Spiro compound, preparation method thereof, light-emitting layer, light-emitting device, display device

Abstract

The application belongs to the field of electroluminescence, and particularly discloses a spiro compound, a preparation method thereof, a light-emitting layer, a light-emitting device and a display device, the spiro compound has a structural formula of formula (I) or formula (II): formula (I); formula (II); the structure of D is ; and the structure of A is. The spiro compound provided by the application can be used as a host material of a light-emitting layer, has excellent organic solvent solubility and good film-forming property, and an organic electroluminescent device prepared by using a solution processing technology has balanced carrier transport performance; the structure of the spiro compound can assist light-emitting materials to realize the advantage of relatively aggregated accumulation, and finally can effectively improve the maximum current efficiency of the device and reduce the efficiency roll-off.

Description

Technical Field

[0001] This invention relates to the field of electroluminescence, and particularly to spirocyclic compounds, their preparation methods, light-emitting layers, light-emitting devices, and display devices. Background Technology

[0002] Organic light-emitting diodes (OLEDs) belong to the category of novel display products. Since Dr. Ching W. Tang first discovered the organic light-emitting effect in 1987, this technology has undergone more than 30 years of rapid development, achieving commercial application through vacuum evaporation processes and holding a significant market share in the small-size display field. However, in the research and development and production of medium- and large-size display products, the imperfections in fine photomask technology and the rising costs of large-scale production equipment have led to a series of problems such as high production costs and low product yields. Under these circumstances, solution-processed OLED technology (especially inkjet printing OLED technology) has the potential to become an effective technological path for the manufacturing of medium- and large-size OLED displays due to its advantages such as high material utilization, less stringent requirements for equipment and environment, and suitability for large-area processing.

[0003] Currently, the key factors restricting the commercial mass production of solution-processed OLEDs mainly encompass two dimensions: First, the development progress of dedicated production equipment has failed to match the actual needs of large-scale mass production; second, most organic materials suitable for vapor deposition processes have poor compatibility in solution processing systems, and the existing types and properties of organic materials are insufficient to support the large-scale commercial production and application of solution-processed OLED devices. A typical OLED display device structure includes an anode, hole injection layer (HIL), hole transport layer (HTL), emissive layer (EML), electron transport layer (ETL), and cathode. The emissive layer is usually composed of a host material and a luminescent material. The host material can be prepared from a single material or a mixture of multiple materials. The core functions of the host material include dispersing the luminescent material to achieve efficient energy transfer from the host material to the luminescent material; simultaneously, it needs to improve the carrier transport efficiency of the device, balance the carrier transport rate, and thus expand the exciton recombination region. Furthermore, the host materials suitable for solution-processed OLED technology must meet several performance requirements: excellent solubility in organic solvents; superior film-forming performance during the film-forming process to ensure uniform morphology of the formed organic film; and good hole and electron transport capabilities to ensure balanced carrier transport in the fabricated OLED device and mitigate efficiency roll-off. Currently, there is a lack of host materials that can meet these comprehensive requirements, making the development of related organic electroluminescent materials and the optimization of device performance critical issues that urgently need to be addressed. Summary of the Invention

[0004] The present invention aims to improve at least one technical problem in the prior art.

[0005] A first aspect of the present invention provides a spirocyclic compound having a structural formula of formula (I) or formula (II):

[0006] Equation (I); Formula (II);

[0007] The structure of D is The structure of A is ;

[0008] R1 and R2 are independently selected from hydrogen, C1-C12 alkyl, C1-C12 alkoxy, C3-C10 cycloalkyl, phenyl, aryl group substituted with at least one C1-C12 alkyl group, and aryl group substituted with at least one C1-C12 alkoxy group.

[0009] The spirocyclic compounds with specific group substitution provided by this invention can be used as the main material for the light-emitting layer. They have excellent organic solvent solubility and good film-forming properties. The organic electroluminescent devices prepared by solution processing have balanced carrier transport performance. Their structure can help the light-emitting materials achieve the advantages of relatively aggregated stacking, which can ultimately effectively improve the maximum current efficiency of the device and reduce efficiency roll-off.

[0010] Preferably, the structure of the spirocyclic compound is one of M1-M12:

[0011]

[0012]

[0013] Preferably, the spirocyclic compound has the structure M8.

[0014] A second aspect of the present invention provides a method for preparing the spirocyclic compound as described above, comprising the following synthetic route:

[0015]

[0016] Optionally, the second raw material is selected from one of compounds RM2-1 to RM2-2:

[0017] .

[0018] Optionally, the third raw material is selected from one of compounds RM3-1 to RM3-3:

[0019] .

[0020] A third aspect of the present invention provides a light-emitting layer comprising a host material, wherein the host material is the aforementioned spirocyclic compound.

[0021] Preferably, the light-emitting layer further includes a light-emitting guest material, the mass content of which is 0.1wt%-20wt%.

[0022] A fourth aspect of the present invention provides an organic electroluminescent device, the organic electroluminescent device comprising, in sequence: an ITO anode, a hole injection layer, the aforementioned light-emitting layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode.

[0023] Spirocyclic compounds containing specific substituents provided by this invention can enable the light-emitting layer to have bipolar balanced carrier transport capabilities, and when fabricated as organic electroluminescent devices, they exhibit lower efficiency roll-off at high brightness.

[0024] A fifth aspect of the present invention provides a display device including the organic electroluminescent device described above.

[0025] The beneficial effects of the present invention are as follows: The spirocyclic compound provided by the present invention can be used as the main material of the light-emitting layer. It has excellent organic solvent solubility and good film-forming properties. The organic electroluminescent device prepared by solution processing technology has balanced carrier transport performance. Its structure can help the light-emitting material achieve the advantages of relatively aggregated stacking, and ultimately can effectively improve the maximum current efficiency of the device and reduce efficiency roll-off. Attached Figure Description

[0026] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0027] Figure 1 This is a schematic diagram of the structure of the organic electroluminescent device prepared in Example 2 of the present invention.

[0028] In the attached diagram: 1-ITO anode; 2-hole injection layer; 3-light-emitting layer; 4-hole blocking layer; 5-electron transport layer; 6-electron injection layer; 7-metal cathode. Detailed Implementation

[0029] The following will provide a clear and complete description of the concept and technical effects of this application in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution and effects of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0030] The structures of compounds M1-M12 mentioned below are shown below:

[0031]

[0032]

[0033] The synthetic routes for the above compounds M1-M12 are shown below:

[0034]

[0035] The raw materials used to synthesize the above compounds are as follows:

[0036] The first raw material specifically used includes the following molecules:

[0037] .

[0038] The second raw material specifically used includes the following molecules:

[0039] .

[0040] The third raw material specifically used includes the following molecules:

[0041] .

[0042] CAS numbers of the above raw materials:

[0043] RM1-1:2259716-82-8; RM1-2:1355363-69-7; RM2-1:1345345-08-5; RM2-2:1672704-46-9; RM3-1: 86-74-8; RM3-2: 37500-95-1; RM3-3: 56525-79-2.

[0044] The structural formulas of the comparative compounds CBP, mCBP, CM1, CM2, CM3, CM4, CM5, and CM6 are as follows:

[0045] .

[0046] In the following description, mass spectrometry data (Mass Spectra: MS) for molecules with a relative molecular weight below 1000 were obtained using a Thermo Fisher ITQ1100 ion trap gas chromatograph-mass spectrometer, while mass spectrometry data for molecules with a relative molecular weight above 1000 were obtained using a Bruker Autoflex Speed ​​matrix-assisted laser desorption / ionization time-of-flight mass spectrometer. Elemental analysis of the final products was performed using an Elemental Analysis Flash EA1112.

[0047] Example 1

[0048] A spirocyclic compound, the structure of which is shown in compound M4;

[0049] The specific preparation steps are as follows:

[0050] (1) Synthesis and characterization of intermediate A1: Starting materials RM1-1 (4.90 g, 10.0 mmol), RM2-1 (3.59 g, 11.0 mmol), and potassium carbonate (2.9 g, 21.0 mmol) were dissolved in a mixed solution of 20 mL water and 40 mL 1,4-dioxane. Tetra(triphenylphosphine)palladium (0.35 g, 0.3 mmol) was added under nitrogen atmosphere, and the mixture was heated to 70 °C and stirred continuously for 12 hours. After the reaction was completed and cooled to room temperature, the mixture was washed three times each with 100 mL dichloromethane and water. The organic phase was concentrated and purified by column chromatography (evolving solvent: petroleum ether) to obtain 4.3 g of white solid (yield: 72%). Mass spectrometry analysis confirmed it to be the target product intermediate A1, MS: 597.21 (calculated value: 597.16).

[0051] intermediate

[0052] A1

[0053] (2) Synthesis and characterization of compound M4: Intermediate A1 (5.98 g, 10.0 mmol), starting material RM3-2 (3.35 g, 12.0 mmol), cuprous iodide (0.95 g, 5.0 mmol), cesium carbonate (4.89 g, 15.0 mmol), and 1,10-phenanthroline (0.90 g, 5.0 mmol) were dissolved in 100 mL of o-dichlorobenzene. The mixture was heated to 180 °C under nitrogen atmosphere and stirred continuously for 24 hours. After the reaction was completed and cooled to room temperature, the mixture was filtered and the reaction solution was extracted with dichloromethane. The organic phase was concentrated and purified by column chromatography (evolving solvent: dichloromethane / petroleum ether) to obtain 5.8 g of white solid (yield 69%). The target product compound M7 was identified by mass spectrometry and elemental analysis. MS: 841.01 (calculated value: 841.07); elemental analysis: C, 85.65; H, 5.76; N, 6.67 (calculated value: C, 85.68; H, 5.75; N, 6.66).

[0054] Compounds M1-M3 and M5-M12 were prepared using the same synthetic method as compound M4. Elemental analysis (C, H, and N percentages) and mass spectrometry molecular weight data of the raw materials and products are shown in Table 1.

[0055] Table 1

[0056]

[0057] Performance testing experiments of spirocyclic compounds

[0058] Organic solvent solubility test:

[0059] Test method: Take 1 mL of solvent and add the corresponding mass x of organic compound to it. After heating at 80℃ for 2 h, observe whether the solution is clear and transparent. If the solution is clear and transparent, it is considered to be completely dissolved; otherwise, it is considered not to be completely dissolved.

[0060] The solubility of M1-M12 and CM1-CM6 was compared using two commonly used organic solvents in solution processing (chlorobenzene and methyl benzoate). These two organic solvents include low-boiling-point solvents (chlorobenzene with a boiling point less than 180℃) and high-boiling-point solvents (methyl benzoate with a boiling point greater than or equal to 180℃), thus providing a certain degree of representativeness. The test results are shown in Table 2.

[0061] Table 2

[0062]

[0063] As shown in Table 2, the organic solvent solubility of the spirocyclic compounds with specific structures proposed in this invention is significantly better than that of the comparative compounds CM1 to CM6, making them more suitable for application in solution-processed OLED technology.

[0064] Example 2

[0065] An organic light-emitting diode (OLED) device, the structure of which is as follows: Figure 1 As shown, it includes, in sequence: ITO anode 1, hole injection layer 2, light-emitting layer 3, hole blocking layer 4, electron transport layer 5, electron injection layer 6, and metal cathode 7.

[0066] The following are methods for fabricating solution-processed OLED devices, including:

[0067] The pre-fabricated ITO glass was ultrasonically cleaned sequentially with cleaning solution, deionized water, and isopropanol for 15 minutes and then dried in a 70°C oven. The dried ITO glass was then treated with a UV ozone cleaner for 15 minutes. Next, 200 μL of Pedot:PSS solution was added to the ITO glass, and the glass was spin-coated at 2000 rpm for 40 seconds. It was then annealed and dried at 150°C for 15 minutes to form a 40 nm thick hole injection layer. Organic compounds M1-M12 were used as the luminescent host, and boron nitride compound 3CzBN was selected as the luminescent guest. The luminescent layer material was dissolved in chlorobenzene solvent at a certain mass ratio to form a first mixture with a concentration of 15 mg / mL. This first mixture was filtered through a 0.22 μm PTFE membrane to form a second mixture. 80 μL of the second mixture was added to the hole injection layer and spin-coated at 2500 rpm for 30 seconds. The device was annealed and dried at ℃ for 60 minutes to form a light-emitting layer with a thickness of approximately 45 nm; the unfinished device was then transferred to the evaporation chamber and dried at 3×10⁻⁶ ℃. -5 Under a vacuum atmosphere of Pa, an electron transport layer with a thickness of 40 nm was formed at a rate of 0.05 nm / s, and TmPyPB was selected as the electron transport layer material; an electron injection layer with a thickness of 2 nm was formed at a rate of 0.01 nm / s, and (8-hydroxyquinoline)lithium was selected as the electron injection layer material; and a cathode layer was formed at a rate of 0.02 nm / s, and aluminum was selected as the cathode layer material.

[0068] Organic electroluminescent devices Device 1-Device 12 were finally obtained. PEDOT:PSS was used as the hole injection layer. In the luminescent layer, the synthesized final product compounds M1-M12 were used as the host material, 3CzBN as the guest material (guest material doping concentration of 2 wt%), TmPyPB as the electron transport material, lithium (8-hydroxyquinoline) as the electron injection layer, and Al as the metal cathode, respectively. Its structure is [ITO / PEDOT:PSS (40 nm) / M1-M12:2.0wt% 3CzBN (45 nm) / TmPyPB (40 nm) / Liq (2 nm) / Al (100 nm)].

[0069] Example 3

[0070] An organic electroluminescent device (OLED device) is prepared using the same method as the device in Example 2, except that M4 is selected as the host material for light emission and the doping concentration of the guest material in the light emission layer is changed to 5 wt% and 10 wt%. Devices 13 and 14 are obtained respectively.

[0071] Comparative Example 1

[0072] An organic electroluminescent device (OLED device) was prepared using the same method as the device in Example 2, except that: the main materials were CBP and mCBP, the concentration of the first mixed solution was 10 mg / ml, and the spin coating speed of the light-emitting layer was 1500 rpm / min, resulting in comparative devices Compare 1 and Compare 2.

[0073] Comparative Example 2

[0074] An organic electroluminescent device (OLED device) is prepared using the same method as the device in Example 2, except that the main materials are CM1, CM2, CM3, CM4, CM5, and CM6, respectively, to obtain comparative devices Compare 3-Compare 8.

[0075] Comparative Example 3

[0076] An organic electroluminescent device (OLED device) was prepared using the same method as the device in Comparative Example 1, except that CBP was selected as the host material and the doping concentration of the luminescent guest material was 5 wt% and 10 wt%. Comparative devices Compare9 and Compare 10 were obtained.

[0077] Performance testing of organic light-emitting diodes (OLED devices)

[0078] The organic electroluminescent devices prepared in Examples 2-3 and Comparative Examples 1-3 were tested. The current, voltage, brightness, and emission spectrum characteristics of the devices were simultaneously tested using a CS2000 spectrophotometer and a Keithley K2400 digital source meter system. The device performance tests were conducted at room temperature and under ambient atmosphere. The test results are shown in Table 3 below.

[0079] Table 3

[0080]

[0081] As shown in Table 3, compared with the comparative devices Compare 1–Compare 8, the maximum current efficiency of Devices 1–Device 12 prepared in Example 2 of this invention using spirocyclic compounds M1–M12 as the main material of the light-emitting layer is higher than 68 cd / A. Compared with CM6, which has the highest maximum current efficiency in the comparative examples, Devices 6–Device 12 all have higher maximum current efficiencies, with Device 8, which uses M8 as the main material of the light-emitting layer, reaching a maximum of 74.1 cd / A. Devices 1–Device 12 prepared in Example 2 of this invention using spirocyclic compounds M1–M12 as the main material of the light-emitting layer maintain high current efficiency at 1000 nits of brightness, significantly better than the comparative examples, and the efficiency roll-off is significantly reduced, indicating that the material of this invention can effectively improve the exciton annihilation phenomenon at high brightness.

[0082] When the doping concentration of the guest material in the emitting layer was increased to 5 wt% and 10 wt%, in Devices 13 and 14 prepared in Example 3, the efficiency roll-off increased slightly. The spectral peak position of Device 13 did not redshift, and the spectral peak position of Device 14 only showed a slight redshift. The full width at half maximum (FWHM) remained basically stable without significant broadening. In Devices Compare 9 and Compare 10 prepared in Comparative Example 3, the spectral peak positions of both devices showed redshift and broadening. Furthermore, the efficiency roll-off was significantly higher than that in Example 3 after the concentration was increased.

[0083] By comparing the device performance of the examples and comparative examples in Table 3, the following conclusions can be drawn: When the spirocyclic compound of the present invention is used as the host material for solution-processed OLED devices, the prepared organic electroluminescent devices achieve good maximum current efficiency and have a smaller efficiency roll-off. At the same time, it can effectively suppress the spectral broadening and spectral redshift caused by the increase of the doping concentration of the guest material in the light-emitting layer, which is beneficial to expanding the process window of the material in device fabrication and making it more applicable.

[0084] The above description is merely a preferred embodiment of this application. This application is not limited to the above-described embodiments. Any embodiment that achieves the technical effect of this application using the same means should fall within the protection scope of this application. Within the protection scope of this application, the technical solutions and / or implementation methods can have various modifications and variations.

Claims

1. A spirocyclic compound, characterized in that: The spirocyclic compound has the structure of formula (II): Formula (II); The structure of D is The structure of A is ; R1 and R2 are independently selected from hydrogen, C1-C12 alkyl, C1-C12 alkoxy, C3-C10 cycloalkyl, and phenyl.

2. The spirocyclic compound according to claim 1, characterized in that, The spirocyclic compound has a structure of one of M7-M12: 。 3. The spirocyclic compound according to claim 2, characterized in that, The structure of the spirocyclic compound is M8.

4. A method for preparing the spirocyclic compound as described in claim 1 or 2, characterized in that, The following synthetic routes are included: 。 5. The method for preparing the spirocyclic compound according to claim 4, characterized in that, The second raw material is selected from one of compounds RM2-1 to RM2-2: 。 6. The method for preparing the spirocyclic compound according to claim 4, characterized in that, The third raw material is selected from one of compounds RM3-1 to RM3-3: 。 7. A light-emitting layer, characterized in that, It includes a host material, wherein the host material is a spirocyclic compound as described in any one of claims 1-3.

8. The light-emitting layer according to claim 7, characterized in that, The light-emitting layer also includes a light-emitting guest material, the mass content of which is 0.1 wt%-20 wt%.

9. An organic electroluminescent device, characterized in that, The organic electroluminescent device comprises, in sequence: an ITO anode, a hole injection layer, the light-emitting layer as described in claim 7, a hole blocking layer, an electron transport layer, an electron injection layer, and a metal cathode.

10. A display device, characterized in that, Including the organic electroluminescent device as described in claim 9.

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