A phosphorescent host material, a preparation method and an organic electroluminescent device comprising the same

Abstract

The application belongs to the technical field of organic photoelectric materials, and provides a phosphorescent host material, a preparation method and an organic electroluminescent device containing the same. A general structure formula of the phosphorescent host material is shown in the specification. The phosphorescent host material provided by the application is applied to a light-emitting device, and shows the characteristics of low driving voltage, high luminous efficiency and long service life, and the comprehensive performance of the obtained green organic electroluminescent device is more excellent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic photoelectric materials, and particularly relates to a phosphorescent host material, a preparation method and an organic electroluminescent device comprising the same. BACKGROUND

[0002] As a new generation of display and lighting technology, organic electroluminescent devices (OLEDs) have been widely used in consumer electronics due to their self-luminescence, high contrast, flexibility and other advantages. With the market extending to large size and high resolution, higher requirements are put forward for the luminous efficiency and service life of the devices. Phosphorescent OLEDs can utilize single and triplet excitons to achieve a theoretical internal quantum efficiency of 100%, and their performance is highly dependent on the host material.

[0003] In phosphorescent OLEDs, N-type host materials are mainly responsible for electron transport, and their energy level structure, carrier mobility and thermal stability directly affect the efficiency and lifetime of the devices. The existing host materials still have performance problems such as driving voltage, luminous efficiency and lifetime. Therefore, developing stable and efficient N-type host materials to improve the comprehensive performance in devices has become a key technical direction to improve the performance of phosphorescent OLEDs. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a phosphorescent host material, a preparation method and an organic electroluminescent device comprising the same. The phosphorescent host material is applied to a light-emitting device, which exhibits low driving voltage, high luminous efficiency and long lifetime, and the comprehensive performance of the obtained green organic electroluminescent device is more excellent.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] The first technical purpose of the present application is to provide a phosphorescent host material, which has a compound structure shown in formula 1:

[0007] ;

[0008] wherein X is selected from O or S;

[0009] R1 is selected from deuterium;

[0010] R2, R3, R4 are each independently selected from deuterium, an unsubstituted or deuterium-substituted group of formula a-d, wherein the total number of unsubstituted or deuterium-substituted groups of formula a-d is 0, 1, 2, 3;

[0011] ;

[0012] m is taken from the values 0, 1, 2, 3, 4, 5, 6;

[0013] n and q are each independently taken from the values ​​0, 1, 2, 3, and 4;

[0014] p is taken from the values ​​0, 1, and 2;

[0015] Ar, Ar1 are independently selected from unsubstituted or substituted C6-C. 24 aryl, unsubstituted or substituted C containing one heteroatom of O, S or N. 12 -C 18 Heteroaryl, unsubstituted or substituted 9,9-dimethylfluorenyl.

[0016] In one embodiment of the invention, Ar1 and Ar are independently selected from the following groups, either unsubstituted or deuterated:

[0017] ,

[0018] The asterisk (*) indicates the junction between the group and a carbon atom on the ring.

[0019] In this invention, the term "unsubstituted or deuterated" means that the group is substituted by one, two or more, up to the maximum number of substituted groups, or has no substituents. "Unsubstituted or substituted" means substituted by one, two or more, up to the maximum number of substituted groups selected from: deuterium, phenyl, phenyl fully or partially substituted with deuterium, or has no substituents.

[0020] In one embodiment of the present invention, the phosphorescent host material is selected from any one of the following compounds:

[0021] .

[0022] The above only lists some specific structural forms, but this series of phosphorescent host materials is not limited to the above molecular structures. Other specific molecular structures can be obtained by simply changing some simple groups and their substituted groups and substitution positions, which will not be elaborated here.

[0023] A second objective of this invention is to provide a method for preparing the aforementioned phosphorescent host material, which can be prepared by synthesis methods known to those skilled in the art. Alternatively, the following reaction process is preferred for preparation.

[0024] After dissolving intermediate 1-a (1.0 eq), reactant 1-b (1.0-1.2 eq) in xylene, adding palladium catalyst (0.01-0.05 eq), phosphine ligand (0.02-0.15 eq), base (2.0-2.4 eq); after addition, slowly warming the reaction temperature to 100-110℃, and stirring the mixture for 8-10 h; after determining the end of the reaction by thin layer chromatography, adding water and dichloromethane to extract, separate the layers, and after combining the organic phases, concentrating, purifying by column chromatography using a mixture of dichloromethane and petroleum ether (V:V = 1:4-1:8) to obtain formula 1.

[0025] The specific synthesis route is as follows: ;

[0026] wherein,

[0027] Hal is selected from F, Cl, Br, I;

[0028] R1, R2, R3, R4, n, m, p, q, X, Ar and Ar1 have the definitions given above.

[0029] Further, the base is selected from K2CO3 (potassium carbonate), K3PO4 (potassium phosphate), Na2CO3 (sodium carbonate), CsF (cesium fluoride), Cs2CO3 (cesium carbonate) or t-BuONa (sodium tert-butoxide);

[0030] The palladium catalyst is selected from Pd2(dba)3 (tris(dibenzylideneacetone)dipalladium), Pd(PPh3)4 (tetrakis(triphenylphosphine)palladium), PdCl2 (palladium dichloride), PdCl2(dppf) ([1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium), Pd(OAc)2 (palladium acetate), Pd(PPh3)2Cl2 (bis(triphenylphosphine)palladium dichloride) or NiCl2(dppf) ((1,1'-bis(diphenylphosphino)ferrocene)nickel dichloride);

[0031] The phosphine ligand is selected from P(t-Bu)3 (tri-tert-butylphosphine), X-phos (2-cyclohexylphosphine-2,4,6-triisopropylbiphenyl), PET3 (triethylphosphine), PMe3 (trimethylphosphine), PPh3 (triphenylphosphine), KPPh2 (potassium diphenylphosphate) or P(t-Bu)2Cl (di-tert-butylchlorophosphine).

[0032] A third object of the present application is to provide the use of the above-mentioned phosphorescent host material in an organic electroluminescent device.

[0033] In the present application, an organic electroluminescent device comprises the phosphorescent host material.

[0034] It should be noted that the light-emitting device comprising the phosphorescent host material of the present application exhibits the characteristics of low driving voltage, high luminous efficiency and long service life, and the comprehensive performance of the device is more excellent.

[0035] Via the technical solution described above, compared with the prior art, the present application has the following beneficial effects:

[0036] 1) The present application provides a parent structure by substituting the 2,3 position of naphthalene ring with benzo-heterocyclic carbazole and triazine groups, wherein the naphthalene ring provides a conjugated plane of appropriate size to facilitate electron transport, reduce driving voltage and improve luminous efficiency; at the same time, ortho-substitution ensures the spatial stereoscopic nature of the structure, avoids excessive interaction between molecules, forms a uniform film and improves device life. The electron-rich carbazole nitrogen atom and the electron-deficient O / S atom are directly adjacent, generating a stronger intramolecular charge transfer effect, which can more effectively stabilize the LUMO energy level, thereby reducing the energy barrier for electron injection, making electron injection smoother, reducing driving voltage and significantly improving luminous efficiency.

[0037] 2) The compound device according to the general formula of the present application has excellent overall performance. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0039] Figure 1 The nuclear magnetic resonance hydrogen spectrum of compound 3 in Example 1 of the present application. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0041] The present application discloses a phosphorescent host material, a preparation method and an organic electroluminescent device comprising the same.

[0042] In addition, it should be noted that the numerical values given in the following examples are as accurate as possible, but those skilled in the art understand that due to unavoidable measurement errors and experimental operation problems, each number should be understood as an approximate number, not an absolutely accurate number.

[0043] Example 1

[0044]

[0045] After dissolving the reactant 3-a (1.0 eq, CAS No: 2861990-92-1) and the reactant 3-b (1.2 eq, CAS No: 2490274-60-5) in xylene, Pd(PPh3)4 (0.01 eq), X-Phos (0.02 eq), t-BuONa (2.0 eq) were added; after the addition, the reaction temperature was slowly warmed to 110°C, and the mixture was stirred for 8 h; after the reaction was determined to be completed by thin layer chromatography, water and dichloromethane were added for extraction, the organic phases were combined and concentrated, and the compound 3 was obtained by column chromatography using a mixed solution of dichloromethane and petroleum ether (V:V = 1:4) as the eluent (yield: 83.7%, test value MS (ESI, m / Z): [M+H]+= 640.43).

[0046] The nuclear magnetic resonance hydrogen spectrum of the compound 3 is shown in Figure 1 .

[0047] Characterization:

[0048] HPLC purity: >99.8%.

[0049] Elemental analysis:

[0050] Test value: C, 80.61; H, 5.70; N, 8.76; S, 5.04.

[0051] Device Example 1: Preparation of a green organic electroluminescent device

[0052] a, ITO anode: ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 150 nm was cleaned in distilled water for 2 times, ultrasonic washing for 30 min, and then repeatedly cleaned with distilled water for 2 times, ultrasonic washing for 10 min, and then baked in a vacuum oven at 220°C for 2 hours. After the baking was completed, the temperature was lowered for use. The substrate was used as an anode, and a device process was performed by evaporation using an evaporation machine. Other functional layers were sequentially evaporated thereon.

[0053] b, HIL (hole injection layer): the hole injection layer materials HT and P-dopant were vacuum evaporated at an evaporation rate of 1 Å / s, and the evaporation rate ratio of the HT and P-dopant was 97:3, and the thickness was 10 nm;

[0054] c, HTL (hole transport layer): 120 nm of HT as a hole transport layer was vacuum evaporated on the hole injection layer at an evaporation rate of 1.5 Å / s;

[0055] d. Prime (light-emitting auxiliary layer): 35 nm of Prime was vacuum deposited on the hole transport layer as a light-emitting auxiliary layer at a deposition rate of 0.5 A / s;

[0056] e. EML (light-emitting layer): 35 nm of a total thickness of a double host material (compound 3 provided by the present application as a first host compound, Host-2 as a second host compound) and a dopant material (Dopant) was vacuum deposited on the light-emitting auxiliary layer as a light-emitting layer at a deposition rate of 1 A / s, wherein the deposition rate ratio of the first host compound, the second host compound, and the dopant compound was 44:44:12.

[0057] f. HB (hole blocking layer): 5.0 nm of HB was vacuum deposited on the light-emitting layer as a hole blocking layer at a deposition rate of 0.5 A / s.

[0058] g. ETL (electron transport layer): 30 nm of ET and Liq was vacuum deposited on the hole blocking layer as an electron transport layer at a deposition rate of 1 A / s; wherein the deposition rate ratio of ET and Liq was 1:1.

[0059] h. EIL (electron injection layer): 1.0 nm of Yb film layer was vacuum deposited on the electron transport layer as an electron injection layer at a deposition rate of 0.5 A / s.

[0060] i. Cathode: 13 nm of magnesium and silver was vacuum deposited on the electron injection layer as a cathode at a deposition rate of 1 A / s, and the deposition rate ratio was 1:9.

[0061] j. Light extraction layer: 60 nm of CPL was vacuum deposited on the cathode as a light extraction layer at a deposition rate of 1 A / s.

[0062] k. Packaging of the substrate after deposition: first, the cleaned cover plate was coated with UV glue using a gluing device, then the coated cover plate was moved to the pressing section, the substrate after deposition was placed on the end of the cover plate, and finally the substrate and the cover plate were bonded under the action of the bonding device, and the UV glue was cured by light at the same time.

[0063] The material structure used in the above device is as follows:

[0064] .

[0065] Device Example 2-Device Example 102:

[0066] The first host material in Device Example 2-Device Example 102 in Table 1 can be replaced with compound 3 in Device Example 1.

[0067] Device Comparative Example 1-Device Comparative Example 26

[0068] Referring to the preparation method provided in Device Example 1 above, comparative compound 1-comparative compound 26 are used to replace compound 3 in Device Example 1, respectively, and are recorded as Device Comparative Example 1-Device Comparative Example 26, wherein the chemical structural formula of comparative compound 1-comparative compound 26 is as follows: .

[0069] The driving voltage, luminous efficiency and lifespan of the organic electroluminescent device obtained from Device Example 1-Device Example 102 and Device Comparative Example 1-Device Comparative Example 26 above are characterized under the brightness of 15000 (nits), and the test results are shown in Table 1 below.

[0070] Table 1 Device test results

[0071]

[0072] As can be seen from Table 1, the organic electroluminescent device prepared using the host of the light-emitting layer provided by the present application exhibits low driving voltage, high luminous efficiency and long lifespan compared with the device prepared using comparative compound 1-comparative compound 26, and the comprehensive performance of the device is more excellent.

[0073] Among them, comparative compound 1 and compound 1 of the present application are parallel comparative examples, the difference lies in the position of the benzothienocarbazole ring. Compound 1 conforming to the general formula of the present application has a rich-electron carbazole nitrogen atom and a poor-electron thiophene sulfur atom directly adjacent, which produces a stronger intramolecular charge transfer effect, can more effectively stabilize the LUMO energy level, thereby reducing the energy barrier of electron injection, making the electron injection more smooth, reducing the driving voltage, and significantly improving the luminous efficiency.

[0074] Comparative compound 2 and compound 1 of the present application are parallel examples, the difference is the substitution position of triazine group and benzothienocarbazole group on the bridging group naphthalene ring. Since naphthalene ring is a large conjugated group, it is in the form of 2,3-position substitution according to the general formula of the present application, which can utilize the aromatic ring characteristics and ensure the strong spatial stereospecificity of the structure, thereby avoiding too close π-π stacking, which is beneficial to the luminous efficiency and device lifetime of the prepared device. Similarly, comparative compound 5 and compound 3 of the present application, comparative compound 6 and compound 3 of the present application, comparative compound 7 and compound 3 of the present application.

[0075] Comparative compound 3 and compound 1 of the present application are parallel examples, the difference is the bridging group of triazine group and benzothienocarbazole group. The use of 2,3-position naphthalene ring as the bridging group in the present application can provide a strong torsion effect compared to 1,3-position dibenzofuran as the bridging group, which reduces the quenching of excitons and improves the luminous efficiency.

[0076] Comparative compound 8 and compound 3 of the present application are parallel examples, and comparative compound 8 uses a biphenyl group as a bridging group. Due to the single bond between the biphenyl groups, the structure is prone to disordered torsion, which leads to low mobility, high driving voltage, unbalanced hole and electron injection, and unsatisfactory luminous efficiency and device lifetime. Similarly, comparative compound 12 and compound 2 of the present application, comparative compound 15 and compound 2 of the present application, comparative compound 18 and compound 2 of the present application.

[0077] Comparative compound 13 and compound 2 of the present application are parallel examples, and comparative compound 13 uses a triphenylene group as a bridging group. Due to the large planar structure of triphenylene, the intermolecular interaction is enhanced, the evaporation temperature is increased, which is not conducive to the long-life characteristics of the device. Similarly, comparative compound 14 and compound 2 of the present application, comparative compound 16 and compound 2 of the present application, and phenanthrene group also provides a larger conjugated plane than naphthalene ring, and the connection position in the comparative compound cannot guarantee the spatial stereospecificity of the structure.

[0078] Comparative compound 11 and compound 17 of the present application are parallel examples, and the difference between the two is the form of the parent nucleus. In comparative compound 11, the phenyl group is connected to N, which will reduce the thermal stability of the molecule due to the vibration of the phenyl group, which is not conducive to the preparation of long-life devices. Similarly, comparative compound 4 and compound 2 of the present application.

[0079] Comparative compound 9 and compound 16 of the present application are parallel examples, the difference is that there is no 2,3-naphthalene ring bridged triazine and benzothiophene carbazole in comparative compound 9. Compared with comparative compound 9, the compound according to the general formula of the present application can improve the stereoscopic nature of the molecule through the bridging group, avoid too strong interaction between molecules, uniform film formation, and improve the device life. Similarly, there are comparative compound 22 and compound 257 of the present application, comparative compound 23 and compound 364 of the present application, comparative compound 24 and compound 353 of the present application, comparative compound 25 and compound 367 of the present application, comparative compound 26 and compound 368 of the present application.

[0080] Comparative compound 10 and compound 16 of the present application are parallel examples, the difference is that phenyl is used as the bridging group in comparative compound 10. The triazine group and benzothiophene carbazole in the two compounds are all ortho-substituted on the bridging group, and the steric hindrance is similar. When the naphthalene bridge with larger conjugated plane is introduced in the compound of the present application, it is more conducive to the transmission of electrons between molecules, thereby reducing the driving voltage and improving the luminous efficiency. Similarly, there are comparative compound 20 and compound 280 of the present application.

[0081] The above description of disclosed embodiments enables one skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Accordingly, the present application is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phosphorescent host material, characterized by, The phosphorescent host material has a structure shown in the following formula 1: ； X is selected from O or S; R1 is selected from deuterium; R2, R3, R4 are each independently selected from deuterium, an unsubstituted or deuterium-substituted group of formula a-d, wherein the total number of unsubstituted or deuterium-substituted groups of formula a-d is 0, 1, 2, 3; ； m is taken from the values 0, 1, 2, 3, 4, 5, 6; n, q are each independently taken from the values 0, 1, 2, 3, 4; p is taken from the values 0, 1, 2; Ar, Ar1 are independently selected from the following groups which are unsubstituted or deuterium-substituted: ; indicates the attachment of the group to the ring carbon.

2. The phosphorescent host material according to claim 1, characterized in that, The phosphorescent host material is selected from any one of the following compounds shown in the following structural formula: 。 3. A method of producing the phosphorescent host material according to claim 1, characterized by, The method specifically comprises the following steps: After dissolving 1.0 eq of intermediate 1-a and 1.0-1.2 eq of reactant 1-b in xylene, 0.01-0.05 eq of a palladium catalyst, 0.02-0.15 eq of a phosphine ligand, and 2.0-2.4 eq of a base are added; after the addition, the reaction temperature is slowly increased to 100-110°C, and the mixture is stirred for 8-10 h; after the reaction is determined to be completed by thin layer chromatography, water and dichloromethane are added for extraction and separation, the organic phases are combined and concentrated, and a mixture of dichloromethane and petroleum ether is used for column chromatography to obtain formula 1; The specific synthesis route is as follows: ； wherein, Hal is selected from F, Cl, Br, I; R1, R2, R3, R4, n, m, p, q, X, Ar and Ar1 have the definitions given in claim 1.

4. The method for preparing the phosphorescent host material according to claim 3, characterized in that, The base is selected from potassium carbonate K2CO3, potassium phosphate K3PO4, sodium carbonate Na2CO3, cesium fluoride CsF, cesium carbonate Cs2CO3, or sodium tert-butoxide t-BuONa; The palladium catalyst is selected from tris(dibenzylideneacetone)dipalladium Pd2(dba)3, tetrakis(triphenylphosphine)palladium Pd(PPh3)4, palladium dichloride PdCl2, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium PdCl2(dppf), palladium acetate Pd(OAc)2, and bis(triphenylphosphine)palladium dichloride Pd(PPh3)2Cl2; The phosphine ligand is selected from tri-tert-butylphosphine P(t-Bu)3, 2-dicyclohexylphosphino-2,4,6-triisopropylbiphenyl X-phos, triethylphosphine PET3, trimethylphosphine PMe3, triphenylphosphine PPh3, potassium diphenylphosphinate KPPh2, and di-tert-butylchlorophosphine P(t-Bu)2Cl.

5. An organic electroluminescent device, characterized by The phosphorescent host material of claim 1 is included.

6. An organic electroluminescent device, characterized by The organic electroluminescent device comprises an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a light-emitting layer, and the light-emitting layer comprises a host material and a dopant material, and the host material comprises the phosphorescent host material of claim 1.

7. The organic electroluminescent device according to claim 6, characterized in that The organic layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting auxiliary layer, a hole blocking layer, an electron transport layer, or an electron injection layer.

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