Patent Application
20240130223
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 and 2, various studies have been made on layering a plurality of emitting layers in order to enhance the performance of an organic EL device. In addition, in order to enhance the performance of the organic EL device, Patent Literature 3 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 organic electroluminescence device described in Patent Literature 1 includes a plurality of emitting layers between an anode and a cathode, in which the emitting layers are each formed of a mixture of a plurality of materials and contain main components different from each other, a combination of adjacent ones of the emitting layers is such that a value obtained by dividing electron mobility of the emitting layer located close to the anode by hole mobility thereof is larger than a value obtained by dividing electron mobility of the emitting layer located close to the cathode by hole mobility thereof, and, in the adjacent ones of the emitting layers, the electron mobility of the emitting layer located close to the anode is larger than the electron mobility of the emitting layer located close to the cathode.
However, reducing the number of the organic compound layer (i.e., economizing the organic compound layer) forming the hole transporting zone provided between the anode and the emitting layer as shown in the organic electroluminescence device of Patent Literature 1 may deteriorate the luminous efficiency. Patent Literature 1, however, does not recognize a decrease in a hole supply amount.
An object of the invention is to provide an organic electroluminescence device capable of decreasing the number of an organic compound layer forming a hole transporting zone while inhibiting a decrease in a device performance improved by layering a plurality of emitting layers, and an electronic device including the organic electroluminescence device.
According to an aspect of the invention, there is provided an organic electroluminescence device according to an aspect of the invention includes: an anode; a cathode; an emitting layer provided between the anode and the cathode; and a hole transporting zone provided between the anode and the emitting layer, in which the hole transporting zone includes at least two organic compound layers, one of which is a first organic compound layer provided close to the anode, the first organic compound layer includes a first organic material and a second organic material, the first organic material and the second organic material are mutually different, a content of the first organic material in the first organic compound layer is less than 10 mass %, the emitting layer includes a first emitting layer and a second emitting layer, the first emitting layer includes a first host material, the second emitting layer includes a second host material, the first host material and the second host material are mutually different, the first emitting layer at least includes 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, 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,
T
1(H1)>T1(H2) (Numerical Formula 1).
According to another aspect of the invention, there is provided an electronic device including the organic electroluminescence device according to the above aspect of the invention.
According to the above aspects of the invention, there can be provided an organic electroluminescence device capable of decreasing the number of an organic compound layer forming a hole transporting zone while inhibiting a decrease in a device performance improved by layering a plurality of emitting layers, and an electronic device including the organic electroluminescence device.
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. For instance, a 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 G11B). (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.
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, benzanthryl group, phenanthryl group, benzophenanthryl group, phenalenyl group, pyrenyl group, chrysenyl group, benzochrysenyl group, triphenylenyl group, benzotriphenylenyl group, tetracenyl group, pentacenyl group, fluorenyl group, 9,9′-spirobifluorenyl group, benzofluorenyl group, dibenzofluorenyl group, fluoranthenyl group, benzofluoranthenyl group, perylenyl group, and monovalent aryl group derived by removing one hydrogen atom from cyclic structures represented by formulae (TEMP-1) to (TEMP-15) below.
an o-tolyl group, m-tolyl group, p-tolyl group, para-xylyl group, meta-xylyl group, ortho-xylyl group, para-isopropylphenyl group, meta-isopropylphenyl group, ortho-isopropylphenyl group, para-t-butylphenyl group, meta-t-butylphenyl group, ortho-t-butylphenyl group, 3,4,5-trimethyl phenyl group, 9,9-dimethylfluorenyl group, 9,9-diphenylfluorenyl group, 9,9-bis(4-methyl phenyl)fluorenyl group, 9,9-bis(4-isopropylphenyl)fluorenyl group, 9,9-bis(4-t-butylphenyl)fluorenyl group, cyanophenyl group, triphenylsilylphenyl group, trim ethylsilylphenyl group, phenylnaphthyl group, naphthylphenyl group, and group derived by substituting at least one hydrogen atom of a monovalent group derived from one of the cyclic structures represented by the formulae (TEMP-1) to (TEMP-15) with a substituent.
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.
a pyrrolyl group, imidazolyl group, pyrazolyl group, triazolyl group, tetrazolyl group, oxazolyl group, isoxazolyl group, oxadiazolyl group, thiazolyl group, isothiazolyl group, thiadiazolyl group, pyridyl group, pyridazynyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, indolyl group, isoindolyl group, indolizinyl group, quinolizinyl group, quinolyl group, isoquinolyl group, cinnolyl group, phthalazinyl group, quinazolinyl group, quinoxalinyl group, benzimidazolyl group, indazolyl group, phenanthrolinyl group, phenanthridinyl group, acridinyl group, phenazinyl group, carbazolyl group, benzocarbazolyl group, morpholino group, phenoxazinyl group, phenothiazinyl group, azacarbazolyl group, and diazacarbazolyl group.
a furyl group, oxazolyl group, isoxazolyl group, oxadiazolyl group, xanthenyl group, benzofuranyl group, isobenzofuranyl group, dibenzofuranyl group, naphthobenzofuranyl group, benzoxazolyl group, benzisoxazolyl group, phenoxazinyl group, morpholino group, dinaphthofuranyl group, azadibenzofuranyl group, diazadibenzofuranyl group, azanaphthobenzofuranyl group, and diazanaphthobenzofuranyl group.
a thienyl group, thiazolyl group, isothiazolyl group, thiadiazolyl group, benzothiophenyl group (benzothienyl group), isobenzothiophenyl group (isobenzothienyl group), dibenzothiophenyl group (dibenzothienyl group), naphthobenzothiophenyl group (nahthobenzothienyl group), benzothiazolyl group, benzisothiazolyl group, phenothiazinyl group, dinaphthothiophenyl group (dinaphthothienyl group), azadibenzothiophenyl group (azadibenzothienyl group), diazadibenzothiophenyl group (diazadibenzothienyl group), azanaphthobenzothiophenyl group (azanaphthobenzothienyl group), and diazanaphthobenzothiophenyl group (diazanaphthobenzothienyl group).
Monovalent Heterocyclic Groups Derived by Removing One Hydrogen Atom from Cyclic Structures Represented by Formulae (TEMP-16) to (TEMP-33) (Specific Example Group G2A4):
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.
a (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.
a phenyldibenzofuranyl group, methyldibenzofuranyl group, t-butyldibenzofuranyl group, and monovalent residue of spiro[9H-xanthene-9,9′-[9H]fluorene].
a phenyldibenzothiophenyl group, methyldibenzothiophenyl group, t-butyldibenzothiophenyl group, and monovalent residue of spiro[9H-thioxanthene-9,9′-[9H]fluorene].
Groups Obtained by Substituting at Least One Hydrogen Atom of Monovalent Heterocyclic Group Derived from Cyclic Structures Represented by Formulae (TEMP-16) to (TEMP-33) with Substituent (Specific Example Group G2B4):
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.
a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, and t-butyl group.
a heptafluoropropyl group (including isomer thereof), pentafluoroethyl group, 2,2,2-trifluoroethyl group, and trifluoromethyl group.
Specific examples (specific example group G4) of the “substituted or unsubstituted alkenyl group” mentioned herein include unsubstituted alkenyl groups (specific example group G4A) and substituted alkenyl groups (specific example group G4B). (Herein, an unsubstituted alkenyl group refers to an “unsubstituted alkenyl group” in a “substituted or unsubstituted alkenyl group,” and a substituted alkenyl group refers to a “substituted alkenyl group” in a “substituted or unsubstituted alkenyl group.”) A simply termed “alkenyl group” herein includes both of an “unsubstituted alkenyl group” and a “substituted alkenyl group”.
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.
a vinyl group, allyl group, 1-butenyl group, 2-butenyl group, and 3-butenyl group.
a 1,3-butanedienyl group, 1-methylvinyl group, 1-methylallyl group, 1,1-dimethylallyl group, 2-methylallyl group, and 1,2-dimethylallyl group.
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.
an ethynyl 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.
a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, 1-adamantyl group, 2-adamantyl group, 1-norbornyl group, and 2-norbornyl group.
a 4-methylcyclohexyl group.
Group Represented by —Si(R901)(R902)(R903)
Specific examples (specific example group G7) of the group represented herein by —Si(R901)(R902)(R903) include:
where:
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. A 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, α-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, diphenyltriazinyl 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 heterocyclic ring 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 bonding 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 Q10 may be mutually bonded through a single bond to form a ring.
In the formulae (TEMP-53) to (TEMP-62), * represents a bonding 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 bonded 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 bonded 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 heterocyclic ring. The “saturated ring” represents an aliphatic hydrocarbon ring or a non-aromatic heterocyclic ring.
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 heterocyclic ring 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 heterocyclic ring.
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 substituents 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: an anode; a cathode; an emitting layer provided between the anode and the cathode; and a hole transporting zone provided between the anode and the emitting layer, in which the hole transporting zone includes at least two organic compound layers, one of which is a first organic compound layer provided close to the anode, the first organic compound layer includes a first organic material and a second organic material, the first organic material and the second organic material are mutually different, a content of the first organic material in the first organic compound layer is less than 10 mass %, the emitting layer includes a first emitting layer and a second emitting layer, the first emitting layer includes a first host material, the second emitting layer includes a second host material, the first host material and the second host material are mutually different, the first emitting layer at least includes a first emitting compound that emits light having a maximum peak wavelength of 500 nm or less, the second emitting layer at least includes 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, 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.
T
1(H1)>T1(H2) (Numerical Formula 1)
Triplet-Triplet-Annihilation (occasionally referred to as TTA) has been known as the technology for improving a luminous efficiency of the organic EL device. 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 3.
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.
3
A*+
3
A*→(4/9)1A+(1/9)1A*+(13/9)3A*
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%.
According to the organic EL device according to the first exemplary embodiment, it is considered that triplet excitons generated by recombination of holes and electrons in the first emitting layer and existing on an interface between the first emitting layer and organic compound 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 compound 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.
The organic electroluminescence device according to the first exemplary embodiment includes at least two emitting layers (i.e., the first and second emitting layers) satisfying a predetermined relationship, in which 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).
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.
The organic electroluminescence device thus 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 produces a difference in triplet energy 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.
Since the organic EL device according to the exemplary embodiment includes the first emitting layer and the second emitting layer satisfying the numerical formula (Numerical Formula 1), the luminous efficiency of the organic EL device is improvable.
Reducing the number of the organic compound layer (i.e., economizing the organic compound layer) forming the hole transporting zone provided between the anode and the emitting layer as shown in the organic electroluminescence device of Patent Literature 1 may deteriorate the luminous efficiency. The organic EL device according to the exemplary embodiment can prevent a deterioration in the device performance (e.g., luminous efficiency) even with the decreased number of the organic compound layer forming the hole transporting zone. Moreover, if a doping amount of a P-type dopant is reduced in the first organic compound layer provided close to the anode, of a plurality of organic compound layers contained in the hole transporting zone, in order to decrease costs for the organic EL device, HOMO of the first organic compound layer may become shallow and a supply amount of holes to the emitting layer may be reduced, thereby lowering the luminous efficiency. In this regard, the organic EL device according to the exemplary embodiment includes a laminate of the first emitting layer and the second emitting layer although the content of the first organic material in the first organic compound layer is less than 10 mass %. This laminate prevents a decrease in the supply amount of holes to the first emitting layer to shift an emitting position from a side of the first emitting layer close to the hole transporting zone to between the first emitting layer and the second emitting layer. The luminous efficiency is thus inhibited from decreasing to prolong a lifetime.
In the organic EL device according to the exemplary embodiment, the content of the first organic material in the first organic compound layer is preferably less than 6 mass %, more preferably less than 5 mass %, and still more preferably 3 mass % or less.
In the organic EL device according to the exemplary embodiment, the content of the first organic material in the first organic compound layer is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and still more preferably 1 mass % or more.
In the organic EL device according to the exemplary embodiment, the content of the second organic material in the first organic compound layer is preferably more than 90 mass %, more preferably more than 94 mass %, and still more preferably more than 95 mass %.
In the organic EL device according to the exemplary embodiment, of the organic compound layers contained in the hole transporting zone, each organic compound layer provided closer to the cathode than the first organic compound layer preferably includes a compound having a different molecular structure from those of the first and second organic materials.
In the organic EL device according to the exemplary embodiment, the hole transporting zone preferably includes the second organic compound layer provided closer to the cathode than the first organic compound layer.
The second organic compound layer is preferably in direct contact with the emitting layer.
The second organic compound layer preferably includes a third organic material having a different molecular structure from those of the first and second organic materials.
In the organic EL device according to the exemplary embodiment, the hole transporting zone may include the third organic compound layer provided closer to the cathode than the second organic compound layer. The third organic compound layer preferably includes at least one fourth organic material having a different molecular structure from that of the third organic material. The fourth organic material is preferably a monoamine compound or a diamine compound. Specific examples of the fourth organic material are, for instance, the compounds of the specific examples of the second organic material or the specific examples of the third organic material. However, the invention is by no means limited to the specific examples.
In the organic EL device according to the exemplary embodiment, the number of the organic compound layer provided between the anode and one of the first emitting layer and the second emitting layer, which is provided closer to the anode, is preferably two.
In the organic EL device according to the exemplary embodiment, the hole transporting zone preferably includes two organic compound layers, that is, the first organic compound layer and the second organic compound layer.
In the organic EL device according to the exemplary embodiment, the first organic compound layer and the second organic compound layer are also preferably in direct contact with each other.
In the organic EL device according to the exemplary embodiment, the first organic compound layer and the anode are also preferably in direct contact with each other.
In the organic EL device according to the exemplary embodiment, it is also preferable that the hole transporting zone includes the first organic compound layer and the second organic compound layer, the second organic compound layer is in direct contact with the first emitting layer or the second emitting layer, and the first organic compound layer is in direct contact with the anode.
In the organic EL device according to the exemplary embodiment, it is also preferable that the hole transporting zone includes at least one organic layer of the hole injecting layer, hole transporting layer, or electron blocking layer.
The hole injecting layer is a layer containing a highly hole-injectable substance. Examples of the highly hole-injectable substance 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 as 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 highly hole-injectable substance. 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) are also usable.
In the organic EL device according to the exemplary embodiment, the first organic compound layer is also preferably a hole injecting layer. In this case, it is also preferable that the first organic material and the second organic material are each independently selected from the group consisting of the highly hole-injectable substance described above. The first organic material is also preferably, for instance, a compound including at least one of a first cyclic structure represented by a formula (P11) below or a second cyclic structure represented by a formula (P12) below. The second organic material is also preferably, for instance, a compound represented by a formula (21) below or a compound represented by a formula (22) below.
In the organic EL device according to the exemplary embodiment, the second organic compound layer is also preferably an electron blocking layer. The electron blocking layer is preferably in direct contact with a side of the emitting layer close to the anode. The electron blocking layer is, for instance, a layer for transporting holes and blocking electrons from reaching a layer close to the anode (e.g., the hole transporting layer or the hole injecting layer) beyond the electron blocking layer. Alternatively, the electron blocking layer may be a layer for blocking excitation energy from leaking out from the emitting layer toward neighboring layer(s). In this case, the electron blocking layer blocks excitons generated in the emitting layer from being transferred to a layer(s) (e.g., the hole transporting layer and the hole injecting layer) closer to the anode beyond the electron blocking layer. In a case where the hole transporting zone includes the hole transporting layer, the electron blocking layer is preferably interposed between the emitting layer and the hole transporting layer.
In the organic EL device according to the exemplary embodiment, in a case where the hole transporting zone includes the hole transporting layer, an aromatic amine derivative, carbazole derivative, anthracene derivative and the like are usable for the hole transporting layer. Specifically, an aromatic amine derivative such as 4-phenyl-4′-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BAFLP) is usable. The aromatic amine derivative used for the hole transporting layer is preferably a monoamine compound.
A highly hole-transportable substance used for the hole transporting layer is, for instance, a substance having a hole mobility of 10−6 cm2/(V·s) or more. However, in addition to the above substances, any substance exhibiting a higher hole transportability than an electron transportability may be used as the substance for the hole transporting layer. It should be noted that the layer including the highly hole-transportable substance may be not only a single layer but also a laminate of two or more layers formed of the above substance.
In the organic EL device according to the exemplary embodiment, a film thickness of the hole transporting zone is preferably 120 nm or less, more preferably 110 nm or less, and still more preferably 100 nm or less. In the organic EL device according to the exemplary embodiment, the film thickness of the hole transporting zone may be 60 nm or less or 50 nm or less.
In the organic EL device according to the exemplary embodiment, in a case where the hole transporting zone includes the first organic compound layer and the second organic compound layer, a film thickness of the first organic compound layer is preferably thinner than a film thickness of the second organic compound layer.
In the organic EL device of the exemplary embodiment, the film thickness of the first organic compound layer is preferably in a range from 5 nm to 15 nm, more preferably from 5 nm to 10 nm.
In the organic EL device according to the exemplary embodiment, the film thickness of the second organic compound layer is preferably in a range from 10 nm to 150 nm.
In the organic EL device according to the exemplary embodiment, a refractive index NM1 of a constituent material contained in the first organic compound layer is preferably larger than a refractive index NM2 of a constituent material contained in the second organic compound layer. A light extraction efficiency of the organic EL device is improved by the refractive index NM1 being larger than the refractive index NM2.
The refractive index NM1 of the constituent material contained in the first organic compound layer corresponds to a refractive index of a mixture of compounds (at least the first organic compound layer and the second organic material) contained in the first organic compound layer. In a case where the second organic compound layer includes a single compound, the refractive index NM2 of the constituent material contained in the second organic compound layer corresponds to a refractive index of the single compound. In a case where the second organic compound layer includes a plurality of compounds, the refractive index NM2 corresponds to a refractive index of a mixture of the plurality of compounds. The refractive index is measurable according to a measurement method described in Examples below. Herein, a value of the refractive index at 2.7 eV in the substrate parallel direction (Ordinary direction), from among the values measured by the variable-angle spectroscopic ellipsometry measurement, is defined as a refractive index of a measurement target material.
In the organic EL device according to the exemplary embodiment, the difference (NM1−NM2) between the refractive index NM1 of the constituent material contained in the first organic compound layer and the refractive index NM2 of the constituent material contained in the second organic compound layer preferably satisfies a relationship of a numerical formula (Numerical Formula N1) below.
NM
1
−NM
2≥0.03 (Numerical Formula N1)
A light extraction efficiency of the organic EL device is improved by satisfying the relationship of the numerical formula (Numerical Formula N1).
In the organic EL device according to the exemplary embodiment, the difference (NM1−NM2) between the refractive index NM1 of the constituent material contained in the first organic compound layer and the refractive index NM2 of the constituent material contained in the second organic compound layer preferably satisfies a relationship of a numerical formula (Numerical Formula N2) below.
NM
1
−NM
2≥0.04 (Numerical Formula N2)
In the organic EL device according to the exemplary embodiment, the difference (NM1−NM2) between the refractive index NM1 of the constituent material contained in the first organic compound layer and the refractive index NM2 of the constituent material contained in the second organic compound layer may satisfy a relationship of a numerical formula (Numerical Formula N3) below or a numerical formula (Numerical Formula N4) below.
NM
1
−NM
2≥0.05 (Numerical Formula N3)
NM
1
−NM
2≥0.10 (Numerical Formula N4)
In the organic EL device according to the exemplary embodiment, it is also preferable that the refractive index NM1 is 1.80 or more and the refractive index NM2 is less than 1.80.
In the organic EL device according to the exemplary embodiment, a refractive index of a compound contained in the second organic compound layer is preferably 1.89 or less.
In the organic EL device according to the exemplary embodiment, a refractive index of the third organic material is preferably 1.89 or less.
In the organic EL device according to the exemplary embodiment, the refractive index of a compound contained in the first organic compound layer is preferably 1.94 or more.
In the organic EL device according to the exemplary embodiment, a refractive index of the second organic material is preferably 1.94 or more.
In the organic EL device according to the exemplary embodiment, one of the first emitting layer and the second emitting layer, which is provided closer to the anode, is preferably in direct contact with the second organic compound layer.
An energy level of a highest occupied molecular orbital of a host material contained in the emitting layer in contact with the second organic compound layer is denoted by HOMO(Host). An energy level of a highest occupied molecular orbital of the third organic material is denoted by HOMO(HT3). An absolute value of a difference between HOMO(Host) and HOMO(HT3) preferably satisfies a relationship of a numerical formula (Numerical Formula 5) below, more preferably a relationship of a numerical formula (Numerical Formula 5A) below, still more preferably a relationship of a numerical formula (Numerical Formula 5B) below, and still further more preferably a relationship of a numerical formula (Numerical Formula 5C) below.
|HOMO(HT3)−HOMO(Host)|<0.4 eV (Numerical Formula 5)
0 eV≤|HOMO(HT3)−HOMO(Host)|<0.4 eV (Numerical Formula 5A)
0 eV≤|HOMO(HT3)−HOMO(Host)|<0.3 eV (Numerical Formula 5B)
0 eV≤|HOMO(HT3)−HOMO(Host)|<0.28 eV (Numerical Formula 5C)
A lower limit of the absolute value of the difference between HOMO(Host) and HOMO(HT3) is preferably 0.2 eV or more. The absolute value of the difference between HOMO(Host) and HOMO(HT3) more preferably satisfies a relationship of a numerical formula (Numerical Formula 5D) below, still more preferably a relationship of a numerical formula (Numerical Formula 5E) below, and still further more preferably a relationship of a numerical formula (Numerical Formula 5F) below.
0.2 eV≤|HOMO(HT3)−HOMO(Host)|<0.4 eV (Numerical Formula 5D)
0.2 eV≤|HOMO(HT3)−HOMO(Host)|<0.3 eV (Numerical Formula 5E)
0.2 eV≤|HOMO(HT3)−HOMO(Host)|<0.28 eV (Numerical Formula 5F)
In the organic EL device according to the exemplary embodiment, the energy level of the highest occupied molecular orbital of the third organic material HOMO(HT3) is preferably −5.7 eV or less.
The energy level of the highest occupied molecular orbital HOMO is herein measured with a photoelectron spectroscope under atmosphere. Specifically, the energy level of the highest occupied molecular orbital HOMO can be measured according to a method described in Examples.
In the organic EL device according to the exemplary embodiment, in a case where the first emitting layer and the second emitting layer are layered in this order from a side on which the anode is provided, the hole mobility of the first host material μh(H1) and the hole mobility of the second host material μh(H2) preferably satisfy a numerical formula (Numerical Formula 2) below.
μh(H1)>μh(H2) (Numerical Formula 2)
In the organic EL device according to the exemplary embodiment, in the case where the first emitting layer and the second emitting layer are layered in this order from a side on which the anode is provided, the hole mobility of the first host material μh(H1), the electron mobility of the first host material μe(H1), the hole mobility of the second host material μh(H2), and the electron mobility of the second host material μe(H2) preferably satisfy a numerical formula (Numerical Formula 3) below.
(μe(H2)/μh(H2))>(μe(H1)/μh(H1)) (Numerical Formula 3)
In the organic EL device according to the exemplary embodiment, in the case where 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 μe(H1) and the electron mobility of the second host material μe(H2) preferably satisfy a numerical formula (Numerical Formula 4) below.
μe(H2)>μe(H1) (Numerical Formula 4)
When the first host material and the second host material satisfy a relationship of the numerical formula (Numerical Formula 4), a recombination ability between holes and electrons in the first emitting layer is improved.
The electron mobility can be measured by the following method according to impedance spectroscopy.
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.
Electron Mobility=(Film Thickness of Measurement Target Layer)2/(Response Time·Voltage)
An organic EL device for evaluating hole mobility is set in an impedance measurement apparatus and an impedance measurement is performed, whereby the hole mobility can be measured, specifically, according to a method described in Examples below.
The first organic material is a compound different from the second organic material.
The first organic material is preferably a compound having at least one of a first cyclic structure represented by a formula (P11) below or a second cyclic structure represented by a formula (P12) below.
The first cyclic structure represented by the formula (P11) is fused with at least one cyclic structure of a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms or a substituted or unsubstituted heterocyclic ring having 5 to 50 ring atoms in a molecule of the first organic material.
A structure represented by ═Z10 is represented by a formula (11a), (11b), (11c), (11d), (11e), (11f), (11g), (11 h), (11i), (11j), (11k), or (11 m).
In the formulae (11a), (11 b), (11c), (11d), (11e), (11f), (11g), (11 h), (11i), (11j), (11k), or (11m), R11 to R14 and R1101 to R1110 are each independently a hydrogen atom, a halogen atom, a hydroxy group, a cyano group, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms, a substituted or unsubstituted alkyl halide group having 1 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 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 (P12):
In the first organic material, R901 to 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;
An ester group herein is at least one group selected from group consisting of an alkyl ester group and an aryl ester group.
An alkyl ester group herein is, for instance, represented by —C(═O)ORE. RE is, for instance, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms (preferably 1 to 10 carbon atoms).
An aryl ester group herein is, for instance, represented by —C(═O)ORAr. RAr is, for instance, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
A siloxanyl group herein is a silicon compound group through an ether bond, and is exemplified by a trimethylsiloxanyl group.
A carbamoyl group herein is represented by —CONH2.
A substituted carbamoyl group herein is, for instance, represented by —CONH—ArC or —CONH—RC. ArC is, for instance, at least one group selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms (preferably 6 to 10 ring carbon atoms) and a substituted or unsubstituted heterocyclic group having 5 to 50 ring atom (preferably 5 to 14 ring atoms) ArC may be a group in which a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms and a substituted or unsubstituted heterocyclic group having 5 to 50 ring atoms are bonded to each other.
RC is, for instance, a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms (preferably 1 to 6 carbon atoms).
In the exemplary embodiment, the first organic material is preferably a fused compound formed by fusing two or three structures each represented by a formula (P13) below to a third cyclic structure selected from a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 50 ring carbon atoms and a substituted or unsubstituted heterocyclic ring having 5 to 50 ring atoms.
In the formula (P13):
The first organic material is also preferably a compound represented by a formula (P14) or (P15) below.
In the formulae (P14) and (P15):
Pr1 in the formulae (P14) and (P15) is preferably a substituted or unsubstituted benzene ring or a substituted or unsubstituted heterocyclic group having 6 ring atoms.
A structure represented by ═X10 in the formula (P11) is preferably represented by the formula (11a).
Specifically, the first cyclic structure represented by the formula (P11) is preferably a cyclic structure represented by a formula (11A) below.
Since a dicyanomethylene group represented by the formula (11a) has a strong electron-withdrawing property and low molecular symmetry, intramolecular dipole moment increases. As a result, a compound having a cyclic structure represented by the formula (11A) has a large electron affinity and is suitably usable as a material for the hole injecting layer.
The first organic material is preferably a compound represented by one of formulae (P141) to (P144) and (P151) below.
In the formulae (P141) to (P144) and (P151), R1141, R1143, R1144, and R1146 are each independently a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, or a cyano group.
The first organic material is also preferably a compound represented by one of formulae (P145) to (P148) and (P152) below.
In the formulae (P145) to (P148) and (P152), Ar141, Ar143, Ar144, and Ar146 are each independently an aromatic hydrocarbon group having 6 to 30 ring carbon atoms and having at least one substituent selected from the group consisting of a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group, or a heterocyclic group having 5 to 30 ring atoms and having at least one substituent selected from the group consisting of a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
The first organic material is also preferably a compound represented by one of formulae (P1451), (P1461), (P1471) and (P1481) below.
R1451 to R1460 in the formula (P1451), R1461 to R1470 in the formula (P1461), R1471 to R1480 in the formula (P1471), and R1481 to R1490 in the formula (P1481) are each independently a hydrogen atom, a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
One or more of R1451 to R1460 are a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
One or more of R1461 to R1470 are a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
One or more of R1471 to R1480 are a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
One or more of R1481 to R1490 are a fluorine atom, a fluoroalkyl group, a fluoroalkoxy group, and a cyano group.
The first organic material is also preferably a compound represented by a formula (P121B) below.
In the formula (P121B):
The first organic material is also preferably a compound represented by a formula (P122D) below.
In the formula (P122D):
The first organic material is also preferably a compound represented by a formula (P122E) below.
In the formula (P122E):
In the formulae (E1), (E2), (E3), and (E4):
The formula (P122E) in which nx is 1 is represented by a formula (1221E) below. The formula (P122E) in which nx is 2 is represented by a formula (1222E) below. The formula (P122E) in which nx is 3 is represented by a formula (1223E) below. The formula (P122E) in which nx is 4 is represented by a formula (1224E) below.
In the formulae (1221E), (1222E), (1223E), and (1224E):
The structures represented by =Zx1, =Zx2, and =Zx3 are each preferably a structure represented by the formula (E3).
A structure represented by the formula (E3) is preferably a structure represented by the formula (11k).
In the formula (11k), it is preferable that R1101 to R1105 are each independently a halogen atom or a cyano group.
In the formula (11k), it is preferable that four of R1101 to R1105 are each independently a halogen atom and one of R1101 to R1105 is a cyano group.
In the formula (11k), it is preferable that R1101, R1102, R1104, and R1105 are each independently a halogen atom and R1103 is a cyano group.
In R1101 to R1105 in the formula (11k), a halogen atom is preferably a fluorine atom.
The first organic material according to the exemplary embodiment can be produced by known methods or by known substitution reactions and materials depending on a target compound in a similar manner as the known methods.
Specific examples of the first organic material according to the exemplary embodiment include compounds below. However, the invention is by no means limited to the specific examples.
The second organic material is a compound different from the first organic material.
The second organic material is preferably a compound represented by a formula (21) or (22) below.
In the formulae (21) and (22):
The second organic material is preferably a monoamine compound having one substituted or unsubstituted amino group in a molecule or a diamine compound having two substituted or unsubstituted amino groups in a molecule.
When LA2 and LB2 are each a single bond, A2 and B2 may be mutually bonded to form a substituted or unsubstituted monocyclic ring, mutually bonded to form a substituted or unsubstituted fused ring, or not bonded.
When LC2 and LD2 are each a single bond, C2 and D2 may be mutually bonded to form a substituted or unsubstituted monocyclic ring, mutually bonded to form a substituted or unsubstituted fused ring, or not bonded.
The second organic material is also preferably a compound represented by a formula (A221) below.
In the formula (A221):
A compound represented by the formula (21) as the second organic material is also preferably a compound represented by a formula (A212) below.
In the formula (A212):
In the formula (21) or (A212), two of A1, B1, and C1 are each preferably a group represented by a formula (Y) below. Two groups represented by the formula (Y) are mutually the same or different.
In the formula (Y):
In the second organic material, R901, R902, R903, R904, 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 organic EL device according to the exemplary embodiment, the second organic material is also preferably at least one compound selected from the group consisting of a compound represented by a formula (cHT2-1) below, a compound represented by a formula (cHT2-2) below, and a compound represented by a formula (cHT2-3) below.
In the formulae (cHT2-1), (cHT2-2), and (cHT2-3):
In an example of the organic EL device according to the exemplary embodiment, a first amino group represented by a formula (c21) below and a second amino group represented by a formula (c22) below in a compound represented by by the formula (cHT2-3) are mutually the same or different.
In the formulae (c21) and (c22), each * represents a bonding position to LB5.
In the organic EL device according to the exemplary embodiment, in a compound represented by the formula (cHT2-1), a compound represented by the formula (cHT2-2), and a compound represented by the formula (cHT2-3), a substituent for “a substituted or unsubstituted” group is also preferably not a group represented by —N(RC6)(RC7).
In the exemplary embodiment: RC6 and RC7 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 ring 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; a plurality of RC6 are mutually the same or different; and a plurality of RC7 are mutually the same or different.
When a substituent for “a substituted or unsubstituted” group is not a group represented by —N(RC6)(RC7), compounds represented by the formulae (cHT2-1) and (cHT2-2) are each a monoamine compound.
When a substituent for “a substituted or unsubstituted” group is not a group represented by —N(RC6)(RC7), a compound represented by the formula (cHT2-3) is a diamine compound.
In the organic EL device according to the exemplary embodiment, the second organic material is preferably a monoamine compound having one substituted or unsubstituted amino group in a molecule.
In an example of the organic EL device according to the exemplary embodiment, compounds represented by the formulae (cHT2-1) and (cHT2-2) are each a monoamine compound.
In an example of the organic EL device according to the exemplary embodiment, the second organic material as a compound contained in a first organic layer close to the anode (first anode-side organic layer) is a diamine compound having two substituted or unsubstituted amino groups in a molecule.
In an example of the organic EL device according to the exemplary embodiment, a compound represented by the formula (cHT2-3) is a diamine compound.
In an example of the organic EL device according to the exemplary embodiment, the second organic material is a triamine compound having three substituted or unsubstituted amino groups in a molecule.
In an example of the organic EL device according to the exemplary embodiment, the second organic material is a tetraamine compound having four substituted or unsubstituted amino groups in a molecule.
Each of the compounds represented by the formulae (cHT2-1) and (cHT2-2) which are each a triamine compound has two groups represented by —N(RC6)(RC7) as substituents for “a substituted or unsubstituted” group.
Each of the compounds represented by the formulae (cHT2-1) and (cHT2-2) which are each a tetraamine compound has three groups represented by —N(RC6)(RC7) as substituents for “a substituted or unsubstituted” group.
A compound represented by the formula (cHT2-3) which is a triamine compound has one group represented by —N(RC6)(RC7) as a substituent for “a substituted or unsubstituted” group.
The compound represented by the formula (cHT2-3) which is a tetraamine compound has two groups represented by —N(RC6)(RC7) as substituents for “a substituted or unsubstituted” group.
In the organic EL device according to the exemplary embodiment, the second organic material also preferably has at least one group selected from the group consisting of a group represented by a formula (2-a) below, a group represented by a formula (2-b) below, a group represented by a formula (2-c) below, a group represented by a formula (2-d) below, a group represented by a formula (2-e) below, and a group represented by a formula (2-f) below.
In an example of the organic EL device according to the exemplary embodiment, the second organic material is at least one compound selected from the group consisting of a compound represented by the formula (cHT2-1), a compound represented by the formula (cHT2-2), and a compound represented by the formula (cHT2-3), in which at least one of Ar112, Ar113, Ar121, Ar122, Ar123, or Ar124 in the formulae (cHT2-1), (cHT2-2), and (cHT2-3) has at least one group selected from the group consisting of a group represented by the formula (2-a) below, a group represented by the formula (2-b) below, a group represented by the formula (2-c) below, a group represented by the formula (2-d) below, a group represented by the formula (2-e) below, and a group represented by the formula (2-f) below.
In the formula (2-a):
In the formula (2-b):
In the formula (2-c):
In the formula (2-d):
In the formula (2-e):
In the formula (2-f):
In the organic EL device according to the exemplary embodiment, in the second organic material being a monoamine compound, it is also preferable that a group represented by the formula (2-a), a group represented by the formula (2-b), a group represented by the formula (2-c), a group represented by the formula (2-d), a group represented by the formula (2-e), and a group represented by the formula (2-f) are each independently bonded to a nitrogen atom of an amino group in the monoamine compound directly, via a phenylene group, or via a biphenylene group.
In an example of the organic EL device according to the exemplary embodiment, the second organic material is a compound represented by the formula (cHT2-1) in which at least one of Ar112 or Ar113 is a group selected from the group consisting of a group represented by the formula (2-a), a group represented by the formula (2-b), a group represented by the formula (2-c), a group represented by the formula (2-d), a group represented by the formula (2-e), and a group represented by the formula (2-f).
In an example of the organic EL device according to the exemplary embodiment, the second organic material is a compound represented by the formula (cHT2-2) in which at least one of Ar112 or Ar113 is a group selected from the group consisting of a group represented by the formula (2-a), a group represented by the formula (2-b), a group represented by the formula (2-c), a group represented by the formula (2-d), a group represented by the formula (2-e), and a group represented by the formula (2-f).
In an example of the organic EL device according to the exemplary embodiment, the second organic material is a compound represented by the formula (cHT2-3) in which at least one of Ar121, Ar122, Ar123, or Ar124 is a group selected from the group consisting of a group represented by the formula (2-a), a group represented by the formula (2-b), a group represented by the formula (2-c), a group represented by the formula (2-d), a group represented by the formula (2-e), and a group represented by the formula (2-f).
In the organic EL device according to the exemplary embodiment, when Z3 is NR319, R312 or R317 is preferably a single bond bonded to *e.
In an example of the organic EL device according to the exemplary embodiment, a group represented by the formula (2-e) is preferably a group represented by a formula (2-e7) below.
In the formula (2-e7): R311 to R316, R318, and R319 respectively represent the same as R311 to R316, R318, and R319 in the formula (2-e); and ** represents a bonding position.
In the organic EL device according to the exemplary embodiment, when Z3 is NR319, R315, R316, or R318 is also preferably a single bond bonded to *e.
In an example of the organic EL device according to the exemplary embodiment, a group represented by the formula (2-e) is a group represented by a formula (2-e4), (2-e5), or (2-e6) below.
In the formulae (2-e4), (2-e5), and (2-e6): R311 to R319 respectively represent the same as R311 to R319 in the formula (2-e); and each ** represents a bonding position.
In the organic EL device according to the exemplary embodiment, a group represented by the formula (2-e) is preferably a group represented by a formula (2-e1), (2-e2), or (2-e3) below.
In the formulae (2-e1), (2-e2), and (2-e3):
In an example of the organic EL device according to the exemplary embodiment, each ** in the formulae (2-a), (2-b), (2-c), (2-d), (2-e), (2-f), (2-e1), (2-e2), (2-e3), (2-e4), (2-e5), (2-e6), and (2-e7) is independently a bonding position to LA2, LA3, LB1, LB2, LB3, or LB4 or a bonding position to a nitrogen atom of an amino group.
In the organic EL device according to the exemplary embodiment, the compound contained in the first organic compound layer is also preferably a compound having no thiophene ring in a molecule.
In the organic EL device according to the exemplary embodiment, the second organic material is also preferably a compound having no thiophene ring in a molecule.
The second organic material according to the exemplary embodiment can be produced by known methods, or by known substitution reactions and materials depending on a target compound in a similar manner as the known methods.
Specific examples of the second organic material according to the exemplary embodiment include compounds below. However, the invention is by no means limited to the specific examples.
In the organic EL device according to the exemplary embodiment, the second organic material contained in the first organic compound layer is also preferably at least one compound selected from the group consisting of compounds listed below.
The third organic material is a compound different from the first organic material and the second organic material.
The third organic material is preferably a compound represented by a formula (310) or (320) below.
In the formula (310):
A compound represented by the formula (310) is also preferably a compound represented by a formula (312) below.
In the formula (312):
In a compound represented by the formula (310), at least one of A3, B3, or C3 is preferably a group selected from the group consisting of groups represented by formulae (31a), (31b), (31c), (31d), and (31e) below.
In the formulae (31a), (31b), (31c), (31d), and (31e):
A3, B3, and C3 not being a group selected from the group consisting of groups represented by the formulae (31a), (31b), (31c), (31d), and (31e) are each independently preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the formula (320):
In a compound represented by the formula (320), when Y6 is a carbon atom bonded to *1 and Y11 is a carbon atom bonded to *2, the formula (320) is represented by a formula (321) below.
A compound represented by the formula (320) is also preferably a compound represented by a formula (321) below.
In the formula (321):
In a compound represented by the formula (320), A31 and A32 are each independently preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In a compound represented by the formula (320), it is preferable that one of A31 and A32 is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms and the other of A31 and A32 is a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted terphenyl group, a substituted or unsubstituted naphthyl group, a naphthylphenyl group, a substituted or unsubstituted triphenylenyl group, or 9,9-biphenylfluorenyl group.
In a compound represented by the formula (320), it is preferable that one of A31 and A32 is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms and the other of A31 and A32 is a substituted or unsubstituted phenyl group, a substituted or unsubstituted p-biphenyl group, a substituted or unsubstituted m-biphenyl group, a substituted or unsubstituted o-biphenyl group, a substituted or unsubstituted 3-naphthylphenyl group, a triphenylenyl group, or 9,9-biphenylfluorenyl group.
In a compound represented by the formula (320), L31 and L32 are each independently preferably a single bond or a substituted or unsubstituted arylene group having 6 to 30 ring carbon atoms.
In the organic EL device according to the exemplary embodiment, the third organic material is also preferably at least one compound selected from the group consisting of a compound represented by a formula (cHT3-1) below, a compound represented by a formula (cHT3-2) below, a compound represented by a formula (cHT3-3) below, and a compound represented by a formula (cHT3-4) below.
In the formulae (cHT3-1), (cHT3-2), (cHT3-3), and (cHT3-4):
In the formula (1-a):
In the formula (1-b):
In the formula (1-c):
In the formula (1-d):
In the organic EL device according to the exemplary embodiment, in a compound represented by the formula (cHT3-1), a compound represented by the formula (cHT3-2), a compound represented by the formula (cHT3-3), and a compound represented by the formula (cHT3-4), a substituent for “a substituted or unsubstituted” group is also preferably not a group represented by —N(RC6)(RC7).
In the exemplary embodiment: RC6 and RC6 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 ring 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; a plurality of RC6 are mutually the same or different; and a plurality of RC6 are mutually the same or different.
When a substituent for “a substituted or unsubstituted” group is not a group represented by —N(RC6)(RC7), compounds represented by the formulae (cHT3-1), (cHT3-2), (cHT3-3), and (cHT3-4) are each a monoamine compound.
In an example of the organic EL device according to the exemplary embodiment, a compound contained in a second organic layer close to the anode (second anode-side organic layer) is a diamine compound having two substituted or unsubstituted amino groups in a molecule.
In an example of the organic EL device according to the exemplary embodiment, a compound contained in the second anode-side organic layer is a triamine compound having three substituted or unsubstituted amino groups in a molecule.
In an example of the organic EL device according to the exemplary embodiment, a compound contained in the second anode-side organic layer is a tetraamine compound having four substituted or unsubstituted amino groups in a molecule.
Each of the compounds represented by the formulae (cHT3-1), (cHT3-2), (cHT3-3), and (cHT3-4) which are each a diamine compound has one group represented by —N(RC6)(RC7) as a substituent for “a substituted or unsubstituted” group.
Each of the compounds represented by the formulae (cHT3-1), (cHT3-2), (cHT3-3), and (cHT3-4) which are each a triamine compound has two groups represented by —N(RC6)(RC7) as substituents for “a substituted or unsubstituted” group.
Each of the compounds represented by the formulae (cHT3-1), (cHT3-2), (cHT3-3), and (cHT3-4) which are each a tetraamine compound has three groups represented by —N(RC6)(RC7) as substituents for “a substituted or unsubstituted” group.
In an example of the organic EL device according to the exemplary embodiment, the third organic material is a monoamine compound, diamine compound, triamine compound, or tetraamine compound.
The third organic material is preferably a monoamine compound having one substituted or unsubstituted amino group in a molecule.
The third organic material is preferably not a diamine compound having two substituted or unsubstituted amino groups in a molecule.
In the organic EL device according to the exemplary embodiment, of the organic compound layers contained in the hole transporting zone, the organic compound layer(s) provided closer to the emitting layer than the first organic compound layer preferably does not contain a diamine compound having two substituted or unsubstituted amino groups in a molecule.
In the organic EL device according to the exemplary embodiment, of the organic compound layers contained in the hole transporting zone, the organic compound layer(s) provided closer to the emitting layer than the first organic compound layer also preferably includes a compound having no substituted or unsubstituted 3-carbazolyl group in a molecule.
In the first organic material, second organic material, and third organic material according to the exemplary embodiment, it is preferable that the groups specified to be “substituted or unsubstituted” are each an “unsubstituted” group.
In the organic EL device according to the exemplary embodiment, it is also preferable that the second organic material is at least one compound selected from the group consisting of a compound represented by the formula (cHT2-1), a compound represented by the formula (cHT2-2), and a compound represented by the formula (cHT2-3) and the third organic material is at least one compound selected from the group consisting of a compound represented by the formula (cHT3-1), a compound represented by the formula (cHT3-2), a compound represented by the formula (cHT3-3), and a compound represented by the formula (cHT3-4).
The third organic material can be produced by a known method. The third organic material 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 third organic material according to the exemplary embodiment include compounds below. However, the invention is by no means limited to the specific examples of the third organic material.
In the organic EL device according to the exemplary embodiment, the third organic material contained in the second organic compound layer is also preferably at least one compound selected from the group consisting of compounds listed below.
The organic electroluminescence device according to the exemplary embodiment preferably emits, when being driven, light whose maximum peak wavelength is 500 nm or less.
The organic electroluminescence device according to the 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).
The first emitting layer contains a first host material. The first host material is a compound different from the second host material contained in the second emitting layer.
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.
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 is preferably a compound that emits light having a maximum peak wavelength of 480 nm or less.
The first emitting compound is preferably a fluorescent compound that emits fluorescence having a maximum peak wavelength of 500 nm or less, more preferably a compound that emits fluorescence having a maximum peak wavelength of 480 nm or less.
In the organic EL device according to the 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 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 exemplary embodiment, the first emitting layer preferably does not contain a metal complex. In the organic EL device according to the exemplary embodiment, the first emitting layer also preferably does not contain a boron-containing complex.
In the organic EL device according to the exemplary embodiment, the first emitting layer preferably does not contain a phosphorescent material (dopant 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 was prepared and put in a quartz cell. An emission spectrum (ordinate axis: luminous intensity, abscissa axis: wavelength) of the thus-obtained sample was 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. Herein, the maximum peak wavelength of fluorescence is sometimes referred to as the fluorescence maximum peak wavelength (FL-peak).
In an emission spectrum of the first emitting 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 first emitting compound, the number of peaks is preferably less than three.
In the organic EL device according to the 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 for 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 (manufactured 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 for 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 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 10) below.
S
1(H1)>S1(D1) (Numerical Formula 10)
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 10), singlet excitons generated on the first host material easily transfer from the first host material to the first emitting compound, thereby contributing to fluorescence of the first dopant material.
In the organic EL device according to the 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 11) below.
T
1(D1)>T1(H1) (Numerical Formula 11)
When the first host material and the first emitting compound satisfy the relationship of the numerical formula (Numerical Formula 11), 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 numerical formula (Numerical Formula 11B) below.
T
1(D1)>T1(H1)>T1(H2) (Numerical Formula 11B)
Herein, a method of measuring the 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 10−4 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 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 λedge [nm] at an intersection of the tangent and the abscissa axis. The calculated energy amount was defined as triplet energy T1.
T
1 [eV]=1239.85/λedge Conversion Equation (F1):
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.
A method of measuring the lowest 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 10−4 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 the lowest singlet energy.
S
1 [eV]=1239.85/λedge Conversion Equation (F2):
Any device for measuring absorption spectrum is usable. For instance, a spectrophotometer (U3310 manufactured 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 exemplary embodiment, the first emitting compound is preferably contained at 0.5 mass % or more in the first emitting layer. The first emitting compound is also preferably contained at more than 1.1 mass % in the first emitting layer. Specifically, the first emitting layer preferably contains the first emitting compound at 0.5 mass % or more, more preferably at 1 mass % or more, still more preferably at more than 1.1 mass %, still further more preferably at 1.2 mass % or more, and yet still further more preferably at 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 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 exemplary embodiment, a film thickness of the first emitting layer is preferably 3 nm or more, more preferably 5 nm or more. The film thickness of the first emitting layer of 3 nm or more is sufficient for causing recombination of holes and electrons in the first emitting layer.
In the organic EL device according to the exemplary embodiment, the film thickness of the first organic compound layer is preferably 15 nm or less, more preferably 10 nm or less. The film thickness of the first emitting layer of 15 nm or less is thin enough for transfer of triplet excitons to the second emitting layer.
In the organic EL device according to the exemplary embodiment, the film thickness of the first emitting layer is more preferably in a range from 3 nm to 15 nm.
In the organic EL device according to the exemplary embodiment, the first emitting layer may contain a compound represented by a formula (HT100) below.
In the organic EL device according to the exemplary embodiment, the first emitting layer may contain the third organic material according to the exemplary embodiment.
The second emitting layer contains a 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 second emitting compound is preferably a compound that emits light having a maximum peak wavelength of 480 nm or less.
The second emitting compound is preferably a fluorescent compound that emits fluorescence having a maximum peak wavelength of 500 nm or less, more preferably a compound that emits fluorescence having a maximum peak wavelength of 480 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 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 exemplary embodiment, a full width at half maximum of the second emitting compound is preferably in a range from 1 nm to 20 nm.
In the organic EL device according to the 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 below.
A measurement target compound is dissolved in toluene at a concentration of 2.0×10−5 mol/L to prepare a measurement sample. The measurement sample is put into a quartz cell and is 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 manufactured by Hitachi High-Tech Science Corporation is usable for the absorption spectrum measurement. A measurement target compound is 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 manufactured by Hitachi High-Tech Science Corporation is usable for the fluorescence spectrum measurement. A difference between an absorption local-maximum wavelength and a fluorescence local-maximum wavelength is calculated from the absorption spectrum and the fluorescence spectrum to obtain a Stokes shift (SS). A unit of the Stokes shift (SS) is denoted by nm.
In the organic EL device according to the exemplary embodiment, the triplet energy of the second host material T1(H2) and a triplet energy of the second emitting compound T1(D2) preferably satisfy a relationship of a numerical formula (Numerical Formula 13) below.
T
1(D2)>T1(H2) (Numerical Formula 13)
In the organic EL device according to the exemplary embodiment, when the second emitting compound and the second host material satisfy the relationship of the numerical formula (Numerical Formula 13), 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 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 12) below.
S
1(H2)>S1(D2) (Numerical Formula 12)
In the organic EL device according to the exemplary embodiment, when the second emitting compound and the second host material satisfy the relationship of the numerical formula (Numerical formula 12), 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 fluorescence of the second emitting compound.
In the organic EL device according to the 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 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 exemplary embodiment, the second emitting layer preferably does not contain a metal complex. In the organic EL device according to the exemplary embodiment, the second emitting layer also preferably does not contain a boron-containing complex.
In the organic EL device according to the exemplary embodiment, the second emitting layer preferably does not contain a phosphorescent material (dopant 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 exemplary embodiment, the second emitting compound is preferably contained at 0.5 mass % or more in the second emitting layer. The second emitting compound is also preferably contained at more than 1.1 mass % in the second emitting layer. Specifically, the second emitting layer preferably contains the second emitting compound at 0.5 mass % or more, more preferably at 1 mass % or more, still more preferably at more than 1.1 mass %, still further more preferably at 1.2 mass % or more, and yet still further more preferably at 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 exemplary embodiment, a film thickness of 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, it is easy to inhibit triplet excitons having transferred from the first emitting layer to the second emitting layer 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 the exemplary embodiment, the film thickness of the second emitting layer is preferably 20 nm or less. When the film thickness of the second emitting layer is 20 nm or less, a density of the triplet excitons in the second emitting layer is improved to cause the TTF phenomenon more easily.
In the organic EL device according to the exemplary embodiment, the film thickness of the second emitting layer is preferably in a range from 5 nm to 20 nm.
In the organic EL device according to the 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 14) below.
T
1(H1)−T1(H2)>0.03 eV (Numerical Formula 14)
In the organic EL device according to the exemplary embodiment, a triplet energy of the first emitting compound or the second emitting compound T1(DX), the triplet energy of the first host material T1(H1), the triplet energy of the second host material T1(H2) preferably satisfy a relationship of a numerical formula (Numerical Formula 20) below.
2.6 eV>T1(DX)>T1(H1)>T1(H2) (Numerical Formula 20)
The triplet energy of the first emitting compound T1(D1) preferably satisfies a relationship of a numerical formula (Numerical Formula 20A) below.
2.6 eV>T1(D1)>T1(H1)>T1(H2) (Numerical Formula 20A)
The triplet energy of the second emitting compound T1(D2) preferably satisfies a relationship of a numerical formula (Numerical Formula 20B) below.
2.6 eV>T1(D2)>T1(H1)>T1(H2) (Numerical Formula 20B)
In the organic EL device according to the exemplary embodiment, the 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 21) below.
0 eV<T1(DX)−T1(H1)<0.6 eV (Numerical Formula 21)
The triplet energy of the first emitting compound T1(D1) preferably satisfies a relationship of a numerical formula (Numerical Formula 21A) below.
0 eV<T1(D1)−T1(H1)<0.6 eV (Numerical Formula 21A)
The triplet energy of the second emitting compound T1(D2) preferably satisfies a relationship of a numerical formula (Numerical Formula 21B) below.
0 eV<T1(D2)−T1(H2)<0.8 eV (Numerical Formula 21B)
In the organic EL device according to the exemplary embodiment, the triplet energy of the first host material T1(H1) preferably satisfies a relationship of a numerical formula (Numerical Formula 15) below.
T
1(H1)>2.0 eV (Numerical Formula 15)
In the organic EL device according to the exemplary embodiment, the triplet energy of the first host material T1(H1) also preferably satisfies a relationship of a numerical formula (Numerical Formula 16) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 16A) below.
T
1(H1)>2.10 eV (Numerical Formula 16)
T
1(H1)>2.15 eV (Numerical Formula 16A)
In the organic EL device according to the exemplary embodiment, when the triplet energy of the first host material T1(H1) satisfies the relationship of the numerical formula (Numerical Formula 16) or the numerical formula (Numerical Formula 16A), 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 exemplary embodiment, the triplet energy of the first host material T1(H1) also preferably satisfies a relationship of a numerical formula (Numerical Formula 17) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 17A) below.
2.08 eV>T1(H1)>1.87 eV (Numerical Formula 17)
2.05 eV>T1(H1)>1.90 eV (Numerical Formula 17A)
In the organic EL device according to the exemplary embodiment, when the triplet energy of the first host material T1(H1) satisfies the relationship of the numerical formula (Numerical Formula 17) or the numerical formula (Numerical Formula 17A), energy of triplet excitons generated in the first emitting layer is likely to be decreased. The organic EL device is thus expected to have a long lifetime.
In the organic EL device according to the exemplary embodiment, the triplet energy of the second host material T1(H2) preferably satisfies a relationship of a numerical formula (Numerical Formula 18) below.
T
1(H2)≥1.9 eV (Numerical Formula 18)
In the organic EL device according to the exemplary embodiment, the triplet energy of the first emitting compound T1(D1) also preferably satisfies a relationship of a numerical formula (Numerical Formula 22) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 23) below.
2.60 eV>T1(D1) (Numerical Formula 22)
2.50 eV>T1(D1) (Numerical Formula 23)
Since the first emitting layer contains the first emitting compound satisfying the relationship of the numerical formula (Numerical Formula 22 or Numerical Formula 23), the lifetime of the organic EL device is prolonged.
In the organic EL device according to the exemplary embodiment, the triplet energy of the second emitting compound T1(D2) also preferably satisfies a relationship of a numerical formula (Numerical Formula 24) below, or also preferably satisfies a relationship of a numerical formula (Numerical Formula 25) below.
2.60 eV>T1(D2) (Numerical Formula 24)
2.50 eV>T1(D2) (Numerical Formula 25)
Since the second emitting layer contains a compound satisfying the relationship of the numerical formula (Numerical Formula 24 or Numerical Formula 25), the lifetime of the organic EL device is prolonged.
In the organic EL device according to the exemplary embodiment, the first emitting layer and the second emitting layer are preferably in direct contact with each other.
Herein, 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.
The organic EL device according to the 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.
T
1(H1)>T1(H3) (Numerical Formula 1A)
In a case where the organic EL device according to the 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.
T
1(H2)>T1(H3) (Numerical Formula 1B)
In a case where the organic EL device according to the 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.
Herein, 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 exemplary embodiments further includes a diffusion layer.
In a case where the organic EL device of the exemplary embodiment includes the diffusion layer, the diffusion layer is preferably provided between the first emitting layer and the second emitting layer.
In the organic EL device according to the exemplary embodiment, it is also preferable that the first emitting layer is provided between the anode and the cathode and the second emitting layer is provided between the first emitting layer and the cathode. In other words, it is also preferable that the first emitting layer is provided closer to the anode than the second emitting layer.
The organic EL device according to the exemplary embodiment may include the first emitting layer and the second emitting layer in this order from the anode, or may include the second emitting layer and the first emitting layer in this order from the anode. Regardless of the order of the first emitting layer and the second emitting layer, the effect obtained by layering the first and second emitting layers can be expected by selecting a combination of materials satisfying the relationship of the numerical formula (Numerical Formula 1).
In a case where the first emitting layer is provided closer to the anode than the second emitting layer, the hole transporting zone and the first emitting layer are preferably in direct contact with each other.
In a case where the second emitting layer is provided closer to the anode than the first emitting layer, the hole transporting zone and the second emitting layer are preferably in direct contact with each other.
Additional Layers of Organic EL Device In addition to the hole transporting zone, the first emitting layer and the second emitting layer, the organic EL device according to the exemplary embodiment may include one or more organic layers. Examples of the organic layer include at least one layer selected from the group consisting of an electron injecting layer, an electron transporting layer, and a hole blocking layer.
The organic EL device according to the exemplary embodiment may consist of the hole transporting zone, the first emitting layer, and the second emitting layer. Alternatively, the organic EL device according to the exemplary embodiment may further include, for instance, at least one layer selected from the group consisting of an electron injecting layer, an electron transporting layer, and a hole blocking layer.
An 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 transporting zone 6, 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. The hole transporting zone 6 includes at least two organic compound layers. In the organic EL device 1 illustrated in
The organic EL device of the invention may have any arrangement without being limited to the arrangement of the organic EL device illustrated in
The arrangement of the organic EL device according to the 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, which is a bendable substrate, is exemplified by a plastic substrate. Examples of a material for the flexible substrate include polycarbonate, polyarylate, polyethersulfone, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, polyimide, and polyethylene naphthalate. Moreover, an inorganic vapor deposition film is also usable.
Anode 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 ITO (Indium Tin Oxide), 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.
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, 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.
In the organic EL device according to the exemplary embodiment, the electron transporting layer is preferably provided between the emitting layer and the cathode.
The electron transporting layer is a layer containing a highly electron-transportable 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 benzoimidazole compound is suitably 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 a single layer or a laminate of two or more layers formed of the above substance.
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), and poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)] (abbreviation: PF-BPy) 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.
A method for forming each layer of the organic EL device in the 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.
A film thickness of each of the organic layers of the organic EL device according to the 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 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 and the second compound represented by a formula (2) below. 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 exemplary embodiment, a 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 (111 b) below.
In the formula (111 b):
In the organic EL device according to the exemplary embodiment, a group represented by the formula (111) is preferably a group represented by a formula (111b) below.
In the organic EL device according to the exemplary embodiment, preferably, ma is 0, 1, or 2 and mb is 0, 1, or 2.
In the organic EL device according to the exemplary embodiment, preferably, ma is 0 or 1 and mb is 0 or 1.
In the organic EL device according to the 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 exemplary embodiment, 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 pyrenyl group, a substituted or unsubstituted phenanthryl group, or a substituted or unsubstituted fluorenyl group.
In the organic EL device according to the 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 exemplary embodiment, the first compound is preferably a compound represented by the formula (101) below.
In the formula (101):
In the organic EL device according to the 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 exemplary embodiment, the first compound is preferably a compound represented by the formula (102) below.
In the formula (102):
In a compound represented by the formula (102), preferably, ma is 0, 1, or 2 and mb is 0, 1, or 2.
In a compound represented by the formula (102), preferably, ma is 0 or 1 and mb is 0 or 1.
In the organic EL device according to the 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 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 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 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 exemplary embodiment, it is preferable 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 exemplary embodiment, R101 to R110 not being a group represented by the formula (11) are each preferably a hydrogen atom.
In the organic EL device according to the exemplary embodiment, the first compound is also preferably a compound represented by a formula (1X) below.
In the formula (1X):
In the organic EL device according to the exemplary embodiment, a group represented by the formula (11X) is preferably a group represented by a formula (111X) below.
In the formula (111X):
Of 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 (111 bX): X1, L111, L112, ma, mb, Ar101, R141, R142, R143, R144, and R145 respectively independently represent the same as X1, L111, L112, ma, mb, Ar101, R141, R142, R143, R144, and R145 in the formula (111X); a plurality of R141 are mutually the same or different; and a plurality of R142 are mutually the same or different.
In the organic EL device according to the exemplary embodiment, a group represented by the formula (111X) is preferably a group represented by the formula (111bX) below.
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 a 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.
A compound represented by the formula (1X) is also preferably represented by a formula (101X) below.
In the formula (101X):
In a 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.
A compound represented by the formula (1X) is also preferably represented by a formula (102X) below.
In the formula (102X):
In a compound represented by the formula (1X), preferably, ma is 1 or 2 and mb is 1 or 2 in the formula (102X).
In a compound represented by the formula (1X), preferably, ma is 1 and mb is 1 in the formula (102X).
In a 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 (11 BX) below.
In the formulae (11 AX) and (11 BX):
A compound represented by the formula (1X) is also preferably represented by a formula (103X) below.
In the formula (103X):
In a compound represented by the formula (1X), L131 is also preferably a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
In a compound represented by the formula (1X), L132 is also preferably a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms.
In a compound represented by the formula (1X), two or more of R101 to R112 are each also preferably a group represented by the formula (11X).
In a 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 a 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 a compound represented by the formula (1X), it is preferable that R101 to R112 not being a group represented by the formula (11X) are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 ring 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 a compound represented by the formula (1X), it is preferable that R101 to R112 not being a group represented by the formula (11X) are each a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 50 ring carbon atoms, or a substituted or unsubstituted cycloalkyl group having 3 to 50 ring carbon atoms.
In a 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 exemplary embodiment, the first compound is also preferably a compound represented by a 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 exemplary embodiment, the first compound is also preferably a compound represented by a formula (13X) below.
In the formula (13X):
In the organic EL device of the exemplary embodiment, none of combinations of adjacent two or more of R1301 to R1310 not being a 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 exemplary embodiment, the first compound is also preferably a compound represented by a formula (14X) below.
In the formula (14X):
Compound Represented by Formula (15X) In the organic EL device according to the exemplary embodiment, the first compound is also preferably a compound represented by a formula (15X) below.
In the formula (15X):
In the organic EL device according to the exemplary embodiment, the first compound is also preferably a compound represented by a formula (16X) below.
In the formula (16X):
In the organic EL device according to the 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. Further, the benzene ring may be fused with a monocyclic ring or fused ring, and the naphthalene ring may be fused with a 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 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 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 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 exemplary embodiment, the cross-linking also preferably includes a double bond.
In the organic EL device according to the 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 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 exemplary embodiment, the second compound is a compound represented by a 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 exemplary embodiment, it is preferable that 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 exemplary embodiment, it is preferable that L201 and L202 are each independently a single bond or a substituted or unsubstituted arylene group having 6 to 50 ring carbon atoms, and Ar201 and Ar202 are each independently a substituted or unsubstituted aryl group having 6 to 50 ring carbon atoms.
In the organic EL device according to the exemplary embodiment, it is preferable that Ar201 and Ar202 are 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 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): L201 and Ar201 respectively represent the same as L201 and Ar201 in the formula (2); and R201 to R208 each independently represent the same as R201 to R208 in the formula (2).
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 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).
It is preferable that L201 is a single bond or a substituted or unsubstituted arylene group having 6 to 22 ring carbon atoms and Ar201 is a substituted or unsubstituted aryl group having 6 to 22 ring carbon atoms.
In the organic EL device according to the 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 host material relative to that of the first host material, so that the relationship of μe(H2)>μe(H1) shown by the numerical formula (Numerical Formula 4) may not be satisfied. In a case where the second compound is used in the second emitting layer, it can be expected that satisfying the relationship of μe(H2)>μe(H1) 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 exemplary embodiment, R201 to R208 in the second compound represented by the formula (2) are also 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).
In the organic EL device according to the 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 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.
A 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):
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 a compound represented by the formula (3) include compounds shown below.
A 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 “heterocyclic ring” 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 “heterocyclic 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 heterocyclic ring 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 heterocyclic ring 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 heterocyclic ring 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 327]
*-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 * are each independently bonded to a ring carbon atom of the aromatic hydrocarbon ring or a ring atom of the heterocyclic ring 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 heterocyclic ring 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.
A 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 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):
R901 to R907 in the third compound and the fourth compound are as defined above.
In an exemplary embodiment, a 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, a 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, a 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, a 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 a 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.
A 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 a compound represented by the formula (5) include compounds shown below.
A 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 heterocyclic ring 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 “heterocyclic ring” 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 “heterocyclic 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 “heterocyclic 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 heterocyclic ring 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 heterocyclic ring. The “heterocyclic ring” in this arrangement includes a nitrogen atom on the fused bicyclic structure at the center of the formula (6). The heterocyclic ring 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 heterocyclic ring, in which the ring including R601 and the ring a are fused. Specific examples of the nitrogen-containing heterocyclic ring 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 heterocyclic ring, 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 heterocyclic ring 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 are 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 may be bonded with R646 to form a substituted or unsubstituted heterocyclic ring. For instance, R631 and R646 may be bonded with each other to form a tri-or-more cyclic fused nitrogen-containing heterocyclic ring, 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 heterocyclic ring 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 at least one of R631 to R651 is 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 (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 selected from the group consisting of 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 ring 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 a compound represented by the formula (6) is not limited thereto.
A compound represented by the formula (7) will be described below.
In the formula (7):
In the formula (7), each of the p ring, q ring, r ring, s ring, and t ring 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 r ring, 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 (71-6), 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 a compound represented by the formula (7) include compounds shown below.
A 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 R11 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 International Publication No. WO 2014/104144.
A compound represented by the formula (9) will be described below.
In the formula (9):
In the formula (92):
At least one ring selected from the group consisting of A91 ring and A92 ring is bonded to a bond * of a structure represented by the formula (92). In other words, the ring carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocyclic ring of the A91 ring in an exemplary embodiment are bonded to the bonds * in a structure represented by the formula (92). Further, the ring carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocyclic ring of the A92 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 each of the A91 ring and A92 ring.
In the formula (93):
In an exemplary embodiment, in addition to the A91 ring, the ring carbon atoms of the aromatic hydrocarbon ring or the ring atoms of the heterocyclic ring of the 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, R91 and R92 are mutually bonded to form a fluorene structure.
In an exemplary embodiment, the rings A91 and A92 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, the ring A93 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 a compound represented by the formula (9) include compounds shown below.
A 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 a 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, a compound represented by the formula (4) is a compound represented by the formula (41-3), the formula (41-4), or the formula (41-5), the 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 heterocyclic ring having 8 to 50 ring atoms.
In an exemplary embodiment, a 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, a 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,
In the formulae (461) to (467):
In an exemplary embodiment, R421 to R427 and R440 to R448 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.
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 respectively 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, a substituent for “a substituted or unsubstituted” group in each of the above 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, a substituent for “a substituted or unsubstituted” group in each of the above 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 second exemplary embodiment is installed with any one of the organic EL devices according to one of the above-described 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 by 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, and more than two emitting layers may be layered on each other. In a case where the organic EL device includes more than two emitting layers, it is only necessary that at least two of the emitting layers should satisfy the requirements mentioned in the above exemplary embodiment. 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.
In a case of a organic EL device including a plurality of emitting layers, the emitting layers may be mutually adjacently provided, or may be layered via an intermediate layer to form a so-called tandem organic EL device.
For instance, a blocking layer may be provided adjacent to a side of the emitting layer close to the cathode. The blocking layer provided in direct contact with the side of the emitting layer close to the cathode preferably blocks at least any of holes or excitons.
For instance, in a case where 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. In a case where the organic EL device includes the electron transporting layer, the blocking layer is preferably interposed between the emitting layer and the electron 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.
The invention will be described in more detail below with reference to Examples. However, the invention is by no means limited to these Examples.
Structures of compounds used for producing organic EL devices in Example 1, Comparative 1, and Reference Examples 1 and 2 are shown below.
The organic EL devices were produced and evaluated as follows.
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 a 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 first organic compound layer (sometimes referred to as a hole injecting layer (HI)). The ratios of the compound HT2 and the compound HA1 in the first organic compound layer were 97 mass % and 3 mass %, respectively.
Subsequent to the formation of the first organic compound layer, a compound HT1 was vapor-deposited on the first organic compound layer to form a 85-nm-thick second organic compound layer (sometimes referred to as a hole transporting layer (HT) or an electron blocking layer (EBL)).
A compound BH1 (first host material (BH)) and a compound BD (first emitting compound (BD)) were co-deposited on the second organic compound layer such that the ratio of the compound BD accounted for 1 mass %, thereby forming a 5-nm-thick first emitting layer.
A compound BH2 (second host material (BH)) and the compound BD (second emitting compound (BD2)) were co-deposited on the first emitting layer such that the ratio of the compound BD accounted for 1 mass %, thereby forming a 15-nm-thick second emitting layer.
A compound ET1 was vapor-deposited on the second emitting layer to form a 5-nm-thick first electron transporting layer (sometimes referred to as a hole blocking layer (HBL)).
A compound ET2 and a compound Liq were co-deposited on the first electron transporting layer 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 %.
The compound 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 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 HT2 and the compound HA1 in the first organic compound layer. The numerals (99%:1%) represented by percentage in the same parentheses indicate a ratio (mass %) between the host material (BH1 or BH2) and the emitting compound (compound BD) 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 second electron transporting layer (ET).
An organic EL device in Comparative 1 was produced in the same manner as the organic EL device in Example 1 except that the first hole transporting layer was formed as follows between the first organic compound layer and the second organic compound layer, the second organic compound layer was formed using the compound shown in Table 1 to have a thickness shown in Table 1, and the second emitting layer was formed to have a thickness shown in Table 1 without forming the first emitting layer.
In Comparative 1, subsequent to the formation of the first organic compound layer, the compound HT2 was vapor-deposited to form an 80-nm-thick first hole transporting layer (hole transporting layer (HT)).
Subsequent to the formation of the first hole transporting layer, a compound HT3 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second organic compound layer (sometimes referred to as an electron blocking layer (EBL)).
The compound BH2 (second host material (BH)) and the compound BD (second emitting compound (BD)) were co-deposited on the second organic compound layer such that the ratio of the compound BD accounted for 1 mass %, thereby forming a 20-nm-thick second emitting layer.
An organic EL device in Reference Example 1 was produced in the same manner as the organic EL device in Example 1 except that the second emitting layer was formed to have a thickness shown in Table 1 without forming the first emitting layer.
An organic EL device in Reference Example 2 was produced in the same manner as the organic EL device in Example 1 except that the first hole transporting layer was formed as follows between the first organic compound layer and the second organic compound layer, and the second organic compound layer was formed using the compound shown in Table 1 to have a thickness shown in Table 1.
In Reference Example 2, subsequent to the formation of the first organic compound layer, the compound HT2 was vapor-deposited to form an 80-nm-thick first hole transporting layer (hole transporting layer (HT)).
Subsequent to the formation of the first hole transporting layer, the compound HT3 was vapor-deposited on the first hole transporting layer to form a 5-nm-thick second organic compound layer (sometimes referred to as an electron blocking layer (EBL)).
The organic EL devices produced were evaluated as follows. Table 1 shows the evaluation results.
Voltage was applied to the organic EL devices 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.
EQE (relative value) (unit: %) was calculated on a basis of the measurement value of EQE of each Example and a numerical formula (Numerical Formula 1X) below.
EQE (relative value)=(EQE of each Example/EQE of Comparative 1)×100 (Numerical Formula 1X)
Voltage was applied to the organic EL device produced in each Example so that a current density was 50 mA/cm2, where a time (LT95 (unit: h)) elapsed before a luminance intensity was reduced to 95% of the initial luminance intensity was measured. The luminance intensity was measured by a spectroradiometer CS-2000 (produced by Konica Minolta, Inc.).
LT95 (relative value) (unit: %) was calculated on a basis of the measurement value of LT95 of each Example and a numerical formula (Numerical Formula 2X) below.
LT95 (relative value)=(LT95 of each Example/LT95 of Comparative 1)×100 (Numerical Formula 2X)
A measurement target compound was dissolved in EPA (diethylether:isopentane:ethanol=5:5:2 in volume ratio) at a concentration of 10 μmol/L to prepare a solution, 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 λedge [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.
T
1 [eV]=1239.85/λedge Conversion Equation (F1):
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 manufactured 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.
S
1 [eV]=1239.85/λedge Conversion Equation (F2):
A spectrophotometer (U3310 manufactured 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.
The energy level of the highest occupied molecular orbital HOMO was herein measured with a photoelectron spectroscope (“AC-3” manufactured by RIKEN KEIKI Co., Ltd.) under atmosphere. Specifically, the material was irradiated with light and the amount of electrons generated by charge separation was measured to measure the energy level of the highest occupied molecular orbital HOMO of the compound.
The electron mobility μe was measured by the following method according to impedance spectroscopy.
A measurement target layer having a 200-m thickness was held between the anode and the cathode, to which a small alternating voltage of 100 mV or less was applied while a bias DC voltage was applied. A value of an alternating current (absolute value and phase) which flowed at this time was measured. This measurement was performed while changing a frequency of the alternating voltage, and complex impedance (Z) was 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) was obtained. The reciprocal number of a frequency ω at which the ImM became the maximum was defined as a response time of electrons carried in the measurement target layer. The electron mobility μe (unit: cm2/(V·s)) was calculated by the following equation.
Electron Mobility μe=(Film Thickness of Measurement Target Layer)2/(Response Time-Voltage)
Hole mobility μh was measured using an organic EL device for mobility evaluation produced according to the following steps.
A glass substrate (size: 25 mm×75 mm×1.1 mm thick, manufactured 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 ITO 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 HA-2 was vapor-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 5-nm-thick hole injecting layer.
Next, the compound HT-A was vapor-deposited on the hole injecting layer to form a 10-nm-thick hole transporting layer.
Subsequently, a compound Target, which was to be measured for the hole mobility pH, was vapor-deposited to form a measurement target layer having a thickness of 200 nm.
Subsequently, metal aluminum (Al) was vapor-deposited on the measurement target layer to form an 80-nm-thick metal cathode.
An arrangement of the above device for mobility evaluation is roughly shown as follows.
Numerals in parentheses represent a film thickness (nm).
Subsequently, the hole mobility was measured using an organic EL device for mobility evaluation produced as described above according to the following steps.
The organic EL device for evaluating the hole mobility was set in an impedance measurement apparatus and an impedance measurement was performed.
In the impedance measurement, a measurement frequency was swept from 1 Hz to 1 MHz. At this time, an alternating current amplitude of 0.1 V and a direct current voltage V were applied to the device.
A modulus M was calculated from the measured impedance Z using a relationship of a calculation formula (C1) below.
M=jωZ Calculation Formula (C1):
In the calculation formula (C1), j is an imaginary unit whose square is −1 and ω is an angular frequency [rad/s].
In a bode plot in which an imaginary part of the modulus M was represented by an ordinate axis and the frequency [Hz] was represented by an abscissa axis, an electrical time constant τ of the organic EL device for mobility evaluation was obtained from a frequency fmax showing a peak using a calculation formula (C2) below.
τ=1/(2πfmax) Calculation Formula (C2):
The hole mobility μh was calculated from a relationship of a calculation formula (C3) below using τ obtained above.
μh=d2/(Vτ) Calculation Formula (C3):
d in the calculation formula (C3) is a total film thickness of organic thin film(s) forming the device. As in the above-described device arrangement for the mobility evaluation, d=215 [nm] is satisfied.
The hole mobility herein is a value obtained in a case where a square root of an electric field intensity meets E1/2=500 [V1/2/cm1/2]. The square root of the electric field intensity, E1/2, can be calculated from a relationship of a calculation formula (C4) below.
E
1/2
=V
1/2
/d
1/2 Calculation Formula (C4):
In Examples, for the impedance measurement, a 1260 type by Solartron Analytical was used as the impedance measurement apparatus, and for a higher accuracy, a 1296 type dielectric constant measurement interface by Solartron Analytical was used together therewith.
The compound BD was dissolved in toluene at a concentration of 4.9×10−6 mol/L to prepare a toluene solution of the compound BD. Using a fluorescence spectrometer (spectrophotofluorometer F-7000 manufactured by Hitachi High-Tech Science Corporation), the toluene solution of the compound BD was excited at 390 nm, where a maximum peak wavelength was measured.
The fluorescence maximum peak wavelength of the compound BD was 455 nm.
/
A refractive index of the constituent material (compound) forming the organic layer was measured as follows.
A measurement target material was vacuum-deposited on a glass substrate to form a film having an approximately 50 nm thickness. Using a spectroscopic ellipsometer (M-2000UI, manufactured by J. A. Woollam Co., Inc. (US)), the obtained sample film was irradiated with incident light (from ultraviolet light through visible light to near-infrared light) every 5 degrees in a measurement angle range from 45 degrees to 75 degrees to measure change in a deflection state of the light reflected by the sample surface. In order to improve measurement accuracy of an extinction coefficient, a transmission spectrum in a substrate normal direction (direction perpendicular to a surface of the substrate of the organic EL device) was also measured using the spectroscopic ellipsometer. A glass substrate alone, on which the measurement target material was not vapor-deposited, was measured in the same manner as the above. The obtained measurement information was subjected to fitting using analysis software (Complete EASE) manufactured by J.A. Woollam.
As fitting conditions, an anisotropic model with uniaxial rotational symmetry was used and a parameter MSE, which indicates a mean square error in the analysis software, was set to be 3.0 or less. With respect to an organic film formed on the substrate, refractive indices in an in-plane direction and a normal direction, extinction coefficients in the in-plane direction and the normal direction, and an order parameter were calculated. A peak close to the long-wavelength region of the extinction coefficient (in-plane direction) was defined as S1, and the order parameter was calculated from a peak wavelength of S1. As fitting conditions for the glass substrate, an isotropic model was used.
A film of a low-molecular-weight material vacuum-deposited on the substrate usually exhibits uniaxial rotational symmetry with the substrate normal direction as the axis of rotation symmetry. Provided that an angle formed by the substrate normal direction and a molecular axis in a thin film formed on the substrate is defined as θ and the extinction coefficients in a substrate parallel direction (Ordinary direction) and a substrate perpendicular direction (Extra-Ordinary direction) obtained by performing variable-angle spectroscopic ellipsometry measurement on the thin film are respectively defined as ko and ke, S′ represented by a formula below is the order parameter.
S′=1−<cos 2θ>=2ko/(ke+2ko)=⅔(1−S)
S=(½)<3 cos 2θ−1>=(ke−ko)/(ke+2ko)
An evaluation method of the molecular orientation is a publicly known method, and details thereof are described in Organic Electronics, volume 10, page 127 (2009). Further, the method for forming the thin film is a vacuum deposition method.
The order parameter S′ obtained through the variable-angle spectroscopic ellipsometry measurement is 1.0 when all molecules are oriented in parallel with the substrate. When molecules are random without orientation, the order parameter S′ is 0.66.
Herein, a value of the refractive index at 2.7 eV in the substrate parallel direction (Ordinary direction), of the above measurement values, is defined as a refractive index of the measurement target material.
In a case where a plurality of compounds (constituent materials) as the measurement target materials were included in one layer, a refractive index of the constituent materials for the layer was measured with a spectroscopic ellipsometer in the same manner as above, the layer being a film formed by co-depositing the plurality of compounds on the glass substrate or a film formed by vapor-depositing a mixture containing the plurality of compounds.
Table 3 shows a value of a refractive index of each constituent material for each organic layer in the hole transporting zone and a value of a difference in refractive indices NM1-NM2.
1 . . . organic electroluminescence device, 10 . . . organic layers, 1A . . . organic electroluminescence device, 2 . . . substrate, 3 . . . anode, 4 . . . cathode, 51 . . . first emitting layer, 2 . . . second emitting layer, 6 . . . hole transporting zone, 61 . . . first organic compound layer, 62 . . . second organic compound layer, 8 . . . electron transporting layer, 9 . . . electron injecting layer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-217949 | Dec 2020 | JP | national |
| 2021-106108 | Jun 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/048349 | 12/24/2021 | WO |
