Electron transport material with asymmetric meta-substituted biphenyl structure and organic electroluminescent device thereof

Abstract

The invention belongs to the technical field of organic electroluminescent materials, and particularly relates to an electron transport material with an asymmetric meta-substituted biphenyl structure and an organic electroluminescent device.According to the electron transport material with the asymmetric meta-substituted biphenyl structure, the asymmetric meta-substituted biphenyl structure is arranged in the middle of the electron transport material, and the asymmetric meta-substituted biphenyl structure is arranged in the middle of the electron transport material; electron withdrawing groups are arranged on two sides. Firstly, electron withdrawing groups on the two sides are groups with good planarity, secondly, the energy level regulation and the solubility regulation of the asymmetric meta-substituted biphenyl structure in the middle are more flexible, and the asymmetric structure can enable accumulation to be more disordered during evaporation, so that a uniform amorphous film is formed, and the pinhole defect is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescent materials, and in particular relates to an electron transport material with an asymmetric meta-substituted biphenyl structure and an organic electroluminescent device thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs), the core of third-generation display technology, are widely used in small and medium-sized displays such as smartphones and laptops due to their self-luminescence, high contrast, wide viewing angle, low energy consumption, and flexibility. They are also gradually penetrating the medium and large-sized markets, including televisions, automotive displays, and lighting. In 2024, OLED shipments in the small and medium-sized panel market will surpass liquid crystal displays (LCDs) for the first time, marking a key breakthrough in its industrialization.

[0003] With domestic panel manufacturers (such as BOE and CSOT) investing in 8.6-generation AMOLED production lines, OLED applications are rapidly expanding from mobile devices to medium and large-sized screens, placing higher demands on material performance: higher electron mobility to match the carrier transport requirements of large-scale devices, better film-forming properties to ensure uniform light emission, and lower driving voltage to extend battery life. However, the limitations of traditional electron transport materials have become a key bottleneck hindering the development of OLEDs towards high efficiency, long life, and low cost.

[0004] In the "sandwich" structure of OLED (anode / hole transport layer / light-emitting layer / electron transport layer / cathode), the electron transport layer (ETL) is responsible for regulating the injection speed and transmission efficiency of electrons from the cathode to the light-emitting layer. Its performance directly affects the luminous efficiency, driving voltage and life of the device.

[0005] The electron mobility of existing ETL materials (such as Alq3, 8-hydroxyquinoline aluminum) is only 10 -6 cm2 / (V·s) level, which is much lower than 10 of hole transport materials (HTL) -3 ~10 -4cm2 / (V·s). This mobility gap of more than 100 times results in: electrons having difficulty effectively transporting to the central region of the light-emitting layer, far from the cathode, resulting in the recombination zone being biased toward the cathode side; uneven exciton distribution triggers non-radiative recombination, reducing luminescence efficiency. To compensate for insufficient electron injection, the driving voltage must be increased, which accelerates device aging. Furthermore, ETL materials must form a uniform and dense film during vacuum evaporation. However, most materials (such as Alq3) have strong intermolecular π-π stacking interactions, which easily form crystalline particles during evaporation. This results in: local defects in the film (pinholes, cracks), increased leakage current, obstructed electron transport channels, and further reduced recombination efficiency. Furthermore, the lowest unoccupied molecular orbital (LUMO) energy level of the ETL material must be precisely matched to the cathode work function and the HOMO-LUMO energy level difference of the light-emitting layer. Conventional materials (such as Alq3) suffer from: excessively high electron injection barriers, requiring additional energy compensation; and sudden energy level gradients that induce exciton interface quenching, exacerbating efficiency roll-off.

[0006] Therefore, the development of organic small molecule ETL materials with high electron mobility, excellent film-forming properties, and precise energy level matching is the core path to achieving high efficiency, long life, and low-voltage drive of OLED devices. It is of strategic significance to promote the comprehensive expansion of the OLED industry from midstream panels to downstream application scenarios. Summary of the Invention

[0007] To solve the problems existing in the background technology, the first object of the present invention is to provide an electron transport material having an asymmetric meta-substituted biphenyl structure, and the technical solution is as follows:

[0008] An electron transport material having an asymmetric meta-substituted biphenyl structure, the structure of which is shown in general formula (I):

[0009]

[0010] Ar1 are the same or different and are independently selected from the following substituted or unsubstituted groups:

[0011]

[0012] When substitution is present, the substituents are each independently selected from C6 to C 18 Aryl or C5~C 18 heteroaryl;

[0013] Ar2 is selected from C6~C 18 Aryl or C5~C 18 of heteroaryl.

[0014] As preferred embodiments of the present invention, Ar1 are the same or different and are independently selected from the following substituted or unsubstituted groups:

[0015] Indicates a connection key.

[0016] As preferred embodiments of the present invention, Ar1 are the same or different and are independently selected from the following substituted groups: Indicates the substitution site.

[0017] As preferred in the present invention, Ar2 is selected from phenyl, biphenyl, naphthyl, and pyridyl.

[0018] As a preferred embodiment of the present invention, when substitution is present, the substituent is selected from phenyl, biphenyl, naphthyl, and pyridyl.

[0019] As a preferred embodiment of the present invention, the structure of the electron transport material is selected from one of the following structures:

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033] Another object of the present invention is to provide an organic electroluminescent device, comprising a first electrode, a second electrode, a hole transport region, a light-emitting layer, and an electron transport region interposed therebetween, characterized in that the material used in the electron transport region is the above-mentioned electron transport material having an asymmetric meta-substituted biphenyl structure.

[0034] As a preferred embodiment of the present invention, the organic electroluminescent device is used to manufacture display devices, lighting sources, signal lights, and signboards. The display devices include mobile phone displays, computer displays, TV displays, smart watch displays, smart car display panels, and VR or AR helmet displays.

[0035] The beneficial effects of the present invention are as follows:

[0036] The electron transport material with an asymmetric meta-substituted biphenyl structure provided by the present invention has an asymmetric meta-substituted biphenyl structure in the middle and electron-withdrawing groups on both sides. First, the electron-withdrawing groups on both sides select groups with better planarity, such as nitrogen-containing ring structures, the degree of conjugation of the molecule is higher, and the planarity is better. For example, the triazine structure has a large number of hydrogen bonds in the molecule and better planarity. Good planarity can increase the mobility of electrons, thereby improving the efficiency and life of the prepared device. Secondly, the energy level regulation and solubility regulation of the asymmetric meta-substituted biphenyl structure in the middle are more flexible because there are two benzene rings that can be differentially modified. The present invention introduces substituted benzene on one of the benzene rings for regulating the energy level and polarity of the molecule. Moreover, the asymmetric structure can make the stacking more disordered during evaporation to form a uniform amorphous film to reduce pinhole defects. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] If the specific conditions are not specified in the examples, the reaction is carried out under conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially. Some reaction compounds are purchased from commodity suppliers (Zhengzhou Alpha Chemical Co., Ltd.), and some compounds that cannot be purchased directly are prepared by simple reactions of commercially available raw materials. The percentages all refer to mass percentages, and the temperatures are in degrees Celsius (°C). The principles, operating procedures, conventional post-treatments, silica gel column, recrystallization and purification of such methods are well known to synthesizers in this field, and the synthesis process can be fully realized to obtain the target product. The reactions in the preparation examples are generally carried out under positive pressure of nitrogen or argon.

[0039] Preparation Example

[0040] Synthesis Example 1: Synthesis of Compound 1

[0041]

[0042] Synthesis of compound 1: 1-1 (3.74 g, 10 mmol), 1-2 (5.12 g, 20 mmol), potassium carbonate (K2CO3) (6.92 g, 50 mmol) and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) (1.16 g, 1.0 mmol) were added to 60 mL of 1,4-dioxane and 30 mL of water, and then heated to 80°C under a nitrogen flow for 12 hours. The organic layer was separated, methanol was added thereto, the crystallized solid was filtered, dissolved in toluene, filtered through silica gel / diatomaceous earth to remove an appropriate amount of the organic solvent, and then the product was recrystallized from toluene to obtain compound 1 (3.94 g, 70%), MS: 562.35.

[0043] Synthesis Example 2: Synthesis of Compound 10

[0044]

[0045] Synthesis of 10-3: 10-1 (5.42 g, 10 mmol), 10-2 (2.40 g, 10 mmol), potassium carbonate (K2CO3) (3.46 g, 25 mmol) and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) (0.58 g, 0.5 mmol) were added to 30 mL of 1,4-dioxane and 15 mL of water, and then heated to 80°C under a nitrogen flow for 12 hours. The organic layer was separated, methanol was added thereto, the crystallized solid was filtered, dissolved in toluene, filtered through silica gel / diatomaceous earth to remove an appropriate amount of organic solvent, and then the product was recrystallized from toluene to obtain 10-3 (4.53 g, 73%).

[0046] Synthesis of compound 10: 10-3 (6.20 g, 10 mmol), 1-2 (2.56 g, 10 mmol), potassium carbonate (K2CO3) (3.46 g, 25 mmol) and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh3)4) (0.58 g, 0.5 mmol) were added to 30 mL of 1,4-dioxane and 15 mL of water, and then heated to 80°C under a nitrogen stream for 12 hours. The organic layer was separated, methanol was added thereto, the crystallized solid was filtered, dissolved in toluene, filtered through silica gel / diatomaceous earth to remove an appropriate amount of the organic solvent, and then the product was recrystallized from toluene to obtain compound 10 (5.07 g, 71%), MS: 714.41.

[0047] Synthesis Example 3: Synthesis of Compound 20

[0048]

[0049] The synthesis method of 20-3 is the same as that of 10-3, except that 20-1 replaces 10-1 and 20-2 replaces 10-2;

[0050] The synthesis method of compound 20 is the same as that of compound 10, except that 10-3 is replaced by 20-3, MS: 755.41.

[0051] Synthesis Example 4: Synthesis of Compound 30

[0052]

[0053] The synthesis method of 30-2 is the same as that of 10-3, except that 10-2 is replaced by 30-1;

[0054] The synthesis method of compound 30 is the same as that of compound 10, except that 10-3 is replaced by 30-2, MS: 687.38.

[0055] Synthesis Example 5: Synthesis of Compound 40

[0056]

[0057] The synthesis method of 40-3 is the same as that of 10-3, except that 10-1 is replaced by 40-1 and 10-2 is replaced by 40-2;

[0058] The synthesis method of compound 40 is the same as that of compound 10, except that 10-3 is replaced by 40-3, and 1-2 is replaced by 40-4. MS: 551.35.

[0059] Synthesis Example 6: Synthesis of Compound 50

[0060]

[0061] The synthesis method of compound 50 is the same as that of compound 1, except that 1-1 is replaced by 50-1, and 1-2 is replaced by 40-4. MS: 590.36.

[0062] Synthesis Example 7: Synthesis of Compound 60

[0063]

[0064] The synthesis method of 60-2 is the same as that of 10-3, except that 40-1 is used to replace 10-1, and 60-1 is used to replace 10-2;

[0065] The synthesis method of compound 60 is the same as that of compound 10, except that 10-3 is replaced by 60-2, and 1-2 is replaced by 40-4. MS: 654.39.

[0066] Synthesis Example 8: Synthesis of Compound 70

[0067]

[0068] The synthesis method of compound 70 is the same as that of compound 1, except that 1-2 is replaced by 70-1, MS: 714.17.

[0069] Synthesis Example 9: Synthesis of Compound 80

[0070]

[0071] The synthesis method of 80-3 is the same as that of 10-3, except that 10-1 is replaced by 80-1 and 10-2 is replaced by 80-2;

[0072] The synthesis method of compound 80 is the same as that of compound 10, except that 10-3 is replaced by 80-3, and 1-2 is replaced by 80-4. MS: 677.14.

[0073] Synthesis Example 10: Synthesis of Compound 90

[0074]

[0075] The synthesis method of compound 90 is the same as that of compound 10, except that 10-3 is replaced by 60-2, and 1-2 is replaced by 80-4. MS: 665.13.

[0076] Synthesis Example 11: Synthesis of Compound 100

[0077]

[0078] The synthesis method of 100-1 is the same as that of 10-3, except that 20-1 is used to replace 10-1, and 30-1 is used to replace 10-2;

[0079] The synthesis method of compound 100 is the same as that of compound 10, except that 100-1 is used to replace 10-3, and 100-2 is used to replace 1-2. MS: 804.40.

[0080] Synthesis Example 12: Synthesis of Compound 110

[0081]

[0082] The synthesis method of 110-2 is the same as that of 10-3, except that 110-1 is used to replace 10-2;

[0083] The synthesis method of compound 110 is the same as that of compound 10, except that 10-3 is replaced by 110-2, and 1-2 is replaced by 110-3. MS: 713.16.

[0084] Synthesis Example 13: Synthesis of Compound 120

[0085]

[0086] The synthesis method of 120-2 is the same as that of 10-3, except that 20-1 is used to replace 10-1, and 120-1 is used to replace 10-2;

[0087] The synthesis method of compound 120 is the same as that of compound 10, except that 10-3 is replaced by 120-2, and 1-2 is replaced by 120-3. MS: 602.34.

[0088] Synthesis Example 14: Synthesis of Compound 130

[0089]

[0090] The synthesis method of 130-1 is the same as that of 10-3, except that 30-1 is used to replace 10-2;

[0091] The synthesis method of compound 130 is the same as that of compound 10, except that 10-3 is replaced by 130-1, and 1-2 is replaced by 120-3. MS: 686.39.

[0092] Synthesis Example 15: Synthesis of Compound 140

[0093]

[0094] The synthesis method of 140-2 is the same as that of 10-3, except that 10-2 is replaced by 140-1;

[0095] The synthesis method of compound 140 is the same as that of compound 10, except that 10-3 is replaced by 140-2, and 1-2 is replaced by 100-2. MS: 981.25.

[0096] Synthesis Example 16: Synthesis of Compound 150

[0097]

[0098] The synthesis method of 150-1 is the same as that of 10-3, except that 20-1 is used to replace 10-1, and 120-1 is used to replace 10-2;

[0099] The synthesis method of compound 150 is the same as that of compound 10, except that 10-3 is replaced by 150-1, and 1-2 is replaced by 150-2. MS: 719.11.

[0100] Synthesis Example 17: Synthesis of Compound 160

[0101]

[0102] The synthesis method of compound 160 is the same as that of compound 10, except that 10-3 is replaced by 130-1, and 1-2 is replaced by 160-1. MS: 853.45.

[0103] Synthesis Example 18: Synthesis of Compound 170

[0104]

[0105] The synthesis method of compound 170 is the same as that of compound 10, except that 10-3 is replaced by 140-2, and 1-2 is replaced by 170-1. MS: 997.21.

[0106] Synthesis Example 19: Synthesis of Compound 180

[0107]

[0108] The synthesis method of compound 180 is the same as that of compound 10, except that 10-3 is replaced by 150-1, and 1-2 is replaced by 180-1. MS: 735.33.

[0109] Synthesis Example 20: Synthesis of Compound 190

[0110]

[0111] The synthesis method of compound 190 is the same as that of compound 10, except that 10-3 is replaced by 130-1, and 1-2 is replaced by 170-1. MS: 895.18.

[0112] Synthesis Example 21: Synthesis of Compound 200

[0113]

[0114] The synthesis method of compound 200 is the same as that of compound 10, except that 10-3 is replaced by 200-1, and 1-2 is replaced by 200-2. MS: 741.16.

[0115] Synthesis Example 22: Synthesis of Compound 210

[0116]

[0117] The synthesis method of compound 210 is the same as that of compound 10, except that 10-3 is replaced by 210-1, and 1-2 is replaced by 210-2. MS: 754.14.

[0118] Synthesis Example 23: Synthesis of Compound 220

[0119]

[0120] The synthesis method of compound 220 is the same as that of compound 10, except that 10-3 is replaced by 60-2, and 1-2 is replaced by 200-2. MS: 768.41.

[0121] Synthesis Example 24: Synthesis of Compound 230

[0122]

[0123] The synthesis of compound 230 was the same as that of compound 10, except that 10-3 was replaced by 200-1, and 1-2 was replaced by 230-1. MS: 687.38.

[0124] Synthesis Example 25: Synthesis of Compound 240

[0125]

[0126] The synthesis method of 240-2 is the same as that of 10-3, except that 80-1 replaces 10-1 and 240-1 replaces 10-2;

[0127] The synthesis method of compound 240 is the same as that of compound 10, except that 10-3 is replaced by 240-2, and 1-2 is replaced by 230-1. MS: 776.42.

[0128] Synthesis Example 26: Synthesis of Compound 250

[0129]

[0130] The synthesis method of 250-2 is the same as that of 10-3, except that 40-1 is used to replace 10-1, and 250-1 is used to replace 10-2;

[0131] The synthesis method of compound 250 is the same as that of compound 10, except that 10-3 is replaced by 250-2, and 1-2 is replaced by 230-1. MS: 790.43.

[0132] In addition, it should be noted that other compounds of the present application can be obtained by referring to the preparation methods of the above-mentioned embodiments, so they will not be listed one by one here.

[0133] Device Examples

[0134] Preparation of Device Example 1:

[0135] It is coated with a thickness of A glass substrate with an ITO (indium tin oxide) thin film was placed in distilled water with a detergent dissolved therein and ultrasonically cleaned. After the ITO was cleaned for 30 minutes, ultrasonic cleaning was repeated twice with distilled water for 10 minutes each. The substrate was then ultrasonically cleaned with isopropyl alcohol, acetone, and methanol solvents, dried, and transferred to a plasma cleaner for cleaning for 5 minutes before being transferred to a vacuum depositor.

[0136] On the ITO transparent electrode, compound [HI] was thermally vacuum deposited to to form a hole injection layer; vacuum depositing compound [HT] on the hole injection layer to To form a hole transport layer; vacuum depositing compound [BH] and compound [BD] on the hole transport layer at a ratio of 97:3 The thickness of the light-emitting layer is to form a light-emitting layer; Compound 1 and compound [LiQ] (lithium quinoline) are vacuum deposited at a ratio of 1:1 on the light-emitting layer to form a layer having a thickness of On the electron transport layer, yttrium (Yb) and magnesium silver (1:9) are sequentially deposited to a thickness of and The cathode is formed. The vacuum during deposition is maintained at 1×10 -7 Up to 5×10 -8 Entrust.

[0137] Preparation of Device Examples 2-26:

[0138] When forming the electron transport layer, the compound shown in Table 1 was used instead of Compound 1 in Example 1, and an organic electroluminescent device was prepared using the same method as in Example 1.

[0139] Preparation of Comparative Device Example 1-2:

[0140] An organic electroluminescent device was prepared by the same method as in Example 1, except that the comparative compound ref-1 or the compound ref-2 was used instead of the compound 1 in Example 1 when forming the electron transport layer.

[0141] The structure of the compound used in the above preparation process is as follows:

[0142]

[0143] At 10 mA / cm 2 The driving voltage and current efficiency of the device embodiments and comparative examples were measured at a current density of 50 mA / cm 2The time required for the brightness to decrease to 97% of the initial brightness (LT97) was measured at a current density of 100 nm. The driving voltage and current efficiency were tested using an IVL (current-voltage-luminance) test system (Suzhou Fushida Scientific Instrument Co., Ltd.). The lifespan test system was the Suzhou Fushida Scientific Instrument Co., Ltd. OLED lifespan test system. The blue light index (BI) = E / CIEy, representing the effective efficiency of the blue light device, where E refers to the current efficiency and CIEy refers to the color point on the ordinate obtained by substituting the device's half-maximum wavelength into the CIE1930 software. The results are shown in Table 1 below:

[0144] Table 1

[0145]

[0146] The series of compounds provided by the present invention are composed of electron-withdrawing groups on both sides and an asymmetric meta-substituted biphenyl structure in the middle. The electron-withdrawing groups with strong planarity on both sides can increase the mobility of electrons, thereby improving the luminous efficiency and service life of the prepared device. As shown in the embodiment compared with comparative example 1, the electron-withdrawing group on one side of comparative example 1 is a pyrimidine with two intramolecular hydrogen bonds, and its planarity is weaker than the nitrogen-containing ring structure or the triazine structure with three intramolecular hydrogen bonds in the present invention, so its efficiency and service life are not as good as the series of compounds of the present invention, and the voltage is slightly high. In addition, the comparative example is also biphenyl, but not all meta-substituted, one of which is para-substituted, and para-substituted belongs to strong conjugation, and energy level regulation and solubility regulation are not as flexible as meta-substituted benzene. The asymmetric meta-substituted biphenyl structure in the middle is compared with the benzene structure with meta-substituted in the middle, as shown in the embodiment compared with comparative example 2, the skeleton rigidity is higher, thereby having a better glass transition temperature, which can reduce the risk of thermal crystallization in the preparation device process, and the two benzene rings can also synergistically enhance the affinity of electrons compared with single benzene, further improving the mobility of electrons.

[0147] The above examples only list the effect data of devices made from a part of the compounds. This is a representative sampling test. According to the experimental data, the overall data is not much different and can represent the effects of other unlisted structures.

[0148] It will be apparent to those skilled in the art that many modifications and variations are possible without departing from the spirit and scope of the present invention. It is therefore contemplated that the present invention encompasses modifications and variations of the present invention provided within the scope of the appended claims and their equivalents.

[0149] The applicant states that while the present invention uses the aforementioned embodiments to illustrate the organic electroluminescent materials and devices of the present invention, the present invention is not limited to these embodiments, nor does it necessarily rely on these embodiments for implementation. Persons skilled in the art should understand that any improvements to the present invention, equivalent substitutions for raw materials in the products of the present invention, additions of auxiliary components, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. An electron transport material having an asymmetric meta-substituted biphenyl structure, characterized in that: Its structure is shown in general formula (I): Ar1 are the same or different and are independently selected from the following substituted or unsubstituted groups: When substitution is present, the substituents are each independently selected from C6 to C 18 Aryl or C5~C 18 heteroaryl; Ar2 is selected from C6~C 18 Aryl or C5~C 18 of heteroaryl.

2. The electron transport material having an asymmetric meta-substituted biphenyl structure according to claim 1, characterized in that Ar1 are the same or different and are independently selected from the following substituted or unsubstituted groups: Indicates a connection key.

3. The electron transport material having an asymmetric meta-substituted biphenyl structure according to claim 2, characterized in that: Ar1 are the same or different and are independently selected from the following groups substituted: Indicates the substitution site.

4. The electron transport material having an asymmetric meta-substituted biphenyl structure according to claim 1, characterized in that Ar2 is selected from phenyl, biphenyl, naphthyl, and pyridyl.

5. The electron transport material having an asymmetric meta-substituted biphenyl structure according to claim 1, characterized in that When substitution is present, the substituent is selected from phenyl, biphenyl, naphthyl, and pyridyl.

6. The electron transport material having an asymmetric meta-substituted biphenyl structure according to claim 1, characterized in that: The structure of the electron transport material is selected from one of the following structures:

7. An organic electroluminescent device comprising a first electrode, a second electrode, a hole transport region, a light-emitting layer, and an electron transport region interposed therebetween, characterized in that: The material used in the electron transport region is the electron transport material having an asymmetric meta-substituted biphenyl structure as claimed in any one of claims 1 to 6.

8. The organic electroluminescent device according to claim 7, characterized in that: The organic electroluminescent device is used to manufacture display devices, lighting sources, signal lights, and signboards. The display devices include mobile phone displays, computer displays, TV displays, smart watch displays, smart car display panels, and VR or AR helmet displays.

Images