An electron transport material and an organic electroluminescent device comprising the same

Abstract

This invention provides an electron transport material and an organic electroluminescent device comprising the same, wherein the electron transport material has the structure shown in Formula I. The electron transport material of this invention not only possesses high stability but also excellent electron transport performance, enabling the organic electroluminescent device to have higher luminous efficiency and a longer lifespan.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials, and relates to an electron transport material and an organic electroluminescent device containing the same. Background Technology

[0002] Electroluminescence (EL) is a physical phenomenon in which luminescent materials directly convert electrical energy into light energy under the influence of an electric field. Commonly used luminescent materials are mainly small organic molecules and organic polymers. One of the most important products in the field of electroluminescence is the organic light-emitting diode (OLED) and the flat panel displays built upon it. These products are characterized by low driving voltage, high luminous brightness and efficiency, fast response speed, wide operating temperature range, relatively simple molding and processing, and the ability to be mass-produced and manufactured over large areas. OLED displays can also be fabricated on flexible substrates to create flexible devices.

[0003] Over the past 20 years, the field of organic electroluminescence has made steady progress and achieved significant advancements. For example, adding buffer layers to the electrodes and organic layers of devices can reduce the interface injection barrier, lower the device operating voltage, and improve device efficiency and stability. The use of triplet-state luminescent materials fully utilizes triplet exciton luminescence, which is normally unable to emit light in organic materials, thus greatly improving the luminous efficiency of the devices. Of course, some issues still need to be addressed in the current OLED field, such as the need for further improvements in device lifetime and stability.

[0004] CN104072405A provides an electron transport material, the structural formula of which is shown below: In the formula, Ar represents the excellent solubility, film-forming properties, and thermal stability of the electron transport material, along with good electron transport performance. This invention also provides a method for preparing the electron transport material and an organic electroluminescent device containing the electron transport material. However, the lifetime and stability of the organic electroluminescent device of this invention still need further improvement.

[0005] Therefore, in this field, there is a desire to develop an electron transport material that can provide longer lifetime and better stability for organic electroluminescent devices. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an electron transport material and an organic electroluminescent device comprising the same. The present invention designs a polycyclic aromatic hydrocarbon compound that can be used as an electron transport material or matrix material, and the OLED device incorporating it exhibits good efficiency and long lifespan.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] On one hand, the present invention provides an electron transport material having the structure shown in Formula I:

[0009]

[0010] Among them, X 1 For O or S, X 2 X 3 X 4 Each is independently N or CR, where R is a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl.

[0011] Ar、Ar 2 Each is independently a substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or when X 2 X 3 or X 4 When it is CR, Ar or Ar 2 With X 2 X 3 or X 4 Any one of the R forms a ring, wherein the ring is a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl;

[0012] (R1) a (R2) b R1 and R2 are each independently hydrogen, halogen atom, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryloxy, substituted or unsubstituted silyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; a and b are each independently integers from 0 to 3. When a ≥ 2, two adjacent R1s can form a ring, and the ring is a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl. When b ≥ 2, two adjacent R2s can form a ring, and the ring is a substituted or unsubstituted aryl or a substituted or unsubstituted heteroaryl.

[0013] The electron transport material provided by this invention, when applied to organic electroluminescent devices, can achieve high luminous efficiency and long service life.

[0014] Preferably, the X 2 X 3 X 4 Each is independently N or CR, where R is a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C6-C30 aryl, or a substituted or unsubstituted C6-C30 heteroaryl.

[0015] Ar、Ar 2Each is independently a substituted or unsubstituted C1-C6 alkyl, a substituted or unsubstituted C2-C6 alkenyl, a substituted or unsubstituted C6-C30 aryl, a substituted or unsubstituted C6-C30 heteroaryl, or when X 2 X 3 or X 4 When it is CR, Ar or Ar 2 With X 2 X 3 or X 4 Any one of the R groups forms a ring, wherein the ring is a substituted or unsubstituted C6-C30 aryl group or a substituted or unsubstituted C6-C30 heteroaryl group.

[0016] (R1) a (R2) b R1 and R2 are each independently hydrogen, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C6-C30 aryl, or substituted or unsubstituted C6-C30 heteroaryl; a and b are each independently integers from 0 to 3. When a ≥ 2, two adjacent R1s can form a ring, and the ring is a substituted or unsubstituted C6-C30 aryl or a substituted or unsubstituted C6-C30 heteroaryl. When b ≥ 2, two adjacent R2s can form a ring, and the ring is a substituted or unsubstituted C6-C30 aryl or a substituted or unsubstituted C6-C30 heteroaryl.

[0017] In this invention, the substituted or unsubstituted C6-C30 aryl group can be a substituted or unsubstituted aryl group of C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24, C25, C26, C27, C28, C29, or C30. The substituted or unsubstituted C6-C30 heteroaryl group can be a substituted or unsubstituted heteroaryl group of C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24, C25, C26, C27, C28, C29, or C30. The substituted or unsubstituted C1-C6 alkyl groups can be substituted or unsubstituted C1, C2, C3, C4, C5, or C6 alkyl groups. The substituted or unsubstituted C2-C6 alkenyl groups can be substituted or unsubstituted C2, C3, C4, C5, or C6 alkenyl groups.

[0018] Preferably, the Ar, Ar 2 Each independently Any one of them, or Ar 2 With X 4 R in the middle forms a ring, and the ring is In this context, the dashed lines represent the connection sites of functional groups.

[0019] Preferably, the (R1) a (R2) b R1 and R2 are each independently hydrogen, substituted or unsubstituted C2-C6 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C6-C20 heteroaryl; a and b are each independently integers from 0 to 3 (e.g., 0, 1, 2, or 3). When a ≥ 2, two adjacent R1s can form a ring, wherein the ring is... When b≥2, two adjacent R2s can form a loop, and the loop is... In this context, the dashed lines represent the connection sites of functional groups.

[0020] Preferably, the electron transport material is selected from any one of compounds C-1 to C-9:

[0021]

[0022]

[0023] This invention does not limit the preparation method of the electron transport material as described above. Exemplarily, the following synthetic route can be used for preparation:

[0024]

[0025] Among them, X 1 X 2 X 3 X 4 Ar, Ar 2 (R1) a (R2) b The limitation is the same as that in the structure shown in Formula I as described in the first aspect above, where X is a chlorine atom, a bromine atom, or an iodine atom.

[0026] In a first aspect, the present invention provides an application of the electron transport material described in the first aspect in an organic electroluminescent device.

[0027] Thirdly, the present invention provides an organic electroluminescent device, the organic electroluminescent device comprising an anode, a cathode and an organic functional layer located between the anode and the cathode, wherein the electron transport layer in the organic functional layer contains an electron transport material as described in the first aspect.

[0028] Preferably, the organic functional layer further includes any one or at least two combinations of a light-emitting layer, an electron blocking layer, an electron injection layer, a hole injection layer, a hole blocking layer, or a hole transport layer.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects:

[0030] The electron transport material of this invention not only possesses high stability but also excellent electron transport performance, enabling organic electroluminescent devices to achieve higher luminous efficiency and longer lifespan. The electron transport material of this invention enables organic electroluminescent devices to achieve a current efficiency ≥10⁵ Cd / A and a lifespan LT95 ≥120 h. Detailed Implementation

[0031] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0032] The following synthesis examples exemplify a method for preparing a specific compound. Compounds for which no preparation method is provided can also be synthesized by similar methods, without being described in detail. Those skilled in the art can synthesize these compounds themselves using the general formula compound synthesis method provided by this invention and existing technology without any difficulty.

[0033] Example 1

[0034] In this embodiment, compound C-1 is synthesized, and the specific preparation method is as follows:

[0035] (1) Preparation of compound 1-1

[0036] Compound A (47.0 g, 200 mmol), 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborane-2-toluidine) (49.1 g, 224 mmol), tetrakis(triphenylphosphine)palladium (5.28 g, 4.6 mmol), and cesium carbonate (163 g, 500 mmol) were placed in a reaction vessel, followed by the addition of toluene (800 mL), EtOH (200 mL), and distilled water (200 mL). The mixture was stirred at 120 °C for 5 hours. After the reaction was complete, the mixture was washed with distilled water and extracted with ethyl acetate. The product was dried over magnesium sulfate, and the solvent was removed using a rotary generator. The product was purified by column chromatography to give compound 1-1 (30.2 g, 61% yield).

[0037] (2) Preparation of compound 1-2

[0038] Compound 1-1 (24.8 g, 100 mmol) and acetonitrile (800 mL) were placed in a reaction vessel, and p-toluenesulfonic acid monohydrate (45.6 g, 240 mmol) was added at 0 °C. After 10 minutes, sodium nitrite (10.66 g, 154.4 mmol) and potassium iodide (32 g, 193.0 mmol) were dissolved in distilled water (600 mL) and then slowly added dropwise to the mixture. After the dropwise addition was complete, the mixture was slowly heated to room temperature and then stirred for another 5 hours. After the reaction was complete, an aqueous solution of sodium thiosulfate was added to stop the reaction. The mixture was then dried over magnesium sulfate, and the solvent was removed using a rotary generator. The product was purified by column chromatography to give compound 1-2 (27.2 g, 75.8% yield).

[0039] (3) Preparation of compounds 1-3

[0040] Compounds 1-2 (25.1 g, 70 mmol), B (21.8 g, 218 mmol), tetrakis(triphenylphosphine)palladium (3.0 g, 2.6 mmol), and cesium carbonate (13.7 g, 130 mmol) were placed in a reaction vessel, followed by the addition of toluene (400 mL), EtOH (100 mL), and distilled water (100 mL). The mixture was stirred at 120 °C for 6 hours. After the reaction was complete, the mixture was washed with distilled water and extracted with ethyl acetate. The product was dried over magnesium sulfate, and the solvent was removed using a rotary generator. The product was purified by column chromatography to give compound 1-3 (25.7 g, 75% yield).

[0041] (4) Preparation of compounds 1-4

[0042] Compounds 1-3 (24.5 g, 50 mmol), palladium(II) acetate (5.62 g, 25 mmol), tri-tert-butylphosphine (20.2 g, 50 mmol), and cesium carbonate (65.1 g, 200 mmol) were placed in a reaction vessel, followed by the addition of o-xylene (350 mL). The mixture was refluxed and stirred for 5 hours. After the reaction was complete, the mixture was washed with distilled water and extracted with ethyl acetate. The product was dried over magnesium sulfate, and the solvent was removed using a rotary generator. The product was purified by column chromatography to give compounds 1-4 (14.4 g, 63% yield).

[0043] (5) Preparation of compounds 1-5

[0044] Compounds 1-4 (22.9 g, 50 mmol) and triphenylphosphine (39.3 g, 150 mmol) were placed in a reaction vessel, followed by the addition of 1,2-dichlorobenzene (250 mL). The mixture was stirred at 200 °C for 5 hours. After the reaction was complete, the mixture was washed with distilled water and extracted with ethyl acetate. The product was dried over magnesium sulfate, and the solvent was removed using a rotary generator. The product was purified by column chromatography to give compounds 1-5 (11.5 g, 54% yield).

[0045] (6) Preparation of compound C-1

[0046] Compounds 1-5 (21.3 g, 50 mmol), 1-chloro-3,5-diphenyltriazine (16 g, 60 mmol), dimethylaminopyridine (DMAP) (3.1 g, 25 mmol), potassium carbonate (6.9 g, 50 mmol), and dimethylamide (250 mL) were placed in a reaction vessel and stirred at 150 °C for 5 hours. The reaction mixture was then cooled to between 5 and 10 °C. MeOH (250 mL) and distilled water (240 mL) were then added, and the mixture was stirred for 30 minutes. The mixture was filtered to obtain compound C-1 (26.3 g, 80% yield).

[0047] The synthesis route is as follows:

[0048]

[0049] Characterization data of compound C-1: 1 H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7.54(1H), 7.33(1H), 7.94(1H). 7.57(1H), 7.37(1H), 7.58(1H), 8.36(4H), 7.50(6H).

[0050] Example 2

[0051] In this embodiment, compound C-2 was synthesized, and the specific preparation method was the same as that of the general formula compound synthesis method and the synthesis method of Example 1.

[0052] Characterization data of compound C-2: 1H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7.54(1H), 7.33(1H), 7.94(1H). 7.57(1H), 7.37(1H), 7.58(1H), 8.36(2H), 7.50(3H), 8.18(1H), 7.68(1H). 7.74(1H), 7.9(1H), 7.38(1H), 7.28(1H), 7.55(1H), 1.69(6H).

[0053] Example 3

[0054] In this embodiment, compound C-3 was synthesized using the same method as the general formula compound synthesis method and the synthesis method in Example 1.

[0055] Characterization data of compound C-3: 1 H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7.54(1H), 7.33(1H), 7.94(1H). 7.57(1H), 7.37(1H), 7.58(1H), 7.96(2H), 7.25(2H), 7.75(2H), 7.49(2H), 7.41 (1H), 8.49(1H), 9.09(1H), 8.08(1H), 8.00(1H), 7.59(1H), 7.61(1H), 8.16(1H).

[0056] Example 4

[0057] In this embodiment, compound C-4 was synthesized, and the specific preparation method was the same as that of the general formula compound synthesis method and the synthesis method of Example 1.

[0058] Characterization data of compound C-4: 1 H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7.54(1 H), 7.33(1H), 7.94(1H), 7,33(1H), 8.24(1H), 7.57(1H), 7.38(1H), 7.74(1H), 8.36(4H), 7.50(6H), 1.69(6H).

[0059] Example 5

[0060] In this embodiment, compound C-5 was synthesized, and the specific preparation method was the same as that of the general formula compound synthesis method and the synthesis method of Example 1.

[0061] Characterization data of compound C-5: 1 H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7. 54(1H), 7.33(1H), 7.94(1H), 7.00(1H), 8.11(1H), 7.69(1H), 7.72(1H), 8.51(1H), 8.36(4H), 7.50(6H).

[0062] Example 6

[0063] In this embodiment, compound C-6 was synthesized, and the specific preparation method was the same as that of the general formula compound synthesis method and the synthesis method of Example 1.

[0064] Characterization data of compound C-6: 1 H NMR DMSO, 7.54(1H), 7.39(1H), 7.31(1H), 7.89(1H), 7.42(1H), 7.49(1H), 8.19(1H), 7.29(1H), 7.72(1H), 7. 00(1H), 8.11(1H), 7.69(1H), 7.72(1H), 8.51(1H), 7.57(1H), 7.37(1H), 7.58(1H), 8.36(4H), 7.50(6H).

[0065] Comparative Example 1

[0066] This comparative example provides a compound as shown below.

[0067]

[0068] Application Examples 1-6 and Comparative Application Example 1

[0069] An OLED device is provided, comprising, from bottom to top, an anode, a hole injection layer, a hole transport layer, an emissive layer, a hole blocking layer, an electron transport layer, an electron injection layer, and a cathode; the electron transport layer comprises a host material and a guest material, wherein the host material is a compound prepared in Examples 1-6 or a compound provided in Comparative Example 1.

[0070] The constituent materials of each layer are as follows:

[0071] Anode: ITO (Indium Tin Oxide), 80nm thick;

[0072] Hole injection layer: host material NPB, guest material F4-TCNQ, the molar percentage of the guest material is 2%; the thickness of the hole injection layer is 50nm;

[0073] Hole transport layer: NPB, with a thickness of 40nm;

[0074] Emitting layer: host material TCTA, guest material Ir(ppy)3, the molar percentage of the guest material is 5%; thickness is 30nm;

[0075] Hole blocking layer: NPB, 20nm thick;

[0076] Electron transport layer: 35 nm thick; host and guest materials and their molar percentages are shown in Table 1;

[0077] Electron injection layer: LiQ, 1 nm thick;

[0078] Cathode: Mg / Ag, thickness 200nm.

[0079] Table 1

[0080] Serial Number Subject and object materials of the electron transport layer Application Example 1 Compound C-1 (50%): LiQ (50%) Application Example 2 Compound C-2 (50%): LiQ (50%) Application Example 3 Compound C-3 (50%): LiQ (50%) Application Example 4 Compound C-4 (50%): LiQ (50%) Application Example 5 Compound C-5 (50%): LiQ (50%) Application Example 6 Compound C-6 (50%): LiQ (50%) Comparative Application Example 1 Compound of Comparative Example 1 (50%): LiQ (50%)

[0081] The preparation method includes the following steps:

[0082] Step S1: An anode with a thickness of 80 nm is formed on the substrate using ITO material.

[0083] Step S2: A hole injection layer with a thickness of 50 nm is formed on the anode by vacuum evaporation. The host material for the hole injection layer is NPB, the guest material is F4-TCNQ, and the molar percentage of the guest material is 2%.

[0084] Step S3: A hole transport layer NPB with a thickness of 40 nm is formed on the hole injection layer by vacuum evaporation.

[0085] Step S4: A light-emitting functional layer with a thickness of 30 nm is formed on the hole transport layer by vacuum evaporation. The host material is TCTA and the guest material is Ir(ppy)3. The molar ratio of the host material to the guest material is 95:5.

[0086] Step S5: A hole blocking layer with a thickness of 20 nm is formed on the light-emitting layer by vacuum evaporation. The material used for evaporating the hole blocking layer is NPB.

[0087] Step S6: An electron transport layer with a thickness of 35 nm is formed on the hole blocking layer by vacuum evaporation. The materials used for the electron transport layer are shown in Table 1.

[0088] Step S6: An electron injection layer with a thickness of 1 nm is formed on the electron transport layer by vacuum evaporation. The material used for evaporating the electron injection layer is LiQ.

[0089] Step S8: A cathode with a thickness of 200 nm is formed on the electron injection layer by vacuum evaporation. The cathode is deposited using Mg / Ag material.

[0090] In the above application examples and comparative application examples, the structural formulas corresponding to the abbreviations of the materials are as follows:

[0091]

[0092] Device performance testing:

[0093] The OLED devices provided in the application examples and comparative application examples were tested for luminous efficiency. The test items included efficiency, driving voltage and lifetime (LT95, the time for brightness to decay to 95%).

[0094] Among them, the current density was measured to be 10 mA / cm². 2 The component lifespan during illumination was determined by the voltage and current efficiency (cd / A). The component lifespan was measured with an initial brightness of 1000 cd / m². 2 The brightness decay time during continuous illumination during driving was measured in cd / m². 2 The time required to reduce to 95% should be noted. It should be noted that the voltage (V), current efficiency (Cd / A), and lifetime values ​​of the application example are expressed as relative values ​​when the component is compared to Application Example 1 with 100.

[0095] The performance test results are shown in Table 2:

[0096] Table 2

[0097] Voltage (V) LE(Cd / A) Color coordinates Lifespan (h) Application Example 1 98 115 0.2959，0.3124 137 Application Example 2 97 107 0.2978，0.3078 130 Application Example 3 96 105 0.2989，0.3111 140 Application Example 4 98 113 0.3017，0.3084 150 Application Example 5 97 108 0.2989，0.3112 143 Application Example 6 98 112 0.2992，0.3164 120 Comparative Application Example 1 100 100 0.2964，0.3120 100

[0098] As shown in Table 2, the material of this invention is suitable for use as an electron transport material in OLED devices and exhibits excellent electron transport performance. Compared with the materials in the comparative examples, the material of this invention has higher efficiency (105-115 Cd / A), lower voltage (96-98 V), and longer lifetime (120-150 h).

[0099] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the electronic transport material and the organic electroluminescent device comprising the same, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An electron transport material, characterized in that, The electron transport material is selected from any one of compounds C-1 to C-6: 。 2. The application of the electron transport material according to claim 1 in organic electroluminescent devices.

3. An organic electroluminescent device, characterized in that, The organic electroluminescent device includes an anode, a cathode, and an organic functional layer located between the anode and the cathode, wherein the electron transport layer in the organic functional layer contains the electron transport material as described in claim 1.

4. The organic electroluminescent device according to claim 3, characterized in that, The organic functional layer further includes any one or at least two combinations of a light-emitting layer, an electron blocking layer, an electron injection layer, a hole injection layer, a hole blocking layer, or a hole transport layer.

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