Light extraction material and organic electroluminescent device thereof

Abstract

The invention provides a light extraction material and an organic electroluminescent device thereof, the structure of the light extraction material is formed by adjusting the molecular stacking density of a central fluorene or fluorene-like structure with certain rigidity, it is ensured that the compound provided by the invention has a high evaporation temperature, is affected by the flexibility of a high-carbon-number alkyl chain, and has an extended molecular space system, and in addition, the light extraction material has a good application prospect. Substituent groups such as CF3 and F are introduced to the outer side of the compound to further weaken the intermolecular interaction, the design of the symmetric structure enables the compound to have the property of low polarity and also plays a certain role in reducing the refractive index of the compound, and on the whole, the compound with the structure of the chemical formula 1 meets the requirement for the low refractive index of the material, and the preparation method is simple. And improvement of the performance of the organic light-emitting device is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of organic electroluminescent materials, and in particular relates to a light extraction material and an organic electroluminescent device thereof. Background Art

[0002] In order to improve the light extraction efficiency of top-emitting devices and avoid brightness and light color deviation at different angles, a layer of high-refractive-index organic small molecule material is usually evaporated on the outside of the cathode of the top-emitting device as a light extraction layer (CPL). The refractive index of organic small molecule materials is generally between 1.7 and 1.9. After years of research and development, many high-refractive-index organic small molecule materials have been obtained. Although the refractive index of some high-refractive organic small molecule materials has reached 2.1-2.3, the subsequent development of new materials has almost reached the ceiling, and it is difficult to increase the refractive index.

[0003] In order to further improve the light extraction efficiency of the top-emitting device, a double-layer covering structure of a high-refractive index CPL material layer and a low-refractive index CPL material layer (the refractive index is generally required to be around 1.5) can repeatedly reflect the light emitted by the device at the interface between the high-refractive index CPL material layer and the low-refractive index CPL material layer and between the high-refractive index CPL material layer and the packaging structure interface, thereby recovering the light that would be lost due to reflection on the surface facing away from the organic electroluminescent device (OLED), thereby achieving higher light extraction efficiency.

[0004] Existing low-refractive index CPL materials have many problems such as high evaporation temperature, severe decomposition after long-term evaporation, high refractive index, limited improvement in light output efficiency, and no obvious improvement in color deviation. Therefore, in order to obtain high-efficiency and long-life OLED devices, the development of low-refractive index CPL materials with excellent performance and combining them with high-refractive index CPL materials as a double cover layer is the key direction of CPL research and development. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the first object of the present invention is to provide a light extraction material, and the technical solution is as follows:

[0006] A light extraction material has a structure as shown in Chemical Formula 1:

[0007]

[0008] In chemical formula 1, Indicates that this position is a single bond connection or no connection relationship, and R1 is independently selected from C1-C 18 alkyl or F or CF3 or TMS; X is independently selected from N or substituted or unsubstituted C, and at least one of all X on the left and right sides is substituted C, and the substituents independently have the structure of Chemical Formula 1-1:

[0009] In Chemical Formula 1-1, L is independently selected from a single bond or a derived fluorenyl group or a phthalimide group or a derived phthalimide group, a substituted or unsubstituted C3-C 18 The arylene or heteroarylene group, the heteroatom is selected from N, and the substituents are independently F or CF3 or TMS;

[0010] The structure of the derived fluorenyl group is

[0011] The structure of the derived phthalimide group is:

[0012] R2 is independently selected from H, F, CF3 or TMS, and at least one F, CF3 or TMS is present in all R2 of Chemical Formula 1-1.

[0013] As a preference of the present invention, each of the Xs is independently selected from substituted or unsubstituted C.

[0014] As a preferred embodiment of the present invention, the L is independently selected from a single bond or a phthalimide group or a derived phthalimide group, a substituted or unsubstituted C6-C 12 arylene group.

[0015] As a preferred embodiment of the present invention, the chemical formula 1 is a symmetrical structure.

[0016] As a preferred embodiment of the present invention, R1 is independently selected from C1-C 18 As the preferred embodiment of the present invention, the chemical formula 1 is selected from the following compounds:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029] Another object of the present invention is to provide an organic electroluminescent device, comprising a cathode and an anode arranged opposite to each other, and an organic layer arranged between the cathode and the anode, and also comprising a light extraction layer arranged on the cathode, wherein the light extraction layer is prepared by the above-mentioned light extraction material.

[0030] As a preferred embodiment of the present invention, the organic electroluminescent device is used in a display device, and the display device is a mobile phone display screen, a computer display screen, a television display screen, a smart watch display screen, a smart car display panel, a VR or AR helmet display screen, and a display screen of various smart devices.

[0031] The beneficial effects of the present invention are as follows:

[0032] The light extraction material provided by the present invention has a structure formed by adjusting the molecular packing density of a central fluorene or fluorene-like structure with a certain rigidity, thereby ensuring that the compound provided by the present invention has a high evaporation temperature. At the same time, affected by the flexibility of the high-carbon alkyl chain, the molecular space system is extended. In addition, the introduction of electron-withdrawing CF3, F and other substituents on the outside of the compound further weakens the intermolecular interaction. The design of the symmetrical structure makes the compound have a low polarity property, which also plays a certain role in reducing the refractive index of the compound. On the whole, the compound having the structure of Chemical Formula 1 of the present invention realizes the low refractive index requirement of the material. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0034] If the specific conditions are not specified in the embodiments, they are carried out under conventional conditions or 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 directly purchased are prepared by simple reactions of commercially available raw materials. The percentages all refer to mass percentages, and the temperatures are degrees Celsius (℃). Such method principles, operating procedures, conventional post-treatments, silica gel columns, recrystallization purification and other means are well known to synthesizers in the art, and the synthesis process can be fully realized to obtain the target product. The reactions in each preparation embodiment are generally carried out under positive pressure of nitrogen or argon.

[0035] Preparation Example

[0036] Example 1: Preparation of Compound 1

[0037]

[0038] Under nitrogen protection, compound 1-1 (10mmol, 5.18g), compound 1-2 (22mmol, 7.48g), tetrakis(triphenylphosphine)palladium (0.4mmol, 0.46g) and potassium carbonate (60mmol, 8.29g) were added to a mixed solvent of toluene, ethanol and water (200ml:50ml:50ml) and heated to 85°C. The mixture was reacted for 10h, cooled to room temperature, and water was added. After the solid was precipitated, it was filtered, the filter cake was dried, purified by column chromatography, and the solvent was removed by a rotary evaporator. The obtained solid was dried to obtain compound 1 (6.92g, yield: 85%, MS: 814.47).

[0039] Example 2: Preparation of Compound 21

[0040]

[0041] The preparation method is the same as that of compound 1, except that compound 2-1 is used to replace compound 1-1, to obtain compound 21 (MS: 928.37).

[0042] Example 3: Preparation of Compound 39

[0043]

[0044] The preparation method is the same as that of compound 1, except that compound 1-1 is replaced by compound 39-1, and compound 1-2 is replaced by compound 39-2, to obtain compound 39 (MS: 594.43).

[0045] Example 4: Preparation of Compound 49

[0046]

[0047] The preparation method is the same as that of compound 1, except that compound 39-1 is used to replace compound 1-1, and compound 49-1 is used to replace compound 1-2, to obtain compound 49 (MS: 1142.44).

[0048] Example 5: Preparation of Compound 85

[0049]

[0050] The preparation method is the same as that of compound 1, except that compound 39-1 is used to replace compound 1-1, and compound 85-1 is used to replace compound 1-2, to obtain compound 85 (MS: 946.46).

[0051] Example 6: Preparation of Compound 98

[0052]

[0053] The preparation method is the same as that of compound 1, except that compound 1-1 is replaced by compound 98-1, and compound 1-2 is replaced by compound 98-2, to obtain compound 98 (MS: 632.56).

[0054] Example 7: Preparation of Compound 114

[0055]

[0056] The preparation method is the same as that of compound 1, except that compound 39-1 is used to replace compound 1-1, and compound 114-1 is used to replace compound 1-2, to obtain compound 114 (MS: 782.48).

[0057] Example 8: Preparation of Compound 120

[0058]

[0059] The preparation method is the same as that of compound 1, except that compound 120-1 is used to replace compound 1-1, and compound 98-2 is used to replace compound 1-2, to obtain compound 120 (MS: 686.63).

[0060] Example 9: Preparation of Compound 130

[0061]

[0062]

[0063] Compound 130-3 (10mmol, 7.62g), compound 130-4 (22mmol, 5.04g), isoquinoline (22mmol, 2.84g) and 4-(dimethylamino)pyridine (NMAP) (0.02mmol, 0.002g) were added to 150mL N-methyl-2-pyrrolidone (NMP), and the mixture was heated to 70°C for 2 hours under nitrogen protection, and then heated to 205°C for reflux reaction for 12 hours. The sample point plate was taken, and after the reaction of compound 130-3 was complete, it was naturally cooled to room temperature, and 200mL of pure water was added to the mixed solution. Solids precipitated, and the mixed solution was filtered to take the filter cake, and the filter cake was placed in a vacuum drying oven for drying, and the crude product was passed through a silica gel column to obtain compound 130 (10.20g, yield: 85%, MS: 1200.19);

[0064] The preparation method of compound 130-3 is the same as that of compound 1, except that compound 130-1 replaces compound 1-2, and compound 130-2 replaces compound 1-1.

[0065] Example 10: Preparation of Compound 144

[0066]

[0067] The preparation method is the same as that of compound 1, except that compound 144-1 is used to replace compound 1-1, and compound 144-2 is used to replace compound 1-2, to obtain compound 144 (MS: 846.49).

[0068] Example 11: Preparation of Compound 171

[0069]

[0070] The preparation method is the same as that of compound 1, except that compound 171-1 is used to replace compound 1-1, and compound 171-2 is used to replace compound 1-2, to obtain compound 171 (MS: 1046.14).

[0071] Example 12: Preparation of Compound 194

[0072]

[0073] The preparation method is the same as that of compound 1, except that compound 194-1 is used to replace compound 1-1, and compound 194-2 is used to replace compound 1-2, to obtain compound 194 (MS: 1082.15).

[0074] Example 13: Preparation of Compound 202

[0075]

[0076] The preparation method is the same as that of compound 1, except that compound 144-1 is used to replace compound 1-1, and compound 202-2 is used to replace compound 1-2, to obtain compound 202 (MS: 1422.59).

[0077] Example 14: Preparation of Compound 215

[0078]

[0079] The preparation method is the same as that of compound 1, except that compound 1-1 is replaced by compound 215-1, and compound 1-2 is replaced by compound 215-2, to obtain compound 215 (MS: 878.42).

[0080] 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.

[0081] Evaluation of optical properties of compounds:

[0082] The monolayer films used for the evaluation of optical properties were prepared by mixing the specific compounds 1, 2, 3, 4, 5, 6, 7, 21, 39, 44, 45, 46, 49, 50, 57, 60, 61, 63, 65, 68, 70, 72, 73, 75, 78, 80, 82, 85, 92, 96, 98, 102, 105, 114, 116, 120, 129, 130, 135, 144, 148, 155, 159, 167, 17 1, 177, 181, 188, 194, 202, 205, 210, 215 and compounds Ref-1 and Ref-2 were respectively used to make vapor-deposited films with a thickness of 80 nm on silicon substrates, and the refractive index n and extinction coefficient k at wavelengths of 460 nm, 530 nm and 620 nm were measured. The measured data are shown in Table 1. The structural formulas of the compounds Ref-1 and Ref-2 are shown below (Ref-1 and Ref-2 are known low refractive index materials).

[0083]

[0084] Table 1

[0085]

[0086]

[0087] Device performance evaluation:

[0088] Several application examples of the low refractive index compound of the present invention in OLED devices are listed below to further illustrate the beneficial effects of the compound of the present invention. The materials used in the examples are purchased from commercial sources or synthesized by the user.

[0089] Preparation of OLED devices: Use an ultrasonic cleaner to wash the top emission substrate with isopropanol, acetone, and distilled water for 15 minutes each, and then perform UV ozone cleaning in the air for 30 minutes. The treated substrate is vacuum-deposited with hole injection (HT:HI, 10nm, 2%), hole transport layer (HT, 100nm), luminescent auxiliary layer (B-prime, 5nm), blue luminescent layer (main material: doping material = compound BH: compound BD (weight ratio 97:3, 30nm), hole blocking layer (HB, 5nm), electron transport layer (compound ET:Liq = 1:1, 30nm), electron injection layer (Yb, 1nm), and then stacked and evaporated in sequence. , co-evaporate Mg and Ag (weight ratio 1:9, 20nm) to make a semi-transparent cathode, then evaporate CPL-L (20nm) as a low-refractive cover layer, and evaporate CPL-H (50nm) as a high-refractive cover layer, the two form a double-covering structure. Then use the glue coating equipment to coat the cleaned cover with UV glue, then move the coated cover to the pressing section, place the evaporated substrate on the upper end of the cover, and finally bond the substrate and cover under the action of the bonding equipment to complete the light curing of the UV glue.

[0090] Structure of OLED device: ITO:Ag:ITO / HT:HI(2%,10nm) / HT(100nm) / B-prime(5nm) / BH:BD(97:3,30nm) / HB(5nm) / ET:Liq(50:50) / Yb(1nm) / Mg:Ag(1:9,20nm) / CP LL(20nm) / CPL-H(50nm).

[0091] The CPL-L in the device examples respectively adopts the compounds listed in Table 2 below, and the CPL-L in the device comparative examples respectively adopts Ref-1 and Ref-2.

[0092] It should be noted that the high-refractive covering layer material used in this embodiment is only exemplary and is not a special limitation of the present invention. The high-refractive covering layer material can be selected from known or unknown materials, and the high-refractive covering layer material CPL-H of the present invention can be conventionally replaced. The molecular structure formula of the relevant material is as follows (particularly preferably selected from the following structure, but it does not mean that the present invention is limited to the following structure):

[0093]

[0094] The driving voltage, BI value, luminous efficiency and life (current density of 50 mA / cm2) of the organic electroluminescent devices obtained from the above device embodiments and device comparative examples at a brightness of 1000 (nits) are shown in FIG. 2 The test results are shown in Table 2 below.

[0095] Table 2

[0096]

[0097]

[0098] In blue top-emitting devices, the luminous efficiency is greatly affected by chromaticity. Therefore, the influence of chromaticity on efficiency is taken into account, and the ratio of luminous efficiency to CIEy is defined as the BI value, that is, BI = (cd / A) / CIEy.

[0099] It can be seen from Table 2 that the device performance of device embodiments 1 to 53 is better than that of device comparison examples 1 to 2, indicating that the combination of high refractive index CPL-H and low refractive index CPL-L has a microcavity effect, which plays a focusing role, further reduces light loss, and is beneficial to improving device performance.

Claims

1. A light extraction material, characterized in that: It has a structure as shown in Chemical Formula 1: In chemical formula 1, Indicates that this position is a single bond connection or no connection relationship, and R1 is independently selected from C1-C 18 alkyl or F or CF3 or TMS; X is independently selected from N or substituted or unsubstituted C, and at least one of all X on the left and right sides is substituted C, and the substituents independently have the structure of Chemical Formula 1-1: In Chemical Formula 1-1, L is independently selected from a single bond or a derived fluorenyl group or a phthalimide group or a derived phthalimide group, a substituted or unsubstituted C3-C 18 The arylene or heteroarylene group, the heteroatom is selected from N, and the substituents are independently F or CF3 or TMS; The structure of the derived fluorenyl group is The structure of the derived phthalimide group is: R2 is independently selected from H, F, CF3 or TMS, and at least one F, CF3 or TMS is present in all R2 of Chemical Formula 1-1.

2. The light extraction material according to claim 1, characterized in that The X is independently selected from substituted or unsubstituted C.

3. The light extraction material according to claim 1, wherein The L is independently selected from a single bond or a phthalimide group or a derived phthalimide group, a substituted or unsubstituted C6-C 12 arylene group.

4. The light extraction material according to claim 1, wherein The chemical formula 1 is a symmetrical structure.

5. The light extraction material according to claim 1, wherein R1 is independently selected from C1-C 18 of alkyl.

6. The light extraction material according to claim 1, wherein The chemical formula 1 is selected from the following compounds:

7. An organic electroluminescent device, comprising a cathode and an anode arranged opposite to each other, and an organic layer arranged between the cathode and the anode, characterized in that: It also includes a light extraction layer disposed on the cathode, wherein the light extraction layer is prepared by the light extraction material described in any one of claims 1-6.

8. The organic electroluminescent device according to claim 7, characterized in that: The organic electroluminescent device is used in a display device, and the display device is a mobile phone display screen, a computer display screen, a television display screen, a smart watch display screen, a smart car display panel, a VR or AR helmet display screen, and a display screen of various smart devices.

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