KR102630691B1 - Novel organic electroluminescent compound, organic light emitting diode and electric apparatus comprising the same - Google Patents

Abstract

The present invention relates to a novel organic electroluminescent compound and an organic electroluminescent device containing the same, and more specifically, to an organic electroluminescent device that exhibits excellent performance by using a novel organic electroluminescent compound as a host material for an organic electroluminescent device. It can be applied to electroluminescent devices and electronic devices.

Description

Novel organic electroluminescent compound, organic electroluminescent device and electronic device containing the same {NOVEL ORGANIC ELECTROLUMINESCENT COMPOUND, ORGANIC LIGHT EMITTING DIODE AND ELECTRIC APPARATUS COMPRISING THE SAME}

The present invention relates to a novel organic electroluminescent compound and an organic electroluminescent device containing the same, and more specifically, to an organic electroluminescent device that exhibits excellent efficiency by using the novel organic electroluminescent compound as a host material for an organic electroluminescent device. It concerns technologies applied to electroluminescent devices and electronic devices.

Compared to existing displays, organic electroluminescent devices (OLEDs) have wide viewing angles, thin films, high brightness, high contrast ratios, low power consumption, and can achieve 100% internal quantum efficiency (IQE) with phosphorescent and thermally activated delayed fluorescent dopants. Due to its advantages, it shows potential growth in research and commercial fields, and progress has been made in the development of materials and devices as next-generation displays.

In general, OLED has an electron transport layer (ETL), electron injection layer (EIL), electron blocking layer (EBL), hole transport layer (HTL), hole injection layer (HIL), and light emitting layer (EML) between the two electrodes of the anode and cathode. It is manufactured with a multi-layer structure, and multi-layer OLED shows significant efficiency improvement.

Compared with electron carriers, hole transport materials play an important role in hole transport and injection to support charge balance in the emissive layer and help with a better charge hopping path from the anode to the emissive layer. An efficient device must select an appropriate hole transport material and have high hole injection and mobility, appropriate frontier molecular orbital energy level, high ionization potential, and thermal stability.

In general, hole transport materials exhibit electron donating properties and their chemical structures consist of diphenylamine, carbazole, and spirobifluorene derivatives. The most commonly used hole transport materials are 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), 2,7-bis[N-(1-naphthyl)anilino]-9 ,9'-spirobi[9H-fluorene] (spiro-NPB), N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4 ,4'-diamine (NPB), and N,N'-bis(3methylphenyl)-N,N'-diphenylbenzidine (TPD). Known materials of this type are of solid interest in the development of small molecule hole transport molecules with specific modifications in the molecular backbone.

Meanwhile, the host material is known to supply energy to the dopant while preventing energy backflow from the dopant, and must have a higher triplet energy than the dopant to make the mechanism possible. Additionally, the host material can suppress triplet-triplet quenching (TTA) and aggregation-induced quenching (ACQ) in the case of phosphorescent OLEDs.

These host materials are of three types depending on their molecular structures: hole transport (HT), electron transport (ET), and bipolar. A desirable host material should have adequate carrier mobility, appropriate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels to reduce the energy barrier to allow smooth transporter transport.

In this regard, carbazole derivatives are well-known backbones for host applications due to their high triplet energy (3 eV), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) is one of the widely used host materials in phosphorescent OLED.

In this way, various hole transport materials and host materials have been developed to improve the efficiency of OLED, but the hole transport materials and host materials developed to date do not show satisfactory performance considering the cost aspect, so they are economical in terms of cost. There is an urgent need to develop hole transport materials and host materials that can exhibit further improved current, power, and external quantum efficiency.

Therefore, the present inventor focused on the fact that if a novel organic electroluminescent compound can be synthesized, it can be used as a host material for an organic electroluminescent device and applied to organic electroluminescent devices and electronic devices showing excellent efficiency, and thus the present invention was developed. It has reached completion.

Non-patent literature 1. Long, Li, et al. Synthetic metals 162.5-6 (2012): 448-452. Non-patent Document 2. D'Andrade, Brian W., and Stephen R. Forrest. Advanced Materials 16.18 (2004): 1585-1595.

The present invention was developed in consideration of the above problems, and the purpose of the present invention is to synthesize a novel organic electroluminescent compound and use it as a host material for an organic electroluminescent device to produce an organic electroluminescent device showing excellent efficiency. This is what I want to apply.

The problem to be solved by the present invention is not limited to the problem(s) mentioned above, and other problem(s) not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention provides an organic electroluminescent compound represented by the following formula (1) or formula (2).

[Formula 1]

[Formula 2]

The organic electroluminescent compound is used as one or more selected from the group consisting of a phosphorescent green host material, a phosphorescent yellow host material, a hole injection material, a hole transport material, an electron injection material, and an electron transport material among materials for an organic electroluminescence device. It may be.

The organic electroluminescent compound is represented by the following Chemical Formula 1-1 or Chemical Formula 2-1, and the organic electroluminescent compound may be used as a phosphorescent green host material or a phosphorescent yellow host material.

[Formula 1-1]

[Formula 2-1]

In addition, the present invention is an organic electroluminescent device in which an organic thin film layer consisting of one or multiple layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one of the organic thin film layers is an organic electroluminescent compound according to the present invention. It provides an organic electroluminescent device containing one type alone or in a combination of one or more types.

The organic electroluminescent device may have a structure in which 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 are stacked in this order.

The light-emitting layer includes a host material containing one type or a combination of one or more types of organic electroluminescent compounds according to the present invention; And it may include a dopant whose dipole orientation is horizontal.

The dopant whose dipole orientation is horizontal is Ir(ppy) ₂ tmd (CAS No. 1171009-96-3), Ir(mphq) ₂ acac (CAS No. 337526-85-9), Ir(phq) ₃ (CAS) No. 435293-93-9) and Ir(mdq) ₂ acac (CAS No. 536755-34-7).

Additionally, the present invention provides an electronic device including the organic electroluminescent device according to the present invention.

The electronic devices include organic integrated circuits (O-IC), organic field-effect transistors (O-FET), organic thin-film transistors (O-TFT), organic electroluminescence transistors (O-LET), and organic solar cells (O-SC). ), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers), or organic electroluminescent devices (OLEDs).

According to the present invention, a novel organic electroluminescent compound can be synthesized and used as a host material for an organic electroluminescent device, which can be applied to organic electroluminescent devices and electronic devices showing excellent efficiency.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 is a graph of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results of Final-1 (Example 1).
Figure 2 is a graph of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results of Final-2 (Example 2).
Figure 3 shows the photoluminescence (PL) spectra of (a) Final-1 and (b) Final-2 under room temperature (RT, 298K) and low temperature (77K) conditions.
Figure 4 is a graph of cyclic voltammetry measurement results of (a) Final-1 and (b) Final-2.
Figure 5 is (a) a schematic diagram showing the device structure of a green phosphorescent OLED using Final-1 and Final-2 as host materials for the emitting layer (EML), and (b) Final-1 and Final-2 as dopants, respectively. These are the structures of Ir(ppy) ₃ and Ir(ppy) ₂ tmd used.
Figure 6 shows electroluminescence spectra measured by varying the types of dopants (Ir(ppy) ₃ and Ir(ppy) ₂ tmd) in a green phosphorescent OLED using CBP (reference material), Final-1, and Final-2 as host materials. (Electroluminescent spectra).
Figure 7 shows the current of the device measured by varying the type of dopant (Ir(ppy) ₃ and Ir(ppy) ₂ tmd) in a green phosphorescent OLED using CBP (reference material), Final-1, and Final-2 as host materials. This is a graph showing current efficiency.
Figure 8 shows the power of the device measured by varying the types of dopants (Ir(ppy) ₃ and Ir(ppy) ₂ tmd) in a green phosphorescent OLED using CBP (reference material), Final-1, and Final-2 as host materials. This is a graph showing power efficiency.
Figure 9 shows the exterior of the device measured by varying the types of dopants (Ir(ppy) ₃ and Ir(ppy) ₂ tmd) in a green phosphorescent OLED using CBP (reference material), Final-1, and Final-2 as host materials. This is a graph showing quantum efficiency.

It should be noted that in the following description, only the parts necessary to understand the embodiments of the present invention are described, and other parts of the description may be omitted as long as they do not distract from the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as limited to their usual or dictionary meanings, and the inventor should use the concept of terminology appropriately to explain his/her invention in the best way. It must be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined clearly. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent the entire technical idea of the present invention, and therefore, various equivalents can be substituted for them at the time of filing the present application. It should be understood that there may be variations.

Hereinafter, the present invention will be described in detail.

According to the present invention, the present invention provides an organic electroluminescent compound represented by the following formula (1) or formula (2).

[Formula 1]

[Formula 2]

Specifically, the carbazole group substituted for the central benzene of the para-terphenyl group may be substituted at either the ortho or meta position.

All organic electroluminescent compounds represented by Formula 1 or Formula 2 have a large volume structure, and thus exhibit excellent thermal and morphological stability when applied as materials for organic electroluminescent devices.

The organic electroluminescent compound is used as one or more selected from the group consisting of a phosphorescent green host material, a phosphorescent yellow host material, a hole injection material, a hole transport material, an electron injection material, and an electron transport material among materials for an organic electroluminescence device. It may be.

According to one embodiment of the present invention, the organic electroluminescent compound is represented by the following Chemical Formula 1-1 or Chemical Formula 2-1, and the organic electroluminescent compound may be used as a phosphorescent green host material or a phosphorescent yellow host material. there is. Specifically, the organic electroluminescent compound may be used as a phosphorescent green host material.

[Formula 1-1]

[Formula 2-1]

In particular, although not explicitly described in the following Examples or Comparative Examples, among the organic electroluminescent compounds represented by Formula 1 or Formula 2 according to the present invention, the compound represented by Formula 1-1 or 2-1 was used for OLED. When used as a green phosphorescent post material, it exhibits a higher triplet energy level, which has a significantly advantageous effect in transferring energy to the dopant material while preventing backflow of energy from the dopant. Additionally, there is an effect of suppressing energy reverse transfer.

In addition, the present invention is an organic electroluminescent device in which an organic thin film layer consisting of one or multiple layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one of the organic thin film layers is an organic electroluminescent compound according to the present invention. It provides an organic electroluminescent device containing one type alone or in a combination of one or more types.

The organic thin film layer may be formed through a soluble process using the organic electroluminescent compound.

The organic electroluminescent device may have a structure in which 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 are stacked in this order.

The light-emitting layer includes a host material containing one type or a combination of one or more types of organic electroluminescent compounds according to the present invention; And it may include a dopant whose dipole orientation is horizontal. In this case, there is an effect of showing significantly superior current efficiency, power efficiency, and power efficiency compared to the case of using a dopant with a vertical dipole orientation.

The dopant whose dipole orientation is horizontal may be any one or more selected from the group consisting of Ir(ppy) ₂ tmd, Ir(mphq) ₂ acac, Ir(phq) ₃ , and Ir(mdq) ₂ acac. Specifically, the dopant whose dipole orientation is horizontal may be Ir(ppy) ₂ tmd.

Additionally, the present invention provides an electronic device including the organic electroluminescent device according to the present invention.

The electronic devices include organic integrated circuits (O-IC), organic field-effect transistors (O-FET), organic thin-film transistors (O-TFT), organic electroluminescence transistors (O-LET), and organic solar cells (O-SC). ), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers), or organic electroluminescent devices (OLEDs).

Below, the organic electroluminescent device will be described as an example. However, the contents illustrated below do not limit the organic electroluminescent device of the present invention.

The organic electroluminescent device may have a structure in which an anode (hole injection electrode), a hole injection layer (HIL) and/or a hole transport layer (HTL), an emission layer (EML), and a cathode (electron injection electrode) are sequentially stacked, Preferably, an electron blocking layer (EBL) may be further included between the anode and the light emitting layer, and an electron transport layer (ETL), an electron injection layer (EIL), or a hole blocking layer (HBL) may be further included between the cathode and the light emitting layer.

In the method of manufacturing the organic electroluminescent device, first, an anode material is coated on the surface of a substrate using a conventional method to form an anode. At this time, the substrate used is preferably a glass substrate or a transparent plastic substrate with excellent transparency, surface smoothness, ease of handling, and waterproofness. In addition, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), etc., which are transparent and have excellent conductivity, can be used as materials for the anode.

Next, a hole injection material is vacuum thermally deposited or spin coated on the surface of the anode using a conventional method to form a hole injection layer (HIL). As such hole injection materials, the organic electroluminescent compounds may be used, and in addition, copper phthalocyanine (CuPc), 4,4',4"-tris(3-methylphenylamino)triphenylamine (m-MTDATA), 4, 4',4"-tris(3-methylphenylamino)phenoxybenzene (m-MTDAPB), 4,4',4"-tri(N-carbazolyl)triphenylamine (TCTA), a starburst type amine ), 4,4',4"-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine (2-TNATA) or IDE406 available from Idemitsu. .

A hole transport layer (HTL) is formed by vacuum thermal evaporation or spin coating on the surface of the hole injection layer using a conventional method. At this time, the organic electroluminescent compound may be used as the hole transport layer material, and in addition, bis(N-(1-naphthyl-n-phenyl))benzidine (α-NPD), N,N'-di(naphthalene- 1-yl)-N,N'-biphenyl-benzidine (NPB) or N,N'-biphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4' -Diamine (TPD) is an example.

An emission layer (EML) material is formed on the surface of the hole transport layer by vacuum thermal evaporation or spin coating using a conventional method. At this time, when the sole light-emitting material or host material among the light-emitting layer materials used is green, the organic electroluminescent compound can be used as a phosphorescent green host material, and when the organic electroluminescent compound is yellow, the organic electroluminescent compound can be used as a phosphorescent yellow host material.

Among the light-emitting layer materials, dopants that can be used together with the host material include IDE102 and IDE105, which are available from Idemitsu as fluorescent dopants, and tris(2-phenylpyridine)iridium(III) (Ir(ppy) as a phosphorescent dopant. ) ₃ ), Iridium(III)bis[(4,6-difluorophenyl)pyridinato-N,C-2']picolinate (FIrpic) (Reference [Chihaya Adachi et al., Appl. Phys Lett., 2001, 79, 3082-3084]), platinum (II) octaethylporphyrin (PtOEP), TBE002 (Covion), etc. can be used.

An electron transport layer (ETL) is formed by vacuum thermal evaporation or spin coating of an electron transport material on the surface of the light emitting layer using a conventional method. At this time, the organic electroluminescent compound can be used as the electron transport material, and tris(8-hydroxyquinolinolato)aluminum (Alq3) can also be used.

Optionally, by additionally forming a hole blocking layer (HBL) between the light emitting layer and the electron transport layer and using a phosphorescent dopant in the light emitting layer, diffusion of triplet excitons or holes into the electron transport layer can be prevented.

The formation of the hole blocking layer can be performed by vacuum thermal evaporation and spin coating of a hole blocking material by conventional methods. The hole blocking material is not particularly limited, but is preferably (8-hydroxyquinolinolato). Lithium (Liq), bis(8-hydroxy-2-methylquinolinolnato)-aluminum biphenoxide (BAlq), bathocuproine (BCP), and LiF can be used.

An electron injection layer (EIL) is formed by vacuum thermal evaporation or spin coating of an electron injection material on the surface of the electron transport layer using a conventional method. At this time, the organic electroluminescent compound can be used as the electron injection material, and other materials such as LiF, Liq, Li ₂ O, BaO, NaCl, or CsF can be used.

Finally, a cathode is formed by vacuum thermal deposition of a cathode material on the surface of the electron injection layer using a conventional method.

At this time, the cathode materials used include lithium (Li), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium (Mg), magnesium-indium (Mg-In), and magnesium-silver. (Mg-Ag) etc. may be used. Additionally, in the case of a top-emitting organic electroluminescent device, indium tin oxide (ITO) or indium zinc oxide (IZO) can be used to form a transparent cathode through which light can transmit.

The organic electroluminescent device may be manufactured in the same order as described above, that is, anode/hole injection layer/hole transport layer/light-emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode, or vice versa, cathode/electron injection layer. It may be manufactured in the following order: /electron transport layer/hole blocking layer/light emitting layer/hole transport layer/hole injection layer/anode.

The above description explains the technical idea of the present invention using one embodiment, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments described in the present invention are not intended to limit the technical idea of the present invention, but are for illustrative purposes, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Hereinafter, the present invention will be described in more detail through examples.

<Material>

All reagents used in the present invention were imported from TCI, Alfa aesar, and GOM Technology and used without further purification. Solvents were purchased from SK Chemical, Daejeong Chemical, and Samjeon Pure Pharmaceutical Co., Ltd., and were purified and dried in a nitrogen stream in the presence of sodium and benzophenone as needed. ^{The 1} H NMR spectrum of the synthesized material was measured using a JEOL FT/NMR (500Mz) Spectrophotometer, and CDCl ₃ was used as a solvent.

Some reactions were carried out in oxygen-free, nitrogen-filled and dried conditions using general techniques.

<Device>

¹ H and ¹³ C NMR characterization was performed using a JEON JNM-ECP FT-NMR spectrometer (Peabody, MA, USA) operating at 500 MHz. Photoluminescence (PL) spectra were recorded with a Jasco FP-8300 spectrophotometer (Easton, MD, USA). Elemental analysis was performed using a ThermoFisher (Flash 2000) elemental analyzer (Loughborough, UK). Mass spectrometry was performed using a Xevo TQ-S spectrometer (Milford Waters, MA, USA). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were measured using PerkinElmer DSC 4000 and TGA 8000 systems (Melville, NY, USA) at a heating rate of 10 °C/min in a nitrogen atmosphere. The triplet energy level (ET) was calculated from the starting wavelength of the emission spectrum at 77 K in 10 ^-5 M toluene. HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) values were determined by cyclic voltammetry. The OLED device was manufactured using a thermal evaporation system under a pressure of 5 × 10 ^-7 torr (Sunicel plus, Seoul, Korea). Current density-voltage-luminescence (JVL) performance was recorded using an OLED IVL test system (Polarmix M6100, Suwon, Korea). Electroluminescence (EL) spectra were measured using a spectroradiometer (Konica Minolta CS-2000, Tokyo, Japan).

<Manufacturing example>

Preparation Example 1: Synthesis of 9-(2,5-dibromophenyl)-9H-carbazole

After installing a reflux device in a 250mL dried two-necked flask, carbazole (2) (3.75g, 1eq), Cs ₂ CO ₃ (14g, 2eq), and a magnetic bar were added and a vacuum state was created. Then, 15 minutes later, nitrogen was filled using a nitrogen balloon, 30 mL of DMF was added using a syringe, and the mixture was stirred at room temperature for 30 minutes.

1,4-Dibromo-2-fluorobenzene (1,4-Dibromo-2-fluorobenzen; 1) (5g, 1eq) and a magnetic bar were added to 100mL of the dried one-necked flask, and a vacuum was created. Then, 15 minutes later, fill nitrogen using a nitrogen balloon, add 20 mL of DMF using a syringe, stir at room temperature for 30 minutes to dissolve, add it to a 250 mL two-necked flask using a syringe, and pour in an oil bath. It was heated and stirred to 150°C using. After 12 hours, the reactant is cooled to room temperature, extracted using brine and MC, and only the organic layer is collected. The remaining moisture was completely removed using sodium sulfate, filtered, separated, and evaporated to dryness. The dried compound was recrystallized using n-hexane to produce 9-(2,5-dibromophenyl)-9H-carbazole (9-(2), which is a white solid product (3) (6g, yield: 76%). , 5-Dibromophenyl)-9H-carbazole) was obtained.

Yield: 76%; white solid; ^1H NMR (500MHz, CDCl ₃ ) 8.13-8.14 (d, J = 7.5Hz, 2H), 7.71-7.73 (d, J = 8.5Hz, 1H), 7.63-7.64 (d, J = 2.5Hz, 1H) , 7.54-7.56 (dd, J ₁ = 8.5Hz, J ₂ = 2.5Hz, 1H), 7.40-7.42 (t, J = 7.5Hz, 2H), 7.29-7.32 (t, J = 7.5Hz, 2H), 7.06-7.08 (d, J = 8.5Hz, 2H).

Preparation Example 2: Synthesis of 9-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole

Add 9-(4-bromophenyl)-9H-carbazole (9-(4-bromophenyl)-9H-carbazole; 4) (11.56g, 1eq) and magnetic bar to 250mL of dried one-necked flask and vacuum. After this, nitrogen was filled using a nitrogen balloon. The solvent was dissolved by adding 100 mL of Dry-THF using a syringe and stirred for 2 to 3 minutes. The temperature was set to -78°C using dry ice and acetone. After 30 minutes, 2.5M n-BuLi (19.8mL, 1.37eq) was slowly added using a syringe and stirred. After 2 hours, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2-isopropoxy-4,4,5,5-tetramethyl-1,3,2 -dioxaborolane; 5) (7.68mL, 1.37eq) was slowly added using a syringe. Then, the temperature was brought to room temperature while stirring and left overnight. After completion of the reaction, extraction was performed using H ₂ O and MC, and only the organic layer was collected. The remaining moisture was completely removed using sodium sulfate, filtered, separated, and evaporated to dryness. The dried compound was recrystallized using n-hexane to produce 9-(4-(4,4,5,5-tetramethyl-1,3,2), which is a white solid product (6) (10g, yield: 38%). -dioxaborolan-2-yl)phenyl)-9H-carbazole (9-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H -carbazole) was obtained.

Yield: 38%; white solid; _1H NMR (500MHz, CDCl ₃ ) 8.17-8.19 (d, J = 8Hz, 2H), 8.07-8.09 (d, J = 7Hz, 2H), 7.65-7.67 (d, J = 6.5Hz, 2H), 7.46 -7.48 (d, J = 7Hz, 2H), 7.38-7.45 (m, 2H), 7.26-7.29(t, J = 8Hz, 2H), 1.45 (s, 12H).

<Example>

Example 1: Synthesis of Final-1

An organic electroluminescent compound represented by the following formula 1-1 was synthesized by the following method. The organic electroluminescent compound represented by the following formula 1-1 is 9,9',9''-([1,1':4',1''-terphenyl]-2',4,4''-tri Named as 1) tris(9H-carbazole) (3,3'-(2-(9H-carbazol-9-yl)-1,4-phenylene)bis(9-phenyl-9H-carbazole)) (8) and is referred to as ‘Final-1’.

After installing a reflux device in a 250mL dried two-necked flask, 9-(2,5-dibromophenyl)-9H-carbazole (3) (3g, 1eq), (9-phenyl-9H-carbazole-3- 1) boronic acid (9-phenyl-9H-carbazol-3-yl)boronicacid; 7) (5.16g, 2.4eq), Pd(PPh3)4 (0.52g, 0.6eq), and a magnetic bar were placed in a vacuum state and then filled with nitrogen using a nitrogen balloon. The solvent was dissolved by adding 80 mL of toluene and 20 mL of ethanol using a syringe, and while heating and stirring to 110°C using an oil bath, 40 ml of 2M K ₂ CO ₃ was slowly added using a syringe. After completion of the reaction, the reactant was cooled to room temperature and extracted using H ₂ O and MC, and only the organic layer was collected. The remaining moisture was completely removed using sodium sulfate, filtered, separated, and evaporated to dryness. The catalyst was removed by flowing only through MC through an open column, filtered, separated, and evaporated to dryness. The dried compound was recrystallized using n-hexane to obtain Final 1, a white solid product (8) (5.15 g, yield: 94%).

Yield: 94%; white solid; 1H NMR (500MHz, CDCl ₃ ) 8.43 (s, 1H), 8.16-8.18 (d, J = 8Hz, 1H), 8.0-8.04 (m, 4H), 7.91-7.92 (d, J = 8Hz, 1H), 7.88 (m, 1H), 7.81-7.83 (d, J = 7.5Hz, 1H), 7.73-7.75 (d, J = 8.5Hz, 1H), 7.58-7.64 (m, 4H), 7.46-7.51 (m, 4H), 7.36-7.42 (m, 5H), 7.26-7.31 (m, 6H), 7.15-7.21 (m, 4H), 7.05-7.07(d, J = 10Hz, 1H), 6.96-6.98 (d, J = 8.5Hz, 1H).

[Formula 1-1]

Example 2: Synthesis of Final-2

An organic electroluminescent compound represented by the following formula 2-1 was synthesized by the following method. The organic electroluminescent compound represented by the following formula 2-1 is 9,9',9''-([1,1':4',1''-terphenyl]-2',4,4''-tri 1) tris(9H-carbazole)(9,9',9''-([1,1':4',1''-terphenyl]-2',4,4''-triyl)tris(9H -carbazole))(9) and is referred to as ‘Final-2’.

After installing a reflux device in a 250mL dried two-necked flask, 9-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carba Sol (6) (6.6g, 2.4eq), Pd(PPh ₃ ) ₄ (0.52g, 0.6eq), and a magnetic bar were added, a vacuum was created, and nitrogen was filled using a nitrogen balloon. The solvent was dissolved by adding 80 mL of toluene and 20 mL of ethanol using a syringe, and while heating and stirring to 110°C using an oil bath, 40 ml of 2M K ₂ CO ₃ was slowly added using a syringe. After completion of the reaction, the reactant was cooled to room temperature and extracted using H ₂ O and MC, and only the organic layer was collected. The remaining moisture was completely removed using sodium sulfate, filtered, separated, and evaporated to dryness. The catalyst was removed by flowing only through MC through an open column, then filtered, separated, and evaporated to dryness. The dried compound was recrystallized using n-hexane to obtain Final-2, a white solid product (9) (3.82 g, yield: 70%).

Wednesday: 70%; white solid; ^1H NMR (500MHz, CDCl ₃ ) 8.16-8.18 (d, J = 7.5Hz, 2H), 8.12-8.14 (d, J = 8Hz, 2H), 8.07-8.09 (d, J = 8Hz, 2H), 8.00 (m, 2H), 7.94-7.95 (m, 3H), 7.70-7.72 (d, J = 8.5Hz, 2H), 7.50-7.51 (d, J = 8Hz, 2H), 7.43-7.46 (t, J = 8Hz, 2H), 7.30-7.37 (m, 6H), 7.20-7.25 (m, 8H), 7.13-7.14 (d, J = 8Hz, 2H), 6.96-6.98 (d, J = 8Hz, 2H).

[Formula 2-1]

Example 3: Fabrication of organic electroluminescent device (OLED) device

The glass substrate coated with indium-tin-oxide (ITO) was washed in an isopropyl alcohol ultrasonic bath and then further washed with deionized water for 20 minutes.

The cleaned substrates were then subjected to UV-ozone treatment for approximately 10 minutes. All organic layers along with the metal cathode were deposited on a pre-cleaned ITO coated glass substrate. The layer deposition rate was applied at about 5×10 ^-7 Torr using a Sunic organic evaporator (Suwon, Korea) inside a glove box under inert conditions.

<Experimental example>

Experimental Example 1. Thermogravimetric analysis and differential scanning calorimetry analysis

In order to confirm the thermal stability of Final-1 (Example 1) and Final-2 (Example 2), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed under a nitrogen atmosphere. The results are shown in Figure 1 (Fina1-1), Figure 2 (Final-2), and Table 1.

The thermal properties of materials used in OLED have a significant impact on the device's stability, lifespan, and efficiency. This is because the heat generated when driving the device may cause deformation of the device. Therefore, materials with a high decomposition temperature (Td) and a high glass transition temperature (Tg) are required.

Referring to Figures 1 and 2 and Table 1, as a result of measuring the glass transition temperatures of Final-1 and Final-2 through DSC, the thermal stability was excellent at 150°C and 288°C, respectively, and through TGA, Final-1 and Final-2 were found to have excellent thermal stability. As a result of measuring the 5% decomposition temperature of Final-2, Td was observed at 578℃ and 573℃, respectively. It can be confirmed that both synthesized materials have very high thermal stability with a decomposition temperature of over 570°C. These thermal characteristics are effective in promoting uniform film formation and morphological stability of the device during the device manufacturing process.

Experimental Example 2. Photophysical analysis using UV-vis absorption and photoluminescence emission

To confirm the singlet state energy and triplet state energy of Final-1 (Example 1) and Final-2 (Example 2), room temperature (RT) in toluene solvent and photoluminescence (PL) emission was measured under low temperature (77K) conditions, and the results are shown in Figure 3 and Table 1.

Referring to Figure 3 and Table 1, the fluorescence onset value was measured at 351.86 nm for Final-1 and 354.14 nm for Final-2, and the phosphorescence onset value was measured at 426 nm for Final-1 and 354.14 nm for Final-2. 2 was measured at 434.61 nm, and the singlet state energy value (S1) derived here was 3.52 eV for Final-1 and 3.50 eV for Final-2, and the triplet state energy value (T1) was 2.91 eV for Final-1. , Final-2 is 2.85 eV, which confirms that the triplet state energy values of both compounds are suitable as green hosts. This was confirmed to be higher than the triplet state energy value of the dopant used in the fabricated device (see Table 1).

In this way, it can be confirmed that both of the above two compounds exhibit higher triplet energy and can prevent energy from flowing back from the dopant when applied as a host material.

Experimental Example 3. Electrochemical property analysis

Analysis of the electrochemical properties of Final-1 (Example 1) and Final-2 (Example 2) was performed through cyclic voltammetry measurement, and the results are shown in Figure 4 and Table 1.

Referring to Figure 4 and Table 1, the HOMO and LUMO values of Final-1 (Example 1) and Final-2 (Example 2) were measured by cyclic voltammetry (CV). The measured HOMO values were -5.388eV for Final-1 and -5.375eV for Final-2, and the LUMO values were -2.039eV for Final-1 and -2.305eV for Final-2. The band gap of the two compounds was calculated from the measured values of 3.350 eV and 3.070 eV for Final-1 and Final-2, respectively.

division Final-1 Final-2 T _g (°C) 150 288 T _d (°C) 578 573 Fluorescence onset (nm) 351.86 354.14 Phosphorescence onset (nm) 426 434.61 S1(eV) 3.52 3.50 T1(eV) 2.91 2.85 △E _st (eV) 0.61 0.65 dopant Ir(ppy) ₃ IR(ppy) _2TMD band gap (eV) 3.350 3.070 Highest Occupied Molecular Orbital (HOMO) (eV) -5.388 -5.375 Lowest Unoccupied Molecular Orbital (LUMO) (eV) -2.039 -2.305

Experimental Example 4. Characteristic analysis of green phosphorescent OLED device

(1) Electroluminescence analysis when applied as host material (HT)

In order to confirm the properties of Final-1 (Example 1) and Final-2 (Example 2) as host materials when applied to OLED devices, a green phosphorescent OLED device was manufactured as follows, and its structure is shown in Figure 5(a). Shown. At this time, as shown in Table 1, for Final-1 (Example 1) and Final-2 (Example 2), Ir(ppy) ₃ with a vertical dipole orientation and horizontal dipole orientation as a dopant, respectively. Ir(ppy) ₂ tmd was used. The reason why measurements were made using two types of dopants with different dipole orientations in the device was because it has been proven that better efficiency is achieved when the dipole properties of the host match the dipole properties of the dopant and the orientation of the host materials in Examples 1 and 2. To determine which orientation is suitable, a device was manufactured using two types of dopants with different dipole orientations.

Electroluminescence (EL) of devices using host materials of Final-1 (Example 1) and Final-2 (Example 2) and two dopants with different dipole orientations was analyzed, and the results are shown in Figure 6. It was.

Referring to FIG. 6, the light emission of the fabricated device showed green emission at 524 nm and 516 nm for Final-1 (Example 1) and Final-2 (Example 2), respectively, and through this, green phosphorescent OLED. It was confirmed that it was suitable for application as a host material.

(2) Current, power and external quantum efficiency analysis when applied as host material (HT)

Current efficiency, power efficiency, and external quantum efficiency (EQE) were measured with devices manufactured from the host materials of Final-1 (Example 1) and Final-2 (Example 2) and two dopants with different dipole orientations, as shown in Figure 7 Shown in Figures 9 and Table 2.

Referring to FIGS. 7 to 9 and Table 2, in devices using an Ir(ppy) ₂ tmd dopant with a horizontally oriented dipole, devices with hosts Final-1 and Final-2 have device efficiencies similar to or better than CBP-based devices. As shown, it can be seen that better efficiency is achieved when Final-1 and Final-2 are applied to OLEDs using dopants with a horizontal dipole orientation.

(Meanwhile, the identification number "C2-513" written in the graph in FIGS. 6 to 9 indicates the production number of the arbitrarily designated device and the emission wavelength at which the experiment was performed, 513 nm, and the ending numbers "1, 4, 3, 4" Additionally, the reference number of the device is simply stated)

division CBP
(Reference) Final-1
+ Ir(ppy) ₃ Final-2
+ Ir(ppy) ₃ Final-1
+ Ir(ppy) ₂ tmd Final-2
+ Ir(ppy) ₂ tmd
Current efficiency (cd/A) 88.07 61.45 65.85 89.39 91.96 Power efficiency (lm/W) 75.95 52.40 48.87 80.58 73.92 EQE (%) 23.15 17.25 18.34 23.45 24.22

As seen, all organic electroluminescent compounds according to the present invention exhibited excellent host properties. Through this, it was confirmed that the host material of the organic electroluminescent compound according to the present invention is a promising OLED material that can replace the conventionally used CBP host material.

Although specific examples of the novel organic electroluminescent compound according to the present invention have been described so far, it is obvious that various modifications can be made without departing from the scope of the present invention.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the claims described below as well as equivalents to these claims.

That is, the above-described embodiments should be understood in all respects as illustrative and not restrictive, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and their equivalents. All changes or modified forms derived from the concept should be construed as falling within the scope of the present invention.

Claims (9)

Organic electroluminescent compound represented by Formula 1 or Formula 2:
[Formula 1]

[Formula 2]
. According to paragraph 1,
The organic electroluminescent compound is used as one or more selected from the group consisting of a phosphorescent green host material, a phosphorescent yellow host material, a hole injection material, a hole transport material, an electron injection material, and an electron transport material among materials for an organic electroluminescence device. An organic electroluminescent compound. According to paragraph 2,
The organic electroluminescent compound is represented by the following formula 1-1 or formula 2-1,
The organic electroluminescent compound is used as a phosphorescent green host material or a phosphorescent yellow host material:
[Formula 1-1]

[Formula 2-1]
. An organic electroluminescent device in which an organic thin film layer consisting of one or multiple layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one of the organic thin film layers contains one type of organic electroluminescent compound according to claim 1 alone. An organic electroluminescent device containing a substance or a combination of one or more types. According to paragraph 4,
The organic electroluminescent device has a structure in which 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 are stacked in this order. According to clause 5,
The light-emitting layer includes a host material containing one type or a combination of one or more types of the organic electroluminescent compound according to claim 1; And an organic electroluminescent device comprising a dopant whose dipole orientation is horizontal. According to clause 6,
The dopant whose dipole orientation is horizontal is at least one selected from the group consisting of Ir(ppy) ₂ tmd, Ir(mphq) ₂ acac, Ir(phq) ₃ and Ir(mdq) ₂ acac, an organic electroluminescent device. An electronic device containing an organic electroluminescent device according to claim 4. According to clause 8,
The electronic devices include organic integrated circuits (O-IC), organic field-effect transistors (O-FET), organic thin-film transistors (O-TFT), organic electroluminescence transistors (O-LET), and organic solar cells (O-SC). ), organic optical detectors, organic photoreceptors, organic field-quenched devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) or organic electroluminescent devices (OLEDs).