WO2011030450A1 - 有機発光素子 - Google Patents
有機発光素子 Download PDFInfo
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- WO2011030450A1 WO2011030450A1 PCT/JP2009/065949 JP2009065949W WO2011030450A1 WO 2011030450 A1 WO2011030450 A1 WO 2011030450A1 JP 2009065949 W JP2009065949 W JP 2009065949W WO 2011030450 A1 WO2011030450 A1 WO 2011030450A1
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- organic light
- light emitting
- guest material
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/06—Luminescent, e.g. electroluminescent, chemiluminescent materials containing organic luminescent materials
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
- H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K50/00—Organic light-emitting devices
- H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
- H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
- H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/30—Coordination compounds
- H10K85/321—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3]
- H10K85/324—Metal complexes comprising a group IIIA element, e.g. Tris (8-hydroxyquinoline) gallium [Gaq3] comprising aluminium, e.g. Alq3
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- H—ELECTRICITY
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
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- H—ELECTRICITY
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/631—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
- H10K85/60—Organic compounds having low molecular weight
- H10K85/649—Aromatic compounds comprising a hetero atom
- H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
- H10K85/6572—Polycyclic condensed heteroaromatic hydrocarbons comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
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- H—ELECTRICITY
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- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K2101/00—Properties of the organic materials covered by group H10K85/00
- H10K2101/30—Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K2101/00—Properties of the organic materials covered by group H10K85/00
- H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
Definitions
- the present invention relates to an organic light emitting device applicable to a flat panel display and an illumination light source.
- the present invention relates to a high-efficiency organic light-emitting element that leads to lower power consumption of a display.
- a color conversion type color display using an organic light emitting element generally uses an organic light emitting element that emits blue to blue-green light (hereinafter referred to as a blue or blue-green organic light emitting element), and a blue pixel has a blue color. Blue light is transmitted using a color filter, and red light is obtained from red pixels by wavelength conversion of EL light using a color conversion layer.
- green light is obtained by transmitting a green component of EL light through a color filter or using a color conversion layer that emits green light.
- a blue or blue-green organic light emitting element is used for any pixel of red, green, and blue. Accordingly, in a color conversion type display, the light emission efficiency of the blue or blue-green organic light emitting element greatly affects the performance such as the power consumption of the display.
- a method using phosphorescence emission has been proposed as a method for realizing higher efficiency (for example, see Non-Patent Document 1). Since phosphorescence is emitted from the triplet state, the probability of exciton generation is high, and a significant improvement in emission efficiency can be realized.
- the light emitting layer includes a host material and a first dopant and a second dopant that satisfy the following relationship.
- the light emitting layer includes a host material and a first dopant and a second dopant that satisfy the following relationship.
- One of them is shown below.
- Eg0> Eg1, Eg2 [Where EV0, EV1, EV2 are the host material, the first dopant, the valence electron level of the second dopant, EC0, EC2 are the host material, the conduction level of the second dopant, Eg0, Eg1, Eg2, respectively. The energy gaps of the light emitting layer material, the first dopant, and the second dopant, respectively. ]
- the other organic light emitting device is as follows.
- EV0, EV1, EV2 are the host material, first dopant, valence level of the second dopant, respectively
- EC0, EC1, EC2 are the conduction levels of the host material, the first dopant, and the second dopant, respectively. It is. ]
- Non-Patent Document 1 when blue or blue-green light emission necessary for the color conversion method is performed, a host material having triplet energy suitable for blue or blue-green light emission, that is, a large band gap. Is required.
- host materials there are currently limited choices of host materials, and no practical host material that achieves both luminous efficiency and driving stability has been proposed.
- driving stability phosphorescent light emission maintains a longer light emission state than fluorescent light emission, so that the light emitting material in an excited state reacts with other materials and is likely to be quenched, resulting in a longer material life. It is considered to be short, and further breakthrough is necessary for practical use.
- Patent Document 2 exemplifies that the light emission efficiency and the light emission lifetime are improved in the embodiment as compared with the example using only one kind of dopant.
- an example in which the technology is applied to a blue or blue-green organic light emitting device is not disclosed.
- an organic light emitting device having a structure capable of emitting both types of dopants has a problem that the driving voltage is essentially high, although the light emitting efficiency and the light emitting lifetime are improved by further using a carrier transporting dopant. This is because both of the two types of dopants have the property of trapping electrons.
- an object of the present invention is to provide a blue or blue-green organic light emitting device having high brightness, high efficiency, and long life.
- the inventors of the present invention have arrived at the present invention as a result of intensive studies aimed at further increasing the efficiency of blue or blue-green organic light emitting devices using fluorescent light emission.
- the organic light-emitting device of the present invention comprises a pair of electrodes, at least one of which has visible light permeability, and an organic EL layer including at least an organic light-emitting layer disposed between the pair of electrodes.
- An organic light emitting device that emits light by applying a voltage to The organic light emitting layer includes an electron transporting host material and at least a first guest material and a second guest material, and each of the first and second guest materials has a light emission peak in a blue to blue-green region.
- the first guest material has an equation (1) with respect to the ionization potential (IPH) and electron affinity (AFH) of the host material.
- IPH ⁇ IPG1 and AFH ⁇ AFG1
- the organic light emitting device of the present invention high efficiency can be realized without affecting the driving voltage.
- the organic EL layer includes at least an organic light emitting layer and has a structure in which a hole injection layer, a hole transport layer, an electron transport layer and / or an electron injection layer are interposed as required. Specifically, an organic EL layer having the following layer structure is employed.
- an organic electroluminescent layer is a layer which exists between an anode and a cathode. The anode and the cathode are either reflective electrodes or transparent electrodes.
- Anode / organic light emitting layer / cathode (2) Anode / hole injection layer / organic light emitting layer / cathode (3) Anode / organic light emitting layer / electron injection layer / cathode (4) Anode / hole injection layer / organic Light emitting layer / electron injection layer / cathode (5) Anode / hole transport layer / organic light emitting layer / electron injection layer / cathode (6) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron injection layer / Cathode (7) Anode / hole injection layer / hole transport layer / organic light emitting layer / electron transport layer / electron injection layer / cathode
- Transparent electrode an electrode having visible light permeability is referred to as a transparent electrode.
- Transparent electrodes are ITO (indium-tin oxide), tin oxide, indium oxide, IZO (indium-zinc oxide), IWO (indium-tungsten oxide), zinc oxide, zinc-aluminum oxide, zinc-gallium oxide. Or a conductive transparent metal oxide obtained by adding a dopant such as F or Sb to these oxides.
- the transparent electrode can be formed using a vapor deposition method, a sputtering method, or a chemical vapor deposition (CVD) method.
- the material that can be used for the hole injection layer of the organic light emitting device in the present invention is generally used in an organic EL device or an organic TFT device such as a material having a triarylamine partial structure, a carbazole partial structure, or an oxadiazole partial structure. Hole transport materials that are used.
- the hole transport material is, for example, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine (TPD), N, N, N ′, N′-tetrakis (4-methoxyphenyl) -benzidine (MeO-TPD), 4,4 ′, 4 ′′ -tris ⁇ 1-naphthyl (phenyl) amino ⁇ triphenylamine (1-TNATA ), 4,4 ′, 4 ′′ -tris ⁇ 2-naphthyl (phenyl) amino ⁇ triphenylamine (2-TNATA), 4,4 ′, 4 ′′ -tris (3-methylphenylphenylamino) triphenylamine ( m-MTDATA), 4,4'-bis ⁇ N- (1-naphthyl) -N-phenylamino ⁇ biphenyl (NPB), 2,2 ', 7,7
- a hole injection layer can be formed using a hole transport material commercially available from each organic electronic material manufacturer.
- an electron-accepting dopant may be added to the hole transport material (p-type doping) to form the hole injection layer.
- the electron accepting dopant may be either an organic semiconductor or an inorganic semiconductor.
- organic semiconductors that can be used include tetracyanoquinodimethane derivatives such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F 4 -TCNQ) and the like.
- An inorganic semiconductor that can be used includes molybdenum oxide (MoO 3 ), tungsten oxide (WO 3 ), vanadium oxide (V 2 O 5 ), or the like.
- a thin film of the above-described electron-accepting dopant can be formed on the anode to form a hole injection layer.
- the hole injection layer can be formed by any method known in the technical field such as a vapor deposition method, particularly a resistance heating vapor deposition method.
- the dopant material and the hole transport material can be formed by co-evaporation or the like, in which a dopant material and a hole transport material are simultaneously evaporated by heating in a vacuum chamber.
- an inorganic oxide thin film such as molybdenum oxide
- electron beam evaporation or sputtering is also preferably used as a forming method in addition to resistance heating evaporation.
- Hole transport layer As materials that can be used for the hole transport layer of the organic EL device in the present invention, among the known materials used for the hole transport material of the organic EL device or organic TFT as exemplified in the hole injection layer. Any one can be selected and used.
- the hole transport layer can be formed by using any method known in the technical field such as a vapor deposition method, particularly a resistance heating vapor deposition method.
- the organic light emitting layer includes an electron transporting host material, at least a first guest material, and a second guest material.
- the first guest material has an ionization potential (IPG1) and an electron affinity (AFG1) that satisfy the relationship of the expression (1) with respect to the ionization potential (IPH) and the electron affinity (AFH) of the host material.
- IPG1 ionization potential
- AVG1 electron affinity
- the first guest material has singlet excitons. It is thought that it can also have a mechanism to directly generate and emit light, so that the amount of excitons generated in the entire organic light emitting layer is improved, and the light emitting efficiency is so high that it is difficult to realize with an organic light emitting layer made of a single guest material. It can be realized.
- the optical band gap of the first guest material (EGG1) and the optical band gap of the host material are used.
- (EGH) satisfies the relationship of formula (2), light emission of the first guest material can be obtained efficiently. This is because extra energy transfer from the first guest material to the host material can be prevented.
- the first guest material traps electrons and directly generates singlet excitons and emits light.
- the first guest material has an electron trapping property, when the doping concentration of the first guest material is increased, the driving voltage of the organic light emitting element is also increased, and the power efficiency may not be improved. Therefore, in the present invention, it is preferable to dope the first guest material at a low concentration from the viewpoint of low voltage driving and improving power efficiency.
- the concentration of the first guest material is preferably 0.05% by mass or more and less than 0.5% by mass, and more preferably 0.08% by mass to 0.2% by mass.
- the second guest material desirably has an ionization potential (IPG2), an electron affinity (AFG2), and an optical band gap (EGG2) that satisfy the relationship of the formula (3).
- IPG2 ionization potential
- AFG2 electron affinity
- EGG2 optical band gap
- An electron transporting host material is a host material that has the same or better electron transport capacity than the hole transport capacity. That is, the material has hole mobility ⁇ electron mobility.
- Examples of the electron-transporting host material for obtaining blue to blue-green light emission include phenylanthracene, naphthylanthracene, diphenylanthracene derivatives, metal complexes, and styrylarylene derivatives.
- the first guest material and the second guest material are materials having an emission peak in a blue to blue-green region.
- the first guest material and the second guest material are selected so as to satisfy the above-described formula (1) or (3) depending on the host material to be used. It is desirable that the first guest material is further selected so as to satisfy the above-described formula (2).
- the first and second guest materials include perylene, 2,5,8,11-tetra-t-butylperylene (TBP), 4,4 ′ in addition to the materials described as host materials.
- the second guest material that emits light with high efficiency in combination with the electron transporting host material is relatively easy to find, and the concentration of the second guest material is 1 mass% to 10 mass%, and the first guest material is added.
- Blue to blue-green organic thin film that combines low voltage, high efficiency, and long life by doping into the light emitting layer at a concentration of 0.05 mass% to 0.5 mass% (based on the total mass of the light emitting layer) An element can be realized.
- the state in which the first guest traps electrons is stable in order to coexist the two types of light emission mechanisms and improve the amount of exciton generation. Accordingly, since the host has an electron transporting property, the hole density is low and recombination hardly occurs on the first guest material even in a region away from the hole injection interface in the light emitting layer. This is because the binding is considered to occur. In the system where the lowest unoccupied molecular orbital (LUMO) energy level (or electron affinity) (AFH and AFG1) of the host material and the first guest material is too close, even if the guest traps electrons, it moves to the host again in a short time. This is not preferable.
- ) between the host material and the first guest material is preferably about 0.2 eV or more.
- the HOMO level (ionization potential IPH, IPG1, IPG2), LUMO level (electron affinity AFH, AFG1, AFG2), and optical band gap (EGH, EGG1, EGG2) of the host material and the two types of guest materials are important. Therefore, it is necessary to measure a physical property value in advance and select a suitable combination.
- an atmospheric photoelectron spectrometer AC-2 (manufactured by Riken Keiki Co., Ltd.) is used to measure the ionization potential (energy difference from the vacuum level to the HOMO level) Ip
- the UV-visible spectrophotometer UV -2100PC (manufactured by Shimadzu Corporation) is used to measure the optical absorption, and the optical band gap Eg is obtained from the absorption edge.
- the electron affinity Af energy difference from the vacuum level to the LUMO level
- Af Ip ⁇ Eg using Eg and Ip.
- the organic EL layer can be formed using any method known in the technical field such as a vapor deposition method.
- the electron transport layer may be optionally provided.
- the electron transport layer comprises 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (PBD), 1,3,5-tris (4-tert-butyl) Oxadiazole derivatives such as phenyl-1,3,4-oxadiazolyl) benzene (TPOB); of 3-phenyl-4- (1′-naphthyl) -5-phenyl-1,2,4-triazole (TAZ)
- TBD 1,3,5-tris (4-tert-butyl) Oxadiazole derivatives such as phenyl-1,3,4-oxadiazolyl) benzene
- TEZ 3-phenyl-4- (1′-naphthyl) -5-phenyl-1,2,4-triazole
- Triazole derivatives triazine derivatives
- phenylquinoxalines 5,5′-bis (dimes
- the high-efficiency light emission and long life due to the first and second dopants described above are effective when the main charge traveling in the light-emitting layer is an electron, so that phenanthroline derivatives, silole derivatives, imidazole
- an electron transport layer material having a high electron transport capability such as a compound is used, it is more effective and suitable for manufacturing a device having a low driving voltage and high power efficiency.
- the electron injection layer is a layer that may optionally be provided between the cathode and the electron transport layer or between the cathode and the light emitting layer, and can be formed of an insulator or a semiconductor.
- the electron injection layer is effective in promoting the movement of electrons from the cathode to the light emitting layer.
- an alkaline earth metal such as Li 2 O, LiO, Na 2 S, Na 2 Se, or an alkali metal oxide or alkali metal chalcogenide such as CaO, BaO, SrO, BeO, BaS, or CaSe oxides or alkaline earth metal chalcogenides, LiF, NaF, KF, CsF , LiCl, alkali metal halides such as KCl or NaCl, CaF 2, BaF 2, SrF 2, MgF 2 or BeF 2 and the like alkaline earth metal
- the electron injection layer can be formed using a halide or an alkali metal carbonate such as Cs2CO3.
- the thickness of the electron injection layer be about 0.5 to 1.0 nm.
- a thin film (thickness of about 1.0 to 5.0 nm) of an alkali metal such as Li, Na, K, or Cs or an alkaline earth metal such as Ca, Ba, Sr, or Mg is used as the electron injection layer. It can also be used.
- alkali metals such as Li, Na, K, or Cs
- alkali metal halides such as LiF, NaF, KF, or CsF
- Cs 2 CO The electron injection layer may be formed using a material doped with an alkali metal carbonate such as 3 .
- the electron injection layer can be formed by using any method known in the technical field such as vapor deposition.
- the metal electrode is formed using a highly reflective metal (Al, Ag, Mo, W, Ni, Cr, etc.), an amorphous alloy (NiP, NiB, CrP, CrB, etc.), or a microcrystalline alloy (NiAl, etc.). can do.
- the metal electrode can be formed by a dry process such as vapor deposition or sputtering.
- Example 1 Preparation of transparent electrode> ITO was deposited on a glass substrate (length 50 mm ⁇ width 50 mm ⁇ thickness 0.7 mm; Corning Eagle 2000 glass) by DC magnetron sputtering to a film thickness of 180 nm at a set substrate temperature of 200 ° C.
- An electrode pattern having a line width of 2 mm was formed by a so-called photolithography method.
- Photoresist “TFR-1250” (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied on the substrate on which the ITO film was formed to a thickness of 1.1 ⁇ m by spin coating.
- the substrate after the formation of the photoresist was exposed with a high-pressure mercury lamp through a photomask in which a shadow of a line pattern having a line width of 2 mm was formed using a mask aligner.
- development with a developer NMD-3 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.), rinsing with pure water, nitrogen blowing, heat drying in a clean oven set at 80 ° C.
- the substrate was immersed in an aqueous oxalic acid solution at 45 ° C., and unnecessary portions of the ITO film were removed by etching. After etching, the substrate was rinsed with pure water and dried with nitrogen blow, and immersed in a stripping solution 106 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) to strip the resist, rinsed with pure water, and dried with nitrogen blow Thus, a substrate on which a transparent electrode was formed was obtained.
- a stripping solution 106 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.)
- the internal pressure of the vacuum chamber was reduced to 1 ⁇ 10 ⁇ 4 Pa or less.
- 2-TNATA was formed to a thickness of 20 nm at a deposition rate of 1 ⁇ / s.
- the hole transport layer was formed by laminating NPB at 1 nm / s at 40 nm.
- the ionization potential (HOMO level) (IPH, IPG1, IPG2) of each material was measured using an atmospheric photoelectron spectrometer AC-2 (manufactured by Riken Keiki Co., Ltd.). Moreover, the optical band gap (EGH, EGG1, EGG2) obtained from the absorption spectrum of the same film was measured. Electron affinity (LUMO level) (AFH, AFG1, AFG2) was calculated using measured values of ionization potential and optical band gap. The deposition rate of each material was set to 2.0 A / s for ADN, 0.06 A / s for DPAVBi, and 0.002 A / s for Alm 23 q 3 .
- the co-evaporated organic light-emitting layer was formed so that the thickness of the host material was 35 nm.
- the deposition rate was adjusted by bringing the position of the film thickness meter closer to the deposition source and increasing the detection sensitivity.
- the component ratio of the organic light emitting layer, DPAVBi is 2.9 vol% (2.4 wt%)
- Alm 23 q 3 was 0.1 vol% (0.1 wt%).
- TPBI As the electron transport layer, TPBI was deposited to a thickness of 20 nm at a deposition rate of 1 nm / s.
- the substrate was moved to the metal film deposition chamber without breaking the vacuum. Subsequently, a 1 nm thick LiF film was formed at a deposition rate of 0.1 ⁇ / s through a metal mask having a 2 mm wide stripe pattern opening perpendicular to the ITO line pattern to form an electron injection layer. . Subsequently, a film of Al was formed thereon at a deposition rate of 100 nm and 3 ⁇ / s to form a metal electrode (cathode).
- the substrate after forming the cathode was moved to a glove box in a dry nitrogen atmosphere (oxygen 10 ppm or less, moisture 1 ppm or less) without being exposed to the air.
- a sealing glass plate (length 41 mm ⁇ width 41 mm ⁇ thickness 1.1 mm, OA-10 manufactured by Nippon Electric Glass) coated with an epoxy adhesive on the four sides is covered with the organic EL layer.
- the blue organic light-emitting device of Example 1 was obtained.
- Example 2 A blue organic light-emitting device was obtained in the same manner as in Example 1 except that the deposition rate of Alm 23 q 3 during the formation of the organic light-emitting layer was 0.006 ⁇ / s.
- the component ratio of the organic light emitting layer, DPAVBi is 2.9 vol% (2.4 wt%)
- Alm 23 q 3 was 0.3 vol% (0.3 wt%).
- Example 3 A blue organic light emitting device was obtained in the same manner as in Example 1 except that the deposition rate of Alm 23 q 3 at the time of forming the organic light emitting layer was set to 0.01 ⁇ / s.
- the component ratio of the organic light emitting layer, DPAVBi is 2.9 vol% (2.4 wt%)
- Alm 23 q 3 was 0.5 vol% (0.5 wt%).
- Example 1 An organic light emitting device was formed by the same method as in Example 1 except that Alm 23 q 3 was not used when forming the organic light emitting layer.
- Example 3 An organic light emitting device was formed in the same manner as in Example 1 except that the deposition rate of Alm 23 q 3 was 0.06 ⁇ / s and DPAVBi was not used when forming the organic light emitting layer.
- Alm 23 q 3 functions as a first guest material satisfying the relationship of the formula (1)
- DPAVBi functions as a second guest material satisfying the relationship of the formula (3).
- Luminous efficiency of the organic light emitting devices of Examples 1, 2, and 3 including both the first and second guest materials is improved as compared with the device of Comparative Example 1.
Abstract
Description
(A)EV0>EV1かつEV0>EV2
(B)EC0≧EC2
(C)Eg0>Eg1,Eg2
[式中、EV0、EV1、EV2はそれぞれホスト材料、第一のドーパント、第二のドーパントの価電子レベル、EC0、EC2はそれぞれホスト材料、第二のドーパントの伝導レベル、Eg0、Eg1、Eg2はそれぞれ発光層材料、第一のドーパント、第二のドーパントのエネルギーギャップである。]
(A’) EV0>EV1かつEV0>EV2
(B’) EC0≧EC1,EC2
[式中、EV0、EV1、EV2はそれぞれホスト材料、第一のドーパント、第二のドーパントの価電子レベル、EC0、EC1、EC2はそれぞれホスト材料、第一のドーパント、第二のドーパントの伝導レベルである。]
前記有機発光層が電子輸送性のホスト材料および、少なくとも第1のゲスト材料および第2のゲスト材料を含み、前記第1および第2のゲスト材料はいずれも青色ないし青緑色領域に発光ピークを有しており、
前記第1のゲスト材料は、前記ホスト材料のイオン化ポテンシャル(IPH)および電子親和力(AFH)に対し、式(1)
IPH≦IPG1、かつAFH<AFG1 (1)
の関係を満たすイオン化ポテンシャル(IPG1)および電子親和力(AFG1)を有することを特徴とする。
有機EL層は、少なくとも有機発光層を含み、必要に応じて正孔注入層、正孔輸送層、電子輸送層および/または電子注入層を介在させた構造を有する。具体的には、有機EL層は下記のような層構造からなるものが採用される。なお、下記には陽極、陰極をも含めて示しているが、有機EL層は陽極と陰極の間に存在する層である。また、陽極および陰極は、反射電極または透明電極のいずれかである。
(2)陽極/正孔注入層/有機発光層/陰極
(3)陽極/有機発光層/電子注入層/陰極
(4)陽極/正孔注入層/有機発光層/電子注入層/陰極
(5)陽極/正孔輸送層/有機発光層/電子注入層/陰極
(6)陽極/正孔注入層/正孔輸送層/有機発光層/電子注入層/陰極
(7)陽極/正孔注入層/正孔輸送層/有機発光層/電子輸送層/電子注入層/陰極
本発明の一対の電極のうち、可視光透過性を有する電極を透明電極と称する。透明電極は、ITO(インジウム-錫酸化物)、酸化スズ、酸化インジウム、IZO(インジウム-亜鉛酸化物)、IWO(インジウム-タングステン酸化物)、酸化亜鉛、亜鉛-アルミニウム酸化物、亜鉛-ガリウム酸化物、またはこれらの酸化物に対してF、Sbなどのドーパントを添加した導電性透明金属酸化物を用いて形成することができる。透明電極は、蒸着法、スパッタ法または化学気相堆積(CVD)法を用いて形成できる。
本発明における有機発光素子の正孔注入層に用いることのできる材料は、トリアリールアミン部分構造、カルバゾール部分構造、またはオキサジアゾール部分構造を有する材料など、一般に有機EL素子または有機TFT素子で用いられている正孔輸送材料を含む。
本発明における有機EL素子の正孔輸送層に用いることのできる材料としては、前記正孔注入層で例示したような、有機EL素子または有機TFTの正孔輸送材料に使用される公知のものの中から任意のものを選択して用いることができる。
本発明において有機発光層は、電子輸送性のホスト材料と、少なくとも第1のゲスト材料、および第2のゲスト材料を含む。第1のゲスト材料は、ホスト材料のイオン化ポテンシャル(IPH)、および電子親和力(AFH)、に対し、式(1)の関係を満たすイオン化ポテンシャル(IPG1)、および電子親和力(AFG1)を有する。
IPH≦IPG1、かつAFH<AFG1 (1)
EGH>EGG1 (2)
IPH≧IPG2、AFH≧AFG2、かつEGH>EGG2(3)
本発明において、電子輸送層は任意選択的に設けてもよい層である。電子輸送層は、2-(4-ビフェニリル)-5-(4-t-ブチルフェニル)-1,3,4-オキサジアゾール(PBD)、1,3,5-トリス(4-t-ブチルフェニル-1,3,4-オキサジアゾリル)ベンゼン(TPOB)のようなオキサジアゾール誘導体;3-フェニル-4-(1’-ナフチル)-5-フェニル-1,2,4-トリアゾール(TAZ)のようなトリアゾール誘導体;トリアジン誘導体;フェニルキノキサリン類;5,5’-ビス(ジメシチルボリル)-2,2’-ビチオフェン(BMB-2T)、5,5’-ビス(ジメシチルボリル)-2,2’:5’2’-ターチオフェン(BMB-3T)のようなチオフェン誘導体;アルミニウムトリス(8-キノリノラート)(Alq3)のようなアルミニウム錯体;4,7-ジフェニル-1,10-フェナントロリン(BPhen)、2,9-ジメチル-4,7-ジフェニル-1,10-フェナントロリン(BCP)のようなフェナントロリン誘導体;あるいは2,5-ジ-(3-ビフェニル)-1,1,-ジメチル-3,4-ジフェニルシラシクロペンタジエン(PPSPP)、1,2-ビス(1-メチル-2,3,4,5-テトラフェニルシラシクロペンタジエニル)エタン(2PSP)、2,5-ビス-(2,2-ビピリジン-6-イル)-1,1-ジメチル-3、4-ジフェニルシラシクロペンタジエン(PyPySPyPy)のようなシロール誘導体、1,3,5-トリス(N-フェニルベンジイミダゾル-2-イル)ベンゼン(TPBI)などのイミダゾール化合物などを用いて形成することができる。電子輸送層は、蒸着法などの当該技術分野において知られている任意の方法を用いて形成することができる。
本発明において、電子注入層は、陰極と電子輸送層との間または陰極と発光層との間に任意選択的に設けてもよい層であり、絶縁体または半導体で形成することができる。電子注入層は、陰極から発光層に至る電子の移動を促進する点において有効である。
金属電極は、高反射率の金属(Al、Ag、Mo、W、Ni、Crなど)、アモルファス合金(NiP、NiB、CrP、CrBなど)、あるいは微結晶性合金(NiAlなど)を用いて形成することができる。金属電極は、蒸着法、スパッタ法などのドライプロセスによって形成することができる。
(実施例1)
<透明電極の作製>
ガラス基板(縦50mm×横50mm×厚さ0.7mm;コーニング製イーグル2000ガラス)上に、ITOをDCマグネトロンスパッタ法にて、設定基板温度200℃にて、膜厚180nmとなるよう成膜し、いわゆるフォトリソグラフ法にて、線幅2mmの電極パターンを形成した。
UV/O3洗浄装置UV-1(サムコ株式会社)を用いて、透明電極パターン表面を洗浄後、透明電極付きガラス基板を抵抗加熱蒸着装置内に装着し、正孔注入層、正孔輸送層、有機発光層、および電子注入層を、真空を破らずに順次成膜した。
有機発光層形成時のAlm23q3の蒸着速度を、0.006Å/sとした点を除いて、実施例1と同様にして青色有機発光素子を得た。このとき、有機発光層の構成比率は、DPAVBiが2.9体積%(2.4質量%)、Alm23q3は0.3体積%(0.3質量%)であった。
有機発光層形成時のAlm23q3の蒸着速度を、0.01Å/sとした点を除いて、実施例1と同様にして青色有機発光素子を得た。このとき、有機発光層の構成比率は、DPAVBiが2.9体積%(2.4質量%)、Alm23q3は0.5体積%(0.5質量%)であった。
有機発光層形成時にAlm23q3を使用しなかった点を除いて、実施例1と同一の方法にて有機発光素子を形成した。
有機発光層形成時にAlm23q3の代わりにDSA-ph(IPG1=5.4eV、AFG1=2.7eV)を用いた点を除いて、実施例1と同一の方法にて有機発光素子を形成した。
有機発光層形成時にAlm23q3の蒸着速度を0.06Å/sとし、DPAVBiを用いなかった点を除いて、実施例1と同一の方法にて有機発光素子を形成した。
各実施例、比較例で作製した有機発光素子の電圧、電流、輝度特性を評価した。電流密度10mA/cm2の時の特性を表1に示す。
Claims (4)
- 少なくとも一方が可視光透過性を有する一対の電極と、該一対の電極間に配置された少なくとも有機発光層を含む有機EL層からなり、前記一対の電極間に電圧を印加することにより発光する有機発光素子であって、
前記有機発光層が電子輸送性のホスト材料および、少なくとも第1のゲスト材料および第2のゲスト材料を含み、前記第1および第2のゲスト材料はいずれも青色ないし青緑色領域に発光ピークを有しており、
前記第1のゲスト材料は、前記ホスト材料のイオン化ポテンシャル(IPH)および電子親和力(AFH)に対し、式(1)
IPH≦IPG1、かつAFH<AFG1 (1)
の関係を満たすイオン化ポテンシャル(IPG1)および電子親和力(AFG1)を有することを特徴とする有機発光素子。 - 前記第1のゲスト材料の光学バンドギャップ(EGG1)と、前記ホスト材料の光学バンドギャップ(EGH)が、下記式(2)
EGH>EGG1 (2)
の関係を満たすことを特徴とする請求項1に記載の有機発光素子。 - 前記第2のゲスト材料が、下記式(3)
IPH≧IPG2、AFH≧AFG2、かつEGH>EGG2(3)
の関係を満たすイオン化ポテンシャル(IPG2)、電子親和力(AFG2)およびバンドギャップ(EGG2)を有することを特徴とする請求項1または2に記載の有機発光素子。 - 前記第1のゲスト材料の添加濃度が、0.5質量%未満であることを特徴とする請求項1または2に記載の有機発光素子。
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WO2021010425A1 (en) | 2019-07-16 | 2021-01-21 | Ricoh Company, Ltd. | Solar cell module, electronic device, and power supply module |
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US8525159B2 (en) | 2013-09-03 |
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