WO2020250979A1 - Élément électroluminescent organique, corps de stratification et procédé électroluminescent - Google Patents

Élément électroluminescent organique, corps de stratification et procédé électroluminescent Download PDF

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WO2020250979A1
WO2020250979A1 PCT/JP2020/023038 JP2020023038W WO2020250979A1 WO 2020250979 A1 WO2020250979 A1 WO 2020250979A1 JP 2020023038 W JP2020023038 W JP 2020023038W WO 2020250979 A1 WO2020250979 A1 WO 2020250979A1
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singlet
layer
light emitting
excitons
triplet
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Japanese (ja)
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弘典 梶
鈴木　克明
啓幹 和田
中川　博道
安達　千波矢
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株式会社Ｋｙｕｌｕｘ
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Publication of WO2020250979A1 publication Critical patent/WO2020250979A1/fr

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    • H10K50/18—Carrier blocking layers
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
    • H10K50/13—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit
    • H10K50/131—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit with spacer layers between the electroluminescent layers
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    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
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    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/615—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
    • H10K85/622—Polycyclic condensed aromatic hydrocarbons, e.g. anthracene containing four rings, e.g. pyrene
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    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
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    • H10K85/631—Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
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    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/649—Aromatic compounds comprising a hetero atom
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    • H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
    • H10K85/6572—Polycyclic condensed heteroaromatic hydrocarbons comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/649—Aromatic compounds comprising a hetero atom
    • H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
    • H10K85/6574—Polycyclic condensed heteroaromatic hydrocarbons comprising only oxygen in the heteroaromatic polycondensed ring system, e.g. cumarine dyes
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    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers

Definitions

  • the present invention relates to a laminate having high exciton generation efficiency and an organic light emitting device using the laminate.
  • the present invention also relates to a light emitting method.
  • the organic electroluminescence element is an organic light emitting element that emits light by radiation deactivation of excitons generated by current excitation of the organic light emitting layer.
  • organic EL element is an organic light emitting element that emits light by radiation deactivation of excitons generated by current excitation of the organic light emitting layer.
  • current excitation singlet excitons and triplet excitons are generated with a probability of 25%: 75% according to the spin statistical law, but radiation deactivation from the excited triplet state to the base singlet state is originally It is a forbidden transition. Therefore, in ordinary organic light-emitting materials, triplet excitons are heat-deactivated before radiation deactivation, and only singlet excitons generated with a probability of 25% can be used for light emission, which limits the improvement of luminous efficiency. was there.
  • thermoactive delayed fluorescence material that can be converted and used for light emission has been developed, and it has become possible to convert singlet and triplet excitons generated by current excitation into light with 100% efficiency.
  • an organic EL device using a singlet splitting material has been proposed. Specifically, in this organic EL element, a singlet exciton and a triplet exciton are generated with a probability of 25%: 75%, and then the singlet exciton splits into two triplet excitons. The upper 125% of triplet excitons will be generated. The 125% exciton generation efficiency is greatly improved compared to the case where the singlet splitting material is not used, but it is due to a simple configuration in which the singlet splitting material is simply mixed with the light emitting layer. It was considered that a larger exciton generation efficiency could be obtained.
  • the present inventors have developed a mechanism in which the theoretical limit value of exciton generation efficiency is higher, and proceeded with diligent studies for the purpose of dramatically increasing the luminous efficiency of the organic light emitting device.
  • the present inventors have obtained the idea of combining the inverse intersystem crossing and the singlet splitting phenomenon. That is, after the singlet excitons and triplet excitons are generated by current excitation with a probability of 25%: 75%, all the generated triplet excitons are converted into singlet excitons by intersystem crossing, and then singlet.
  • the present invention has been proposed based on such an idea, and specifically has the following configuration.
  • An organic light emitting device containing a material capable of converting triplet excitons to singlet excitons and a singlet splitting material.
  • a means for suppressing the direct transfer of the energy of the triplet excitons to the singlet splitting material in the material capable of converting the triplet excitons to the singlet excitons is provided [1].
  • the organic light emitting element according to. [3] a difference Delta] E ST of the lowest excited singlet energy level (E S1) and the lowest excited triplet energy level of the possible conversion from triplet excitons to singlet excitons material (E T1)
  • E S1 lowest excited singlet energy level
  • E T1 The organic light emitting element according to [1] or [2], which is 0.3 eV or less.
  • [4] It has a structure in which an exciton generating layer containing a material capable of converting a triplet exciton to a singlet exciton, a block layer, and a singlet splitting layer containing a singlet splitting material are laminated in this order.
  • the organic light emitting element according to any one of [1] to [3].
  • [5] The organic light emitting device according to [4], wherein the singlet split layer contains a light emitting material.
  • the lowest excited singlet energy level E S1 of the light emitting material 0.2 eV than the lowest excited singlet energy level E S1 of the possible material conversion from triplet excitons to singlet excitons
  • the organic light emitting element according to [5] which is higher than the above.
  • the organic light emitting device according to any one of [1] to [11], wherein the material capable of converting the triplet exciton to the singlet exciton is a delayed fluorescent material.
  • the singlet split layer has a first singlet split layer and a second singlet split layer, and the block layer has a first block layer and a second block layer.
  • [4] to [12] having a structure in which the singlet split layer, the first block layer, the exciton generation layer, the second block layer, and the second singlet split layer are laminated in this order.
  • the organic light emitting element according to any one item.
  • the organic light emitting device wherein the first block layer contains a material having a hole transport property, and the second block layer contains a material having an electron transport property.
  • the first block layer contains a compound having an aromatic ring in which at least one hydrogen atom is substituted with a substituent bonded by a nitrogen atom, and the second block layer contains at least one nitrogen atom.
  • the anode and the cathode are arranged between the anode and the cathode, and the first singlet split layer, the first block layer, the exciton generation layer, and the second block layer are arranged in this order from the anode side.
  • the first block layer contains a material having a hole transport property
  • the second block layer has an electron transport property, and includes a laminate having a structure in which a second singlet split layer is laminated in order.
  • the organic light emitting device according to any one of [1] to [16] which is an organic electroluminescence device.
  • Lamination having a structure in which an exciton generation layer containing a material capable of converting a triplet exciton to a singlet exciton, a block layer, and a singlet splitting layer containing a singlet splitting material are laminated in order. body.
  • a material capable of converting triplet excitons to singlet excitons is current excited. The energy of the singlet exciter generated by the current excitation and the inverse intersystem crossing is transferred to the singlet splitting material to generate the singlet exciter of the singlet splitting material, and the singlet exciter of the singlet splitting material is split.
  • a light emitting method including causing.
  • the organic light emitting device and the light emitting method of the present invention have an extremely high theoretical limit value of exciton generation efficiency of 200%. Therefore, by utilizing the present invention, it is possible to realize dramatically high luminous efficiency.
  • FIG. 1 It is a schematic diagram for demonstrating the exciton generation mechanism and the light emission mechanism of the comparative laminate 1 produced in Comparative Example 1. It is an energy level diagram of the comparative laminate 2 produced in Comparative Example 2. It is a schematic diagram for demonstrating the exciton generation mechanism and the light emission mechanism of the comparative laminate 2 produced in the comparative example 2. FIG. It is an energy level diagram of the comparative laminate 3 produced in Comparative Example 3. It is an emission spectrum of the laminated body 1 and the comparative laminated body 1 to 3. It is an emission spectrum of the organic electroluminescence device produced in Example 2.
  • the contents of the present invention will be described in detail below.
  • the description of the constituent elements described below may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples.
  • the numerical range represented by using "-" in the present specification means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
  • the isotope species of the hydrogen atom existing in the molecule of the compound used in the present invention is not particularly limited, and for example, all the hydrogen atoms in the molecule may be 1 H, or part or all of them may be 2 H. (Duterium D) may be used.
  • the "fluorescent material” is a light emitting material whose fluorescence emission intensity is higher than that of phosphorescence when luminescence is observed at 20 ° C.
  • the "phosphorescence material” is defined as a "phosphorescence material”.
  • the luminescence material has a higher luminescence intensity of phosphorescence than the luminescence intensity of fluorescence.
  • the “delayed fluorescence material” is a material that emits light from an excited singlet, and is a material in which both fluorescence having a short emission lifetime at 20 ° C. and fluorescence having a long emission lifetime (delayed fluorescence) are observed.
  • Normal fluorescence fluorescence that is not delayed fluorescence
  • phosphorescence is a material that emits light from a triplet and usually has an emission lifetime. It is more than ⁇ s order.
  • intersystem crossing means conversion from triplet excitons to singlet excitons.
  • the thickness of each layer (exciton generation layer, block layer, singlet split layer, and other layers) constituting the laminate is measured by, for example, a stylus profiling system.
  • the organic light emitting device of the present invention is characterized by including a material capable of converting triplet excitons to singlet excitons and a singlet splitting material.
  • the organic light emitting element of the present invention it is possible to efficiently emit light by transferring energy from a material capable of converting triplet excitons to singlet excitons to a singlet splitting material. More specifically, the singlet exciter of the singlet fission material is transferred by transferring the energy of the singlet exciton in the material capable of converting the triplet exciton to the singlet exciter to the singlet fission material.
  • phosphorescence may be emitted directly from the singlet splitting material, or the energy of triplet excitons in the singlet splitting material may be transferred to the light emitting material to emit light from the light emitting material. Good.
  • the "material capable of converting triplet excitons to singlet excitons" in the present invention means that the triplet excitons of the material can be converted to singlet excitons on a one-to-one basis. Moreover, it means a material in which singlet excitons can be used for light emission. In the present invention, it is not desirable that the material itself capable of converting triplet excitons to singlet excitons emits light, but it is possible to divert the material that emits light by itself under conditions other than the present invention to the present invention. Is.
  • the one-to-one conversion means that one triplet exciton is converted into one singlet exciton, and for example, Triplet-triplet annihilation (TTA) is excluded.
  • singlet excitons for light emission means that the singlet excitons emit fluorescence when they return to the ground state, and the energy of the singlet excitons is used to generate excitators in other materials. Finally, it includes inducing light emission. Therefore, it is possible to convert triplet excitons into singlet excitors on a one-to-one basis, and the energy of the singlet excitons is transferred to the singlet splitting material according to the light emission method of the present invention. Any material that can be used for light emission falls under the category of "a material that can convert a triplet exciter to a singlet exciter" regardless of its structure.
  • higher excited triplet energy level (Delta] E Tn) can intersystem crossing to the lowest excited singlet energy level of a material (e.g., material according to WO2014185408A1) can be exemplified.
  • a material that actually emits delayed fluorescence and a material that induces delayed fluorescence emission are also "materials capable of converting triplet excitons to singlet excitons".
  • specific examples of the "capable material conversion from triplet excitons to singlet excitons” will be described with reference to "Delta] E ST is equal to or less than 0.3eV material".
  • the description of the constituent elements described below may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples.
  • “Delta] E ST is equal to or less than 0.3eV material” in the following description can be replaced by other "that can be converted from a triplet exciton to the singlet excitons material”.
  • the difference between the Delta] E ST of "Delta] E ST is equal to or less than 0.3eV material" in the present invention, a lowest excited triplet energy level lowest excited singlet energy level (E S1) (E T1) (E S1 - It means ET1 ).
  • "Delta] E ST is equal to or less than 0.3eV material", for the lowest excited singlet energy level (E S1) and the lowest excited triplet energy level (E T1) is close, excited singlet from excited triplet state It is easy to cause an intersystem crossing to the state. Therefore, by using the "Delta] E ST is equal to or less than 0.3eV material" as the material of the exciton generating layer, it is possible to efficiently generate the singlet excitons in the layer.
  • Delayed fluorescence is the fluorescence emitted when the inverse intersystem crossing from the excited triple-term state to the excited single-term state occurs and then returns from the excited single-term state to the ground state, and the directly generated excited single-term fluorescence. It is the fluorescence observed later than the fluorescence from the term state (normal fluorescence).
  • Delta] E ST "Materials Delta] E ST is equal to or less than 0.3eV" is preferably not more than 0.2 eV, more preferably less 0.1 eV, and more preferably less 0.05 eV. Method of measuring the Delta] E ST, can be referred to in the column below (E S1, E T1, the measurement method of Delta] E ST).
  • the "singlet splitting material" in the present invention means a material in which each singlet exciton generated there can split into two triplet excitons after transitioning to the excited singlet state. Singlet splitting of a compound results in an increase in the number of triplet excitons. Therefore, it can be confirmed that the material is a singlet splitting material by using the triplet generation efficiency ⁇ ISC as an index. Specifically, a solution containing the target compound to be determined at different concentrations is irradiated with pump light as excitation light, and immediately after that, the amount of change in absorbance ⁇ ABS with respect to the probe light is measured.
  • the triplet formation efficiency ⁇ ISC obtained from the ⁇ ABS by the following formula (I) shows a correlation that increases as the concentration of the target compound increases, so that the target compound is a singlet splitting material.
  • amount of change in absorbance ⁇ ABS means the amount of change in absorbance with respect to the absorbance ABS 0 with respect to the probe light before irradiation with the pump light, and here, with respect to the probe light measured immediately after the irradiation with the pump light.
  • Absorbance ABS EX minus ABS 0 the concentration of the target compound in the solution is selected within a concentration range in which concentration quenching is substantially suppressed.
  • concentration of the target compound in the solution is selected within a concentration range in which concentration quenching is substantially suppressed.
  • the fact that the material is a singlet splitting material may be confirmed by observing phenomena and signs indicating that the number of triplet excitons has increased due to singlet splitting, and a measurement method other than the above is adopted. You may confirm by.
  • ⁇ ISC indicates the triple term generation efficiency
  • I 0 indicates the intensity of the pump light irradiating the solution (excitation light intensity)
  • ⁇ ABS indicates the amount of change in absorbance (ABS EX- ABS 0 ).
  • ⁇ indicates the molar extinction coefficient of the target compound at the pump light wavelength
  • ⁇ T indicates the molar extinction coefficient of the target compound at the probe light wavelength
  • c indicates the concentration of the target compound in the solution
  • L is used for the measurement.
  • the optical path length (1 mm) of the cell is shown.
  • the organic light-emitting device of the present invention preferably has a means for suppressing the energy of triplet excitons materials Delta] E ST is less than 0.3eV is directly moved to the singlet fission materials.
  • the triplet exciton energy referred to here may be the energy of the triplet exciton converted by the singlet exciton, or may be, for example, the energy of the triplet exciton directly generated by current excitation.
  • the means of suppressing the direct transfer of triplet exciton energy to the singlet splitting material is as long as more triplet exciton energy is transferred to the singlet splitting material in the absence of such means. , The type is not particularly limited.
  • Delta] E ST can be mentioned blocking layer formed between the singlet fission layer comprising exciton generating layer and a singlet fission material containing a material or less 0.3 eV.
  • the "blocking layer” in the present invention is disposed between the exciton generating layer and a singlet fission layer, from the "Delta] E ST is equal to or less than 0.3eV material" exciton generating layer contains, singlet fission layer including preventing the Dexter transfer of triplet energy of the "singlet fission materials", and from “Delta] E ST is equal to or less than 0.3eV material" exciton generating layer comprises, "single including singlet fission layer A layer that allows Felster transfer of excited singlet energy to a "term splitting material".
  • Blocking layer must Delta] E ST is a layer energy transfer is suppressed from materials and singlet fission material or less 0.3 eV.
  • the structure in which the exciton generation layer, the block layer, and the singlet split layer are laminated in this order is referred to as the “laminate of the present invention”.
  • the laminate of the present invention has such a structure, when the molecules in the excitation generation layer are excited by the energy or carriers that cause excitation from the outside, the singlet exciter is efficient in the excitation generation layer. It is well generated and its excited singlet energy is transferred to the singlet split layer, where the singlet excitons generated split into two triplet excitons. Therefore, high exciton generation efficiency can be obtained, and for example, when the singlet splitting layer contains a light emitting material, or when the singlet splitting material itself emits light, high luminous efficiency can be obtained.
  • the exciton generation mechanism and the luminescence mechanism will be described with reference to FIGS. 1 and 2 by taking the case where the singlet split layer contains a phosphorescent material as an example.
  • S 1 represents a "singlet excitons of the lowest excited singlet state”
  • T 1 represents the “lowest excited triplet excitons of the triplet state”
  • S n is "lowest excited singlet It represents both a “singlet-state singlet exciton” and a "higher-order excited singlet-state singlet exciton” having a degree of 2 to n (n represents a natural number).
  • S 1, S n each energy level of T 1, respectively, E S1, E Sn, and be expressed as E T1. Incidentally, the energy relationship shown in FIG. 1 and FIG.
  • N 0 indicates the amount of excitons (initial excitons) directly generated in the exciton generation layer by excitation, and N 1 is single due to the initial excitons in the subsequent process.
  • N 0 is , Indicates the amount of excitons (initial excitons) directly generated in the singlet split layer or light emitting layer by excitation, N 1 is generated in the singlet split layer or light emitting layer due to the initial excitons.
  • the sum of the amount of excitons (secondary excitons) generated and the amount of initial excitons remaining without being subjected to the generation of secondary excitons is shown.
  • the secondary exciton refers to excitons generated due to the initial excitons, but in the present invention, for example, it is generated from a singlet splitting material by receiving the transfer of excitation energy from the initial excitons.
  • These are singlet excitons, triplet excitons split from singlet excitons, and the like.
  • carrier exciton generating layer of the laminate (h +, e -) are injected, when Delta] E ST carrier recombination occurs in the material is less than 0.3 eV, Singlet exciton S 1 and triplet exciton T 1 are generated with a 25%: 75% probability, and the triplet exciton T 1 crosses the inverse intersystem crossing from the excited triplet state to the excited singlet state. raised and converted to singlet excitons S 1.
  • Energy generated by the excitons generated layer singlet excitons S 1 is the Förster mechanism to move to the excited singlet energy level E Sn singlet fission materials (n is a natural number.).
  • the laminate of the present invention due to the provision of a "means for suppressing the energy of triplet excitons Delta] E ST is less than 0.3eV material is directly moved to the singlet fission materials", excitation triplet excitons T 1 generated in the child generation layer, direct energy transfer to singlet fission materials is prevented.
  • the transfer mechanism of the excited triplet energy is a Dexter mechanism different from the transfer mechanism of the excited singlet energy. Therefore, energy generated by the excitons generated layer triplet excitons T 1 is moved to the singlet fission materials is prevented by providing a blocking layer, as shown in FIG. 2, for example.
  • the triplet exciter T 1 generated with a probability of 75% is, at the maximum, all of them are subjected to the intersystem crossing and converted into the singlet exciter S 1 , and the excited singlet energy is also single. It moves to the excited singlet energy level E Sn of the term splitting material. Therefore, Delta] E ST energy of the singlet excitons S 1 generated in a material less 0.3eV triplet excitons T 1 is theoretically the excitation of the 100% singlet fission materials as excited singlet energy Can move to the singlet energy level E Sn .
  • triplet excitator T 1 is generated with an exciter generation efficiency of 200%.
  • the energy of triplet excitons T 1 is moved to the lowest excited triplet energy level E T1 phosphorescent material, by radiative deactivation, resulting in phosphorescence.
  • the triplet exciton generation efficiency is theoretically 200%, compared with a normal light emitting layer in which only triplet excitons generated with a probability of 75% are used for phosphorescent light emission.
  • the carrier is injected into the singlet split layer, whereby the singlet is formed.
  • the splitting material singlet excitons and triplet excitons are generated with a 25%: 75% probability, of which the singlet excitons split into two triplet excitons.
  • the laminate of the present invention includes all of the exciton generation layer, the block layer and the singlet split layer, so that the theoretical limit value of the exciton generation efficiency is high and the luminous efficiency is high.
  • Delta] E ST is equal to or less than 0.3eV to singlet fission materials
  • Delta] E ST is less than 0.3eV material
  • the thickness of the block layer is preferably 2 to 10 nm.
  • the lower limit of the thickness of the block layer is more preferably 2.5 nm or more, further preferably 3 nm or more, particularly preferably 5 nm or more, and the upper limit of the thickness of the block layer is 10 nm. It is more preferably less than or equal to, further preferably 8 nm or less, and particularly preferably 7 nm or less.
  • Delta] E ST is the energy of triplet excitons generated in the material is less than 0.3 eV, natural number excited triplet energy level E Tn (n singlet fission materials and luminescent materials It moves to) by the Dexter mechanism.
  • the material Delta] E ST is less than 0.3 eV, the probability of reverse intersystem crossing occurs from the excited triplet state (T 1) to the excited singlet state (S 1) is low, the singlet excitons It will not be possible to increase it sufficiently.
  • Förster from Delta] E ST is material lowest excited singlet energy level E S1 of at most 0.3eV to the excited singlet energy level E Sn singlet fission materials Resonance energy transfer is less likely to occur, and the excited element doubling mechanism of the singlet splitting material may not work sufficiently.
  • Delta] E ST is that higher than 0.2eV than the lowest excited singlet energy level E S1 materials is less than 0.3eV It is preferably 0.3 eV or more, and more preferably 0.3 eV or more.
  • Delta] E ST from the lowest excited singlet energy level E S1 materials is less than 0.3 eV, energy transfer to the lowest excited singlet energy level E S1 of blocking layer material and light emitting material is suppressed, Delta] E ST energy of singlet excitons generated in the material or less 0.3eV moves efficiently to the excited singlet energy level E Sn singlet fission materials.
  • the exciton doubling mechanism of the singlet splitting material can be effectively used.
  • the lowest excited triplet energy level E T1 of the material of the blocking layer is higher it is preferably at least 0.2eV than Delta] E ST is the lowest excited triplet energy level E of the material is less than 0.3 eV T1, 0 It is more preferable that it is higher than .3 eV.
  • the energy of Delta] E ST triplet excitons generated in the material or less 0.3eV is excited singlet fission material through the energy transfer to the lowest excited triplet energy level E T1 of the block layer Mie It is possible to avoid moving to the term energy level ETn .
  • the emission peak of the compound Delta] E ST is less than 0.3 eV, and overlaps the light absorption band of the singlet fission materials, and, in the wavelength region where they overlap, and emitting materials of the blocking layer is a light absorbing It is preferable not to show.
  • the emission peak of the compound Delta] E ST is less than 0.3 eV, and overlaps the light absorption band of the singlet fission materials, and, in the wavelength region where they overlap, and emitting materials of the blocking layer is a light absorbing It is preferable not to show.
  • the mechanism by which the laminate of the present invention is effective is not limited to such a mechanism.
  • the excited states are limited to “S 1 " and “T 1 ", but the excited singlet state and excited triplet state taken by each material of the laminate are at least.
  • excited singlet state (S 1) and lowest excitation is not limited to the triplet state (T 1), which from the even order excited singlet state S 2, S 3 ⁇ S n , excited triplet
  • T 2 , T 3 ... T n may be satisfied. In that case as well, a similar mechanism works to obtain high exciton generation efficiency and high luminous efficiency.
  • the excited triplet energy of the triplet exciter generated by the singlet splitting is transferred to the excited triplet energy level ET1 of the light emitting material and the light emitting material ( It may be the energy level of the electronically excited state in the central metal of the metal complex).
  • the luminescent material may be an organic phosphorescent material or an inorganic phosphorescent material.
  • a material which can be converted into singlet excitons from triplet excitons here, rather than the light emission from the T n, may be emitted from S n.
  • E S1, E T1 the measurement method of Delta] E ST
  • Lowest excited singlet energy level ES1 A sample is prepared by dissolving the compound to be measured in toluene at a concentration of 10-4 M or 10-5 M, and the fluorescence spectrum of this sample is measured at room temperature (300 K). The fluorescence spectrum of this sample is measured at room temperature (300K).
  • the maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the maximum value on the shortest wavelength side described above, and the slope value closest to the maximum value on the shortest wavelength side is the maximum.
  • the tangent line drawn at the point where the value is taken is taken as the tangent line to the rising edge of the phosphorescent spectrum on the short wavelength side.
  • Exciton generating layer comprises a material Delta] E ST is less than 0.3 eV.
  • Exciton generating layer is to Delta] E ST may be composed of only material or less 0.3eV, besides Delta] E ST is the material is less than 0.3eV, Delta] E ST is less than 0.3eV material It may contain materials other than (other materials).
  • E ST is equal to or less than 0.3eV material
  • Materials Delta] E ST is less than 0.3 eV, it can be preferably used a delayed fluorescent material.
  • Delta] E ST compounds of the delayed fluorescent material can be used as a material is less than 0.3eV examples.
  • Preferred delayed fluorescent materials include paragraphs 0008 to 0048 and 0995 to 0133 of WO 2013/154864, paragraphs 0007 to 0047 and 0073 to 985 of WO 2013/011954, and paragraphs 0007 to 0033 and 0059 to 0066 of WO 2013/011955.
  • WO 2013/081088 paragraphs 0008 to 0071 and 0118 to 0133
  • Japanese Patent Application Laid-Open No. 2013-256490 paragraphs 0009 to 0046 and 093 to 0134
  • Japanese Patent Application Laid-Open No. 2013-116975 paragraphs 0008 to 0020 and 0038 to 0040.
  • WO2014 / 136860A WO2014 / 196585, WO2014 / 189122, WO2014 / 168101, WO2015 / 008580, WO2014 / 203840, WO2015 / 002213, WO2015 / 016200, WO2015 / 019725, WO2015 / 072470, WO2015 / 108049, WO2015 / 080182, WO2015 / 072537, WO2015 / 080183, JP2015-129240, WO2015 / 129714, It is described in WO2015 / 129715, WO2015 / 133501, WO2015 / 136880, WO2015 / 137244, WO2015 / 137202, WO2015 / 137136, WO2015 / 146541, WO2015 / 159541.
  • a light emitting material that emits delayed fluorescence can also be preferably adopted. It should be noted that the above publications described in this paragraph are cited herein as part of this specification. Materials These Delta] E ST is less than 0.3eV may be used one kind alone or may be used in combination of two or more.
  • Exciton generating layer may contain a Delta] E ST is less than 0.3eV other than Ingredients (Other materials).
  • a host material can be mentioned. If exciton generating layer comprises a host material, to the material Delta] E ST is equal to or less than 0.3eV may be present uniformly dispersed in a host material, even though localized on a part of the area Good.
  • the content of the material Delta] E ST is less than 0.3eV is preferably 1 wt% or more of the materials the total amount of the exciton generating layer, 5 wt% More preferably, it is more preferably 10% by weight or more.
  • the thickness of the exciton generation layer is not particularly limited, but is preferably 1 nm to 25 nm, more preferably 3 nm to 20 nm, and even more preferably 5 nm to 15 nm.
  • the material of the blocking layer its lowest excited singlet energy level E S1 is, Delta] E ST is 0.2eV higher than the lowest excited singlet energy level E S1 materials is less than 0.3eV It is preferable to use a high one, and it is more preferable to use a high one of 0.3 eV or more. Furthermore the material of the blocking layer, the lowest excited triplet energy level E T1 is higher it is preferably at least 0.2eV than Delta] E ST is the lowest excited triplet energy level E of the material is less than 0.3 eV T1, It is more preferable that the value is 0.3 eV or more.
  • the laminate when used for the light emitting portion of the organic electroluminescence device, it is preferable to select the material of the block layer in consideration of the carrier transport property.
  • the block layer arranged on the anode side of the exciton generation layer preferably contains a material having hole transporting property, and the block layer arranged on the cathode side of the exciton generation layer is It is preferable to include a material having electron transportability.
  • the material having a hole transporting property include a compound having an aromatic ring in which at least one hydrogen atom is substituted with a substituent bonded by a nitrogen atom.
  • the aromatic ring may be a monocyclic ring, a condensed ring in which two or more aromatic rings are condensed, or a linked ring in which two or more aromatic rings are linked.
  • two or more aromatic rings When two or more aromatic rings are connected, they may be linearly connected or may be branched.
  • the number of carbon atoms in the aromatic ring is preferably 6 to 40, more preferably 6 to 22, further preferably 6 to 18, further preferably 6 to 14, and even more preferably 6 to 10. Is particularly preferable.
  • Specific examples of the aromatic ring include a benzene ring, a naphthalene ring, and a biphenyl ring.
  • Examples of the substituent bonded at the nitrogen atom include a substituted or unsubstituted diphenylamino group and a structure in which the phenyl groups of the substituted or unsubstituted diphenylamino group are linked by a single bond or a linking group (for example, an alkylene group). Examples thereof include a heteroaryl group having a three-ring structure. Examples of the material having electron transportability include a compound having an aromatic hetero-six-membered ring containing at least one nitrogen atom as a ring member.
  • examples of the aromatic hetero-six-membered ring include a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and a triazine ring.
  • examples of preferable compounds that can be used as a material for the block layer are given.
  • the material of these block layers one kind may be used alone, or two or more kinds may be used in combination. Further, the material of the blocking layer, between the material Delta] E ST is less than 0.3eV, so as to satisfy the above preferred energy relationships, Delta] E ST is taken into account the combination of the material is less than 0.3eV It is preferable to select.
  • Preferred combinations of Delta] E ST is equal to or less than 0.3eV material and the block layer material, a combination of ACR-XTN and mAP used in the examples infra, there may be mentioned a combination of ACR-XTN and B3PyMPM, other Examples thereof include a combination of DACT-II and mCP, a combination of DACT-II and PPF, a combination of DMAC-TRZ and mCP, DMAC-TRZ and Bphen, and the like.
  • the above description can be referred to for a preferable range of the thickness of the block layer.
  • the singlet split layer contains the singlet split material.
  • the singlet split layer may be composed of only the singlet split material, or may contain a material other than the singlet split material (other material) in addition to the singlet split material.
  • the singlet splitting material is a material in which each singlet exciton generated there can split into two triplet excitons after transitioning to the excited singlet state.
  • Lowest excited singlet energy level E S1 singlet fission materials, Delta] E ST is preferably lower than the lowest excited singlet energy level E S1 materials or less 0.3 eV. 0 More specifically, the lowest excited singlet energy level E of singlet fission material (f) S1, rather than Delta] E ST is the lowest excited singlet energy level E of the material is less than 0.3 eV (f) S1 .1 eV or more is more preferable, and 0.2 eV or more is more preferable.
  • the absorption spectrum of the emission spectrum and the singlet fission materials of Delta] E ST is less than 0.3eV overlap sufficiently.
  • Delta] E ST is the energy of singlet excitons generated in the material is less than 0.3 eV, it can be easily moved to the lowest excited singlet energy level E S1 singlet fission materials.
  • the absorption peak wavelength of the emission peak wavelength and singlet fission materials of Delta] E ST is equal to or less than 0.3eV is within 100 nm, more preferably within 50 nm, and still more preferably within 30 nm.
  • Examples of the compound that can be used as the singlet splitting material include acenes such as anthracene, tetracene, and pentacene.
  • acenes are substituted with an alkenyl group in which at least one hydrogen atom is substituted with a substituted or unsubstituted aryl group, an alkenyl group substituted with a substituted or unsubstituted aryl group, or an alkynyl group substituted with a substituted or unsubstituted aryl group. It may have been. Description and the preferred range of substituted or unsubstituted aryl group, specific examples may refer to description and preferred ranges for a substituted or unsubstituted aryl group in R 1 of the following general formula (1), specific examples ..
  • R 1 represents a substituted or unsubstituted aryl group.
  • One of R 2 and R 3 is a hydrogen atom and the other represents a substituted or unsubstituted aryl group.
  • the substituted or unsubstituted aryl group represented by one of R 2 and R 3 and the substituted or unsubstituted aryl group represented by R 1 may be the same or different from each other, but are preferably the same.
  • the aryl group referred to as "substituted or unsubstituted aryl group" (in the case of a substituted aryl group, the portion excluding the substituent) preferably has a ring skeleton constituent atoms of 6 to 26, more preferably 6 to 22, and 6 to 18 Is even more preferable.
  • the aryl group include a phenyl group, a 1-naphthalenyl group, a 2-naphthalenyl group, a 1-anthrasenyl group, a 2-anthrasenyl group, a 9-anthrasenyl group, a 1-tetrasenyl group, a 2-tetrasenyl group and a 5-tetrasenyl group.
  • Examples thereof include a 1-pyrenyl group and a 2-pyrenyl group.
  • the aryl group that can be taken by R 1 to R 3 may be substituted with a substituent or unsubstituted, but at least one of R 1 to R 3 is preferably an unsubstituted aryl group.
  • the substituent is preferably an alkyl group or an aryl group.
  • the alkyl group may be linear, branched or cyclic.
  • the number of carbon atoms is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6.
  • a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group and the like can be exemplified.
  • the preferable range and specific examples of the aryl group the preferable range and specific example of the aryl group referred to in the above-mentioned "substituted or unsubstituted aryl group" can be referred to.
  • the alkyl group and the aryl group as the substituent may be further substituted, and the alkyl group and the aryl group can be preferably mentioned as the substituent in that case.
  • the total number of carbon atoms of the substituted or unsubstituted aryl group that R 1 to R 3 can take is preferably 6 to 32, more preferably 6 to 28, and even more preferably 6 to 24.
  • substituted aryl groups examples include alkylphenyl groups (trill group, tert-butylphenyl group, etc.), biphenyl groups, alkylbiphenyl groups (methylbiphenyl group, tert-butylbiphenyl group, etc.), and tel.
  • One type of these singlet splitting materials may be used alone, or two or more types may be used in combination.
  • the singlet split layer may contain a material (other material) other than the singlet split material, if necessary. Examples of other materials include a light emitting material and a host material.
  • the singlet split layer contains a light emitting material, the energy of triplet excitons generated by the singlet split in the singlet split material can be transferred to the light emitting material by a Dexter mechanism, and the light emitting material can be made to emit light.
  • triplet excitons are generated in the singlet split layer with high exciton generation efficiency, so that the light emitting material can be efficiently emitted light.
  • a luminescent organic compound that can receive energy from a triplet exciter and emit light by using the energy can be used, and even if it is a metal complex, it is an organic compound other than the metal complex. It may be a phosphorescent material or a delayed fluorescent material.
  • Phosphorescent materials is a metal complex receives the energy of triplet excitons transition to the lowest excited triplet energy level E T1, deactivation from its lowest excited triplet energy level E T1 to the ground singlet state Phosphorus may be emitted along with the above, or the energy of the triplet exciter is received, and the state transitions to a higher energy electronic state (electron excited state) in the central metal, and the electron excited state is changed to the original. Phosphorus may be emitted as it transitions to the electronic state (basal electronic state) of.
  • the phosphorescent material facilitates excitation triplet energy transfer from the triplet excitons generated in the singlet fission, and, to confine the triplet energy in the molecule, the lowest excited triplet energy level E T1 but singlet divide at lower than the lowest excited triplet energy level E T1 triplet excitons produced and the energy level of the excited states in the central metal, triplet excitation generated in singlet fission it can be preferably used less than the lowest excited triplet energy level E T1 child.
  • the phosphorescent material which is a metal complex, is preferably a metal complex having lanthanide as a central metal, and more preferably a metal complex having Er as a central metal.
  • the delayed fluorescent material receives the energy of the triplet exciter and transitions to the lowest excited triplet energy level, and then transitions to the lowest excited singlet energy level by intersystem crossing, and the lowest excited singlet energy. It emits delayed fluorescence with deactivation from the level. Therefore, the delayed fluorescence material used for a light-emitting material, together with the energy difference Delta] E ST between the lowest excited singlet energy level and the lowest excited triplet energy level is less than 0.3 eV, resulting triplet excited by singlet fission
  • the lowest excited triplet energy level ET1 is the lowest excitation of the triplet exciter generated by singlet splitting. it is preferably lower than the triplet energy level E T1.
  • the wavelength of light emitted by the light emitting material is not particularly limited, and may be, for example, a visible region or a near infrared region. Since the emission wavelength is in the visible region, the laminated body can be applied to a light emitting part or illumination of a display device for displaying images, characters, symbols, etc., and the emission wavelength is in the near infrared region. This makes it possible to apply the laminate to a light source used in a near-infrared sensor or bioimaging.
  • Ar represents an aryl group.
  • the singlet split layer contains a luminescent material
  • the luminescent material is uniform in the singlet split layer. It may be dispersed in, or it may be localized in a part of the region.
  • the content of the luminescent material in the singlet split layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and 50% by weight, based on the total amount of the material in the singlet split layer. % Or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.
  • the thickness of the singlet split layer is not particularly limited, but is preferably 1 nm to 20 nm, more preferably 3 nm to 15 nm, and even more preferably 5 nm to 10 nm.
  • the laminate of the present invention has a structure in which an exciton generation layer, a block layer, and a singlet split layer are laminated in this order.
  • the laminated body of the present invention may be configured by laminating only these three layers in order, or may have other layers.
  • Other layers may be arranged between the exciton generation layer and the block layer, between the block layer and the singlet split layer, on the opposite side of the exciton generation layer from the block layer, or on the singlet split layer. It may be arranged on the opposite side of the block layer.
  • the other layer may be a layer selected from the exciton generation layer, the block layer and the singlet split layer, or may be a layer other than these layers.
  • a layer selected from an exciton generation layer, a block layer and a singlet split layer is provided as another layer, the materials and composition ratios of a plurality of exciton generation layers, block layers or singlet split layers are used.
  • the thickness may be the same or different from each other.
  • a five-layer structure consisting of a second singlet split layer can be mentioned.
  • first singlet split layer and the second singlet split layer correspond to the "singlet split layer", respectively, and the first block layer and the second block layer are respectively "block layers”. Equivalent to.
  • the material, composition ratio, and thickness of the first singlet split layer and the second singlet split layer, and the first block layer and the second block layer may be the same or different from each other.
  • each layer constituting the laminated body may have a single-layer structure or a multi-layer structure.
  • the laminate of the present invention has a high theoretical limit value of exciton generation efficiency, and when a luminescent material is added to the singlet split layer, it is compared with the singlet split layer alone to which the luminescent material is added. Therefore, the luminous efficiency can be dramatically increased. Therefore, by using the laminate of the present invention as a light emitting unit of an organic photoluminescence element (organic PL element) or an organic electroluminescence element (organic EL element), it is possible to provide an organic light emitting element having high luminous efficiency.
  • the organic photoluminescence element has a structure in which at least a light emitting portion is formed on a substrate.
  • the organic electroluminescence element has at least an anode, a cathode, and a structure in which an organic layer is formed between the anode and the cathode.
  • the organic layer includes at least a light emitting portion, and may be composed of only a light emitting portion, or may have one or more organic layers in addition to the light emitting portion. Examples of such 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, an exciton blocking layer, and the like.
  • 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.
  • FIG. 3 A specific structural example of the organic electroluminescence device is shown in FIG.
  • 1 is a substrate
  • 2 is an anode
  • 3 is a hole injection layer
  • 4 is a hole transport layer
  • 5 is a light emitting part
  • 6 is an electron transport layer
  • 7 is a cathode.
  • each member and each layer of the organic electroluminescence device will be described.
  • the description of the substrate and the light emitting portion also applies to the substrate and the light emitting portion of the organic photoluminescence element.
  • the organic electroluminescence element of the present invention is preferably supported by a substrate.
  • the substrate is not particularly limited as long as it is conventionally used for organic electroluminescence devices, and for example, one made of glass, transparent plastic, quartz, silicon, or the like can be used.
  • anode As the anode in the organic electroluminescence element, a metal having a large work function (4 eV or more), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is preferably used.
  • electrode materials include metals such as Au and conductive transparent materials such as CuI, indium zinc oxide (ITO), SnO 2 , and ZnO.
  • a material such as IDIXO (In 2 O 3- ZnO) which is amorphous and can produce a transparent conductive film may be used.
  • a thin film may be formed by forming a thin film of these electrode materials by a method such as thin film deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not required so much (about 100 ⁇ m or more). ), A pattern may be formed through a mask having a desired shape during vapor deposition or sputtering of the electrode material.
  • a coatable material such as an organic conductive compound
  • a wet film forming method such as a printing method or a coating method can also be used.
  • the sheet resistance as the anode is preferably several hundred ⁇ / ⁇ or less.
  • the film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.
  • cathode a metal having a small work function (4 eV or less) (referred to as an electron-injectable metal), an alloy, an electrically conductive compound, or a mixture thereof is used as an electrode material.
  • 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 ) Examples thereof include a mixture, an indium, a lithium / aluminum mixture, and a rare earth metal.
  • a mixture of an electron injectable metal and a second metal which is a stable metal having a larger work function value than this for example, a magnesium / silver mixture.
  • a magnesium / silver mixture Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al 2 O 3 ) mixture, lithium / aluminum mixture, aluminum and the like are suitable.
  • the cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering.
  • the sheet resistance of 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. Since the emitted light is transmitted, it is convenient that the emission brightness is improved if either the anode or the cathode of the organic electroluminescence element is transparent or translucent.
  • a transparent or translucent cathode can be manufactured, and by applying this, an element in which both the anode and the cathode have transparency can be obtained. Can be made.
  • the light emitting portion is composed of the laminate of the present invention, and after holes and electrons injected from the anode and the cathode are recombined in the exciton generation layer of the laminate to generate excitons, It is a layer that emits light.
  • the laminated body of the present invention the description in the above ⁇ Laminated body> column can be referred to.
  • the laminate of the present invention since the laminate of the present invention has a high theoretical limit value of exciton generation efficiency, high luminous efficiency can be obtained by using this for the light emitting portion.
  • the laminate constituting the light emitting portion of the organic electroluminescence element preferably contains a light emitting material in the singlet split layer, and the first singlet split layer / first block layer / exciton generation layer / second block. It is more preferable to have a layer structure of a layer / second singlet split layer.
  • the first singlet split layer is arranged on the anode side and the second singlet split layer is arranged on the cathode side.
  • the block layer (first block) on the anode side of the exciton generation layer among the first block layer and the second block layer.
  • the layer) preferably contains a material having a hole transport property
  • the block layer (second block layer) on the cathode side of the exciton generation layer preferably contains a material having an electron transport property.
  • the description in the column of (block layer) above can be referred to.
  • light emission is generated from a light emitting material contained in the singlet split layer.
  • This light emission may be phosphorescent light emission or delayed fluorescence light emission. Further, a part of the light emission may be emitted from the material of the exciton generation layer, the material of the block layer, or the singlet splitting material of the singlet splitting layer.
  • the injection layer is a layer provided between the electrode and the organic layer in order to reduce the driving voltage and improve the emission brightness.
  • the injection layer can be provided as needed.
  • the blocking layer is a layer capable of blocking the diffusion of electric charges (electrons or holes) and / or excitons existing in the light emitting portion to the outside of the light emitting portion.
  • the electron blocking layer can be arranged between the light emitting section and the hole transporting layer to prevent electrons from passing through the light emitting section toward the hole transporting layer.
  • the hole blocking layer can be placed between the light emitting section and the electron transporting layer to prevent holes from passing through the light emitting section towards the electron transporting layer.
  • the blocking layer can also be used to prevent excitons from diffusing outside the light emitting section. That is, the electron blocking layer and the hole blocking layer can also function as exciton blocking layers, respectively.
  • the electron blocking layer or exciton blocking layer referred to in the present specification is used in the sense that one layer includes a layer having the functions of an electron blocking layer and an exciton blocking layer.
  • the hole blocking layer has a function of an electron transporting layer in a broad sense.
  • the hole blocking layer has a role of blocking the holes from reaching the electron transporting layer while transporting electrons, which can improve the recombination probability of electrons and holes in the light emitting portion.
  • As the material of the hole blocking layer a material of the electron transport layer described later can be used as needed.
  • the electron blocking layer has a function of transporting holes in a broad sense.
  • the electron blocking layer has a role of blocking the electrons from reaching the hole transporting layer while transporting holes, which can improve the probability that the electrons and holes in the light emitting portion are recombined. ..
  • the exciton blocking layer is a layer for preventing excitons generated by recombination of holes and electrons in the light emitting portion from diffusing into the charge transport layer, and the exciton is efficiently inserted by inserting this layer.
  • the light emitting unit can be confined to the light emitting unit, and the light emitting efficiency of the element can be improved.
  • the exciton blocking layer can be inserted into either the anode side or the cathode side adjacent to the light emitting portion, and both can be inserted at the same time.
  • the layer when the exciton blocking layer is provided on the anode side, the layer can be inserted between the hole transport layer and the light emitting portion adjacent to the light emitting portion, and when inserted on the cathode side, the light emitting portion and electrons can be inserted.
  • the layer can be inserted between the transport layer and the light emitting portion adjacent to the light emitting portion.
  • a hole injection layer, a hole transport layer, an electron blocking layer and the like can be provided between the anode and the exciton blocking layer adjacent to the exciton blocking layer of the light emitting portion, and the cathode and the light emitting portion can be provided.
  • An electron injection layer, an electron transport layer, a hole blocking layer, and the like can be provided between the exciton blocking layer adjacent to the cathode side.
  • the blocking layer it is preferable that at least one of the excited singlet energy and the excited triplet energy of the material used as the blocking layer is higher than the excited singlet energy and the excited triplet energy of the light emitting material.
  • the hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer may be provided with a single layer or a plurality of layers.
  • the hole transporting material has either injection or transport of holes or an electron barrier property, and may be either an organic substance or an inorganic substance.
  • Known hole transporting 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, etc.
  • the electron transport layer is made of a material having a function of transporting electrons, and the electron transport layer may be provided with a single layer or a plurality of layers.
  • the electron transporting 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 portion.
  • Examples of the electron transporting layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, freolenidenemethane derivatives, anthracinodimethane and anthrone derivatives, and oxadiazole derivatives.
  • a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is replaced 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 film forming method for each layer of the laminate constituting the organic electroluminescence device and the other layers is not particularly limited, and may be produced by either a dry process or a wet process.
  • a preferable compound that can be used as a host material when the exciton generation layer or the singlet split layer contains a host material is listed.
  • preferable compounds as materials that can be further added are given.
  • it may be added as a stabilizing material.
  • the organic electroluminescence device produced by the above 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 the excitation triplet energy, the wavelength corresponding to the energy level is confirmed as phosphorescent light. In the case of light emission by excitation singlet energy, light having a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. Further, since normal fluorescence has a shorter fluorescence lifetime than delayed fluorescence emission, the emission lifetime can be distinguished by fluorescence and delayed fluorescence.
  • the organic electroluminescence device can be applied to any of a single device, a device having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix.
  • an organic light emitting device having greatly improved exciton generation efficiency and luminous efficiency can be obtained.
  • An organic light emitting device such as an organic electroluminescence device using the laminate of the present invention can be further applied to various applications. For example, it is possible to manufacture an organic electroluminescence display device using this organic electroluminescence element.
  • Organic electroluminescence element can also be applied to organic electroluminescence lighting and backlights, which are in great demand.
  • ACR-XTN, mAP, B3PyMPM the lowest excited singlet energy level E S1 and the lowest excited triplet energy level E T1 rubrene and Er (hfa), as well as the 4 I 13/2 level of Er (hfa) It is shown in Table 1.
  • Table 1 the lowest excited singlet energy level E S1 and the lowest excited triplet energy level E T1 of ACR-XTN is, Nakanotani et al., Nat.
  • Example 1 Preparation and evaluation of a laminate 1 composed of a first singlet split layer / first block layer / exciton generation layer / second block layer / second singlet split layer on a quartz substrate , Each thin film was laminated with a vacuum degree of less than 10 -4 Pa by a vacuum vapor deposition method.
  • rubrene and Er (hfa) were deposited on a quartz substrate from different vapor deposition sources and formed to a thickness of 10 nm to form a first singlet split layer.
  • the concentration of Er (hfa) was set to 2.0% by weight.
  • mAP is deposited on the first singlet split layer to form a first block layer having a thickness of 2 nm
  • ACR-XTN is deposited on the first block layer to form an exciton having a thickness of 15 nm.
  • a formation layer was formed.
  • B3PyMPM was vapor-deposited on it to form a second block layer having a thickness of 2 nm.
  • rubrene and Er (hfa) were deposited on the second block layer from different vapor deposition sources and formed to a thickness of 10 nm to form a second singlet split layer. At this time, the concentration of Er (hfa) was set to 2.0% by weight.
  • the energy level diagram of the produced laminate 1 is shown in FIG. 4, and the estimated light emission mechanism is shown in FIG.
  • the numerical value shown on the lower side of each layer is the absolute value of the energy level of HOMO (Highest Occupied Molecular Orbital) of that layer, and the numerical value shown on the upper side of each layer is the absolute value.
  • the meanings of these numerical values are the same in FIGS. 6, 8 and 10. As shown in FIG.
  • rubrene singlet fission layer 2 contains, moves to the lowest excited singlet energy level E S1.
  • the rubrene received the excited singlet energy the singlet excitons S 1 is split into two triplet excitons T 1, its triplet energy, the Dexter mechanism, 4 I of Er of Er (hfa) Move to 13/2 level.
  • the phosphorescence is emitted with to alleviate the 4 I 13/2 level to 4 I 15/2 level.
  • the energy of excitons S 1, T 1 generated in the exciton generation layer of the laminate 1 at the maximum, all of which, to rubrene of the lowest excited singlet energy level E S1 as excited singlet energy It moves, and each singlet excitator S 1 generated there splits into two triplet excitators T 1 . Therefore, the theoretical limit value of the exciton generation efficiency of the laminated body 1 is 200%.
  • Comparative Example 1 Preparation and evaluation of a comparative laminate 1 composed of a first singlet split layer / exciton generation layer / second singlet split layer Do not form a first block layer and a second block layer.
  • a comparative laminate 1 was produced in the same manner as in Example 1 except for the above.
  • the energy level diagram of the produced comparative laminate 1 is shown in FIG. 6, and the estimated light emission mechanism is shown in FIG.
  • ACR-XTN in FIG 6 corresponds to the material which is Delta] E ST ⁇ 0.3 eV in Fig. 7
  • rubrene 6 corresponds to singlet fission material of FIG. 7
  • Er in FIG. 6 (hfa) is It corresponds to the phosphorescent material of FIG.
  • FIG. 1 Comparative Example 1
  • the resulting in exciton formation layer singlet excitons S 1 energy and triplet excitons energy T 1 is both moved to singlet fission material for the first singlet fission layer or second singlet fission layer (rubrene), singlet fission materials (rubrene) in singlet excitons S 1 and triple
  • the term exciton T 1 is generated.
  • the singlet exciter S 1 is split into two triplet excitators T 1 , and the excited triplet energy is used for phosphorescent emission of Er (hfa).
  • the triplet exciter T 1 is As it is, the excited triplet energy is used for phosphorescent emission of Er (hfa).
  • Comparative Example 2 Preparation and evaluation of a comparative laminate 2 composed of a first light emitting layer / exciton generation layer / second light emitting layer Instead of forming a first singlet split layer and a second singlet split layer
  • a comparative laminate 2 was produced in the same manner as in Example 2 except that a first light emitting layer and a second light emitting layer having a thickness of 10 nm were formed by using only Er (hfa) as a vapor deposition source.
  • the energy level diagram of the produced comparative laminate 2 is shown in FIG. 8, and the estimated light emission mechanism is shown in FIG.
  • ACR-XTN in Figure 8 corresponds to the material which is Delta] E ST ⁇ 0.3 eV in Fig. 9, Er in FIG.
  • FIG. 11 shows the emission spectra of the singlet split layers prepared in the laminated body 1, the comparative laminated bodies 1, 2 and the comparative example 3 by the 400 nm excitation light.
  • FIG. 11A is an emission spectrum in the range of 450 to 700 nm
  • FIG. 11B is an emission spectrum in the range of 1400 to 1650 nm.
  • the emission peak near 510 nm is derived from the emission of ACR-XTN
  • the emission peak near 560 nm is derived from the emission of rubrene.
  • the emission peak near 1500 nm is derived from the emission of Er (hfa).
  • Er Er
  • the rubrene layer (first and second singlet split layers) containing Er (hfa), the mAP layer (first block layer), the ACR-XTN layer (exciton generation layer),
  • the emission from Er (hfa) showed higher intensity than the emission from ACR-XTN and the emission from rubrene.
  • the comparative laminated body 1 having no block layer had a lower intensity of light emission derived from Er (hfa) than the laminated body 1. It is considered that this is because the exciton doubling mechanism due to the singlet splitting of rubrene does not work sufficiently because the excited triplet energy generated by ACR-XTN also moves to rubrene.
  • the laminate of Comparative Example 2 in which rubrene was not used had a high emission intensity derived from ACR-XTN, and the emission intensity derived from Er (hfa) was lower than that of the laminate 1. It is considered that the high emission intensity derived from ACR-XTN is due to the fact that the excitation singlet energy generated by ACR-XTN did not move to Er (hfa) and was used for emission of ACR-XTN. It is considered that the reason why the emission intensity derived from (hfa) is low is that the excited singlet energy generated by ACR-XTN does not contribute to the emission of Er (hfa) at all.
  • the singlet split layer alone prepared in Comparative Example 3 had the lowest luminescence intensity derived from Er (hfa) among the prepared layers. This is because the singlet split layer does not have an exciton generating layer that supplies excitons. From the above, by using a structure in which the exciton generation layer, the block layer, and the singlet split layer are laminated in order, the exciton amplification action of the singlet split material works effectively, and the luminous efficiency of phosphorescence is remarkable. It turned out to improve.
  • Example 2 Fabrication of an organic electroluminescence device having a laminated body composed of a first singlet split layer / first block layer / exciter generation layer / second block layer / second singlet split layer. Evaluation Each thin film was laminated on a glass substrate on which an anode made of indium tin oxide (ITO) having a film thickness of 100 nm was formed by a vacuum vapor deposition method at a degree of vacuum of less than 10-4 Pa. First, TAPC was formed on ITO to a thickness of 50 nm.
  • ITO indium tin oxide
  • ACR-XTN layer (exciton generation layer), B3PyMPM layer (second block layer), and rubrene layer (second singlet split layer) containing 1.8% by weight of Er (hfa) were formed in this order.
  • B3PyMPM was formed on the laminate to a thickness of 55 nm.
  • 8-quinolina tritium (Liq) was formed to a thickness of 0.8 nm, and aluminum (Al) was vapor-deposited on it to a thickness of 80 nm to form a cathode, thereby forming an organic electroluminescence device. ..
  • the emission spectrum of the produced organic electroluminescence device is shown in FIG. As shown in FIG. 12, the emission peak near 1500 nm derived from Er (hfa) emission could also be observed from the organic electroluminescence device to which the laminate of the present invention was applied.
  • the laminate of the present invention has a high theoretical limit value of exciton generation efficiency. Therefore, by using the laminate of the present invention for the light emitting portion of the organic light emitting element, the luminous efficiency can be dramatically improved. Therefore, the present invention has high industrial applicability.

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  • Chemical & Material Sciences (AREA)
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  • Materials Engineering (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Inorganic Chemistry (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

L'invention concerne un élément électroluminescent organique présentant une efficacité électroluminescente élevée et comprenant une structure dans laquelle une couche de génération d'excitons comprenant un matériau ayant un ΔEST de 0,3 eV ou moins, une couche de bloc et une couche de fission de singulet comprenant un matériau de fission de singulet, sont stratifiées dans cet ordre.
PCT/JP2020/023038 2019-06-14 2020-06-11 Élément électroluminescent organique, corps de stratification et procédé électroluminescent WO2020250979A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012005009A1 (fr) * 2010-07-09 2012-01-12 出光興産株式会社 Dérivés d'imidazopyridine et éléments électroluminescents organiques les contenant
US20130240850A1 (en) * 2012-03-13 2013-09-19 The Regents Of The University Of Michigan Ultra-high efficiency (125%) phosphorescent organic light emitting diodes using singlet fission
WO2014129330A1 (fr) * 2013-02-20 2014-08-28 株式会社カネカ Elément électroluminescent organique, dispositif d'éclairage utilisant celui-ci et dispositif d'affichage
WO2019022120A1 (fr) * 2017-07-25 2019-01-31 国立大学法人九州大学 Matériau à fission de singulet, sensibilisateur de triplet, composé et film mince

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012005009A1 (fr) * 2010-07-09 2012-01-12 出光興産株式会社 Dérivés d'imidazopyridine et éléments électroluminescents organiques les contenant
US20130240850A1 (en) * 2012-03-13 2013-09-19 The Regents Of The University Of Michigan Ultra-high efficiency (125%) phosphorescent organic light emitting diodes using singlet fission
WO2014129330A1 (fr) * 2013-02-20 2014-08-28 株式会社カネカ Elément électroluminescent organique, dispositif d'éclairage utilisant celui-ci et dispositif d'affichage
WO2019022120A1 (fr) * 2017-07-25 2019-01-31 国立大学法人九州大学 Matériau à fission de singulet, sensibilisateur de triplet, composé et film mince

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