KR102469690B1 - Space-through charge transfer compound, and Organic light emitting diode device and Display device using the same - Google Patents

Abstract

In the present invention, an electron donor moiety selected from carbazole or diphenyl amine and an electron acceptor moiety selected from pyrimidine, diphenyltriazine, and triazole A space charge transfer compound having a molecular formula in which Ti is each bonded to the paracyclophane core directly or through a substituted or unsubstituted benzene linker.

Description

Space-through charge transfer compound, and organic light emitting diode device and display device using the same}

The present invention relates to a luminescent material. More specifically, it relates to a space charge transfer compound in which charge transfer between an electron donor moiety and an electron acceptor moiety is directly performed through an intramolecular space, an organic light emitting diode device including the same, and a display device. .

Recently, demand for a flat display device that occupies less space is increasing according to the size of the display device. is developing into

An organic light emitting diode device emits light when electrons and holes are injected from the cathode and anode into the light emitting material layer formed between the electron injecting electrode (cathode) and the hole injecting electrode (anode), and then the electrons and holes form pairs and then disappear. . The device can be formed on a flexible transparent substrate such as plastic, can be driven at a low voltage (less than 10V), consumes relatively little power, and has excellent color sense.

An organic light emitting diode device is formed on a substrate and includes a first electrode serving as an anode, a second electrode spaced apart from and facing the first electrode, and an organic light emitting layer positioned between the first electrode and the second electrode.

In order to improve luminous efficiency, the organic light emitting layer includes a hole injection layer (HIL), a hole transporting layer (HTL), and an emitting material layer (EML) sequentially stacked on the first electrode. , an electron transporting layer (ETL), and an electron injection layer (EIL).

Holes move from the first electrode, which is an anode, to the light emitting material layer through the hole injection layer and the hole transport layer, and electrons move from the second electrode, which is a cathode, to the light emitting material layer through the electron injection layer and the electron transport layer.

Holes and electrons moved to the light-emitting material layer combine to form excitons, and are excited to an unstable energy state, then return to a stable energy state to emit light.

The external quantum efficiency (η _ext ) of the light emitting material used in the light emitting material layer can be obtained by the following formula.

η _ext = η _int × г × Φ × η _{out - coupling}

(Where, η _int : internal quantum efficiency, г: charge balance factor, Φ: radiative quantum efficiency, η _{out - coupling} : out coupling efficiency)

Charge balance factor (г) means the balance of electrons and holes that form exciton, and generally has a value of '1' assuming 1:1 matching of 100%. Radiative quantum efficiency (Φ) is a value related to the luminous efficiency of the actual light emitting material, and in the host-dopant system, it depends on the fluorescence quantum efficiency of the dopant.

The internal quantum efficiency (η _int ) is the rate at which generated excitons are converted into light, and has a limiting value of up to 0.25 in the case of fluorescent materials. When an exciton is formed by combining a hole and an electron, a singlet exciton and a triplet exciton are generated at a ratio of 1:3 according to the spin arrangement. However, in fluorescent materials, only singlet excitons participate in light emission, and the remaining 75% of triplet excitons do not participate in light emission.

Out coupling efficiency (η _{out - coupling} ) is the ratio of light extracted to the outside among emitted light. In general, when isotropic molecules are thermally deposited to form a thin film, individual light emitting molecules do not have a certain directionality and exist in a disordered state. The out-coupling efficiency in this random orientation state is generally assumed to be 0.2.

Therefore, the maximum light emitting efficiency of the organic light emitting diode device using the fluorescent material is about 5% or less.

In order to overcome the low efficiency problem of fluorescent materials, a phosphorescent material having a light emitting mechanism that converts both singlet excitons and triplet excitons into light has been developed.

In the case of red and green, phosphorescent materials having high luminous efficiency have been developed, but in the case of blue, phosphorescent materials satisfying the required luminous efficiency and reliability have not been developed.

Therefore, in a fluorescent material that satisfies reliability, there is a need to develop a material capable of increasing luminous efficiency by increasing quantum efficiency.

The present invention is intended to solve the problem of low quantum efficiency of fluorescent materials.

In order to solve the above problems, the present invention provides a space charge transfer compound having a structure in which an electron donor moiety and an electron acceptor moiety are bonded directly or through a linker to a paracyclophane core.

The electron donor moiety is selected from carbazole or diphenylamine, the electron acceptor moiety is selected from pyrimidine, diphenyltriazine, and triazole, and the linker may be substituted or unsubstituted benzene.

That is, the space charge transfer compound of the present invention is represented by the following formula, D is selected from carbazole or diphenylamine, A is selected from pyrimidine, diphenyltriazine, and triazole, and each of L1 and L2 is It is selected from substituted or unsubstituted benzene, and each of n1 and n2 is 0 or 1.

In addition, the present invention provides an organic light emitting diode device and a display device in which the organic light emitting layer includes the space charge transfer compound described above.

In the space charge transfer compound of the present invention, an electron donor moiety and an electron acceptor moiety are bound in a molecule, and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (HOMO) LUMO) is reduced, thereby forming a charge transfer complex, thereby improving the luminous efficiency of the compound. That is, in the space charge transfer compound of the present invention, since excitons in the triplet state are used for light emission, the light emission efficiency is improved.

In addition, since the electron donor moiety and the electron acceptor moiety are bonded to benzene of paracyclophane, the distance between the electron donor moiety and the electron acceptor moiety is minimized. Therefore, since the transfer of charge is directly performed through the space between the electron donor moiety and the electron acceptor moiety, compared to a charge transfer complex in which charge moves through a bonding orbital of a molecule, a conjugate The conjugation length is shortened and the red shift problem of light emitted from the compound is minimized. That is, it is possible to provide a blue compound having deep blue emission characteristics.

In addition, a compound having a stable structure can be obtained by introducing a benzene linker capable of minimizing steric hinderance between the electron donor moiety and the electron acceptor moiety.

Accordingly, the light emitting efficiency of the organic light emitting diode device and the display device including the space charge transfer compound of the present invention is improved, and high quality images can be realized.

1 is a view for explaining a light emitting mechanism of a space charge transfer compound according to an embodiment of the present invention.
2a to 2c are graphs showing delayed fluorescence characteristics of delayed fluorescence compounds according to embodiments of the present invention.
3 is a schematic cross-sectional view of an organic light emitting diode device according to an embodiment of the present invention.

In the present invention, an electron donor moiety selected from carbazole or diphenyl amine and an electron acceptor moiety selected from pyrimidine, triazine, and triazole are A space charge transfer compound having a molecular formula each bonded to the paracyclophane core directly or through a substituted or unsubstituted benzene linker.

In another aspect, the present invention is represented by Formula 1 below, D is selected from Formula 2, A is selected from Formula 3 below, L1 and L2 are each selected from substituted or unsubstituted benzene, n1, Each n2 is 0 or 1 to provide a space charge transfer compound.

[Formula 1]

[Formula 2]

[Formula 3]

In the space charge transfer compound of the present invention, the difference between singlet energy and triplet energy may be 0.3 eV or less.

From another point of view, the present invention includes a first electrode, a second electrode facing the first electrode, and an organic light emitting layer positioned between the first and second electrodes, wherein the organic light emitting layer includes carbazole ( An electron donor moiety selected from carbazole or diphenyl amine and an electron acceptor moiety selected from pyrimidine, triazine, and triazole are directly, substituted or unsubstituted Provided is an organic light emitting diode device including space charge transfer compounds having a molecular formula each bonded to a paracyclophane core through a benzene linker.

From another point of view, the present invention includes a first electrode, a second electrode facing the first electrode, and an organic light emitting layer positioned between the first and second electrodes, wherein the organic light emitting layer comprises Chemical Formula 1 below. , D is selected from Formula 2, A is selected from Formula 3, L1 and L2 are each independently selected from substituted or unsubstituted benzene, and n1 and n2 are each 0 or 1 space charge. An organic light emitting diode device comprising a mobile compound is provided.

[Formula 1]

[Formula 2]

[Formula 3]

In the organic light emitting diode device of the present invention, a difference between singlet energy and triplet energy of the space charge transfer compound may be 0.3 eV or less.

In the organic light emitting diode device of the present invention, the space charge transfer compound is used as a dopant, and the organic light emitting layer may further include a host.

In the organic light emitting diode device of the present invention, the difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the host The difference (|LUMO _Host - LUMO _Dopant |) between the lowest level unoccupied molecular orbital level (LUMO _Host ) of the dopant and the lowest level unoccupied molecular orbital level (LUMO _Dopant ) of the dopant may be 0.5 eV or less.

In the organic light emitting diode device of the present invention, the space charge transfer compound is used as a host, and the organic light emitting layer may further include a dopant.

In the organic light emitting diode device of the present invention, the space charge transfer compound is used as a first dopant, the organic light emitting layer further includes a host and a second dopant, and the first triplet energy of the first dopant is the host It may be smaller than the second triplet energy of and greater than the third triplet energy of the second dopant.

In the organic light emitting diode device of the present invention, the organic light emitting layer includes a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer, and an electron injection layer, and the hole injection layer, the hole transport layer, and the above At least one of the light emitting material layer, the electron transport layer, and the electron injection layer may include the space charge transfer compound.

In another aspect, the present invention provides a substrate, the above-described organic light emitting diode device disposed on the substrate, an encapsulation film covering the organic light emitting diode device, and a cover window on the encapsulation film. display device is provided.

Hereinafter, a structure of a space charge transfer compound according to an embodiment of the present invention, a synthesis example thereof, and an organic light emitting diode device using the same will be described.

The space charge transfer compound according to an embodiment of the present invention has a structure in which an electron donor moiety and an electron acceptor moiety are bonded to a paracyclophane core through a substituted or unsubstituted benzene linker or directly, respectively, represented by Formula 1 below. do.

[Formula 1]

In this case, n is 0 or 1, and each of n1 and n2 is 0 or 1.

That is, the compound represented by Chemical Formula 1 may have structures represented by Chemical Formulas 2-1 to 2-4 below.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

That is, it has a structure in which the electron donor moiety and the electron acceptor moiety are directly bonded to the paracyclophane core (n1=n2=0, Chemical Formula 2-1), or the electron donor moiety and the electron acceptor moiety are paracyclophane. It may have a structure (n1=n2=1, Chemical Formula 2-2) bonded to the core through a linker. In addition, the electron donor moiety is bonded to the paracyclophane core through a linker and the electron acceptor moiety has a structure directly bonded to the paracyclophane core (n1 = 0, n2 = 1, Formula 2-3), or electron The donor moiety may have a structure (n1 = 1, n2 = 0, Chemical Formula 2-4) in which the donor moiety is directly bonded to the paracyclophane core and the electron acceptor moiety is bonded to the paracyclophane core through a linker.

In Formula 1, the electron-donating moiety D may be selected from carbazole or diphenyl amine. For example, the electron-donating moiety D may be selected from materials represented by Formula 3 below.

[Formula 3]

In addition, in Formula 1, the electron acceptor moiety A may be selected from pyrimidine, diphenyltriazine, and triazole. For example, the electron acceptor moiety A may be selected from materials represented by Formula 4 below.

[Formula 4]

In addition, in Formula 1, each of the linkers L1 and L2 may be independently selected from substituted or unsubstituted benzene. For example, each of the linkers L1 and L2 may be a substance represented by Chemical Formula 5 below.

[Formula 5]

In Formula 5, R may be selected from hydrogen or C1-C10 alkyl.

In such a space charge transfer compound, the electron donor moiety and the electron acceptor moiety are combined in a molecule, and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (HOMO) are formed. By reducing the overlapping of LUMO), charge transfer complexes are formed and the luminous efficiency of the compound is improved. That is, in the space charge transfer compound of the present invention, since excitons in the triplet state are used for light emission, the light emission efficiency is improved.

In other words, since the space charge transfer compound of the present invention includes both an electron donor moiety and an electron acceptor moiety, charge transfer easily occurs in the molecule and luminous efficiency is improved.

In particular, in the space charge transfer compound of the present invention, the electron donor moiety and the electron acceptor moiety are bonded to the paracyclophane core, thereby minimizing the distance between the electron donor moiety and the electron acceptor moiety. Therefore, since the transfer of charge is directly performed through the space between the electron donor moiety and the electron acceptor moiety, compared to a charge transfer complex in which charge moves through a bonding orbital of a molecule, a conjugate The conjugation length is shortened and the problem of red shift of light emitted from the compound is avoided. That is, it is possible to provide a blue compound having deep blue emission characteristics.

In addition, a compound having a stable structure can be obtained by introducing a substituted or unsubstituted benzene linker capable of minimizing steric hinderance between the electron donor moiety and the electron acceptor moiety.

Referring to FIG. 1, which is a diagram for explaining a light emitting mechanism of a space charge transfer compound according to an embodiment of the present invention, in the space charge transfer compound of the present invention, both singlet excitons and triplet excitons participate in light emission, resulting in quantum efficiency. this improves

That is, in the space charge transfer compound of the present invention, triplet excitons are activated by an electric field, and the triplet excitons and singlet excitons move to an intermediate state (I ₁ ) and ground state (S). ₀ ) and emits light. In other words, a transition occurs from the singlet state (S ₁ ) and triplet state (T ₁ ) to the intermediate state (I ₁ ) (S ₁ -> I ₁ <-T ₁ ), and both singlet and triplet excitons By participating in light emission, the light emission efficiency is improved. This is referred to as a filed activated delayed fluorescence (FADF) compound.

Conventional fluorescent materials cannot interconvert between a singlet state and a triplet state because HOMO and LUMO are spread throughout the molecule. (selection rule)

However, in the FADF compound as in the present invention, the interaction between HOMO and LUMO is small because the intramolecular HOMO and LUMO overlap is small. Therefore, a change in spin state of an electron does not affect other electrons, and a new charge transfer band that does not follow the selection rule is formed.

In addition, since the electron acceptor moiety and the electron donor moiety are spaced apart in the molecule, the dipole moment in the molecule exists in a polarized form. In a state where the dipole moment is polarized, the interaction between the HOMO and the LUMO becomes small, and the selection rule may not be followed. Therefore, in the FADF compound, a transition is possible from the triplet state (T ₁ ) and the singlet state (S ₁ ) to the intermediate state (I ₁ ), and triplet excitons participate in light emission.

When an organic light emitting diode device is driven, 25% of singlet state (S ₁ ) excitons and 75% of triplet state (T ₁ ) excitons undergo a systemic transition to an intermediate state (I ₁ ) by an electric field and ground state (S 1 ). ₀ ), the internal quantum efficiency theoretically becomes 100%.

For example, the space charge transfer compound of Chemical Formula 1 may be any one of the compounds of Chemical Formula 6 below.

[Formula 6]

In addition, the space charge transfer compound of the present invention has a wide energy band gap, so that the luminous efficiency of the organic light emitting diode device including the same is further improved.

Hereinafter, synthetic examples of space charge transfer compounds according to embodiments of the present invention will be described.

synthesis example

1. Synthesis of Compound 1

(1) Synthesis of compound a

[Scheme 1-1]

4,16-dibromo[2,2]paracyclophane and diphenylamine (1.1 equiv.), Pd(OAc) ₂ (0.019 equiv.), P(t-Bu) ₃ (50 wt%, 0.046 equiv.), NaOt-Bu in a nitrogen atmosphere. (sodium tert-butoxide, 1.9 equivalent) was added to the toluene solvent and stirred. The mixture was stirred under reflux at 120° C. for 12 hours. After completion of the reaction, the mixture was cooled to room temperature and extracted with water and ethyl acetate. Moisture was removed from the extracted organic layer using magnesium sulfate (MgSO ₄ ), and the remaining organic solvent was removed. Compound a was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 65%)

(2) Synthesis of compound b

[Scheme 1-2]

Compound a (17.9 mmol) was dissolved in a tetrahydrofurane (THF) solvent and stirred in a nitrogen environment. After slowly adding n-bytyllithium (26.9 mmol) at -78°C, the mixture was stirred for 1 hour. While maintaining a low-temperature environment, triethylborate (21.6 mmol) was added to bring the mixture to room temperature, followed by stirring. The reaction was terminated after stirring at room temperature for 12 hours. Distilled water was added slowly and distilled water:HCl (8:2) was added to make pH 2. Extraction was performed using distilled water and ethyl acetate, and moisture was removed from the extracted organic layer using magnesium sulfate. After removing the remaining organic solvent, compound b was obtained through column chromatography wet purification using ethyl acetate and hexane. (Yield: 80%)

(3) Synthesis of Compound 1

[Scheme 1-3]

2-chloro-4,6-diphenyl-1,3,5-triazine, compound b (1 equivalent) and sodium carbonate (NaCO ₃ , 0.6 equivalent) were added to toluene/dioxane/distilled water (1:1:0.7) solvent and nitrogen Atmosphere was stirred. Tetrakis(triphenylphosphine)palladium(0) (0.3 eq.) was additionally added and stirred at reflux for 16 hours. After completion of the reaction, it was cooled to room temperature, and the organic layer was washed with silica gel and distilled water and filtered. The solvent and distilled water were removed, recrystallized with chloroform and dried to obtain Compound 1. (Yield: 75%)

2. Synthesis of Compound 2

(1) Synthesis of compound c

[Scheme 2-1]

After dissolving carbazole in 1,4-dioxane solvent in a nitrogen environment, CuI and K ₃ PO ₄ were added. 4,16-dibromo[2,2]paracyclophane (1.1 eq) and trans-1,2-diaminocyclohexane were additionally added, and the mixture was refluxed and stirred at 110°C for 24 hours. After completion of the reaction, the mixture was cooled to room temperature and extracted with ethyl acetate and distilled water. Moisture was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound c was obtained through column chromatography wet purification using ethylacetate and hexane. (Yield: 63%)

(2) Synthesis of Compound 2

[Scheme 2-2]

2-chloro-4,6-diphenyl-1,3,5-triazine, compound c (1 equivalent), and sodium carbonate (NaCO ₃ , 0.6 equivalent) were added to toluene/dioxane/distilled water (1:1:0.7) solvent and nitrogen Atmosphere was stirred. Tetrakis(triphenylphosphine)palladium(0) (0.3 eq.) was additionally added and stirred at reflux for 16 hours. After completion of the reaction, it was cooled to room temperature, and the organic layer was washed with silica gel and distilled water and filtered. The solvent and distilled water were removed, recrystallized with chloroform and dried to obtain Compound 2. (Yield: 70%)

3. Synthesis of Compound 3

[Scheme 3]

In a nitrogen atmosphere, the reactants of compound a, 5-pyrimidylboronic acid (1.5 equivalents), Pd(dppf)Cl ₂ (4 mol%) and K ₃ PO ₄ (2 equivalents) were added to a toluene solvent and stirred, followed by stirring for 24 hours. It was refluxed while stirring. After completion of the reaction, it was cooled to room temperature, diluted by adding toluene, and then hydrolyzed with 10% NaOH. Extraction was performed using ethyl acetate, and water was removed from the organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound 3 was obtained by column chromatography wet purification using ethyl acetate and hexane. (Yield: 80%)

4. Synthesis of Compound 4

[Scheme 4]

In a nitrogen atmosphere, the reactants of compound c, 5-pyrimidylboronic acid (1.5 equivalents), Pd(dppf)Cl ₂ (4 mol%) and K ₃ PO ₄ (2 equivalents) were added to a toluene solvent and stirred, followed by stirring for 24 hours. It was refluxed while stirring. After completion of the reaction, it was cooled to room temperature, diluted by adding toluene, and then hydrolyzed with 10% NaOH. Extraction was performed using ethyl acetate, and water was removed from the organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound 4 was obtained by column chromatography wet purification using ethyl acetate and hexane. (Yield: 70%)

5. Synthesis of Compound 5

[Scheme 5]

In a nitrogen atmosphere, add 1,2,4-triazole (1.5 equivalents), compound c, K ₂ CO ₃ (2 equivalents), and copper(Ⅰ)3-methylsalicylate (0.01 equivalents) to dimethyl sulfoxide (DMSO) solvent and stir did Stir at 110° C. for 3 hours and cool to room temperature. The cooled solution was filtered and then washed with a small amount of DMSO. Extraction was performed with cold distilled water and ethyl acetate, and water was removed from the extracted organic layer using MgSO ₄ . After removing the remaining organic solvent, compound 5 was obtained by wet purification through column chromatography and recrystallization using ethyl acetate and hexane. (Yield: 50%)

6. Synthesis of Compound 6

(1) Synthesis of compound d

[Scheme 6-1]

In a nitrogen atmosphere, carbazole (29.9 mmol), 1,4-dibromobenzene (44.9 mmol), palladium (II) acetate (2 mol%), tri-tert-butylphosphate (5 mol%), sodium-tert-butoxide (2.03 equiv.) Mixed with toluene solvent and stirred. The mixed solution was stirred under reflux and reacted for 12 hours. After completion of the reaction, it was extracted with distilled water and ethyl acetate. In the extracted organic layer, water was removed using MgSO4, water was removed using MgSO4, and the remaining organic solvent was removed. Compound d was obtained by column chromatography and wet purification using ethyl acetate and hexane. (Yield: 80%)

(2) synthesis of compound e

[Scheme 6-2]

Compound d (17.9 mmol) was dissolved in THF solvent and stirred in a nitrogen environment. After slowly adding n-butyllithium (26.9 mmol) at -78°C, the mixture was stirred for 1 hour. While maintaining the low-temperature environment, triethylborate (21.6 mmol) was added to bring the mixture to room temperature, followed by stirring. After stirring at room temperature for 12 hours, the reaction was terminated. Distilled water was slowly added and a mixture of distilled water and hydrochloric acid (8:2) was added to make pH 2. Extraction was performed using distilled water and ethyl acetate, and water was removed from the extracted organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound e was obtained through column chromatography wet purification using ethylacetate and hexane. (Yield: 87%)

(3) Synthesis of compound f

[Scheme 6-3]

In a nitrogen atmosphere, 1,2,4-triazole (1 equivalent), 1,4-dibromobenzene, K ₂ CO ₃ (2 equivalents), and copper(Ⅰ)3-methylsalicylate (0.01 equivalent) were added to the DMSO solvent and stirred. . The mixture was stirred at 110° C. for 3 hours and allowed to cool to room temperature. The cooled solution was filtered and then washed with a small amount of DMSO. Extraction was performed with cold distilled water and ethyl acetate, and water was removed from the extracted organic layer using MgSO ₄ . After removing the remaining organic solvent, compound f was obtained by wet purification through column chromatography and recrystallization using ethyl acetate and hexane. (Yield: 56%)

(4) synthesis of compound g

[Formula 6-4]

Compound f was dissolved in THF solvent and stirred in a nitrogen environment. After slowly adding n-butyllithium (1.5 equivalents) at -78°C, the mixture was stirred for 1 hour. While maintaining a low-temperature environment, triethylborate (1.2 equivalents) was added to bring the temperature to room temperature, followed by stirring. After completion of the reaction by stirring at room temperature for 12 hours, distilled water was slowly added and a mixture of distilled water: hydrochloric acid (8:2) was added to make pH 2. Extraction was performed using distilled water and ethylacetate, and water was removed from the extracted organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound g was obtained through column chromatography wet purification using ethylacetate and hexane. (Yield: 79%)

(5) Synthesis of compound h

[Scheme 6-5]

In a nitrogen atmosphere, the reactants of 4,16-dibromo[2,2]paracyclophane, compound e (1.1 equiv.), Pd(dppf)Cl ₂ (4 mol%) and K ₃ PO ₄ (2 equiv.) were mixed in toluene solvent. It was added and stirred. Thereafter, the mixture was stirred under reflux for 24 hours. After completion of the reaction, it was cooled to room temperature, diluted by adding toluene, and then hydrolyzed with 10% NaOH. Extraction was performed using ethyl acetate, and water was removed from the extracted organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound h was obtained through column chromatography wet purification using ethylacetate and hexane. (Yield: 65%)

(6) Synthesis of Compound 6

[Scheme 6-6]

In a nitrogen atmosphere, reactants of compound h, compound g (1.3 equivalent), Pd(dppf)Cl ₂ (4 mol%), and K ₃ PO ₄ (2 equivalent) were added to a toluene solvent and stirred. Thereafter, the mixture was stirred under reflux for 24 hours. After completion of the reaction, it was cooled to room temperature, diluted by adding toluene, and then hydrolyzed with 10% NaOH. Extraction was performed using ethyl acetate, and water was removed from the extracted organic layer using MgSO ₄ . The remaining organic solvent was removed, and compound 6 was obtained through column chromatography wet purification using ethylacetate and hexane. (Yield: 58%)

The mass spectrometry results of compounds 1 to 6 are shown in Table 1.

The luminescent properties of the compounds 1, 3, and 5 (Com1, Com3, and Com5) were measured under O ₂ -free conditions using Hamamatsu's Quantarus tau equipment, and the measurement results are shown in Table 2 and FIGS. 2a to 2c.

As shown in Table 2 and FIGS. 2a to 2c, each of compounds 1, 3, and 5 (Com1, Com3, Com5), which are delayed fluorescence compounds according to the present invention, exhibits a delayed fluorescence phenomenon of thousands to tens of thousands of nano-seconds (ns). seemed

As described above, the space charge transfer compound of the present invention is field activated, so that the singlet state (S ₁ ) excitons and the triplet state (T ₁ ) excitons are transferred to an intermediate state (I ₁ ), and both of them are participate in luminescence;

These field-activated complexes are monomolecular compounds having both an electron donor moiety and an electron acceptor moiety in one molecule, and electrons easily move through the intramolecular space. In the field-activated complex, electrons may move from the electron donor moiety to the electron acceptor moiety through a space between the electron donor moiety and the electron acceptor moiety under certain conditions, and thus charge separation may occur in the molecule.

The field activation complex is formed by the external environment, which can be easily confirmed by comparing the absorption wavelength and emission wavelength of the solution state using various solvents.

In the above equation, Δν is the stock shift value, and νabs and νfl are the wavenumbers of the maximum absorption wavelength and maximum emission wavelength, respectively. Also, h is Plank's constant, c is the velocity of light, a is the onsager cavity radius, and Δμ is the difference between the dipole moment of the excited state and the dipole moment of the ground state (Δμ = μ _e -μ _g ).

Δf is a value representing the orientational polarizability of the solvent and is expressed by the dielectric constant (ε) and the refractive index (n) of the solvent as shown in the following formula.

Formation of the field-activated complex can be confirmed by comparing absorption wavelengths and emission wavelengths in a solution state using various solvents. This is because the degree of polarization (magnitude of the dipole moment) at the time of excitation is determined by the polarity of the surroundings.

The directional polarization of the mixed solvent, Δf, can be used by calculating the directional polarization values of the pure solvent as a ratio of the mole fraction, and the formation of the field activated complex can be determined by using the above equation (Lippert-Mataga equation) to determine Δf and Δν It can be judged by checking whether a linear relationship appears when plotting .

That is, the field activation complex is stabilized according to the directional polarization of the solvent, and the emission wavelength shifts to a longer wavelength according to the stabilization degree. Accordingly, when the field-activated complex is formed, Δf and Δν form a linear graph, and conversely, when Δf and Δν form a linear graph, it can be seen that the light emitting material is a field-activated complex.

In the space charge transfer compound of the present invention, 25% of the singlet state excitons and 75% of the triplet state excitons are generated by the external environment, for example, the electromagnetic field generated when the organic light emitting diode device is driven. Intersystem crossing is interpreted as an intermediate state, and quantum efficiency is improved because light emission occurs while going from this intermediate state to the ground state. That is, luminous efficiency is improved by not only singlet state excitons but also triplet state excitons participating in light emission in the fluorescent material.

Hereinafter, the performance of the organic light emitting diode using the space charge transfer compound of the present invention and the organic light emitting diode using the comparative material of Chemical Formula 6 will be compared and described.

device fabrication

After the ITO substrate was patterned so that the light emitting area had a size of 3 mm X 3 mm, it was cleaned. Next, the substrate was transferred into a vacuum deposition chamber. After setting the base pressure to about 10 ^-6 ~ 10 ^-7 Torr, on the anode, ITO, i) hole injection layer (500Å, NPB (N,N'-di(naphthalen-1-yl)-N,N'- diphenyl-benzidine)), ii) hole transport layer (100Å, mCP (N,N'-Dicarbazolyl-3,5-benzene)), iii) light-emitting material layer (350Å, host (bis{2-[di(phenyl)phosphino ]phenyl}ether oxide/dopant (6%)), iv) electron transport layer (300Å, 1,3,5-tri(phenyl-2-benzimidazole)-benzene), v) electron injection layer (LiF), vi) cathode (Al) was sequentially laminated.

(1) Comparative Example (Ref)

In the above-described device, the compound of formula 7 was used as a dopant of the light emitting material layer.

(2) Experimental Example 1 (Ex1)

In the device described above, Compound 1 was used as a dopant for the light emitting material layer.

(3) Experimental Example 2 (Ex2)

In the above device, compound 3 was used as a dopant for the light emitting material layer.

(4) Experimental Example 3 (Ex3)

In the above device, compound 5 was used as a dopant for the light emitting material layer.

[Formula 7]

As can be seen from Table 3, the organic light emitting diode device using the space charge transfer compound of the present invention has improved characteristics in terms of driving voltage and luminous efficiency.

An embodiment of an organic light emitting diode device including the space charge transfer compound of the present invention is shown in FIG. 3 .

As shown in FIG. 3, the organic light emitting diode device includes a light emitting diode (E) positioned on a substrate (not shown).

The light emitting diode (E) includes a first electrode 110 serving as an anode, a second electrode 130 serving as a cathode, and an organic light emitting layer 120 formed between the first and second electrodes 110 and 130. made up of

Meanwhile, although not shown, a display device may be formed by including an encapsulation film including an inorganic layer and an organic layer and covering the light emitting diode E, and a cover window on the encapsulation film. In this case, since the substrate and the cover window have flexible characteristics, a flexible display device may be formed.

The first electrode 110 is made of a material having a relatively high work function value, for example, indium-tin-oxide (ITO), and the second electrode 130 is made of a material having a relatively low work function value, for example, indium-tin-oxide (ITO). For example, it is made of aluminum (Al) or aluminum alloy (AlNd). In addition, the organic light emitting layer 120 is composed of red, green, and blue organic light emitting patterns.

The organic light emitting layer 120 may have a single-layer structure, or may have a multi-layer structure to improve light emitting efficiency. For example, a hole injection layer (HIL) 121, a hole transporting layer (HTL) 122, and an emitting material layer (EML) are sequentially formed from the first electrode 110. 123, an electron transporting layer (ETL) 124, and an electron injection layer (EIL) 125.

Here, at least one of the hole injection layer 121, the hole transport layer 122, the light emitting material layer 123, the electron transport layer 124, and the electron injection layer 125 contains a space charge transfer compound represented by Chemical Formula 1. can be made including

For example, the light emitting material layer 123 may include the space charge transfer compound represented by Formula 1 above. The light emitting material layer 123 includes the space charge transfer compound of the present invention as a dopant material, may be doped with a host at about 1 to 30 wt%, and emits blue light.

The difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the lowest level unoccupied molecular orbital level of the host (LUMO _Host ) and the lowest unoccupied molecular orbital level (LUMO _Dopant ) of the dopant (|LUMO _Host -LUMO _Dopant |) is set to be 0.5 eV or less. Accordingly, charge transfer efficiency from the host to the dopant is improved.

At this time, the triplet energy of the dopant is smaller than the triplet energy of the host, and the difference between the singlet energy of the dopant and the triplet energy of the dopant (ΔE _ST ) is characterized in that 0.3 eV or less. The smaller ΔE _ST , the higher the luminous efficiency, and in the space charge transfer compound of the present invention, even if the difference between the singlet energy and the triplet energy (ΔE _ST ) of the dopant is relatively large, about 0.3 eV, the singlet state ( S ₁ ) excitons and triplet state (T ₁ ) excitons may transition to an intermediate state (I ₁ ). (ΔE _ST ≤0.3)

For example, as a host that satisfies these conditions, any one of Formula 8 below may be used. (Bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT), 2,8-di(9H-carbazol-9-yl)dibenzothiophene (DCzDBT), m respectively -bis(carbazol-9-yl)biphenyl (m-CBP), diphenyl-4-triphenylsilylphenyl-phosphine oxide (TPSO1), 9-(9-phenyl-9H-carbazol-6-yl)-9H-carbazole (CCP) )

[Formula 8]

Meanwhile, the light emitting material layer 123 may include the space charge transfer compound of the present invention as a host material and a dopant doped in an amount of about 1 to 30 wt% with respect to the host material, and emit blue light. Since development of a blue host with excellent properties is not sufficient, the degree of freedom in host selection can be increased by using the space charge transfer compound of the present invention as a host material.

At this time, the triplet energy of the dopant is smaller than the triplet energy of the host, which is the space charge transfer compound of the present invention.

In addition, the light emitting material layer 123 includes the space charge transfer compound of the present invention as a first dopant material and further includes a host material and a second dopant material, and the sum of the doped first and second dopant materials is It is doped at about 1 to 30 wt% with respect to the host material, thereby emitting blue light. Since the light emitting material layer 123 includes a host material and first and second dopant materials, light emitting efficiency and color are further improved.

At this time, the triplet energy of the first dopant, which is the space charge transfer compound of the present invention, is smaller than the triplet energy of the host and greater than the triplet energy of the second dopant. Also, at this time, the difference between the singlet energy of the first dopant and the triplet energy of the first dopant (ΔE _ST ) is 0.3 eV or less. The smaller ΔE _ST is, the higher the luminous efficiency is, and even if the difference between singlet energy and triplet energy (ΔE _ST ) of the first dopant, which is the space charge transfer compound of the present invention, is relatively large, about 0.3 eV, it is in a singlet state by an electric field. (S ₁ ) excitons and triplet state (T ₁ ) excitons may transition to an intermediate state (I ₁ ). (ΔE _ST ≤0.3)

As described above, in the space charge transfer compound of the present invention, the electron donor moiety and the electron acceptor moiety are bound in a molecule, and the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital ( The overlapping of the lowest unoccupied molecular orbital (LUMO) is reduced to form a charge transfer complex, thereby improving the luminous efficiency of the compound. That is, in the space charge transfer compound of the present invention, since excitons in the triplet state are used for light emission, the light emission efficiency is improved.

In addition, since the electron donor moiety and the electron acceptor moiety are coupled to the paracyclophane core, the distance between the electron donor moiety and the electron acceptor moiety is minimized. Therefore, since the transfer of charge is directly performed through the space between the electron donor moiety and the electron acceptor moiety, compared to a charge transfer complex in which charge moves through a bonding orbital of a molecule, a conjugate The conjugation length is shortened and the problem of red shift of light emitted from the compound is avoided. That is, it is possible to provide a blue compound having deep blue emission characteristics.

Accordingly, the light emitting efficiency of the organic light emitting diode device including the space charge transfer compound of the present invention is improved and high quality images can be realized.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention within the scope not departing from the technical spirit and scope of the present invention described in the claims below. You will understand that it can be done.

110: first electrode 120: organic light emitting layer
121: hole injection layer 122: hole transport layer
123: light emitting material layer 124: electron transport layer
125: electron injection layer 130: second electrode
E: organic light emitting diode

Claims (12)

delete Represented by Formula 1 below, D is selected from Formula 2, A is selected from Formula 3, L1 and L2 are each independently selected from unsubstituted benzene, and each of n1 and n2 is 0 or 1. charge transfer compounds.
[Formula 1]

[Formula 2]

[Formula 3]

According to claim 2,
A difference between singlet energy and triplet energy of the space charge transfer compound is 0.3 eV or less.

delete a first electrode;
a second electrode facing the first electrode;
An organic light emitting layer positioned between the first and second electrodes;
The organic light emitting layer,
Represented by Formula 1 below, D is selected from Formula 2, A is selected from Formula 3, L1 and L2 are each independently selected from unsubstituted benzene, and each of n1 and n2 is 0 or 1. An organic light emitting diode device comprising a charge transfer compound.
[Formula 1]

[Formula 2]

[Formula 3]

According to claim 5,
An organic light emitting diode device in which a difference between singlet energy and triplet energy of the space charge transfer compound is 0.3 eV or less.
According to claim 5,
The space charge transfer compound is used as a dopant, and the organic light emitting layer further comprises a host.
According to claim 7,
The difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the lowest level unoccupied molecular orbital level of the host (LUMO _Host ) and the lowest unoccupied molecular orbital level (LUMO _Dopant ) of the dopant (|LUMO _Host - LUMO _Dopant |) is less than 0.5eV organic light emitting diode device.
According to claim 5,
The space charge transfer compound is used as a host, and the organic light emitting layer further comprises a dopant.
According to claim 5,
The space charge transfer compound is used as a first dopant, and the organic emission layer further includes a host and a second dopant;
A first triplet energy of the first dopant is less than a second triplet energy of the host and greater than a third triplet energy of the second dopant.
According to claim 5,
The organic light emitting layer includes a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer and an electron injection layer,
At least one of the hole injection layer, the hole transport layer, the light emitting material layer, the electron transport layer and the electron injection layer includes the space charge transfer compound.
a substrate;
an organic light emitting diode element of claim 5 positioned on the substrate;
an encapsulation film covering the organic light emitting diode device;
A display device including a cover window on the encapsulation film.

Images