Light-emitting layer host material for organic light-emitting element
阅读说明：本技术 用于有机发光元件的发光层主体材料 (Light-emitting layer host material for organic light-emitting element ) 是由 杜啟仁 萧清文 王仁宗 许朝胜 周孟义 于 2019-04-16 设计创作，主要内容包括：一种用于有机发光元件的发光层主体材料,同时兼具电子与电洞传输的特性,其应用于有机发光二极管元件的制造时,可简化发光层的主体材料为单一成份；不仅材料生产更加简易,且有利于有机发光元件的制程稳定性,并促使此元件具有极佳的发光效率的效果。(A main material of a luminescent layer for an organic light-emitting element has the characteristics of electron and hole transmission, and when the material is applied to the manufacturing of an organic light-emitting diode element, the main material of the luminescent layer can be simplified into a single component; the material is easier to produce, and is beneficial to the stability of the manufacturing process of the organic light-emitting component, and the component has excellent light-emitting efficiency.)
1. A light-emitting layer host material for an organic light-emitting element, characterized by a chemical formula:
donor having a fragment of carbazolyl molecular architecture, X1And X2Each independently hydrogen, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C6 to C30 aromatic ring, substituted or unsubstituted C2 to C18 heteroaromatic ring, benzo, [4,5 ] C]-benzo- [ a]-thieno, substituent positions 1,2, 3, 4,5, 6, 7, 8;
having a 4,4' -bipyridine molecular architectureAcceptor of fragment, Y1And Y2And Y3Each independently hydrogen, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C6 to C18 aromatic ring, substituted or unsubstituted C2 to C18 heteroaromatic ring, benzo, the substituent positions are 5, 6, 2', 3', 5 ', 6';
the receptor and the donor are connected by a connecting segment [ L ]]nL is a 1, 2-phenylene group, a 1, 3-phenylene group, or a 1, 4-phenylene group, and n represents the number of linked segments of 0 or 1.
Technical Field
The invention mainly relates to a luminescent layer main body material for an organic luminescent element.
Background
Discovery of phosphorescent organic materials a major breakthrough in organic light emitting diodes is due to the fact that phosphorescent materials have an exciton utilisation capacity of 75% of theoretical. In a light-emitting layer material of an organic light-emitting element, a phosphorescent guest material having high efficiency is doped in a host material, and energy is transferred from the host material to the guest material to emit light. Therefore, the matching of the guest material and the host material, the transmission efficiency of the host material and the balance between electrons and holes are all closely related to each performance index of the device.
The electrons and holes in the light-emitting layer are not always balanced and equal, and a typical light-emitting layer host material is usually combined with a material having an electron blocking function or a hole blocking function to balance the transmission of the electrons and holes, so that the light-emitting layer host material can be effectively applied to an organic light-emitting device. In order to achieve good electron and hole transport performance of the host material, many researches have been conducted to mix two compounds having electron transport and hole transport functions into a light-emitting host material, which is also called a co-host (co-host), in proportion.
The hybrid host material of patent No. CN103842339A, which achieves excellent effects by mixing two functional materials, is still not efficient for application to organic light emitting elements. With the development of technology, various hybrid host materials have been reported, and the hybrid host material of patent No. CN105579550A has been applied to organic light emitting devices, and its light emitting efficiency has been improved significantly. However, the hybrid host material still has many disadvantages to be improved, such as the complicated production process is required, two materials are required to be produced simultaneously for use, and the ratio of the organic light emitting device in the process is easy to change gradually with the operation time, which results in unstable process.
Bipolar host materials (bipolar host) have attracted much attention in both academic and industrial fields, because of their molecular structures, having two separate donor and acceptor portions, they have excellent electron and hole transport performance, and compared with the common mixed host materials on the market, the single component property of the materials has more practical advantages, not only the material production is easier, but also the stability of process control is more favorable in the subsequent fabrication of organic light emitting devices. Patent No. WO2010/136109A is a typical bipolar host material, but its luminance is not high and the driving voltage still needs to be improved.
Bipolar host materials combine both donor and acceptor structures with appropriate connecting segments in the molecular structure, effectively achieving bipolar properties. How to design the molecular structure for connecting donor and acceptor is the main research topic of bipolar host materials. There are many materials that can be used as donors, and among them, carbazole (carbazole) derivatives are very suitable as donor moieties in host materials because of their high triplet state (-3 eV), excellent hole transport ability, and good thermal stability. In addition, as an acceptor material, for example, oxadiazole (oxadiazole), triazole (triazole), benzimidazole (benzimidazole), pyridine (pyridine), triazine (triazine), diphenylphosphine oxide (diphenylphosphinoxide), and the like have been reported in many cases. However, studies using bipyridine (dipyridine) as an acceptor have been rare.
Therefore, how to improve the above problems is the primary subject to be solved by the present invention.
Disclosure of Invention
The main material of the light-emitting layer of the organic light-emitting element is shown as [ chemical formula I ]:
wherein D represents a donor.
(1) Is a fragment with carbazolyl molecular framework in the formula.
(2)X1And X2Each independently hydrogen, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C6 to C18 aromatic ring, substituted or unsubstituted C2 to C30 heteroaromatic ring, benzo, [4,5 ] C]-benzo- [ a]Thieno,
[L]nShowing the linking segment.
(1) L is 1, 2-phenylene or 1, 3-phenylene or 1, 4-phenylene.
(2) n represents the number of connected segments and is 0 or 1.
A represents an acceptor.
(1) Is a fragment with 4,4' -bipyridine molecular framework in the formula.
(2)Y1And Y2And Y3Each independently hydrogen, substituted or unsubstituted C1 to C8 alkyl, substituted or unsubstituted C6 to C18 aromatic ring, substituted or unsubstituted C2 to C18 heteroaromatic ring, benzo, the substituent positions are 5, 6, 2', 3', 5 ', 6'.
According to the different molecular architecture fragments and substituent positions in formula I, the following compound structures may be possible:
the invention has the beneficial effects that:
the invention provides a light-emitting layer main body material for an organic light-emitting element, and the bipolar main body material has better efficiency compared with a common main body material.
Drawings
Fig. 1 is a structural view of an organic light emitting device of the present invention.
Fig. 2 shows organic light emitting diode materials used in experimental examples and comparative examples of the present invention, which include 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, host materials GH-1 and GH-2 having light emitting functions, and a material ET-1 having an electron transport function.
FIG. 3 is a graph of voltage-current density curves of the organic light emitting devices in the experimental example and the comparative example, which are obtained by adjusting different voltages and measuring the voltage variation.
Fig. 4 is a voltage-luminance graph of the organic light emitting devices in the experimental example and the comparative example, which is obtained by adjusting different voltages and measuring the luminance variation.
Fig. 5 is a graph of luminance-efficiency curves of the organic light emitting devices in the experimental examples and the comparative examples of the present invention, which is obtained by adjusting different voltages, measuring the results of luminance and current density changes, and analyzing and sorting the data to obtain a luminance-efficiency correlation curve.
Fig. 6 is a graph of current density-luminance curves of the organic light emitting devices in the experimental example and the comparative example, which is obtained by adjusting different voltages and measuring the current density and luminance variations.
FIG. 7 is a graph showing the spectra of organic light emitting devices in the experimental example and comparative example of the present invention at a luminance of 10000cd/m2Time measured spectra.
Detailed Description
The embodiment of the invention is roughly divided into three parts, namely, firstly, the synthesis and purification of the bipolar host material, then, the fabrication of the organic light-emitting element, and finally, the data analysis and the performance evaluation are carried out.
First, synthesis example of host Material
I-3 Synthesis example
2-chloro-2 ',6,6' -triphenyl-4, 4' -bipyridine (41.9g, 0.1mol), 3-phenyl-9H-carbazole (24.3g, 0.1mol), sodium tert-butoxide (19.2g, 0.2mol), palladium acetate (0.23g, 1mmol), tri-tert-butylphosphine (0.4g, 2mmol) and toluene (600mL) are placed in a three-necked flask, a condenser tube and a temperature controller are erected, the temperature is raised to reflux under a nitrogen system, the reaction is finished, water and saline are added for extraction, an organic layer is taken out and dried by anhydrous magnesium sulfate, the organic layer is purified by a column chromatography method, and the crude product is obtained by reduced pressure concentration, wherein the yield is about 75%. Then carrying out sublimation purification, setting the temperature at 300 ℃, and the vacuum degree at 1 x 10- 6torr. After about 4 hours the sublimation process was complete and I-3 was obtained as pale yellow crystals.
Synthesis example I-21
2-chloro-2 ',6,6' -triphenyl-4, 4' -bipyridine (41.9g, 0.1mol), 9-phenyl-9H, 9' H- [3,3']Bicarbazole (40.8g, 0.1mol), sodium tert-butoxide (19.2g, 0.2mol), palladium acetate (0.23g, 1mmol), tri-tert-butylphosphine (0.4g, 2mmol) and toluene (600mL) were placed in a three-necked flask, and a condenser tube was set upAnd a temperature controller device, heating to reflux in a nitrogen system, heating for 2 hours, adding water and saline solution for extraction after the reaction is finished, taking out an organic layer, drying by anhydrous magnesium sulfate, purifying by a column chromatography, and concentrating under reduced pressure to obtain a crude product with the yield of about 74%. Then, sublimation purification was carried out at a set temperature of 410 ℃ under a vacuum of 1 × 10-6torr. After about 4 hours the sublimation process was complete and I-21 was obtained as pale yellow crystals.
Synthesis example I-23
2-chloro-4- (2, 6-bisphenylpyridin-4-yl) quinoline (39.3g, 0.1mol), 9-phenyl-9H, 9'H- [3,3']Bicarbazole (40.8g, 0.1mol), sodium tert-butoxide (19.2g, 0.2mol), palladium acetate (0.23g, 1mmol), tri-tert-butylphosphine (0.4g, 2mmol) and toluene (600mL) are placed in a three-necked flask, a condenser tube and a temperature controller device are erected, the temperature is raised to reflux under a nitrogen system, the heating is carried out for 2 hours, water and saline are added for extraction after the reaction is finished, an organic layer is taken out and dried by anhydrous magnesium sulfate, the organic layer is purified by a column chromatography method, the crude product is obtained by concentration under reduced pressure, and the yield is about 78%. Then carrying out sublimation purification, setting the temperature at 400 ℃, and the vacuum degree at 1 x 10-6torr. After about 4 hours the sublimation process was complete and I-23 was obtained as pale yellow crystals.
Preparing the finished host luminescent materials, and identifying the structures by NMR respectively; identifying the purity by HPLC; and measuring the HOMO/LUMO energy level by electrochemical method. The energy level measuring method comprises the steps of measuring the oxidation-reduction potential of a material by using CV, converting the oxidation-reduction potential into the energy level, using dichloromethane as a solvent, and using tetrabutylammonium tetrafluoroborate as an electrolyte. The results of analyzing the basic properties of the materials in the synthesis examples are shown in Table I.
Table one-basic properties of various host materials in the synthesis examples
Application of bipolar host material in organic light-emitting element
The fabrication of organic light emitting devices generally includes substrate pretreatment, organic layer evaporation, metal cathode evaporation, and packaging. The organic light emitting device structure is shown in fig. 1, and includes a
TABLE II comparison table of host materials of organic light emitting devices in experimental examples and comparative examples
TABLE III-measurement results of performance indexes of organic light-emitting devices in experimental examples and comparative examples
Experimental example 1
The host material I-21 is used as a luminescent layer to manufacture an organic luminescent element structure for testing. The detailed manufacturing method is that firstly, a hole injection layer with the thickness of 3nm is vapor-plated on an indium tin oxide anode, and the material is HT-1; then a hole transport layer of 65nm made of HT-2 and a light emitting layer of 30nm, wherein 10% GD-1 is doped in I-21; then an electron transport layer with the thickness of 10nm is formed, and the material is ET-1; then an electron injection layer with the thickness of 1nm is made of the material of Lithium Fluoride; finally, the metal cathode is 100nm, and the material is Aluminum.
Experimental example 2
The host material I-23 is used as a luminescent layer to manufacture an organic luminescent element structure for testing. The detailed manufacturing method is that firstly, a hole injection layer with the thickness of 3nm is vapor-plated on an indium tin oxide anode, and the material is HT-1; then a hole transmission layer of 65nm made of HT-2; then a luminescent layer is 30nm, and GD-1 with 10 percent of material is doped in I-23; then an electron transport layer with the thickness of 10nm is formed, and the material is ET-1; then an electron injection layer with the thickness of 1nm is made of the material of Lithium Fluoride; finally, the metal cathode is 100nm, and the material is Aluminum.
Experimental example 3
The host material I-3 is used as a luminescent layer to manufacture an organic luminescent element structure for testing. The detailed manufacturing method is that firstly, a hole injection layer with the thickness of 3nm is vapor-plated on an indium tin oxide anode, and the material is HT-1; followed by a hole transport layer of 65 nm; then a luminescent layer is 30nm, and GD-1 with 10 percent of material is doped in I-3; then an electron transport layer with the thickness of 10nm is formed, and the material is ET-1; then an electron injection layer with the thickness of 1nm is made of LithiumFluoride; finally, the metal cathode is 100nm, and the material is Aluminum.
Comparative example 1
A typical host material GH-1 is used as a light-emitting layer to manufacture an organic light-emitting element structure for testing. The detailed manufacturing method is that firstly, a hole injection layer with the thickness of 3nm is vapor-plated on an indium tin oxide anode, and the material is HT-1; then a hole transmission layer of 65nm made of HT-2; then a light-emitting layer is 30nm, and GD-1 with 10% of material is doped in GH-1; then an electron transport layer with the thickness of 10nm is formed, and the material is ET-1; then an electron injection layer with the thickness of 1nm is made of the material of Lithium Fluoride; finally, the metal cathode is 100nm, and the material is Aluminum.
Comparative example 2
The organic light-emitting element structure is manufactured by taking a typical host material GH-2 as a light-emitting layer and is tested. The detailed manufacturing method is that firstly, a hole injection layer with the thickness of 3nm is vapor-plated on an indium tin oxide anode, and the material is HT-1; then a hole transmission layer of 65nm made of HT-2; then a light-emitting layer is 30nm, and GD-1 with 10% of material is doped in GH-2; then an electron transport layer with the thickness of 10nm is formed, and the material is ET-1; then an electron injection layer with the thickness of 1nm is made of the material of Lithium Fluoride; finally, the metal cathode is 100nm, and the material is Aluminum.
Evaluation:
after the fabricated organic light emitting element was analyzed, the data was collated and detailed in table three. Different host materials not only have different levels, but also have different electron and hole transport rates. FIG. 3, FIG. 4, FIG. 5 and FIG. 6 are the analysis results of the voltage-current density curve, the voltage-luminance curve, the luminance-efficiency curve and the current density-luminance curve, respectively, and FIG. 7 is the luminance 10000cd/m2Time measured spectra.
The organic light emitting devices were fabricated using the bipolar host materials as in experimental examples 1,2 and 3. The organic light emitting devices of experimental examples 1 and 3 exhibited the best performance, and not only were low in driving voltage, but also efficiencies as high as 67.8cd/a and 67.5cd/a, respectively; the efficiency of Experimental example 2 was slightly lower, 61.7 cd/A. From the view point of the molecular structure design of the bipolar host material, the acceptor parts of I-21 and I-3 are the same, and the donor is slightly different; the acceptor structures of I-21 and I-23 are different and the donor portions are the same, and it was found that the bipyridine acceptors of I-21 and I-3 are suitable as organic light emitting devices with excellent efficiency.
Compared with the common main body material, the bipolar main body material has better efficiency. The maximum efficiency of the experimental example 1 was 67.8cd/A, and the maximum efficiency of the comparative examples 1 and 2 were 50.0cd/A and 59.0cd/A, respectively.
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