Organic light-emitting element, method for evaluating delayed fluorescent material, method for designing delayed fluorescent material, method for designing organic light-emitting element, and program

Abstract

To provide an organic light emitting element with excellent durability, including a delayed fluorescent material in the emission layer.SOLUTION: A delayed fluorescent material with a ΔPBHT of 0.01 or more is used in the emission layer of an organic light emitting element. PBHT(T1) represents the PBHT of the lowest excited triplet state of the delayed fluorescent material and PBHT(Tn) represents the PBHT of the lowest energy excited triplet state among the excited triplet states whose energy is greater than the lowest excited singlet energy of the delayed fluorescent material. ΔPBHT=PBHT(Tn)-PBHT(T1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a highly durable organic light-emitting device and a design method thereof, a method for evaluating and designing a delayed fluorescent material useful as a material for the organic light-emitting device, and a program for carrying out these methods. [Background technology]

[0002] Research into improving the luminous efficiency of organic light-emitting elements such as organic electroluminescence elements (organic EL elements) has been actively conducted. In particular, various efforts have been made to improve the luminous efficiency of elements by developing new materials for the luminescent layer that constitutes the organic light-emitting element. Among these efforts, there has been research into organic electroluminescence elements that use delayed fluorescent materials as materials for the luminescent layer.

[0003] Delayed fluorescent materials are compounds that undergo reverse intersystem crossing from an excited triplet state to an excited singlet state in an excited state, and then emit fluorescence upon returning from that excited singlet state to the ground state. The fluorescence emitted via this pathway is observed later than the fluorescence emitted from the excited singlet state (normal fluorescence) that arises directly from the ground state, hence the term delayed fluorescence. For example, when an organic molecule is excited by carrier injection, the probability of the excited singlet state and the excited triplet state occurring is statistically 25%:75%. Therefore, conventional fluorescent materials, which only utilize the energy of the excited singlet state that arises directly from the ground state, have limitations in improving their luminous efficiency. In contrast, delayed fluorescent materials can utilize not only the excited singlet state but also the excited triplet state for fluorescence emission via the reverse intersystem crossing pathway described above, resulting in higher luminous efficiency than conventional delayed fluorescent materials.

[0004] By the way, the reverse intersystem crossing from triplet to singlet as described above occurs when the difference between the lowest excited singlet energy and the lowest excited triplet energy, ΔE ST The smaller the ΔE, the more likely it is to occur. STThe smaller the overlap between the HOMO and LUMO orbitals, the smaller the value of ΔE ST For this reason, in the research and development of conventional delayed fluorescence materials, for example, ΔE ST Molecular design is being carried out with the aim of making the PBHT value, which is an index indicating the degree of overlap between the HOMO and LUMO orbitals, less than 0.2 and making it closer to the PBHT value (see Non-Patent Document 1). The PBHT value is a calculated value that ranges from 0 to 1, and the closer the PBHT value is to 0, the smaller the degree of orbital overlap. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] J. Chem. Phys. 128, 044118 (2008) Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, up until now, ΔE ST The molecular design of delayed fluorescent materials is carried out using the ΔE ST When we investigated the relationship between the PBHT value and the delayed fluorescence rate, we found that ΔE ST Although materials with a small PBHT or a PBHT value close to 0 tend to have a fast delayed fluorescence rate, some of these materials do not exhibit a sufficient delayed fluorescence rate. It was found that when such delayed fluorescent materials are used in the emitting layer, the durability of the device is reduced due to the long-lived triplet excitons.

[0007] Therefore, the present inventors have conducted extensive research with the aim of providing an organic light-emitting element that contains a delayed fluorescent material in the light-emitting layer and has excellent durability. [Means for solving the problem]

[0008] As a result of intensive research, the present inventors have found that among delayed fluorescent materials, compounds in which the PBHT value of the higher excited triplet state Tn is greater than the PBHT value of the lowest excited triplet state T1 tend to have a fast delayed fluorescence rate.Then, they have found that by using such delayed fluorescent materials in the light-emitting layer, an organic light-emitting device with excellent durability can be realized. The present invention has been proposed based on these findings, and specifically has the following configuration.

[0009] [1] An organic light-emitting device having an emitting layer containing a delayed fluorescent material having a ΔPBHT of 0.01 or more as defined by the following formula (I): Formula (I) ΔPBHT = PBHT(Tn)- PBHT(T1) [In formula (I), PBHT(T1) represents the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) represents the PBHT value of the excited triplet state with the lowest energy among the excited triplet states with energy higher than the lowest excited singlet energy of the delayed fluorescent material.] [2] The organic light-emitting device according to [1], wherein the delayed fluorescent material is a compound represented by any one of the following general formulas (1) to (6): [ka] JPEG0007780189000002.jpg152144 [In the general formulas (1) to (6), D 1 ~D 10 Each independently represents a group represented by the following general formula (7): 1 and D 2 , D 3 and D 4 , D 6 and D 7 , D 9 and D 10 The chemical structures of the two D 1 , the three Ds 2 , two D 3 , two D 4 , the three Ds 5 , two D6 , two D 8 , two D 9 have the same chemical structure. [ka] [In general formula (7), L 11 represents a single bond or a divalent linking group. 41 ~R 48 R each independently represents a hydrogen atom or a substituent. 41 and R 42 , R 42 and R 43 , R 43 and R 44 , R 44 and R 45 , R 45 and R 46 , R 46 and R 47 , R 47 and R 48 may be bonded to each other to form a cyclic structure. [3] The organic light-emitting element according to [2], wherein in each of the general formulae (1) to (6), at least one of the groups represented by the general formula (7) is a group represented by any of the following general formulae (8) to (13): [ka] [In the general formulas (8) to (13), L 21 ~L 26 represents a single bond or a divalent linking group. 51 ~R 110 R each independently represents a hydrogen atom or a substituent. 51 and R 52 , R 52 and R 53 , R 53 and R 54 , R 54 and R 55 , R 55 and R 56 , R 56 and R 57 , R 57 and R 58 , R 58 and R 59 , R 59 and R60 , R 61 and R 62 , R 62 and R 63 , R 63 and R 64 , R 65 and R 66 , R 66 and R 67 , R 67 and R 68 , R 68 and R 69 , R 69 and R 70 , R 72 and R 73 , R 73 and R 74 , R 74 and R 75 , R 75 and R 76 , R 76 and R 77 , R 77 and R 78 , R 78 and R 79 , R 79 and R 80 , R 81 and R 82 , R 82 and R 83 , R 83 and R 84 , R 84 and R 85 , R 86 and R 87 , R 87 and R 88 , R 88 and R 89 , R 89 and R 90 , R 91 and R 92 , R 93 and R 94 , R 94 and R 95 , R 95 and R 96 , R 96 and R 97 , R 97 and R 98 , R 99 and R 100 , R 101 and R 102 , R 102 and R 103, R 103 and R 104 , R 104 and R 105 , R 105 and R 106 , R 107 and R 108 , R 108 and R 109 , R 109 and R 110 may be bonded to each other to form a cyclic structure. [4] The organic light-emitting device according to any one of [1] to [3], wherein the PBHT(Tn) is PBHT(T3) in a third excited triplet state. [5] The organic light-emitting device according to [4], wherein the delayed fluorescent material is a compound represented by the general formula (2). [6] D in the general formula (2) 4 is a group represented by the general formula (13). [7] The organic light-emitting device according to any one of [1] to [3], wherein the PBHT(Tn) is PBHT(T2) in a second excited triplet state. [8] The organic light-emitting device according to [7], wherein the delayed fluorescent material is a compound represented by the general formula (4) or (5). [9] D in the general formula (4) 6 , D in the general formula (5) 8 is a group represented by the general formula (13).

[10] A method for evaluating a delayed fluorescent material, comprising evaluating the luminescence characteristics of the delayed fluorescent material based on ΔPBHT defined by the formula (I).

[11] The evaluation method according to

[10] , comprising a step of predicting the delayed fluorescence rate of a delayed fluorescent material based on ΔPBHT.

[12] A step of determining the relationship between ΔPBHT and delayed fluorescence rate τ2 based on the ΔPBHT and delayed fluorescence rate of multiple reference delayed fluorescence materials having different ΔPBHTs; Calculating the ΔPBHT of the delayed fluorescence material to be evaluated, determining the value of the delayed fluorescence rate corresponding to the ΔPBHT of the evaluation target from the relationship between the ΔPBHT and the delayed fluorescence rate τ2, and predicting this value as the delayed fluorescence rate of the evaluation target; The evaluation method according to

[10] or

[11] , comprising a step of evaluating the luminescence characteristics of the evaluation target based on the predicted delayed fluorescence rate.

[13] The evaluation method according to

[12] , wherein the delayed fluorescence rate of the reference delayed fluorescence material is an actually measured value.

[14] A method for designing a delayed fluorescent material, comprising molecular design of the delayed fluorescent material based on the relationship between the structure of the delayed fluorescent material and ΔPBHT defined by the formula (I).

[15] A first step of calculating the ΔPBHT of a specific delayed fluorescent material; A second step of designing a modified compound by modifying a part of the structure of the specific delayed fluorescent material and calculating ΔPBHT of the modified compound; a third step of designing a re-modified compound by modifying a part of the structure of the modified compound and calculating ΔPBHT of the re-modified compound; A fourth step of determining the relationship between the structure of the compound and ΔPBHT based on the structures of the specific delayed fluorescent material, the modified compound, and the re-modified compound and the calculated ΔPBHT; The design method according to

[14] , further comprising a fifth step of extracting a compound structure corresponding to a target range of ΔPBHT from the relationship between the compound structure and ΔPBHT, and selecting a delayed fluorescent material to be synthesized from a group of compounds having the extracted structure.

[16] The design method according to

[15] , wherein the partial changes in the structures of the specific delayed fluorescent material and the modified compound are quantifiable changes.

[17] Furthermore, for the specific delayed fluorescent material, the modified compound, and the re-modified compound, the difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy ST In the fifth step, ΔE ST The design method according to

[15] or

[16] , wherein a delayed fluorescent material to be synthesized is selected from the group of compounds based on the above.

[18] The design method according to any one of

[15] to

[17] , wherein the re-modified compound designed in the third step is regarded as a modified compound, and the third step is repeated.

[19] A method for designing an organic light-emitting element, comprising: selecting a delayed fluorescent material based on ΔPBHT defined by the formula (I); and designing an organic light-emitting element using the selected delayed fluorescent material.

[20] A step of searching for a delayed fluorescent material having a ΔPBHT of 0.01 or more from a database of delayed fluorescent materials storing the ΔPBHT of multiple delayed fluorescent materials as data; selecting a delayed fluorescent material to be used in an organic light-emitting element from the group of delayed fluorescent materials found in the search of the step; The design method according to

[19] , comprising a step of designing an organic light-emitting element using the delayed fluorescent material selected in the step.

[21] The database of delayed fluorescent materials further includes a difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy of the plurality of delayed fluorescent materials. ST and in the step of searching for the delayed fluorescent material, a delayed fluorescent material having a ΔPBHT of 0.01 or more and a ΔE ST The design method according to

[20] , wherein a delayed fluorescent material having a λ of 0.3 eV or less is searched for.

[22] A program for carrying out the method according to any one of

[10] to

[21] . [Effects of the Invention]

[0010] According to the present invention, by using a delayed fluorescent material having a ΔPBHT of 0.01 or more, an organic light-emitting device with excellent durability can be realized. Furthermore, according to the evaluation method of the delayed fluorescent material of the present invention, the luminescence characteristics of the delayed fluorescent material, such as the delayed fluorescence rate, can be easily evaluated. Furthermore, according to the design method of the delayed fluorescent material of the present invention, a delayed fluorescent material with a high delayed fluorescence rate can be designed. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the relationship between ΔPBHT(T3-T1) and delayed fluorescence rate. [Figure 2] 1 is a graph showing the relationship between ΔPBHT(T2-T1) and delayed fluorescence rate. [Figure 3] 1 is a graph showing the relationship between ΔPBHT(T3-T1) and LT95. [Figure 4] 1 is a graph showing the relationship between ΔPBHT(T2-T1) and LT95. [Figure 5] 1 is a graph showing the relationship between ΔPBHT(T2-T1) and delayed fluorescence rate. [Figure 6] 1 is a graph showing the relationship between ΔPBHT(T2-T1) and LT95. [Figure 7] 1 is a flowchart showing a method for designing a delayed fluorescent material. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. In this application, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In addition, in this application, "consisting of" means that the compound consists only of what is described before "consisting of" and does not include anything else. In addition, some or all of the hydrogen atoms present in the molecules of the compound used in the present invention may be replaced by deuterium atoms ( 2In the chemical structural formulas herein, hydrogen atoms are represented by H or omitted. For example, when the atom bonded to a carbon atom constituting the ring skeleton of a benzene ring is omitted, H is assumed to be bonded to the carbon atom constituting the ring skeleton at the omitted position. In this specification, the term "substituent" refers to an atom or group of atoms other than hydrogen atoms and deuterium atoms. On the other hand, the expressions "substituted or unsubstituted" and "optionally substituted" mean that a hydrogen atom may be substituted with a deuterium atom or a substituent. In addition, "transparent" in the present invention refers to a visible light transmittance of 50% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 99% or more. Visible light transmittance can be measured using an ultraviolet-visible spectrophotometer.

[0013] <Organic light-emitting element> The organic light-emitting device of the present invention has a light-emitting layer containing a delayed fluorescent material having a ΔPBHT of 0.01 or more as defined by the following formula (I). Formula (I) ΔPBHT= PBHT(Tn)- PBHT(T1) In formula (I), PBHT(T1) is the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) is the PBHT value of the lowest excited triplet state among the excited triplet states having energy greater than the lowest excited singlet energy of the delayed fluorescent material. In the following description, the "lowest excited triplet state among the excited triplet states having energy greater than the lowest excited singlet energy" in the present invention may be collectively referred to as the "higher excited triplet state Tn." For example, the delayed fluorescent material has the lowest excited triplet state T1, the second excited triplet state T2, and the third excited triplet state T3 as excited triplet states, and the energy E S1 , the energy of the lowest excited triplet state E T1 , the energy of the second excited triplet state E T2 , the energy of the third excited triplet state E T3 When the relationship shown in the following formula is satisfied, E T1<E S1 <E T2 <E T3 The PBHT value of the second excited triplet state T2, PBHT(T2), corresponds to PBHT(Tn), and ΔPBHT is calculated by the following formula: ΔPBHT = PBHT(T2) - PBHT(T1) Also, the energy of the lowest excited singlet state, E S1 , the energy of the lowest excited triplet state E T1 , the energy of the second excited triplet state E T2 , the energy of the third excited triplet state E T3 When the relationship shown in the following formula is satisfied, E T1 <E T2 <E S1 <E T3 The PBHT value of the third excited triplet state T3, PBHT(T3), corresponds to PBHT(Tn), and ΔPBHT is calculated by the following formula: ΔPBHT = PBHT(T3) - PBHT(T1) Here, the energies of the "lowest excited singlet energy" and the "lowest excited triplet state" in the present invention are the lowest excited singlet energy (E S1 ) and the lowest excited triplet energy (E T1 The energies of higher excited triplet states Tn, such as the second excited triplet state T2 and the third excited triplet state T3, are values ​​calculated using the quantum chemical calculation B3LYP / 6-31G molecular orbital calculation.

[0014] The "PBHT value" in the present invention is a value proposed by Michael J. Peach, Peter Benfield, Trygve Helgaker, and David J. Tozer, and is named by combining the initials of their surnames. The PBHT value is a numerical value that represents the orbital properties of an excited state. There are singlet and triplet PBHT values, but the present invention uses the triplet PBHT value. A small PBHT value indicates that the excited state is charge transfer (CT)-type, and a large PBHT value indicates that the excited state is localized electron (LE)-type. The PBHT value is the value Λ calculated by the following formula:

[0015]

number

[0016] The definitions of each term in the above formula are as follows:

[0017]

number

[0018] The method for calculating the PBHT value is described in detail in J. Chem. Phys. 128, 044118 (2008) "Excitation energies in density functional theory: An evaluation and a diagnostic test," the entire contents of which are incorporated herein by reference. The PBHT value indicates the degree of overlap between the HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital), and takes a value between 0 and 1. A PBHT value of 0 indicates that there is no overlap between the HOMO and LUMO, and a PBHT value of 1 indicates that the HOMO and LUMO completely overlap.

[0019] The organic light-emitting device of the present invention exhibits excellent durability by containing in the light-emitting layer a delayed fluorescent material having a ΔPBHT of 0.01 or more as defined above. This is presumably due to the following reasons. In other words, a ΔPBHT of 0.01 or greater indicates a greater degree of overlap between the HOMO and LUMO in the higher excited triplet state Tn than in the lowest excited triplet state T1, indicating a significant difference in the molecular orbital distribution between T1 and Tn. Therefore, it can be inferred that a delayed fluorescent material with a ΔPBHT of 0.01 or greater has a charge-transfer (CT) lowest excited triplet state T1 and a localized electron (LE) highest excited triplet state Tn. In such delayed fluorescent materials, after the transition from the lowest excited triplet state T1 to the higher excited triplet state Tn, effective spin-orbit interaction facilitates triplet-singlet spin conversion, resulting in a high delayed fluorescence rate (reverse intersystem crossing rate). Alternatively, similarly effective spin conversion occurs when T1 is LE and Tn is CT. Therefore, organic light-emitting devices containing a delayed fluorescent material with a ΔPBHT of 0.01 or greater in the emissive layer are expected to exhibit excellent durability by suppressing degradation due to long-lived triplet excitons.

[0020] The delayed fluorescent material having a ΔPBHT of 0.01 or more that can be used in the present invention will be described in detail below.

[0021] [Delayed fluorescent material] The "delayed fluorescent material" in the present invention is an organic compound that undergoes reverse intersystem crossing from an excited triplet state to an excited singlet state in an excited state, and emits fluorescence (delayed fluorescence) when returning from the excited singlet state to the ground state. In the present invention, a delayed fluorescent material is one that emits fluorescence with an emission lifetime of 100 ns (nanoseconds) or more when the emission lifetime is measured using a fluorescence lifetime measurement system (such as a streak camera system manufactured by Hamamatsu Photonics KK). In the present invention, among these delayed fluorescent materials, those having a ΔPBHT of 0.01 or more as defined by the above formula (I) are used. ΔPBHT is preferably 0.02 or more, more preferably 0.03 or more, and may be selected from the range of, for example, 0.04 or more, 0.05 or more, 0.06 or more, or 0.07 or more.

[0022] The delayed fluorescent material used in the present invention, having a ΔPBHT of 0.01 or more, has a difference ΔE ST is preferably 0.3 eV or less, more preferably 0.25 eV or less, more preferably 0.2 eV or less, more preferably 0.15 eV or less, even more preferably 0.1 eV or less, even more preferably 0.07 eV or less, even more preferably 0.05 eV or less, even more preferably 0.03 eV or less, and particularly preferably 0.01 eV or less.

[0023] It is preferable that a delayed fluorescent material having a ΔPBHT of 0.01 or more does not contain metal atoms. For example, a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and sulfur atoms can be selected as a delayed fluorescent material having a ΔPBHT of 0.01 or more. For example, a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms can be selected as a delayed fluorescent material having a ΔPBHT of 0.01 or more. For example, a compound consisting of carbon atoms, hydrogen atoms, and nitrogen atoms can be selected as a delayed fluorescent material having a ΔPBHT of 0.01 or more.

[0024] A delayed fluorescent material having a ΔPBHT of 0.01 or more can be selected from a group of compounds having a structure in which an aromatic hydrocarbon is substituted with one or more electron-withdrawing groups and one or more electron-donating groups. The aromatic ring constituting the aromatic hydrocarbon may be a monocyclic ring or a fused ring in which two or more rings are fused. A preferred example of an aromatic ring is a benzene ring. The electron-withdrawing group is a group that has the property of withdrawing electrons from the ring to which the electron-withdrawing group is bonded, and can be selected, for example, from groups with a positive Hammett σp value. The electron-donating group is a group that has the property of donating electrons to the ring to which the electron-donating group is bonded, and can be selected, for example, from groups with a negative Hammett σp value. Here, the "Hammett σp value" was proposed by L.P. Hammett and quantifies the effect of a substituent on the reaction rate or equilibrium of a para-substituted benzene derivative. For an explanation of the "Hammett σp value" in the present invention and the numerical values ​​of each substituent, please refer to the description of the σp value in Hansch, C. et al., Chem. Rev., 91, 165-195 (1991). Examples of the acceptor group include a cyano group and a six-membered aromatic heterocyclic group containing a nitrogen atom as a ring-constituting atom. Examples of the six-membered aromatic heterocyclic group containing a nitrogen atom as a ring-constituting atom include a substituted or unsubstituted pyridyl group, a substituted or unsubstituted pyrimidyl group, a substituted or unsubstituted pyridazyl group, a substituted or unsubstituted pyrazyl group, and a substituted or unsubstituted triazyl group. Examples of the donor group include a substituted or unsubstituted diphenylamino group and a group represented by the general formula (7) described below. Particularly preferred examples of delayed fluorescent materials that can be used in the present invention include delayed fluorescent materials that are compounds represented by any of the following general formulas (1) to (6) and have a ΔPBHT of 0.01 or more.

[0025] [ka] JPEG0007780189000008.jpg152159

[0026] In the general formulas (1) to (6), D 1 ~D 10 Each independently represents a group represented by the following general formula (7): 1 and D 2 , D 3 and D 4 , D 6 and D 7 , D 9 and D 10 Each combination of D has a different chemical structure. 1 , the three Ds 2 , two D 3 , two D 4 , the three Ds 5 , two D 6 , two D 8 , two D 9 The combinations have the same chemical structure. At least one hydrogen atom in the general formulae (1) to (6) and the following general formulae (7) to (13) may be substituted with a deuterium atom.

[0027] [ka]

[0028] The group represented by general formula (7) is preferably a group represented by any one of the following general formulae (8) to (13). [ka]

[0029] In the general formulas (7) to (13), L 11 and L 21 ~L 26 represents a single bond or a divalent linking group. Examples of the divalent linking group include a substituted or unsubstituted arylene group and a substituted or unsubstituted heteroarylene group. In the general formulas (7) to (13), R 41 ~R 110 R each independently represents a hydrogen atom or a substituent. 41 and R 42 , R42 and R 43 , R 43 and R 44 , R 44 and R 45 , R 45 and R 46 , R 46 and R 47 , R 47 and R 48 , R 51 and R 52 , R 52 and R 53 , R 53 and R 54 , R 54 and R 55 , R 55 and R 56 , R 56 and R 57 , R 57 and R 58 , R 58 and R 59 , R 59 and R 60 , R 61 and R 62 , R 62 and R 63 , R 63 and R 64 , R 65 and R 66 , R 66 and R 67 , R 67 and R 68 , R 68 and R 69 , R 69 and R 70 , R 72 and R 73 , R 73 and R 74 , R 74 and R 75 , R 75 and R 76 , R 76 and R 77 , R 77 and R 78 , R 78 and R 79 , R 79 and R 80 , R 81 and R 82 , R 82 and R 83 , R 83and R 84 , R 84 and R 85 , R 86 and R 87 , R 87 and R 88 , R 88 and R 89 , R 89 and R 90 , R 91 and R 92 , R 93 and R 94 , R 94 and R 95 , R 95 and R 96 , R 96 and R 97 , R 97 and R 98 , R 99 and R 100 , R 101 and R 102 , R 102 and R 103 , R 103 and R 104 , R 104 and R 105 , R 105 and R 106 , R 107 and R 108 , R 108 and R 109 , R 109 and R 110may be bonded to each other to form a cyclic structure. The cyclic structure formed by bonding to each other may be an aromatic ring or an aliphatic ring, may contain a heteroatom, and may further be a fused ring of two or more rings. The heteroatom referred to here is preferably selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom. Examples of the cyclic structure formed include a benzene ring, a naphthalene ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a pyrrole ring, an imidazole ring, a pyrazole ring, an imidazoline ring, an oxazole ring, an isoxazole ring, a thiazole ring, an isothiazole ring, a cyclohexadiene ring, a cyclohexene ring, a cyclopentaene ring, a cycloheptatriene ring, a cycloheptadiene ring, a cycloheptaene ring, a furan ring, a thiophene ring, a naphthyridine ring, a quinoxaline ring, and a quinoline ring. For example, a ring formed by condensing multiple rings, such as a phenanthrene ring or a triphenylene ring, may also be formed. The number of rings contained in the group represented by general formula (7) may be selected from the range of 3 to 5, or may be selected from the range of 5 to 7. The number of rings contained in the groups represented by general formulas (8) to (13) may be selected from the range of 5 to 7, or may be 5. R 41 ~R 110 Examples of the substituent that R may have include the groups in the following substituent group B, and preferably an unsubstituted alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms which may be substituted with an unsubstituted alkyl group having 1 to 10 carbon atoms. In a preferred embodiment of the present invention, R 41 ~R 110 is a hydrogen atom or an unsubstituted alkyl group having 1 to 10 carbon atoms. In a preferred embodiment of the present invention, R 41 ~R 110 is a hydrogen atom or an unsubstituted aryl group having 6 to 10 carbon atoms. In a preferred embodiment of the present invention, R 41 ~R 110 are all hydrogen atoms. R in general formulas (7) to (13) 41 ~R 110The carbon atoms to which CR is bonded (carbon atoms constituting the ring skeleton) may each independently be substituted with a nitrogen atom. 41 ~CR 110 may each independently be substituted with N. The number of nitrogen atoms substituted is preferably 0 to 4, and more preferably 1 to 2, among the groups represented by general formulas (7) to (13). In one embodiment of the present invention, the number of nitrogen atoms substituted is 0. Furthermore, when two or more groups are substituted with nitrogen atoms, the number of nitrogen atoms substituted in one ring is preferably 1. In the general formulas (7) to (13), X 1 ~X 6 represents an oxygen atom, a sulfur atom or NR. In one embodiment of the present invention, X 1 ~X 6 is an oxygen atom. In one aspect of the present invention, X 1 ~X 6 is a sulfur atom. In one embodiment of the present invention, X 1 ~X 6 is NR. R represents a hydrogen atom or a substituent, and is preferably a substituent. Examples of the substituent include a substituent selected from the above-mentioned Substituent Group A. For example, an unsubstituted phenyl group or a phenyl group substituted with one group or a combination of two or more groups selected from the group consisting of alkyl groups and aryl groups can be preferably used. In the general formulae (7) to (13), * represents a bonding position.

[0030] The group represented by general formula (7) may be a substituted or unsubstituted 9-carbazolyl group, an aryl group substituted with a substituted or unsubstituted 9-carbazolyl group, or a heteroaryl group substituted with a substituted or unsubstituted 9-carbazolyl group. Here, the preferred position of the substituent in the 9-carbazolyl group is at least one of the 3-position and the 6-position. However, it is preferable that at least one of the groups represented by the general formula (7) is a group represented by any one of the general formulas (8) to (13). 1 and D2 At least one of the following, D in general formula (2) 3 and D 4 At least one of the following, D in general formula (3) 5 , D in general formula (4) 6 and D 7 At least one of the following, D in general formula (5) 8 , D in general formula (6) 9 and D 10 At least one of the groups represented by general formulas (8) to (13) is preferably a group represented by any one of general formulas (1), (2), (4), and (6). 2 , D 4 , D 6 , D 9 is a group represented by any one of general formulas (8) to (13), and D 1 , D 3 , D 7 , D 10 It is also preferred that is a substituted or unsubstituted 9-carbazolyl group, an aryl group substituted with a substituted or unsubstituted 9-carbazolyl group, or a heteroaryl group substituted with a substituted or unsubstituted 9-carbazolyl group.

[0031] In the general formulas (2) and (5), Ar 1 and Ar 2 Each of Ar independently represents a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group (excluding the group represented by general formula (7)). 1 and Ar 2 is preferably a substituted or unsubstituted aryl group, more preferably a substituted or unsubstituted phenyl group, and even more preferably an unsubstituted phenyl group or a phenyl group in which at least one hydrogen atom has been substituted with a deuterium atom.

[0032] In a preferred embodiment of the present invention, the delayed fluorescent material is a compound represented by general formula (2), in which PBHT(Tn) is in the third excited triplet state, PBHT(T3). In a more preferred embodiment of the present invention, the delayed fluorescent material is a compound represented by general formula (2), 4is a group represented by general formula (13), and PBHT(Tn) is PBHT(T3) in the third excited triplet state. In another preferred embodiment of the present invention, the delayed fluorescent material is a compound represented by general formula (4) or (5), in which PBHT(Tn) is in the second excited triplet state, PBHT(T2). In another more preferred embodiment of the present invention, the delayed fluorescent material is represented by general formula (4), 6 is a group represented by general formula (13), and PBHT(Tn) is a compound in which PBHT(T2) is in the second excited triplet state. In yet another more preferred embodiment of the present invention, the delayed fluorescent material is a compound represented by general formula (5), 8 is a group represented by general formula (13), and PBHT(Tn) is PBHT(T2) in the second excited triplet state.

[0033] Specific examples of delayed fluorescent materials that can be used in the present invention and have a ΔPBHT of 0.01 or more are shown below. However, the delayed fluorescent materials that can be used in the present invention should not be construed as being limited by these specific examples.

[0034] [ka] JPEG0007780189000012.jpg239126

[0035] Among the above compounds T1 to T12, in compounds T1 to T5, PBHT (T3) in the third excited triplet state T3 corresponds to PBHT (Tn), and in compounds T6 to T12, PBHT (T2) in the second excited triplet state T2 corresponds to PBHT (Tn).

[0036] In this specification, the term "alkyl group" may be linear, branched, or cyclic. It may also contain two or more of the linear, cyclic, and branched moieties. The number of carbon atoms in the alkyl group may be, for example, 1 or more, 2 or more, or 4 or more. The number of carbon atoms may be 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, an n-hexyl group, an isohexyl group, a 2-ethylhexyl group, an n-heptyl group, an isoheptyl group, an n-octyl group, an isooctyl group, an n-nonyl group, an isononyl group, an n-decanyl group, an isodecanyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. The alkyl group may be further substituted with an aryl group. The "alkenyl group" may be linear, branched, or cyclic. It may also contain two or more of the linear, cyclic, and branched moieties. The alkenyl group may have, for example, two or more carbon atoms, or four or more carbon atoms. It may also have 30 or less, 20 or less, 10 or less, 6 or less, or 4 or less carbon atoms. Specific examples of the alkenyl group include ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl, n-pentenyl, isopentenyl, n-hexenyl, isohexenyl, and 2-ethylhexenyl. The substituted alkenyl group may be further substituted with a substituent. The "aryl group" and "heteroaryl group" may be a single ring or a fused ring in which two or more rings are fused. In the case of a fused ring, the number of fused rings is preferably 2 to 6, and can be selected from, for example, 2 to 4. Specific examples of the ring include a benzene ring, a pyridine ring, a pyrimidine ring, a triazine ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, a quinoline ring, a pyrazine ring, a quinoxaline ring, and a naphthyridine ring, and these may be fused rings. Specific examples of the aryl group or heteroaryl group include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthracenyl group, a 2-anthracenyl group, a 9-anthracenyl group, a 2-pyridyl group, a 3-pyridyl group, and a 4-pyridyl group. The number of atoms constituting the ring skeleton of the aryl group is preferably 6 to 40, more preferably 6 to 20, and may be selected within a range of 6 to 14, or may be selected within a range of 6 to 10. The number of atoms constituting the ring skeleton of the heteroaryl group is preferably 4 to 40, more preferably 5 to 20, and may be selected from the range of 5 to 14, or may be selected from the range of 5 to 10. The terms "arylene group" and "heteroaryl group" can be understood by changing the valence of the aryl group and heteroaryl group from 1 to 2.

[0037] In the present specification, "substituent group A" refers to a hydroxyl group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group (for example, having 1 to 40 carbon atoms), an alkoxy group (for example, having 1 to 40 carbon atoms), an alkylthio group (for example, having 1 to 40 carbon atoms), an aryl group (for example, having 6 to 30 carbon atoms), an aryloxy group (for example, having 6 to 30 carbon atoms), an arylthio group (for example, having 6 to 30 carbon atoms), a heteroaryl group (for example, having 5 to 30 ring skeleton atoms), a heteroaryloxy group (for example, having 5 to 30 ring skeleton atoms), a heteroaryl group, ... It means one group or a combination of two or more groups selected from the group consisting of heteroarylthio groups (for example, having 5 to 30 atoms constituting the ring skeleton), acyl groups (for example, having 1 to 40 carbon atoms), alkenyl groups (for example, having 1 to 40 carbon atoms), alkynyl groups (for example, having 1 to 40 carbon atoms), alkoxycarbonyl groups (for example, having 1 to 40 carbon atoms), aryloxycarbonyl groups (for example, having 1 to 40 carbon atoms), heteroaryloxycarbonyl groups (for example, having 1 to 40 carbon atoms), silyl groups (for example, trialkylsilyl groups having 1 to 40 carbon atoms), and nitro groups. In this specification, the term "substituent group B" refers to one group or a combination of two or more groups selected from the group consisting of alkyl groups (e.g., having 1 to 40 carbon atoms), alkoxy groups (e.g., having 1 to 40 carbon atoms), aryl groups (e.g., having 6 to 30 carbon atoms), aryloxy groups (e.g., having 6 to 30 carbon atoms), heteroaryl groups (e.g., having 5 to 30 ring skeleton atoms), heteroaryloxy groups (e.g., having 5 to 30 ring skeleton atoms), and diarylaminoamino groups (e.g., having 0 to 20 carbon atoms). In this specification, the term "substituent group C" refers to one group or a combination of two or more groups selected from the group consisting of alkyl groups (e.g., having 1 to 20 carbon atoms), aryl groups (e.g., having 6 to 22 carbon atoms), heteroaryl groups (e.g., having 5 to 20 ring skeleton atoms), and diarylamino groups (e.g., having 12 to 20 carbon atoms). In this specification, the term "substituent group D" refers to one group or a combination of two or more groups selected from the group consisting of alkyl groups (e.g., having 1 to 20 carbon atoms), aryl groups (e.g., having 6 to 22 carbon atoms), and heteroaryl groups (e.g., having 5 to 20 ring skeleton atoms). In this specification, the term "substituent group E" refers to one group or a combination of two or more groups selected from the group consisting of alkyl groups (for example, having 1 to 20 carbon atoms) and aryl groups (for example, having 6 to 22 carbon atoms). In the present specification, when a "substituent" or "substituted or unsubstituted" is used, the substituent may be selected from, for example, Substituent Group A, Substituent Group B, Substituent Group C, Substituent Group D, or Substituent Group E.

[0038] As used herein, the lowest excited singlet energy (E S1 ) and the lowest excited triplet energy (E T1 ) is a value calculated by the following procedure. ST is E S1 -E T1 This is the value obtained by calculating (1) The lowest excited singlet energy (E S1 ) Thin film or toluene solution (concentration 10 -5 A sample is prepared at a concentration of 1000 mol / L. The fluorescence spectrum of this sample is measured at room temperature (300K). The fluorescence spectrum has the emission on the vertical axis and the wavelength on the horizontal axis. A tangent line is drawn to the rising edge of the short wavelength side of this emission spectrum, and the wavelength value λedge [nm] at the intersection of this tangent line and the horizontal axis is found. This wavelength value is converted to an energy value using the following conversion formula and is called E. S1 Let's say. Conversion formula: E S1 [eV]=1239.85 / λedge In the examples described below, emission spectra were measured using an LED light source (M300L4, manufactured by Thorlabs) as the excitation light source and a detector (PMA-12 multichannel spectrometer C10027-01, manufactured by Hamamatsu Photonics KK). (2) The lowest excited triplet energy (E T1 ) The lowest excited singlet energy (E S1The same sample used in the measurement of ) is cooled to 77[K] with liquid nitrogen, and the sample for phosphorescence measurement is irradiated with excitation light (300 nm), and the phosphorescence is measured using a detector. The emission from 100 milliseconds after irradiation with excitation light is taken as the phosphorescence spectrum. A tangent line is drawn to the rising edge of the short wavelength side of this phosphorescence spectrum, and the wavelength value λedge[nm] at the intersection of this tangent line and the horizontal axis is found. This wavelength value is converted to an energy value using the following conversion formula, and the value is called E T1 Let's say. Conversion formula: E T1 [eV]=1239.85 / λedge The tangent to the rising edge of the phosphorescence spectrum on the short wavelength side is drawn as follows: When moving along the spectral curve from the short wavelength side of the phosphorescence spectrum to the shortest maximum of the spectral maxima, consider the tangent at each point on the curve toward the long wavelength side. The slope of this tangent increases as the curve rises (i.e., as the vertical axis increases). The tangent drawn at the point where this slope is at its maximum is considered to be the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side. Note that a maximum point having a peak intensity that is 10% or less of the maximum peak intensity of the spectrum is not included in the above-mentioned maximum value on the shortest wavelength side, and the tangent drawn at the point where the slope value is the maximum value that is closest to the maximum value on the shortest wavelength side is defined as the tangent to the rising edge on the short wavelength side of the phosphorescence spectrum.

[0039] [Other components of the light-emitting layer] The light-emitting layer may be composed solely of a delayed fluorescent material having a ΔPBHT of 0.01 or more, or may contain other components, such as a host material.

[0040] (host material) The host material preferably has a function of transporting carriers. Furthermore, the host material preferably has a function of trapping the energy of a delayed fluorescent material having a ΔPBHT of 0.01 or more within the compound. This allows a delayed fluorescent material having a ΔPBHT of 0.01 or more to efficiently convert the energy generated by the recombination of holes and electrons within the molecule and the energy received from the host material into light emission. To achieve this energy trapping function, the host material preferably has a higher minimum excited singlet energy than a delayed fluorescent material having a ΔPBHT of 0.01 or more, and more preferably has a higher minimum excited singlet energy and a higher minimum excited triplet energy than a delayed fluorescent material having a ΔPBHT of 0.01 or more. The host material is preferably an organic compound that has hole transporting ability and electron transporting ability, prevents the emission wavelength from shifting to a longer wavelength, and has a high glass transition temperature. In a preferred embodiment of the present invention, the host material is selected from compounds that do not emit delayed fluorescence. The emission from the host material is preferably less than 1% of the emission from the organic electroluminescence device of the present invention, more preferably less than 0.1%, and may be, for example, less than 0.01%, or even below the detection limit. It is preferable that the host material does not contain metal atoms. For example, a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and sulfur atoms can be selected as the host material. For example, a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms can be selected as the host material. For example, a compound consisting of carbon atoms, hydrogen atoms, and nitrogen atoms can be selected as the host material. Preferred compounds that can be used as the host material are listed below.

[0041] [ka] JPEG0007780189000014.jpg236170JPEG0007780189000015.jpg239162JPEG0007780189000016.jpg44170

[0042] When a host material is used, the content of the delayed fluorescent material having a ΔPBHT of 0.01 or more in the light-emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and is preferably 50% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.

[0043] [Overall configuration of organic light-emitting element] The organic light-emitting element of the present invention may be an organic photoluminescence element or an organic electroluminescence element. An organic photoluminescence element (organic PL element) has a structure in which at least an emitting layer is formed on a substrate. An organic electroluminescence element has an anode, a cathode, and at least one organic layer including an emitting layer between the anode and the cathode. The organic layer constituting the organic electroluminescence element may be composed of only the emitting layer, or may include an organic layer other than the emitting layer. For example, an organic layer may or may not be interposed between the anode and the emitting layer, and between the emitting layer and the cathode. In other words, the anode and the emitting layer may be laminated so as to be in direct contact with each other, or may not be in direct contact with each other. Furthermore, the emitting layer and the cathode may be laminated so as to be in direct contact with each other, or may not be in direct contact with each other. The emitting layer is preferably located between the anode and the cathode, and the entire emitting layer is preferably disposed without extending into the region between the anode and the cathode. The organic electroluminescent device of the present invention may have a substrate supporting an anode, a cathode, and at least one organic layer including an emitting layer. In this case, the substrate may be disposed on the opposite side of the anode from the emitting layer, or on the opposite side of the cathode from the emitting layer. The organic electroluminescent device of the present invention may be a top-emission device in which most of the light is emitted from the side opposite the substrate, or a bottom-emission device in which most of the light is emitted from the substrate side. Here, "most of the light" means light that accounts for 60% or more of the amount of light emitted from the device. Each component and each layer of the organic electroluminescent element will be described below. The description of the substrate and the light-emitting layer also applies to the substrate and the light-emitting layer of the organic photoluminescent element.

[0044] (light-emitting layer) The light-emitting layer of the organic light-emitting device of the present invention contains a delayed fluorescent material having a ΔPBHT of 0.01 or more. The light-emitting layer may further contain a host material. For a description of the delayed fluorescent material having a ΔPBHT of 0.01 or more, please refer to the description in the above [Delayed Fluorescent Material] section, and for a description of the host material, please refer to the description in the above (Host Material) section. The light-emitting layer may be configured so that, in addition to the delayed fluorescent material having a ΔPBHT of 0.01 or more and the host material, it does not contain any compounds that transfer charge or energy or any metal elements other than boron. The light-emitting layer may also be configured solely from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, deuterium atoms, nitrogen atoms, boron atoms, oxygen atoms, and sulfur atoms. For example, the light-emitting layer may be configured solely from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, deuterium atoms, nitrogen atoms, boron atoms, and oxygen atoms. For example, the light-emitting layer may be configured solely from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, deuterium atoms, nitrogen atoms, boron atoms, and oxygen atoms. For example, the light-emitting layer can be composed solely of compounds consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, nitrogen, and boron atoms. For example, the light-emitting layer can be composed solely of compounds consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, nitrogen, oxygen, and sulfur atoms. For example, the light-emitting layer can be composed solely of compounds consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, and nitrogen atoms. The light-emitting layer may contain a delayed fluorescent material consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, nitrogen, oxygen, and sulfur atoms. The light-emitting layer may also contain a delayed fluorescent material consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, and nitrogen atoms. The light-emitting layer may also contain a host material consisting of atoms selected from the group consisting of carbon, hydrogen, nitrogen, and oxygen atoms, and a delayed fluorescent material consisting of atoms selected from the group consisting of carbon, hydrogen, deuterium, nitrogen, oxygen, and sulfur atoms.The light-emitting layer may also contain a host material composed of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms, and a delayed fluorescent material composed of atoms selected from the group consisting of carbon atoms, hydrogen atoms, deuterium atoms, and nitrogen atoms. The light-emitting layer may be formed by vapor-depositing a delayed fluorescent material having a ΔPBHT of 0.01 or more, or by co-depositing a delayed fluorescent material having a ΔPBHT of 0.01 or more and a host material, or by vapor-depositing a mixture prepared in advance by mixing a delayed fluorescent material having a ΔPBHT of 0.01 or more and a host material as a vapor deposition source, or by coating a solution in which a delayed fluorescent material having a ΔPBHT of 0.01 or more is dissolved, or a solution in which a delayed fluorescent material having a ΔPBHT of 0.01 or more and a host material are dissolved.

[0045] Each component of the organic electroluminescence element and each layer other than the light-emitting layer will be described below.

[0046] Base material: In some embodiments, the organic electroluminescent device of the present invention is supported by a substrate, and the substrate is not particularly limited and may be any material commonly used in organic electroluminescent devices, such as glass, transparent plastic, quartz, and silicon.

[0047] anode: In some embodiments, the anode of the organic electroluminescent device is made of a metal, an alloy, a conductive compound, or a combination thereof. In some embodiments, the metal, alloy, or conductive compound has a high work function (4 eV or greater). In some embodiments, the metal is Au. In some embodiments, the conductive transparent material is selected from CuI, indium tin oxide (ITO), SnO, and ZnO. In some embodiments, an amorphous material capable of forming a transparent conductive film, such as In2O3-ZnO, is used. In some embodiments, the anode is a thin film. In some embodiments, the thin film is formed by evaporation or sputtering. In some embodiments, the film is patterned by a photolithography method. In some embodiments, if the pattern does not need to be highly precise (e.g., greater than about 100 μm), the pattern may be formed using a mask with a shape suitable for evaporation or sputtering of the electrode material. In some embodiments, when a coating material, such as an organic conductive compound, can be applied, a wet film formation method, such as a printing method or a coating method, is used. In some embodiments, the anode has a transmittance of greater than 10% when emitted light passes through it, and the anode has a sheet resistance of several hundred ohms per unit area or less. In some embodiments, the anode has a thickness of 10 to 1,000 nm. In some embodiments, the anode has a thickness of 10 to 200 nm. In some embodiments, the thickness of the anode varies depending on the material used.

[0048] cathode: In some embodiments, the cathode is made of an electrode material such as a metal with a low work function (4 eV or less) (referred to as an electron-injecting metal), alloy, conductive compound, or a combination thereof. In some embodiments, the electrode material is selected from sodium, sodium-potassium alloy, magnesium, lithium, magnesium-copper mixture, magnesium-silver mixture, magnesium-aluminum mixture, magnesium-indium mixture, aluminum-aluminum oxide (Al2O3) mixture, indium, lithium-aluminum mixture, and rare earth elements. In some embodiments, a mixture of an electron-injecting metal and a second metal, which is a stable metal having a higher work function than the electron-injecting metal, is used. In some embodiments, the mixture is selected from magnesium-silver mixture, magnesium-aluminum mixture, magnesium-indium mixture, aluminum-aluminum oxide (Al2O3) mixture, lithium-aluminum mixture, and aluminum. In some embodiments, the mixture improves electron-injecting properties and oxidation resistance. In some embodiments, the cathode is fabricated by forming the electrode material as a thin film by evaporation or sputtering. In some embodiments, the cathode has a sheet resistance of several hundred ohms per unit area or less. In some embodiments, the cathode has a thickness of 10 nm to 5 μm. In some embodiments, the cathode has a thickness of 50 to 200 nm. In some embodiments, one of the anode and cathode of the organic electroluminescent device is transparent or semitransparent to transmit emitted light. In some embodiments, a transparent or semitransparent electroluminescent device improves light radiance. In some embodiments, the cathode is formed from a conductive, transparent material as described above for the anode, thereby forming a transparent or semi-transparent cathode. In some embodiments, a device includes an anode and a cathode, both of which are transparent or semi-transparent.

[0049] Injection layer: An injection layer is a layer between an electrode and an organic layer. In some embodiments, the injection layer reduces driving voltage and enhances light radiance. In some embodiments, the injection layer comprises a hole injection layer and an electron injection layer. The injection layer can be disposed between the anode and the emissive layer or the hole transport layer, and between the cathode and the emissive layer or the electron transport layer. In some embodiments, an injection layer is present. In some embodiments, an injection layer is not present. Preferred examples of compounds that can be used as hole injection materials are listed below.

[0050] [ka]

[0051] Next, preferred examples of compounds that can be used as the electron injection material will be listed. [ka]

[0052] Barrier layer: A blocking layer is a layer that can prevent charges (electrons or holes) and / or excitons present in the light-emitting layer from diffusing outside the light-emitting layer. In some embodiments, an electron blocking layer is present between the light-emitting layer and the hole transport layer and prevents electrons from passing through the light-emitting layer to the hole transport layer. In some embodiments, a hole blocking layer is present between the light-emitting layer and the electron transport layer and prevents holes from passing through the light-emitting layer to the electron transport layer. In some embodiments, a blocking layer prevents excitons from diffusing outside the light-emitting layer. In some embodiments, the electron blocking layer and the hole blocking layer constitute an exciton blocking layer. As used herein, the terms "electron blocking layer" or "exciton blocking layer" include layers that have both the functionality of an electron blocking layer and an exciton blocking layer.

[0053] Hole blocking layer: The hole blocking layer functions as an electron transport layer. In some embodiments, the hole blocking layer prevents holes from reaching the electron transport layer during electron transport. In some embodiments, the hole blocking layer increases the probability of recombination of electrons and holes in the light-emitting layer. The materials used for the hole blocking layer can be the same materials as those described above for the electron transport layer. Preferred examples of compounds that can be used in the hole blocking layer are listed below.

[0054] [ka]

[0055] Electron barrier layer: The electron blocking layer transports holes. In some embodiments, during hole transport, the electron blocking layer prevents electrons from reaching the hole transport layer. In some embodiments, the electron blocking layer increases the probability of recombination of electrons and holes in the light-emitting layer. The materials used for the electron blocking layer can be the same materials as those described above for the hole transport layer. Specific examples of preferred compounds that can be used as electron blocking materials are listed below.

[0056] [ka]

[0057] Exciton blocking layer: The exciton blocking layer prevents excitons generated through the recombination of holes and electrons in the emissive layer from diffusing to the charge transport layer. In some embodiments, the exciton blocking layer enables effective confinement of excitons in the emissive layer. In some embodiments, the light emission efficiency of the device is improved. In some embodiments, the exciton blocking layer is adjacent to the emissive layer on either the anode side or the cathode side, and on both sides. In some embodiments, when the exciton blocking layer is present on the anode side, it may be present between the hole transport layer and the emissive layer and adjacent to the emissive layer. In some embodiments, when the exciton blocking layer is present on the cathode side, it may be present between the emissive layer and the cathode and adjacent to the emissive layer. In some embodiments, a hole injection layer, an electron blocking layer, or a similar layer is present between the anode and the exciton blocking layer adjacent to the emissive layer on the anode side. In some embodiments, a hole injection layer, an electron blocking layer, a hole blocking layer, or a similar layer is present between the cathode and the exciton blocking layer adjacent to the emissive layer on the cathode side. In some embodiments, the exciton blocking layer comprises an excited singlet energy and an excited triplet energy, at least one of which is higher than the excited singlet energy and excited triplet energy, respectively, of the light-emitting material.

[0058] Hole transport layer: The hole transport layer comprises a hole transport material. In some embodiments, the hole transport layer is a single layer. In some embodiments, the hole transport layer has multiple layers. In some embodiments, the hole transport material has one of hole injection or transport properties and electron blocking properties. In some embodiments, the hole transport material is an organic material. In some embodiments, the hole transport material is an inorganic material. Examples of known hole transport materials that can be used in the present invention include, but are not limited to, triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, allylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers (especially thiophene oligomers), or combinations thereof. In some embodiments, the hole transport material is selected from porphyrin compounds, aromatic tertiary amine compounds, and styrylamine compounds. In some embodiments, the hole transport material is an aromatic tertiary amine compound. Specific examples of preferred compounds that can be used as hole transport materials are listed below.

[0059] [ka]

[0060] Electron transport layer: The electron transport layer comprises an electron transport material. In some embodiments, the electron transport layer is a single layer. In some embodiments, the electron transport layer has multiple layers. In some embodiments, the electron transport material only needs to transport electrons injected from the cathode to the light-emitting layer. In some embodiments, the electron transport material also functions as a hole-blocking material. Examples of electron transport layers that can be used in the present invention include, but are not limited to, nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethanes, anthrone derivatives, oxadiazole derivatives, azole derivatives, azine derivatives, or combinations thereof, or polymers thereof. In some embodiments, the electron transport material is a thiadiazole derivative or a quinoxaline derivative. In some embodiments, the electron transport material is a polymer material. Specific examples of preferred compounds that can be used as electron transport materials are listed below.

[0061] [ka]

[0062] Furthermore, examples of compounds that can be added to each organic layer are given below, which may be added as a stabilizing material, for example.

[0063] [ka]

[0064] Although specific examples of preferred materials that can be used in organic electroluminescence devices have been given, the materials that can be used in the present invention should not be construed as being limited to the following exemplary compounds. Furthermore, even compounds exemplified as materials having specific functions can be diverted to be used as materials having other functions.

[0065] device: In some embodiments, the light-emitting layer is incorporated into a device, including, but not limited to, an OLED bulb, an OLED lamp, a television display, a computer monitor, a mobile phone, and a tablet. In some embodiments, the electronic device comprises an OLED having an anode, a cathode, and at least one organic layer comprising an emissive layer between the anode and the cathode. In some embodiments, the compositions described herein can be incorporated into various photosensitive or photoactivated devices, such as OLEDs or optoelectronic devices. In some embodiments, the compositions can be useful for facilitating charge or energy transfer within devices and / or as hole transport materials, such as organic light-emitting diodes (OLEDs), organic integrated circuits (OICs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic solar cells (O-SCs), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), light-emitting fuel cells (LECs), or organic laser diodes (O-lasers).

[0066] Bulb or Lamp: In some embodiments, the electronic device comprises an OLED comprising an anode, a cathode, and at least one organic layer comprising an emissive layer between the anode and the cathode. In some embodiments, the device includes OLEDs of different colors. In some embodiments, the device includes an array including a combination of OLEDs. In some embodiments, the combination of OLEDs is a three-color combination (e.g., RGB). In some embodiments, the combination of OLEDs is a combination of colors that are not red, green, or blue (e.g., orange and yellow-green). In some embodiments, the combination of OLEDs is a two-color, four-color, or more-color combination. In some embodiments, the device comprises: a circuit board having a first side with a mounting surface and an opposite second side, the circuit board defining at least one opening; at least one OLED on the mounting surface, the at least one OLED having a light-emitting configuration including an anode, a cathode, and at least one organic layer including a light-emitting layer between the anode and the cathode; a housing for the circuit board; and at least one connector disposed on an end of the housing, the housing and the connector defining a package suitable for attachment to a lighting fixture. In some embodiments, the OLED light comprises multiple OLEDs mounted on a circuit board such that light is emitted in multiple directions. In some embodiments, some of the light emitted in a first direction is polarized and emitted in a second direction. In some embodiments, a reflector is used to polarize the light emitted in the first direction.

[0067] Display or Screen: In some embodiments, the light-emitting layer of the present invention can be used in a screen or display. In some embodiments, the compounds of the present invention are deposited onto a substrate using processes such as, but not limited to, vacuum evaporation, deposition, vapor deposition, or chemical vapor deposition (CVD). In some embodiments, the substrate is a photoplate structure useful for two-sided etching to provide pixels with unique aspect ratios. The screen (also called a mask) is used in the manufacturing process of OLED displays. The corresponding artwork pattern design allows for the placement of very steep, narrow tie bars between pixels in the vertical direction and large, wide, beveled openings in the horizontal direction. This allows for the fine patterning of pixels required for high-resolution displays while optimizing chemical vapor deposition onto the TFT backplane. Internal pixel patterning allows for the construction of three-dimensional pixel openings with various aspect ratios in the horizontal and vertical directions. Furthermore, the use of imaged "stripes" or halftone circles within the pixel area protects etching in specific regions until these specific patterns are undercut and removed from the substrate. At that point, all pixel areas are subjected to similar etch rates, but the depth varies depending on the halftone pattern. Varying the size and spacing of the halftone patterns allows for etching with varying degrees of protection within the pixel, enabling the deep, localized etching required to create steep vertical bevels. The preferred material for the deposition mask is Invar, a metal alloy that is cold-rolled into long, thin sheets at steel mills. Invar cannot be electrodeposited onto the spin mandrel as a nickel mask. A suitable, low-cost method for forming open areas in the deposition mask is by wet chemical etching. In some embodiments, the screen or display pattern is a pixel matrix on a substrate. In some embodiments, the screen or display pattern is fabricated using lithography (e.g., photolithography and e-beam lithography). In some embodiments, the screen or display pattern is fabricated using wet chemical etching. In further embodiments, the screen or display pattern is fabricated using plasma etching.

[0068] Device manufacturing method: OLED displays are generally manufactured by forming a large mother panel and then cutting the mother panel into cell panels. Typically, each cell panel on the mother panel is formed by forming a thin film transistor (TFT) having an active layer and source / drain electrodes on a base substrate, applying a planarizing film to the TFT, sequentially forming a pixel electrode, an emissive layer, a counter electrode, and an encapsulation layer, and then cutting the mother panel. OLED displays are generally manufactured by forming a large mother panel and then cutting the mother panel into cell panels. Typically, each cell panel on the mother panel is formed by forming a thin film transistor (TFT) having an active layer and source / drain electrodes on a base substrate, applying a planarizing film to the TFT, sequentially forming a pixel electrode, an emissive layer, a counter electrode, and an encapsulation layer, and then cutting the mother panel.

[0069] In another aspect of the present invention, there is provided a method for manufacturing an organic light emitting diode (OLED) display, the method comprising: forming a barrier layer on a base substrate of the mother panel; forming a plurality of display units on the barrier layer in cell panel units; forming an encapsulation layer over each of the display units of the cell panel; and applying an organic film to the interface between the cell panels. In some embodiments, the barrier layer is an inorganic film, for example, made of SiNx, and the edges of the barrier layer are covered with an organic film made of polyimide or acrylic. In some embodiments, the organic film helps the mother panel to be softly cut into individual cell panels. In some embodiments, the thin film transistor (TFT) layer includes a light-emitting layer, a gate electrode, and source / drain electrodes. Each of the plurality of display units may include a thin film transistor (TFT) layer, a planarization film formed on the TFT layer, and a light-emitting unit formed on the planarization film, and the organic film applied to the interface is formed of the same material as the planarization film and is formed simultaneously with the planarization film. In some embodiments, the light-emitting unit is connected to the TFT layer by a passivation layer, the planarization film therebetween, and an encapsulation layer that covers and protects the light-emitting unit. In some embodiments of the manufacturing method, the organic film is not connected to either the display unit or the encapsulation layer.

[0070] Each of the organic film and the planarization film may comprise one of polyimide and acrylic. In some embodiments, the barrier layer may be an inorganic film. In some embodiments, the base substrate may be formed of polyimide. The method may further include attaching a carrier substrate formed of a glass material to one surface of the base substrate formed of polyimide before forming the barrier layer on the other surface of the base substrate, and separating the carrier substrate from the base substrate before cutting along the interface. In some embodiments, the OLED display is a flexible display. In some embodiments, the passivation layer is an organic film disposed on the TFT layer to cover the TFT layer. In some embodiments, the planarization film is an organic film formed on the passivation layer. In some embodiments, the planarization film is formed of polyimide or acrylic, as is the organic film formed on the edge of the barrier layer. In some embodiments, the planarization film and the organic film are formed simultaneously during the manufacture of an OLED display. In some embodiments, the organic film may be formed on the edge of the barrier layer, such that a portion of the organic film directly contacts the base substrate and a remaining portion of the organic film contacts the barrier layer while surrounding the edge of the barrier layer.

[0071] In some embodiments, the light-emitting layer comprises a pixel electrode, a counter electrode, and an organic light-emitting layer disposed between the pixel electrode and the counter electrode, hi some embodiments, the pixel electrode is coupled to a source / drain electrode of the TFT layer. In some embodiments, when a voltage is applied to the pixel electrode through the TFT layer, a suitable voltage is formed between the pixel electrode and the counter electrode, which causes the organic light-emitting layer to emit light, thereby forming an image. Hereinafter, an image-forming unit having a TFT layer and a light-emitting unit is referred to as a display unit. In some embodiments, the encapsulation layer that covers the display units and prevents penetration of external moisture may be formed into a thin-film encapsulation structure in which organic films and inorganic films are alternately stacked. In some embodiments, the encapsulation layer has a thin-film encapsulation structure in which multiple thin films are stacked. In some embodiments, the organic film applied to the interface portion is disposed at an interval with each of the multiple display units. In some embodiments, the organic film is formed in such a manner that a portion of the organic film directly contacts the base substrate and the remaining portion of the organic film contacts the barrier layer while surrounding the edge of the barrier layer.

[0072] In one embodiment, the OLED display is flexible and uses a flexible base substrate formed of polyimide, hi some embodiments, the base substrate is formed on a carrier substrate formed of a glass material, and the carrier substrate is then separated. In some embodiments, a barrier layer is formed on the surface of the base substrate opposite the carrier substrate. In one embodiment, the barrier layer is patterned according to the size of each cell panel. For example, while the base substrate is formed on all surfaces of the mother panel, the barrier layer is formed according to the size of each cell panel, thereby forming grooves at the interfaces between the barrier layers of the cell panels. Each cell panel can be cut along the grooves.

[0073] In some embodiments, the manufacturing method further includes a step of cutting along the interface, in which a groove is formed in the barrier layer and at least a portion of the organic film is formed in the groove, so that the groove does not penetrate the base substrate. In some embodiments, the TFT layer of each cell panel is formed, and a passivation layer (an inorganic film) and a planarization film (an organic film) are disposed on and cover the TFT layer. At the same time as the planarization film (e.g., polyimide or acrylic) is formed, the grooves at the interface are covered with an organic film (e.g., polyimide or acrylic). This prevents cracks from occurring when each cell panel is cut along the grooves at the interface by allowing the organic film to absorb any impacts that may occur. That is, if all barrier layers were completely exposed without the organic film, the impacts would be transmitted to the barrier layers when each cell panel was cut along the grooves at the interface, thereby increasing the risk of cracks. However, in one embodiment, the grooves at the interface between the barrier layers are covered with an organic film to absorb any impacts that would otherwise be transmitted to the barrier layers, allowing each cell panel to be cut softly and preventing cracks from occurring in the barrier layers. In one embodiment, the organic film and the planarizing film covering the groove of the interface portion are spaced apart from each other. For example, if the organic film and the planarizing film are connected to each other as one layer, external moisture may penetrate into the display unit through the planarizing film and the remaining portion of the organic film, so the organic film and the planarizing film are spaced apart from each other so that the organic film is spaced apart from the display unit.

[0074] In some embodiments, the display unit is formed by forming a light-emitting unit, and an encapsulation layer is disposed on the display unit to cover the display unit. Thus, after the mother panel is completely manufactured, the carrier substrate carrying the base substrate is separated from the base substrate. In some embodiments, when a laser beam is irradiated onto the carrier substrate, the carrier substrate is separated from the base substrate due to the difference in thermal expansion coefficient between the carrier substrate and the base substrate. In some embodiments, the mother panel is cut into individual cell panels. In some embodiments, the mother panel is cut along the interface between the cell panels using a cutter. In some embodiments, the grooves at the interface along which the mother panel is cut are covered with an organic film, which absorbs shock during cutting. In some embodiments, this can prevent cracks from occurring in the barrier layer during cutting. In some embodiments, the method reduces product rejection rates and stabilizes product quality. Another embodiment is an OLED display having a barrier layer formed on a base substrate, a display unit formed on the barrier layer, an encapsulation layer formed on the display unit, and an organic film applied to the edges of the barrier layer.

[0075] <Evaluation method for delayed fluorescent materials> Next, a method for evaluating the delayed fluorescent material of the present invention will be described. The evaluation method for a delayed fluorescent material of the present invention includes evaluating the luminescence characteristics of the delayed fluorescent material based on ΔPBHT defined by the above formula (I). For an explanation of ΔPBHT, please refer to the description in the above section on <Organic Light-Emitting Element>. There are no particular limitations on the delayed fluorescent material evaluated by the evaluation method of the present invention, and it may be a known delayed fluorescent material or an unknown delayed fluorescent material. Furthermore, the delayed fluorescent material evaluated by the evaluation method of the present invention may be a delayed fluorescent material having a ΔPBHT of 0.01 or more, a delayed fluorescent material having a ΔPBHT of 0, or a delayed fluorescent material having a negative ΔPBHT. For the definition of delayed fluorescent materials and the explanation of delayed fluorescent materials having a ΔPBHT of 0.01 or more, please refer to the description in the above [Delayed Fluorescent Material] section. As shown in the examples below, there is a correlation between the ΔPBHT and delayed fluorescence rate of a delayed fluorescent material. Therefore, by calculating the ΔPBHT of the delayed fluorescent material to be evaluated and determining the value of the delayed fluorescence rate corresponding to the ΔPBHT of the material from the correlation diagram between ΔPBHT and the delayed fluorescence rate τ2 (τ2 / ΔPBHT correlation diagram), it is possible to predict that this value is the delayed fluorescence rate of the material to be evaluated. This makes it possible to evaluate the delayed fluorescence rate of the material to be evaluated and the luminescence characteristics related to the delayed fluorescence rate. Examples of luminescence characteristics related to the delayed fluorescence rate include luminous efficiency, Förster energy transfer efficiency, luminescence spectrum, half-width, and element durability.

[0076] In one embodiment of the present invention, a method for evaluating a delayed fluorescent material includes the steps of: determining the relationship between ΔPBHT and the delayed fluorescence rate τ2 (for example, a τ2 / ΔPBHT correlation diagram) based on the ΔPBHT and delayed fluorescence rate of a plurality of reference delayed fluorescent materials having different ΔPBHTs; calculating the ΔPBHT of the delayed fluorescent material to be evaluated; determining the value of the delayed fluorescence rate corresponding to the ΔPBHT of the material to be evaluated from the relationship between ΔPBHT and the delayed fluorescence rate τ2; and predicting this value to be the delayed fluorescence rate of the material to be evaluated; and evaluating the luminescence characteristics of the material to be evaluated based on the predicted delayed fluorescence rate. Here, the delayed fluorescence rate of the reference delayed fluorescent material may be a measured value or a calculated value, but it is preferable to use the measured value actually measured for the delayed fluorescent material.In addition, the relationship between ΔPBHT and the delayed fluorescence rate τ2 may be obtained for each group by classifying the reference delayed fluorescent material into groups that have a common ring structure.In this case, by using the correlation obtained for the group of reference delayed fluorescent materials that have a common or similar ring structure with the evaluation object, the delayed fluorescence rate of the evaluation object can be accurately predicted.

[0077] <Method for designing delayed fluorescent materials> The method for designing a delayed fluorescent material of the present invention includes molecular design of a delayed fluorescent material based on the relationship between the structure of the delayed fluorescent material and ΔPBHT defined by the above formula (I). For the preferred range of the explanation of ΔPBHT, please refer to the description in the above section of <Organic Light-Emitting Element>. The delayed fluorescent material designed in the present invention may be a delayed fluorescent material having a ΔPBHT of 0.01 or more, a delayed fluorescent material having a ΔPBHT of 0, or a delayed fluorescent material having a negative ΔPBHT. By designing a delayed fluorescent material so that the ΔPBHT is 0.01 or more, it is possible to obtain a delayed fluorescent material that has a high delayed fluorescence rate and is advantageous for improving the durability of organic light-emitting devices. For the definition of delayed fluorescent materials and the explanation and preferred range of delayed fluorescent materials having a ΔPBHT of 0.01 or more, please refer to the description in the above [Delayed Fluorescent Material] section. In the present invention, the "relationship between the structure of a delayed fluorescent material and ΔPBHT" refers to the correspondence relationship between the structure and ΔPBHT, determined based on the ΔPBHT of a specific delayed fluorescent material and multiple compounds obtained by partially modifying the structure of the specific delayed fluorescent material. It is preferable that the partial modification of the structure of the delayed fluorescent material be a modification that can be quantified. This allows the "relationship between the structure of a delayed fluorescent material and ΔPBHT" to be expressed as the relationship between the quantity and ΔPBHT. Examples of structural modifications that can be quantified include a change in the number of carbon atoms, a change in the number of substitutions of substituents or deuterium atoms, a change in the substitution arrangement of substituents or deuterium atoms, a change in the number of condensed rings, a change in the Hammett's σp value of the substituent, and a substitution of the number of atoms such as nitrogen, oxygen, and sulfur. In addition, in the design method of the present invention, the difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy ST For example, the structure of the delayed fluorescent material and ΔE ST By carrying out molecular design taking into consideration the relationship between ΔE and ΔE, it is possible to accurately design a delayed fluorescent material that exhibits the desired luminescence characteristics. ST For the explanation and preferred range of the above, the corresponding descriptions in the <Organic Light-Emitting Device> and [Delayed Fluorescence Material] sections can be referred to.

[0078] In one embodiment of the present invention, the method for designing a delayed fluorescent material includes, as shown in Figure 7, a first step (S1) of calculating the ΔPBHT of a specific delayed fluorescent material, a second step (S2) of designing a modified compound by modifying a part of the structure of the specific delayed fluorescent material, and calculating the ΔPBHT of the modified compound, a third step (S3) of designing a re-modified compound by modifying a part of the structure of the modified compound, and calculating the ΔPBHT of the re-modified compound, a fourth step (S4) of determining the relationship between the structure of the compound and ΔPBHT based on the structure of the specific delayed fluorescent material, the modified compound, and the re-modified compound and the calculated ΔPBHT, and a fifth step (S5) of extracting a compound structure corresponding to the target ΔPBHT from the relationship between the compound structure and ΔPBHT, and selecting a delayed fluorescent material to be synthesized from a group of compounds having the extracted structure. Here, the third step may be repeated by regarding the re-modified compound designed in this step as a modified compound. In a preferred embodiment of the present invention, the difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy of a specific delayed fluorescent material, modified compound, and re-modified compound is further ST and a process for determining the structure of a specific delayed fluorescent material, modified compound, and re-modified compound, and their ΔE ST Based on the compound structure and ΔE ST In the fifth step, the structure of the compound and ΔE ST From the relationship, the target range ΔE ST The structure of a compound corresponding to the above is extracted, and among the structures, one that overlaps with the structure of the compound extracted from the relationship between the compound structure and ΔPBHT is selected as the structure of the delayed fluorescent material to be synthesized. In each aspect of the present invention described above, the structures of the specific delayed fluorescent material used in the first step, the modified compound designed in the second step, and the re-modified compound designed in the third step can be selected from, for example, the structures represented by any of the above general formulas (1) to (6), but are not limited thereto. Steps 1 to 5 may be performed in this order, or may be performed in a different order. For example, the calculation of ΔPBHT in each step may be performed each time a compound is designed, or after a modified compound or a re-modified compound is designed, ΔPBHT may be calculated collectively for a specific delayed fluorescent material, modified compound, and re-modified compound.

[0079] <Design method of organic light-emitting element> The design method for an organic light-emitting device of the present invention includes selecting a delayed fluorescent material based on the ΔPBHT defined by the above formula (I) and designing an organic light-emitting device using the selected delayed fluorescent material. For the preferred range of ΔPBHT, please refer to the description in the above section "Organic Light-Emitting Device." In the design method of the present invention, by selecting a delayed fluorescent material having a ΔPBHT of 0.01 or more and using it in the design of an organic light-emitting device, an organic light-emitting device with high durability can be realized. For the definition of the delayed fluorescent material and the description and preferred range of the delayed fluorescent material having a ΔPBHT of 0.01 or more, please refer to the description in the above section "Delayed Fluorescent Material." For the configuration of the organic light-emitting device, please refer to the description in the above section "Overall Configuration of Organic Light-Emitting Device." In one embodiment of the present invention, a method for designing an organic light-emitting element includes the steps of: searching for a delayed fluorescent material having a ΔPBHT of 0.01 or more from a delayed fluorescent material database storing the ΔPBHT of a plurality of delayed fluorescent materials; selecting a delayed fluorescent material to be used in the organic light-emitting element from the group of delayed fluorescent materials found in the search; and designing the organic light-emitting element using the selected delayed fluorescent material. In a preferred embodiment of the present invention, the database of delayed fluorescent materials further includes a difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy of a plurality of delayed fluorescent materials. STIn the step of searching for the delayed fluorescent material, a delayed fluorescent material having a ΔPBHT of 0.01 or more and a ΔE ST Search for delayed fluorescent materials with ΔE of 0.3 eV or less. ST For the explanation and preferred range of the above, the corresponding descriptions in the <Organic Light-Emitting Device> and [Delayed Fluorescence Material] sections can be referred to.

[0080] <Program> The program of the present invention is a program for carrying out at least one of the method for evaluating a delayed fluorescent material of the present invention, the method for designing a delayed fluorescent material of the present invention, and the method for designing an organic light-emitting element of the present invention. For the steps constituting the program, reference can be made to the descriptions in the above sections <Method for evaluating delayed fluorescent material>, <Method for designing delayed fluorescent material>, and <Method for designing organic light-emitting element>. The program of the present invention may be a program for carrying out any one of the delayed fluorescence material evaluation method of the present invention, the delayed fluorescence material design method of the present invention and the organic light-emitting device design method of the present invention, or may be a program for carrying out two or more of these methods.As an example of the latter, it includes a step for carrying out the delayed fluorescence material evaluation method of the present invention and a step for carrying out the delayed fluorescence material design method of the present invention, and can be exemplified by an embodiment in which the delayed fluorescence material designed by the delayed fluorescence material design method of the present invention is evaluated by the delayed fluorescence material evaluation method of the present invention. [Example]

[0081] The features of the present invention will be explained in more detail below with reference to examples. The materials, processing details, processing procedures, etc. described below can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. The luminescence performance was evaluated using a source meter (Keithley: 2400 Series), a semiconductor parameter analyzer (Agilent Technologies: E5273A), an optical power meter (Newport: 1930C), an optical spectrometer (Ocean Optics: USB2000), a spectroradiometer (Topcon: SR-3), and a streak camera (Hamamatsu Photonics: C4334). The delayed fluorescence rate was measured using a Quantaurus-Tau compact fluorescence lifetime measurement system (Hamamatsu Photonics: C16361-01).

[0082] Example 1: Preparation of an organic electroluminescence device using compound T1 Each thin film was deposited by vacuum deposition on a 2 mm thick glass substrate with a 50 nm thick indium tin oxide (ITO) anode at a vacuum of 5.0 × 10 -5 The layers were laminated using a Pa process. First, HATCN was formed on ITO to a thickness of 10 nm, and NPD was formed on top of that to a thickness of 30 nm. Next, TrisPCz was formed to a thickness of 10 nm, and PYD2Cz was formed on top of that to a thickness of 5 nm. Next, compound PYD2Cz and compound T1 were co-evaporated from separate evaporation sources to form a 30 nm thick light-emitting layer. At this time, the concentration of compound T1 was 35 wt%. Next, SF3TRZ was formed to a thickness of 10 nm. Next, SF3TRZ and Liq were co-evaporated from separate evaporation sources to form a 30 nm thick light-emitting layer. At this time, the concentration of Liq was 30 wt%. Furthermore, Liq was formed to a thickness of 2 nm, and aluminum (Al) was evaporated on top of it to a thickness of 100 nm to form a cathode, completing the organic electroluminescence device (EL device 1).

[0083] (Examples 2 to 12, Comparative Examples 1 to 7) Preparation of organic electroluminescence devices using compounds T2 to T12 or comparative compounds T1 to T7 Organic electroluminescence devices (EL devices 2 to 12, comparative EL devices 1 to 7) were produced in the same manner as in Example 1, except that the light-emitting layer was formed using compounds T2 to T12 or comparative compounds T1 to T7 instead of compound T1.

[0084] The delayed fluorescence rate (delay rate) and LT95 of each fabricated EL device were measured to examine the correlation with ΔPBHT. The results are shown in Figures 1 to 6. Here, LT95 is 2.0 mA / cm 2 The plots show the time it takes for the luminance to reach 95% of the initial luminance when the device is continuously driven at 1000 kJ / s. Compounds T1 to T12 and comparative compounds T1 to T6 shown in Figures 1 to 6 are delayed fluorescent materials contained in the emitting layer of the EL device corresponding to the plots. "ΔPBHT(T3-T1)" on the horizontal axis of Figures 1 and 3 represents ΔPBHT calculated from PBHT(T3)-PBHT(T1), and "ΔPBHT(T2-T1)" on the horizontal axis of Figures 2, 4 to 6 represents ΔPBHT calculated from PBHT(T2)-PBHT(T1). As shown in Figures 1, 2, and 5, the EL devices using compounds T1 to T12, which have a ΔPBHT of 0.01 or more, exhibited a higher delayed fluorescence speed than the comparative EL devices using comparative compounds T1 to T7. Furthermore, as shown in Figures 3, 4, and 6, the EL devices using compounds T1 to T12 had a much longer LT95 and a longer life than the comparative EL devices using comparative compounds T1 to T7. Furthermore, a correlation was observed in which the larger the ΔPBHT of the delayed fluorescent material, the better the delayed fluorescence speed and LT95.

[0085] [ka]

[0086] [ka] [Industrial Applicability]

[0087] In the present invention, the durability of an organic light-emitting device can be improved by using a delayed fluorescent material having a ΔPBHT of 0.01 or more. Therefore, according to the present invention, a delayed fluorescent organic light-emitting device with excellent practicality can be provided. Therefore, the present invention has a high industrial applicability.

Claims

1. An organic light-emitting device having an emitting layer containing a delayed fluorescent material having a ΔPBHT of 0.01 or more as defined by the following formula (I): The delayed fluorescent material is a compound represented by any one of the following general formulas (1) to (6), but is not any of the following compounds T1, T5, T9, and T10. Formula (I) ΔPBHT = PBHT(Tn) - PBHT(T1) [In formula (I), PBHT(T1) represents the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) represents the PBHT value of the excited triplet state with the lowest energy among the excited triplet states with energy higher than the lowest excited singlet energy of the delayed fluorescent material.] 【Chemistry 1】 【Chemistry 2】 【change】 [In general formulas (1) to (6), D 1 to D 10 each independently represent a group represented by the following general formula (7). However, D 1 and D 2 , D 3 and D 4 , D 6 and D 7 , and D 9 and D 10 have different chemical structures, and two D 1 s, three D 2 s, two D 3 s, two D 4 s, three D 5 s, two D 6 s, two D 8 s, and two D 9 s have the same chemical structure. In general formulas (2) and (5), Ar 1 and Ar 2 each independently represent a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group (excluding the group represented by general formula (7)).] 【Transformation 3】 [In general formula (7), L 11 represents a single bond or a divalent linking group. R 41 to R 48 each independently represent a hydrogen atom or a substituent. R 41 and R 42 , R 42 and R 43 , R 43 and R 44 , R 44 and R 45 , R 45 and R 46 , R 46 and R 47 , and R 47 and R 48 may be bonded to each other to form a cyclic structure.]

2. In each of the general formulas (1) to (6), at least one of the groups represented by the general formula (7) is a group represented by any of the following general formulas (8) to (13): The organic light-emitting element according to claim 1. 【Chemistry 4】 [In the general formulas (8) to (13), L ２１ ~L ２６ represents a single bond or a divalent linking group. X 1 to X 6 represent an oxygen atom, a sulfur atom, or N—R. R and R ５１ ~R １１０ R each independently represents a hydrogen atom or a substituent. ５１ and R ５２ , R ５２ and R ５３ , R ５３ and R ５４ , R ５４ and R ５５ , R ５５ and R ５６ , R ５６ and R ５７ , R ５７ and R ５８ , R ５８ and R ５９ , R ５９ and R ６０ , R ６１ and R ６２ , R ６２ and R ６３ , R ６３ and R ６４ , R ６５ and R ６６ , R ６６ and R ６７ , R ６７ and R ６８ , R ６８ and R ６９ , R ６９ and R ７０ , R ７２ and R ７３ , R ７３ and R ７４ , R ７４ and R ７５ , R ７５ and R ７６ , R ７６ and R ７７ , R ７７ and R ７８ , R ７８ and R ７９ , R ７９ and R ８０ , R ８１ and R ８２ , R ８２ and R ８３ , R ８３ and R ８４ , R ８４ and R ８５ , R ８６ and R ８７ , R ８７ and R ８８ , R ８８ and R ８９ , R ８９ and R ９０ , R ９１ and R ９２ , R ９３ and R ９４ , R ９４ and R ９５ , R ９５ and R ９６ , R ９６ and R ９７ , R ９７ and R ９８ , R ９９ and R １００ , R １０１ and R １０２ , R １０２ and R １０３ , R １０３ and R １０４ , R １０４ and R １０５ , R １０５ and R １０６ , R １０７ and R １０８ , R １０８ and R １０９ , R １０９ and R １１０ may be bonded to each other to form a cyclic structure.

3. The organic light-emitting element according to claim 1 or 2, wherein the PBHT(Tn) is PBHT(T3) in a third excited triplet state.

4. The organic light-emitting device according to claim 3 , wherein the delayed fluorescent material is a compound represented by the general formula (2):

5. D of the general formula (2) ４ The organic light-emitting device according to claim 4 , wherein is a group represented by the following general formula (13): 【Transformation 5】 [In general formula (13), L 26 represents a single bond or a divalent linking group. X 6 represents an oxygen atom, a sulfur atom, or N—R. R and R 101 to R 110 each independently represent a hydrogen atom or a substituent. R 101 and R 102 , R 102 and R 103 , R 103 and R 104 , R 104 and R 105 , R 105 and R 106 , R 107 and R 108 , R 108 and R 109 , and R 109 and R 110 may be bonded to each other to form a cyclic structure.]

6. The organic light-emitting element according to claim 1 or 2, wherein the PBHT(Tn) is PBHT(T2) in a second excited triplet state.

7. The organic light-emitting device according to claim 6 , wherein the delayed fluorescent material is a compound represented by the general formula (4) or (5).

8. D of the general formula (4) ６ , D in the general formula (5) ８ The organic light-emitting device according to claim 7 , wherein is a group represented by the following general formula (13): 【Transformation 6】 [In general formula (13), L 26 represents a single bond or a divalent linking group. X 6 represents an oxygen atom, a sulfur atom, or N—R. R and R 101 to R 110 each independently represent a hydrogen atom or a substituent. R 101 and R 102 , R 102 and R 103 , R 103 and R 104 , R 104 and R 105 , R 105 and R 106 , R 107 and R 108 , R 108 and R 109 , and R 109 and R 110 may be bonded to each other to form a cyclic structure.]

9. A method for evaluating a delayed fluorescent material, comprising evaluating the luminescence characteristics of the delayed fluorescent material based on ΔPBHT defined by the following formula (I): Formula (I) ΔPBHT = PBHT(Tn) - PBHT(T1) [In formula (I), PBHT(T1) represents the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) represents the PBHT value of the excited triplet state with the lowest energy among the excited triplet states with energy higher than the lowest excited singlet energy of the delayed fluorescent material.]

10. The evaluation method according to claim 9, comprising a step of predicting the delayed fluorescence rate of the delayed fluorescent material based on ΔPBHT.

11. A step of determining the relationship between ΔPBHT and delayed fluorescence rate τ2 based on the ΔPBHT and delayed fluorescence rate of multiple reference delayed fluorescence materials having different ΔPBHT values; Calculating the ΔPBHT of the delayed fluorescence material to be evaluated, and determining the value of the delayed fluorescence rate corresponding to the ΔPBHT of the evaluation target from the relationship between the ΔPBHT and the delayed fluorescence rate τ2, and predicting this value as the delayed fluorescence rate of the evaluation target; The evaluation method according to claim 9 or 10, comprising a step of evaluating the luminescence characteristics of the evaluation object based on the predicted delayed fluorescence rate.

12. The evaluation method according to claim 11, wherein the delayed fluorescence rate of the reference delayed fluorescence material is an actual measured value.

13. A method for designing a delayed fluorescent material, comprising: designing a molecule of the delayed fluorescent material based on the relationship between the structure of the delayed fluorescent material and ΔPBHT defined by the following formula (I): Formula (I) ΔPBHT = PBHT(Tn) - PBHT(T1) [In formula (I), PBHT(T1) represents the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) represents the PBHT value of the excited triplet state with the lowest energy among the excited triplet states with energy higher than the lowest excited singlet energy of the delayed fluorescent material.]

14. A first step of calculating ΔPBHT of a specific delayed fluorescent material; A second step of designing a modified compound by modifying a part of the structure of the specific delayed fluorescent material and calculating ΔPBHT of the modified compound; a third step of designing a re-modified compound by modifying a part of the structure of the modified compound and calculating the ΔPBHT of the re-modified compound; A fourth step of determining a relationship between the structure of the compound and ΔPBHT based on the structures of the specific delayed fluorescence material, the modified compound, and the re-modified compound and the calculated ΔPBHT; 14. The design method according to claim 13, further comprising: extracting a compound structure corresponding to a target range of ΔPBHT from the relationship between the compound structure and ΔPBHT; and selecting a delayed fluorescent material to be synthesized from a group of compounds having the extracted structure.

15. The design method according to claim 14, wherein the partial changes in the structure of the specific delayed fluorescent material and the modified compound are quantifiable changes.

16. Furthermore, for the specific delayed fluorescent material, the modified compound, and the re-modified compound, the difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy ＳＴ In the fifth step, ΔE ＳＴ The design method according to claim 14 or 15, wherein a delayed fluorescent material to be synthesized is selected from the group of compounds based on the formula:

17. The design method according to any one of claims 14 to 16, wherein the re-modified compound designed in the third step is regarded as a modified compound, and the third step is repeatedly performed.

18. A method for designing an organic light-emitting device, comprising: selecting a delayed fluorescent material based on ΔPBHT defined by the following formula (I); and designing an organic light-emitting device using the selected delayed fluorescent material. Formula (I) ΔPBHT = PBHT(Tn) - PBHT(T1) [In formula (I), PBHT(T1) represents the PBHT value of the lowest excited triplet state of the delayed fluorescent material, and PBHT(Tn) represents the PBHT value of the excited triplet state with the lowest energy among the excited triplet states with energy higher than the lowest excited singlet energy of the delayed fluorescent material.]

19. A step of searching for a delayed fluorescent material having a ΔPBHT of 0.01 or more from a delayed fluorescent material database storing data on the ΔPBHT of a plurality of delayed fluorescent materials; selecting a delayed fluorescent material to be used in an organic light-emitting element from the group of delayed fluorescent materials found in the search of the step; The design method according to claim 18 , further comprising a step of designing an organic light-emitting element using the delayed fluorescent material selected in the step.

20. The database of delayed fluorescent materials further includes a difference ΔE between the lowest excited singlet energy and the lowest excited triplet energy of the plurality of delayed fluorescent materials. ＳＴ and in the step of searching for the delayed fluorescent material, a delayed fluorescent material having a ΔPBHT of 0.01 or more and a ΔE ＳＴ The design method according to claim 19, wherein a delayed fluorescent material having a λ / 2 of 0.3 eV or less is searched for.

21. A program for carrying out the method according to any one of claims 9 to 20.

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