting device.
The first light-emitting device includes a first electrode, a second electrode, a first unit, and a first layer. The first unit is between the first electrode and the second electrode and the first layer is between the first unit and the first electrode.
The first unit comprises the organic compound and the first layer includes a second organic compound having a halogen group or a cyano group, or a transition metal oxide.
The second light-emitting device is adjacent to the first light-emitting device and includes a third electrode, a fourth electrode, a second unit, and a second layer. A space is between the third electrode and the first electrode, the second unit is between the third electrode and the fourth electrode, and the second layer is between the second unit and the third electrode.
The second unit includes a light-emitting material and the second layer includes the second organic compound or the transition metal oxide.
The second layer includes a region that is thinner than the first layer between the second layer and the first layer and overlaps with the space.
Thus, current flowing through the region can be suppressed, for example. Moreover, current flowing between the first layer and the second layer can be suppressed. Furthermore, a phenomenon in which the second light-emitting device that is adjacent to the first light-emitting device unintentionally emits light in accordance with the operation of the first light-emitting device can be suppressed. As a result, a novel display device that is highly convenient, useful, or reliable can be provided.
(9) Another embodiment of the present invention is a display device including the above-described light-emitting device, and a transistor or a substrate.
(10) Another embodiment of the present invention is an electronic device including the above-described display device, and a sensor, an operation button, a speaker, or a microphone.
(11) Another embodiment of the present invention is a light-emitting apparatus including the above-described light-emitting device, and a transistor or a substrate.
(12) Another embodiment of the present invention is a lighting device including the above-described light-emitting apparatus and a housing.
Although the block diagram in drawings attached to this specification shows components classified based on their functions in independent blocks, it is difficult to classify actual components based on their functions completely, and one component can have a plurality of functions.
Note that the light-emitting apparatus in this specification includes, in its category, an image display device that uses a light-emitting device. The light-emitting apparatus may also include, in its category, a module in which a light-emitting device is provided with a connector such as an anisotropic conductive film or a tape carrier package (TCP), a module in which a printed wiring board is provided at the end of a TCP, and a module in which an integrated circuit (IC) is directly mounted on a light-emitting device by a chip on glass (COG) method. Furthermore, a lighting device or the like may include the light-emitting apparatus.
With one embodiment of the present invention, a novel organic compound that is highly convenient, useful, or reliable can be provided. One embodiment of the present invention can provide a novel light-emitting device that is highly convenient, useful, or reliable. One embodiment of the present invention can provide a novel display device that is highly convenient, useful, or reliable. One embodiment of the present invention can provide a novel electronic device that is highly convenient, useful, or reliable. One embodiment of the present invention can provide a novel light-emitting apparatus that is highly convenient, useful, or reliable. One embodiment of the present invention can provide a novel lighting device that is highly convenient, useful, or reliable. A novel organic compound can be provided. A novel light-emitting device can be provided. A novel display device can be provided. A novel electronic device can be provided. A novel light-emitting apparatus can be provided. A novel lighting device can be provided.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all these effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.
In the accompanying drawings:
An organic compound of one embodiment of the present invention is represented by General Formula (G0).
Note that in General Formula (G0), R101 to R111 each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms, n is 1 or 2, and L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R20′ each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
Thus, in the organic compound represented by General Formula (G0), the meta position of a pyridine ring coordinated to iridium has a high spin density in a triplet excited state; thus, the use of a deuterated alkyl group as a substituent can stabilize the compound. In addition, in the organic compound represented by General Formula (G0), LUMO concentrates at the meta position of the pyridine ring coordinated to iridium; thus, the use of a deuterated alkyl group as a substituent can improve the stability of the compound in a state where LUMO receives electrons, i.e., a reduction state. Also in the ligand represented by General Formula (L0), the meta position of a pyridine ring coordinated to iridium has a high spin density in a triplet excited state; thus, the use of a deuterated alkyl group as a substituent can stabilize the compound. Also in the ligand represented by General Formula (L0), LUMO concentrates at the meta position of the pyridine ring coordinated to iridium; thus, the use of a deuterated alkyl group as a substituent can improve the stability of the compound in a state where LUMO receives electrons, i.e., a reduction state. Moreover, an effect of adjusting the shape of an emission spectrum so that light emitted from the compound includes light with a short wavelength can be expected. When the organic compound represented by General Formula (G0) is used with a fluorescent material, energy transfer by the Dexter mechanism from the organic compound to the fluorescent material can be inhibited and energy transfer by the Forster mechanism can be promoted. When a phenyl group is introduced as a substituent into a carbon atom adjacent to the meta position of the pyridine ring coordinated to iridium in the organic compound represented by General Formula (G0), the LUMO can be widened. Moreover, the LUMO is stabilized and the stability of the compound in a reduction state can be improved. The deuterated alkyl group can exhibit a steric hindrance effect against the phenyl group. The rotation of the phenyl group can be suppressed and the thermophysical property, e.g., the sublimation property of the compound can be improved. The vibration of the compound can be suppressed and thermal deactivation from the excited state can be suppressed. High emission efficiency can be achieved. A ligand is selected so that a heteroleptic structure is formed, and the shape of an emission spectrum can be adjusted. The shape of the emission spectrum can be adjusted so that light emitted from the compound includes light with a short wavelength as compared with light emitted from a homoleptic compound. The thermophysical property, e.g., the sublimation property of the compound can be improved. As a result, a novel organic compound that is highly convenient, useful, or reliable can be provided.
Embodiments will be described in detail with reference to the drawings. Note that the embodiments of the present invention are not limited to the following description, and it will be readily appreciated by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description in the following embodiments. Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and the description thereof is not repeated.
In this embodiment, an organic compound of one embodiment of the present invention will be described.
An organic compound of one embodiment of the present invention described in this embodiment is represented by General Formula (G0).
Note that in General Formula (G0), R101 to R111 each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms. Note that n is 1 or 2. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. The hydrogen may be substituted by deuterium, and some or all of hydrogen atoms of the alkyl group having 1 to 6 carbon atoms may be substituted by deuterium.
Moreover, L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R208 each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. The hydrogen may be substituted by deuterium, and some or all of hydrogen atoms of the alkyl group having 1 to 6 carbon atoms may be substituted by deuterium.
An organic compound of another embodiment of the present invention described in this embodiment is represented by General Formula (G1-1).
Note that in General Formula (G1-1), n is 1 or 2.
Moreover, L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
Specific examples of the organic compound having the above-described structure are shown below.
An organic compound of another embodiment of the present invention described in this embodiment is represented by General Formula (G1-2).
Note that in General Formula (G1-2), n is 1 or 2.
Moreover, L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R20′ each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
In an organic compound of another embodiment of the present invention described in this embodiment, the ligand L has an alkyl group in which one or more hydrogen atoms are substituted by deuterium. Accordingly, bond dissociation energy of the compound can be made higher than that of carbon-hydrogen bond by utilizing carbon-deuterium bond. In addition, a molecular structure can be stable. Bond dissociation in the structure of the compound in an excited state can be suppressed. Deterioration or a change in quality of the compound due to carbon-deuterium bond dissociation can be suppressed. For example, the organic compound can be suitably used for a light-emitting layer of a light-emitting device. For example, the organic compound can be suitably used for a layer in contact with a light-emitting layer of a light-emitting device.
An organic compound of another embodiment of the present invention described in this embodiment includes the ligand L represented by Structural Formula (L1-1).
Specific examples of the organic compound having the above-described structure are shown below.
An organic compound of another embodiment of the present invention described in this embodiment includes the ligand L represented by Structural Formula (L1-2).
Specific examples of the organic compound having the above-described structure are shown below.
Therefore, a deuterated alkyl group is introduced into a carbon atom having a high spin density in a triplet excited state, and the stability of the compound in an excited state can be improved. In addition, the deuterated alkyl group is introduced into a carbon atom at which LUMO concentrates, and the stability of the compound in a state where the LUMO receives electrons, i.e., a reduction state can be improved. A phenyl group is introduced into a carbon atom adjacent to the carbon atom at which the LUMO concentrates, and the LUMO can be widened. Moreover, the LUMO is stabilized and the stability of the compound in a reduction state can be improved. The deuterated alkyl group can exhibit a steric hindrance effect against the phenyl group. The rotation of the phenyl group can be suppressed and the thermophysical property, e.g., the sublimation property of the compound can be improved. The vibration of the compound can be suppressed and thermal deactivation from the excited state can be suppressed. High emission efficiency can be achieved. A ligand is selected so that a heteroleptic structure is formed, and the shape of an emission spectrum can be adjusted. The shape of the emission spectrum can be adjusted so that light emitted from the compound includes light with a short wavelength as compared with light emitted from a homoleptic compound. The thermophysical property, e.g., the sublimation property of the compound can be improved. As a result, a novel organic compound that is highly convenient, useful, or reliable can be provided.
A method for synthesizing an organic compound of one embodiment of the present invention will be described. Note that the synthesis method is not limited to this. The organic compound can be synthesized by another synthesis method or a known synthesis method.
An organic compound of one embodiment of the present invention is represented by General Formula (G0).
Note that in General Formula (G0), R101 to R111 each independently represent hydrogen or an alkyl group having 1 to 6 carbon atoms.
Moreover, L represents a ligand represented by General Formula (L0).
In General Formula (L0), R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
For example, a dinuclear complex (A) is reacted with a pyridine compound (B) in an inert gas atmosphere, whereby the organic compound of one embodiment of the present invention can be synthesized (see Synthesis Scheme (a)).
In Synthesis Scheme (a) above, X represents halogen and the dinuclear complex (A) has a halogen-bridged structure. In addition, R201 to R208 each independently represent hydrogen, deuterium, or an alkyl group having 1 to 6 carbon atoms, and some or all of hydrogen atoms of the alkyl group may be substituted by deuterium.
The pyridine compound (B) includes R101 to R111 each independently representing hydrogen or an alkyl group having 1 to 6 carbon atoms. In addition, n is 1 or 2.
Note that the organic compound obtained in the above-described manner may be irradiated with light or heat to obtain an isomer such as a geometrical isomer or an optical isomer. This isomer is also the organic compound of one embodiment of the present invention represented by General Formula (G0).
After the dinuclear complex (A) having a halogen-bridged structure is reacted with a dehalogenating agent such as silver trifluoromethanesulfonate to precipitate a silver halide, a supernatant liquid may be reacted with the pyridine compound (B) in an inert gas atmosphere.
Various kinds of dinuclear complexes (A), pyridine compounds (B), and ligands represented by General Formula (L0) are commercially available and can be synthesized. As a result, a wide variety of kinds of organic compounds can be synthesized by the above-described method. In addition, the organic compound of one embodiment of the present invention represented by General Formula (G0) features abundant variations in ligands.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a structure of a light-emitting device 550X of one embodiment of the present invention is described with reference to
The light-emitting device 550X described in this embodiment includes an electrode 551X, an electrode 552X, and a unit 103X. The electrode 552X overlaps with the electrode 551X, and the unit 103X is located between the electrode 552X and the electrode 551X.
The unit 103X has a single-layer structure or a stacked-layer structure. The unit 103X includes a layer 111X, a layer 112, and a layer 113, for example (see
The layer 111X is located between the layer 113 and the layer 112, the layer 113 is located between the electrode 552X and the layer 111X, and the layer 112 is located between the layer 111X and the electrode 551X.
For example, a layer selected from functional layers such as a light-emitting layer, a hole-transport layer, an electron-transport layer, and a carrier-blocking layer can be used for the unit 103X. A layer selected from functional layers such as a hole-injection layer, an electron-injection layer, an exciton-blocking layer, and a charge-generation layer can also be used for the unit 103X.
A hole-transport material can be used for the layer 112, for example. The layer 112 can be referred to as a hole-transport layer. A material having a wider bandgap than the light-emitting material contained in the layer 111X is preferably used for the layer 112. In that case, transfer of energy from excitons generated in the layer 111X to the layer 112 can be inhibited.
A material having a hole mobility of 1×10−6 cm2/Vs or higher can be suitably used as the hole-transport material.
As the hole-transport material, an amine compound or an organic compound having a π-electron rich heteroaromatic ring skeleton can be used, for example. Specifically, a compound having an aromatic amine skeleton, a compound having a carbazole skeleton, a compound having a thiophene skeleton, a compound having a furan skeleton, or the like can be used. The compound having an aromatic amine skeleton and the compound having a carbazole skeleton are particularly preferable because these compounds are highly reliable and have high hole-transport properties to contribute to a reduction in driving voltage.
The following are examples that can be used as a compound having an aromatic amine skeleton: 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-4,4′-diaminobiphenyl (abbreviation: TPD), N,N′-bis(9,9′-spirobi[9H-fluoren]-2-yl)-N,N′-diphenyl-4,4′-diaminobiphenyl (abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), 9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), and N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF).
As a compound having a carbazole skeleton, 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), or 9,9′-diphenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCP) can be used, for example.
As a compound having a thiophene skeleton, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation: DBT3P-II), 2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene (abbreviation: DBTFLP-III), or 4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene (abbreviation: DBTFLP-IV) can be used, for example.
As a compound having a furan skeleton, 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation: DBF3P-II) or 4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran (abbreviation: mmDBFFLBi-II) can be used, for example.
An electron-transport material, a material having an anthracene skeleton, and a mixed material can be used for the layer 113, for example. The layer 113 can be referred to as an electron-transport layer. A material having a wider bandgap than the light-emitting material contained in the layer 111X is preferably used for the layer 113. In that case, transfer of energy from excitons generated in the layer 111X to the layer 113 can be inhibited.
A material having an electron mobility higher than or equal to 1×10−7 cm2/Vs and lower than or equal to 5×10−5 cm2/Vs when the square root of the electric field strength [V/cm] is 600 can be suitably used as the electron-transport material. In this case, the electron-transport property in the electron-transport layer can be suppressed. The amount of electrons injected into the light-emitting layer can be controlled. The light-emitting layer can be prevented from having excess electrons.
For example, a metal complex or an organic compound having a π-electron deficient heteroaromatic ring skeleton can be used as the electron-transport material.
As a metal complex, bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq2), bis(2-methyl-8-quinolinolato) (4-phenylphenolato)aluminum(III) (abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq), bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ) can be used, for example.
As an organic compound having a π-electron deficient heteroaromatic ring skeleton, a heterocyclic compound having a polyazole skeleton, a heterocyclic compound having a diazine skeleton, a heterocyclic compound having a pyridine skeleton, or a heterocyclic compound having a triazine skeleton can be used, for example. In particular, the heterocyclic compound having a diazine skeleton or the heterocyclic compound having a pyridine skeleton has favorable reliability and thus are preferable. In addition, the heterocyclic compound having a diazine (pyrimidine or pyrazine) skeleton has a high electron-transport property to contribute to a reduction in driving voltage.
As a heterocyclic compound having a polyazole skeleton, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (abbreviation: TAZ), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: OXD-7), 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation: CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (abbreviation: TPBI), or 2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole (abbreviation: mDBTBIm-II) can be used, for example.
As a heterocyclic compound having a diazine skeleton, 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II), 2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II), 2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation: 4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II), or 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzo[h]quinazoline (abbreviation: 4,8mDBtP2Bqn) can be used, for example.
As a heterocyclic compound having a pyridine skeleton, 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy) or 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB) can be used, for example.
As a heterocyclic compound having a triazine skeleton, 2-[3′-(9,9-dimethyl-9H-fluoren-2-yl)biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine (abbreviation: mFBPTzn), 2-[(1,1′-biphenyl)-4-yl]-4-phenyl-6-[9,9′-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine (abbreviation: BP-SFTzn), 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn), or 2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: mBnfBPTzn-02) can be used, for example.
An organic compound having an anthracene skeleton can be used for the layer 113. In particular, an organic compound having both an anthracene skeleton and a heterocyclic skeleton can be suitably used.
For example, an organic compound having both an anthracene skeleton and a nitrogen-containing five-membered ring skeleton can be used for the layer 113. Alternatively, an organic compound having both an anthracene skeleton and a nitrogen-containing five-membered ring skeleton where two heteroatoms are included in a ring can be used for the layer 113. Specifically, a pyrazole ring, an imidazole ring, an oxazole ring, a thiazole ring, or the like can be suitably used as the heterocyclic skeleton.
For example, an organic compound having both an anthracene skeleton and a nitrogen-containing six-membered ring skeleton can be used for the layer 113. Alternatively, an organic compound having both an anthracene skeleton and a nitrogen-containing six-membered ring skeleton where two heteroatoms are included in a ring can be used for the layer 113. Specifically, a pyrazine ring, a pyrimidine ring, a pyridazine ring, or the like can be suitably used as the heterocyclic skeleton.
A material in which a plurality of kinds of substances are mixed can be used for the layer 113. Specifically, a mixed material which contains an alkali metal, an alkali metal compound, or an alkali metal complex and an electron-transport substance can be used for the layer 113. Note that the electron-transport material preferably has a highest occupied molecular orbital (HOMO) level of −6.0 eV or higher.
Note that the mixed material can be suitably used for the layer 113 in combination with a structure using a composite material described later for a layer 104. For example, a composite material of an electron-accepting substance and a hole-transport material can be used for the layer 104. Specifically, a composite material of an electron-accepting substance and a substance having a relatively deep HOMO level HM1, which is higher than or equal to −5.7 eV and lower than or equal to −5.4 eV, can be used for the layer 104 (see
Furthermore, a structure using a hole-transport material for the layer 112 is preferably combined with the structure using the mixed material for the layer 113 and the composite material for the layer 104. For example, a substance having a HOMO level HM2, which differs by −0.2 eV to 0 eV from the relatively deep HOMO level HM1, can be used for the layer 112 (see
The concentration of the alkali metal, the alkali metal compound, or the alkali metal complex preferably changes in the thickness direction of the layer 113 (including the case where the concentration is 0).
For example, a metal complex having an 8-hydroxyquinolinato structure can be used. A methyl-substituted product of the metal complex having an 8-hydroxyquinolinato structure (e.g., a 2-methyl-substituted product or a 5-methyl-substituted product) or the like can also be used.
As the metal complex having an 8-hydroxyquinolinato structure, 8-hydroxyquinolinato-lithium (abbreviation: Liq), 8-hydroxyquinolinato-sodium (abbreviation: Naq), or the like can be used. In particular, a complex of a monovalent metal ion, especially a complex of lithium is preferable, and Liq is further preferable.
Either a structure containing a light-emitting material or a structure containing a light-emitting material and a host material can be employed for the layer 111X, for example. The layer 111X can be referred to as a light-emitting layer. The layer 111X is preferably provided in a region where holes and electrons are recombined. This allows efficient conversion of energy generated by recombination of carriers into light and emission of the light.
Furthermore, the layer 111X is preferably provided apart from a metal used for the electrode or the like. In that case, a quenching phenomenon caused by the metal used for the electrode or the like can be inhibited.
It is preferable that a distance from an electrode or the like having reflectivity to the layer 111X be adjusted and the layer 111X be placed in an appropriate position in accordance with an emission wavelength. With this structure, the amplitude can be increased by utilizing an interference phenomenon between light reflected by the electrode or the like and light emitted from the layer 111X. Light with a predetermined wavelength can be intensified and the spectrum of the light can be narrowed. In addition, bright light emission colors with high intensity can be obtained. In other words, the layer 111X is placed in an appropriate position, for example, between electrodes and the like, and thus a microcavity structure can be formed.
For example, a phosphorescent substance can be used for the light-emitting material. Thus, energy generated by recombination of carriers can be released as light ELX from the light-emitting material (see
A phosphorescent substance can be used for the layer 111X. For example, the organic compound of one embodiment of the present invention described in Embodiment 1 can be used for the layer 111X.
For the layer 111X, {2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-K]phenyl-κC}bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(5m4dppy-d3)), bis{2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-K]phenyl-κC}[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(5m4dppy-d3)2(ppy)), or {2-[4-(3,5-di-tert-butylphenyl)-5-(methyl-d3)-2-pyridinyl-KM]phenyl-κC}bis{2-[4-(methyl-d3)-5-(2-methylpropyl-1,1-d2)-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3)) can be used, for example.
Therefore, the layer 111X includes the organic compound of one embodiment of the present invention. The layer 111X can easily receive holes. Since the LUMO is widened in the organic compound of one embodiment of the present invention, the layer 111X can easily receive electrons. In addition, the driving voltage of a light-emitting device can be reduced. Moreover, the light-emitting device can exhibit abroad emission spectrum. A phenomenon in which the luminance of the light-emitting device decreases in use can be suppressed. The reliability of the light-emitting device can be increased. As a result, a novel light-emitting device that is highly convenient, useful, or reliable can be provided.
A carrier-transport material can be used as the host material. For example, a hole-transport material, an electron-transport material, a substance exhibiting thermally activated delayed fluorescence (TADF) (also referred to as a TADF material), a material having an anthracene skeleton, or a mixed material can be used as the host material. A material having a wider bandgap than the light-emitting material contained in the layer 111X is preferably used as the host material. Thus, transfer of energy from excitons generated in the layer 111X to the host material can be inhibited.
A material having a hole mobility of 1×10−6 cm2/Vs or higher can be suitably used as the hole-transport material. For example, a hole-transport material that can be used for the layer 112 can be used as the host material.
A metal complex or an organic compound having a π-electron deficient heteroaromatic ring skeleton can be used as the electron-transport material. For example, an electron-transport material that can be used for the layer 113 can be used as the host material.
A material in which a plurality of kinds of substances are mixed can be used as the host material. For example, a material which includes an electron-transport material and a hole-transport material can be used as the mixed material. The weight ratio between the hole-transport material and the electron-transport material contained in the mixed material may be (the hole-transport material/the electron-transport material)=(1/19) or more and (19/1) or less. Thus, the carrier-transport property of the layer 111X can be easily adjusted and a recombination region can be easily controlled.
The organic compound of one embodiment of the present invention can be used as the host material. The organic compound of one embodiment of the present invention is a phosphorescent substance, and when a fluorescent substance is used as the light-emitting substance, the phosphorescent substance can be used as an energy donor for supplying excitation energy to the fluorescent substance.
Light emitted from the organic compound of one embodiment of the present invention includes light with a wavelength shorter than 500 nm and the emission spectrum of the organic compound covers a wavelength shorter than 500 nm, so that when the organic compound is used with a fluorescent material (e.g., a green fluorescent material) having an absorption spectrum partly overlapping with the emission spectrum, energy can be efficiently transferred to the fluorescent material. A phenomenon in which the luminance of the light-emitting device decreases in use can be suppressed. The reliability of the light-emitting device can be increased. As a result, a novel light-emitting device that is highly convenient, useful, or reliable can be provided.
A mixed material containing a material to form an exciplex can be used as the host material. For example, a material in which an emission spectrum of a formed exciplex overlaps with a wavelength of the absorption band on the lowest energy side of the light-emitting substance can be used as the host material. This enables smooth energy transfer and improves emission efficiency. The driving voltage can be reduced. With such a structure, light emission can be efficiently obtained by exciplex-triplet energy transfer (ExTET), which is energy transfer from the exciplex to the light-emitting substance (phosphorescent material).
A phosphorescent substance can be used as at least one of the materials forming an exciplex. Accordingly, reverse intersystem crossing can be used. Triplet excitation energy can be efficiently converted into singlet excitation energy.
Combination of an electron-transport material and a hole-transport material whose HOMO level is higher than or equal to that of the electron-transport material is preferable for forming an exciplex. The LUMO level of the hole-transport material is preferably higher than or equal to the LUMO level of the electron-transport material. Thus, an exciplex can be efficiently formed. Note that the LUMO levels and the HOMO levels of the materials can be derived from the electrochemical characteristics (the reduction potentials and the oxidation potentials). Specifically, the reduction potentials and the oxidation potentials can be measured by cyclic voltammetry (CV).
The formation of an exciplex can be confirmed by a phenomenon in which the emission spectrum of the mixed film in which the hole-transport material and the electron-transport material are mixed is shifted to the longer wavelength side than the emission spectra of each of the materials (or has another peak on the longer wavelength side) observed by comparison of the emission spectra of the hole-transport material, the electron-transport material, and the mixed film of these materials, for example. Alternatively, the formation of an exciplex can be confirmed by a difference in transient response, such as a phenomenon in which the transient PL lifetime of the mixed film has longer lifetime components or a larger proportion of delayed components than that of each of the materials, observed by comparison of transient photoluminescence (PL) of the hole-transport material, the electron-transport material, and the mixed film of the materials. The transient PL can be rephrased as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in transient response observed by comparison of the transient EL of the hole-transport material, the electron-transport material, and the mixed film of the materials.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a structure of the light-emitting device 550X of one embodiment of the present invention is described with reference to
The light-emitting device 550X described in this embodiment includes the electrode 551X, the electrode 552X, the unit 103X, and the layer 104. The electrode 552X overlaps with the electrode 551X, and the unit 103X is located between the electrode 551X and the electrode 552X. The layer 104 is located between the electrode 551X and the unit 103X. For example, the structure described in Embodiment 2 can be employed for the unit 103X.
For example, a conductive material can be used for the electrode 551X. Specifically, a single layer or a stack using a metal, an alloy, or a film containing a conductive compound can be used for the electrode 551X.
A film that efficiently reflects light can be used for the electrode 551X, for example. Specifically, an alloy containing silver, copper, and the like, an alloy containing silver, palladium, and the like, or a metal film of aluminum or the like can be used for the electrode 551X.
For example, a metal film that transmits part of light and reflects another part of light can be used for the electrode 551X. Thus, a microcavity structure can be provided in the light-emitting device 550X. Alternatively, light with a predetermined wavelength can be extracted more efficiently than light with the other wavelengths. Alternatively, light with a narrow spectral half-width can be extracted. Alternatively, light of a bright color can be extracted.
A film having a visible-light-transmitting property can be used for the electrode 551X, for example. Specifically, a single layer or a stack using a metal film, an alloy film, a conductive oxide film, or the like that is thin enough to transmit light can be used for the electrode 551X.
In particular, a material having a work function higher than or equal to 4.0 eV can be suitably used for the electrode 551X.
For example, a conductive oxide containing indium can be used. Specifically, indium oxide, indium oxide-tin oxide (abbreviation: ITO), indium oxide-tin oxide containing silicon or silicon oxide (abbreviation: ITSO), indium oxide-zinc oxide, indium oxide containing tungsten oxide and zinc oxide (abbreviation: IWZO), or the like can be used.
For another example, a conductive oxide containing zinc can be used. Specifically, zinc oxide, zinc oxide to which gallium is added, zinc oxide to which aluminum is added, or the like can be used.
Furthermore, for example, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or a nitride of a metal material (e.g., titanium nitride) can be used. Graphene can also be used.
A hole-injection material can be used for the layer 104, for example. The layer 104 can be referred to as a hole-injection layer.
For example, a material having a hole mobility lower than or equal to 1×10−3 cm2/Vs when the square root of the electric field strength [V/cm] is 600 can be used for the layer 104. A film having an electrical resistivity greater than or equal to 1×104 [Ω·cm] and less than or equal to 1×107 [Ω·cm] can be used as the layer 104. The electrical resistivity of the layer 104 is preferably greater than or equal to 5×104 [Ω·cm] and less than or equal to 1×107 [Ω·cm], further preferably greater than or equal to 1×105 [Ω·cm] and less than or equal to 1×107 [Ω·cm].
Specifically, an electron-accepting substance can be used for the layer 104. Alternatively, a composite material containing a plurality of kinds of substances can be used for the layer 104. This can facilitate the injection of holes from the electrode 551X, for example. Alternatively, the driving voltage of the light-emitting device 550X can be reduced.
An organic compound or an inorganic compound can be used as the electron-accepting substance. The electron-accepting substance can extract electrons from an adjacent hole-transport layer or a hole-transport material by the application of an electric field.
For example, a compound having an electron-withdrawing group (a halogen or cyano group) can be used as the electron-accepting substance. Note that an electron-accepting organic compound is easily evaporated, which facilitates film deposition. Thus, the productivity of the light-emitting device 550X can be increased.
Specifically, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation: HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane (abbreviation: F6-TCNNQ), 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile, or the like can be used.
A compound in which electron-withdrawing groups are bonded to a condensed aromatic ring having a plurality of heteroatoms, such as HAT-CN, is particularly preferable because it is thermally stable.
A [3]radialene derivative having an electron-withdrawing group (in particular, a cyano group or a halogen group such as a fluoro group) has a very high electron-accepting property and thus is preferred.
Specifically, α,α′,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile], α,α′,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile], or the like can be used.
For the electron-accepting substance, a transition metal oxide such as a molybdenum oxide, a vanadium oxide, a ruthenium oxide, a tungsten oxide, or a manganese oxide can be used.
It is possible to use any of the following materials: phthalocyanine-based complex compounds such as phthalocyanine (abbreviation: H2Pc) and copper phthalocyanine (abbreviation: CuPc); and compounds each having an aromatic amine skeleton such as 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB) and N,N′-bis[4-bis(3-methylphenyl)aminophenyl]-N,N′-diphenyl-4,4′-diaminobiphenyl (abbreviation: DNTPD).
In addition, high molecular compounds such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (abbreviation: PEDOT/PSS), and the like can be used.
For example, a composite material containing an electron-accepting substance and a hole-transport material can be used for the layer 104. Accordingly, not only a material having a high work function but also a material having a low work function can also be used for the electrode 551X. Alternatively, a material used for the electrode 551X can be selected from a wide range of materials regardless of its work function.
For the hole-transport material in the composite material, for example, a compound having an aromatic amine skeleton, a carbazole derivative, an aromatic hydrocarbon, an aromatic hydrocarbon having a vinyl group, or a high molecular compound (such as an oligomer, a dendrimer, or a polymer) can be used. A material having a hole mobility of 1×10−6 cm2/Vs or higher can be suitably used as the hole-transport material in the composite material. For example, a hole-transport material that can be used for the layer 112 can be used for the mixed material.
A substance having a relatively deep HOMO level can be suitably used for the hole-transport material in the composite material. Specifically, the HOMO level is preferably higher than or equal to −5.7 eV and lower than or equal to −5.4 eV. Accordingly, hole injection to the unit 103X can be facilitated. Hole injection to the layer 112 can be facilitated. The reliability of the light-emitting device 550X can be increased.
As the compound having an aromatic amine skeleton, for example, N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation: DTDPPA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), N,N′-bis[4-bis(3-methylphenyl)aminophenyl]-N,N′-diphenyl-4,4′-diaminobiphenyl (abbreviation: DNTPD), or 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B) can be used.
As the carbazole derivative, for example, 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), or 1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene can be used.
As the aromatic hydrocarbon, for example, 2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA), 2-tert-butyl-9,10-di(1-naphthyl)anthracene, 9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA), 2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA), 9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene (abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene (abbreviation: DMNA), 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene, 2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene, 2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl, 10,10′-diphenyl-9,9′-bianthryl, 10,10′-bis(2-phenylphenyl)-9,9′-bianthryl, 10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene, tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, pentacene, or coronene can be used.
As aromatic hydrocarbon having a vinyl skeleton, for example, 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi) or 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (abbreviation: DPVPA) can be used.
As the high molecular compound, for example, poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), or poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine](abbreviation: Poly-TPD) can be used.
Furthermore, a substance having any of a carbazole skeleton, a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthracene skeleton can be suitably used as the hole-transport material in the composite material, for example. Moreover, a substance including any of the following can be used as the hole-transport material in the composite material: an aromatic amine having a substituent that includes a dibenzofuran ring or a dibenzothiophene ring, an aromatic monoamine that includes a naphthalene ring, and an aromatic monoamine in which a 9-fluorenyl group is bonded to nitrogen of amine through an arylene group. With use of a substance including an N,N′-bis(4-biphenyl)amino group, the reliability of the light-emitting device 550X can be increased.
Specific examples of the above-described substances include N-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BnfABP), N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf), 4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4″-phenyltriphenylamine (abbreviation: BnfBB1BP), N,N′-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation: BBABnf(6)), N,N′-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine (abbreviation: BBABnf(8)), N,N′-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation: BBABnf(II)(4)), N,N′-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl (abbreviation: DBfBB1TP), N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine (abbreviation: ThBA1BP), 4-(2-naphthyl)-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNB), 4-[4-(2-naphthyl)phenyl]-4′,4″-diphenyltriphenylamine (abbreviation: BBAβNBi), 4,4′-diphenyl-4″-(6;1′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNβNB), 4,4′-diphenyl-4″-(7;1′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAαNpβNB-03), 4,4′-diphenyl-4″-(7-phenyl)naphthyl-2-yl)triphenylamine (abbreviation: BBAPβNB-03), 4,4′-diphenyl-4″-(6;2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAβN2)B), 4,4′-diphenyl-4″-(7;2′-binaphthyl-2-yl)triphenylamine (abbreviation: BBAβN2)B-03), 4,4′-diphenyl-4″-(4;2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβINαNB), 4,4′-diphenyl-4″-(5;2′-binaphthyl-1-yl)triphenylamine (abbreviation: BBAβNαNB-02), 4-(4-biphenylyl)-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: TPBiAβINB), 4-(3-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: mTPBiβNBi), 4-(4-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine (abbreviation: TPBiAβNBi), 4-phenyl-4′-(1-naphthyl)triphenylamine (abbreviation: αNBA1BP), 4,4′-bis(1-naphthyl)triphenylamine (abbreviation: αNBB1BP), 4,4′-diphenyl-4″-[4′-(carbazol-9-yl)biphenyl-4-yl]triphenylamine (abbreviation: YGTBi1BP), 4′-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(1,1′-biphenyl-4-yl)amine (abbreviation: YGTBi1BP-02), 4-[4′-(carbazol-9-yl)biphenyl-4-yl]-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation: YGTBiβNB), N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBNBSF), N,N′-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: BBASF), N,N′-bis(biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: BBASF(4)), N-(1,1′-biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-4-amine (abbreviation: oFBiSF), N-(biphenyl-4-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine (abbreviation: FrBiF), N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine (abbreviation: mPDBfBNBN), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: mBPAFLP), 4-phenyl-4′-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine (abbreviation: BPAFLBi), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBANB), 4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBNBB), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation: PCBASF), N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), N,N′-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-4-amine, N,N′-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-3-amine, N,N′-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-2-amine, and N,N′-bis(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi-9H-fluoren-1-amine.
For example, a composite material including an electron-accepting substance, a hole-transport material, and a fluoride of an alkali metal or a fluoride of an alkaline earth metal can be used as the hole-injection material. In particular, a composite material in which the proportion of fluorine atoms is higher than or equal to 20% can be suitably used. Thus, the refractive index of the layer 104 can be reduced. A layer with a low refractive index can be formed inside the light-emitting device 550X. The external quantum efficiency of the light-emitting device 550X can be improved.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a structure of the light-emitting device 550X of one embodiment of the present invention is described with reference to
The light-emitting device 550X described in this embodiment includes the electrode 551X, the electrode 552X, the unit 103X, and a layer 105. The electrode 552X includes a region overlapping with the electrode 551X, and the unit 103X includes a region located between the electrode 551X and the electrode 552X. The layer 105 includes a region located between the unit 103X and the electrode 552X. For example, the structure described in Embodiment 2 can be employed for the unit 103X.
For example, a conductive material can be used for the electrode 552X. Specifically, a single layer or a stack using a metal, an alloy, or a film containing a conductive compound can be used for the electrode 552X.
For example, the material that can be used for the electrode 551X described in Embodiment 3 can be used for the electrode 552X. In particular, a material with a lower work function than the electrode 551X can be suitably used for the electrode 552X. Specifically, a material having a work function lower than or equal to 3.8 eV is preferably used.
For example, an element belonging to Group 1 of the periodic table, an element belonging to Group 2 of the periodic table, a rare earth metal, or an alloy containing any of these elements can be used for the electrode 552X.
Specifically, an element such as lithium (Li) or cesium (Cs), an element such as magnesium (Mg), calcium (Ca), or strontium (Sr), an element such as europium (Eu) or ytterbium (Yb), or an alloy containing any of these elements such as an alloy of magnesium and silver or an alloy of aluminum and lithium can be used for the electrode 552X.
An electron-injection material can be used for the layer 105, for example. The layer 105 can be referred to as an electron-injection layer.
Specifically, an electron-donating substance can be used for the layer 105. Alternatively, a material in which an electron-donating substance and an electron-transport material are combined can be used for the layer 105. Alternatively, electride can be used for the layer 105. This can facilitate the injection of electrons from the electrode 552X, for example. Alternatively, not only a material having a low work function but also a material having a high work function can also be used for the electrode 552X. Alternatively, a material used for the electrode 552X can be selected from a wide range of materials regardless of its work function. Specifically, Al, Ag, ITO, indium oxide-tin oxide containing silicon or silicon oxide, or the like can be used for the electrode 552X. The driving voltage of the light-emitting device 550X can be reduced.
For example, an alkali metal, an alkaline earth metal, a rare earth metal, or a compound thereof (an oxide, a halide, a carbonate, or the like) can be used for the electron-donating substance. Alternatively, an organic compound such as tetrathianaphthacene (abbreviation: TTN), nickelocene, or decamethylnickelocene can be used as the electron-donating substance.
As an alkali metal compound (including an oxide, a halide, and a carbonate), lithium oxide, lithium fluoride (LiF), cesium fluoride (CsF), lithium carbonate, cesium carbonate, 8-hydroxyquinolinato-lithium (abbreviation: Liq), or the like can be used.
As an alkaline earth metal compound (including an oxide, a halide, and a carbonate), calcium fluoride (CaF2) or the like can be used.
A material composed of two or more kinds of substances can be used as the electron-injection material. For example, an electron-donating substance and an electron-transport material can be used for the composite material.
A material having an electron mobility higher than or equal to 1×10−7 cm2/Vs and lower than or equal to 5×10−5 cm2/Vs when the square root of the electric field strength [V/cm] is 600 can be suitably used as the electron-transport material. In this case, the amount of electrons injected into the light-emitting layer can be controlled. The light-emitting layer can be prevented from having excess electrons.
A metal complex or an organic compound having a π-electron deficient heteroaromatic ring skeleton can be used as the electron-transport material. For example, an electron-transport material that can be used for the layer 113 can be used as the composite material.
A material including a fluoride of an alkali metal in a microcrystalline state and an electron-transport material can be used for the composite material. Alternatively, a material including a fluoride of an alkaline earth metal in a microcrystalline state and an electron-transport material can be used for the composite material. In particular, a composite material including a fluoride of an alkali metal or an alkaline earth metal at 50 wt % or higher can be suitably used. Alternatively, a composite material including an organic compound having a bipyridine skeleton can be suitably used. Thus, the refractive index of the layer 105 can be reduced. The external quantum efficiency of the light-emitting device 550X can be improved.
For example, a composite material of a first organic compound including an unshared electron pair and a first metal can be used for the layer 105. The sum of the number of electrons of the first organic compound and the number of electrons of the first metal is preferably an odd number. The molar ratio of the first metal to 1 mol of the first organic compound is preferably greater than or equal to 0.1 and less than or equal to 10, more preferably greater than or equal to 0.2 and less than or equal to 2, further more preferably greater than or equal to 0.2 and less than or equal to 0.8.
Accordingly, the first organic compound including an unshared electron pair interacts with the first metal and thus can form a singly occupied molecular orbital (SOMO). Furthermore, in the case where electrons are injected from the electrode 552X into the layer 105, a barrier therebetween can be reduced.
The layer 105 can adopt a composite material that allows the spin density measured by an electron spin resonance (ESR) method to be preferably greater than or equal to 1×1016 spins/cm3, more preferably greater than or equal to 5×1016 spins/cm3, further more preferably greater than or equal to 1×1017 spins/cm3.
For example, an electron-transport material can be used for the organic compound including an unshared electron pair. For example, a compound having an electron deficient heteroaromatic ring can be used. Specifically, a compound with at least one of a pyridine ring, a diazine ring (a pyrimidine ring, a pyrazine ring, and a pyridazine ring), and a triazine ring can be used. Accordingly, the driving voltage of the light-emitting device 550X can be reduced.
Note that the LUMO level of the organic compound having an unshared electron pair is preferably higher than or equal to −3.6 eV and lower than or equal to −2.3 eV. In general, the HOMO level and the LUMO level of an organic compound can be estimated by cyclic voltammetry (CV), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, or the like.
For example, 4,7-diphenyl-1,10-phenanthroline (abbreviation: BPhen), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), diquinoxalino[2,3-a:2′, 3′-c]phenazine (abbreviation: HATNA), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), or the like can be used as the organic compound having an unshared electron pair. Note that NBPhen has a higher glass transition temperature (Tg) than BPhen and thus has high heat resistance.
Alternatively, for example, copper phthalocyanine can be used for the organic compound including an unshared electron pair. The number of electrons of the copper phthalocyanine is an odd number.
When the number of electrons of the first organic compound including an unshared electron pair is an even number, for example, a composite material of the first metal and the first organic compound, which belongs to an odd-numbered group in the periodic table, can be used for the layer 105.
For example, manganese (Mn), which is a metal belonging to Group 7, cobalt (Co), which is a metal belonging to Group 9, copper (Cu), silver (Ag), and gold (Au), which are metals belonging to Group 11, aluminum (Al) and indium (In), which are metals belonging to Group 13 are odd-numbered groups in the periodic table. Note that elements belonging to Group 11 have a lower melting point than elements belonging to Group 7 or Group 9 and thus are suitable for vacuum evaporation. In particular, Ag is preferable because of its low melting point. By using a metal having a low reactivity with water or oxygen as the first metal, the moisture resistance of the light-emitting device 550X can be improved.
The use of Ag for the electrode 552X and the layer 105 can increase the adhesion between the layer 105 and the electrode 552X.
When the number of electrons of the first organic compound including an unshared electron pair is an odd number, a composite material of the first metal and the first organic compound, which belongs to an even-numbered group in the periodic table, can be used for the layer 105. For example, iron (Fe), which is a metal belonging to Group 8, is an element belonging to an even-numbered group in the periodic table.
For example, a substance obtained by adding electrons at high concentration to an oxide where calcium and aluminum are mixed can be used, for example, as the electron-injection material.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a structure of the light-emitting device 550X of one embodiment of the present invention is described with reference to
The light-emitting device 550X described in this embodiment includes the electrode 551X, the electrode 552X, the unit 103X, and a layer 106 (see
The layer 106 has a function of supplying electrons to the anode side and supplying holes to the cathode side when voltage is applied. The layer 106 can be referred to as a charge-generation layer.
For example, a hole-injection material that can be used for the layer 104 described in Embodiment 3 can be used for the layer 106. Specifically, a composite material can be used for the layer 106.
Alternatively, for example, a stacked film in which a film including the composite material and a film including a hole-transport material are stacked can be used for the layer 106. Note that the film including a hole-transport material is located between the film including the composite material and the cathode.
A stacked film in which a layer 106_1 and a layer 106_2 are stacked can be used for the layer 106. The layer 106_1 includes a region located between the unit 103X and the electrode 552X and the layer 106_2 includes a region located between the unit 103X and the layer 106_1.
For example, a hole-injection material that can be used for the layer 104 described in Embodiment 3 can be used for the layer 106_1. Specifically, a composite material can be used for the layer 106_1. A film having an electrical resistivity greater than or equal to 1×104 [Ω·cm] and less than or equal to 1×107 [Ω·cm] can be used as the layer 106_1. The electrical resistivity of the layer 106_1 is preferably greater than or equal to 5×104 [Ω·cm] and less than or equal to 1×107 [Ω·cm], further preferably greater than or equal to 1×105 [Ω·cm] and less than or equal to 1×107 [Ω·cm].
For example, a material that can be used for the layer 105 described in Embodiment 4 can be used for the layer 106_2.
A stacked film in which the layer 106_1, the layer 1062, and a layer 106_3 are stacked can be used for the layer 106. The layer 106_3 includes a region located between the layer 106_1 and the layer 106_2.
For example, an electron-transport material can be used for the layer 106_3. The layer 106_3 can be referred to as an electron-relay layer. With the layer 1063, a layer that is on the anode side and in contact with the layer 106_3 can be distanced from a layer that is on the cathode side and in contact with the layer 106_3. Interaction between the layer that is on the anode side and in contact with the layer 106_3 and the layer that is on the cathode side and in contact with the layer 106_3 can be reduced. Electrons can be smoothly supplied to the layer that is on the anode side and in contact with the layer 106_3.
A substance whose LUMO level is positioned between the LUMO level of the electron-accepting substance contained in the layer that is on the cathode side and in contact with the layer 106_3 and the LUMO level of the substance contained in the layer that is on the anode side and in contact with the layer 106_3 can be suitably used.
For example, a material having a LUMO level in a range higher than or equal to −5.0 eV, preferably higher than or equal to −5.0 eV and lower than or equal to −3.0 eV, can be used for the layer 106_3.
Specifically, a phthalocyanine-based material can be used for the layer 106_3. For example, copper phthalocyanine (abbreviation: CuPc) or a metal complex having a metal-oxygen bond and an aromatic ligand can be used for the layer 106_3.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a structure of the light-emitting device 550X of one embodiment of the present invention is described with reference to
The light-emitting device 550X described in this embodiment includes the electrode 551X, the electrode 552X, the unit 103X, the layer 106, and a unit 103X2 (see
The unit 103X is located between the electrode 552X and the electrode 551X, and the layer 106 is located between the electrode 552X and the unit 103X.
The unit 103X2 is located between the electrode 552X and the layer 106. The unit 103X2 has a function of emitting light ELX2.
In other words, the light-emitting device 550X includes the stacked units between the electrode 551X and the electrode 552X. The number of stacked units is not limited to two and may be three or more. A structure including the stacked units located between the electrode 551X and the electrode 552X and the layer 106 located between the units is referred to as a stacked light-emitting device or a tandem light-emitting device in some cases.
This structure enables high luminance emission while the current density is kept low. Reliability can be improved. The driving voltage can be reduced in comparison with that of the light-emitting device with the same luminance. The power consumption can be reduced.
The unit 103X2 includes a layer 111X2, a layer 1122, and a layer 113_2. The layer 111X2 is located between the layer 112_2 and the layer 113_2.
The structure that can be employed for the unit 103X can be employed for the unit 103X2. For example, the same structure as the unit 103X can be employed for the unit 103X2.
The structure that is different from the structure of the unit 103X can be employed for the unit 103X2. For example, the unit 103X2 can have a structure emitting light whose hue is different from that of light emitted from the unit 103X.
Specifically, a stack including the unit 103X emitting red light and green light and the unit 103X2 emitting blue light can be employed. With this structure, a light-emitting device emitting light of a desired color can be provided. A light-emitting device emitting white light can be provided, for example.
The layer 106 has a function of supplying electrons to one of the unit 103X and the unit 103X2 and supplying holes to the other. For example, the layer 106 described in Embodiment 5 can be used.
For example, each of the electrode 551X, the electrode 552X, the unit 103X, the layer 106, and the unit 103X2 can be formed by a dry process, a wet process, an evaporation method, a droplet discharging method, a coating method, a printing method, or the like. A formation method may differ between components of the device.
Specifically, the light-emitting device 550X can be manufactured with a vacuum evaporation machine, an ink-jet machine, a coating machine such as a spin coater, a gravure printing machine, an offset printing machine, a screen printing machine, or the like.
For example, the electrode can be formed by a wet process or a sol-gel method using a paste of a metal material. In addition, an indium oxide-zinc oxide film can be formed by a sputtering method using a target obtained by adding indium zinc to indium oxide at a concentration higher than or equal to 1 wt % and lower than or equal to 20 wt %. Furthermore, an indium oxide film containing tungsten oxide and zinc oxide (IWZO) can be formed by a sputtering method using a target containing, with respect to indium oxide, tungsten oxide at a concentration higher than or equal to 0.5 wt % and lower than or equal to 5 wt % and zinc oxide at a concentration higher than or equal to 0.1 wt % and lower than or equal to 1 wt %.
This embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, structures of a display device 700 of one embodiment of the present invention will be described with reference to
In this specification, an integer variable of 1 or more may be used for reference numerals. For example, “(p)” where p is an integer variable of 1 or more may be used for part of a reference numeral that specifies any one of up top components. For another example, “(m,n)” where each of m and n is an integer variable of 1 or more may be used for part of a reference numeral that specifies any one of up to m×n components.
The display device 700 described in this embodiment includes a light-emitting device 550X(i,j) and a light-emitting device 550Y(i,j) (see
Note that the display device 700 includes a substrate 510 and a functional layer 520. The functional layer 520 includes an insulating film 521, and the light-emitting devices 550X(i,j) and 550Y(i,j) are formed over the insulating film 521. The functional layer 520 is located between the substrate 510 and the light-emitting device 550X(i,j).
The light-emitting device 550X(i,j) includes an electrode 551X(i,j), an electrode 552X(i,j), and a unit 103X(i,j). The electrode 552X(i,j) overlaps with the electrode 551X(i,j), and the unit 103X(i,j) is located between the electrode 552X(i,j) and the electrode 551X(i,j). The light-emitting device 550X(i,j) includes a layer 104X(i,j) and a layer 105X(i,j). The layer 104X(i,j) is located between the unit 103X(i,j) and the electrode 551X(i,j), and the layer 105X(i,j) is located between the electrode 552X(i,j) and the unit 103X(i,j). Note that the unit 103X(i,j) includes a layer 111X(i,j), a layer 112X(i,j), and a layer 113X(i,j).
For example, the light-emitting device 550X described in any one of Embodiments 2 to 6 can be used as the light-emitting device 550X(i,j). Specifically, a structure that can be employed for the electrode 551X and a structure that can be employed for the electrode 552X can be respectively employed for the electrode 551X(i,j) and the electrode 552X(i,j). A structure that can be employed for the unit 103X can be employed for the unit 103X(i,j). A structure that can be employed for the layer 104 and a structure that can be employed for the layer 105 can be respectively employed for the layer 104X(i,j) and the layer 105X(i,j). A structure that can be employed for the layer 111X, a structure that can be employed for the layer 112, and a structure that can be employed for the layer 113 can be respectively employed for the layer 111X(i,j), the layer 112X(i,j), and the layer 113X(i,j).
The light-emitting device 550Y(i,j) includes an electrode 551Y(i,j), an electrode 552Y(i,j), and a unit 103Y(i,j). The electrode 552Y(i,j) overlaps with the electrode 551Y(i,j), and the unit 103Y(i,j) is located between the electrode 552Y(i,j) and the electrode 551Y(i,j). The light-emitting device 550Y(i,j) includes a layer 104Y(i,j) and a layer 105Y(i,j). The layer 104Y(i,j) is located between the unit 103Y(i,j) and the electrode 551Y(i,j), and the layer 105Y(i,j) is located between the electrode 552Y(i,j) and the unit 103Y(i,j).
The electrode 551Y(i,j) is adjacent to the electrode 551X(i,j), and a space 551XY(i,j) is provided between the electrode 551X(i,j) and the electrode 551Y(i,j).
Note that part of a structure that can be employed as a structure of the light-emitting device 550X(i,j) can be employed as a structure of the light-emitting device 550Y(i,j). For example, part of a conductive film that can be used for the electrode 552X(i,j) can be used for the electrode 552Y(i,j). A structure that can be employed for the electrode 551X can be employed for the electrode 551Y(i,j). A structure that can be employed for the layer 104 and a structure that can be employed for the layer 105 can be respectively employed for the layer 104Y(i,j) and the layer 105Y(i,j). Thus, the structure can be employed in common. In addition, the manufacturing process can be simplified.
Moreover, the light-emitting device 550Y(i,j) can have a structure emitting light whose hue is the same as that of light emitted from the light-emitting device 550X(i,j).
For example, both the light-emitting device 550X(i,j) and the light-emitting device 550Y(i,j) may emit white light. A coloring layer is provided to overlap with the light-emitting device 550X(i,j), whereby light of a predetermined hue can be extracted from white light. Another coloring layer is provided to overlap with the light-emitting device 550Y(i,j), whereby light of another predetermined hue can be extracted from white light.
For example, both the light-emitting device 550X(i,j) and the light-emitting device 550Y(i,j) may emit blue light. A color conversion layer is provided to overlap with the light-emitting device 550X(i,j), whereby blue light can be converted into light of a predetermined hue. Another coloring layer is provided to overlap with the light-emitting device 550Y(i,j), whereby blue light can be converted into light of another predetermined hue. Blue light can be converted into green light or red light, for example.
Moreover, the light-emitting device 550Y(i,j) can have a structure emitting light whose hue is different from that of light emitted from the light-emitting device 550X(i,j). For example, the hue of light ELY emitted from the unit 103Y(i,j) can be differentiated from that of the light ELX.
The light-emitting device 550Y(i,j) is different from the light-emitting device 550X(i,j) in the structure of a layer 111Y(i,j). Different parts will be described in detail below, and the above description is referred to for parts having the same structure as the above.
Either a structure containing a light-emitting material or a structure containing a light-emitting material and a host material can be employed for the layer 111Y(i,j), for example. The layer 111Y(i,j) can be referred to as a light-emitting layer. The layer 111Y(i,j) is preferably provided in a region where holes and electrons are recombined. This allows efficient conversion of energy generated by recombination of carriers into light and emission of the light.
Furthermore, the layer 111Y(i,j) is preferably provided apart from a metal used for the electrode or the like. In that case, a quenching phenomenon caused by the metal used for the electrode or the like can be inhibited.
It is preferable that a distance from an electrode or the like having reflectivity to the layer 111Y(i,j) be adjusted and the layer 111Y(i,j) be placed in an appropriate position in accordance with an emission wavelength. With this structure, the amplitude can be increased by utilizing an interference phenomenon between light reflected by the electrode or the like and light emitted from the layer 111Y(i,j). Light with a predetermined wavelength can be intensified and the spectrum of the light can be narrowed. In addition, bright light emission colors with high intensity can be obtained. In other words, the layer 111Y(i,j) is placed in an appropriate position, for example, between electrodes and the like, and thus a microcavity structure can be formed.
For example, a fluorescent substance, a phosphorescent substance, or a TADF material can be used for the light-emitting material. Thus, energy generated by recombination of carriers can be released as the light ELY from the light-emitting material (see
A fluorescent substance can be used for the layer 111Y(i,j). For example, fluorescent substances described below as examples can be used for the layer 111Y(i,j). Note that fluorescent substances that can be used for the layer 111Y(i,j) are not limited to the following, and a variety of known fluorescent substances can be used for the layer 111Y(i,j).
Specifically, any of the following fluorescent substances can be used: 5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation: PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine (abbreviation: PAPP2BPy), N,N-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6FLPAPrn), N,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine (abbreviation: YGA2S), 4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine (abbreviation: YGAPA), 4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine (abbreviation: 2YGAPPA), N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), 4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBAPA), N,N′-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA), N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine (abbreviation: 2PCAPPA), N,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03), 3,10-bis[N-(9-phenyl-9H-carbazol-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran (abbreviation: 3,10PCA2Nbf(IV)-02), 3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran (abbreviation: 3,10FrA2Nbf(IV)-02), and the like.
Condensed aromatic diamine compounds typified by pyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPrn, and 1,6BnfAPrn-03 are particularly preferable because of their high hole-trapping properties, high emission efficiency, or high reliability.
Other examples of fluorescent substances include N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPPA), N,N,N,N,N′,N′,N″,N″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine (abbreviation: DBC1), coumarin 30, 9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-carbazol-3-yl)-amino]-anthracene (abbreviation: 2PCAPA), N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine (abbreviation: 2PCABPhA), N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPAPA), N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine (abbreviation: 2DPABPhA), 9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracene-2-amine (abbreviation: 2YGABPhA), N,N,9-triphenylanthracene-9-amine (abbreviation: DPhAPhA), coumarin 545T, N,N-diphenylquinacridone (abbreviation: DPQd), rubrene, and 5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT).
Other examples of fluorescent substances include 2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), 2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2), N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation: p-mPhTD), 7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (abbreviation: p-mPhAFD), 2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTI), 2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCJTB), 2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile (abbreviation: BisDCM), and 2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: BisDCJTM).
A phosphorescent substance can be used for the layer 111Y(i,j). For example, phosphorescent substances described below as examples can be used for the layer 111Y(i,j). Note that phosphorescent substances that can be used for the layer 111Y(i,j) are not limited to the following, and a variety of known phosphorescent substances can be used for the layer 111Y(i,j).
For example, any of the following can be used for the layer 111Y(i,j): an organometallic iridium complex having a 4H-triazole skeleton, an organometallic iridium complex having a 1H-triazole skeleton, an organometallic iridium complex having an imidazole skeleton, an organometallic iridium complex having a phenylpyridine derivative with an electron-withdrawing group as a ligand, an organometallic iridium complex having a pyrimidine skeleton, an organometallic iridium complex having a pyrazine skeleton, an organometallic iridium complex having a pyridine skeleton, a rare earth metal complex, a platinum complex, and the like.
As an organometallic iridium complex having a 4H-triazole skeleton or the like, tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III) (abbreviation: [Ir(mpptz-dmp)3]), tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III) (abbreviation: [Ir(Mptz)3]), tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(iPrptz-3b)3]), or the like can be used.
As an organometallic iridium complex having a 1H-triazole skeleton or the like, tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Mptz1-mp)3]), tris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato]iridium(III) (abbreviation: [Ir(Prptz1-Me)3]), or the like can be used.
As an organometallic iridium complex having an imidazole skeleton or the like, fac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III) (abbreviation: [Ir(iPrpim)3]), tris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III) (abbreviation: [Ir(dmpimpt-Me)3]), or the like can be used.
As an organometallic iridium complex having a phenylpyridine derivative with an electron-withdrawing group as a ligand, or the like, bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) tetrakis(1-pyrazolyl)borate (abbreviation: FIr6), bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) picolinate (abbreviation: FIrpic), bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C2′}iridium(III) picolinate (abbreviation: Ir(CF3ppy)2(pic)), bis[2-(4′,6′-difluorophenyl)pyridinato-N,C2′]iridium(III) acetylacetonate (abbreviation: FIracac), or the like can be used.
These are compounds that exhibit blue phosphorescent light and have an emission wavelength peak at 440 nm to 520 nm.
As an organometallic iridium complex having a pyrimidine skeleton or the like, tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)3]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)3]), (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(mppm)2(acac)]), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III) (abbreviation: [Ir(tBuppm)2(acac)]), (acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(nbppm)2(acac)]), (acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)2(acac)]), (acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III) (abbreviation: [Ir(dppm)2(acac)]), or the like can be used.
As an organometallic iridium complex having a pyrazine skeleton or the like, (acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-Me)2(acac)]), (acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III) (abbreviation: [Ir(mppr-iPr)2(acac)]), or the like can be used.
As an organometallic iridium complex having a pyridine skeleton or the like, tris(2-phenylpyridinato-N,C2′)iridium(III) (abbreviation: [Ir(ppy)3]), bis(2-phenylpyridinato-N,C2′)iridium(III) acetylacetonate (abbreviation: [Ir(ppy)2(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate (abbreviation: [Ir(bzq)2(acac)]), tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)3]), tris(2-phenylquinolinato-N,C2′)iridium(III) (abbreviation: [Ir(pq)3]), bis(2-phenylquinolinato-N,C2′)iridium(III) acetylacetonate (abbreviation: [Ir(pq)2(acac)]), [2-d3-methyl-8-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(5-d3-methyl-2-pyridinyl-κN2)phenyl-κC]iridium(III) (abbreviation: [Ir(5mppy-d3)2(mbfpypy-d3)]), [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: [Ir(ppy)2(mbfpypy-d3)]), or the like can be used.
Examples of a rare earth metal complex are tris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation: Tb(acac)3(Phen)), and the like.
These are compounds that mainly exhibit green phosphorescent light and have an emission wavelength peak at 500 nm to 600 nm. Note that an organometallic iridium complex having a pyrimidine skeleton has distinctively high reliability or emission efficiency.
As an organometallic iridium complex having a pyrimidine skeleton or the like, (diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)2(dibm)]), bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(5mdppm)2(dpm)]), bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III) (abbreviation: [Ir(d1npm)2(dpm)]), or the like can be used.
As an organometallic iridium complex having a pyrazine skeleton or the like, (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III) (abbreviation: [Ir(tppr)2(acac)]), bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III) (abbreviation: [Ir(tppr)2(dpm)]), (acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III) (abbreviation: [Ir(Fdpq)2(acac)]), or the like can be used.
As an organometallic iridium complex having a pyridine skeleton or the like, tris(1-phenylisoquinolinato-N,C2′)iridium(III) (abbreviation: [Ir(piq)3]), bis(1-phenylisoquinolinato-N,C2′)iridium(III) acetylacetonate (abbreviation: [Ir(piq)2(acac)]), or the like can be used.
As a rare earth metal complex or the like, tris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III) (abbreviation: [Eu(DBM)3(Phen)]), tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III) (abbreviation: [Eu(TTA)3(Phen)]), or the like can be used.
As a platinum complex or the like, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II) (abbreviation: PtOEP) or the like can be used.
These are compounds that exhibit red phosphorescent light and have an emission peak at 600 nm to 700 nm. Furthermore, the organometallic iridium complexes having a pyrazine skeleton can provide red light emission with chromaticity favorably used for display devices.
A TADF material can be used for the layer 111Y(i,j). When a TADF material is used as the light-emitting substance, the S1 level of the host material is preferably higher than that of the TADF material. In addition, the T1 level of the host material is preferably higher than that of the TADF material.
For example, TADF materials described below as examples can be used as the light-emitting material. Note that without being limited thereto, a variety of known TADF materials can be used as the light-emitting material.
In the TADF material, the difference between the S1 level and the T1 level is small, and reverse intersystem crossing (upconversion) from the triplet excited state into the singlet excited state can be achieved by a small amount of thermal energy. Thus, the singlet excited state can be efficiently generated from the triplet excited state. In addition, the triplet excitation energy can be converted into luminescence.
An exciplex whose excited state is formed of two kinds of substances has an extremely small difference between the S1 level and the T1 level and functions as a TADF material capable of converting triplet excitation energy into singlet excitation energy.
A phosphorescent spectrum observed at a low temperature (e.g., 77 K to 10 K) is used for an index of the T1 level. When the level of energy with a wavelength of the line obtained by extrapolating a tangent to the fluorescent spectrum at a tail on the short wavelength side is the S1 level and the level of energy with a wavelength of the line obtained by extrapolating a tangent to the phosphorescent spectrum at a tail on the short wavelength side is the T1 level, the difference between the S1 level and the T1 level of the TADF material is preferably smaller than or equal to 0.3 eV, further preferably smaller than or equal to 0.2 eV.
Examples of the TADF material include a fullerene, a derivative thereof, an acridine, a derivative thereof, and an eosin derivative. Furthermore, porphyrin containing a metal such as magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), or palladium (Pd) can also be used for the TADF material.
Specifically, the following materials whose structural formulae are shown below can be used: a protoporphyrin-tin fluoride complex (SnF2(Proto IX)), a mesoporphyrin-tin fluoride complex (SnF2(Meso IX)), a hematoporphyrin-tin fluoride complex (SnF2(Hemato IX)), a coproporphyrin tetramethyl ester-tin fluoride complex (SnF2(Copro III-4Me)), an octaethylporphyrin-tin fluoride complex (SnF2(OEP)), an etioporphyrin-tin fluoride complex (SnF2(Etio I)), an octaethylporphyrin-platinum chloride complex (PtCl2OEP), and the like.
Furthermore, a heterocyclic compound including one or both of a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring can be used, for example, as the TADF material.
Specifically, the following compounds whose structural formulae are shown below can be used: 2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine (abbreviation: PIC-TRZ), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCzTzn), 2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine (abbreviation: PCCzPTzn), 2-[4-(10H-phenoxazine-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine (abbreviation: PXZ-TRZ), 3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole (abbreviation: PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation: ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (abbreviation: DMAC-DPS), 10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation: ACRSA), and the like.
Such a heterocyclic compound is preferable because of having excellent electron-transport and hole-transport properties owing to a π-electron rich heteroaromatic ring and a π-electron deficient heteroaromatic ring. Among skeletons having the π-electron deficient heteroaromatic ring, in particular, a pyridine skeleton, a diazine skeleton (a pyrimidine skeleton, a pyrazine skeleton, and a pyridazine skeleton), and a triazine skeleton are preferred because of their high stability and reliability. In particular, a benzofuropyrimidine skeleton, a benzothienopyrimidine skeleton, a benzofuropyrazine skeleton, and a benzothienopyrazine skeleton are preferred because of their high electron-accepting properties and high reliability.
Among skeletons having the π-electron rich heteroaromatic ring, an acridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, a furan skeleton, a thiophene skeleton, and a pyrrole skeleton have high stability and reliability; thus, at least one of these skeletons is preferably included. A dibenzofuran skeleton is preferable as a furan skeleton, and a dibenzothiophene skeleton is preferable as a thiophene skeleton. As a pyrrole skeleton, an indole skeleton, a carbazole skeleton, an indolocarbazole skeleton, a bicarbazole skeleton, and a 3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularly preferable.
Note that a substance in which the π-electron rich heteroaromatic ring is directly bonded to the π-electron deficient heteroaromatic ring is particularly preferred because the electron-donating property of the π-electron rich heteroaromatic ring and the electron-accepting property of the π-electron deficient heteroaromatic ring are both improved, the energy difference between the S1 level and the T1 level becomes small, and thus thermally activated delayed fluorescence can be obtained with high efficiency. Note that an aromatic ring to which an electron-withdrawing group such as a cyano group is bonded may be used instead of the π-electron deficient heteroaromatic ring. As a π-electron rich skeleton, an aromatic amine skeleton, a phenazine skeleton, or the like can be used.
As a π-electron deficient skeleton, a xanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazole skeleton, a triazole skeleton, an imidazole skeleton, an anthraquinone skeleton, a skeleton containing boron such as phenylborane and boranthrene, an aromatic ring or a heteroaromatic ring having a nitrile group or a cyano group such as benzonitrile or cyanobenzene, a carbonyl skeleton such as benzophenone, a phosphine oxide skeleton, a sulfone skeleton, or the like can be used.
As described above, a π-electron deficient skeleton and a π-electron rich skeleton can be used instead of at least one of the π-electron deficient heteroaromatic ring and the π-electron rich heteroaromatic ring.
A carrier-transport material can be used as the host material. For example, a hole-transport material, an electron-transport material, a TADF material, a material having an anthracene skeleton, or a mixed material can be used as the host material. A material having a wider bandgap than the light-emitting material contained in the layer 111Y(i,j) is preferably used as the host material. Thus, transfer of energy from excitons generated in the layer 111Y(i,j) to the host material can be inhibited.
A material having a hole mobility of 1×10−6 cm2/Vs or higher can be suitably used as the hole-transport material. For example, a hole-transport material that can be used for the layer 112 can be used as the host material.
A metal complex or an organic compound having a π-electron deficient heteroaromatic ring skeleton can be used as the electron-transport material. For example, an electron-transport material that can be used for the layer 113 can be used as the host material.
An organic compound having an anthracene skeleton can be used as the host material. An organic compound having an anthracene skeleton is particularly preferable in the case where a fluorescent substance is used as a light-emitting substance. Thus, a light-emitting device with high emission efficiency and high durability can be obtained.
Among the organic compounds having an anthracene skeleton, an organic compound having a diphenylanthracene skeleton, in particular, a 9,10-diphenylanthracene skeleton, is chemically stable and thus is preferable. The host material preferably has a carbazole skeleton because the hole-injection and hole-transport properties are improved. In particular, the host material preferably has a dibenzocarbazole skeleton because the HOMO level thereof is shallower than that of carbazole by approximately 0.1 eV so that holes enter the host material easily, the hole-transport property is improved, and the heat resistance is increased. Note that in terms of the hole-injection and hole-transport properties, instead of a carbazole skeleton, a benzofluorene skeleton or a dibenzofluorene skeleton may be used.
Thus, a substance having both a 9,10-diphenylanthracene skeleton and a carbazole skeleton, a substance having both a 9,10-diphenylanthracene skeleton and a benzocarbazole skeleton, or a substance having both a 9,10-diphenylanthracene skeleton and a dibenzocarbazole skeleton is preferable as the host material.
Examples of the substances that can be used include 6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation: 2mBnfPPA), 9-phenyl-10-[4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl]anthracene (abbreviation: FLPPA), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole (abbreviation: cgDBCzPA), and 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN).
In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPA have excellent characteristics.
A TADF material can be used as the host material. When the TADF material is used as the host material, triplet excitation energy generated in the TADF material can be converted into singlet excitation energy by reverse intersystem crossing. Moreover, excitation energy can be transferred to the light-emitting substance. In other words, the TADF material functions as an energy donor, and the light-emitting substance functions as an energy acceptor. Thus, the emission efficiency of the light-emitting device can be increased.
This is very effective in the case where the light-emitting substance is a fluorescent substance. In that case, the S1 level of the TADF material is preferably higher than that of the fluorescent substance in order that high emission efficiency be achieved. Furthermore, the T1 level of the TADF material is preferably higher than the S1 level of the fluorescent substance. Therefore, the T1 level of the TADF material is preferably higher than that of the fluorescent substance.
It is also preferable to use a TADF material that emits light whose wavelength overlaps with the wavelength on a lowest-energy-side absorption band of the fluorescent substance. This enables smooth transfer of excitation energy from the TADF material to the fluorescent substance and accordingly enables efficient light emission, which is preferable.
In addition, in order to efficiently generate singlet excitation energy from the triplet excitation energy by reverse intersystem crossing, carrier recombination preferably occurs in the TADF material. It is also preferable that the triplet excitation energy generated in the TADF material not be transferred to the triplet excitation energy of the fluorescent substance. For that reason, the fluorescent substance preferably has a protecting group around a luminophore (a skeleton which causes light emission) of the fluorescent substance. As the protecting group, a substituent having no π bond and a saturated hydrocarbon are preferably used. Specific examples include an alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbon atoms. It is further preferable that the fluorescent substance have a plurality of protecting groups. The substituents having no π bond are poor in carrier-transport performance; therefore, the TADF material and the luminophore of the fluorescent substance can be made away from each other with little influence on carrier-transportation or carrier recombination.
Here, the luminophore refers to an atomic group (skeleton) that causes light emission in a fluorescent substance. The luminophore is preferably a skeleton having a π bond, further preferably includes an aromatic ring, and still further preferably includes a condensed aromatic ring or a condensed heteroaromatic ring.
Examples of the condensed aromatic ring or the condensed heteroaromatic ring include a phenanthrene skeleton, a stilbene skeleton, an acridone skeleton, a phenoxazine skeleton, and a phenothiazine skeleton. In particular, a fluorescent substance having any of a naphthalene skeleton, an anthracene skeleton, a fluorene skeleton, a chrysene skeleton, a triphenylene skeleton, a tetracene skeleton, a pyrene skeleton, a perylene skeleton, a coumarin skeleton, a quinacridone skeleton, and a naphthobisbenzofuran skeleton is preferred because of its high fluorescence quantum yield.
For example, the TADF material that can be used as the light-emitting material can be used as the host material.
A material in which a plurality of kinds of substances are mixed can be used as the host material. For example, a material which includes an electron-transport material and a hole-transport material can be used as the mixed material. The weight ratio between the hole-transport material and the electron-transport material contained in the mixed material may be (the hole-transport material/the electron-transport material)=(1/19) or more and (19/1) or less. Thus, the carrier-transport property of the layer 111Y(i,j) can be easily adjusted and a recombination region can be easily controlled.
A material mixed with a phosphorescent substance can be used as the host material. When a fluorescent substance is used as the light-emitting substance, the phosphorescent substance can be used as an energy donor for supplying excitation energy to the fluorescent substance.
A mixed material containing a material to form an exciplex can be used as the host material. For example, a material in which an emission spectrum of a formed exciplex overlaps with a wavelength of the absorption band on the lowest energy side of the light-emitting substance can be used as the host material. This enables smooth energy transfer and improves emission efficiency. The driving voltage can be reduced. With such a structure, light emission can be efficiently obtained by exciplex-triplet energy transfer (ExTET), which is energy transfer from the exciplex to the light-emitting substance (phosphorescent material).
A phosphorescent substance can be used as at least one of the materials forming an exciplex. Accordingly, reverse intersystem crossing can be used. Triplet excitation energy can be efficiently converted into singlet excitation energy.
Combination of an electron-transport material and a hole-transport material whose HOMO level is higher than or equal to that of the electron-transport material is preferable for forming an exciplex. The LUMO level of the hole-transport material is preferably higher than or equal to the LUMO level of the electron-transport material. Thus, an exciplex can be efficiently formed. Note that the LUMO levels and the HOMO levels of the materials can be derived from the electrochemical characteristics (the reduction potentials and the oxidation potentials). Specifically, the reduction potentials and the oxidation potentials can be measured by cyclic voltammetry (CV).
The formation of an exciplex can be confirmed by a phenomenon in which the emission spectrum of the mixed film in which the hole-transport material and the electron-transport material are mixed is shifted to the longer wavelength side than the emission spectra of each of the materials (or has another peak on the longer wavelength side) observed by comparison of the emission spectra of the hole-transport material, the electron-transport material, and the mixed film of these materials, for example. Alternatively, the formation of an exciplex can be confirmed by a difference in transient response, such as a phenomenon in which the transient PL lifetime of the mixed film has longer lifetime components or a larger proportion of delayed components than that of each of the materials, observed by comparison of transient photoluminescence (PL) of the hole-transport material, the electron-transport material, and the mixed film of the materials. The transient PL can be rephrased as transient electroluminescence (EL). That is, the formation of an exciplex can also be confirmed by a difference in transient response observed by comparison of the transient EL of the hole-transport material, the electron-transport material, and the mixed film of the materials.
The display device 700 described in this embodiment includes an insulating film 528 (see
The insulating film 528 has openings; one opening overlaps with the electrode 551X(i,j) and the other opening overlaps with the electrode 551Y(i,j). The insulating film 528 overlaps with the space 551XY(i,j).
The space 551XY(i,j) located between the electrode 551X(i,j) and the electrode 551Y(i,j) has a groove-like shape, for example. Thus, a step is formed along the groove. A deposited film is partly split or thinned between the space 551XY(i,j) and the electrode 551X(i,j).
When an anisotropic deposition method such as a thermal evaporation method is employed, a split or thinned portion is formed along the step in a space 104XY(i,j) located between the layer 104X(i,j) and the layer 104Y(i,j).
Thus, current flowing through the region 104XY(i,j) can be suppressed, for example. Moreover, current flowing between the layer 104X(i,j) and the layer 104Y(i,j) can be suppressed. Furthermore, a phenomenon in which the light-emitting device 550Y(i,j) that is adjacent to the light-emitting device 550X(i,j) unintentionally emits light in accordance with the operation of the light-emitting device 550X(i,j) can be suppressed.
The display device 700 described in this embodiment includes the light-emitting device 550X(i,j) and the light-emitting device 550Y(i,j) (see
The display device 700 described with reference to
The film 529_1 has openings; one opening overlaps with the electrode 551X(i,j) and the other opening overlaps with the electrode 551Y(i,j) (see
The insulating film 529_2 has openings; one opening overlaps with the electrode 551X(i,j) and the other opening overlaps with the electrode 551Y(i,j). The film 529_2 overlaps with the space 551XY(i,j).
The film 529_2 includes a region in contact with the layer 104X(i,j) and the unit 103X(i,j).
The film 529_2 includes a region in contact with the layer 104Y(i,j) and the unit 103Y(i,j).
The film 529_2 includes a region in contact with the insulating film 521. The film 529_2 can be formed by an atomic layer deposition (ALD) method, for example. Thus, a film with favorable coverage can be formed. Specifically, a metal oxide film or the like can be used as the film 529_2. Aluminum oxide can be used, for example.
The insulating film 529_3 has openings; one opening overlaps with the electrode 551X(i,j) and the other opening overlaps with the electrode 551Y(i,j). A groove formed in a region overlapping with the space 551XY(i,j) is filled with the film 529_3. The film 529_3 can be formed using a photosensitive resin, for example. Specifically, an acrylic resin or the like can be used.
Thus, the layer 104X(i,j) can be electrically isolated from the layer 104Y(i,j), for example. In addition, current flowing through the region 104XY(i,j) can be suppressed, for example. A phenomenon in which the light-emitting device 550Y(i,j) that is adjacent to the light-emitting device 550X(i,j) unintentionally emits light in accordance with the operation of the light-emitting device 550X(i,j) can be suppressed. A step formed between a top surface of the unit 103X(i,j) and a top surface of the unit 103Y(i,j) can be reduced. Occurrence of a phenomenon in which a split or thinned portion due to the step is formed between the electrode 552X(i,j) and the electrode 552Y(i,j) can be suppressed. A continuous conductive film can be used for the electrode 552X(i,j) and the electrode 552Y(i,j).
Note that part or the whole of the structure that can be employed for the light-emitting device 550X(i,j) or the light-emitting device 550Y(i,j) can be removed from a portion overlapping with the space 551XY(i,j) by using a photolithography method, for example. In this specification and the like, a device formed using a metal mask or a fine metal mask (FMM) may be referred to as a device having a metal mask (MM) structure. In this specification and the like, a device formed without using a metal mask or an FMM may be referred to as a device having a metal maskless (MML) structure.
Specifically, in a first step, a film to be the unit 103Y(i,j) later is formed over the space 551XY(i,j).
In a second step, a first film to be the film 529_1 later is formed over the film to be the unit 103Y(i,j) later.
In a third step, an opening overlapping with the space 551XY(i,j) is formed in the first film by a photolithography method.
In a fourth step, with use of the first film as a resist, part or the whole of the structure of the light-emitting device 550Y(i,j) is removed from a region overlapping with the space 551XY(i,j). For example, the unit 103Y(i,j) is removed by a dry etching method. Specifically, an organic compound can be removed with use of an oxygen-containing gas. Accordingly, a groove is formed in the region overlapping with the space 551XY(i,j).
In a fifth step, a second film to be the film 529_2 later is formed over the first film by an ALD method, for example.
In a sixth step, the film 529_3 is formed with use of a photosensitive polymer, for example. Accordingly, the groove formed in the region overlapping with the space 551XY(i,j) is filled with the film 529_3.
In a seventh step, an opening overlapping with the electrode 551Y(i,j) is formed in the first film and the second film by a photolithography method, whereby the film 529_1 and the film 529_2 are formed.
In an eighth step, the layer 105Y(i,j) is formed over the unit 103Y(i,j) and the electrode 552Y(i,j) is formed over the layer 105Y(i,j).
Note that this embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, structures of the display device 700 of one embodiment of the present invention will be described with reference to
The display device 700 described in this embodiment includes the light-emitting device 550X(i,j) and a photoelectric conversion device 550S(i,j) (see
The display device 700 includes the substrate 510 and the functional layer 520. The functional layer 520 includes the insulating film 521, and the light-emitting device 550X(i,j) and the photoelectric conversion device 550S(i,j) are formed over the insulating film 521. The functional layer 520 is located between the substrate 510 and the light-emitting device 550X(i,j).
The light-emitting device 550X(i,j) includes the electrode 551X(i,j), the electrode 552X(i,j), and the unit 103X(i,j). The electrode 552X(i,j) overlaps with the electrode 551X(i,j), and the unit 103X(i,j) is located between the electrode 552X(i,j) and the electrode 551X(i,j). The light-emitting device 550X(i,j) includes the layer 104X(i,j) and the layer 105X(i,j). The layer 104X(i,j) is located between the unit 103X(i,j) and the electrode 551X(i,j), and the layer 105X(i,j) is located between the electrode 552X(i,j) and the unit 103X(i,j).
For example, the light-emitting device 550X described in any one of Embodiments 2 to 6 can be used as the light-emitting device 550X(i,j). Specifically, a structure that can be employed for the electrode 551X and a structure that can be employed for the electrode 552X can be respectively employed for the electrode 551X(i,j) and the electrode 552X(i,j). A structure that can be employed for the unit 103X can be employed for the unit 103X(i,j). A structure that can be employed for the layer 104 and a structure that can be employed for the layer 105 can be respectively employed for the layer 104X(i,j) and the layer 105X(i,j).
The photoelectric conversion device 550S(i,j) includes an electrode 551S(i,j), an electrode 552S(i,j), and a unit 103S(i,j). The electrode 552S(i,j) overlaps with the electrode 551S(i,j), and the unit 103S(i,j) is located between the electrode 551S(i,j) and the electrode 552S(i,j). The photoelectric conversion device 550S(i,j) includes a layer 104S(i,j) and a layer 105S(i,j). The layer 104S(i,j) is located between the unit 103S(i,j) and the electrode 551S(i,j), and the layer 105S(i,j) is located between the electrode 552S(i,j) and the unit 103S(i,j).
The electrode 551S(i,j) is adjacent to the electrode 551X(i,j), and a space 551XS(i,j) is provided between the electrode 551X(i,j) and the electrode 551S(i,j).
Note that part of a structure that can be employed as a structure of the light-emitting device 550X(i,j) described in any one of Embodiments 2 to 6 can be employed as a structure of the photoelectric conversion device 550S(i,j). For example, part of a conductive film that can be used for the electrode 552X(i,j) can be used for the electrode 552S(i,j). A structure that can be employed for the electrode 551X can be employed for the electrode 551S(i,j). A structure that can be employed for the layer 104 and a structure that can be employed for the layer 105 can be respectively employed for the layer 104S(i,j) and the layer 105S(i,j). Thus, the structure can be employed in common. In addition, the manufacturing process can be simplified.
Note that the photoelectric conversion device 550S(i,j) is different from the light-emitting device 550X(i,j) in that the unit 103S(i,j) having a function of converting light into current is included instead of the unit 103X(i,j) having a function of emitting light. Different parts will be described in detail below, and the above description is referred to for parts having the same structure as the above.
The unit 103S(i,j) has a single-layer structure or a stacked-layer structure. The unit 103S(i,j) can include, for example, a layer selected from functional layers such as a hole-transport layer, an electron-transport layer, and a carrier-blocking layer, besides a photoelectric conversion layer.
The unit 103S(i,j) includes a layer 114S(i,j), a layer 112S(i,j), and a layer 113S(i,j) (see
Note that the unit 103S(i,j) has a function of absorbing light hv and supplying electrons to one electrode and supplying holes to the other. For example, the unit 103S(i,j) supplies holes to the electrode 551S(i,j), and supplies electrons to the electrode 552S(i,j).
Note that part of a structure that can be employed as a structure of the unit 103X described in Embodiment 2 can be employed as a structure of the unit 103S(i,j). For example, a structure that can be employed for the layer 112 and a structure that can be employed for the layer 113 can be respectively employed for the layer 112S(i,j) and the layer 113S(i,j). Thus, the structure can be employed in common. In addition, the manufacturing process can be simplified.
The layer 114S(i,j) can be referred to as a photoelectric conversion layer. The layer 114S(i,j) absorbs the light hv, supplies electrons to a layer in contact with one side of the layer 114S(i,j), and supplies holes to a layer in contact with the other side of the layer 114S(i,j). For example, the layer 114S(i,j) supplies holes to the layer 112S(i,j), and supplies electrons to the layer 113S(i,j). For example, a material that can be used for an organic solar cell can be used for the layer 114S(i,j). Specifically, an electron-accepting material and an electron-donating material can be used for the layer 114S(i,j).
As the electron-accepting material, a fullerene derivative or a non-fullerene electron acceptor can be used, for example.
As the electron-accepting material, a C60 fullerene, a C70 fullerene, [6,6]-phenyl-C71-butyric acid methyl ester (abbreviation: PC71BM), [6,6]-phenyl-C61-butyric acid methyl ester (abbreviation: PC61BM), 1′,1″,4′,4″-tetrahydro-di[1,4]methanonaphthaleno[1,2:2′,3′,56,60:2″,3″ ][5,6]fullerene-C60 (abbreviation: ICBA), or the like can be used.
As the non-fullerene electron acceptor, a perylene derivative, a compound having a dicyanomethyleneindanone group, or the like can be used. For example, NN-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (abbreviation: Me-PTCDI) can be used.
As the electron-donating material, a phthalocyanine compound, a tetracene derivative, a quinacridone derivative, a rubrene derivative, or the like can be used.
As the electron-donating material, copper(II) phthalocyanine (abbreviation: CuPc), tin(II) phthalocyanine (SnPc), zinc phthalocyanine (ZnPc), tetraphenyldibenzoperiflanthene (DBP), rubrene, or the like can be used.
The layer 114S(i,j) can have a single-layer structure or a stacked-layer structure, for example. Specifically, the layer 114S(i,j) can have a bulk heterojunction structure. Alternatively, the layer 114S(i,j) can have a heterojunction structure.
A mixed material containing an electron-accepting material and an electron-donating material can be used for the layer 114S(i,j), for example (see
Specifically, a mixed material containing a C70 fullerene and DBP can be used for the layer 114S(i,j).
A layer 114N(i,j) and a layer 114P(i,j) can be used for the layer 114S(i,j) (see
An n-type semiconductor can be used for the layer 114N(i,j). For example, Me-PTCDI can be used for the layer 114N(i,j).
A p-type semiconductor can be used for the layer 114P(i,j). For example, rubrene can be used for the layer 114P(i,j).
Note that the photoelectric conversion device 550S(i,j) in which the layer 114P(i,j) is in contact with the layer 114N(i,j) can be referred to as a pn-junction photodiode.
In this embodiment, the structure of a device of one embodiment of the present invention will be described with reference to
The display device 700 of one embodiment of the present invention includes a region 231 (see
The pixel set 703(i,j) includes a pixel 702X(i,j) (see
The pixel 702X(i,j) includes a pixel circuit 530X(i,j) and the light-emitting device 550X(i,j). The light-emitting device 550X(i,j) is electrically connected to the pixel circuit 530X(i,j).
For example, the light-emitting device described in any one of Embodiments 2 to 6 can be used as the light-emitting device 550X(i,j). The display device 700 has a function of displaying an image.
In addition, the display device 700 of one embodiment of the present invention includes a functional layer 540 and a functional layer 520 (see
The functional layer 540 includes the light-emitting device 550X(i,j).
The functional layer 520 includes the pixel circuit 530X(i,j) and a wiring (see
In addition, the display device 700 of one embodiment of the present invention includes a driver circuit GD and a driver circuit SD (see
The driver circuit GD supplies a first selection signal and a second selection signal.
The driver circuit SD supplies a first control signal and a second control signal.
As wirings, a conductive film G1(i), a conductive film G2(i), a conductive film S1(j), a conductive film S2(j), a conductive film ANO, a conductive film VCOM2, and a conductive film V0 are included (see
The conductive film G1(i) is supplied with the first selection signal, and the conductive film G2(i) is supplied with the second selection signal.
The conductive film S1(j) is supplied with the first control signal, and the conductive film S2(j) is supplied with the second control signal.
The pixel circuit 530X(i,j) is electrically connected to the conductive film G1(i) and the conductive film S1(j). The conductive film G1(i) supplies the first selection signal, and the conductive film S1(j) supplies the first control signal.
The pixel circuit 530X(i,j) drives the light-emitting device 550X(i,j) in response to the first selection signal and the first control signal. The light-emitting device 550X(i,j) emits light.
One electrode of the light-emitting device 550X(i,j) is electrically connected to the pixel circuit 530X(i,j) and the other electrode is electrically connected to the conductive film VCOM2.
The pixel circuit 530X(i,j) includes a switch SW21, a switch SW22, a transistor M21, a capacitor C21, and a node N21.
The transistor M21 includes a gate electrode electrically connected to the node N21, a first electrode electrically connected to the light-emitting device 550X(i,j), and a second electrode electrically connected to the conductive film ANO.
The switch SW21 includes a first terminal electrically connected to the node N21, a second terminal electrically connected to the conductive film S1(j), and a gate electrode having a function of controlling an on/off state of the switch SW21 according to the potential of the conductive film G1(i).
The switch SW22 includes a first terminal electrically connected to the conductive film S2(j), and a gate electrode having a function of controlling an on/off state of the switch SW22 according to the potential of the conductive film G2(i).
The capacitor C21 includes a conductive film electrically connected to the node N21 and a conductive film electrically connected to a second electrode of the switch SW22.
Accordingly, an image signal can be stored in the node N21. Alternatively, the potential of the node N21 can be changed using the switch SW22. Alternatively, the intensity of light emitted from the light-emitting device 550X(i,j) can be controlled with the potential of the node N21. As a result, a novel device that is highly convenient, useful, or reliable can be provided.
The pixel circuit 530X(i,j) includes a switch SW23, a node N22, and a capacitor C22.
The switch SW23 includes a first terminal electrically connected to the conductive film V0, a second terminal electrically connected to the node N22, and a gate electrode having a function of controlling an on/off state of the switch SW23 according to the potential of the conductive film G2(i).
The capacitor C22 includes a conductive film electrically connected to the node N21 and a conductive film electrically connected to the node N22.
The first electrode of the transistor M21 is electrically connected to the node N22.
The pixel 702X(i,j) includes the light-emitting device 550X(i,j) and the pixel circuit 530X(i,j) (see
The light-emitting device 550X(i,j) is a top-emission light-emitting device and emits the light ELX to the side where the functional layer 520 is not provided.
The coloring layer CFX transmits part of light emitted from the light-emitting device 550X(i,j). For example, the coloring layer CFX may transmit part of white light, so that blue, green, or red light can be extracted. Note that a color conversion layer can be used instead of the coloring layer CFX. Accordingly, light with a short wavelength can be converted into light with a long wavelength.
The pixel 702X(i,j) described with reference to
The functional layer 520 includes a region 520T that transmits the light ELX. The functional layer 520 includes the coloring layer CFX that overlaps with the region 520T.
Note that this embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this embodiment, a light-emitting apparatus including the light-emitting device described in any one of Embodiments 2 to 6 will be described.
In this embodiment, the light-emitting apparatus fabricated using the light-emitting device described in any one of Embodiments 2 to 6 is described with reference to
A lead wiring 608 is a wiring for transmitting signals to be input to the source line driver circuit 601 and the gate line driver circuit 603 and receives signals such as a video signal, a clock signal, a start signal, and a reset signal from a flexible printed circuit (FPC) serving as an external input terminal 609. Although only the FPC is illustrated here, a printed wiring board (PWB) may be attached to the FPC. The light-emitting apparatus in this specification includes, in its category, not only the light-emitting apparatus itself but also the light-emitting apparatus provided with the FPC or the PWB.
Next, a cross-sectional structure is described with reference to
The element substrate 610 may be a substrate formed of glass, quartz, an organic resin, a metal, an alloy, or a semiconductor or a plastic substrate formed of fiber reinforced plastics (FRP), poly(vinyl fluoride) (PVF), polyester, an acrylic resin, or the like.
The structures of transistors used in pixels or driver circuits are not particularly limited. For example, inverted staggered transistors or staggered transistors may be used. Furthermore, top-gate transistors or bottom-gate transistors may be used. A semiconductor material used for the transistors is not particularly limited, and for example, silicon, germanium, silicon carbide, or gallium nitride can be used. Alternatively, an oxide semiconductor containing at least one of indium, gallium, and zinc, such as an In—Ga—Zn-based metal oxide, may be used.
There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and either an amorphous semiconductor or a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partly including crystal regions) can be used. It is preferable that a semiconductor having crystallinity be used, in which case deterioration of the transistor characteristics can be suppressed.
Here, an oxide semiconductor is preferably used for semiconductor devices such as the transistors provided in the pixels or driver circuits and transistors used for touch sensors described later, and the like. In particular, an oxide semiconductor having a wider band gap than silicon is preferably used. When an oxide semiconductor having a wider band gap than silicon is used, the off-state current of the transistors can be reduced.
The oxide semiconductor preferably contains at least indium (In) or zinc (Zn). Further preferably, the oxide semiconductor contains an oxide represented by an In-M-Zn-based oxide (M represents a metal such as Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).
As a semiconductor layer, it is particularly preferable to use an oxide semiconductor film including a plurality of crystal parts whose c-axes are aligned perpendicular to a surface on which the semiconductor layer is formed or the top surface of the semiconductor layer and in which the adjacent crystal parts have no grain boundary.
The use of such materials for the semiconductor layer makes it possible to provide a highly reliable transistor in which a change in the electrical characteristics is suppressed.
Charge accumulated in a capacitor through a transistor including the above-described semiconductor layer can be held for a long time because of the low off-state current of the transistor. When such a transistor is used in a pixel, operation of a driver circuit can be stopped while a gray scale of an image displayed in each display region is maintained. As a result, an electronic device with extremely low power consumption can be obtained.
For stable characteristics or the like of the transistor, a base film is preferably provided. The base film can be formed with a single-layer structure or a stacked-layer structure using an inorganic insulating film such as a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a silicon nitride oxide film. The base film can be formed by a sputtering method, a chemical vapor deposition (CVD) method (e.g., a plasma CVD method, a thermal CVD method, or a metal organic CVD (MOCVD) method), an ALD method, a coating method, a printing method, or the like. Note that the base film is not necessarily provided.
Note that an FET 623 is illustrated as a transistor formed in the source line driver circuit 601. In addition, the driver circuit may be formed with any of a variety of circuits such as a CMOS circuit, a PMOS circuit, or an NMOS circuit. Although a driver integrated type in which the driver circuit is formed over the substrate is illustrated in this embodiment, the driver circuit is not necessarily formed over the substrate, and the driver circuit can be formed outside.
Although the pixel portion 602 includes a plurality of pixels each including a switching FET 611, a current controlling FET 612, and a first electrode 613 electrically connected to a drain of the current controlling FET 612, one embodiment of the present invention is not limited to this structure. The pixel portion 602 may include three or more FETs and a capacitor in combination.
Note that an insulator 614 is formed to cover an end portion of the first electrode 613. Here, the insulator 614 can be formed using a positive photosensitive acrylic resin film.
In order to improve coverage with an EL layer or the like which is formed later, the insulator 614 is formed to have a curved surface with curvature at its upper or lower end portion. For example, in the case where a positive photosensitive acrylic resin is used for a material of the insulator 614, only the upper end portion of the insulator 614 preferably has a surface with a curvature radius (greater than or equal to 0.2 μm and less than or equal to 3 μm). As the insulator 614, either a negative photosensitive resin or a positive photosensitive resin can be used.
An EL layer 616 and a second electrode 617 are formed over the first electrode 613. Here, as a material used for the first electrode 613 functioning as an anode, a material having a high work function is desirably used. For example, a single-layer film of an ITO film, an indium tin oxide film containing silicon, an indium oxide film containing zinc oxide at 2 wt % to 20 wt %, a titanium nitride film, a chromium film, a tungsten film, a Zn film, a Pt film, or the like, a stack of a titanium nitride film and a film containing aluminum as its main component, or a stack of three layers of a titanium nitride film, a film containing aluminum as its main component, and a titanium nitride film can be used. The stacked-layer structure enables low wiring resistance, favorable ohmic contact, and a function as an anode.
The EL layer 616 is formed by any of a variety of methods such as an evaporation method using an evaporation mask, an inkjet method, and a spin coating method. The EL layer 616 has the structure described in any one of Embodiments 2 to 6. As another material included in the EL layer 616, a low molecular compound or a high molecular compound (including an oligomer or a dendrimer) may be used.
As a material used for the second electrode 617, which is formed over the EL layer 616 and functions as a cathode, a material having a low work function (e.g., Al, Mg, Li, and Ca, or an alloy or a compound thereof, such as MgAg, MgIn, and AlLi) is preferably used. In the case where light generated in the EL layer 616 passes through the second electrode 617, a stack including a thin metal film and a transparent conductive film (e.g., ITO, indium oxide containing zinc oxide at 2 wt % or higher and 20 wt % or lower, indium tin oxide containing silicon, or zinc oxide (ZnO)) is preferably used for the second electrode 617.
Note that the light-emitting device is formed with the first electrode 613, the EL layer 616, and the second electrode 617. The light-emitting device is the light-emitting device described in any one of Embodiments 2 to 6. In the light-emitting apparatus of this embodiment, the pixel portion, which includes a plurality of light-emitting devices, may include both the light-emitting device described in any one of Embodiments 2 to 6 and a light-emitting device having a different structure.
The sealing substrate 604 is attached to the element substrate 610 with the sealing material 605, so that a light-emitting device 618 is provided in the space 607 surrounded by the element substrate 610, the sealing substrate 604, and the sealing material 605. The space 607 is filled with a filler, and may be filled with an inert gas (such as nitrogen or argon) or the sealing material. It is preferable that the sealing substrate be provided with a recessed portion and a drying agent be provided in the recessed portion, in which case degradation due to influence of moisture can be suppressed.
An epoxy-based resin or glass frit is preferably used for the sealing material 605. It is preferable that such a material not be permeable to moisture and oxygen as much as possible. As the sealing substrate 604, a glass substrate, a quartz substrate, or a plastic substrate formed of FRP, PVF, polyester, an acrylic resin, or the like can be used.
Although not illustrated in
The protective film can be formed using a material through which an impurity such as water does not permeate easily. Thus, diffusion of an impurity such as water from the outside into the inside can be effectively suppressed.
As a material of the protective film, an oxide, a nitride, a fluoride, a sulfide, a ternary compound, a metal, a polymer, or the like can be used. For example, a material containing aluminum oxide, hafnium oxide, hafnium silicate, lanthanum oxide, silicon oxide, strontium titanate, tantalum oxide, titanium oxide, zinc oxide, niobium oxide, zirconium oxide, tin oxide, yttrium oxide, cerium oxide, scandium oxide, erbium oxide, vanadium oxide, or indium oxide; a material containing aluminum nitride, hafnium nitride, silicon nitride, tantalum nitride, titanium nitride, niobium nitride, molybdenum nitride, zirconium nitride, or gallium nitride; or a material containing a nitride containing titanium and aluminum, an oxide containing titanium and aluminum, an oxide containing aluminum and zinc, a sulfide containing manganese and zinc, a sulfide containing cerium and strontium, an oxide containing erbium and aluminum, or an oxide containing yttrium and zirconium can be used.
The protective film is preferably formed using a deposition method with favorable step coverage. One such method is an ALD method. A material that can be formed by an ALD method is preferably used for the protective film. A dense protective film having reduced defects such as cracks or pinholes or a uniform thickness can be formed by an ALD method. Furthermore, damage caused to a process member in forming the protective film can be reduced.
By an ALD method, a uniform protective film with few defects can be formed even on, for example, a surface with a complex uneven shape or upper, side, and rear surfaces of a touch panel.
As described above, the light-emitting apparatus fabricated using the light-emitting device described in any one of Embodiments 2 to 6 can be obtained.
The light-emitting apparatus in this embodiment is fabricated using the light-emitting device described in any one of Embodiments 2 to 6 and thus can have favorable characteristics. Specifically, since the light-emitting device described in any one of Embodiments 2 to 6 has high emission efficiency, the light-emitting apparatus can achieve low power consumption.
In
The above-described light-emitting apparatus has a structure in which light is extracted from the substrate 1001 side where FETs are formed (a bottom emission structure), but may have a structure in which light is extracted from the sealing substrate 1031 side (atop emission structure).
The electrodes 1024W, 1024R, 1024G, and 1024B of the light-emitting devices each serve as an anode here, but may serve as a cathode. Furthermore, in the case of the top-emission light-emitting apparatus illustrated in
In the case of a top emission structure as illustrated in
In the top-emission light-emitting apparatus, a microcavity structure can be favorably employed. A light-emitting device with a microcavity structure is formed with use of a reflective electrode as the first electrode and a semi-transmissive and semi-reflective electrode as the second electrode. The light-emitting device with a microcavity structure includes at least an EL layer between the reflective electrode and the semi-transmissive and semi-reflective electrode, which includes at least a light-emitting layer serving as a light-emitting region.
Note that the reflective electrode has a visible light reflectivity higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 70% and lower than or equal to 100%, and a resistivity of 1×10−2 Ω·cm or lower. In addition, the semi-transmissive and semi-reflective electrode has a visible light reflectivity higher than or equal to 20% and lower than or equal to 80%, preferably higher than or equal to 40% and lower than or equal to 70%, and a resistivity of 1×10−2 Ω·cm or lower.
Light emitted from the light-emitting layer included in the EL layer is reflected and resonated by the reflective electrode and the semi-transmissive and semi-reflective electrode.
In the light-emitting device, by changing the thickness of the transparent conductive film, the composite material, the carrier-transport material, or the like, the optical path length between the reflective electrode and the semi-transmissive and semi-reflective electrode can be changed. Thus, light with a wavelength that is resonated between the reflective electrode and the semi-transmissive and semi-reflective electrode can be intensified while light with a wavelength that is not resonated therebetween can be attenuated.
Note that light that is reflected back by the reflective electrode (first reflected light) considerably interferes with light that directly enters the semi-transmissive and semi-reflective electrode from the light-emitting layer (first incident light). For this reason, the optical path length between the reflective electrode and the light-emitting layer is preferably adjusted to (2n−1)λ/4 (n is a natural number of 1 or larger and λ is a wavelength of light to be amplified). By adjusting the optical path length, the phases of the first reflected light and the first incident light can be aligned with each other and the light emitted from the light-emitting layer can be further amplified.
Note that in the above structure, the EL layer may include a plurality of light-emitting layers or may include a single light-emitting layer. The tandem light-emitting device described above may be combined with a plurality of EL layers; for example, a light-emitting device may have a structure in which a plurality of EL layers are provided, a charge-generation layer is provided between the EL layers, and each EL layer includes a plurality of light-emitting layers or a single light-emitting layer.
With the microcavity structure, emission intensity with a specific wavelength in the front direction can be increased, whereby power consumption can be reduced. Note that in the case of a light-emitting apparatus which displays images with subpixels of four colors, red, yellow, green, and blue, the light-emitting apparatus can have favorable characteristics because the luminance can be increased owing to yellow light emission and each subpixel can employ a microcavity structure suitable for wavelengths of the corresponding color.
The light-emitting apparatus in this embodiment is fabricated using the light-emitting device described in any one of Embodiments 2 to 6 and thus can have favorable characteristics. Specifically, since the light-emitting device described in any one of Embodiments 2 to 6 has high emission efficiency, the light-emitting apparatus can achieve low power consumption.
An active matrix light-emitting apparatus is described above, whereas a passive matrix light-emitting apparatus is described below.
Since many minute light-emitting devices arranged in a matrix in the light-emitting apparatus described above can each be controlled, the light-emitting apparatus can be suitably used as a display device for displaying images.
This embodiment can be freely combined with any of the other embodiments.
In this embodiment, an example in which the light-emitting device described in any one of Embodiments 2 to 6 is used for a lighting device will be described with reference to
In the lighting device in this embodiment, a first electrode 401 is formed over a substrate 400 which is a support and has a light-transmitting property. The first electrode 401 corresponds to the electrode 551X in any one of Embodiments 2 to 6. When light is extracted from the first electrode 401 side, the first electrode 401 is formed using a material having a light-transmitting property.
A pad 412 for applying voltage to a second electrode 404 is provided over the substrate 400.
An EL layer 403 is formed over the first electrode 401. The EL layer 403 corresponds to the structure in which the layer 104, the unit 103X, and the layer 105 are combined, the structure in which the layer 104, the unit 103X, the layer 106, the unit 103X2, and the layer 105 are combined, or the like in any one of Embodiments 2 to 6. Refer to the corresponding description for these structures.
The second electrode 404 is formed to cover the EL layer 403. The second electrode 404 corresponds to the electrode 552X in any one of Embodiments 2 to 6. The second electrode 404 is formed using a material having high reflectance when light is extracted from the first electrode 401 side. The second electrode 404 is connected to the pad 412, whereby voltage is applied.
As described above, the lighting device described in this embodiment includes a light-emitting device including the first electrode 401, the EL layer 403, and the second electrode 404. Since the light-emitting device is a light-emitting device with high emission efficiency, the lighting device in this embodiment can be a lighting device with low power consumption.
The substrate 400 provided with the light-emitting device having the above structure is fixed to a sealing substrate 407 with sealing materials 405 and 406 and sealing is performed, whereby the lighting device is completed. It is possible to use only either the sealing material 405 or the sealing material 406. The inner sealing material 406 (not illustrated in
When parts of the pad 412 and the first electrode 401 are extended to the outside of the sealing materials 405 and 406, the extended parts can serve as external input terminals. An IC chip 420 mounted with a converter or the like may be provided over the external input terminals, for example.
The lighting device described in this embodiment includes the light-emitting device described in any one of Embodiments 2 to 6 as an EL element, and thus can be a lighting device with low power consumption.
In this embodiment, examples of electronic devices each including the light-emitting device described in any one of Embodiments 2 to 6 will be described. The light-emitting device described in any one of Embodiments 2 to 6 has high emission efficiency and low power consumption. As a result, the electronic devices described in this embodiment can each include a light-emitting portion having low power consumption.
Examples of the electronic device including the above light-emitting device include television devices (also referred to as TV or television receivers), monitors for computers and the like, digital cameras, digital video cameras, digital photo frames, cellular phones (also referred to as mobile phones or mobile phone devices), portable game machines, portable information terminals, audio playback devices, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown below.
The television device can be operated with an operation switch of the housing 7101 or a separate remote controller 7110. With operation keys 7109 of the remote controller 7110, channels or volume can be controlled and images displayed on the display portion 7103 can be controlled. Furthermore, the remote controller 7110 may be provided with a display portion 7107 and data output from the remote controller 7110 may be displayed on the display portion 7107.
Note that the television device is provided with a receiver, a modem, or the like. With use of the receiver, a general television broadcast can be received. Moreover, when the television device is connected to a communication network with or without wires via the modem, one-way (from a sender to a receiver) or two-way (between a sender and a receiver or between receivers) data communication can be performed.
When the display portion 7402 of the portable terminal illustrated in
The display portion 7402 has mainly three screen modes. The first mode is a display mode mainly for displaying images. The second mode is an input mode mainly for inputting information such as text. The third mode is a display-and-input mode in which the two modes, the display mode and the input mode, are combined.
For example, in the case of making a call or creating an e-mail, a text input mode mainly for inputting text is selected for the display portion 7402 so that text displayed on the screen can be input. In this case, it is preferable to display a keyboard or number buttons on almost the entire screen of the display portion 7402.
When a sensing device including a sensor such as a gyroscope sensor or an acceleration sensor for detecting inclination is provided inside the portable terminal, display on the screen of the display portion 7402 can be automatically changed in direction by determining the orientation of the portable terminal (whether the portable terminal is placed horizontally or vertically).
The screen modes are switched by touching the display portion 7402 or operating the operation buttons 7403 of the housing 7401. Alternatively, the screen modes can be switched depending on the kind of images displayed on the display portion 7402. For example, when a signal of an image displayed on the display portion is a signal of moving image data, the screen mode is switched to the display mode. When the signal is a signal of text data, the screen mode is switched to the input mode.
Moreover, in the input mode, when input by touching the display portion 7402 is not performed for a certain period while a signal sensed by an optical sensor in the display portion 7402 is sensed, the screen mode may be controlled so as to be switched from the input mode to the display mode.
The display portion 7402 may also function as an image sensor. For example, an image of a palm print, a fingerprint, or the like is taken when the display portion 7402 is touched with the palm or the finger, whereby personal authentication can be performed. Furthermore, by providing a backlight or a sensing light source which emits near-infrared light in the display portion, an image of a finger vein, a palm vein, or the like can be taken.
A cleaning robot 5100 includes a display 5101 on its top surface, a plurality of cameras 5102 on its side surface, a brush 5103, and operation buttons 5104. Although not illustrated, the bottom surface of the cleaning robot 5100 is provided with a tire, an inlet, and the like. Furthermore, the cleaning robot 5100 includes various sensors such as an infrared sensor, an ultrasonic sensor, an acceleration sensor, a piezoelectric sensor, an optical sensor, and a gyroscope sensor. The cleaning robot 5100 has a wireless communication means.
The cleaning robot 5100 is self-propelled, detects dust 5120, and sucks up the dust through the inlet provided on the bottom surface.
The cleaning robot 5100 can determine whether there is an obstacle such as a wall, furniture, or a step by analyzing images taken by the cameras 5102. When the cleaning robot 5100 detects an object that is likely to be caught in the brush 5103 (e.g., a wire) by image analysis, the rotation of the brush 5103 can be stopped.
The display 5101 can display the remaining capacity of a battery, the amount of collected dust, or the like. The display 5101 may display a path on which the cleaning robot 5100 has run. The display 5101 may be a touch panel, and the operation buttons 5104 may be provided on the display 5101.
The cleaning robot 5100 can communicate with a portable electronic device 5140 such as a smartphone. The portable electronic device 5140 can display images taken by the cameras 5102. Accordingly, an owner of the cleaning robot 5100 can monitor his/her room even when the owner is not at home. The owner can also check the display on the display 5101 by the portable electronic device 5140 such as a smartphone.
The light-emitting apparatus of one embodiment of the present invention can be used for the display 5101.
A robot 2100 illustrated in
The microphone 2102 has a function of detecting a speaking voice of a user, an environmental sound, and the like. The speaker 2104 also has a function of outputting sound. The robot 2100 can communicate with a user using the microphone 2102 and the speaker 2104.
The display 2105 has a function of displaying various kinds of information. The robot 2100 can display information desired by a user on the display 2105. The display 2105 may be provided with a touch panel. Moreover, the display 2105 may be a detachable information terminal, in which case charging and data communication can be performed when the display 2105 is set at the home position of the robot 2100.
The upper camera 2103 and the lower camera 2106 each have a function of taking an image of the surroundings of the robot 2100. The obstacle sensor 2107 can detect an obstacle in the direction where the robot 2100 advances with the moving mechanism 2108. The robot 2100 can move safely by recognizing the surroundings with the upper camera 2103, the lower camera 2106, and the obstacle sensor 2107. The light-emitting apparatus of one embodiment of the present invention can be used for the display 2105.
The light-emitting apparatus of one embodiment of the present invention can be used for the display portion 5001 and the display portion 5002.
The light-emitting device described in any one of Embodiments 2 to 6 can also be used for an automobile windshield or an automobile dashboard.
The display regions 5200 and 5201 are display devices which are provided in the automobile windshield and in which the light-emitting device described in any one of Embodiments 2 to 6 is incorporated. When the light-emitting device described in any one of Embodiments 2 to 6 is fabricated using a first electrode and a second electrode each of which has a light-transmitting property, what is called a see-through display device, through which the opposite side can be seen, can be provided. Such see-through display devices can be provided even in the automobile windshield without hindering the view. In the case where a driving transistor or the like is provided, a transistor having a light-transmitting property, such as an organic transistor including an organic semiconductor material or a transistor including an oxide semiconductor, is preferably used.
A display device incorporating the light-emitting device described in any one of Embodiments 2 to 6 is provided in the display region 5202 in a pillar portion. The display region 5202 can compensate for the view hindered by the pillar by displaying an image taken by an imaging unit provided in the car body. Similarly, the display region 5203 provided in the dashboard portion can compensate for the view hindered by the car body by displaying an image taken by an imaging unit provided on the outside of the automobile. Thus, blind areas can be eliminated to enhance the safety. Images that compensate for the areas which a driver cannot see enable the driver to ensure safety easily and comfortably.
The display region 5203 can provide a variety of kinds of information by displaying navigation data, speed, a tachometer, a mileage, a fuel level, a gearshift state, air-condition setting, and the like. The content or layout of the display can be changed freely by a user as appropriate. Note that such information can also be displayed on the display regions 5200 to 5202. The display regions 5200 to 5203 can also be used as lighting devices.
A display panel 9311 is supported by three housings 9315 joined together by hinges 9313. Note that the display panel 9311 may be a touch panel (an input/output device) including a touch sensor (an input device). By folding the display panel 9311 at the hinges 9313 between two housings 9315, the portable information terminal 9310 can be reversibly changed in shape from the opened state to the folded state. The light-emitting apparatus of one embodiment of the present invention can be used for the display panel 9311.
Note that the structure described in this embodiment can be combined with any of the structures described in Embodiments 2 to 6 as appropriate.
As described above, the application range of the light-emitting apparatus including the light-emitting device described in any one of Embodiments 2 to 6 is wide, and thus the light-emitting apparatus can be applied to electronic devices in a variety of fields. By using the light-emitting device described in any one of Embodiments 2 to 6, an electronic device with low power consumption can be obtained.
Note that this embodiment can be combined with any of the other embodiments in this specification as appropriate.
In this example, physical properties of the organic compounds of embodiments of the present invention and methods for synthesizing the organic compounds will be described with reference to
This synthesis example describes a synthesis example of {2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(5m4dppy-d3)) represented by Structural Formula (101) in Embodiment 1.
5.00 g of 2,4-dichloro-5-methylpyridine, 8.31 g of phenylboronic acid, 180 mL of toluene, 18 mL of water, and 43.30 g of tripotassium phosphate were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then, 0.28 g of tris(dibenzylideneacetone)dipalladium(0) (abbreviation: Pd2(dba)3) and 0.51 g of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (abbreviation: S-Phos) were added thereto. The mixture was reacted at 110° C. for 6.5 hours while being stirred. Synthesis Scheme (la) of Step 1 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of toluene. The toluene was distilled off from the extracted solution and the obtained residue was purified by silica gel column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=10:1) as a mobile phase to give 7.75 g of a pyridine derivative as a yellow oily substance (yield: 100%).
2.79 g of 5-methyl-2,4-diphenylpyridine obtained in Step 1 above, 0.66 g of sodium tert-butoxide (abbreviation: tBuONa), and 16 mL of deuterated dimethyl sulfoxide (abbreviation: DMSO-d6) were put into a recovery flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with argon. This reaction container was heated by irradiation with microwaves (2.45 GHz, 100 W) for 2 hours. Synthesis Scheme (1b) of Step 2 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of ethyl acetate. The ethyl acetate was distilled off from the extracted solution and the obtained residue was purified by flash column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=10:1) as a mobile phase to give 2.23 g of a pyridine derivative as a yellowish white solid (yield: 79%).
10.0 g of di-p-chloro-tetrakis[2-(2-pyridinyl-κN)phenyl-κC]diiridium(III) (abbreviation: [Ir(ppy)2Cl]2) and 465 mL of dichloromethane (CH2Cl2) were put into a light-shielded three-neck flask, and the atmosphere in the flask was replaced with nitrogen. A mixed solution of 7.21 g of silver trifluoromethanesulfonate and 280 mL of methanol was dripped into the flask, followed by stirring at room temperature for 24 hours. After a predetermined time elapsed, the reaction mixture was filtered with use of Celite as a filter aid. The obtained filtrate was concentrated to give 14.0 g of a yellow brown solid.
5.00 g of the yellow brown solid obtained above, 1.68 g of 5-(methyl-d3)-2,4-diphenylpyridine (abbreviation: H5m4dppy-d3), 70 mL of 2-ethoxyethanol, and 70 mL of N,N′-dimethylformamide (abbreviation: DMF) were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture was reacted at 160° C. for 7 hours while being stirred. Synthesis Scheme (1c) of Step 3 is shown below.
After a predetermined time elapsed, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography using toluene as a mobile phase and high performance liquid chromatography using chloroform as a mobile phase. Moreover, from a mixed solution of the obtained solid, toluene, and hexane, 1.61 g of a yellow solid (yield: 15%) was obtained by a recrystallization method. By a train sublimation method, 1.61 g of the yellow solid was sublimated and purified to give 1.42 g of a target substance as a yellow solid (yield: 88%). Note that in the sublimation purification, the solid was heated at 305° C. under a pressure of 2.6 Pa with a flow rate of an argon gas at 10 mL/min.
Measurement results obtained by nuclear magnetic resonance (1H-NMR) spectroscopy revealed that the yellow solid obtained in Step 3 above is Ir(ppy)2(5m4dppy-d3). A 1H-NMR chart is shown in
1H-NMR. δ (CD2Cl2): 6.73-6.99 (m, 11H), 7.40-7.44 (m, 4H), 7.48 (t, 2H), 7.61-7.71 (m, 7H), 7.79 (s, 1H), 7.94 (dd, 2H).
The measurement of the absorption spectrum was conducted at room temperature, for which an ultraviolet-visible light spectrophotometer (V550 manufactured by JASCO Corporation) was used and the dichloromethane solution (0.0107 mmol/L) was put in a quartz cell. Note that the absorption spectrum in
In addition, the measurement of the emission spectrum was performed at room temperature, for which a spectrofluorometer (FP-8600DS manufactured by JASCO Corporation) was used and the deoxidized dichloromethane solution (0.0107 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.).
In addition, the measurement of the luminescence quantum yield was conducted at room temperature, for which an absolute PL quantum yield measurement system (C11347-01 manufactured by Hamamatsu Photonics K.K.) was used and the deoxidized dichloromethane solution (0.0107 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.). Ir(ppy)2(5m4dppy-d3) excited with use of light with a wavelength of 410 nm emitted light in a luminescence quantum yield of 85%. It can be said that the luminescence quantum yield is extremely high compared with the luminescence quantum yield, 73%, of [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)). A light-emitting device containing Ir(ppy)2(5m4dppy-d3) can be expected to have high emission efficiency.
In addition, the measurement of the luminescence quantum yield of Ir(ppy)2(mbfpypy-d3) was conducted at room temperature, for which an absolute PL quantum yield measurement system (C11347-01 manufactured by Hamamatsu Photonics K.K.) was used and the deoxidized dichloromethane solution (0.0103 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.). Ir(ppy)2(mbfpypy-d3) excited with use of light with a wavelength of 460 nm emitted light in a luminescence quantum yield of 73%.
This synthesis example describes a synthesis example of bis{2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(5m4dppy-d3)2(ppy)) represented by Structural Formula (102) in Embodiment 1.
Note that Step 3 of a synthesis method described in Synthesis example 2 is different from that of the synthesis method described in Synthesis example 1. The step different from that in Synthesis example 1 is described in detail below, and the above description is referred to for the other similar steps.
10.0 g of di-p-chloro-tetrakis[2-(2-pyridinyl-κN)phenyl-κC]diiridium(III) (abbreviation: [Ir(ppy)2Cl]2) and 465 mL of dichloromethane were put into a light-shielded three-neck flask, and the atmosphere in the flask was replaced with nitrogen. A mixed solution of 7.21 g of silver trifluoromethanesulfonate (abbreviation: AgOTf) and 280 mL of methanol was dripped into the flask, followed by stirring at room temperature for 24 hours. After a predetermined time elapsed, the reaction mixture was filtered with use of Celite as a filter aid. The obtained filtrate was concentrated to give 14.0 g of a yellow brown solid.
5.00 g of the yellow brown solid obtained above, 1.68 g of 5-(methyl-d3)-2,4-diphenylpyridine (abbreviation: H5m4dppy-d3), 70 mL of 2-ethoxyethanol, and 70 mL of N,N-dimethylformamide (abbreviation: DMF) were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture was reacted at 160° C. for 7 hours while being stirred. Synthesis Scheme (2c) of Step 3 is shown below.
After a predetermined time elapsed, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography using toluene as a mobile phase and high performance liquid chromatography using chloroform as a mobile phase. Moreover, from a mixed solution of the obtained solid, toluene, and hexane, 0.79 g of a yellow solid (yield: 7%) was obtained by a recrystallization method. By a train sublimation method, 0.79 g of the yellow solid was sublimated and purified to give 0.61 g of a target substance as a yellow solid (yield: 77%). Note that in the sublimation purification, the solid was heated at 288° C. under a pressure of 2.6 Pa with a flow rate of an argon gas at 10 mL/min.
Measurement results obtained by nuclear magnetic resonance (1H-NMR) spectroscopy revealed that the yellow solid obtained in Step 3 above is Ir(5m4dppy-d3)2(ppy). A 1H-NMR chart is shown in
1H-NMR. δ (CD2Cl2): 6.72-6.93 (m, 9H), 7.00 (t, 1H), 7.41-7.50 (m, 11H), 7.53 (s, 1H), 7.63-7.74 (m, 5H), 7.80 (d, 2H), 7.95 (d, 1H).
The measurement of the absorption spectrum was conducted at room temperature, for which an ultraviolet-visible light spectrophotometer (V550 manufactured by JASCO Corporation) was used and the dichloromethane solution (0.0103 mmol/L) was put in a quartz cell. Note that the absorption spectrum in
In addition, the measurement of the emission spectrum was performed at room temperature, for which a spectrofluorometer (FP-8600DS manufactured by JASCO Corporation) was used and the deoxidized dichloromethane solution (0.0103 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.).
In addition, the measurement of the luminescence quantum yield was conducted at room temperature, for which an absolute PL quantum yield measurement system (C11347-01 manufactured by Hamamatsu Photonics K.K.) was used and the deoxidized dichloromethane solution (0.0103 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.). Ir(5m4dppy-d3)2(ppy) excited with use of light with a wavelength of 450 nm emitted light in a luminescence quantum yield of 87%. It can be said that the luminescence quantum yield is extremely high compared with the luminescence quantum yield, 73%, of Ir(ppy)2(mbfpypy-d3). Alight-emitting device containing Ir(5m4dppy-d3)2(ppy) can be expected to have high emission efficiency.
This synthesis example describes a synthesis example of {2-[4-(3,5-di-tert-butylphenyl)-5-(methyl-d3)-2-pyridinyl-κN]phenyl-κC}bis{2-[4-(methyl-d3)-5-(2-methylpropyl-1,1-d2)-2-pyridinyl-κN]phenyl-κC}iridium(III) (abbreviation: Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3)) represented by Structural Formula (107) in Embodiment 1.
10.00 g of 2,4-dichloro-5-methylpyridine, 7.75 g of phenylboronic acid, 110 mL of toluene, 55 mL of ethanol, 18 mL of water, and 11.66 g of potassium carbonate were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then, 1.43 g of tetrakis(triphenylphosphine)palladium(0) (abbreviation: Pd(PPh3)4) was added thereto. The mixture was reacted at 90° C. for 7 hours while being stirred. Synthesis Scheme (3a) of Step 1 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of toluene. The toluene was distilled off from the extracted solution and the obtained residue was purified by silica gel column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=10:1) as a mobile phase to give 11.32 g of a pyridine derivative as a white solid (yield: 90%).
11.32 g of 4-chloro-5-methyl-2-phenylpyridine obtained in Step 1 above, 14.32 g of 3,5-di-tert-butylphenylboronic acid, 330 mL of toluene, 33 mL of water, and 35.33 g of tripotassium phosphate were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then, 0.51 g of tris(dibenzylideneacetone)dipalladium(0) (abbreviation: Pd2(dba)3) and 0.91 g of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (abbreviation: S-Phos) were added thereto. The mixture was reacted at 110° C. for 7 hours while being stirred. Synthesis Scheme (3b) of Step 2 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of toluene. The toluene was distilled off from the extracted solution, and hexane was added to the obtained residue and the mixture was suction-filtered and washed with use of the hexane. The obtained solid was dissolved in dichloromethane, and the reaction product was filtered through a filter aid in which Celite, aluminum oxide, and Celite were stacked in this order. The obtained filtrate was concentrated to give 11.47 g of a pyridine derivative as a white solid (yield: 58%).
11.47 g of 4-(3,5-di-tert-butylphenyl)-5-methyl-2-phenylpyridine obtained in Step 2 above, 1.85 g of sodium tert-butoxide, and 45 mL of dimethyl sulfoxide were put into a recovery flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with argon. This reaction container was heated by irradiation with microwaves (2.45 GHz, 100 W) for 1.5 hours. Synthesis Scheme (3c) of Step 3 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of ethyl acetate. The ethyl acetate was distilled off from the extracted solution, the obtained residue was dissolved in dichloromethane, and the reaction product was filtered through a filter aid in which Celite, aluminum oxide, and Celite were stacked in this order. The obtained filtrate was concentrated to give 6.61 g of a pyridine derivative as a white solid (yield: 57%).
6.31 g of 5-bromo-4-methyl-2-phenylpyridine, 5.20 g of isobutylboronic acid, 255 mL of toluene, and 21.71 g of tripotassium phosphate were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture in the flask was degassed by being stirred under reduced pressure, and then, 0.24 g of tris(dibenzylideneacetone)dipalladium(0) (abbreviation: Pd2(dba)3) and 0.42 g of 2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (abbreviation: S-Phos) were added thereto. The mixture was reacted at 120° C. for 6 hours while being stirred. Synthesis Scheme (3d) of Step 4 is shown below.
After a predetermined time elapsed, the solvent was concentrated. The obtained residue was purified by silica gel column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=20:1) as a mobile phase to give 3.89 g of a pyridine derivative as a pale yellow oily substance (yield: 68%).
3.89 g of 4-methyl-5-(2-methylpropyl)-2-phenylpyridine obtained in Step 4 above, 1.02 g of sodium tert-butoxide, and 25 mL of dimethyl sulfoxide were put into a recovery flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with argon. This reaction container was heated by irradiation with microwaves (2.45 GHz, 100 W) for 2 hours. Synthesis Scheme (3e) of Step 5 is shown below.
After a predetermined time elapsed, a target substance was extracted with use of ethyl acetate. The ethyl acetate was distilled off from the extracted solution and the obtained residue was purified by silica gel column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=20:1) as a mobile phase to give 3.23 g of a pyridine derivative as a pale yellow oily substance (yield: 81%).
15 mL of 2-ethoxyethanol, 5 mL of water, 3.23 g of H5iBu4mppy-d5 obtained in Step 5 above, and 2.03 g of iridium chloride hydrate (IrCl3·H2O) were put into a recovery flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with argon. This reaction container was heated by irradiation with microwaves (2.45 GHz, 100 W) for one hour. Synthesis Scheme (3f) of Step 6 is shown below.
After a predetermined time elapsed, the mixture in the flask was suction-filtered and washed with methanol to give 2.38 g of a dinuclear complex (abbreviation: [Ir(5iBu4mppy-d5)2Cl]2) as a yellow solid (yield: 52%).
2.35 g of di-p-chloro-tetrakis{2-[4-(methyl-d3)-5-(2-methylpropyl-1,1-d2)-2-pyridinyl-κN]phenyl-κC}diiridium(III) (abbreviation: [Ir(5iBu4mppy-d5)2Cl]2) obtained in Step 6 above and 84 mL of dichloromethane were put into a light-shielded three-neck flask, and the atmosphere in the flask was replaced with nitrogen. A mixed solution of 1.32 g of silver trifluoromethanesulfonate and 17 mL of methanol was dripped into the flask, followed by stirring at room temperature for 18 hours. After a predetermined time elapsed, the reaction mixture was filtered with use of Celite as a filter aid. The obtained filtrate was concentrated to give 2.99 g of a yellow brown solid.
2.99 g of the yellow brown solid obtained above, 1.25 g of 4-(3,5-di-tert-butylphenyl)-5-(methyl-d3)-2-phenylpyridine (abbreviation: H4mmtBup5mppy-d3), 35 mL of 2-ethoxyethanol, and 35 mL of N,N′-dimethylformamide (DMF) were put into a three-neck flask equipped with a reflux pipe, and the atmosphere in the flask was replaced with nitrogen. The mixture was reacted at 145° C. for 7 hours while being stirred. Synthesis Scheme (3g) of Step 7 is shown below.
After a predetermined time elapsed, the solvent was distilled off and the obtained residue was purified by silica gel column chromatography using a mixed solvent of hexane and ethyl acetate (hexane:ethyl acetate=2:1) as a mobile phase and high performance liquid chromatography using chloroform as a mobile phase. Moreover, from a mixed solution of the obtained solid, toluene, and ethanol, 0.78 g of a yellow solid (yield: 22%) was obtained by a recrystallization method. By a train sublimation method, 0.76 g of the yellow solid was sublimated and purified to give 0.67 g of a target substance as a yellow solid (yield: 88%). Note that in the sublimation purification, the solid was heated at 280° C. under a pressure of 2.7 Pa with a flow rate of an argon gas at 5 mL/min.
Measurement results obtained by nuclear magnetic resonance (1H-NMR) spectroscopy revealed that the yellow solid obtained in Step 7 above is Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3). A 1H-NMR chart is shown in
1H-NMR. δ (CD2Cl2): 0.77-0.84 (m, 12H), 1.35 (s, 18H), 1.65-1.69 (m, 2H), 6.71-6.90 (m, 9H), 7.19-7.21 (m, 3H), 7.27 (s, 1H), 7.49-7.52 (m, 2H), 7.58 (dd, 1H), 7.63 (t, 2H), 7.67 (s, 1H), 7.71 (s, 1H), 7.79 (s, 1H).
The measurement of the absorption spectrum was conducted at room temperature, for which an ultraviolet-visible light spectrophotometer (V550 manufactured by JASCO Corporation) was used and the dichloromethane solution (0.0104 mmol/L) was put in a quartz cell. Note that the absorption spectrum in
In addition, the measurement of the emission spectrum was performed at room temperature, for which a spectrofluorometer (FP-8600DS manufactured by JASCO Corporation) was used and the deoxidized dichloromethane solution (0.0104 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.).
In addition, the measurement of the luminescence quantum yield was conducted at room temperature, for which an absolute PL quantum yield measurement system (C11347-01 manufactured by Hamamatsu Photonics K.K.) was used and the deoxidized dichloromethane solution (0.0104 mmol/L) was sealed in a quartz cell under a nitrogen atmosphere in a glove box (LABstar M13 (1250/780) manufactured by Bright Co., Ltd.). Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3) excited with use of light with a wavelength of 400 nm emitted light in a luminescence quantum yield of 84%. It can be said that the luminescence quantum yield is extremely high compared with the luminescence quantum yield, 73%, of Ir(ppy)2(mbfpypy-d3). A light-emitting device containing Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3) can be expected to have high emission efficiency.
In this example, a light-emitting device 1, a light-emitting device 2, and a light-emitting device 3 of one embodiments of the present invention are described with reference to
The fabricated light-emitting device 1, which is described in this example, has a structure similar to that of the light-emitting device 550X (see
The light-emitting device 1 includes the electrode 551X, the electrode 552X, and the unit 103X. The unit 103X is located between the electrode 551X and the electrode 552X and contains {2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}bis[2-(2-pyridinyl-N)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(5m4dppy-d3)), which is the organic compound of one embodiment of the present invention.
Table 1 shows the structure of the light-emitting device 1. Structural formulae of materials used in the light-emitting devices described in this example are shown below. Note that in the tables in this example, subscript and superscript characters are written in ordinary size for convenience. For example, a subscript character in an abbreviation or a superscript character in a unit are written in ordinary size in the tables. The corresponding description in the specification gives an accurate reading of such notations in the tables.
The light-emitting device 1 described in this example was fabricated using a method including the following steps.
In the first step, the electrode 551X was formed specifically by a sputtering method using indium oxide-tin oxide containing silicon or silicon oxide (abbreviation: ITSO) as a target.
The electrode 551X includes ITSO and has a thickness of 70 nm and an area of 4 mm2 (2 mm×2 mm).
Next, a base over which the electrode 551X was formed was washed with water, baked at 200° C. for one hour, and then subjected to UV ozone treatment for 370 seconds. Then, the base was transferred into a vacuum evaporation apparatus where the pressure was reduced to approximately 10−4 Pa, and vacuum baking was performed at 170° C. for 30 minutes in a heating chamber of the vacuum evaporation apparatus. Then, the base was cooled down for approximately 30 minutes.
In the second step, the layer 104 was formed over the electrode 551X. Specifically, materials of the layer 104 were co-deposited by a resistance-heating method.
The layer 104 contains N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) and an electron acceptor material (abbreviation: OCHD-003) at PCBBiF: OCHD-003=1:0.03 in a weight ratio and has a thickness of 10 nm. Note that OCHD-003 contains fluorine, and has a molecular weight of 672.
In the third step, a layer 112_1 was formed over the layer 104. Specifically, a material of the layer 112_1 was deposited by a resistance-heating method.
The layer 112_1 contains PCBBiF and has a thickness of 40 nm.
In the fourth step, a layer 112_2 was formed over the layer 1121. Specifically, a material of the layer 112_2 was deposited by a resistance-heating method.
The layer 112_2 contains 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBBi1BP) and has a thickness of 10 nm.
In the fifth step, the layer 111X was formed over the layer 112_2. Specifically, materials of the layer 111X were co-deposited by a resistance-heating method.
The layer 111X contains 8-(1,1′-biphenyl-4-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-[1]benzofuro[3,2-d]pyrimidine (abbreviation: 8BP-4mDBtPBfpm), 9,9′-diphenyl-9H,9′H-3,3′-bicarbazole (abbreviation: PCCP), and {2-[5-(methyl-d3)-4-phenyl-2-pyridinyl-κN]phenyl-κC}bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(5m4dppy-d3)) at 8BP-4mDBtPBfpm: PCCP: Ir(ppy)2(5m4dppy-d3)=0.5:0.5:0.1 in a weight ratio and has a thickness of 40 nm.
In the sixth step, a layer 113_1 was formed over the layer 111X. Specifically, a material of the layer 113_1 was deposited by a resistance-heating method.
The layer 113_1 contains 8BP-4mDBtPBfpm and has a thickness of 10 nm.
In the seventh step, a layer 113_2 was formed over the layer 113_1. Specifically, a material of the layer 113_2 was deposited by a resistance-heating method.
The layer 113_2 contains 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen) and has a thickness of 20 nm.
In the eighth step, the layer 105 was formed over the layer 113_2. Specifically, a material of the layer 105 was deposited by a resistance-heating method.
The layer 105 includes lithium fluoride (abbreviation: LiF) and has a thickness of 1 nm.
In the ninth step, the electrode 552X was formed over the layer 105. Specifically, a material of the electrode 552X was deposited by a resistance-heating method.
The electrode 552X contains aluminum (Al) and has a thickness of 200 nm.
When supplied with electric power, the light-emitting device 1 emitted light EL1 (see
Table 2 shows main initial characteristics of the fabricated light-emitting device emitting light at a luminance of approximately 1000 cd/m2. Table 3 shows a time LT90 taken for the luminance to drop to 90% of its initial value at a constant current density of 50 mA/cm2, which were obtained under the condition where the light-emitting devices each emitted light. Table 2 and Table 3 also show the characteristics of another light-emitting device having a structure described later.
The light-emitting device 1 was found to exhibit favorable properties. For example, the light-emitting device 1 had higher reliability than a comparative device 1. The light-emitting device 1 was able to emit light at a luminance of approximately 1000 cd/m2 at a lower voltage than the comparative device 1. The light-emitting device 1 had higher external quantum efficiency than the comparative device 1. A reduction in driving voltage and an increase in external quantum efficiency increase efficiency of energy for converting electric power into light. Light emitted from the light-emitting device 1 includes light with a short wavelength as compared with light emitted from the comparative device 1. By using Ir(ppy)2(5m4dppy-d3) and a green fluorescent material for the layer 111X, for example, efficient energy transfer to the fluorescent material can be expected. Furthermore, light emission with high efficiency can be expected.
The fabricated light-emitting device 2, which is described in this example, has a structure similar to that of the light-emitting device 550X (see
The light-emitting device 2 described in this example was fabricated using a method including the following steps.
In the fifth step, the layer 111X was formed over the layer 112_2. Specifically, materials of the layer 111X were co-deposited by a resistance-heating method.
Note that the layer 111X contains 8BP-4mDBtPBfpm, PCCP, and Ir(5m4dppy-d3)2(ppy) at 8BP-4mDBtPBfpm: PCCP: Ir(5m4dppy-d3)2(ppy)=0.5:0.5:0.1 (weight ratio), and has a thickness of 40 nm.
When supplied with electric power, the light-emitting device 2 emitted the light EL1 (see
Table 2 shows main initial characteristics of the fabricated light-emitting device emitting light at a luminance of approximately 1000 cd/m2. Table 3 shows a time LT90 taken for the luminance to drop to 90% of its initial value at a constant current density of 50 mA/cm2, which were obtained under the condition where the light-emitting devices each emitted light.
The light-emitting device 2 was found to exhibit favorable properties. For example, the light-emitting device 2 had higher reliability than the comparative device 1. The light-emitting device 2 also had higher reliability than the light-emitting device 1. Note that Ir(5m4dppy-d3)2(ppy) has a larger number of ligands each having a deuterated alkyl group than Ir(ppy)2(5m4dppy-d3). In other words, Ir(5m4dppy-d3)2(ppy) has a smaller number of ligands each having no deuterated alkyl group than Ir(ppy)2(5m4dppy-d3). The light-emitting device 2 was able to emit light at a luminance of approximately 1000 cd/m2 at a lower voltage than the comparative device 1. The light-emitting device 2 had higher external quantum efficiency than the comparative device 1. A reduction in driving voltage and an increase in external quantum efficiency increase efficiency of energy for converting electric power into light. Light emitted from the light-emitting device 2 includes light with a short wavelength as compared with light emitted from the comparative device 1. By using Ir(5m4dppy-d3)2(ppy) and a green fluorescent material for the layer 111X, for example, efficient energy transfer to the fluorescent material can be expected. Furthermore, light emission with high efficiency can be expected.
The fabricated light-emitting device 3, which is described in this example, has a structure similar to that of the light-emitting device 550X (see
The light-emitting device 3 described in this example was fabricated using a method including the following steps.
In the fifth step, the layer 111X was formed over the layer 112_2. Specifically, materials of the layer 111X were co-deposited by a resistance-heating method.
Note that the layer 111X contains 8BP-4mDBtPBfpm, PCCP, and Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3) at 8BP-4mDBtPBfpm: PCCP: Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3)=0.5:0.5:0.1 (weight ratio), and has a thickness of 40 nm.
When supplied with electric power, the light-emitting device 3 emitted the light EL1 (see
Table 2 shows main initial characteristics of the fabricated light-emitting device emitting light at a luminance of approximately 1000 cd/m2. Table 3 shows a time LT90 taken for the luminance to drop to 90% of its initial value at a constant current density of 50 mA/cm2, which were obtained under the condition where the light-emitting devices each emitted light.
The light-emitting device 3 was found to exhibit favorable properties. For example, the light-emitting device 3 had higher reliability than the comparative device 1. Light emitted from the light-emitting device 3 includes light with a short wavelength as compared with light emitted from the comparative device 1. By using Ir(5iBu4mppy-d5)2(4mmtBup5mppy-d3) and a green fluorescent material for the layer 111X, for example, efficient energy transfer to the fluorescent material can be expected. Furthermore, light emission with high efficiency can be expected.
The fabricated comparative device 1, which is described in this reference example, has a structure similar to that of the light-emitting device 550X (see
The comparative device 1 is different from the light-emitting device 1 in using [2-d3-methyl-(2-pyridinyl-κN)benzofuro[2,3-b]pyridine-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III) (abbreviation: Ir(ppy)2(mbfpypy-d3)) instead of Ir(ppy)2(5m4dppy-d3). A structural formula of Ir(ppy)2(mbfpypy-d3) is shown below.
The comparative device 1 described in this reference example was fabricated by a method including the following steps. The method for fabricating the comparative device 1 is different from the method for fabricating the light-emitting device 1 in using Ir(ppy)2(mbfpypy-d3) instead of Ir(ppy)2(5m4dppy-d3) in the step of forming the layer 111X. Different portions will be described in detail below, and the above description is referred to for portions where a method similar to the above was employed.
In the fifth step, the layer 111X was formed over the layer 112_2. Specifically, materials of the layer 111X were co-deposited by a resistance-heating method.
Note that the layer 111X contains 8BP-4mDBtPBfpm, PCCP, and Ir(ppy)2(mbfpypy-d3) at 8BP-4mDBtPBfpm: PCCP: Ir(ppy)2(mbfpypy-d3)=0.5:0.5:0.1 (weight ratio), and has a thickness of 40 nm.
In this example, calculation results of molecular orbitals of an organic compound will be described with reference to
The molecular orbitals of the organic compound having the following structure are calculated.
In the organic compound, the meta position of a pyridine ring coordinated to iridium has a high spin density in a triplet excited state (see
Note that Gaussian 09 program is used for molecular orbital calculations. As a functional, B3PW91 is used, as a basis function of Ir, LANL2DZ is used, and as a basis function of the other atoms, 6-311G (d,p) is used. Structural optimization is performed on the singlet ground state (S0) and the triplet excited state (T1).
This application is based on Japanese Patent Application Serial No. 2022-019671 filed with Japan Patent Office on Feb. 10, 2022, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-019671 | Feb 2022 | JP | national |
