JP7630160B2 - Organic light-emitting device - Google Patents

Description

The present invention relates to an organic light-emitting device using a delayed fluorescent material.

Research into improving the luminous efficiency of organic light-emitting elements such as organic electroluminescence elements (organic EL elements) is being actively conducted. In particular, various studies have been conducted to improve the luminous efficiency by developing and combining newly developed electron transport materials, hole transport materials, host materials, luminescent materials, etc. that make up organic electroluminescence elements. Among these, there is also research into organic light-emitting elements that use delayed fluorescent materials.

A delayed fluorescent material is a compound that emits fluorescence when it returns from an excited singlet state to a ground state after reverse intersystem crossing from an excited triplet state to an excited singlet state in an excited state. Fluorescence from this route is observed later than fluorescence from an excited singlet state that occurs directly from the ground state (normal fluorescence), and is therefore called delayed fluorescence. Here, for example, when a luminescent compound is excited by carrier injection, the probability of occurrence of an excited singlet state and an excited triplet state is statistically 25%:75%, so there is a limit to the improvement of luminous efficiency when only the fluorescence from the directly generated excited singlet state is used. On the other hand, delayed fluorescent materials can use not only the excited singlet state but also the excited triplet state for fluorescence emission via the above-mentioned reverse intersystem crossing route, and therefore can obtain a higher luminous efficiency than normal delayed fluorescent materials.

As such delayed fluorescent materials, benzene derivatives having a heteroaryl group such as a carbazolyl group or a diphenylamino group and at least two cyano groups have been proposed, and it has been confirmed that high luminous efficiency was obtained in organic EL elements using such benzene derivatives in the light-emitting layer (see Patent Document 1).
In addition, Non-Patent Document 1 reports that a carbazolyldicyanobenzene derivative (4CzTPN) is a thermally activated delayed fluorescent material, and that an organic electroluminescence element using this carbazolyldicyanobenzene derivative has achieved high internal EL quantum efficiency.

On the other hand, it has also been proposed to use a delayed fluorescent material in the light-emitting layer as an assist dopant, rather than as the light-emitting material (see Patent Document 2). This document describes how the light-emitting efficiency can be improved by adding a delayed fluorescent material having the lowest excited singlet energy intermediate between the host material and the fluorescent material to the light-emitting layer, in addition to the host material and the fluorescent material.

JP 2014-43541 A JP 2015-179809 A

H. Uoyama, et al., Nature 492, 234 (2012)

As described above, Patent Document 1, Patent Document 2, and Non-Patent Document 1 report that high luminous efficiency was obtained in an organic electroluminescence element using a delayed fluorescent material. However, when the present inventors fabricated an organic electroluminescence element according to the descriptions in Patent Document 1 and Patent Document 2, they found that it was not easy to ensure a sufficient life span.

Under these circumstances, the inventors have conducted extensive research with the aim of improving the lifetime of organic light-emitting devices that use delayed fluorescent materials.

As a result of intensive research to achieve the above object, the inventors have found that by adding a host material, a delayed fluorescent material, a light-emitting material, and an adjusting agent that satisfy specific conditions to the light-emitting layer, it is possible to realize an organic light-emitting element that has a long light-emitting lifetime and is stable. The present invention has been proposed based on this knowledge, and specifically has the following configuration.

[1] An organic light-emitting device having a light-emitting layer including a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound, which satisfy the following conditions (a) and (b):
the second organic compound is a delayed fluorescent material,
The organic light-emitting element, wherein a maximum component of the light emitted from the organic light-emitting element is light emitted from the third organic compound.
Condition (a) E _S1 (1)>E _S1 (4)>E _S1 (2)>E _S1 (3)
Condition (b) E _T1 (1)>E _T1 (2)>E _T1 (3)>E _T1 (4)
(In the above formula,
E _S1 (1) represents the lowest excited singlet energy of the first organic compound.
E _S1 (2) represents the lowest excited singlet energy of the second organic compound.
E _S1 (3) represents the lowest excited singlet energy of the third organic compound.
E _S1 (4) represents the lowest excited singlet energy of the fourth organic compound.
E _T1 (1) represents the lowest excited triplet energy of the first organic compound.
E _T1 (2) represents the lowest excited triplet energy of the second organic compound.
E _T1 (3) represents the lowest excited triplet energy of the third organic compound.
E _T1 (4) represents the lowest excited triplet energy of the fourth organic compound.
[2] The organic light-emitting element according to [1], further satisfying the following condition (c):
Condition (c) Conc(1)>Conc(2)>Conc(4)
(In the above formula,
Conc(1) represents the concentration of the first organic compound in the light-emitting layer.
Conc(2) represents the concentration of the second organic compound in the light-emitting layer.
Conc(4) represents the concentration of the fourth organic compound in the light-emitting layer.
[3] The organic light-emitting device according to [2], further satisfying the following condition (c1):
Condition (c1) Conc(1)>Conc(2)>Conc(4)>Conc(3)
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer.)
[4] The organic light-emitting element according to [2] or [3], which further satisfies the following condition (d):
Condition (d) Conc(2)/Conc(3)>5
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer.)
[5] The organic light-emitting device according to any one of [2] to [4], further satisfying the following condition (e):
Condition (e) Conc(4)/Conc(3)>1.5
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer.)
[6] The organic light-emitting element according to any one of [1] to [5], further satisfying the following condition (f):
Condition (f) Conc(4)≦5% by weight
(In the above formula, Conc(4) represents the concentration of the fourth organic compound in the light-emitting layer.)
[7] The organic light-emitting element according to any one of [1] to [6], further satisfying the following condition (g):
Condition (g) Conc(3)≦1% by weight
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer.)
[8] The organic light-emitting element according to any one of [1] to [7], wherein the second organic compound has an energy difference ΔE _st between the lowest excited singlet state and the lowest excited triplet state at 77 K of 0.3 eV or less.
[9] The organic light-emitting element according to any one of [1] to [8], wherein the third organic compound has an energy difference ΔE _st between the lowest excited singlet state and the lowest excited triplet state at 77 K of 0.3 eV or less.
[10] The organic light-emitting element according to any one of [1] to [9], wherein the light-emitting layer is composed only of a compound having atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, oxygen atoms, and sulfur atoms.
[11] The organic light-emitting device according to any one of [1] to [10], wherein the first organic compound, the second organic compound, and the fourth organic compound are each independently a compound containing atoms selected from the group consisting of carbon atoms, hydrogen atoms, and nitrogen atoms.
[12] The organic light-emitting device according to any one of [1] to [11], wherein the fourth organic compound is a compound constituted only by carbon atoms and hydrogen atoms.
[13] The organic light-emitting device according to any one of [1] to [12], wherein the second organic compound contains a cyanobenzene structure.
[14] [Step 1] Evaluating the luminous efficiency and lifetime of a composition that contains a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound, which are delayed fluorescent materials, and that satisfies the following conditions (a) and (b):
[Step 2] Evaluating the luminous efficiency and lifetime of a composition in which at least one of the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound, which are delayed fluorescent materials, is changed within a range that satisfies the following conditions (a) and (b), at least once:
[Step 3] Select the combination with the best evaluated luminous efficiency and lifetime.
A method for designing a light-emitting composition, comprising each of the steps.
Condition (a) E _S1 (1)>E _S1 (4)>E _S1 (2)>E _S1 (3)
Condition (b) E _T1 (1)>E _T1 (2)>E _T1 (3)>E _T1 (4)
(In the above formula,
E _S1 (1) represents the lowest excited singlet energy of the first organic compound.
E _S1 (2) represents the lowest excited singlet energy of the second organic compound.
E _S1 (3) represents the lowest excited singlet energy of the third organic compound.
E _S1 (4) represents the lowest excited singlet energy of the fourth organic compound.
E _T1 (1) represents the lowest excited triplet energy of the first organic compound.
E _T1 (2) represents the lowest excited triplet energy of the second organic compound.
E _T1 (3) represents the lowest excited triplet energy of the third organic compound.
E _T1 (4) represents the lowest excited triplet energy of the fourth organic compound.
[15] A program for carrying out the method according to [14].

The organic light-emitting device of the present invention can achieve long-life light emission.

FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of an organic electroluminescence element.

The contents of the present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment or specific example of the present invention, but the present invention is not limited to such an embodiment or specific example. In this application, a numerical range expressed using "to" means a range including the numerical values described before and after "to" as the lower and upper limits. In this application, "consists of" means that it consists only of what is described before "consists of", and does not include anything else. In addition, the isotope species of hydrogen atoms present in the molecules of the compound used in the present invention are not particularly limited, and for example, all hydrogen atoms in the molecule may be ¹ H, or some or all of them may be ² H (deuterium D).

(Characteristics of organic light-emitting devices)
The organic light-emitting device of the present invention has an emission layer including a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound. Among these, the second organic compound is a delayed fluorescent material. These organic compounds satisfy the following conditions (a) and (b).
Condition (a) E _S1 (1)>E _S1 (4)>E _S1 (2)>E _S1 (3)
Condition (b) E _T1 (1)>E _T1 (2)>E _T1 (3)>E _T1 (4)

In the present application, E _S1 (1) represents the lowest excited singlet energy of the first organic compound, E _S1 (2) represents the lowest excited singlet energy of the second organic compound, E _S1 (3) represents the lowest excited singlet energy of the third organic compound, and E _S1 (4) represents the lowest excited singlet energy of the fourth organic compound. In the present application, eV is used as a unit.
E _T1 (1) represents the lowest excited triplet energy of the first organic compound, E _T1 (2) represents the lowest excited triplet energy of the second organic compound, E _T1 (3) represents the lowest excited triplet energy of the third organic compound, and E _T1 (4) represents the lowest excited triplet energy of the fourth organic compound. In this application, eV is used as the unit.
Conc(1) represents the concentration of the first organic compound in the light-emitting layer, Conc(2) represents the concentration of the second organic compound in the light-emitting layer, Conc(3) represents the concentration of the third organic compound in the light-emitting layer, and Conc(4) represents the concentration of the fourth organic compound in the light-emitting layer. In this application, weight percent is used as a unit.

The organic light-emitting element of the present invention simultaneously satisfies the conditions (a) and (b) for the lowest excited singlet energy. Therefore, the lowest excited singlet energy E _S1 (2) and the lowest excited triplet energy E _T1 (2) of the second organic compound, and the lowest excited singlet energy E _S1 (3) and the lowest excited triplet energy E _T1 (3) of the third organic compound are all between the lowest excited singlet energy E _S1 (4) and the lowest excited triplet energy E _T1 (4) of the fourth organic compound. Therefore, the fourth organic compound has a difference ΔE _ST (4) between the lowest excited singlet energy and the lowest excited triplet energy of 77K that is larger than that of the second organic compound and the third organic compound. The ΔE _ST (4) of the fourth organic compound is preferably 0.5 eV or more, more preferably 0.6 eV or more, and more preferably 0.7 eV or more. ΔE _ST (4) of the fourth organic compound can be, for example, in the range of 1.5 eV or less, in the range of 1.2 eV or less, or in the range of 0.9 eV or less.
The difference E _S1 (4)-E _S1 (2) between the lowest excited singlet energies of the fourth organic compound and the second compound is preferably 0.05 eV or more, more preferably 0.10 eV or more, and can be 0.15 eV or more. _{E S1} (4)-E _S1 (2) can be, for example, in the range of 0.7 eV or less, 0.5 eV or less, or 0.3 eV or less.
The difference E _T1 (3)-E _T1 (4) in the lowest excited triplet energy between the third organic compound and the fourth compound is preferably 0.10 eV or more, more preferably 0.30 eV or more, and can be 0.45 eV or more. E _T1 (3)-E _T1 (4) can be, for example, in the range of 0.9 eV or less, 0.7 eV or less, or 0.5 eV or less.
The difference E _S1 (1)-E _S1 (2) in the lowest excited singlet energy between the first organic compound and the second compound can be in the range of 0.3 eV or more, 0.5 eV or more, or 0.7 eV or more, and can be in the range of 1.6 eV or less, 1.3 eV or less, or 0.9 eV or less.
The difference E _S1 (1)-E _S1 (4) in the lowest excited singlet energy between the first organic compound and the fourth compound can be in the range of 0.2 eV or more, 0.4 eV or more, or 0.6 eV or more, and can be in the range of 1.5 eV or less, 1.2 eV or less, or 0.8 eV or less.
The lowest excited triplet energy E _T1 (1) of the first organic compound may be greater than the lowest excited singlet energy E _S1 (4) of the fourth compound. For example, E _T1 (1)-E _S1 (4) may be in the range of 0.05 eV or more, 0.10 eV or more, or 0.15 eV or more. It may also be in the range of 0.7 eV or less, 0.5 eV or less, or 0.3 eV or less.

In the organic light-emitting device of the present invention, it is preferable that the contents of the first compound, the second compound, and the fourth compound satisfy the relationship of condition (c).
Condition (c) Conc(1)>Conc(2)>Conc(4)
In the organic light-emitting device of the present invention, it is preferable that the contents of the first to fourth compounds satisfy the relationship of condition (c1).
Condition (c1) Conc(1)>Conc(2)>Conc(4)>Conc(3)
Conc(1) is preferably 30% by weight or more, and can be in the range of 50% by weight or more, or 65% by weight or more, and can be in the range of 99% by weight or less, or 85% by weight or less, or 75% by weight or less.
Conc(2) is preferably 10% by weight or more, and may be in the range of 20% by weight or more, or 30% by weight or more, and may be in the range of 45% by weight or less, or 40% by weight or less, or 35% by weight or less.
Conc(3) is preferably 5% by weight or less, more preferably 3% by weight or less. Conc(3) can be in the range of 1% by weight or less, 0.5% by weight or less, 0.01% by weight or more, 0.1% by weight or more, or 0.3% by weight or more.
Conc(4) is preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less. Conc(4) can be in the range of 0.01% by weight or more, 1% by weight or more, 3% by weight or more, or 4% by weight or more.

It is preferable that the organic light-emitting device of the present invention further satisfies the following condition (d).
Condition (d) Conc(2)/Conc(3)>5
Conc(2)/Conc(3) can be in the range of 10 or more, 30 or more, or 50 or more, and can be in the range of 500 or less, 300 or less, or 100 or less.
It is preferable that the organic light-emitting device of the present invention further satisfies the following condition (e).
Condition (e) Conc(4)/Conc(3)>1.5
Conc(4)/Conc(3) can be in the range of 2 or more, 5 or more, or 10 or more, and can be in the range of 500 or less, 100 or less, or 50 or less.

The second organic compound used in the organic light-emitting element of the present invention is a 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).
The second organic compound preferably has a difference ΔE _ST (2) between the lowest excited singlet energy and the lowest excited triplet energy at 77 K of 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.
If ΔE _ST (2) is small, the second organic compound functions as a thermally activated delayed fluorescent material because it is easy to undergo reverse intersystem crossing from an excited singlet state to an excited triplet state by absorbing thermal energy. The thermally activated delayed fluorescent material absorbs heat emitted by the device and relatively easily undergoes reverse intersystem crossing from an excited triplet state to an excited singlet state, and the excited triplet energy can efficiently contribute to light emission.

In the present application, the lowest excited singlet energy (E _S1 ) and the lowest excited triplet energy (E _T1 ) of a compound are values determined by the following procedure: ΔE _ST is a value determined by calculating E _S1 -E _T1 .
(1) Lowest excited singlet energy (E _S1 )
A thin film or toluene solution (concentration 10 ^-5 mol/L) of the compound to be measured is prepared as a sample. The fluorescence spectrum of this sample is measured at room temperature (300K). In the fluorescence spectrum, the vertical axis represents emission and the horizontal axis represents wavelength. 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 determined. This wavelength value is converted to an energy value using the following conversion formula and the value is defined as E _S1 .
Conversion formula: E _S1 [eV] = 1239.85/λedge
The emission spectra in the examples described later were measured using an LED light source (M300L4, manufactured by Thorlabs) as an excitation light source and a detector (PMA-12 multichannel spectrometer C10027-01, manufactured by Hamamatsu Photonics KK).
(2) Lowest excited triplet energy (E _T1 )
The same sample used in the measurement of the lowest excited singlet energy (E _S1 ) is cooled to 77 [K] with liquid nitrogen, and the phosphorescence measurement sample is irradiated with excitation light (300 nm), and the phosphorescence is measured using a detector. The emission from 100 milliseconds after irradiation with the excitation light is taken as the phosphorescence spectrum. A tangent line is drawn to the rising edge on the short wavelength side of this phosphorescence spectrum, and the wavelength value λedge [nm] at the intersection point between the tangent line and the horizontal axis is determined. This wavelength value is converted into an energy value using the following conversion formula and taken as E _T1 .
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 the slope is at its maximum value is regarded as the tangent to the rising edge of the phosphorescence spectrum on the short wavelength side.
Note that a maximum point having a peak intensity of 10% or less of the maximum peak intensity of the spectrum is not included in the maximum value on the shortest wavelength side described above, and a tangent drawn at a point where the slope value is the maximum value that is closest to the maximum value on the shortest wavelength side is defined as a tangent to the rising edge on the short wavelength side of the phosphorescence spectrum.

(First organic compound)
The first organic compound is an organic compound having a minimum excited singlet energy greater than those of the second organic compound, the third organic compound, and the fourth organic compound, and has a function as a host material responsible for transporting carriers and a function of trapping the energy of the third organic compound within the compound. This allows the third organic compound to efficiently convert energy generated by recombination of holes and electrons within the molecule and energy received from the first organic compound and the second organic compound into light emission.
The first organic compound is preferably an organic compound that has a hole transporting ability and an electron transporting ability, prevents the emission wavelength from becoming longer, and has a high glass transition temperature. In a preferred embodiment of the present invention, the first organic compound is selected from compounds that do not emit delayed fluorescence.
Preferred compounds that can be used as the first organic compound are listed below.

(Second organic compound)
The second organic compound is a delayed fluorescent material having a lower minimum excited singlet energy than the first organic compound and the fourth organic compound, and a higher minimum excited singlet energy than the third organic compound. The second organic compound is a delayed fluorescent material having a lower minimum excited triplet energy than the first organic compound and a higher minimum excited triplet energy than the third organic compound and the fourth organic compound. The second organic compound may be a compound capable of emitting delayed fluorescence under some conditions, and it is not essential that the second organic compound emits delayed fluorescence derived from the second organic compound in the organic light-emitting device of the present invention. In the organic light-emitting device of the present invention, the second organic compound receives energy from the first organic compound and the fourth organic compound in the excited singlet state to transition to the excited singlet state. The second organic compound may receive energy from the first organic compound in the excited triplet state to transition to the excited triplet state. Since the second organic compound has a small ΔE _ST , the second organic compound in the excited triplet state is likely to undergo reverse intersystem crossing to the second organic compound in the excited singlet state. The second organic compound in an excited singlet state generated by these pathways provides energy to the third organic compound, causing the third organic compound to transition to an excited singlet state.

Preferred compounds that can be used as the second organic compound are listed below. In the structural formulas of the following exemplary compounds, t-Bu represents a tertiary butyl group.

As the second organic compound, other known delayed fluorescent materials may be appropriately combined and used. Even unknown delayed fluorescent materials may be used.
Preferred delayed fluorescent materials include those described in paragraphs 0008 to 0048 and 0095 to 0133 of WO2013/154064, paragraphs 0007 to 0047 and 0073 to 0085 of WO2013/011954, paragraphs 0007 to 0033 and 0059 to 0066 of WO2013/011955, and paragraphs 0008 to 0076 of WO2013/081088. No. 0071 and No. 0118 to No. 0133, paragraphs No. 0009 to No. 0046 and No. 0093 to No. 0134 of JP 2013-256490 A, paragraphs No. 0008 to No. 0020 and No. 0038 to No. 0040 of JP 2013-116975 A, paragraphs No. 0007 to No. 0032 and No. 0079 to No. 0084 of WO 2013/133359 A, paragraph No. 000 of WO 2013/161437 A 8 to 0054 and 0101 to 0121, paragraphs 0007 to 0041 and 0060 to 0069 of JP 2014-9352 A, paragraphs 0008 to 0048 and 0067 to 0076 of JP 2014-9224 A, paragraphs 0013 to 0025 of JP 2017-119663 A, paragraphs 0013 to 0026 of JP 2017-119664 A, Compounds included in the general formulas described in paragraphs 0012 to 0025 of JP-222623 A, paragraphs 0010 to 0050 of JP-A-2017-226838, paragraphs 0012 to 0043 of JP-A-2018-100411, and paragraphs 0016 to 0044 of WO2018/047853, particularly exemplary compounds that emit delayed fluorescence, can be mentioned. Also, JP2013-253121A, WO2013/133359A, WO2014/034535A, WO2014/115743A, WO2014/122895A, WO2014/126200A, WO2014/136758A, WO2014/133121A, WO2014/1 36860, WO2014/196585, WO2014/189122, WO2014/168101, WO2015/008580 No. Publication, WO2014/203840 Publication, WO2015/002213 Publication, WO2015/016200 Publication, WO2015/019725 Publication, WO JP2015/072470A, WO2015/108049A, WO2015/080182A, WO2015/072537A, WO2015/080183A, JP2015-129240A, WO2015/129714A, WO2015/129715A, WO2015/133501 The luminescent materials described in WO2015/136880, WO2015/137244, WO2015/137202, WO2015/137136, WO2015/146541, and WO2015/159541, which emit delayed fluorescence, can be preferably used. Note that the above publications described in this paragraph are hereby incorporated by reference as part of this specification.

A compound represented by the following general formula (1) and emitting delayed fluorescence can be preferably used as the delayed fluorescence material of the present invention. In a preferred embodiment of the present invention, the compound represented by general formula (1) can be used as the second organic compound.

In general formula (1), X ¹ to X ⁵ represent N or C-R. R represents a hydrogen atom or a substituent. When two or more of X ¹ to X ⁵ represent C-R, those C-R may be the same or different from each other. However, at least one of X ¹ to X ^{5 is C-D (here, D represents a donor group). When all of X 1 to X 5 are C} -R, Z represents an acceptor group, and when at least one of X ¹ to X ⁵ is N, Z represents a hydrogen atom or a substituent.
Among the compounds represented by the general formula (1), particularly preferred compounds are those represented by the following general formula (2):

In general formula (2), X ¹ to X ⁵ represent N or C-R. R represents a hydrogen atom or a substituent. When two or more of X ¹ to X ⁵ represent C-R, those C-R may be the same or different. However, at least one of X ¹ to X ⁵ is C-D (here, D represents a donor group).

For the description and preferred range of the substituent represented by Z in general formula (1), the description and preferred range of the substituent in general formula (7) described below can be referred to. The acceptor group represented by Z in general formula (1) is a group having the property of donating electrons to the ring to which Z is bonded, and can be selected, for example, from groups having a positive Hammett σp value. The donor group represented by D in general formula (1) and general formula (2) is a group having the property of withdrawing electrons to the ring to which D is bonded, and can be selected, for example, from groups having a negative Hammett σp value. Hereinafter, the acceptor group may be referred to as A.
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. Specifically, the following formula is established between the substituent in the para-substituted benzene derivative and the reaction rate constant or equilibrium constant:
log(k/k ₀ ) = ρσp
or
log(K/K ₀ ) = ρσp
In the above formula, k is the rate constant of a benzene derivative having no substituent, k ₀ is the rate constant of a benzene derivative substituted with a substituent, K is the equilibrium constant of a benzene derivative having no substituent, K ₀ is the equilibrium constant of a benzene derivative substituted with a substituent, and ρ is a reaction constant determined by the type and conditions of the reaction. For an explanation of the "Hammett σp value" in the present invention and the numerical values of each substituent, the description of the σp value in Hansch, C. et.al., Chem.Rev., 91, 165-195 (1991) can be referred to.

In general formula (1) and general formula (2), X ¹ to X ⁵ represent N or C-R, but at least one is C-D. The number of N among X ¹ to X ⁵ is 0 to 4, and examples thereof include cases where X ¹ , X ³ and X ⁵ , X ¹ and X ³ , X ¹ and X ⁴ , X ² and X ³ , X ¹ and X ⁵ , X ² and X ⁴ , only X ¹ , only X ² , and only X ³ are N. The number of C-D among X ¹ to X ⁵ is 1 to 5, and preferably 2 to 5. For example, ^X1 , ^X2 , ^X3 , ^X4 , and ^X5 , ^X1 , ^X2 , ^X4 , and ^X5 , ^X1 , ^X2 , ^X3 , and ^X4 , ^X1 , X3, ^{X4, and X5 , X1} , ^X3 , and ^X5 , ^X1 , ^X2 , and ^{X5 , X1} , ^X2 , and ^X4 , ^X1 , X3, and ^X4 , ^X1 , ^X3 , ^X1 , ^X4 , ^X2 , and ^X3 , ^X1 , ^{X5 , X2} , and ^X4 , only ^X1 , only ^X2 , and only ^X3 are C-D. At least one of ^X1 to ^X5 may be C-A. Here, A represents an acceptor group. Among X ¹ to X ⁵ , the number of CA is preferably 0 to 2, and more preferably 0 or 1. Preferred examples of A in CA include a cyano group and a heterocyclic aromatic group having an unsaturated nitrogen atom. Furthermore, X ¹ to X ⁵ may each independently be CD or CA.
When two adjacent ones of X ¹ to X ⁵ represent C-R, the two R may 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 condensed 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 in which multiple rings are condensed, such as a phenanthrene ring or a triphenylene ring, may be formed.

The donor group D in the general formulae (1) and (2) is preferably a group represented by the following general formula (3), for example.

In the general formula (3), R ¹¹ and R ¹² each independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. R ¹¹ and R ¹² may be bonded to each other to form a cyclic structure. L represents a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. The substituent that can be introduced into the arylene group or heteroarylene group of L may be a group represented by general formula (1) or general formula (2), or a group represented by general formulas (3) to (6) described later. These groups represented by (1) to (6) may be introduced up to the maximum number of substituents that can be introduced into L. In addition, when a plurality of groups represented by general formulas (1) to (6) are introduced, the substituents may be the same or different from each other. * represents the bonding position to the carbon atom (C) constituting the ring skeleton of the ring in general formula (1) or general formula (2).
The "alkyl group" referred to here may be linear, branched, or cyclic. In addition, two or more of the linear, cyclic, and branched portions may be mixed. The number of carbon atoms in the alkyl group may be, for example, 1 or more, 2 or more, or 4 or more. In addition, 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 as a substituent may be further substituted with an aryl group.
The "alkenyl group" may be linear, branched, or cyclic. In addition, two or more of the linear portion, the cyclic portion, and the branched portion may be mixed. The number of carbon atoms in the alkenyl group may be, for example, 2 or more, 4 or more. In addition, 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 alkenyl group include an ethenyl group, an n-propenyl group, an isopropenyl group, an n-butenyl group, an isobutenyl group, an n-pentenyl group, an isopentenyl group, an n-hexenyl group, an isohexenyl group, and a 2-ethylhexenyl group. The alkenyl group as a substituent may be further substituted with a substituent.
The "aryl group" and the "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. Specific examples of the aryl group or the 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 "arylene group" and the "heteroaryl group" can be obtained by replacing the valence of the aryl group and the heteroaryl group from 1 to 2.
The substituent means a monovalent group that can be substituted for a hydrogen atom, and does not include condensed groups. For the explanation and preferred range of the substituent, the explanation and preferred range of the substituent of the general formula (7) described later can be referred to.

The compound represented by the general formula (3) is preferably a compound represented by any one of the following general formulas (4) to (6).

In the general formulas (4) to (6), R ⁵¹ to R ⁶⁰ , R ⁶¹ to R ⁶⁸ , and R ⁷¹ to R ⁷⁸ each independently represent a hydrogen atom or a substituent. For the description and preferred range of the substituents, the description and preferred range of the substituents in the general formula (7) described below can be referred to. It is also preferable that R ⁵¹ to R ⁶⁰ , R ⁶¹ to R ⁶⁸ , and R ⁷¹ to R ⁷⁸ each independently represent a group represented by any one of the general formulas (4) to (6). The number of substituents in the general formulas (4) to (6) is not particularly limited. It is also preferable that all of them are unsubstituted (i.e., hydrogen atoms). In addition, when there are two or more substituents in each of the general formulas (4) to (6), the substituents may be the same or different. When a substituent is present in general formulae (4) to (6), the substituent is preferably any one of R ⁵² to R ⁵⁹ in general formula (4), preferably any one of R ⁶² to R ⁶⁷ in general formula (5), and preferably any one of R ⁷² to R ⁷⁷ in general formula (6).

In the general formulae (4) to (6), 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 ⁷¹ and R ⁷² , R ⁷² and R ⁷³ , R ⁷³ and R ⁷⁴ , R ⁷⁵ and R ⁷⁶ , R ⁷⁶ and R ⁷⁷ , R ⁷⁷ and R ⁷⁸ may be bonded to each other to form a cyclic structure. For the description and preferred examples of the cyclic structure, reference may be made to the description and preferred examples of the cyclic structures in X ¹ to X ⁵ in the above general formula (1) and general formula (2).

In the general formula (6), X represents a divalent oxygen atom, a sulfur atom, a substituted or unsubstituted nitrogen atom, a substituted or unsubstituted carbon atom, a substituted or unsubstituted silicon atom, a carbonyl group, or a divalent substituted or unsubstituted ethylene group, a substituted or unsubstituted vinylene group, a substituted or unsubstituted o-arylene group, or a substituted or unsubstituted o-heteroarylene group, each of which has a linking chain length of 2 atoms. For specific examples and preferred ranges of the substituents, the descriptions of the substituents in the above general formulas (1) and (2) can be referred to.

In the general formulas (4) to (6), L ¹² to L ¹⁴ represent a single bond, a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group. For the description and preferred range of the arylene group or heteroarylene group represented by L ¹² to L ¹⁴ , the description and preferred range of the arylene group or heteroarylene group represented by L can be referred to. L ¹² to L ¹⁴ are preferably a single bond or a substituted or unsubstituted arylene group. The substituent of the arylene group or heteroarylene group referred to here may be a group represented by general formulas (1) to (6). The group represented by general formulas (1) to (6) may be introduced into L ¹¹ to L ¹⁴ up to the maximum number of substituents that can be introduced. In addition, when a plurality of groups represented by general formulas (1) to (6) are introduced, the substituents may be the same or different from each other. * indicates the bonding position to the carbon atom (C) constituting the ring skeleton of the ring in general formula (1) or general formula (2).

In the present invention, a compound represented by the following general formula (7) that emits delayed fluorescence can be particularly preferably used as the delayed fluorescent material. In a preferred embodiment of the present invention, the compound represented by general formula (7) can be used as the second organic compound.

In general formula (7), 0 to 4 of R ¹ to R ⁵ represent a cyano group, at least one of R ¹ to R ⁵ represents a substituted amino group, and the remaining R ¹ to R ⁵ represent a hydrogen atom or a substituent other than a cyano group or a substituted amino group.
The substituted amino group referred to here is preferably a substituted or unsubstituted diarylamino group, and the two aryl groups constituting the substituted or unsubstituted diarylamino group may be linked to each other. The linkage may be a single bond (in which case a carbazole ring is formed) or a linking group such as -O-, -S-, -N(R ⁶ )-, -C(R ⁷ )(R ⁸ )-, or -Si(R ⁹ )(R ¹⁰ )-. Here, R ⁶ to R ¹⁰ represent a hydrogen atom or a substituent, and R ⁷ and R ⁸ , and R ⁹ and R ¹⁰ may be linked to each other to form a ring structure.
The substituted amino group may be any of R ¹ to R ⁵ , and for example, R ¹ and R ² , R ¹ and R ³ , R ¹ and R ⁴ , R ¹ and R ⁵ , R ² and R ³ , R ² and R ⁴ , R ¹ and R ² and R ³ , R ¹ and R ² and R ⁴ , R ¹ and R ² and R ⁵ , R ¹ and R ³ and R ⁴ , R ¹ and R ³ and R ⁵ , R ² and R ³ and R ⁴ , R ¹ and R ² and R ³ and R ⁴ , R ¹ and R ² and R ³ and R ⁵ , R ¹ and R ² and R ⁴ and R ⁵ , and R ¹ and R ² and R ³ and R ⁴ and R ⁵ can be substituted amino groups. The cyano group may be any of R ¹ to R ^5. For example, R ¹ , R ² , R ³ , R ¹ and R ² , R ¹ and R ³ , R ¹ and R ⁴ , R ¹ and R ⁵ , R ² and R ³ , R ² and R ⁴ , R ¹ , R ² and R ³ , R ¹ , R ² and R ⁴ , R ¹ , R ² and R ⁵ , R ¹ , R ³ and R ⁴ , R ¹ , R ³ and R ⁵ , or R ² , R ³ and R ⁴ can be cyano groups.
R ¹ to R ⁵ that are not a cyano group or a substituted amino group represent a hydrogen atom or a substituent. Examples of the substituent include a hydroxyl group, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), an alkyl group (e.g., having 1 to 40 carbon atoms), an alkoxy group (e.g., having 1 to 40 carbon atoms), an alkylthio group (e.g., having 1 to 40 carbon atoms), an aryl group (e.g., having 6 to 30 carbon atoms), an aryloxy group (e.g., having 6 to 30 carbon atoms), an arylthio group (e.g., having 6 to 30 carbon atoms), a heteroaryl group (e.g., having 5 to 30 atoms constituting the ring skeleton), a heteroaryloxy group (e.g., having 5 to 30 atoms constituting the ring skeleton), a heteroarylthio group, (e.g., having 5 to 30 ring skeleton atoms), acyl group (e.g., having 1 to 40 carbon atoms), alkenyl group (e.g., having 1 to 40 carbon atoms), alkynyl group (e.g., having 1 to 40 carbon atoms), alkoxycarbonyl group (e.g., having 1 to 40 carbon atoms), aryloxycarbonyl group (e.g., having 1 to 40 carbon atoms), heteroaryloxycarbonyl group (e.g., having 1 to 40 carbon atoms), silyl group (e.g., a trialkylsilyl group having 1 to 40 carbon atoms), nitro group, and substituent group A consisting of the groups enumerated here and further substituted with one or more groups enumerated here. Preferable examples of the substituent when the aryl group of the diarylamino group is substituted include the substituents in substituent group A above, and further examples include a cyano group and a substituted amino group.
For specific examples of the compounds and compounds encompassed by the general formula (7), reference can be made to paragraphs 0008 to 0048 of WO2013/154064, paragraphs 0009 to 0030 of WO2015/080183, paragraphs 0006 to 0019 of WO2015/129715, paragraphs 0013 to 0025 of JP-A-2017-119663, and paragraphs 0013 to 0026 of JP-A-2017-119664, all of which are cited herein as part of the present specification.

In addition, a compound represented by the following general formula (8) and emitting delayed fluorescence can also be particularly preferably used as the delayed fluorescence material of the present invention. In a preferred embodiment of the present invention, the compound represented by general formula (8) can be used as the second organic compound.

In the general formula (8), any two of Y ¹ , Y ² and Y ³ are nitrogen atoms and the remaining one is a methine group, or all of Y ¹ , Y ² and Y ³ are nitrogen atoms. ^{Z 1} and Z ² each independently represent a hydrogen atom or a substituent. R ¹¹ to R ¹⁸ each independently represent a hydrogen atom or a substituent, and it is preferable that at least one of R ¹¹ to R ¹⁸ is a substituted or unsubstituted arylamino group or a substituted or unsubstituted carbazolyl group. The benzene ring constituting the arylamino group and the benzene ring constituting the carbazolyl group may form a single bond or a linking group together with R ¹¹ to R ¹⁸ , respectively. In addition, the compound represented by the general formula (8) contains at least two carbazole structures in the molecule. Examples of the substituents that ^{Z 1} and Z ² can take include the substituents in the above-mentioned substituent group A. Specific examples of the substituents which R ¹¹ to R ¹⁸ , the arylamino group, and the carbazolyl group may have include the substituents in the above-mentioned Substituent Group A, a cyano group, a substituted arylamino group, and a substituted alkylamino group. R ¹¹ and R ¹² , R ¹² and R ¹³ , R ¹³ and R ¹⁴ , R ¹⁵ and R ¹⁶ , R ¹⁶ and R ¹⁷ , and R ¹⁷ and R ¹⁸ may be bonded to each other to form a cyclic structure.
Among the compounds represented by formula (8), the compounds represented by formula (9) are particularly useful.

In the general formula (9), any two of Y ¹ , Y ² and Y ³ are nitrogen atoms and the remaining one is a methine group, or all of Y ¹ , Y ² and Y ³ are nitrogen atoms. Z ² represents a hydrogen atom or a substituent. R ¹¹ to R ¹⁸ and R ²¹ to R ²⁸ each independently represent a hydrogen atom or a substituent. At least one of R ¹¹ to R ¹⁸ and/or at least one of R ²¹ to R ²⁸ preferably represents a substituted or unsubstituted arylamino group, or a substituted or unsubstituted carbazolyl group. The benzene ring constituting the arylamino group and the benzene ring constituting the carbazolyl group may form a single bond or a linking group together with R ¹¹ to R ¹⁸ or R ²¹ to R ²⁸ , respectively. Examples of the substituent that ^{Z 2} can take include the substituents in the above-mentioned substituent group A. Specific examples of the substituents which may be adopted by R ¹¹ to R ¹⁸ , R ²¹ to R ²⁸ , the above arylamino group, and the carbazolyl group include the above substituents in the substituent group A, a cyano group, a substituted arylamino group, and a substituted alkylamino group. R ¹¹ and R ¹² , R ¹² and R ¹³ , R ¹³ and R ¹⁴ , R ¹⁵ and R ¹⁶ , R ¹⁶ and R ¹⁷ , R ¹⁷ and R ¹⁸ , R ²¹ and R ²² , R ²² and R ²³ , R ²³ and R ²⁴ , R ²⁵ and R ²⁶ , R ²⁶ and R ²⁷ , and R ²⁷ and R ²⁸ may be bonded to each other to form a cyclic structure.
For the group of compounds included in the general formula (9) and specific examples of the compounds, reference can be made to the compounds described in paragraphs 0020 to 0062 of WO2013/081088, which are incorporated herein by reference, and Appl. Phys. Let, 98, 083302 (2011).

In addition, a compound represented by the following general formula (10) that emits delayed fluorescence can also be particularly preferably used as the delayed fluorescence material of the present invention.

In the general formula (10), R ⁹¹ to R ⁹⁶ each independently represent a hydrogen atom, a donor group, or an acceptor group, at least one of which is the donor group, and at least two of which are the acceptor groups. The substitution positions of the at least two acceptor groups are not particularly limited, but it is preferable that the two acceptor groups are in a meta-position relationship with each other. For example, when R ⁹¹ is a donor group, a structure in which at least R ⁹² and R ⁹⁴ are acceptor groups, or a structure in which at least R ⁹² and R ⁹⁶ are acceptor groups can be preferably exemplified. The acceptor groups present in the molecule may all be the same or different from each other, but it is possible to select a structure in which they are all the same, for example. The number of acceptor groups is preferably 2 to 3, and for example, 2 can be selected. In addition, two or more donor groups may be present, and in that case, the donor groups may all be the same or different from each other. The number of donor groups is preferably 1 to 3, and may be, for example, only 1 or 2. For the explanation and preferred ranges of the donor group and the acceptor group, the explanation and preferred ranges of D and Z in general formula (1) can be referred to. In particular, in general formula (10), the donor group is preferably represented by general formula (3), and the acceptor group is preferably a cyano group or represented by the following general formula (11).

In the general formula (11), Y ⁴ to Y ⁶ each represent a nitrogen atom or a methine group, at least one of which is a nitrogen atom, and preferably all of which represent a nitrogen atom. R ¹⁰¹ to R ¹¹⁰ each independently represent a hydrogen atom or a substituent, and at least one of which is preferably an alkyl group. For the explanation and preferred range of the substituent, the explanation and preferred range of the substituent in the above-mentioned general formula (7) can be referred to. L ¹⁵ represents a single bond or a linking group, and the explanation and preferred range of L in the above-mentioned general formula (3) can be referred to. In a preferred embodiment of the present invention, L ¹⁵ in the general formula (11) is a single bond. * represents the bonding position to the carbon atom (C) constituting the ring skeleton of the ring in the general formula (10).

In another preferred embodiment of the present invention, a compound represented by general formula (12) can be used as the second organic compound.

Among the compounds represented by the general formula (12), particularly preferred compounds are compounds represented by the following general formula (13) and compounds represented by the general formula (14).

In the general formulae (12) to (14), D represents a donor group, A represents an acceptor group, and R represents a hydrogen atom or a substituent. For the explanation and preferred ranges of the donor group and the acceptor group, the corresponding explanation and preferred ranges of the general formula (1) above can be referred to. Examples of the substituent of R include an alkyl group, and an aryl group which may be substituted with one group selected from the group consisting of an alkyl group and an aryl group, or a group consisting of a combination of two or more groups.
Specific examples of donor groups preferred as D in general formulae (12) to (14) are given below. In the following specific examples, * represents the bonding position, and "D" represents deuterium.

Specific examples of the acceptor group preferred as A in the general formulae (12) to (14) are given below. In the following specific examples, * represents the bonding position, and "D" represents deuterium.

Preferred examples of R in the general formulae (12) to (14) are given below. In the following specific examples, * represents the bonding position, and "D" represents deuterium.

(Third organic compound)
The third organic compound is a compound having a lower minimum excited singlet energy than the first organic compound, the second organic compound, and the fourth organic compound. The third organic compound is a compound having a lower minimum excited triplet energy than the first organic compound and the second organic compound, and a higher minimum excited triplet energy than the fourth organic compound. The organic light-emitting element of the present invention emits fluorescence derived from the third organic compound. The light emission from the third organic compound usually includes delayed fluorescence. The maximum component of the light emission from the organic light-emitting element of the present invention is the light emission from the third organic compound. That is, the amount of light emission from the third organic compound is the largest among the light emission from the organic light-emitting element of the present invention. The third organic compound receives energy from the first organic compound in an excited singlet state, the second organic compound in an excited singlet state, the fourth organic compound in an excited singlet state, and the second organic compound that has undergone reverse intersystem crossing from the excited triplet state to an excited singlet state, and transitions to an excited singlet state. In a preferred embodiment of the present invention, the third organic compound receives energy from the second organic compound in an excited singlet state and from the second organic compound which has undergone reverse intersystem crossing from an excited triplet state to an excited singlet state, and transitions to the excited singlet state. The resulting excited singlet state of the third organic compound then emits fluorescence when it returns to the ground state.
The fluorescent material used as the third organic compound is not particularly limited as long as it can receive energy from the first organic compound, the second organic compound, and the fourth organic compound and emit light, and the emitted light may include any of fluorescence, delayed fluorescence, and phosphorescence. It is preferable that the emitted light includes fluorescence or delayed fluorescence, and it is more preferable that the maximum component of the emitted light from the third organic compound is fluorescence.
Two or more third organic compounds may be used as long as they satisfy the conditions of the present invention. For example, by using two or more third organic compounds having different luminescent colors in combination, it is possible to emit light of a desired color. Alternatively, one type of third compound may be used to emit monochromatic light from the third compound.
In the present invention, the maximum emission wavelength of the compound that can be used as the third organic compound is not particularly limited. Therefore, it is possible to appropriately select and use a luminescent material having a maximum emission wavelength in the visible region (380 to 780 nm) or a luminescent material having a maximum emission wavelength in the infrared region (780 nm to 1 mm). A fluorescent material having a maximum emission wavelength in the visible region is preferable. For example, a luminescent material having a maximum emission wavelength in the range of 380 to 570 nm in the region of 380 to 780 nm may be selected and used, a luminescent material having a maximum emission wavelength in the range of 380 to 500 nm may be selected and used, a luminescent material having a maximum emission wavelength in the range of 380 to 480 nm may be selected and used, or a luminescent material having a maximum emission wavelength in the range of 420 to 480 nm may be selected and used.
In a preferred embodiment of the present invention, the compounds are selected and combined such that there is an overlap between the emission wavelength region of the second organic compound and the absorption wavelength region of the third organic compound. In particular, it is preferred that the short wavelength edge of the emission spectrum of the second organic compound overlaps with the long wavelength edge of the absorption spectrum of the third organic compound.
Preferred compounds that can be used as the third organic compound are listed below. In the structural formulas of the following exemplary compounds, Et represents an ethyl group.

Preferred compounds include compounds E1 to E5 and derivatives having their skeletons. Derivatives include compounds substituted with an alkyl group, an aryl group, a heteroaryl group, or a diarylamino group.

The compounds described in paragraphs 0220 to 0239 of WO2015/022974 can also be particularly preferably used as the third organic compound of the present invention.

(Fourth organic compound)
The fourth organic compound is a compound having a lower minimum excited singlet energy than the first organic compound and a higher minimum excited singlet energy than the second organic compound and the third organic compound. The fourth organic compound is also a compound having a lower minimum excited triplet energy than the first organic compound, the second organic compound and the third organic compound. In the organic light-emitting device of the present invention, the fourth organic compound receives energy from the first organic compound, the second organic compound and the third organic compound in the excited triplet state and transitions to the excited triplet state. In particular, since the fourth organic compound receives energy from the second organic compound and the third organic compound in the excited triplet state and can deactivate these triplet excitons, it is possible to suppress the effects of triplet-triplet interaction and triplet-charge interaction in these organic compounds and improve the element durability.

The fourth organic compound may be any compound as long as it satisfies the conditions (a) and (b). In a preferred embodiment of the present invention, the fourth organic compound is a compound represented by the following general formula (15).

In general formula (15), R ^a and R ^b each independently represent a substituted or unsubstituted aryl group. R ^c and R ^d each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted amino group, a halogen atom, a cyano group, or a substituted or unsubstituted silyl group. ^{R c} and R ^d are preferably a hydrogen atom, or a substituted or unsubstituted aryl group.
In the general formula (15), the alkyl group, the alkoxy group, the aryl group, the aryloxy group and the silyl group may have a substituent, which may include an alkyl group, an alkoxy group, an aryl group, an aryloxy group, a halogen atom, a cyano group and a silyl group. Preferred substituents are an alkyl group and an aryl group.
For the aryl group, alkyl group, aryl portion of the aryloxy group, and alkyl portion of the alkoxy group, the explanation and specific examples of the aryl group and alkyl group in the general formula (3) can be referred to. Examples of halogen atoms include fluorine atom, chlorine atom, bromine atom, and iodine atom. The silyl group is preferably a substituted or unsubstituted trialkylsilyl group, and the explanation and specific examples of the alkyl group in the general formula (3) can be referred to for the alkyl portion constituting the trialkylsilyl group. The aryl group may be condensed with a ring containing a heteroatom. Examples of heteroatoms include a nitrogen atom, an oxygen atom, and a sulfur atom.

In a preferred embodiment of the present invention, R ^a and R ^b are the same, and R ^c and R ^d are hydrogen atoms. In another preferred embodiment of the present invention, R ^a and R ^b are different, and R ^c and R ^d are hydrogen atoms.
In a preferred embodiment of the present invention, at least one of R ^c and R ^d is a hydrogen atom.
In a preferred embodiment of the present invention, R ^a , R ^b and R ^c are each independently a substituted or unsubstituted aryl group. In this case, R ^d can be a hydrogen atom. Alternatively, R ^d can be a substituted or unsubstituted aryl group.

In a preferred embodiment of the present invention, the fourth organic compound is a compound represented by the following general formula (16):

In the general formula (16), R ^e , R ^f , R ^g and R ^h each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted amino group, a halogen atom, a cyano group, or a substituted or unsubstituted silyl group. For the description and preferred range of these substituents, the description and preferred range of the corresponding substituents in the general formula (15) can be referred to. In a preferred embodiment of the present invention, R ^e and R ^g each independently represent a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted amino group, a halogen atom, a cyano group, or a substituted or unsubstituted silyl group, and R ^f and R ^h each represent a hydrogen atom. In another preferred embodiment of the present invention, R ^e and R ^g each independently represent a substituted or unsubstituted amino group, and R ^f and R ^h each represent a hydrogen atom. R ^e , R ^f , R ^g and R ^h may all be hydrogen atoms.

In another preferred embodiment of the present invention, the fourth organic compound is a compound represented by the following general formula (17):
General formula (17)
HetAr ¹ -L ²¹ -HetAr ²

In the general formula (17), HetAr ¹ and HetAr ² each independently represent a group represented by the general formula (18), and at least one of them is a group represented by the general formula (18) substituted with the general formula (19). L ²¹ represents a linking group, and the description and preferred range of L in the general formula (3) above can be referred to. In a preferred embodiment of the present invention, L ²¹ in the general formula (17) is an unsubstituted arylene group (having 6 to 16 carbon atoms).

In the general formula (18), X' represents an oxygen atom, a sulfur atom, or N-R ^89. One of R ⁸¹ to R ⁸⁹ is bonded to L, and the remaining R ⁸¹ to R ⁸⁹ each independently represent a hydrogen atom or a substituent. For the description and preferred range of the substituents referred to here, the description and preferred range of the substituents in the general formula (7) above can be referred to. For the description and preferred range of the substituents referred to here, the description and preferred range of R ^c and R ^d in the general formula (15) above can be referred to (except for the case of a hydrogen atom). Note that R ⁸¹ and R ⁸² , R ⁸² and R ⁸³ , R ⁸³ and R ⁸⁴ , R ⁸⁵ and R ⁸⁶ , R ⁸⁶ and R ⁸⁷ , and R ⁸⁷ and R ⁸⁸ may be bonded to each other to form a cyclic structure.

In general formula (19), n represents an integer of 0 or more, and R ⁹¹ to R ⁹⁶ each independently represent a hydrogen atom or a substituent. For the explanation and preferred range of the substituents referred to here, the explanation and preferred range of the substituents in general formula (7) above can be referred to. For the explanation and preferred range of the substituents referred to here, the explanation and preferred range of R ^c and R ^d in general formula (15) above can be referred to (excluding the case where they are hydrogen atoms). n is preferably 0 to 3, and can be, for example, 0 or 1. * represents the bonding position to the carbon atom constituting the ring skeleton of the ring in general formula (18).

Among the compounds represented by the general formula (17), a compound represented by the following general formula (20) can be particularly preferably used.

In the general formula (20), X represents an oxygen atom, a sulfur atom, or N-R ^p . ^{R i} , R ^j , R ^k , R ^m , R ⁿ , and R ^p each independently represent a substituent. For the description and preferred range of the substituents referred to here, the description and preferred range of the substituents in the general formula (18) above can be referred to. In the general formula (20), i, k, m, and n each independently represent an integer of 0 to 4. j represents an integer of 0 to 3. i, j, k, m, and n each independently may be selected, for example, within the range of 0 to 2, may be selected within the range of 0 to 1, or may all be 0. In a preferred embodiment of the present invention, X represents an oxygen atom. In another preferred embodiment of the present invention, X represents an oxygen atom or a sulfur atom, and is bonded to the central benzene ring of the general formula (20) at the 2-position of the dibenzofuran ring or dibenzothiophene ring containing X. In another preferred embodiment of the invention, the three-ring structure containing X is attached to the central benzene ring at the meta position of the 9-carbazolyl group.

In a preferred embodiment of the present invention, the fourth organic compound is a symmetrical compound.
Two or more types of the fourth organic compound may be used as long as they satisfy the conditions (a) and (b).

Preferred compounds that can be used as the fourth organic compound are listed below.

(Light Emitting Layer)
The light-emitting layer of the organic light-emitting device of the present invention includes a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound that satisfy the conditions (a) and (b). The light-emitting layer can be configured to not include compounds that transfer electric charge or energy or metal elements other than the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound. The light-emitting layer can also be configured only from the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound. Furthermore, the light-emitting layer can also be configured only from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, oxygen atoms, and sulfur atoms. For example, the light-emitting layer can be configured only from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, and oxygen atoms. For example, the light-emitting layer can be configured only from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, and sulfur atoms. For example, the light-emitting layer can be configured only from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, and sulfur atoms. For example, the light-emitting layer can be configured only from compounds consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, and sulfur atoms. For example, the light-emitting layer can be composed of only a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and sulfur atoms. For example, the light-emitting layer can be composed of only a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and nitrogen atoms. Alternatively, the first organic compound, the second organic compound, and the fourth organic compound contained in the light-emitting layer can each independently be a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms, and sulfur atoms. For example, the first organic compound, the second organic compound, and the fourth organic compound can each independently be a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and oxygen atoms. For example, the first organic compound, the second organic compound, and the fourth organic compound can each independently be a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and sulfur atoms. For example, the first organic compound, the second organic compound, and the fourth organic compound can each independently be a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, and sulfur atoms.
The light-emitting layer may be formed by co-evaporating the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound, or may be formed by a coating method using a solution in which the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound are dissolved. When forming the light-emitting layer by co-evaporation, two or more of the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound may be mixed in advance and placed in a crucible or the like to form a deposition source, and the light-emitting layer may be formed by co-evaporation using the deposition source. For example, the second organic compound, the third organic compound, and the fourth organic compound may be mixed in advance to create one deposition source, and the light-emitting layer may be formed by co-evaporating the deposition source and the deposition source of the first organic compound.

(Layer structure of organic light-emitting element)
By forming a light-emitting layer containing the first organic compound, the second organic compound, the third organic compound and the fourth organic compound that satisfy the conditions (a) and (b), it is possible to provide an excellent organic light-emitting element such as an organic photoluminescence element (organic PL element) or an organic electroluminescence element (organic EL element).
The thickness of the light-emitting layer can be, for example, 1 to 15 nm, 2 to 10 nm, or 3 to 7 nm.
The organic photoluminescence element has a structure in which at least a light-emitting layer is formed on a substrate. The organic electroluminescence element has a structure in which at least an anode, a cathode, and an organic layer are formed between the anode and the cathode. The organic layer includes at least a light-emitting layer, and may be composed of only a light-emitting layer, or may have one or more organic layers in addition to the light-emitting layer. Examples of such other organic layers include a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, and an exciton blocking layer. The hole transport layer may be a hole injection transport layer having a hole injection function, and the electron transport layer may be an electron injection transport layer having an electron injection function. A specific structural example of an organic electroluminescence element is shown in FIG. 1. In FIG. 1, 1 represents a substrate, 2 represents an anode, 3 represents a hole injection layer, 4 represents a hole transport layer, 5 represents a light-emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.
When the organic light-emitting element of the present invention is a multi-wavelength emission type organic light-emitting element, the shortest wavelength emission may include delayed fluorescence. Alternatively, the shortest wavelength emission may not include delayed fluorescence.

The following describes each component of the organic electroluminescence element and each layer other than the light-emitting layer.

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

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 more). In some embodiments, the metal is Au. In some embodiments, the conductive transparent material is selected from CuI, indium tin oxide (ITO), _SnO2 , and ZnO. In some embodiments, an amorphous material capable of forming a transparent conductive film, such as IDIXO ( _In2O3 - _ZnO ), is used. In some embodiments, the anode is a thin film. In some embodiments, the thin film is made by evaporation or sputtering. In some embodiments, the film is patterned by a photolithographic method. In some embodiments, if the pattern does not need to be highly accurate (e.g., about 100 μm or more), the pattern may be formed using a mask with a shape suitable for evaporation or sputtering onto 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 the anode, 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.

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), an alloy, a conductive compound, or a combination thereof. In some embodiments, the electrode material is selected from sodium, sodium-potassium alloys, magnesium, lithium, magnesium-copper mixtures, magnesium-silver mixtures, magnesium-aluminum mixtures, magnesium-indium mixtures, aluminum-aluminum oxide (Al ₂ O ₃ ) mixtures, indium, lithium-aluminum mixtures, and rare earth elements. In some embodiments, a mixture of an electron injecting metal and a second metal is used, the second metal being a stable metal with a higher work function than the electron injecting metal. In some embodiments, the mixture is selected from magnesium-silver mixtures, magnesium-aluminum mixtures, magnesium-indium mixtures, aluminum-aluminum oxide (Al ₂ O ₃ ) mixtures, lithium-aluminum mixtures, and aluminum. In some embodiments, the mixture improves electron injection properties and resistance to oxidation. 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 a few hundred ohms or less per unit area. 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, either one of the anode and cathode of the organic electroluminescent device is transparent or semi-transparent to allow emitted light to pass through. In some embodiments, a transparent or semi-transparent electroluminescent device enhances 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, hi some embodiments, an element includes an anode and a cathode, both of which are transparent or semi-transparent.

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 light emitting layer or the hole transport layer, and between the cathode and the light emitting 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 the hole injection material are given below.

Next, preferred examples of compounds that can be used as the electron injection material will be given.

Barrier layer:
A barrier 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 barrier 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 barrier 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 barrier layer prevents excitons from diffusing outside the light-emitting layer. In some embodiments, the electron barrier layer and the hole barrier layer constitute an exciton barrier layer. As used herein, the term "electron barrier layer" or "exciton barrier layer" includes layers that have both the functions of an electron barrier layer and of an exciton barrier layer.

Hole blocking layer:
The hole blocking layer functions as an electron transport layer. In some embodiments, during electron transport, the hole blocking layer prevents holes from reaching the electron transport layer. 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 given below.

Electron Barrier Layer:
The electron blocking layer transports holes. In some embodiments, during hole transport, the electron blocking layer blocks 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 the electron blocking material are given below.

Exciton blocking layer:
The exciton blocking layer prevents excitons generated through the recombination of holes and electrons in the light-emitting layer from diffusing to the charge transport layer. In some embodiments, the exciton blocking layer allows for effective confinement of excitons in the light-emitting layer. In some embodiments, the light emission efficiency of the device is improved. In some embodiments, the exciton blocking layer is adjacent to the light-emitting 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, the layer may be present between the hole transport layer and the light-emitting layer and adjacent to the light-emitting layer. In some embodiments, when the exciton blocking layer is present on the cathode side, the layer may be present between the light-emitting layer and the cathode and adjacent to the light-emitting 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 light-emitting 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 light-emitting 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.

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 the following properties: hole injection or transport property and electron blocking property. 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 given below.

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, fluorenylidene methane 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 polymeric material. Specific examples of preferred compounds that can be used as electron transport materials are given below.

In addition, examples of compounds that can be added to each organic layer are given below. For example, they can be added as stabilizing materials.

Specific examples of preferred materials that can be used in organic electroluminescence elements have been given, but the materials that can be used in the present invention should not be interpreted as being limited to the following exemplary compounds. In addition, even if a compound is given as an example of a material having a specific function, it can also be used as a material having other functions.

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, an electronic device includes an OLED having an anode, a cathode, and at least one organic layer including an emissive layer between the anode and the cathode.
In some embodiments, the compositions described herein may be incorporated into various photosensitive or photoactivated devices, such as OLEDs or optoelectronic devices. In some embodiments, the compositions may be useful in 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).

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 having a mounting surface and an opposing 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 a plurality of OLEDs mounted on a circuit board such that the OLEDs emit light in a plurality of directions. In some embodiments, a portion 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.

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 in two-sided etching to provide pixels with unique aspect ratios. The screen (also called a mask) is used in the manufacturing process of an OLED display. The corresponding artwork pattern design allows for the placement of very steep narrow tie bars between pixels in the vertical direction, as well as large wide angled 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.
The internal patterning of the pixel allows for the construction of three-dimensional pixel openings of various aspect ratios in the horizontal and vertical directions. Additionally, the use of imaged "stripes" or halftone circles in the pixel area protects etching in certain areas until those particular patterns are undercut and removed from the substrate. At that point, all pixel areas are treated with similar etch rates, but the depth varies with the halftone pattern. Varying the size and spacing of the halftone patterns allows etching with different protection rates within the pixel, allowing for the localized deep etching required to create steep vertical bevels.
The preferred material for the deposition mask is Invar. Invar is 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 and 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.

How the device is manufactured:
OLED displays are generally manufactured by forming a large mother panel and then cutting the mother panel into cell panels. Usually, 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, coating a planarizing film on the TFT, sequentially forming a pixel electrode, a light-emitting layer, a counter electrode and an encapsulation layer, and then cutting the cell panel from the mother panel.
OLED displays are generally manufactured by forming a large mother panel and then cutting the mother panel into cell panels. Usually, 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, coating a planarizing film on the TFT, sequentially forming a pixel electrode, a light-emitting layer, a counter electrode and an encapsulation layer, and then cutting the cell panel from the mother panel.

In another aspect of the invention, there is provided a method for manufacturing an organic light emitting diode (OLED) display, the method comprising the steps of:
forming a barrier layer on a base substrate of a mother panel;
forming a plurality of display units on the barrier layer in the form of a cell panel;
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 ends 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 cut softly into cell panels.
In some embodiments, the thin film transistor (TFT) layer has a light-emitting layer, a gate electrode, and source/drain electrodes. Each of the plurality of display units may have 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 at the same time as 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 the display unit or the encapsulation layer.

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 prior to forming a barrier layer on the other surface of the base substrate, and separating the carrier substrate from the base substrate prior to 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 for covering 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 is in direct contact with the base substrate and a remaining portion of the organic film is in contact with the barrier layer while surrounding the edge of the barrier layer.

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 a 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 the penetration of external moisture may be formed into a thin-film encapsulation structure in which organic films and inorganic films are alternately laminated. In some embodiments, the encapsulation layer has a thin-film encapsulation structure in which a plurality of thin films are laminated. In some embodiments, the organic film applied to the interface portion is disposed at an interval with each of the plurality of 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 end of the barrier layer.

In one embodiment, the OLED display is flexible and uses a flexible base substrate formed from polyimide, hi some embodiments, the base substrate is formed on a carrier substrate formed from a glass material, and the carrier substrate is then separated.
In some embodiments, a barrier layer is formed on a 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, the base substrate is formed on all surfaces of the mother panel, while 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.

In some embodiments, the manufacturing method further includes a step of cutting along the interface, where a groove is formed in the barrier layer and at least a portion of the organic film is formed in the groove, and the groove does not penetrate the base substrate. In some embodiments, the TFT layer of each cell panel is formed, and a passivation layer, which is an inorganic film, and a planarization film, which is an organic film, are disposed on the TFT layer to cover the TFT layer. At the same time that the planarization film, for example made of polyimide or acrylic, is formed, the groove of the interface is covered with an organic film, for example made of polyimide or acrylic. This prevents cracks from occurring when each cell panel is cut along the groove at the interface by having the organic film absorb the impact that occurs. That is, if all the barrier layers are completely exposed without the organic film, when each cell panel is cut along the groove at the interface, the impact that occurs is transmitted to the barrier layer, thereby increasing the risk of cracks. However, in one embodiment, the interface grooves between the barrier layers are covered with an organic film to absorb shocks 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 planarizing film covering the interface grooves are spaced apart from each other. For example, if the organic film and planarizing film were connected to each other as one layer, there would be a risk of external moisture penetrating the display unit through the planarizing film and the remaining organic film, so the organic film and planarizing film are spaced apart from each other such that the organic film is spaced apart from the display unit.

In some embodiments, the display unit is formed by forming a light-emitting unit, and the 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, the barrier layer is prevented from cracking during cutting.
In some embodiments, the methods reduce product defect rates and stabilize product quality.
Another aspect 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.

(Method of Designing a Light-Emitting Composition)
The present application also provides methods for designing compositions of the present invention that have long luminescence lifetimes and excellent stability.
The method for designing a light-emitting composition of the present invention includes the following steps 1 to 3.
[Step 1] Evaluating the luminous efficiency and lifetime of a composition that contains a first organic compound, a second organic compound that is a delayed fluorescent material, a third organic compound, and a fourth organic compound, and that satisfies the conditions (a) and (b);
[Step 2] Evaluating the luminous efficiency and lifetime of a composition in which at least one of the first organic compound, the second organic compound as a delayed fluorescent material, the third organic compound, and the fourth organic compound is changed within a range satisfying the conditions (a) and (b), at least once;
[Step 3] The combination with the best evaluated luminous efficiency and lifetime is selected.

The luminous efficiency and life may be evaluated by actually making the luminous composition emit light, or may be evaluated by calculation. In addition, the luminous composition may be actually made to emit light and evaluated using a calculation method. It is preferable to perform the evaluation from a comprehensive perspective using the high practicality as an index. In the design method of the luminous composition of the present invention, it is necessary to select and replace the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound within a range that satisfies the condition (a) and the condition (b). In addition, it is necessary to select and replace the organic compound from a delayed fluorescent material secondly. It is preferable to replace the compound in step 2 with a compound that is likely to obtain a better evaluation. Step 2 may be performed, for example, 10 times or more, 100 times or more, 1000 times or more, or 10000 times or more.
The method for designing a light-emitting composition of the present invention can be stored as a program and used. The program can be stored in a recording medium, and can also be transmitted and received by electronic means.

The features of the present invention will be described in more detail below with reference to examples. The materials, processing contents, processing procedures, etc. shown below can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. The evaluation of the emission characteristics was performed using a source meter (Keithley: 2400 series), a semiconductor parameter analyzer (Agilent Technologies: E5273A), an optical power meter measuring device (Newport: 1930C), an optical spectrometer (Ocean Optics: USB2000), a spectroradiometer (Topcon: SR-3) and a streak camera (Hamamatsu Photonics C4334 type). The lowest excited singlet energy E _S1 and the lowest excited triplet energy E _T1 of the compounds used in the following examples and comparative examples are as shown in the following table.

Example 1
On a glass substrate on which an anode made of indium tin oxide (ITO) having a thickness of 100 nm was formed, each thin film was laminated by vacuum deposition at a vacuum degree of 1×10 ⁻⁶ Pa. First, HATCN was formed on ITO to a thickness of 10 nm, NPD was formed thereon to a thickness of 30 nm, and TrisPCz was formed thereon to a thickness of 10 nm. Next, compound H1 was formed to a thickness of 5 nm. Furthermore, compound H1 (68.5 wt%), compound T13 (30 wt%), compound E1 (0.5 wt%) and compound Z1 (1 wt%) were co-deposited from different deposition sources to form a light-emitting layer having a thickness of 30 nm. Next, SF3TRZ was formed as a hole blocking layer having a thickness of 10 nm. Subsequently, SF3TRZ and Liq were co-deposited from different deposition sources to form an electron transport layer having a thickness of 30 nm. At this time, the weight ratio of SF3TRZ:Liq was 7:3. Furthermore, Liq was formed to a thickness of 2 nm, and then aluminum (Al) was evaporated to a thickness of 100 nm to form a cathode. In this way, the organic electroluminescence element of Example 1 was produced.

Example 2
An organic electroluminescence element of Example 2 was prepared in the same manner as in Example 1, except that the concentrations of the compound H1 (64.5% by weight), the compound T13 (30% by weight), the compound E1 (0.5% by weight) and the compound Z1 (5% by weight) in the light-emitting layer were changed.

(Example 2, Comparative Examples 1 and 2)
Organic electroluminescence elements of Example 2, Comparative Example 1, and Comparative Example 2 were prepared in the same manner as in Example 1, except that the concentration of the light-emitting layer was changed as shown in Table 2 below.

When electricity was applied to each of the produced organic electroluminescence elements, the emission of delayed fluorescence derived from the third organic compound E1 was observed (all had a maximum emission wavelength of 471 nm). The organic electroluminescence element of Comparative Example 1 had a low external quantum efficiency, so other performances were not evaluated. On the other hand, the LT95 of Comparative Example 2, Example 1, and Example 2, which showed significantly higher external quantum efficiency than Comparative Example 1, was measured at 2 mA / cm ^2. As a result, it was confirmed that Example 1 had a lifespan 2.83 times longer than Comparative Example 2, and Example 2 had a lifespan 12.4 times longer than Comparative Example 2. It was also confirmed that increasing the concentration of compound Z1 further extended the lifespan.

The present invention can provide an organic light-emitting element that has a long life and is stable. Therefore, the present invention has a high industrial applicability.

Reference Signs List 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Cathode

Claims (15)

An organic light-emitting device having a light-emitting layer including a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound, which satisfy the following conditions (a) and (b):
the second organic compound is a delayed fluorescent material,
The organic light-emitting element, wherein a maximum component of the light emitted from the organic light-emitting element is light emitted from the third organic compound.
Condition (a) E _S1 (1)>E _S1 (4)>E _S1 (2)>E _S1 (3)
Condition (b) E _T1 (1)>E _T1 (2)>E _T1 (3)>E _T1 (4)
(In the above formula,
E _S1 (1) represents the lowest excited singlet energy of the first organic compound (unit: eV) .
E _S1 (2) represents the lowest excited singlet energy of the second organic compound (unit: eV) .
E _S1 (3) represents the lowest excited singlet energy of the third organic compound (unit: eV) .
E _S1 (4) represents the lowest excited singlet energy of the fourth organic compound (unit: eV) .
E _T1 (1) represents the lowest excited triplet energy of the first organic compound (unit: eV) .
E _T1 (2) represents the lowest excited triplet energy of the second organic compound (unit: eV) .
E _T1 (3) represents the lowest excited triplet energy of the third organic compound (unit: eV) .
E _T1 (4) represents the lowest excited triplet energy of the fourth organic compound (unit: eV) . The organic light-emitting device according to claim 1 , further satisfying the following condition (c):
Condition (c) Conc(1)>Conc(2)>Conc(4)
(In the above formula,
Conc(1) represents the concentration of the first organic compound in the light-emitting layer (unit: weight %) .
Conc(2) represents the concentration of the second organic compound in the light-emitting layer (unit: weight %) .
Conc(4) represents the concentration of the fourth organic compound in the light-emitting layer (unit: weight %) . The organic light-emitting device according to claim 2 , further satisfying the following condition (c1):
Condition (c1) Conc(1)>Conc(2)>Conc(4)>Conc(3)
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer (unit: weight %) . The organic light-emitting device according to claim 2 or 3, further satisfying the following condition (d):
Condition (d) Conc(2)/Conc(3)>5
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer (unit: weight %) . The organic light-emitting device according to any one of claims 2 to 4, further satisfying the following condition (e):
Condition (e) Conc(4)/Conc(3)>1.5
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer (unit: weight %) . The organic light-emitting device according to any one of claims 1 to 5, further satisfying the following condition (f):
Condition (f) Conc(4)≦5% by weight
(In the above formula, Conc(4) represents the concentration of the fourth organic compound in the light-emitting layer (unit: weight %) . The organic light-emitting device according to any one of claims 1 to 6, further satisfying the following condition (g):
Condition (g) Conc(3)≦1% by weight
(In the above formula, Conc(3) represents the concentration of the third organic compound in the light-emitting layer (unit: weight %) . 8. The organic light-emitting element according to claim 1, wherein the second organic compound has an energy difference ΔE _st between the lowest excited singlet state and the lowest excited triplet state at 77 K of 0.3 eV or less. 9. The organic light-emitting device according to claim 1, wherein the third organic compound has an energy difference ΔE _st between the lowest excited singlet state and the lowest excited triplet state at 77 K of 0.3 eV or less. The organic light-emitting element according to any one of claims 1 to 9, wherein the light-emitting layer is composed only of a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, boron atoms, oxygen atoms, and sulfur atoms. The organic light-emitting device according to any one of claims 1 to 10, wherein the first organic compound, the second organic compound, and the fourth organic compound are each independently a compound consisting of atoms selected from the group consisting of carbon atoms, hydrogen atoms, and nitrogen atoms. The organic light-emitting element according to any one of claims 1 to 11, wherein the fourth organic compound is a compound composed only of carbon atoms and hydrogen atoms. The organic light-emitting device according to any one of claims 1 to 12, wherein the second organic compound includes a cyanobenzene structure. [Step 1] Evaluating the luminous efficiency and lifetime of a composition that contains a first organic compound, a second organic compound, a third organic compound, and a fourth organic compound, which are delayed fluorescent materials, and that satisfies the following conditions (a) and (b):
[Step 2] Evaluating the luminous efficiency and lifetime of a composition in which at least one of the first organic compound, the second organic compound, the third organic compound, and the fourth organic compound, which are delayed fluorescent materials, is changed within a range that satisfies the following conditions (a) and (b), at least once:
[Step 3] Select the combination with the best evaluated luminous efficiency and lifetime.
A method for designing a light-emitting composition, comprising each of the steps.
Condition (a) E _S1 (1)>E _S1 (4)>E _S1 (2)>E _S1 (3)
Condition (b) E _T1 (1)>E _T1 (2)>E _T1 (3)>E _T1 (4)
(In the above formula,
E _S1 (1) represents the lowest excited singlet energy of the first organic compound (unit: eV) .
E _S1 (2) represents the lowest excited singlet energy of the second organic compound (unit: eV) .
E _S1 (3) represents the lowest excited singlet energy of the third organic compound (unit: eV) .
E _S1 (4) represents the lowest excited singlet energy of the fourth organic compound (unit: eV) .
E _T1 (1) represents the lowest excited triplet energy of the first organic compound (unit: eV) .
E _T1 (2) represents the lowest excited triplet energy of the second organic compound (unit: eV) .
E _T1 (3) represents the lowest excited triplet energy of the third organic compound (unit: eV) .
E _T1 (4) represents the lowest excited triplet energy of the fourth organic compound (unit: eV) . A program for carrying out the method according to claim 14.