WO2017002893A1 - Organic electroluminescent element - Google Patents

Organic electroluminescent element Download PDF

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Publication number
WO2017002893A1
WO2017002893A1 PCT/JP2016/069373 JP2016069373W WO2017002893A1 WO 2017002893 A1 WO2017002893 A1 WO 2017002893A1 JP 2016069373 W JP2016069373 W JP 2016069373W WO 2017002893 A1 WO2017002893 A1 WO 2017002893A1
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layer
organic electroluminescence
light emitting
organic
electroluminescence device
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PCT/JP2016/069373
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French (fr)
Japanese (ja)
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ピン クエン ダニエル ザン
安達 千波矢
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国立大学法人九州大学
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Priority claimed from JP2016001879A external-priority patent/JP6769712B2/en
Application filed by 国立大学法人九州大学 filed Critical 国立大学法人九州大学
Priority to EP16818001.6A priority Critical patent/EP3319140A4/en
Priority to US15/740,145 priority patent/US11101440B2/en
Priority to CN201680038144.3A priority patent/CN107710442B/en
Priority to KR1020187003138A priority patent/KR102339891B1/en
Publication of WO2017002893A1 publication Critical patent/WO2017002893A1/en

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    • HELECTRICITY
    • H10SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14Carrier transporting layers
    • H10K50/16Electron transporting layers
    • HELECTRICITY
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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    • H10K50/00Organic light-emitting devices
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/12OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
    • HELECTRICITY
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14Carrier transporting layers
    • H10K50/15Hole transporting layers
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/17Carrier injection layers
    • H10K50/171Electron injection layers
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/18Carrier blocking layers
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/80Constructional details
    • H10K50/805Electrodes
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    • H10K50/00Organic light-emitting devices
    • H10K50/80Constructional details
    • H10K50/805Electrodes
    • H10K50/82Cathodes
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    • H10K71/00Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/70Testing, e.g. accelerated lifetime tests
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30Coordination compounds
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    • H10K85/00Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60Organic compounds having low molecular weight
    • H10K85/649Aromatic compounds comprising a hetero atom
    • H10K85/654Aromatic compounds comprising a hetero atom comprising only nitrogen as heteroatom
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    • H10K2101/00Properties of the organic materials covered by group H10K85/00
    • H10K2101/10Triplet emission
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    • H10K2101/00Properties of the organic materials covered by group H10K85/00
    • H10K2101/90Multiple hosts in the emissive layer
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    • H10KORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00Organic light-emitting devices
    • H10K50/10OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14Carrier transporting layers
    • H10K50/16Electron transporting layers
    • H10K50/166Electron transporting layers comprising a multilayered structure
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    • H10K85/00Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30Coordination compounds
    • H10K85/341Transition metal complexes, e.g. Ru(II)polypyridine complexes
    • H10K85/342Transition metal complexes, e.g. Ru(II)polypyridine complexes comprising iridium

Definitions

  • the present invention relates to an organic electroluminescence element, and more particularly to extending the life of an organic electroluminescence element.
  • organic light-emitting devices such as organic electroluminescence devices (organic EL devices).
  • organic EL devices organic electroluminescence devices
  • various attempts have been made to enhance the performance of organic electroluminescent elements by using various functional layers that promote injection and movement of charges from the electrodes in combination with the light emitting layer.
  • organometallic complexes containing a group 1 atom such as Liq (8-hydroxyquinolinolato-lithium) as a material for a functional layer can also be found.
  • Patent Document 1 a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer are formed in this order on a glass substrate (ITO glass substrate) on which indium tin oxide (ITO) is formed.
  • ITO glass substrate indium tin oxide
  • an organic EL element was manufactured by depositing Liq on the electron transport layer to form an electron injection layer and then depositing Al on the layer to form an electrode.
  • Patent Document 2 a hole transport layer and a light emitting layer are sequentially formed on an ITO glass substrate, and then Liq is vapor-deposited on the light emitting layer to form an electron injection layer. It describes that an organic EL element was manufactured by evaporating Al.
  • the organic EL device manufactured in Patent Document 1 has a Liq layer formed at the interface between the electron transport layer and the cathode
  • the organic EL device manufactured in Patent Document 2 has a light emitting layer and a cathode.
  • a Liq layer is formed at the interface.
  • the LIq layer is provided as the electron injection layer.
  • the present inventors provided a Liq layer at a site other than the position in contact with the cathode, and comprehensively studied to evaluate the performance of the organic electroluminescence device.
  • the present inventors have further studied the layer provided at the interface between the light emitting layer and the electron transport layer, and the deterioration of performance over time during driving can be suppressed, and a long-life organic electroluminescence element can be obtained.
  • the present inventors mainly cause the deterioration in performance over time that occurs when driving an organic electroluminescence element due to accumulation of charges in deep trap levels inside the element.
  • the deterioration of performance over time during device driving is effectively suppressed, and the organic electroluminescence device is notable. It has been found that a long life can be achieved.
  • the present invention has been proposed based on these findings, and specifically has the following configuration.
  • An organic electroluminescence device having a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and having a charge trap concentration decreasing layer at the interface between the light emitting layer and the electron transport layer.
  • An organic electroluminescence device characterized.
  • the charge trap concentration-decreasing layer contains a first group atom, second group atom or transition metal atom.
  • a second electron transport layer is provided on the cathode side of the electron transport layer, and a first group atom, second group atom or transition metal atom is provided between the electron transport layer and the second electron transport layer.
  • the organic electroluminescence device according to any one of [1] to [6], which has a functional layer containing.
  • the organic electroluminescence device according to any one of [7] to [10], wherein the second electron transport layer does not contain a metal atom.
  • Ar 1 , Ar 2 and Ar 3 each independently represent a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.
  • R 1 , R 2 and R 3 each independently represent a substituent, and the substituent is not a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.
  • n1, n2 and n3 each independently represents an integer of 1 to 5.
  • n11, n12 and n13 each independently represents an integer of 0 to 4.
  • the organic electroluminescence device of the present invention by having the charge trap concentration-decreasing layer at the interface between the light emitting layer and the electron transport layer, deterioration of performance over time during driving can be suppressed, and the lifetime can be greatly extended. be able to.
  • 3 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescence element having a charge trap concentration-decreasing layer and an organic electroluminescence element not having a charge trap concentration-decreasing layer of Example 1.
  • 4 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer of Example 1.
  • 3 is a graph showing the change over time in the luminance ratio and voltage change amount of the organic electroluminescence element having the charge trap concentration reduction layer of Example 1 and the organic electroluminescence element not having the charge trap concentration reduction layer.
  • An organic electroluminescence device having a 1 nm-thick charge trap concentration-reducing layer and a functional layer having various thicknesses an organic electroluminescence device having a 1-nm-thick charge trap concentration-reducing layer and no functional layer, and charge It is an emission spectrum of the organic electroluminescent element which does not have a trap density
  • Organic electroluminescence device having 1 nm-thick charge trap concentration reducing layer and functional layer having various thicknesses organic electroluminescence device having 1 nm-thick charge trap concentration reducing layer and no functional layer, and charge trap concentration reducing layer It is a graph which shows the time-dependent change of the luminance ratio and voltage variation
  • An organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and a functional layer having various thicknesses of Example 2 an organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and having no functional layer, It is a graph which shows the voltage-current density-luminance characteristic of the organic electroluminescent element which does not have a trap density
  • An organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and a functional layer having various thicknesses of Example 2 an organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and having no functional layer, It is a graph which shows a time-dependent change of the luminance ratio and voltage variation
  • 6 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescent element having an Alq3 layer of various thicknesses of Comparative Example 2 and an organic electroluminescent element not having an Alq3 layer.
  • 5 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having an Alq3 layer of various thicknesses in Comparative Example 2. Changes in luminance ratio and voltage change over time of the organic electroluminescence element having the Alq3 layer of Comparative Example 2, the organic electroluminescence element having the Liq layer, and the organic electroluminescence element having neither the Alq3 layer nor the Liq layer It is a graph to show.
  • FIG. 6 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having the charge trap concentration-decreasing layer of Example 3 and the light emitting layer containing T2T (second host material). It is a graph which shows a time-dependent change of the luminance ratio and voltage change amount of the organic electroluminescent element which has a charge trap density
  • the voltage-current density-luminance characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 4, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show.
  • the current density-external quantum efficiency characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 4, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show.
  • FIG. 10 is a diagram showing an energy diagram of an organic electroluminescence device having a charge trap concentration-decreasing layer of Example 5 and a second electron transport layer containing Liq, and a light emitting layer having a multilayer structure, and multilayer structures A to D. It is an emission spectrum of the organic electroluminescent element which has the charge trap density
  • FIG. 10 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer and a second electron transport layer containing Liq in Example 5 and a light-emitting layer having a multilayer structure.
  • 6 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer and a second electron transport layer containing Liq of Example 5 and having a light-emitting layer having a multilayer structure.
  • the current density-external quantum efficiency characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 6, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show.
  • Time course of luminance ratio and voltage change amount of organic electroluminescence device having charge trap concentration decreasing layer of Example 6, light emitting layer containing T2T (second host material), and second electron transporting layer containing Liq It is a graph which shows a change.
  • a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
  • the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be 1 H, or a part or all of them are 2 H. (Deuterium D) may be used.
  • the organic electroluminescence device of the present invention has a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and has a charge trap concentration reducing layer at the interface between the light emitting layer and the electron transport layer.
  • the “charge trap concentration-decreasing layer” means a layer in which the peak area between 250 and 320 K in the thermally stimulated current (TSC) measurement is reduced by forming the layer.
  • TSC thermally stimulated current
  • an organic electroluminescence element having a charge trap concentration-decreasing layer is referred to as a “target element”, and an organic electroluminescence element having the same configuration as that of the target element except that it does not have a charge trap concentration-decreasing layer is referred to as a “reference element”.
  • a target element an organic electroluminescence element having the same configuration as that of the target element except that it does not have a charge trap concentration-decreasing layer.
  • Thermally stimulated current measurement is a measurement in which a charge trapped in a localized level of an organic semiconductor thin film is released by heat and detected as a current value to obtain a TSC profile (temperature profile of current value).
  • the depth of the localized level can be determined from the temperature of the peak of the TSC profile, and the charge concentration at the localized level can be estimated from the peak area of the peak.
  • the charge includes both a negative charge due to electrons and a positive charge due to holes.
  • the thermal stimulation current measurement in the present invention is performed as follows.
  • the organic electroluminescence element to be measured is cooled to the liquid nitrogen temperature (77 K) in the vacuum chamber.
  • a bias current of 2 mA / cm 2 is supplied to the organic electroluminescence element for 2 minutes to accumulate charges in the trap level inside the element.
  • the temperature is increased at a rate of 5 ° C./min while applying a collecting voltage of ⁇ 0.01 V to the organic electroluminescence element, and the current detected at that time is observed to obtain a TSC profile.
  • Such thermal stimulation current measurement can be performed using a thermal stimulation current measuring machine (trade name TSC-FETT EL2000) manufactured by Rigaku Corporation. Then, in the obtained TSC profile, the peak area of the peak appearing between 250 and 320K is measured.
  • the number of peaks appearing between 250 and 320K may be one or plural.
  • the sum of the peak areas of the peaks corresponds to the above-mentioned “peak area between 250 and 320K”.
  • FIG. 1 A typical example of a TSC profile measured with an organic electroluminescence device is shown in FIG.
  • the TSC profile shown in FIG. 1 is an example, and the TSC profile observed in the organic electroluminescence element of the present invention is not limited to the one shown in FIG.
  • “target element” represents an organic electroluminescence element in which a Liq layer is formed as a charge trap concentration reduction layer
  • “reference element” is manufactured in the same manner as the target element except that a charge trap concentration reduction layer is not formed.
  • the TSC profiles of the target element and the reference element each have one peak in the low temperature region near 105K and in the high temperature region of 250 to 320K.
  • the peak in the low temperature region corresponds to the discharge of the charge accumulated in the shallow trap level
  • the peak in the high temperature region corresponds to the discharge of the charge accumulated in the deep trap level
  • the peak area of each peak reflects the concentration of charge accumulated in each trap level.
  • the peak intensity in the high temperature region of the target element is significantly reduced as compared with that of the reference element, and the peak area is 1 of the peak area of the reference element. /1.41. This means that the charge concentration in the deep trap level is decreased by the charge trap concentration decreasing layer.
  • the “charge trap concentration reducing layer” in the present invention is a material layer provided at the interface between the light emitting layer and the electron transport layer, and the peak area in the high temperature region (250 to 320 K) of the TSC profile thus obtained is referred to.
  • the target element is smaller than the element.
  • Such a charge trap concentration reducing layer effectively suppresses the formation of deep trap levels inside the device and the accumulation of charges in the deep trap levels when driving the organic electroluminescence device. Conceivable. Thereby, deterioration of the EL performance with time can be suppressed, and the lifetime of the organic electroluminescence element can be significantly prolonged.
  • the organic electroluminescence device of the present invention has a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and a charge trap concentration reducing layer is provided at the interface between the light emitting layer and the electron transport layer.
  • the organic electroluminescence device of the present invention has a second electron transport layer on the cathode side of the electron transport layer, and a first group atom and a second group element between the electron transport layer and the second electron transport layer.
  • the organic electroluminescent element of the present invention has such a basic structure
  • its layer structure is not particularly limited.
  • an anode 2 and a light emitting layer 3 are formed on a substrate 1.
  • the charge trap concentration decreasing layer 4, the electron transport layer 5, and the cathode 6 are laminated in this order, or as shown in FIG. 3, the anode 2, the light emitting layer 3, the charge trap concentration decreasing layer 4 and the electrons are formed on the substrate 1.
  • stacked the transport layer 5, the functional layer 7, the 2nd electron carrying layer 8, and the cathode 6 in this order can be mentioned.
  • the organic electroluminescent element may have an organic layer having other functions in combination with the charge trap concentration reducing layer, the electron transport layer, or the functional layer.
  • organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer.
  • the hole transport layer may be a hole injection / transport layer having a hole injection function
  • the electron transport layer may be an electron injection / transport layer having an electron injection function.
  • 1 is a substrate
  • 2 is an anode
  • 9 is a hole injection layer
  • 10 is a hole transport layer
  • 3 is a light emitting layer
  • 4 is a charge trap concentration reducing layer
  • 5 is an electron transport layer
  • 6 is a cathode.
  • the organic electroluminescence device of the present invention is preferably supported on a substrate.
  • the substrate is not particularly limited and may be any substrate conventionally used for organic electroluminescence elements.
  • a substrate made of glass, transparent plastic, quartz, silicon, or the like can be used.
  • an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used.
  • electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO 2 , and ZnO.
  • conductive transparent materials such as CuI, indium tin oxide (ITO), SnO 2 , and ZnO.
  • an amorphous material such as IDIXO (In 2 O 3 —ZnO) that can form a transparent conductive film may be used.
  • a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 ⁇ m or more) ), A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.
  • wet film-forming methods such as a printing system and a coating system, can also be used.
  • the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred ⁇ / ⁇ or less.
  • the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.
  • cathode a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used.
  • electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al 2 O 3 ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like.
  • a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this for example, a magnesium / silver mixture
  • Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al 2 O 3 ) mixture, a lithium / aluminum mixture, aluminum and the like.
  • the cathode 5 can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
  • the sheet resistance as the cathode is preferably several hundred ⁇ / ⁇ or less, and the film thickness is usually selected in the range of 10 nm to 5 ⁇ m, preferably 50 to 200 nm.
  • the emission luminance is advantageously improved.
  • a transparent or semi-transparent cathode can be produced. By applying this, an element in which both the anode and the cathode are transparent is used. Can be produced.
  • the light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and the light emitting material may be used alone for the light emitting layer. , Preferably including a luminescent material and a host material.
  • the light emitting material contained in the light emitting layer may be a fluorescent light emitting material or a phosphorescent light emitting material.
  • the light emitting material may be a delayed fluorescent material that emits delayed fluorescence together with normal fluorescence. Among these, high luminous efficiency can be obtained by using the delayed fluorescent material as the light emitting material.
  • the organic electroluminescence device of the present invention In order for the organic electroluminescence device of the present invention to exhibit high luminous efficiency, it is important to confine singlet excitons and triplet excitons generated in the light emitting material in the light emitting material. Therefore, it is preferable to use a host material in addition to the light emitting material in the light emitting layer.
  • a host material an organic compound in which at least one of excited singlet energy and excited triplet energy has a value higher than that of the light-emitting material can be used.
  • singlet excitons and triplet excitons generated in the light emitting material can be confined in the molecules of the light emitting material of the present invention, and the light emission efficiency can be sufficiently extracted.
  • the organic electroluminescence device of the present invention light emission is generated from the light emitting material of the present invention contained in the light emitting layer.
  • This light emission may be any of fluorescent light emission, delayed fluorescent light emission, and phosphorescent light emission, and these light emission may be mixed.
  • light emission from the host material may be partly or partly emitted.
  • the amount of the light emitting material contained in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% by weight or less.
  • the host material in the light-emitting layer is preferably an organic compound that has a hole transporting ability and an electron transporting ability, prevents the emission of longer wavelengths, and has a high glass transition temperature.
  • a host material When a host material is used, one type of host material may be contained alone in the light emitting layer, or a combination of two or more types may be contained in the light emitting layer. When two or more types of host materials are used, it is preferable to use a combination of at least the first host material and a second host material having characteristics such as energy level and carrier transportability different from those of the first host material. Thereby, it becomes easy to control characteristics, such as the luminous efficiency and lifetime of an organic electroluminescent element. In this case, from the viewpoint of further improving the lifetime of the device, each of the first host material and the second host material has a lowest excited triplet energy level higher than the lowest excited triplet energy level of the light emitting material.
  • the difference T1 h ⁇ T1 d (hereinafter, “the lowest excited triplet energy level T1 h of at least one of the first host material and the second host material) and the lowest excited triplet energy level T1 d of the light emitting material”
  • the energy level difference ⁇ T1 is preferably greater than 0 eV, preferably 1 eV or less, more preferably 0.7 eV or less, and even more preferably 0.5 eV or less.
  • the relationship between the lowest excited singlet energy level S1 d of the light emitting material and each lowest excited singlet energy level S1 h of the first host material and the second host material is not particularly limited, but the first host material and the second host are not limited.
  • the material has a lowest excited singlet energy level S1 h that is higher than the lowest excited singlet energy level S1 d of the luminescent material.
  • S1 h the lowest excited singlet energy level
  • S1 d the lowest excited singlet energy level
  • the lowest excited singlet energy levels S1 d and S1 h and the lowest excited triplet energy levels T1 d and T1 h of the light emitting material, the first host material, and the second host material are: It is a value obtained by the following procedure.
  • S1 (S1 d , S1 h ) A sample to be measured is deposited on a Si substrate to prepare a sample, and the fluorescence spectrum of this sample is measured at room temperature (300 K). The fluorescence spectrum has light emission on the vertical axis and wavelength on the horizontal axis.
  • a tangent line is drawn with respect to the falling edge of the emission spectrum on the short wave side, and a wavelength value ⁇ edge [nm] at the intersection of the tangent line and the horizontal axis is obtained.
  • a value obtained by converting this wavelength value into an energy value by the following conversion formula is defined as S1.
  • Conversion formula: S1 [eV] 1239.85 / ⁇ edge
  • T1 d , T1 h Lowest excited triplet energy level
  • T1 d , T1 h The same sample as the singlet energy S1 is cooled to 77 [K]
  • the phosphorescence measurement sample is irradiated with excitation light (337 nm), and the phosphorescence intensity is measured using a streak camera.
  • a tangent line is drawn with respect to the rising edge of the phosphorescence spectrum on the short wavelength side, and a wavelength value ⁇ edge [nm] at the intersection of the tangent line and the horizontal axis is obtained.
  • a value obtained by converting this wavelength value into an energy value by the following conversion formula is defined as T1.
  • the maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the above-mentioned maximum value on the shortest wavelength side, and has the maximum slope value closest to the maximum value on the shortest wavelength side.
  • the tangent drawn at the point where the value is taken is taken as the tangent to the rise on the short wavelength side of the phosphorescence spectrum.
  • the second host material preferably has an electron transporting property. Thereby, electrons can be smoothly moved in the light emitting layer, performance deterioration with time can be further suppressed, and the life can be further extended.
  • a second host material it is preferable to use the same material as the constituent material of the electron transport layer adjacent to the cathode side of the charge trap concentration reducing layer.
  • the second host material preferably has a HOMO level or LUMO level significantly different from that of the first host material. Thereby, characteristics such as lifetime can be improved by controlling the recombination zone of electrons and holes.
  • the HOMO level is lower than the HOMO levels of the light-emitting material and the first host material
  • the LUMO level is higher than the LUMO level of the light-emitting material
  • the first One lower than the LUMO level of one host material can be preferably used.
  • the following compounds can be preferably used.
  • a compound represented by the following general formula (1) can be preferably used.
  • Ar represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.
  • n represents an integer of 1 to 3.
  • n is preferably 2 or more.
  • the plurality of Ars may be the same or different from each other, and are preferably the same.
  • Ar refers to the explanation and preferred embodiments of Ar 1 , Ar 2 and Ar 3 in the following general formula (2).
  • the compound represented by the general formula (1) may be a rotationally symmetric body or may not be a rotationally symmetric body.
  • the compound represented by the general formula (1) is preferably a compound represented by the following general formula (2).
  • Ar 1 , Ar 2 and Ar 3 each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.
  • Ar 1 , Ar 2 and Ar 3 may be the same or different from each other, and are preferably the same.
  • n1, n2 and n3 each independently represents an integer of 1 to 5.
  • n1, n2 and n3 are preferably 1 to 3, more preferably 1 or 2.
  • n1, n2 and n3 may be the same or different, but are preferably the same.
  • the two or more Ar 1 s may be the same or different from each other.
  • n2 is 2 or more
  • the two or more Ar 2 s are the same or different from each other.
  • n3 is 2 or more, the two or more Ar 3 s may be the same as or different from each other.
  • the aromatic ring constituting the substituted or unsubstituted aryl group that Ar 1 , Ar 2, and Ar 3 can take may be a single ring or a fused ring in which two or more aromatic rings are fused.
  • the number of carbon atoms constituting the ring skeleton of the aromatic ring is preferably 6-22, more preferably 6-18, still more preferably 6-14, and even more preferably 6-10. preferable.
  • the aromatic ring constituting the aryl group examples include a benzene ring and a naphthalene ring.
  • the heteroaromatic ring constituting the substituted or unsubstituted heteroaryl group that Ar 1 , Ar 2 and Ar 3 can take is a single ring, a fusion in which one or more heterocycles and one or more aromatic rings are fused It may be a ring or a fused ring in which two or more heterocycles are fused.
  • the ring having a bond of Ar 1 , Ar 2 and Ar 3 is a heterocyclic ring.
  • the number of atoms constituting the heterocyclic ring skeleton is preferably 5 to 22, more preferably 5 to 18, still more preferably 5 to 14, and even more preferably 5 to 10. preferable.
  • the number of carbon atoms constituting the heterocyclic ring skeleton is preferably 4 to 21, more preferably 4 to 17, still more preferably 4 to 13, and still more preferably 4 to 9. .
  • the hetero atom constituting the heterocyclic ring skeleton is preferably a nitrogen atom, an oxygen atom, or a sulfur atom, and more preferably a nitrogen atom.
  • aromatic ring constituting the heteroaryl group examples include a pyridine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a triazole ring, and a benzotriazole ring.
  • the substituent that can be substituted with the aryl group that Ar 1 , Ar 2, and Ar 3 can take, and the substituent that can be substituted with the heteroaryl group that Ar 1 , Ar 2, and Ar 3 can take are not particularly limited.
  • substituents examples include a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, and an alkyl-substituted amino group having 1 to 20 carbon atoms.
  • acyl group having 2 to 20 carbon atoms aryl group having 6 to 40 carbon atoms, aryloxy group having 6 to 40 carbon atoms, arylthio group having 6 to 40 carbon atoms, heteroaryl group having 3 to 40 carbon atoms, carbon Heteroaryloxy group having 3 to 40 carbon atoms, heteroarylthio group having 3 to 40 carbon atoms, alkenyl group having 2 to 10 carbon atoms, alkynyl group having 2 to 10 carbon atoms, alkoxycarbonyl group having 2 to 10 carbon atoms, carbon An alkylsulfonyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an amide group, an alkylamide group having 2 to 10 carbon atoms, and a trialkylsilyl group having 3 to 20 carbon atoms , Trialkylsilyl group having 4 to 20 carbon atoms, trialkylsilyl alkenyl group having 5
  • substituents are a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, carbon A substituted or unsubstituted aryloxy group having 6 to 40 carbon atoms, a substituted or unsubstituted heteroaryl group having 3 to 40 carbon atoms, a substituted or unsubstituted heteroaryloxy group having 3 to 40 carbon atoms, and 1 to 20 carbon atoms A dialkyl-substituted amino group.
  • substituents are a fluorine atom, a chlorine atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted group having 6 to 15 carbon atoms.
  • it is an unsubstituted aryl group or a substituted or unsubstituted heteroaryl group having 3 to 12 carbon atoms.
  • the number of substituents is preferably from 0 to 5, more preferably from 0 to 4.
  • R 1 , R 2 and R 3 in the general formula (2) each independently represent a substituent.
  • the substituent is not a substituted or unsubstituted aryl group and a substituted or unsubstituted heteroaryl group.
  • n11, n12 and n13 each independently represents an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1. Further, at least one of n11, n12 and n13 is preferably 0, and more preferably all.
  • the two or more R 1 s may be the same or different from each other.
  • the two or more R 2 s are the same or different from each other.
  • R 3 s When n13 is 2 or more, the two or more R 3 s may be the same as or different from each other. Moreover, (R 1 ) n11 , (R 2 ) n12 , and (R 3 ) n13 may be the same or different, but are preferably the same.
  • R 1 , R 2 and R 3 see the explanation and preferred ranges of the substituents which can be substituted on the aryl group which Ar 1 , Ar 2 and Ar 3 can take. Can do.
  • the compound represented by the general formula (2) may have a rotationally symmetric structure in which the structures at the 2nd, 4th and 6th positions of the triazine ring are all the same, and the 2nd, 4th and 6th positions. Of these, only two sites may have the same structure, or all three sites may have different structures, but preferably have a rotationally symmetric structure.
  • Specific examples of the compound represented by the general formula (1) include T2T and derivatives thereof. Moreover, not only the compound represented by General formula (1) but the following compound can be illustrated as a compound which can be preferably used as a 2nd host, for example. However, the second host that can be used in the present invention should not be construed as being limited by these specific examples.
  • the combination of the first host material and the second host material include, for example, mCBP / T2T, mCP / T2T, CBP / T2T, mCBP / TmPyPB, mCP / TmPyPB, CBP / TmPyPB, TCTA / TPBi, TCTA / B3PYMPM, A combination of mCBP / TPBi, mCP / TPBi, CBP / TPBi, mCBP / TCTA, mCP / TCTA, CBP / TCTA, and the like can be given.
  • the content of the light emitting material in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, further preferably 5% by weight or more based on the total amount of the light emitting layer. . Further, the content of the light emitting material in the light emitting layer is preferably 50% by weight or less, more preferably 20% by weight or less, and further preferably 15% by weight or less based on the total amount of the light emitting layer. . When the light emitting layer contains the first host material and the second host material, the content of the first host material in the light emitting layer is preferably 10% by weight or more based on the total amount of the host material contained in the light emitting layer. 70% by weight or more, more preferably 80% by weight or more.
  • the content of the first host material in the light emitting layer is preferably 95% by weight or less, more preferably 90% by weight or less, based on the total amount of the host material contained in the light emitting layer.
  • the content of the second host material in the light emitting layer is preferably 5% by weight or more based on the total amount of the host material contained in the light emitting layer. More preferably, it is 10% by weight or more.
  • the content of the second host material in the light emitting layer is preferably 90% by weight or less, more preferably 30% by weight or less, and more preferably 20% by weight with respect to the total amount of the host material contained in the light emitting layer. More preferably, it is as follows.
  • the light emitting layer may have a multilayer structure in which a plurality of layers having different concentrations of the light emitting material are stacked.
  • the number of layers in the multilayer structure is preferably 2 to 20, and for example, the upper limit can be set to 10 or less, 5 or less, or 3 or less.
  • the concentration of the luminescent material in each layer may be increased, decreased, or randomized toward the charge trap concentration decreasing layer side, but the charge trap concentration decreasing layer side may be increased. Is preferable from the viewpoint of extending the life. In particular, it is preferable that the concentration of the light emitting material of the layer on the charge trap concentration decreasing layer side is larger than the concentration of the light emitting material of other layers constituting the light emitting layer.
  • the density difference between the lowest density layer and the highest density layer can be set to 0.1 to 50%, for example, preferably 1 to 20%, and 2 to 15%. Is more preferable. Further, the density difference between adjacent layers can be set to 0.1 to 50%, for example, preferably 1 to 10%, and more preferably 2 to 7%. .
  • the thickness of each layer may be the same or different, but is preferably the same.
  • the light emitting layer may be continuously changed as the concentration of the light emitting material moves toward the charge trap concentration decreasing layer side. For example, it can be set to increase continuously toward the charge trap concentration decreasing layer side.
  • the light emitting material of the light emitting layer is preferably a delayed fluorescent material because high light emission efficiency can be obtained.
  • High luminous efficiency can be obtained by the delayed fluorescent material based on the following principle.
  • an organic electroluminescence element carriers are injected into a light emitting material from both positive and negative electrodes to generate an excited light emitting material and emit light.
  • 25% of the generated excitons are excited to the excited singlet state, and the remaining 75% are excited to the excited triplet state. Therefore, the use efficiency of energy is higher when phosphorescence, which is light emission from an excited triplet state, is used.
  • excitons in the excited triplet state absorb heat generated by the device and cross between the excited singlets to emit fluorescence.
  • the light lifetime (luminescence lifetime) generated by the reverse intersystem crossing from the excited triplet state to the excited singlet state is normal. Since the fluorescence becomes longer than the fluorescence and phosphorescence, it is observed as fluorescence delayed from these. This can be defined as delayed fluorescence. If such a heat-activated exciton transfer mechanism is used, the ratio of the compound in an excited singlet state, which normally generated only 25%, is increased to 25% or more by absorbing thermal energy after carrier injection. It can be raised.
  • the heat of the device will sufficiently cause intersystem crossing from the excited triplet state to the excited singlet state and emit delayed fluorescence. Efficiency can be improved dramatically.
  • the electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer can be provided as a single layer or a plurality of layers.
  • the electron transport material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer, but preferably does not contain a metal atom. .
  • Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like.
  • a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material.
  • a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.
  • the charge trap concentration reducing layer is provided at the interface between the light emitting layer and the electron transport layer.
  • the charge trap concentration-decreasing layer is a layer in which the peak area between 250 and 320 K (the peak area of the high temperature region) in the thermally stimulated current (TSC) measurement is reduced by forming the layer. It has a function of reducing the concentration of charges (electrons and holes) at deep trap levels.
  • Peak area of the high temperature region of the organic electroluminescent device having a charge trapping density-reduced layer when the peak area of the high temperature region of the reference element having no charge trapping density reducing layer was S 0, preferably less than S 0 0.71 ⁇ S 0 or less, more preferably 0.30 ⁇ S 0 or less, even more preferably 0.10 ⁇ S 0 or less, ideally preferred Zero.
  • Such a charge trap concentration reducing layer effectively reduces the charge concentration in the deep trap level, and can significantly extend the lifetime of the organic electroluminescence element.
  • the material of the charge trap concentration reducing layer is not particularly limited as long as the peak area between 250 and 320 K in TSC measurement is reduced by forming a layer made of the material.
  • materials containing transition metal atoms materials containing europium, ruthenium, gadolinium, terbium, dysprosium, erbium, ytterbium, rhenium, osmium, platinum, and gold can be preferably used. These atoms may be contained alone in the charge trap concentration-reducing layer, or may be contained in the charge trap concentration-reducing layer as a compound containing these atoms, but as a compound containing these atoms, It is preferably contained in the charge trap concentration reducing layer.
  • the compound containing these atoms is preferably a compound or organometallic compound in which these atoms and an organic ligand are combined, more preferably a compound in which these atoms and an organic ligand are combined, and 8-hydroxy A quinolinolato derivative is preferable, and 8-hydroxyquinolinolato-lithium (Liq) is particularly preferable.
  • the formation of deep trap levels inside the device is known to be due to exciton-polaron annihilation, but Liq has a low excited triplet energy level, so the excited triplet energy of the exciton is low. Is likely to move to Liq and can suppress exciton-polaron annihilation.
  • the charge trap concentration decreasing layer made of Liq can effectively reduce the amount of charges in the deep trap level.
  • the charge trap concentration-decreasing layer includes a group 1 atom, a group 2 atom, and a transition metal atom as long as the layer is formed of a material that can reduce the peak area between 250 and 320 K in TSC measurement. None of the compounds may coexist.
  • the content of the compound containing the first group atom, second group atom or transition metal atom in the charge trap concentration-decreasing layer is 80% by mass or more of the total mass of the charge trap concentration-decreasing layer, more preferably 90 masses. % Or more, more preferably 95% by mass or more, and may be 100% by mass.
  • the deterioration of performance over time during driving can be remarkably suppressed by including in the charge trap concentration-decreasing layer a compound in which these atoms and an organic ligand are combined in the above-described content.
  • the average film thickness of the charge trap concentration reducing layer is not particularly limited, but is preferably 0.1 to 100 nm, more preferably 0.5 to 10 nm, and further preferably 1 to 3 nm.
  • the second electron transport layer is made of an electron transport material and can be provided as a single layer or a plurality of layers.
  • the explanation and preferred range of the electron transport material used for the second electron transport layer can be referred to.
  • the organic electroluminescence device of the present invention preferably contains a compound containing a first group atom, second group atom or transition metal atom in at least one of the electron transport layer and the second electron transport layer.
  • the transport layer and the second electron transport layer are each a single layer, it is more preferable that the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom.
  • Group 1 atoms, Group 2 atoms, transition metal atoms, and compounds containing these atoms see Group 1 atoms, Group 2 atoms, transitions used in the charge trap concentration-reducing layer described above. Reference can be made to preferred ranges and specific examples of metal atoms and compounds containing these atoms.
  • the electron transport layer and the second electron transport layer contain a compound containing these atoms, the compound may be the same as or different from the constituent material of the charge trap concentration-reducing layer. Preferably there is.
  • an electron carrying layer and a 2nd electron carrying layer contain the compound containing a 1st group atom, a 2nd group atom, or a transition metal atom
  • content of the compound containing these atoms is the whole quantity of each electron carrying layer. Is preferably 10% by weight or more, more preferably 50% by weight or more. Further, the content thereof is preferably 90% by weight or less, and more preferably 75% by weight or less, with respect to the total amount of the electron transport layer.
  • the functional layer is made of a material containing a first group atom, a second group atom or a transition metal atom, and is provided between the electron transport layer and the second electron transport layer.
  • a material containing a first group atom, a second group atom or a transition metal atom used in the functional layer, and the preferred range of the content ratio of the material and the average thickness of the functional layer, the above charge trap concentration reduction Reference can be made to the corresponding description in the layers.
  • the injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission.
  • the injection layer can be provided as necessary.
  • the blocking layer is a layer that can prevent diffusion of charges (electrons or holes) and / or excitons existing in the light emitting layer to the outside of the light emitting layer.
  • the electron blocking layer can be disposed between the light emitting layer and the hole transport layer and blocks electrons from passing through the light emitting layer toward the hole transport layer.
  • a hole blocking layer can be disposed between the light emitting layer and the electron transporting layer to prevent holes from passing through the light emitting layer toward the electron transporting layer.
  • the charge trap concentration decreasing layer disposed between the light emitting layer and the electron transporting layer can also function as the hole blocking layer.
  • the charge trap concentration decreasing layer made of Liq has a function as a hole blocking layer.
  • the blocking layer can also be used to block excitons from diffusing outside the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also function as an exciton blocking layer.
  • the term “electron blocking layer” or “exciton blocking layer” as used herein is used in the sense of including a layer having the functions of an electron blocking layer and an exciton blocking layer in one layer.
  • the hole blocking layer has a function of an electron transport layer in a broad sense.
  • the hole blocking layer has a role of blocking holes from reaching the electron transport layer while transporting electrons, thereby improving the recombination probability of electrons and holes in the light emitting layer.
  • the function of the hole blocking layer can be combined with the charge trap concentration reducing layer.
  • the electron blocking layer has a function of transporting holes in a broad sense.
  • the electron blocking layer has a role to block electrons from reaching the hole transport layer while transporting holes, thereby improving the probability of recombination of electrons and holes in the light emitting layer. .
  • the exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved.
  • the exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously.
  • the layer when the exciton blocking layer is provided on the anode side, the layer can be inserted adjacent to the light emitting layer between the hole transport layer and the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode Between the luminescent layer and the light-emitting layer.
  • a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the excitation adjacent to the cathode and the cathode side of the light emitting layer can be provided.
  • an electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided between the child blocking layer.
  • the blocking layer When the blocking layer is disposed, at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is preferably higher than the excited singlet energy and the excited triplet energy of the light emitting material.
  • the function of the exciton blocking layer can also serve as the charge trap concentration reducing layer.
  • the hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
  • the hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic.
  • hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Examples include amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.
  • An aromatic tertiary amine compound and an styrylamine compound are preferably used, and an aromatic tertiary amine compound is more preferably used.
  • the organic electroluminescence element of the present invention can be produced, for example, by sequentially forming each of the above layers in accordance with the lamination position.
  • the method for forming each layer is not particularly limited, and it may be produced by either a dry process or a wet process.
  • the preferable material which can be used for an organic electroluminescent element is illustrated concretely.
  • the material that can be used in the present invention is not limited to the following exemplary compounds.
  • R, R ′, and R 1 to R 10 each independently represent a hydrogen atom or a substituent.
  • X represents a carbon atom or a hetero atom forming a ring skeleton
  • n represents an integer of 3 to 5
  • Y represents a substituent
  • m represents an integer of 0 or more.
  • the light emitting material used for the light emitting layer may be a light emitting material that emits fluorescence or a light emitting material that emits phosphorescence.
  • the fluorescent light-emitting material may be a light-emitting material that emits delayed fluorescence or a light-emitting material that does not emit delayed fluorescence. Examples of preferable compounds that can be used as the light emitting material of the light emitting layer include the following compounds.
  • Preferred examples include compounds, particularly exemplified compounds. These publications are hereby incorporated by reference as part of this specification. Further, as a light emitting material (delayed phosphor) that emits delayed fluorescence, JP2013-253121A, WO2013 / 133359, WO2014 / 034535, WO2014 / 115743, WO2014 / 122895, WO2014 / No.
  • the organic electroluminescence device produced by the above-described method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, if the light is emitted by excited singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. In addition, in the case of light emission by excited triplet energy, a wavelength corresponding to the energy level is confirmed as phosphorescence. Since normal fluorescence has a shorter fluorescence lifetime than delayed fluorescence, the emission lifetime can be distinguished from fluorescence and delayed fluorescence.
  • the excited triplet energy in ordinary organic compounds, the excited triplet energy is unstable and converted to heat, etc., and the lifetime is short, and it is immediately deactivated.
  • the excited triplet energy of a normal organic compound it can be measured by observing light emission under extremely low temperature conditions.
  • the organic electroluminescence element of the present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the present invention, since the charge trap concentration decreasing layer is provided at the interface between the light emitting layer and the electron transport layer, deterioration of performance over time during driving is suppressed, and light is emitted with high luminance over a long period of time. In addition, an organic electroluminescence element capable of being driven at a low voltage is obtained.
  • the organic electroluminescence device of the present invention can be further applied to various uses.
  • organic electroluminescence display device using the organic electroluminescence element of the present invention.
  • Organic electroluminescence element of the present invention For details, see “Organic EL Display” (Ohm Co., Ltd.) written by Shizushi Tokito, Chiba Adachi and Hideyuki Murata. ) Can be referred to.
  • the organic electroluminescence device of the present invention can be applied to organic electroluminescence illumination and backlights that are in great demand.
  • Thermally stimulated current (TSC) measurement was performed using a thermally stimulated current measuring instrument (trade name: TSC-FETT EL2000) manufactured by Rigaku Corporation, under the conditions described in the above definition of “charge trap concentration reducing layer”. According to the same procedure. Further, each energy level of the energy diagram was measured using an atmospheric photoelectron spectrometer (RIKEN KEIKI: AC3) for HOMO, and a UV-visible near infrared spectrometer (Perkin Elmer: LAMBDA950) for LUMO.
  • TSC thermally stimulated current measuring instrument
  • the concentration of 4CzIPN was 15% by weight.
  • Liq was deposited to a thickness of 1 nm to form a charge trap concentration reducing layer.
  • T2T was vapor deposited to a thickness of 10 nm to form an electron transport layer
  • BPy-TP2 was vapor deposited to a thickness of 40 nm thereon to form a second electron transport layer.
  • lithium fluoride (LiF) was vapor-deposited to 0.8 nm, and then aluminum (Al) was vapor-deposited to a thickness of 100 nm to form a cathode, whereby an organic electroluminescence element (organic EL element) was obtained.
  • an organic EL device was produced in the same manner as described above except that the Liq deposition thickness was changed to 2 nm or 3 nm when the charge trap concentration-decreasing layer was formed. Further, as a comparison, an organic EL element was produced in the same manner as described above except that the charge trap concentration reducing layer was not formed.
  • the TSC profile of the fabricated organic EL device is shown in FIG. 5, the emission spectrum is shown in FIG. 6, the voltage-current density-luminance characteristics are shown in FIG. 7, the current density-external quantum efficiency characteristics are shown in FIG. FIG. 9 shows changes over time in the amount of voltage change.
  • Ref Represents an organic EL element in which no charge trap concentration-reducing layer is formed, and “1 nm”, “2 nm”, and “3 nm” respectively represent the charge trap concentration-reducing layer with the thickness.
  • the formed organic EL element is represented.
  • “L 0 / L” represents the luminance ratio of the measured luminance L to the initial luminance L 0 (1000 cd / m 2 ), and ⁇ V represents the amount of voltage change from the initial voltage.
  • “L 0 / L” and “ ⁇ V” in FIGS. 13, 16, 17, 20, 25, and 30 below have the same meaning.
  • Table 1 summarizes the device characteristics of the organic EL element produced in Example 1. Referring to the TSC profile in FIG.
  • the organic EL element in which the charge trap concentration decreasing layer is formed with a thickness of 1 nm is 250 to 320 K compared to the organic EL element (Ref.) In which the charge trap concentration decreasing layer is not formed.
  • the peak intensity between is clearly small.
  • the organic EL element in which the charge trap concentration-decreasing layer is formed with a thickness of 2 nm or 3 nm the TSC measurement range is limited to 320K, so the profile on the higher temperature side is unknown. However, inferred from the current change up to that temperature, the peak intensity on the high temperature side of these organic EL elements is also higher than the peak intensity between 250 and 320 K of the organic EL elements not formed with the charge trap concentration reducing layer. Can be estimated to be small.
  • the Liq layer functions as a charge trap concentration reducing layer.
  • the organic EL element in which the charge trap concentration reducing layer is formed has a decrease in luminance ratio and an increase in voltage change over time compared to an organic EL element in which the charge trap concentration reducing layer is not formed. It is remarkably suppressed, and it can be seen that the effect increases as the thickness of the charge trap concentration decreasing layer increases. From this, it was confirmed that the charge trap concentration decreasing layer greatly contributes to the extension of the lifetime of the organic EL element.
  • the organic EL element in which the charge trap concentration reducing layer is formed is slightly smaller than the organic EL element in which the charge trap concentration reducing layer is not formed. This effect is remarkable, and it can be evaluated that the usefulness of the organic EL element is greatly improved.
  • Example 2 Production and evaluation of organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and a functional layer made of Liq
  • the thickness of the charge trap concentration-decreasing layer was set to 1 nm or 3 nm.
  • An organic electroluminescent element (EL element) was produced in the same manner as in Example 1 except that a functional layer made of Liq was formed with a thickness of 1 nm, 2 nm, or 3 nm by an evaporation method between the electron transport layers.
  • FIG. 10 shows the emission spectrum of the organic EL device in which the thickness of the charge trap concentration decreasing layer is 1 nm and the functional layer is formed in various thicknesses.
  • FIG. 11 shows the voltage-current density-luminance characteristics, and the current density-external quantum efficiency.
  • FIG. 12 shows the characteristics
  • FIG. 13 shows changes with time in the luminance ratio and the voltage change amount.
  • FIG. 14 shows the voltage-current density-luminance characteristics of the organic EL device in which the thickness of the charge trap concentration-decreasing layer is 3 nm and the functional layer is formed in various thicknesses
  • FIG. 15 shows the current density-external quantum efficiency characteristics.
  • FIG. 16 shows changes over time in the ratio and the amount of voltage change. Also, in each figure, the measurement result of the organic EL element produced in the same manner except that the functional layer is not formed, and the organic EL element produced in the same manner except that the charge trap concentration reducing layer and the functional layer are not formed.
  • Ref. Represents an organic EL element in which neither a charge trap concentration-reducing layer nor a functional layer is formed, and “0 nm” represents a charge trap concentration-reducing layer formed at 1 nm or 3 nm.
  • “1 nm”, “2 nm”, and “3 nm” are organic EL elements in which a functional layer is formed with the thickness and a charge trap concentration reduction layer is formed with 1 nm or 3 nm, respectively.
  • Table 1 summarizes the device characteristics of the organic EL element produced in Example 2.
  • the luminance with time is further increased as compared with the organic EL element in which the charge trap concentration-decreasing layer is formed and the functional layer is not formed.
  • the charge trap concentration decreasing layer was 3 nm (see FIG. 16). From this, it was confirmed that the lifetime of the organic EL element can be further extended by providing the functional layer together with the charge trap concentration decreasing layer.
  • Comparative example 1 Preparation and evaluation of an organic electroluminescence device having a functional layer made of Liq without a charge trap concentration reduction layer. Without forming a charge trap concentration reduction layer, an electron transport layer and a second electron transport layer In the meantime, an organic EL device was produced in the same manner as in Example 1 except that a functional layer made of Liq was formed with a thickness of 1 nm, 2 nm, or 3 nm by vapor deposition.
  • Table 1 shows the device characteristics of the organic EL element produced in Comparative Example 1.
  • FIG. 17 shows changes over time in the luminance ratio and voltage change amount of the manufactured organic EL element.
  • FIG. 17 also shows the measurement results of the organic EL element produced in the same manner except that the functional layer made of Liq is not formed.
  • “Ref.” Represents an organic EL element in which a functional layer made of Liq is not formed, and “1 nm”, “2 nm”, and “3 nm” respectively represent a functional layer made of Liq in the thickness.
  • the formed organic EL element is represented. From FIG. 17, the organic EL element in which the functional layer made of Liq is formed between the electron transport layer and the second electron transport layer has an organic layer in which the functional layer is not formed when the thickness of the functional layer is 1 nm. Although a life equivalent to that of the EL element can be obtained, there is a tendency that the luminance ratio is greatly decreased when the thickness of the functional layer is increased. From this, it was found that even if the Liq layer was disposed only between the electron transport layer and the second electron transport layer, the effect of extending the life could not be obtained.
  • Example 2 Preparation and evaluation of organic electroluminescence device having Alq3 layer between light emitting layer and electron transport layer No charge trap concentration decreasing layer made of Liq was formed, instead of the light emitting layer and the electron transport layer.
  • An organic EL device was produced in the same manner as in Example 1 except that an organic layer (Alq3 layer) composed of Alq3 represented by the following formula was formed with a thickness of 1 nm, 3 nm, or 5 nm by vapor deposition. .
  • FIG. 18 shows the voltage-current density-luminance characteristics of the fabricated organic EL device
  • FIG. 19 shows the current density-external quantum efficiency characteristics
  • FIG. 20 shows the changes over time in the luminance and drive voltage.
  • FIG. 18 and 20 also show the measurement results of an organic EL element produced in the same manner except that the Alq3 layer is not formed.
  • “Ref.” Represents an organic EL element in which no Alq3 layer is formed.
  • “1 nm”, “3 nm”, and “5 nm” each represent an organic EL element in which an Alq3 layer is formed with that thickness.
  • “Ref.” Represents an organic EL element in which no Alq3 layer is formed
  • Alq3 represents an organic EL element in which an Alq3 layer is formed with a thickness of 3 nm
  • “Liq” represents an Alq3 layer.
  • an organic EL element in which a Liq layer is formed with a thickness of 3 nm is shown.
  • the organic EL element in which the Alq3 layer is formed between the light-emitting layer and the electron transport layer has a large decrease in luminance rather than the organic EL element (Ref.) In which the Alq3 layer is not formed. Yes. From this, it was found that the effect of extending the lifetime of the organic EL element cannot be obtained with the Alq3 layer.
  • Example 3 Production and evaluation of an organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and the light emitting layer containing T2T (second host material) A charge trap concentration-decreasing layer is formed with a thickness of 1 nm. Then, an organic electroluminescence element (organic EL element) was produced in the same manner as in Example 1 except that a light emitting layer having a thickness of 30 nm was formed by co-evaporation of 4CzIPN, mCBP, and T2T from different evaporation sources.
  • FIG. 21 shows an energy diagram of the produced organic EL device
  • FIG. 22 shows an emission spectrum
  • FIG. 23 shows a voltage-current density-luminance characteristic
  • FIG. 24 shows a current density-external quantum efficiency characteristic
  • a luminance ratio shows changes with time in the amount of voltage change.
  • the bottom represents the absolute value of the HOMO level of each organic layer
  • the top represents the absolute value of the LUMO level of each organic layer.
  • the upper and lower solid lines indicate the energy level of mCBP
  • the outer dotted line indicates the energy level of T2T
  • the inner dotted line indicates the energy level of 4CzIPN. 22 to 25, “5%”, “10%”, “15%”, and “20%” represent organic EL elements in which the light emitting layer contains 4CzIPN at the respective concentrations.
  • Example 25 a characteristic diagram of an element having a 4CzIPN concentration of 15%, and an element having a thickness of a charge trap concentration-decreasing layer of 1 nm among the organic EL elements (Example 1) shown in FIG.
  • the organic EL element of this example (the organic EL element in which the light emitting layer contains T2T) is compared with the organic EL element in Example 1 (the organic EL element in which the light emitting layer does not contain T2T). It can be seen that the decrease in luminance ratio and the increase in voltage change over time are further suppressed. From this, it was found that when the charge trap concentration decreasing layer is formed and T2T (second host material) is further added to the light emitting layer, the lifetime of the organic EL element is further improved.
  • Example 4 Production and evaluation of an organic electroluminescence device having a charge trap concentration reducing layer made of Liq, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq
  • the second electron transport layer having a thickness of 4CzIPN in the layer was set to 10% by weight and the second electron transport layer having a thickness of 40 nm was formed in the same manner as in Example 3 except that BPy-TP2 and Liq were co-deposited from different deposition sources.
  • An electroluminescence element (organic EL element) was produced. At this time, the concentration of Liq in the second electron transport layer was 50% by weight or 75% by weight, and two types of organic EL elements having different Liq concentrations were produced.
  • the energy diagram of the produced organic EL device is shown in FIG. 26, the emission spectrum is shown in FIG. 27, the voltage-current density-luminance characteristic is shown in FIG. 28, the current density-external quantum efficiency characteristic is shown in FIG. FIG. 30 shows changes with time in the amount of voltage change.
  • the significance of the numerical values in FIG. 26 is the same as the significance of the numerical values in FIG.
  • the upper and lower solid lines indicate the energy level of BPy-TP2
  • the dotted line indicates the energy level of Liq. 27 to 30, “50%” and “75%” represent organic EL elements in which the second electron transport layer contains Liq at the respective concentrations.
  • the organic EL element of this example (the second electron transport layer is Liq). It can be seen that the rate of decrease in the luminance ratio is significantly smaller in the organic EL element containing) than in the organic EL element in Example 3 (the organic EL element in which the second electron transport layer does not contain Liq). Therefore, a charge trap concentration decreasing layer is formed, T2T (second host material) is added to the light emitting layer, and then Liq (the same material as the constituent material of the charge trap concentration decreasing layer) is added to the second electron transport layer. When it added, it turned out that the lifetime of an organic EL element is improved significantly.
  • Example 4 when the 4CzIPN concentration of the light emitting layer of Example 4 was fixed to 15%, an organic EL device in which the second electron transport layer had a Liq concentration of 50% and 75% was manufactured, and the same test was performed. The same tendency as in Example 4 was confirmed.
  • Example 5 Preparation and evaluation of an organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and a second electron transport layer containing Liq, and a light-emitting layer having a multilayer structure. 50% of the second electron transport layer
  • An organic electroluminescence element (EL element) was produced in the same manner as in Example 1 except that Liq was included and the light emitting layer was changed to have any one of the multilayer structures A to D in FIG.
  • the numerical value of each layer in A to D in FIG. 31 indicates the 4CzIPN concentration.
  • FIG. 31 shows an energy diagram of the produced organic EL device
  • FIG. 32 shows an emission spectrum
  • FIG. 33 shows a voltage-current density-luminance characteristic
  • FIG. 31 shows an energy diagram of the produced organic EL device
  • FIG. 32 shows an emission spectrum
  • FIG. 33 shows a voltage-current density-luminance characteristic
  • FIG. 34 shows a current density-external quantum efficiency characteristic, and a luminance ratio.
  • FIG. 35 shows changes over time in the amount of voltage change.
  • the emission spectrum of FIG. 32 shows that it was the same in any of A to D. From the results of FIG. 35, it was confirmed that both of the multilayer structures B and C whose lifetimes were tested had a long lifetime, but it was found that a long lifetime could be achieved particularly in the multilayer structure B.
  • Example 6 Production and evaluation of an organic electroluminescence device having a charge trap concentration reducing layer made of Liq, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq
  • concentration of 4CzIPN in the layer is 15% by weight
  • the weight ratio of the total amount of T2T host is 15%, 30%, 50%, and 70%
  • the Liq concentration of the second electron transport layer is fixed at 50%.
  • an organic electroluminescence element (organic EL element) was produced in the same manner as in Example 4.
  • FIG. 36 shows the emission spectrum of the fabricated organic EL element
  • FIG. 37 shows the voltage-current density-luminance characteristics
  • the organic EL element) containing T2T in an amount of 30% or less of the total amount of the host has a low reduction rate of the luminance ratio. From this, a charge trap concentration decreasing layer is formed, Liq (the same material as the constituent material of the charge trap concentration decreasing layer) is added to the second electron transport layer, and T2T is added in an amount of 30% or less of the total amount of the light emitting layer host. It was found that the lifetime of the organic EL element was further improved by using (second host material).
  • the organic electroluminescence device of the present invention has a very long life because the deterioration of performance over time during driving is suppressed. For this reason, this invention has high industrial applicability.

Abstract

An organic electroluminescent element provided with a structure in which at least an anode 2, a light emitting layer 3, an electron transport layer 5, and a cathode 6 are layered in that order, wherein a charge trap concentration reducing layer 4 is provided at the interface between the light emitting layer 3 and the electron transport layer 5. As a result, the deterioration in performance over time from driving of the organic electroluminescent element is suppressed and it is possible to lengthen the operating life of the organic electroluminescent element.

Description

有機エレクトロルミネッセンス素子Organic electroluminescence device
 本発明は、有機エレクトロルミネッセンス素子に関し、特に、有機エレクトロルミネッセンス素子の長寿命化に関する。 The present invention relates to an organic electroluminescence element, and more particularly to extending the life of an organic electroluminescence element.
 有機エレクトロルミネッセンス素子(有機EL素子)などの有機発光素子の性能を高める研究が盛んに行われている。特に、電極からの電荷の注入や移動を促進する各種機能層を発光層と併用して有機エレクトロルミネッセンス素子を構成することにより、その性能を高める工夫が種々なされてきている。その中には、Liq(8-ヒドロキシキノリノラト-リチウム)などの第一族原子を含む有機金属錯体を機能層の材料に使用した有機エレクトロルミネッセンス素子に関する研究も見受けられる。 Active research is being conducted to improve the performance of organic light-emitting devices such as organic electroluminescence devices (organic EL devices). In particular, various attempts have been made to enhance the performance of organic electroluminescent elements by using various functional layers that promote injection and movement of charges from the electrodes in combination with the light emitting layer. Among them, research on organic electroluminescent devices using organometallic complexes containing a group 1 atom such as Liq (8-hydroxyquinolinolato-lithium) as a material for a functional layer can also be found.
 特許文献1には、インジウム・スズ酸化物(ITO)が成膜されたガラス基板(ITOガラス基板)上に、正孔注入層、正孔輸送層、発光層、電子輸送層を順に形成した後、電子輸送層の上部にLiqを蒸着して電子注入層を形成し、その上にAlを蒸着して電極を形成することにより有機EL素子を製造したことが記載されている。
 また、特許文献2には、ITOガラス基板上に、正孔輸送層、発光層を順に形成した後、発光層の上にLiqを蒸着して電子注入層を形成し、その上に、陰極となるAlを蒸着することで有機EL素子を製造したことが記載されている。
In Patent Document 1, a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer are formed in this order on a glass substrate (ITO glass substrate) on which indium tin oxide (ITO) is formed. In addition, it is described that an organic EL element was manufactured by depositing Liq on the electron transport layer to form an electron injection layer and then depositing Al on the layer to form an electrode.
In Patent Document 2, a hole transport layer and a light emitting layer are sequentially formed on an ITO glass substrate, and then Liq is vapor-deposited on the light emitting layer to form an electron injection layer. It describes that an organic EL element was manufactured by evaporating Al.
特開2008-258603号公報JP 2008-258603 A 特開平11―233262号公報JP-A-11-233262
 上記のように、特許文献1で製造している有機EL素子は電子輸送層と陰極の界面にLiq層が形成されており、特許文献2で製造している有機EL素子は発光層と陰極の界面にLiq層が形成されている。そして、これらの文献には、いずれもLIq層を電子注入層として設けたことが明記されている。
 これに対して、本発明者らが、陰極と接する位置以外の部位にLiq層を設け、有機エレクトロルミネッセンス素子の性能を評価する検討を網羅的に行ったところ、特に発光層と電子輸送層の界面にLiq層を設けると、有機EL素子を長時間駆動させたときに生じる、経時的な輝度の低下や電圧上昇が顕著に抑制され、有機EL素子の寿命が大きく延長することを初めて見出した。特許文献1および2では、いずれもLiq層を陰極と接する位置に設けて電子注入層として機能させることを前提としており、Liq層を発光層と電子輸送層の界面に実際に形成した例や、Liq層に電子注入層以外の機能を発現させることは全く記載されていない。このため、これらの文献からは、発光層と電子輸送層の界面にLiq層を設けることで得られる素子寿命を延長する効果は予測がつかない。
 このような状況下において本発明者らは、発光層と電子輸送層の界面に設ける層について、さらに検討を進め、駆動時の経時的な性能劣化が抑えられ、長寿命の有機エレクトロルミネッセンス素子を得ることを目的として鋭意検討を進めた。
As described above, the organic EL device manufactured in Patent Document 1 has a Liq layer formed at the interface between the electron transport layer and the cathode, and the organic EL device manufactured in Patent Document 2 has a light emitting layer and a cathode. A Liq layer is formed at the interface. In these documents, it is specified that the LIq layer is provided as the electron injection layer.
On the other hand, the present inventors provided a Liq layer at a site other than the position in contact with the cathode, and comprehensively studied to evaluate the performance of the organic electroluminescence device. It has been found for the first time that when a Liq layer is provided at the interface, a decrease in luminance and a voltage increase over time that occur when the organic EL element is driven for a long time are remarkably suppressed, and the life of the organic EL element is greatly extended. . In Patent Documents 1 and 2, it is assumed that the Liq layer is provided at a position in contact with the cathode and functions as an electron injection layer, and the Liq layer is actually formed at the interface between the light emitting layer and the electron transport layer, It is not described at all that the Liq layer exhibits functions other than the electron injection layer. Therefore, from these documents, the effect of extending the device lifetime obtained by providing the Liq layer at the interface between the light emitting layer and the electron transport layer cannot be predicted.
Under such circumstances, the present inventors have further studied the layer provided at the interface between the light emitting layer and the electron transport layer, and the deterioration of performance over time during driving can be suppressed, and a long-life organic electroluminescence element can be obtained. We have intensively studied for the purpose of obtaining.
 本発明者らは、上記の課題を解決するために、有機エレクトロルミネッセンス素子の駆動時に生じる経時的な性能劣化には、素子内部の深いトラップ準位に電荷が蓄積することが主な原因になっていることに着目して鋭意検討を行った。その結果、発光層と電子輸送層の界面に電荷トラップ濃度を減少させる機能を有する層を挿入することにより、素子駆動時の経時的な性能劣化が効果的に抑制され、有機エレクトロルミネッセンス素子の顕著な長寿命化を達成しうることを見出した。このように、電子輸送層と発光層の界面に極めて薄い層を挿入するだけで、有機エレクトロルミネッセンス素子の顕著な長寿命化を図れることは驚くべき発見である。
 本発明はこれらの知見に基づいて提案されたものであり、具体的に以下の構成を有する。
In order to solve the above-mentioned problems, the present inventors mainly cause the deterioration in performance over time that occurs when driving an organic electroluminescence element due to accumulation of charges in deep trap levels inside the element. We focused on the fact that we studied. As a result, by inserting a layer having a function of reducing the charge trap concentration at the interface between the light emitting layer and the electron transport layer, the deterioration of performance over time during device driving is effectively suppressed, and the organic electroluminescence device is notable. It has been found that a long life can be achieved. As described above, it is a surprising discovery that the lifetime of the organic electroluminescent device can be significantly increased by simply inserting a very thin layer at the interface between the electron transport layer and the light emitting layer.
The present invention has been proposed based on these findings, and specifically has the following configuration.
[1] 少なくとも陽極、発光層、電子輸送層、陰極をこの順に積層した構造を有する有機エレクトロルミネッセンス素子であって、前記発光層と前記電子輸送層の界面に電荷トラップ濃度減少層を有することを特徴とする有機エレクトロルミネッセンス素子。
[2] 前記電荷トラップ濃度減少層の平均膜厚が0.1~100nmである[1]に記載の有機エレクトロルミネッセンス素子。
[3] 前記電荷トラップ濃度減少層が第一族原子、第二族原子または遷移金属原子を含有する[1]または[2]に記載の有機エレクトロルミネッセンス素子。
[4] 前記電荷トラップ濃度減少層がLiを含有する層である[3]に記載の有機エレクトロルミネッセンス素子。
[5] 前記電荷トラップ濃度減少層が8-ヒドロキシキノリノラト誘導体からなる層である[4]に記載の有機エレクトロルミネッセンス素子。
[6] 前記電子輸送層が金属原子を含まない[1]~[5]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[7] 前記電子輸送層の陰極側に第2電子輸送層を有しており、前記電子輸送層と前記第2電子輸送層との間に第一族原子、第二族原子または遷移金属原子を含有する機能層を有する[1]~[6]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[8] 前記機能層の平均膜厚が0.1~100nmである[7]に記載の有機エレクトロルミネッセンス素子。
[9] 前記機能層がLiを含有する層である[7]または[8]に記載の有機エレクトロルミネッセンス素子。
[10] 前記機能層が8-ヒドロキシキノリノラト誘導体からなる層である[9]に記載の有機エレクトロルミネッセンス素子。
[11] 前記第2電子輸送層が金属原子を含まない[7]~[10]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[12] 前記発光層が第1ホスト材料と第2ホスト材料を含有する[1]~[11]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[13] 前記第1ホスト材料と前記第2ホスト材料が、いずれも前記発光層が含有する発光材料の最低励起三重項エネルギー準位よりも高い最低励起三重項エネルギー準位を有する[12]に記載の有機エレクトロルミネッセンス素子。
[14] 前記第2ホスト材料が電子輸送性を有するものである[12]または[13]に記載の有機エレクトロルミネッセンス素子。
[15] 前記第2ホスト材料が、前記電荷トラップ濃度減少層に隣接する前記電子輸送層の構成材料と同じ材料からなるものである[12]~[14]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[16] 前記第2ホスト材料が下記一般式(1)で表される化合物である[12]~[15]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
Figure JPOXMLDOC01-appb-C000003
[一般式(1)において、Arは、置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。nは1~3の整数を表す。nが2以上であるとき、複数のArは互いに同一であっても、異なっていてもよい。]
[17] 前記一般式(1)で表される化合物が下記一般式(2)で表される化合物である[16]に記載の有機エレクトロルミネッセンス素子。
Figure JPOXMLDOC01-appb-C000004
[一般式(2)において、Ar1、Ar2およびAr3は、各々独立に置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。R1、R2およびR3は、各々独立に置換基を表し、該置換基は置換もしくは無置換のアリール基、および置換もしくは無置換のヘテロアリール基ではない。n1、n2およびn3は、各々独立に1~5の整数を表す。n11、n12およびn13は、各々独立に0~4の整数を表す。]
[18] 前記発光層が発光材料濃度が異なる多層構造を有する[1]~[17]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[19] 前記電子輸送層および前記第2電子輸送層の少なくとも一方に、第一族原子、第二族原子または遷移金属原子を含有する化合物を含有する[7]~[18]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[20] 前記第2電子輸送層に、第一族原子、第二族原子または遷移金属原子を含む化合物を含有する[19]に記載の有機エレクトロルミネッセンス素子。
[21] 前記化合物がLiを含有する化合物である[19]または[20]に記載の有機エレクトロルミネッセンス素子。
[22] 前記化合物が8-ヒドロキシキノリノラト誘導体である[19]~[21]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[23] 前記第2電子輸送層が前記電荷トラップ濃度減少層の構成材料と同じ材料を含有する[7]~[22]のいずれか一項に記載の有機エレクトロルミネッセンス素子。
[1] An organic electroluminescence device having a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and having a charge trap concentration decreasing layer at the interface between the light emitting layer and the electron transport layer. An organic electroluminescence device characterized.
[2] The organic electroluminescence device according to [1], wherein the charge trap concentration reducing layer has an average film thickness of 0.1 to 100 nm.
[3] The organic electroluminescence device according to [1] or [2], wherein the charge trap concentration-decreasing layer contains a first group atom, second group atom or transition metal atom.
[4] The organic electroluminescence device according to [3], wherein the charge trap concentration-decreasing layer is a layer containing Li.
[5] The organic electroluminescence device according to [4], wherein the charge trap concentration-decreasing layer is a layer made of an 8-hydroxyquinolinolato derivative.
[6] The organic electroluminescence device according to any one of [1] to [5], wherein the electron transport layer does not contain a metal atom.
[7] A second electron transport layer is provided on the cathode side of the electron transport layer, and a first group atom, second group atom or transition metal atom is provided between the electron transport layer and the second electron transport layer. The organic electroluminescence device according to any one of [1] to [6], which has a functional layer containing.
[8] The organic electroluminescence element according to [7], wherein the functional layer has an average film thickness of 0.1 to 100 nm.
[9] The organic electroluminescence device according to [7] or [8], wherein the functional layer is a layer containing Li.
[10] The organic electroluminescence device according to [9], wherein the functional layer is a layer made of an 8-hydroxyquinolinolato derivative.
[11] The organic electroluminescence device according to any one of [7] to [10], wherein the second electron transport layer does not contain a metal atom.
[12] The organic electroluminescent element according to any one of [1] to [11], wherein the light emitting layer contains a first host material and a second host material.
[13] Both the first host material and the second host material have a lowest excited triplet energy level higher than the lowest excited triplet energy level of the light emitting material contained in the light emitting layer. The organic electroluminescent element of description.
[14] The organic electroluminescence device according to [12] or [13], wherein the second host material has an electron transporting property.
[15] The organic material according to any one of [12] to [14], wherein the second host material is made of the same material as the constituent material of the electron transport layer adjacent to the charge trap concentration reducing layer. Electroluminescence element.
[16] The organic electroluminescence device according to any one of [12] to [15], wherein the second host material is a compound represented by the following general formula (1).
Figure JPOXMLDOC01-appb-C000003
[In General Formula (1), Ar represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. n represents an integer of 1 to 3. When n is 2 or more, the plurality of Ars may be the same as or different from each other. ]
[17] The organic electroluminescence device according to [16], wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).
Figure JPOXMLDOC01-appb-C000004
[In General Formula (2), Ar 1 , Ar 2 and Ar 3 each independently represent a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. R 1 , R 2 and R 3 each independently represent a substituent, and the substituent is not a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. n1, n2 and n3 each independently represents an integer of 1 to 5. n11, n12 and n13 each independently represents an integer of 0 to 4. ]
[18] The organic electroluminescence device according to any one of [1] to [17], wherein the light emitting layer has a multilayer structure having different light emitting material concentrations.
[19] Any one of [7] to [18], wherein at least one of the electron transport layer and the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom. The organic electroluminescent element of the item.
[20] The organic electroluminescence device according to [19], wherein the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom.
[21] The organic electroluminescence device according to [19] or [20], wherein the compound is a compound containing Li.
[22] The organic electroluminescence device according to any one of [19] to [21], wherein the compound is an 8-hydroxyquinolinolato derivative.
[23] The organic electroluminescence device according to any one of [7] to [22], wherein the second electron transport layer contains the same material as the constituent material of the charge trap concentration reducing layer.
 本発明の有機エレクトロルミネッセンス素子によれば、発光層と電子輸送層の界面に電荷トラップ濃度減少層を有することにより、駆動時の経時的な性能劣化が抑えられ、その寿命の大幅な延長を図ることができる。 According to the organic electroluminescence device of the present invention, by having the charge trap concentration-decreasing layer at the interface between the light emitting layer and the electron transport layer, deterioration of performance over time during driving can be suppressed, and the lifetime can be greatly extended. be able to.
有機エレクトロルミネッセンス素子で測定されるTSCプロファイルの一例を示す特性図である。It is a characteristic view which shows an example of the TSC profile measured with an organic electroluminescent element. 有機エレクトロルミネッセンス素子の層構成例を示す概略断面図である。It is a schematic sectional drawing which shows the layer structural example of an organic electroluminescent element. 有機エレクトロルミネッセンス素子の他の層構成例を示す概略断面図である。It is a schematic sectional drawing which shows the other layer structural example of an organic electroluminescent element. 有機エレクトロルミネッセンス素子のさらに他の層構成例を示す概略断面図である。It is a schematic sectional drawing which shows the other layer structural example of an organic electroluminescent element. 実施例1の電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層を有しない有機エレクトロルミネッセンス素子のTSCプロファイルである。2 is a TSC profile of an organic electroluminescence element having a charge trap concentration reduction layer of Example 1 and an organic electroluminescence element having no charge trap concentration reduction layer. 実施例1の電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層を有しない有機エレクトロルミネッセンス素子の発光スペクトルである。It is an emission spectrum of the organic electroluminescent element which has a charge trap density | concentration reduction layer of Example 1, and the organic electroluminescent element which does not have a charge trap density | concentration reduction layer. 実施例1の電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層を有しない有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。3 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescence element having a charge trap concentration-decreasing layer and an organic electroluminescence element not having a charge trap concentration-decreasing layer of Example 1. 実施例1の電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。4 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer of Example 1. 実施例1の電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層を有しない有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。3 is a graph showing the change over time in the luminance ratio and voltage change amount of the organic electroluminescence element having the charge trap concentration reduction layer of Example 1 and the organic electroluminescence element not having the charge trap concentration reduction layer. 実施例2の1nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、1nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層および機能層を有しない有機エレクトロルミネッセンス素子の発光スペクトルである。An organic electroluminescence device having a 1 nm-thick charge trap concentration-reducing layer and a functional layer having various thicknesses, an organic electroluminescence device having a 1-nm-thick charge trap concentration-reducing layer and no functional layer, and charge It is an emission spectrum of the organic electroluminescent element which does not have a trap density | concentration reduction | decrease layer and a functional layer. 実施例2の1nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、1nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層および機能層を有しない有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。An organic electroluminescence device having a 1 nm-thick charge trap concentration-reducing layer and a functional layer having various thicknesses, an organic electroluminescence device having a 1-nm-thick charge trap concentration-reducing layer and no functional layer, and charge It is a graph which shows the voltage-current density-luminance characteristic of the organic electroluminescent element which does not have a trap density | concentration reduction | decrease layer and a functional layer. 実施例2の1nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、1nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。Current density of the organic electroluminescence device having the 1 nm-thick charge trap concentration reducing layer and the functional layer having various thicknesses of Example 2 and the organic electroluminescence device having the 1 nm-thick charge trap concentration reducing layer and no functional layer -A graph showing external quantum efficiency characteristics. 1nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、1nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層および機能層を有しない有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。Organic electroluminescence device having 1 nm-thick charge trap concentration reducing layer and functional layer having various thicknesses, organic electroluminescence device having 1 nm-thick charge trap concentration reducing layer and no functional layer, and charge trap concentration reducing layer It is a graph which shows the time-dependent change of the luminance ratio and voltage variation | change_quantity of an organic electroluminescent element which does not have a functional layer. 実施例2の3nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、3nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層および機能層を有しない有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。An organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and a functional layer having various thicknesses of Example 2, an organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and having no functional layer, It is a graph which shows the voltage-current density-luminance characteristic of the organic electroluminescent element which does not have a trap density | concentration reduction | decrease layer and a functional layer. 実施例2の3nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、3nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。Current density of the organic electroluminescence device having the charge trap concentration decreasing layer of 3 nm thickness and the functional layer of various thicknesses of Example 2 and the organic electroluminescence device having the charge trap concentration decreasing layer of 3 nm thickness and having no functional layer -A graph showing external quantum efficiency characteristics. 実施例2の3nm厚の電荷トラップ濃度減少層および各種厚みの機能層を有する有機エレクトロルミネッセンス素子と、3nm厚の電荷トラップ濃度減少層を有し、機能層を有しない有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層および機能層を有しない有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。An organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and a functional layer having various thicknesses of Example 2, an organic electroluminescent device having a charge trap concentration-decreasing layer having a thickness of 3 nm and having no functional layer, It is a graph which shows a time-dependent change of the luminance ratio and voltage variation | change_quantity of the organic electroluminescent element which does not have a trap density | concentration reduction | decrease layer and a functional layer. 比較例1の電荷トラップ濃度減少層を有さず、各種厚みの機能層を有する有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。It is a graph which shows the time-dependent change of the luminance ratio and voltage change amount of the organic electroluminescent element which does not have the charge trap density | concentration reduction | decrease layer of the comparative example 1, and has a functional layer of various thickness. 比較例2の各種厚みのAlq3層を有する有機エレクトロルミネッセンス素子と、Alq3層を有しない有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。6 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescent element having an Alq3 layer of various thicknesses of Comparative Example 2 and an organic electroluminescent element not having an Alq3 layer. 比較例2の各種厚みのAlq3層を有する有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。5 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having an Alq3 layer of various thicknesses in Comparative Example 2. 比較例2のAlq3層を有する有機エレクトロルミネッセンス素子と、Liq層を有する有機エレクトロルミネッセンス素子と、Alq3層およびLiq層のいずれも有しない有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。Changes in luminance ratio and voltage change over time of the organic electroluminescence element having the Alq3 layer of Comparative Example 2, the organic electroluminescence element having the Liq layer, and the organic electroluminescence element having neither the Alq3 layer nor the Liq layer It is a graph to show. 実施例3の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子のエネルギーダイアグラムである。It is an energy diagram of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 3, and a light emitting layer contains T2T (2nd host material). 実施例3の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子の発光スペクトルである。It is an emission spectrum of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 3, and a light emitting layer contains T2T (2nd host material). 実施例3の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。6 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer of Example 3 and having a light emitting layer containing T2T (second host material). 実施例3の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。6 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having the charge trap concentration-decreasing layer of Example 3 and the light emitting layer containing T2T (second host material). 実施例3の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。It is a graph which shows a time-dependent change of the luminance ratio and voltage change amount of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 3, and a light emitting layer contains T2T (2nd host material). 実施例4の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子のエネルギーダイアグラムである。It is an energy diagram of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 4, a light emitting layer contains T2T (2nd host material), and a 2nd electron carrying layer contains Liq. 実施例4の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の発光スペクトルである。It is an emission spectrum of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 4, a light emitting layer contains T2T (2nd host material), and a 2nd electron carrying layer contains Liq. 実施例4の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。The voltage-current density-luminance characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 4, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show. 実施例4の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。The current density-external quantum efficiency characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 4, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show. 実施例4の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。Time course of luminance ratio and voltage change amount of organic electroluminescence element having charge trap concentration decreasing layer of Example 4, light emitting layer containing T2T (second host material), and second electron transporting layer containing Liq. It is a graph which shows a change. 実施例5の電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子のエネルギーダイアグラムと、多層構造A~Dを示す図である。FIG. 10 is a diagram showing an energy diagram of an organic electroluminescence device having a charge trap concentration-decreasing layer of Example 5 and a second electron transport layer containing Liq, and a light emitting layer having a multilayer structure, and multilayer structures A to D. 実施例5の電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子の発光スペクトルである。It is an emission spectrum of the organic electroluminescent element which has the charge trap density | concentration reduction | decrease layer of Example 5, and the 2nd electron carrying layer containing Liq, and a light emitting layer is a multilayer structure. 実施例5の電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。10 is a graph showing voltage-current density-luminance characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer and a second electron transport layer containing Liq in Example 5 and a light-emitting layer having a multilayer structure. 実施例5の電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。6 is a graph showing current density-external quantum efficiency characteristics of an organic electroluminescence device having a charge trap concentration-decreasing layer and a second electron transport layer containing Liq of Example 5 and having a light-emitting layer having a multilayer structure. 実施例5の電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。It is a graph which shows a time-dependent change of the luminance ratio and voltage change amount of the organic electroluminescent element which has the charge trap density | concentration reduction | decrease layer of Example 5, and the 2nd electron carrying layer containing Liq, and a light emitting layer is a multilayer structure. 実施例6の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の発光スペクトルである。It is an emission spectrum of the organic electroluminescent element which has a charge trap density | concentration reduction | decrease layer of Example 6, a light emitting layer contains T2T (2nd host material), and a 2nd electron carrying layer contains Liq. 実施例6の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の電圧-電流密度-輝度特性を示すグラフである。The voltage-current density-luminance characteristics of the organic electroluminescence device having the charge trap concentration reduction layer of Example 6, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show. 実施例6の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の電流密度-外部量子効率特性を示すグラフである。The current density-external quantum efficiency characteristics of the organic electroluminescence device having the charge trap concentration reducing layer of Example 6, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq It is a graph to show. 実施例6の電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の輝度比と電圧変化量の経時的変化を示すグラフである。Time course of luminance ratio and voltage change amount of organic electroluminescence device having charge trap concentration decreasing layer of Example 6, light emitting layer containing T2T (second host material), and second electron transporting layer containing Liq It is a graph which shows a change.
 以下において、本発明の内容について詳細に説明する。以下に記載する構成要件の説明は、本発明の代表的な実施態様や具体例に基づいてなされることがあるが、本発明はそのような実施態様や具体例に限定されるものではない。なお、本明細書において「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値および上限値として含む範囲を意味する。また、本発明に用いられる化合物の分子内に存在する水素原子の同位体種は特に限定されず、例えば分子内の水素原子がすべて1Hであってもよいし、一部または全部が2H(デューテリウムD)であってもよい。 Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. In addition, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all the hydrogen atoms in the molecule may be 1 H, or a part or all of them are 2 H. (Deuterium D) may be used.
 本発明の有機エレクトロルミネッセンス素子は、少なくとも陽極、発光層、電子輸送層、陰極をこの順に積層した構造を有し、発光層と電子輸送層の界面に電荷トラップ濃度減少層を有することを特徴とする。
 本発明において「電荷トラップ濃度減少層」とは、その層を形成することによって熱刺激電流(TSC)測定における250~320Kの間のピーク面積が減少する層のことを意味する。換言すれば、電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子と、電荷トラップ濃度減少層を有しないこと以外は該有機エレクトロルミネッセンス素子と同じ構成の有機エレクトロルミネッセンス素子について熱刺激電流測定を行ったとき、そのプロファイルの250~320Kの間に出現するピークのピーク面積が、前者の有機エレクトロルミネッセンス素子の方が後者の有機エレクトロルミネッセンス素子よりも小さくなるような層のことをいう。以下の説明では、電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子を「対象素子」といい、電荷トラップ濃度減少層を有しないこと以外は対象素子と同じ構成の有機エレクトロルミネッセンス素子を「参照素子」ということがある。
 TSCプロファイルにおける250~320Kの間のピーク面積を測定するには、まず、有機エレクトロルミネッセンス素子について熱刺激電流測定を行う。
 熱刺激電流測定とは、有機半導体薄膜の局在準位にトラップされている電荷を熱により放出させ、電流値として検出することによりTSCプロファイル(電流値の温度プロファイル)を得る測定である。TSCプロファイルのピークの温度から局在準位の深さを判定することができ、ピークのピーク面積から局在準位における電荷の濃度を見積もることができる。ここで、電荷とは、電子による負電荷および正孔による正電荷の両方を含む。
 本発明における熱刺激電流測定は、具体的には次のようにして行う。測定対象である有機エレクトロルミネッセンス素子を、真空チャンバー内で液体窒素温度(77K)まで冷却する。次に、77Kに保持した状態で、有機エレクトロルミネッセンス素子に2mA/cm2のバイアス電流を2分間供給し、素子内部のトラップ準位に電荷を蓄積させる。続いて、有機エレクトロルミネッセンス素子に-0.01Vのコレクティング電圧を印加しつつ5℃/分の速度で昇温を行い その際に検出される電流を観測してTSCプロファイルを得る。こうした熱刺激電流測定は、理学電機株式会社製の熱刺激電流測定機(商品名TSC-FETT EL2000)を用いて行うことができる。
 そして、得られたTSCプロファイルにおいて、250~320Kの間に出現するピークのピーク面積を測定する。ここで、250~320Kの間に出現するピークの数は1つであってもよいし、複数であってもよい。250~320Kの間に出現するピークの数が複数である場合、各ピークのピーク面積を合計した和が上記の「250~320Kの間のピーク面積」に対応する。
The organic electroluminescence device of the present invention has a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and has a charge trap concentration reducing layer at the interface between the light emitting layer and the electron transport layer. To do.
In the present invention, the “charge trap concentration-decreasing layer” means a layer in which the peak area between 250 and 320 K in the thermally stimulated current (TSC) measurement is reduced by forming the layer. In other words, when a thermally stimulated current measurement is performed on an organic electroluminescent element having the same structure as the organic electroluminescent element except that the organic electroluminescent element has a charge trap concentration decreasing layer and no charge trap concentration decreasing layer. A layer in which the peak area of a peak appearing between 250 and 320 K in the profile is such that the former organic electroluminescent element is smaller than the latter organic electroluminescent element. In the following description, an organic electroluminescence element having a charge trap concentration-decreasing layer is referred to as a “target element”, and an organic electroluminescence element having the same configuration as that of the target element except that it does not have a charge trap concentration-decreasing layer is referred to as a “reference element”. There is.
In order to measure the peak area between 250 and 320 K in the TSC profile, first, thermally stimulated current measurement is performed on the organic electroluminescence element.
Thermally stimulated current measurement is a measurement in which a charge trapped in a localized level of an organic semiconductor thin film is released by heat and detected as a current value to obtain a TSC profile (temperature profile of current value). The depth of the localized level can be determined from the temperature of the peak of the TSC profile, and the charge concentration at the localized level can be estimated from the peak area of the peak. Here, the charge includes both a negative charge due to electrons and a positive charge due to holes.
Specifically, the thermal stimulation current measurement in the present invention is performed as follows. The organic electroluminescence element to be measured is cooled to the liquid nitrogen temperature (77 K) in the vacuum chamber. Next, in a state where the temperature is maintained at 77 K, a bias current of 2 mA / cm 2 is supplied to the organic electroluminescence element for 2 minutes to accumulate charges in the trap level inside the element. Subsequently, the temperature is increased at a rate of 5 ° C./min while applying a collecting voltage of −0.01 V to the organic electroluminescence element, and the current detected at that time is observed to obtain a TSC profile. Such thermal stimulation current measurement can be performed using a thermal stimulation current measuring machine (trade name TSC-FETT EL2000) manufactured by Rigaku Corporation.
Then, in the obtained TSC profile, the peak area of the peak appearing between 250 and 320K is measured. Here, the number of peaks appearing between 250 and 320K may be one or plural. When there are a plurality of peaks that appear between 250 and 320K, the sum of the peak areas of the peaks corresponds to the above-mentioned “peak area between 250 and 320K”.
 有機エレクトロルミネッセンス素子で測定されるTSCプロファイルの典型例を図1に示す。なお、図1に示すTSCプロファイルは一例であり、本発明の有機エレクトロルミネッセンス素子で観測されるTSCプロファイルは、図1で示すものに限定的に解釈されることはない。図1において、「対象素子」はLiq層を電荷トラップ濃度減少層として形成した有機エレクトロルミネッセンス素子を表し、「参照素子」は電荷トラップ濃度減少層を形成しないこと以外は対象素子と同様にして作製した有機エレクトロルミネッセンス素子を表す。
 図1に示すように、この対象素子および参照素子のTSCプロファイルは、105K付近の低温領域と250~320Kの高温領域に、それぞれ1つのピークを有している。このうち低温領域のピークは、浅いトラップ準位(Shallow trap)に蓄積した電荷の放出に対応し、高温領域のピークは、深いトラップ準位に蓄積した電荷の放出に対応する。また、各ピークのピーク面積は、各トラップ準位に蓄積した電荷の濃度を反映する。ここで、各素子の高温領域でのピークを比較すると、対象素子の高温領域でのピーク強度は、参照素子のそれに比べて顕著に減少しており、そのピーク面積は参照素子のピーク面積の1/1.41になっている。このことは、電荷トラップ濃度減少層により、深いトラップ準位における電荷濃度が減少したことを意味している。
 本発明における「電荷トラップ濃度減少層」とは、発光層と電子輸送層の界面に設けられた材料層であって、こうして求められるTSCプロファイルの高温領域(250~320K)でのピーク面積が参照素子よりも対象素子で小さくなるものである。このような電荷トラップ濃度減少層は、有機エレクトロルミネッセンス素子の駆動の際、素子内部に深いトラップ準位が形成されることや、深いトラップ準位に電荷が蓄積することを効果的に抑えるものと考えられる。これにより、経時的なEL性能の劣化が抑えられ、有機エレクトロルミネッセンス素子の顕著な長寿命化を達成することができる。
A typical example of a TSC profile measured with an organic electroluminescence device is shown in FIG. In addition, the TSC profile shown in FIG. 1 is an example, and the TSC profile observed in the organic electroluminescence element of the present invention is not limited to the one shown in FIG. In FIG. 1, “target element” represents an organic electroluminescence element in which a Liq layer is formed as a charge trap concentration reduction layer, and “reference element” is manufactured in the same manner as the target element except that a charge trap concentration reduction layer is not formed. Represents an organic electroluminescence device.
As shown in FIG. 1, the TSC profiles of the target element and the reference element each have one peak in the low temperature region near 105K and in the high temperature region of 250 to 320K. Among these, the peak in the low temperature region corresponds to the discharge of the charge accumulated in the shallow trap level, and the peak in the high temperature region corresponds to the discharge of the charge accumulated in the deep trap level. Further, the peak area of each peak reflects the concentration of charge accumulated in each trap level. Here, when the peaks in the high temperature region of each element are compared, the peak intensity in the high temperature region of the target element is significantly reduced as compared with that of the reference element, and the peak area is 1 of the peak area of the reference element. /1.41. This means that the charge concentration in the deep trap level is decreased by the charge trap concentration decreasing layer.
The “charge trap concentration reducing layer” in the present invention is a material layer provided at the interface between the light emitting layer and the electron transport layer, and the peak area in the high temperature region (250 to 320 K) of the TSC profile thus obtained is referred to. The target element is smaller than the element. Such a charge trap concentration reducing layer effectively suppresses the formation of deep trap levels inside the device and the accumulation of charges in the deep trap levels when driving the organic electroluminescence device. Conceivable. Thereby, deterioration of the EL performance with time can be suppressed, and the lifetime of the organic electroluminescence element can be significantly prolonged.
 上記のように、本発明の有機エレクトロルミネッセンス素子は、少なくとも、陽極、発光層、電子輸送層、陰極をこの順に積層した構造を有し、発光層と電子輸送層の界面に電荷トラップ濃度減少層を有する。さらに、本発明の有機エレクトロルミネッセンス素子は、電子輸送層の陰極側に第2電子輸送層を有し、電子輸送層と第2電子輸送層との間に、第一族原子、第二族元素または遷移金属原子を含有する機能層を有していてもよい。電荷トラップ濃度減少層とともに上記の機能層を設けることにより、有機エレクトロルミネッセンス素子の寿命をより一層延長することができる。本発明の有機エレクトロルミネッセンス素子は、こうした基本構造を有するものであれば、その層構成は特に限定されないが、具体例として、図2に示すように、基板1上に、陽極2、発光層3、電荷トラップ濃度減少層4、電子輸送層5、陰極6をこの順に積層した構造や、図3に示すように、基板1上に、陽極2、発光層3、電荷トラップ濃度減少層4、電子輸送層5、機能層7、第2電子輸送層8、陰極6をこの順に積層した構造を挙げることができる。
 また、有機エレクトロルミネッセンス素子は、上記の電荷トラップ濃度減少層や電子輸送層、機能層と併用して、その他の機能を有する有機層を有していてもよい。その他の有機層としては、正孔輸送層、正孔注入層、電子阻止層、正孔阻止層、電子注入層、電子輸送層、励起子阻止層などを挙げることができる。正孔輸送層は正孔注入機能を有した正孔注入輸送層でもよく、電子輸送層は電子注入機能を有した電子注入輸送層でもよい。これらの有機層を併用した有機エレクトロルミネッセンス素子の構造例を図4に示す。図4において、1は基板、2は陽極、9は正孔注入層、10は正孔輸送層、3は発光層、4は電荷トラップ濃度減少層、5は電子輸送層、6は陰極を表わす。
 以下において、有機エレクトロルミネッセンス素子の各部材および各層について説明する。
As described above, the organic electroluminescence device of the present invention has a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order, and a charge trap concentration reducing layer is provided at the interface between the light emitting layer and the electron transport layer. Have Furthermore, the organic electroluminescence device of the present invention has a second electron transport layer on the cathode side of the electron transport layer, and a first group atom and a second group element between the electron transport layer and the second electron transport layer. Or you may have a functional layer containing a transition metal atom. By providing the functional layer together with the charge trap concentration reducing layer, the lifetime of the organic electroluminescence element can be further extended. As long as the organic electroluminescent element of the present invention has such a basic structure, its layer structure is not particularly limited. As a specific example, as shown in FIG. 2, an anode 2 and a light emitting layer 3 are formed on a substrate 1. , The charge trap concentration decreasing layer 4, the electron transport layer 5, and the cathode 6 are laminated in this order, or as shown in FIG. 3, the anode 2, the light emitting layer 3, the charge trap concentration decreasing layer 4 and the electrons are formed on the substrate 1. The structure which laminated | stacked the transport layer 5, the functional layer 7, the 2nd electron carrying layer 8, and the cathode 6 in this order can be mentioned.
Moreover, the organic electroluminescent element may have an organic layer having other functions in combination with the charge trap concentration reducing layer, the electron transport layer, or the functional layer. Examples of other organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer. The hole transport layer may be a hole injection / transport layer having a hole injection function, and the electron transport layer may be an electron injection / transport layer having an electron injection function. An example of the structure of an organic electroluminescence element using these organic layers in combination is shown in FIG. In FIG. 4, 1 is a substrate, 2 is an anode, 9 is a hole injection layer, 10 is a hole transport layer, 3 is a light emitting layer, 4 is a charge trap concentration reducing layer, 5 is an electron transport layer, and 6 is a cathode. .
Below, each member and each layer of an organic electroluminescent element are demonstrated.
[基板]
 本発明の有機エレクトロルミネッセンス素子は、基板に支持されていることが好ましい。この基板については、特に制限はなく、従来から有機エレクトロルミネッセンス素子に慣用されているものであればよく、例えば、ガラス、透明プラスチック、石英、シリコンなどからなるものを用いることができる。
[substrate]
The organic electroluminescence device of the present invention is preferably supported on a substrate. The substrate is not particularly limited and may be any substrate conventionally used for organic electroluminescence elements. For example, a substrate made of glass, transparent plastic, quartz, silicon, or the like can be used.
[陽極]
 有機エレクトロルミネッセンス素子における陽極としては、仕事関数の大きい(4eV以上)金属、合金、電気伝導性化合物およびこれらの混合物を電極材料とするものが好ましく用いられる。このような電極材料の具体例としてはAu等の金属、CuI、インジウムチンオキシド(ITO)、SnO2、ZnO等の導電性透明材料が挙げられる。また、IDIXO(In23-ZnO)等非晶質で透明導電膜を作製可能な材料を用いてもよい。陽極はこれらの電極材料を蒸着やスパッタリング等の方法により、薄膜を形成させ、フォトリソグラフィー法で所望の形状のパターンを形成してもよく、あるいはパターン精度をあまり必要としない場合は(100μm以上程度)、上記電極材料の蒸着やスパッタリング時に所望の形状のマスクを介してパターンを形成してもよい。あるいは、有機導電性化合物のように塗布可能な材料を用いる場合には、印刷方式、コーティング方式等湿式成膜法を用いることもできる。この陽極より発光を取り出す場合には、透過率を10%より大きくすることが望ましく、また陽極としてのシート抵抗は数百Ω/□以下が好ましい。さらに膜厚は材料にもよるが、通常10~1000nm、好ましくは10~200nmの範囲で選ばれる。
[anode]
As the anode in the organic electroluminescence element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO 2 , and ZnO. Alternatively, an amorphous material such as IDIXO (In 2 O 3 —ZnO) that can form a transparent conductive film may be used. For the anode, a thin film may be formed by vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the material which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.
[陰極]
 一方、陰極としては、仕事関数の小さい(4eV以下)金属(電子注入性金属と称する)、合金、電気伝導性化合物およびこれらの混合物を電極材料とするものが用いられる。このような電極材料の具体例としては、ナトリウム、ナトリウム-カリウム合金、マグネシウム、リチウム、マグネシウム/銅混合物、マグネシウム/銀混合物、マグネシウム/アルミニウム混合物、マグネシウム/インジウム混合物、アルミニウム/酸化アルミニウム(Al23)混合物、インジウム、リチウム/アルミニウム混合物、希土類金属等が挙げられる。これらの中で、電子注入性および酸化等に対する耐久性の点から、電子注入性金属とこれより仕事関数の値が大きく安定な金属である第二金属との混合物、例えば、マグネシウム/銀混合物、マグネシウム/アルミニウム混合物、マグネシウム/インジウム混合物、アルミニウム/酸化アルミニウム(Al23)混合物、リチウム/アルミニウム混合物、アルミニウム等が好適である。陰極5はこれらの電極材料を蒸着やスパッタリング等の方法により薄膜を形成させることにより、作製することができる。また、陰極としてのシート抵抗は数百Ω/□以下が好ましく、膜厚は通常10nm~5μm、好ましくは50~200nmの範囲で選ばれる。なお、発光した光を透過させるため、有機エレクトロルミネッセンス素子の陽極または陰極のいずれか一方が、透明または半透明であれば発光輝度が向上し好都合である。
 また、陽極の説明で挙げた導電性透明材料を陰極に用いることで、透明または半透明の陰極を作製することができ、これを応用することで陽極と陰極の両方が透過性を有する素子を作製することができる。
[cathode]
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al 2 O 3 ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al 2 O 3 ) mixture, a lithium / aluminum mixture, aluminum and the like. The cathode 5 can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic electroluminescence element is transparent or translucent, the emission luminance is advantageously improved.
In addition, by using the conductive transparent material mentioned in the description of the anode as a cathode, a transparent or semi-transparent cathode can be produced. By applying this, an element in which both the anode and the cathode are transparent is used. Can be produced.
[発光層]
 発光層は、陽極および陰極のそれぞれから注入された正孔および電子が再結合することにより励起子が生成した後、発光する層であり、発光材料を単独で発光層に使用しても良いが、好ましくは発光材料とホスト材料を含む。
 発光層に含まれる発光材料は、蛍光発光材料であってもよいし、りん光発光材料であってもよい。また、発光材料は、通常の蛍光とともに遅延蛍光を放射する遅延蛍光材料であってもよい。このうち、遅延蛍光材料を発光材料として用いることにより、高い発光効率を得ることができる。
 また、本発明の有機エレクトロルミネッセンス素子が高い発光効率を発現するためには、発光材料に生成した一重項励起子および三重項励起子を、発光材料中に閉じ込めることが重要である。従って、発光層中に発光材料に加えてホスト材料を用いることが好ましい。ホスト材料としては、励起一重項エネルギー、励起三重項エネルギーの少なくとも何れか一方が発光材料よりも高い値を有する有機化合物を用いることができる。その結果、発光材料に生成した一重項励起子および三重項励起子を、本発明の発光材料の分子中に閉じ込めることが可能となり、その発光効率を十分に引き出すことが可能となる。もっとも、一重項励起子および三重項励起子を十分に閉じ込めることができなくても、高い発光効率を得ることが可能な場合もあるため、高い発光効率を実現しうるホスト材料であれば特に制約なく本発明に用いることができる。本発明の有機エレクトロルミネッセンス素子において、発光は発光層に含まれる本発明の発光材料から生じる。この発光は蛍光発光、遅延蛍光発光、燐光発光のいずれであってもよく、これらの発光が混在していてもよい。また、発光の一部或いは部分的にホスト材料からの発光があってもかまわない。
 ホスト材料を用いる場合、発光材料が発光層中に含有される量は0.1重量%以上であることが好ましく、1重量%以上であることがより好ましく、また、50重量%以下であることが好ましく、20重量%以下であることがより好ましく、10重量%以下であることがさらに好ましい。
 発光層におけるホスト材料としては、正孔輸送能、電子輸送能を有し、かつ発光の長波長化を防ぎ、なおかつ高いガラス転移温度を有する有機化合物であることが好ましい。
[Light emitting layer]
The light emitting layer is a layer that emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and the light emitting material may be used alone for the light emitting layer. , Preferably including a luminescent material and a host material.
The light emitting material contained in the light emitting layer may be a fluorescent light emitting material or a phosphorescent light emitting material. The light emitting material may be a delayed fluorescent material that emits delayed fluorescence together with normal fluorescence. Among these, high luminous efficiency can be obtained by using the delayed fluorescent material as the light emitting material.
In order for the organic electroluminescence device of the present invention to exhibit high luminous efficiency, it is important to confine singlet excitons and triplet excitons generated in the light emitting material in the light emitting material. Therefore, it is preferable to use a host material in addition to the light emitting material in the light emitting layer. As the host material, an organic compound in which at least one of excited singlet energy and excited triplet energy has a value higher than that of the light-emitting material can be used. As a result, singlet excitons and triplet excitons generated in the light emitting material can be confined in the molecules of the light emitting material of the present invention, and the light emission efficiency can be sufficiently extracted. However, even if singlet excitons and triplet excitons cannot be sufficiently confined, there are cases where high luminous efficiency can be obtained, so that host materials that can achieve high luminous efficiency are particularly limited. And can be used in the present invention. In the organic electroluminescence device of the present invention, light emission is generated from the light emitting material of the present invention contained in the light emitting layer. This light emission may be any of fluorescent light emission, delayed fluorescent light emission, and phosphorescent light emission, and these light emission may be mixed. In addition, light emission from the host material may be partly or partly emitted.
When the host material is used, the amount of the light emitting material contained in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% by weight or less. Is preferably 20% by weight or less, more preferably 10% by weight or less.
The host material in the light-emitting layer is preferably an organic compound that has a hole transporting ability and an electron transporting ability, prevents the emission of longer wavelengths, and has a high glass transition temperature.
 ホスト材料を用いる場合、ホスト材料は1種類を単独で発光層に含有させてもよいし、2種類以上を組み合わせて発光層に含有させてもよい。2種類以上のホスト材料を用いる場合には、少なくとも第1ホスト材料と、該第1ホスト材料とはエネルギー準位やキャリア輸送能等の特性が異なる第2ホスト材料を組み合わせて用いることが好ましい。これにより、有機エレクトロルミネッセンス素子の発光効率や寿命等の特性を制御し易くなる。
 また、この場合、素子の寿命をより改善する観点から、第1ホスト材料および第2ホスト材料は、いずれも発光材料の最低励起三重項エネルギー準位よりも高い最低励起三重項エネルギー準位を有することが好ましく、第1ホスト材料および第2ホスト材料の少なくとも一方の最低励起三重項エネルギー準位T1hと発光材料の最低励起三重項エネルギー準位T1dの差T1h-T1d(以下、「エネルギー準位差ΔT1」という)は0eV超であることが好ましく、また、1eV以下であることが好ましく、0.7eV以下であることがより好ましく、0.5eV以下であることがさらに好ましい。
 発光材料の最低励起一重項エネルギー準位S1dと第1ホスト材料および第2ホスト材料の各最低励起一重項エネルギー準位S1hとの関係は特に制限されないが、第1ホスト材料および第2ホスト材料が、発光材料の最低励起一重項エネルギー準位S1dよりも高い最低励起一重項エネルギー準位S1hを有することが好ましい。これにより、発光材料に生成した一重項励起子が発光材料の分子中に閉じ込められ、その一重項励起子のエネルギーを光の放射に有効利用することができる。
When a host material is used, one type of host material may be contained alone in the light emitting layer, or a combination of two or more types may be contained in the light emitting layer. When two or more types of host materials are used, it is preferable to use a combination of at least the first host material and a second host material having characteristics such as energy level and carrier transportability different from those of the first host material. Thereby, it becomes easy to control characteristics, such as the luminous efficiency and lifetime of an organic electroluminescent element.
In this case, from the viewpoint of further improving the lifetime of the device, each of the first host material and the second host material has a lowest excited triplet energy level higher than the lowest excited triplet energy level of the light emitting material. It is preferable that the difference T1 h −T1 d (hereinafter, “the lowest excited triplet energy level T1 h of at least one of the first host material and the second host material) and the lowest excited triplet energy level T1 d of the light emitting material” The energy level difference ΔT1 ”is preferably greater than 0 eV, preferably 1 eV or less, more preferably 0.7 eV or less, and even more preferably 0.5 eV or less.
The relationship between the lowest excited singlet energy level S1 d of the light emitting material and each lowest excited singlet energy level S1 h of the first host material and the second host material is not particularly limited, but the first host material and the second host are not limited. Preferably, the material has a lowest excited singlet energy level S1 h that is higher than the lowest excited singlet energy level S1 d of the luminescent material. Thus, singlet excitons generated in the light emitting material are confined in the molecules of the light emitting material, and the energy of the singlet excitons can be effectively used for light emission.
 ここで、本明細書中において発光材料、第1ホスト材料および第2ホスト材料の各最低励起一重項エネルギー準位S1d、S1h、各最低励起三重項エネルギー準位T1d、T1hは、以下の手順により求められる値である。
(1)最低励起一重項エネルギー準位S1(S1d、S1h
 測定対象化合物をSi基板上に蒸着して試料を作製し、常温(300K)でこの試料の蛍光スペクトルを測定する。蛍光スペクトルは、縦軸を発光、横軸を波長とする。この発光スペクトルの短波側の立ち下がりに対して接線を引き、その接線と横軸との交点の波長値 λedge[nm]を求める。この波長値を次に示す換算式でエネルギー値に換算した値をS1とする。
  換算式:S1[eV]=1239.85/λedge
 発光スペクトルの測定には、励起光源に窒素レーザー(Lasertechnik Berlin社製、MNL200)を検出器には、ストリークカメラ(浜松ホトニクス社製、C4334)を用いることができる。
Here, in the present specification, the lowest excited singlet energy levels S1 d and S1 h and the lowest excited triplet energy levels T1 d and T1 h of the light emitting material, the first host material, and the second host material are: It is a value obtained by the following procedure.
(1) Lowest excited singlet energy level S1 (S1 d , S1 h )
A sample to be measured is deposited on a Si substrate to prepare a sample, and the fluorescence spectrum of this sample is measured at room temperature (300 K). The fluorescence spectrum has light emission on the vertical axis and wavelength on the horizontal axis. A tangent line is drawn with respect to the falling edge of the emission spectrum on the short wave side, and a wavelength value λedge [nm] at the intersection of the tangent line and the horizontal axis is obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula is defined as S1.
Conversion formula: S1 [eV] = 1239.85 / λedge
For measurement of the emission spectrum, a nitrogen laser (Lasertechnik Berlin, MNL200) is used as an excitation light source, and a streak camera (Hamamatsu Photonics, C4334) is used as a detector.
(2)最低励起三重項エネルギー準位T1(T1d、T1h
 一重項エネルギーS1と同じ試料を77[K]に冷却し、励起光(337nm)を燐光測定用試料に照射し、ストリークカメラを用いて、燐光強度を測定する。この燐光スペクトルの短波長側の立ち上がりに対して接線を引き、その接線と横軸との交点の波長値λedge[nm]を求める。この波長値を次に示す換算式でエネルギー値に換算した値をT1とする。
  換算式:T1[eV]=1239.85/λedge
 燐光スペクトルの短波長側の立ち上がりに対する接線は以下のように引く。燐光スペクトルの短波長側から、スペクトルの極大値のうち、最も短波長側の極大値までスペクトル曲線上を移動する際に、長波長側に向けて曲線上の各点における接線を考える。この接線は、曲線が立ち上がるにつれ(つまり縦軸が増加するにつれ)、傾きが増加する。この傾きの値が極大値をとる点において引いた接線を、当該燐光スペクトルの短波長側の立ち上がりに対する接線とする。
 なお、スペクトルの最大ピーク強度の10%以下のピーク強度をもつ極大点は、上述の最も短波長側の極大値には含めず、最も短波長側の極大値に最も近い、傾きの値が極大値をとる点において引いた接線を当該燐光スペクトルの短波長側の立ち上がりに対する接線とする。
(2) Lowest excited triplet energy level T1 (T1 d , T1 h )
The same sample as the singlet energy S1 is cooled to 77 [K], the phosphorescence measurement sample is irradiated with excitation light (337 nm), and the phosphorescence intensity is measured using a streak camera. A tangent line is drawn with respect to the rising edge of the phosphorescence spectrum on the short wavelength side, and a wavelength value λ edge [nm] at the intersection of the tangent line and the horizontal axis is obtained. A value obtained by converting this wavelength value into an energy value by the following conversion formula is defined as T1.
Conversion formula: T1 [eV] = 1239.85 / λedge
The tangent to the rising edge on the short wavelength side of the phosphorescence spectrum is drawn as follows. When moving on the spectrum curve from the short wavelength side of the phosphorescence spectrum to the maximum value on the shortest wavelength side among the maximum values of the spectrum, tangents at each point on the curve are considered toward the long wavelength side. The slope of this tangent line increases as the curve rises (that is, as the vertical axis increases). The tangent drawn at the point where the slope value takes the maximum value is taken as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.
In addition, the maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the above-mentioned maximum value on the shortest wavelength side, and has the maximum slope value closest to the maximum value on the shortest wavelength side. The tangent drawn at the point where the value is taken is taken as the tangent to the rise on the short wavelength side of the phosphorescence spectrum.
 第1ホスト材料および第2ホスト材料のうち、少なくとも第2ホスト材料は電子輸送性を有することが好ましい。これにより、電子を発光層中で円滑に移動させることができ、経時的な性能劣化がより抑制され、さらに寿命を延長することができる。こうした第2ホスト材料としては、上記の電荷トラップ濃度減少層の陰極側に隣接する電子輸送層の構成材料と同じ材料を用いことが好ましい。
 また、第2ホスト材料は、第1ホスト材料とHOMO準位やLUMO準位が有意に異なることが好ましい。これにより、電子と正孔の再結合ゾーンを制御して寿命等の特性を改善することができる。そのような第2ホスト材料として、例えば、そのHOMO準位が発光材料および第1ホスト材料の各HOMO準位よりも低く、そのLUMO準位が発光材料のLUMO準位よりも高く、且つ、第1ホスト材料のLUMO準位よりも低いものを好ましく用いることができる。
Of the first host material and the second host material, at least the second host material preferably has an electron transporting property. Thereby, electrons can be smoothly moved in the light emitting layer, performance deterioration with time can be further suppressed, and the life can be further extended. As such a second host material, it is preferable to use the same material as the constituent material of the electron transport layer adjacent to the cathode side of the charge trap concentration reducing layer.
The second host material preferably has a HOMO level or LUMO level significantly different from that of the first host material. Thereby, characteristics such as lifetime can be improved by controlling the recombination zone of electrons and holes. As such a second host material, for example, the HOMO level is lower than the HOMO levels of the light-emitting material and the first host material, the LUMO level is higher than the LUMO level of the light-emitting material, and the first One lower than the LUMO level of one host material can be preferably used.
 第1ホストとして、例えば下記の化合物を好ましく用いることができる。
Figure JPOXMLDOC01-appb-C000005
As the first host, for example, the following compounds can be preferably used.
Figure JPOXMLDOC01-appb-C000005
 第2ホストとして、例えば下記一般式(1)で表される化合物を好ましく用いることができる。
Figure JPOXMLDOC01-appb-C000006
 一般式(1)において、Arは、置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。nは1~3の整数を表す。nは2以上であることが好ましい。nが2以上であるとき、複数のArは互いに同一であっても異なっていてもよく、同一であることが好ましい。Arの説明と好ましい態様については、下記の一般式(2)のAr1、Ar2およびAr3の説明と好ましい態様を参照することができる。また、一般式(1)で表される化合物は、回転対称体であってもよいし、回転対称体でなくてもよい。
As the second host, for example, a compound represented by the following general formula (1) can be preferably used.
Figure JPOXMLDOC01-appb-C000006
In the general formula (1), Ar represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. n represents an integer of 1 to 3. n is preferably 2 or more. When n is 2 or more, the plurality of Ars may be the same or different from each other, and are preferably the same. For the explanation and preferred embodiments of Ar, reference can be made to the explanation and preferred embodiments of Ar 1 , Ar 2 and Ar 3 in the following general formula (2). Further, the compound represented by the general formula (1) may be a rotationally symmetric body or may not be a rotationally symmetric body.
 前記一般式(1)で表される化合物は、下記一般式(2)で表される化合物であることが好ましい。
Figure JPOXMLDOC01-appb-C000007
The compound represented by the general formula (1) is preferably a compound represented by the following general formula (2).
Figure JPOXMLDOC01-appb-C000007
 一般式(2)において、Ar1、Ar2およびAr3は、各々独立に置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。Ar1、Ar2およびAr3は、互いに同一であっても異なっていてもよく、同一であることが好ましい。n1、n2およびn3は、各々独立に1~5の整数を表す。n1、n2およびn3は、1~3であることが好ましく、1または2であることがより好ましい。n1、n2およびn3は、同一であっても異なっていてもよいが、同一であることが好ましい。n1が2以上であるとき、その2以上のAr1は互いに同一であっても異なっていてもよく、n2が2以上であるとき、その2以上のAr2は互いに同一であっても異なっていてもよく、n3が2以上であるとき、その2以上のAr3は互いに同一であっても異なっていてもよい。
 Ar1、Ar2およびAr3がとりうる置換もしくは無置換のアリール基を構成する芳香環は、単環であっても、2以上の芳香環が融合した融合環であってもよい。芳香環の環骨格を構成する炭素数は、6~22であることが好ましく、6~18であることがより好ましく、6~14であることがさらに好ましく、6~10であることがさらにより好ましい。アリール基を構成する芳香環の具体例として、ベンゼン環、ナフタレン環を挙げることができる。Ar1、Ar2およびAr3がとりうる置換もしくは無置換のヘテロアリール基を構成する複素芳香環は、単環であっても、1以上の複素環と1以上の芳香環とが融合した融合環であってもよいし、2以上の複素環が融合した融合環であってもよい。ただし、Ar1、Ar2およびAr3の結合手を持つ環は複素環である。複素環の環骨格を構成する原子数は、5~22であることが好ましく、5~18であることがより好ましく、5~14であることがさらに好ましく、5~10であることがさらにより好ましい。複素環の環骨格を構成する炭素数は4~21であることが好ましく、4~17であることがより好ましく、4~13であることがさらに好ましく、4~9であることがさらにより好ましい。複素環の環骨格を構成する複素原子は窒素原子、酸素原子、硫黄原子であることが好ましく、窒素原子であることがより好ましい。ヘテロアリール基を構成する芳香環の具体例として、ピリジン環、ピリダジン環、ピリミジン環、トリアジン環、トリアゾール環、ベンゾトリアゾール環を挙げることができる。
 Ar1、Ar2およびAr3がとりうるアリール基に置換しうる置換基と、Ar1、Ar2およびAr3がとりうるヘテロアリール基に置換しうる置換基は、特に制限されない。置換基として、例えばヒドロキシ基、ハロゲン原子、シアノ基、炭素数1~20のアルキル基、炭素数1~20のアルコキシ基、炭素数1~20のアルキルチオ基、炭素数1~20のアルキル置換アミノ基、炭素数2~20のアシル基、炭素数6~40のアリール基、炭素数6~40のアリールオキシ基、炭素数6~40のアリールチオ基、炭素数3~40のヘテロアリール基、炭素数3~40のヘテロアリールオキシ基、炭素数3~40のヘテロアリールチオ基、炭素数2~10のアルケニル基、炭素数2~10のアルキニル基、炭素数2~10のアルコキシカルボニル基、炭素数1~10のアルキルスルホニル基、炭素数1~10のハロアルキル基、アミド基、炭素数2~10のアルキルアミド基、炭素数3~20のトリアルキルシリル基、炭素数4~20のトリアルキルシリルアルキル基、炭素数5~20のトリアルキルシリルアルケニル基、炭素数5~20のトリアルキルシリルアルキニル基およびニトロ基等が挙げられる。これらの具体例のうち、さらに置換基により置換可能なものは置換されていてもよい。より好ましい置換基は、ハロゲン原子、シアノ基、炭素数1~20の置換もしくは無置換のアルキル基、炭素数1~20のアルコキシ基、炭素数6~40の置換もしくは無置換のアリール基、炭素数6~40の置換もしくは無置換のアリールオキシ基、炭素数3~40の置換もしくは無置換のヘテロアリール基、炭素数3~40の置換もしくは無置換のヘテロアリールオキシ基、炭素数1~20のジアルキル置換アミノ基である。さらに好ましい置換基は、フッ素原子、塩素原子、シアノ基、炭素数1~10の置換もしくは無置換のアルキル基、炭素数1~10の置換もしくは無置換のアルコキシ基、炭素数6~15の置換もしくは無置換のアリール基、炭素数3~12の置換もしくは無置換のヘテロアリール基である。置換基の数は0~5個であることが好ましく、0~4個であることがより好ましい。
In the general formula (2), Ar 1 , Ar 2 and Ar 3 each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. Ar 1 , Ar 2 and Ar 3 may be the same or different from each other, and are preferably the same. n1, n2 and n3 each independently represents an integer of 1 to 5. n1, n2 and n3 are preferably 1 to 3, more preferably 1 or 2. n1, n2 and n3 may be the same or different, but are preferably the same. When n1 is 2 or more, the two or more Ar 1 s may be the same or different from each other. When n2 is 2 or more, the two or more Ar 2 s are the same or different from each other. When n3 is 2 or more, the two or more Ar 3 s may be the same as or different from each other.
The aromatic ring constituting the substituted or unsubstituted aryl group that Ar 1 , Ar 2, and Ar 3 can take may be a single ring or a fused ring in which two or more aromatic rings are fused. The number of carbon atoms constituting the ring skeleton of the aromatic ring is preferably 6-22, more preferably 6-18, still more preferably 6-14, and even more preferably 6-10. preferable. Specific examples of the aromatic ring constituting the aryl group include a benzene ring and a naphthalene ring. Even if the heteroaromatic ring constituting the substituted or unsubstituted heteroaryl group that Ar 1 , Ar 2 and Ar 3 can take is a single ring, a fusion in which one or more heterocycles and one or more aromatic rings are fused It may be a ring or a fused ring in which two or more heterocycles are fused. However, the ring having a bond of Ar 1 , Ar 2 and Ar 3 is a heterocyclic ring. The number of atoms constituting the heterocyclic ring skeleton is preferably 5 to 22, more preferably 5 to 18, still more preferably 5 to 14, and even more preferably 5 to 10. preferable. The number of carbon atoms constituting the heterocyclic ring skeleton is preferably 4 to 21, more preferably 4 to 17, still more preferably 4 to 13, and still more preferably 4 to 9. . The hetero atom constituting the heterocyclic ring skeleton is preferably a nitrogen atom, an oxygen atom, or a sulfur atom, and more preferably a nitrogen atom. Specific examples of the aromatic ring constituting the heteroaryl group include a pyridine ring, a pyridazine ring, a pyrimidine ring, a triazine ring, a triazole ring, and a benzotriazole ring.
The substituent that can be substituted with the aryl group that Ar 1 , Ar 2, and Ar 3 can take, and the substituent that can be substituted with the heteroaryl group that Ar 1 , Ar 2, and Ar 3 can take are not particularly limited. Examples of the substituent include a hydroxy group, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, and an alkyl-substituted amino group having 1 to 20 carbon atoms. Group, acyl group having 2 to 20 carbon atoms, aryl group having 6 to 40 carbon atoms, aryloxy group having 6 to 40 carbon atoms, arylthio group having 6 to 40 carbon atoms, heteroaryl group having 3 to 40 carbon atoms, carbon Heteroaryloxy group having 3 to 40 carbon atoms, heteroarylthio group having 3 to 40 carbon atoms, alkenyl group having 2 to 10 carbon atoms, alkynyl group having 2 to 10 carbon atoms, alkoxycarbonyl group having 2 to 10 carbon atoms, carbon An alkylsulfonyl group having 1 to 10 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an amide group, an alkylamide group having 2 to 10 carbon atoms, and a trialkylsilyl group having 3 to 20 carbon atoms , Trialkylsilyl group having 4 to 20 carbon atoms, trialkylsilyl alkenyl group having 5 to 20 carbon atoms, and the like trialkylsilyl alkynyl group and a nitro group having 5 to 20 carbon atoms. Among these specific examples, those that can be substituted with a substituent may be further substituted. More preferred substituents are a halogen atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms, carbon A substituted or unsubstituted aryloxy group having 6 to 40 carbon atoms, a substituted or unsubstituted heteroaryl group having 3 to 40 carbon atoms, a substituted or unsubstituted heteroaryloxy group having 3 to 40 carbon atoms, and 1 to 20 carbon atoms A dialkyl-substituted amino group. More preferable substituents are a fluorine atom, a chlorine atom, a cyano group, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, and a substituted group having 6 to 15 carbon atoms. Alternatively, it is an unsubstituted aryl group or a substituted or unsubstituted heteroaryl group having 3 to 12 carbon atoms. The number of substituents is preferably from 0 to 5, more preferably from 0 to 4.
 一般式(2)のR1、R2およびR3は、各々独立に置換基を表す。ただし、該置換基は置換もしくは無置換のアリール基、および置換もしくは無置換のヘテロアリール基ではない。n11、n12およびn13は、各々独立に0~4の整数を表し、0~2の整数であることが好ましく、0または1であることがより好ましい。また、n11、n12およびn13は、少なくとも1つが0であることが好ましく、全てが0であることがより好ましい。n11が2以上であるとき、その2以上のR1は互いに同一であっても異なっていてもよく、n12が2以上であるとき、その2以上のR2は互いに同一であっても異なっていてもよく、n13が2以上であるとき、その2以上のR3は互いに同一であっても異なっていてもよい。また、(R1n11、(R2n12、(R3n13は、同一であっても異なっていてもよいが、同一であることが好ましい。
 R1、R2およびR3が表す置換基の説明と好ましい範囲については、上記のAr1、Ar2およびAr3がとりうるアリール基に置換しうる置換基の説明と好ましい範囲を参照することができる。
R 1 , R 2 and R 3 in the general formula (2) each independently represent a substituent. However, the substituent is not a substituted or unsubstituted aryl group and a substituted or unsubstituted heteroaryl group. n11, n12 and n13 each independently represents an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1. Further, at least one of n11, n12 and n13 is preferably 0, and more preferably all. When n11 is 2 or more, the two or more R 1 s may be the same or different from each other. When n12 is 2 or more, the two or more R 2 s are the same or different from each other. When n13 is 2 or more, the two or more R 3 s may be the same as or different from each other. Moreover, (R 1 ) n11 , (R 2 ) n12 , and (R 3 ) n13 may be the same or different, but are preferably the same.
For the explanation and preferred ranges of the substituents represented by R 1 , R 2 and R 3 , see the explanation and preferred ranges of the substituents which can be substituted on the aryl group which Ar 1 , Ar 2 and Ar 3 can take. Can do.
 一般式(2)で表される化合物は、トリアジン環の2位、4位、6位の構造が全て同じである回転対称構造をとっていてもよいし、2位、4位、6位のうち2つの部位のみが同じ構造であってもよいし、3つの部位の全てが異なる構造であってもよいが、回転対称構造をとっていることが好ましい。 The compound represented by the general formula (2) may have a rotationally symmetric structure in which the structures at the 2nd, 4th and 6th positions of the triazine ring are all the same, and the 2nd, 4th and 6th positions. Of these, only two sites may have the same structure, or all three sites may have different structures, but preferably have a rotationally symmetric structure.
 一般式(1)で表される化合物の具体例として、T2Tやその誘導体を例示することができる。
 また、一般式(1)で表される化合物に限らず、第2ホストとして好ましく使用できる化合物として、例えば下記の化合物を例示することができる。ただし、本発明において用いることができる第2ホストはこれらの具体例によって限定的に解釈されるべきものではない。
Specific examples of the compound represented by the general formula (1) include T2T and derivatives thereof.
Moreover, not only the compound represented by General formula (1) but the following compound can be illustrated as a compound which can be preferably used as a 2nd host, for example. However, the second host that can be used in the present invention should not be construed as being limited by these specific examples.
Figure JPOXMLDOC01-appb-C000008
Figure JPOXMLDOC01-appb-C000008
 第1ホスト材料と第2ホスト材料の組み合わせの具体例として、例えば、mCBP/T2T,mCP/T2T,CBP/T2T,mCBP/TmPyPB,mCP/TmPyPB,CBP/TmPyPB,TCTA/TPBi,TCTA/B3PYMPM,mCBP/TPBi,mCP/TPBi,CBP/TPBi,mCBP/TCTA,mCP/TCTA,CBP/TCTAの組み合わせ等を挙げることができる。 Specific examples of the combination of the first host material and the second host material include, for example, mCBP / T2T, mCP / T2T, CBP / T2T, mCBP / TmPyPB, mCP / TmPyPB, CBP / TmPyPB, TCTA / TPBi, TCTA / B3PYMPM, A combination of mCBP / TPBi, mCP / TPBi, CBP / TPBi, mCBP / TCTA, mCP / TCTA, CBP / TCTA, and the like can be given.
 発光層における発光材料の含有量は、発光層の全量に対して0.1重量%以上であることが好ましく、1重量%以上であることがより好ましく、5重量%以上であることがさらに好ましい。また、発光層における発光材料の含有量は、発光層の全量に対して50重量%以下であることが好ましく、20重量%以下であることがより好ましく、15重量%以下であることがさらに好ましい。
 発光層に第1ホスト材料と第2ホスト材料を含有させる場合、発光層における第1ホスト材料の含有量は、発光層が含有するホスト材料の全量に対して10重量%以上であることが好ましく、70重量%以上であることがより好ましく、80重量%以上であることがさらに好ましい。また、発光層における第1ホスト材料の含有量は、発光層が含有するホスト材料の全量に対して95重量%以下であることが好ましく、90重量%以下であることがより好ましい。
 発光層に第1ホスト材料と第2ホスト材料を含有させる場合、発光層における第2ホスト材料の含有量は、発光層が含有するホスト材料の全量に対して5重量%以上であることが好ましく、10重量%以上であることがより好ましい。また、発光層における第2ホスト材料の含有量は、発光層が含有するホスト材料の全量に対して90重量%以下であることが好ましく、30重量%以下であることがより好ましく、20重量%以下であることがさらに好ましい。
 発光層は、発光材料の濃度が異なる複数の層を積層した多層構造を有していてもよい。多層構造とするときの層の数は、2~20であることが好ましく、例えば上限値は10以下、5以下、3以下に設定することができる。各層の発光材料の濃度は、電荷トラップ濃度減少層側へ向かうに従って大きくなるようにしても、小さくなるようにしても、ランダムになるようにしてもよいが、電荷トラップ濃度減少層側が大きくなるようにすることが長寿命化の点で好ましい。特に、電荷トラップ濃度減少層側の層の発光材料濃度が、発光層を構成する他の層の発光材料濃度よりも大きくなるようにすることが好ましい。最も濃度が小さい層と最も濃度が大きい層の濃度差は、例えば0.1~50%に設定することが可能であり、1~20%に設定することが好ましく、2~15%にすることがより好ましい。また、隣接する層の間の濃度差は、例えば0.1~50%に設定することが可能であり、1~10%に設定することが好ましく、2~7%に設定することがより好ましい。各層の厚みは同じであっても異なっていてもよいが、同じにすることが好ましい。
 また、発光層は、発光材料の濃度が電荷トラップ濃度減少層側へ向かうに従って連続的に変化するようにしてもよい。例えば、電荷トラップ濃度減少層側へ向かうに従って連続的に増加するように設定することができる。
The content of the light emitting material in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, further preferably 5% by weight or more based on the total amount of the light emitting layer. . Further, the content of the light emitting material in the light emitting layer is preferably 50% by weight or less, more preferably 20% by weight or less, and further preferably 15% by weight or less based on the total amount of the light emitting layer. .
When the light emitting layer contains the first host material and the second host material, the content of the first host material in the light emitting layer is preferably 10% by weight or more based on the total amount of the host material contained in the light emitting layer. 70% by weight or more, more preferably 80% by weight or more. The content of the first host material in the light emitting layer is preferably 95% by weight or less, more preferably 90% by weight or less, based on the total amount of the host material contained in the light emitting layer.
When the light emitting layer contains the first host material and the second host material, the content of the second host material in the light emitting layer is preferably 5% by weight or more based on the total amount of the host material contained in the light emitting layer. More preferably, it is 10% by weight or more. Further, the content of the second host material in the light emitting layer is preferably 90% by weight or less, more preferably 30% by weight or less, and more preferably 20% by weight with respect to the total amount of the host material contained in the light emitting layer. More preferably, it is as follows.
The light emitting layer may have a multilayer structure in which a plurality of layers having different concentrations of the light emitting material are stacked. The number of layers in the multilayer structure is preferably 2 to 20, and for example, the upper limit can be set to 10 or less, 5 or less, or 3 or less. The concentration of the luminescent material in each layer may be increased, decreased, or randomized toward the charge trap concentration decreasing layer side, but the charge trap concentration decreasing layer side may be increased. Is preferable from the viewpoint of extending the life. In particular, it is preferable that the concentration of the light emitting material of the layer on the charge trap concentration decreasing layer side is larger than the concentration of the light emitting material of other layers constituting the light emitting layer. The density difference between the lowest density layer and the highest density layer can be set to 0.1 to 50%, for example, preferably 1 to 20%, and 2 to 15%. Is more preferable. Further, the density difference between adjacent layers can be set to 0.1 to 50%, for example, preferably 1 to 10%, and more preferably 2 to 7%. . The thickness of each layer may be the same or different, but is preferably the same.
In addition, the light emitting layer may be continuously changed as the concentration of the light emitting material moves toward the charge trap concentration decreasing layer side. For example, it can be set to increase continuously toward the charge trap concentration decreasing layer side.
 上記のように、発光層の発光材料は、高い発光効率が得られることから、遅延蛍光材料であることが好ましい。遅延蛍光材料により高い発光効率が得られるのは、以下の原理による。
 有機エレクトロルミネッセンス素子においては、正負の両電極より発光材料にキャリアを注入し、励起状態の発光材料を生成し、発光させる。通常、キャリア注入型の有機エレクトロルミネッセンス素子の場合、生成した励起子のうち、励起一重項状態に励起されるのは25%であり、残り75%は励起三重項状態に励起される。従って、励起三重項状態からの発光であるリン光を利用するほうが、エネルギーの利用効率が高い。しかしながら、励起三重項状態は寿命が長いため、励起状態の飽和や励起三重項状態の励起子との相互作用によるエネルギーの失活が起こり、一般にリン光の量子収率が高くないことが多い。一方、遅延蛍光材料は、項間交差等により励起三重項状態へとエネルギーが遷移した後、三重項-三重項消滅あるいは熱エネルギーの吸収により、励起一重項状態に逆項間交差され蛍光を放射する。有機エレクトロルミネッセンス素子においては、なかでも熱エネルギーの吸収による熱活性化型の遅延蛍光材料が特に有用であると考えられる。有機エレクトロルミネッセンス素子に遅延蛍光材料を利用した場合、励起一重項状態の励起子は通常通り蛍光を放射する。一方、励起三重項状態の励起子は、デバイスが発する熱を吸収して励起一重項へ項間交差され蛍光を放射する。このとき、励起一重項からの発光であるため蛍光と同波長での発光でありながら、励起三重項状態から励起一重項状態への逆項間交差により、生じる光の寿命(発光寿命)は通常の蛍光やりん光よりも長くなるため、これらよりも遅延した蛍光として観察される。これを遅延蛍光として定義できる。このような熱活性化型の励起子移動機構を用いれば、キャリア注入後に熱エネルギーの吸収を経ることにより、通常は25%しか生成しなかった励起一重項状態の化合物の比率を25%以上に引き上げることが可能となる。100℃未満の低い温度でも強い蛍光および遅延蛍光を発する化合物を用いれば、デバイスの熱で充分に励起三重項状態から励起一重項状態への項間交差が生じて遅延蛍光を放射するため、発光効率を飛躍的に向上させることができる。
As described above, the light emitting material of the light emitting layer is preferably a delayed fluorescent material because high light emission efficiency can be obtained. High luminous efficiency can be obtained by the delayed fluorescent material based on the following principle.
In an organic electroluminescence element, carriers are injected into a light emitting material from both positive and negative electrodes to generate an excited light emitting material and emit light. In general, in the case of a carrier injection type organic electroluminescence element, 25% of the generated excitons are excited to the excited singlet state, and the remaining 75% are excited to the excited triplet state. Therefore, the use efficiency of energy is higher when phosphorescence, which is light emission from an excited triplet state, is used. However, since the excited triplet state has a long lifetime, energy saturation occurs due to saturation of the excited state and interaction with excitons in the excited triplet state, and in general, the quantum yield of phosphorescence is often not high. On the other hand, delayed fluorescent materials, after energy transition to an excited triplet state due to intersystem crossing, etc., are then crossed back to an excited singlet state due to triplet-triplet annihilation or absorption of thermal energy, and emit fluorescence. To do. In the organic electroluminescence device, it is considered that a thermally activated delayed fluorescent material by absorption of thermal energy is particularly useful. When a delayed fluorescent material is used for the organic electroluminescence element, excitons in the excited singlet state emit fluorescence as usual. On the other hand, excitons in the excited triplet state absorb heat generated by the device and cross between the excited singlets to emit fluorescence. At this time, since the light is emitted from the excited singlet, the light is emitted at the same wavelength as the fluorescence, but the light lifetime (luminescence lifetime) generated by the reverse intersystem crossing from the excited triplet state to the excited singlet state is normal. Since the fluorescence becomes longer than the fluorescence and phosphorescence, it is observed as fluorescence delayed from these. This can be defined as delayed fluorescence. If such a heat-activated exciton transfer mechanism is used, the ratio of the compound in an excited singlet state, which normally generated only 25%, is increased to 25% or more by absorbing thermal energy after carrier injection. It can be raised. If a compound that emits strong fluorescence and delayed fluorescence even at a low temperature of less than 100 ° C is used, the heat of the device will sufficiently cause intersystem crossing from the excited triplet state to the excited singlet state and emit delayed fluorescence. Efficiency can be improved dramatically.
[電子輸送層]
 電子輸送層とは電子を輸送する機能を有する材料からなり、電子輸送層は単層または複数層設けることができる。
 電子輸送材料(正孔阻止材料を兼ねる場合もある)としては、陰極より注入された電子を発光層に伝達する機能を有していればよいが、金属原子を含まないものであることが好ましい。
 使用できる電子輸送層としては例えば、ニトロ置換フルオレン誘導体、ジフェニルキノン誘導体、チオピランジオキシド誘導体、カルボジイミド、フレオレニリデンメタン誘導体、アントラキノジメタンおよびアントロン誘導体、オキサジアゾール誘導体等が挙げられる。さらに、上記オキサジアゾール誘導体において、オキサジアゾール環の酸素原子を硫黄原子に置換したチアジアゾール誘導体、電子吸引基として知られているキノキサリン環を有するキノキサリン誘導体も、電子輸送材料として用いることができる。さらにこれらの材料を高分子鎖に導入した、またはこれらの材料を高分子の主鎖とした高分子材料を用いることもできる。
[Electron transport layer]
The electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer can be provided as a single layer or a plurality of layers.
The electron transport material (which may also serve as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light emitting layer, but preferably does not contain a metal atom. .
Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide oxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.
[電荷トラップ濃度減少層]
 電荷トラップ濃度減少層は、発光層と電子輸送層の界面に設けられる。上記のように、この電荷トラップ濃度減少層は、その層を形成することによって熱刺激電流(TSC)測定における250~320Kの間のピーク面積(高温領域のピーク面積)が減少する層であり、深いトラップ準位における電荷(電子や正孔)の濃度を減少させる機能を有する。本発明の有機エレクトロルミネッセンス素子は、こうした電荷トラップ濃度減少層を有することにより、経時的な性能劣化が抑えられ、長い寿命を得ることができる。
 電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子の高温領域のピーク面積は、電荷トラップ濃度減少層を有しない参照素子の高温領域のピーク面積をS0としたとき、S0未満であることが好ましく、0.71・S0以下であることがより好ましく、0.30・S0以下であることがさらに好ましく、0.10・S0以下であることがさらにより好ましく、理想的に好ましいのはゼロである。こうした電荷トラップ濃度減少層は、深いトラップ準位における電荷の濃度を効果的に減少させるものであり、有機エレクトロルミネッセンス素子の寿命を顕著に延長することができる。
 電荷トラップ濃度減少層の材料としては、その材料からなる層を形成することによってTSC測定における250~320Kの間のピーク面積が減少するものであれば特に限定されないが、第一族原子、第二族原子または遷移金属原子を含有するものであることが好ましく、第一族原子または第二族原子を含有するものであることがより好ましく、リチウム原子を含有するものであることがさらに好ましい。また、遷移金属原子を含有する材料の中では、ユーロピウム、ルテニウム、ガドリニウム、テルビウム、ジスプロシウム、エルビウム、イッテルビウム、レニウム、オスミウム、白金、金を含有するものを好ましく用いることができる。
 これらの原子は、それ単体で電荷トラップ濃度減少層に含有されていてもよいし、これらの原子を含む化合物として電荷トラップ濃度減少層に含有されていてもよいが、これらの原子を含む化合物として電荷トラップ濃度減少層に含有されていることが好ましい。また、これらの原子を含む化合物は、これらの原子と有機リガンドを組み合わせた化合物や有機金属化合物であることが好ましく、これらの原子と有機リガンドを組み合わせた化合物であることがより好ましく、8-ヒドロキシキノリノラト誘導体であることが好ましく、なかでも8-ヒドロキシキノリノラト-リチウム(Liq)であることが特に好ましい。素子内部の深いトラップ準位の形成には、励起子-ポーラロン消滅が起因していることが知られているが、Liqは励起三重項エネルギー準位が低いために、励起子の励起三重項エネルギーがLiqに移動し易く、励起子-ポーラロン消滅を抑制しうると推測される。これにより、Liqからなる電荷トラップ濃度減少層は、深いトラップ準位における電荷の量を効果的に減少させることができる。
 また、電荷トラップ濃度減少層は、その層を形成することによってTSC測定における250~320Kの間のピーク面積が減少する材料であれば、第一族原子、第二族原子および遷移金属原子を含まない化合物が併存していてもよい。ただし、電荷トラップ濃度減少層における第一族原子、第二族原子または遷移金属原子を含む化合物の含有量は、電荷トラップ濃度減少層の全質量の80質量%以上であり、より好ましくは90質量%以上であり、さらに好ましくは95質量%以上であり、100質量%であってもよい。特に、これらの原子と有機リガンドを組み合わせた化合物を上記の含有量で電荷トラップ濃度減少層に含有させることにより、駆動時の経時的な性能劣化を顕著に抑制することができる。
 電荷トラップ濃度減少層の平均膜厚は、特に限定されないが、0.1~100nmであることが好ましく、0.5~10nmであることがより好ましく、1~3nmであるがさらに好ましい。
[Charge trap concentration decreasing layer]
The charge trap concentration reducing layer is provided at the interface between the light emitting layer and the electron transport layer. As described above, the charge trap concentration-decreasing layer is a layer in which the peak area between 250 and 320 K (the peak area of the high temperature region) in the thermally stimulated current (TSC) measurement is reduced by forming the layer. It has a function of reducing the concentration of charges (electrons and holes) at deep trap levels. By having such a charge trap concentration decreasing layer, the organic electroluminescence element of the present invention can suppress deterioration in performance over time and obtain a long life.
Peak area of the high temperature region of the organic electroluminescent device having a charge trapping density-reduced layer, when the peak area of the high temperature region of the reference element having no charge trapping density reducing layer was S 0, preferably less than S 0 0.71 · S 0 or less, more preferably 0.30 · S 0 or less, even more preferably 0.10 · S 0 or less, ideally preferred Zero. Such a charge trap concentration reducing layer effectively reduces the charge concentration in the deep trap level, and can significantly extend the lifetime of the organic electroluminescence element.
The material of the charge trap concentration reducing layer is not particularly limited as long as the peak area between 250 and 320 K in TSC measurement is reduced by forming a layer made of the material. It is preferably one containing a group atom or transition metal atom, more preferably one containing a group 1 atom or group 2 atom, and further preferably one containing a lithium atom. Among materials containing transition metal atoms, materials containing europium, ruthenium, gadolinium, terbium, dysprosium, erbium, ytterbium, rhenium, osmium, platinum, and gold can be preferably used.
These atoms may be contained alone in the charge trap concentration-reducing layer, or may be contained in the charge trap concentration-reducing layer as a compound containing these atoms, but as a compound containing these atoms, It is preferably contained in the charge trap concentration reducing layer. Further, the compound containing these atoms is preferably a compound or organometallic compound in which these atoms and an organic ligand are combined, more preferably a compound in which these atoms and an organic ligand are combined, and 8-hydroxy A quinolinolato derivative is preferable, and 8-hydroxyquinolinolato-lithium (Liq) is particularly preferable. The formation of deep trap levels inside the device is known to be due to exciton-polaron annihilation, but Liq has a low excited triplet energy level, so the excited triplet energy of the exciton is low. Is likely to move to Liq and can suppress exciton-polaron annihilation. Thereby, the charge trap concentration decreasing layer made of Liq can effectively reduce the amount of charges in the deep trap level.
In addition, the charge trap concentration-decreasing layer includes a group 1 atom, a group 2 atom, and a transition metal atom as long as the layer is formed of a material that can reduce the peak area between 250 and 320 K in TSC measurement. None of the compounds may coexist. However, the content of the compound containing the first group atom, second group atom or transition metal atom in the charge trap concentration-decreasing layer is 80% by mass or more of the total mass of the charge trap concentration-decreasing layer, more preferably 90 masses. % Or more, more preferably 95% by mass or more, and may be 100% by mass. In particular, the deterioration of performance over time during driving can be remarkably suppressed by including in the charge trap concentration-decreasing layer a compound in which these atoms and an organic ligand are combined in the above-described content.
The average film thickness of the charge trap concentration reducing layer is not particularly limited, but is preferably 0.1 to 100 nm, more preferably 0.5 to 10 nm, and further preferably 1 to 3 nm.
[第2電子輸送層]
 第2電子輸送層は、電子輸送材料からなり、単層または複数層設けることができる。第2電子輸送層に用いる電子輸送材料の説明と好ましい範囲については、上記の電子輸送層の説明と好ましい範囲を参照することができる。
[Second electron transport layer]
The second electron transport layer is made of an electron transport material and can be provided as a single layer or a plurality of layers. For the explanation and preferred range of the electron transport material used for the second electron transport layer, the explanation and preferred range of the electron transport layer can be referred to.
 本発明の有機エレクトロルミネッセンス素子は、上記の電子輸送層および第2電子輸送層の少なくとも1層に、第一族原子、第二族原子または遷移金属原子を含む化合物を含有することが好ましく、電子輸送層および第2電子輸送層がそれぞれ単層である場合には、第2電子輸送層に第一族原子、第二族原子または遷移金属原子を含む化合物を含有することがより好ましい。これにより、有機エレクトロルミネッセンス素子の経時的な性能劣化をより抑制して、寿命をさらに延長することができる。第一族原子、第二族原子、遷移金属原子、およびこれらの原子を含む化合物の好ましい範囲と具体例については、上記の電荷トラップ濃度減少層で用いる第一族原子、第二族原子、遷移金属原子、およびこれらの原子を含む化合物の好ましい範囲と具体例を参照することができる。ここで、電子輸送層、第2電子輸送層がこれらの原子を含む化合物を含有する場合、その化合物は電荷トラップ濃度減少層の構成材料と同じであっても異なっていてもよいが、同じであることが好ましい。
 また、電子輸送層、第2電子輸送層が第一族原子、第二族原子または遷移金属原子を含有する化合物を含む場合、これらの原子を含む化合物の含有量は、各電子輸送層の全量に対して10重量%以上であることが好ましく、50重量%以上であることがより好ましい。また、その含有量は、電子輸送層の全量に対して90重量%以下であることが好ましく、75重量%以下であることがさらに好ましい。
The organic electroluminescence device of the present invention preferably contains a compound containing a first group atom, second group atom or transition metal atom in at least one of the electron transport layer and the second electron transport layer. When the transport layer and the second electron transport layer are each a single layer, it is more preferable that the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom. Thereby, the performance deterioration with time of the organic electroluminescence element can be further suppressed, and the life can be further extended. For preferred ranges and specific examples of Group 1 atoms, Group 2 atoms, transition metal atoms, and compounds containing these atoms, see Group 1 atoms, Group 2 atoms, transitions used in the charge trap concentration-reducing layer described above. Reference can be made to preferred ranges and specific examples of metal atoms and compounds containing these atoms. Here, when the electron transport layer and the second electron transport layer contain a compound containing these atoms, the compound may be the same as or different from the constituent material of the charge trap concentration-reducing layer. Preferably there is.
Moreover, when an electron carrying layer and a 2nd electron carrying layer contain the compound containing a 1st group atom, a 2nd group atom, or a transition metal atom, content of the compound containing these atoms is the whole quantity of each electron carrying layer. Is preferably 10% by weight or more, more preferably 50% by weight or more. Further, the content thereof is preferably 90% by weight or less, and more preferably 75% by weight or less, with respect to the total amount of the electron transport layer.
[機能層]
 機能層は、第一族原子、第二族原子または遷移金属原子を含有する材料からなり、電子輸送層と第2電子輸送層の間に設けられる。
 機能層で用いる第一族原子、第二族原子または遷移金属原子を含有する材料の説明と好ましい範囲、材料の含有比率および機能層の平均膜厚の好ましい範囲については、上記の電荷トラップ濃度減少層における対応する説明を参照することができる。
[Functional layer]
The functional layer is made of a material containing a first group atom, a second group atom or a transition metal atom, and is provided between the electron transport layer and the second electron transport layer.
For the explanation and preferred range of the material containing the first group atom, second group atom or transition metal atom used in the functional layer, and the preferred range of the content ratio of the material and the average thickness of the functional layer, the above charge trap concentration reduction Reference can be made to the corresponding description in the layers.
[注入層]
 注入層とは、駆動電圧低下や発光輝度向上のために電極と有機層間に設けられる層のことで、正孔注入層と電子注入層があり、陽極と発光層または正孔輸送層の間、および陰極と電子輸送層との間に存在させてもよい。注入層は必要に応じて設けることができる。
[Injection layer]
The injection layer is a layer provided between the electrode and the organic layer for lowering the driving voltage and improving the luminance of light emission. There are a hole injection layer and an electron injection layer, and between the anode and the light emitting layer or the hole transport layer. And may be present between the cathode and the electron transport layer. The injection layer can be provided as necessary.
[阻止層]
 阻止層は、発光層中に存在する電荷(電子もしくは正孔)および/または励起子の発光層外への拡散を阻止することができる層である。電子阻止層は、発光層および正孔輸送層の間に配置されることができ、電子が正孔輸送層の方に向かって発光層を通過することを阻止する。同様に、正孔阻止層は発光層および電子輸送層の間に配置されることができ、正孔が電子輸送層の方に向かって発光層を通過することを阻止する。本発明では、発光層と電子輸送層の間に配置される電荷トラップ濃度減少層に、この正孔阻止層の機能を兼ねさせることができる。例えば、Liqからなる電荷トラップ濃度減少層は正孔阻止層としての機能を有することが実験により確認されている。阻止層はまた、励起子が発光層の外側に拡散することを阻止するために用いることができる。すなわち電子阻止層、正孔阻止層はそれぞれ励起子阻止層としての機能も兼ね備えることができる。本明細書でいう電子阻止層または励起子阻止層は、一つの層で電子阻止層および励起子阻止層の機能を有する層を含む意味で使用される。
[Blocking layer]
The blocking layer is a layer that can prevent diffusion of charges (electrons or holes) and / or excitons existing in the light emitting layer to the outside of the light emitting layer. The electron blocking layer can be disposed between the light emitting layer and the hole transport layer and blocks electrons from passing through the light emitting layer toward the hole transport layer. Similarly, a hole blocking layer can be disposed between the light emitting layer and the electron transporting layer to prevent holes from passing through the light emitting layer toward the electron transporting layer. In the present invention, the charge trap concentration decreasing layer disposed between the light emitting layer and the electron transporting layer can also function as the hole blocking layer. For example, it has been experimentally confirmed that the charge trap concentration decreasing layer made of Liq has a function as a hole blocking layer. The blocking layer can also be used to block excitons from diffusing outside the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also function as an exciton blocking layer. The term “electron blocking layer” or “exciton blocking layer” as used herein is used in the sense of including a layer having the functions of an electron blocking layer and an exciton blocking layer in one layer.
[正孔阻止層]
 正孔阻止層とは広い意味では電子輸送層の機能を有する。正孔阻止層は電子を輸送しつつ、正孔が電子輸送層へ到達することを阻止する役割があり、これにより発光層中での電子と正孔の再結合確率を向上させることができる。上記のように、本発明では、この正孔阻止層の機能を電荷トラップ濃度減少層に兼ねさせることができる。
[Hole blocking layer]
The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking holes from reaching the electron transport layer while transporting electrons, thereby improving the recombination probability of electrons and holes in the light emitting layer. As described above, in the present invention, the function of the hole blocking layer can be combined with the charge trap concentration reducing layer.
[電子阻止層]
 電子阻止層とは、広い意味では正孔を輸送する機能を有する。電子阻止層は正孔を輸送しつつ、電子が正孔輸送層へ到達することを阻止する役割があり、これにより発光層中での電子と正孔が再結合する確率を向上させることができる。
[Electron blocking layer]
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role to block electrons from reaching the hole transport layer while transporting holes, thereby improving the probability of recombination of electrons and holes in the light emitting layer. .
[励起子阻止層]
 励起子阻止層とは、発光層内で正孔と電子が再結合することにより生じた励起子が電荷輸送層に拡散することを阻止するための層であり、本層の挿入により励起子を効率的に発光層内に閉じ込めることが可能となり、素子の発光効率を向上させることができる。励起子阻止層は発光層に隣接して陽極側、陰極側のいずれにも挿入することができ、両方同時に挿入することも可能である。すなわち、励起子阻止層を陽極側に有する場合、正孔輸送層と発光層の間に、発光層に隣接して該層を挿入することができ、陰極側に挿入する場合、発光層と陰極との間に、発光層に隣接して該層を挿入することができる。また、陽極と、発光層の陽極側に隣接する励起子阻止層との間には、正孔注入層や電子阻止層などを有することができ、陰極と、発光層の陰極側に隣接する励起子阻止層との間には、電子注入層、電子輸送層、正孔阻止層などを有することができる。阻止層を配置する場合、阻止層として用いる材料の励起一重項エネルギーおよび励起三重項エネルギーの少なくともいずれか一方は、発光材料の励起一重項エネルギーおよび励起三重項エネルギーよりも高いことが好ましい。本発明では、この励起子阻止層の機能も電荷トラップ濃度減少層に兼ねさせることができる。
[Exciton blocking layer]
The exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting layer from diffusing into the charge transport layer. It becomes possible to efficiently confine in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both can be inserted simultaneously. That is, when the exciton blocking layer is provided on the anode side, the layer can be inserted adjacent to the light emitting layer between the hole transport layer and the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode Between the luminescent layer and the light-emitting layer. Further, a hole injection layer, an electron blocking layer, or the like can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the excitation adjacent to the cathode and the cathode side of the light emitting layer can be provided. Between the child blocking layer, an electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided. When the blocking layer is disposed, at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is preferably higher than the excited singlet energy and the excited triplet energy of the light emitting material. In the present invention, the function of the exciton blocking layer can also serve as the charge trap concentration reducing layer.
[正孔輸送層]
 正孔輸送層とは正孔を輸送する機能を有する正孔輸送材料からなり、正孔輸送層は単層または複数層設けることができる。
 正孔輸送材料としては、正孔の注入または輸送、電子の障壁性のいずれかを有するものであり、有機物、無機物のいずれであってもよい。使用できる公知の正孔輸送材料としては例えば、トリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、カルバゾール誘導体、インドロカルバゾール誘導体、ポリアリールアルカン誘導体、ピラゾリン誘導体およびピラゾロン誘導体、フェニレンジアミン誘導体、アリールアミン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントラセン誘導体、フルオレノン誘導体、ヒドラゾン誘導体、スチルベン誘導体、シラザン誘導体、アニリン系共重合体、また導電性高分子オリゴマー、特にチオフェンオリゴマー等が挙げられるが、ポルフィリン化合物、芳香族第3級アミン化合物およびスチリルアミン化合物を用いることが好ましく、芳香族第3級アミン化合物を用いることがより好ましい。
[Hole transport layer]
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material has any one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. Known hole transport materials that can be used include, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Examples include amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. An aromatic tertiary amine compound and an styrylamine compound are preferably used, and an aromatic tertiary amine compound is more preferably used.
 本発明の有機エレクトロルミネッセンス素子は、例えば、上記の各層を積層位置に合わせて順に製膜することにより作製することができる。各層の製膜方法は特に限定されず、ドライプロセス、ウェットプロセスのどちらで作製してもよい。 The organic electroluminescence element of the present invention can be produced, for example, by sequentially forming each of the above layers in accordance with the lamination position. The method for forming each layer is not particularly limited, and it may be produced by either a dry process or a wet process.
 以下に、有機エレクトロルミネッセンス素子に用いることができる好ましい材料を具体的に例示する。ただし、本発明において用いることができる材料は、以下の例示化合物によって限定的に解釈されることはない。また、特定の機能を有する材料として例示した化合物であっても、その他の機能を有する材料として転用することも可能である。なお、以下の例示化合物の構造式におけるR、R’、R1~R10は、各々独立に水素原子または置換基を表す。Xは環骨格を形成する炭素原子または複素原子を表し、nは3~5の整数を表し、Yは置換基を表し、mは0以上の整数を表す。 Below, the preferable material which can be used for an organic electroluminescent element is illustrated concretely. However, the material that can be used in the present invention is not limited to the following exemplary compounds. Moreover, even if it is a compound illustrated as a material which has a specific function, it can also be diverted as a material which has another function. In the structural formulas of the following exemplary compounds, R, R ′, and R 1 to R 10 each independently represent a hydrogen atom or a substituent. X represents a carbon atom or a hetero atom forming a ring skeleton, n represents an integer of 3 to 5, Y represents a substituent, and m represents an integer of 0 or more.
 発光層に用いる発光材料は、蛍光を放射する発光材料であってもリン光を放射する発光材料であってもよい。蛍光発光材料は、遅延蛍光を放射する発光材料であっても、遅延蛍光を放射しない発光材料であってもよい。発光層の発光材料として用いることができる好ましい化合物として、下記の化合物を挙げることができる。 The light emitting material used for the light emitting layer may be a light emitting material that emits fluorescence or a light emitting material that emits phosphorescence. The fluorescent light-emitting material may be a light-emitting material that emits delayed fluorescence or a light-emitting material that does not emit delayed fluorescence. Examples of preferable compounds that can be used as the light emitting material of the light emitting layer include the following compounds.
Figure JPOXMLDOC01-appb-C000009
Figure JPOXMLDOC01-appb-C000009
Figure JPOXMLDOC01-appb-C000010
Figure JPOXMLDOC01-appb-C000010
Figure JPOXMLDOC01-appb-C000011
Figure JPOXMLDOC01-appb-C000011
Figure JPOXMLDOC01-appb-C000012
Figure JPOXMLDOC01-appb-C000012
Figure JPOXMLDOC01-appb-C000013
Figure JPOXMLDOC01-appb-C000013
 遅延蛍光を放射する発光材料(遅延蛍光体)として、WO2013/154064号公報の段落0008~0048および0095~0133、WO2013/011954号公報の段落0007~0047および0073~0085、WO2013/011955号公報の段落0007~0033および0059~0066、WO2013/081088号公報の段落0008~0071および0118~0133、特開2013-256490号公報の段落0009~0046および0093~0134、特開2013-116975号公報の段落0008~0020および0038~0040、WO2013/133359号公報の段落0007~0032および0079~0084、WO2013/161437号公報の段落0008~0054および0101~0121、特開2014-9352号公報の段落0007~0041および0060~0069、特開2014-9224号公報の段落0008~0048および0067~0076に記載される一般式に包含される化合物、特に例示化合物を好ましく挙げることができる。これらの公報は、本明細書の一部としてここに引用している。
 また、遅延蛍光を放射する発光材料(遅延蛍光体)として、特開2013-253121号公報、WO2013/133359号公報、WO2014/034535号公報、WO2014/115743号公報、WO2014/122895号公報、WO2014/126200号公報、WO2014/136758号公報、WO2014/133121号公報、WO2014/136860号公報、WO2014/196585号公報、WO2014/189122号公報、WO2014/168101号公報、WO2015/008580号公報、WO2014/203840号公報、WO2015/002213号公報、WO2015/016200号公報、WO2015/019725号公報、WO2015/072470号公報、WO2015/108049号公報、WO2015/080182号公報、WO2015/072537号公報、WO2015/080183号公報、特開2015-129240号公報、WO2015/129714号公報、WO2015/129715号公報、WO2015/133501号公報、WO2015/136880号公報、WO2015/137244号公報、WO2015/137202号公報、WO2015/137136号公報、WO2015/146541号公報、WO2015/159541号公報に記載される一般式に包含される化合物、特に例示化合物を好ましく挙げることができる。これらの公報も、本明細書の一部としてここに引用している。
As luminescent materials that emit delayed fluorescence (delayed phosphors), paragraphs 0008 to 0048 and 0095 to 0133 of WO 2013/154064, paragraphs 0007 to 0047 and 0073 to 0085 of WO 2013/011954, and WO 2013/011955 Paragraphs 0007 to 0033 and 0059 to 0066, paragraphs 0008 to 0071 and 0118 to 0133 of WO2013 / 081088, paragraphs 0009 to 0046 and 0093 to 0134 of JP2013-256490A, paragraphs of JP2013-116975A 0008-0020 and 0038-0040, paragraphs 0007-0032 and 0079-0084 of WO2013 / 133359, paragraph 000 of WO2013 / 161437 To 0054 and 0101 to 0121, paragraphs 0007 to 0041 and 0060 to 0069 of JP2014-9352, and paragraphs 0008 to 0048 and 0067 to 0076 of JP2014-9224. Preferred examples include compounds, particularly exemplified compounds. These publications are hereby incorporated by reference as part of this specification.
Further, as a light emitting material (delayed phosphor) that emits delayed fluorescence, JP2013-253121A, WO2013 / 133359, WO2014 / 034535, WO2014 / 115743, WO2014 / 122895, WO2014 / No. 126200, WO2014 / 136758, WO2014 / 133121, WO2014 / 136860, WO2014 / 196585, WO2014 / 189122, WO2014 / 168101, WO2015 / 008580, WO2014 / 203840 Publication, WO2015 / 002213 publication, WO2015 / 016200 publication, WO2015 / 019725 publication, WO2015 / 072470 publication, O2015 / 108049, WO2015 / 080182, WO2015 / 072537, WO2015 / 080183, JP2015-129240, WO2015 / 129714, WO2015 / 129715, WO2015 / 133501, Compounds included in the general formulas described in WO2015 / 136880, WO2015 / 137244, WO2015 / 137202, WO2015 / 137136, WO2015 / 146541, and WO2015 / 159541, particularly exemplary compounds Can be preferably mentioned. These publications are also cited herein as part of this specification.
 次に、発光層のホスト材料としても用いることができる好ましい化合物を挙げる。 Next, preferred compounds that can also be used as a host material for the light emitting layer are listed.
Figure JPOXMLDOC01-appb-C000014
Figure JPOXMLDOC01-appb-C000014
Figure JPOXMLDOC01-appb-C000015
Figure JPOXMLDOC01-appb-C000015
Figure JPOXMLDOC01-appb-C000016
Figure JPOXMLDOC01-appb-C000016
Figure JPOXMLDOC01-appb-C000017
Figure JPOXMLDOC01-appb-C000017
Figure JPOXMLDOC01-appb-C000018
Figure JPOXMLDOC01-appb-C000018
 次に、正孔注入材料として用いることができる好ましい化合物例を挙げる。 Next, preferred examples of compounds that can be used as the hole injection material are given.
Figure JPOXMLDOC01-appb-C000019
Figure JPOXMLDOC01-appb-C000019
 次に、正孔輸送材料として用いることができる好ましい化合物例を挙げる。 Next, preferred examples of compounds that can be used as a hole transport material are given.
Figure JPOXMLDOC01-appb-C000020
Figure JPOXMLDOC01-appb-C000020
Figure JPOXMLDOC01-appb-C000021
Figure JPOXMLDOC01-appb-C000021
Figure JPOXMLDOC01-appb-C000022
Figure JPOXMLDOC01-appb-C000022
Figure JPOXMLDOC01-appb-C000023
Figure JPOXMLDOC01-appb-C000023
Figure JPOXMLDOC01-appb-C000024
Figure JPOXMLDOC01-appb-C000024
Figure JPOXMLDOC01-appb-C000025
Figure JPOXMLDOC01-appb-C000025
 次に、電子阻止材料として用いることができる好ましい化合物例を挙げる。 Next, preferred examples of compounds that can be used as an electron blocking material are given.
Figure JPOXMLDOC01-appb-C000026
Figure JPOXMLDOC01-appb-C000026
 次に、電子輸送材料として用いることができる好ましい化合物例を挙げる。 Next, preferred compound examples that can be used as an electron transporting material are listed.
Figure JPOXMLDOC01-appb-C000027
Figure JPOXMLDOC01-appb-C000027
Figure JPOXMLDOC01-appb-C000028
Figure JPOXMLDOC01-appb-C000028
Figure JPOXMLDOC01-appb-C000029
Figure JPOXMLDOC01-appb-C000029
 次に、電子注入材料として用いることができる好ましい化合物例を挙げる。 Next, preferred examples of compounds that can be used as an electron injection material will be given.
Figure JPOXMLDOC01-appb-C000030
Figure JPOXMLDOC01-appb-C000030
 さらに添加可能な材料として好ましい化合物例を挙げる。例えば、安定化材料として添加すること等が考えられる。 Further preferred compound examples are given as materials that can be added. For example, adding as a stabilizing material can be considered.
Figure JPOXMLDOC01-appb-C000031
Figure JPOXMLDOC01-appb-C000031
 上述の方法により作製された有機エレクトロルミネッセンス素子は、得られた素子の陽極と陰極の間に電界を印加することにより発光する。このとき、励起一重項エネルギーによる発光であれば、そのエネルギーレベルに応じた波長の光が、蛍光発光および遅延蛍光発光として確認される。また、励起三重項エネルギーによる発光であれば、そのエネルギーレベルに応じた波長が、りん光として確認される。通常の蛍光は、遅延蛍光発光よりも蛍光寿命が短いため、発光寿命は蛍光と遅延蛍光で区別できる。
 一方、りん光については、通常の有機化合物では、励起三重項エネルギーは不安定で熱等に変換され、寿命が短く直ちに失活するため、室温では殆ど観測できない。通常の有機化合物の励起三重項エネルギーを測定するためには、極低温の条件での発光を観測することにより測定可能である。
The organic electroluminescence device produced by the above-described method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, if the light is emitted by excited singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. In addition, in the case of light emission by excited triplet energy, a wavelength corresponding to the energy level is confirmed as phosphorescence. Since normal fluorescence has a shorter fluorescence lifetime than delayed fluorescence, the emission lifetime can be distinguished from fluorescence and delayed fluorescence.
On the other hand, in the case of phosphorescence, in ordinary organic compounds, the excited triplet energy is unstable and converted to heat, etc., and the lifetime is short, and it is immediately deactivated. In order to measure the excited triplet energy of a normal organic compound, it can be measured by observing light emission under extremely low temperature conditions.
 本発明の有機エレクトロルミネッセンス素子は、単一の素子、アレイ状に配置された構造からなる素子、陽極と陰極がX-Yマトリックス状に配置された構造のいずれにおいても適用することができる。本発明によれば、発光層と電子輸送層の界面に電荷トラップ濃度減少層が設けられていることにより、駆動時の経時的な性能劣化が抑えられ、長期間に亘って高い輝度で発光し、且つ低電圧駆動が可能な有機エレクトロルミネッセンス素子が得られる。本発明の有機エレクトロルミネッセンス素子は、さらに様々な用途へ応用することが可能である。例えば、本発明の有機エレクトロルミネッセンス素子を用いて、有機エレクトロルミネッセンス表示装置を製造することが可能であり、詳細については、時任静士、安達千波矢、村田英幸共著「有機ELディスプレイ」(オーム社)を参照することができる。また、特に本発明の有機エレクトロルミネッセンス素子は、需要が大きい有機エレクトロルミネッセンス照明やバックライトに応用することもできる。 The organic electroluminescence element of the present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the present invention, since the charge trap concentration decreasing layer is provided at the interface between the light emitting layer and the electron transport layer, deterioration of performance over time during driving is suppressed, and light is emitted with high luminance over a long period of time. In addition, an organic electroluminescence element capable of being driven at a low voltage is obtained. The organic electroluminescence device of the present invention can be further applied to various uses. For example, it is possible to produce an organic electroluminescence display device using the organic electroluminescence element of the present invention. For details, see “Organic EL Display” (Ohm Co., Ltd.) written by Shizushi Tokito, Chiba Adachi and Hideyuki Murata. ) Can be referred to. In particular, the organic electroluminescence device of the present invention can be applied to organic electroluminescence illumination and backlights that are in great demand.
 以下に実施例を挙げて本発明の特徴をさらに具体的に説明する。以下に示す材料、処理内容、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更することができる。したがって、本発明の範囲は以下に示す具体例により限定的に解釈されるべきものではない。なお、発光特性の評価は、ソースメータ(ケースレー社製:2400シリーズ)、半導体パラメータ・アナライザ(アジレント・テクノロジー社製:E5273A)、光パワーメータ測定装置(ニューポート社製:1930C)、光学分光器(オーシャンオプティクス社製:USB2000)、分光放射計(トプコン社製:SR-3)およびストリークカメラ(浜松ホトニクス(株)製C4334型)を用いて行った。
 また、熱刺激電流(TSC)測定は、理学電機株式会社製の熱刺激電流測定機(商品名TSC-FETT EL2000)を用い、上記の「電荷トラップ濃度減少層」の定義のところで説明した条件に準じて行った。
 また、エネルギーダイアグラムの各エネルギー準位の測定は、HOMOは、大気中光電子分光装置(理研計器:AC3)、LUMOは、UV可視近赤外分光装置(パーキンエルマー:LAMBDA950)を用いて行った。
The features of the present invention will be described more specifically with reference to the following examples. The following materials, processing details, processing procedures, and the like can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. Note that the evaluation of the light emission characteristics is as follows: source meter (manufactured by Keithley: 2400 series), semiconductor parameter analyzer (manufactured by Agilent Technologies: E5273A), optical power meter measuring device (manufactured by Newport: 1930C), optical spectrometer (Ocean Optics, USB2000), spectroradiometer (Topcon, SR-3) and streak camera (Hamamatsu Photonics C4334) were used.
Thermally stimulated current (TSC) measurement was performed using a thermally stimulated current measuring instrument (trade name: TSC-FETT EL2000) manufactured by Rigaku Corporation, under the conditions described in the above definition of “charge trap concentration reducing layer”. According to the same procedure.
Further, each energy level of the energy diagram was measured using an atmospheric photoelectron spectrometer (RIKEN KEIKI: AC3) for HOMO, and a UV-visible near infrared spectrometer (Perkin Elmer: LAMBDA950) for LUMO.
(実施例1) Liqからなる電荷トラップ濃度減少層を有する有機エレクトロルミネッセンス素子の作製と評価
 膜厚100nmのインジウム・スズ酸化物(ITO)からなる陽極が形成されたガラス基板上に、各薄膜を真空蒸着法にて、真空度10-5Paで積層した。まず、ITO上にHAT-CNを10nmの厚さに形成し、その上に、Tris-PCzを30nmの厚さに形成した。次に、4CzIPNとmCBPを異なる蒸着源から共蒸着し、30nmの厚さの層を形成して発光層とした。この時、4CzIPNの濃度は15重量%とした。次に、Liqを1nmの厚さに蒸着して電荷トラップ濃度減少層を形成した。続いて、T2Tを10nmの厚さに蒸着して電子輸送層を形成し、その上に、BPy-TP2を40nmの厚さに蒸着して第2電子輸送層を形成した。さらにフッ化リチウム(LiF)を0.8nm蒸着し、次いでアルミニウム(Al)を100nmの厚さに蒸着することにより陰極を形成し、有機エレクトロルミネッセンス素子(有機EL素子)とした。
 また、これとは別に、電荷トラップ濃度減少層を形成する際、Liqの蒸着厚さを2nmまたは3nmに変更すること以外は、上記と同様にして有機EL素子を作製した。
 さらに、比較として、電荷トラップ濃度減少層を形成しないこと以外は、上記と同様にして有機EL素子を作製した。
 作製した有機EL素子のTSCプロファイルを図5に示し、発光スペクトルを図6に示し、電圧-電流密度-輝度特性を図7に示し、電流密度-外部量子効率特性を図8に示し、輝度比と電圧変化量の経時的変化を図9に示す。これらの図中、「Ref.」は電荷トラップ濃度減少層を形成していない有機EL素子を表し、「1nm」、「2nm」、「3nm」は、それぞれ、その厚みで電荷トラップ濃度減少層を形成した有機EL素子を表す。また、図9において、「L0/L」は、初期輝度L0(1000cd/m2)に対する測定輝度Lの輝度比を表し、ΔVは初期電圧からの電圧変化量を表す。下記の図13、16、17、20、25、30の「L0/L」、「ΔV」も、これと同じ意味である。
 また、実施例1で作製した有機EL素子のデバイス特性を表1にまとめて示す。
 図5のTSCプロファイルを見ると、電荷トラップ濃度減少層を1nmの厚みで形成した有機EL素子は、電荷トラップ濃度減少層を形成していない有機EL素子(Ref.)に比べて250~320Kの間のピーク強度が明らかに小さい。また、電荷トラップ濃度減少層を2nmまたは3nmの厚みで形成した有機EL素子については、TSCの測定範囲が320Kまでに限定されるため、それよりも高温側のプロファイルは不明である。しかし、その温度までの電流変化から推測して、これらの有機EL素子の高温側のピーク強度も、電荷トラップ濃度減少層を形成していない有機EL素子の250~320Kの間のピーク強度に比べて小さいと推定しうる。これらのことから、Liq層が電荷トラップ濃度減少層として機能することを確認することができた。
 また、図9から、電荷トラップ濃度減少層を形成した有機EL素子は、電荷トラップ濃度減少層を形成していない有機EL素子に比べて、経時的な輝度比の低下および電圧変化量の上昇が顕著に抑えられており、その効果は、電荷トラップ濃度減少層の厚さが厚くなる程大きくなることがわかる。このことから、電荷トラップ濃度減少層は、有機EL素子の長寿命化に大きく寄与することが確認された。なお、外部量子効率については、電荷トラップ濃度減少層を形成した有機EL素子の方が、電荷トラップ濃度減少層を形成していない有機EL素子よりも若干小さくなっているが、上記の長寿命化の効果は顕著であり、これにより、有機EL素子の有用性が大きく向上すると評価することができる。
(Example 1) Production and evaluation of an organic electroluminescence device having a charge trap concentration reducing layer made of Liq Each thin film was formed on a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed. Lamination was performed at a vacuum degree of 10 −5 Pa by a vacuum deposition method. First, HAT-CN was formed to a thickness of 10 nm on ITO, and Tris-PCz was formed to a thickness of 30 nm thereon. Next, 4CzIPN and mCBP were co-evaporated from different evaporation sources to form a layer having a thickness of 30 nm as a light emitting layer. At this time, the concentration of 4CzIPN was 15% by weight. Next, Liq was deposited to a thickness of 1 nm to form a charge trap concentration reducing layer. Subsequently, T2T was vapor deposited to a thickness of 10 nm to form an electron transport layer, and BPy-TP2 was vapor deposited to a thickness of 40 nm thereon to form a second electron transport layer. Further, lithium fluoride (LiF) was vapor-deposited to 0.8 nm, and then aluminum (Al) was vapor-deposited to a thickness of 100 nm to form a cathode, whereby an organic electroluminescence element (organic EL element) was obtained.
Separately from this, an organic EL device was produced in the same manner as described above except that the Liq deposition thickness was changed to 2 nm or 3 nm when the charge trap concentration-decreasing layer was formed.
Further, as a comparison, an organic EL element was produced in the same manner as described above except that the charge trap concentration reducing layer was not formed.
The TSC profile of the fabricated organic EL device is shown in FIG. 5, the emission spectrum is shown in FIG. 6, the voltage-current density-luminance characteristics are shown in FIG. 7, the current density-external quantum efficiency characteristics are shown in FIG. FIG. 9 shows changes over time in the amount of voltage change. In these drawings, “Ref.” Represents an organic EL element in which no charge trap concentration-reducing layer is formed, and “1 nm”, “2 nm”, and “3 nm” respectively represent the charge trap concentration-reducing layer with the thickness. The formed organic EL element is represented. In FIG. 9, “L 0 / L” represents the luminance ratio of the measured luminance L to the initial luminance L 0 (1000 cd / m 2 ), and ΔV represents the amount of voltage change from the initial voltage. “L 0 / L” and “ΔV” in FIGS. 13, 16, 17, 20, 25, and 30 below have the same meaning.
Table 1 summarizes the device characteristics of the organic EL element produced in Example 1.
Referring to the TSC profile in FIG. 5, the organic EL element in which the charge trap concentration decreasing layer is formed with a thickness of 1 nm is 250 to 320 K compared to the organic EL element (Ref.) In which the charge trap concentration decreasing layer is not formed. The peak intensity between is clearly small. In addition, regarding the organic EL element in which the charge trap concentration-decreasing layer is formed with a thickness of 2 nm or 3 nm, the TSC measurement range is limited to 320K, so the profile on the higher temperature side is unknown. However, inferred from the current change up to that temperature, the peak intensity on the high temperature side of these organic EL elements is also higher than the peak intensity between 250 and 320 K of the organic EL elements not formed with the charge trap concentration reducing layer. Can be estimated to be small. From these facts, it was confirmed that the Liq layer functions as a charge trap concentration reducing layer.
Further, from FIG. 9, the organic EL element in which the charge trap concentration reducing layer is formed has a decrease in luminance ratio and an increase in voltage change over time compared to an organic EL element in which the charge trap concentration reducing layer is not formed. It is remarkably suppressed, and it can be seen that the effect increases as the thickness of the charge trap concentration decreasing layer increases. From this, it was confirmed that the charge trap concentration decreasing layer greatly contributes to the extension of the lifetime of the organic EL element. As for the external quantum efficiency, the organic EL element in which the charge trap concentration reducing layer is formed is slightly smaller than the organic EL element in which the charge trap concentration reducing layer is not formed. This effect is remarkable, and it can be evaluated that the usefulness of the organic EL element is greatly improved.
(実施例2)Liqからなる電荷トラップ濃度減少層とLiqからなる機能層を有する有機エレクトロルミネッセンス素子の作製と評価
 電荷トラップ濃度減少層の厚みを1nmまたは3nmとし、さらに、電子輸送層と第2電子輸送層の間に、蒸着法により、Liqからなる機能層を1nm、2nmまたは3nmの厚みで形成したこと以外は、実施例1と同様にして有機エレクトロルミネッセンス素子(EL素子)を作製した。
 電荷トラップ濃度減少層の厚みを1nmとし、機能層を各種厚みで形成した有機EL素子の発光スペクトルを図10に示し、電圧-電流密度-輝度特性を図11に示し、電流密度-外部量子効率特性を図12に示し、輝度比と電圧変化量の経時的変化を図13に示す。電荷トラップ濃度減少層の厚みを3nmとし、機能層を各種厚みで形成した有機EL素子の電圧-電流密度-輝度特性を図14に示し、電流密度-外部量子効率特性を図15に示し、輝度比と電圧変化量の経時的変化を図16に示す。また、各図には、機能層を形成しないこと以外は同様にして作製した有機EL素子と、電荷トラップ濃度減少層および機能層を形成しないこと以外は同様にして作製した有機EL素子の測定結果も併せて示す。これらの図中、「Ref.」は電荷トラップ濃度減少層および機能層のいずれも形成していない有機EL素子を表し、「0nm」は電荷トラップ濃度減少層を1nmまたは3nmで形成し、機能層を形成していない有機EL素子を表し、「1nm」、「2nm」、「3nm」は、それぞれ、その厚みで機能層を形成し、電荷トラップ濃度減少層を1nmまたは3nmで形成した有機EL素子を表す。
 また、実施例2で作製した有機EL素子のデバイス特性を表1にまとめて示す。
 図13、16から、電荷トラップ濃度減少層および機能層を形成した有機EL素子において、電荷トラップ濃度減少層を形成し、機能層を形成していない有機EL素子よりも、さらに経時的な輝度の低下が抑えられる傾向が見られた。この効果は、特に電荷トラップ濃度減少層を3nmとした場合(図16参照)に顕著であった。このことから、電荷トラップ濃度減少層とともに機能層を設けることにより、さらに有機EL素子の寿命を延長しうることが確認された。
(Example 2) Production and evaluation of organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and a functional layer made of Liq The thickness of the charge trap concentration-decreasing layer was set to 1 nm or 3 nm. An organic electroluminescent element (EL element) was produced in the same manner as in Example 1 except that a functional layer made of Liq was formed with a thickness of 1 nm, 2 nm, or 3 nm by an evaporation method between the electron transport layers.
FIG. 10 shows the emission spectrum of the organic EL device in which the thickness of the charge trap concentration decreasing layer is 1 nm and the functional layer is formed in various thicknesses. FIG. 11 shows the voltage-current density-luminance characteristics, and the current density-external quantum efficiency. FIG. 12 shows the characteristics, and FIG. 13 shows changes with time in the luminance ratio and the voltage change amount. FIG. 14 shows the voltage-current density-luminance characteristics of the organic EL device in which the thickness of the charge trap concentration-decreasing layer is 3 nm and the functional layer is formed in various thicknesses, and FIG. 15 shows the current density-external quantum efficiency characteristics. FIG. 16 shows changes over time in the ratio and the amount of voltage change. Also, in each figure, the measurement result of the organic EL element produced in the same manner except that the functional layer is not formed, and the organic EL element produced in the same manner except that the charge trap concentration reducing layer and the functional layer are not formed. Also shown. In these figures, “Ref.” Represents an organic EL element in which neither a charge trap concentration-reducing layer nor a functional layer is formed, and “0 nm” represents a charge trap concentration-reducing layer formed at 1 nm or 3 nm. "1 nm", "2 nm", and "3 nm" are organic EL elements in which a functional layer is formed with the thickness and a charge trap concentration reduction layer is formed with 1 nm or 3 nm, respectively. Represents.
Table 1 summarizes the device characteristics of the organic EL element produced in Example 2.
13 and 16, in the organic EL element in which the charge trap concentration-decreasing layer and the functional layer are formed, the luminance with time is further increased as compared with the organic EL element in which the charge trap concentration-decreasing layer is formed and the functional layer is not formed. There was a tendency to suppress the decline. This effect was particularly remarkable when the charge trap concentration decreasing layer was 3 nm (see FIG. 16). From this, it was confirmed that the lifetime of the organic EL element can be further extended by providing the functional layer together with the charge trap concentration decreasing layer.
Figure JPOXMLDOC01-appb-T000032
Figure JPOXMLDOC01-appb-T000032
(比較例1)電荷トラップ濃度減少層を有さず、Liqからなる機能層を有する有機エレクトロルミネッセンス素子の作製と評価
 電荷トラップ濃度減少層を形成せず、電子輸送層と第2電子輸送層の間に、蒸着法により、Liqからなる機能層を1nm、2nmまたは3nmの厚みで形成したこと以外は、実施例1と同様にして有機EL素子を作製した。比較例1で作製した有機EL素子のデバイス特性を表1に示す。
 作製した有機EL素子の輝度比と電圧変化量の経時的変化を図17に示す。また、図17には、Liqからなる機能層を形成しないこと以外は同様にして作製した有機EL素子の測定結果も併せて示す。図17中、「Ref.」はLiqからなる機能層を形成していない有機EL素子を表し、「1nm」、「2nm」、「3nm」は、それぞれ、その厚さでLiqからなる機能層を形成した有機EL素子を表す。
 図17から、電子輸送層と第2電子輸送層の間にLiqからなる機能層を形成した有機EL素子は、機能層の厚さが1nmである場合には、機能層を形成していない有機EL素子と同等の寿命が得られるものの、機能層の厚さを厚くしていくと、逆に輝度比の低下が大きくなる傾向が見られた。このことから、Liq層を電子輸送層と第2電子輸送層の間のみに配しても、長寿命化の効果は得られないことがわかった。
(Comparative example 1) Preparation and evaluation of an organic electroluminescence device having a functional layer made of Liq without a charge trap concentration reduction layer. Without forming a charge trap concentration reduction layer, an electron transport layer and a second electron transport layer In the meantime, an organic EL device was produced in the same manner as in Example 1 except that a functional layer made of Liq was formed with a thickness of 1 nm, 2 nm, or 3 nm by vapor deposition. Table 1 shows the device characteristics of the organic EL element produced in Comparative Example 1.
FIG. 17 shows changes over time in the luminance ratio and voltage change amount of the manufactured organic EL element. FIG. 17 also shows the measurement results of the organic EL element produced in the same manner except that the functional layer made of Liq is not formed. In FIG. 17, “Ref.” Represents an organic EL element in which a functional layer made of Liq is not formed, and “1 nm”, “2 nm”, and “3 nm” respectively represent a functional layer made of Liq in the thickness. The formed organic EL element is represented.
From FIG. 17, the organic EL element in which the functional layer made of Liq is formed between the electron transport layer and the second electron transport layer has an organic layer in which the functional layer is not formed when the thickness of the functional layer is 1 nm. Although a life equivalent to that of the EL element can be obtained, there is a tendency that the luminance ratio is greatly decreased when the thickness of the functional layer is increased. From this, it was found that even if the Liq layer was disposed only between the electron transport layer and the second electron transport layer, the effect of extending the life could not be obtained.
(比較例2)発光層と電子輸送層の間にAlq3層を有する有機エレクトロルミネッセンス素子の作製と評価
 Liqからなる電荷トラップ濃度減少層を形成せず、その代わりに、発光層と電子輸送層の間に、蒸着法により、下記式で表されるAlq3からなる有機層(Alq3層)を1nm、3nmまたは5nmの厚みで形成したこと以外は、実施例1と同様にして有機EL素子を作製した。
Figure JPOXMLDOC01-appb-C000033
 作製した有機EL素子の電圧-電流密度-輝度特性を図18に示し、電流密度-外部量子効率特性を図19に示し、輝度と駆動電圧の経時的変化を図20に示す。また、図18と図20には、Alq3層を形成しないこと以外は同様にして作製した有機EL素子の測定結果も併せて示す。図18中、「Ref.」はAlq3層を形成していない有機EL素子を表す。図18、図19中、「1nm」、「3nm」、「5nm」は、それぞれ、その厚さでAlq3層を形成した有機EL素子を表す。また、図20中、「Ref.」はAlq3層を形成していない有機EL素子を表し、「Alq3」はAlq3層を3nmの厚みで形成した有機EL素子を表し、「Liq」はAlq3層の代わりにLiq層を3nmの厚みで形成した有機EL素子を表す。
 図20を見ると、発光層と電子輸送層の間にAlq3層を形成した有機EL素子は、Alq3層を形成していない有機EL素子(Ref.)よりも、むしろ輝度の低下が大きくなっている。このことから、Alq3層では、有機EL素子を長寿命化する効果が得られないことがわかった。
(Comparative Example 2) Preparation and evaluation of organic electroluminescence device having Alq3 layer between light emitting layer and electron transport layer No charge trap concentration decreasing layer made of Liq was formed, instead of the light emitting layer and the electron transport layer. An organic EL device was produced in the same manner as in Example 1 except that an organic layer (Alq3 layer) composed of Alq3 represented by the following formula was formed with a thickness of 1 nm, 3 nm, or 5 nm by vapor deposition. .
Figure JPOXMLDOC01-appb-C000033
FIG. 18 shows the voltage-current density-luminance characteristics of the fabricated organic EL device, FIG. 19 shows the current density-external quantum efficiency characteristics, and FIG. 20 shows the changes over time in the luminance and drive voltage. 18 and 20 also show the measurement results of an organic EL element produced in the same manner except that the Alq3 layer is not formed. In FIG. 18, “Ref.” Represents an organic EL element in which no Alq3 layer is formed. In FIG. 18 and FIG. 19, “1 nm”, “3 nm”, and “5 nm” each represent an organic EL element in which an Alq3 layer is formed with that thickness. In FIG. 20, “Ref.” Represents an organic EL element in which no Alq3 layer is formed, “Alq3” represents an organic EL element in which an Alq3 layer is formed with a thickness of 3 nm, and “Liq” represents an Alq3 layer. Instead, an organic EL element in which a Liq layer is formed with a thickness of 3 nm is shown.
Referring to FIG. 20, the organic EL element in which the Alq3 layer is formed between the light-emitting layer and the electron transport layer has a large decrease in luminance rather than the organic EL element (Ref.) In which the Alq3 layer is not formed. Yes. From this, it was found that the effect of extending the lifetime of the organic EL element cannot be obtained with the Alq3 layer.
(実施例3)Liqからなる電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有する有機エレクトロルミネッセンス素子の作製と評価
 電荷トラップ濃度減少層を1nmの厚さで形成し、厚さ30nmの発光層を、4CzIPN、mCBPおよびT2Tを異なる蒸着源から共蒸着して形成したこと以外は、実施例1と同様にして有機エレクトロルミネッセンス素子(有機EL素子)を作製した。ただし、発光層におけるT2Tの濃度は10重量%に固定し、4CzIPNの濃度は10重量%、15重量%または20重量%の各濃度として4CzIPN濃度が異なる4種類の有機EL素子を作製した。
 本実施例で使用した発光層の材料の最低励起三重項エネルギー準位は、4CzIPNが2.40eVであり、mCBPが2.90eVであり、T2Tが2.70eVであった。
 作製した有機EL素子のエネルギーダイアグラムを図21に示し、発光スペクトルを図22に示し、電圧-電流密度-輝度特性を図23に示し、電流密度-外部量子効率特性を図24に示し、輝度比と電圧変化量の経時的変化を図25に示す。図21中の数値は、下が各有機層のHOMO準位の絶対値を表し、上が各有機層のLUMO準位の絶対値を表す。ITO側から3番目の有機層(発光層)において、上下の実線はmCBPのエネルギー準位を示し、外側点線はT2Tのエネルギー準位を示し、内側点線は4CzIPNのエネルギー準位を示す。図22~25中、「5%」、「10%」、「15%」、「20%」は、それぞれ、その濃度で4CzIPNを発光層が含有する有機EL素子を表す。
 図25に示す有機EL素子のうち、4CzIPN濃度が15%である素子の特性図と、図9に示す有機EL素子(実施例1)のうち、電荷トラップ濃度減少層の厚さが1nmの素子の特性図を比較すると、本実施例の有機EL素子(発光層がT2Tを含有する有機EL素子)の方が、実施例1の有機EL素子(発光層がT2Tを含有していない有機EL素子)よりも経時的な輝度比の低下および電圧変化量の上昇がより抑えられていることがわかる。このことから、電荷トラップ濃度減少層を形成した上で、さらに発光層にT2T(第2ホスト材料)を添加すると、有機EL素子の寿命が一段と改善されることがわかった。
(Example 3) Production and evaluation of an organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and the light emitting layer containing T2T (second host material) A charge trap concentration-decreasing layer is formed with a thickness of 1 nm. Then, an organic electroluminescence element (organic EL element) was produced in the same manner as in Example 1 except that a light emitting layer having a thickness of 30 nm was formed by co-evaporation of 4CzIPN, mCBP, and T2T from different evaporation sources. However, the concentration of T2T in the light emitting layer was fixed to 10% by weight, and four types of organic EL elements having different 4CzIPN concentrations were prepared with the concentration of 4CzIPN being 10% by weight, 15% by weight, or 20% by weight.
The lowest excited triplet energy level of the material of the light emitting layer used in this example was 4CzIPN 2.40 eV, mCBP 2.90 eV, and T2T 2.70 eV.
FIG. 21 shows an energy diagram of the produced organic EL device, FIG. 22 shows an emission spectrum, FIG. 23 shows a voltage-current density-luminance characteristic, FIG. 24 shows a current density-external quantum efficiency characteristic, and a luminance ratio. FIG. 25 shows changes with time in the amount of voltage change. In the numerical values in FIG. 21, the bottom represents the absolute value of the HOMO level of each organic layer, and the top represents the absolute value of the LUMO level of each organic layer. In the third organic layer (light emitting layer) from the ITO side, the upper and lower solid lines indicate the energy level of mCBP, the outer dotted line indicates the energy level of T2T, and the inner dotted line indicates the energy level of 4CzIPN. 22 to 25, “5%”, “10%”, “15%”, and “20%” represent organic EL elements in which the light emitting layer contains 4CzIPN at the respective concentrations.
25, a characteristic diagram of an element having a 4CzIPN concentration of 15%, and an element having a thickness of a charge trap concentration-decreasing layer of 1 nm among the organic EL elements (Example 1) shown in FIG. The organic EL element of this example (the organic EL element in which the light emitting layer contains T2T) is compared with the organic EL element in Example 1 (the organic EL element in which the light emitting layer does not contain T2T). It can be seen that the decrease in luminance ratio and the increase in voltage change over time are further suppressed. From this, it was found that when the charge trap concentration decreasing layer is formed and T2T (second host material) is further added to the light emitting layer, the lifetime of the organic EL element is further improved.
(実施例4)Liqからなる電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の作製と評価
 発光層における4CzIPNの濃度を10重量%とし、厚さ40nmの第2電子輸送層を、BPy-TP2とLiqを異なる蒸着源から共蒸着して形成したこと以外は、実施例3と同様にして有機エレクトロルミネッセンス素子(有機EL素子)を作製した。この時、第2電子輸送層におけるLiqの濃度は50重量%または75重量%としてLiq濃度が異なる2種類の有機EL素子を作製した。
 作製した有機EL素子のエネルギーダイアグラムを図26に示し、発光スペクトルを図27に示し、電圧-電流密度-輝度特性を図28に示し、電流密度-外部量子効率特性を図29に示し、輝度比と電圧変化量の経時的変化を図30に示す。図26中の数値の意義は図21中の数値の意義と同じである。ただし、LiF/Al側から1番目の有機層(第2電子輸送層)において、上下の実線はBPy-TP2のエネルギー準位を示し、点線はLiqのエネルギー準位を示す。図27~30中、「50%」、「75%」は、それぞれ、その濃度でLiqを第2電子輸送層が含有する有機EL素子を表す。
 図30に示す特性図と、図25に示す特性図(実施例3)のうち、4CzIPN濃度が10%であるものを比較すると、本実施例の有機EL素子(第2電子輸送層がLiqを含有する有機EL素子)の方が、実施例3の有機EL素子(第2電子輸送層がLiqを含有していない有機EL素子)よりも輝度比の低下速度が顕著に小さいことがわかる、このことから、電荷トラップ濃度減少層を形成し、発光層にT2T(第2ホスト材料)を添加した上で、さらに第2電子輸送層にLiq(電荷トラップ濃度減少層の構成材料と同じ材料)を添加すると、有機EL素子の寿命が格段に改善されることがわかった。
 なお、実施例4の発光層の4CzIPN濃度を15%に固定して、第2電子輸送層がLiq濃度を50%、75%とした有機EL素子も製造して同様の試験を行ったところ、実施例4と同じ傾向が確認された。
(Example 4) Production and evaluation of an organic electroluminescence device having a charge trap concentration reducing layer made of Liq, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq The second electron transport layer having a thickness of 4CzIPN in the layer was set to 10% by weight and the second electron transport layer having a thickness of 40 nm was formed in the same manner as in Example 3 except that BPy-TP2 and Liq were co-deposited from different deposition sources. An electroluminescence element (organic EL element) was produced. At this time, the concentration of Liq in the second electron transport layer was 50% by weight or 75% by weight, and two types of organic EL elements having different Liq concentrations were produced.
The energy diagram of the produced organic EL device is shown in FIG. 26, the emission spectrum is shown in FIG. 27, the voltage-current density-luminance characteristic is shown in FIG. 28, the current density-external quantum efficiency characteristic is shown in FIG. FIG. 30 shows changes with time in the amount of voltage change. The significance of the numerical values in FIG. 26 is the same as the significance of the numerical values in FIG. However, in the first organic layer (second electron transport layer) from the LiF / Al side, the upper and lower solid lines indicate the energy level of BPy-TP2, and the dotted line indicates the energy level of Liq. 27 to 30, “50%” and “75%” represent organic EL elements in which the second electron transport layer contains Liq at the respective concentrations.
When comparing the characteristic diagram shown in FIG. 30 with the characteristic diagram shown in FIG. 25 (Example 3) having a 4CzIPN concentration of 10%, the organic EL element of this example (the second electron transport layer is Liq). It can be seen that the rate of decrease in the luminance ratio is significantly smaller in the organic EL element containing) than in the organic EL element in Example 3 (the organic EL element in which the second electron transport layer does not contain Liq). Therefore, a charge trap concentration decreasing layer is formed, T2T (second host material) is added to the light emitting layer, and then Liq (the same material as the constituent material of the charge trap concentration decreasing layer) is added to the second electron transport layer. When it added, it turned out that the lifetime of an organic EL element is improved significantly.
In addition, when the 4CzIPN concentration of the light emitting layer of Example 4 was fixed to 15%, an organic EL device in which the second electron transport layer had a Liq concentration of 50% and 75% was manufactured, and the same test was performed. The same tendency as in Example 4 was confirmed.
(実施例5)Liqからなる電荷トラップ濃度減少層とLiqを含む第2電子輸送層を有し、発光層が多層構造である有機エレクトロルミネッセンス素子の作製と評価
 第2電子輸送層が50%のLiqを含み、発光層が図31のA~Dのいずれかの多層構造を有するように変更したこと以外は実施例1と同様にして有機エレクトロルミネッセンス素子(EL素子)を作製した。図31のA~Dにおける各層の数値は、4CzIPN濃度を示す。
 作製した有機EL素子のエネルギーダイアグラムを図31に示し、発光スペクトルを図32に示し、電圧-電流密度-輝度特性を図33に示し、電流密度-外部量子効率特性を図34に示し、輝度比と電圧変化量の経時的変化を図35に示す。図32の発光スペクトルは、A~Dのいずれにおいても同じであったことを示している。
 図35の結果から、寿命を試験した多層構造BとCのいずれにおいても長寿命であることが確認されたが、特に多層構造Bにおいて長寿命化が達成できることが判明した。
(Example 5) Preparation and evaluation of an organic electroluminescence device having a charge trap concentration-decreasing layer made of Liq and a second electron transport layer containing Liq, and a light-emitting layer having a multilayer structure. 50% of the second electron transport layer An organic electroluminescence element (EL element) was produced in the same manner as in Example 1 except that Liq was included and the light emitting layer was changed to have any one of the multilayer structures A to D in FIG. The numerical value of each layer in A to D in FIG. 31 indicates the 4CzIPN concentration.
FIG. 31 shows an energy diagram of the produced organic EL device, FIG. 32 shows an emission spectrum, FIG. 33 shows a voltage-current density-luminance characteristic, FIG. 34 shows a current density-external quantum efficiency characteristic, and a luminance ratio. FIG. 35 shows changes over time in the amount of voltage change. The emission spectrum of FIG. 32 shows that it was the same in any of A to D.
From the results of FIG. 35, it was confirmed that both of the multilayer structures B and C whose lifetimes were tested had a long lifetime, but it was found that a long lifetime could be achieved particularly in the multilayer structure B.
(実施例6)Liqからなる電荷トラップ濃度減少層を有し、発光層がT2T(第2ホスト材料)を含有し、第2電子輸送層がLiqを含有する有機エレクトロルミネッセンス素子の作製と評価
 発光層における4CzIPNの濃度を15重量%とし、T2Tのホスト全量にしめる重量割合を15%、30%、50%、70%の各濃度とし、第2電子輸送層のLiq濃度を50%に固定したこと以外は、実施例4と同様にして有機エレクトロルミネッセンス素子(有機EL素子)を作製した。
 作製した有機EL素子の発光スペクトルを図36に示し、電圧-電流密度-輝度特性を図37に示し、電流密度-外部量子効率特性を図38に示し、輝度比と電圧変化量の経時的変化を図39に示す。図36では、いずれの有機EL素子もほぼ同じ発光スペクトルであった。図37~39中、「15%」、「30%」、「50%」、「70%」は、それぞれ、発光層中のホスト全量にしめるT2Tの割合を表す。
 図39に示す特性図と、図25に示す特性図(実施例3)のうち、4CzIPN濃度が15%であるものを比較すると、本実施例の有機EL素子(第2電子輸送層がLiqを含有する有機EL素子)であって、ホスト全量の30%以下の量でT2Tを含むものが、輝度比の低下速度が小さいことがわかる。このことから、電荷トラップ濃度減少層を形成し、第2電子輸送層にLiq(電荷トラップ濃度減少層の構成材料と同じ材料)を添加し、発光層のホスト全量の30%以下の量でT2T(第2ホスト材料)を使用することにより、一段と有機EL素子の寿命が改善されることがわかった。
(Example 6) Production and evaluation of an organic electroluminescence device having a charge trap concentration reducing layer made of Liq, the light emitting layer containing T2T (second host material), and the second electron transporting layer containing Liq The concentration of 4CzIPN in the layer is 15% by weight, the weight ratio of the total amount of T2T host is 15%, 30%, 50%, and 70%, and the Liq concentration of the second electron transport layer is fixed at 50%. Except for the above, an organic electroluminescence element (organic EL element) was produced in the same manner as in Example 4.
FIG. 36 shows the emission spectrum of the fabricated organic EL element, FIG. 37 shows the voltage-current density-luminance characteristics, and FIG. 38 shows the current density-external quantum efficiency characteristics, and the luminance ratio and the voltage change over time. Is shown in FIG. In FIG. 36, all the organic EL elements had substantially the same emission spectrum. In FIGS. 37 to 39, “15%”, “30%”, “50%”, and “70%” each represent the ratio of T2T to be the total amount of the host in the light emitting layer.
When comparing the characteristic diagram shown in FIG. 39 with the characteristic diagram shown in FIG. 25 (Example 3) having a 4CzIPN concentration of 15%, the organic EL element of this example (the second electron transport layer is Liq). It can be seen that the organic EL element) containing T2T in an amount of 30% or less of the total amount of the host has a low reduction rate of the luminance ratio. From this, a charge trap concentration decreasing layer is formed, Liq (the same material as the constituent material of the charge trap concentration decreasing layer) is added to the second electron transport layer, and T2T is added in an amount of 30% or less of the total amount of the light emitting layer host. It was found that the lifetime of the organic EL element was further improved by using (second host material).
Figure JPOXMLDOC01-appb-C000034
Figure JPOXMLDOC01-appb-C000034
 本発明の有機エレクトロルミネッセンス素子は、駆動時の経時的な性能劣化が抑えられ、非常に長い寿命を有する。このため、本発明は産業上の利用可能性が高い。 The organic electroluminescence device of the present invention has a very long life because the deterioration of performance over time during driving is suppressed. For this reason, this invention has high industrial applicability.
 1 基板
 2 陽極
 3 発光層
 4 電荷トラップ濃度減少層
 5 電子輸送層
 6 陰極
 7 機能層
 8 第2電子輸送層
 9 正孔注入層
 10 正孔輸送層
DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Light emitting layer 4 Charge trap concentration decreasing layer 5 Electron transport layer 6 Cathode 7 Functional layer 8 Second electron transport layer 9 Hole injection layer 10 Hole transport layer

Claims (23)

  1.  少なくとも陽極、発光層、電子輸送層、陰極をこの順に積層した構造を有する有機エレクトロルミネッセンス素子であって、
     前記発光層と前記電子輸送層の界面に電荷トラップ濃度減少層を有することを特徴とする有機エレクトロルミネッセンス素子。
    An organic electroluminescence device having a structure in which at least an anode, a light emitting layer, an electron transport layer, and a cathode are laminated in this order,
    An organic electroluminescence device comprising a charge trap concentration reducing layer at an interface between the light emitting layer and the electron transport layer.
  2.  前記電荷トラップ濃度減少層の平均膜厚が0.1~100nmである請求項1に記載の有機エレクトロルミネッセンス素子。 2. The organic electroluminescence device according to claim 1, wherein the charge trap concentration decreasing layer has an average film thickness of 0.1 to 100 nm.
  3.  前記電荷トラップ濃度減少層が第一族原子、第二族原子または遷移金属原子を含有する請求項1または2に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 1 or 2, wherein the charge trap concentration-decreasing layer contains a first group atom, second group atom or transition metal atom.
  4.  前記電荷トラップ濃度減少層がLiを含有する層である請求項3に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 3, wherein the charge trap concentration-decreasing layer is a layer containing Li.
  5.  前記電荷トラップ濃度減少層が8-ヒドロキシキノリノラト誘導体からなる層である請求項4に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 4, wherein the charge trap concentration-decreasing layer is a layer made of an 8-hydroxyquinolinolato derivative.
  6.  前記電子輸送層が金属原子を含まない請求項1~5のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 1 to 5, wherein the electron transport layer does not contain a metal atom.
  7.  前記電子輸送層の陰極側に第2電子輸送層を有しており、前記電子輸送層と前記第2電子輸送層との間に第一族原子、第二族原子または遷移金属原子を含有する機能層を有する請求項1~6のいずれか一項に記載の有機エレクトロルミネッセンス素子。 A second electron transport layer is provided on the cathode side of the electron transport layer, and contains a first group atom, second group atom or transition metal atom between the electron transport layer and the second electron transport layer. The organic electroluminescence device according to any one of claims 1 to 6, which has a functional layer.
  8.  前記機能層の平均膜厚が0.1~100nmである請求項7に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 7, wherein the functional layer has an average film thickness of 0.1 to 100 nm.
  9.  前記機能層がLiを含有する層である請求項7または8に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescent element according to claim 7 or 8, wherein the functional layer is a layer containing Li.
  10.  前記機能層が8-ヒドロキシキノリノラト誘導体からなる層である請求項9に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 9, wherein the functional layer is a layer made of an 8-hydroxyquinolinolato derivative.
  11.  前記第2電子輸送層が金属原子を含まない請求項7~10のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 7 to 10, wherein the second electron transport layer does not contain a metal atom.
  12.  前記発光層が第1ホスト材料と第2ホスト材料を含有する請求項1~11のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 1 to 11, wherein the light emitting layer contains a first host material and a second host material.
  13.  前記第1ホスト材料と前記第2ホスト材料が、いずれも前記発光層が含有する発光材料の最低励起三重項エネルギー準位よりも高い最低励起三重項エネルギー準位を有する請求項12に記載の有機エレクトロルミネッセンス素子。 The organic material according to claim 12, wherein each of the first host material and the second host material has a lowest excited triplet energy level higher than a lowest excited triplet energy level of a light emitting material contained in the light emitting layer. Electroluminescence element.
  14.  前記第2ホスト材料が電子輸送性を有するものである請求項12または13に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescent element according to claim 12 or 13, wherein the second host material has an electron transporting property.
  15.  前記第2ホスト材料が、前記電荷トラップ濃度減少層に隣接する前記電子輸送層の構成材料と同じ材料からなるものである請求項12~14のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 12 to 14, wherein the second host material is made of the same material as the constituent material of the electron transport layer adjacent to the charge trap concentration reducing layer.
  16.  前記第2ホスト材料が下記一般式(1)で表される化合物である請求項12~15のいずれか一項に記載の有機エレクトロルミネッセンス素子。
    Figure JPOXMLDOC01-appb-C000001
    [一般式(1)において、Arは、置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。nは1~3の整数を表す。nが2以上であるとき、複数のArは互いに同一であっても、異なっていてもよい。]
    The organic electroluminescence device according to any one of claims 12 to 15, wherein the second host material is a compound represented by the following general formula (1).
    Figure JPOXMLDOC01-appb-C000001
    [In General Formula (1), Ar represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. n represents an integer of 1 to 3. When n is 2 or more, the plurality of Ars may be the same as or different from each other. ]
  17.  前記一般式(1)で表される化合物が下記一般式(2)で表される化合物である請求項16に記載の有機エレクトロルミネッセンス素子。
    Figure JPOXMLDOC01-appb-C000002
    [一般式(2)において、Ar1、Ar2およびAr3は、各々独立に置換もしくは無置換のアリール基、または置換もしくは無置換のヘテロアリール基を表す。R1、R2およびR3は、各々独立に置換基を表し、該置換基は置換もしくは無置換のアリール基、および置換もしくは無置換のヘテロアリール基ではない。n1、n2およびn3は、各々独立に1~5の整数を表す。n11、n12およびn13は、各々独立に0~4の整数を表す。]
    The organic electroluminescence device according to claim 16, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).
    Figure JPOXMLDOC01-appb-C000002
    [In General Formula (2), Ar 1 , Ar 2 and Ar 3 each independently represent a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. R 1 , R 2 and R 3 each independently represent a substituent, and the substituent is not a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. n1, n2 and n3 each independently represents an integer of 1 to 5. n11, n12 and n13 each independently represents an integer of 0 to 4. ]
  18.  前記発光層が発光材料濃度が異なる多層構造を有する請求項1~17のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescent element according to any one of claims 1 to 17, wherein the light emitting layer has a multilayer structure having different light emitting material concentrations.
  19.  前記電子輸送層および前記第2電子輸送層の少なくとも一方に、第一族原子、第二族原子または遷移金属原子を含有する化合物を含有する請求項7~18のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic material according to any one of claims 7 to 18, wherein at least one of the electron transport layer and the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom. Electroluminescence element.
  20.  前記第2電子輸送層に、第一族原子、第二族原子または遷移金属原子を含む化合物を含有する請求項19に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 19, wherein the second electron transport layer contains a compound containing a first group atom, a second group atom or a transition metal atom.
  21.  前記化合物がLiを含有する化合物である請求項19または20に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to claim 19 or 20, wherein the compound is a compound containing Li.
  22.  前記化合物が8-ヒドロキシキノリノラト誘導体である請求項19~21のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 19 to 21, wherein the compound is an 8-hydroxyquinolinolato derivative.
  23.  前記第2電子輸送層が前記電荷トラップ濃度減少層の構成材料と同じ材料を含有する請求項7~22のいずれか一項に記載の有機エレクトロルミネッセンス素子。 The organic electroluminescence device according to any one of claims 7 to 22, wherein the second electron transport layer contains the same material as the constituent material of the charge trap concentration reducing layer.
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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005268022A (en) * 2004-03-18 2005-09-29 Fuji Photo Film Co Ltd Organic electroluminescent element
JP2008524848A (en) * 2004-12-17 2008-07-10 イーストマン コダック カンパニー Phosphorescent OLED with exciton blocking layer
JP2009231265A (en) * 2008-02-28 2009-10-08 Fujifilm Corp Manufacturing method of organic electroluminescent element, and organic electroluminescent element manufactured by the same
JP2011503879A (en) * 2007-11-09 2011-01-27 ユニバーサル ディスプレイ コーポレイション Stable blue phosphorescent organic light emitting device
WO2012008331A1 (en) * 2010-07-12 2012-01-19 出光興産株式会社 Organic electroluminescent element
WO2012070330A1 (en) * 2010-11-25 2012-05-31 日本精機株式会社 Organic el element
JP2012248405A (en) * 2011-05-27 2012-12-13 Nippon Seiki Co Ltd Organic el element and method for manufacturing the same
WO2013076948A1 (en) * 2011-11-24 2013-05-30 パナソニック株式会社 El display device and method for producing same
JP2015019071A (en) * 2013-07-10 2015-01-29 上海和輝光電有限公司Everdisplay Optronics (Shanghai) Limited Inverted organic light-emitting diode display apparatus and method for manufacturing the same
JP2015119182A (en) * 2013-12-17 2015-06-25 ザ レジェンツ オブ ザ ユニバーシティ オブ ミシガン Extended oled operational lifetime through phosphorescent dopant profile management

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4514841B2 (en) 1998-02-17 2010-07-28 淳二 城戸 Organic electroluminescent device
KR100858816B1 (en) 2007-03-14 2008-09-17 삼성에스디아이 주식회사 Organic light emitting device comprising anthracene derivative compound
KR20130050713A (en) * 2011-11-08 2013-05-16 삼성디스플레이 주식회사 Organic light-emitting diode, manufacturing method thereof, and flat display device comprising the same
KR101908385B1 (en) * 2012-03-02 2018-10-17 삼성디스플레이 주식회사 Organic light emitting diode
JP2016530702A (en) 2013-07-02 2016-09-29 メルク、パテント、ゲゼルシャフト、ミット、ベシュレンクテル、ハフツングMerck Patent GmbH Organic electroluminescence device

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005268022A (en) * 2004-03-18 2005-09-29 Fuji Photo Film Co Ltd Organic electroluminescent element
JP2008524848A (en) * 2004-12-17 2008-07-10 イーストマン コダック カンパニー Phosphorescent OLED with exciton blocking layer
JP2011503879A (en) * 2007-11-09 2011-01-27 ユニバーサル ディスプレイ コーポレイション Stable blue phosphorescent organic light emitting device
JP2009231265A (en) * 2008-02-28 2009-10-08 Fujifilm Corp Manufacturing method of organic electroluminescent element, and organic electroluminescent element manufactured by the same
WO2012008331A1 (en) * 2010-07-12 2012-01-19 出光興産株式会社 Organic electroluminescent element
WO2012070330A1 (en) * 2010-11-25 2012-05-31 日本精機株式会社 Organic el element
JP2012248405A (en) * 2011-05-27 2012-12-13 Nippon Seiki Co Ltd Organic el element and method for manufacturing the same
WO2013076948A1 (en) * 2011-11-24 2013-05-30 パナソニック株式会社 El display device and method for producing same
JP2015019071A (en) * 2013-07-10 2015-01-29 上海和輝光電有限公司Everdisplay Optronics (Shanghai) Limited Inverted organic light-emitting diode display apparatus and method for manufacturing the same
JP2015119182A (en) * 2013-12-17 2015-06-25 ザ レジェンツ オブ ザ ユニバーシティ オブ ミシガン Extended oled operational lifetime through phosphorescent dopant profile management

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