WO2019022120A1

WO2019022120A1 - Singlet fission material, triplet sensitizer, compound, and thin film

Info

Publication number: WO2019022120A1
Application number: PCT/JP2018/027847
Authority: WO
Inventors: 弘典梶; 功將志津; 壮太郎檜垣; 安達　千波矢; 憲一合志
Original assignee: 国立大学法人九州大学
Priority date: 2017-07-25
Filing date: 2018-07-25
Publication date: 2019-01-31
Also published as: JP7214142B2; JPWO2019022120A1

Abstract

The compound represented by general formula (1) is useful as a singlet fission material and as a triplet sensitizer. R1 in general formula (1) represents a substituted or unsubstituted aryl group. One of R2and R3 is a hydrogen atom, while the other represents a substituted or unsubstituted aryl group.

Description

Singlet fission materials, triplet sensitizers, compounds and thin films

The present invention relates to compounds useful as singlet fission materials and triplet sensitizers.

Since acenes having a structure in which a plurality of benzene rings are linearly condensed have a wide π conjugated system, applications as functional materials of organic devices such as organic semiconductor materials and light emitting materials are expected, and useful applications are Research is in progress to find out. Among them, there are some examples in which a compound having a tetracene skeleton is used as a material of an organic light emitting device.

For example, for a compound having the following structure, Patent Document 1 describes an example in which this compound is used as a dopant of a light emitting layer, and Patent Document 2 describes an example in which this compound is used in a hole transport layer ing.

Japanese Patent Application Laid-Open No. 2006-114844 JP 2007-258462 A

As described above, the compound having a tetracene skeleton is known to be used as a dopant of a light emitting layer of an organic light emitting device or a hole transporting material. However, the properties of the compound having a tetracene skeleton have not been sufficiently studied, and it is considered that many untouched areas remain for its usefulness. Therefore, in order to develop new materials having higher utility, it is required to conduct further research on compounds having a tetracene skeleton.
Under these circumstances, we investigated the characteristics and usefulness of the compound having a tetracene skeleton, and conducted intensive studies for the purpose of finding out new applications.

As a result of intensive studies, the present inventors have found that tetracene compounds having a specific structure have useful properties of causing singlet splitting and increasing the number of triplet excitons. And it came to the thought that the organic device with high efficiency will be realized by utilizing the characteristic of the tetracene compound. The present invention has been proposed based on these findings, and specifically has the following configuration.

[1] A singlet fission material comprising a compound represented by the following general formula (1).

[In the general formula (1), R ¹ represents a substituted or unsubstituted aryl group. One of R ² and R ³ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. ]
[2] The singlet fission material according to [1], wherein R ¹ and R ² are each independently an unsubstituted aryl group.
[3] The singlet fission material according to [1] or [2], wherein R ¹ and R ² are the same.
[4] A triplet sensitizer comprising the compound represented by the following general formula (1).

[In the general formula (1), R ¹ represents a substituted or unsubstituted aryl group. One of R ² and R ³ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. ]
[5] The triplet sensitizer described in [4], wherein R ¹ and R ² are each independently an unsubstituted aryl group.
[6] The triplet sensitizer according to [4] or [5], wherein R ¹ and R ² are the same.
[7] A compound represented by the following general formula (2).

[In the general formula (2), one of R ⁴ and R ⁵ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. One of R ⁶ and R ⁷ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. n is 0 or 1. ]
[8] The compound according to [7], wherein R ⁴ and R ⁶ are each independently an unsubstituted aryl group.
[9] The compound according to [7] or [8], wherein R ⁴ and R ⁶ are the same.
[10] A thin film containing the compound represented by the above general formula (2).

The compounds in the present invention are useful as singlet fission materials and triplet sensitizers. High efficiency can be realized by using the singlet fission material or the triplet sensitizer of the present invention as the functional material of the organic device.

It is a schematic sectional drawing which shows the layer structural example of an organic electroluminescent element. It is the light absorption spectrum of each toluene solution containing the compound 1 or the compound 2, and the emission spectrum of the thin film of ACRXTN and mCBP. FIG. 10 shows the emission spectra of respective toluene solutions containing Compound 1, Compound 3 or Compound 4. FIG. It is an emission spectrum of each thin film in which the concentration of compound 1 is 0% by weight, 6% by weight, 30% by weight or 100% by weight. It is a transient absorption decay curve at 530 nm of a chloroform solution in which the concentration of Compound 1 is 5 × 10 ⁻² mol / L. It is a transient absorption decay curve at 530 nm of a chloroform solution in which the concentration of Compound 1 is 1 × 10 ⁻¹ mol / L. The concentration of the compound 1 is 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, 2.5 × 10 ⁻² mol / L, 5 × 10 ⁻² mol / L, or 1 × 10 ⁻¹ mol It is a transient absorption decay curve in 530 nm of each chloroform solution which is / L. For each chloroform solution in which the concentration of Compound 1 is 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, or 2.5 × 10 ⁻² mol / L, change in absorbance ΔABS at 520 nm It is a correlation diagram which plotted the axis and excitation light intensity as a horizontal axis. The concentration of the compound 1 is 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, 2.5 × 10 ⁻² mol / L, 5 × 10 ⁻² mol / L, or 1 × 10 ⁻¹ FIG. 6 is a correlation diagram in which the amount of change in absorbance ΔABS at 530 nm is plotted on the vertical axis and the intensity of excitation light on the horizontal axis for certain chloroform solutions. 5 is a graph showing the concentration dependency of the triplet exciton generation efficiency IS _ISC of Compound 1. FIG.

Hereinafter, the contents of the present invention will be described in detail. Although the description of the configuration requirements described below may be made based on typical embodiments and examples of the present invention, the present invention is not limited to such embodiments and examples. In the present specification, a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value. Also, the isotope species of the hydrogen atom present in the molecule of the compound used in the present invention is not particularly limited. For example, all hydrogen atoms in the molecule may be ¹ H, or some or all of the hydrogen atoms may be ² H (Deuterium D) may be used.
Furthermore, in the present specification, the “fluorescent material” is a light emitting material in which the emission intensity of fluorescence is higher than that of phosphorescence when light emission is observed at 20 ° C. The “phosphorescent material” is When light emission is observed at 20 ° C., it is a light emitting material in which the light emission intensity of phosphorescence is higher than the light emission intensity of fluorescence. The “delayed fluorescent material” is a material in which both fluorescence having a short emission lifetime at 20 ° C. and fluorescence having a long emission lifetime (delayed fluorescence) are observed. Normal fluorescence (fluorescence that is not delayed fluorescence) has an emission lifetime on the order of ns, and phosphorescence generally has an emission lifetime on the order of ms, so that fluorescence and phosphorescence can be distinguished by the emission lifetime. In addition, a light emitting organic compound other than the organometallic complex is usually a fluorescent material or a delayed fluorescent material. Furthermore, in the present specification, “thin film” means a film having a thickness of 1000 nm or less, preferably 500 nm or less, and more preferably 100 nm or less.

[Compound represented by General Formula (1)]
The singlet fission material and the triplet sensitizer of the present invention are characterized by comprising the compound represented by the following general formula (1).

In the general formula (1), R ¹ represents a substituted or unsubstituted aryl group. One of R ² and R ³ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. The substituted or unsubstituted aryl group represented by one of R ² and R ³ and the substituted or unsubstituted aryl group represented by R ¹ may be the same as or different from each other, but are preferably the same. The aryl group (a part excluding a substituent in the case of a substituted aryl group) in the "substituted or unsubstituted aryl group" preferably has 6 to 26 ring atoms, more preferably 6 to 22 and more preferably 6 to 18 Is more preferred. Specific examples of the aryl group include phenyl group, 1-naphthalenyl group, 2-naphthalenyl group, 1-anthracenyl group, 2-anthracenyl group, 9-anthracenyl group, 1-tetracenyl group, 2-tetracenyl group, 5-tetracenyl group, 1-pyrenyl group and 2-pyrenyl group can be mentioned.
The aryl group that can be taken by R ¹ to R ³ may be substituted or unsubstituted with a substituent, but at least one of R ¹ to R ³ is preferably an unsubstituted aryl group It is preferable that all of the substituted or unsubstituted aryl groups that R ¹ to R ³ can be substituted be unsubstituted aryl groups. When the aryl group has a substituent, the substituent is preferably an alkyl group or an aryl group. The alkyl group may be linear, branched or cyclic. The preferred carbon number is 1 to 20, more preferably 1 to 10, and still more preferably 1 to 6. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group and the like can be exemplified. For the preferable range and specific example of the aryl group, the preferable range and specific example of the aryl group in the above-mentioned "substituted or unsubstituted aryl group" can be referred to. Moreover, the alkyl group and aryl group which are substituents may be further substituted, and an alkyl group and an aryl group can be mentioned preferably as a substituent in that case.
The total carbon number of the substituted or unsubstituted aryl group that can be taken by R ¹ to R ³ is preferably 6 to 32, more preferably 6 to 28, and still more preferably 6 to 24. Examples of substituted aryl groups that R ¹ to R ³ may be include alkylphenyl group (tolyl group, tert-butylphenyl group etc.), biphenyl group, alkylbiphenyl group (methylbiphenyl group, tert-butylbiphenyl group etc.), ter Phenyl group, alkyl terphenyl group (methyl terphenyl group, tert-butyl terphenyl group etc.), phenyl naphthyl group, alkyl naphthyl group (methyl naphthyl group, tert-butyl naphthyl group etc.), phenyl anthracenyl group, naphthyl anthracene Cenyl group, alkyl anthracenyl group (methyl anthracenyl group, tert-butyl anthracenyl group, etc.), phenyl tetracenyl group, naphthyl tetracenyl group, alkyl tetracenyl group (methyl tetracenyl group, (tert-butyl tetracenyl group etc.), phenyl pyrenyl group, naphthyl pyrenyl group, Rukirupireniru group (Mechirupireniru group, tert- Buchirupireniru group) can be exemplified.

Below, the specific example of a compound represented by General formula (1) is illustrated. However, the compounds represented by the general formula (1) which can be used in the present invention should not be construed as being limited by these specific examples.

[Compound represented by General Formula (2)]
Among the compounds represented by the general formula (1), the compound represented by the following general formula (2) is a novel compound.

In the general formula (2), one of R ⁴ and R ⁵ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. One of R ⁶ and R ⁷ is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. n is 0 or 1. The description and the preferred range of the substituted or unsubstituted aryl group in the general formula (2) and the specific examples can be referred to the description of the substituted or unsubstituted aryl group in the general formula (1). The substituted or unsubstituted aryl group represented by one of R ⁴ and R ⁵ and the substituted or unsubstituted aryl group represented by one of R ⁶ and R ⁷ may be the same or different.
Preferred examples of the compound represented by the general formula (2) include compounds wherein R ⁴ and R ⁶ are each independently a substituted or unsubstituted aryl group, and R ⁵ and R ⁷ are a hydrogen atom. .

[Synthesis Method of Compound Represented by General Formula (2)]
The compounds represented by the general formula (2) can be synthesized by combining known reactions. For example, a compound in which n in the general formula (2) is 0 and R ⁴ and R ⁶ are the same aryl group can be synthesized by the reaction shown in the following reaction formula.

For the explanation of R in the above reaction formula, the description of the substituted or unsubstituted aryl group in the general formula (2) can be referred to. The bitetracenone used here may be either cis or trans, or a mixture of cis and trans. The details of the above reaction can be referred to the synthesis examples described below. Moreover, the compound represented by General formula (2) can also be synthesize | combined by combining other well-known synthetic | combination reaction.

[Utility of Compound Represented by General Formula (1)]
The compounds represented by the general formula (1) are useful as singlet fission materials.
In the present specification, “singlet splitting” refers to a phenomenon in which a singlet exciton is split into two triplet excitons, and “singlet splitting material” in the present invention means an excited singlet state S. _A material that causes singlet splitting when excited to one. The fact that it is a singlet fission material means, for example, that each thin film formed by adding the compound represented by General Formula (1) in different concentrations to the host material was irradiated with excitation light to measure the photoluminescence quantum yield Sometimes, it can be confirmed by the correlation that the photoluminescence quantum yield decreases as the concentration of the compound increases.
Here, when the compound undergoes singlet splitting, as a result, the number of triplet excitons increases. Thus, the compound represented by the general formula (1), which is a singlet fission material, is also useful as a triplet sensitizer. That is, the "triplet sensitizer" in the present invention means the material to increase the number of causing the singlet fission triplet excitons when excited to an excited singlet state S _1. In the following description, the effect of increasing the number of triplet excitons by singlet splitting may be referred to as "triplet exciton sensitization effect". The fact that it is a triplet sensitizer means that the solution containing the compounds represented by the general formula (1) in different concentrations is irradiated with pump light as excitation light, and immediately thereafter, the change in absorbance to the probe light when measuring the amount .DELTA.ABS, confirmed by from the .DELTA.ABS using the following formula (I) is a triplet exciton generation efficiency [Phi _ISC obtained, correlation increases with the concentration of the compound is high is observed can do. “Absorbance change amount ΔABS” means the change amount of absorbance based on the absorbance ABS ₀ with respect to probe light before pump light irradiation, and here, from absorbance ABS _{EX with} respect to probe light measured immediately after pump light irradiation ABS The value minus ₀ . For the details of the measurement method of ΔABS, the description in the column of Examples can be referred to.

In the formula (I), IS _ISC indicates the triplet exciton generation efficiency, I ₀ indicates the intensity of pump light (excitation light intensity) irradiated to the solution, and ΔABS indicates the change in absorbance (ABS _EX -ABS ₀ ) Denotes the molar absorption coefficient of the target compound at the pump light wavelength, ε _T denotes the molar absorption coefficient of the target compound at the probe light wavelength, c denotes the concentration of the target compound in the solution, and L denotes the measurement The optical path length (1 mm) of the used cell is shown.
Here, light of 337 nm in the absorption band of the target compound can be used as pump light, and light of 510-540 nm in the absorption band of the target compound can be used as probe light.
By using a triplet sensitizer composed of the compound represented by the general formula (1) for the material of the organic device, the efficiency can be dramatically improved.

For example, by using a triplet sensitizer composed of a compound represented by the general formula (1) as a material of the organic semiconductor layer of the organic solar cell, light irradiated to the organic semiconductor layer in the organic solar cell is The compound represented by the general formula (1) can be absorbed to form a singlet exciton, and a triplet amplification system can be realized in which the singlet exciton is split into two triplet excitons. In such an organic solar cell, triplet excitons are efficiently generated by light irradiation, and since the triplet excitons have a long lifetime, triplet excitation is generated at the p / n junction interface of the organic semiconductor layer. The probability of charge arrival and separation of charge is high, and holes and electrons can be efficiently extracted to the electrode. Therefore, compared with the organic solar cell which does not contain a triplet sensitizer, high photoelectric conversion efficiency can be obtained.

In addition, by using a triplet sensitizer composed of a compound represented by the general formula (1) as a host material of the light emitting layer of the organic light emitting device, the organic light emitting device was formed with the host material of an excited singlet state It is possible to realize an excited triplet energy amplification system in which a singlet exciton is split into two triplet excitons and their excited triplet energy is transferred to the light emitting material by the Dexter transfer mechanism. In such an organic light emitting device, the excitation triplet energy is efficiently generated by the excitation of the host material and supplied to the light emitting material, so that the host material does not have the triplet exciton sensitizing effect. In comparison, high luminous efficiency can be obtained. Here, the light emitting material may be any phosphorescent material that can emit light upon receiving excitation triplet energy from the host material, and may emit light by radiative relaxation from the excitation triplet state, or the excitation triplet state It may be a delayed fluorescent material which emits light by radiative relaxation from the excited singlet state after producing an inverse intersystem crossing from the light emitting element to the excited singlet state.
In the organic light emitting device using such a triplet sensitizer of the present invention as a host material of the light emitting layer, in order to obtain higher luminous efficiency, transfer of excited triplet energy from the host material to the light emitting material is facilitated. It is preferable to confine the excited triplet energy received by the light emitting material in the molecule of the light emitting material. Therefore, the host material preferably has a lowest excitation triplet energy level higher than the lowest excitation triplet energy level of the light emitting material. Furthermore, in order to confine the excited singlet energy generated in the light emitting material in the molecule of the light emitting material, the host material is required to have its lowest singlet excitation energy level higher than the lowest singlet excitation energy level of the light emitting material preferable.
In addition, a singlet sensitizing layer containing a singlet sensitizer may be provided next to the light emitting layer in the organic light emitting device using the triplet sensitizer of the present invention as a host material of the light emitting layer, and further An electron and triplet exciton blocking layer may be provided between the light emitting layer and the singlet sensitizing layer. Here, the “singlet sensitizer” refers to a material having a generation probability [S ₁ / (S ₁ + T ₁ )] of the excited singlet state S ₁ generated by current excitation larger than 25%, for example A delayed fluorescent material can be used. The singlet sensitizer preferably has a lowest excited singlet energy level higher than the lowest excited singlet energy level of the host material, and the lowest excited singlet energy level and the lowest excited triplet energy level The difference ΔE _ST is preferably 0.3 eV or less. As a specific example of a singlet sensitizer, ACRXTN mentioned later can be mentioned. The “electron and triplet exciton blocking layer” refers to a layer having a function of blocking the transfer of electrons and triplet excitons from the singlet sensitizing layer to the light emitting layer. By providing these layers, excited singlet energy is efficiently generated in the singlet sensitizing layer and supplied to the host material (triplet sensitizer) of the light emitting layer, so that triplet excitons are generated. The efficiency is further enhanced, and higher luminous efficiency can be obtained.

Moreover, the triplet sensitizer which consists of a compound represented by General formula (1) can be used also as an assist dopant of the light emitting layer of an organic light emitting element. Here, “assist dopant” has a function of receiving excited singlet energy from a host material, converting it into excited triplet energy, and transferring the excited triplet energy to a light emitting material. A light emitting material which receives excitation triplet energy from the assist dopant is excited by the energy to emit light. When a triplet sensitizer composed of a compound represented by the general formula (1) is used as such an assist dopant, singlet excitons generated when the assist dopant receives excited singlet energy become two triplet excitons. Since the light is split and thereby the number of triplet excitons is increased, the light emitting material can be more efficiently supplied with excitation triplet energy. Therefore, higher luminous efficiency can be obtained as compared with the case of using an assist dopant having no triplet exciton sensitization effect. In the system using this assist dopant, a usual host material can be used as a host material, but it is preferable to use a delayed fluorescent material because it can efficiently generate excited singlet energy. The light-emitting material may be any material as long as it can emit light by receiving excitation triplet energy from the assist dopant, and a phosphorescent material or a delayed fluorescent material can be used.
Moreover, in the organic light emitting device using the triplet sensitizer of the present invention as the assist dopant, in order to obtain higher luminous efficiency, transfer of excited singlet energy from the host material to the assist dopant, transfer from the assist dopant to the light emitting material It is preferable to facilitate the transfer of the excited triplet energy and to confine the excited triplet energy received by the light emitting material in the molecule of the light emitting material. Therefore, the host material preferably has a lowest excited singlet energy level higher than the lowest excited singlet energy level of the assist dopant, and a lowest excited triplet energy level corresponds to the lowest excited triplet energy quasi of the assist dopant. And higher than the lowest excitation triplet energy level of the luminescent material. The assist dopant preferably has a lowest excitation triplet energy level higher than the lowest excitation triplet energy level of the light emitting material. Furthermore, in order to confine the excited singlet energy generated in the light emitting material in the molecule of the light emitting material, the host material and the assist dopant have their lowest singlet excitation energy level higher than the lowest singlet excitation energy level of the light emitting material Higher is more preferred.

As described above, since the compound represented by the general formula (1) causes singlet splitting to increase the number of triplet excitons, an organic device other than the organic solar cell and the organic light emitting element, for example, an organic imaging element Even when used as a material for a vein authentication apparatus, a blood glucose level monitor, etc., it contributes to the improvement of the efficiency, and can be effectively used as a functional material of various organic devices.
In addition, the compound represented by the general formula (1) is also characterized in that it can be formed as an amorphous solid. Therefore, destruction of the organic film structure due to repeated driving and property deterioration which would be a problem in an organic device using a crystalline singlet fission material can be avoided, and an organic device having high stability can be realized.
Next, as a representative example of the organic device using the triplet sensitizer of the present invention, the layer configuration of the organic light emitting element and the material used for each layer will be described.

[Organic light emitting device]
As described above, the triplet sensitizer consisting of the compound represented by the general formula (1) of the present invention can be effectively used as a host material or an assist dopant of the light emitting layer of the organic light emitting device. An organic photoluminescence device (organic PL device) or an organic electroluminescence device (organic compound) by using a triplet sensitizer comprising the compound represented by the general formula (1) of the present invention as a host material or assist dopant of a light emitting layer An excellent organic light emitting device such as an EL device) can be provided.
The organic photoluminescent device has a structure in which at least a light emitting layer is formed on a substrate. The organic electroluminescent device has a structure in which an organic layer is formed at least an anode, a cathode, and between the anode and the cathode. The organic layer includes at least a light emitting layer, and may be formed only of the light emitting layer, or may have one or more organic layers in addition to the light emitting layer. As such another organic layer, a hole transport layer, a hole injection layer, an electron blocking layer, a hole blocking layer, an electron injection layer, an electron transport layer, an exciton blocking layer and the like can be mentioned. 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 the organic electroluminescent device is shown in FIG. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is a light emitting layer, 6 is an electron transport layer, and 7 is a cathode.
Each member and each layer of an organic electroluminescent element are demonstrated below. The description of the substrate and the light emitting layer also applies to the substrate and the light emitting layer of the organic photoluminescence device.

(substrate)
The organic electroluminescent device of the present invention is preferably supported on a substrate. The substrate is not particularly limited as long as it is conventionally used conventionally in organic electroluminescent devices, and for example, those made of glass, transparent plastic, quartz, silicon or the like can be used.

(anode)
As an anode in an organic electroluminescent element, what makes an electrode material the large (4 eV or more) metal of a work function, an alloy, an electrically conductive compound, and these mixtures is used preferably. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ -ZnO) which can be used to form a transparent conductive film may be used. The anode may form a thin film by depositing or sputtering these electrode materials, and may form a pattern of a desired shape by photolithography, or if it does not require much pattern accuracy (about 100 μm or more). ), A pattern may be formed through a mask of a desired shape during deposition or sputtering of the electrode material. Or when using the material which can be apply | coated like an organic conductive compound, the wet film-forming methods, such as a printing method and a coating method, can also be used. In the case of taking out light emission from this anode, it is desirable to make the transmittance larger than 10%, and the sheet resistance as the anode is preferably several hundreds Ω / sq or less. Furthermore, the film thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

(cathode)
On the other hand, as the cathode, one having a metal having a small work function (4 eV or less) (referred to as electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O) ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals etc. may be mentioned. Among them, a mixture of an electron-injectable metal and a second metal which is a stable metal having a larger work function value, such as a magnesium / silver mixture, Magnesium / aluminium mixtures, magnesium / indium mixtures, aluminum / aluminium oxide (Al ₂ O ₃ ) mixtures, lithium / aluminium mixtures, aluminum etc. are preferred. The cathode can be produced by forming a thin film of such an electrode material by a method such as vapor deposition or sputtering. Further, the sheet resistance as the cathode is preferably several hundred ohms / square or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In addition, in order to permeate | transmit the light-emitting light, if either one of the anode of an organic electroluminescent element or a cathode is transparent or semi-transparent, a light emission luminance will improve and it is convenient.
In addition, by using the conductive transparent material mentioned in the description of the anode for the cathode, a transparent or translucent cathode can be produced, and by applying this, an element in which both the anode and the cathode are transparent can be produced. It can be made.

(Emitting layer)
The light emitting layer is a layer which emits light after excitons are generated by recombination of holes and electrons injected from each of the anode and the cathode, and contains a host material and a light emitting material, or a host material and an assist material. It contains a dopant and a light emitting material.

When the light emitting layer contains a host material and a light emitting material, as the host material, one or two or more selected from the compound group represented by General Formula (1), which is a triplet sensitizer of the present invention It can be used. In addition, as a light-emitting material, one which can emit light upon being excited by excited triplet energy transferred from a host material is used. For the explanation of the light emitting material used here and the explanation of the energy levels of the host material and the light emitting material, reference can be made to the corresponding description in the column of [Utility of compound represented by General Formula (1)]. . When the light emitting layer contains such a host material and a light emitting material, excited triplet energy is efficiently generated by the triplet exciton sensitizing effect of the host material and is utilized for light emission of the light emitting material, so that high light emission Efficiency can be obtained.
In the organic light emitting device (organic photoluminescent device and electroluminescent device) using the triplet sensitizer of the present invention as a host material, light emission is generated from the light emitting material contained in the light emitting layer. This light emission may be either phosphorescence light emission or delayed fluorescence light emission, may include both light emission, and may include normal fluorescence light emission. In addition, part or part of light emission may be emitted from the host material.
When the triplet sensitizer of the present invention is used as a host material, the amount of the light emitting material contained in the light emitting layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, The content is preferably 50% by weight or less, more preferably 20% by weight or less, and still more preferably 10% by weight or less.

When the light emitting layer contains a host material, an assist dopant, and a light emitting material, as the assist dopant, one or two selected from the compound group represented by General Formula (1) which is a triplet sensitizer of the present invention More than species can be used. In addition, as the host material, one which can transfer the excited singlet energy generated in the host material to the assist dopant is used, and the light emitting material receives the excited triplet energy transferred from the assist dopant and emits light. Use what you get. For the description of the host material and the light emitting material used here, and the description of the energy levels of the host material, the assist dopant, and the light emitting material, the corresponding description in the column of [Utility of compound represented by General Formula (1)] Can be referenced. By including the host material, the assist dopant, and the light emitting material in the light emitting layer, the excited singlet energy generated in the host material is efficiently converted to the excited triplet energy by the triplet exciton sensitizing effect of the assist dopant to emit light. Since it is used for light emission of the material, high light emission efficiency can be obtained.
In the organic light emitting device (organic photoluminescent device and electroluminescent device) using the triplet sensitizer of the present invention as the assist dopant, light emission is generated from the light emitting material contained in the light emitting layer. This light emission may be either phosphorescence light emission or delayed fluorescence light emission, may include both light emission, and may include normal fluorescence light emission. In addition, part or part of light emission may be emitted from the host material or the assist dopant.
When the triplet sensitizer of the present invention is used as an assist dopant, the content of the assist dopant is less than the content of the host material and more than the content of the light emitting material, that is, “the content of the light emitting material It is preferable to satisfy the relationship of <content of assist dopant <content of host material>. Specifically, the content of the assist dopant in the light emitting layer is preferably less than 50% by weight. Further, the upper limit value of the content of the assist dopant is preferably less than 40% by weight, and the upper limit value of the content may be, for example, less than 30% by weight, less than 20% by weight, and less than 10% by weight. The lower limit is preferably 0.1% by weight or more, and may be, for example, more than 1% by weight and more than 3% by weight.

(Injection layer)
The injection layer is a layer provided between the electrode and the organic layer to lower the driving voltage and improve the luminance, and includes the hole injection layer and the electron injection layer, and 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. An injection layer can be provided as needed.

(Blocking layer)
The blocking layer is a layer capable of blocking the diffusion of charges (electrons or holes) present in the light emitting layer and / or excitons out of the light emitting layer. An electron blocking layer can be disposed between the light emitting layer and the hole transport layer to block electrons from passing through the light emitting layer towards the hole transport layer. Similarly, a hole blocking layer can be disposed between the light emitting layer and the electron transport layer to block holes from passing through the light emitting layer towards the electron transport layer. The blocking layer can also be used to block the diffusion of excitons out of the light emitting layer. That is, each of the electron blocking layer and the hole blocking layer can also have the function as an exciton blocking layer. The electron blocking layer or the exciton blocking layer as used herein is used in a sense including one layer having a function of the electron blocking layer and the exciton blocking layer.

(Hole blocking layer)
The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer plays the role of transporting electrons and blocking the arrival of holes to the electron transporting layer, which can improve the recombination probability of electrons and holes in the light emitting layer. As the material of the hole blocking layer, the material of the electron transport layer described later can be used as needed.

(Electron blocking layer)
The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer plays the role of transporting holes and blocking the arrival of electrons to the hole transport layer, which can improve the probability of recombination of electrons and holes in the light emitting layer. .

(Exciton blocking layer)
The exciton blocking layer is a layer for blocking the diffusion of excitons generated by the recombination of holes and electrons in the light emitting layer into the charge transport layer, and the insertion of this layer results in the formation of excitons. The light can be efficiently confined in the light emitting layer, and the light emission efficiency of the device can be improved. The exciton blocking layer can be inserted on either the anode side or the cathode side adjacent to the light emitting layer, or both of them can be simultaneously inserted. That is, when an exciton blocking layer is provided on the anode side, the layer can be inserted between the hole transport layer and the light emitting layer adjacent to the light emitting layer, and when inserted on the cathode side, the light emitting layer and the cathode And the light emitting layer may be inserted adjacent to the light emitting layer. In addition, a hole injection layer or an electron blocking layer can be provided between the anode and the exciton blocking layer adjacent to the anode side of the light emitting layer, and the cathode and the excitation adjacent to the cathode side of the light emitting layer Between the electron blocking layer, an electron injecting layer, an electron transporting layer, a hole blocking layer, and the like can be provided. When the blocking layer is disposed, at least one of the excitation singlet energy and the excitation triplet energy of the material used as the blocking layer is preferably higher than the excitation singlet energy and the excitation triplet energy of the light emitting material.

(Hole transport layer)
The hole transport layer is made of a hole transport material having a function of transporting holes, and the hole transport layer can be provided as a single layer or a plurality of layers.
The hole transport material is one having either hole injection or transport or electron barrier properties, and may be either organic or inorganic. Examples of known hole transport materials that can be used include triazole derivatives, oxadiazole derivatives, imidazole derivatives, carbazole derivatives, indolocarbazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, Amino substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers, etc., but porphyrin compounds, aroma Group tertiary amine compounds and styrylamine compounds are preferred, and aromatic tertiary amine compounds are more preferred.

(Electron transport layer)
The electron transporting layer is made of a material having a function of transporting electrons, and the electron transporting layer can be provided in a single layer or a plurality of layers.
The electron transporting material (which may also be a hole blocking material) may have a function of transferring electrons injected from the cathode to the light emitting layer. Examples of the electron transport layer that can be used include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, carbodiimides, flareylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like. Furthermore, in the above-mentioned oxadiazole derivative, a thiadiazole derivative h wherein the oxygen atom of the oxadiazole ring is substituted by a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. it can. Furthermore, it is also possible to use a polymer material in which these materials are introduced into a polymer chain, or in which these materials are used as a polymer main chain.

When the organic electroluminescent element is produced, the triplet sensitizer of the present invention may be used not only in the light emitting layer but also in layers other than the light emitting layer. At this time, the triplet sensitizer used in the light emitting layer and the triplet sensitizer used in layers other than the light emitting layer may be the same or different. For example, a triplet sensitizer may be used for the above-mentioned injection layer, blocking layer, hole blocking layer, electron blocking layer, exciton blocking layer, hole transporting layer, electron transporting layer, and the like. The film forming method of these layers is not particularly limited, and may be produced by either a dry process or a wet process.

Below, the preferable material which can be used for an organic electroluminescent element is illustrated concretely. However, the materials that can be used in the present invention are not limitedly interpreted by the following exemplified compounds. Moreover, even if it is the compound illustrated as a material which has a specific function, it is also possible to divert it as a material which has another function.
First, as a preferable example of the light emitting material which can be used for the light emitting layer, a compound example of the delayed fluorescence material is mentioned.

As preferred delayed fluorescence materials, paragraphs 0008 to 0048 and 0095 to 0133 of WO 2013/154064, paragraphs 0007 to 0047 and 0073 to 0085 of WO 2013/011954, paragraphs 0007 to 0033 and 0059 to 0066 of WO 2013/011955. Paragraphs 0008 to 0071 and 0118 to 0133 of WO 2013/0810 88, paragraphs 0009 to 0046 and 0093 to 0134 of JP 2013-256490 A, paragraphs 0008 to 0020 and 0038 to 0040 of JP 2013-116975 A, Paragraphs 0007 to 0032 and 0079 to 0084 of WO 2013/133359, paragraphs 0008 to 0054 of WO 2013/161437 and 101 to 0121, paragraphs 0007 to 0041 and 0060 to 0069 of JP 2014-9352 A, compounds included in the general formulas described in paragraphs 0008 to 0048 and 0067 to 0076 of JP 2014-9224 A, in particular, It is an exemplary compound which emits delayed fluorescence. Moreover, Unexamined-Japanese-Patent 2013-253121, WO2013 / 133359, WO2014 / 034535, WO2014 / 115743, WO2014 / 122895, WO2014 / 126200, WO2014 / 136758, WO2014 / 133121 are included. WO 2014/136860, WO 2014/196585, WO 2014/189122, WO 2014/168101, WO 2015/008580, WO 2014/203840, WO 2015/002213, WO 2015/016200, WO 2015/019725, WO 2015/072470, WO 2015/108049, WO 2015 / 80182, WO2015 / 072537, WO2015 / 080183, JP2015-129240, WO2015 / 129714, WO2015 / 129715, WO2015 / 133501, WO2015 / 136880, WO2015 / No. 137244, WO2015 / 137202, WO2015 / 137136, WO2015 / 146541, WO2015 / 159541, and a light emitting material that emits delayed fluorescence can be preferably employed. . In addition, the above-mentioned gazette described in this paragraph is quoted here as a part of this specification.

Next, examples of compounds of phosphorescent materials that can be used as a light emitting material of a light emitting layer are given. In the following formulae, Ar represents an aryl group.

Next, when the light emitting layer contains a host material, an assist dopant and a light emitting material, preferable compounds which can be used as the host material are listed. Further, as the host material in this case, a delayed fluorescence material can be preferably used. For examples of compounds of delayed fluorescence materials that can be used as host materials, reference can be made to the examples of compounds of delayed fluorescence materials given as preferable examples of light emitting materials. In addition, ACRXTN used in the examples can also be preferably used as a host material.

Next, examples of preferable compounds that can be used as a hole injection material are given.

Next, examples of preferable compounds that can be used as a hole transport material are given.

Next, examples of preferable compounds that can be used as the electron blocking material are given.

Next, examples of preferable compounds that can be used as a hole blocking material are given.

Next, examples of preferable compounds that can be used as an electron transport material are listed.

Next, examples of preferable compounds that can be used as the electron injecting material are given.

Further, examples of preferable compounds as materials which can be added will be mentioned. For example, addition as a stabilization material etc. can be considered.

The organic electroluminescent device produced by the above-mentioned method emits light by applying an electric field between the anode and the cathode of the obtained device. At this time, in the case of light emission by excited singlet energy, light of a wavelength corresponding to the energy level is confirmed as fluorescence emission and delayed fluorescence emission. Moreover, in the case of light emission by excited triplet energy, a wavelength corresponding to the energy level is confirmed as phosphorescence. Since the ordinary fluorescence has a shorter fluorescence lifetime than the delayed fluorescence, the emission lifetime can be distinguished by the fluorescence and the delayed fluorescence.
On the other hand, with regard to phosphorescence, in the case of ordinary organic compounds, the excitation triplet energy is unstable and converted to heat, etc., and its lifetime is short and it is immediately inactivated, so it can hardly be observed at room temperature. In order to measure the excited triplet energy of a normal organic compound, it can be measured by observing the light emission under conditions of extremely low temperature.

The organic electroluminescent device can be applied to any of a single device, a device having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the present invention, an organic light-emitting device whose emission efficiency is greatly improved by containing a triplet sensitizer comprising the compound represented by the general formula (1) as a host material or assist dopant for the light-emitting layer is provided. can get. The organic light emitting device such as the organic electroluminescent device using the triplet sensitizer of the present invention can be applied to various applications. For example, it is possible to manufacture an organic electroluminescent display device using this organic electroluminescent device, and for details, see “Organic EL Display” (Ohm Corporation) by Shiho Tokishi, Chika Adachi, Hideyuki Murata You can refer to it. Furthermore, in particular, this organic electroluminescent device can also be applied to organic electroluminescent illumination and back light which are in high demand.

The characteristics of the present invention will be more specifically described below by referring to synthesis examples and examples. Materials, processing contents, processing procedures, and the like described below can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as limited by the specific examples shown below. In addition, evaluation of the light emission characteristic, source meter (made by Keithley: 2400 series), semiconductor parameter analyzer (manufactured by Agilent Technologies: E5273A), optical power meter measuring device (manufactured by Newport: 1930C), optical spectroscope (Ocean Optics, Inc .: USB 2000), a spectroradiometer (Topcon, SR: 3) and a streak camera (Hamamatsu Photonics Co., Ltd., C4334 type) were used. In addition, the measurement of absorbance change amount ΔABS is performed using Quasi-CW laser (made by IPG Photonics Co., Ltd.) as a probe light source, an absorbance detection system having a monochromator and a detector, and excitation with a nitrogen laser (wavelength The light irradiation system was used, and the solution of the target compound was injected into a quartz cell with an optical path length of 1 mm.

Synthesis Example 1 Synthesis of Compound 3 Synthesis Process of Intermediate 1

Tetracene-5,12-dione (1.50 g, 5.80 mmol) and tin powder (3.00 g) were placed in a 100 mL Schlenk tube, 35 mL of acetic acid was added, and the mixture was stirred for 1 hour while heating to 120 ° C. Hydrochloric acid (35%, 11.5 M, 4 mL) was added and filtered while keeping the reaction solution at high temperature, then the filtrate was concentrated to half volume and allowed to cool to room temperature. The resulting precipitate was collected by filtration and washed with pure water to obtain a pale yellow solid. By subjecting this pale yellow solid to recrystallization from hot ethanol, Intermediate 1 (5-tetracenone) as an ocher needle-like crystal was obtained in a yield of 894 mg (3.66 mmol) in a yield of 63%.

[2] Synthetic process of intermediate 2

Intermediate 1 (871 mg, 3.56 mmol) is placed in a 300 mL two-necked eggplant flask, and pyridine (40 mL) and piperidine (4 mL) are added and dissolved, and then pyridine N-oxide (4.00 g, 42.0 mmol) And heptahydrate of iron (II) sulfate (102 mg, 0.36 mmol) were added and stirred at 100 ° C. for 5 hours. The reaction solution was cooled to room temperature, hydrochloric acid (6 M, 20 mL) was added while cooling with ice water, and the mixture was stirred until smoke and heat ceased. The resulting precipitate was collected by filtration, washed with ice water, and dissolved in chloroform. The solution is dried over sodium sulfate, filtered, and the filtrate is concentrated to give 560 mg of Intermediate 2 (a mixture of cis-trans isomers of bitetracenone based on trans) as a dark brown solid. Obtained.

[3] Synthetic process of intermediate 3

Bromobenzene (0.24 mL, 2.27 mmol) and dehydrated tetrahydrofuran (2.5 mL) are placed in a 100 mL two-necked eggplant flask under Ar atmosphere and cooled to −78 ° C. with 1.6 M n-butyllithium A hexane solution (1.7 mL, 2.72 mmol) was slowly added and stirred for 2 hours while keeping at -78.degree. While the reaction solution was cooled, a suspension of Intermediate 2 (550 mg, 1.13 mmol) and dehydrated tetrahydrofuran (25 mL) was added dropwise thereto, and the mixture was stirred overnight while slowly warming to room temperature. To the reaction solution was added brine, and extracted with dichloromethane, dried over sodium sulfate, and filtered. The filtrate was concentrated to give Intermediate 3 as a brown solid in a yield of 562 mg.

[4] Synthesis process of compound 3

Intermediate 3, sodium iodide (1.33 g, 8.87 mmol) and sodium phosphinate monohydrate (1.15 g, 10.8 mmol) are placed in a 300 mL two-necked flask, and acetic acid (100 mL) is added to give 120 ° C. And stirred for 2 and a half hours. The reaction solution was poured into ice water, the resulting precipitate was suction filtered, and the filtrate was washed with pure water and then dissolved in dichloromethane. The solution was dried by adding sodium sulfate and filtered, and the filtrate was concentrated to obtain a reddish brown solid. The solid is purified by silica gel column chromatography using a mixed solvent of dichloromethane: hexane = 1: 3 as a developing solvent, and concentrated to give compound 3 (12,12′-diphenyl-5,5 as an orange solid). '-Bitetracene) was obtained in a yield of 220 mg (0.36 mmol). The yield of compound 3 throughout this synthetic route was 15.2%.
¹ H NMR (600 mHz, CDCl ₃ ): δ 8.45 (s, 2 H), 7.89 (d, J = 6.0 Hz, 2 H), 7.85 (s, 2 H), 7.75-7. 83 (m, 14 H), 7.57 (d, J = 6.0 Hz, 2 H), 7.34-7.36 (m, 2 H), 7.29-7.32 (m, 2 H), 7. 19-7.22 (m, 2 H), 7.13-7. 16 (m, 2 H), 7.03 (d, J = 6.0 Hz, 2 H).

Synthesis Example 2 Synthesis of Compound 4

Orange was used in the same manner as in Synthesis Example 1 except that gel permeation chromatography was performed instead of silica gel chromatography in step [4] using 2-bromonaphthalene instead of bromobenzene in step [3]. Compound 4 (12,12′-dinaphthyl-5,5′-bitetracene) was synthesized as a solid.
¹ H NMR (600 mHz, Acetone-D6): δ 8.60 (s, 2 H), 8.32 to 8.36 (m, 4 H), 8.21 to 8.24 (m, 2 H), 8.17 (T, J = 6.0 Hz, 2 H), 8.03 (d, J = 3.0 Hz, 2 H), 7.95 to 7.97 (dd, J = 6.0 Hz, 1 H), 7.85 7. 92 (m, 5 H), 7.72-7. 76 (m, 4 H), 7.51 (dd, J = 6.0 Hz, 2 H), 7.34-7. 37 (m, 2 H), 7.30 (t, J = 9.0 Hz, 2H), 7.16-7.25 (m, 6H).

Experimental Example 1 Study of Host Material to be Combined with Compound 1 and Compound 2 Each toluene solution containing Compound 1 or Compound 2 was prepared in a glove box under an Ar atmosphere. At this time, the concentration of each compound in the toluene solution was 1 × 10 ⁻⁵ mol / L, respectively.
The light absorption spectrum of each prepared toluene solution is shown in FIG.
It can be seen from FIG. 2 that the absorption peak of each toluene solution of Compound 1 or Compound 2 largely overlaps with the emission peak of the thin film of ACRXTN and mCBP. This indicates that the excited singlet energy generated in ACRXTN can be transferred to Compound 1 and Compound 2 by the Forster energy transfer mechanism, and that ACRXTN can be used as a host material in combination with Compound 1 and Compound 2. all right.

Experimental Example 2 Evaluation of Luminescent Properties of Compound 1, Compound 3, and Compound 4 Each toluene solution containing Compound 1, Compound 3, or Compound 4 was prepared in a glove box under an Ar atmosphere. At this time, the concentration of each compound in the toluene solution was 1 × 10 ⁻⁵ mol / L, respectively. The emission spectra of each of the prepared toluene solutions at 435, 470 and 468 nm excitation light are shown in FIG.
It was found that the emission peaks of the respective toluene solutions were almost identical, and that the compound 1, the compound 3 and the compound 4 had very similar emission characteristics.

Example 1 Evaluation of Singlet Splitting Performance and Triplet Sensitizing Performance of Compound 1 Evaluation by Photoluminescence Quantum Yield A thin film of Compound 1 (the concentration of Compound 1 is 100% by weight on a quartz substrate by spin coating) And a thin film of ACRXTN (a thin film in which the concentration of Compound 1 is 0% by weight).
Also, separately from this, various thin films were also formed by changing the concentration of Compound 1 to 6 wt%, 10 wt%, 20 wt%, 30 wt%, and 60 wt% by spin coating.
The emission spectrum of each thin film formed by 371 nm excitation light is shown in FIG. In addition, when the photoluminescence quantum yield of each thin film was measured, the photoluminescence quantum yield of the thin film of ACRXTN (the thin film with a concentration of 0 wt% of compound 1) was as high as 70%, whereas It was confirmed that the photoluminescence quantum yield decreases as the concentration is increased to 6 to 100% by weight. This is considered to be because the increase in the concentration of Compound 1 reduces the distance between the molecules of Compound 1 and promotes singlet division occurring between the molecules of Compound 1. Thus, this result indicates that Compound 1 is a singlet fission material, and indicates the usefulness as a triplet sensitizer.

Triplet exciton formation efficiency 効率 _ISC evaluation Chloroform solution containing Compound 1 in a glove box of an Ar atmosphere, 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, 2.5 × 10 ⁻ It prepared at each concentration of ² mol / L, 5 × 10 ⁻² mol / L, or 1 × 10 ⁻¹ mol / L.
Each prepared chloroform solution was irradiated with 337 nm pump light (excitation light), and a transient decay curve of absorbance change amount ΔABS with respect to 530 nm probe light was measured. The results are shown in FIGS. Here, the absorbance change amount ΔABS is a value obtained by subtracting the absorbance ABS ₀ of the solution before pump light irradiation from the absorbance ABS _EX of the solution after pump light irradiation. Among FIGS. 5 to 7, FIG. 5 shows that when a chloroform solution containing compound 1 at a concentration of 5 × 10 ⁻² mol / L is irradiated with pump light at 10 μJ / pulse, 15 μJ / pulse or 20 μJ / pulse. Absorption and decay curve, and Figure 6 shows that a chloroform solution containing Compound 1 at a concentration of 1 × 10 ^-1 mol / L was irradiated with pump light at 10 μJ / pulse, 15 μJ / pulse or 20 μJ / pulse. FIG. 7 shows that Compound 1 is 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, 2.5 × 10 ⁻² mol / L, 5 × 10 ^−2. A transient absorption decay curve is shown when pump light is irradiated at 15 μJ / pulse to each chloroform solution contained at a concentration of mol / L or 1 × 10 ⁻¹ mol / L. In FIG. 5 and FIG. 6, white circles indicate plots that form a fitting curve.
In addition, for each chloroform solution containing Compound 1 at a concentration of 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, or 2.5 × 10 ⁻² mol / L, the amount of change in absorbance at 520 nm A correlation diagram in which ΔABS is plotted on the vertical axis and excitation light intensity is plotted on the horizontal axis is shown in FIG. 8. Compound 1 is 1 × 10 ⁻³ mol / L, 1 × 10 ⁻² mol / L, 2.5 × 10 ⁻² For each chloroform solution containing a concentration of mol / L, 5 × 10 ^-2 mol / L, or 1 × 10 ^-1 mol / L, the absorbance change amount ΔABS at 530 nm is the vertical axis, and the excitation light intensity is the horizontal axis The plotted correlation diagram is shown in FIG. The absorbance change amount ΔABS in FIGS. 8 and 9 is a value obtained by subtracting the absorbance ABS ₀ of the solution before the excitation light irradiation from the absorbance ABS _{EX of the} solution measured immediately after the irradiation of the pump light of 337 nm.
Further, among the data plotted in FIG. 8 and FIG. 9, the triplet exciton generation efficiency IS _ISC was determined from the value of ΔABS measured immediately after irradiation with the pump light of 337 nm using the above formula (I) . The results of examining the concentration dependency of the triplet exciton generation efficiency IS _ISC of compound 1 are shown in FIG. Here, the triplet exciton generation efficiency IS _ISC was calculated by setting the molar absorption coefficient ε for pump light to 2793 L / (mol cm) and setting the optical path length L of the cell to 1 mm. The scale of the vertical axis in FIG. 10 indicates the relative value obtained by standardizing Φ _ISC at each concentration with Φ _ISC at 1 × 10 ⁻³ mol / L as 1.
As shown in FIG. 10, the triplet exciton generation efficiency Φ _ISC of compound 1 improves as the compound concentration increases, and at the probe light wavelength of 530 nm, the triplet exciton at 1 × 10 ⁻¹ mol / L generation efficiency [Phi _ISC reached approximately 10 times the triplet exciton generation efficiency [Phi _ISC at 1 × ¹⁰ -3 mol / L. Thus, the fact that the triplet exciton generation efficiency IS _ISC has been improved depending on the concentration of Compound 1 is that the intermolecular distance of Compound 1 becomes short due to the increase of the concentration of Compound 1 and occurs between molecules It shows that singlet splitting process (electron transfer) and triplet exciton generation via the singlet splitting process are promoted. From this, it could be confirmed that Compound 1 is useful as a singlet fission material and a triplet sensitizer.

The compounds of the present invention are useful as singlet fission materials and triplet sensitizers. By using the triplet sensitizer of the present invention, the efficiency of an organic device such as an organic light emitting element or an organic solar cell can be dramatically improved. For this reason, the present invention has high industrial applicability.

1 substrate 2 anode 3 hole injection layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 cathode

Claims

The singlet fission material which consists of a compound represented by following General formula (1).

[In the general formula (1), R 1 represents a substituted or unsubstituted aryl group. One of R 2 and R 3 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. ]
The singlet fission material according to claim 1, wherein R 1 and R 2 are each independently an unsubstituted aryl group.
The singlet fission material according to claim 1 or 2, wherein R 1 and R 2 are identical.
The triplet sensitizer which consists of a compound represented by following General formula (1).

[In the general formula (1), R 1 represents a substituted or unsubstituted aryl group. One of R 2 and R 3 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. ]
The triplet sensitizer according to claim 4, wherein R 1 and R 2 are each independently an unsubstituted aryl group.
The triplet sensitizer according to claim 4 or 5, wherein R 1 and R 2 are the same.
The compound represented by following General formula (2).

[In the general formula (2), one of R 4 and R 5 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. One of R 6 and R 7 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. n is 0 or 1. ]
The compound according to claim 7, wherein R 4 and R 6 are each independently an unsubstituted aryl group.
9. A compound according to claim 7 or 8 wherein R 4 and R 6 are identical.
The thin film containing the compound represented by following General formula (2).

[In the general formula (2), one of R 4 and R 5 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. One of R 6 and R 7 is a hydrogen atom, and the other is a substituted or unsubstituted aryl group. n is 0 or 1. ]