Patent Grant
12127478
The entire disclosure of Japanese Patent Application No. 2020-102555 filed Jun. 12, 2020 is expressly incorporated by reference herein.
The present invention relates to an organic electroluminescence device and an electronic device.
When a voltage is applied to an organic electroluminescence device (hereinafter, occasionally referred to as “organic EL device”), holes are injected from an anode and electrons are injected from a cathode into an emitting layer. The injected electrons and holes 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%.
A fluorescent organic EL device using light emission from singlet excitons has been applied to a full-color display such as a mobile phone and a television set, but an internal quantum efficiency is said to be at a limit of 25%. Accordingly, studies has been made to improve a performance of the organic EL device.
For instance, it is expected to further efficiently emit the organic EL device using triplet excitons in addition to singlet excitons. In view of the above, a highly efficient fluorescent organic EL device using thermally activated delayed fluorescence (hereinafter, sometimes simply referred to as “delayed fluorescence”) has been proposed and studied.
A TADF (Thermally Activated Delayed Fluorescence) mechanism uses such a phenomenon that inverse intersystem crossing from triplet excitons to singlet excitons thermally occurs when a material having a small energy difference (ΔST) between singlet energy level and triplet energy level is used. Thermally activated delayed fluorescence is explained in “Yuki Hando-tai no Debaisu Bussei (Device Physics of Organic Semiconductors)” (edited by ADACHI, Chihaya, published by Kodansha, issued on Apr. 1, 2012, on pages 261-268).
As a compound exhibiting TADF properties (hereinafter also referred to as a TADF compound), for example, a compound in which a donor moiety and an acceptor moiety are bonded in a molecule is known.
Examples of literatures relating to organic EL devices include Literature 1 (Chinese Patent Application Publication No. 110492006) and Literature 2 (Chinese Patent Application Publication No. 107964017).
Literature 1 discloses, in Examples, a device in which a TADF compound (e.g., a compound DB-1), an indenocarbazole compound such as a compound H6 or H7, and “a compound in which monocyclic azine (nitrogen-containing six-membered ring) is substituted by indenocarbazole” such as and a compound H4 are used in an emitting layer.
Literature 2 discloses, in Examples, a device in which a TADF compound, a carbazole compound such as a compound GH-204, and “a compound in which azatriphenylene is substituted by benzofurocarbazole” such as a compound 102 are used in an emitting layer.
In order to improve performance of an electronic device such as a display, an organic EL device has been required to be further improved in performance.
An object of the invention is to provide an organic electroluminescence device with higher performance, in particular, with improved luminous efficiency and an electronic device including the organic electroluminescence device.
According to an aspect of the invention, an organic electroluminescence device includes: an anode; a cathode; and an emitting layer provided between the anode and the cathode, in which
m1 is 1, 2, 3, 4, or 5;
According to another aspect of the invention, an electronic device including the organic electroluminescence device according to the above aspect of the invention is provided.
According to still another aspect of the invention, it is possible to provide an organic-electroluminescence-device with higher performance, in particular, with improved luminous efficiency and an electronic device including the organic electroluminescence device.
Arrangement(s) of an organic EL device according to a first exemplary embodiment of the invention will be described below.
The organic EL device includes an anode, a cathode, and at least one organic layer between the anode and the cathode. The organic layer includes at least one layer formed of an organic compound. Alternatively, the organic layer includes a plurality of layers formed of an organic compound(s). The organic layer may further contain an inorganic compound. At least one of the organic layer(s) of the organic EL device of the exemplary embodiment is an emitting layer. Accordingly, the organic layer may, for instance, be provided by a single emitting layer, or include a layer(s) usable for an organic EL device. Examples of the layer usable in the organic EL device, which are not particularly limited, include at least one layer selected from the group consisting of a hole injecting layer, hole transporting layer, electron blocking layer, electron injecting layer, electron transporting layer, and hole blocking layer.
The organic EL device of the exemplary embodiment includes an emitting layer between the anode and the cathode.
An organic EL device 1 includes a light-transmissive substrate 2, an anode 3, a cathode 4, and an organic layer 10 provided between the anode 3 and the cathode 4. The organic layer 10 includes a hole injecting layer 6, a hole transporting layer 7, an emitting layer 5, an electron transporting layer 8, and an electron injecting layer 9, which are sequentially laminated on the anode 3.
In an arrangement of the exemplary embodiment, the emitting layer may contain a metal complex.
In an arrangement of the exemplary embodiment, it is preferable that the emitting layer does not contain a phosphorescent material (dopant material).
In an arrangement of the exemplary embodiment, it is preferable that the emitting layer 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 an arrangement of the exemplary embodiment, it is also preferable that the emitting layer does not contain a metal complex.
In the organic EL device of the exemplary embodiment, the emitting layer contains a first compound represented by a formula (1x) or a formula (1Y), a second compound, and a third compound that exhibits delayed fluorescence.
The second compound and the first compound are mutually different in a structure.
The second compound and the third compound are mutually different in a structure.
The first compound and the second compound are preferably a host material.
In the exemplary embodiment, it is preferable that the third compound that exhibits delayed fluorescence is also a host material.
Herein, in order to distinguish between the first, second, and third compounds, the first and second compounds each in a form of a host material are occasionally referred to as a “matrix” for convenience of explanation.
A case where the first and second compounds coexist is occasionally referred to as a “co-matrix”.
The third compound in a form of a host material is occasionally referred to simply as a “host material” or “host”.
A host material exhibiting hole injectability is occasionally referred to as a “p-host”, and a host material exhibiting electron injectability is occasionally referred to as a “n-host”.
In the following description, the first compound, the second compound, and the third compound in a form of a host material, unless particularly distinguished from each other, are collectively referred to as a “host material” or “host”.
In the exemplary embodiment, the first compound is preferably a matrix with relatively high electron injectability (i.e., n-host). The second compound is preferably a matrix with relatively high hole injectability (i.e., p-host).
The inventors have found that an organic EL device can be highly improved in performance, in particular, in luminous efficiency by using the first compound represented by the formula (1x) or (1Y) and the second compound as the “comatrix” together with the third compound that exhibits delayed fluorescence.
As a result of dedicated studies, the inventors have found that luminous efficiency is improved by using “a compound in which monocyclic azine is substituted by benzofurocarbazole or benzothienocarbazole (the first compound of the exemplary embodiment)”, as the n-host, in an emitting layer containing a delayed fluorescent compound.
In general, in a delayed fluorescent compound, a moiety having a large absolute value of energy level of LUMO (lowest unoccupied molecular orbital) is often introduced into a molecule in order to reduce ΔST. However, if the emitting layer contains a delayed fluorescent compound into which the moiety is introduced, electron transportability of the emitting layer may be hindered.
Literature 1 discloses a device in which an electron injectable “compound (compound H4: n-host) in which monocyclic azine (nitrogen-containing six-membered ring) is substituted by indenocarbazole” and another matrix are contained as the “co-matrix” in an emitting layer containing a delayed fluorescent compound. The device described in Literature 1 corresponds to organic EL devices in Comparatives 1 to 3 below, and luminous efficiency thereof is lower than in all the Examples. The reason thereof is considered as follows.
In the “compound in which monocyclic azine is substituted by indenocarbazole” disclosed by Literature 1, hole injectability is too high for electron injectability. This may excessively increase an amount of holes and reduce luminous efficiency by introducing the “compound in which monocyclic azine is substituted by indenocarbazole” in the emitting layer. It is considered that electron transportability of the emitting layer may be hindered, in particular, in a device containing a delayed fluorescent compound, which may remarkably reduce luminous efficiency.
In contrast, it is considered that in a case where the “compound in which monocyclic azine is substituted by benzofurocarbazole or benzothienocarbazole (the first compound of the exemplary embodiment)” is used as the n-host, instead of the “compound in which monocyclic azine is substituted by indenocarbazole” as disclosed by Literature 1, a hole injecting amount to the emitting layer is inhibited as appropriate, thus highly improving the device in efficiency.
Further, it is considered that a “co-matrix” type emitting layer to which another matrix is added has an advantage that a device performance is improved because crystallization is inhibited by multiple components to improve film quality.
In the exemplary embodiment, it is considered that the emitting layer contains the “compound in which monocyclic azine is substituted by benzofurocarbazole or benzothienocarbazole (the first compound of the exemplary embodiment)” as the n-host and another matrix (preferably, the p-host exhibiting hole injectability) (the second compound of the exemplary embodiment) together with a delayed fluorescent compound (the third compound of the exemplary embodiment), and thus the device is highly improved in efficiency when a supply amount of holes is inhibited as appropriate.
Literature 2 discloses a “compound in which azatriphenylene is substituted by benzofurocarbazole” such as a compound 102. A device in which the compound 102, another host, and a delayed fluorescent compound are contained in an emitting layer corresponds to organic EL devices in Comparatives 4 and 5 below, and luminous efficiency thereof is lower than in all the Examples. The reason thereof is considered that, due to an azatriphenylene compound exhibiting low electron transportability, an amount of holes remains excessive even if azatriphenylene is substituted by benzofurocarbazole.
Accordingly, the organic EL device according to the exemplary embodiment can exhibit higher luminous efficiency than conventional organic EL devices.
Further, according to the exemplary embodiment, a high-performance organic EL device is achievable.
High performance means at least one of luminous efficiency, device lifetime, drive voltage, and luminance is improved.
According to the exemplary embodiment, it is expected to improve, in addition to luminous efficiency, at least one of device lifetime, drive voltage, and luminance.
Explanation is made below about an arrangement of the first exemplary embodiment where the emitting layer contains the first compound, the second compound, and the third compound, and further contains a fourth compound that fluoresces.
Emitting Layer
First Compound
The emitting layer of the exemplary embodiment contains the first compound represented by a formula (1X) or a formula (1Y) below.
The first compound of the exemplary embodiment may be a thermally activated delayed fluorescent compound or a compound exhibiting no thermally activated delayed fluorescence.
The first compound of the exemplary embodiment is preferably a compound exhibiting no thermally activated delayed fluorescence.
In the formulae (1X) and (1Y): A is a group represented by a formula (a1), a formula (a2), a formula (a3), a formula (a4), a formula (a5), or a formula (a6) below.
In the formulae (1X) and (1Y):
In the formula (1Z):
In the formulae (a1) to (a6):
In the formula (1X), L being a single bond means that A is directly bonded to a carbon atom in a six-membered ring in the formula (1X). The above means, for example, when A is a group represented by the formula (a1), a carbon atom in a six-membered ring in the formula (1X) is directly bonded to one of positions R110 to R119 and R11. The same applies to a case where A is a group represented by one of the formulae (a2) to (a6).
In the formula (1Y), L being a single bond means that A is directly bonded to a carbon atom in a six-membered ring in the formula (1Y). The above means, for example, when A is a group represented by the formula (a1), a carbon atom in a six-membered ring in the formula (1Y) is directly bonded to one of positions R110 to R119 and R11. The same applies to a case where A is a group represented by one of the formulae (a2) to (a6).
In the formula (1Z), L12 being a single bond means that: L11 is directly bonded to R4X when m1 is 1; L11 is directly bonded to two R4X when m1 is 2; L11 is directly bonded to three R4X when m1 is 3; L11 is directly bonded to four R4X when m1 is 4; and L11 is directly bonded to five R4X when m1 is 5.
In the formula (1Z), “a trivalent group derived from the arylene group” in L11 is a group obtained by removing one hydrogen atom from the arylene group. In the formula (1Z), “a tetravalent group derived from the arylene group” in L11 is a group obtained by removing two hydrogen atoms from the arylene group. In the formula (1Z), “a pentavalent group derived from the arylene group” in L11 is a group obtained by removing three hydrogen atoms from the arylene group. In the formula (1Z), “a hexavalent group derived from the arylene group” in L11 is a group obtained by removing four hydrogen atoms from the arylene group.
The same applies to “a trivalent group derived from the divalent heterocyclic group”, “a tetravalent group derived from the divalent heterocyclic group”, “a pentavalent group derived from the divalent heterocyclic group”, and “a hexavalent group derived from the divalent heterocyclic group”.
A bonding form of the group represented by the formula (1Z) is determined depending on a value of m1.
In the formula (1Z), when m1 is 1, the bonding form is represented by a formula (1Z-1). In this case, L11 is, for example, the “arylene group”.
In the formula (1Z), when m1 is 2, the bonding form is represented by a formula (1Z-2). In this case, L11 is, for example, “a trivalent group derived from the arylene group”.
In the formula (1Z), when m1 is 3, the bonding form is represented by a formula (1Z-3). In this case, L11 is, for example, “a tetravalent group derived from the arylene group”.
In the formula (1Z), when m1 is 4, the bonding form is represented by a formula (1Z-4). In this case, L11 is, for example, “a pentavalent group derived from the arylene group”.
In the formula (1Z), when m1 is 5, the bonding form is represented by a formula (1Z-5). In this case, L11 is, for example, “a hexavalent group derived from the arylene group”.
In the formulae (1Z-1) to (1Z-5), * represents a bonding position to a carbon atom in a six-membered ring in the formula (1X) or (1Y).
In the formula (1Z), when m1 is 1 and L11 is, for example, “a divalent group formed by bonding two groups that are a substituted or unsubstituted arylene group L111 having 6 to 22 ring carbon atoms and a substituted or unsubstituted divalent heterocyclic group L112 having 5 to 22 ring atoms”, the bonding form is exemplified by a formula (1Z-6).
In the formula (1Z), when m1 is 2 and L11 is, for example, “a trivalent group formed by bonding two groups that are the arylene group L111 and the divalent heterocyclic group L112”, the bonding form is exemplified by a formula (1Z-7).
In the formula (1Z), when m1 is 3 and L11 is, for example, “a tetravalent group formed by bonding two groups that are the arylene group L111 and the divalent heterocyclic group L112”, the bonding form is exemplified by a formula (1Z-8).
In the formula (1Z), when m1 is 4 and L11 is, for example, “a pentavalent group formed by bonding two groups that are the arylene group L111 and the divalent heterocyclic group L12”, the bonding form is exemplified by a formula (1Z-9).
In the formula (1Z), when m1 is 5 and L11 is, for example, “a hexavalent group formed by bonding two groups that are the arylene group L111 and the divalent heterocyclic group L112”, the bonding form is exemplified by a formula (1Z-10).
In the formulae (1Z-6) to (1Z-10), * represents a bonding position to a carbon atom in a six-membered ring in the formula (1X) or (1Y).
In the first compound of the exemplary embodiment, A is preferably a group represented by the formula (a1), (a2), (a3), (a4), or (a6).
In the first compound of the exemplary embodiment, A is more preferably a group represented by the formula (a1), (a2), (a3), or (a4).
In the first compound of the exemplary embodiment, A is further preferably a group represented by the formula (a1) or (a4).
In the first compound of the exemplary embodiment, A is still further preferably a group represented by the formula (a1).
In the first compound of the exemplary embodiment, X11, X12, X13, X14, X15 and X16 are each preferably an oxygen atom.
The first compound of the exemplary embodiment is preferably a compound represented by a formula (11X), (12X), (13X), (14X), (15X), or (16X) below.
In the formula (11X), L, R1X, R2X, Y11 to Y13, R110 to R119 and X11 each independently represent the same as L, R1X, R2X, Y11 to Y13, R110 to R119 and X11 in the formulae (1X) and (a1);
In the first compound of the exemplary embodiment, R110 to R169, Ry, R1X, R2X, R3X, and R4X are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms; and
In the first compound of the exemplary embodiment, it is more preferable that R110 to R169, Ry, R1X, R2X, R3X, and R4X are each independently a hydrogen atom or a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, and R11 to R16 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the first compound of the exemplary embodiment, it is also preferable that R110 to R169 are each a hydrogen atom, and R11 to R16 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the first compound of the exemplary embodiment, R110 to R169, Ry, R1X, R2X, R3X, and R4X are preferably each independently a hydrogen atom, an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms, or an unsubstituted alkyl group having 1 to 30 carbon atoms; and
R11 to R16 are preferably each independently an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms, or an unsubstituted alkyl group having 1 to 30 carbon atoms.
In the first compound of the exemplary embodiment, L is preferably a single bond, a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, or a substituted or unsubstituted divalent heterocyclic group having 5 to 22 ring atoms.
In the first compound of the exemplary embodiment, it is more preferable that L is a single bond or a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms.
In the first compound of the exemplary embodiment, L is preferably a single bond, an unsubstituted arylene group having 6 to 25 ring carbon atoms, or an unsubstituted divalent heterocyclic group having 5 to 22 ring atoms.
In the first compound of the exemplary embodiment, L is preferably a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a substituted or unsubstituted terphenylene group.
In the first compound of the exemplary embodiment, L is preferably an unsubstituted phenylene group, an unsubstituted biphenylene group, or an unsubstituted terphenylene group.
It is preferable that the first compound of the exemplary embodiment is represented by the formula (1X), and Y11, Y12, and Y13 in the formula (1X) are each a nitrogen atom.
In the first compound of the exemplary embodiment, Ry, R1X, R2X, R3X, and R4X serving as the substituents are preferably each independently one of groups represented by formulae (b1) to (b17) below.
In the formulae (b1) to (b17), Ra is a hydrogen atom or a substituent, or one or more pairs of adjacent ones of Ra are mutually bonded to form a ring, and a plurality of Ra are mutually the same or different;
In the formulae (b1) to (b17), Ra is preferably a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, more preferably a hydrogen atom.
In the formule (b3) to (b4), it is preferable that Rb1 and Rb2 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a pair of Rb1 and Rb2 are bonded to each other to form a ring.
In the formula (b5), Rb3 is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
In the first compound of the exemplary embodiment, when Ry, R1X, R2X, R3X, and R4X serving as the substituents are each independently one of groups represented by the formulae (b1) to (b17), it is preferable that one or more pairs of adjacent ones of Ra are not mutually bonded.
In the first compound of the exemplary embodiment, when Ry, R1X, R2X, R3X, and R4X serving as the substituents are each independently one of the groups represented by the formulae (b1) to (b17), it is also preferable that one or more pairs of adjacent ones of Ra are mutually bonded.
In the first compound of the exemplary embodiment, L11 is preferably a single bond, or a divalent, trivalent, tetravalent, pentavalent, or hexavalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
In the first compound of the exemplary embodiment, L11 is preferably a single bond, or a divalent, trivalent, tetravalent, pentavalent, or hexavalent group derived from a group selected from the group consisting of an unsubstituted phenyl group, an unsubstituted biphenyl group, an unsubstituted naphthyl group, and an unsubstituted terphenyl group.
In the first compound of the exemplary embodiment, L12 is preferably a single bond, or a divalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
In the first compound of the exemplary embodiment, L12 is preferably a single bond, or a divalent group derived from a group selected from the group consisting of an unsubstituted phenyl group, an unsubstituted biphenyl group, an unsubstituted naphthyl group, and an unsubstituted terphenyl group.
Manufacturing Method of First Compound
The first compound of the exemplary embodiment can be manufactured, for instance, by a method described later in Examples. The first compound of the exemplary embodiment can be manufactured, for instance, by application of known substitution reactions and/or materials depending on a target compound according to reactions described later in Examples.
Specific Examples of First Compound
Specific examples of the first compound of the exemplary embodiment include, for example, the following compounds. It should however be noted that the invention is not limited to the specific examples of the compound.
Second Compound
The second compound of the exemplary embodiment may be a thermally activated delayed fluorescent compound or a compound exhibiting no thermally activated delayed fluorescence.
The second compound of the exemplary embodiment is preferably a compound exhibiting no thermally activated delayed fluorescence.
The emitting layer of the exemplary embodiment preferably contains the second compound represented by a formula (2) below.
C-M-D (2)
In the formula (2):
In the formula (C1):
In the formula (C1), the ring Cx is preferably a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heterocycle having 5 to 30 ring atoms.
In the formula (2), M being a single bond means that C is directly bonded to D. Specifically, the above means that D is directly bonded to one of positions of R1C to R9C and carbon atoms forming the ring Cx in the formula (C1).
Substituent of Second Compound Represented by Formula (2)
R1C to R9C in Formula (C1)
It is preferable that R1C to R9C serving as the substituents are each independently a group selected from a substituent group A below.
The ring Cx is preferably a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heterocycle having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen. The ring Cx is particularly preferably a substituted or unsubstituted heterocycle having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen.
When R1C to R9C and the ring Cx serving as the substituents are further substituted, the substituents (substituents for the substituted or unsubstituted groups in R1C to R9C and the ring Cx) are preferably each independently a group selected from the substituent group A, more preferably a group selected from the substituent group B.
The substitutents in the substituent group A and the substituent group B are groups exhibiting relatively high electron donating property.
Substituent Group A: a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkyl halide group having 1 to 30 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, a substituted or unsubstituted alkylsilyl group having 3 to 30 carbon atoms, a substituted or unsubstituted arylsilyl group having 6 to 60 ring carbon atoms, a substituted or unsubstituted arylphosphoryl group having 6 to 60 ring carbon atoms, a hydroxy group a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 30 ring carbon atoms, a group represented by —N(Rz)2, where Rz is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and two Rz in —N(Rz)2 are mutually the same or different, a thiol group a substituted or unsubstituted alkylthio group having 1 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 ring carbon atoms, a substituted germanium group, and a substituted or unsubstituted arylthio group having 6 to 30 ring carbon atoms.
Substituent Group B: an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen, an unsubstituted alkyl group having 1 to 30 carbon atoms, an unsubstituted alkyl halide group having 1 to 30 carbon atoms, an unsubstituted alkenyl group having 2 to 30 carbon atoms, an unsubstituted alkynyl group having 2 to 30 carbon atoms, an unsubstituted alkylsilyl group having 3 to 30 carbon atoms an unsubstituted arylsilyl group having 6 to 60 ring carbon atoms, an unsubstituted arylphosphoryl group having 6 to 60 ring carbon atoms, a hydroxy group, an unsubstituted alkoxy group having 1 to 30 carbon atoms, an unsubstituted aryloxy group having 6 to 30 ring carbon atoms, a group represented by N(Rz)2, where Rz is an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms, or an unsubstituted alkyl group having 1 to 30 carbon atoms, and two Rz in —N(Rz)2 are mutually the same or different, a thiol group, an unsubstituted alkylthio group having 1 to 30 carbon atoms, an unsubstituted aralkyl group having 7 to 30 ring carbon atoms, a substituted germanium group, and an unsubstituted arylthio group having 6 to 30 ring carbon atoms.
“D” in Formula (2)
The substituent E1 is preferably each independently a group selected from the substituent group A, more preferably each independently a group selected from the substituent group B.
The substituent E1 is also preferably a group selected from a substituent group C below, also more preferably a group selected from a substituent group D below.
When the substituent E1 is further substituted, the substituent (substituent (substituent E2) for the substituted or unsubstituted group in the substituent E1) is preferably each independently a group selected from the substituent group A, more preferably a group selected from the substituent group B.
When the substituent E2 is further substituted, the substituent (substituent (substituent E3) for the substituted or unsubstituted group in the substituent E2) is preferably each independently a group selected from the substituent group A, more preferably each independently a group selected from the substituent group B.
When the substituent E3 is further substituted, the substituent (substituent (substituent E4) for the substituted or unsubstituted group in the substituent E3) is preferably each independently a group selected from the substituent group B.
The substitutents in the substituent group C and the substituent group D are groups exhibiting relatively high electron donating property.
Substituent Group C: 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 except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen.
Substituent Group D: an unsubstituted aryl group having 6 to 50 ring carbon atoms, and an unsubstituted heterocyclic groups having 5 to 50 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen.
“M” in Formula (2)
When M is a linking group, M is preferably each independently a group selected from a substituent group E below.
When M is further substituted, the substituent (substituent for the substituted or unsubstituted group in M) is preferably each independently a group selected from the substituent group A, more preferably a group selected from the substituent group B.
The substitutents in the substituent group E are groups exhibiting relatively high electron donating property.
Substituent Group E: a substituted or unsubstituted arylene group having 6 to 22 ring carbon atoms, a substituted or unsubstituted divalent heterocyclic groups having 5 to 22 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen, a divalent group formed by bonding two groups selected from the group consisting of a substituted or unsubstituted arylene group having 6 to 22 ring carbon atoms and the divalent heterocyclic group not including the partial structure in which at least one carbon of benzene is substituted by nitrogen, and a divalent group formed by bonding three groups selected from the group consisting of a substituted or unsubstituted arylene group having 6 to 22 ring carbon atoms and the divalent heterocyclic group not including the partial structure in which at least one carbon of benzene is substituted by nitrogen.
The second compound of the exemplary embodiment is preferably a compound represented by a formula (21) below.
In the formula (21), M, D, and R1C to R9C each independently represent the same as M, D, and R1C to R9C in the formulae (2) and (C1).
In the second compound of the exemplary embodiment, M is preferably a single bond, a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, or a substituted or unsubstituted divalent heterocyclic group having 5 to 22 ring atoms.
In the second compound of the exemplary embodiment, M is more preferably a single bond or a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms.
In the second compound of the exemplary embodiment, M is preferably a single bond, an unsubstituted arylene group having 6 to 25 ring carbon atoms, or an unsubstituted divalent heterocyclic group having 5 to 22 ring atoms.
In the second compound of the exemplary embodiment, M is preferably a substituted or unsubstituted paraphenylene group, a substituted or unsubstituted para-biphenylene group, or a substituted or unsubstituted para-terphenylene group.
In the second compound of the exemplary embodiment, M is preferably an unsubstituted paraphenylene group, an unsubstituted para-biphenylene group, or an unsubstituted para-terphenylene group.
In the second compound of the exemplary embodiment, D is preferably one of groups represented by formulae (d1) to (d17) below.
In the formulae (d1) to (d17), Ra is a hydrogen atom or a substituent, or one or more pairs of adjacent ones of Ra are mutually bonded to form a ring, and a plurality of Ra are mutually the same or different;
In the second compound of the exemplary embodiment, when D is a group represented by one of the formulae (d1) to (d17), Ra is preferably a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, more preferably a hydrogen atom.
In the second compound of the exemplary embodiment, when D is a group represented by the formula (d3) or (d4), it is preferable that Rb1 and Rb2 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a pair of Rb1 and Rb2 are bonded to each other to form a ring.
In the second compound of the exemplary embodiment, when D is a group represented by the formula (d5), Rb3 is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms.
In the second compound of the exemplary embodiment, when D is one of groups represented by the formulae (d1) to (d17), it is preferable that one or more pairs of adjacent ones of Ra are not mutually bonded.
In the second compound of the exemplary embodiment, when D is one of groups represented by the formulae (d1) to (d17), it is also preferable that one or more pairs of adjacent ones of Ra are mutually bonded.
In the second compound of the exemplary embodiment, C is preferably one of groups represented by formulae (C-1) to (C-6) below.
In the formulae (C-1) to (C-6):
In the second compound of the exemplary embodiment, R210 to R269, R20C and R21C are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms;
In the second compound of the exemplary embodiment, R210 to R269, R20C and R21C are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms;
R21 to R26 and R22C are preferably each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms except for one having a partial structure of benzene in which at least one carbon is substituted by nitrogen, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms.
In the second compound of the exemplary embodiment, X21, X22, X23, X24, X25 and X26 in the formulae (C-1) to (C-6) are each preferably an oxygen atom or a sulfur atom.
In the second compound of the exemplary embodiment, X21, X22, X23, X24, X25 and X26 in the formulae (C-1) to (C-6) are each preferably an oxygen atom.
Manufacturing Method of Second Compound
The second compound of the exemplary embodiment can be manufactured, for instance, by a method described later in Examples. The second compound of the exemplary embodiment can be manufactured, for instance, by application of known substitution reactions and/or materials depending on a target compound according to reactions described later in Examples.
Specific Examples of Second Compound
Specific examples of the second compound of the exemplary embodiment include, for example, the following compounds. It should however be noted that the invention is not limited to the specific examples of the compound.
Third Compound
The emitting layer of the exemplary embodiment contains a third compound that exhibits delayed fluorescence.
Delayed Fluorescence
Delayed fluorescence is explained in “Yuki Hando-tai no Debaisu Bussei (Device Physics of Organic Semiconductors)” (edited by ADACHI, Chihaya, published by Kodansha, on pages 261-268). This document describes that, if an energy difference ΔE13 of a fluorescent material between a singlet state and a triplet state is reducible, a reverse energy transfer from the triplet state to the singlet state, which usually occurs at a low transition probability, would occur at a high efficiency to express thermally activated delayed fluorescence (TADF). Further, a mechanism of generating delayed fluorescence is explained in FIG. 10.38 in the document. The third compound of the exemplary embodiment is preferably a compound exhibiting thermally activated delayed fluorescence generated by such a mechanism.
In general, emission of delayed fluorescence can be confirmed by measuring the transient PL (Photo Luminescence).
The behavior of delayed fluorescence can also be analyzed based on the decay curve obtained from the transient PL measurement. The transient PL measurement is a method of irradiating a sample with a pulse laser to excite the sample, and measuring the decay behavior (transient characteristics) of PL emission after the irradiation is stopped. PL emission in TADF materials is classified into a light emission component from a singlet exciton generated by the first PL excitation and a light emission component from a singlet exciton generated via a triplet exciton. The lifetime of the singlet exciton generated by the first PL excitation is on the order of nanoseconds and is very short. Therefore, light emission from the singlet exciton rapidly attenuates after irradiation with the pulse laser.
On the other hand, the delayed fluorescence is gradually attenuated due to light emission from a singlet exciton generated via a triplet exciton having a long lifetime. As described above, there is a large temporal difference between the light emission from the singlet exciton generated by the first PL excitation and the light emission from the singlet exciton generated via the triplet exciton. Therefore, the luminous intensity derived from delayed fluorescence can be determined.
An example of a method of measuring a transient PL and an example of behavior analysis of delayed fluorescence will be described using
A transient PL measuring device 100 in
The sample to be housed in the sample chamber 102 is obtained by doping a host material with a doping material at a concentration of 12 mass % and forming a thin film on a quartz substrate.
The thin film sample housed in the sample chamber 102 is irradiated with the pulse laser from the pulse laser 101 to excite the doping material. Emission is extracted in a direction of 90 degrees with respect to a radiation direction of the excited light. The extracted emission is divided by the spectrometer 103 to form a two-dimensional image in the streak camera 104. As a result, the two-dimensional image is obtainable in which the ordinate axis represents a time, the abscissa axis represents a wavelength, and a bright spot represents a luminous intensity. When this two-dimensional image is taken out at a predetermined time axis, an emission spectrum in which the ordinate axis represents the luminous intensity and the abscissa axis represents the wavelength is obtainable. Moreover, when this two-dimensional image is taken out at the wavelength axis, a decay curve (transient PL) in which the ordinate axis represents a logarithm of the luminous intensity and the abscissa axis represents the time is obtainable.
For instance, a thin film sample A was manufactured as described above from a reference compound H1 as the host material and a reference compound D1 as the doping material and was measured in terms of the transient PL.
The decay curve was analyzed with respect to the above thin film sample A and a thin film sample B. The thin film sample B was manufactured in the same manner as described above from a reference compound H2 as the host material and the reference compound D1 as the doping material.
As described above, an emission decay curve in which the ordinate axis represents the luminous intensity and the abscissa axis represents the time can be obtained by the transient PL measurement. Based on the emission decay curve, a fluorescence intensity ratio between fluorescence emitted from a singlet state generated by photo-excitation and delayed fluorescence emitted from a singlet state generated by inverse energy transfer via a triplet state can be estimated. In a delayed fluorescent material, a ratio of the intensity of the slowly decaying delayed fluorescence to the intensity of the promptly decaying fluorescence is relatively large.
Specifically, Prompt emission and Delay emission are present as emission from the delayed fluorescent material. Prompt emission is observed promptly when the excited state is achieved by exciting the compound of the exemplary embodiment with a pulse beam (i.e., a beam emitted from a pulse laser) having a wavelength absorbable by the delayed fluorescent material. Delay emission is observed not promptly when the excited state is achieved but after the excited state is achieved.
An amount of Prompt emission, an amount of Delay emission and a ratio between the amounts thereof can be obtained according to the method as described in “Nature 492, 234-238, 2012” (Reference Document 1). The amount of Prompt emission and the amount of Delay emission may be calculated using a device different from one described in Reference Document 1 or one shown in
Herein, a sample manufactured by a method shown below is used for measuring delayed fluorescence of the third compound. For instance, the third compound is dissolved in toluene to prepare a dilute solution with an absorbance of 0.05 or less at the excitation wavelength to eliminate the contribution of self-absorption. In order to prevent quenching due to oxygen, the sample solution is frozen and degassed and then sealed in a cell with a lid under an argon atmosphere to obtain an oxygen-free sample solution saturated with argon.
The fluorescence spectrum of the sample solution is measured with a spectrofluorometer FP-8600 (manufactured by JASCO Corporation), and the fluorescence spectrum of a 9,10-diphenylanthracene ethanol solution is measured under the same conditions. Using the fluorescence area intensities of both spectra, the total fluorescence quantum yield is calculated by an equation (1) in Morris et al. J. Phys. Chem. 80 (1976) 969.
An amount of Prompt emission, an amount of Delay emission and a ratio between the amounts thereof can be obtained according to the method as described in “Nature 492, 234-238, 2012” (Reference Document 1). The amount of Prompt emission and the amount of Delay emission may be calculated using a device different from one described in Reference Document 1 or one shown in
In the exemplary embodiment, provided that an amount of Prompt emission of a measurement target compound (third compound) is denoted by XP and an amount of Delay emission is denoted by XD, a value of XD/XP is preferably 0.05 or more.
The amounts of Prompt emission and Delay emission and a ratio of the amounts thereof in compounds other than the third compound herein are measured in the same manner as those of the third compound.
Examples of the third compound include, for example, a compound represented by a formula (31) below.
In the formula (31):
In the formula (3a):
In the formula (3b):
In the formula (3c):
In the formula (311), R2009 and R2010 are each independently a hydrogen atom or a substituent, or are bonded to a part of an adjacent cyclic structure to form a ring, or a pair of R2009 and R2010 are mutually bonded to form a ring.
In the formula (312), X201 is CR2011R2012, NR2013, a sulfur atom, or an oxygen atom, and R2011, R2012 and R2013 are each independently a hydrogen atom or a substituent, or R2011 and R2012 are mutually bonded to form a ring; and
In the formula (311), R2009 and R2010 are each independently bonded to a part of an adjacent cyclic structure to form a ring, which specifically means any of (1) to (IV) below.
Further, in the formula (311), a pair of R2009 and R2010 are mutually bonded to form a ring, which specifically means (V) below.
(I) When the cyclic structures represented by the formula (311) are adjacent to each other, between the two adjacent rings, at least one pair of the following are mutually bonded to form a ring: R2009 of one of the rings and R2009 of the other of the rings; R2009 of one of the rings and R2010 of the other of the rings; or R2010 of one of the rings and R2010 of the other of the rings.
(II) When the cyclic structure represented by the formula (311) and the benzene ring having R25 to R28 in the formula (3b) are adjacent to each other, between two adjacent rings, at least one pair of the following are mutually bonded to form a ring: R2009 of one of the rings and R25 of the other of the rings; R2009 of one of the rings and R28 of the other of the rings; R2010 of one of the rings and R25 of the other of the rings; or R2010 of one of the rings and R28 of the other of the rings.
(111) When the cyclic structure represented by the formula (311) and the benzene ring having R2001 to R2004 in the formula (3c) are adjacent to each other, between two adjacent rings, at least one pair of the following are mutually bonded to form a ring: R2009 of one of the rings and R2001 of the other of the rings; R2009 of one of the rings and R2004 of the other of the rings; R2010 of one of the rings and R2001 of the other of the rings; or R2010 of one of the rings and R2004 of the other of the rings.
(IV) When the cyclic structure represented by the formula (311) and the benzene ring having R2005 to R2008 in the formula (3c) are adjacent to each other, between two adjacent rings, at least one pair of the following are mutually bonded to form a ring: R2009 of one of the rings and R2005 of the other of the rings; R2009 of one of the rings and R2008 of the other of the rings; R2010 of one of the rings and R2005 of the other of the rings; or R2010 of one of the rings and R2008 of the other of the rings.
(V) The pair of R2009 and R2010 of the cyclic structure represented by the formula (311) are mutually bonded to form a ring. In other words, (V) means that the pair of R2009 and R2010 bonded to the same ring are mutually bonded to form a ring.
In the third compound of the exemplary embodiment, Rx is each independently a hydrogen atom, an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms, or an unsubstituted alkyl group having 1 to 30 carbon atoms; and
Herein, the triazinyl group refers to a group obtained by excluding one hydrogen atom from 1,3,5-triazine, 1,2,4-triazine, or 1,2,3-triazine.
The triazinyl group is preferably a group obtained by excluding one hydrogen atom from 1,3,5-triazine.
In the third compound of the exemplary embodiment, Rx is more preferably each independently a hydrogen atom, an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted dibenzofuranyl group, or an unsubstituted dibenzothienyl group.
In the third compound of the exemplary embodiment, Rx is further preferably a hydrogen atom.
In the third compound of the exemplary embodiment, R1 to R8, R21 to R28, R2001 to R2008, R2009 to R2010, and R2011 to R2013 serving as the substituents are preferably each independently an unsubstituted aryl group having 6 to 30 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 30 ring atoms, or an unsubstituted alkyl group having 1 to 30 carbon atoms.
In the third compound of the exemplary embodiment, D1 is preferably one of groups represented by formulae (D-21) to (D-27) below.
In the formula (D-21), R83 to R90 are each independently a hydrogen atom or a substituent;
In the third compound of the exemplary embodiment, it is also more preferable that D1 is a group represented by the formula (D-21), (D-23) or (D-24).
In the third compound of the exemplary embodiment, it is also further preferable that D1 is a group represented by the formula (D-21) or (D-23).
In the third compound of the exemplary embodiment, R83 to R90, R201 to R260, R151 and R152 are preferably each independently a hydrogen atom, an unsubstituted aryl group having 6 to 14 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 14 ring atoms, or an unsubstituted alkyl group having 1 to 6 carbon atoms.
In the third compound of the exemplary embodiment, R83 to R90 and R201 to R260 are each preferably a hydrogen atom.
In the third compound of the exemplary embodiment, R151 and R152 are preferably each independently an unsubstituted aryl group having 6 to 14 ring carbon atoms, an unsubstituted heterocyclic group having 5 to 14 ring atoms, or an unsubstituted alkyl group having 1 to 6 carbon atoms.
Examples of the third compound include, for example, a compound represented by a formula (32) below.
In the formula (32):
In the formulae (1a) to (1j), X1 to X20 are each independently a nitrogen atom (N) or a carbon atom bonded with RA1 (C—RA1);
In the formula (1a), when X1 to X8 are each a carbon atom bonded with RA1 (C—RA1), a plurality of RA1 preferably form no ring.
In the formulae (1a) to (1j), Ara is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.
The formula (1a) is represented by a formula (1aa) below when A1 is a single bond, represented by a formula (1ab) below when A1 is an oxygen atom, represented by a formula (1ac) below when A1 is a sulfur atom, represented by a formula (1ad) below when A1 is C(R2021)(R2022), represented by a formula (1ae) below when A1 is Si(R2023)(R2024), represented by a formula (1af) below when A1 is C(═O), represented by a formula (1ag) below when A1 is S(═O), represented by a formula (1ah) below when A1 is SO2, and represented by a formula (1ai) below when A1 is N(R2025). In the formulae (1aa) to (1ai), X1 to X8 and R2021 to R2025 represent the same as the above. Also in the formulae (1b), (1c), (1e), and (1g) to (1j), connection between rings by A1 and A2 is the same as that in the formulae (1aa) to (1ai). In the formula (1aa), when X1 to X8 are each a carbon atom bonded with RA1 (C—RA1), a plurality of RA1 serving as the substituents preferably form no ring.
The third compound is preferably represented by a formula (221) below.
In the formula (221), Ar1, ArEWG, Arx, n and a ring (A) respectively represent the same as Ar1, ArEWG, Arx, n and the ring (A) in the formula (32).
The third compound is also preferably represented by a formula (222) below.
In the formula (222), Y1 to Y5 are each independently a nitrogen atom (N), a carbon atom bonded with a cyano group (C—CN), or a carbon atom bonded with RA2 (C—RA2), and at least one of Y1 to Y5 is N or C—CN.
A plurality of RA2 are mutually the same or different.
RA2 are each independently a hydrogen atom or a substituent, RA2 serving as the substituent being a group selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted fluoroalkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, a substituted phosphoryl group, a substituted silyl group, a cyano group, a nitro group, and a carboxy group; and a plurality of RA2 are mutually the same or different.
In the formula (222), Ar1 represents the same as Ar1 in the formula (32).
In the formula (222), Ar2 to Ar5 are each independently a hydrogen atom or a substituent, Ar2 to Ar5 serving as the substituents being each independently a group selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted fluoroalkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 30 ring carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 30 carbon atoms, a substituted phosphoryl group, a substituted silyl group, a cyano group, a nitro group, a carboxy group, and the groups represented by the formulae (1a) to (1c).
In the formula (222), at least one of Ar1 to Ar5 is a group selected from the group consisting of the groups represented by the formulae (1a) to (1c).
The third compound is also preferably a compound represented by a formula (11aa), a formula (11bb), or a formula (11cc) below.
In the formulae (11aa), (11bb), and (11cc), Y1 to Y5, RA2, Ar2 to Ar5, X1 to X16, RA1, and Ara represent the same as above-described Y1 to Y5, RA2, Ar2 to Ar5, X1 to X16, RA1, and Ara, respectively.
Examples of the third compound include, for example, a compound represented by a formula (23) below.
In the formula (23):
Az is a cyclic structure selected from the group consisting of a substituted or unsubstituted pyridine ring, a substituted or unsubstituted pyrimidine ring, a substituted or unsubstituted triazine ring, and a substituted or unsubstituted pyrazine ring;
In the formula (23a):
In the formulae (23b), (23c), and (23d), Y21 to Y23 and Y51 to Y58 are each independently a nitrogen atom or CRA4;
Z21 and Z22 are each independently any one selected from the group consisting of an oxygen atom, a sulfur atom, NR45 and CR46R47;
When Z21 is NR45, R45 is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
Z22 is preferably NR45.
When Z22 is NR45, R45 is preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
Y51 to Y58 are preferably CRA4, provided that at least one of Y51 to Y58 is a carbon atom bonded to a cyclic structure represented by the formula (23a).
Cz is also preferably represented by the formula (23d) in which n is 1.
Az is preferably a cyclic structure selected from the group consisting of a substituted or unsubstituted pyrimidine ring and a substituted or unsubstituted triazine ring.
Az is a cyclic structure selected from the group consisting of a substituted pyrimidine ring and a substituted triazine ring, in which a substituent of each of the substituted pyrimidine ring and the substituted triazine ring is more preferably a group selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms and a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, further preferably a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
When the pyrimidine ring and the triazine ring as Az have a substituted or unsubstituted aryl group as a substituent, the aryl group preferably has 6 to 20 ring carbon atoms, more preferably 6 to 14 ring carbon atoms, further preferably 6 to 12 ring carbon atoms.
When Az has a substituted or unsubstituted aryl group as a substituent, the substituent is preferably a substituent selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthryl group, a substituted or unsubstituted terphenyl group, and a substituted or unsubstituted fluorenyl group, more preferably a substituent selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, and a substituted or unsubstituted naphthyl group.
When Az has a substituted or unsubstituted heteroaryl group as a substituent, the substituent is preferably a substituent selected from the group consisting of a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, and a substituted or unsubstituted dibenzothienyl group.
It is preferable that RA4 is each independently a hydrogen atom or a substituent, and RA4 serving as the substituent is a substituent selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms and a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms.
When RA4 serving as the substituent is a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, RA4 serving as the substituent is preferably a substituent selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, a substituted or unsubstituted phenanthryl group, a substituted or unsubstituted terphenyl group, and a substituted or unsubstituted fluorenyl group, more preferably a substituent selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, and a substituted or unsubstituted naphthyl group.
When RA4 serving as the substituent is a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, RA4 serving as the substituent is preferably a substituent selected from the group consisting of a substituted or unsubstituted carbazolyl group, a substituted or unsubstituted dibenzofuranyl group, and a substituted or unsubstituted dibenzothienyl group.
R45, R46, and R47 serving as the substituents are preferably each independently a substituent selected from the group consisting of a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heteroaryl group having 5 to 30 ring atoms, and a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms.
Manufacturing Method of Third Compound According to the Exemplary Embodiment
The third compound according to the exemplary embodiment can be manufactured by a known method.
Specific Examples of Third Compound
Specific examples of the third compound of the exemplary embodiment include, for example, the following compounds. It should however be noted that the invention is not limited to the specific examples of the compound.
Fourth Compound
The emitting layer of the exemplary embodiment preferably contains the fourth compound that fluoresces.
The fourth compound of the exemplary embodiment is not a phosphorescent metal complex. The fourth compound of the exemplary embodiment is preferably not a heavy metal complex. The fourth compound of the exemplary embodiment is preferably not a metal complex.
The fourth compound of the exemplary embodiment is preferably a compound exhibiting no thermally activated delayed fluorescence.
A fluorescent material is usable as the fourth compound of the exemplary embodiment. Specific examples of the fluorescent material include a bisarylaminonaphthalene derivative, aryl-substituted naphthalene derivative, bisarylaminoanthracene derivative, aryl-substituted anthracene derivative, bisarylaminopyrene derivative, aryl-substituted pyrene derivative, bisarylamino chrysene derivative, aryl-substituted chrysene derivative, bisarylaminofluoranthene derivative, aryl-substituted fluoranthene derivative, indenoperylene derivative, acenaphthofluoranthene derivative, compound including a boron atom, pyromethene boron complex compound, compound having a pyromethene skeleton, metal complex of the compound having a pyrromethene skeleton, diketopyrrolopyrrole derivative, perylene derivative, and naphthacene derivative.
Compound Represented by Formula (20)
In the exemplary embodiment, the fourth compound is preferably a compound represented by a formula (20) below.
In the formula (20): X is a nitrogen atom, or a carbon atom bonded to Y;
When the fourth compound is a fluorescent compound, the main peak wavelength of the fourth compound is preferably in a range from 400 nm to 700 nm.
Herein, the main peak wavelength means a peak wavelength of a fluorescence spectrum exhibiting a maximum luminous intensity among fluorescence spectra measured in a toluene solution in which a measurement target compound is dissolved at a concentration ranging from 10−6 mol/l to 10−5 mol/l. A spectrophotofluorometer (F-7000 manufactured by Hitachi High-Tech Science Corporation) is used as a measurement device.
The fourth compound preferably exhibits red or green light emission.
Herein, the red light emission refers to light emission whose main peak wavelength of fluorescence spectrum is in a range from 600 nm to 660 nm.
When the fourth compound is a red fluorescent compound, the main peak wavelength of the fourth compound is preferably in a range from 600 nm to 660 nm, more preferably in a range from 600 nm to 640 nm, further preferably in a range from 610 nm to 630 nm.
Herein, the green light emission refers to light emission whose main peak wavelength of fluorescence spectrum is in a range from 500 nm to 560 nm.
When the fourth compound is a green fluorescent compound, the main peak wavelength of the fourth compound is preferably in a range from 500 nm to 560 nm, more preferably in a range from 500 nm to 540 nm, further preferably in a range from 510 nm to 540 nm.
Herein, the blue light emission refers to a light emission in which a main peak wavelength of fluorescence spectrum is in a range from 430 nm to 480 nm.
When the fourth compound is a blue fluorescent compound, the main peak wavelength of the fourth compound is preferably in a range from 430 nm to 480 nm, more preferably in a range from 440 nm to 480 nm.
A main peak wavelength of light from an organic EL device is measured as follows.
Voltage is applied on the organic EL devices such that a current density becomes 10 mA/cm2, where spectral radiance spectrum is measured by a spectroradiometer CS-2000 (manufactured 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 the main peak wavelength (unit: nm).
Manufacturing Method of Fourth Compound
The fourth compound can be manufactured by a known method.
Specific Examples of Fourth Compound
Specific examples of the fourth compound (compound represented by the formula (20)) according to the exemplary embodiment are shown below. It should however be noted that the invention is not limited to the specific examples of the compound.
A coordinate bond between a boron atom and a nitrogen atom in a pyrromethene skeleton is shown by various means such as a solid line, a broken line, an arrow, and omission. Herein, the coordinate bond is shown by a solid line or a broken line, or the description of the coordinate bond is omitted.
Relationship between First Compound, Second Compound, Third Compound, and Fourth Compound in Emitting Layer
In the organic EL device of the exemplary embodiment, a singlet energy S1(M1) of the first compound and a singlet energy S1(M3) of the third compound satisfy a relationship of a numerical formula (Numerical Formula 1) below.
Further, a singlet energy Si(M2) of the second compound and a singlet energy S1(M3) of the third compound satisfy a relationship of a numerical formula (Numerical Formula 2) below.
S1(M1)>S1(M3) (Numerical Formula 1)
S1(M2)>S1(M3) (Numerical Formula 2)
In the organic EL device according to the exemplary embodiment, an energy gap T77K(M1) at 77K of the first compound and an energy gap T77K(M3) at 77K of the third compound preferably satisfy a relationship of a numerical formula (Numerical Formula 1a) below.
Further, an energy gap T77K(M2) at 77K of the second compound and the energy gap T77K(M3) at 77K of the third compound preferably satisfy a relationship of a numerical formula (Numerical Formula 2b) below.
T77K(M1)>T77K(M3) (Numerical Formula 1a)
T77K(M2)>T77K(M3) (Numerical Formula 2b)
In the organic EL device of the exemplary embodiment, the emitting layer preferably further contains the fourth compound that fluoresces. In this arrangement, the singlet energy S1(M3) of the third compound and a singlet energy S1(M4) of the fourth compound preferably satisfy a relationship of a numerical formula (Numerical Formula 3) below.
S1(M3)>S1(M4) (Numerical Formula 3)
The singlet energy S1(M1) of the first compound and the singlet energy S1(M4) of the fourth compound preferably satisfy a relationship of a numerical formula (Numerical Formula 4) below.
The singlet energy S1(M2) of the second compound and the singlet energy S1(M4) of the fourth compound preferably satisfy a relationship of a numerical formula (Numerical Formula 5) below.
S1(M1)>S1(M4) (Numerical Formula 4)
S1(M2)>S1(M4) (Numerical Formula 5)
The singlet energy S1(M1) of the first compound, the singlet energy S1(M3) of the third compound, and the singlet energy S1(M4) of the fourth compound preferably satisfy a relationship of a numerical formula (Numerical Formula 6) below.
S1(M1)>S1(M3)>S1(M4) (Numerical Formula 6)
The singlet energy S1(M2) of the second compound, the singlet energy S1(M3) of the third compound, and the singlet energy S1(M4) of the fourth compound preferably satisfy a relationship of a numerical formula (Numerical Formula 7) below.
S1(M2)>S1(M3)>S1(M4) (Numerical Formula 7)
A magnitude relationship between the singlet energy S1(M1) of the first compound and the singlet energy S1(M2) of the second compound does not matter. Specifically, the singlet energy S1(M1) of the first compound is larger or smaller than the singlet energy S1(M2) of the second compound, or the singlet energy S1(M1) of the first compound is the same as the singlet energy S1(M2) of the second compound.
When the organic EL device of the exemplary embodiment emits light, it is preferable that the first compound and the second compound do not mainly emit light in the emitting layer. Further, it is preferable that the third compound also does not mainly emit light.
When the organic EL device of the exemplary embodiment emits light, it is preferable that the fourth compound that fluoresces mainly emits light in the emitting layer.
The organic EL device of the exemplary embodiment preferably emits red light or green light.
Relationship Between Triplet Energy and Energy Gap at 77K
Here, a relationship between a triplet energy and an energy gap at 77K will be described. In the exemplary embodiment, the energy gap at 77K is different from a typical triplet energy in some aspects.
The triplet energy is measured as follows. First, a solution in which a compound (measurement target) is dissolved in an appropriate solvent is encapsulated in a quartz glass tube to prepare a sample. A phosphorescent spectrum (ordinate axis: phosphorescent luminous intensity, abscissa axis: wavelength) of the sample is measured at a low temperature (77K). A tangent is drawn to the rise of the phosphorescent spectrum close to the short-wavelength region. The triplet energy is calculated by a predetermined conversion equation based on a wavelength value at an intersection of the tangent and the abscissa axis.
Here, the thermally activated delayed fluorescent compound among the compounds of the exemplary embodiment is preferably a compound having a small ΔST. When ΔST is small, intersystem crossing and inverse intersystem crossing are likely to occur even at a low temperature (77K), so that the singlet state and the triplet state coexist. As a result, the spectrum to be measured in the same manner as the above includes emission from both the singlet state and the triplet state. Although it is difficult to distinguish the emission from the singlet state from the emission from the triplet state, the value of the triplet energy is basically considered dominant.
Accordingly, in the exemplary embodiment, the triplet energy is measured by the same method as a typical triplet energy T, but a value measured in the following manner is referred to as an energy gap T77K in order to differentiate the measured energy from the typical triplet energy in a strict meaning. The measurement target compound is dissolved in EPA (diethylether:isopentane:ethanol=5:5:2 in volume ratio) at a concentration of 10 μmol/L, and the obtained solution is encapsulated in a quartz cell to provide a measurement sample. A phosphorescent spectrum (ordinate axis: phosphorescent luminous intensity, abscissa axis: wavelength) of the sample is measured at a low temperature (77K). A tangent is drawn to the rise of the phosphorescent spectrum close to the short-wavelength region. An energy amount is calculated by a conversion equation (F1) below based on a wavelength value λedge [nm] at an intersection of the tangent and the abscissa axis and is defined as an energy gap T77K at 77K.
T77K [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) 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.
Singlet Energy S1
A method of measuring a 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 of 10 μmol/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 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 the singlet energy.
S1 [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 exemplary embodiment, a difference (S1-T77K) between the singlet energy S1 and the energy gap T77K at 77K is defined as ΔST.
In the exemplary embodiment, a difference ΔST(M3) between the singlet energy S1(M3) of the third compound and the energy gap T77K(M3) at 77K of the third compound is preferably less than 0.3 eV, more preferably less than 0.2 eV, further preferably less than 0.1 eV, still further preferably less than 0.01 eV. In other words, ΔST(M3) preferably satisfies a relationship of one of numerical formulae (Numerical Formula 1A to Numerical Formula 1D) below.
ΔST(M3)=S1(M3)−T77K(M3)<0.3 eV (Numerical Formula 1A)
ΔST(M3)=S1(M3)−T77K(M3)<0.2 eV (Numerical Formula 1B)
ΔST(M3)=S1(M3)−T77K(M3)<0.1 eV (Numerical Formula 1C)
ΔST(M3)=S1(M3)−T77K(M3)<0.01 eV (Numerical Formula 1D)
Film Thickness of Emitting Layer
A film thickness of the emitting layer of the organic EL device in the exemplary embodiment is preferably in a range from 5 nm to 50 nm, more preferably in a range from 7 nm to 50 nm, most preferably in a range from 10 nm to 50 nm. When the film thickness of the emitting layer is 5 nm or more, the formation of the emitting layer and the adjustment of the chromaticity are easy. When the film thickness of the emitting layer is 50 nm or less, an increase in the drive voltage is likely to be reducible.
Content Ratios of Compounds in Emitting Layer
Content ratios of the first, second, third and fourth compounds in the emitting layer preferably fall, for instance, within a range below.
The content ratio of the total of the first and second compounds in the emitting layer is preferably in a range from 10 mass % to 80 mass %.
The ratio of the content ratio of the first compound to the content ratio of the second compound in the emitting layer is preferably 1:9 to 9:1, more preferably 3:7 to 7:3, further preferably 4:6 to 6:4.
The content ratio of the third compound is preferably in a range from 10 mass % to 80 mass %, more preferably in a range from 10 mass % to 60 mass %, further preferably in a range from 20 mass % to 60 mass %.
The content ratio of the fourth compound is preferably in a range from 0.01 mass % to 10 mass %, more preferably in a range from 0.01 mass % to 5 mass %, further preferably in a range from 0.01 mass % to 1 mass %.
An upper limit of the total of the respective content ratios of the first, second, third, and fourth compounds in the emitting layer is 100 mass %. It should be noted that the emitting layer of the exemplary embodiment may further contain material(s) other than the first, second, third, and fourth compounds.
The emitting layer may contain a single type of the first compound or may contain two or more types of the first compound. The emitting layer may contain a single type of the second compound or may contain two or more types of the second compound. The emitting layer may contain a single type of the third compound or may contain two or more types of the third compound. The emitting layer may contain a single type of the fourth compound or may contain two or more types of the fourth compound.
In
As shown in
The inverse intersystem crossing caused in the third compound enables (i) and (ii), as follows: (i) when the emitting layer contains a fluorescent dopant with the lowest singlet state S1 (fourth compound that fluoresces in the first exemplary embodiment) smaller than the lowest singlet state S1(M3) of the third compound, light emission from the fluorescent dopant can be observed; (ii) when the emitting layer does not contain the fluorescent dopant with the lowest singlet state S1 smaller than the lowest singlet state S1(M3) of the third compound, light emission from the lowest singlet state S1(M3) of the third compound can be observed.
The emitting layer of the first exemplary embodiment corresponds to (i). An emitting layer of a second exemplary embodiment described later corresponds to (ii).
A dashed arrow directed from S1(M3) to S1(M4) in
As shown in
In the organic EL device according to the first exemplary embodiment, the emitting layer contains, together with the third compound that exhibits delayed fluorescence, the first compound having the singlet energy larger than that of the third compound and the second compound having the singlet energy larger than that of the third compound, the first and second compounds being as the co-matrix, and further contains the fourth compound that fluoresces.
According to the first exemplary embodiment, the organic EL device with higher performance, in particular, with improved luminous efficiency can be achieved.
The organic EL device according to the first exemplary embodiment is applicable to an electronic device such as a display device and a light-emitting device.
An arrangement of an organic EL device will be further described below.
Substrate
The substrate is used as a support for the organic EL device. For instance, glass, quartz, plastics and the like are usable for the substrate. A flexible substrate is also usable. The flexible substrate is a bendable substrate, which is exemplified by a plastic substrate. Examples of the material for the plastic substrate include polycarbonate, polyarylate, polyethersulfone, polypropylene, polyester, polyvinyl fluoride, polyvinyl chloride, polyimide, and polyethylene naphthalate. Moreover, an inorganic vapor deposition film is also usable.
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.
Cathode
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, the alkali metal such as lithium (Li) and cesium (Cs), the 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, the 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.
Hole Injecting Layer
The hole injecting layer is a layer containing a substance exhibiting a high hole injectability. Examples of the substance exhibiting a high hole injectability include molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chrome oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten oxide, and manganese oxide.
In addition, the examples of the highly hole-injectable substance include: an aromatic amine compound, which is a low-molecule organic compound, such that 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), 4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation: DPAB), 4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl (abbreviation: DNTPD), 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene (abbreviation: DPA3B), 3-[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazole-3-yl)-N-phenylamino]-9-phenylcarbazole (abbreviation: PCzPCA2), and 3-[N-(1-naphthyl)-N-(9-phenylcarbazole-3-yl)amino]-9-phenylcarbazole (abbreviation: PCzPCN1); and dipyrazino[2,3-f:20,30-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HAT-CN).
In addition, a high polymer compound (e.g., oligomer, dendrimer and polymer) is usable as the substance exhibiting a high hole injectability. Examples of the high-molecule compound include poly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), and poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation: Poly-TPD). Moreover, an acid-added high polymer compound such as poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) and polyaniline/poly(styrene sulfonic acid) (PAni/PSS) are also usable.
Hole Transporting Layer
The hole transporting layer is a layer containing a highly hole-transporting substance. An aromatic amine compound, carbazole derivative, anthracene derivative and the like are usable for the hole transporting layer. Specific examples of a material for the hole transporting layer include 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB), N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (abbreviation: TPD), 4-phenyl-4′-(9-phenylfluorene-9-yl)triphenylamine (abbreviation: BAFLP), 4,4′-bis[N-(9,9-dimethylfluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: DFLDPBi), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (abbreviation: MTDATA), and 4,4′-bis[N-(spiro-9,9′-bifluorene-2-yl)-N-phenylamino]biphenyl (abbreviation: BSPB). The above-described substances mostly have a hole mobility of 10−6 cm2/(V·s) or more.
For the hole transporting layer, a carbazole derivative such as CBP, 9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (CzPA), and 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (PCzPA) and an anthracene derivative such as t-BuDNA, DNA, and DPAnth may be used. A high polymer compound such as poly(N-vinylcarbazole) (abbreviation: PVK) and poly(4-vinyltriphenylamine) (abbreviation: PVTPA) is also usable.
However, in addition to the above substances, any substance exhibiting a higher hole transportability than an electron transportability may be used. It should be noted that the layer containing the substance exhibiting a high hole transportability may be not only a single layer but also a laminate of two or more layers formed of the above substance(s).
When the hole transporting layer includes two or more layers, one of the layers with a larger energy gap is preferably provided closer to the emitting layer. Examples of the material with a larger energy gap include compounds EBL and EBL-2 used in later-described Examples.
Electron Transporting Layer
The electron transporting layer is a layer containing a highly electron-transporting substance. For the electron transporting layer, 1) a metal complex such as an aluminum complex, beryllium complex, and zinc complex, 2) a hetero aromatic compound such as imidazole derivative, benzimidazole derivative, azine derivative, carbazole derivative, and phenanthroline derivative, and 3) a high polymer compound are usable. Specifically, as a low-molecule organic compound, a metal complex such as Alq, tris(4-methyl-8-quinolinato)aluminum (abbreviation: Almq3), bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq2), BAlq, Znq, ZnPBO and ZnBTZ is usable. In addition to the metal complex, a heteroaromatic compound such as 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis[5-(ptert-butylphenyl)-1,3,4-oxadiazole-2-yl]benzene (abbreviation: OXD-7), 3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: TAZ), 3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole (abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen), bathocuproine (abbreviation: BCP), and 4,4′-bis(5-methylbenzoxazole-2-yl) stilbene (abbreviation: BzOs) is usable. In the present exemplary embodiment, a benzimidazole compound is preferably usable. The above-described substances mostly have an electron mobility of 10−6 cm2/(V·s) or more. It should be noted that any substance other than the above substance may be used for the electron transporting layer as long as the substance exhibits a higher electron transportability than the hole transportability. The electron transporting layer may be provided in the form of a single layer or a laminate of two or more layers of the above substance(s).
Further, a high polymer compound is usable for the electron transporting layer. For instance, poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) and the like are usable.
Electron Injecting Layer
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.
Layer Formation Method
A method for forming each layer of the organic EL device in the present 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.
In the exemplary embodiment, the emitting layer is also preferably formed by using, as a vapor deposition source, a composition containing the first and second compounds. Use of the composition can reduce the number of vapor deposition sources for forming the emitting layer.
Film Thickness
A thickness of each of the organic layers in the organic EL device according to the exemplary embodiment is not limited except for the above particular description. In general, the thickness preferably ranges from several nanometers to 1 μm because excessively small film thickness is likely to cause defects (e.g. pin holes) and excessively large thickness leads to the necessity of applying high voltage and consequent reduction in efficiency.
An arrangement of an organic EL device according to a second exemplary embodiment will be described below. In the description of the second exemplary embodiment, the same components as those in the first exemplary embodiment are denoted by the same reference signs and names to simplify or omit an explanation of the components. In the second exemplary embodiment, the same materials and compounds as described in the first exemplary embodiment are usable, unless otherwise specified.
The organic EL device according to the second exemplary embodiment is different from the organic EL device according to the first exemplary embodiment in that the emitting layer of the second exemplary embodiment does not contain the fluorescent dopant with the lowest singlet state S1 (fourth compound that fluoresces in the first exemplary embodiment) smaller than the lowest singlet state S1(M3) of the third compound. Other components are the same as those in the first exemplary embodiment.
That is, in the second exemplary embodiment, the emitting layer contains the first compound represented by the formula (1) and the second compound represented by the formula (2) as the co-matrix, together with the third compound that exhibits delayed fluorescence. The emitting layer, however, does not contain the fluorescent dopant with the lowest singlet state S1 (fourth compound that fluoresces in the first exemplary embodiment) smaller than the lowest singlet state S1(M3) of the third compound.
Relationship between First Compound, Second Compound and Third Compound in Emitting Layer
The organic EL devices according to the first and second exemplary embodiments are the same in the relationship between the singlet energy S1 of the first compound and the singlet energy S1 of the second compound and the singlet energy S1 of the third compound in the emitting layer as well as the relationship between the energy gap T77K at 77K of the first compound and the energy gap T77K at 77K of the second compound and the energy gap T77K at 77K of the third compound. That is, S1 and T77K of the first, second, and third compounds according to the second exemplary embodiment satisfy relationships of Numerical Formulae 1, 2, 1a, and 2b below.
S1(M1)>S1(M3) (Numerical Formula 1)
S1(M2)>S1(M3) (Numerical Formula 2)
T77K(M1)>T77K(M3) (Numerical Formula 1a)
T77K(M2)>T77K(M3) (Numerical Formula 2b)
When the organic EL device of the exemplary embodiment emits light, it is preferable that the first compound and the second compound do not mainly emit light in the emitting layer.
Content Ratios of Compounds in Emitting Layer
Content ratios of the first, second, and third compounds contained in the emitting layer preferably fall, for instance, within a range below.
The content ratio of the total of the first and second compounds in the emitting layer is preferably in a range from 20 mass % to 90 mass %, more preferably in a range from 40 mass % to 90 mass %, further preferably in a range from 40 mass % to 80 mass %.
The ratio of the content ratio of the first compound to the content ratio of the second compound in the emitting layer is preferably 1:9 to 9:1, more preferably 3:7 to 7:3, further preferably 4:6 to 6:4.
The content ratio of the third compound is preferably in a range from 10 mass % to 80 mass %, more preferably in a range from 10 mass % to 60 mass %, further preferably in a range from 20 mass % to 60 mass %.
An upper limit of the total of the respective content ratios of the first, second, and third compounds in the emitting layer is 100 mass %. It is not excluded that the emitting layer of the exemplary embodiment further contains a material(s) other than the first, second, and third compounds.
The emitting layer may contain a single type of the first compound or may contain two or more types of the first compound.
The emitting layer may contain a single type of the second compound or may contain two or more types of the second compound.
The emitting layer may contain a single type of the third compound or may contain two or more types of the third compound.
In the organic EL device according to the second exemplary embodiment, the emitting layer contains, together with the third compound that exhibits delayed fluorescence, the first compound having the singlet energy larger than that of the third compound and the second compound having the singlet energy larger than that of the third compound as the co-matrix.
According to the second exemplary embodiment, the organic EL device with higher performance, in particular, with improved luminous efficiency can be achieved.
The organic EL device according to the second exemplary embodiment is applicable to an electronic device such as a display device and a light-emitting device.
Composition
A composition that is an exemplary arrangement of the third exemplary embodiment contains the first compound represented by the formula (1x) or the formula (1Y), and the second compound represented by the formula (2).
The first compound contained in the composition according to the third exemplary embodiment corresponds to the first compound described in the first exemplary embodiment.
The second compound contained in the composition according to the third exemplary embodiment corresponds to the second compound described in the first exemplary embodiment.
Preferable arrangements of the first and second compounds contained in the composition according to the third exemplary embodiment are the same as those in the first exemplary embodiment, which will be specifically shown below. Preferable
Arrangements of First Compound Contained in Composition of Third Exemplary Embodiment
In the first compound contained in the composition, A is preferably a group represented by the formula (a1), (a2), (a3), (a4), or (a6), more preferably a group represented by the formula (a1), (a2), (a3), or (a4), further preferably a group represented by the formula (a1) or (a4), still further preferably a group represented by the formula (a1).
In the first compound contained in the composition, X11, X12, X13, X14, X15 and X16 are each preferably an oxygen atom.
The first compound contained in the composition is preferably a compound represented by the formula (11X), (12X), (13X), (14X), (15X), or (16X).
In the first compound contained in the composition, it is preferable that: R110 to R169, Ry, R1X, R2X, R3X, and R4X are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms; and
In the first compound contained in the composition, it is more preferable that: R110 to R169, Ry, R1X, R2X, R3X, and R4X are each independently a hydrogen atom, or a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms; and
In the first compound contained in the composition, it is also preferable that R110 to R169 are each a hydrogen atom, and R11 to R16 are each independently a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the first compound contained in the composition, L is preferably a single bond, a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, or a substituted or unsubstituted divalent heterocyclic group having 5 to 22 ring atoms, more preferably a single bond or a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, further preferably a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a substituted or unsubstituted terphenylene group.
It is preferable that the first compound contained in the composition is represented by the formula (1X), and Y11, Y12, and Y13 in the formula (1X) are each a nitrogen atom.
In the first compound contained in the composition, Ry, R1X, R2X, R3X, and R4X serving as the substituents are preferably each independently one of the groups represented by the formulae (b1) to (b17).
In the first compound contained in the composition, it is preferable that L11 is a single bond, or a divalent, trivalent, tetravalent, pentavalent, or hexavalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
It is preferable that L12 is a single bond, or a divalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
Specific examples of the first compound contained in the composition according to the third exemplary embodiment are shown in the specific examples of the first compound described in the first exemplary embodiment.
Preferable Arrangements of Second Compound Contained in Composition of Third Exemplary Embodiment
The second compound contained in the composition is preferably a compound represented by the formula (21).
In the second compound contained in the composition, M is preferably a single bond, a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, or a substituted or unsubstituted divalent heterocyclic group having 5 to 22 ring atoms, more preferably a single bond or a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, further preferably a substituted or unsubstituted paraphenylene group, a substituted or unsubstituted para-biphenylene group, or a substituted or unsubstituted para-terphenylene group.
In the second compound contained in the composition, D is preferably one of the groups represented by the formulae (d1) to (d17), more preferably one of the groups represented by the formulae (d1) to (d6).
In the second compound contained in the composition, when D is one of the groups represented by the formulae (d1) to (d17), it is preferable that one or more pairs of adjacent ones of Ra are not mutually bonded.
In the second compound contained in the composition, C is preferably one of the groups represented by the formulae (C-1) to (C-6).
In the second compound contained in the composition, when C is one of the groups represented by the formulae (C-1) to (C-6), X21, X22, X23, X24, X25 and X26 are each preferably an oxygen atom or a sulfur atom, more preferably an oxygen atom.
Specific examples of the second compound contained in the composition according to the third exemplary embodiment are shown in the specific examples of the second compound described in the first exemplary embodiment.
The ratio of the content ratio (mass %) of the first compound to the content ratio (mass %) of the second compound in the composition according to the third exemplary embodiment is preferably 1:9 to 9:1, more preferably 3:7 to 7:3, further preferably 4:6 to 6:4.
An upper limit of the total of the respective content ratios of the first and second compounds in the composition according to the third exemplary embodiment is 100 mass %. It is not excluded that the composition of the exemplary embodiment further contains a material(s) other than the first and second compounds.
The composition according to the third exemplary embodiment may contain a single type of the first compound or may contain two or more types of the first compound.
The composition according to the third exemplary embodiment may contain a single type of the second compound or may contain two or more types of the second compound.
The emitting layer is preferably formed by using, as a vapor deposition source, the composition according to the third exemplary embodiment (composition containing the first and second compounds). For example, the emitting layer according to each of the first and second exemplary embodiments can be formed by using at least the vapor deposition source that is the composition of the third exemplary embodiment and any other compound(s).
Using the composition according to the third exemplary embodiment can reduce the number of vapor deposition sources for forming a desired layer (e.g., emitting layer).
The emitting layer with higher performance, in particular, with improved luminous efficiency can be formed using the composition according to the third exemplary embodiment, thus resulting in the organic EL device with higher efficiency.
The composition according to the third exemplary embodiment may further contain an additional compound. When the composition according to the third exemplary embodiment contains the additional compound, the additional compound may be a solid or a liquid.
Organic EL Device
An organic EL device that is an exemplary arrangement according to a fourth exemplary embodiment includes an anode, a cathode, and an emitting layer interposed between the anode and the cathode;
The organic EL device that is an exemplary arrangement according to the fourth exemplary embodiment is an organic EL device in which the first compound represented by the formula (1X) or (1Y) in the organic EL device according to the first exemplary embodiment is replaced by the first compound represented by the formula (11X) or (11Y). That is, the organic EL device according to the fourth exemplary embodiment is different from the organic EL element according to the first exemplary embodiment.
Thus, “the first compound represented by the formula (11X) or (11Y)” different from that in the first exemplary embodiment will be mainly explained in the fourth exemplary embodiment, and descriptions on the same arrangements as those in the first exemplary embodiment will be simplified or omitted.
In the formulae (11X) and (11Y): A is a group represented by a formula (c11), (c12), (c13), (c14), (c15), or (c16) below.
In the formulae (11X) and (11Y):
A is a group represented by the formula (c11), (c12), (c13), (c14), (c15), or (c16);
The organic EL device that is an exemplary arrangement according to the fourth exemplary embodiment is an organic EL device in which the first compound in the organic EL device according to the first exemplary embodiment is replaced by the first compound represented by the formula (11X) or (11Y).
The preferable arrangements of the organic EL device according to the fourth exemplary embodiment are the same as those according to the first exemplary embodiment except for the structure of the first compound, which will be specifically shown below.
In the organic EL device according to the fourth exemplary embodiment, it is preferable that the emitting layer further contains a fourth compound that fluoresces, and the singlet energy S1(M3) of the third compound and a singlet energy S1(M4) of the fourth compound satisfy a relationship of a numerical formula (Numerical Formula 3) below.
S1(M3)>S1(M4) (Numerical Formula 3)
In the organic EL device according to the fourth exemplary embodiment, it is preferable that: an energy gap T77K(M1) at 77K of the first compound represented by the formula (11X) or (11Y) and an energy gap T77K(M3) at 77K of the third compound satisfy a relationship of a numerical formula (Numerical Formula 1a) below; and
In the organic EL device according to the fourth exemplary embodiment, A in the formula (11X) or (11Y) is preferably a group represented by the formula (c11), (c12), (c13), (c14), or (c16), more preferably a group represented by the formula (c11), (c12), (c13), or (c14), further preferably a group represented by the formula (c11) or (c14), still further preferably a group represented by the formula (c11).
In the first compound represented by the formulae (11X) and (11Y), R110 to R169 and R1c to R9c in the formulae (c11), (c12), (c13), (c14), (c15), and (c16) are each independently a hydrogen atom, a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, or a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms;
In the first compound represented by the formulae (11X) and (11Y), R110 to R169 and R1c to R9c in the formulae (c11), (c12), (c13), (c14), (c15), and (c16) are more preferably each independently a hydrogen atom, or a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms, and R11C R13C are more preferably each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the first compound represented by the formulae (11X) and (11Y), R110 to R169 and R1c to R9c in the formulae (c11), (c12), (c13), (c14), (c15), and (c16) are each further preferably a hydrogen atom, and R11C to R13C are further preferably each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 ring carbon atoms.
In the first compound represented by the formulae (11X) and (11Y), in the formula (11C), L is preferably a single bond, a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, or a substituted or unsubstituted divalent heterocyclic group having 5 to 22 ring atoms, more preferably a single bond or a substituted or unsubstituted arylene group having 6 to 25 ring carbon atoms, further preferably a substituted or unsubstituted phenylene group, a substituted or unsubstituted biphenylene group, or a substituted or unsubstituted terphenylene group.
In the first compound represented by the formulae (11X) and (11Y), the first compound is preferably represented by the formula (11X) and Y11, Y12, and Y13 in the formula (11X) are each preferably a nitrogen atom.
In the first compound represented by the formulae (11X) and (11Y), Ry, R1X, R2X, R3X, and R4X serving as the substituents are preferably each independently one of the groups represented by the formulae (b1) to (b17) in the first compound according to the first exemplary embodiment.
In the first compound represented by the formulae (11X) and (11Y), it is preferable that L11 is a single bond, or a divalent, trivalent, tetravalent, pentavalent, or hexavalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
In the first compound represented by the formulae (11X) and (11Y), it is preferable that L12 is a single bond, or a divalent group derived from a group selected from the group consisting of a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted terphenyl group.
The second compound according to the fourth exemplary embodiment is preferably the second compound represented by the formula (2) according to the first exemplary embodiment.
The preferable arrangements of the second compound according to the fourth exemplary embodiment are the same as those of the second compound according to the first exemplary embodiment.
The emitting layer according to the fourth exemplary embodiment is preferably formed by using, as a vapor deposition source, “a composition containing the first compound represented by the formula (11X) or (11Y) and the second compound represented by the formula (2)”. For example, the emitting layer according to the fourth exemplary embodiment can be formed by using at least the vapor deposition source that is “the composition containing the first compound represented by the formula (11X) or (11Y) and the second compound represented by the formula (2)” and the third compound.
Using the “composition containing the first compound represented by the formula (11X) or (11Y) and the second compound” can reduce the number of vapor deposition sources for forming a desired layer (e.g., emitting layer).
The organic EL device that is an exemplary arrangement of the fourth exemplary embodiment can also achieve higher performance, in particular, improved luminous efficiency.
Electronic Device
An electronic device according to the present exemplary embodiment is installed with any one of the organic EL devices according to the above exemplary embodiments. Examples of the electronic device include a display device and a light-emitting device. 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.
Organic-EL-Device Material
An organic-EL-device material according to a sixth exemplary embodiment contains at least the first compound (compound represented by the formula (1X) or (1Y)), the second compound (compound represented by the formula (2)), and the third compound that exhibits delayed fluorescence according to the first or second exemplary embodiment.
The organic-EL-device material of the sixth exemplary embodiment can provide an organic EL device with higher performance, in particular, improved luminous efficiency.
The organic-EL-device material according to the sixth exemplary embodiment may further contain an additional compound. When the organic-EL-device material according to the sixth exemplary embodiment further contains the additional compound, the additional compound may be solid or liquid.
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 emitting layer is not limited to a single layer, but may be provided by laminating a plurality of emitting layers. When the organic EL device has the plurality of emitting layers, it is only required that at least one of the emitting layers satisfies the conditions described in the above exemplary embodiment. For instance, in some embodiments, the rest of the emitting layers is a fluorescent emitting layer or a phosphorescent emitting layer with use of emission caused by electron transfer from the triplet excited state directly to the ground state.
When the organic EL device includes a plurality of emitting layers, these emitting layers may be mutually adjacently provided, or may form a so-called tandem organic EL device, in which a plurality of emitting units are layered via an intermediate layer.
For instance, a blocking layer may be provided adjacent to at least one of a side of the emitting layer close to the anode or a side of the emitting layer close to the cathode. The blocking layer is preferably provided in contact with the emitting layer to block holes, electrons, excitons or combinations thereof.
For instance, when the blocking layer is provided in contact with the side of the emitting layer close to the cathode, the blocking layer permits transport of electrons and blocks holes from reaching a layer provided closer to the cathode (e.g., the electron transporting layer) beyond the blocking layer. When the organic EL device includes the electron transporting layer, the blocking layer is preferably disposed between the emitting layer and the electron transporting layer.
When the blocking layer is provided in contact with the side of the emitting layer close to the anode, the blocking layer permits transport of holes and blocks electrons from reaching a layer provided closer to the anode (e.g., the hole transporting layer) beyond the blocking layer. When the organic EL device includes the hole transporting layer, the blocking layer is preferably disposed between the emitting layer and the hole transporting layer.
Alternatively, the blocking layer may be provided adjacent to the emitting layer so that the excitation energy does not leak out from the emitting layer toward neighboring layer(s). The blocking layer blocks excitons generated in the emitting layer from being transferred to a layer(s) (e.g., the electron transporting layer and the hole transporting layer) closer to the electrode(s) beyond the blocking layer.
The emitting layer is preferably bonded with the blocking layer.
Specific structure, shape and the like of the components in the invention may be designed in any manner as long as an object of the invention can be achieved.
Other Explanations
Herein, numerical ranges represented by “x to y” represents a range whose lower limit is the value (x) recited before “to” and whose upper limit is the value (y) recited after “to.”
Herein, the phrase “Rx and Ry are mutually bonded to form a ring” means, for instance, that Rx and Ry include a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom or a silicon atom, the atom(s) contained in Rx (a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom or a silicon atom) and the atom(s) contained in Ry (a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom or a silicon atom) are bonded via a single bond(s), a double bond(s), a triple bond, and/or a divalent linking group(s) to form a ring having 5 or more ring atoms (specifically, a heterocycle or an aromatic hydrocarbon ring). x represents a number, a character or a combination of a number and a character. y represents a number, a character or a combination of a number and a character.
The divalent linking group is not limited. Examples of the divalent linking group include —O—, —CO—, —CO2—, —S—, —SO—, —SO2—, —NH—, —NRa—, and a group provided by a combination of two or more of these linking group.
Specific examples of the heterocyclic ring include a cyclic structure (heterocyclic ring) obtained by removing a bond from a “heteroaryl group Sub2” exemplarily shown in the later-described “Description of Each Substituent in Formula.” The heterocyclic ring may have a substituent.
Specific examples of the heterocyclic ring include cyclic structures (heterocyclic rings) obtained by removing a bond from an “aryl group Sub1” exemplarily shown in the later-described “Description of Each Substituent in Formula.” The aromatic hydrocarbon ring may have a substituent.
Examples of Ra include a substituted or unsubstituted alkyl group Sub3 having 1 to 30 carbon atoms, a substituted or unsubstituted aryl group Sub1 having 6 to 30 ring carbon atoms, and a substituted or unsubstituted heteroaryl group Sub2 having 5 to 30 ring atoms, which are exemplarily shown in the later-described “Description of Each Substituent in Formula.”
Rx and Ry are mutually bonded to form a ring, which means, for instance, that: an atom contained in Rx1 and an atom contained in Ry1 in a molecular structure represented by a formula (E1) below form a ring (cyclic structure) E represented by a formula (E2); an atom contained in Rx1 and an atom contained in Ry1 in a molecular structure represented by a formula (F1) below form a ring (cyclic structure) F represented by a formula (F2); an atom contained in Rx1 and an atom contained in Ry1 in a molecular structure represented by a formula (G1) below form a ring (cyclic structure) G represented by a formula (G2); an atom contained in Rx1 and an atom contained in Ry1 in a molecular structure represented by a formula (H1) below form a ring (cyclic structure) H represented by a formula (H2); and an atom contained in Rx1 and an atom contained in Ry1 in a molecular structure represented by a formula (I1) below form a ring (cyclic structure) I represented by a formula (I2).
In the formulae (E1) to (I1), * each independently represents a bonding position to another atom in a molecule. The two * in the formulae (E1), (F1), (G1), (H1) and (I1) correspond to two * in the formulae (E2), (F2), (G2), (H2) and (I2), respectively.
In the molecular structures represented by the formulae (E2) to (I2), E to I each represent a cyclic structure (the ring having 5 or more ring atoms). In the formulae (E2) to (I2), * each independently represents a bonding position to another atom in a molecule. The two * in the formula (E2) correspond to two * in the formula (E1). Similarly, two * in each of the formulae (F2) to (I2) correspond one-to-one to two * in in each of the formulae (F1) to (I1).
For instance, in the formula (E1), when Rx1 and Ry1 are mutually bonded to form the ring E in the formula (E2) and the ring E is an unsubstituted benzene ring, the molecular structure represented by the formula (E1) is a molecular structure represented by a formula (E3) below. Herein, two * in the formula (E3) each independently correspond to two * in the formula (E2) and the formula (E1).
For instance, in the formula (E1), when Rx1 and Ry1 are mutually bonded to form the ring E in the formula (E2) and the ring E is an unsubstituted pyrrole ring, the molecular structure represented by the formula (E1) is a molecular structure represented by a formula (E4) below. Herein, two * in the formula (E4) each independently correspond to two * in the formula (E2) and the formula (E1). In the formulae (E3) and (E4), * each independently represents a bonding position to another atom in a molecule.
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, crosslinking 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 specifically described, 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 pyridinyl group has 5 ring carbon atoms, and a furanyl group has 4 ring carbon atoms. When a benzene ring and/or a naphthalene ring is substituted by a substituent (e.g., an alkyl group), the number of carbon atoms of the alkyl group is not counted in the number of the ring carbon atoms. When a fluorene ring is substituted by a substituent (e.g., a fluorene ring) (i.e., a spirofluorene ring is included), the number of carbon atoms of the fluorene ring as the substituent is not counted in the number of the ring carbon atoms of the fluorene ring.
Herein, the ring atoms refer to the number of atoms forming a ring of a compound (e.g., a monocyclic compound, fused-ring compound, crosslinking 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, ring assembly). Atom(s) not forming a ring and atom(s) included in a substituent when the ring is substituted by the substituent are not counted in the number of the ring atoms. Unless specifically described, the same applies to the “ring atoms” described later. For instance, a pyridine ring has six ring atoms, a quinazoline ring has ten ring atoms, and a furan ring has five ring atoms. A hydrogen atom(s) and/or an atom(s) of a substituent which are bonded to carbon atoms of a pyridine ring and/or quinazoline ring are not counted in the ring atoms. When a fluorene ring is substituted by a substituent (e.g., a fluorene ring) (i.e., a spirofluorene ring is included), the number of atoms of the fluorene ring as the substituent is not counted in the number of the ring atoms of the fluorene ring.
Description of Each Substituent in Formulae Herein
The aryl group (occasionally referred to as an aromatic hydrocarbon group) herein is exemplified by an aryl group Sub1. The aryl group Sub1 is at least one group selected from the group consisting of a phenyl group, biphenyl group, terphenyl group, naphthyl group, anthryl group, phenanthryl group, fluorenyl group, pyrenyl group, chrysenyl group, fluoranthenyl group, benz[a]anthryl group, benzo[c]phenanthryl group, triphenylenyl group, benzo[k]fluoranthenyl group, benzo[g]chrysenyl group, benzo[b]triphenylenyl group, picenyl group, and perylenyl group.
Herein, the aryl group Sub1 preferably has 6 to 30 ring carbon atoms, more preferably 6 to 20 ring carbon atoms, further preferably 6 to 14 ring carbon atoms, further more preferably 6 to 12 ring carbon atoms. Among the aryl group Sub1, a phenyl group, biphenyl group, naphthyl group, phenanthryl group, terphenyl group and fluorenyl group are preferable. A carbon atom in a position 9 of each of 1-fluorenyl group, 2-fluorenyl group, 3-fluorenyl group and 4-fluorenyl group is preferably substituted by a substituted or unsubstituted alkyl group Sub3 or a substituted or unsubstituted aryl group Sub1 described later herein.
The heteroaryl group (occasionally referred to as a heterocyclic group, heteroaromatic ring group or aromatic heterocyclic group) herein is exemplified by a heterocyclic group Sub2. The heterocyclic group Sub2 is a group containing, as a hetero atom(s), at least one atom selected from the group consisting of nitrogen, sulfur, oxygen, silicon, selenium atom and germanium atom. The heterocyclic group Sub2 preferably contains, as a hetero atom(s), at least one atom selected from the group consisting of nitrogen, sulfur and oxygen.
The heterocyclic group Sub2 herein are, for instance, at least one group selected from the group consisting of a pyridyl group, pyrimidinyl group, pyrazinyl group, pyridazinyl group, triazinyl group, quinolyl group, isoquinolinyl group, naphthyridinyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, phenanthridinyl group, acridinyl group, phenanthrolinyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, triazolyl group, tetrazolyl group, indolyl group, benzimidazolyl group, indazolyl group, imidazopyridinyl group, benzotriazolyl group, carbazolyl group, furyl group, thienyl group, oxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, oxadiazolyl group, thiadiazolyl group, benzofuranyl group, benzothienyl group, benzoxazolyl group, benzothiazolyl group, benzisoxazolyl group, benzisothiazolyl group, benzoxadiazolyl group, benzothiadiazolyl group, dibenzofuranyl group, dibenzothienyl group, piperidinyl group, pyrrolidinyl group, piperazinyl group, morpholyl group, phenazinyl group, phenothiazinyl group, and phenoxazinyl group.
Herein, the heterocyclic group Sub2 preferably has 5 to 30 ring atoms, more preferably 5 to 20 ring atoms, further preferably 5 to 14 ring atoms. Among the above heterocyclic group Sub2, a 1-dibenzofuranyl group, 2-dibenzofuranyl group, 3-dibenzofuranyl group, 4-dibenzofuranyl group, 1-dibenzothienyl group, 2-dibenzothienyl group, 3-dibenzothienyl group, 4-dibenzothienyl group, 1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group, 4-carbazolyl group, and 9-carbazolyl group are further more preferable. A nitrogen atom in position 9 of 1-carbazolyl group, 2-carbazolyl group, 3-carbazolyl group and 4-carbazolyl group is preferably substituted by the substituted or unsubstituted aryl group Sub1 or the substituted or unsubstituted heterocyclic group Sub2 described herein.
Herein, the heterocyclic group Sub2 may be a group derived from any one of moieties represented by formulae (XY-1) to (XY-18) below.
In the formulae (XY-1) to (XY-18), XA and YA each independently represent a hetero atom, and preferably represent an oxygen atom, sulfur atom, selenium atom, silicon atom or germanium atom. Each of the moieties represented by the respective formulae (XY-1) to (XY-18) has a bond at any position to provide a heterocyclic group. The heterocyclic group may be substituted.
Herein, the heterocyclic group Sub2 may be a group represented by one of formulae (XY-19) to (XY-22) below. Moreover, the position of the bond may be changed as needed.
The alkyl group herein may be any one of a linear alkyl group, branched alkyl group and cyclic alkyl group.
The alkyl group herein is exemplified by an alkyl group Sub3.
The linear alkyl group herein is exemplified by a linear alkyl group Sub31.
The branched alkyl group herein is exemplified by a branched alkyl group Sub32.
The cyclic alkyl group herein is exemplified by a cyclic alkyl group Sub33.
For instance, the alkyl group Sub3 is at least one group selected from the group consisting of the linear alkyl group Sub31, branched alkyl group Sub32, and cyclic alkyl group Sub33.
The linear alkyl group Sub31 or branched alkyl group Sub32 is exemplified by at least one group selected from the group consisting of a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, neopentyl group, amyl group, isoamyl group, 1-methylpentyl group, 2-methylpentyl group, 1-pentylhexyl group, 1-butylpentyl group, 1-heptyloctyl group, and 3-methylpentyl group.
Herein, the linear alkyl group Sub31 or branched alkyl group Sub32 preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, further preferably 1 to 10 carbon atoms, further more preferably 1 to 6 carbon atoms. The linear alkyl group Sub31 or branched alkyl group Sub32 is further more preferably a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, s-butyl group, isobutyl group, t-butyl group, n-pentyl group, n-hexyl group, amyl group, isoamyl group and neopentyl group.
Herein, the cyclic alkyl group Sub33 is exemplified by a cycloalkyl group Sub331.
The cycloalkyl group Sub331 herein is exemplified by at least one group selected from the group consisting of a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, 4-metylcyclohexyl group, adamantyl group and norbornyl group. The cycloalkyl group Sub331 preferably has 3 to 30 ring carbon atoms, more preferably 3 to 20 ring carbon atoms, further preferably 3 to 10 ring carbon atoms, further more preferably 5 to 8 ring carbon atoms. Among the cycloalkyl group Sub331, a cyclopentyl group and a cyclohexyl group are further more preferable.
Herein, an alkyl halide group is exemplified by an alkyl halide group Sub4. The alkyl halide group Sub4 is provided by substituting the alkyl group Sub3 with at least one halogen atom, preferably at least one fluorine atom.
Herein, the alkyl halide group Sub4 is exemplified by at least one group selected from the group consisting of a fluoromethyl group, difluoromethyl group, trifluoromethyl group, fluoroethyl group, trifluoromethylmethyl group, trifluoroethyl group, and pentafluoroethyl group.
Herein, a substituted silyl group is exemplified by a substituted silyl group Sub5. The substituted silyl group Sub5 is exemplified by at least one group selected from the group consisting of an alkylsilyl group Sub51 and an arylsilyl group Sub52.
Herein, the alkylsilyl group Sub51 is exemplified by a trialkylsilyl group Sub511 having the above-described alkyl group Sub3.
The trialkylsilyl group Sub511 is exemplified by at least one group selected from the group consisting of a trimethylsilyl group, triethylsilyl group, tri-n-butylsilyl group, tri-n-octylsilyl group, triisobutylsilyl group, dimethylethylsilyl group, dimethylisopropylsilyl group, dimethyl-n-propylsilyl group, dimethyl-n-butylsilyl group, dimethyl-t-butylsilyl group, diethylisopropylsilyl group, vinyl dimethylsilyl group, propyldimethylsilyl group, and triisopropylsilyl group. Three alkyl groups Sub3 in the trialkylsilyl group Sub511 may be mutually the same or different.
Herein, the arylsilyl group Sub52 is exemplified by at least one group selected from the group consisting of a dialkylarylsilyl group Sub521, alkyldiarylsilyl group Sub522 and triarylsilyl group Sub523.
The dialkylarylsilyl group Sub521 is exemplified by a dialkylarylsilyl group including two alkyl groups Sub3 and one aryl group Sub1. The dialkylarylsilyl group Sub521 preferably has 8 to 30 carbon atoms.
The alkyldiarylsilyl group Sub522 is exemplified by an alkyldiarylsilyl group including one alkyl group Sub3 and two aryl groups Sub1. The alkyldiarylsilyl group Sub522 preferably has 13 to 30 carbon atoms.
The triarylsilyl group Sub523 is exemplified by a triarylsilyl group including three aryl groups Sub1. The triarylsilyl group Sub523 preferably has 18 to 30 carbon atoms.
Herein, a substituted or unsubstituted alkyl sulfonyl group is exemplified by an alkyl sulfonyl group Sub6. The alkyl sulfonyl group Sub6 is represented by —SO2Rw. Rw in —SO2Rw represents a substituted or unsubstituted alkyl group Sub3 described above.
Herein, an aralkyl group (occasionally referred to as an arylalkyl group) is exemplified by an aralkyl group Sub7. An aryl group in the aralkyl group Sub7 includes, for instance, at least one of the above-described aryl group Sub1 and the above-described heteroaryl group Sub2.
The aralkyl group Sub7 herein is preferably a group having the aryl group Sub1 and is represented by —Z3-Z4. Z3 is exemplified by an alkylene group corresponding to the above alkyl group Sub3. Z4 is exemplified by the above aryl group Sub1.
In this aralkyl group Sub7, an aryl moiety has 6 to 30 carbon atoms (preferably 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms) and an alkyl moiety has 1 to 30 carbon atoms (preferably 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, further preferably 1 to 6 carbon atoms). The aralkyl group Sub7 is exemplified by at least one group selected from the group consisting of a benzyl group, 2-phenylpropane-2-yl 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.
The alkoxy group herein is exemplified by an alkoxy group Sub8. The alkoxy group Sub8 is represented by —OZ1. Z1 is exemplified by the above alkyl group Sub3. The alkoxy group Sub8 is exemplified by at least one group selected from the group consisting of a methoxy group, ethoxy group, propoxy group, butoxy group, pentyloxy group and hexyloxy group. The alkoxy group Sub8 preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms.
Herein, an alkoxy halide group is exemplified by an alkoxy halide group Sub9. The alkoxy halide group Sub9 is provided by substituting the alkoxy group Sub8 with at least one halogen atom, preferably at least one fluorine atom.
Herein, an aryloxy group (occasionally referred to as an arylalkoxy group) is exemplified by an arylalkoxy group Sub10. An aryl group in the arylalkoxy group Sub10 includes at least one of the aryl group Sub1 and the heteroaryl group Sub2.
The arylalkoxy group Sub10 herein is represented by —OZ2. Z2 is exemplified by the aryl group Sub1 or the heteroaryl group Sub2. The arylalkoxy group Sub10 preferably has 6 to 30 ring carbon atoms, more preferably 6 to 20 ring carbon atoms. The arylalkoxy group Sub10 is exemplified by a phenoxy group.
Herein, a substituted amino group is exemplified by a substituted amino group Sub11. The substituted amino group Sub11 is exemplified by at least one group selected from the group consisting of an arylamino group Sub111 and an alkylamino group Sub112.
The arylamino group Sub11 is represented by —NHRV1 or —N(RV1)2. RV1 is exemplified by the aryl group Sub1. Two RV1 in —N(RV1)2 are mutually the same or different.
The alkylamino group Sub112 is represented by —NHRV2 or —N(RV2)2. RV2 is exemplified by the alkyl group Sub3. Two RV2 in —N(RV2)2 are mutually the same or different.
Herein, the alkenyl group is exemplified by an alkenyl group Sub12. The alkenyl group Sub12, which is linear or branched, is exemplified by at least one group selected from the group consisting of a vinyl group, propenyl group, butenyl group, oleyl group, eicosapentaenyl group, docosahexaenyl group, styryl group, 2,2-diphenylvinyl group, 1,2,2-triphenylvinyl group, and 2-phenyl-2-propenyl group.
The alkynyl group herein is exemplified by an alkynyl group Sub13. The alkynyl group Sub13 may be linear or branched and is at least one group selected from the group consisting of an ethynyl group, a propynyl group and a 2-phenylethynyl group.
The alkylthio group herein is exemplified by an alkylthio group Sub14.
The alkylthio group Sub14 is represented by —SRV3. RV3 is exemplified by the alkyl group Sub3. The alkylthio group Sub14 preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms.
The arylthio group herein is exemplified by an arylthio group Sub15.
The arylthio group Sub15 is represented by —SRV4. RV4 is exemplified by the aryl group Sub1. The arylthio group Sub15 preferably has 6 to 30 ring carbon atoms, more preferably 6 to 20 ring carbon atoms.
Herein, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, among which a fluorine atom is preferable.
A substituted phosphino group herein is exemplified by a substituted phosphino group Sub16. The substituted phosphino group Sub16 is exemplified by a phenyl phosphanyl group.
An arylcarbonyl group herein is exemplified by an arylcarbonyl group Sub17. The arylcarbonyl group Sub17 is represented by —COY′. Y′ is exemplified by the aryl group Sub1. Herein, the arylcarbonyl group Sub17 is exemplified by at least one group selected from the group consisting of a phenyl carbonyl group, diphenyl carbonyl group, naphthyl carbonyl group, and triphenyl carbonyl group.
An acyl group herein is exemplified by an acyl group Sub11. The acyl group Sub18 is represented by —COR′. R′ is exemplified by the alkyl group Sub3. The acyl group Sub18 herein is exemplified by at least one group selected from the group consisting of an acetyl group and a propionyl group.
A substituted phosphoryl group herein is exemplified by a substituted phosphoryl group Sub19. The substituted phosphoryl group Sub19 is represented by a formula (P) below.
In the formula (P), ArP1 and ArP2 are any one substituent selected from the group consisting of the above alkyl group Sub3 and the above aryl group Sub1.
An ester group herein is exemplified by an ester group Sub20. The ester group Sub20 is exemplified by at least one group selected from the group consisting of an alkyl ester group and an aryl ester group.
An alkyl ester group herein is exemplified by an alkyl ester group Sub201. The alkyl ester group Sub201 is represented by —C(═O)ORE. RE is exemplified by a substituted or unsubstituted alkyl group Sub3 described above.
An aryl ester group herein is exemplified by an aryl ester group Sub202. The aryl ester group Sub202 is represented by —C(═O)ORAr. RAr is exemplified by a substituted or unsubstituted aryl group Sub1 described above.
A siloxanyl group herein is exemplified by a siloxanyl group Sub21. The siloxanyl group Sub21 is a silicon compound group through an ether bond. The siloxanyl group Sub21 is exemplified by a trimethylsiloxanyl group.
A carbamoyl group herein is represented by —CONH2.
A substituted carbamoyl group herein is exemplified by a carbamoyl group Sub22. The carbamoyl group Sub22 is represented by —CONH—ArC or —CONH—RC. ArC is exemplified by at least one group selected from the group consisting of the above-described aryl group Sub1 (preferably 6 to 10 ring carbon atoms) and the above-described heteroaryl group Sub2 (preferably 5 to 14 ring atoms). ArC may be a group formed by bonding the aryl group Sub1 and the heteroaryl group Sub2.
RC is exemplified by a substituted or unsubstituted alkyl group Sub3 described above (preferably having 1 to 6 carbon atoms).
Herein, “carbon atoms forming a ring (ring carbon atoms)” mean carbon atoms forming a saturated ring, unsaturated ring, or aromatic ring. “Atoms forming a ring (ring atoms)” mean carbon atoms and hetero atoms forming a ring including a saturated ring, unsaturated ring, or aromatic ring.
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 or tritium) is bonded to each of bondable positions that are not annexed with signs “R” or the like or “D” representing a deuterium.
Hereinafter, an alkyl group Sub3 means at least one group of a linear alkyl group Sub31, a branched alkyl group Sub32, and a cyclic alkyl group Sub33 described in “Description of Each Substituent.”
Similarly, a substituted silyl group Sub5 means at least one group of an alkylsilyl group Sub51 and an arylsilyl group Sub52.
Similarly, a substituted amino group Sub11 means at least one group of an arylamino group Sub111 and an alkylamino group Sub112.
Herein, a substituent for a “substituted or unsubstituted” group is exemplified by a substituent RF1. The substituent RF1 is at least one group selected from the group consisting of an aryl group Sub1, heteroaryl group Sub2, alkyl group Sub3, alkyl halide group Sub4, substituted silyl group Sub5, alkylsulfonyl group Sub6, aralkyl group Sub7, alkoxy group Sub8, alkoxy halide group Sub9, arylalkoxy group Sub10, substituted amino group Sub11, alkenyl group Sub12, alkynyl group Sub13, alkylthio group Sub14, arylthio group Sub15, substituted phosphino group Sub16, arylcarbonyl group Sub17, acyl group Sub18, substituted phosphoryl group Sub19, ester group Sub20, siloxanyl group Sub21, carbamoyl group Sub22, unsubstituted amino group, unsubstituted silyl group, halogen atom, cyano group, hydroxy group, nitro group, and carboxy group.
Herein, the substituent RF1 for a “substituted or unsubstituted” group may be a diaryl boron group (ArB1ArB2B—). ArB1 and ArB2 are exemplified by the above-described aryl group Sub1. ArB1 and ArB2 in ArB1ArB2B— are the same or different.
Specific examples and preferable examples of the substituent RF1 are the same as those of the substituents described in “Description of Each Substituent” (e.g., an aryl group Sub1, heteroaryl group Sub2, alkyl group Sub3, alkyl halide group Sub4, substituted silyl group Sub5, alkylsulfonyl group Sub6, aralkyl group Sub7, alkoxy group Sub8, alkoxy halide group Sub9, arylalkoxy group Sub10, substituted amino group Sub11, alkenyl group Sub12, alkynyl group Sub13, alkylthio group Sub14, arylthio group Sub15, substituted phosphino group Sub11, arylcarbonyl group Sub17, acyl group Sub18, substituted phosphoryl group Sub19, ester group Sub20, siloxanyl group Sub21, and carbamoyl group Sub22).
The substituent RF1 for a “substituted or unsubstituted” group may be further substituted by at least one group (hereinafter, also referred to as a substitutent RF2) selected from the group consisting of an aryl group Sub1, heteroaryl group Sub2, alkyl group Sub3, alkyl halide group Sub4, substituted silyl group Sub5, alkylsulfonyl group Sub6, aralkyl group Sub7, alkoxy group Sub8, alkoxy halide group Sub9, arylalkoxy group Sub10, substituted amino group Sub11, alkenyl group Sub12, alkynyl group Sub13, alkylthio group Sub14, arylthio group Sub15, substituted phosphino group Sub16, arylcarbonyl group Sub17, acyl group Sub18, substituted phosphoryl group Sub19, ester group Sub20, siloxanyl group Sub21, carbamoyl group Sub22, unsubstituted amino group, unsubstituted silyl group, halogen atom, cyano group, hydroxy group, nitro group, and carboxy group. Moreover, a plurality of substituents RF2 may be bonded to each other to form a ring.
“Unsubstituted” for a “substituted or unsubstituted” group means that a group is not substituted by the above-described substituent RF1 but bonded with a hydrogen atom.
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 the substituent RF1 of the substituted ZZ group.
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 do not include atoms of the substituent RF1 of the substituted ZZ group.
The same description as the above applies to “substituted or unsubstituted” in compounds or moieties thereof described herein.
Herein, when the substituents are bonded to each other to form a ring, the ring is structured to be a saturated ring, an unsaturated ring, an aromatic hydrocarbon ring or a hetero ring.
Herein, examples of the aromatic hydrocarbon group in the linking group include a divalent or multivalent group obtained by eliminating one or more atoms from the above monovalent aryl group Sub1.
Herein, examples of the heterocyclic group in the linking group include a divalent or multivalent group obtained by eliminating one or more atoms from the above monovalent heteroaryl group Sub2.
Compounds
The first compound used for manufacturing organic EL devices are shown below.
The second compound used for manufacturing organic EL devices are shown below.
Structures of compounds used for manufacturing organic EL devices in Comparatives are shown below.
Structures of other compounds used for manufacturing the organic EL devices according to Examples and Comparatives are shown below.
Preparation of Organic EL Device
The organic EL devices were prepared and evaluated as follows.
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 one minute. A film of ITO was 130 nm thick.
After the glass substrate having the transparent electrode line was cleaned, the glass substrate was mounted on a substrate holder of a vacuum evaporation apparatus. Firstly, a compound HT and a compound HA were co-deposited on a surface of the glass substrate where the transparent electrode line was provided in a manner to cover the transparent electrode, thereby forming a 10-nm-thick hole injecting layer. The concentrations of the compound HT and the compound HA in the hole injecting layer were 97 mass % and 3 mass %, respectively.
Next, the compound HT was vapor-deposited on the hole injecting layer to form a 200-nm-thick hole transporting layer.
Next, a compound EBL was vapor-deposited on the hole transporting layer to form a 10-nm-thick electron blocking layer.
Next, a compound na as the first compound, a compound pa as the second compound, a compound TADF as the third compound, and RD as the fourth compound were co-deposited on the electron blocking layer to form a 25-nm-thick emitting layer. The concentrations of the compound na, the compound pa, the compound TADF, and the compound RD in the emitting layer were 37 mass %, 37 mass %, 25 mass %, and 1 mass % respectively.
Next, the compound HBL was vapor-deposited on the emitting layer to form a 10-nm-thick hole blocking layer.
Next, the compound ET was vapor-deposited on the hole blocking layer to form a 30-nm-thick electron transporting layer.
Next, lithium fluoride (LiF) was vapor-deposited on the electron transporting layer to form a 1-nm-thick electron injecting electrode (cathode).
Subsequently, metal aluminum (Al) was vapor-deposited on the electron injectable electrode to form an 80-nm-thick metal Al cathode.
A device arrangement of the organic EL device of Example 1 is roughly shown as follows.
ITO(130)/HT:HA(10.97%:3%)/HT(200)/EBL(10)/na:pa:TADF:RD(25.37%:37%:25%:1%)/HBL(10)/ET(30)/LiF(1)/Al(80)
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 HT and the compound HA in the hole injecting layer, and the numerals (37%:37%:25%:1%) represented by percentage in the same parentheses indicate a ratio (mass %) between the compound na and the compound pa and the compound TADF and the compound RD in the emitting layer.
The organic EL devices in Examples 2 to 4 and Comparatives 1 to 5 were manufactured in the same manner as in Example 1 except that compounds shown in Table 1 were used in place of the compound na and the compound pa in the emitting layer of Example 1.
Evaluation of Organic EL Devices
The organic EL devices manufactured in Examples 1 to 4 and Comparatives 1 to 5 were evaluated as follows. The results are shown in Table 1. Although compounds Ref-nb and Ref-nc used in Comparatives 1 to 5 do not correspond to the first compound, Ref-nb and Ref-nc are shown in the same column as the compound na in Example 1 for convenience.
Main Peak Wavelength (λp)
Voltage was applied on each of the organic EL devices such that a current density of the organic EL device was 10 mA/cm2, where spectral radiance spectrum was measured by a spectroradiometer CS-2000 (manufactured by Konica Minolta, Inc.). The main peak wavelength λp (unit: nm) was calculated based on the obtained spectral-radiance spectra.
External Quantum Efficiency EQE
Voltage was applied on each of the organic EL devices such that a current density was 10 mA/cm2, where spectral radiance spectra were measured by a spectroradiometer CS-2000 (manufactured 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 (%) of Comparative 1 was set to be 100 and EQE (%) of each of Examples and Comparatives was obtained as a “EQE (relative value: %)” using a numerical formula (numerical formula 100) below.
EQE (relative value: %) of each of Examples and Comparatives=(EQE (%) of each of Examples and Comparatives/EQE (%) of Comparative 1)×100 (Numerical Formula 100)
Explanation of Table 1
“<0.01” represents ΔST of less than 0.01 eV.
The organic EL devices in Examples 1 to 4 exhibited an improved external quantum efficiency EQE as compared with the organic EL devices in Comparatives 1 to 5 in which the compounds Ref-nb and Ref-nc were used in place of the first compound in the emitting layer.
Here, the organic EL devices of Comparatives 1 and 2 correspond to Examples of Literature 1. From the comparison of Comparatives 1, 2 to Examples 1 to 4, it is understood that the luminous efficiency is improved as compared with that in Literature 1 by using the first compound of the first exemplary embodiment or the like of the present specification (together with the second compound). The organic EL device of Comparative 3 uses the compound Ref-nc, which is used in Examples of Literature 1, together with the second compound pa of Examples 1, 2. Also from the comparison of Comparative 3 to Examples 1, 2, it is understood that the luminous efficiency is improved as compared with that in Literature 1 by using the first compound of the first exemplary embodiment or the like of the present specification (together with the second compound).
Here, the organic EL device of Comparative 4 corresponds to Examples of Literature 2. From the comparison of Comparative 4 to Examples 1 to 4, it is understood that the luminous efficiency is improved as compared with that in Literature 2 by using the first compound of the first exemplary embodiment or the like of the present specification (together with the second compound). The organic EL device of Comparative 5 uses the compound Ref-nb, which is used in Examples of Literature 2, together with the second compound pa of Examples 1, 2. Also from the comparison of Comparative 5 to Examples 1, 2, it is understood that the luminous efficiency is improved as compared with that in Literature 1 by using the first compound of the first exemplary embodiment or the like of the present specification (together with the second compound).
Evaluation of Compounds
Values of physical properties of the compounds shown in Table 1 were measured by the following method.
Thermally Activated Delayed Fluorescence
Delayed Fluorescence of Compound TADF
Delayed fluorescence properties were checked by measuring transient photoluminescence (PL) using a device shown in
The fluorescence spectrum of the above sample solution was measured with a spectrofluorometer FP-8600 (manufactured by JASCO Corporation), and the fluorescence spectrum of a 9,10-diphenylanthracene ethanol solution was measured under the same conditions. Using the fluorescence area intensities of both spectra, the total fluorescence quantum yield is calculated by an equation (1) in Morris et al. J. Phys. Chem. 80 (1976) 969.
Prompt emission was observed immediately when the excited state was achieved by exciting the compound TADF with a pulse beam (i.e., a beam emitted from a pulse laser) having a wavelength to be absorbed by the compound TADF, and Delay emission was observed not immediately when the excited state was achieved but after the excited state was achieved. The delayed fluorescence in Examples means that an amount of Delay Emission is 5% or more with respect to an amount of Prompt Emission. Specifically, provided that the amount of Prompt emission is denoted by XP and the amount of Delay emission is denoted by XD, the delayed fluorescence means that a value of XD/XP is 0.05 or more.
An amount of Prompt emission, an amount of Delay emission and a ratio between the amounts thereof can be obtained according to the method as described in “Nature 492, 234-238, 2012” (Reference Document 1). The amount of Prompt emission and the amount of Delay emission may be calculated using a device different from one described in Reference Document 1 or one shown in
It was confirmed that the amount of Delay Emission was 5% or more with respect to the amount of Prompt Emission in the compound TADF.
Specifically, it was found that a value of XD/XP was 0.05 or more in the compound TADF.
Singlet Energy S1
Singlet energy S1 of each of the compounds na, nb, pa, pc, pd, pe, pf, TADF, RD and comparative compounds Ref-nb, Ref-nc was measured according to the above-described solution method.
Energy Gap T77K at 77K
An energy gap T77K of each of the compounds na, nb, pa, pc, pd, pe, pf, TADF and comparative compounds Ref-nb, Ref-nc was measured according to the measurement method of energy gap T77K described in the above “Relationship between Triplet Energy and Energy Gap at 77K.” Δ ST was checked from the measurement results of T77K and the values of the singlet energy S1 described above.
Main Peak Wavelength λ of Compound
A main peak wavelength λ of each of the compounds RD and TADF was measured by the following method.
A 5-μmol/L toluene solution of each of the compounds (measurement target) was prepared and put in a quartz cell. An emission spectrum (ordinate axis: luminous intensity, abscissa axis: wavelength) of each of the samples was measured at a normal temperature (300K). In Examples, the emission spectrum was measured using a spectrophotometer manufactured by Hitachi, Ltd. (device name: F-7000). 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 the maximum luminous intensity was defined as a main peak wavelength A.
Synthesis of Compounds
A compound na represented by a formula (1X) and a compound pb represented by a formula (2) were synthesized.
A synthesis scheme of the compound na is shown below.
Under nitrogen atmosphere, xylene (40 mL) was added into a mixture of 12H-benzofuro[2,3-a]carbazole (2.06 g, 8.00 mmol), 2-(3′-bromo-[1,1′-biphenyl]-3-yl)-4,6-diphenyl-1,3,5-triazine (3.71 g, 8.00 mmol), palladium acetate (35.9 mg, 0.160 mmol), tri-tert-butylphosphonium tetrafluoroborate (92.8 mg, 0.32 mmol), and sodium tert-butoxide (2.31 g, 24.0 mmol), and stirred at 130 degrees C. for six hours. After the reaction, a solid was filtrated and recrystallized with toluene to obtain the compound na (3.52 g, a yield of 69%). The obtained compound was identified as the compound na by analysis according to LC-MS (Liquid chromatography mass spectrometry).
A synthesis scheme of the compound pb is shown below.
Under nitrogen atmosphere, xylene (675 mL) was added into a mixture of 12H-benzofuro[2,3-a]carbazole (26.6 g, 103 mmol), 9-(4′-bromo-[1,1′-biphenyl]-4-yl)-9H-carbazole (41.2 g, 103 mmol), tris(dibenzylideneacetone)dipalladium (1.90 g, 2.07 mmol), tri-tert-butylphosphonium tetrafluoroborate (1.20 mg, 4.14 mmol), and sodium tert-butoxide (11.9 g, 124 mmol), and stirred at 130 degrees C. for eight hours. After the reaction, a solid was collected by filtration. The solid collected by filtration was recrystallized with toluene to obtain the compound pb (51.5 g, a yield of 87%). The obtained compound was identified as the compound pb by analysis according to LC-MS.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-102555 | Jun 2020 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20150053938 | Zeng | Feb 2015 | A1 |
| 20210050546 | Li et al. | Feb 2021 | A1 |
| Number | Date | Country |
|---|---|---|
| 107964017 | Apr 2018 | CN |
| 110492006 | Nov 2019 | CN |
| Entry |
|---|
| Adachi, “Yuki Hando-tai no Debaisu Bussei (Device Physics of Organic Semiconductors)”, Kodansha, Apr. 1, 2012, 19 pages (with English Machine Translation). |
| Uoyama et al., “Highly efficient organic light-emitting diodes from delayed fluorescence”, Nature, vol. 492, 2012, 7 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220006026 A1 | Jan 2022 | US |
