Compound for covering layer, OLED (Organic Light Emitting Diode) with compound and organic light emitting device

Abstract

The invention relates to the technical field of preparation of organic photoelectric materials, in particular to a compound for a covering layer, an OLED with the compound and an organic light-emitting device with the compound. The compound for the covering layer contains a benzo five-membered nitrogen-containing heterocyclic ring, and fused aryl and fused heteroaryl are matched as core substituent groups, so that the compound for the covering layer can be used as the covering layer to improve the light extraction efficiency of a device and improve the dependence on angles, and the compound for the covering layer can be used as a material of the covering layer to manufacture an organic EL element. The light-emitting efficiency of the organic light-emitting device can be effectively improved, and the application prospect is very good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic photoelectric material preparation, in particular to a compound for a cover layer, an OLED and an organic light-emitting device having the compound. BACKGROUND

[0002] An organic electroluminescent diode (OLED) is also known as an organic electroluminescent device. It is a technology that can convert electrical energy into light energy through organic light-emitting materials by applying a voltage to an organic electroluminescent element to inject holes from an anode and electrons from a cathode into a light-emitting layer, and then recombine the injected holes and electrons to form excitons to cause light emission.

[0003] In recent years, the industry has adopted a top-emitting structure light-emitting element in which a high work function metal is used for the anode and light is emitted from the top. The pixel circuit is not blocked, and the light-emitting area can be enlarged. Due to the deviation between the total refractive index of the constituent elements and materials of the organic light-emitting device (such as glass substrate, organic material and electrode material) and the optimal refractive index depending on the emission wavelength of the organic light-emitting device, part of the light is totally reflected when the emitted light is emitted at a certain angle from the organic layer to the cathode, and only part of the light is utilized. In order to improve the light extraction efficiency and improve the color deviation, a light-emitting element with a high refractive index "cover layer" is usually provided outside the low refractive index semi-transparent electrode to improve the performance of the OLED device. However, the current cover layer material has problems such as too high evaporation temperature, low light extraction efficiency, and not obvious improvement of device light-emitting efficiency; resulting in high requirements for the preparation process, large differences in the quality of the obtained device products, and low yield.

[0004] Therefore, it is necessary to develop a cover layer material that can be evaporated and has good evaporation stability and can maintain excellent film quality, and to find a suitable OLED optoelectronic functional material for the OLED device to solve the above problems. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a compound for a cover layer, an OLED and a display or lighting device having the compound. The provided compound for a cover layer is combined with a benzopentanitrogen-containing heterocyclic ring and a fused aromatic system, so that the compound for a cover layer can maintain high stability in the evaporation process, and at the same time the device can have high efficiency.

[0006] The compound for a cover layer provided by the present application is realized by the following technical scheme:

[0007] A compound for a cover layer, the compound for a cover layer has the following formula (I) structure:

[0008]

[0009] In formula (I), X1represents an O or S atom; L1-L3are each independently selected from a single bond, a C6-C30arylene group, a C5-C36heteroarylene group; Ar1, Ar2are each independently selected from a cyano group, a cyano-substituted or unsubstituted C6-C30aryl group, a C5-C36heteroaryl group; and at least one of L2, L3, Ar1, Ar2has a structure of formula 2:

[0010] In formula 2, X2is selected from an O or S atom, X3-X6are each independently selected from a CR or N atom, R is independently selected from a hydrogen, a cyano group, a C1-C20alkyl group, a C3-C20cycloalkyl group, a C6-C30aryl group, a C5-C36heteroaryl group, and when any two adjacent ones of X3-X6are both selected from a CR, the adjacent R can be fused to form a ring C;

[0011] Ring B is independently selected from nothing or a C6-C30aryl group, a C5-C36heteroaryl group fused to the adjacent aryl ring; and the structure of formula 2 is not a dibenzofuranyl group or a dibenzothiophenyl group.

[0012] Preferably, in formula (I), L1is selected from a single bond or a phenyl group.

[0013] Preferably, in formula (I), L2, L3are each independently selected from a single bond, a phenyl group, or a structure; Ar1, Ar2are each independently selected from a cyano group, a cyano-substituted or unsubstituted phenyl group, a pyridyl group, or a structure.

[0014] Preferably, in formula 2, when X3-X6are all selected from a CR, the structure of formula 2 can be represented by any one of the following formula 2-1 to formula 2-2: Ring B is independently selected from nothing or a C6-C30aryl group, a C5-C36heteroaryl group fused to the adjacent aryl ring; and the structure of formula 2 is not a dibenzofuranyl group or a dibenzothiophenyl group.

[0015] When any one of X3-X6is selected from a N atom, and the rest are CR, the structure of formula 2 can be represented by any one of the following formula 2-3 to formula 2-4: wherein R can be independently selected from a hydrogen, a cyano group, a C1-C20alkyl group, a C3-C20cycloalkyl group, a C6-C30aryl group, a C5-C36heteroaryl group; when any two adjacent ones of X3-X6are both selected from a CR, the adjacent R can be fused to form a ring C, which is independently selected from a phenyl group, a naphthyl group, a pyridyl group, a quinolyl group fused to the adjacent aryl ring; Ring B is independently selected from nothing or a phenyl group, a naphthyl group, a pyridyl group, a quinolyl group fused to the adjacent aryl ring.

[0016] More preferably, in the formula 2-1, formula 2-2, each of the ring B is independently selected from naphthyl, pyridyl, quinolyl; in the formula 2-3, formula 2-4, each of the ring B is independently selected from phenyl, naphthyl, and when the ring C exists, the ring C is independently selected from phenyl, naphthyl.

[0017] According to one or more embodiments, the present application provides a compound for a cover layer, selected from any one of the following chemical structures:

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027] Preferably, the compound satisfies the following conditions: the refractive index n value at 460nm-620nm wavelength is between 1.80-2.30, and the extinction coefficient k value is between 0.005-0.030.

[0028] The present application also provides an application of the compound for a cover layer as described above in an organic electroluminescent device.

[0029] The present application also provides an organic electroluminescent device, comprising:

[0030] a substrate layer;

[0031] a first electrode, above the substrate;

[0032] an organic light-emitting functional layer, above the first electrode;

[0033] a second electrode, above the organic light-emitting functional layer;

[0034] a cover layer, above the second electrode; the cover layer comprises a compound for a cover layer as described above.

[0035] The present application also provides a composition comprising the compound for a cover layer as shown in formula (I).

[0036] The present application also provides a preparation comprising the compound for a cover layer as shown in formula (I) or the composition as described above and at least one solvent. The solvent is not particularly limited, and the unsaturated hydrocarbon solvents known to those skilled in the art such as toluene, xylene, mesitylene, tetralin, decalin, dicyclohexane, n-butylbenzene, sec-butylbenzene, tert-butylbenzene, halogenated saturated hydrocarbon solvents such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, chlorobutane, bromobutane, chloropentane, bromopentane, chlorohexane, bromohexane, chlorocyclohexane, bromocyclohexane, halogenated unsaturated hydrocarbon solvents such as chlorobenzene, dichlorobenzene, trichlorobenzene, ether solvents such as tetrahydrofuran, tetrahydropyran, ester solvents such as benzoic acid alkyl ester, and the like can be used.

[0037] The organic electroluminescent device of the present application can be used in an OLED lighting or display device.

[0038] The present application also provides a display or lighting device comprising one or more of the organic electroluminescent devices as described above.

[0039] In summary, compared with the prior art, the present application has the following beneficial effects:

[0040] The compound for a cover layer of the present application, by limiting the benzopentazole ring containing nitrogen to be a fused aromatic group or a fused heteroaromatic group as a core substituent group, has excellent light-emitting efficiency and good evaporation stability. Meanwhile, the compound for a cover layer provided by the present application is used in a device, which facilitates the smooth progress of the evaporation process of the device and effectively improves the light-emitting efficiency of the organic light-emitting device. DETAILED DESCRIPTION

[0041] The technical solutions of the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0042] As used herein, the term "aryl" or "aromatic" refers to a group of one or more aromatic rings, which can be monocyclic or fused ring polycyclic. The aryl group can be an aryl group having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms. Examples can include phenyl, biphenyl, terphenyl, triphenylene, tetraphenylene, naphthyl, anthryl, phenanthryl, or pyrenyl, but are not limited thereto. As used herein, both non-fused and fused systems are contemplated. The aryl group can be an aryl group having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms. Examples of aryl groups include phenyl, biphenyl, terphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, pyrene, phenanthrene, fluorene, pyrene, perylene, and azulene, preferably phenyl, biphenyl, terphenyl, triphenylene, fluorene, and naphthalene. Examples of non-fused aryl groups include phenyl, biphenyl-2-yl, biphenyl-3-yl, biphenyl-4-yl, p-terphenyl-4-yl, p-terphenyl-3-yl, p-terphenyl-2-yl, m-terphenyl-4-yl, m-terphenyl-3-yl, m-terphenyl-2-yl, o-tolyl, m-tolyl, p-tolyl, p-(2-phenylpropyl)phenyl, 4'-methylbiphenyl, 4"-tert-butyl-p-terphenyl-4-yl, o-cumyl, m-cumyl, p-cumyl, 2,3-xylyl, 3,4-xylyl, 2,5-xylyl, mesityl, and m-quaterphenyl.

[0043] As used herein, the term "heteroaryl" refers to a group of one or more aromatic rings in which one or more ring carbons are replaced by a heteroatom, including but not limited to oxygen, sulfur, silicon, or nitrogen atoms. The heteroaryl group can be a monocyclic heteroaryl group or a fused ring heteroaryl group, and can be a heteroaryl group having 5 to 36 carbon atoms, preferably 6 to 20 carbon atoms. Examples can include pyrrolyl, pyridyl, thienyl, furanyl, indolyl, quinolyl, isoquinolyl, benzothienyl, benzofuranyl, dibenzofuranyl, dibenzothienyl, carbazolyl, and the like, but are not limited thereto.

[0044] Throughout this specification, unless expressly stated to the contrary, "comprising" means "comprehending, including, or encompassing", and "comprise, comprises, and comprising" will be understood to be open-ended, and will be interpreted to mean that compositions, methods, and the like that "comprise, include, or encompass" items listed after the term is allowed, but items not listed after the term are not excluded. In addition, it will be understood that, throughout this specification, when an element such as a layer, film, region, or substrate is referred to as being "on" or "over" another element, it can be "directly on" the other element, or an intervening element can also be present. In addition, "on" or "over" refers to being positioned above the target portion, without necessarily referring to being positioned above in the direction of gravity.

[0045] An object of the present application is to provide an organic electroluminescent device comprising: a substrate layer; a first electrode over the substrate; an organic light-emitting functional layer over the first electrode; a second electrode over the organic light-emitting functional layer; a cover layer over the second electrode; the cover layer comprising the defined material of the benzopentaheterocyclic nitrogen-containing ring according to the present application.

[0046] In one embodiment of the present application, the cover layer in an organic electroluminescent (OLED) device comprises one or more components of the compound according to the general formula (I) as described above as the cover layer material.

[0047] In a preferred embodiment of the present application, an OLED is provided, comprising a substrate, an anode, a cathode, an organic light-emitting functional layer, a cover layer, wherein the organic light-emitting functional layer can comprise a light-emitting layer, a hole transport layer, a hole injection layer, an electron transport layer, an electron injection layer, etc., and can also only comprise a light-emitting layer and one or more other layers; wherein the cover layer comprises one or more components of the compound according to the general formula (I) as described above; and further comprises one or more compounds according to the general formula (I) as described above. Optionally, there is also a protective layer and / or an encapsulation layer over the cover layer.

[0048] The substrate according to the present application can be any substrate used in a typical organic light-emitting device. It can be a glass or transparent plastic substrate, or a substrate of non-transparent material such as silicon or stainless steel, or a flexible PI film. Different substrates have different mechanical strength, thermal stability, transparency, surface smoothness, and water resistance, and the use direction is different according to the properties of the substrate.

[0049] As the material for the hole injection layer, the hole transport layer, and the electron injection layer, any material known for use in OLED devices can be selected and used.

[0050] As the host-guest material capable of producing blue fluorescence, green fluorescence, and blue-green fluorescence, not only does it need to have extremely high fluorescence quantum yield efficiency, but it also needs to have appropriate energy level matching.

[0051] The present application will be described in detail below with reference to specific examples. All raw materials and solvents used in the synthesis examples are commercially available unless otherwise specified, and the solvents are used directly without further treatment.

[0052] Examples

[0053] Example 1: Synthesis of compound CP001

[0054] Synthetic route:

[0055]

[0056] Synthetic method:

[0057] (1) Into a reaction flask, P1 (10 mmol), P2 (25 mmol), sodium tert-butoxide (10 mmol), toluene 200 ml, after nitrogen replacement, pd2(dba)3 (5 x 10 -2 mmol), Sphos (5 x 10 -2 mmol) were added, and the temperature was raised to 100-120°C, and the reaction was refluxed for 6 hours, and the reaction was stopped. The temperature was lowered to 30-40°C, 200 ml of water was added, and the layers were separated. After washing with water twice, the toluene was concentrated, 100 ml of n-heptane was added, and the slurry was obtained. The target product CP001 was obtained.

[0058] LC-MS (m / z) was analyzed by liquid chromatography-mass spectrometry: the theoretical value was 644.18, and the test value was 644.64.

[0059] Example 2: Synthesis of compound 012

[0060] Referring to the synthesis steps and reaction conditions of Example 1, compound 012 was synthesized, and LC-MS (m / z) was analyzed by liquid chromatography-mass spectrometry: the theoretical value was 676.14, and the test value was 676.52.

[0061] Example 3: Synthesis of compound 028

[0062] Referring to the synthesis steps and reaction conditions of Example 1, compound 028 was synthesized, and LC-MS (m / z) was analyzed by liquid chromatography-mass spectrometry: the theoretical value was 660.16, and the test value was 660.58.

[0063] Example 4: Synthesis of compound 030

[0064] Referring to the synthesis steps and reaction conditions of Example 1, compound 030 was synthesized, and LC-MS (m / z) was analyzed by liquid chromatography-mass spectrometry: the theoretical value was 636.16, and the test value was 636.62.

[0065] Example 5: Synthesis of compound 033

[0066] Referring to the synthesis steps and reaction conditions of Example 1, compound 033 was synthesized, and LC-MS (m / z) was analyzed by liquid chromatography-mass spectrometry: the theoretical value was 620.18, and the test value was 620.66.

[0067] Example 6: Synthesis of compound 035

[0068] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 035 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 620.18 calculated, 620.68 found.

[0069] Example 7: Synthesis of compound 052

[0070] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 052 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 620.18 calculated, 620.60 found.

[0071] Example 8: Synthesis of compound 054

[0072] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 054 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 695.22 calculated, 695.66 found.

[0073] Example 9: Synthesis of compound 055

[0074] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 055 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 696.22 calculated, 696.68 found.

[0075] Example 10: Synthesis of compound 056

[0076] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 056 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 696.22 calculated, 696.66 found.

[0077] Example 11: Synthesis of compound 069

[0078] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 069 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 669.21 calculated, 669.65 found.

[0079] Example 12: Synthesis of compound 073

[0080] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 073 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 669.21 calculated, 669.67 found.

[0081] Example 13: Synthesis of compound 079

[0082] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 079 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 685.18 calculated, 685.76 found.

[0083] Example 14: Synthesis of compound 081

[0084] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 081 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 696.22 calculated, 696.68 found.

[0085] Example 15: Synthesis of compound 082

[0086] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 082 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 620.18 calculated, 620.64 found.

[0087] Example 16: Synthesis of compound 083

[0088] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 083 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 593.17 calculated, 593.61 found.

[0089] Example 17: Synthesis of compound 084

[0090] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 084 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 669.21 calculated, 669.73 found.

[0091] Example 18: Synthesis of compound 087

[0092] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 087 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 720.22 calculated, 720.74 found.

[0093] Example 19: Synthesis of compound 094

[0094] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 094 was synthesized. Analysis by liquid chromatography-mass spectrometry gave LC-MS (m / z): 745.24 calculated, 745.80 found.

[0095] Example 20: Synthesis of compound 097

[0096] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 097 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 742.23 (theoretical) and 742.81 (found).

[0097] Example 21: Synthesis of compound 098

[0098] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 098 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 742.23 (theoretical) and 742.79 (found).

[0099] Example 22: Synthesis of compound 103

[0100] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 103 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 698.15 (theoretical) and 698.77 (found).

[0101] Example 23: Synthesis of compound 111

[0102] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 111 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 670.20 (theoretical) and 670.72 (found).

[0103] Example 24: Synthesis of compound 121

[0104] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 121 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 670.20 (theoretical) and 670.70 (found).

[0105] Example 25: Synthesis of compound 123

[0106] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 123 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 670.20 (theoretical) and 670.72 (found).

[0107] Example 26: Synthesis of compound 125

[0108] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 125 was synthesized. Analytical LC-MS (m / z) of the compound gave a value of 602.20 (theoretical) and 602.68 (found).

[0109] Example 27: Synthesis of compound 127

[0110] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 127 was synthesized. LC-MS (m / z): [M+H]+calcd 652.22 found 652.70.

[0111] Example 28: Synthesis of compound 130

[0112] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 130 was synthesized. LC-MS (m / z): [M+H]+calcd 701.16 found 701.76.

[0113] Example 29: Synthesis of compound 133

[0114] Following the synthetic procedure and reaction conditions of Reference Example 1, compound 133 was synthesized. LC-MS (m / z): [M+H]+calcd 701.16 found 701.78.

[0115] The following examples illustrate the use of the compounds of the present application as a cover layer in an OLED device. The materials used in the examples were either commercially available or synthesized in-house.

[0116] Fabrication of OLED device:

[0117] As a reference to the device example, the present application evaporated ITO / Ag / ITO (ITO:Ag:ITO weight ratio = 1:(10-20):1) of 50-500 nm on an alkali-free glass substrate as an anode, evaporated a hole injection layer (5-20 nm), a hole transport layer (50-150 nm), a light emitting auxiliary layer (5-120 nm), a light emitting layer (20-50 nm), a hole blocking layer (5-20 nm), an electron transport layer (20-80 nm), an electron injection layer (1-10 nm) on the anode, and then evaporated Mg and Ag (weight ratio 1:9, 10-15 nm) as a semi-transparent cathode, and evaporated a cover layer compound (50-90 nm). Finally, the light emitting device was encapsulated with an epoxy adhesive under a nitrogen atmosphere.

[0118] In a preferred embodiment, the OLED device of the present application was prepared as follows: The alkali-free glass substrate was cleaned with isopropanol for 15 minutes using an ultrasonic cleaner, and then subjected to UV ozone washing in air for 30 minutes. The cleaned substrate was vacuum deposited with ITO / Ag / ITO (ITO:Ag:ITO weight ratio = 1:10:1, 100 nm) as an anode, and then sequentially deposited with a hole injection layer (HT:PD, 10 nm, PD 2% by weight), a hole transport layer (HT, 130 nm), a light-emitting auxiliary layer (BP, 5 nm), a blue light-emitting layer (host material:dopant = BH:BD (weight ratio 98:2, 30 nm)), a hole blocking layer (HBL, 5 nm), an electron transport layer (ET:Liq = 1:1, 30 nm), an electron injection layer (Yb, 1 nm), and a semi-transparent cathode (Mg:Ag (weight ratio 1:9, 13 nm) and a cover layer (compound CP001, 65 nm). The light-emitting device was encapsulated with an epoxy adhesive under a nitrogen atmosphere, and was designated as Example 1. The molecular structures of the relevant materials are shown below (particularly preferred from the following structures, but not limited to the following structures):

[0119]

[0120] Examples 2 to 29 and Comparative Examples 1 to 3 were prepared by the method described in Example 1 above, except that the compounds listed in Table 1 were used as the cover layer material instead of compound CP001 in Example 1. The structures of Ref-1, Ref-2 and Ref-3 used in Comparative Examples 1 to 3 are as follows:

[0121] Evaluation of the performance of the OLED device:

[0122] Performance test I, refractive index of the material

[0123] In order to measure the optical properties of the compounds, the glass substrate (0.7T) was cleaned in ethanol, deionized water, and acetone for 10 minutes, respectively, and then the compound CP001 was evaporated on the glass substrate to a thickness of 50 nm to produce a single layer film, which is referred to as Example 1. Except that each compound shown in Table 1 was used to replace the compound CP001, the single layer film was produced in the same manner as in Example 1. The n (refractive index) and k (extinction coefficient) of the compounds prepared in Examples 1-29 and the compound of Comparative Example 1 were measured at different wavelengths by an ellipsometer of J. A. WOOLLAM. When the n and k values of the CPL material were tested by the ellipsometer, the n and k values obtained by different ellipsometer modeling methods were different for the same CPL material. In the present application, the n and k values of the materials of the examples and Ref-1, Ref-2, and Ref-3 were simultaneously tested by the adaptive modeling method, and the simultaneous test results were more convincing. The optical properties of the compounds of the examples and the comparative examples are shown in Table 1.

[0124] Table 1. n (refractive index) and k (extinction coefficient) of the compounds at different wavelengths

[0125]

[0126]

[0127] Performance test two, device light-emitting performance characterization

[0128] The current of the OLED device at different voltages was tested by a Keithley 2365A digital nanovoltmeter, and then the current density of the OLED device at different voltages was obtained by dividing the current by the light-emitting area. The luminance and radiant flux density of the OLED device at different voltages were tested by a Konicaminolta CS-2000 spectroradiometric luminance meter. According to the current density and luminance of the OLED device at different voltages, the operating voltage Volt and current efficiency (cd / A) at the same current density (10 mA / cm2) were obtained. BI refers to Blue Index in blue light, which is also a parameter for measuring the blue light-emitting efficiency. E refers to current efficiency, and CIEy refers to the ordinate color point obtained by inputting the half-peak width wavelength of the device light emission into CIE1930 software. The test data are shown in Table 2.

[0129] Table 2. Device and electronic light-emitting properties of the covering layer material application examples

[0130]

[0131]

[0132] In the art, for high-refractive CPL materials, a high refractive index n value is indeed more conducive to the coupling out of light, but a high refractive index often corresponds to a high extinction coefficient k value. The larger the extinction coefficient k value, the more light is absorbed by the material itself while being taken out, which will greatly reduce the luminous efficiency, especially in the blue light (460 nm) band. When the k value is greater than 0.03, this phenomenon is particularly evident. Therefore, it is difficult to design a CPL material with a higher refractive index n value while taking into account a smaller extinction coefficient k value. As can be seen from Table 1, the CPL materials of embodiments 1-29 of the present application can simultaneously take into account a high refractive index n value and a smaller extinction coefficient k value compared to the materials of comparative examples 1-3, so the device performance is particularly outstanding.

[0133] As can be seen from Table 2, compared with comparative examples 1-3, application examples 1 to 29 have lower operating voltage and higher BI luminous efficiency. The performance improvement of each application example is based on the better film stability and higher refractive index of the compound material for the cover layer according to the present application. The compound obtained by fixing the N atom side to a benzopentazocane containing nitrogen heterocyclic ring and coordinating with the fused heteroaromatic ring with the other two sides of the defined structure has good thermal stability, and when applied to the cover layer, it can improve the luminous efficiency of the device and reduce the power consumption of the device.

[0134] The specific embodiments are merely an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A compound for a cover layer, characterized by The covering layer compound is selected from any one of the following chemical structures:

2. The compound for a cover layer according to claim 1, characterized by The compound satisfies the following conditions: the refractive index n value at 460-620 nm wavelength is between 1.80-2.30, and the extinction coefficient k value is between 0.005-0.

030.

3. A formulation characterized in that, The preparation comprises the covering layer compound according to any one of claims 1-2 and at least one solvent.

4. A composition characterized in that, The composition comprises the covering layer compound according to any one of claims 1-2.

5. Use of the covering layer compound according to any one of claims 1-2 in the preparation of an organic electroluminescent device.

6. An organic electroluminescent device, characterized by The organic electroluminescent device comprises: a substrate layer; a first electrode on the substrate; an organic light-emitting functional layer on the first electrode; a second electrode on the organic light-emitting functional layer; a covering layer on the second electrode; the covering layer comprises the covering layer compound according to any one of claims 1-2.

7. A display or illumination device, characterized in that The device comprises the organic electroluminescent device according to claim 6.

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