TW201904956A - Bipolar compound for serving as light emitting material capable of improving the performance indexes of an organic light emitting device by adjusting the function of host material - Google Patents

Abstract

Provided is a bipolar compound for serving as a light emitting material, which has both electron and hole transmission characteristics. When being applied to the manufacture of an organic light emitting diode device, the host material of the light emitting layer can be simplified as a single component, so as to not only simplify the material production, but also facilitate the process stability of the organic light emitting device, thereby enabling the device to have the effect of providing excellent light emitting efficiency.

Description

Bipolar compound which can be used as a light-emitting material and organic light-emitting element using the same

The present invention is primarily a bipolar compound that can act as a luminescent material.

The discovery of phosphorescent organic materials is a major breakthrough for organic light-emitting diodes because phosphorescent materials have a theoretical value of 75% exciton utilization. In the light-emitting layer material of the organic light-emitting element, a highly efficient phosphorescent guest material is doped into the host material, and energy can be transmitted from the host material to the guest material to emit light. Therefore, the combination of the guest material and the host material; the transmission efficiency of the host material and the balance between the electron and the hole are closely related to the performance indicators of the component.

The electrons and holes in the luminescent layer do not necessarily balance the same amount. In order to balance the transmission of electrons and holes, the typical luminescent layer body material usually needs to be matched with the electron blocking function or the hole blocking function to be effectively applied to organic. Light-emitting element. In order to make the host material have good electron and hole transmission efficiency at the same time, many studies have separately mixed two compounds with electron transport and hole transport functions into a light-emitting host material. These materials are also called hybrids. Type body material (co-host).

The hybrid host material of Chinese Patent No. CN103842339A, which achieves excellent effects by mixing two functional materials, but its efficiency in application to organic light-emitting elements is still not high. With the development of technology, various hybrid main materials have also been continuously reported. The hybrid main material of Chinese Patent No. CN105579550A is applied to organic light-emitting elements, and its luminous efficiency has been significantly improved. However, there are still many shortcomings in such hybrid main materials that need to be improved. For example, the production process is complicated, and it is necessary to simultaneously produce two materials before use. In addition, the proportion of the organic light-emitting device is easily changed with the operation time, resulting in a process. Unstable.

Bipolar host has attracted much attention in both academia and industry because the molecular structure of these materials has two parts, the donor and the acceptor, so it has both electrons and holes. Excellent transmission performance, and compared with the common mixed host materials on the market, the single component nature of the material has more practical advantages, not only the material production is more simple, but also facilitates the process control in the subsequent fabrication of organic light-emitting components. Stability. PCT Patent No. WO2010/136109A is a typical bipolar body material, but its brightness is not high and the driving voltage still needs to be improved.

The bipolar host material can effectively achieve bipolar properties by combining the donor and acceptor structures and the appropriate connecting segments in the molecular structure. How to design the molecular structure connecting the donor and the acceptor is the main research topic of the bipolar host material. There are many materials that can be used as donors, in which carbazole derivatives are highly suitable as donor parts in the host material due to their high triplet state (~3eV); excellent hole transportability and good thermal stability. . In addition, common acceptor materials such as oxadiazole, triazole, benzimidazole, pyridine, triazine, diphenylphosphine oxide, etc. There have been many reports. However, studies using bipyridine as an acceptor are rare.

Controlling the molecular structure and connection position of the donor and acceptors not only produces various electronic couplings, but also adjusts the electron and hole transport capabilities, and also changes the three-dimensional structure such as molecular geometry, thereby changing the molecular arrangement of the film and the function of the host material. Sexual fine-tuning to improve the performance indicators of organic light-emitting components.

In view of this, how to improve the above problems is the primary problem to be solved by the present invention.

The carbazole group containing an oxazolyl group for an organic light-emitting element provided by the present invention is a donor and a bipolar group derivative in which a bispyridyl group is a acceptor is as shown in [Chemical Formula I]:

[Chemical Formula I]

Wherein D represents the donor.

(1) A 3-phenyl-carbazolyl molecular structure fragment as described above.

(2) - [NAr ¹ Ar ² ] is a di-aryl cyclic amine, each of Ar ¹ or Ar ² is a phenyl or biphenyl structure, and Ar ¹ Ar ² may also be combined into a 2,2'-extended biphenyl structure.

(3) C–Ar ¹ is a chemical bond, m=0 indicates no linkage, and m=1 indicates linkage.

[L] _n indicates the link segment.

(1) L is 1,2-phenylene or 1,3-phenylene or 1,4-phenylene.

(2) n indicates the number of connected segments, which is 0 or 1.

A indicates the acceptor.

(1) A fragment having a 4,4'-bipyridine molecular structure as described above.

(2) The substituent is 2 or 3 positions.

The chemical formula I according to different molecular framework fragments and substituent positions may be the following compound structures:

I-1 I-2 I-3 I-4

I-5 I-6 I-7 I-8

I-9 I-10 I-11 I-12

I-13 I-14 I-15 I-16

I-17 I-18 I-19 I-20

I-21 I-22 I-23 I-24

The embodiment of the present invention is roughly divided into three parts, firstly the synthesis and purification of the bipolar host material, followed by the fabrication of the organic light-emitting element, and finally the data analysis and performance evaluation.

First, the main material synthesis example

A-1 synthesis example

2-Bromo-4-iodopyridine (56 g, 0.2 mol), 4-pyridineboronic acid (24.6 g, 0.2 mol), sodium hydrogencarbonate (67.2 g, 0.8 mol) and tetrakis(triphenylphosphine)palladium (23.12 g) , 0.02 mol) placed in a three-necked flask, set up a condenser tube and a temperature controller device, under the nitrogen system, add DME / H ₂ O (7 / 3, 400mL), warmed to 80 ° C, heated for 16 hours, the reaction was completed After cooling to room temperature, the solvent was removed by concentration under reduced pressure, and the aqueous layer was extracted with dichloromethane. The organic layer was washed with 0.1 M aqueous sodium hydroxide and purified water, dried and solvent was removed, and column chromatography (running) The liquid was toluene: ethyl acetate: triethylamine = 50:50:5).

I-7 synthesis example

Under a nitrogen system, A-1 (23 g, 0.1 mol), 9-phenyl-9H, 9'H-[3,3']bicarbazole (45 g, 0.11 mol), copper iodide (2) g, 0.01 mol), 18-crown-6 (8.72 g, 3.3 mmol), potassium carbonate (28 g, 0.2 mol) and traces of 1,3-dimethylpropenyl urea were placed in a sealed reaction flask. Heat to 210 ° C and stir for 48 hours. After the completion of the reaction, the mixture was cooled to room temperature and the reaction was quenched with EtOAc EtOAc (EtOAc)EtOAc. The product was purified by column chromatography eluting with EtOAc (EtOAc:EtOAc:EtOAc: . Sublimation purification was then carried out at a set temperature of 350 ° C and a vacuum of 1*10 ^-6 torr. After about 6 hours, the pure Hua treatment was completed to obtain I-7, and the appearance was yellow crystals.

I-13 synthesis example

Under a nitrogen system, A-1 (23 g, 0.1 mol), 9'-[1,1-biphenyl-3-yl]-9H, 9H'-3,3'-bicarbazole (54 g, 0.11 mol), copper iodide (2 g, 0.01 mol), 18-crown-6 (8.72 g, 3.3 mmol), potassium carbonate (28 g, 0.2 mol) and traces of 1,3-dimethylpropene The urea was placed in a sealed reaction flask, heated to 210 ° C and stirred for 48 hours. After the completion of the reaction, the mixture was cooled to room temperature and the reaction was quenched with EtOAc EtOAc (EtOAc)EtOAc. The product was purified by column chromatography eluting with EtOAc EtOAc:EtOAc: . Sublimation purification was then carried out at a set temperature of 350 ° C and a vacuum of 1*10 ^-6 torr. After about 6 hours, the pure Hua treatment was completed to obtain I-13, and the appearance was yellow crystals.

The prepared host luminescent materials were identified by MNR, respectively; the purity was determined by HPLC; and the HOMO/LUMO energy level was measured by electrochemical method. Among them, HPLC identification is to dissolve the material in methylene chloride, and the energy level measurement method is to measure the redox potential of the material by CV, and then convert it into energy level, wherein the solvent used is dichloromethane and the electrolyte is four- Butylamine tetrafluoroboric acid. The analysis results of the respective materials in the synthesis examples are shown in Table 1.

Table 1 - Analysis results of various host materials in the synthesis example

Second, the bipolar body material is applied to the organic light-emitting element

The fabrication of organic light-emitting elements generally includes substrate pretreatment, organic layer evaporation, metal cathode evaporation, and packaging. The organic light-emitting device structure, as shown in FIG. 1 , comprises a 000 substrate, a 100 indium tin oxide anode, a 105 hole injection layer, a 110 hole transport layer, a 115 electron blocking layer, a 120 light emitting layer, and a 125 hole blocking. Layer, 130 electron transport layer, 135 electron injection layer and 140 metal cathode and other structures. When the bipolar host material of the present invention is applied to an organic light-emitting element, it can be used as a light-emitting layer host material of the organic light-emitting element. Adjusting the structure of the components to optimize the material combination can effectively improve the performance indexes of the organic light-emitting elements. The fabrication conditions of the different component structures in the respective embodiments and comparative examples are detailed in Table 2. The molecular structure of each layer of material used in the structure of the element is shown in Fig. 2. The completed organic light-emitting element is subjected to appropriate packaging, and then the electrical and optical properties are measured, and various data are sorted for evaluation. The voltage and current measurement equipment is Keithley 2230, and the spectral measurement equipment is Konica Minolta CS-1000A. The initial setting is 3V, which is gradually increased to 5V, and the current and brightness changes are measured simultaneously. The component analysis results of the respective examples and comparative examples are detailed as shown in Table 3.

Table 2 - Comparison Table of Organic Light-Emitting Element Body Materials in Examples and Comparative Examples

Table 3 - Measurement results of various performance indexes of organic light-emitting elements in the examples and comparative examples

Example 1

The host material I-7 was used as a light-emitting layer, and an organic light-emitting device structure was fabricated and tested. The detailed production method is as follows: first, a hole injection layer of 10 nm is deposited on the indium tin oxide anode, and 5% of the material is doped with HT-1; then the hole transport layer is 55 nm, and the material is HT-2. Then, the luminescent layer is 30 nm, the material is 10% GD-1 doped in I-7; the electron transport layer is 10 nm, the material is ET-1; then the electron injection layer is 1 nm, the material is Lithium Fluoride; The metal cathode is 100 nm and the material is Aluminum.

Example 2

The host material I-13 was used as a light-emitting layer, and an organic light-emitting device structure was fabricated and tested. The detailed production method is as follows: first, a hole injection layer of 10 nm is deposited on the indium tin oxide anode, and 5% of the material is doped with HT-1; then the hole transport layer is 55 nm, and the material is HT-2. Then, the luminescent layer is 30 nm, the material is 10% GD-1 is doped in I-13; then the electron transport layer is 10 nm, the material is ET-1; then the electron injection layer is 1 nm, the material is Lithium Fluoride; The metal cathode is 100 nm and the material is Aluminum.

Comparative example 1

A typical host material GH-1 was used as a light-emitting layer, and an organic light-emitting device structure was fabricated for testing. The detailed production method is as follows: first, a hole injection layer of 10 nm is deposited on the indium tin oxide anode, and 5% of the material is doped with HT-1; then the hole transport layer is 55 nm, and the material is HT-2. Then, the luminescent layer is 30 nm, the material is 10% GD-1 is doped in GH-1; the electron transport layer is 10 nm, the material is ET-1; then the electron injection layer is 1 nm, the material is Lithium Fluoride; The metal cathode is 100 nm and the material is Aluminum.

Comparative example 2

A typical host material GH-2 was used as a light-emitting layer, and an organic light-emitting device structure was fabricated for testing. The detailed production method is as follows: first, a hole injection layer of 10 nm is deposited on the indium tin oxide anode, and 5% of the material is doped with HT-1; then the hole transport layer is 55 nm, and the material is HT-2. Then, the luminescent layer is 30 nm, the material is 10% GD-1 is doped in GH-2; then the electron transport layer is 10 nm, the material is ET-1; then the electron injection layer is 1 nm, the material is Lithium Fluoride; The metal cathode is 100 nm and the material is Aluminum.

After the completed organic light-emitting elements were measured and analyzed, the data was sorted and detailed as shown in Table 3. Different host materials not only have different energy levels, but also different transmission rates of electrons and holes. The adjustment structure helps to control the effective combination of the light-emitting layers, which is the key to improving the efficiency of the organic light-emitting elements. For example, Figures 3-6 show the analysis results of voltage-current density curve, voltage-luminance curve, brightness-efficiency curve and current density-luminance curve.

After the structure of the bipolar host material was finely adjusted, the organic light emitting element was fabricated as in Example 1 and Example 2. The organic light-emitting device of the first embodiment has poor performance, low efficiency, and low brightness. The LUMO from the host material I-7 is too high to match the guest material, and the electrons are not easily able to cross the energy barrier. It is impossible to effectively combine electrons and holes in the light-emitting area. By controlling the molecular structure, adjusting the appropriate energy level, and optimizing the balance between electrons and holes, the efficiency can be significantly improved. For example, the organic light-emitting element of Embodiment 2 has good efficiency, as shown in Fig. 7, which is a scheme. The spectrum of the organic light-emitting element in the comparative example was measured at a luminance of 10000 cd/m2.

The bipolar host material of the present invention has better efficiency than the general host material. In Example 2, host material I-13 was used as the light-emitting layer, and the maximum efficiency was 61.7 cd/A, and Comparative Example 1 and Comparative Example 2 were 50.0 cd/A and 59.0 cd/A, respectively.

However, the above description of the embodiments is merely illustrative of the invention and is not intended to limit the invention, and the replacement of equivalent elements is still within the scope of the invention.

In summary, it will be apparent to those skilled in the art that the present invention can achieve the foregoing objectives and is in accordance with the provisions of the Patent Law.

000‧‧‧Substrate

100‧‧‧Indium tin oxide anode

105‧‧‧ hole injection layer

110‧‧‧ hole transport layer

115‧‧‧Electronic barrier

120‧‧‧Lighting layer

125‧‧‧ hole barrier

130‧‧‧Electronic transport layer

135‧‧‧electron injection layer

140‧‧‧Metal cathode

Fig. 1 is a structural view of an organic light-emitting element of the present invention. 2 is an embodiment and a comparative example of the present invention, comprising a material HT-1 having a hole injection function, a material HT-2 having a hole transport function, a guest material GD-1 having a light-emitting function, and a host material having a light-emitting function. GH-1 and GH-2, material ET-1 with electron transport function. Fig. 3 is a graph showing voltage-current density curves of organic light-emitting elements in the examples and comparative examples of the present invention, adjusting different voltages and measuring voltage variations. Fig. 4 is a graph showing voltage-luminance curves of organic light-emitting elements in the examples and comparative examples of the present invention, adjusting different voltages and measuring the result of luminance change. Fig. 5 is a graph showing brightness-efficiency curves of organic light-emitting elements in the examples and comparative examples of the present invention, adjusting different voltages and measuring the results of changes in brightness and current density, and then analyzing the brightness to efficiency by data analysis. Fig. 6 is a graph showing current density-luminance curves of organic light-emitting elements in the examples and comparative examples of the present invention, adjusting different voltages, and measuring current density and brightness variations. Fig. 7 is a spectrum diagram of the organic light-emitting element in the examples and comparative examples of the present invention, and measured at a luminance of 10000 cd/m ² .

Claims (4)

A bipolar compound which can be used as a luminescent material, and has the chemical formula: a 4,4'-bipyridine molecular structural unit, defined as an acceptor; a 3-phenyl-carbazolyl molecular structural unit, defined as a donor; The body and the donor are joined by a linking unit [L] _n , [L] _n is 1,2-phenyl or 1,3-phenyl or 1,4-phenyl; the donor is additionally connected – [NAr ¹ Ar ² ], -[NAr ¹ Ar ² ] is a diaryl cyclic amine, each of Ar ¹ or Ar ² is a phenyl or biphenyl unit, and Ar ¹ Ar ² may also be a ² , 2'-extension. The phenyl molecular building unit, C-Ar ¹ is a chemical bond, m equal to 0 means unlinked, and m equal to 1 means linkage. As a bipolar compound which can be used as a luminescent material according to the first aspect of the patent application, n represents the number of connected segments, and may be 0 or 1. The bipolar compound which can be used as a luminescent material according to the first aspect of the patent application, the substituent position of the acceptor is limited to the 2-position or the 3-position. An organic light-emitting element using the bipolar compound according to any one of claims 1 to 3, comprising a substrate sequentially disposed, an indium tin oxide anode layer, a hole injection layer, a hole transport layer, an electron blocking layer, and a double A light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode layer composed of a polar compound.