TWI646085B - Space charge transfer compound, organic light emitting diode using the same, and display device - Google Patents

Abstract

The present invention provides a space charge transfer compound comprising: a pair of cycloarane nuclei; an electron donating group selected from the group consisting of triphenylamine and diphenylamine; and an electron receiving group selected from pyrimidine A group consisting of diphenyltriazabenzene and triazole, wherein the electron donating group and the electron accepting group are respectively indirectly or directly bound to the paracyclophane with or without a linker.

Description

Space charge transfer compound, organic light emitting diode using the same, and display Device

The present invention relates to an organic light emitting diode (OLED), and more particularly, to a space light transfer compound having excellent light emitting efficiency, and an organic light emitting diode and a display device using the space charge transfer compound.

Due to the demand for large-sized display devices, flat-panel displays have been gradually developed as image display devices on the market. Among many types of flat-panel displays, organic light emitting diode display devices have developed rapidly.

In the organic light emitting diode, the cathode is used as an electron injection electrode, and the anode is used as a hole injection electrode. When the electrons of the cathode and the holes of the anode are injected into the luminescent material layer, the electrons and holes are combined and combined. An exciton is generated so that it can emit light from an organic light emitting diode. Flexible substrates, such as plastic substrates, can be used as substrate materials for organic light emitting diodes, and organic light emitting diodes have excellent voltage driving, power saving, and color purity characteristics.

The organic light emitting diode includes a first electrode as an anode on a substrate, a second electrode facing the first electrode as a cathode, and an organic light emitting layer provided between the first electrode and the second electrode.

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

The hole is transmitted by the first electrode to the luminescent material layer through the hole injection layer and the hole transport layer, and the electrons are transmitted to the luminescent material layer by the second electrode through the electron injection layer and the electron transport layer.

The aforementioned electrons and holes are combined in the light-emitting material layer to generate excitons, and these excitons transition from an excited state to a ground state to generate light.

The external quantum efficiency of the luminescent material in the luminescent material layer can be expressed by the following equation: η _ext = η _int × Γ × Φ × η _out-coupling .

In the above equation, "η _int " represents internal quantum efficiency, "r" represents charge balance constant, "Φ" represents emission quantum efficiency, and "η _out-coupling " represents light extraction efficiency.

The charge balance constant "r" refers to the balance constant between holes and electrons when an exciton is generated. In general, when the hole and electron match is 1: 1, the value of the charge balance constant is 1. The emission quantum efficiency "Φ" refers to the value of the light-emitting material with respect to the effective light-emitting efficiency. In the main emitter-dopant system, the emission quantum efficiency depends on the fluorescent photon efficiency of the dopant.

The internal quantum efficiency "η _int " refers to the ratio of the excitons that generate light to the excitons that are generated by the combination of holes and electrons. In fluorescent compounds, the maximum internal quantum efficiency is 0.25. When holes and electrons are combined to generate excitons, the ratio of singlet excitons to triplet excitons based on the spin structure is 1: 3. However, in fluorescent compounds, only singlet excitons, not triplet excitons, are used to emit light.

The light extraction efficiency "η _out-coupling " refers to the ratio of the light emitted from the display device to the light emitted from the light-emitting material layer. When an isotropic compound is deposited by thermal evaporation to form a thin film, the luminescent substance is diffuse. At this time, the light extraction efficiency of the display device can be assumed to be 0.2.

Therefore, the maximum luminous efficiency of an organic light emitting diode containing a fluorescent compound as a light emitting material is less than about 5%.

In order to overcome the disadvantage of poor luminous efficiency of fluorescent compounds, singlet excitation can be used at the same time. Phosphorescent compounds that emit electrons and triplet excitons have been developed for organic light emitting diodes.

Therefore, red and green phosphorescent compounds with relatively high luminous efficiency have been introduced and developed. However, there are currently no blue phosphorescent compounds that meet the requirements of luminous efficiency and reliability.

Therefore, the embodiments of the present invention relate to a space charge transfer compound and an OLED and a display device using the same, which can substantially avoid the limitations and disadvantages of the related prior art.

An object of the embodiments of the present invention is to provide a space-charge transfer compound having high luminous efficiency.

Another object of the embodiments of the present invention is to provide an OLED and a display device having improved light emitting efficiency.

The remaining features and advantages of the present invention will be described in detail below, some of which can be clearly understood from the description of the specification, or be understood through the implementation of the present invention. The objects and advantages of the present invention can be understood and understood from the structure specifically pointed out in the description and the drawings.

In order to achieve the objectives and advantages of the embodiments of the present invention, the embodiments of the present invention relate to a space charge transfer compound. The space charge transfer compound includes: a pair of cycloarane nuclei; an electron donating group, which is selected from the group consisting of A group consisting of triphenylamine and diphenylamine; and an electron-accepting group selected from the group consisting of pyrimidine, diphenyltriazabenzene, and triazole, wherein the electron-donating group and the electron-accepting group The groups are bound, indirectly or directly, to the paracycloalkane core with or without a linker, respectively.

The embodiment of the present invention also relates to a method such as A space charge transfer compound shown, where D is selected from , And A is selected from , Where each of L1 and L2 is selected from And each of n1 and n2 is 0 (zero) or 1, wherein R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl.

An embodiment of the present invention also relates to an organic light emitting diode. The organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting layer located on the first electrode. And the second electrode and includes a space-charge transfer compound, wherein the space-charge transfer compound includes: a pair of cycloarane nuclei; and an electron donating group selected from the group consisting of triphenylamine and diphenylamine A group; and an electron-accepting group selected from the group consisting of pyrimidine, diphenyltriazabenzene, and triazole, wherein the electron-donating group and the electron-accepting group use or do not use a linker Each indirectly or directly binds to the pair of cycloarane nuclei.

An embodiment of the present invention also relates to an organic light emitting diode. The organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting layer located on the first electrode. And the second electrode and includes Illustrated by a space charge transfer compound, wherein D is selected from , And A is selected from , Where each of L1 and L2 is selected from And each of n1 and n2 is 0 (zero) or 1, wherein R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl.

An embodiment of the present invention also relates to a display device. The display device includes: a substrate; an organic light emitting diode connected to the substrate; the organic light emitting diode includes: a first electrode; facing the first electrode; A second electrode; and an organic light emitting layer between the first electrode and the second electrode and including a space charge transfer compound; a coating film attached to the organic light emitting diode; and A cover window attached to the coating film, wherein the space charge transfer compound includes: a pair of cycloarane nuclei; an electron donating group selected from the group consisting of triphenylamine and diphenylamine; and An electron-accepting group, which is selected from the group consisting of pyrimidine, diphenyltriazabenzene, and triazole, wherein the electron-donating group and the electron-accepting group are indirectly or directly with or without a linker, respectively. Binding to the paracycloalkane core.

An embodiment of the present invention also relates to a display device including a substrate; an organic light emitting diode attached to the substrate and including: a first electrode; a second electrode facing the first electrode; And an organic light emitting layer located between the first electrode and the second electrode and including a space charge transfer compound as shown in Chemical Formula 1; a coating film attached to the organic light emitting diode; and A cover window is attached to the covering film.

[Chemical Formula 1]

Where D is selected from , And A is selected from , Where each of L1 and L2 is selected from And each of n1 and n2 is 0 (zero) or 1, wherein R is selected from the group consisting of hydrogen and a C1 alkyl group to a C10 alkyl group.

It can be understood that the foregoing description and the following detailed description are only used to further explain the requested embodiments or explanatory examples of the present invention.

110‧‧‧first electrode

120‧‧‧organic light emitting layer

121‧‧‧ Hole injection layer

122‧‧‧ Hole Transmission Layer

123‧‧‧luminescent material layer

124‧‧‧ electron transmission layer

125‧‧‧ electron injection layer

130‧‧‧Second electrode

E‧‧‧Organic Light Emitting Diode

S ₁ ‧‧‧single state

T ₁ ‧‧‧ triplet

I ₁ ‧‧‧ intermediate state

The drawings are provided to provide a further understanding of the present invention and constitute a part of this specification. The description and description of the embodiments of the present invention are used to explain the principle of the present invention.

FIG. 1 is a diagram showing a light-emitting mechanism through a space charge transfer compound according to the present invention; FIGS. 2A to 2C are diagrams showing a delayed fluorescence property by a space charge transfer compound according to the present invention; and FIG. 3 is based on A schematic cross-sectional view of an organic light emitting diode (OLED) of the present invention.

The meanings of the terms used in this manual are as follows.

Regarding the identification of the singular and plural, unless otherwise stated, all singular terms include the status of the plural. Regarding similar terms such as "first" and "second", only the elements are distinguished, and the scope of the present invention is not limited to these terms. Similar terms such as "including" and "having" mean that one or more features, integer values, steps, methods of operation, elements, components, or combinations thereof that may be added are not excluded. The term "at least one" includes a combination of one or more items, such as: "at least one selected from the first, second and third items", not only selected from each of the first, second and third items The third item also includes all combinations of two or more of the first item, the second item, and the third item. In addition, when an element is referred to as being "on" another element, it may be directly disposed on the upper surface of the other element or a third element may be interposed therebetween.

Reference will now be made in detail to the embodiments, which will also be described in conjunction with the drawings.

The space charge transfer compound of the present invention has a structure in which an electron-donating group and an electron-accepting group are bonded to or linked to a para-cycloarane core with or without a linker. The space charge transfer compound has the following chemical formula 1.

[Chemical Formula 1]

In Chemical Formula 1, each of n1 and n2 is 0 (zero) or 1. That is, the space charge transfer compound in Chemical Formula 1 has a structure selected from the following Chemical Formulas 2-1 to 2-4.

[Chemical Formula 2-1]

[Chemical Formula 2-2]

[Chemical Formula 2-3]

[Chemical Formula 2-4]

That is, the space charge transfer compound has a structure in which an electron donating group "D" and an electron accepting group "A" are directly bonded or connected to a paracycloparane core as shown in Chemical Formula 2-1 (n1 = n2 = 0). The first structure shown in the figure; or has a structure in which the electron donating group "D" and the electron receiving group "A" are bonded or linked to the paracycloparane core using linkers "L1" and "L2" as shown in Chemical Formula 2-2 ( n1 = n2 = 1). Alternatively, the space charge transfer compound has a structure in which an electron donating group "D" is bonded to a paracycloparaffinic nucleus using a linker "L2", and an electron receiving group "A" is directly bonded to a paracycloparaffinic nucleus such as a chemical formula The third structure shown by 2-3 (n1 = 0, n2 = 1). The space charge transfer compound may also have a compound in which the electron donating group "D" is directly bonded to the paracycloparane nucleus, and the electron receiving group "A" is bonded to the paracycloparane nucleus using a linker "L1" as in the chemical formula The fourth structure shown by 2-4 (n1 = 1, n2 = 0).

In Chemical Formula 1, the electron-donating group "D" is selected from the group consisting of triphenylamine and diphenylamine. For example, the electron-donating group "D" may be selected from the following Chemical Formula 3.

[Chemical Formula 3]

In Chemical Formula 1, the electron-accepting group "A" is selected from the group consisting of pyrimidine, phenyltriazine, and triazole. For example, the electron-accepting group "A" may be selected from the following Chemical Formula 4.

[Chemical Formula 4]

In Chemical Formula 1, the linkers "L1" and "L2" may be each independently selected from substituted or unsubstituted benzene. For example, the linkers "L1" and "L2" may be each independently selected from the following Chemical Formula 5.

[Chemical Formula 5]

In Chemical Formula 5, R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl.

In the space charge transfer compound, the electron donating group and the electron receiving group are combined or connected in the molecule, so that the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is reduced. Therefore, a charge transfer complex is generated, and the luminous efficiency of the space charge transfer compound is improved. That is, in this space charge transfer compound, a triplet exciton is used for light emission, and the light emission efficiency is improved.

In other words, since the space charge transfer compound of the present invention includes both an electron donating group and an electron receiving group, the charge can be easily transferred in the molecule, and thus the luminous efficiency can be improved.

In the space-charge transfer compound of the present invention, since the electron-donating group and the electron-receiving group are bonded or connected to the paracycloparane, the gap or distance between the electron-donating group and the electron-receiving group is changed. Reduce or minimize. Therefore, the charge can be directly transferred in the space between the electron donating group and the electron receiving group, so that the conjugate length in the space charge transfer compound is shorter than that in other compounds that generate charge transfer through the bonding orbital domain. Therefore, it is possible to prevent the problem of red shift caused when emitting light, and the space charge transfer compound of the present invention can provide deep blue light emission.

In addition, the space charge transfer compound of the present invention includes a benzene linker, which can minimize the steric hindrance between the electron donating group and the electron receiving group, thereby improving the stability of the compound.

Please refer to FIG. 1, which is a diagram showing a light emitting mechanism through a space charge transfer compound according to the present invention. In the space charge transfer compound of the present invention, both triplet excitons and singlet excitons are used to emit light, so that the luminous efficiency is improved.

That is, the triplet exciton is activated by the electric field, and the triplet exciton and singlet exciton are transitioned to the intermediate state "I ₁ ", and then transition to the ground state "S ₀ " to emit light. In other words, both the singlet state "S ₁ " and the triplet state "T ₁ " are transitioned to the intermediate state "I ₁ " (S _1- > I ₁ <-T ₁ ), while the singlet in the intermediate state "I ₁ " Both the heavy exciton and the triplet exciton are used to emit light, thereby improving the luminous efficiency. The compound having the aforementioned light emitting mechanism may be referred to as a field activated delayed fluorescence (FADF).

In some related fluorescent compounds, since the highest occupied molecular orbital and the lowest unoccupied molecular orbital are dispersed throughout the molecule, it is impossible to convert between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (selection rules ).

However, in the field-activated delayed fluorescent compounds, since the overlap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital in the molecule is relatively small, the interaction between the two is also small. Therefore, changes in the spin state of one electron do not affect other electrons. Therefore, A new charge transport band is created that does not conform to the selection rules.

In addition, because the electron-donating group and the electron-receiving group are in a space separated from each other in the molecule, a dipole moment is generated in the polarization state. In the polarization state, the interaction between the highest occupied molecular orbital and the lowest unoccupied molecular orbital is further reduced, making the light emission mechanism not in accordance with the selection rules. Thus, the activation delay field fluorescent compound, can be generated by the triplet "T _1" and the singlet state "S _1" to the intermediate state "I _1" transition, so that a triplet exciton can be used for light emission.

When the organic light emitting diode is driven, an intersystem crossing that generates 25% singlet "S ₁ " excitons and 75% triplet "T ₁ " excitons transitions to the intermediate state "I ₁ ", and These singlet or triplet excitons in the intermediate state "I ₁ " are then transitioned to the ground state to emit light. Therefore, the electric field activated delayed fluorescent compound (FADF) theoretically has a luminous efficiency of 100%.

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

[Chemical Formula 6]

The space charge transfer compound of the present invention has a wide band gap, so that the luminous efficiency of an OLED using the compound can be improved.

synthesis

1. Synthesis of compound 1

(1) Compound a

[Reaction formula 1-1]

In a nitrogen purifying system, 4,16 dibromo [2,2] diylene xylene (4,16-dibromo [2,2] paracyclophane), diphenylamine (1.1 equivalent), Pd (OAc) ₂ ( 0.019 equivalent), P (t-Bu) ₃ (50 wt%, 0.046 equivalent), and NaOt-Bu (sodium tert-butoxide, 1.9 equivalent) were added to the toluene solvent and stirred. The solution was then refluxed and stirred at a temperature of 120 ° C for 12 hours. After the reaction was completed, the solution was cooled to room temperature and extracted with water and ethyl acetate. After that, water was removed from the extracted organic layer by using magnesium sulfate (MgSO ₄ ), and then the solvent was removed. Compound a (yield: 65%) can be obtained by wet purification in a column chromatography using n-hexane and ethyl acetate.

(2) Compound b

[Reaction formula 1-2]

In a nitrogen purge system, compound a (17.9 mmol) was dissolved in tetrahydrofuran (THF) and stirred. At a temperature of -78 ° C, n-butyllithium (26.9 mmol) was slowly added, and the mixed solution was stirred for 1 hour. While maintaining the low temperature, (tri) ethyl borate (21.6 mmol) was added and stirred at room temperature. After the mixed solution was stirred at room temperature for 12 hours, the reaction was completed. Distilled water and a mixed solution of distilled water / hydrochloric acid (HCl) (8: 2) were slowly added to reach pH 2. The solution was then extracted with distilled water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the solvent was removed. Compound b (yield: 80%) can be obtained by wet purification using a column chromatography using n-hexane and ethyl acetate.

(3) Compound 1

[Reaction formula 1-3]

In a nitrogen purification system, add 2-chloro-4,6-diphenyl-1,3,5-triazabenzene, compound b (1 equivalent), sodium carbonate (Na ₂ CO ₃ , 0.6 equivalent) to In a solution of toluene / dioxane / distilled water (1: 1: 0.7) and stir. Pd (PPh ₃ ) ₄ (tetrakis (triphenylphosphine) palladium (0) (tetrakis (triphenylphosphine) Pd (0)), 0.3 equivalent) was further added and stirred for 16 hours. After the reaction was completed, the solution was cooled to room temperature. Rinse and filter the organic layer in silicone with distilled water. The solvent and distilled water were then removed, and the product was recrystallized from chloroform and dried to obtain Compound 1 (yield: 75%).

2. Synthesis of Compound 2

(1) Compound c

[Reaction formula 2-1]

In a nitrogen purge system, carbazole was dissolved in a 1,4-dioxane solvent, and copper iodide and potassium phosphate were added. In addition, 4,16 dibromo [2,2] xylene (1.1 equivalents) and trans-1,2-diaminocyclohexane were added. The solution was refluxed and stirred at a temperature of 110 ° C for 24 hours. After the reaction was completed, the solution was cooled to room temperature and extracted with water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Compound c was obtained by wet purification in a column chromatography using n-hexane and ethyl acetate (yield: 63%).

(2) Compound 2

[Reaction formula 2-2]

In a nitrogen purifying system, 2-chloro-4,6-diphenyl-1,3,5-triazine (2-chloro-4,6-diphenyl-1,3,5-triazine), compound c ( 1 equivalent), sodium carbonate (Na ₂ CO ₃ , 0.6 equivalent) was added to a toluene / dioxane / distilled water (1: 1: 0.7) solvent and stirred. Additional Pd (PPh ₃ ) ₄ (tetrakis (triphenylphosphine) palladium (0), 0.3 equivalent) was added and stirred for 16 hours. After the reaction was completed, the solution was cooled to room temperature. Rinse and filter the organic layer in silicone with distilled water. The solvent and distilled water were then removed, and the product was recrystallized from chloroform and dried to obtain compound 2 (yield: 70%).

3. Synthesis of Compound 3

[Reaction formula 3]

In a nitrogen purifying system, compound a, 5-pyrimidineboronic 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. The solution was refluxed and stirred for 24 hours. After the reaction was completed, the solution was cooled to room temperature and diluted with toluene. The solution was hydrolyzed with 10% NaOH and extracted with ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Compound 3 was obtained by wet purification using ethyl acetate and n-hexane in a column chromatography (yield: 80%).

4. Synthesis of compound 4

[Reaction formula 4]

In a nitrogen purifying system, compound c, 5-pyrimidineboronic 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. The solution was refluxed and stirred for 24 hours. After the reaction was completed, the solution was cooled to room temperature and diluted with addition of toluene. The solution was hydrolyzed with 10% NaOH, and the solution was extracted with ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Compound 4 (yield: 70%) can be obtained by wet purification using ethyl acetate and n-hexane in a column chromatography.

5. Synthesis of Compound 5

[Reaction formula 5]

In a nitrogen purge system, 1,2,4-triazole (1.5 equivalents), compound c, K ₂ CO ₃ (2 equivalents), and copper (I) 3-methylsalicylic acid (0.01 equivalents) were added to Dimethyl sulfene (DMSO) and stirred. The solution was stirred at 110 ° C for 3 hours and cooled to room temperature. The solution was filtered and washed with a small amount of dimethyl sulfoxide (DMSO). The solution was extracted with cooled distilled water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Finally, ethyl acetate and n-hexane were used for wet purification in a column chromatography, and after recrystallization, compound 5 was obtained (yield: 50%).

6. Synthesis of Compound 6

(1) Compound d

[Reaction formula 6-1]

In a nitrogen purification system, triphenylamine (29.9 equivalents), 1,4-dibromobenzene (44.9 mmol), palladium (II) acetate (2mol%), and tri-tert-butylphosphine (5mol %), And sodium tert-butoxide (2.03 equivalents) were added to a toluene solvent and stirred. The solution was refluxed and stirred for 12 hours for reaction. After the reaction was completed, the solution was extracted with distilled water and ethyl acetate. After using magnesium sulfate (MgSO ₄₎ removing moisture from the organic layer was extracted out, and remove the remaining solvent. After ethyl acetate and n-hexane were subjected to wet purification in a column chromatography and recrystallized, compound d was obtained (yield: 80%).

(2) Compound e

[Reaction formula 6-2]

In a nitrogen purge system, compound d (17.9 mmol) was dissolved in a THF solution and stirred. N-butyllithium (26.9 mmol) was slowly added to the solution at a temperature of -78 ° C, and the mixed solution was stirred for 1 hour. While maintaining the low temperature, trimethyl borate (21.6 mmol) was added, and the mixed solution was stirred at room temperature. After the mixed solution was stirred at room temperature for 12 hours, the reaction was completed. Distilled water and a mixed solution of distilled water / hydrochloric acid (HCl) (8: 2) were slowly added until pH 2 was reached. The solution was extracted with distilled water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the solvent was removed. Compound e (yield: 87%) can be obtained by wet purification using n-hexane and ethyl acetate in a column chromatography.

(3) Compound f

[Reaction formula 6-3]

In a nitrogen purge system, 1,2,4-triazole (1 equivalent), 1,4-dibromobenzene, K ₂ CO ₃ (2 equivalents), and copper (I) 3-methylsalicylic acid ( 0.01 equivalent) was added to dimethylsulfinium (DMSO) and stirred. The solution was stirred at 110 ° C for 3 hours and cooled to room temperature. The solution was filtered and washed with a small amount of DMSO. The solution was extracted with cooled distilled water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Finally, ethyl acetate and n-hexane were used for wet purification in a column chromatography, and after recrystallization, compound f was obtained (yield: 56%).

(4) Compound g

[Reaction formula 6-4]

In a nitrogen purge system, compound f was dissolved in a THF solution and stirred. N-butyllithium (1.5 equivalents) was slowly added to the solution at a temperature of -78 ° C, and stirred for 1 hour. While maintaining low temperature, trimethyl borate (1.2 equivalents) was added, and the mixed solution was stirred at room temperature. After the mixed solution was stirred at room temperature for 12 hours, the reaction was completed. Distilled water and a mixed solution of distilled water / hydrochloric acid (HCl) (8: 2) were slowly added until pH 2 was reached. The solution was extracted with distilled water and ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the solvent was removed. Compound g was then obtained by wet purification using a column chromatography using n-hexane and ethyl acetate (yield: 79%).

(5) Compound h

[Reaction formula 6-5]

In a nitrogen purification system, 4,16 dibromo [2,2] xylene reactants, compound e (1.1 equivalents), Pd (dppf) Cl ₂ (4 mol%), and K ₃ PO ₄ (2 equivalents) ) Was added to the toluene solvent and stirred. The solution was refluxed and stirred for 24 hours. After the reaction was completed, the solution was cooled to room temperature and diluted with addition of toluene. The solution was hydrolyzed with 10% NaOH, and the solution was extracted with ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Compound h (yield: 80%) can be obtained by wet purification using ethyl acetate and n-hexane in a column chromatography.

(6) Compound 6

[Reaction formula 6-6]

In a nitrogen purifying system, compound h, compound g (1.3 equivalents), Pd (dppf) Cl ₂ (4 mol%), and K ₃ PO ₄ (2 equivalents) were added to a toluene solvent and stirred. The solution was refluxed and stirred for 24 hours. After the reaction was completed, the solution was cooled to room temperature, and diluted by adding toluene. The solution was hydrolyzed with 10% NaOH, and the solution was extracted with ethyl acetate. Thereafter, water was removed from the extracted organic layer using magnesium sulfate, and the remaining organic solvent was removed. Compound 6 (yield: 58%) can be obtained by wet purification using ethyl acetate and n-hexane in a column chromatography.

The mass spectrum data of the above compounds 1 to 6 are shown in Table 1.

The light emission characteristics of the above compounds 1, 3, and 5 were measured, and the results are shown in Table 2 and Figs. 2A to 2C. (Quantarus tau apparatus of Hamamatsu Co., Ltd., under anaerobic conditions).

As shown in Table 2 and FIGS. 2A to 2C, the space charge transfer compounds 1, 3, and 5 according to the present invention have delayed light emission of thousands to tens of thousands of nanoseconds (ns) compared to fluorescent light emission (instantaneous). (Delay) characteristics.

As described above, according to the present invention by the space charge transport compound is activated after the electric field, the singlet state "S _1" and triplet "T _1" are transition to the intermediate state "I _1." Therefore, both singlet excitons and triplet excitons can be used for light emission.

The electric field activated delayed fluorescent compound (FADF) is a single-molecule compound having an electron-donating group and an electron-accepting group in a single molecule, so charge transfer is easily generated through a space in the molecule. In the FADF under special conditions, the charge can be separated from the electron donating group to the electron accepting group through the space between the electron donating group and the electron receiving group.

Electric field activation delays the activation of fluorescent compounds by external factors. It can be confirmed by comparing the difference between the absorption peak and the emission peak of the compound solution.

In the above formula, "△ υ" refers to the stock-shift value, and "υabs" and "υfl" refer to the wave numbers of the maximum absorption peak and the maximum emission peak, respectively. "H" refers to Planck's constant, "c" refers to the speed of light, "a" refers to the onsager cavity radius, and "△ μ" refers to the coupling between the excited state and the ground state Polar moment difference (△ μ = μe-μg).

"△ f" refers to the orientational polarizability of the solvent, which can be a function of the dielectric constant (ε) of the solvent and the refractive index (n) of the solvent.

Since the intensity of the dipole moment in the excited state is determined by the peripheral polarity (such as the polarity of the solvent), the electric field activation delayed fluorescent compound can be confirmed by comparing the difference between the absorption peak and the emission peak of the compound solution.

The orientation polarizability (△ f) of the mixed solvent can be obtained by using each pure solvent and its mole fraction. When using the aforementioned Lippert-Mataga equation to make Δf and Δυ have a linear relationship, the compound may provide FADF luminescence.

That is, when the FADF complex is stabilized due to the orientation polarizability of the solvent, the emission peak will shift by a long wavelength according to the stabilized angle. Therefore, when the compound provides FADF luminescence, the relationship between Δf and Δυ is a straight line on the graph. That is, when Δf and Δυ are linearly related, the compound provides FADF light emission.

In the delayed fluorescent compound of the present invention, 25% singlet excitons and 75% triplet excitons are transitioned to an intermediate state (such as an intersystem transition) by an external force (such as an electric field generated when an organic light emitting diode is driven). ). The excitons in the intermediate state are then transitioned to the ground state to emit light. That is, in the delayed fluorescent compound, both the singlet exciton and the triplet exciton are used to emit light, thereby improving the luminous efficiency.

Organic light emitting diode (OLED)

An indium tin oxide layer is deposited on a substrate and etched to form an anode (3mm * 3mm). The substrate is placed in a vacuum space, sequentially forming a hole injection layer (500Å, N, N'- di (naphthyl on the bottom surface of the anode pressure of about 10 ^-6 to 10 ^-7 torr -1- Group) -N, N'-diphenyl-diaminobiphenyl (N, N'-di (naphthalen-1-yl) -N, N'-diphenyl-benzidine)), NPB), a hole transport layer (100Å, N, N'-Diazolyl-3,5-benzene (N, N'-Dicarbazolyl-3,5-benzene, mCP)), a luminescent material layer (350Å, main emitter: two [2- ((Oxo) diphenylphosphino) phenyl] ether (bis {2- [di (phenyl) phosphino] phenyl} ether oxide) and 6% dopants), an electron transport layer (300Å, 1,3 , 5-tris (phenyl-2-benzimidazole) benzene (1,3,5-tri (phenyl-2-benzimidazole) -benzene)), an electron injection layer (lithium fluoride), and a cathode (aluminum) .

(1) Comparative example (control)

The control compound in the following chemical formula 7 is used as a dopant to form OLED.

(2) Example 1

Compound 1 is used as a dopant to form an OLED.

(3) Example 2

Compound 3 is used as a dopant to form an OLED.

(4) Example 3

Compound 5 is used as a dopant to form an OLED.

[Chemical Formula 7]

As shown in Table 3, the OLEDs using the compounds of the present invention (Examples 1 to 3) have improved driving voltage and emission efficiency.

FIG. 3 is a schematic cross-sectional view of an OLED according to the present invention.

As shown in FIG. 3, the organic light emitting diode E is formed on a substrate (not shown). The organic light emitting diode E includes a first electrode 110 as an anode and a second electrode as a cathode. 130, and an organic light emitting layer 120 in between.

Although not shown in the figure, a covering film including at least one inorganic layer and at least one organic layer is covered on the organic light emitting diode E, and a covering window may be further formed on the covering film to manufacture the organic light emitting diode. Display device for polar body E. The substrate, the cover film, and the cover window may have flexible characteristics, so as to provide a flexible display device.

The first electrode 110 is made of a material having a relatively high work function, and the second electrode 120 is made of a material having a relatively low work function. For example, the first electrode 110 may be made of an indium tin oxide (ITO) material, and the second electrode 130 may be made of an aluminum or aluminum alloy (AlNd) material. The organic light emitting layer 120 may include red, green, and blue light emitting types.

The organic light emitting layer 120 may have a single-layer structure. In addition, in order to improve the light emitting efficiency, the organic light emitting layer 120 may include a hole injection layer 121, a hole transport layer 122, a light emitting material layer 123, an electron transport layer 124, and an electron injection layer 125 sequentially stacked on the first electrode 110.

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 includes a space charge transfer compound as shown in Chemical Formula 1.

For example, the light emitting material layer 123 may include a compound through a space charge transfer as in Chemical Formula 1. The space charge transfer compound is used as a dopant, and the light emitting material layer 123 may further include a main light emitting body to emit blue light. In this case, the dopant is approximately 1 to 30% by weight with respect to the main light-emitting body.

The difference between the HOMO (HOMO _Host ) of the main emitter and the HOMO (HOMO _Dopant ) of the dopant, or the difference between the LUMO (LUMO _Host ) of the main emitter and the LUMO (LUMO _Dopant ) of the dopant is less than 0.5eV [(HOMO _Host -HOMO _Dopant ) 0.5eV or (LUMO _Hos -LUMO _Dopant ) 0.5eV]. In this example, the charge transfer efficiency from the main emitter to the dopant is improved.

The triplet energy of the dopant is smaller than the triplet energy of the main emitter, and the difference between the singlet energy of the dopant and the triplet energy of the dopant is less than 0.3eV (△ E _ST 0.3eV). The smaller the ΔE _ST value, the higher the luminous efficiency. In the space charge transfer compound of the present invention, even if the difference ΔEST between the singlet energy of the dopant and the triplet energy of the dopant is about 0.3eV, although this value is quite large, the singlet state "S ₁ The exciton and triplet "T ₁ " excitons can still transition to the intermediate state "I ₁ ".

For example, the main luminous body satisfying the above conditions may be selected from the materials in Chemical Formula 8. (Its sequence is: bis [2-((oxo) diphenylphosphino) phenyl] ether [(Bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO)], 2,8-bis (bis Phenyloxyphosphino) dibenzothiophene [2,8-bis (diphenylphosphoryl) dibenzothiophene (PPT)], 2,8-bis (9H-triphenylamine-9-yl) dibenzothiophene [2,8-di (9H-carbazol-9-yl) dibenzothiophene (DCzDBT)], m-bis (triphenylamine-9-yl) biphenyl [m-bis (carbazol-9-yl) biphenyl (m-CBP)], diphenyl Diphenyl-4-triphenylsilylphenyl-phosphine oxide (TPSO1)] and 9- (9-phenyl-9H-triphenyl-6-yl) -9H-triphenyl [9 -(9-phenyl-9H-carbazol-6-yl) -9H-carbazole (CCP)].)

[Chemical Formula 8]

On the other hand, the space charge transfer compound of the present invention can be used as a main light emitter in the light emitting material layer 123, and the light emitting material layer 123 further includes a dopant to emit blue light. In this case, the dopant is approximately 1 to 30% by weight with respect to the main light-emitting body. Due to the lack of development of a blue light main light emitting body with excellent characteristics, the space charge transfer compound of the present invention can be used as a main light emitting body to increase the degree of freedom of the main light emitting body. In this case, the triplet energy of the dopant may be smaller than the triplet energy of the main emitter of the space charge transfer compound of the present invention.

The light emitting material layer 123 may include a first dopant, a main light emitter, and a second dopant through the space charge transfer compound of the present invention. The sum of the weight% of the first and second dopants may be about 1 to 30 to emit blue light. In this case, the luminous efficiency and color purity can be further improved.

In this case, the triplet energy of the first dopant (ie, by the space charge transfer compound as in the present invention) may be smaller than the triplet energy of the main light emitter and larger than the triplet energy of the second dopant. In addition, the difference between the singlet energy of the first dopant and the triplet energy of the first dopant is less than 0.3eV (△ E _ST 0.3eV). The smaller the ΔE _ST value, the higher the luminous efficiency. In the space charge transfer compound of the present invention, even if the difference between the singlet energy of the dopant and the triplet energy of the dopant ΔE _{ST is} about 0.3eV, although this value is quite large, the singlet state "S ₁ "and triplet excitons" T ₁ "still exciton transition to the intermediate state" I _1. "

As described above, in the space charge transfer compound of the present invention, since the electron donating group and the electron receiving group are combined or connected in one molecule, and the overlap between HOMO and LUMO is reduced, the passage space of the present invention is reduced. The charge transfer compound, such as the same charge transfer complex, can improve the luminous efficiency of the compound. That is, in the space charge transfer compound of the present invention, excitons in triplet energy participate in light emission, so that the light emission efficiency of the compound is improved.

In addition, since the electron-donating group and the electron-receiving group are bonded or connected to the paracycloalkane core, the space between the electron-donating group and the electron-receiving group is reduced or minimized. Therefore, the charge can be directly transferred through the space between the electron donating group and the electron receiving group, thereby reducing the conjugate length. Therefore, it is possible to prevent the problem that the emitted light is red-shifted. That is, the organic light emitting diode using the space charge transfer compound of the present invention can emit deep blue light. Therefore, the organic light emitting diode using the space charge transfer compound of the present invention is more excellent in terms of light emission efficiency and image quality.

Anyone skilled in this art can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application and its equivalent.

The present invention claims the priority of Korean Patent Application No. 10-2014-0173911 filed on December 5, 2014 and Korean Patent Application No. 10-2015-0144199 filed on October 15, 2015, the entirety of which are incorporated herein by reference. invention.

Claims (16)

A space charge transfer compound comprising: a pair of cycloarane nuclei; an electron donating group selected from the group consisting of triphenylamine and diphenylamine; and an electron receiving group selected from the group consisting of pyrimidine and diphenyl A group consisting of a triazine and a triazole, wherein the electron donating group and the electron receiving group are respectively indirectly or directly bound to the paracyclophane with or without a linker. When the azole is directly bonded to the pair of cycloarene cores without a linker, the nitrogen atom of the triazole is bonded to the pair of cycloarene cores, and the singlet state of the space charge transfer compound can be related to the space space charge The triplet energy of the transferred compound differs by less than 0.3 eV. A space charge transfer compound represented by Chemical Formula 1: Where D is selected from Chemical Formula 2 and A is selected from Chemical Formula 3, wherein each L1 and L2 is selected from Chemical Formula 4, and each n1 and n2 are 0 (zero) or 1, [Chemical Formula 2] And wherein R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl, and wherein both the singlet energy of the space charge transfer compound and the triplet energy of the space charge transfer compound are The phase difference is less than 0.3eV. An organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting layer between the first electrode and the second electrode. The organic light emitting layer A space charge transfer compound is included, wherein the space charge transfer compound includes: a pair of cycloarane nuclei; an electron donating group selected from the group consisting of triphenylamine and diphenylamine; and An electron-accepting group selected from the group consisting of pyrimidine, diphenyltriazabenzene, and triazole, wherein the electron-donating group and the electron-accepting group use or do not use a linker. Respectively indirectly or directly bound to the pair of naphthene nuclei, wherein when triazole is directly bound to the pair of naphthene nuclei without a linker, the nitrogen atom of the triazole is bonded to the pair of naphthene nuclei, and The difference between the singlet energy of the space charge transfer compound and the triplet energy of the space charge transfer compound is less than 0.3 eV. The organic light emitting diode according to item 3 of the scope of patent application, wherein the organic light emitting layer includes a hole injection layer (HIL), a hole transport layer (HTL), a light emitting material layer (EML), an electron A transport layer (ETL) and an electron injection layer (EIL), and at least one of the hole injection layer, the hole transmission layer, the luminescent material layer, the electron transport layer, and the electron injection layer includes the Space charge transfer compounds. According to the organic light emitting diode according to item 3 of the scope of the patent application, wherein the organic light emitting layer further includes a main light emitting body, and the space charge transfer compound is used as a dopant. According to the organic light-emitting diode according to item 5 of the scope of patent application, wherein the highest occupied molecular orbital (HOMO) of the main emitter is different from the highest occupied molecular orbital of the dopant, or the main emitter The difference between the lowest unoccupied molecular orbital (LUMO) and the lowest unoccupied molecular orbital of the dopant is less than 0.5 eV. According to the organic light-emitting diode according to item 3 of the patent application scope, wherein the organic light-emitting layer further includes a dopant, and the space-charge-transfer compound system serves as a main light-emitting body. The organic light-emitting diode according to item 3 of the patent application scope, wherein the organic light-emitting layer further includes a main light-emitting body and a first dopant, and the space charge transfer compound system serves as a second dopant And wherein the triplet energy of the second dopant is smaller than the triplet energy of the main light emitter, but larger than the triplet energy of the first dopant. An organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting layer between the first electrode and the second electrode. The organic light emitting layer Including a space charge transfer compound as shown in Chemical Formula 1, Where D is selected from Chemical Formula 2, and A is selected from Chemical Formula 3, wherein each of L1 and L2 is selected from Chemical Formula 4, and each of n1 and n2 is 0 (zero) or 1, [Chemical Formula 4] And wherein R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl, and wherein both the singlet energy of the space charge transfer compound and the triplet energy of the space charge transfer compound are The phase difference is less than 0.3eV. The organic light-emitting diode according to item 9 of the scope of patent application, wherein the organic light-emitting layer includes: a hole injection layer (HIL), a hole transport layer (HTL), a light-emitting material layer (EML), a An electron transport layer (ETL) and an electron injection layer (EIL), wherein at least one of the hole injection layer, the hole transport layer, the luminescent material layer, the electron transport layer, and the electron injection layer includes the Space charge transfer compounds. According to the organic light emitting diode according to item 9 of the scope of the patent application, wherein the organic light emitting layer further includes a main light emitting body, and the space charge transfer compound is used as a dopant. According to the organic light-emitting diode according to item 11 of the scope of patent application, wherein the highest occupied molecular orbital (HOMO) of the main emitter and the highest occupied molecular orbital of the dopant are different, or the main emitter The difference between the lowest unoccupied molecular orbital (LUMO) and the lowest unoccupied molecular orbital of the dopant is less than 0.5 eV. According to the organic light emitting diode according to item 9 of the scope of the patent application, wherein the organic light emitting layer further includes a dopant, and the space charge transfer compound is used as a main light emitting body. The organic light-emitting diode according to item 9 of the scope of patent application, wherein the organic light-emitting layer further includes a main light-emitting body and a first dopant, and the space charge transfer compound system serves as a second dopant And wherein the triplet energy of the second dopant is smaller than the triplet energy of the main light emitter, but larger than the triplet energy of the first dopant. A display device includes: a substrate; an organic light emitting diode attached to the substrate; the organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting diode A layer between the first electrode and the second electrode, the organic light emitting layer includes a space charge transfer compound; a coating film attached to the organic light emitting diode; and a cover window attached to On the coating film, the space-charge transfer compound includes: a pair of cycloarane nuclei; an electron donating group, the electron donating group is selected from the group consisting of triphenylamine and diphenylamine; and an electron Receiving group, the electron receiving group is selected from the group consisting of pyrimidine, diphenyltriazabenzene, and triazole, wherein the electron donating group and the electron receiving group are indirect with or without a linker, respectively Or directly bonded to the pair of naphthene nuclei, wherein when triazole is directly bonded to the pair of naphthene nuclei without a linker, the nitrogen atom of the triazole is bonded to the pair of naphthene nuclei, and wherein, Should pass Both the charge transfer between the singlet energy transfer compound and a compound of the space charge by the triplet energy by less than 0.3eV. A display device includes: a substrate; an organic light emitting diode attached to the substrate; the organic light emitting diode includes: a first electrode; a second electrode facing the first electrode; and an organic light emitting diode A layer between the first electrode and the second electrode, the organic light emitting layer including a space charge transfer compound as shown in Chemical Formula 1; a coating film attached to the organic light emitting diode; and A cover window attached to the coating film, [Chemical Formula 1] Where D is selected from Chemical Formula 2, and A is selected from Chemical Formula 3, wherein each of L1 and L2 is selected from Chemical Formula 4, and each of n1 and n2 is 0 (zero) or 1, And wherein R is selected from the group consisting of hydrogen and C ₁ alkyl to C ₁₀ alkyl, and wherein both the singlet energy of the space charge transfer compound and the triplet energy of the space charge transfer compound are The phase difference is less than 0.3eV.