Classifications

• • 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
• • 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
• • 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
  • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
  • H10K85/626—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• • 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
  • C09K2211/00—Chemical nature of organic luminescent or tenebrescent compounds
  • C09K2211/10—Non-macromolecular compounds
  • C09K2211/1003—Carbocyclic compounds
• • 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
  • C09K2211/00—Chemical nature of organic luminescent or tenebrescent compounds
  • C09K2211/10—Non-macromolecular compounds
  • C09K2211/1018—Heterocyclic compounds
  • C09K2211/1025—Heterocyclic compounds characterised by ligands
  • C09K2211/1029—Heterocyclic compounds characterised by ligands containing one nitrogen atom as the heteroatom
• • 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
  • C09K2211/00—Chemical nature of organic luminescent or tenebrescent compounds
  • C09K2211/18—Metal complexes
• • 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
  • C09K2211/00—Chemical nature of organic luminescent or tenebrescent compounds
  • C09K2211/18—Metal complexes
  • C09K2211/185—Metal complexes of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• • 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
  • H10K2101/10—Triplet emission
• • 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
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/115—Polyfluorene; Derivatives thereof
• • 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
  • H10K85/341—Transition metal complexes, e.g. Ru(II)polypyridine complexes
  • H10K85/342—Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising iridium
• • 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
  • H10K85/631—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
  • H10K85/633—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• • 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
  • H10K85/631—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
  • H10K85/636—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine comprising heteroaromatic hydrocarbons as substituents on the nitrogen atom

Definitions

• the present invention relates to a light- emitting device using an organic compound.
• the present invention relates to an organic electroluminescent device (organic EL device) .
• Figs. IA and IB each show the basic structure of the device. As shown in Figs. IA and IB, the organic EL device is generally composed of a plurality of organic layers interposed between a transparent electrode 5 on a transparent substrate 6 and a metal electrode 1.
• the organic layers are composed of an electron-transporting layer 2, a light-emitting layer 3, and a hole-transporting layer 4.
• ITO having a large work function is used for the transparent electrode 5 to provide good property of injecting a hole from the transparent electrode 5 to the hole-transporting layer 4.
• a metal material having a small work function such as aluminum, magnesium, or an alloy- thereof is used for the metal electrode 1 to provide good property of injecting electrons to the organic layers.
• Those electrodes each have a thickness in the range of 50 to 200 nm.
• an aluminum-quinolinol complex (typified by Alq3 shown below) having electron- transporting and light-emitting properties is used for the light-emitting layer 3.
• a material having electron-donating property such as a biphenyl diamine derivative (typified by ⁇ -NPD shown below) is used for the hole-transporting layer 4.
• An oxadiazole. derivative or the like can be used for the electron-transporting layer 2.
• Fluorescence upon transition of a singlet exciton of a molecule as a light-emitting center to a ground state has been heretofore taken as light emission generally used in an organic EL device.
• a device utilizing not fluorescent emission via a singlet ⁇ exciton but phosphorescence via a triplet exciton has been under investigation ("Improved energy transfer in electrophosphorescent device” (D. F. O'Brien et al• , Applied Physics Letters VoI 74, No 3, p 422 (1999)) and "Very high- efficiency green organic light-emitting devices basd on electrophosphorescence" (M. A.
• a four-layer structure composed of organic layers shown in Fig. IB is mainly used.
• the four-layer structure is composed of the hole-transporting layer 4, the light-emitting layer 3, an exciton diffusion blocking layer 7, and the electron-transporting layer 2 in this order from the side of an anode.
• the materials used are the following carrier-transporting materials and phosphorescent materials. Abbreviations of the respective materials are as follows.
• AIq 3 aluminum-quinolinol complex ⁇ -NPD: N4,N4'-Di-naphthalen-l-yl-N4,N4'-diphenyl- biphenyl-4, 4'-diamine
• CBP 4,4'-N,N'-dicarbazole-biphenyl
• a phosphorescent material has been attracting considerable attention because it is expected to provide high emission efficiency on principle.
• the reason for this is that excitons generated by carrier recombination are composed of singlet excitons and triplet excitons, and the ratio between the number of singlet excitons and the number of triplet excitons is 1 : 3.
• An organic EL device utilizing a singlet has taken fluorescence upon transition from a singlet exciton to a ground state as light emission.
• the luminescence yield of the device was 25% of the number of generated excitons, and the value was an upper limit on principle.
• an yield at least 3 times as high as that of the above yield is expected on principle.
• an organic EL device utilizing phosphorescence the organic EL device using, as a light-emitting material, a phosphorescent compound containing a halogen atom in its molecular structure, involves a problem in that the organic EL device has an extremely short device lifetime, although the reason by which such problem occurs is unclear.
• An object of the present invention is to provide an organic EL device utilizing phosphorescence which can be driven at a low voltage, which realizes high luminance and high efficiency, and which has a long lifetime.
• the inventors of the present invention have made extensive studies to achieve the above object, thus completing the present invention.
• a light-emitting device including: an anode, a cathode, and an organic light- emitting layer interposed between the anode and the cathode, wherein the organic light-emitting layer is composed of a host material and at least one kind of dopants, the at least one kind of the dopants is a phosphorescent compound containing a halogen atom, and the host material is a linear aromatic compound having no aromatic substituent at a side thereof.
• an organic electroluminescent device using, as a light-emitting material, a phosphorescent compound containing a 1 halogen atom, which realizes a low threshold voltage and a long lifetime.
• Figs. IA and IB are views each showing an example of a light-emitting device, of the present invention.
• the light-emitting device of the present invention includes an anode, a cathode, and an organic light-emitting layer interposed between the anode and the cathode.
• the layer structure of the light-emitting device is not particularly limited, and examples thereof include such structures as shown in Figs. IA and IB.
• a method of producing the light- emitting device is not limited to vacuum evaporation, and may be a wet method typified by coating.
• the light-emitting device of the present invention has an organic light-emitting layer composed of a host material and at least one kind of dopant.
• the at least one kind of dopant to be incorporated into the host material is a phosphorescent compound containing a halogen atom.
• the phosphorescent compound is preferably an iridium complex containing a halogen atom, or more preferably an iridium complex having one or more ligands each having a 1-phenylisoquinoline skeleton with at least one halogen atom as a substituent. Examples of the phosphorescent compound containing a halogen atom to be used in the present invention are shown below.
• a dopant concentration is not particularly- limited, but is preferably 50 wt% or less, or more preferably 5 to 20 wt%.
• the phosphorescent compound to serve as a dopant in the present invention has a halogen atom.
• a halogen atom (especially a fluorine atom) is introduced as a substituent into the phosphorescent compound for the purpose of improving at least one of the ease of ' controlling an emission wavelength, the suppression of concentration quenching, the ease of vapor deposition, and the like.
• a phosphorescent compound (more specifically an iridium complex) having such a substituent may involve problems of a reduction in current conductivity, difficulties in reducing a drive voltage and a threshold voltage, and an extremely short device lifetime.
• an iridium complex containing fluorine having extremely high electronegativity may serve as a trap even when it becomes a charge carrier, to thereby reduce charge conductivity.
• a charge balance in a light-emitting layer may be lost to cause a sudden reduction in efficiency.
• a complex having a chlorine atom or a bromine atom in its molecular skeleton is expected to have lower electrical stability than that of one having a fluorine atom in its molecular skeleton because the chlorine atom or the bromine atom is more weakly bonded than the fluorine atom.
• driving at a constant current may cause a sudden reduction in efficiency to thereby additionally shorten a lifetime.
• Charge injected into a light-emitting layer may be recombined on a dopant (direction excitation type) or on a host (indirect excitation type) .
• the two processes are expected to occur at a certain ratio in the light-emitting layer.
• 100% of the charge is recombined on the dopant (direct excitation) .
• the dopant has only to cause smooth energy transfer even when the charge is recombined on the host (indirect excitation) .
• it is disadvantageous to use an electrically unstable dopant because the dopant temporarily becomes a charge carrier.
• the time period during which the dopant itself serves as a charge carrier is expected to be shorter.
• a device in the case where a dopant having low electrical stability is used, a device will be allowed to emit light for a long time period if a host material capable of realizing Foerster-type or Dexter-type energy transfer with ease or with high efficiency can be provided.
• the case where a dopant having low electrical stability is used refers to the case where a dopant unstable in a cation state or an anion state is used.
• a linear aromatic compound having no aromatic substituent at a side thereof is used as a host material to allow a device containing, as a dopant for a light-emitting layer, a phosphorescent compound containing a halogen atom to be driven at a low voltage, and provide the device with a long lifetime.
• the linear aromatic compound is a compound having a plurality of aromatic units bonded mutually, and is a compound whose main skeleton can be said to have a molecular major axis.
• the linear aromatic compound is not necessarily- composed of the same kind of aromatic units and may be composed of different kinds of aromatic units bonded mutually.
• the aromatic units include a phenyl ring, a carbazole ring, and the like.
• side in the linear aromatic compound means a direction intersecting the molecular major axis. If the aromatic units are phenyl rings and are bonded at 1- and 4-positions to another aromatic unit, respectively, the intersecting direction is a direction of any one of 2-, 3-, 5-, and 6-positions. Therefore, in the case where the aromatic units in the linear aromatic compound are phenyl rings, the phrase "having no aromatic substituent at a side” means that there is no aromatic substituent at 2-, 3-, 5-, and 6-positions of the phenyl ring.
• the intersecting direction is a direction of any one of 1-, 4-, 5-, 8-, and 9-positions. Therefore, in the case where the aromatic units in the linear aromatic compound are fluorene rings, the phrase "having no aromatic substituent at a side" means that there is no aromatic substituent at 1-, 4-, 5-, 8-, and 9- positions of the fluorene ring. In the case where the aromatic units in the linear aromatic compound are fluorene rings, the aromatic units are preferably bonded at 2- and 7-positions to another aromatic unit, respectively.
• Examples of an aromatic substituent not present in a side of the linear aromatic compound of the present invention include a phenyl ring.
• the examples further include aromatic groups having a fused ring, such as a carbazole ring, an anthracene ring and a fluorene ring.
• the linear aromatic compound of the present invention preferably has 3 or more fluorene rings constituting a major axis thereof.
• the number of fluorene rings is more preferably 3 to 5. Still more preferably, the linear aromatic compound has 4 or 5 fluorene rings as a main skeleton.
• a linear aromatic compound having 3 or more fluorene rings does not mean a high-molecular-weight compound.
• a high-molecular-weight compound is not preferable because it is difficult to remove impurities to be produced at the time of, for example, the synthesis of the compound and the removal of the impurities may be incomplete.
• the linear aromatic compound of the present invention is a compound having a single molecular weight with no molecular weight distribution.
• the linear aromatic compound of the present invention preferably has a glass transition temperature (Tg) of 120 0 C or higher.
• Tg glass transition temperature
• a linear aromatic compound having a single molecular weight without an aromatic substituent at a side thereof and having a molecular major axis composed only of a fluorene ring can exhibit a high glass transition temperature (Tg) of 120 0 C or higher.
• linear aromatic compound of the present invention will be shown below; provided, however, that the present invention is not limited to the examples.
• the light-emitting device with high efficiency according to the present invention can be applied to products requiring energy savings and high luminance.
• Applied examples of the light-emitting device include light sources for a display apparatus, a lighting system and a printer; and a backlight for a liquid crystal display apparatus.
• a flat panel display having energy savings, high visibility, and lightweight can be achieved when the device of the present invention is applied to a display apparatus.
• a light source for a printer a laser light source portion of a laser beam printer currently in active use can be replaced with the light-emitting device of the present invention.
• Devices that can be independently addressed are arranged on an array and desired exposure is carried out on a photosensitive drum, whereby an image is formed.
• the use of the device of the present invention significantly reduces an apparatus volume.
• An energy saving effect of the present invention is expected to be exerted on a lighting system or a backlight.
• a light-emitting device having 3 organic layers shown in Fig. IA was used as a device structure.
• ITO transparent electrode 5 having a thickness of 100 nm was patterned onto a glass substrate (transparent substrate 6) to have an opposing electrode area of 3 mm 2 .
• the following organic layers and electrode layers were continuously formed onto the ITO substrate by vacuum deposition by using resistance heating in a vacuum chamber at 10 ⁇ 5
• Hole-transporting layer 4 (20 nm) : FL03
• Light-emitting layer 3 (30 nm) : [host] Compound 2
• Electron-transporting layer 2 (45 nm) : Bphen
• Metal electrode layer 1 (1 nm) : KF Metal electrode layer 1 (100 nm) : Al
• Light-emitting devices were produced in the same manner as in Example 1 except that a host material for a light-emitting layer was changed to a host material shown in Table 1.
• Example 1 has a device lifetime 55 to 550 times the device lifetimes of the devices of Comparative Examples 1 to
• a threshold voltage can be lowered, and a device lifetime can be lengthened, by doping a linear aromatic compound having a single molecular weight without an aromatic side substituent with an iridium complex containing a fluorine atom.
• Example 2 and Comparative Example 5
• a light-emitting device was produced in the same manner as in Example 1 except that a host material and a dopant for a light-emitting layer were changed to those shown in Table 1.
• Example 5 was 0.05 hr.
• the luminance half hour in Example 2 was 0.3 hr, which is 60 times as high as that of Comparative Example 5.
• the current density used here was 100 mA/cm 2 , which is about 25 times as high as a current density to be generally used.
• Ir(4Clpiq)3 used was an unsublimated purified product, The device lifetime is susceptible to improvement because impurities greatly affecting the device lifetime cannot be completely removed from the product.
• the threshold voltage in Example 2 was found to be lower than that in Comparative Example 5 by 0.8 V.
• a light-emitting device was produced in the same manner as in Example 1 except that a dopant for a light-emitting layer was changed to that shown in Table 1.
• an assist doping device (assist compound: Ir(bq) 3 ) obtained by doping a linear aromatic compound having a single molecular weight without an aromatic side substituent with an iridium complex containing a fluorine atom had an excellent effect on the device lifetime and threshold voltage.
• the assist compound used herein is a compound which is added to an organic EL device for the purpose of promoting the energy transfer from a host to a dopant, adjusting an amount of carriers such as holes or electrons in the light-emitting layer.
• An organic EL device containing the assist compound is herein referred to as an assist doping device.
• a light-emitting device structure used in Example 4 was as follows. Hole-transporting layer (40 nm) : FL03 Light-emitting layer (20 nm) : Compound 21 + Ir(46Fppy) 3 8 wt% Electron-transporting layer (20 nm) : Bphen Metal electrode layer (1 nm) : KF Metal electrode layer (100 nm) : Al
• the device of this example had an efficiency of 6.2 cd/A (200 cd/rn 2 ) and an emission wavelength of 460 nm. When continuous energization was performed on the device, stable light emission was observed.
• a light-emitting device structure used in Example 5 is as follows.
• Hole-transporting layer (40 nm) FL03
• Light-emitting layer (25 nm) Compound 23 + Ir(4 , F5mpiq) 3 14 wt%
• Electron-transporting layer 50 nm
• Bphen Metal electrode layer (1 nm) : KF
• the device of this example had an efficiency of 15.8 cd/A, 13.6 lm/W (600 cd/m 2 ) and an emission wavelength of 605 nm. In addition, the device showed a luminance half hour (hr) of 500 hr and a threshold voltage of 2.8 V when driven at a constant current (100 mA/cm 2 ) .
• Synthesis Example 3 Synthesis of Exemplified Compound 25
• a light-emitting device was produced in the same manner as in Example 5 except that the host material used for Example 5 was changed from Compound 23 to Compound 25.
• a light-emitting device was produced in.the same manner as in Example 5 except that the host material used for Example 5 was changed from Compound 23 to Compound 26.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Optics & Photonics (AREA)
• Electroluminescent Light Sources (AREA)

Priority Applications (2)

Applications Claiming Priority (4)

Publications (1)

Family

ID=36118789

Family Applications (1)

Country Status (4)

Families Citing this family (15)

Citations (7)

Family Cites Families (15)

• 2005
  • 2005-08-12 JP JP2005234233A patent/JP2006128624A/ja not_active Withdrawn
  • 2005-09-14 US US11/570,191 patent/US7914907B2/en not_active Expired - Fee Related
  • 2005-09-14 WO PCT/JP2005/017325 patent/WO2006035640A1/en not_active Ceased
  • 2005-09-14 EP EP05785874A patent/EP1787338A4/en not_active Withdrawn

Patent Citations (7)

Non-Patent Citations (3)

Also Published As

Similar Documents

Legal Events