ORGANIC ELECTROLUMINESCENT ELEMENT AND COMPOSITION FOR ORGANIC MATERIALS
The present invention addresses the problem of providing: an organic electroluminescent element which is capable of emitting light with high luminous efficiency, while having a long service life; and a composition for organic materials. An organic electroluminescent element according to the present invention comprises a positive electrode, a negative electrode and one or more organic functional layers arranged between the positive electrode and the negative electrode, and is characterized in that: the organic functional layers contain a phosphorescent metal complex and a fluorescent compound; the phosphorescent metal complex is a compound having a structure that is represented by a specific general formula; and the phosphorescent metal complex is a core-shell type dopant that satisfies a specific formula.
1 . An organic electroluminescent element comprising an anode, a cathode and one or a plurality of organic functional layers interposed between the anode and the cathode, wherein the organic functional layer contains a phosphorescent metal complex and a fluorescent compound, the phosphorescent metal complex is a compound having a structure represented by Formula (1), and the phosphorescent metal complex satisfies the following Expression (a),
in Formula (1): M represents Ir or Pt; A 1 , A 2 , B 1 and B 2 each independently represent a carbon atom or a nitrogen atom; a ring Z 1 represents a 6-membered aromatic hydrocarbon ring, or a 5- or 6-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; a ring Z 2 represents a 5- or 6-membered aromatic heterocyclic ring formed with B 1 and B 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; among a bond between A 1 and M, and a bond between B 1 and M, one is a coordinate bond and the other is a covalent bond; the ring Z 1 and the ring Z 2 each independently may have a substituent, and the ring Z 1 and the ring Z 2 have at least one substituent represented by Formula (2); the substituent of the ring Z 1 and the substituent of the ring Z 2 may be bonded to form a condensed ring structure, and ligands represented by the ring Z 1 and the ring Z 2 may be linked to each other; L represents a monoanionic bidentate ligand coordinated to M, and L may have a substituent; m represents an integer of 0 to 2, n represents an integer of 1 to 3, when M represents Ir, m+n is 3, and when m represents Pt, m+n is 2, when m or n is 2 or more, the ligands represented by the ring Z 1 and the ring Z 2 , or L may be the same or different; the ligand represented by the ring Z 1 and the ring Z 2 may be linked to L,
in Formula (2), a symbol * represents a linking site with the ring Z 1 or the ring Z 2 in Formula (1); L′ represents a single bond or a linking group; R represents a hydrogen atom or a substituent; n′ represents an integer of 3 or more; a plurality of Rs may be the same or different; and A represents a hydrogen atom or a substituent,
{
V
all
/
V
core
}
>
2
Expression
(
a
)
in Expression (a), V all represents a molecular volume of a compound having a chemical structure represented by Formula (1) including the substituents bonded to the ring Z 1 and the ring Z 2 ; when M represents Ir, n=3 and m=0 are fixed, and when M represents Pt, n=2 and m=0 are fixed; V core represents a molecular volume of a compound having a chemical structure in which the substituent bonded to the ring Z 1 and the ring Z 2 is replaced with a hydrogen atom from the chemical structure indicating the molecular volume of V all ; and when there are plural types of ligands represented by the ring Z 1 and the ring Z 2 , V all and V core satisfy Expression (a) in all cases expressed by the aforesaid conditions;
wherein the organic functional layer is a light emitting layer;
wherein an emission spectrum of the phosphorescent metal complex and an absorption spectrum of the fluorescent compound are overlapped;
wherein the phosphorescent metal complex is a sensitizer that transfers energy to the fluorescent compound to cause fluorescent light to be emitted from the fluorescent compound.
2 . The organic electroluminescent element described in claim 1 , wherein L′ in Formula (2) represents a non-conjugated linking group.
3 . The organic electroluminescent element described in claim 1 , wherein the ligands represented by Z 1 and Z 2 in Formula (1) contain three or more substituents.
4 . The organic electroluminescent element described in claim 1 , wherein the phosphorescent metal complex is a compound having a structure represented by any one of Formulas (3) to (5), and the phosphorescent metal complex satisfies the following Expression (b),
in Formulas (3) to (5): M represents Ir or Pt; A 1 to A 3 , and B 1 to B 4 each independently represent a carbon atom or a nitrogen atom; among a bond between A 1 and M, and a bond between B 1 and M, one is a coordinate bond and the other is a covalent bond; L represents a monoanionic bidentate ligand coordinated to M, and L may have a substituent; m represents an integer of 0 to 2, n represents an integer of 1 to 3, when M represents Ir, m+n is 3, and when m represents Pt, m+n is 2, when m or n is 2 or more, ligands represented by a ring Z 3 and a ring Z 4 , ligands represented by a ring Z 5 and a ring Z 6 , and ligands represented by a ring Z 7 and a ring Z 8 , or L may be the same or different; the ligands represented by the ring Z 3 to Z 8 may be linked to L,
in Formula (3), the ring Z 3 represents a 5-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing the aforesaid ring; the ring Z 4 represents a 5-membered aromatic heterocyclic ring formed with B 1 to B 3 , or an aromatic condensed ring containing the aforesaid ring; R 1 represents a substituent having 2 or more carbon atoms; the ring Z 3 and the ring Z 4 may have a substituent besides R 1 and may form a condensed ring structure by bonding of the substituents of the ring Z 3 and the ring Z4; the ligands represented by the ring Z 3 and the ring Z 4 may be linked to each other,
in Formula (4), the ring Z 5 represents a 6-membered aromatic hydrocarbon ring, a 6-membered aromatic heterocyclic ring formed with A 1 to A 3 , or an aromatic condensed ring containing at least one of the aforesaid rings; the ring Z 6 represents a 5-membered aromatic heterocyclic ring formed with B 1 to B 3 , or an aromatic condensed ring containing at least one of the aforesaid rings; R 2 and R 3 each represent a hydrogen atom or a substituent, at least one of R 2 and R 3 represents a substituent having 2 or more carbon atoms; the ring Z 5 and the ring Z 6 may have a substituent besides R 2 and R 3 and may form a condensed ring structure by bonding of the substituents of the ring Z 5 and the ring Z 6 , and the ligands represented by the ring Z 5 and the ring Z 6 may be linked to each other,
in Formula (5), the ring Z 7 represents a 6-membered aromatic hydrocarbon ring, a 6-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; the ring Z 8 represents a 6-membered aromatic hydrocarbon ring or a 6-membered aromatic heterocyclic ring formed with B 1 to B 4 , or an aromatic condensed ring containing at least one of the aforesaid rings; R 4 and R 5 each represent a hydrogen atom or a substituent, at least one of R 4 and R 5 represents a substituent having 2 or more carbon atoms; the ring Z 7 and the ring Z 8 may have a substituent besides R 4 and R 5 and may form a condensed ring structure by bonding of the substituents of the ring Z 7 and the ring Z 8 , and the ligands represented by the ring Z 7 and the ring Z 8 may be linked to each other,
{
V
all
/
V
core
}
>
2
Expression
(
b
)
In Expression (b), V all represents a molecular volume of a compound having a chemical structure represented by any one of Formulas (3) to (5) including the substituents bonded to the ring Z 3 to the ring Z 8 ; when M represents Ir, n=3 and m=0 are fixed, and when M represents Pt, n=2 and m=0 are fixed; V core represents a molecular volume of a compound having a chemical structure in which the substituent bonded to the ring Z 3 to the ring Z 8 is replaced with a hydrogen atom from the chemical structure indicating the molecular volume of V all ; and when there are a plurality of ligands represented by the ring Z 3 and the ring Z 4 , ligands represented by the ring Z 5 and the ring Z 6 , ligands represented by the ring Z 7 and the ring Z 8 , V all and V core satisfy Expression (b) in all cases expressed by the aforesaid conditions.
5 . The organic electroluminescent element described in claim 4 , wherein the ligands represented by the ring Z 3 and the ring Z 4 in Formula (3), the ligands represented by the ring Z 5 and the ring Z 6 in Formula (4), or the ligands represented by the ring Z 7 and the ring Z 8 in Formula (5) have three or more substituents.
6 . The organic electroluminescent element described in claim 1 , wherein the phosphorescent metal complex and the fluorescent compound satisfy the following Expression (A1);
0
<
τ
/
τ
0
,
≤
0.7
;
Expression
(
A1
)
in Expression (A1), r is the light emission-attenuation lifetime of the light emitting layer single layer; to is the light emission-attenuation lifetime of the single film of the phosphorescent compound;
wherein the light emitting layer single layer refers to an evaluation thin film prepared as a spectrum measurement sample that includes a host compound, a phosphorescent compound, and a fluorescent compound;
wherein the single film of the phosphorescent compound refers to a thin film containing the host compound and the phosphorescent compound among the evaluation films that contains the host compound, the phosphorescent compound and the fluorescent compound.
7 . The organic electroluminescent element described in claim 1 , wherein the phosphorescent metal complex and the fluorescent compound satisfy at least one of the following Expression (c) and Expression (d),
P
(
HOMO
)
>
FL
(
HOMO
)
Expression
(
c
)
in Expression (c), P(HOMO) represents a HOMO energy level of the phosphorescent metal complex, and FL(HOMO) represents a HOMO energy level of the fluorescent compound,
P
(
LUMO
)
<
FL
(
LUMO
)
Expression
(
d
)
in Expression (d), P(LUMO) represents a LUMO energy level of the phosphorescent metal complex, and FL(LUMO) represents a LUMO energy level of the fluorescent compound.
8 . The organic electroluminescent element described in claim 1 , wherein the phosphorescent metal complex and the fluorescent compound satisfy the following Expression (A2);
0.6
≤
PLQE
/
PLQE
0
≤
1
;
Expression
(
A2
)
in Expression (A2), PLQE is the absolute quantum yield of the light emitting layer single layer; PLQE 0 is the absolute quantum yield of the single film of the phosphorescent compound;
wherein the light emitting layer single layer refers to an evaluation thin film prepared as a spectrum measurement sample that includes a host compound, a phosphorescent compound, and a fluorescent compound;
wherein the single film of the phosphorescent compound refers to a thin film containing the host compound and the phosphorescent compound among the evaluation films that contains the host compound, the phosphorescent compound and the fluorescent compound.
9 . The organic electroluminescent element described in claim 1 , wherein {V all /V core }>2.5.
10 . The organic electroluminescent element described in claim 1 , wherein the fluorescent compound is selected from the group consisting of an anthracene derivative, a pyrene derivative, a chrysene derivative, a fluoranthene derivative, a perylene derivative, a fluorene derivative, an arylacetylene derivative, a styrylarylene derivative, a styrylamine derivative, an arylamine derivative, a boron complex, a coumarin derivative, a pyran derivative, a cyanine derivative, a croconium derivative, a squarylium derivative, an oxobenzanthracene derivative, a fluorescein derivative, a rhodamine derivative, a pyrylium derivative, a perylene derivative, a polythiophene derivative, and a rare earth complex compound.
11 . The organic electroluminescent element described in claim 1 , wherein the fluorescent compound is a boron complex.
12 . The organic electroluminescent element described in claim 1 , wherein the fluorescent compound is a delayed fluorescent compound.
13 . The organic electroluminescent element described in claim 1 , wherein the fluorescent compound comprises a fused ring system having at least five rings.
14 . The organic electroluminescent element described in claim 1 , wherein the fluorescent compound comprises at least four alkyl substituents.
15 . A composition for organic materials containing a phosphorescent metal complex and a fluorescent compound, wherein the phosphorescent metal complex is a compound having a structure represented by Formula (1), and the phosphorescent metal complex satisfies the following Expression (a),
in Formula (1): M represents Ir or Pt; A 1 , A 2 , B 1 and B 2 each independently represent a carbon atom or a nitrogen atom; a ring Z 1 represents a 6-membered aromatic hydrocarbon ring, or a 5- or 6-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; a ring Z 2 represents a 5- or 6-membered aromatic heterocyclic ring formed with B 1 and B 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; among a bond between A 1 and M, and a bond between B 1 and M, one is a coordinate bond and the other is a covalent bond; the ring Z 1 and the ring Z 2 each independently may have a substituent, and the ring Z 1 and the ring Z 2 have at least one substituent represented by Formula (2); the substituent of the ring Z 1 and the substituent of the ring Z 2 may be bonded to form a condensed ring structure, and ligands represented by the ring Z 1 and the ring Z 2 may be linked to each other; L represents a monoanionic bidentate ligand coordinated to M, and L may have a substituent; m represents an integer of 0 to 2, n represents an integer of 1 to 3, when M represents Ir, m+n is 3, and when m represents Pt, m+n is 2, when m or n is 2 or more, the ligands represented by the ring Z 1 and the ring Z 2 , or L may be the same or different; the ligand represented by the ring Z 1 and the ring Z 2 may be linked to L,
in Formula (2), a symbol * represents a linking site with the ring Z 1 or the ring Z 2 in Formula (1); L′ represents a single bond or a linking group; R represents a hydrogen atom or a substituent; n′ represents an integer of 3 or more; a plurality of Rs may be the same or different; and A represents a hydrogen atom or a substituent,
{
V
all
/
V
core
}
>
2
Expression
(
a
)
in Expression (a), V all represents a molecular volume of a compound having a chemical structure represented by Formula (1) including the substituents bonded to the ring Z 1 and the ring Z 2 ; when M represents Ir, n=3 and m=0 are fixed, and when M represents Pt, n=2 and m=0 are fixed; V core represents a molecular volume of a compound having a chemical structure in which the substituent bonded to the ring Z 1 and the ring Z 2 is replaced with a hydrogen atom from the chemical structure indicating the molecular volume of V all ; and when there are plural types of ligands represented by the ring Z 1 and the ring Z 2 , V all and V core satisfy Expression (a) in all cases expressed by the aforesaid conditions;
wherein an emission spectrum of the phosphorescent metal complex and an absorption spectrum of the fluorescent compound are overlapped;
wherein when the composition is used in a light emitting layer of an organic electroluminescent element, the phosphorescent metal complex is as a sensitizer that transfers energy to the fluorescent compound to cause fluorescent light to be emitted from the fluorescent compound.
16 . The composition described in claim 15 , wherein the phosphorescent metal complex is a compound having a structure represented by any one of Formulas (3) to (5), and the phosphorescent metal complex satisfies the following Expression (b),
in Formulas (3) to (5): M represents Ir or Pt; A 1 to A 3 , and B 1 to B 4 each independently represent a carbon atom or a nitrogen atom; among a bond between A 1 and M, and a bond between B 1 and M, one is a coordinate bond and the other is a covalent bond; L represents a monoanionic bidentate ligand coordinated to M, and L may have a substituent; m represents an integer of 0 to 2, n represents an integer of 1 to 3, when M represents Ir, m+n is 3, and when m represents Pt, m+n is 2, when m or n is 2 or more, ligands represented by a ring Z 3 and a ring Z 4 , ligands represented by a ring Z 5 and a ring Z 6 , and ligands represented by a ring Z 7 and a ring Z 8 , or L may be the same or different; the ligands represented by the ring Z 3 to Z 8 may be linked to L,
in Formula (3), the ring Z 3 represents a 5-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing the aforesaid ring; the ring Z 4 represents a 5-membered aromatic heterocyclic ring formed with B 1 to B 3 or an aromatic condensed ring containing the aforesaid ring; R 1 represents a substituent having 2 or more carbon atoms; the ring Z 3 and the ring Z 4 may have a substituent besides R 1 and may form a condensed ring structure by bonding of the substituents of the ring Z 3 and the ring Z4; the ligands represented by the ring Z 3 and the ring Z 4 may be linked to each other,
in Formula (4), the ring Z 5 represents a 6-membered aromatic hydrocarbon ring, a 6-membered aromatic heterocyclic ring formed with A 1 to A 3 , or an aromatic condensed ring containing at least one of the aforesaid rings; the ring Z 6 represents a 5-membered aromatic heterocyclic ring formed with B 1 to B 3 , or an aromatic condensed ring containing at least one of the aforesaid rings; R 2 and R 3 each represent a hydrogen atom or a substituent, at least one of R 2 and R 3 represents a substituent having 2 or more carbon atoms; the ring Z 5 and the ring Z 6 may have a substituent besides R 2 and R 3 and may form a condensed ring structure by bonding of the substituents of the ring Z 5 and the ring Z 6 , and the ligands represented by the ring Z 5 and the ring Z 6 may be linked to each other,
in Formula (5), the ring Z 7 represents a 6-membered aromatic hydrocarbon ring, a 6-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; the ring Z 8 represents a 6-membered aromatic hydrocarbon ring or a 6-membered aromatic heterocyclic ring formed with B 1 to B 4 , or an aromatic condensed ring containing at least one of the aforesaid rings; R 4 and R 5 each represent a hydrogen atom or a substituent, at least one of R 4 and R 5 represents a substituent having 2 or more carbon atoms; the ring Z 7 and the ring Z 8 may have a substituent besides R 4 and R 5 and may form a condensed ring structure by bonding of the substituents of the ring Z 7 and the ring Z 8 , and the ligands represented by the ring Z 7 and the ring Z 8 may be linked to each other,
{
V
all
/
V
core
}
>
2
Expression
(
b
)
in Expression (b), V all represents a molecular volume of a compound having a chemical structure represented by any one of Formulas (3) to (5) including the substituents bonded to the ring Z 3 to the ring Z 8 ; when M represents Ir, n=3 and m=0 are fixed, and when M represents Pt, n=2 and m=0 are fixed; V core represents a molecular volume of a compound having a chemical structure in which the substituent bonded to the ring Z 3 to the ring Z 8 is replaced with a hydrogen atom from the chemical structure indicating the molecular volume of V a n; and when there are a plurality of ligands represented by the ring Z 3 and the ring Z 4 , ligands represented by the ring Z 5 and the ring Z 6 , ligands represented by the ring Z 7 and the ring Z 8 , V all and V core satisfy Expression (b) in all cases expressed by the aforesaid conditions.
17 . The composition described in claim 15 , wherein the fluorescent compound is selected from the group consisting of an anthracene derivative, a pyrene derivative, a chrysene derivative, a fluoranthene derivative, a perylene derivative, a fluorene derivative, an arylacetylene derivative, a styrylarylene derivative, a styrylamine derivative, an arylamine derivative, a boron complex, a coumarin derivative, a pyran derivative, a cyanine derivative, a croconium derivative, a squarylium derivative, an oxobenzanthracene derivative, a fluorescein derivative, a rhodamine derivative, a pyrylium derivative, a perylene derivative, a polythiophene derivative, and a rare earth complex compound.
18 . The composition described in claim 15 , wherein the fluorescent compound is a boron complex.
19 . The composition described in claim 15 , wherein the fluorescent compound comprises a fused ring system having at least five rings.
20 . An organic electroluminescent element comprising an anode, a cathode and one or a plurality of organic functional layers interposed between the anode and the cathode, wherein the organic functional layer contains a phosphorescent metal complex and a fluorescent compound, the phosphorescent metal complex is a compound having a structure represented by Formula (1), and the phosphorescent metal complex satisfies the following Expression (a),
in Formula (1): M represents Ir or Pt; A 1 , A 2 , B 1 and B 2 each independently represent a carbon atom or a nitrogen atom; a ring Z 1 represents a 6-membered aromatic hydrocarbon ring, or a 5- or 6-membered aromatic heterocyclic ring formed with A 1 and A 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; a ring Z 2 represents a 5- or 6-membered aromatic heterocyclic ring formed with B 1 and B 2 , or an aromatic condensed ring containing at least one of the aforesaid rings; among a bond between A 1 and M, and a bond between B 1 and M, one is a coordinate bond and the other is a covalent bond; the ring Z 1 and the ring Z 2 each independently may have a substituent, and the ring Z 1 and the ring Z 2 have at least one substituent represented by Formula (2); the substituent of the ring Z 1 and the substituent of the ring Z 2 may be bonded to form a condensed ring structure, and ligands represented by the ring Z 1 and the ring Z 2 may be linked to each other; L represents a monoanionic bidentate ligand coordinated to M, and L may have a substituent; m represents an integer of 0 to 2, n represents an integer of 1 to 3, when M represents Ir, m+n is 3, and when m represents Pt, m+n is 2, when m or n is 2 or more, the ligands represented by the ring Z 1 and the ring Z 2 , or L may be the same or different; the ligand represented by the ring Z 1 and the ring Z 2 may be linked to L,
in Formula (2), a symbol * represents a linking site with the ring Z 1 or the ring Z 2 in Formula (1); L′ represents a single bond or a linking group; R represents a hydrogen atom or a substituent; n′ represents an integer of 3 or more; a plurality of Rs may be the same or different; and A represents a hydrogen atom or a substituent,
{
V
all
/
V
core
}
>
2
Expression
(
a
)
in Expression (a), V all represents a molecular volume of a compound having a chemical structure represented by Formula (1) including the substituents bonded to the ring Z 1 and the ring Z 2 ; when M represents Ir, n=3 and m=0 are fixed, and when M represents Pt, n=2 and m=0 are fixed; V core represents a molecular volume of a compound having a chemical structure in which the substituent bonded to the ring Z 1 and the ring Z 2 is replaced with a hydrogen atom from the chemical structure indicating the molecular volume of V all ; and when there are plural types of ligands represented by the ring Z 1 and the ring Z 2 , V all and V core satisfy Expression (a) in all cases expressed by the aforesaid conditions;
wherein the organic functional layer is a light emitting layer;
wherein an emission spectrum of the phosphorescent metal complex and an absorption spectrum of the fluorescent compound are overlapped;
wherein the phosphorescent metal complex is a sensitizer that transfers energy to the fluorescent compound to cause fluorescent light to be emitted from the fluorescent compound;
wherein the fluorescent compound is a boron complex.