Patent Application
20240407185
The present invention relates to an organic electroluminescence device and an electronic device.
An organic electroluminescence device (hereinafter, occasionally referred to as “organic EL device”) has found its application in a full-color display for mobile phones, televisions, and the like. When voltage is applied to an organic EL device, holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected holes and electrons are recombined in the emitting layer to form excitons. Specifically, according to the electron spin statistics theory, singlet excitons and triplet excitons are generated at a ratio of 25%:75%.
For instance, in Patent Literatures 1 to 4 and 6 to 7, various studies have been made on a compound to be used for an organic EL device in order to enhance the performance of the organic EL device. In addition, in order to enhance the performance of the organic EL device, Patent Literature 5 describes a phenomenon in which a singlet exciton is generated by collision and fusion of two triplet excitons (hereinafter, occasionally referred to as a Triplet-Triplet Fusion (TTF) phenomenon). The performance of the organic EL device is evaluable in terms of, for instance, luminance, emission wavelength, chromaticity, luminous efficiency, drive voltage, and lifetime.
An object of the invention is to provide an organic electroluminescence device excellent in performance. Another object of the invention is to provide an organic electroluminescence device excellent in luminous efficiency and an electronic device including the organic electroluminescence device.
According to an aspect of the invention, there is provided an organic electroluminescence device including: a first emitting layer and a second emitting layer provided between an anode and a cathode, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, a total of a film thickness of the first emitting layer and a film thickness of the second emitting layer is 20 nm or less, the first emitting compound and the second emitting compound are mutually the same or different, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1) below.
According to another aspect of the invention, there is provided an organic electroluminescence device including: a first emitting layer and a second emitting layer provided between an anode and a cathode, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, a ratio of a total of the film thicknesses of the first and second emitting layers to a distance from the cathode to the second emitting layer, the total of the film thicknesses of the first and second emitting layers/the distance from the cathode to the second emitting layer, is 0.8 or less, the first emitting compound and the second emitting compound are mutually the same or different, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1 below.
According to still another aspect of the invention, there is provided an organic electroluminescence device including: an anode; a cathode; one or more first emitting layers provided between the anode and the cathode; one or more second emitting layers provided between the one or more first emitting layers and the cathode; and an intermediate layer provided between a pair of emitting layers selected from a plurality of emitting layers consisting of the one or more first emitting layers and the one or more second emitting layers, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the first emitting compound and the second emitting compound are mutually the same or different, the intermediate layer contains no metal atom, materials forming the intermediate layer are each contained in the intermediate layer at a content ratio of 10 mass % or more, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1) below.
According to a further aspect of the invention, there is provided an electronic device including the organic electroluminescence device according to the aspect of the invention.
According to the aspect of the invention, an organic electroluminescence device excellent in performance can be provided. According to the aspect of the invention, an organic electroluminescence device excellent in luminous efficiency can be provided. According to the aspect of the invention, an electronic device including the organic electroluminescence device can be provided.
Herein, a hydrogen atom includes isotope having different numbers of neutrons, specifically, protium, deuterium and tritium.
In chemical formulae herein, it is assumed that a hydrogen atom (i.e. protium, deuterium and tritium) is bonded to each of bondable positions that are not annexed with signs “R” or the like or “D” representing a deuterium.
Herein, the ring carbon atoms refer to the number of carbon atoms among atoms forming a ring of a compound (e.g., a monocyclic compound, fused-ring compound, cross-linking compound, carbon ring compound, and heterocyclic compound) in which the atoms are bonded to each other to form the ring. When the ring is substituted by a substituent(s), carbon atom(s) contained in the substituent(s) is not counted in the ring carbon atoms. Unless otherwise specified, the same applies to the “ring carbon atoms” described later. For instance, a benzene ring has 6 ring carbon atoms, a naphthalene ring has 10 ring carbon atoms, a pyridine ring has 5 ring carbon atoms, and a furan ring has 4 ring carbon atoms. Further, for instance, 9,9-diphenylfluorenyl group has 13 ring carbon atoms and 9,9′-spirobifluorenyl group has 25 ring carbon atoms.
When a benzene ring is substituted by a substituent in a form of, for instance, an alkyl group, the number of carbon atoms of the alkyl group is not counted in the number of the ring carbon atoms of the benzene ring. Accordingly, the benzene ring substituted by an alkyl group has 6 ring carbon atoms. When a naphthalene ring is substituted by a substituent in a form of, for instance, an alkyl group, the number of carbon atoms of the alkyl group is not counted in the number of the ring carbon atoms of the naphthalene ring. Accordingly, the naphthalene ring substituted by an alkyl group has 10 ring carbon atoms.
Herein, the ring atoms refer to the number of atoms forming a ring of a compound (e.g., a monocyclic compound, fused-ring compound, cross-linking compound, carbon ring compound, and heterocyclic compound) in which the atoms are bonded to each other to form the ring (e.g., monocyclic ring, fused ring, and ring assembly). Atom(s) not forming the ring (e.g., hydrogen atom(s) for saturating the valence of the atom which forms the ring) and atom(s) in a substituent by which the ring is substituted are not counted as the ring atoms. Unless otherwise specified, the same applies to the “ring atoms” described later. For instance, a pyridine ring has 6 ring atoms, a quinazoline ring has 10 ring atoms, and a furan ring has 5 ring atoms. For instance, the number of hydrogen atom(s) bonded to a pyridine ring or the number of atoms forming a substituent is not counted as the pyridine ring atoms. Accordingly, a pyridine ring bonded to a hydrogen atom(s) or a substituent(s) has 6 ring atoms. For instance, the hydrogen atom(s) bonded to carbon atom(s) of a quinazoline ring or the atoms forming a substituent are not counted as the quinazoline ring atoms. Accordingly, a quinazoline ring bonded to hydrogen atom(s) or a substituent(s) has 10 ring atoms.
Herein, “XX to YY carbon atoms” in the description of “substituted or unsubstituted ZZ group having XX to YY carbon atoms” represent carbon atoms of an unsubstituted ZZ group and do not include carbon atoms of a substituent(s) of the substituted ZZ group. Herein, “YY” is larger than “XX,” “XX” representing an integer of 1 or more and “YY” representing an integer of 2 or more.
Herein, “XX to YY atoms” in the description of “substituted or unsubstituted ZZ group having XX to YY atoms” represent atoms of an unsubstituted ZZ group and does not include atoms of a substituent(s) of the substituted ZZ group. Herein, “YY” is larger than “XX,” “XX” representing an integer of 1 or more and “YY” representing an integer of 2 or more.
Herein, an unsubstituted ZZ group refers to an “unsubstituted ZZ group” in a “substituted or unsubstituted ZZ group,” and a substituted ZZ group refers to a “substituted ZZ group” in a “substituted or unsubstituted ZZ group.”
Herein, the term “unsubstituted” used in a “substituted or unsubstituted ZZ group” means that a hydrogen atom(s) in the ZZ group is not substituted with a substituent(s). The hydrogen atom(s) in the “unsubstituted ZZ group” is protium, deuterium, or tritium.
Herein, the term “substituted” used in a “substituted or unsubstituted ZZ group” means that at least one hydrogen atom in the ZZ group is substituted with a substituent. Similarly, the term “substituted” used in a “BB group substituted by AA group” means that at least one hydrogen atom in the BB group is substituted with the AA group.
Substituent mentioned herein will be described below.
An “unsubstituted aryl group” mentioned herein has, unless otherwise specified herein, 6 to 50, preferably 6 to 30, more preferably 6 to 18 ring carbon atoms.
An “unsubstituted heterocyclic group” mentioned herein has, unless otherwise specified herein, 5 to 50, preferably 5 to 30, more preferably 5 to 18 ring atoms.
An “unsubstituted alkyl group” mentioned herein has, unless otherwise specified herein, 1 to 50, preferably 1 to 20, more preferably 1 to 6 carbon atoms.
An “unsubstituted alkenyl group” mentioned herein has, unless otherwise specified herein, 2 to 50, preferably 2 to 20, more preferably 2 to 6 carbon atoms.
An “unsubstituted alkynyl group” mentioned herein has, unless otherwise specified herein, 2 to 50, preferably 2 to 20, more preferably 2 to 6 carbon atoms.
An “unsubstituted cycloalkyl group” mentioned herein has, unless otherwise specified herein, 3 to 50, preferably 3 to 20, more preferably 3 to 6 ring carbon atoms.
An “unsubstituted arylene group” mentioned herein has, unless otherwise specified herein, 6 to 50, preferably 6 to 30, more preferably 6 to 18 ring carbon atoms.
An “unsubstituted divalent heterocyclic group” mentioned herein has, unless otherwise specified herein, 5 to 50, preferably 5 to 30, more preferably 5 to 18 ring atoms.
An “unsubstituted alkylene group” mentioned herein has, unless otherwise specified herein, 1 to 50, preferably 1 to 20, more preferably 1 to 6 carbon atoms.
Specific examples (specific example group G1) of the “substituted or unsubstituted aryl group” mentioned herein include unsubstituted aryl groups (specific example group G1A) below and substituted aryl groups (specific example group G1B). (Herein, an unsubstituted aryl group refers to an “unsubstituted aryl group” in a “substituted or unsubstituted aryl group”, and a substituted aryl group refers to a “substituted aryl group” in a “substituted or unsubstituted aryl group.”) A simply termed “aryl group” herein includes both of an “unsubstituted aryl group” and a “substituted aryl group”.
The “substituted aryl group” refers to a group derived by substituting at least one hydrogen atom in an “unsubstituted aryl group” with a substituent. Examples of the “substituted aryl group” include a group derived by substituting at least one hydrogen atom in the “unsubstituted aryl group” in the specific example group G1A below with a substituent, and examples of the substituted aryl group in the specific example group G1B below. It should be noted that the examples of the “unsubstituted aryl group” and the “substituted aryl group” mentioned herein are merely exemplary, and the “substituted aryl group” mentioned herein includes a group derived by further substituting a hydrogen atom bonded to a carbon atom of a skeleton of a “substituted aryl group” in the specific example group G1B below, and a group derived by further substituting a hydrogen atom of a substituent of the “substituted aryl group” in the specific example group G1B below.
The “heterocyclic group” mentioned herein refers to a cyclic group having at least one hetero atom in the ring atoms. Specific examples of the hetero atom include a nitrogen atom, oxygen atom, sulfur atom, silicon atom, phosphorus atom, and boron atom.
The “heterocyclic group” mentioned herein is a monocyclic group or a fused-ring group.
The “heterocyclic group” mentioned herein is an aromatic heterocyclic group or a non-aromatic heterocyclic group.
Specific examples (specific example group G2) of the “substituted or unsubstituted heterocyclic group” mentioned herein include unsubstituted heterocyclic groups (specific example group G2A) and substituted heterocyclic groups (specific example group G2B). (Herein, an unsubstituted heterocyclic group refers to an “unsubstituted heterocyclic group” in a “substituted or unsubstituted heterocyclic group,” and a substituted heterocyclic group refers to a “substituted heterocyclic group” in a “substituted or unsubstituted heterocyclic group.”) A simply termed “heterocyclic group” herein includes both of an “unsubstituted heterocyclic group” and a “substituted heterocyclic group.”
The “substituted heterocyclic group” refers to a group derived by substituting at least one hydrogen atom in an “unsubstituted heterocyclic group” with a substituent. Specific examples of the “substituted heterocyclic group” include a group derived by substituting at least one hydrogen atom in the “unsubstituted heterocyclic group” in the specific example group G2A below with a substituent, and examples of the substituted heterocyclic group in the specific example group G2B below. It should be noted that the examples of the “unsubstituted heterocyclic group” and the “substituted heterocyclic group” mentioned herein are merely exemplary, and the “substituted heterocyclic group” mentioned herein includes a group derived by further substituting a hydrogen atom bonded to a ring atom of a skeleton of a “substituted heterocyclic group” in the specific example group G2B below, and a group derived by further substituting a hydrogen atom of a substituent of the “substituted heterocyclic group” in the specific example group G2B below.
The specific example group G2A includes, for instance, unsubstituted heterocyclic groups including a nitrogen atom (specific example group G2A1) below, unsubstituted heterocyclic groups including an oxygen atom (specific example group G2A2) below, unsubstituted heterocyclic groups including a sulfur atom (specific example group G2A3) below, and monovalent heterocyclic groups (specific example group G2A4) derived by removing a hydrogen atom from cyclic structures represented by formulae (TEMP-16) to (TEMP-33) below.
The specific example group G2B includes, for instance, substituted heterocyclic groups including a nitrogen atom (specific example group G2B1) below, substituted heterocyclic groups including an oxygen atom (specific example group G2B2) below, substituted heterocyclic groups including a sulfur atom (specific example group G2B3) below, and groups derived by substituting at least one hydrogen atom of the monovalent heterocyclic groups (specific example group G2B4) derived from the cyclic structures represented by formulae (TEMP-16) to (TEMP-33) below.
In the formulae (TEMP-16) to (TEMP-33), XA and YA are each independently an oxygen atom, a sulfur atom, NH or CH2, with a proviso that at least one of XA or YA is an oxygen atom, a sulfur atom, or NH.
When at least one of XA or YA in the formulae (TEMP-16) to (TEMP-33) is NH or CH2, the monovalent heterocyclic groups derived from the cyclic structures represented by the formulae (TEMP-16) to (TEMP-33) include a monovalent group derived by removing one hydrogen atom from NH or CH2.
(9-phenyl)carbazolyl group, (9-biphenylyl)carbazolyl group, (9-phenyl)phenylcarbazolyl group, (9-naphthyl)carbazolyl group, diphenylcarbazole-9-yl group, phenylcarbazole-9-yl group, methylbenzimidazolyl group, ethylbenzimidazolyl group, phenyltriazinyl group, biphenylyltriazinyl group, diphenyltriazinyl group, phenylquinazolinyl group, and biphenylquinazolinyl group.
The “at least one hydrogen atom of a monovalent heterocyclic group” means at least one hydrogen atom selected from a hydrogen atom bonded to a ring carbon atom of the monovalent heterocyclic group, a hydrogen atom bonded to a nitrogen atom of at least one of XA or YA in a form of NH, and a hydrogen atom of one of XA and YA in a form of a methylene group (CH2).
Specific examples (specific example group G3) of the “substituted or unsubstituted alkyl group” mentioned herein include unsubstituted alkyl groups (specific example group G3A) and substituted alkyl groups (specific example group G3B) below. (Herein, an unsubstituted alkyl group refers to an “unsubstituted alkyl group” in a “substituted or unsubstituted alkyl group,” and a substituted alkyl group refers to a “substituted alkyl group” in a “substituted or unsubstituted alkyl group.”) A simply termed “alkyl group” herein includes both of an “unsubstituted alkyl group” and a “substituted alkyl group”.
The “substituted alkyl group” refers to a group derived by substituting at least one hydrogen atom in an “unsubstituted alkyl group” with a substituent. Specific examples of the “substituted alkyl group” include a group derived by substituting at least one hydrogen atom of an “unsubstituted alkyl group” (specific example group G3A) below with a substituent, and examples of the substituted alkyl group (specific example group G3B) below. Herein, the alkyl group for the “unsubstituted alkyl group” refers to a chain alkyl group. Accordingly, the “unsubstituted alkyl group” include linear “unsubstituted alkyl group” and branched “unsubstituted alkyl group.” It should be noted that the examples of the “unsubstituted alkyl group” and the “substituted alkyl group” mentioned herein are merely exemplary, and the “substituted alkyl group” mentioned herein includes a group derived by further substituting a hydrogen atom of a skeleton of the “substituted alkyl group” in the specific example group G3B, and a group derived by further substituting a hydrogen atom of a substituent of the “substituted alkyl group” in the specific example group G3B.
The “substituted alkenyl group” refers to a group derived by substituting at least one hydrogen atom in an “unsubstituted alkenyl group” with a substituent. Specific examples of the “substituted alkenyl group” include an “unsubstituted alkenyl group” (specific example group G4A) substituted by a substituent, and examples of the substituted alkenyl group (specific example group G4B) below. It should be noted that the examples of the “unsubstituted alkenyl group” and the “substituted alkenyl group” mentioned herein are merely exemplary, and the “substituted alkenyl group” mentioned herein includes a group derived by further substituting a hydrogen atom of a skeleton of the “substituted alkenyl group” in the specific example group G4B with a substituent, and a group derived by further substituting a hydrogen atom of a substituent of the “substituted alkenyl group” in the specific example group G4B with a substituent.
Specific examples (specific example group G5) of the “substituted or unsubstituted alkynyl group” mentioned herein include unsubstituted alkynyl groups (specific example group G5A) below. (Herein, an unsubstituted alkynyl group refers to an “unsubstituted alkynyl group” in a “substituted or unsubstituted alkynyl group.”) A simply termed “alkynyl group” herein includes both of “unsubstituted alkynyl group” and “substituted alkynyl group”.
The “substituted alkynyl group” refers to a group derived by substituting at least one hydrogen atom in an “unsubstituted alkynyl group” with a substituent. Specific examples of the “substituted alkynyl group” include a group derived by substituting at least one hydrogen atom of the “unsubstituted alkynyl group” (specific example group G5A) below with a substituent.
Substituted or Unsubstituted Cycloalkyl Group Specific examples (specific example group G6) of the “substituted or unsubstituted cycloalkyl group” mentioned herein include unsubstituted cycloalkyl groups (specific example group G6A) and substituted cycloalkyl groups (specific example group G6B). (Herein, an unsubstituted cycloalkyl group refers to an “unsubstituted cycloalkyl group” in a “substituted or unsubstituted cycloalkyl group,” and a substituted cycloalkyl group refers to a “substituted cycloalkyl group” in a “substituted or unsubstituted cycloalkyl group.”) A simply termed “cycloalkyl group” herein includes both of “unsubstituted cycloalkyl group” and “substituted cycloalkyl group”.
The “substituted cycloalkyl group” refers to a group derived by substituting at least one hydrogen atom of an “unsubstituted cycloalkyl group” with a substituent. Specific examples of the “substituted cycloalkyl group” include a group derived by substituting at least one hydrogen atom of the “unsubstituted cycloalkyl group” (specific example group G6A) below with a substituent, and examples of the substituted cycloalkyl group (specific example group G6B) below. It should be noted that the examples of the “unsubstituted cycloalkyl group” and the “substituted cycloalkyl group” mentioned herein are merely exemplary, and the “substituted cycloalkyl group” mentioned herein includes a group derived by substituting at least one hydrogen atom bonded to a carbon atom of a skeleton of the “substituted cycloalkyl group” in the specific example group G6B with a substituent, and a group derived by further substituting a hydrogen atom of a substituent of the “substituted cycloalkyl group” in the specific example group G6B with a substituent.
Specific examples (specific example group G7) of the group represented herein by —Si(R901)(R902)(R903) include:
Specific examples (specific example group G8) of a group represented by —O—(R904) herein include: —O(G1); —O(G2); —O(G3); and —O(G6);
Specific examples (specific example group G9) of a group represented herein by —S—(R905) include: —S(G1); —S(G2); —S(G3); and —S(G6);
Specific examples (specific example group G10) of a group represented herein by —N(R906)(R907) include: —N(G1)(G1); —N(G2)(G2); —N(G1)(G2); —N(G3)(G3); and —N(G6)(G6),
Specific examples (specific example group G11) of “halogen atom” mentioned herein include a fluorine atom, chlorine atom, bromine atom, and iodine atom.
The “substituted or unsubstituted fluoroalkyl group” mentioned herein refers to a group derived by substituting at least one hydrogen atom bonded to at least one of carbon atoms forming an alkyl group in the “substituted or unsubstituted alkyl group” with a fluorine atom, and also includes a group (perfluoro group) derived by substituting all of hydrogen atoms bonded to carbon atoms forming the alkyl group in the “substituted or unsubstituted alkyl group” with fluorine atoms. An “unsubstituted fluoroalkyl group” has, unless otherwise specified herein, 1 to 50, preferably 1 to 30, more preferably 1 to 18 carbon atoms. The “substituted fluoroalkyl group” refers to a group derived by substituting at least one hydrogen atom in a “fluoroalkyl group” with a substituent. It should be noted that the examples of the “substituted fluoroalkyl group” mentioned herein include a group derived by further substituting at least one hydrogen atom bonded to a carbon atom of an alkyl chain of a “substituted fluoroalkyl group” with a substituent, and a group derived by further substituting at least one hydrogen atom of a substituent of the “substituted fluoroalkyl group” with a substituent. Specific examples of the “unsubstituted fluoroalkyl group” include a group derived by substituting at least one hydrogen atom of the “alkyl group” (specific example group G3) with a fluorine atom.
The “substituted or unsubstituted haloalkyl group” mentioned herein refers to a group derived by substituting at least one hydrogen atom bonded to carbon atoms forming the alkyl group in the “substituted or unsubstituted alkyl group” with a halogen atom, and also includes a group derived by substituting all hydrogen atoms bonded to carbon atoms forming the alkyl group in the “substituted or unsubstituted alkyl group” with halogen atoms. An “unsubstituted haloalkyl group” has, unless otherwise specified herein, 1 to 50, preferably 1 to 30, and more preferably 1 to 18 carbon atoms. The “substituted haloalkyl group” refers to a group derived by substituting at least one hydrogen atom in a “haloalkyl group” with a substituent. It should be noted that the examples of the “substituted haloalkyl group” mentioned herein include a group derived by further substituting at least one hydrogen atom bonded to a carbon atom of an alkyl chain of a “substituted haloalkyl group” with a substituent, and a group derived by further substituting at least one hydrogen atom of a substituent of the “substituted haloalkyl group” with a substituent. Specific examples of the “unsubstituted haloalkyl group” include a group derived by substituting at least one hydrogen atom of the “alkyl group” (specific example group G3) with a halogen atom. The haloalkyl group is sometimes referred to as a halogenated alkyl group.
Specific examples of a “substituted or unsubstituted alkoxy group” mentioned herein include a group represented by —O(G3), G3 being the “substituted or unsubstituted alkyl group” in the specific example group G3. An “unsubstituted alkoxy group” has, unless otherwise specified herein, 1 to 50, preferably 1 to 30, more preferably 1 to 18 carbon atoms.
Specific examples of a “substituted or unsubstituted alkylthio group” mentioned herein include a group represented by —S(G3), G3 being the “substituted or unsubstituted alkyl group” in the specific example group G3. An “unsubstituted alkylthio group” has, unless otherwise specified herein, 1 to 50, preferably 1 to 30, more preferably 1 to 18 carbon atoms.
Specific examples of a “substituted or unsubstituted aryloxy group” mentioned herein include a group represented by —O(G1), G1 being the “substituted or unsubstituted aryl group” in the specific example group G1. An “unsubstituted aryloxy group” has, unless otherwise specified herein, 6 to 50, preferably 6 to 30, more preferably 6 to 18 ring carbon atoms.
Specific examples of a “substituted or unsubstituted arylthio group” mentioned herein include a group represented by —S(G1), G1 being the “substituted or unsubstituted aryl group” in the specific example group G1. An “unsubstituted arylthio group” has, unless otherwise specified herein, 6 to 50, preferably 6 to 30, more preferably 6 to 18 ring carbon atoms.
Specific examples of a “trialkylsilyl group” mentioned herein include a group represented by —Si(G3)(G3)(G3), G3 being the “substituted or unsubstituted alkyl group” in the specific example group G3. The plurality of G3 in —Si(G3)(G3)(G3) are mutually the same or different. Each of the alkyl groups in the “trialkylsilyl group” has, unless otherwise specified herein, 1 to 50, preferably 1 to 20, more preferably 1 to 6 carbon atoms.
Specific examples of a “substituted or unsubstituted aralkyl group” mentioned herein include a group represented by -(G3)-(G1), G3 being the “substituted or unsubstituted alkyl group” in the specific example group G3, G1 being the “substituted or unsubstituted aryl group” in the specific example group G1. Accordingly, the “aralkyl group” is a group derived by substituting a hydrogen atom of the “alkyl group” with a substituent in a form of the “aryl group,” which is an example of the “substituted alkyl group.” An “unsubstituted aralkyl group,” which is an “unsubstituted alkyl group” substituted by an “unsubstituted aryl group,” has, unless otherwise specified herein, 7 to 50 carbon atoms, preferably 7 to 30 carbon atoms, more preferably 7 to 18 carbon atoms.
Specific examples of the “substituted or unsubstituted aralkyl group” include a benzyl group, 1-phenylethyl group, 2-phenylethyl group, 1-phenylisopropyl group, 2-phenylisopropyl group, phenyl-t-butyl group, a-naphthylmethyl group, 1-α-naphthylethyl group, 2-α-naphthylethyl group, 1-α-naphthylisopropyl group, 2-α-naphthylisopropyl group, β-naphthylmethyl group, 1-β-naphthylethyl group, 2-β-naphthylethyl group, 1-β-naphthylisopropyl group, and 2-β-naphthylisopropyl group.
Preferable examples of the substituted or unsubstituted aryl group mentioned herein include, unless otherwise specified herein, a phenyl group, p-biphenyl group, m-biphenyl group, o-biphenyl group, p-terphenyl-4-yl group, p-terphenyl-3-yl group, p-terphenyl-2-yl group, m-terphenyl-4-yl group, m-terphenyl-3-yl group, m-terphenyl-2-yl group, o-terphenyl-4-yl group, o-terphenyl-3-yl group, o-terphenyl-2-yl group, 1-naphthyl group, 2-naphthyl group, anthryl group, phenanthryl group, pyrenyl group, chrysenyl group, triphenylenyl group, fluorenyl group, 9,9′-spirobifluorenyl group, 9,9-dimethylfluorenyl group, and 9,9-diphenylfluorenyl group.
Preferable examples of the substituted or unsubstituted heterocyclic group mentioned herein include, unless otherwise specified herein, a pyridyl group, pyrimidinyl group, triazinyl group, quinolyl group, isoquinolyl group, quinazolinyl group, benzimidazolyl group, phenanthrolinyl group, carbazolyl group (1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, 4-carbazolyl group, or 9-carbazolyl group), benzocarbazolyl group, azacarbazolyl group, diazacarbazolyl group, dibenzofuranyl group, naphthobenzofuranyl group, azadibenzofuranyl group, diazadibenzofuranyl group, dibenzothiophenyl group, naphthobenzothiophenyl group, azadibenzothiophenyl group, diazadibenzothiophenyl group, (9-phenyl)carbazolyl group ((9-phenyl)carbazole-1-yl group, (9-phenyl)carbazole-2-yl group, (9-phenyl)carbazole-3-yl group, or (9-phenyl)carbazole-4-yl group), (9-biphenylyl)carbazolyl group, (9-phenyl)phenylcarbazolyl group, diphenylcarbazole-9-yl group, phenylcarbazole-9-yl group, phenyltriazinyl group, biphenylyltriazinyl group, diphenylttnazinyl group, phenyldibenzofuranyl group, and phenyldibenzothiophenyl group.
The carbazolyl group mentioned herein is, unless otherwise specified herein, specifically a group represented by one of formulae below.
The (9-phenyl)carbazolyl group mentioned herein is, unless otherwise specified herein, specifically a group represented by one of formulae below.
In the formulae (TEMP-Cz1) to (TEMP-Cz9), * represents a bonding position.
The dibenzofuranyl group and dibenzothiophenyl group mentioned herein are, unless otherwise specified herein, each specifically represented by one of formulae below.
In the formulae (TEMP-34) to (TEMP-41), * represents a bonding position.
Preferable examples of the substituted or unsubstituted alkyl group mentioned herein include, unless otherwise specified herein, a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, and t-butyl group.
The “substituted or unsubstituted arylene group” mentioned herein is, unless otherwise specified herein, a divalent group derived by removing one hydrogen atom on an aryl ring of the “substituted or unsubstituted aryl group.” Specific examples of the “substituted or unsubstituted arylene group” (specific example group G12) include a divalent group derived by removing one hydrogen atom on an aryl ring of the “substituted or unsubstituted aryl group” in the specific example group G1.
The “substituted or unsubstituted divalent heterocyclic group” mentioned herein is, unless otherwise specified herein, a divalent group derived by removing one hydrogen atom on a heterocycle of the “substituted or unsubstituted heterocyclic group.” Specific examples of the “substituted or unsubstituted divalent heterocyclic group” (specific example group G13) include a divalent group derived by removing one hydrogen atom on a heterocyclic ring of the “substituted or unsubstituted heterocyclic group” in the specific example group G2.
The “substituted or unsubstituted alkylene group” mentioned herein is, unless otherwise specified herein, a divalent group derived by removing one hydrogen atom on an alkyl chain of the “substituted or unsubstituted alkyl group.” Specific examples of the “substituted or unsubstituted alkylene group” (specific example group G14) include a divalent group derived by removing one hydrogen atom on an alkyl chain of the “substituted or unsubstituted alkyl group” in the specific example group G3.
The substituted or unsubstituted arylene group mentioned herein is, unless otherwise specified herein, preferably any one of groups represented by formulae (TEMP-42) to (TEMP-68) below.
In the formulae (TEMP-42) to (TEMP-52), Q1 to Q10 are each independently a hydrogen atom or a substituent.
In the formulae (TEMP-42) to (TEMP-52), * represents a banding position.
In the formulae (TEMP-53) to (TEMP-62), Q1 to Q10 are each independently a hydrogen atom or a substituent.
In the formulae, Q9 and Qow may be mutually banded through a single band to form a ring.
In the formulae (TEMP-53) to (TEMP-62), * represents a banding position.
In the formulae (TEMP-63) to (TEMP-68), Q1 to Q8 are each independently a hydrogen atom or a substituent.
In the formulae (TEMP-63) to (TEMP-68), * represents a bonding position.
The substituted or unsubstituted divalent heterocyclic group mentioned herein is, unless otherwise specified herein, preferably a group represented by any one of formulae (TEMP-69) to (TEMP-102) below.
In the formulae (TEMP-69) to (TEMP-82), Q1 to Q9 are each independently a hydrogen atom or a substituent.
In the formulae (TEMP-83) to (TEMP-102), Q1 to Q8 are each independently a hydrogen atom or a substituent.
The substituent mentioned herein has been described above.
Instances where “at least one combination of adjacent two or more (of . . . ) are mutually banded to form a substituted or unsubstituted monocyclic ring, mutually bonded to form a substituted or unsubstituted fused ring, or not mutually bonded” mentioned herein refer to instances where “at least one combination of adjacent two or more (of . . . ) are mutually banded to form a substituted or unsubstituted monocyclic ring, “at least one combination of adjacent two or more (of . . . ) are mutually bonded to form a substituted or unsubstituted fused ring,” and “at least one combination of adjacent two or more (of . . . ) are not mutually bonded.”
Instances where “at least one combination of adjacent two or more (of . . . ) are mutually bonded to form a substituted or unsubstituted monocyclic ring” and “at least one combination of adjacent two or more (of . . . ) are mutually bonded to form a substituted or unsubstituted fused ring” mentioned herein (these instances will be sometimes collectively referred to as an instance of “bonded to form a ring” hereinafter) will be described below. An anthracene compound having a basic skeleton in a form of an anthracene ring and represented by a formula (TEMP-103) below will be used as an example for the description.
For instance, when “at least one combination of adjacent two or more of R921 to R930 are mutually bonded to form a ring,” the combination of adjacent ones of R921 to R930 (i.e. the combination at issue) is a combination of R921 and R922, a combination of R922 and R923, a combination of R923 and R924, a combination of R924 and R930, a combination of R930 and R925, a combination of R925 and R926, a combination of R926 and R927, a combination of R927 and R928, a combination of R928 and R929, or a combination of R929 and R921.
The term “at least one combination” means that two or more of the above combinations of adjacent two or more of R921 to R930 may simultaneously form rings. For instance, when R921 and R922 are mutually bonded to form a ring QA and R925 and R926 are simultaneously mutually bonded to form a ring QB, the anthracene compound represented by the formula (TEMP-103) is represented by a formula (TEMP-104) below.
The instance where the “combination of adjacent two or more” form a ring means not only an instance where the “two” adjacent components are bonded but also an instance where adjacent “three or more” are bonded. For instance, R921 and R922 are mutually bonded to form a ring QA and R922 and R923 are mutually bonded to form a ring Qc, and mutually adjacent three components (R921, R922 and R923) are mutually bonded to form a ring fused to the anthracene basic skeleton. In this case, the anthracene compound represented by the formula (TEMP-103) is represented by a formula (TEMP-105) below. In the formula (TEMP-105) below, the ring QA and the ring Qc share R922.
The formed “monocyclic ring” or “fused ring” may be, in terms of the formed ring in itself, a saturated ring or an unsaturated ring. When the “combination of adjacent two” form a “monocyclic ring” or a “fused ring,” the “monocyclic ring” or “fused ring” may be a saturated ring or an unsaturated ring. For instance, the ring QA and the ring QB formed in the formula (TEMP-104) are each independently a “monocyclic ring” or a “fused ring.” Further, the ring QA and the ring Qc formed in the formula (TEMP-105) are each a “fused ring.” The ring QA and the ring Qc in the formula (TEMP-105) are fused to form a fused ring. When the ring QA in the formula (TEMP-104) is a benzene ring, the ring QA is a monocyclic ring. When the ring QA in the formula (TEMP-104) is a naphthalene ring, the ring QA is a fused ring.
The “unsaturated ring” represents an aromatic hydrocarbon ring or an aromatic heterocycle. The “saturated ring” represents an aliphatic hydrocarbon ring or a non-aromatic heterocycle.
Specific examples of the aromatic hydrocarbon ring include a ring formed by terminating a bond of a group in the specific example of the specific example group G1 with a hydrogen atom.
Specific examples of the aromatic heterocycle include a ring formed by terminating a bond of an aromatic heterocyclic group in the specific example of the specific example group G2 with a hydrogen atom.
Specific examples of the aliphatic hydrocarbon ring include a ring formed by terminating a bond of a group in the specific example of the specific example group G6 with a hydrogen atom.
The phrase “to form a ring” herein means that a ring is formed only by a plurality of atoms of a basic skeleton, or by a combination of a plurality of atoms of the basic skeleton and one or more optional atoms. For instance, the ring QA formed by mutually bonding R921 and R922 shown in the formula (TEMP-104) is a ring formed by a carbon atom of the anthracene skeleton bonded to R921, a carbon atom of the anthracene skeleton bonded to R922, and one or more optional atoms. Specifically, when the ring QA is a monocyclic unsaturated ring formed by R921 and R922, the ring formed by a carbon atom of the anthracene skeleton bonded to R921, a carbon atom of the anthracene skeleton bonded to R922, and four carbon atoms is a benzene ring.
The “optional atom” is, unless otherwise specified herein, preferably at least one atom selected from the group consisting of a carbon atom, nitrogen atom, oxygen atom, and sulfur atom. A bond of the optional atom (e.g. a carbon atom and a nitrogen atom) not forming a ring may be terminated by a hydrogen atom or the like or may be substituted by an “optional substituent” described later. When the ring includes an optional element other than carbon atom, the resultant ring is a heterocycle.
The number of “one or more optional atoms” forming the monocyclic ring or fused ring is, unless otherwise specified herein, preferably in a range from 2 to 15, more preferably in a range from 3 to 12, further preferably in a range from 3 to 5.
Unless otherwise specified herein, the ring, which may be a “monocyclic ring” or “fused ring,” is preferably a “monocyclic ring.”
Unless otherwise specified herein, the ring, which may be a “saturated ring” or “unsaturated ring,” is preferably an “unsaturated ring.”
Unless otherwise specified herein, the “monocyclic ring” is preferably a benzene ring.
Unless otherwise specified herein, the “unsaturated ring” is preferably a benzene ring.
When “at least one combination of adjacent two or more” (of . . . ) are “mutually bonded to form a substituted or unsubstituted monocyclic ring” or “mutually bonded to form a substituted or unsubstituted fused ring,” unless otherwise specified herein, at least one combination of adjacent two or more of components are preferably mutually bonded to form a substituted or unsubstituted “unsaturated ring” formed of a plurality of atoms of the basic skeleton, and 1 to 15 atoms of at least one element selected from the group consisting of carbon, nitrogen, oxygen and sulfur.
When the “monocyclic ring” or the “fused ring” has a substituent, the substituent is the substituent described in later-described “optional substituent.” When the “monocyclic ring” or the “fused ring” has a substituent, specific examples of the substituent are the substituent described in the above under the subtitle “Substituent Mentioned Herein.”
When the “saturated ring” or the “unsaturated ring” has a substituent, the substituent is the substituent described in later-described “optional substituent.” When the “monocyclic ring” or the “fused ring” has a substituent, specific examples of the substituent are the substituents described in the above under the subtitle “Substituent Mentioned Herein.”
The above is the description for the instances where “at least one combination of adjacent two or more (of . . . ) are mutually bonded to form a substituted or unsubstituted monocyclic ring” and “at least one combination of adjacent two or more (of . . . ) are mutually bonded to form a substituted or unsubstituted fused ring” mentioned herein (sometimes referred to as an instance of “bonded to form a ring”).
In an exemplary embodiment herein, the substituent for the substituted or unsubstituted group (sometimes referred to as an “optional substituent” hereinafter), is for instance, a group selected from the group consisting of an unsubstituted alkyl group having 1 to 50 carbon atoms, an unsubstituted alkenyl group having 2 to 50 carbon atoms, an unsubstituted alkynyl group having 2 to 50 carbon atoms, an unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, —Si(R901)(R902)(R903), —O—(R904), —S—(R905), —N(R906)(R907), a halogen atom, a cyano group, a nitro group, an unsubstituted aryl group having 6 to 50 ring carbon atoms, and an unsubstituted heterocyclic group having 5 to 50 ring atoms;
In an exemplary embodiment, the substituent for the substituted or unsubstituted group is a group selected from the group consisting of an alkyl group having 1 to 50 carbon atoms, an aryl group having 6 to 50 ring carbon atoms, and a heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, the substituent for the substituted or unsubstituted group is a group selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 18 ring carbon atoms, and a heterocyclic group having 5 to 18 ring atoms.
Specific examples of the above optional substituent are the same as the specific examples of the substituent described in the above under the subtitle “Substituent Mentioned Herein.”
Unless otherwise specified herein, adjacent ones of the optional substituents may form a “saturated ring” or an “unsaturated ring,” preferably a substituted or unsubstituted saturated five-membered ring, a substituted or unsubstituted saturated six-membered ring, a substituted or unsubstituted unsaturated five-membered ring, or a substituted or unsubstituted unsaturated six-membered ring, more preferably a benzene ring.
Unless otherwise specified herein, the optional substituent may further include a substituent. Examples of the substituent for the optional substituent are the same as the examples of the optional substituent.
Herein, numerical ranges represented by “AA to BB” represent a range whose lower limit is the value (AA) recited before “to” and whose upper limit is the value (BB) recited after “to.”
An organic electroluminescence device according to the first exemplary embodiment includes a first emitting layer and a second emitting layer, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, a total of a film thickness of the first emitting layer and a film thickness of the second emitting layer is 20 nm or less, the first emitting compound and the second emitting compound are mutually the same or different, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1) below.
The inventors have found out that luminous efficiency is improvable by providing at least two emitting layers (i.e., the first and second emitting layers), making the triplet energy of the first host material T1(H1) in the first emitting layer and the triplet energy of the second host material T1(H2) in the second emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1), and reducing the thickness of the first and second emitting layers so that the total of the film thickness of the first emitting layer and the film thickness of the second emitting layer is 20 nm or less. Presumably, the reason thereof is as below.
First, Triplet-Triplet-Annihilation (occasionally referred to as TTA), known as the technology for enhancing the luminous efficiency of the organic EL device, will be described.
TTA is a mechanism in which triplet excitons collide with one another to generate singlet excitons. The TTA mechanism is also referred to as a TTF mechanism as described in Patent Literature 5.
The TTF phenomenon will be described. Holes injected from an anode and electrons injected from a cathode are recombined in an emitting layer to generate excitons. As for the spin state, as is conventionally known, singlet excitons account for 25% and triplet excitons account for 75%. In a conventionally known fluorescent device, light is emitted when singlet excitons of 25% are relaxed to the ground state. The remaining triplet excitons of 75% are returned to the ground state without emitting light through a thermal deactivation process. Accordingly, the theoretical limit value of the internal quantum efficiency of the conventional fluorescent device is believed to be 25%.
The behavior of triplet excitons generated within an organic substance has been theoretically examined. According to S. M. Bachilo et al. (J. Phys. Chem. A, 104, 7711 (2000)), assuming that high-order excitons such as quintet excitons are quickly returned to triplet excitons, triplet excitons (hereinafter abbreviated as 3A*) collide with one another with an increase in density thereof, whereby a reaction shown by the following formula occurs. In the formula, 1A represents the ground state and 1A* represents the lowest singlet excitons.
In other words, 53A*→41A+1A* is satisfied, and it is expected that, among triplet excitons initially generated, which account for 75%, one fifth thereof (i.e., 20%) is changed to singlet excitons. Accordingly, the amount of singlet excitons which contribute to emission is 40%, which is a value obtained by adding 15% (75%×(1/5)=15%) to 25%, which is the amount ratio of initially generated singlet excitons. At this time, a ratio of luminous intensity derived from TTF (TTF ratio) relative to the total luminous intensity is 15/40, i.e., 37.5%. Assuming that singlet excitons are generated by collision of initially generated triplet excitons accounting for 75% (i.e., one singlet exciton is generated from two triplet excitons), a significantly high internal quantum efficiency of 62.5% is obtained, which is a value obtained by adding 37.5% (75%×(1/2)=37.5%) to 25% (the amount ratio of initially generated singlet excitons). At this time, the TTF ratio is 37.5/62.5=60%.
Subsequently, the significance that the triplet energy of the first host material T1(H1) in the first emitting layer and the triplet energy of the second host material T1(H2) in the second emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1) in the organic EL device of the first exemplary embodiment is explained below.
In the organic EL device according to the first exemplary embodiment, it is considered that since the relationship of the numerical formula (Numerical Formula 1) is satisfied, triplet excitons generated by recombination of holes and electrons in the first emitting layer and present on an interface between the first emitting layer and organic layer(s) in direct contact therewith are not likely to be quenched even under the presence of excessive carriers on the interface between the first emitting layer and the organic layer(s). For instance, the presence of a recombination region locally on an interface between the first emitting layer and a hole transporting layer or an electron blocking layer is considered to cause quenching by excessive electrons. Meanwhile, the presence of a recombination region locally on an interface between the first emitting layer and an electron transporting layer or a hole blocking layer is considered to cause quenching by excessive holes.
In the organic EL device according to the first exemplary embodiment, by including the first emitting layer and the second emitting layer so as to satisfy the relationship of the numerical formula (Numerical Formula 1), triplet excitons generated in the first emitting layer can transfer to the second emitting layer without being quenched by excessive carriers and be inhibited from back-transferring from the second emitting layer to the first emitting layer. Consequently, the second emitting layer exhibits the TTF mechanism to effectively generate singlet excitons, thereby improving the luminous efficiency.
Accordingly, the organic EL device includes, as different regions, the first emitting layer mainly generating triplet excitons and the second emitting layer mainly exhibiting the TTF mechanism using triplet excitons having transferred from the first emitting layer, and has a difference in triplet energy provided by using a compound having a smaller triplet energy than that of the first host material in the first emitting layer as the second host material in the second emitting layer. The luminous efficiency is thus improved compared to a case where the relationship of the numerical formula (Numerical Formula 1) is not satisfied.
Subsequently, explanation is made about the significance of reducing the thickness of the first and second emitting layers so that the total of the film thickness of the first emitting layer and the film thickness of the second emitting layer is 20 nm or less.
As described above, in order to improve the luminous efficiency, the organic EL device of the first exemplary embodiment is designed by layering the emitting layers and using the first host material and the second host material that satisfy the relationship of the numerical formula (Numerical Formula 1).
In the organic EL device with layered emitting layers, the function of a Singlet emitting region is separated from that of an emitting region derived from TTF. The two emitting regions separated from each other expand an emission distribution, which may reduce light-extraction efficiency.
In order to solve this problem, the thickness of the emitting layers (first emitting layer and the second emitting layer) is reduced in the organic EL device of the exemplary embodiment, so that the Singlet emitting region and the TTF emitting region provided in the two respective emitting layers are close to each other. As a result, interference may be usable more efficiently to enhance light-extraction efficiency to the outside, resulting in higher luminous efficiency.
Thus, in the organic EL device of the exemplary embodiment, high luminous efficiency is achievable even when the thickness of emitting layers is reduced by making the triplet energy of the first host material T1(H1) in the first emitting layer and the triplet energy of the second host material T1(H2) in the second emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1), and making the total of the film thickness of the first emitting layer and the film thickness of the second emitting layer 20 nm or less. Since the organic EL device of the exemplary embodiment includes the emitting layers with a small thickness, drive voltage is also reducible.
The organic EL device according to the first exemplary embodiment may be a bottom emission type organic EL device or a top emission type organic EL device. The top emission type organic EL device is preferable in view of further improving luminous efficiency.
That is, the organic EL device of the first exemplary embodiment is preferably an organic EL device in which the anode is a reflective electrode and light is extracted through the cathode.
Note that the anode may be a transparent electrode. In this arrangement, a light reflection layer is preferably disposed on an opposite side of the emitting layer with respect to the anode. In a case of
The organic EL device 1 includes a light-transmissive substrate 2, an anode 3, a cathode 4, and organic layers 10 provided between the anode 3 and the cathode 4. The organic layers 10 include a hole injecting layer 6, a hole transporting layer 7, a first emitting layer 51, a second emitting layer 52, an electron transporting layer 8, and an electron injecting layer 9 that are layered on the anode 3 in this order. In
The organic EL device 1 includes the first emitting layer 51 and the second emitting layer 52 that contain the host materials satisfying the relationship of the numerical formula (Numerical Formula 1).
Further, in the organic EL device 1, the total of a film thickness d1 (unit: nm) of the first emitting layer 51 and a film thickness d2 (unit: nm) of the second emitting layer 52 is 20 nm or less. The total (d1+d2) of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 thus satisfies a numerical formula (Numerical Formula 100) below.
The organic EL device 1 according to the first exemplary embodiment may have any arrangement without being limited to the arrangement of the organic EL device 1 shown in
A preferable arrangement of the organic EL device 1 of the first exemplary embodiment will be explained.
In the organic EL device 1 of the first exemplary embodiment, the total of the film thickness of the first emitting layer 51 and the film thickness of the second emitting layer 52 is preferably 17 nm or less.
In the organic EL device 1 of the first exemplary embodiment, the total of the film thickness of the first emitting layer 51 and the film thickness of the second emitting layer 52 is more preferably 15 nm or less.
Thus, the total (d1+d2) of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 preferably satisfies a numerical formula (Numerical Formula 101) below, more preferably satisfies a numerical formula (Numerical Formula 102) below. Note that a lower limit of the total (d1+d2) of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 is preferably 6 nm or more.
In the organic EL device 1 of the first exemplary embodiment, the film thickness d1 of the first emitting layer 51 is preferably smaller than the film thickness d2 of the second emitting layer 52.
When the film thickness d1 of the first emitting layer 51 is smaller than the film thickness d2 of the second emitting layer 52 in the organic EL device 1 of the first exemplary embodiment, triplet excitons generated in the first emitting layer 51 are not likely to remain in the first emitting layer 51 but diffused efficiently to the second emitting layer 52. Thus, the film thickness d1 of the first emitting layer 51 is preferably smaller than the film thickness d2 of the second emitting layer 52. For the above reason, although not particularly limited, the film thickness d1 of the first emitting layer 51 is, for instance, preferably in a range from 3 nm to 10 nm, more preferably in a range from 5 nm to 8 nm.
In the organic EL device 1 of the first exemplary embodiment, the film thickness d2 of the second emitting layer 52 is preferably in a range from 3 nm to 15 nm and more preferably in a range from 5 nm to 15 nm, in order that the Singlet emitting region mainly generated in the first emitting layer and the Triplet emitting region mainly generated in the second emitting layer are close to each other.
Further, the film thickness d2 of the second emitting layer 52 is preferably larger than the film thickness d1 of the first emitting layer 51, in order that triplet excitons generated in the first emitting layer 51 are efficiently diffused from the first emitting layer 51 to the second emitting layer 52.
The film thickness d1 of the first emitting layer 51 is measured as follows. A central portion (CL in
It should be noted that the central portion of the organic EL device 1 means a central portion of a shape of the organic EL device 1 projected through the cathode 4. When the projected shape is, for instance, rectangular, the central portion of the organic EL device 1 means an intersection of the diagonal lines of the rectangle.
The same measurement method applies to the film thickness d2 of the second emitting layer 52.
Further, the same measurement method applies to “a distance D2 from the cathode 4 to the second emitting layer 52” and “a total D1 of the film thicknesses of the first emitting layer 51 and the second emitting layer 52”.
An organic electroluminescence device according to a second exemplary embodiment includes a first emitting layer and a second emitting layer, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, a ratio of a total of film thicknesses of the first and second emitting layers to a distance from the cathode to the second emitting layer, the total of film thicknesses of the first and second emitting layers/the distance from the cathode to the second emitting layer, is 0.8 or less, the first emitting compound and the second emitting compound are mutually the same or different, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1) below.
The inventors have found out that luminous efficiency is improvable by providing at least two emitting layers (i.e., the first and second emitting layers), making the triplet energy of the first host material T1(H1) in the first emitting layer and the triplet energy of the second host material T1(H2) in the second emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1), and making the above ratio (the total of film thicknesses of the first and second emitting layers/the distance from the cathode to the second emitting layer) 0.8 or less.
Here, the wording “making the above ratio (the total of film thicknesses of the first and second emitting layers/the distance from the cathode to the second emitting layer) 0.8 or less” means that the ratio of the total of the film thicknesses of the first and second emitting layers to the distance from the cathode to the second emitting layer is small. In other words, the above ratio being 0.8 or less means that the thickness of the emitting layers (first and second emitting layers) is smaller than that of an electron transporting zone.
The organic EL device of the second exemplary embodiment thus has improved luminous efficiency even when the above ratio is 0.8 or less for the same reason as the first exemplary embodiment. Further, drive voltage is also reducible in the organic EL device of the second exemplary embodiment.
The organic EL device according to the second exemplary embodiment may be a bottom emission type organic EL device or a top emission type organic EL device. The top emission type organic EL device is preferable in view of further improving luminous efficiency.
That is, the organic EL device of the second exemplary embodiment is preferably an organic EL device in which the anode is a reflective electrode and light is extracted through the cathode.
An organic EL device 1A includes the light-transmissive substrate 2, the anode 3, the cathode 4, and organic layers 10 provided between the anode 3 and the cathode 4. The organic layers 10 include the hole injecting layer 6, the hole transporting layer 7, the first emitting layer 51, the second emitting layer 52, the electron transporting layer 8, and the electron injecting layer 9 that are layered on the anode 3 in this order. The anode 3 is a reflective electrode. In
The organic EL device 1A includes the first emitting layer 51 and the second emitting layer 52 that contain the host materials satisfying the relationship of the numerical formula (Numerical Formula 1).
Further, in the organic EL device 1A, a ratio of a total D2 (unit: nm) of film thicknesses of the first emitting layer 51 and the second emitting layer 52 to a distance D1 (unit: nm) from the cathode 4 to the second emitting layer 52 (a total D2 of film thicknesses of the first emitting layer 51 and the second emitting layer 52/a distance D1 from the cathode 4 to the second emitting layer 52) (hereinafter, also referred to as ratio (D2/D1)) is 0.8 or less. That is, the above ratio (D2/D1) satisfies a numerical formula (Numerical Formula 200) below.
In a case of
The organic EL device 1A according to the second exemplary embodiment may have any arrangement without being limited to the arrangement of the organic EL device 1A shown in
A preferable arrangement of the organic EL device 1A of the second exemplary embodiment will be explained.
In the organic EL device 1A according to the second exemplary embodiment, the above ratio (D2/D1) preferably satisfies a numerical formula (Numerical Formula 201) below, more preferably satisfies a numerical formula (Numerical Formula 202) below. Note that a lower limit of the above ratio (D2/D1) is preferably 0.2 or more.
In the organic EL device 1A of the second exemplary embodiment, the distance D1 from the cathode 4 to the second emitting layer 52 is preferably in a range from 25 nm to 45 nm, more preferably in a range from 25 nm to 35 nm.
In the organic EL device 1A of the second exemplary embodiment, the total D2 of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 is preferably in the same range as the total (d1+d2) of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 described in the first exemplary embodiment. That is, the total D2 of the film thicknesses of the first emitting layer 51 and the second emitting layer 52 is preferably 20 nm or less, more preferably 17 nm or less, and still more preferably 15 nm or less.
The film thickness of the first emitting layer 51 is preferably in the same range as the film thickness d1 of the first emitting layer 51 described in the first exemplary embodiment. That is, the film thickness of the first emitting layer 51 is preferably in a range from 3 nm to 10 nm, more preferably in a range from 5 nm to 8 nm.
The film thickness of the second emitting layer 52 is preferably in the same range as the film thickness d2 of the second emitting layer 52 described in the first exemplary embodiment. That is, the film thickness of the second emitting layer 52 is preferably in a range from 3 nm to 15 nm, more preferably in a range from 5 nm to 15 nm.
An organic electroluminescence device according to a third exemplary embodiment includes: an anode; a cathode; one or more first emitting layers provided between the anode and the cathode; one or more second emitting layers provided between the one or more first emitting layers and the cathode; and an intermediate layer provided between a pair of emitting layers selected from a plurality of emitting layers consisting of the one or more first emitting layers and the one or more second emitting layers, in which the first emitting layer contains a first host material, the second emitting layer contains a second host material, the first host material and the second host material are mutually different, the first emitting layer at least contains a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least contains a second emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the first emitting compound and the second emitting compound are mutually the same or different, the intermediate layer contains no metal atom, materials forming the intermediate layer are each contained in the intermediate layer at a content ratio of 10 mass % or more, and a triplet energy of the first host material T1(H1) and a triplet energy of the second host material T1(H2) satisfy a relationship of a numerical formula (Numerical Formula 1) below.
In the third exemplary embodiment, in order to inhibit an overlap between a Singlet emitting region and a TTF emitting region, the intermediate layer contains no emitting compound or may contain an emitting compound in an insubstantial amount provided that the overlap can be inhibited.
For instance, the intermediate layer contains 0 mass % of an emitting compound. Alternatively, for instance, the intermediate layer may contain an emitting compound provided that the emitting compound contained is a component accidentally mixed in a production process or a component contained as impurities in a material.
For instance, when the intermediate layer consists of a material A, a material B, and a material C, the content ratios of the materials A, B, and C in the intermediate layer are each 10 mass % or more, and the total of the content ratios of the materials A, B, and C is 100 mass %.
In the following, the intermediate layer is occasionally referred to as a “non-doped layer”. A layer containing an emitting compound is occasionally referred to as a “doped layer”.
The inventors have found out that the organic EL device has improved luminous efficiency by providing one or more first emitting layers and one or more second emitting layers that contain host materials satisfying the relationship of the numerical formula (Numerical Formula 1), and inserting the non-doped layer (intermediate layer) between a pair of emitting layers selected from the plurality of emitting layers. Presumably, the reason thereof is as below.
Explanation for Triplet-Triplet-Annihilation (occasionally referred to as TTA), known as the technology for enhancing the luminous efficiency of the organic EL device, is as described in the first exemplary embodiment.
The significance of making the triplet energy of the first host material T1(H1) in the first emitting layer and the triplet energy of the second host material T1(H2) in the second emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1) is as described in the first exemplary embodiment.
Explanation is made about the significance of making the organic EL device of the third exemplary embodiment include one or more first emitting layers, one or more second emitting layers, and a non-doped layer (intermediate layer) between a pair of emitting layers selected from the plurality of emitting layers.
It is considered that luminous efficiency is improvable in an arrangement including layered emitting layers because the Singlet emitting region and the TTF emitting region are typically likely to be separated from each other.
As described above, in order to improve the luminous efficiency, the organic EL device of the third exemplary embodiment is designed by layering the emitting layers and using the first host material and the second host material that satisfy the relationship of the numerical formula (Numerical Formula 1).
However, the Singlet emitting region and the TTF emitting region partially overlap with each other even in such an organic EL device (organic EL device including layered emitting layers and using host materials that satisfy the relationship of the numerical formula (Numerical Formula 1)). Thus, triplet excitons and carriers (electrons and holes) are more likely to collide with each other in the overlapped region, which may decrease TTF efficiency and consequently lead to insufficient luminous efficiency.
In the organic EL device of the third exemplary embodiment, the non-doped layer (intermediate layer) is inserted between a pair of emitting layers selected from a plurality of emitting layers to reduce an overlapped region of the Singlet emitting region and the TTF emitting region, thus inhibiting a decrease in TTF efficiency that may otherwise be caused by the collision between triplet excitons and carriers. That is, inserting the non-doped layer is considered to contribute to the improvement in TTF emission efficiency.
The organic EL device of the third exemplary embodiment thus has improved luminous efficiency by including one or more first emitting layers and one or more second emitting layers that contain host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and including the non-doped layer (intermediate layer) inserted between a pair of emitting layers selected from the plurality of emitting layers.
A preferable arrangement of the organic EL device of the third exemplary embodiment will be explained.
As an arrangement including one or more first emitting layers, one or more second emitting layers, and an intermediate layer provided between a pair of emitting layers selected from the plurality of emitting layers, any arrangement is applicable provided that the Singlet emitting region and the TTF emitting region are inhibited from overlapping with each other. Exemplary arrangements thereof are shown below. Each layer represents a single layer.
Exemplary arrangements below are preferable in view of further improving luminous efficiency.
Exemplary arrangements below are more preferable in view of further improving luminous efficiency.
The intermediate layer is described below. The first emitting layer and the second emitting layer will be described later.
The intermediate layer is a non-doped layer.
The intermediate layer contains no metal atom. The intermediate layer thus contains no metal complex.
The intermediate layer contains an intermediate layer material. The intermediate layer material is not an emitting compound.
The intermediate layer material may be any material except for the emitting compound.
Examples of the intermediate layer material include: 1) a heterocyclic compound such as an oxadiazole derivative, benzimidazole derivative, or phenanthroline derivative; 2) a fused aromatic compound such as a carbazole derivative, anthracene derivative, phenanthrene derivative, pyrene derivative or chrysene derivative; and 3) an aromatic amine compound such as a triarylamine derivative or a fused polycyclic aromatic amine derivative.
One or both of the first host material and the second host material may be used as the intermediate layer material. The intermediate layer material may be any material provided that the Singlet emitting region and the TTF emitting region are separated from each other and the Singlet emission and the TTF emission are not hindered.
In the organic EL device according to the third exemplary embodiment, materials forming the intermediate layer are each contained in the intermediate layer at a content ratio of 10 mass % or more.
The intermediate layer contains the intermediate layer material as a material forming the intermediate layer.
The intermediate layer preferably contains 60 mass % or more of the intermediate layer material, more preferably contains 70 mass % or more of the intermediate layer material, still more preferably contains 80 mass % or more of the intermediate layer material, still further more preferably 90 mass % or more of the intermediate layer material, and yet still further more preferably 95 mass % or more of the intermediate layer material, with respect to the total mass of the intermediate layer.
The intermediate layer may contain a single type of the intermediate layer material or may contain two or more types of the intermediate layer material.
When the intermediate layer contains two or more types of the intermediate layer material, the upper limit of the total of the content ratios of the two or more types of the intermediate layer material is 100 mass %.
It should be noted that the intermediate layer of the third exemplary embodiment may further contain any other material(s) than the intermediate layer material.
The intermediate layer may be provided in the form of a single layer or a laminate of two or more layers.
As long as the overlap between the Singlet emitting region and the TTF emitting region is inhibited, the film thickness of the intermediate layer is not particularly limited but each layer in the intermediate layer is preferably in a range from 3 nm to 15 nm, more preferably in a range from 5 nm to 10 nm.
The intermediate layer having a film thickness of 3 nm or more easily separates the Singlet emitting region from the emitting region derived from TTF.
The intermediate layer having a film thickness of 15 nm or less easily inhibits a phenomenon where the host material of the intermediate layer emits light.
In the organic EL device of the third exemplary embodiment, preferably, the first emitting layer is in the form of a single layer, the second emitting layer is in the form of a single layer, and the intermediate layer is provided between the first emitting layer and the second emitting layer.
In the following description, an organic EL device in which the first emitting layer is in the form of a single layer, the second emitting layer is in the form of a single layer, and an intermediate layer in the form of a single layer is provided between the first emitting layer and the second emitting layer is occasionally referred to as an “organic EL device according to Arrangement A”.
The organic EL device according to Arrangement A is exemplified by an organic EL device shown in
In the organic EL device according to Arrangement A, the film thickness of the intermediate layer is preferably smaller than the film thickness of the second emitting layer.
In the organic EL device according to Arrangement A, the hole transporting layer is preferably provided between the anode and the first emitting layer, and the electron transporting layer is preferably provided between the second emitting layer and the cathode.
In the organic EL device according to Arrangement A, the intermediate layer preferably contains at least one intermediate layer material as a material forming the intermediate layer, and the triplet energy of the first host material T1(H1), the triplet energy of the second host material T1(H2), and a triplet energy of the at least one intermediate layer material T1(Mmid) preferably satisfy a relationship of a numerical formula (Numerical Formula 21) below.
When the intermediate layer contains two or more intermediate layer materials as materials forming the intermediate layer, the triplet energy of the first host material T1(H1), the triplet energy of the second host material T1(H2), and a triplet energy of each of the intermediate layer materials T1(MEA) more preferably satisfy a relationship of a numerical formula (Numerical Formula 21A) below.
An organic EL device 1C is an exemplary organic EL device according to Arrangement A.
The organic EL device 1C includes the light-transmissive substrate 2, an anode 3A, the cathode 4, and organic layers 10A provided between the anode 3A and the cathode 4. The organic layers 10A include the hole injecting layer 6, the hole transporting layer 7, the first emitting layer 51, an intermediate layer 61 (non-doped layer), the second emitting layer 52, the electron transporting layer 8, and the electron injecting layer 9 that are layered on the anode 3A in this order. In
The organic EL device 1C according to the third exemplary embodiment may have any arrangement without being limited to the arrangement of the organic EL device shown in
An arrangement of an organic EL device of a fourth exemplary embodiment will be explained. In the description of the fourth exemplary embodiment, the same components as those in the third exemplary embodiment are denoted by the same reference signs and names to simplify or omit explanation of the components. In the fourth exemplary embodiment, the same materials and compounds as described in the third exemplary embodiment are usable, unless otherwise specified.
The organic EL device of the fourth exemplary embodiment includes two second emitting layers (anode-side second emitting layer and cathode-side second emitting layer), which is a difference from the “organic EL device according to Arrangement A” of the third exemplary embodiment. The rest of the arrangement of the organic EL device of the fourth exemplary embodiment is the same as that of the “organic EL device according to Arrangement A”.
In the organic EL device of the fourth exemplary embodiment, the second emitting layer is in the form of two emitting layers including an anode-side second emitting layer and a cathode-side second emitting layer, the anode-side second emitting layer is disposed closer to the anode than the cathode-side second emitting layer, the anode-side second emitting layer is provided between the first emitting layer and the intermediate layer, and the intermediate layer is provided between the anode-side second emitting layer and the cathode-side second emitting layer.
The organic EL device according to the fourth exemplary embodiment is exemplified by an organic EL device shown in
In the organic EL device of the fourth exemplary embodiment, the hole transporting layer is preferably provided between the anode and the first emitting layer, and the electron transporting layer is preferably provided between the cathode-side second emitting layer and the cathode.
Luminous efficiency is improvable in the organic EL device of the fourth exemplary embodiment.
In the organic EL device of the fourth exemplary embodiment, the intermediate layer preferably contains at least one intermediate layer material as a material forming the intermediate layer, the triplet energy of the first host material T1(H1), a triplet energy of the second host material contained in the cathode-side second emitting layer T1(H22), and the triplet energy of the at least one intermediate layer material T1(Mmid) preferably satisfy a relationship of a numerical formula (Numerical Formula 23A).
When the intermediate layer contains two or more intermediate layer materials as materials forming the intermediate layer, the triplet energy of the first host material T1(H1), the triplet energy of the second host material contained in the cathode-side second emitting layer T1(H22), and the triplet energy of each of the intermediate layer materials T1(MEA) more preferably satisfy a relationship of a numerical formula (Numerical Formula 23B) below.
In the organic EL device of the fourth exemplary embodiment, the first emitting layer and the anode-side second emitting layer as well as the first emitting layer and the cathode-side second emitting layer each independently satisfy the relationship of the numerical formula (Numerical Formula 1) described in the third exemplary embodiment. The anode-side second emitting layer and the cathode-side second emitting layer may be mutually the same or different in structure.
Preferably, the first emitting layer and the anode-side second emitting layer as well as the first emitting layer and the cathode-side second emitting layer each independently satisfy at least one relationship of Numerical Formulae 2, 2A, 2B, 3 to 6, 11, 11A, 11B, 12, 12A, 12B, 12C, 12D, or 13 described herein.
The organic EL device according to the fourth exemplary embodiment may further include the third emitting layer.
As the third emitting layer of the organic EL device according to the fourth exemplary embodiment, the third emitting layer described herein is usable.
Preferably, the first emitting layer and the third emitting layer satisfy a relationship of a numerical formula (Numerical Formula 1A) described herein.
Preferably, the anode-side second emitting layer and the third emitting layer as well as the cathode-side second emitting layer and the third emitting layer each independently satisfy a relationship of a numerical formula (Numerical Formula 1B) described herein.
An organic EL device 1D includes the light-transmissive substrate 2, the anode 3A, the cathode 4, and organic layers 10B provided between the anode 3A and the cathode 4. The organic layers 10B include the hole injecting layer 6, the hole transporting layer 7, the first emitting layer 51, an anode-side second emitting layer 521, the intermediate layer 61 (non-doped layer), a cathode-side second emitting layer 522, the electron transporting layer 8, and the electron injecting layer 9 that are layered on the anode 3A in this order. In
The organic EL device 1D according to the fourth exemplary embodiment may have any arrangement without being limited to the arrangement of the organic EL device 4 shown in
An arrangement of an organic EL device of a fifth exemplary embodiment will be explained. In the description of the fifth exemplary embodiment, the same components as those in the third and fourth exemplary embodiments are denoted by the same reference signs and names to simplify or omit explanation of the components. In the fifth exemplary embodiment, the same materials and compounds as described in the third and fourth exemplary embodiments are usable, unless otherwise specified.
The organic EL device of the fifth exemplary embodiment includes two first emitting layers (anode-side first emitting layer and cathode-side first emitting layer), which is a difference from the “organic EL device according to Arrangement A” of the third exemplary embodiment. The rest of the arrangement of the organic EL device of the fifth exemplary embodiment is the same as that of the “organic EL device according to Arrangement A”.
In the organic EL device of the fifth exemplary embodiment, the first emitting layer is in the form of two emitting layers including an anode-side first emitting layer and a cathode-side first emitting layer, the anode-side first emitting layer is disposed closer to the anode than the cathode-side first emitting layer, the intermediate layer is provided between the anode-side first emitting layer and the cathode-side first emitting layer, and the cathode-side first emitting layer is provided between the intermediate layer and the second emitting layer.
The organic EL device according to the fifth exemplary embodiment is exemplified by an organic EL device shown in
In the organic EL device of the fifth exemplary embodiment, the hole transporting layer is preferably provided between the anode and the anode-side first emitting layer, and the electron transporting layer is preferably provided between the second emitting layer and the cathode.
Luminous efficiency is improvable in the organic EL device of the fifth exemplary embodiment.
In the organic EL device of the fifth exemplary embodiment, the intermediate layer preferably contains at least one intermediate layer material as a material forming the intermediate layer, and a triplet energy of the first host material contained in the anode-side first emitting layer T1(H11), the triplet energy of the at least one intermediate layer material T1(Mmid), and the triplet energy of the second host material T1(H2) preferably satisfy a relationship of a numerical formula (Numerical Formula 22A) below.
When the intermediate layer contains two or more intermediate layer materials as materials forming the intermediate layer, the triplet energy of the first host material contained in the anode-side first emitting layer T1(H11), the triplet energy of each of the intermediate layer materials T1(MEA), and the triplet energy of the second host material T1(H2) more preferably satisfy a relationship of a numerical formula (Numerical Formula 22B) below.
In the organic EL device of the fifth exemplary embodiment, the anode-side first emitting layer and the second emitting layer as well as the cathode-side first emitting layer and the second emitting layer each independently satisfy the relationship of the numerical formula (Numerical Formula 1) described in the third exemplary embodiment. The anode-side first emitting layer and the cathode-side first emitting layer may be mutually the same or different in structure.
Preferably, the anode-side first emitting layer and the second emitting layer as well as the cathode-side first emitting layer and the second emitting layer each independently satisfy at least one relationship of Numerical Formulae 2, 2A, 2B, 3 to 6, 11, 11A, 11B, 12, 12A, 12B, 12C, 12D, or 13 described herein.
The organic EL device of the fifth exemplary embodiment may further include the third emitting layer.
As the third emitting layer of the organic EL device according to the fifth exemplary embodiment, the third emitting layer described herein is usable.
Preferably, the anode-side first emitting layer and the third emitting layer as well as the cathode-side first emitting layer and the third emitting layer each independently satisfy the relationship of the numerical formula (Numerical Formula 1A) described herein.
Preferably, the second emitting layer and the third emitting layer satisfy the relationship of the numerical formula (Numerical Formula 1B) described herein.
An organic EL device 1B includes the light-transmissive substrate 2, the anode 3A, the cathode 4, and organic layers 10C provided between the anode 3A and the cathode 4. The organic layers 10C include the hole injecting layer 6, the hole transporting layer 7, an anode-side first emitting layer 511, the intermediate layer 61 (non-doped layer), a cathode-side first emitting layer 512, the second emitting layer 52, the electron transporting layer 8, and the electron injecting layer 9 that are layered on the anode 3A in this order. In
The organic EL device 1B according to the fifth exemplary embodiment may have any arrangement without being limited to the arrangement of the organic EL device shown in
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of each layer in the first emitting layer is preferably 3 nm or more, more preferably 5 nm or more. A film thickness of 3 nm or more of the first emitting layer is sufficient for causing recombination of holes and electrons in the first emitting layer.
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of each layer in the first emitting layer is preferably 15 nm or less, more preferably 10 nm or less. A film thickness of 15 nm or less of the first emitting layer is thin enough for transfer of triplet excitons to the second emitting layer.
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of each layer in the first emitting layer is preferably in a range from 3 nm to 15 nm.
When the film thickness of the first emitting layer is smaller than the film thickness of the second emitting layer, triplet excitons generated in the first emitting layer are not likely to remain in the first emitting layer but diffused efficiently to the second emitting layer. Thus, the film thickness of the first emitting layer is preferably smaller than the film thickness of the second emitting layer. For the above reason, although not particularly limited, the film thickness of the first emitting layer is, for instance, more preferably in a range from 3 nm to 10 nm, still more preferably in a range from 5 nm to 8 nm.
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of each layer in the second emitting layer is preferably 5 nm or more, more preferably 15 nm or more. When the film thickness of the second emitting layer is 5 nm or more, triplet excitons having transferred from the first emitting layer to the second emitting layer are easily inhibited from returning to the first emitting layer. Further, when the film thickness of the second emitting layer is 5 nm or more, triplet excitons can be sufficiently separated from the recombination portion in the first emitting layer.
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of each layer in the second emitting layer is preferably 20 nm or less.
In the organic EL device according to each of the third to fifth exemplary embodiments, the film thickness of the second emitting layer is preferably in a range from 5 nm to 20 nm.
Subsequently, preferable arrangements common in the organic EL device 1 according to the first exemplary embodiment, the organic EL device 1A according to the second exemplary embodiment, the organic EL device 1C according to the third exemplary embodiment, the organic EL device 1D according to the fourth exemplary embodiment, and the organic EL device 1B according to the fifth exemplary embodiment will be explained. It should be noted that the reference numerals are occasionally omitted below.
Herein, the arrangements common in the organic EL devices according to the first to fifth exemplary embodiments are occasionally referred to as “the organic EL device according to the above exemplary embodiment”.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the first host material T1(H1) and the triplet energy of the second host material T1(H2) preferably satisfy a relationship of a numerical formula (Numerical Formula 5) below.
Herein, the “host material” refers to, for instance, a material that accounts for “50 mass % or more of the layer”. That is, for instance, the first emitting layer contains 50 mass % or more of the first host material with respect to the total mass of the first emitting layer. For instance, the second emitting layer contains 50 mass % or more of the second host material with respect to the total mass of the second emitting layer.
In the organic EL device according to the above exemplary embodiment, the “first emitting compound that emits light having a maximum peak wavelength of 500 nm or less” is preferably a compound having a singlet energy S1 smaller than a singlet energy S1 of the first host material.
In the organic EL device according to the above exemplary embodiment, the “second emitting compound that emits light having a maximum peak wavelength of 500 nm or less” is preferably a compound having a singlet energy S1 smaller than a singlet energy S1 of the second host material.
The organic EL device according to the above exemplary embodiment preferably emits, when being driven, light whose maximum peak wavelength is 500 nm or less.
The organic EL device according to the above exemplary embodiment more preferably emits, when being driven, light whose maximum peak wavelength is in a range from 430 nm to 480 nm.
The maximum peak wavelength of the light emitted from the organic EL device when being driven is measured as follows. Voltage is applied on the organic EL device such that a current density becomes 10 mA/cm2, where spectral radiance spectrum is measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). A peak wavelength of an emission spectrum, at which the luminous intensity of the resultant spectral radiance spectrum is at the maximum, is measured and defined as a maximum peak wavelength (unit: nm).
In the organic EL device according to the above exemplary embodiment, the first emitting layer contains the first host material. The first host material is a compound different from the second host material contained in the second emitting layer.
The first emitting layer at least contains the first emitting compound that emits light having a maximum peak wavelength of 500 nm or less. The first emitting compound contained in the first emitting layer is preferably a compound that emits fluorescence having a maximum peak wavelength of 500 nm or less.
In the organic EL device according to the above exemplary embodiment, the first emitting compound and the second emitting compound may be mutually different compounds or the same compound.
In the organic EL device according to the above exemplary embodiment, the first emitting compound is preferably a compound containing no azine ring structure in a molecule.
In the organic EL device according to the above exemplary embodiment, the first emitting compound is preferably not a boron-containing complex, more preferably not a complex.
In the organic EL device according to the above exemplary embodiment, the first emitting layer preferably does not contain a metal complex. In the organic EL device according to the above exemplary embodiment, the first emitting layer also preferably does not contain a boron-containing complex.
In the organic EL device according to the above exemplary embodiment, the first emitting layer preferably does not contain a phosphorescent material.
Further, the first emitting layer preferably does not contain a heavy-metal complex and a phosphorescent rare earth metal complex. Examples of the heavy-metal complex herein include iridium complex, osmium complex, and platinum complex.
A method of measuring the maximum peak wavelength of the compound is as follows. A toluene solution of a measurement target compound at a concentration of 5 μmol/L is prepared and put in a quartz cell. An emission spectrum (ordinate axis: luminous intensity, abscissa axis: wavelength) of the thus-obtained sample is measured at a normal temperature (300K). The emission spectrum can be measured using a spectrophotometer (machine name: F-7000) produced by Hitachi High-Tech Science Corporation. It should be noted that the machine for measuring the emission spectrum is not limited to the machine used herein.
A peak wavelength of the emission spectrum exhibiting a maximum luminous intensity is defined as the maximum peak wavelength.
In an emission spectrum of the compound, where a peak exhibiting the maximum luminous intensity is defined as a maximum peak and a height of the maximum peak is defined as 1, heights of other peaks appearing in the emission spectrum are preferably less than 0.6. It should be noted that the peaks in the emission spectrum are defined as local maximum values.
Moreover, in the emission spectrum of the compound, the number of peaks is preferably less than three.
In the organic EL device according to the above exemplary embodiment, the first emitting layer preferably emits light whose maximum peak wavelength is 500 nm or less when the device is driven.
The maximum peak wavelength of the light emitted from the emitting layer when the device is driven is measured as follows.
Maximum Peak Wavelength λp of Light Emitted from Emitting Layer when Organic EL Device Is Driven
For a maximum peak wavelength λp1 of light emitted from the first emitting layer when the organic EL device is driven, the organic EL device is produced by using the material of the first emitting layer for the first emitting layer and the second emitting layer, and voltage is applied to the organic EL device so that a current density becomes 10 mA/cm2, where spectral radiance spectrum is measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). The maximum peak wavelength λp1 (unit: nm) is calculated from the obtained spectral radiance spectrum.
For a maximum peak wavelength λp2 of light emitted from the second emitting layer when the organic EL device is driven, the organic EL device is produced by using the material of the second emitting layer for the first emitting layer and the second emitting layer, and voltage is applied to the organic EL device so that a current density becomes 10 mA/cm2, where spectral radiance spectrum is measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). The maximum peak wavelength λp2 (unit: nm) is calculated from the obtained spectral radiance spectrum.
In the organic EL device according to the above exemplary embodiment, a singlet energy of the first host material S1(H1) and a singlet energy of the first emitting compound S1(D1) preferably satisfy a relationship of a numerical formula (Numerical Formula 2) below.
The singlet energy S1 means an energy difference between the lowest singlet state and the ground state.
When the first host material and the first emitting compound satisfy the relationship of the numerical formula (Numerical Formula 2), singlet excitons generated on the first host material easily energy-transfer from the first host material to the first emitting compound, thereby contributing to emission (preferably fluorescence) of the first emitting compound.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the first host material T1(H1) and a triplet energy of the first emitting compound T1(D1) preferably satisfy a relationship of a numerical formula (Numerical Formula 2A) below.
When the first host material and the first emitting compound satisfy the relationship of the numerical formula (Numerical Formula 2A), triplet excitons generated in the first emitting layer transfer not onto the first emitting compound having higher triplet energy but onto the first host material, thereby easily transferring to the second emitting layer.
The organic EL device according to the above exemplary embodiment preferably satisfies a relationship of a numerical formula (Numerical Formula 2B) below.
Herein, a method of measuring a triplet energy T1 is exemplified by a method below.
A measurement target compound is dissolved in EPA (diethylether isopentane:ethanol=5:5:2 in volume ratio) so as to fall within a range from 10−5 mol/L to 104 mol/L, and the obtained solution is encapsulated in a quartz cell to provide a measurement sample. A phosphorescence spectrum (ordinate axis: phosphorescent luminous intensity, abscissa axis: wavelength) of the measurement sample is measured at a low temperature (77K). A tangent is drawn to the rise of the phosphorescence spectrum close to the short-wavelength region. An energy amount is calculated by a conversion equation (F1) below on a basis of a wavelength value λedge [nm] at an intersection of the tangent and the abscissa axis. The calculated energy amount is defined as triplet energy T1.
The tangent to the rise of the phosphorescence spectrum close to the short-wavelength region is drawn as follows. While moving on a curve of the phosphorescence spectrum from the short-wavelength region to the local maximum value closest to the short-wavelength region among the local maximum values of the phosphorescence spectrum, a tangent is checked at each point on the curve toward the long-wavelength of the phosphorescence spectrum. An inclination of the tangent is increased along the rise of the curve (i.e., a value of the ordinate axis is increased). A tangent drawn at a point of the local maximum inclination (i.e., a tangent at an inflection point) is defined as the tangent to the rise of the phosphorescence spectrum close to the short-wavelength region.
A local maximum point where a peak intensity is 15% or less of the maximum peak intensity of the spectrum is not counted as the above-mentioned local maximum peak intensity closest to the short-wavelength region. The tangent drawn at a point that is closest to the local maximum peak intensity closest to the short-wavelength region and where the inclination of the curve is the local maximum is defined as a tangent to the rise of the phosphorescence spectrum close to the short-wavelength region.
For phosphorescence measurement, a spectrophotofluorometer body F-4500 (produced by Hitachi High-Technologies Corporation) is usable. Any device for phosphorescence measurement is usable. A combination of a cooling unit, a low temperature container, an excitation light source and a light-receiving unit may be used for phosphorescence measurement.
Herein, a method of measuring the singlet energy S1 with use of a solution (occasionally referred to as a solution method) is exemplified by a method below. A toluene solution of a measurement target compound at a concentration ranging from 10−5 mol/L to 104 mol/L is prepared and put in a quartz cell. An absorption spectrum (ordinate axis: absorption intensity, abscissa axis: wavelength) of the thus-obtained sample is measured at a normal temperature (300K). A tangent is drawn to the fall of the absorption spectrum close to the long-wavelength region, and a wavelength value λedge [nm] at an intersection of the tangent and the abscissa axis is assigned to a conversion equation (F2) below to calculate singlet energy.
Any device for measuring absorption spectrum is usable. For instance, a spectrophotometer (U3310 produced by Hitachi, Ltd.) is usable.
The tangent to the fall of the absorption spectrum close to the long-wavelength region is drawn as follows. While moving on a curve of the absorption spectrum from the local maximum value closest to the long-wavelength region, among the local maximum values of the absorption spectrum, in a long-wavelength direction, a tangent at each point on the curve is checked. An inclination of the tangent is decreased and increased in a repeated manner as the curve falls (i.e., a value of the ordinate axis is decreased). A tangent drawn at a point where the inclination of the curve is the local minimum closest to the long-wavelength region (except when absorbance is 0.1 or less) is defined as the tangent to the fall of the absorption spectrum close to the long-wavelength region.
The local maximum absorbance of 0.2 or less is not counted as the above-mentioned local maximum absorbance closest to the long-wavelength region.
In the organic EL device according to the above exemplary embodiment, when the first emitting layer and the second emitting layer are layered in this order from a side on which the anode is provided, an electron mobility of the first host material μE1, a hole mobility of the first host material pH1, an electron mobility of the second host material λE2, and a hole mobility of the second host material pH2 preferably satisfy a formula (Numerical Formula 15) below.
In the organic EL device according to the above exemplary embodiment, when the first emitting layer and the second emitting layer are layered in this order from a side on which the anode is provided, the electron mobility of the first host material μE1 and the electron mobility of the second host material μE2 preferably satisfy a formula (Numerical Formula 16) below.
When the first host material and the second host material satisfy a relationship of the numerical formula (Numerical Formula 16), a recombination ability between holes and electrons in the first emitting layer is improved.
Herein, the electron mobility can be measured according to impedance spectroscopy, as follows.
A measurement target layer having a thickness in a range from 100 nm to 200 nm is held between the anode and the cathode, to which a small alternating voltage of 100 mV or less is applied while a bias DC voltage is applied. A value of an alternating current (absolute value and phase) which flows at this time is measured. This measurement is performed while changing a frequency of the alternating voltage, and complex impedance (Z) is calculated from the current value and the voltage value. A frequency dependency of the imaginary part (ImM) of the modulus M=iωZ (i: imaginary unit, ω: angular frequency) is obtained. The reciprocal number of a frequency ω at which the ImM becomes the maximum is defined as a response time of electrons carried in the measurement target layer. The electron mobility is calculated by the following equation.
In the organic EL device according to the above exemplary embodiment, the first emitting compound may be contained in the first emitting layer. Specifically, the first emitting layer may contain the first emitting compound at 0.5 mass % or more, exceeding 1.1 mass %, 1.2 mass % or more, or 1.5 mass % or more with respect to the total mass of the first emitting layer.
The first emitting layer contains the first emitting compound preferably at 10 mass % or less, more preferably at 7 mass % or less, and still more preferably at 5 mass % less with respect to the total mass of the first emitting layer.
In the organic EL device according to the above exemplary embodiment, the first emitting layer contains a first compound as the first host material preferably at 60 mass % or more, more preferably at 70 mass % or more, still more preferably at 80 mass % or more, still further more preferably at 90 mass % or more, and yet still further more preferably at 95 mass % or more, with respect to the total mass of the first emitting layer.
The first emitting layer preferably contains the first host material at 99 mass % or less with respect to the total mass of the first emitting layer.
When the first emitting layer contains the first host material and the first emitting compound, the upper limit of a total of the content ratios of the first host material and the first emitting compound is 100 mass %.
In the organic EL device according to the above exemplary embodiment, the first emitting layer may further contain any other material than the first host material and the first emitting compound.
The first emitting layer may contain a single type of the first host material or may contain two or more types of the first host material. The first emitting layer may contain a single type of the first emitting compound or may contain two or more types of the first emitting compound.
In the organic EL device according to the above exemplary embodiment, the second emitting layer contains the second host material. The second host material is a compound different from the first host material contained in the first emitting layer.
The second emitting layer at least contains the second emitting compound that emits light having a maximum peak wavelength of 500 nm or less. The first emitting compound and the second emitting compound may be mutually the same or different. The second emitting compound contained in the second emitting layer is preferably a compound that emits fluorescence having a maximum peak wavelength of 500 nm or less.
A method of measuring the maximum peak wavelength of the compound is as follows.
In the organic EL device according to the above exemplary embodiment, the second emitting layer preferably emits light whose maximum peak wavelength is 500 nm or less when the device is driven.
In the organic EL device according to the above exemplary embodiment, a Stokes shift of the second emitting compound preferably exceeds 7 nm.
When the Stokes shift of the second emitting compound exceeds 7 nm, a decrease in the luminous efficiency due to self-absorption is easily inhibited.
The self-absorption is a phenomenon in which emitted light is absorbed by the same compound to reduce luminous efficiency. The self-absorption is notably observed in a compound having a small Stokes shift (i.e., a large overlap between an absorption spectrum and a fluorescence spectrum). Accordingly, in order to reduce the self-absorption, it is preferable to use a compound having a large Stokes shift (i.e., a small overlap between the absorption spectrum and the fluorescence spectrum). The Stokes shift can be measured by a method described in Examples.
In the organic EL device according to the above exemplary embodiment, a triplet energy of the second emitting compound T1(D2) and the triplet energy of the second host material T1(H2) preferably satisfy a relationship of a numerical formula (Numerical Formula 3) below.
In the organic EL device according to the above exemplary embodiment, when the second emitting compound and the second host material satisfy the relationship of the numerical formula (Numerical Formula 3), in transfer of triplet excitons generated in the first emitting layer to the second emitting layer, the triplet excitons energy-transfer not onto the second emitting compound having higher triplet energy but onto molecules of the second host material. In addition, triplet excitons generated by recombination of holes and electrons on the second host material do not transfer to the second emitting compound having higher triplet energy. Triplet excitons generated by recombination on molecules of the second emitting compound quickly energy-transfer to molecules of the second host material. Triplet excitons in the second host material do not transfer to the second emitting compound but efficiently collide with one another on the second host material to generate singlet excitons by the TTF phenomenon.
In the organic EL device according to the above exemplary embodiment, a singlet energy of the second host material S1(H2) and a singlet energy of the second emitting compound S1(D2) preferably satisfy a relationship of a numerical formula (Numerical Formula 4) below.
In the organic EL device according to the above exemplary embodiment, when the second emitting compound and the second host material satisfy the relationship of the numerical formula (Numerical formula 4), due to the singlet energy of the second emitting compound being smaller than the singlet energy of the second host material, singlet excitons generated by the TTF phenomenon energy-transfer from the second host material to the second emitting compound, thereby contributing to emission (preferably fluorescence) of the second emitting compound.
In the organic EL device according to the above exemplary embodiment, the second emitting compound is preferably a compound containing no azine ring structure in a molecule.
In the organic EL device according to the above exemplary embodiment, the second emitting compound is preferably not a boron-containing complex, more preferably not a complex.
In the organic EL device according to the above exemplary embodiment, the second emitting layer preferably does not contain a metal complex. In the organic EL device according to the above exemplary embodiment, the second emitting layer also preferably does not contain a boron-containing complex.
In the organic EL device according to the above exemplary embodiment, the second emitting layer preferably does not contain a phosphorescent material.
Further, the second emitting layer preferably does not contain a heavy-metal complex and a phosphorescent rare earth metal complex. Examples of the heavy-metal complex herein include iridium complex, osmium complex, and platinum complex.
In the organic EL device according to the above exemplary embodiment, the second emitting compound may be contained in the second emitting layer. Specifically, the second emitting layer may contain the second emitting compound at 0.5 mass % or more, exceeding 1.1 mass %, 1.2 mass % or more, or 1.5 mass % or more with respect to the total mass of the second emitting layer.
The second emitting layer contains the second emitting compound preferably at 10 mass % or less, more preferably at 7 mass % or less, and still more preferably at 5 mass % less with respect to the total mass of the second emitting layer.
The second emitting layer contains a second compound as the second host material preferably at 60 mass % or more, more preferably at 70 mass % or more, still more preferably at 80 mass % or more, still further more preferably at 90 mass % or more, and yet still further more preferably at 95 mass % or more, with respect to the total mass of the second emitting layer.
The second emitting layer preferably contains the second host material at 99 mass % or less with respect to the total mass of the second emitting layer.
When the second emitting layer contains the second host material and the second emitting compound, the upper limit of a total of the content ratios of the second host material and the second emitting compound is 100 mass %.
In the organic EL device according to the above exemplary embodiment, the second emitting layer may further contain any other material than the second host material and the second emitting compound.
The second emitting layer may contain a single type of the second host material or may contain two or more types of the second host material. The second emitting layer may contain a single type of the second emitting compound or may contain two or more types of the second emitting compound.
In the organic EL device according to the above exemplary embodiment, a triplet energy of the first emitting compound or the second emitting compound T1(DX) and the triplet energy of the first host material T1(H1) preferably satisfy a relationship of a numerical formula (Numerical Formula 11) below.
When the first emitting layer contains the first emitting compound, the triplet energy of the first emitting compound T1(D1) preferably satisfies a relationship of a numerical formula (Numerical Formula 11A) below.
When the second emitting layer contains the second emitting compound, the triplet energy of the second emitting compound T1(D2) preferably satisfies a relationship of a numerical formula (Numerical Formula 11B) below.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the first host material T1(H1) preferably satisfies a relationship of a numerical formula (Numerical Formula 12) below.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the first host material T1(H1) also preferably satisfies a relationship of a numerical formula (Numerical Formula 12A) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 12B) below.
In the organic EL device according to the above exemplary embodiment, when the triplet energy of the first host material T1(H1) satisfies the relationship of the numerical formula (Numerical Formula 12A) or the numerical formula (Numerical Formula 12B), triplet excitons generated in the first emitting layer easily transfer to the second emitting layer, and also are easily inhibited from back-transferring from the second emitting layer to the first emitting layer. Consequently, singlet excitons are efficiently generated in the second emitting layer, thereby improving luminous efficiency.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the first host material T1(H1) also preferably satisfies a relationship of a numerical formula (Numerical Formula 12C) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 12D) below.
In the organic EL device according to the above exemplary embodiment, when the triplet energy of the first host material T1(H1) satisfies the relationship of the numerical formula (Numerical Formula 12C) or the numerical formula (Numerical Formula 12D), energy of triplet excitons generated in the first emitting layer is not likely to be large beyond necessity, stabilizing the excited state. The organic EL device is thus expected to have a long lifetime.
In the organic EL device according to the above exemplary embodiment, the triplet energy of the second host material T1(H2) preferably satisfies a relationship of a numerical formula (Numerical Formula 13) below.
The layers of the organic EL device according to each of the first and second exemplary embodiments may consist of the first emitting layer and the second emitting layer. In addition to the first emitting layer and the second emitting layer, the organic EL device according to each of the first and second exemplary embodiments preferably includes one or more organic layers. Examples of the organic layer include at least one layer selected from the group consisting of a hole injecting layer, a hole transporting layer, an emitting layer, an electron injecting layer, an electron transporting layer, a hole blocking layer, and an electron blocking layer.
The organic EL device according to each of the first and second exemplary embodiments may further include, for instance, at least one layer selected from the group consisting of a hole injecting layer, a hole transporting layer, an electron injecting layer, an electron transporting layer, a hole blocking layer, and an electron blocking layer.
In the organic EL device according to each of the first and second exemplary embodiments, the anode, the first emitting layer, the second emitting layer, and the cathode may be provided in this order. Alternatively, the anode, the second emitting layer, the first emitting layer, and the cathode may be provided in this order. All of the above arrangements are expected to exhibit the effect obtained by layering the emitting layers when a combination of materials satisfying the relationship of the numerical formula (Numerical Formula 1) is selected.
In addition to the first emitting layer, the second emitting layer, and the intermediate layer, the organic EL device according to each of the third to fifth exemplary embodiments may include one or more organic layers. Examples of the organic layer include at least one layer selected from the group consisting of a hole injecting layer, a hole transporting layer, an emitting layer, an electron injecting layer, an electron transporting layer, a hole blocking layer, and an electron blocking layer.
In the organic EL device according to each of the third to fifth exemplary embodiments, the anode, the first emitting layer, the second emitting layer, and the cathode may be provided in this order. Alternatively, the anode, the second emitting layer, the first emitting layer, and the cathode may be provided in this order. All of the above arrangements are expected to exhibit the effect obtained by layering the emitting layers when a combination of materials satisfying the relationship of the numerical formula (Numerical Formula 1) is selected.
The layers of the organic EL device according to each of the third to fifth exemplary embodiments may consist of the first emitting layer, the second emitting layer, and the intermediate layer. Alternatively, the organic EL device according to each of the third to fifth exemplary embodiments may further include, for instance, at least one layer selected from the group consisting of a hole injecting layer, a hole transporting layer, an electron injecting layer, an electron transporting layer, a hole blocking layer, and an electron blocking layer.
The organic EL device according to each of the first and second exemplary embodiments preferably includes the hole transporting layer between the first emitting layer and the anode.
The organic EL device according to each of the third to fifth exemplary embodiments preferably includes the hole transporting layer between the anode and one of the first emitting layers that is disposed closest to the anode.
In the organic EL device according to each of the first and second exemplary embodiments, the electron transporting layer is preferably provided between the second emitting layer and the cathode.
The organic EL device according to each of the third to fifth exemplary embodiments preferably includes the electron transporting layer between the cathode and one of the second emitting layers that is disposed closest to the cathode.
The organic EL device according to the above exemplary embodiment may further include a third emitting layer.
Preferably, the third emitting layer contains a third host material, the first host material, the second host material, and the third host material are different from each other, the third emitting layer at least contains a third emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the first emitting compound, the second emitting compound, and the third emitting compound are mutually the same or different, and the triplet energy of the first host material T1(H1) and a triplet energy of the third host material T1(H3) satisfy a relationship of a numerical formula (1A) below.
When the organic EL device according to the above exemplary embodiment includes the third emitting layer, the triplet energy of the second host material T1(H2) and the triplet energy of the third host material T1(H3) preferably satisfy a relationship of a numerical formula (Numerical Formula 1B) below.
The third emitting compound contained in the third emitting layer is preferably a compound that emits fluorescence having a maximum peak wavelength of 500 nm or less.
In the organic EL device according to each of the first and second exemplary embodiments, the first emitting layer and the second emitting layer are preferably in direct contact with each other.
In the organic EL device according to each of the first and second exemplary embodiments, a layer arrangement in which “the first emitting layer and the second emitting layer are in direct contact with each other” may include one of embodiments (LS1), (LS2), and (LS3) below.
(LS1) An embodiment in which a region containing both the first host material and the second host material is generated in a process of vapor-depositing the compound of the first emitting layer and vapor-depositing the compound of the second emitting layer, and is present on the interface between the first emitting layer and the second emitting layer.
(LS2) An embodiment in which in a case of containing an emitting compound in the first emitting layer and the second emitting layer, a region containing the first host material, the second host material and the emitting compound is generated in a process of vapor-depositing the compound of the first emitting layer and vapor-depositing the compound of the second emitting layer, and is present on the interface between the first emitting layer and the second emitting layer.
(LS3) An embodiment in which in a case of containing an emitting compound in the first emitting layer and the second emitting layer, a region containing the emitting compound, a region containing the first host material or a region containing the second host material is generated in a process of vapor-depositing the compound of the first emitting layer and vapor-depositing the compound of the second emitting layer, and is present on the interface between the first emitting layer and the second emitting layer.
When the organic EL device according to the first exemplary embodiment or the second exemplary embodiment includes the third emitting layer, preferably, the first emitting layer and the second emitting layer are in direct contact with each other and the second emitting layer and the third emitting layer are in direct contact with each other.
In the organic EL device according to the first exemplary embodiment or the second exemplary embodiment, a layer arrangement in which “the second emitting layer and the third emitting layer are in direct contact with each other” may include one of embodiments (LS4), (LS5) and (LS6) below.
(LS4) An embodiment in which a region containing both the second host material and the third host material is generated in a process of vapor-depositing the compound of the second emitting layer and vapor-depositing the compound of the third emitting layer, and is present on the interface between the second emitting layer and the third emitting layer.
(LS5) An embodiment in which in a case of containing an emitting compound in the second emitting layer and the third emitting layer, a region containing the second host material, the third host material and the emitting compound is generated in a process of vapor-depositing the compound of the second emitting layer and vapor-depositing the compound of the third emitting layer, and is present on the interface between the second emitting layer and the third emitting layer.
(LS6) An embodiment in which in a case of containing an emitting compound in the second emitting layer and the third emitting layer, a region containing the emitting compound, a region containing the second host material or a region containing the third host material is generated in a process of vapor-depositing the compound of the second emitting layer and vapor-depositing the compound of the third emitting layer, and is present on the interface between the second emitting layer and the third emitting layer.
Also preferably, the organic EL device according to the first exemplary embodiment or the second exemplary embodiment further includes a diffusion layer.
The diffusion layer is provided for smoothly transferring triplet excitons from the first emitting layer to the second emitting layer. The diffusion layer contains a diffusion layer material. The diffusion layer material may be any material that satisfies a relationship of a numerical formula (Numerical Formula 23) below.
That is, when the organic EL device according to the above exemplary embodiment further includes a diffusion layer, the triplet energy of the first host material T1(H1), a triplet energy of at least one diffusion layer material T1 (diffusion layer material), and the triplet energy of the second host material T1(H2) preferably satisfy the relationship of the numerical formula (Numerical Formula 23).
The excitation lifetime of triplet excitons is expected to be long by providing the diffusion layer for the organic EL device according to the first exemplary embodiment and the second exemplary embodiment.
The diffusion rate of triplet excitons is expected to improve by providing the diffusion layer for the organic EL device according to the above exemplary embodiment.
The diffusion layer is capable of containing a diffusion layer material at 60 mass % or more, 70 mass % or more, or 80 mass % or more, with respect to the total mass of the diffusion layer.
The diffusion layer may contain a single type of the diffusion layer material or may contain two or more types of the diffusion layer material.
The diffusion layer included in the organic EL device according to the first exemplary embodiment or the second exemplary embodiment is preferably provided between the first emitting layer and the second emitting layer.
The arrangement of the organic EL device according to the above exemplary embodiment will be further described below. It should be noted that the reference numerals are occasionally omitted below.
The substrate is used as a support for the organic EL device. For instance, glass, quartz, plastics and the like are usable for the substrate. A flexible substrate is also usable. The flexible substrate is a bendable substrate, which is exemplified by a plastic substrate. Examples of the material for the plastic substrate include polycarbonate, polyarylate, polyethersulfone, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, polyimide, and polyethylene naphthalate. Moreover, an inorganic vapor deposition film is also usable.
Metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a large work function (specifically, 4.0 eV or more) is preferably used as the anode formed on the substrate. Specific examples of the material include indium tin oxide (ITO), indium oxide-tin oxide containing silicon or silicon oxide, indium oxide-zinc oxide, indium oxide containing tungsten oxide and zinc oxide, and graphene. In addition, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chrome (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), titanium (Ti), and nitrides of a metal material (e.g., titanium nitride) are usable.
The material is typically formed into a film by a sputtering method. For instance, the indium oxide-zinc oxide can be formed into a film by the sputtering method using a target in which zinc oxide in a range from 1 mass % to 10 mass % is added to indium oxide. Moreover, for instance, the indium oxide containing tungsten oxide and zinc oxide can be formed by the sputtering method using a target in which tungsten oxide in a range from 0.5 mass % to 5 mass % and zinc oxide in a range from 0.1 mass % to 1 mass % are added to indium oxide. In addition, the anode may be formed by a vacuum deposition method, a coating method, an inkjet method, a spin coating method or the like.
Among the organic layers formed on the anode, since the hole injecting layer adjacent to the anode is formed of a composite material into which holes are easily injectable irrespective of the work function of the anode, a material usable as an electrode material (e.g., metal, an alloy, an electroconductive compound, a mixture thereof, and the elements belonging to the group 1 or 2 of the periodic table) is also usable for the anode.
A material having a small work function such as elements belonging to Groups 1 and 2 in the periodic table of the elements, specifically, an alkali metal such as lithium (Li) and cesium (Cs), an alkaline earth metal such as magnesium (Mg), calcium (Ca) and strontium (Sr), alloys (e.g., MgAg and AlLi) including the alkali metal or the alkaline earth metal, a rare earth metal such as europium (Eu) and ytterbium (Yb), alloys including the rare earth metal are also usable for the anode. It should be noted that the vacuum deposition method and the sputtering method are usable for forming the anode using the alkali metal, alkaline earth metal and the alloy thereof. Further, when a silver paste is used for the anode, the coating method and the inkjet method are usable.
When the organic EL device according to the above exemplary embodiment is of a top emission type, the anode has a reflection layer. The reflection layer is preferably formed from a metallic material having light reflectivity. The light reflectivity means a property of reflecting 50% or more (preferably 80% or more) of light emitted from the emitting layer.
Examples of the metallic material include single materials such as Al, Ag, Ta, Zn, Mo, W, Ni and Cr, or alloy materials containing these metals as main components (preferably 50 mass % or more of the whole), amorphous alloys (e.g., NiP, NiB, CrP, and CrB), and microcrystalline alloys (e.g., NiAl and silver alloys).
Also, as the metallic material, APC (silver, palladium and copper alloy), ARA (silver, rubidium and gold alloy), MoCr (molybdenum and chromium alloy), NiCr (nickel and chromium alloy) and the like are usable.
The reflection layer may be provided by a single layer or a plurality of layers.
The anode may be formed only of the reflection layer, but may be a multilayer structure having the reflection layer and a conductive layer (preferably a transparent conductive layer). When the anode includes the reflection layer and the conductive layer, the conductive layer is preferably provided between the reflection layer and a hole transporting zone. Alternatively, the anode may have a multilayer structure in which the reflection layer is provided between two conductive layers (first conductive layer and second conductive layer). In such a multilayer structure, the first and second conductive layers may be formed from the same material or mutually different materials.
Metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a large work function (specifically, 4.0 eV or more) is preferably used as the conductive layer.
The above material having a small work function such as elements belonging to Groups 1 and 2 in the periodic table of the elements, specifically, an alkali metal such as lithium (Li) and cesium (Cs), an alkaline earth metal such as magnesium (Mg), calcium (Ca) and strontium (Sr), alloys (e.g., MgAg and AlLi) including the alkali metal or the alkaline earth metal, a rare earth metal such as europium (Eu) and ytterbium (Yb), alloys including the rare earth metal are also usable for the conductive layer.
It is preferable to use metal, an alloy, an electroconductive compound, a mixture thereof, or the like having a small work function (specifically, 3.8 eV or less) for the cathode. Examples of the material for the cathode include elements belonging to Groups 1 and 2 in the periodic table of the elements, specifically, an alkali metal such as lithium (Li) and cesium (Cs), an alkaline earth metal such as magnesium (Mg), calcium (Ca) and strontium (Sr), alloys (e.g., MgAg and AlLi) including the alkali metal or the alkaline earth metal, a rare earth metal such as europium (Eu) and ytterbium (Yb), and alloys including the rare earth metal.
It should be noted that the vacuum deposition method and the sputtering method are usable for forming the cathode using the alkali metal, alkaline earth metal and the alloy thereof. Further, when a silver paste is used for the cathode, the coating method and the inkjet method are usable.
By providing the electron injecting layer, various conductive materials such as Al, Mg, Ag, ITO, graphene, and indium oxide-tin oxide containing silicon or silicon oxide may be used for forming the cathode regardless of the work function. The conductive materials can be formed into a film using the sputtering method, inkjet method, spin coating method and the like.
When the organic EL device according to the above exemplary embodiment is of a top emission type, the cathode is preferably formed of a light-transmissive or semi-transmissive metallic material that transmits light from the emitting layer. The light-transmissive or semi-transmissive property means a property of allowing transmissivity of 50% or more (preferably 80% or more) of the light emitted from the emitting layer.
Preferably, metal, an alloy, an electrically conductive compound, a mixture thereof, or the like having a small work function (specifically, 3.8 eV or less) as described above is used for the cathode.
The hole injecting layer is a layer containing a substance exhibiting a high hole injectability. Examples of the substance exhibiting a high hole injectability include molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chrome oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten oxide, and manganese oxide.
In addition, the examples of the highly hole-injectable substance include: an aromatic amine compound, which is a low-molecule organic compound, such that 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation: DPAB), 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), and 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1); and dipyrazino[2,3-f:20,30-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN).
In addition, a high polymer compound (e.g., oligomer, dendrimer and polymer) is usable as the substance exhibiting a high hole injectability. Examples of the high-molecule compound include poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), and poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation: Poly-TPD). Moreover, an acid-added high polymer compound such as poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) and polyaniline/poly(styrene sulfonic acid) (PAni/PSS) is also usable.
The hole transporting layer is a layer containing a highly hole-transporting substance. An aromatic amine compound, carbazole derivative, anthracene derivative and the like are usable for the hole transporting layer. Specific examples of a material for the hole transporting layer include 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (abbreviation: TPD), 4-phenyl-4′-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BAFLP), 4,4′-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: DFLDPBi), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), and 4,4′-bis[N-(spiro-9,9′-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). The above-described substances mostly have a hole mobility of 10−6 cm2/(V·s) or more.
For the hole transporting layer, a carbazole derivative such as CBP, 9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (CzPA), and 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (PCzPA) and an anthracene derivative such as t-BuDNA, DNA, and DPAnth may be used. A high polymer compound such as poly(N-vinylcarbazole) (abbreviation: PVK) and poly(4-vinyltiphenylamine) (abbreviation: PVTPA) is also usable.
However, in addition to the above substances, any substance exhibiting a higher hole transportability than an electron transportability may be used. It should be noted that the layer containing the substance exhibiting a high hole transportability may be not only a single layer but also a laminate of two or more layers formed of the above substance(s).
The electron transporting layer is a layer containing a highly electron-transporting substance. For the electron transporting layer, 1) a metal complex such as an aluminum complex, beryllium complex, and zinc complex, 2) a hetero aromatic compound such as imidazole derivative, benzimidazole derivative, azine derivative, carbazole derivative, and phenanthroline derivative, and 3) a high polymer compound are usable. Specifically, as a low-molecule organic compound, a metal complex such as Alq, tris(4-methyl-8-quinolinato)aluminum (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq2), BAlq, Znq, ZnPBO and ZnBTZ is usable. In addition to the metal complex, a heteroaromatic compound such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(ptert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP), and 4,4′-bis(5-methylbenzoxazole-2-yl)stilbene (abbreviation: BzOs) is usable. In the exemplary embodiment, a benzimidazole compound is preferably usable. The above-described substances mostly have an electron mobility of 10−6 cm2/(V·s) or more. It should be noted that any substance other than the above substance may be used for the electron transporting layer as long as the substance exhibits a higher electron transportability than the hole transportability. The electron transporting layer may be provided in the form of a single layer or a laminate of two or more layers of the above substance(s).
Further, a high polymer compound is usable for the electron transporting layer. For instance, poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)] (abbreviation: PF-BPy) and the like are usable.
The electron injecting layer is a layer containing a highly electron-injectable substance. Examples of a material for the electron injecting layer include an alkali metal, alkaline earth metal and a compound thereof, examples of which include lithium (Li), cesium (Cs), calcium (Ca), lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF2), and lithium oxide (LiOx). In addition, the alkali metal, alkaline earth metal or the compound thereof may be added to the substance exhibiting the electron transportability in use. Specifically, for instance, magnesium (Mg) added to Alq may be used. In this case, the electrons can be more efficiently injected from the cathode.
Alternatively, the electron injecting layer may be provided by a composite material in a form of a mixture of the organic compound and the electron donor. Such a composite material exhibits excellent electron injectability and electron transportability since electrons are generated in the organic compound by the electron donor. In this case, the organic compound is preferably a material excellent in transporting the generated electrons. Specifically, the above examples (e.g., the metal complex and the hetero aromatic compound) of the substance forming the electron transporting layer are usable. As the electron donor, any substance exhibiting electron donating property to the organic compound is usable. Specifically, the electron donor is preferably alkali metal, alkaline earth metal and rare earth metal such as lithium, cesium, magnesium, calcium, erbium and ytterbium. The electron donor is also preferably alkali metal oxide and alkaline earth metal oxide such as lithium oxide, calcium oxide, and barium oxide. Moreover, a Lewis base such as magnesium oxide is usable. Further, the organic compound such as tetrathiafulvalene (abbreviation: TTF) is usable.
Preferably, the organic EL device of a top emission type according to the above exemplary embodiment has a capping layer on the top of the cathode.
As the capping layer, for instance, a high polymer compound, metal oxide, metal fluoride, metal boride, silicon nitride, and silicon compound (silicon oxide or the like) are usable.
Further, an aromatic amine derivative, an anthracene derivative, a pyrene derivative, a fluorene derivative, or a dibenzofuran derivative is usable for the capping layer.
Furthermore, a laminate obtained by layering layers containing these substances is also usable as the capping layer.
A method for forming each layer of the organic EL device according to the above exemplary embodiment is subject to no limitation except for the above particular description. However, known methods of dry film-forming such as vacuum deposition, sputtering, plasma or ion plating and wet film-forming such as spin coating, dipping, flow coating or ink-jet are applicable.
The film thickness of each of the organic layers of the organic EL device according to the above exemplary embodiment is not limited unless otherwise specified in the above. In general, the thickness preferably ranges from several nanometers to 1 μm because an excessively small film thickness is likely to cause defects (e.g. pin holes) and an excessively large thickness leads to the necessity of applying high voltage and consequent reduction in efficiency.
In the organic EL device according to the above exemplary embodiment, the first host material, the second host material, and the third host material are exemplified by the first compound represented by a formula (1), (1X), (12X), (13X), (14X), (15X), or (16X) below, the second compound represented by a formula (2) below, and the like. Further, the first compound is also usable as the first host material and the second host material. In this case, the compound represented by the formula (1), (1X), (12X), (13X), (14X), (15X), or (16X) that is used as the second host material is occasionally referred to as the second compound for convenience.
In the formula (1):
In the first compound according to the exemplary embodiment, R901, R902, R903, R904, R905, R906, R907, R801 and R802 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms;
In the organic EL device according to the above exemplary embodiment, the group represented by the formula (11) is preferably a group represented by a formula (111) below.
In the formula (111):
Among positions *1 to *8 of carbon atoms in a cyclic structure represented by a formula (111a) below in the group represented by the formula (111), L111 is bonded to one of the positions *1 to *4, R121 is bonded to each of three positions of the rest of *1 to *4, L112 is bonded to one of the positions *5 to *8, and R122 is bonded to each of three positions of the rest of *5 to *8.
For instance, in the group represented by the formula (111), when L111 is bonded to a carbon atom at a position *2 in the cyclic structure represented by the formula (111a) and L112 is bonded to a carbon atom at a position *7 in the cyclic structure represented by the formula (111a), the group represented by the formula (111) is represented by a formula (111b) below.
In the formula (111b):
In the organic EL device according to the above exemplary embodiment, the group represented by the formula (111) is preferably a group represented by the formula (111b).
In the organic EL device according to the above exemplary embodiment, it is preferable that ma is 0, 1, or 2, and mb is 0, 1, or 2.
In the organic EL device according to the above exemplary embodiment, it is preferable that ma is 0 or 1, and mb is 0 or 1.
In the organic EL device according to the above exemplary embodiment, Ar101 is preferably a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the organic EL device according to the above exemplary embodiment, it is preferable that Ar101 is a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted pyrenyl group, a substituted or unsubstituted phenanthryl group, or a substituted or unsubstituted fluorenyl group.
In the organic EL device according to the above exemplary embodiment, Ar101 is also preferably a group represented by a formula (12), a formula (13), or a formula (14) below.
In the formulae (12), (13), and (14):
In the organic EL device according to the above exemplary embodiment, the first compound is preferably represented by a formula (101) below.
In the formula (101):
In the organic EL device according to the above exemplary embodiment, L101 is preferably a single bond, or a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
In the organic EL device according to the above exemplary embodiment, the first compound is preferably represented by a formula (102) below.
In the formula (102):
In the compound represented by the formula (102), it is preferable that ma is 0, 1, or 2, and mb is 0, 1, or 2.
In the compound represented by the formula (102), it is preferable that ma is 0 or 1, and mb is 0 or 1.
In the organic EL device according to the above exemplary embodiment, it is preferable that two or more of R101 to R110 are each a group represented by the formula (11).
In the organic EL device according to the above exemplary embodiment, it is preferable that two or more of R101 to R110 are each a group represented by the formula (11) and Ar101 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the organic EL device according to the above exemplary embodiment, it is preferable that Ar101 is not a substituted or unsubstituted pyrenyl group, L101 is not a substituted or unsubstituted pyrenylene group, and the substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms for R101 to R110 not being the group represented by the formula (11) is not a substituted or unsubstituted pyrenyl group.
In the organic EL device according to the above exemplary embodiment, it is preferable that R101 to R110 not being the group represented by the formula (11) are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In the organic EL device according to the above exemplary embodiment, it is preferable that R101 to R110 not being the group represented by the formula (11) are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms.
In the organic EL device according to the above exemplary embodiment, R101 to R110 not being the group represented by the formula (11) are each preferably a hydrogen atom.
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by a formula (1X) below.
In the formula (1X):
R101 to R112 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted haloalkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a group represented by —Si(R901)(R902)(R903), a group represented by —O—(R904), a group represented by —S—(R905), a substituted or unsubstituted aralkyl group having 7 to 50 carbon atoms, a group represented by —C(═O)R801, a group represented by —COOR802, a halogen atom, a cyano group, a nitro group, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms, or a group represented by the formula (11X);
In the organic EL device according to the above exemplary embodiment, the group represented by the formula (11X) is preferably a group represented by a formula (111X) below.
In the formula (111X):
Among positions *1 to *8 of carbon atoms in a cyclic structure represented by a formula (111aX) below in the group represented by the formula (111X), L111 is bonded to one of the positions *1 to *4, R141 is bonded to each of three positions of the rest of *1 to *4, L112 is bonded to one of the positions *5 to *8, and R142 is bonded to each of three positions of the rest of *5 to *8.
For instance, in the group represented by the formula (111X), when L111 is bonded to a carbon atom at *2 in the cyclic structure represented by the formula (111aX) and L112 is bonded to a carbon atom at *7 in the cyclic structure represented by the formula (111aX), the group represented by the formula (111X) is represented by a formula (111bX) below.
In the formula (111bX):
In the organic EL device according to the above exemplary embodiment, the group represented by the formula (111X) is preferably a group represented by the formula (111bX).
In the compound represented by the formula (1X), preferably, ma is 1 or 2 and mb is 1 or 2.
In the compound represented by the formula (1X), preferably, ma is 1 and mb is 1.
In the compound represented by the formula (1X), Ar101 is preferably a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the compound represented by the formula (1X), Ar101 is preferably a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted benz[a]anthryl group; a substituted or unsubstituted pyrenyl group, a substituted or unsubstituted phenanthryl group, or a substituted or unsubstituted fluorenyl group.
The compound represented by the formula (1X) is also preferably represented by a formula (101X) below.
In the formula (101X):
In the compound represented by the formula (1X), L101 is preferably a single bond, or a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
The compound represented by the formula (1X) is also preferably represented by a formula (102X) below.
In the formula (102X):
In the compound represented by the formula (1X), preferably, ma is 1 or 2 and mb is 1 or 2 in the formula (102X).
In the compound represented by the formula (1X), preferably, ma is 1 and mb is 1 in the formula (102X).
In the compound represented by the formula (1X), the group represented by the formula (11X) is also preferably a group represented by a formula (11AX) or a group represented by a formula (11BX) below.
In the formulae (11AX) and (11BX):
The compound represented by the formula (1X) is also preferably represented by a formula (103X) below.
In the formula (103X):
In the compound represented by the formula (1X), L131 is also preferably a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
In the compound represented by the formula (1X), L132 is also preferably a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
In the compound represented by the formula (1X), two or more of R101 to R112 are each also preferably a group represented by the formula (11).
In the compound represented by the formula (1X), it is preferable that two or more of R101 to R112 are each a group represented by the formula (11X) and Ar101 in the formula (11X) is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the compound represented by the formula (1X), it is also preferable that Ar101 is not a substituted or unsubstituted benz[a]anthryl group, L101 is not a substituted or unsubstituted benz[a]anthrylene group, and, the substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms for R101 to R110 not being the group represented by the formula (11X) is not a substituted or unsubstituted benz[a]anthryl group.
In the compound represented by the formula (1X), R101 to R112 not being the group represented by the formula (11X) are preferably each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In the compound represented by the formula (1X), R101 to R112 not being the group represented by the formula (11X) are each preferably a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms.
In the compound represented by the formula (1X), R101 to R112 not being the group represented by the formula (11X) are each preferably a hydrogen atom.
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by the formula (12X) below.
In the formula (12X):
In the formula (12X), combinations of adjacent two of R1201 to R1210 refer to a combination of R1201 and R1202, a combination of R1202 and R1203, a combination of R1203 and R1204, a combination of R1204 and R1205, a combination of R1205 and R1206, a combination of R1207 and R1208, a combination of R1208 and R1209, and a combination of R1209 and R1210.
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by the formula (13X) below.
In the formula (13X):
In the organic EL device according to the above exemplary embodiment, none of combinations of adjacent two or more of R1301 to R1310 not being the group represented by the formula (131) are bonded to each other. Combinations of adjacent two of R1301 to R1310 in the formula (13X) refer to a combination of R1301 and R1302, a combination of R1302 and R1303, a combination of R1303 and R1304, a combination of R1304 and R1305, a combination of R1305 and R1306, a combination of R1307 and R1308, a combination of R1308 and R1309, and a combination of R1309 and R1310.
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by the formula (14X) below.
In the formula (14X):
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by the formula (15X) below.
In the formula (15X):
In the organic EL device according to the above exemplary embodiment, the first compound is also preferably a compound represented by the formula (16X) below.
In the formula (16X):
In the organic EL device according to the above exemplary embodiment, also preferably, the first host material has, in a molecule, a linking structure including a benzene ring and a naphthalene ring linked to each other with a single bond, in which the benzene ring and the naphthalene ring in the linking structure are each independently fused or not fused with a further monocyclic ring or fused ring, and the benzene ring and the naphthalene ring in the linking structure are further linked to each other by cross-linking at at least one site other than the single bond.
When the first host material has the linking structure including such cross-linking, deterioration in the chromaticity of the organic EL device is expected to be inhibited.
The first host material in the above case is only required to have a linking structure as the minimum unit in a molecule, the linking structure including a benzene ring and a naphthalene ring linked to each other with a single bond (occasionally referred to as a benzene-naphthalene linking structure), the linking structure being as represented by a formula (X1) or a formula (X2) below. The benzene ring may be fused with a further monocyclic ring or fused ring, and the naphthalene ring may be fused with a further monocyclic ring or fused ring. The benzene ring may be fused with a further monocyclic ring or fused ring, and the naphthalene ring may be fused with a further monocyclic ring or fused ring. For instance, also in a case where the first host material has, in a molecule, a linking structure including a naphthalene ring and a naphthalene ring linked to each other with a single bond (occasionally referred to as a naphthalene-naphthalene linking structure) and being as represented by a formula (X3), a formula (X4), or a formula (X5) below, the naphthalene-naphthalene linking structure is regarded as including the benzene-naphthalene linking structure since one of the naphthalene rings includes a benzene ring.
In the organic EL device according to the above exemplary embodiment, the cross-linking also preferably includes a double bond. Specifically, the first host material also preferably has a structure in which the benzene ring and the naphthalene ring are further linked to each other at any other site than the single bond by the cross-linking structure including a double bond.
Assuming that the benzene ring and the naphthalene ring in the benzene-naphthalene linking structure are further linked to each other at at least one site other than the single bond by cross-linking, for instance, a linking structure (fused ring) represented by a formula (X11) below is obtained in a case of the formula (X1), and a linking structure (fused ring) represented by a formula (X31) below is obtained in a case of the formula (X3).
Assuming that the benzene ring and the naphthalene ring in the benzene-naphthalene linking structure are further linked to each other at any other site than the single bond by cross-linking including a double bond, for instance, a linking structure (fused ring) represented by a formula (X12) below is obtained in a case of the formula (X1), a linking structure (fused ring) represented by a formula (X21) or formula (X22) below is obtained in a case of the formula (X2), a linking structure (fused ring) represented by a formula (X41) below is obtained in a case of the formula (X4), and a linking structure (fused ring) represented by a formula (X51) below is obtained in a case of the formula (X5).
Assuming that the benzene ring and the naphthalene ring in the benzene-naphthalene linking structure are further linked to each other at at least one site other than the single bond by cross-linking including a hetero atom (e.g., an oxygen atom), for instance, a linking structure (fused ring) represented by a formula (X13) below is obtained in a case of the formula (X1).
In the organic EL device according to the above exemplary embodiment, also preferably, the first host material has, in a molecule, a biphenyl structure including a first benzene ring and a second benzene ring linked to each other with a single bond, and the first benzene ring and the second benzene ring in the biphenyl structure are further linked to each other by cross-linking at at least one site other than the single bond.
In the organic EL device according to the above exemplary embodiment, also preferably, the first benzene ring and the second benzene ring in the biphenyl structure are further linked to each other by the cross-linking at one site other than the single bond. When the first host material has the biphenyl structure including such cross-linking, deterioration in the chromaticity of the organic EL device is expected to be inhibited.
In the organic EL device according to the above exemplary embodiment, the cross-linking also preferably includes a double bond.
In the organic EL device according to the above exemplary embodiment, the cross-linking also preferably includes no double bond.
Also preferably, the first benzene ring and the second benzene ring in the biphenyl structure are further linked to each other by the cross-linking at two sites other than the single bond.
In the organic EL device according to the above exemplary embodiment, also preferably, the first benzene ring and the second benzene ring in the biphenyl structure are further linked to each other by the cross-linking at two sites other than the single bond, and the cross-linking includes no double bond. When the first host material has the biphenyl structure including such cross-linking, deterioration in the chromaticity of the organic EL device is expected to be inhibited.
For instance, assuming that the first benzene ring and the second benzene ring in the biphenyl structure represented by a formula (BP1) below are further linked to each other by cross-linking at at least one site other than the single bond, the biphenyl structure is exemplified by linking structures (fused rings) represented by formulae (BP11) to (BP15) below.
The formula (BP11) represents a linking structure in which the first benzene ring and the second benzene ring are linked to each other at one site other than the single bond by cross-linking including no double bond.
The formula (BP12) represents a linking structure in which the first benzene ring and the second benzene ring are linked to each other at one site other than the single bond by cross-linking including a double bond.
The formula (BP13) represents a linking structure in which the first benzene ring and the second benzene ring are linked to each other at two sites other than the single bond by cross-linking including no double bond.
The formula (BP14) represents a linking structure in which the first benzene ring and the second benzene ring are linked to each other by cross-linking including no double bond at one of two sites other than the single bond, and the first benzene ring and the second benzene ring are linked to each other by cross-linking including a double bond at the other of the two sites other than the single bond.
The formula (BP15) represents a linking structure in which the first benzene ring and the second benzene ring are linked to each other at two sites other than the single bond by cross-linking including a double bond.
In the first compound and the second compound, the groups specified to be “substituted or unsubstituted” are each preferably an “unsubstituted” group.
The first compound can be produced by a known method. The first compound can also be produced based on a known method through a known alternative reaction using a known material(s) tailored for the target compound.
Specific examples of the first compound include the following compounds. It should however be noted that the invention is not limited to the specific examples of the first compound.
In the specific examples of the compound herein, D represents a deuterium atom, Me represents a methyl group, and tBu represents a tert-butyl group.
In the organic EL device according to the above exemplary embodiment, the second compound is a compound represented by the formula (2) below.
In the formula (2):
In the second compound according to the exemplary embodiment, R901, R902, R903, R904, R905, R906, R907, R801 and R802 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms;
In the organic EL device according to the above exemplary embodiment, preferably R201 to R208 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted haloalkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a group represented by —Si(R901)(R902)(R903), a group represented by —O—(R904), a group represented by —S—(R905), a group represented by —N(R906)(R907), a substituted or unsubstituted aralkyl group having 7 to 50 carbon atoms, a group represented by —C(═O)R801, a group represented by —COOR802, a halogen atom, a cyano group, or a nitro group;
In the organic EL device according to the above exemplary embodiment, preferably L201 and L202 are each independently a single bond, or a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms; and
In the organic EL device according to the above exemplary embodiment, Ar201 and Ar202 are preferably each independently a phenyl group, naphthyl group, phenanthryl group, biphenyl group, terphenyl group, diphenylfluorenyl group, dimethylfluorenyl group, benzodiphenylfluorenyl group, benzodimethylfluorenyl group, dibenzofuranyl group, dibenzothienyl group, naphthobenzofuranyl group, or naphthobenzothienyl group.
In the organic EL device according to the above exemplary embodiment, the second compound represented by the formula (2) is preferably a compound represented by a formula (201), a formula (202), a formula (203), a formula (204), a formula (205), a formula (206), a formula (207), a formula (208), or a formula (209) below.
In the formulae (201) to (209):
The second compound represented by the formula (2) is also preferably a compound represented by a formula (221), a formula (222), a formula (223), a formula (224), a formula (225), a formula (226), a formula (227), a formula (228), or a formula (229) below.
In the formulae (221), (222), (223), (224), (225), (226), (227), (228) and (229):
The second compound represented by the formula (2) is also preferably a compound represented by a formula (241), a formula (242), a formula (243), a formula (244), a formula (245), a formula (246), a formula (247), a formula (248), or a formula (249) below.
In the formulae (241), (242), (243), (244), (245), (246), (247), (248) and (249):
In the second compound represented by the formula (2), R201 to R208 not being the group represented by the formula (21) are preferably each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, or a group represented by —Si(R901)(R902)(R903).
Preferably, L101 is a single bond, or an unsubstituted arylene group having 6 to 22 ring carbon atoms; and
In the organic EL device according to the above exemplary embodiment, R201 to R208 that are substituents of an anthracene skeleton in the second compound represented by the formula (2) are preferably hydrogen atoms in terms of preventing inhibition of intermolecular interaction and inhibiting decrease in electron mobility. However, R201 to R208 may be a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
Assuming that R201 to R208 each are a bulky substituent such as an alkyl group and a cycloalkyl group, intermolecular interaction may be inhibited to decrease the electron mobility of the second compound relative to that of the first host material, so that the relationship of μE2>μE1 shown by the numerical formula (Numerical Formula 16) may not be satisfied. When the second compound is used in the second emitting layer, it can be expected that satisfying the relationship of μE2>μE1 inhibits a decrease in a recombination ability between holes and electrons in the first emitting layer and a decrease in luminous efficiency. It should be noted that substituents, namely, a haloalkyl group, alkenyl group, alkynyl group, group represented by —Si(R901)(R902)(R903), group represented by —O—(R904), group represented by —S—(R905), group represented by —N(R906)(R907), aralkyl group, group represented by —C(═O)R801, group represented by —COOR802, halogen atom, cyano group, and nitro group are likely to be bulky, and an alkyl group and cycloalkyl group are likely to be further bulky.
In the second compound represented by the formula (2), R201 to R208, which are the substituents on the anthracene skeleton, are each preferably not a bulky substituent and preferably not an alkyl group and cycloalkyl group. More preferably, R201 to R208 are each not an alkyl group, cycloalkyl group, haloalkyl group, alkenyl group, alkynyl group, group represented by —Si(R901)(R902)(R903), group represented by —O—(R904), group represented by —S—(R905), group represented by —N(R906)(R907), aralkyl group, group represented by —C(═O)R801, group represented by —COOR802, halogen atom, cyano group, and nitro group.
In the organic EL device according to the above exemplary embodiment, also preferably, R201 to R208 in the second compound represented by the formula (2) are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, or a group represented by —Si(R901)(R902)(R903).
In the organic EL device according to the above exemplary embodiment, R201 to R208 in the second compound represented by the formula (2) are each preferably a hydrogen atom.
In the second compound, examples of the substituent for the “substituted or unsubstituted” group on R201 to R208 also preferably do not include the above-described substituent that is likely to be bulky, especially a substituted or unsubstituted alkyl group and a substituted or unsubstituted cycloalkyl group. When examples of the substituent for the “substituted or unsubstituted” group on R201 to R208 do not include a substituted or unsubstituted alkyl group and a substituted or unsubstituted cycloalkyl group, inhibition of intermolecular interaction to be caused by presence of a bulky substituent such as an alkyl group and a cycloalkyl group can be prevented, thereby preventing a decrease in the electron mobility. Moreover, when the second compound described above is used in the second emitting layer, a decrease in a recombination ability between holes and electrons in the first emitting layer and a decrease in the luminous efficiency can be inhibited.
Further preferably, R201 to R208 that are the substituents on the anthracene skeleton are not bulky substituents and R201 to R208 as substituents are unsubstituted. Assuming that R201 to R208 that are the substituents on the anthracene skeleton are not bulky substituents and substituents are bonded to R201 to R208 that are not bulky substituents, the substituents bonded to R201 to R208 are preferably not bulky substituents; and the substituents bonded to R201 to R208 serving as substituents are preferably not an alkyl group and cycloalkyl group, more preferably not an alkyl group, cycloalkyl group, haloalkyl group, alkenyl group, alkynyl group, group represented by —Si(R901)(R902)(R903), group represented by —O—(R904), group represented by —S—(R905), group represented by —N(R906)(R907), aralkyl group, group represented by —C(═O)R801, group represented by —COOR802, halogen atom, cyano group, and nitro group.
In the second compound, the groups specified to be “substituted or unsubstituted” are each preferably an “unsubstituted” group.
The second compound can be produced by a known method. The second compound can also be produced based on a known method through a known alternative reaction using a known material(s) tailored for the target compound.
Specific examples of the second compound include the following compounds. It should however be noted that the invention is not limited to the specific examples of the second compound.
In the organic EL device according to the above exemplary embodiment, the first emitting compound, the second emitting compound, and the third emitting compound are, for instance, a third compound and a fourth compound below.
The third compound and the fourth compound are each independently at least one compound selected from the group consisting of a compound represented by a formula (3) below, a compound represented by a formula (4) below, a compound represented by a formula (5) below, a compound represented by a formula (6) below, a compound represented by a formula (7) below, a compound represented by a formula (8) below, a compound represented by a formula (9) below, and a compound represented by a formula (10) below.
The compound represented by the formula (3) will be described below.
In the formula (3):
In the formula (31):
In the third and fourth compounds, R901, R902, R903, R904, R905, R906, and R907 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms;
In the formula (3), two of R301 to R310 are each preferably a group represented by the formula (31).
In an exemplary embodiment, the compound represented by the formula (3) is a compound represented by a formula (33) below.
In the formula (33):
In the formula (31), L301 is preferably a single bond, and L302 and L303 are each preferably a single bond.
In an exemplary embodiment, the compound represented by the formula (3) is represented by a formula (34) or a formula (35) below.
In the formula (34):
R311 to R318 each independently represent the same as R301 to R310 in the formula (3) that are not a monovalent group represented by the formula (31);
In the formula (35):
In the formula (31), at least one of Ar301 or Ar302 is preferably a group represented by a formula (36) below.
In the formulae (33) to (35), at least one of Ar312 or Ar313 is preferably a group represented by the formula (36).
In the formulae (33) to (35), at least one of Ar315 or Ar316 is preferably a group represented by the formula (36).
In the formula (36):
X3 is preferably an oxygen atom.
At least one of R321 to R327 is preferably a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In the formula (31), preferably, Ar301 is a group represented by the formula (36) and Ar302 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the formulae (33) to (35), preferably, Ar312 is a group represented by the formula (36) and Ar313 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the formulae (33) to (35), preferably, Ar315 is a group represented by the formula (36) and Ar316 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, the compound represented by the formula (3) is represented by a formula (37) below.
In the formula (37):
Specific examples of the compound represented by the formula (3) include compounds shown below.
The compound represented by the formula (4) will be described below.
In the formula (4):
The “aromatic hydrocarbon ring” for the A1 ring and A2 ring has the same structure as a compound formed by introducing a hydrogen atom to the “aryl group” described above.
Ring atoms of the “aromatic hydrocarbon ring” for the A1 ring and A2 ring include two carbon atoms on a fused bicyclic structure at the center of the formula (4).
Specific examples of the “substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms” include a compound formed by introducing a hydrogen atom to the “aryl group” described in the specific example group G1.
The “heterocycle” for the A1 ring and A2 ring has the same structure as a compound formed by introducing a hydrogen atom to the “heterocyclic group” described above.
Ring atoms of the “heterocycle” for the A1 ring and A2 ring include two carbon atoms on a fused bicyclic structure at the center of the formula (4).
Specific examples of the “substituted or unsubstituted heterocycle having 5 to 50 ring atoms” include a compound formed by introducing a hydrogen atom to the “heterocyclic group” described in the specific example group G2.
Rb is bonded to any one of carbon atoms forming the aromatic hydrocarbon ring as the A1 ring or any one of atoms forming the heterocycle as the A1 ring.
Rc is bonded to any one of carbon atoms forming the aromatic hydrocarbon ring as the A2 ring or any one of atoms forming the heterocycle as the A2 ring.
At least one of Ra, Rb, or Rc is preferably a group represented by a formula (4a) below. More preferably, at least two of Ra, Rb, or Rc are each a group represented by the formula (4a).
[Formula 225]
*-L401-Ar401 (4a)
In the formula (4a):
In the formula (4b):
In an exemplary embodiment, the compound represented by the formula (4) is represented by a formula (42) below.
In the formula (42):
At least one of R401 to R411 is preferably a group represented by the formula (4a). More preferably, at least two of R401 to R411 are each a group represented by the formula (4a).
R404 and R411 are each preferably a group represented by the formula (4a).
In an exemplary embodiment, the compound represented by the formula (4) is a compound formed by bonding a structure represented by a formula (4-1) or a formula (4-2) below to the A1 ring.
Further, in an exemplary embodiment, the compound represented by the formula (42) is a compound formed by bonding the structure represented by the formula (4-1) or the formula (4-2) to a ring bonded to R404 to R407.
In the formula (4-1), two bonds * are each independently bonded to a ring-forming carbon atom of the aromatic hydrocarbon ring or a ring atom of the heterocycle as the A1 ring in the formula (4) or bonded to one of R404 to R407 in the formula (42);
In an exemplary embodiment, the compound represented by the formula (4) is a compound represented by a formula (41-3), a formula (41-4) or a formula (41-5) below.
In the formulae (41-3), (41-4), and (41-5):
In an exemplary embodiment, a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms as the A1 ring in the formula (41-5) is a substituted or unsubstituted naphthalene ring, or a substituted or unsubstituted fluorene ring.
In an exemplary embodiment, a substituted or unsubstituted heterocycle having 5 to 50 ring atoms as the A1 ring in the formula (41-5) is a substituted or unsubstituted dibenzofuran ring, a substituted or unsubstituted carbazole ring, or a substituted or unsubstituted dibenzothiophene ring.
In an exemplary embodiment, the compound represented by the formula (4) or the formula (42) is selected from the group consisting of compounds represented by formulae (461) to (467) below.
In the formulae (461), (462), (463), (464), (465), (466), and (467):
In an exemplary embodiment, at least one combination of adjacent two or more of R401 to R411 in the compound represented by the formula (42) are mutually bonded to form a substituted or unsubstituted monocyclic ring, or mutually bonded to form a substituted or unsubstituted fused ring. This exemplary embodiment will be described in detail below as a compound represented by a formula (45) below.
The compound represented by the formula (45) will be described below.
In the formula (45):
In the formula (45), Rn and Rn+1 (n being an integer selected from 461, 462, 464 to 466, and 468 to 470) are mutually bonded to form a substituted or unsubstituted monocyclic ring or fused ring together with two ring-forming carbon atoms bonded to Rn and Rn+1. The ring is preferably formed of atoms selected from the group consisting of a carbon atom, an oxygen atom, a sulfur atom, and a nitrogen atom, and is made of preferably 3 to 7 atoms, more preferably 5 or 6 atoms.
The number of the above cyclic structures in the compound represented by the formula (45) is, for instance, 2, 3, or 4. The two or more of the cyclic structures may be present on the same benzene ring on the basic skeleton represented by the formula (45) or may be present on different benzene rings. For instance, when three cyclic structures are present, each of the cyclic structures may be present on the corresponding one of the three benzene rings of the formula (45).
Examples of the above cyclic structures in the compound represented by the formula (45) include structures represented by formulae (451) to (460) below.
In the formulae (451) to (457):
In the formulae (458) to (460):
In the formula (45), preferably, at least one of R462, R464, R465, R470 or R471 (preferably, at least one of R462, R465 or R470, more preferably R462) is a group forming no cyclic structure.
(i) A substituent, if present, for a cyclic structure formed by Rn and Rn+1 in the formula (45), (ii) R461 to R471 forming no cyclic structure in the formula (45), and (iii) R4501 to R4514, R4515 to R4525 in the formulae (451) to (460) are preferably each independently any one of groups selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a group represented by —N(R906)(R907), a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms, or groups represented by formulae (461) to (464) below.
In the formulae (461) to (464):
In an exemplary embodiment, the compound represented by the formula (45) is represented by one of formulae (45-1) to (45-6) below.
In the formulae (45-1) to (45-6):
In an exemplary embodiment, the compound represented by the formula (45) is represented by one of formulae (45-7) to (45-12) below.
In the formulae (45-7) to (45-12):
In an exemplary embodiment, the compound represented by the formula (45) is represented by one of formulae (45-13) to (45-21) below.
In the formulae (45-13) to (45-21):
When the ring g or the ring h further has a substituent, examples of the substituent include a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, a group represented by the formula (461), a group represented by the formula (463), and a group represented by the formula (464).
In an exemplary embodiment, the compound represented by the formula (45) is represented by one of formulae (45-22) to (45-25) below.
In the formulae (45-22) to (45-25):
In an exemplary embodiment, the compound represented by the formula (45) is represented by a formula (45-26) below.
In the formula (45-26):
Specific Examples of Compound Represented by Formula (4) Specific examples of the compound represented by the formula (4) include compounds shown below. In the specific examples below, Ph represents a phenyl group, and D represents a deuterium atom.
The compound represented by the formula (5) will be described below. The compound represented by the formula (5) corresponds to a compound represented by the formula (41-3).
In the formula (5):
“A combination of adjacent two or more of R501 to R507 and R511 to R517” refers to, for instance, a combination of R501 and R502, a combination of R502 and R503, a combination of R503 and R504, a combination of R505 and R506, a combination of R506 and R507, and a combination of R501, R502, and R503.
In an exemplary embodiment, at least one, preferably two of R501 to R507 or R511 to R517 are each a group represented by —N(R906)(R907).
In an exemplary embodiment, R501 to R507 and R511 to R517 are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, the compound represented by the formula (5) is a compound represented by a formula (52) below.
In the formula (52):
In an exemplary embodiment, the compound represented by the formula (5) is a compound represented by a formula (53) below.
In the formula (53), R551, R552 and R561 to R564 each independently represent the same as R551, R552 and R561 to R564 in the formula (52).
In an exemplary embodiment, R561 to R564 in the formulae (52) and (53) are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms (preferably a phenyl group).
In an exemplary embodiment, R521 and R522 in the formula (5) and R551 and R552 in the formulae (52) and (53) are each a hydrogen atom.
In an exemplary embodiment, the substituent for the “substituted or unsubstituted” group in the formulae (5), (52) and (53) is a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
Specific examples of the compound represented by the formula (5) include compounds shown below.
The compound represented by the formula (6) will be described below.
In the formula (6):
The ring a, ring b and ring c are each a ring (a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocycle having 5 to 50 ring atoms) fused with a fused bicyclic structure formed of a boron atom and two nitrogen atoms at the center of the formula (6).
The “aromatic hydrocarbon ring” for the rings a, b, and c has the same structure as a compound formed by introducing a hydrogen atom to the “aryl group” described above.
Ring atoms of the “aromatic hydrocarbon ring” for the ring a include three carbon atoms on the fused bicyclic structure at the center of the formula (6).
Ring atoms of the “aromatic hydrocarbon ring” for the rings b and c include two carbon atoms on the fused bicyclic structure at the center of the formula (6).
Specific examples of the “substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms” include a compound formed by introducing a hydrogen atom to the “aryl group” described in the specific example group G1.
The “heterocycle” for the rings a, b, and c has the same structure as a compound formed by introducing a hydrogen atom to the “heterocyclic group” described above.
Ring atoms of the “heterocycle” for the ring a include three carbon atoms on the fused bicyclic structure at the center of the formula (6). Ring atoms of the “heterocycle” for the rings b and c include two carbon atoms on the fused bicyclic structure at the center of the formula (6). Specific examples of the “substituted or unsubstituted heterocycle having 5 to 50 ring atoms” include a compound formed by introducing a hydrogen atom to the “heterocyclic group” described in the specific example group G2.
R601 and R602 may be each independently bonded with the ring a, ring b, or ring c to form a substituted or unsubstituted heterocycle. The “heterocycle” in this arrangement includes a nitrogen atom on the fused bicyclic structure at the center of the formula (6). The heterocycle in the above arrangement optionally includes a hetero atom other than the nitrogen atom. R601 and R602 being bonded with the ring a, ring b, or ring c specifically means that atoms forming R601 and R602 are bonded with atoms forming the ring a, ring b, or ring c. For instance, R601 may be bonded with the ring a to form a bicyclic (or tri-or-more cyclic) fused nitrogen-containing heterocycle, in which the ring including R601 and the ring a are fused. Specific examples of the nitrogen-containing heterocycle include a compound corresponding to the nitrogen-containing bi(or-more)cyclic fused heterocyclic group in the specific example group G2.
The same applies to R601 bonded with the ring b, R602 bonded with the ring a, and R602 bonded with the ring c.
In an exemplary embodiment, the ring a, ring b and ring c in the formula (6) are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms.
In an exemplary embodiment, the ring a, ring b and ring c in the formula (6) are each independently a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring.
In an exemplary embodiment, R601 and R602 in the formula (6) are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms; preferably a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, the compound represented by the formula (6) is a compound represented by a formula (62) below.
In the formula (62):
R601A and R602A in the formula (62) are groups corresponding to R601 and R602 in the formula (6), respectively.
For instance, R601A and R611 are optionally bonded with each other to form a bicyclic (or tri-or-more cyclic) fused nitrogen-containing heterocycle, in which the ring including R601A and R611 and a benzene ring corresponding to the ring a are fused. Specific examples of the nitrogen-containing heterocycle include a compound corresponding to the nitrogen-containing bi(or-more)cyclic fused heterocyclic group in the specific example group G2. The same applies to R601A bonded with R621, R602A bonded with R613, and R602A bonded with R614.
At least one combination of adjacent two or more of R611 to R621 may be mutually bonded to form a substituted or unsubstituted monocyclic ring, or mutually bonded to form a substituted or unsubstituted fused ring.
For instance, R611 and R612 are optionally mutually bonded to form a structure in which a benzene ring, indole ring, pyrrole ring, benzofuran ring, benzothiophene ring or the like is fused to the six-membered ring bonded with R611 and R612, the resultant fused ring forming a naphthalene ring, carbazole ring, indole ring, dibenzofuran ring, or dibenzothiophene ring, respectively.
In an exemplary embodiment, R611 to R621 not contributing to ring formation are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, R611 to R621 not contributing to ring formation are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, R611 to R621 not contributing to ring formation are each independently a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms.
In an exemplary embodiment, R611 to R621 not contributing to ring formation are each independently a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms; and
In an exemplary embodiment, the compound represented by the formula (62) is a compound represented by a formula (63) below.
In the formula (63):
R631 is bonded with R646 to form a substituted or unsubstituted heterocycle, or not bonded therewith to form no substituted or unsubstituted heterocycle;
R631 is optionally bonded with R646 to form a substituted or unsubstituted heterocycle. For instance, R631 and R646 are optionally bonded with each other to form a tri-or-more cyclic fused nitrogen-containing heterocycle, in which a benzene ring bonded with R646, a ring including a nitrogen atom, and a benzene ring corresponding to the ring a are fused. Specific examples of the nitrogen-containing heterocycle include a compound corresponding to a nitrogen-containing tri(-or-more)cyclic fused heterocyclic group in the specific example group G2. The same applies to R633 bonded with R647, R634 bonded with R651, and R641 bonded with R642.
In an exemplary embodiment, R631 to R651 not contributing to ring formation are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, R631 to R651 not contributing to ring formation are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, R631 to R651 not contributing to ring formation are each independently a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms.
In an exemplary embodiment, R631 to R651 not contributing to ring formation are each independently a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms; and
In an exemplary embodiment, the compound represented by the formula (63) is a compound represented by a formula (63A) below.
In the formula (63A):
In an exemplary embodiment, R661 to R665 are each independently a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, R661 to R665 are each independently a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms.
In an exemplary embodiment, the compound represented by the formula (63) is a compound represented by a formula (63B) below.
In the formula (63B):
In an exemplary embodiment, the compound represented by the formula (63) is a compound represented by a formula (63B′) below.
In the formula (63B′), R672 to R675 each independently represent the same as R672 to R675 in the formula (63B).
In an exemplary embodiment, at least one of R671 to R675 is a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a group represented by —N(R906)(R907), or a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment: R672 is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a group represented by —N(R906)(R907), or a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms; and
In an exemplary embodiment, the compound represented by the formula (63) is a compound represented by a formula (63C) below.
In the formula (63C):
In an exemplary embodiment, the compound represented by the formula (63) is a compound represented by a formula (63C′) below.
In the formula (63C′), R683 to R686 each independently represent the same as R683 to R686 in the formula (63C).
In an exemplary embodiment, R681 to R686 are each independently a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, R681 to R686 are each independently a substituted or unsubstituted aryl group having 6 to 50 carbon atoms.
The compound represented by the formula (6) is producible by initially bonding the ring a, ring b and ring c with linking groups (a group including N—R601 and a group including N—R602) to form an intermediate (first reaction), and bonding the ring a, ring b and ring c with a linking group (a group including a boron atom) to form a final product (second reaction). In the first reaction, an amination reaction (e.g. Buchwald-Hartwig reaction) is applicable. In the second reaction, Tandem Hetero-Friedel-Crafts Reactions or the like is applicable.
Specific examples of the compound represented by the formula (6) are shown below. It should however be noted that these specific examples are merely exemplary and do not limit the compound represented by the formula (6).
The compound represented by the formula (7) will be described below.
In the formula (7):
In the formula (7), each of the ring p, ring q, ring r, ring s, and ring t is fused with an adjacent ring(s) sharing two carbon atoms. The fused position and orientation are not limited but may be defined as required.
In an exemplary embodiment, in the formula (72) or the formula (73) representing the ring r, m1=0 or m2=0 is satisfied.
In an exemplary embodiment, the compound represented by the formula (7) is represented by any one of formulae (71-1) to (71-6) below.
In the formulae (71-1) to (71-), R701, X7, Ar701, Ar702, L701, m1 and m3 respectively represent the same as R701, X7, Ar701, Ar702, L701, m1 and m3 in the formula (7).
In an exemplary embodiment, the compound represented by the formula (7) is represented by any one of formulae (71-11) to (71-13) below.
In the formulae (71-11) to (71-13), R701, X7, Ar701, Ar702, L701, m1, m3 and m4 respectively represent the same as R701, X7, Ar701, Ar702, L701, m1, m3 and m4 in the formula (7).
In an exemplary embodiment, the compound represented by the formula (7) is represented by any one of formulae (71-21) to (71-25) below.
In the formulae (71-21) to (71-25), R701, X7, Ar701, Ar702, L701, m1 and m4 respectively represent the same as R701, X7, Ar701, Ar702, L701, m1 and m4 in the formula (7).
In an exemplary embodiment, the compound represented by the formula (7) is represented by any one of formulae (71-31) to (71-33) below.
In the formulae (71-31) to (71-33), R701, X7, Ar701, Ar702, L701, and m2 to m4 respectively represent the same as R701, X7, Ar701, Ar702, L701, and m2 to m4 in the formula (7).
In an exemplary embodiment, Ar701 and Ar702 are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, one of Ar701 and Ar702 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, and the other of Ar701 and Ar702 is a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
Specific examples of the compound represented by the formula (7) include compounds shown below.
The compound represented by the formula (8) will be described below.
In the formula (8):
At least one of R801 to R804 not forming the divalent group represented by the formula (82) or R811 to R814 is a monovalent group represented by a formula (84) below;
In the formula (84):
In the formula (8), the positions for the divalent group represented by the formula (82) and the divalent group represented by the formula (83) to be formed are not specifically limited but the divalent groups may be formed at any possible positions on R801 to R808.
In an exemplary embodiment, the compound represented by the formula (8) is represented by any one of formulae (81-1) to (81-6) below.
In the formulae (81-1) to (81-6):
In an exemplary embodiment, the compound represented by the formula (8) is represented by any one of formulae (81-7) to (81-18) below.
In the formulae (81-7) to (81-18):
R801 to R808 not forming the divalent group represented by the formula (82) or (83) and not being the monovalent group represented by the formula (84), and R811 to R814 and R821 to R824 not being the monovalent group represented by the formula (84) are preferably each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 50 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 50 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
The monovalent group represented by the formula (84) is preferably represented by a formula (85) or (86) below.
In the formula (85):
In the formula (86):
In the formula (87):
Specific examples of the compound represented by the formula (8) include compounds shown below as well as the compounds disclosed in WO 2014/104144.
The compound represented by the formula (9) will be described below.
In the formula (9):
A91 ring and A92 ring are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocycle having 5 to 50 ring atoms; and
In the formula (92):
At least one of A91 ring or A92 ring is bonded to a bond * of a structure represented by the formula (92). In other words, the ring-forming carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocycle of A91 ring in an exemplary embodiment are bonded to the bonds * in a structure represented by the formula (92). Further, the ring-forming carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocycle of Ar92 ring in an exemplary embodiment are bonded to the bonds * in a structure represented by the formula (92).
In an exemplary embodiment, a group represented by a formula (93) below is bonded to one or both of Ar91 ring and A92 ring.
In the formula (93):
In an exemplary embodiment, in addition to A91 ring, the ring-forming carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocycle of A92 ring are bonded to * in a structure represented by the formula (92). In this case, the structures represented by the formula (92) may be mutually the same or different.
In an exemplary embodiment, R91 and R92 are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, A91 ring and A92 ring are each independently a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms, example of which is a substituted or unsubstituted benzene ring.
In an exemplary embodiment, A93 ring is a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms, example of which is a substituted or unsubstituted benzene ring.
In an exemplary embodiment, X9 is an oxygen atom or a sulfur atom.
Specific examples of the compound represented by the formula (9) include compounds shown below.
The compound represented by the formula (10) will be described below.
In the formula (10):
In an exemplary embodiment, Ar1001 is a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In an exemplary embodiment, Ax3 ring is a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms, example of which is a substituted or unsubstituted benzene ring, a substituted or unsubstituted naphthalene ring, or a substituted or unsubstituted anthracene ring.
In an exemplary embodiment, R1003 and R1004 are each independently a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms.
In an exemplary embodiment, ax is 1.
Specific examples of the compound represented by the formula (10) include compounds shown below.
In an exemplary embodiment, the emitting layer contains, as at least one of the third compound or the fourth compound, at least one compound selected from the group consisting of a compound represented by the formula (4), a compound represented by the formula (5), a compound represented by the formula (7), a compound represented by the formula (8), a compound represented by the formula (9) and a compound represented by a formula (63a) below.
In the formula (63a):
In an exemplary embodiment, the compound represented by the formula (4) is a compound represented by the formula (41-3), the formula (41-4), or the formula (41-5), A1 ring in the formula (41-5) being a substituted or unsubstituted fused aromatic hydrocarbon ring having 10 to 50 ring carbon atoms, or a substituted or unsubstituted fused heterocycle having 8 to 50 ring atoms.
In an exemplary embodiment, the substituted or unsubstituted fused aromatic hydrocarbon ring having 10 to 50 ring carbon atoms in the formulae (41-3), (41-4) and (41-5) is a substituted or unsubstituted naphthalene ring, a substituted or unsubstituted anthracene ring, or a substituted or unsubstituted fluorene ring; and
In an exemplary embodiment, the substituted or unsubstituted fused aromatic hydrocarbon ring having 10 to 50 ring carbon atoms in the formula (41-3), (41-4) or (41-5) is a substituted or unsubstituted naphthalene ring, or a substituted or unsubstituted fluorene ring; and
In an exemplary embodiment, the compound represented by the formula (4) is selected from the group consisting of a compound represented by a formula (461) below, a compound represented by a formula (462) below, a compound represented by a formula (463) below, a compound represented by a formula (464) below, a compound represented by a formula (465) below, a compound represented by a formula (466) below, and a compound represented by a formula (467) below.
In the formulae (461) to (467):
In an exemplary embodiment, R421 to R427 and R440 to R448 are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, R421 to R427 and R440 to R447 are each independently selected from the group consisting of a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 18 ring carbon atoms, and a substituted or unsubstituted heterocyclic group having 5 to 18 ring atoms.
In an exemplary embodiment, the compound represented by the formula (41-3) is a compound represented by a formula (41-3-1) below.
In the formula (41-3-1), R423, R425, R426, R442, R444 and R445 each independently represent the same as R423, R425, R426, R442, R444 and R445 in the formula (41-3).
In an exemplary embodiment, the compound represented by the formula (41-3) is a compound represented by a formula (41-3-2) below.
In the formula (41-3-2), R421 to R427 and R440 to R448 each independently represent the same as R421 to R427 and R440 to R448 in the formula (41-3); and
In an exemplary embodiment, two of R421 to R427 and R440 to R446 in the formula (41-3-2) are each a group represented by —N(R906)(R907).
In an exemplary embodiment, the compound represented by the formula (41-3-2) is a compound represented by a formula (41-3-3) below.
In the formula (41-3-3), R421 to R424, R440 to R443, R447, and R448 each independently represent the same as R421 to R424, R440 to R443, R447, and R448 in the formula (41-3); and
In an exemplary embodiment, the compound represented by the formula (41-3-3) is a compound represented by a formula (41-3-4) below.
In the formula (41-3-4), R447, R448, RA, RB, RC and RD each independently represent the same as R447, R448, RA, RB, RC and RD in the formula (41-3-3).
In an exemplary embodiment, RA, RB, RC, and RD are each independently a substituted or unsubstituted aryl group having 6 to 18 ring carbon atoms.
In an exemplary embodiment, RA, RB, RC, and RD are each independently a substituted or unsubstituted phenyl group.
In an exemplary embodiment, R447 and R448 are each a hydrogen atom.
In an exemplary embodiment, the substituent for “the substituted or unsubstituted” group in each of the formulae is an unsubstituted alkyl group having 1 to 50 carbon atoms, an unsubstituted alkenyl group having 2 to 50 carbon atoms, an unsubstituted alkynyl group having 2 to 50 carbon atoms, an unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms, —Si(R901a)(R902a)(R903a), —O—(R904a), —S—(R905a), —N(R906a)(R907a), a halogen atom, a cyano group, a nitro group, an unsubstituted aryl group having 6 to 50 ring carbon atoms, or an unsubstituted heterocyclic group having 5 to 50 ring atoms;
In an exemplary embodiment, the substituent for “the substituted or unsubstituted” group in each of the formulae is an unsubstituted alkyl group having 1 to 50 carbon atoms, an unsubstituted aryl group having 6 to 50 ring carbon atoms, or an unsubstituted heterocyclic group having 5 to 50 ring atoms.
In an exemplary embodiment, the substituent for “the substituted or unsubstituted” group in each of the formulae is an unsubstituted alkyl group having 1 to 18 carbon atoms, an unsubstituted aryl group having 6 to 18 ring carbon atoms, or an unsubstituted heterocyclic group having 5 to 18 ring atoms.
An electronic device according to a sixth exemplary embodiment is installed with any one of the organic EL devices according to the above exemplary embodiments. Examples of the electronic device include a display device and a light-emitting unit. Examples of the display device include a display component (e.g., an organic EL panel module), TV, mobile phone, tablet and personal computer. Examples of the light-emitting unit include an illuminator and a vehicle light.
The scope of the invention is not limited to the above-described exemplary embodiments but includes any modification and improvement as long as such modification and improvement are compatible with the invention.
For instance, the number of emitting layers is not limited to two or three, and more than two or three emitting layers may be provided and layered with each other. When the organic EL device includes more than two or three emitting layers, it is only necessary that at least two of the emitting layers should satisfy the requirements mentioned in the above exemplary embodiments. For instance, the rest of the emitting layers may be a fluorescent emitting layer or a phosphorescent emitting layer with use of emission caused by electron transfer from the triplet excited state directly to the ground state.
When the organic EL device includes a plurality of emitting layers, these emitting layers may be mutually adjacently provided, or may form a so-called tandem organic EL device, in which a plurality of emitting units are layered via an intermediate layer.
For instance, a blocking layer may be provided adjacent to at least one of a side of the emitting layer close to the anode or a side of the emitting layer close to the cathode. The blocking layer is preferably provided in contact with the emitting layer to block at least one of holes, electrons, or excitons.
For instance, when the blocking layer is provided in contact with the side of the emitting layer close to the cathode, the blocking layer permits transport of electrons, and blocks holes from reaching a layer provided closer to the cathode (e.g., the electron transporting layer) beyond the blocking layer. When the organic EL device includes the electron transporting layer, the blocking layer is preferably interposed between the emitting layer and the electron transporting layer.
When the blocking layer is provided in contact with the side of the emitting layer close to the anode, the blocking layer permits transport of holes and blocks electrons from reaching a layer provided closer to the anode (e.g., the hole transporting layer) beyond the blocking layer. When the organic EL device includes the hole transporting layer, the blocking layer is preferably interposed between the emitting layer and the hole transporting layer.
Alternatively, the blocking layer may be provided adjacent to the emitting layer so that the excitation energy does not leak out from the emitting layer toward neighboring layer(s). The blocking layer blocks excitons generated in the emitting layer from being transferred to a layer(s) (e.g., the electron transporting layer and the hole transporting layer) closer to the electrode(s) beyond the blocking layer.
The emitting layer is preferably bonded with the blocking layer.
Specific structure, shape and the like of the components in the invention may be designed in any manner as long as an object of the invention can be achieved.
Structures of compounds as the first host material and the second host material in Examples 1 to 3 are shown below.
Structures of other compounds used for producing organic EL devices in Examples 1 to 3 and Comparatives 1 to 4 are shown below.
The organic EL devices were produced and evaluated as follows.
An APC (Ag—Pd—Cu) layer (reflection layer) having a film thickness of 100 nm, which was a silver alloy layer, and an indium zinc oxide (IZO: registered trademark) layer having a thickness of 10 nm were sequentially formed by sputtering on a glass substrate.
Subsequently, with a normal lithography technique, this conductive material layer was patterned by etching using a resist pattern as a mask to form an anode. The substrate formed with the lower electrode was ultrasonic-cleaned in isopropyl alcohol for five minutes, and then UV-ozone-cleaned for 30 minutes.
Next, a compound HT1 and a compound HA1 were co-deposited by vacuum deposition to form a hole injecting layer having a film thickness of 10 nm. The concentrations of the compound HT1 and the compound HA1 in the hole injecting layer were 97 mass % and 3 mass %, respectively.
Next, the compound HT1 was vapor-deposited on the hole injecting layer to form a 115-nm-thick first hole transporting layer (HT).
A compound EB1 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second hole transporting layer (also referred to as an electron blocking layer) (EBL).
A compound BH1-1 (first host material (BH)) and a compound BD1 (first emitting compound (BD)) were co-deposited on the second hole transporting layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick first emitting layer.
A compound BH2-1 (second host material (BH)) and the compound BD1 (second emitting compound (BD)) were co-deposited on the first emitting layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick second emitting layer.
A compound HB1 was vapor-deposited on the second emitting layer to form a 5-nm-thick first electron transporting layer (also referred to as a hole blocking layer) (HBL).
A compound ET1 and a compound Liq were co-deposited on the first electron transporting layer (HBL) to form a 35-nm-thick second electron transporting layer (ET). The ratios of the compound ET1 and the compound Liq in the second electron transporting layer (ET) were both 50 mass %. Liq is an abbreviation of (8-quinolinolato)lithium ((8-Quinolinolato)lithium).
Yb (ytterbium) was vapor-deposited on the second electron transporting layer to form a 1-nm-thick electron injecting layer.
Mg and Ag were vapor-deposited at a film thickness ratio of 10:90 on the electron injecting layer to form a 12-nm-thick cathode formed of semi-transparent MgAg alloy. Cap was used to form a film on the cathode by vacuum deposition to form a 65-nm capping layer.
A device arrangement of the organic EL device in Example 1 is roughly shown as follows.
Numerals in parentheses represent a film thickness (unit: nm).
The numerals (97%:3%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound HT1 and the compound HA1 in the hole injecting layer. The numerals (98%:2%) represented by percentage in the same parentheses indicate a ratio (mass %) between the host material (compound BH1-1 or BH2-1) and the emitting compound (compound BD1) in the first emitting layer or the second emitting layer. The numerals (50%:50%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound ET1 and the compound Liq in the electron transporting layer (ET).
The organic EL device in Example 2 was produced in the same manner as in Example 1 except that the film thickness of the second emitting layer was changed so that the total of the film thicknesses of the first and second emitting layers was changed to 15 nm and that the film thickness of the second electron transporting layer was changed to 30 nm.
The organic EL device in Example 3 was produced in the same manner as in Example 1 except that the film thickness of the second emitting layer was changed so that the total of the film thicknesses of the first and second emitting layers was changed to 16 nm and that the film thickness of the second electron transporting layer was changed to 29 nm.
The organic EL device in Comparative 1 was produced in the same manner as in Example 1 except that the film thickness of the second emitting layer was changed so that the total of the film thicknesses of the first and second emitting layers was changed to 25 nm and that the film thickness of the second electron transporting layer was changed to 20 nm.
The organic EL device in Comparative 2 was produced in the same manner as in Example 1 except that a single emitting layer having a film thickness of 10 nm was formed in place of the first and second emitting layers.
The organic EL device in Comparative 3 was produced in the same manner as in Example 2 except that a single emitting layer having a film thickness of 15 nm was formed in place of the first and second emitting layers.
The organic EL device in Comparative 4 was produced in the same manner as in Comparative 1 except that a single emitting layer having a film thickness of 25 nm was formed in place of the first and second emitting layers.
The organic EL devices produced in Examples 1 to 3 and Comparatives 1 to 4 were evaluated as follows. Tables 1 and 2 show the results.
For the organic EL devices produced in Examples 1 to 3 and Comparative 1, voltage was applied to the organic EL devices such that a current density became 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-1000 (produced by Konica Minolta, Inc.). A current efficiency (unit: cd/A) was calculated from the obtained spectral radiance spectrum.
Using a formula (Numerical Formula 30) below, the current efficiency (cd/A) of each Example was calculated as a “current efficiency (relative value: %)” relative to the current efficiency (cd/A) of Comparative 1 defined as 100.
For the organic EL devices produced in Comparatives 2 to 4, voltage was applied to the organic EL devices such that a current density became 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). The external quantum efficiency EQE (unit: %) was calculated based on the obtained spectral radiance spectra, assuming that the spectra was provided under a Lambertian radiation.
Using a formula (Numerical Formula 40) below, the EQE (%) of each Example was calculated as an “EQE (relative value: %)” relative to the EQE (%) of Comparative 4 defined as 100.
Maximum Peak Wavelength λp of Light Emitted from Device When Being Driven Voltage was applied to the organic EL device so that a current density of the organic EL device was 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). A maximum peak wavelength λp (unit: nm) was calculated from the obtained spectral radiance spectrum.
In Table 1, Ratio (Total film thickness of emitting layers/Distance from cathode to second emitting layer) refers to the ratio (the total of the film thicknesses of the first and second emitting layers/the distance from the cathode to the second emitting layer).
In Table 2, Ratio (Film thickness of emitting layer/Distance from cathode to emitting layer) refers to the ratio (the film thickness of the emitting layer/the distance from the cathode to the second emitting layer).
For Examples 1 to 3 and Comparative 1 in which the emitting layers were layered, Examples 1 to 3 where the total film thickness was 20 nm or less exhibited higher EQE than Comparative 1 where the total film thickness was 25 nm, as shown in Table 1.
For Comparatives 2 to 4 in which a single emitting layer was provided, Comparatives 2 and 3 where the film thickness was 20 nm or less exhibited lower EQE than Comparative 4 where the film thickness was 25 nm, as shown in Table 2.
Examples 1 and 2 where the emitting layers were layered and the respective total film thicknesses were 10 nm and 15 nm exhibited higher EQE than Comparatives 2 and 3 where the respective emitting layers were replaced by the single emitting layer.
In the organic EL device with layered emitting layers, the function of the Singlet emitting region is separated from that of the TTF emitting region. This expands an emission distribution and light-extraction efficiency may decrease in view of optical interference. However, since the film thickness of emitting layers was reduced in the organic EL devices including layered emitting layers in Examples 1 to 3, the emission distribution was narrowed in a state where the function of the Singlet emitting region was separated from that of the TTF emitting region. EQE was thus improvable in Examples 1 to 3. On the other hand, in the organic EL devices including a single emitting layer in Comparatives 2 to 4, the function of the Singlet emitting region was not separated from that of the TTF emitting region. EQE was thus not improved even when the thickness of the emitting layer was small.
According to the organic EL devices in Examples 1 to 3, luminous efficiency is improvable by including the first emitting layer and the second emitting layer that contain host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and making the total of the film thickness of the first emitting layer and the film thickness of the second emitting layer 20 nm or less.
According to the organic EL devices in Examples 1 to 3, EQE is improvable by including the first emitting layer and the second emitting layer that contain host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and making the ratio in Table 1 (Total film thickness of emitting layers/Distance from cathode to second emitting layer) 0.8 or less.
Structures of compounds as the first host material and the second host material in Examples 1A to 3A are shown below.
Structures of other compounds used for producing organic EL devices in Examples 1A to 3A and Comparatives 1A to 2A are shown below.
A glass substrate (size: 25 mm×75 mm×1.1 mm thick, produced by Geomatec Co., Ltd.) having an ITO transparent electrode (anode) was ultrasonic-cleaned in isopropyl alcohol for five minutes, and then UV-ozone-cleaned for 30 minutes. The film thickness of the ITO transparent electrode was 130 nm.
After the glass substrate having the transparent electrode line was cleaned, the glass substrate was mounted on a substrate holder of a vacuum deposition apparatus. Firstly, the compound HT1 and the compound HA1 were co-deposited on a surface of the glass substrate where the transparent electrode line was provided in a manner to cover the transparent electrode, thereby forming a 10-nm-thick hole injecting layer (HI). The ratios of the compound HT1 and the compound HA1 in the hole injecting layer were 97 mass % and 3 mass %, respectively.
After forming the hole injecting layer, the compound HT1 was vapor-deposited to form an 85-nm-thick first hole transporting layer (HT).
The compound EB1 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second hole transporting layer (also referred to as an electron blocking layer) (EBL).
A compound BH1-1 (first host material (BH)) and a compound BD1 (first emitting compound (BD)) were co-deposited on the second hole transporting layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick first emitting layer.
A compound BH2-1A (intermediate layer material) was vapor-deposited on the first emitting layer to form a 5-nm-thick intermediate layer (non-doped layer).
The compound BH2-1A (second host material (BH)) and the compound BD1 (second emitting compound (BD)) were co-deposited on the intermediate layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 10-nm-thick second emitting layer.
The compound HB1 was vapor-deposited on the second emitting layer to form a 5-nm-thick first electron transporting layer (also referred to as a hole blocking layer) (HBL).
The compound ET1 and the compound Liq were co-deposited on the first electron transporting layer (HBL) to form a 25-nm-thick second electron transporting layer (ET). The ratios of the compound ET1 and the compound Liq in the second electron transporting layer (ET) were both 50 mass %. Liq is an abbreviation of (8-quinolinolato)lithium ((8-Quinolinolato)lithium).
Liq was vapor-deposited on the second electron transporting layer to form a 1-nm-thick electron injecting layer.
Metal Al was vapor-deposited on the electron injecting layer to form an 80-nm-thick cathode.
A device arrangement of the organic EL device in Example 1A is roughly shown as follows.
Numerals in parentheses represent a film thickness (unit: nm).
The numerals (97%:3%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound HT1 and the compound HA1 in the hole injecting layer. The numerals (98%:2%) represented by percentage in the same parentheses indicate a ratio (mass %) between the host material (compound BH1-1 or BH2-1A) and the emitting compound (compound BD1) in the first emitting layer or the second emitting layer. The numerals (50%:50%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound ET1 and the compound Liq in the electron transporting layer (ET). Similar notations apply to the description below.
The organic EL device in Comparative 1A was produced in the same manner as in Example 1A except that no intermediate layer was formed and that the film thickness of the second emitting layer was changed to 15 nm.
The organic EL devices produced in Examples 1A and Comparative 1A were evaluated as follows. Table 3 shows the evaluation results.
Voltage was applied to the organic EL device such that a current density was 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). The external quantum efficiency EQE (unit: %) was calculated based on the obtained spectral radiance spectra, assuming that the spectra was provided under a Lambertian radiation.
Maximum Peak Wavelength λp of Light Emitted from Device when being Driven
Voltage was applied to the organic EL device so that a current density of the organic EL device was 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.). A maximum peak wavelength λp (unit: nm) was calculated from the obtained spectral radiance spectrum.
The organic EL device in Example 1A, which included the first emitting layer and the second emitting layer containing host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and included the non-doped layer (intermediate layer) between the first emitting layer and the second emitting layer, exhibited higher EQE than the organic EL device in Comparative 1A where the non-doped layer was not provided.
A glass substrate (size: 25 mm×75 mm×1.1 mm thick, produced by Geomatec Co., Ltd.) having an ITO transparent electrode (anode) was ultrasonic-cleaned in isopropyl alcohol for five minutes, and then UV-ozone-cleaned for 30 minutes. The film thickness of the ITO transparent electrode was 130 nm.
After the glass substrate having the transparent electrode line was cleaned, the glass substrate was mounted on a substrate holder of a vacuum deposition apparatus. Firstly, a compound HT2 and the compound HA1 were co-deposited on a surface of the glass substrate where the transparent electrode line was provided in a manner to cover the transparent electrode, thereby forming a 10-nm-thick hole injecting layer (HI). The ratios of the compound HT2 and the compound HA1 in the hole injecting layer were 97 mass % and 3 mass %, respectively.
After forming the hole injecting layer, the compound HT2 was vapor-deposited to form an 85-nm-thick first hole transporting layer (HT).
A compound EB2 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second hole transporting layer (also referred to as an electron blocking layer) (EBL).
The compound BH1-1 (first host material (BH)) and a compound BD2 (first emitting compound (BD)) were co-deposited on the second hole transporting layer such that the ratio of the compound BD2 accounted for 2 mass %, thereby forming a 5-nm-thick first emitting layer.
A compound BH2-2 (intermediate layer material) was vapor-deposited on the first emitting layer to form a 5-nm-thick intermediate layer (non-doped layer).
The compound BH2-2 (second host material (BH)) and the compound BD1 (second emitting compound (BD)) were co-deposited on the intermediate layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 10-nm-thick second emitting layer.
The compound HB2 was vapor-deposited on the second emitting layer to form a 5-nm-thick first electron transporting layer (also referred to as a hole blocking layer) (HBL).
A compound ET2 and the compound Liq were co-deposited on the first electron transporting layer (HBL) to form a 25-nm-thick second electron transporting layer (ET). The ratios of the compound ET2 and the compound Liq in the second electron transporting layer (ET) were both 50 mass %.
Yb was vapor-deposited on the second electron transporting layer to form a 1-nm-thick electron injecting layer.
Metal Al was vapor-deposited on the electron injecting layer to form an 80-nm-thick cathode.
A device arrangement of the organic EL device in Example 2A is roughly shown as follows.
Numerals in parentheses represent a film thickness (unit: nm).
The numerals (97%:3%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound HT2 and the compound HA1 in the hole injecting layer. The numerals (98%:2%) represented by percentage in the same parentheses indicate a ratio (mass %) between the host material (compound BH1-1 or BH2-2) and the emitting compound (compound BD2 or BD1) in the first emitting layer or the second emitting layer. The numerals (50%:50%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound ET2 and the compound Liq in the electron transporting layer (ET).
The organic EL device in Comparative 2A was produced in the same manner as in Example 2A except that no intermediate layer was formed and that the film thickness of the second emitting layer was changed to 15 nm.
The organic EL devices produced in Examples 2A and Comparative 2A were evaluated in the same manner as in Example 1A. Table 4 shows the evaluation results.
The organic EL device in Example 2A, which included the first emitting layer and the second emitting layer containing host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and included the non-doped layer (intermediate layer) between the first emitting layer and the second emitting layer, exhibited higher EQE than the organic EL device in Comparative 2A where the non-doped layer was not provided.
A glass substrate (size: 25 mm×75 mm×1.1 mm thick, produced by Geomatec Co., Ltd.) having an ITO transparent electrode (anode) was ultrasonic-cleaned in isopropyl alcohol for five minutes, and then UV-ozone-cleaned for 30 minutes. The film thickness of the ITO transparent electrode was 130 nm.
After the glass substrate having the transparent electrode line was cleaned, the glass substrate was mounted on a substrate holder of a vacuum deposition apparatus. Firstly, the compound HT1 and the compound HA1 were co-deposited on a surface of the glass substrate where the transparent electrode line was provided in a manner to cover the transparent electrode, thereby forming a 10-nm-thick hole injecting layer (HI). The ratios of the compound HT1 and the compound HA1 in the hole injecting layer were 97 mass % and 3 mass %, respectively.
After forming the hole injecting layer, the compound HT1 was vapor-deposited to form an 85-nm-thick first hole transporting layer (HT).
The compound EB1 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second hole transporting layer (also referred to as an electron blocking layer) (EBL).
The compound BH1-1 (first host material (BH)) and the compound BD1 (first emitting compound (BD)) were co-deposited on the second hole transporting layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick first emitting layer.
The compound BH2-1A (second host material (BH)) and the compound BD1 (second emitting compound (BD)) were co-deposited on the first emitting layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick second emitting layer (anode-side second emitting layer).
The compound BH2-1A (intermediate layer material) was vapor-deposited on the anode-side second emitting layer to form a 5-nm-thick intermediate layer (non-doped layer).
The compound BH2-1A (second host material (BH)) and the compound BD1 (second emitting compound (BD)) were co-deposited on the intermediate layer such that the ratio of the compound BD1 accounted for 2 mass %, thereby forming a 5-nm-thick second emitting layer (cathode-side second emitting layer).
The compound HB1 was vapor-deposited on the cathode-side second emitting layer to form a 5-nm-thick first electron transporting layer (also referred to as a hole blocking layer) (HBL).
The compound ET1 and the compound Liq were co-deposited on the first electron transporting layer (HBL) to form a 25-nm-thick second electron transporting layer (ET). The ratios of the compound ET1 and the compound Liq in the second electron transporting layer (ET) were both 50 mass %.
Liq was vapor-deposited on the second electron transporting layer to form a 1-nm-thick electron injecting layer.
Metal Al was vapor-deposited on the electron injecting layer to form an 80-nm-thick cathode.
A device arrangement of the organic EL device in Example 3A is roughly shown as follows.
Numerals in parentheses represent a film thickness (unit: nm).
The organic EL device produced in Example 3A was evaluated in the same manner as in Example 1A. Table 5 shows the evaluation results.
The organic EL device in Example 3A, which included one or more first emitting layers and one or more second emitting layers that contained host materials satisfying the relationship of the numerical formula (Numerical Formula 1) and included the non-doped layer (intermediate layer) between a pair of emitting layers (anode-side second emitting layer and cathode-side second emitting layer), exhibited a high EQE value.
A measurement target compound was dissolved in EPA (diethylether isopentane:ethanol=5:5:2 in volume ratio) at a concentration of 10 μmol/L, and the obtained solution was put in a quartz cell to provide a measurement sample. A phosphorescence spectrum (ordinate axis: phosphorescent luminous intensity, abscissa axis: wavelength) of the measurement sample was measured at a low temperature (77K). A tangent was drawn to the rise of the phosphorescence spectrum close to the short-wavelength region. An energy amount was calculated by a conversion equation (F1) below on a basis of a wavelength value A. [nm] at an intersection of the tangent and the abscissa axis. The calculated energy amount was defined as triplet energy T1. It should be noted that the triplet energy T1 may have an error of about plus or minus 0.02 eV depending on measurement conditions.
The tangent to the rise of the phosphorescence spectrum close to the short-wavelength region is drawn as follows. While moving on a curve of the phosphorescence spectrum from the short-wavelength region to the local maximum value closest to the short-wavelength region among the local maximum values of the phosphorescence spectrum, a tangent is checked at each point on the curve toward the long-wavelength of the phosphorescence spectrum. An inclination of the tangent is increased along the rise of the curve (i.e., a value of the ordinate axis is increased). A tangent drawn at a point of the local maximum inclination (i.e., a tangent at an inflection point) is defined as the tangent to the rise of the phosphorescence spectrum close to the short-wavelength region.
A local maximum point where a peak intensity is 15% or less of the maximum peak intensity of the spectrum is not counted as the above-mentioned local maximum peak intensity closest to the short-wavelength region. The tangent drawn at a point that is closest to the local maximum peak intensity closest to the short-wavelength region and where the inclination of the curve is the local maximum is defined as a tangent to the rise of the phosphorescence spectrum close to the short-wavelength region.
For phosphorescence measurement, a spectrophotofluorometer body F-4500 produced by Hitachi High-Technologies Corporation was used.
A toluene solution of a measurement target compound at a concentration of 10 μmol/L was prepared and put in a quartz cell. An absorption spectrum (ordinate axis: absorption intensity, abscissa axis: wavelength) of the thus-obtained sample was measured at a normal temperature (300K). A tangent was drawn to the fall of the absorption spectrum close to the long-wavelength region, and a wavelength value λedge (nm) at an intersection of the tangent and the abscissa axis was assigned to a conversion equation (F2) below to calculate singlet energy.
A spectrophotometer (U3310 produced by Hitachi, Ltd.) was used for measuring absorption spectrum.
The tangent to the fall of the absorption spectrum close to the long-wavelength region is drawn as follows. While moving on a curve of the absorption spectrum from the local maximum value closest to the long-wavelength region, among the local maximum values of the absorption spectrum, in a long-wavelength direction, a tangent at each point on the curve is checked. An inclination of the tangent is decreased and increased in a repeated manner as the curve falls (i.e., a value of the ordinate axis is decreased). A tangent drawn at a point where the inclination of the curve is the local minimum closest to the long-wavelength region (except when absorbance is 0.1 or less) is defined as the tangent to the fall of the absorption spectrum close to the long-wavelength region.
The local maximum absorbance of 0.2 or less is not counted as the above-mentioned local maximum absorbance closest to the long-wavelength region.
Tables show measurement values of the singlet energy S1 and the triplet energy T1 of the compounds BH1-1, BH2-1, BH2-1A, and BH2-2.
The singlet energy S1 of the compound BD1 was 2.71 eV.
The triplet energy T1 of the compound BD1 was 2.64 eV.
The singlet energy S1 of the compound BD2 was 2.73 eV.
The triplet energy T1 of the compound BD2 was 2.29 eV.
Stokes Shift (SS) (nm) A measurement target compound was dissolved in toluene at a concentration of 2.0×10−5 mol/L to prepare a measurement sample. The measurement sample was put into a quartz cell and was irradiated with continuous light falling within an ultraviolet-to-visible region at a room temperature (300K) to measure an absorption spectrum (ordinate axis: absorbance, abscissa axis: wavelength). A spectrophotometer U-3900/3900H produced by Hitachi High-Tech Science Corporation was used for the absorption spectrum measurement. Further, a measurement target compound was dissolved in toluene at a concentration of 4.9×10−6 mol/L to prepare a measurement sample. The measurement sample was put into a quartz cell and was irradiated with excited light at a room temperature (300K) to measure fluorescence spectrum (ordinate axis: fluorescence intensity, abscissa axis: wavelength). A spectrophotofluorometer F-7000 produced by Hitachi High-Tech Science Corporation was used for the fluorescence spectrum measurement.
A difference between an absorption local-maximum wavelength and a fluorescence local-maximum wavelength was calculated from the absorption spectrum and the fluorescence spectrum to obtain a Stokes shift (SS). A unit of the Stokes shift (SS) was denoted by nm.
A Stokes shift (SS) of the compound BD1 was 14 nm.
The compound BD1 was dissolved in toluene at a concentration of 4.9×10−6 mol/L to prepare a toluene solution of the compound BD1. Similar to the above, a toluene solution of the compound BD2 was prepared.
Using a fluorescence spectrometer (spectrophotofluorometer F-7000 produced by Hitachi High-Tech Science Corporation), the toluene solution of the compound BD1 was excited at 390 nm, where a maximum peak wavelength was measured. From the fluorescence spectrum measured, a full width at half maximum FWHM (unit: nm) of the maximum peak of the compound BD1 was measured.
The maximum peak wavelength of the compound BD1 was 455 nm.
The full width at half maximum FWHM of the maximum peak of the compound BD1 was 23 nm.
The maximum peak wavelength of the compound BD2 was 453 nm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-200042 | Dec 2020 | JP | national |
| 2020-202096 | Dec 2020 | JP | national |
The present application claims priority under 35 U.S.C. § 371 to International Patent Application No. PCT/JP2021/044016, filed Dec. 1, 2021, which claims priority to and the benefit of Japanese Patent Application Nos. 2020-200042, filed on Dec. 2, 2020, and 2020-202096, filed on Dec. 4, 2020. The contents of these applications are hereby incorporated by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/044016 | 12/1/2021 | WO |
