Light emitting device

Abstract

To enhance emission efficiency of a fluorescent light-emitting element by effectively utilizing triplet excitons generated in a light-emitting layer.SOLUTION: A light-emitting layer of a light-emitting element includes at least a host material and a guest material, triplet excitons generated from the host material in the light-emitting layer are converted into singlet excitons by triplet-triplet annihilation (TTA), and the guest material (fluorescent dopant) is made to emit light by energy transfer from the singlet excitons, whereby the emission efficiency of the light-emitting element is improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention is a light-emitting element, a light-emitting device including the light-emitting element, an electronic device, and a lighting device. Regarding. [Background technology]

[0002] A light-emitting element having a structure in which a light-emitting layer containing an organic compound as a light-emitting substance is provided between a pair of electrodes. With its thin, lightweight, fast response, and low DC voltage drive characteristics, it is expected to become the next generation flat panel display. This light-emitting element is attracting attention as a display element. It also boasts excellent reliability and image quality, as well as a wide viewing angle.

[0003] The light-emitting mechanism of a light-emitting element is to apply a voltage between a pair of electrodes to inject electrons and positive charges. It is said that the recombination of electrons and holes forms excitons, which then emit light. Each has a spin of 1 / 2, and when an electron and a hole recombine to form an exciton, the spin According to the spin statistics, the proportion of spin-0 singlet excitons is 25% and that of spin-1 triplet excitons is 75%. It is said that fluorescence is generated when singlet excitons are emitted. The theoretical limit of the internal quantum efficiency of the ion beam is 25%. The triplet exciton of spin 1 does not usually contribute to the emission, so it remains in the ground state without emitting light. In some cases, multiple triplet excitons can relax into triplet-triplet Triplet-triplet annihilation (TTA) occurs. It is also known that TTA occurs when two triplet excitons collide to release energy. The exchange and transfer of the electron and spin angular momentum occurs. It is said that doublet excitons are generated.

[0004] As a method for effectively utilizing triplet excitons generated in the light emission mechanism, A compound capable of converting energy into light (hereinafter referred to as a phosphorescent compound) is added to the above luminescent material. By using this, phosphorescence can be obtained by transitions between energies with different multiplicities. Taking advantage of this, the development of phosphorescent light-emitting devices that exhibit internal quantum efficiencies exceeding the theoretical value is being pursued. This has been proposed along with development (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2005 / 105746 Pamphlet Summary of the Invention [Problem to be solved by the invention]

[0006] In one embodiment of the present invention, triplet excitons generated in the light-emitting layer are effectively utilized. This increases the luminous efficiency of the fluorescent light emitting element. [Means for solving the problem]

[0007] In one aspect of the present invention, a light-emitting layer of a light-emitting element contains at least a host material and a guest material. This structure allows efficient generation of triplet-triplet annihilation (TTA) in the light-emitting layer. This converts triplet excitons, which do not contribute to light emission, into singlet excitons, and the energy from the singlet excitons is then released. The guest material (fluorescent dopant) emits light due to energy transfer, which increases the luminous efficiency of the light-emitting element. It is characterized by improving the luminous efficiency by TTA (triplet-triplet annihilation). The improvement in spin speed is estimated to be about 15% based on spin statistics, and TTA does not occur. Theoretically, an internal quantum efficiency of 40% can be achieved by combining this with an internal quantum efficiency of 25% when no photocatalyst is used. It is possible.

[0008] In the light-emitting layer, the TTA caused by triplet excitons generated from the host material is efficiently In order to generate triplet excitons efficiently, it is important to increase the collision probability between triplet excitons present in the light-emitting layer. It is essential.

[0009] Therefore, the T1 level (lowest triplet exciton energy level) of the host material in the emitting layer is , which is preferably lower than the T1 level of the guest material. Usually, the abundance ratio in the light-emitting layer is The host material is overwhelmingly higher. The T1 level of the host material is lower than the T1 level of the guest material. By forming the light emitting element so that the triplet excitons generated in the light emitting layer are Triplet excitations are trapped and localized in rare guest materials. This can prevent a decrease in the probability of collisions between children and increase the probability of TTA occurring.

[0010] Furthermore, to prevent triplet excitons generated in the light-emitting layer from escaping to the outside of the light-emitting layer, The material used for the hole transport layer (HTL) formed on the anode side of the light-emitting element in contact with the light-emitting layer is It is preferable to use a material having a T1 higher than that of the host material. This makes it difficult for triplet excitons generated in the light-emitting layer to move from the light-emitting layer to the HTL. can be done.

[0011] When TTA occurs, the fluorescence lifetime of the fluorescent material is longer than when TTA does not occur. Such delayed fluorescence is generated by the light-emitting element. When steady carrier injection is interrupted at a certain point, the decay of the light emission after the interruption is measured. It can be confirmed by observing the delayed fluorescence. Even after the current is cut off, the luminous intensity is 0.01 or more compared to the luminous intensity when the current is steadily injected. The intensity ratio is 1×10 -6 The light emission should last for more than 5 seconds. The delayed fluorescence spectrum and the emission spectrum during steady carrier injection are identical in shape.

[0012] Therefore, one embodiment of the present invention has an EL layer between a pair of electrodes, and the EL layer has a light-emitting layer and a hole transport layer. The light-emitting layer has at least a guest material and a host material having a T1 level lower than that of the guest material. the hole transport layer includes a hole transporting material, and the hole transporting material is more This light-emitting device is characterized by having a higher T1 level than that of the other light-emitting devices.

[0013] Another embodiment of the present invention is a light-emitting layer including an EL layer between a pair of electrodes. The light-emitting layer has at least a transport layer, and the light-emitting layer is made of a guest material and a hole transport layer having a T1 level lower than that of the guest material. the hole transport layer includes a hole transporting material, and the hole transporting material includes a guest material; and a light-emitting element characterized in that the T1 level is higher than that of the host material.

[0014] Another embodiment of the present invention is a light-emitting layer including an EL layer between a pair of electrodes. The light-emitting layer has at least a transport layer, and the light-emitting layer is made of a guest material and a hole transport layer having a T1 level lower than that of the guest material. The hole transport layer includes a hole transporting material having a higher T1 level than the host material. The shape of the delayed fluorescence spectrum of TTA is the same as the fluorescence spectrum of the guest material. and the delay component has a constant current injection intensity of 0.0. 1 x 10 -6 sec or more. .

[0015] Another embodiment of the present invention is a light-emitting layer including an EL layer between a pair of electrodes. The light-emitting layer has at least a transport layer, and the light-emitting layer is made of a guest material and a hole transport layer having a T1 level lower than that of the guest material. The hole transport layer includes a guest material and a host material, and the hole transport layer has a hole transport layer having a T1 level higher than that of the guest material and the host material. The shape of the delayed fluorescence spectrum of the TTA is similar to the fluorescence spectrum of the guest material. The shape of the tor is the same as that of the tor, and the intensity of the delay component is constant. The luminescence of 0.01 or more in the state of 1 × 10 -6 sec or more can be obtained. It is a light emitting element.

[0016] Note that one embodiment of the present invention is not only a light-emitting device having a light-emitting element, but also an electric device having a light-emitting device. The term "light-emitting device" as used herein also includes a child device and a lighting device. This refers to an image display device or a light source (including lighting equipment). For example, FPC (Flexible printed circuit), TCP (Tape Carrier Package) mounted module, TCP A module with a printed wiring board or a light emitting element with COG (Chip On Glass) All modules with ICs (integrated circuits) directly mounted using the Glass method are light-emitting devices. This shall be included in the [Effects of the Invention]

[0017] According to one embodiment of the present invention, a highly efficient fluorescent light-emitting element can be provided. A low-power light-emitting device, electronic device, or lighting device can be provided. [Brief explanation of the drawings]

[0018] [Figure 1] A diagram explaining the mechanism by which TTA is used for luminescence. [Figure 2] 1A and 1B illustrate a structure of a light-emitting element according to one embodiment of the present invention. [Figure 3] 1A to 1C illustrate a structure of a light-emitting element. [Figure 4] 1A and 1B are diagrams illustrating light-emitting elements. [Figure 5] 1A and 1B illustrate a light-emitting device. [Figure 6] 1A and 1B are diagrams illustrating electronic devices. [Figure 7] 1A and 1B are diagrams illustrating electronic devices. [Figure 8] 1A and 1B are diagrams illustrating a lighting device. [Figure 9] 1A to 1C illustrate a structure of a light-emitting element. [Figure 10] FIG. 10 is a graph showing the fluorescence lifetimes of the light-emitting element 1 and the comparative light-emitting element 2. [Figure 11] FIG. 2 shows a fluorescence spectrum of the light-emitting element 1. [Figure 12] FIG. 10 is a graph showing the fluorescence lifetimes of the light-emitting element 1 and the comparative light-emitting element 2. [Figure 13] FIG. 10 is a graph showing the fluorescence lifetimes of the light-emitting element 3 and the comparative light-emitting element 4. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the above description, and the embodiments and details thereof may be modified without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the embodiments described below. It should not be construed as being limited to the content.

[0020] (Embodiment 1) In this embodiment, the mechanism of a light-emitting element, which is one aspect of the present invention, will be described.

[0021] A light-emitting element, which is one aspect of the present invention, has at least a light-emitting layer between a pair of electrodes (an anode and a cathode), and further has a hole transport layer in contact with the light-emitting layer between the light-emitting layer and the anode, and is characterized in that . The light-emitting layer contains a host material and a guest material.

[0022] In the light-emitting element, when holes are injected from the anode and electrons are injected from the cathode, singlet excitons and triplet excitons are generated at a ratio of 1:3 in the light-emitting layer portion. At this time, the light-emitting element, which is one aspect of the present invention, has a T1 level (T1(h)) of the host material 102 contained in the light-emitting layer 101 as shown in FIG. 1, which is designed to be lower in energy than the T1 level (T1(g)) of the guest material 103. Therefore, triplet excitons are usually not trapped by the guest material 103, which is present only in a trace amount (about 5 wt%) with respect to the host material 102, but are concentrated on the host material 102 which is present in a large amount in the light-emitting layer. From this, in order to increase the generation probability of T TA (triplet-triplet annihilation) described later, it is important to have a relationship of T1(h) < T1(g) .

[0023] In addition, singlet excitons emit fluorescence, but triplet excitons usually disappear without contributing to light emission. However, as shown in FIG. 1, when two triplet excitons collide and undergo energy and spin angular momentum exchange and transfer, so-called triplet-triplet annihilation ( TTA) occurs, singlet excitons can be newly generated and contribute to light emission.​​​

[0024] When the newly generated singlet excitons satisfy the condition of T1(h) < T1(g) as described above, they are located at the S1 level (S1(h)) of the host material. However, since the S1 level of the host material is designed to be higher than the S1 level of the guest, the energy of the singlet excitons moves from the S1 of the host to the S1 of the guest, contrary to the energy transfer of triplet excitons. As a result, fluorescence from the guest material can be obtained. たすときはホスト材料のS1準位(S1(h))に位置するが、ホスト材料のS1準位は ゲストのS1準位より高く設計されているため、三重項励起子のエネルギー移動とは反対 に、一重項励起子のエネルギーはホストのS1からゲストのS1へ移動する。これによっ て、ゲスト材料からの蛍光を得ることができる。

[0025] Therefore, in the case of the configuration shown in FIG. 1, fluorescence from the guest material due to singlet excitons and fluorescence from the guest material based on TTA due to triplet excitons can be obtained, so that a very high-efficiency fluorescence emitting device can be formed. 重項励起子によるTTAに基づくゲスト材料からの蛍光が得られるため、非常に高効率な 蛍光発光素子を形成することができる。

[0026] Furthermore, the light-emitting device according to one aspect of the present invention has a configuration as shown in FIG. 2 in order to prevent the triplet excitons generated in the light-emitting layer from escaping outside the light-emitting layer. 層の外へ逃さないようにするため、図2に示すような構成を有する。

[0027] That is, as shown in FIG. 2, in the hole transport layer 201 and the light-emitting layer 202 formed between the first electrode (anode) 211 and the second electrode (cathode) 212, the T1 level of the hole transporting material (HT) 203 contained in the hole transport layer 201 is made higher than the T1 level of the host material (h) 204 contained in the light-emitting layer 202. By doing so, the transfer of triplet excitons from T1(h) to T1(HT) can be suppressed, and the triplet excitons generated in the light-emitting layer 202 can be retained in the light-emitting layer 202. Furthermore, making the T1 level of the hole transporting material (HT) 203 higher than the T1 level of the guest material (g) 205 contained in the light-emitting layer 202 is との間に形成される正孔輸送層201と発光層202において、正孔輸送層201に含ま れる正孔輸送性材料(HT)203のT1準位を、発光層202に含まれるホスト材料( h)204のT1準位よりも高くする。このようにすることで、T1(h)からT1(H T)への三重項励起子の移動を抑制し、発光層202において生じた三重項励起子を発光 [[ID=XXX]] 位を、発光層202に含まれるゲスト材料(g)205のT1準位よりも高くすることは ​, the transfer of triplet excitons from T1(g) to T1(HT) is also less likely to occur, It is preferable that the hole transport layer 201 having such a high T1 level has a recombination region where light is emitted. This is particularly preferred when it is on the anode side in layer 202 .

[0028] For the same reason, the layer (electron transport layer) formed on the cathode side of the light-emitting element in contact with the light-emitting layer 202 The materials used in the light-emitting layer 202 (e.g., the ETL) are more favorable than the host and guest materials in the light-emitting layer 202. When a material with a high level is used, triplet excitons generated in the light-emitting layer 202 are confined in the light-emitting layer. It is preferable that the electron transport layer having such a high T1 level is It is particularly preferred if the bonding region is on the cathode side in the light-emitting layer.

[0029] In FIG. 2, a first electrode (anode) 211 is provided between the first electrode (anode) 211 and the hole transport layer 201. A hole injection layer 213 having a function of enhancing the injection of holes from the electrode 211 may be provided. In addition, a second electrode (cathode) 212 is provided between the second electrode (cathode) 212 and the light-emitting layer 202. The electron injection layer 215 enhances the electron injection property from the silicon dioxide, and the electron transport layer 214 has high electron transport property. It may be provided.

[0030] As described above, by using a light-emitting element which is one embodiment of the present invention, a light-emitting device with high emission efficiency It is possible to realize an electronic device or a lighting device. A child device or a lighting device can be realized.

[0031] The structure described in this embodiment mode can be used in appropriate combination with structures described in other embodiments. This can be done.

[0032] (Embodiment 2) In this embodiment, a light-emitting element which is one embodiment of the present invention will be described with reference to FIGS.

[0033] The light-emitting element shown in this embodiment has a pair of electrodes (a first electrode (anode) and a second electrode (cathode)) as shown in FIG. A light-emitting layer 306 and holes (or holes) are disposed between a first electrode (cathode) 301 and a second electrode (cathode) 302. The EL layer 303 including the transport layer 305 is sandwiched between the EL layer 303 and the light-emitting layer 306. The hole transport layer 305 contains a host material 311 and a guest material 312. 3B, the EL layer 303 includes a light-emitting layer 306 and a In addition to the hole transport layer 305, a hole injection layer 304, an electron transport layer 307, an electron The implanted layer 308 is formed as well.

[0034] By applying a voltage to such a light emitting element, light is injected from the first electrode 301 side. The holes injected from the second electrode 302 and the electrons injected from the second electrode 302 are recombined in the light-emitting layer 306. Then, the triplet excitons are converted to singlet excitons by TTA. The guest material 312 contained in the light-emitting layer 306 emits light via energy transfer from the guest material and the exciton. It glows.

[0035] The hole injection layer 304 in the EL layer 303 is made of a material having a high hole transporting property and an acceptor. The layer contains an acceptor material, and electrons are transferred from a material with high hole transporting properties to the acceptor material. Therefore, holes are generated from the hole injection layer 304. Holes are injected into the light-emitting layer 306 through the transport layer 305 .

[0036] Note that a layer containing a substance with a high hole transporting property and an acceptor substance has an acceptor property. The electrons are extracted from the highly hole-transporting material by the highly porous material. It can be seen as a layer that generates electrons. In other words, by providing it on the cathode side, Electrons can be injected into the light-emitting layer 306 through the electron transport layer 307. A so-called charge generating layer having a function of generating charges such as electrons and the like is used in a light emitting device. The functional layer can be appropriately provided in the light-emitting element of one embodiment of the present invention. .

[0037] A specific example of manufacturing the light-emitting element described in this embodiment mode will be described below.

[0038] The first electrode (anode) 301 and the second electrode (cathode) 302 are made of a metal, an alloy, an electrically conductive material, or the like. Conductive compounds and mixtures thereof can be used. Indium tin oxide, silicon or silicon oxide Indium oxide-tin oxide, indium oxide-zinc oxide (Indium Zinc O xide), indium oxide containing tungsten oxide and zinc oxide, gold (Au), white Gold (Pt), Nickel (Ni), Tungsten (W), Chromium (Cr), Molybdenum (M o), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti ), as well as elements belonging to Groups 1 and 2 of the Periodic Table, such as lithium (Li) and cerium (Ce). Alkali metals such as Cs, calcium (Ca), and strontium (Sr) Alkaline earth metals such as magnesium (Mg), and alloys containing these (MgAg, A Rare earth metals such as Zn(Li), europium (Eu), ytterbium (Yb) and An alloy containing the compound, graphene, etc. can be used. The first and second electrodes (cathode) 302 are formed by, for example, sputtering or vapor deposition (vacuum deposition). It can be formed by the following method.

[0039] The positive hole injection layer 304 and the positive hole transport layer 305 (including the charge generation layer) are As a material with high hole transport properties, for example, 3-[4-(1-naphthyl)-phenyl]-9- Phenyl-9H-carbazole (abbreviation: PCPN), 3-[4-(9-phenanthryl) -phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn), 4-phenyl -4'-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation: PCBA1BP), 4,4'-di(1-naphthyl)-4''-(9-phenyl-9H-carboxylate), PCBNBB, 4-phenyldiphenyl Phenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation: PCA1BP) ), 3,3'-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP), N-[ 4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline Phosphorus (abbreviation: YGA1BP), 1,3,5-tri(dibenzothiophen-4-yl)-benzyl Benzene (abbreviation: DBT3P-II), 4,4',4''-(benzene-1,3,5-trimethylsilyl) yl)tri(dibenzofuran) (abbreviation: DBF3P-II), 4-phenyl-4'-(9 -phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP), 4-[ 3-(triphenylen-2-yl)phenyl]dibenzothiophene (abbreviation: mDBTPT p-II), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB or α-NPD) and N,N'-bis(3-methylphenyl)-N,N' -Diphenyl-[1,1'-biphenyl]-4,4'-diamine (abbreviation: TPD), 4, 4',4''-Tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA ), 4,4',4''-tris(N,N-diphenylamino)triphenylamine (abbreviation :TDATA), 4,4',4''-tris[N-(3-methylphenyl)-N-phenyl 4,4'-bis[N-(spiro)amino]triphenylamine (abbreviation: MTDATA) -9,9'-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation: BS PB), 3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]- 9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenyl [N-(4-amino-1-phenyl-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation :PCzPCA2), 3-[N-(1-naphthyl)-N-(9-phenylcarbazole- 3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1), etc. Other examples include 4,4'-di(N-carbazolyl)biphenyl (abbreviation: CBP), 1,3, Carbohydrates such as 5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB) dibenzothiophene compounds, dibenzofuran compounds, furan compounds, A fluorene compound, a triphenylene compound, a phenanthrene compound, etc. can be used. The substances mentioned here are mainly 1×10 -6 cm 2 / Vs or more However, other materials may be used as long as they have a higher hole transporting property than electron transporting property. Note that among these materials, a hole-transport layer of a light-emitting element according to one embodiment of the present invention may contain a The above-mentioned compound is added between the host material and the guest material in the hole transport layer 305 and the light emitting layer 306. The combination should be selected to satisfy the relationship for the energy of the T1 level. preferable.

[0040] Furthermore, poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriflate) Phenylamine) (abbreviation: PVTPA), poly[N-(4-{N'-[4-(4-diphenyl (N'-phenylamino)phenyl]phenyl-N'-phenylamino}phenyl)methacrylamide (abbreviation: PTPDMA) Poly[N,N'-bis(4-butylphenyl)-N,N'-bis (phenyl)benzidine (abbreviated as Poly-TPD) It is also possible.

[0041] In addition, the acceptor material used in the hole injection layer 304 (including the charge generation layer described above) Specifically, transition metal oxides and oxides of metals belonging to groups 4 to 8 of the periodic table are used. Specifically, molybdenum oxide is particularly preferred.

[0042] The light-emitting layer 306 contains a host material and a guest material as described in Embodiment 1. The T1 level of the material is lower than the T1 level of the guest material.

[0043] A preferred example of the host material is 3-[4-(1-naphthyl)-phenyl]-9-phenyl. Phenyl-9H-carbazole (abbreviated as PCPN) and 9-phenyl-3-[4-(10- Phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA), 9 -[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation Name: CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-di Benzo[c,g]carbazole (abbreviation: cgDBCzPA), 6-[3-(9,10-di (phenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan (abbreviation Name: 2mBnfPPA), 9-phenyl-10-{4-(9-phenyl-9H-fluorene {phenyl-9-yl}biphenyl-4'-yl}anthracene (abbreviation: FLPPA) and other anthracenes Anthracene compounds have high S1 levels and low T1 levels. Therefore, it is preferable.

[0044] A preferred example of the guest material is 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-( 9-phenyl-9H-fluoren-9-yl)phenyl]-N,N'-diphenylpyrene -1,6-diamine (abbreviation: 1,6FLPAPrn), N,N'-bis(dibenzofuran) -2-yl)-N,N'-diphenylpyrene-1,6-diamine (abbreviation: 1,6FrAP rn), N,N'-bis(dibenzothiophen-2-yl)-N,N'-diphenylpyrene Pyrene compounds such as 1,6-thanediamine (abbreviated as 1,6ThAPrn), anthracene derivatives compounds, triphenylene compounds, fluorene compounds, carbazole compounds, dibenzothiophene compounds Dibenzofuran compounds, dibenzoquinoxaline compounds, quinoxaline compounds pyridine compounds, pyrimidine compounds, phenanthrene compounds, naphthalene compounds, etc. In particular, pyrene compounds are preferred because they have a high luminescence quantum yield. The light-emitting layer of the light-emitting device includes the above-mentioned host material and guest material. The combination must be selected to satisfy the energy relationship.

[0045] The electron transport layer 307 is a layer containing a substance with a high electron transport property. Alq3, tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: A lmq3), bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation Name: BeBq2), BAlq, Zn(BOX)2, bis[2-(2-hydroxyphenyl )benzothiazolato]zinc(II) (abbreviation: Zn(BTZ)2) and other metal complexes. In addition, 2-(4-biphenylyl)-5-(4-tert-butylphenyl) )-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(p-ter t-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (abbreviation: O XD-7), 3-(4'-tert-butylphenyl)-4-phenyl-5-(4''- Biphenyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butyl 4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4- Triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen), Bathocuproine (abbreviation: BCP), 4,4'-bis(5-methylbenzoxazole- Heteroaromatic compounds such as 2-yl)stilbene (abbreviation: BzOs) can also be used. In addition, poly(2,5-pyridinediyl) (abbreviation: PPy), poly[(9,9-dihexyl) PF -Py), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2 '-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) The substances mentioned here are mainly 1×10 -6 cm 2 / Vs or more electron transfer In addition, if a substance has a higher electron transporting property than a hole transporting property, The above substance may be used for the electron-transport layer 307. Of these materials, the electron transport layer 307 and the phosphorus in the light-emitting layer 306 are used. The above-mentioned relationship between the host material and the guest material in terms of the energy of the T1 level is satisfied. It is preferable to select a combination that satisfies the above requirements.

[0046] The electron transport layer 307 may be not only a single layer, but also a layer of two or more layers made of the above-mentioned materials. It may also be layered.

[0047] The electron injection layer 308 is a layer containing a substance with high electron injection properties. Lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2) Alkali metals, alkaline earth metals, magnesium, lithium oxide (LiOx), etc. Magnesium (Mg), or compounds thereof, can be used. Erbium fluoride (E A rare earth metal compound such as rF3 can be used. Substances that make up 07 can also be used.

[0048] The electron injection layer 308 is made of a composite material obtained by mixing an organic compound and an electron donor (donor). Such composite materials may be formed by electron donors giving electrons to organic compounds. In this case, the organic compound is It is preferable that the material has excellent transport properties for the generated electrons. Specifically, the material has the above-mentioned electron transport properties. The material constituting the transport layer 307 (metal complex, heteroaromatic compound, etc.) can be used. The electron donor may be any substance that exhibits electron donating properties to organic compounds. Preferred are alkali metals, alkaline earth metals, rare earth metals, etc. Specifically, lithium, cesium, Examples include sulphur, calcium, erbium, ytterbium, and magnesium. In addition, alkali metal oxides and alkaline earth metal oxides are preferred, and lithium oxide, calcium oxide, Examples of suitable oxides include ammonium oxide, barium oxide, etc. Also, Lewis salts such as magnesium oxide In addition, organic compounds such as tetrathiafulvalene (TTF) can also be used. can also be used.

[0049] The hole injection layer 304, the hole transport layer 305, the light emitting layer 306, and the electron transport layer 30 7. The electron injection layer 308 (including the charge generation layer) is formed by evaporation (vacuum evaporation). The insulating layer can be formed by a method such as an ink jet method or a coating method.

[0050] In the light-emitting element described above, light emitted from the light-emitting layer 306 is transferred to the first electrode 301. and the second electrode 302. Either or both of the first electrode 301 and the second electrode 302 are light-transmitting. This becomes the electrode.

[0051] The light-emitting devices described above typically emit light by triplet-triplet annihilation (TTA). The fluorescent light-emitting device utilizes singlet excitons generated from triplet excitons that do not contribute to the emission of light. Therefore, it is possible to realize a light-emitting device with higher efficiency than a light-emitting device using a normal fluorescent compound. It is possible.

[0052] Note that the light-emitting element shown in this embodiment mode utilizes energy transfer by TTA for light emission. The light emitting device having the above-mentioned light emitting element is configured as follows: In addition to the passive matrix type light emitting device and the active matrix type light emitting device, To manufacture a light-emitting device having a microcavity structure, which includes a light-emitting element having the structure. and all of these are included in the present invention.

[0053] In the case of an active matrix type light emitting device, the structure of the TFT is not particularly limited. For example, a staggered or inverted staggered TFT can be used as appropriate. The driver circuit formed on the FT substrate can be made up of N-type and P-type TFTs. Alternatively, it may be composed of only one of N-type TFTs or P-type TFTs. Furthermore, there are no particular limitations on the crystallinity of the semiconductor film used in the TFT. For example, Amorphous semiconductor films and crystalline semiconductor films can be used. In addition to V group (silicon, germanium, etc.) semiconductors and compound semiconductors (including oxide semiconductors), An organic semiconductor or the like can be used.

[0054] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. It shall be possible to do so.

[0055] (Embodiment 3) In this embodiment, as one embodiment of the present invention, a structure having a plurality of EL layers sandwiching a charge generation layer is described. A light emitting device having such a structure (hereinafter referred to as a tandem light emitting device) will be described.

[0056] The light-emitting element shown in this embodiment has a pair of electrodes (first electrode 40) as shown in FIG. A plurality of EL layers (first EL layer 402(1), second EL layer 402(2), and second EL layer 404) are disposed between the first and second electrodes. It is a tandem light emitting device having an L layer 402(2).

[0057] In this embodiment, the first electrode 401 is an electrode that functions as an anode, and the second electrode The electrode 404 functions as a cathode. The same structure as that of the second embodiment can be used for the EL layer 404. At least one of the first EL layer 402(1) and the second EL layer 402(2) is the same as that of the first embodiment. The hole transport layer and the light emitting layer in contact with it have the same structure as the EL layer shown in It is preferable to use the same configuration as that shown in the first embodiment.

[0058] In addition, between the plurality of EL layers (the first EL layer 402(1) and the second EL layer 402(2)), The charge generation layer (I) 405 is provided on the first electrode. When a voltage is applied between the first electrode 401 and the second electrode 404, electrons are injected into one EL layer and the other In this embodiment, the first electrode 401 has a function of injecting holes into the EL layer. When a voltage is applied so that the potential becomes higher than that of the second electrode 404, the charge generation layer (I) 40 Electrons are injected from the first EL layer 402(1) to the second EL layer 402(2) and holes are injected from the second EL layer 402(3). It is injected.

[0059] The charge generating layer (I) 405 is transparent to visible light from the viewpoint of light extraction efficiency. (specifically, the transmittance of visible light to the charge generating layer (I) 405 is 40% or more) ) is preferable. In addition, the charge generation layer (I) 405 is preferably a layer having a thickness of 100 nm or less, and is preferably a layer having a thickness of 100 nm or less. It works even with conductivities lower than 04.

[0060] The charge generation layer (I) 405 is formed by adding an electron acceptor (acceptor) to an organic compound having high hole transport properties. ) is added, the electron donor (donor) is added to the organic compound with high electron transport properties. Alternatively, both of these structures may be laminated.

[0061] In the case where an electron acceptor is added to an organic compound having a high hole transporting property, Examples of organic compounds with high transportability include NPB, TPD, TDATA, and MTDATA. , 4,4'-bis[N-(spiro-9,9'-bifluoren-2-yl)-N-phenyl Aromatic amine compounds such as bis(amino)biphenyl (abbreviation: BSPB) can be used. The substances mentioned here are mainly 1×10 -6 cm 2 Materials with hole mobility of / Vs or higher However, any organic compound that has a higher hole transporting property than electron transporting property can be used. It's okay if they are there.

[0062] In addition, 7,7,8,8-tetracyano-2,3,5,6-tetramethyl ... Examples include fluoroquinodimethane (abbreviation: F4TCNQ) and chloranil. Further, transition metal oxides can be mentioned. Examples of oxides of metals belonging to the group include vanadium oxide, niobium oxide, Tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, lenium oxide Molybdenum oxide is particularly stable in the atmosphere. It is preferable because it has low hygroscopicity and is easy to handle.

[0063] On the other hand, in the case where an electron donor is added to an organic compound having high electron transport properties, Examples of organic compounds with high electron transport properties include Alq, Almq3, BeBq2, and B Metal complexes having a quinoline or benzoquinoline skeleton, such as Alq, can be used. In addition, oxazole-based compounds such as Zn(BOX)2 and Zn(BTZ)2, Metal complexes having azole-based ligands can also be used. Other than this, PBD, OXD-7, TAZ, Bphen, BCP, etc. can also be used. The substances mentioned in are mainly 1×10 -6 cm 2 It is a material with an electron mobility of 1 / Vs or higher. Note that, other organic compounds may be used as long as they have a higher electron transporting property than hole transporting property. No.

[0064] The electron donor may be an alkali metal, an alkaline earth metal, a rare earth metal, or or metals belonging to Groups 2 and 13 of the periodic table, and their oxides and carbonates. Specifically, lithium (Li), cesium (Cs), magnesium (Mg ), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide It is preferable to use cesium carbonate or the like. The compound may be used as an electron donor.

[0065] By forming the charge generating layer (I) 405 using the above-mentioned materials, an EL layer can be formed. When the layers are stacked, the increase in driving voltage can be suppressed.

[0066] In this embodiment mode, a light-emitting element having two EL layers has been described. As shown in the figure, n (where n is 3 or more) EL layers (402(1) to 402(n)) are stacked. The same can be applied to a light emitting device in which a light emitting element is layered. When a plurality of EL layers are disposed between a pair of electrodes, as in the case of a device, the EL layers are By arranging the charge generation layers (I) (405(1) to 405(n-1)), the current density It is possible to emit light in a high brightness range while keeping the current density low. In addition, when applied to lighting, the voltage drop due to the resistance of the electrode material It is possible to reduce the size of the LED, enabling uniform light emission over a large area. A light emitting device with low power consumption can be realized.

[0067] In addition, by making the luminescent color of each EL layer different, the desired luminescence color can be obtained as a whole. For example, in a light-emitting element having two EL layers, the first By making the luminous color of the first EL layer and the luminous color of the second EL layer complementary to each other, It is also possible to obtain a light-emitting element that emits white light as a whole. In other words, the relationship between complementary colors and the light of an object that emits light is called achromatic color. When mixed with light obtained from other materials, white light can be obtained.

[0068] The same applies to a light-emitting element having three EL layers. For example, The luminescent color of the first EL layer is red, the luminescent color of the second EL layer is green, and the luminescent color of the third EL layer is blue. In this case, the light emitting element as a whole can emit white light.

[0069] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. You can be there.

[0070] (Fourth embodiment) In this embodiment, a light-emitting device manufactured using a light-emitting element according to one embodiment of the present invention will be described. and explain.

[0071] The light emitting device may be a passive matrix light emitting device or an active matrix light emitting device. The light-emitting device shown in this embodiment may be the light-emitting device described in the other embodiments. A light emitting element can be applied.

[0072] In this embodiment mode, an active matrix light emitting device will be described with reference to FIG. .

[0073] 5A is a top view showing the light emitting device, and FIG. 5B is a top view showing the light emitting device as seen from the dashed line A- 1 is a cross-sectional view taken along line A' of the active matrix light emitting device according to the present embodiment. 5, a pixel section 502 provided on an element substrate 501, and a driving circuit section (source line driving circuit) 50 3 and a driving circuit section (gate line driving circuit) 504 (504a and 504b). The pixel portion 502, the driver circuit portion 503, and the driver circuit portion 504 are sealed by a sealant 505. It is sealed between the element substrate 501 and the sealing substrate 506 .

[0074] On the element substrate 501, a driving circuit section 503 and a driving circuit section 504 are provided. Signals (e.g., video signals, clock signals, start signals, reset signals, etc.) and potentials A wiring 507 is provided to connect an external input terminal that transmits the signal. An example of providing an FPC (flexible printed circuit) 508 as an external input terminal is shown. Although only the FPC is shown here, this FPC also has a printed wiring board. The light emitting device in this specification may be a light emitting device itself. This includes not only the body but also the state in which an FPC or PWB is attached to it.

[0075] Next, the cross-sectional structure will be described with reference to FIG. A driver circuit portion 503, which is a source line driver circuit, is formed in this example. 5, a pixel portion 502 is shown.

[0076] The driving circuit section 503 is a combination of an n-channel TFT 509 and a p-channel TFT 510. This shows an example in which a CMOS circuit is formed by combining the above. It may be formed of various CMOS circuits, PMOS circuits, or NMOS circuits. In the embodiment, a driver integrated type in which a drive circuit is formed on a substrate is shown, but this is not necessarily required. It is not necessary to form the driving circuit on the substrate, but it is also possible to form the driving circuit externally.

[0077] The pixel section 502 includes a switching TFT 511, a current control TFT 512, and a current The first TFT 512 is electrically connected to the wiring (source electrode or drain electrode) of the control TFT 512. The first electrode (anode) 513 is formed of a plurality of pixels. An insulator 514 is formed covering the end of the substrate 13. In this example, a positive photosensitive acrylic It is formed by using a resin.

[0078] In order to improve the covering property of the film formed on the upper layer, the upper end of the insulator 514 It is preferable that a curved surface having a curvature is formed at the upper or lower end. The material of the object 514 is either a negative photosensitive resin or a positive photosensitive resin. Not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride can be used. Both of these can be used.

[0079] An EL layer 515 and a second electrode (cathode) 516 are stacked on the first electrode (anode) 513. The EL layer 515 is provided with at least a light-emitting layer, and in addition to the light-emitting layer, a positive electrode A hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer, etc. may be provided as appropriate. do.

[0080] The total thickness of the first electrode (anode) 513, the EL layer 515 and the second electrode (cathode) 516 is The light-emitting element 517 is formed by the layer structure. The first electrode (anode) 513, the EL layer 515 The material used for the second electrode (cathode) 516 is the material shown in Embodiment 2. Although not shown here, the second electrode (cathode) 516 can be connected to an external input terminal The FPC 508 is electrically connected to the FPC 508.

[0081] In addition, although only one light-emitting element 517 is shown in the cross-sectional view of FIG. 5B, In the pixel section 502, a plurality of light emitting elements are arranged in a matrix. 02 is selectively formed with light-emitting elements that can emit three types of light (R, G, B), It is possible to form a light-emitting device capable of full-color display. By combining these, a light emitting device capable of full color display may be obtained.

[0082] Furthermore, by bonding a sealing substrate 506 to the element substrate 501 with a sealing material 505, The light is emitted into a space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealant 505. The structure is provided with an element 517. The space 518 is filled with an inert gas (nitrogen or In addition to the case where the cavity is filled with a gas such as argon, a configuration where the cavity is filled with a sealing material 505 is also included. .

[0083] It is preferable to use epoxy resin or glass frit for the sealing material 505. In addition, it is desirable that these materials be as impermeable to moisture and oxygen as possible. The sealing substrate 506 may be made of glass or quartz, or may be made of FRP (Fiber-Reinforced Plastic). Reinforced Plastics), PVF (Polyvinyl Fluoride), Polyethylene A plastic substrate made of stainless steel, acrylic, or the like can be used as a sealing material. When glass frit is used, the element substrate 501 and the sealing substrate 50 6 is preferably a glass substrate.

[0084] In this manner, an active matrix light emitting device can be obtained.

[0085] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. You can be there.

[0086] (Embodiment 5) In this embodiment, a light-emitting device manufactured using a light-emitting element according to one embodiment of the present invention is used. Examples of various electronic devices completed using this method will be described with reference to FIGS. 6 and 7.

[0087] Examples of electronic devices to which light-emitting devices are applied include television sets (television sets, or television sets (also known as TV receivers), computer monitors, digital cameras, digital video digital cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), Examples include portable game machines, personal digital assistants, sound players, and large game machines such as pachinko machines. Specific examples of these electronic devices are shown in Figure 6.

[0088] FIG. 6A shows an example of a television device. The television device 7100 includes: A display unit 7103 is built into the housing 7101. The display unit 7103 displays images. The light-emitting device can be used in the display portion 7103. 7 shows a configuration in which a housing 7101 is supported by a stand 7105.

[0089] The television device 7100 can be operated using an operation switch provided on the housing 7101 or a separate remote control. This can be done by using the remote control operation device 7110. The channel and volume can be controlled by the -7109, and the information displayed on the display 7103 In addition, the remote control unit 7110 can be used to control the video. A display unit 7107 for displaying information output from the device 7110 may be provided.

[0090] The television device 7100 includes a receiver, a modem, and the like. It is possible to receive general television broadcasts by this, and furthermore, to receive them by wired or wireless connection via a modem. By connecting to a communication network, it is possible to communicate in one direction (from sender to receiver) or two directions ( It is also possible to communicate information between a sender and a receiver, or between receivers.

[0091] FIG. 6B shows a computer, which includes a main body 7201, a housing 7202, a display unit 7203, and a keyboard. keyboard 7204, external connection port 7205, pointing device 7206, etc. Note that the computer can be manufactured by using a light-emitting device for the display portion 7203. This can be done.

[0092] FIG. 6C shows a smartwatch, which includes a housing 7302, a display panel 7304, and an operation button. Includes: Tan 7311, 7312, connecting terminal 7313, band 7321, clasp 7322, etc. do.

[0093] The display panel 7304 mounted on the housing 7302, which also serves as a bezel, is a non-rectangular display panel. The display panel 7304 has an icon 7305 that indicates the time, other icons, Con7306 etc. can be displayed.

[0094] The smartwatch shown in FIG. 6(C) can have various functions. For example, functions to display various information (still images, videos, text images, etc.) on the display, Panel function, calendar, date or time display function, various software (programs) It has the functions of controlling processing by RAM, wireless communication functions, and various computers using wireless communication functions. Functions for connecting to computer networks, sending or receiving various data using wireless communication functions The function of reading out the program or data recorded on the recording medium and displaying it on the display unit. It may have the function of:

[0095] In addition, a speaker, a sensor (force, displacement, position, velocity, acceleration, angle) Speed, rotation speed, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, Includes functions to measure voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays The smartwatch may have a light-emitting device, a microphone, etc. The display panel 7304 can be manufactured by using the above.

[0096] FIG. 6D shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, and the like. The device is used in the display portion 7402 .

[0097] In a mobile phone 7400 shown in FIG. 6D, information can be displayed by touching the display portion 7402 with a finger or the like. You can also make calls, write emails, and perform other operations. This can be done by touching the display portion 7402 with a finger or the like.

[0098] The screen of the display unit 7402 has three main modes. The first is a mode that mainly displays images. The first mode is a display mode, and the second mode is an input mode that mainly inputs information such as characters. This is a display + input mode that combines the display mode and the input mode.

[0099] For example, when making a call or creating an email, the display portion 7402 is used for inputting characters. In this case, you can input characters displayed on the screen. In this case, it is preferable to display a keyboard or number buttons on most of the screen of the display portion 7402. Desirable.

[0100] In addition, the mobile phone 7400 includes a sensor for detecting tilt, such as a gyro or an acceleration sensor. By providing a detection device having the above, the orientation of the mobile phone 7400 (portrait or landscape) can be determined, The screen display on the display portion 7402 can be automatically switched.

[0101] The screen mode can be switched by touching the display portion 7402 or operating the housing 7401. The type of image displayed on the display unit 7402 can be selected by operating the create button 7403. For example, the image signal to be displayed on the display unit can be switched by If the data is text data, the mode switches to display mode, and if the data is text data, the mode switches to input mode.

[0102] In the input mode, a signal detected by the optical sensor of the display unit 7402 is detected and displayed. If there is no input by touch operation on the display unit 7402 for a certain period of time, the screen mode is changed to the input mode. Alternatively, the display mode may be switched from the normal mode to the display mode.

[0103] The display portion 7402 can also function as an image sensor. By touching 402 with the palm or fingers and capturing an image of the palm print, fingerprint, etc., personal authentication can be performed. In addition, a backlight that emits near-infrared light to the display unit or a sensing light that emits near-infrared light By using a source, it is also possible to image finger veins, palm veins, etc.

[0104] Figures 7(A) and 7(B) show foldable tablet terminals. Figure 7(A) shows In the open state, the tablet terminal includes a housing 9630, a display unit 9631a, a display unit 96 31b, display mode changeover switch 9034, power switch 9035, power saving mode changeover switch The switch 9036, the fastener 9033, and the operation switch 9038 are included. The tablet terminal has a light emitting device in one or both of the display portions 9631a and 9631b. It is produced by using

[0105] A part of the display portion 9631a can be used as a touch panel area 9632a. By touching the operation keys 9637, data can be input. In 31a, for example, half of the area has a display function only, and the other half Although the display area 96 has a touch panel function, the display area 96 is not limited to this configuration. The entire area of ​​the display unit 9 may have a touch panel function. The entire surface of 631a is a touch panel for displaying keyboard buttons, and the display part 9631b is a display screen. It can be used as a surface.

[0106] In addition, in the display unit 9631b, as in the display unit 9631a, The area can be used as a touch panel area 9632b. Touch the area where the display switch button 9639 is displayed with your finger or a stylus. This allows keyboard buttons to be displayed on the display portion 9631b.

[0107] In addition, the touch panel area 9632a and the touch panel area 9632b are simultaneously You can also use touch input.

[0108] A display mode changeover switch 9034 is used to change the display orientation, such as portrait or landscape. You can switch between black and white and color display. The switch 9036 is an external switch that is detected by a light sensor built into the tablet terminal. The display brightness can be optimized according to the amount of light. In addition to sensors, other detection devices such as gyros and acceleration sensors that detect tilt are also available. may be incorporated.

[0109] FIG. 7A shows an example in which the display area of ​​the display portion 9631b is the same as that of the display portion 9631a. However, there is no particular limitation, and one size may be different from the other, and the display For example, one display panel may be capable of displaying images with higher resolution than the other. It may also be possible to use the following.

[0110] FIG. 7B shows the tablet terminal in a closed state. The tablet terminal includes a housing 9630 and a solar cell 96 33, a charge / discharge control circuit 9634, a battery 9635, and a DC / DC converter 9636 7B, a battery 9635 is used as an example of the charge / discharge control circuit 9634. A configuration having a DC-DC converter 9636 is shown.

[0111] In addition, since the tablet device can be folded in half, when not in use, the case 9630 is closed. Therefore, the display portions 9631a and 9631b can be protected. This makes it possible to provide a tablet device that is highly durable and reliable even for long-term use.

[0112] In addition, the tablet terminals shown in Fig. 7(A) and Fig. 7(B) can also display various information. (still images, videos, text images, etc.) Functions to display calendars, dates, or times Functions for displaying information on the display unit, touch input for operating or editing the information displayed on the display unit Functions, functions to control processing by various software (programs), etc. can be done.

[0113] The solar cell 9633 attached to the surface of the tablet terminal supplies power to the touch panel. The solar cell 9633 can be supplied to a display unit, a video signal processor, or the like. , which can be provided on one or both sides of the housing 9630, and can efficiently charge the battery 9635. The battery 9635 can be a lithium-ion battery. The use of a pond has the advantage of being able to make the facility smaller.

[0114] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 7B are shown in FIG. A block diagram is shown in Figure 7(C) and will be explained. , DC-DC converter 9636, converter 9638, switches SW1 to SW3, display The figure shows the part 9631, the battery 9635, the DC-DC converter 9636, The inverter 9638 and the switches SW1 to SW3 are connected to the charge / discharge control circuit 96 shown in FIG. This corresponds to 34.

[0115] First, an example of operation when external light is received and power is generated by the solar cell 9633 will be described. The power generated by the solar cell 9633 becomes the voltage for charging the battery 9635. The voltage is increased or decreased by the DC-DC converter 9636. When power from the solar cell 9633 is used to operate 1, switch SW1 is turned on. The converter 9638 increases or decreases the voltage to a level required for the display unit 9631 . When not displaying on the display unit 9631, the switch SW1 is turned off and the switch The configuration can be such that SW2 is turned on to charge the battery 9635.

[0116] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Other power generation methods such as piezoelectric elements and thermoelectric conversion elements (Peltier elements) For example, the battery 9635 may be charged wirelessly (contactlessly). A wireless power transmission module that receives and charges, or a structure that combines other charging methods It may also be composed.

[0117] As described above, an electronic device can be obtained by applying the light-emitting device which is one embodiment of the present invention. The range of applications for light-emitting devices is extremely wide, and they can be used in electronic devices in a wide range of fields. is.

[0118] Note that the structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. You can be there.

[0119] (Embodiment 6) In this embodiment, a lighting device using a light-emitting device including a light-emitting element according to one embodiment of the present invention is described. An example of this will be described with reference to FIG.

[0120] FIG. 8 shows an example in which the light emitting device is used as an indoor lighting device 8001. It is also possible to make it larger, so it is possible to form a large-area lighting device. By using a housing having such a curved surface, it is possible to form a lighting device 8002 having a light-emitting region with a curved surface. The light-emitting element included in the light-emitting device shown in this embodiment mode has a thin film shape, and the design of the housing Therefore, lighting devices with various elaborate designs can be created. Furthermore, a large lighting device 8003 may be provided on the wall of the room.

[0121] In addition, by using a light emitting device on the surface of a table, it is possible to make a lighting device that functions as a table. The lighting device 8004 can be used as a lighting device. This allows the lighting device to function as furniture.

[0122] As described above, various lighting devices using the light-emitting device can be obtained. This device is included in one aspect of the present invention.

[0123] The structure described in this embodiment mode may be used in appropriate combination with structures described in other embodiments. You can be there. [Example]

[0124] In this example, the T1 level of a substance used in a light-emitting element according to one embodiment of the present invention is calculated. and S1 levels were measured.

[0125] The light-emitting element according to one embodiment of the present invention is a fluorescent light-emitting element. The emission from the triplet state is very weak, making it difficult to measure the T1 level. The T1 level was calculated by quantum chemical calculation. This was estimated by measuring the torque.

[0126] The calculation method is as follows. The quantum chemistry calculation program is Ga The calculation was performed using a high-performance computer (SGI, This was performed using a 3D printer (Altix4700).

[0127] First, the most stable structure in the singlet state was calculated using density functional theory. 11 (triple split valence orbitals using three contraction functions) The basis functions of the rence basis set were applied to all atoms. For hydrogen atoms, the 1s to 3s orbitals are considered, and for carbon atoms, the 1s to 4s orbitals are considered. s, 2p to 4p orbitals are considered. Furthermore, to improve the accuracy of the calculation, the polarization basis As a system, p function was added to hydrogen atoms and d function was added to atoms other than hydrogen atoms. The functional is B3LY. P was used.

[0128] Next, we calculated the most stable structure in the triplet state. The energy of the T1 level was calculated from the energy difference. The basis set was 6-311G(d, p) was used. The functional used was B3LYP.

[0129] The method for estimating the S1 level is as follows. First, a thin film (approximately 5 A thin film sample was prepared by vacuum deposition of 1000 nm of ZnO, and the absorption spectrum was measured. The absorption spectrum was measured using an ultraviolet-visible spectrophotometer (JASCO Corporation, V550 model). The absorption spectrum of quartz was subtracted from the spectrum of the measured sample. The absorption edge of the spectrum was determined and designated as the S1 level.

[0130] The fluorescent material used for the measurements was N,N'-bis(3-methylphenyl)-N, N'-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]-pyrene 1,6-diamine (abbreviation: 1,6mMemFLPAPrn), 9-[4-(10-phenyl 3-[(9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), 4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCP N), 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H The results are shown in Table 1 below.

[0131] [Table 1]

[0132] Next, in this example, phosphorescence measurements of the material were performed to support the quantum chemical calculations. The substance used in the light-emitting element of one embodiment of the present invention has extremely high fluorescence quantum efficiency, and the material alone It is very difficult to directly observe phosphorescence using low-temperature PL measurements in the thin film samples used. Therefore, phosphorescence measurement was performed using the triplet sensitizer method described below, and T1 The level was estimated.

[0133] The method involves adding Ir(ppy)3 as a triplet sensitizer to the fluorescent material to be measured. A co-evaporated film was prepared and measured by low-temperature PL measurement. From the measured phosphorescence spectrum, The T1 level was estimated. The measurement was performed using a micro PL microscope, LabRAM HR-PL (LabRAM Corporation). The measurement temperature was 10 K, and the excitation light was a He-Cd laser (325 nm ) was used, and a CCD detector was used as the detector. This increases the probability of intersystem crossing of the fluorescent material to be measured, which is difficult to achieve without co-evaporation. This allows for the measurement of phosphorescence from optical materials.

[0134] The thin film was formed on a quartz substrate to a thickness of 30 nm, and the quartz substrate was heated in a nitrogen atmosphere. Then, another quartz substrate was attached to the deposition surface side, and the measurement was performed. The measurement results are shown in Table 2. From this result, it can be seen that the value of the T1 level measured in this example is the same as that calculated by quantum chemical calculation. Therefore, the value of the T1 level obtained in this example is These can be cited as parameters for manufacturing a light-emitting element according to one embodiment of the present invention. It can be said that.

[0135] [Table 2] [Example]

[0136] In this example, a light-emitting element according to one embodiment of the present invention is prepared using a light-emitting element containing T1 We fabricated a light-emitting device 1 using a high-level hole transport material (PCPN: abbreviation) as the hole transport layer. The results of measuring the properties of the prepared EL device are shown below. Comparative emission using hole transport material (PCzPA: abbreviation) with the same or lower level as the hole transport layer The results of measuring the characteristics of the device 2 are also shown. The light-emitting element 1 and the comparative light-emitting element 2 will be described with reference to FIG. The chemical formula of the material is shown below:

[0137] [ka]

[0138] <Fabrication of Light-Emitting Element 1 and Comparative Light-Emitting Element 2> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 900. A film was formed by sputtering to form a first electrode 901 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0139] Next, as a pretreatment for forming a light emitting element on the substrate 900, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0140] Then, 10 -4 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the deposition apparatus, the substrate 900 was It was left to cool for about 0 minutes.

[0141] Next, the substrate 900 is placed in a vacuum deposition apparatus so that the surface on which the first electrode 901 is formed faces downward. In this example, the EL layer 902 was formed by vacuum deposition. The hole injection layer 911, the hole transport layer 912, the light emitting layer 913, the electron transport layer 914, and the A case where the child implantation layers 915 are formed sequentially will be described.

[0142] 10 in the vacuum chamber -4 After reducing the pressure to 100 Pa, 9-phenyl-3-[4-(10-phenyl -9-anthryl)phenyl]-9H-carbazole (abbreviation: PCzPA) and molybdenum oxide PCzPA and molybdenum (VI) were co-evaporated at a mass ratio of 4:2. By this, a hole injection layer 911 was formed on the first electrode 901. The film thickness was 50 nm. Co-evaporation is the process of simultaneously evaporating multiple different substances from different evaporation sources. This is a vapor deposition method.

[0143] Next, 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPN) was evaporated to a thickness of 30 nm to form a hole transport layer 912 of the light-emitting element 1. In addition, the comparative light-emitting element 2 was fabricated by depositing PCzPA to a thickness of 30 nm on the hole injection layer 911. In this way, a hole transport layer 912 was formed.

[0144] Next, the light-emitting layer 913 was formed on the hole-transporting layer 912. N,(9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA), N'-bis(3-methylphenyl)-N,N'-bis[3-(9-phenyl-9H-fluoro)-N ...'-bis(3-methylphenyl)-N'-bis[3-(9-phenyl-9H-fluoro)-N'-bis(3-methylphenyl)-N'-bis[3-(9-phenyl-9H

[0023] [1,6mMemFL]-[(2-phenyl-9-olen-9-yl)phenyl]-pyrene-1,6-diamine (abbreviated as 1,6mMemFL) PAPrn) was mixed with CzPA:1,6mMemFLPAPrn = 1:0.05 (weight ratio). The film thickness was set to 25 nm. Successful.

[0145] Next, bathophenanthroline (abbreviation: Bphen) was vapor-deposited on the light-emitting layer 913 to a thickness of 25 nm. In this way, an electron transport layer 914 was formed. An electron injection layer 915 was formed by depositing 1 nm of silicon.

[0146] Finally, aluminum was evaporated onto the electron injection layer 915 to a thickness of 200 nm. A second electrode 903 serving as a cathode was formed, and a light-emitting element 1 was obtained. All deposition was performed using a resistance heating method.

[0147] Table 3 shows the element structures of the thus obtained light-emitting element 1 and comparative light-emitting element 2.

[0148] [Table 3]

[0149] The fabricated light-emitting element 1 and comparative light-emitting element 2 were placed in a nitrogen atmosphere to avoid exposure to the air. The device was sealed in a glove box (sealing material was applied around the device, and the sealing time was 8 hours). Heat treated at 0°C for 1 hour).

[0150] <Fluorescence lifetime measurement of light-emitting element 1 and comparative light-emitting element 2> The fluorescence lifetime of the fabricated light-emitting element 1 and comparative light-emitting element 2 was measured. A cosine fluorescence lifetime measurement system (Hamamatsu Photonics) was used. In order to measure the lifetime of the fluorescent light emitted from the light emitting element, a rectangular pulse voltage is applied to the light emitting element, and the voltage is The decaying light emission from the downward direction is measured by a time-resolved streak camera. By applying a frequency of 0 Hz and integrating the repeatedly measured data, a high S / N ratio can be achieved. The measurements were performed at room temperature (300 K), with an applied pulse voltage of 3.5 V and an applied pulse The measurement was performed under the conditions of a time width of 10 μsec and a measurement time range of 20 μsec. The measurement results are shown in Figure 1. In FIG. 10, the vertical axis represents the state in which carriers are steadily injected ( The horizontal axis shows the normalized intensity, with the light emission intensity at pulse voltage ON set to 1. This indicates the elapsed time from the fall of the source voltage.

[0151] The decay curve obtained for the light-emitting element 1 shown in FIG. 10 was fitted with an exponential function. As a result, the fluorescence lifetime τ of the light-emitting element 1 was estimated to be 1.50 μsec. Since the lifetime of fluorescence is usually several nanoseconds, the light-emitting element 1 emits a delayed fluorescence component. It is believed that the measured fluorescence includes the following: The lifetime τ was estimated to be 1.52 μsec. It is believed that Device 2 emits fluorescence containing delayed fluorescence components.

[0152] In the fluorescence measurement shown in Figure 10, the cause of delayed fluorescence is triplet-triplet In addition to the generation of singlet excitons by term annihilation (TTA), the internal When carriers remain in the exciton, the recombination of these carriers leads to the generation of singlet excitons. Therefore, we have developed a method to suppress the recombination of residual carriers. In order to measure the light-emitting element 1 and the comparative light-emitting element 2, the samples were measured as shown in FIG. Using the same device, we added the condition that a negative bias voltage (-5V) was always applied to the same Measurements were carried out under the same conditions. The measurement results are shown in Figure 12. Compared with the measurement results in Figure 10, A bias is applied under conditions that are thought to suppress the recombination of residual carriers. The measurement results in Figure 12 also showed that fluorescence emission containing delayed fluorescence components was measured. The delayed fluorescence component shown in the measurement results in Figure 12 is due to the emission from TTA. It was confirmed that this was the case.

[0153] However, the normalized emission spectra of the delayed fluorescence component of the comparative light-emitting element 2 in FIGS. It can be seen that the light intensity is smaller than the normalized luminescence intensity of the delayed fluorescence component of the light-emitting element 1. The results show that the T1 level of the hole transport material (PCPN) used in the hole transport layer of the light-emitting element 1 is The T1 level of the comparative light-emitting element 2 is larger than that of the host material (CzPA) in the light-emitting layer. The T1 level of the hole transporting material (PCzPA) used in the hole transporting layer is This is thought to be due to the fact that the T1 level of P is equal to or lower than that of CzPA. The S1 level of CPN is also higher than that of CzPA, and the excited state energy of CzPA is It is considered that the structure shown in the light-emitting element 1 makes it difficult for the This allows triplet excitons generated in the light-emitting layer to be confined within the light-emitting layer, increasing the probability of TTA occurring. It is believed that this is what has been achieved.

[0154] The emission spectrum of the delayed fluorescence component of the light-emitting element 1 shown in FIG. 10 is shown by a solid line in FIG. 11. As a comparative example, a state in which carriers are steadily injected into the light-emitting element 1 (pulse The dashed line shows the fluorescence emission spectrum when the power supply voltage is ON. The normalized intensity is shown with the intensity set to 1.

[0155] Figure 11 shows the spectral shape of the delayed fluorescence component and the constant carrier injection. The shape of the fluorescence spectrum when the pulse voltage is ON is almost the same. Both of these were found to be emissions from the guest material (1,6mMemFLPAPrn). Therefore, the delayed fluorescence, which is thought to correspond to the emission from the singlet generated by TTA, The light is thought to be emitted from the guest material, not from the host material. It can be done.

[0156] <Operation characteristics of light-emitting element 1 and comparative light-emitting element 2> Next, the operating characteristics of the fabricated light-emitting element 1 and comparative light-emitting element 2 were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

[0157] Here, 1000 cd / m 2 The main initial values ​​of the light-emitting element 1 and the comparative light-emitting element 2 in the vicinity The property values ​​are shown in Table 4 below.

[0158] [Table 4]

[0159] From the above results, it can be seen that the light-emitting element 1 fabricated in this example has a higher current than the comparative light-emitting element 2. It can be seen that the efficiency and external quantum efficiency are high.

[0160] That is, a material having a higher T1 level than the host material used in the light-emitting layer is used in the hole transport layer. This prevents triplet excitons generated in the light-emitting layer from diffusing out of the light-emitting layer, It is believed that TTA can be efficiently induced in the layer. It is believed that the intensity of the extended luminescence component increases, and as a result, the luminescence characteristics of the light-emitting element 1 are improved. can be. [Example]

[0161] In this example, in a light-emitting element according to one embodiment of the present invention, a guest material (a fluorescent dopant ) and CzPA, which has a lower T1 level. The light-emitting device 3 was fabricated using the material in the light-emitting layer. dopant) and 35D, which has a higher T1 level than that. Comparative light-emitting element 4 was fabricated using CzPPy as the host material in the light-emitting layer, and the characteristics of each were investigated. The results of measurements are shown below. 35DCzPPy is the PCP used in the hole transport layer. PCPPn has a higher T1 level than 1,6mMemFLPAPrn. In addition, both 35DCzPPy and PCPPn have the same 1,6mMemFLP The S1 level is higher than that of APrn. For clarity, the explanation will be given using FIG. 9 as in Example 2. The chemical formulas of the materials used in this example are as follows: Shown below.

[0162] [ka]

[0163] <Fabrication of Light-Emitting Element 3 and Comparative Light-Emitting Element 4> First, indium tin oxide containing silicon oxide (ITSO) is deposited on a glass substrate 900. A film was formed by sputtering to form a first electrode 901 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm x 2 mm.

[0164] Next, as a pretreatment for forming a light emitting element on the substrate 900, the substrate surface is washed with water. After baking at 200°C for 1 hour, UV ozone treatment was performed for 370 seconds.

[0165] Then, 10 -4 The substrate is placed in a vacuum deposition apparatus whose inside pressure has been reduced to about 100 Pa. After vacuum baking at 170° C. for 30 minutes in the heating chamber of the deposition apparatus, the substrate 900 was It was left to cool for about 0 minutes.

[0166] Next, the substrate 900 is placed in a vacuum deposition apparatus so that the surface on which the first electrode 901 is formed faces downward. In this example, the EL layer 902 was formed by vacuum deposition. The hole injection layer 911, the hole transport layer 912, the light emitting layer 913, the electron transport layer 914, and the A case where the child implantation layers 915 are formed sequentially will be described.

[0167] 10 in the vacuum chamber -4 After reducing the pressure to 100 Pa, 9-{4-(9-H-9-phenylcarbazo ((3-yl)-phenyl}-phenanthrene (abbreviation: PCPPn) and molybdenum oxide (VI) were co-evaporated in a ratio of PCPPn:molybdenum oxide = 1:0.5 (mass ratio). By this, a hole injection layer 911 was formed on the first electrode 901. The film thickness was 20 nm. Co-evaporation is the process of simultaneously evaporating multiple different substances from different evaporation sources. This is a vapor deposition method.

[0168] Next, PCPPn was deposited to a thickness of 20 nm to form the light-emitting element 3 and the comparative light-emitting element 4. A hole transport layer 912 was formed.

[0169] Next, a light-emitting layer 913 was formed on the hole-transporting layer 912. First, in the case of the light-emitting element 3, 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole ( Abbreviation: CzPA), N,N'-bis(3-methylphenyl)-N,N'-bis[3-(9 -phenyl-9H-fluoren-9-yl)phenyl)-pyrene-1,6-diamine (abbreviation Name: 1,6mMemFLPAPrn), CzPA: 1,6mMemFLPAPrn = 1 The co-deposition was carried out so that the weight ratio was 0.05. The film thickness was 25 nm. In the case of the comparative light-emitting element 4, 3,5-bis[3-(9H-carbazol-9-yl)phenyl] 35DCzPPy, 1,6mMemFLPAPrn, Co-evaporation was performed to give a weight ratio of CzPPy:1,6mMemFLPAPrn=1:0.05. The film thickness was set to 25 nm. In this way, the light-emitting layer 913 was formed.

[0170] Next, an electron transport layer 914 was formed on the light-emitting layer 913. In the case of the light-emitting element 3, CzP After depositing 10 nm of A, bathophenanthroline (abbreviation: Bphen) was deposited to 15 nm. In the case of comparative light-emitting element 4, after 10 nm of 35DCzPPy was vapor-deposited, Further, on the electron transport layer 914, lithium fluoride was deposited. An electron injection layer 915 was formed by depositing 1 nm of silicon.

[0171] Finally, aluminum was evaporated onto the electron injection layer 915 to a thickness of 200 nm. A second electrode 903 serving as a cathode was formed, and the light-emitting element 3 and the comparative light-emitting element 4 were obtained. In the above-mentioned deposition process, the deposition was all carried out by a resistance heating method.

[0172] Table 5 shows the element structures of the thus obtained light-emitting element 3 and comparative light-emitting element 4.

[0173] [Table 5]

[0174] The fabricated light-emitting element 3 and comparative light-emitting element 4 were placed in a nitrogen atmosphere to avoid exposure to the air. The device was sealed in a glove box (sealing material was applied around the device, and the sealing time was 8 hours). Heat treated at 0°C for 1 hour).

[0175] <Fluorescence Lifetime Measurement of Light-Emitting Element 3 and Comparative Light-Emitting Element 4> The fluorescence lifetime of the fabricated light-emitting element 3 and the comparative light-emitting element 4 was measured. A cosine fluorescence lifetime measurement system (Hamamatsu Photonics) was used. In order to measure the lifetime of the fluorescent light emitted from the light emitting element, a rectangular pulse voltage is applied to the light emitting element, and the voltage is The decaying light emission from the downward direction is measured by a time-resolved streak camera. By applying a frequency of 0 Hz and integrating the repeatedly measured data, a high S / N ratio can be achieved. The measurements were performed at room temperature (300 K) with an applied pulse voltage of 3.5 V (light-emitting element). 3), 5.2V (comparison light-emitting element 4) (the current flowing through the element is The voltage was adjusted for each element so that the voltage was the same for each element.) Applied pulse duration: 100 μ The measurement was performed under the following conditions: 100 μsec, negative bias voltage (-10 V), and measurement time range: 50 μsec. The measurement results are shown in Figure 13. In Figure 13, the vertical axis indicates the time when carriers are steadily injected. The intensity is normalized by taking the light emission intensity when the pulse voltage is ON as 1. The horizontal axis indicates the time elapsed from the fall of the pulse voltage.

[0176] The decay curve obtained for the light-emitting element 3 shown in FIG. 13 was fitted with an exponential function. As a result, the light-emitting element 3 exhibited a higher proportion of delayed fluorescence than the comparative light-emitting element 4. Therefore, the guest material (fluorescent dopant) 1,6mMem A light-emitting device using CzPA, which has a lower T1 level than FLPAPrn, as a host material in the light-emitting layer. The third molecule possesses 35DCzPPy, which has a higher T1 level than 1,6mMemFLPAPrn. The triplet-triplet annihilation (TTA) was more pronounced than that of comparative light-emitting element 4, which used a tertiary material as the light-emitting layer. It was confirmed that this occurs more frequently.

[0177] <Operation Characteristics of Light-Emitting Element 3 and Comparative Light-Emitting Element 4> Next, the operating characteristics of the fabricated light-emitting element 3 and comparative light-emitting element 4 were measured. The measurements were carried out at room temperature (atmosphere maintained at 25°C).

[0178] Here, 1000 cd / m 2The main initial values ​​of the light-emitting element 3 and the comparative light-emitting element 4 in the vicinity The property values ​​are shown in Table 6 below.

[0179] [Table 6]

[0180] From the above results, it can be seen that the light-emitting element 3 fabricated in this example has a higher current than the comparative light-emitting element 4. It can be seen that the efficiency and external quantum efficiency are high.

[0181] That is, the results of measuring the fluorescence lifetime and the operating characteristics of the light-emitting element 3 and the comparative light-emitting element 4 are as follows: The T1 level of the guest material is higher than the T1 level of the host material, whereas the opposite is true. TTA occurs more easily than in the case of GaN. As a result, the operating characteristics of the light-emitting device, such as the external quantum efficiency and current efficiency, deteriorate. This indicates that the guest material, which is present in only a small amount in the light-emitting layer, Triplet excitons are trapped and localized in the material, resulting in collisions between triplet excitons. This is because it is possible to prevent a decrease in the probability of collision and increase the probability of TTA occurring. [Explanation of symbols]

[0182] 101 Light-emitting layer 102 Host Material 103 Guest Materials 201 Hole transport layer 202 Light-emitting layer 211 First electrode (anode) 212 Second electrode (cathode) 213 Hole injection layer 214 Electron transport layer 215 Electron injection layer 301 First electrode (anode) 302 Second electrode (cathode) 303 EL layer 304 Hole injection layer 305 Hole transport layer 306 Light-emitting layer 307 Electron transport layer 308 Electron injection layer 311 Host Materials 312 Guest Materials 313 Hole transport materials 401 First electrode 402(1) First EL layer 402(2) Second EL layer 402(n-1)th EL layer 402(n) EL layer (n) 404 Second electrode 405 Charge generation layer (I) 405(1) First charge generating layer (I) 405(2) Second charge generating layer (I) 405(n-2) (n-2)th charge generating layer (I) 405(n-1) (n-1)th charge generating layer (I) 501 Element substrate 502 pixel section 503 Driver circuit section (source line driver circuit) 504a, 504b Drive circuit section (gate line drive circuit) 505 Sealing material 506 Sealing substrate 507 Wiring 508 FPC (Flexible Printed Circuit) 509 n-channel TFT 510 p-channel TFT 511 Switching TFT 512 Current control TFT 513 First electrode (anode) 514 Insulators 515 EL layer 516 Second electrode (cathode) 517 Light-emitting element 518 Space 900 boards 901 First electrode 902 EL layer 903 Second electrode 911 Hole injection layer 912 Hole transport layer 913 Light-emitting layer 914 Electron transport layer 915 Electron injection layer 7100 Television equipment 7101 Housing 7103 Display section 7105 Stand 7107 Display section 7109 Operation key 7110 Remote control device 7201 Main unit 7202 Case 7203 Display section 7204 keyboard 7205 External connection port 7206 Pointing Device 7302 Housing 7304 Display Panel 7305 Time Icon 7306 Other Icons 7311 7312 Operation buttons 7313 Connection terminal 7321 Band 7322 Clasp 7400 mobile phone 7401 Housing 7402 Display section 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 8001 Lighting equipment 8002 Lighting equipment 8003 Lighting equipment 8004 Lighting equipment 9033 Fasteners 9034 Display mode switch 9035 Power Switch 9036 Power saving mode switch 9038 Operation switch 9630 chassis 9631 Display section 9631a Display section 9631b Display section 9632a Touch Panel Area 9632b Touch panel area 9633 Solar Cells 9634 Charge / Discharge Control Circuit 9635 Battery 9636 DC / DC Converter 9637 Operation Key 9638 Converter 9639 Button

Claims

1. a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer between a pair of electrodes; the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are each independently a carbazole compound, a dibenzothiophene compound, a dibenzofuran compound, a triphenylene compound, or a phenanthrene compound; The host material is a compound having an anthracene skeleton.

2. a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer between a pair of electrodes; the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are carbazole compounds, The host material is a compound having an anthracene skeleton.

3. A tandem light-emitting element having a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a charge generation layer between a pair of electrodes, the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are each independently a carbazole compound, a dibenzothiophene compound, a dibenzofuran compound, a triphenylene compound, or a phenanthrene compound; the host material is a compound having an anthracene skeleton, The light-emitting element, wherein the charge generating layer comprises lithium, cesium, magnesium, calcium, ytterbium, or indium.

4. A tandem light-emitting element having a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a charge generation layer between a pair of electrodes, the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are carbazole compounds, the host material is a compound having an anthracene skeleton, The light-emitting element, wherein the charge generating layer comprises lithium, cesium, magnesium, calcium, ytterbium, or indium.

5. A tandem light-emitting element having a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a charge generation layer between a pair of electrodes, the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are each independently a carbazole compound, a dibenzothiophene compound, a dibenzofuran compound, a triphenylene compound, or a phenanthrene compound; the host material is a compound having an anthracene skeleton, The light-emitting element, wherein the charge generating layer contains ytterbium or indium.

6. A tandem light-emitting element having a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a charge generation layer between a pair of electrodes, the light-emitting layer includes a guest material and a host material having a T1 level lower than that of the guest material, the electron transport layer includes a first compound having a T1 level higher than that of the host material, the hole transport layer includes a second compound having a higher T1 level than the host material; the hole injection layer comprises a third compound; the first hole transport material and the second hole transport material are carbazole compounds, the host material is a compound having an anthracene skeleton, The light-emitting element, wherein the charge generating layer contains ytterbium or indium.

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