CN110951482A

CN110951482A - Phosphorescent compound and organic electroluminescent device using same

Info

Publication number: CN110951482A
Application number: CN201911010625.5A
Authority: CN
Inventors: 郑贤哲; 王世超; 吴信蔚; 华万鸣
Original assignee: Uiv Chem Yurui Shanghai Chemical Co ltd
Current assignee: Uiv Chem Yurui Shanghai Chemical Co ltd
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-04-03

Abstract

The invention relates to the technical field of organic electroluminescence, in particular to a phosphorescent compound and an organic electroluminescent device using the same. The structural formula is shown as formula 1 and formula 2:

in the above structural formulae 1 and 2, Z is independently selected from the following structures:

wherein X1 toX2 is independently selected from a N atom or a C atom; wherein at least one of X1 to X2 is N; wherein Ar is independently selected from the group consisting of C6-C30 aryl, C2-C30 heteroaryl. The organic electroluminescent device of the present invention has reduced visibility with increased color purity, operates efficiently at low voltage even when the color purity is high, has increased current efficiency and high luminous efficiency with high internal quantum efficiency, and has simple manufacturing process, high process efficiency and low production cost by using a phosphorescent compound as a luminescent material of the organic electroluminescent device.

Description

Phosphorescent compound and organic electroluminescent device using same

Technical Field

The invention relates to the technical field of organic electroluminescence, in particular to a phosphorescent compound and an organic electroluminescent device using the same.

Background

Recently, the demand for flat panel displays (e.g., liquid crystal displays and plasma display panels) is increasing. However, these flat panel displays have a lower response time and a narrower viewing angle than Cathode Ray Tubes (CRTs). An Organic Light Emitting Diode (OLED) device is one of the next-generation flat panel displays that can solve the above problems and have a small footprint.

The elements of the OLED device may be formed on a flexible substrate, such as a plastic substrate. In addition, OLED devices have advantages in view angle, driving voltage, power consumption, and color purity. Outside, the OLED device is sufficient to produce full color images. In general, a light emitting diode of an OLED device includes an anode, a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an Emitting Material Layer (EML), an Electron Transport Layer (ETL), an Electron Injection Layer (EIL), and a cathode. The OLED device emits light by: electrons and holes are injected into the light-emitting compound layer from the cathode as an electron injection electrode and from the anode as a hole injection electrode, respectively, so that the electrons and the holes are recombined to generate excitons, and the excitons are made to transition from an excited state to a ground state.

The principle of luminescence can be divided into fluorescence and phosphorescence. In fluorescence emission, organic molecules in a singlet excited state transition to a ground state, thereby emitting light. On the other hand, in phosphorescence, organic molecules in a triplet excited state transition to a ground state, thereby emitting light. When the light emitting material layer emits light corresponding to the energy band gap, singlet excitons having 0 spin and triplet excitons having 1 spin are generated in a ratio of 1: 3. The ground state of the organic material is a singlet state, which allows singlet excitons to transition to the ground state with accompanying light emission. However, since the triplet excitons cannot undergo transition accompanied by light emission, the internal quantum efficiency of the OLED device using the fluorescent material is limited to within 25%.

On the other hand, if the spin orbit coupling momentum is high, the singlet state and the triplet state are mixed so that an intersystem crossing occurs between the singlet state and the triplet state, and the triplet exciton may also transition to the ground state with accompanying light emission. The phosphorescent material may use triplet excitons and singlet excitons, so that an OLED device using the phosphorescent material may have an internal quantum efficiency of 100%.

Recently, iridium complexes, such as bis (2-phenylquinoline) (acetylacetonate) iridium (iii) (Ir (2-phq)2(acac)), bis (2-benzo [ b ] thiophen-2-ylpyridine) (acetylacetonate) iridium (iii) (Ir (btp)2(acac)), and tris (2-phenylquinoline) iridium (iii) Ir (2-phq)3 dopants have been introduced. In order to obtain high current luminous efficiency (Cd/a) using a phosphorescent material, excellent internal quantum efficiency, high color purity, and long lifetime are required. In particular, the higher the color purity, i.e., the higher the cie (x), the poorer the color sensitivity. As a result, it is very difficult to obtain light emission efficiency at high internal quantum efficiency. Therefore, there is a need for novel red phosphorescent compounds having excellent color purity (CIE (X) ≧ 0.65) and high luminous efficiency.

On the other hand, in addition to the iridium complex described above, for example, 4, 4-N, N-Carbazole Biphenyl (CBP) or other metal complexes are used as the red phosphorescent compound. However, these compounds do not have ideal solubility in a solvent, and thus cannot form a light emitting layer by a solution process. The light emitting layer should be formed through a deposition process, and thus, the manufacturing process is very complicated and the process efficiency is very low. In addition, the amount of waste material in the deposition process is very large, resulting in increased production costs.

Disclosure of Invention

The present invention is directed to providing a phosphorescent compound and an organic electroluminescent device using the same to solve some or all of the disadvantages of the related art.

In order to achieve the above objects, the present invention provides a phosphorescent compound having a structural formula as shown in formula 1 and formula 2:

wherein X1 to X2 are independently selected from N atoms or C atoms;

wherein at least one of X1 to X2 is N;

wherein Ar is independently selected from the group consisting of C6-C30 aryl, C2-C30 heteroaryl.

Preferably, the C6-C30 aryl group is one selected from phenyl, naphthyl, biphenyl, terphenyl and phenanthryl.

Preferably, the C2-C30 heteroaryl group is one selected from the group consisting of a pyridyl group, a bipyridyl group, a quinolyl group, an isoquinolyl group, a phenanthrolinyl group and a triazinyl group.

Preferably, Ar is independently selected from the following:

preferably, the phosphorescent compounds are independently selected from the following compounds:

an organic electroluminescent device using the above phosphorescent compound comprises an organic electroluminescent device comprising an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode deposited in this order, the phosphorescent compound serving as a host material of the light emitting layer.

Compared with the prior art, the invention has the beneficial effects that:

1. in the phosphorescent compound and the organic electroluminescent device using the same, the luminance can reach 1101cd/m2 under the condition that the current is 0.9mA, while the luminance of a common luminescent material is only 780cd/m2 under the condition of the same current, so that the luminance of a light source is effectively improved.

2. In the phosphorescent compound and the organic electroluminescent device using the same, the current efficiency can reach 11.0cd/A under the condition that the current is 0.9mA, while the current efficiency of the common luminescent material is only 7.8cd/A under the condition of the same current, and the current efficiency is increased by more than 40%.

3. In the phosphorescent compound and the organic electroluminescent device using the same, the maximum power efficiency can reach 5.7Im/W under the condition that the current is 0.9mA, and the power efficiency of a common luminescent material is only 3.3Im/W under the condition of the same current, so that the power efficiency is effectively improved.

4. In the phosphorescent compound and the organic electroluminescent device using the same, the lowest voltage for driving the organic electroluminescent device to work is only 6.0V under the condition that the current is 0.9mA, and the voltage of a common luminescent material is 7.5V under the condition of the same current, so that the energy-saving effect is realized.

5. In the phosphorescent compound and the organic electroluminescent device using the same, when the color purity is high, the voltage of an organic light-emitting tube provided by the invention is 6.2V, and the power efficiency is as high as 5.1Im/W, while when the color purity is the same, the voltage of a common light-emitting material is 7.5V, the power efficiency is only 3.3Im/W, and the current efficiency is increased by more than 45%.

6. The phosphorescent compound and the organic electroluminescent device using the same adopt the phosphorescent compound as a light-emitting element, and have the advantages of simple manufacturing process, high process efficiency and low production cost.

7. In the phosphorescent compound and the organic electroluminescent device using the same, N is at X2 position, the performance is better, and the service life is doubled under the same condition.

Drawings

FIG. 1 is a schematic diagram of a structural formula of a red phosphorescent compound of the present invention;

FIG. 2 is a schematic diagram of a structural formula II of the red phosphorescent compound of the present invention;

FIG. 3 is a structural layer diagram of an organic light emitting device according to the present invention;

fig. 4 is a graph showing a relationship between luminance chromaticity and visibility of the organic light emitting device of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Referring to fig. 1-4, the present invention provides a solution:

the invention provides a phosphorescent compound, which has a structural formula shown as formula 1 and formula 2:

wherein X1 to X2 are independently selected from N atoms or C atoms;

wherein at least one of X1 to X2 is N;

The C6-C30 aryl is selected from one of phenyl, naphthyl, biphenyl, terphenyl and phenanthryl.

The C2-C30 heteroaryl is selected from one of pyridyl, bipyridyl, quinolyl, isoquinolyl, phenanthrolinyl and triazinyl.

Ar is independently selected from the following:

the phosphorescent compounds are independently selected from the following compounds:

an organic electroluminescent device using the phosphorescent compound comprises an organic electroluminescent device, wherein the organic electroluminescent device sequentially comprises an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode which are deposited, and the phosphorescent compound is used as a host material of the light-emitting layer.

In order to make the technical means, the original characteristics, the achieved purposes and the effects of the invention easy to understand, the invention is further described with reference to the figures and the specific embodiments.

As the red phosphorescent compounds with the structural formulas shown as formula 1 and formula 2 have excellent pure chromaticity, high brightness and excellent luminous efficiency, the technical scheme and the achieved technical effect provided by the invention are proved by taking RH-001, RH-007, RH-073 and RH-079 as examples of preparation methods and test results.

In the following embodiments, NPB is 4, 4 ' -bis [ N- (1-naphthyl) -N-phenylamino ] biphenyl, CBP is 4, 4 ' -N, N ' -dicarbakisbiphenyl, CuPc is copper phthalocyanine, LiF lithium fluoride, ITO is indium tin oxide, and Alq3 is tris (8-hydroxyquinoline) aluminum.

LC-MS, liquid chromatography-mass spectrometer, M/Z: ratio of number of protons/number of charges.

The compounds copper (II) phthalocyanine (CuPc), NPB, (btp)2Ir (acac), Alq3 and CBP used in the present embodiment have the following structural formulae.

Examples of formation

1. Synthesis of intermediate Sub-1:

in a 2000mL reaction flask was charged M-bromoiodobenzene (50.0g, 176.7mmol), 2-amino-1-bromonaphthalene (43.2g, 194.4mmol, dry and degassed toluene (1000mL) was added as solvent, then sodium tert-butoxide (51.0g, 530.2mmol), palladium acetate (2 mol%) and 1, 1 '-binaphthyl-2, 2' -bis-diphenylphosphine (4 mol%). after the end of the addition, the temperature was raised to 110 ℃ for reaction 16H, the reaction was terminated and cooled to room temperature, filtered after adsorption with activated carbon, the solvent was removed, recrystallized using toluene and ethanol to give intermediate Sub-1(56.6g, yield 85%). LC-MS: M/Z378.1 (M + H) +.

2. Synthesis of intermediate Sub-2:

intermediate Sub-1(50.0g, 132.6mmol) was added to a 2000mL reaction flask, followed by the use of dried and degassed DMF (1000mL) as solvent. After 15 minutes of nitrogen substitution, the catalysts palladium acetate (2 mol%) and potassium acetate (89.3g, 397.8mmol) were added. After the addition was complete, the temperature was raised to 160 ℃ and the reaction was carried out for 14 h. After the reaction was completed, the reaction mixture was cooled to room temperature, and water was added thereto and stirred for 1 hour to form a solid. The mixture is pumped, filtered, washed with a little ethanol and dried. Recrystallization from toluene and ethanol gave intermediate Sub-2(34.6g, yield 88%). LC-MS: M/Z297.2(M + H) +.

3. Synthesis of intermediate Sub-3:

a1000 mL reaction flask was charged with intermediate Sub-2(30.0g, 101.3mmol), phenylboronic acid (14.8g, 121.6mmol), tetrakis (triphenylphosphine) palladium (5 mol%), 2M-K2CO3(150mL), toluene (300mL) and ethanol (150 mL). The reaction system is heated to 120 ℃ and reacts for 12 hours under the protection of nitrogen. After completion of the reaction, the reaction solution was cooled to room temperature and extracted with o-dichlorobenzene and water. The organic layer was dried over anhydrous magnesium sulfate, concentrated, and recrystallized to give a crude product, which was then passed through a silica gel column to give an intermediate, Sub-3(23.2g, yield 78%). LC-MS: M/Z294.4(M + H) +.

4. Synthesis of intermediate Sub-4:

intermediate Sub-3(25.0g, 85.2mmol), NaCl (74.7g, 1278.3mmol) and AlCl3(340.9g, 2556.6mmol) were added to a 1000ml reaction flask and dissolved in benzene, washed after hydrolysis with water and aqueous sodium bicarbonate solution, dried over magnesium sulfate and concentrated. The concentrate was then column-filtered in a small amount of hot p-xylene and the residue was recrystallized from methylcyclohexane to give intermediate 4. intermediate Sub-4(7.4g, yield 30%). LC-MS: M/Z292.4(M + H) +.

5. Synthesis of intermediate Sub-5:

a500 mL reaction flask was charged with intermediate I-1(10.0g, 31.7mmol), (9-phenyl-9H-carbazol-3-yl) boronic acid (9.1g, 31.7mmol), potassium carbonate (11.0g, 79.3mmol), tetrakistriphenylphosphine palladium (5 mol%), 1, 4-dioxane (140mL) and water (70 mL). The reaction system is heated to 60 ℃ and reacts for ten hours under the protection of nitrogen. The reaction solution was poured into 450mL of methanol, and the precipitated solid was filtered. The solid separated out was dissolved in chlorobenzene and filtered through a funnel containing celite and silica gel powder. The orange liquid obtained by filtration was concentrated to dryness and recrystallized from methanol to give intermediate Sub-5(10.8g, yield 65%), LC-MS: M/Z523.0(M + H) +.

Synthesis of RH-001:

a250 mL three-necked flask was charged with intermediate Sub-5(5g, 9.6mmol), intermediate Sub-4(3.1g, 10.5mmol), tris (dibenzylideneacetone) dipalladium (4 mol%), tri-tert-butylphosphine (8 mol%), potassium tert-butoxide (3.2g, 28.7mmol) and o-xylene (80 mL). The reaction system is heated to 120 ℃ and reacts for 12 hours under the protection of nitrogen. After completion of the reaction, the reaction solution was cooled to room temperature and extracted with o-dichlorobenzene and water. The organic layer was dried over anhydrous magnesium sulfate, concentrated, and the crude product obtained by recrystallization was passed through a silica gel column to obtain RH-001(5.6, yield 75%). LC-MS: M/Z777.9(M + H) +.

7. Synthesis of intermediate Sub-6:

to a 500mL reaction flask were added intermediate I-1(10.0g, 31.7mmol), 9- (4-biphenyl) -3-boronic acid carbazole (11.5g, 31.7mmol), potassium carbonate (11.0g, 79.3mmol), tetrakistriphenylphosphine palladium (5 mol%), 1, 4-dioxane (140mL) and water (70 mL). The reaction system is heated to 60 ℃ and reacts for ten hours under the protection of nitrogen. The reaction solution was poured into 450mL of methanol, and the precipitated solid was filtered. The solid separated out was dissolved in chlorobenzene and filtered through a funnel containing celite and silica gel powder. The orange liquid obtained by filtration was concentrated to dryness and recrystallized from methanol to give intermediate Sub-6(11.4g, yield 60%), LC-MS: M/Z599.1(M + H) +.

Synthesis of RH-007:

a250 mL three-necked flask was charged with intermediate Sub-6(5g, 8.4mmol), intermediate Sub-4(2.7g, 9.2mmol), tris (dibenzylideneacetone) dipalladium (4 mol%), tri-tert-butylphosphine (8 mol%), potassium tert-butoxide (2.8g, 25.1mmol) and o-xylene (80 mL). The reaction system is heated to 120 ℃ and reacts for 12 hours under the protection of nitrogen. After completion of the reaction, the reaction solution was cooled to room temperature and extracted with o-dichlorobenzene and water. The organic layer was dried over anhydrous magnesium sulfate, concentrated, and recrystallized to give RH-007(4.7g, yield 65%) through a silica gel column. LC-MS: M/Z854.0(M + H) +.

9. Synthesis of intermediate Sub-7:

a500 mL reaction flask was charged with intermediate I-1(10.0g, 31.7mmol), (9-phenyl-9H-carbazol-2-yl) boronic acid (9.1g, 31.7mmol), potassium carbonate (11.0g, 79.3mmol), tetrakistriphenylphosphine palladium (5 mol%), 1, 4-dioxane (140mL) and water (70 mL). The reaction system is heated to 60 ℃ and reacts for ten hours under the protection of nitrogen. The reaction solution was poured into 450mL of methanol, and the precipitated solid was filtered. The solid separated out was dissolved in chlorobenzene and filtered through a funnel containing celite and silica gel powder. The orange liquid obtained by filtration was concentrated to dryness and recrystallized from methanol to give intermediate Sub-7(10.3g, yield 62%).

10. Synthesis of intermediate Sub-8:

to a 500mL reaction flask were added intermediate I-1(10.0g, 31.7mmol), 9- (4-biphenyl) -2-boronic acid carbazole (11.5g, 31.7mmol), potassium carbonate (11.0g, 79.3mmol), tetrakistriphenylphosphine palladium (5 mol%), 1, 4-dioxane (140mL) and water (70 mL). The reaction system is heated to 60 ℃ and reacts for ten hours under the protection of nitrogen. The reaction solution was poured into 450mL of methanol, and the precipitated solid was filtered. The solid separated out was dissolved in chlorobenzene and filtered through a funnel containing celite and silica gel powder. The orange liquid obtained by filtration was concentrated to dryness and recrystallized from methanol to give intermediate Sub-8(11.6g, yield 61%), LC-MS: M/Z599.1(M + H) +.

Detailed description of the preferred embodiments

1. First embodiment

The ITO glass substrate was patterned to have a light-emitting area of 3mm × 3 mm. Then, the patterned ITO glass substrate was washed. The substrate is then placed in a vacuum chamber. The standard pressure was set at 1X 10-6 Torr. Thereafter, CuPc was applied onto the ITO substrate

NPB

RH-001+(btp)2Ir(acac)((5％)

Alq3

LiF

And Al

The sequence of (a) and (b) forming layers of organic material.

At 0.9mA, the brightness was equal to 1088d/m2 (6.0V). In this case, CIEx is 0.659 and y is 0.329.

2. Second embodiment

NPB

RH-007+(btp)2Ir(acac)(5％)

Alq3

LiF

And Al

The sequence of (a) and (b) forming layers of organic material.

At 0.9mA, the luminance was equal to 1012cd/m2 (6.2V). In this case, CIEx is 0.659y is 0.330.

3. Third embodiment

NPB

RH-073+(btp)2Ir(acac)(5％)

Alq3

LiF

And Al

The sequence of (a) and (b) forming layers of organic material.

At 0.9mA, the luminance was equal to 1101cd/m2 (6.1V). In this case, CIEx is 0.659 and y is 0.329.

4. Fourth embodiment

NPB

RH-079+(btp)2Ir(acac)(5％)

Alq3

LiF

And Al

The sequence of (a) and (b) forming layers of organic material.

At 0.9mA, the luminance was equal to 1037cd/m2 (6.3V). In this case, CIEx is 0.659 and y is 0.330.

5. Comparative example

The ITO glass substrate was patterned to have a light-emitting area of 3mm × 3 mm. Then, the patterned ITO glass substrate was washed. The substrate is then placed in a vacuum chamber. The standard pressure was set at 1X 10-6 Torr. Using CuPc on ITO substrate

NPB

CPB+(btp)2Ir(acac)(5％)

Alq3

LiF

And Al

The sequence of (a) and (b) forming layers of organic material.

At 0.9mA, the luminance was equal to 780cd/m2 (7.5V). In this case, CIEx is 0.659 and y is 0.329.

As shown in fig. 4, it is shown that the color purity of the organic electroluminescent device increases (i.e., the X value becomes larger as the chromaticity coordinate becomes larger) and the visibility decreases.

The characteristics of efficiency, chromaticity coordinates, and luminance according to the above-described embodiments and comparative examples are shown in table 1 below.

TABLE 1

Device with a metal layer	Voltage (V)	Current (mA)	Luminance (cd/m2)	Current efficiency (cd/A)	Power efficiency (Im/W)	CIE(x)	CIE(y)
								First embodiment	6.0	0.9	1088	10.9	5.7	0.659	0.329
Second embodiment	6.2	0.9	1012	10.1	5.1	0.659	0.330
								Third embodiment	6.1	0.9	1101	11.0	5.7	0.659	0.329
Fourth embodiment	6.3	0.9	1037	10.4	5.2	0.659	0.330
								Comparative example	7.5	0.9	780	7.8	3.3	0.659	0.329

As shown in table 1, the device operates at high efficiency at low voltage even when the color purity is high. Also, the current efficiency of the second embodiment is increased by 45% or more compared to the comparative example.

Meanwhile, N is on X2 position, the performance is better, and the service life is doubled under the same condition.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention, and that various changes and modifications may be made without departing from the spirit and scope of the present invention, which fall within the scope of the claimed invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A phosphorescent compound having a structural formula as shown in formula 1 and formula 2:

wherein X1 to X2 are independently selected from N atoms or C atoms;

wherein at least one of X1 to X2 is N;

2. The phosphorescent compound according to claim 1, wherein: the C6-C30 aryl is selected from one of phenyl, naphthyl, biphenyl, terphenyl and phenanthryl.

3. The phosphorescent compound according to claim 1, wherein: the C2-C30 heteroaryl is selected from one of pyridyl, bipyridyl, quinolyl, isoquinolyl, phenanthrolinyl and triazinyl.

4. The phosphorescent compound according to claim 1, wherein: ar is independently selected from the following:

5. phosphorescent compound according to any of claims 1 to 4, characterized in that: the phosphorescent compounds are independently selected from the following compounds:

6. an organic electroluminescent device comprising the phosphorescent compound according to claim 5, wherein: the organic electroluminescent device sequentially comprises a deposited anode, a hole injection layer, a hole transport layer, a luminescent layer, an electron transport layer, an electron injection layer and a cathode, and the phosphorescent compound is used as a main body material of the luminescent layer.