An organic electroluminescent compound and an organic electroluminescent device comprising the same

Abstract

The application discloses an organic electroluminescent compound and an organic electroluminescent device containing the same. The organic electroluminescent compound is selected from a general structure shown in the following formula I. In the application, a special molecular structure is formed by introducing aryl substituents at two specific positions, namely Ar2 and Ar3 positions, which produces the following effects: first, the carbon-hydrogen bond of the fused aryl fragment on the relatively weak fused arylbenzofuran is changed into a more stable carbon-carbon bond after being substituted by aryl; second, the special spatial structure can improve the transport of carriers, reduce the residence of polarons on a single molecule in the device, and reduce the probability of interaction between polarons, excitons and carriers, thereby reducing the quenching and degradation of the host material during the operation of the device, improving the service life of the device and improving the efficiency of the device; third, the carrier recombination energy is obviously reduced, the carrier transport is faster, and the device voltage is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of OLEDs, and specifically comprises an organic electroluminescent compound and an organic electroluminescent device comprising the same. BACKGROUND

[0002] As a new generation of flat panel display technology, organic electroluminescent devices (OLEDs) have gradually become the core technology in the display field after more than 20 years of rapid development, with their ultra-thin structure, fast response and excellent display performance. This technology can accurately present high-saturation red, green and blue three primary colors through high-contrast display effect and wide color gamut coverage, thereby creating a colorful and realistic visual experience. Based on these significant advantages, OLEDs have not only been successfully applied to mainstream fields such as flat panel displays and flexible displays, but also have shown unique technical value in vehicle display systems and solid-state lighting solutions, continuously driving the innovation process of the display industry.

[0003] In the performance optimization research of blue light devices, the development of light-emitting layer host materials faces multiple technical bottlenecks. The current mainstream phosphorescent materials and traditional thermally activated delayed fluorescence (TADF) materials have not achieved commercial breakthroughs due to significant efficiency roll-off; while fluorescent materials and multiple resonance TADF (MR-TADF) materials are still limited by the theoretical limit of 25% single-state exciton in electroluminescence. In view of this core challenge, the academic community proposes an innovative solution of host-guest doped system, that is, by introducing anthracene host materials with a triplet-triplet exciton fusion (TTU) mechanism, the internal quantum efficiency of the device can theoretically break through the traditional limit and reach a theoretical peak of 40%. This mechanism can significantly improve the exciton utilization rate by promoting the effective fusion of triplet excitons. However, in practical applications, only a few material systems can approach the theoretical limit of 40%. This is mainly due to the non-linear quenching effect caused by the increase in exciton density: the intensification of singlet exciton-polaron quenching (SPA) and triplet exciton-triplet exciton annihilation (TTA) imposes strict spatial constraints on the distribution of the light-emitting layer recombination region. In order to effectively suppress such non-radiative losses, the host material needs to have excellent charge transport ability and carrier balance ability. However, the current anthracene material system generally has a problem of hole mobility significantly higher than electron mobility, which leads to a carrier transport imbalance phenomenon, resulting in a broadened recombination region and becoming a key factor restricting the further improvement of device efficiency.

[0004] In recent years, by introducing dibenzofuran, naphthalene benzofuran fragments on anthracene host material, using the large electronegativity of oxygen, improve the material's electron transport performance. However, the carbon oxygen bond may be broken in anion state so that the material degradation, shorten the service life of the material. In order to improve this problem, using perdeuteration or partial deuteration can improve the stability of the material, however, using deuteration, especially after all deuteration may cause slow transmission, in addition, the cost of deuteration is higher, and the deuteration rate is not easy to monitor and control. Therefore, how to modify the current mainstream anthracene host material containing furan fragment without deliberately using deuteration modification, so that it can have higher efficiency, better charge transport, carrier balance performance and excellent stability, is still an important task to be solved and improved in the industry. SUMMARY

[0005] In view of the above problems existing in the prior art, the present application provides an organic electroluminescent compound and an organic electroluminescent device comprising the same.

[0006] To achieve the above object, the technical scheme adopted by the present application comprises:

[0007] The first aspect of the present application provides an organic electroluminescent compound, the organic electroluminescent compound is selected from the general structure of formula I as follows:

[0008] I;

[0009] wherein,

[0010] Ar1 is selected from any one or combination of substituted or unsubstituted aryl with carbon atoms number of 6 to 60, substituted or unsubstituted fused ring aryl with carbon atoms number of 10 to 60, substituted or unsubstituted fused ring heteroaryl with carbon atoms number of 8 to 60, when Ar1 has a substituent, the substituent is selected from deuterium or phenyl;

[0011] Ar4 is selected from one of the structures of formula II-1 to formula II-4:

[0012] II-1, II-2, II-3, II-4;

[0013] Ar2, Ar3 are each independently selected from any one of deuterated or non-deuterated phenyl, deuterated or non-deuterated naphthyl;

[0014] D represents deuterium, and · represents the bonding site with anthracene in formula I;

[0015] n1 is selected from 0 or 8, n2, n4, n5 are each independently selected from 0 or 6, n3 is selected from 0 or 3, n6 is selected from 0 or 4.

[0016] Further, Ar1 is selected from any one or a combination of more of a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted condensed ring aryl group having 10 to 30 carbon atoms, a substituted or unsubstituted condensed ring heteroaryl group having 8 to 30 carbon atoms.

[0017] Further, the aryl group is selected from any one of a phenyl group, a biphenyl group, a dimethylfluorenyl group, a diphenylfluorenyl group, a spirofluorenyl group.

[0018] Further, the condensed ring aryl group is selected from any one of a naphthyl group, a phenanthryl group, a pyrenyl group, a benzanthryl group, a benzophenanthryl group, a chrysenyl group, a fluoranthenyl group.

[0019] Further, the heteroatom in the condensed ring heteroaryl group is selected from any one of oxygen, nitrogen, silicon.

[0020] Further, the condensed ring heteroaryl group is selected from one of the following structures:

[0021] .

[0022] Further, Ar2, Ar3 are selected from a phenyl group.

[0023] Further, Ar1 is selected from a phenyl group.

[0024] Further, the organic electroluminescence compound is selected from one of the following structures:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] .

[0055] A second aspect of the present application provides an organic electroluminescent device, comprising an anode, a hole transport region, a light-emitting layer, an electron transport region, and a cathode, which are sequentially arranged on a substrate; wherein the light-emitting layer comprises one or more organic electroluminescent compounds as described above.

[0056] Further, the light-emitting layer comprises a host material and a guest material, wherein the host material comprises one or more organic electroluminescent compounds as described above.

[0057] Further, the light-emitting layer comprises a first host material, a second host material and a guest material, i.e. the device is a double host device, the first host material is selected from a compound of the following formula III, and the second host material comprises one or more organic electroluminescent compounds as described above:

[0058] III;

[0059] Ar5is selected from any one of an aryl group having 6 to 30 carbon atoms, a phenyl-substituted aryl group having 6 to 30 carbon atoms, a condensed ring aryl group having 10 to 30 carbon atoms, and a phenyl-substituted condensed ring aryl group having 10 to 30 carbon atoms;

[0060] Ar6is selected from any one of an aryl group having 6 to 30 carbon atoms, a phenyl-substituted aryl group having 6 to 30 carbon atoms, a condensed ring aryl group having 10 to 30 carbon atoms, a phenyl-substituted condensed ring aryl group having 10 to 30 carbon atoms, and 2-dibenzofuran;

[0061] Further, in the double host device, the first host material is selected from one of the following structures:

[0062] .

[0063] Further, the light-emitting layer comprises a first light-emitting layer on top of the hole transport zone and a second light-emitting layer on top of the first light-emitting layer, i.e. the device is a double light-emitting layer device, wherein the first light-emitting layer comprises a first host material and a guest material, the first host material is selected from a compound of the following formula IV, and the second light-emitting layer comprises a second host material and a guest material, the second host material comprises one or more organic electroluminescent compounds as described above:

[0064] IV;

[0065] Ar7is selected from any one of H, an aryl group having 6 to 30 carbon atoms, and a condensed ring aryl group having 10 to 30 carbon atoms;

[0066] Ar8is selected from any one of H, an aryl group having 6 to 30 carbon atoms, and a condensed ring aryl group having 10 to 30 carbon atoms;

[0067] L is selected from one of a phenyl group and a biphenyl group.

[0068] Further, in the double light-emitting layer device, the first host material is selected from one of the following structures:

[0069] .

[0070] Advantages of the present application:

[0071] The present application provides an organic electroluminescent compound, by introducing aryl substituents at two specific positions (i.e. Ar2 and Ar3 positions), a special molecular structure is formed, which produces the following effects: first, the carbon-hydrogen bond on the phenyl group connected in parallel with the furan on the relatively weak fused aryl benzofuran is replaced by an aryl group, which becomes a more stable carbon-carbon bond, improving the thermal stability of the material; second, the special spatial structure can improve the transport of carriers, reduce the time for polaron to stay on a single molecule in the device, and reduce the probability of interaction between polarons, excitons, and carriers, thereby reducing the quenching and degradation of the host material during device operation, thereby improving the lifetime of the device; third, significantly reducing the carrier recombination energy, making the carrier transport faster, thereby facilitating the reduction of device voltage and improving device efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 It is a structural schematic diagram of the organic electroluminescent device of the present application, wherein 101 is a substrate, 102 is an anode, 103 is a hole injection layer, 104 is a hole transport layer, 105 is a light-emitting auxiliary layer, 106 is a light-emitting layer, 107 is a hole blocking layer, 108 is an electron transport layer, 109 is an electron injection layer, and 1010 is a cathode.

[0073] Figure 2 It is a molecular conformation diagram of compound C3.

[0074] Figure 3 It is a molecular conformation diagram of compound DB01.

[0075] Figure 4 It is a molecular conformation diagram of compound DB10.

[0076] Figure 5 It is a structural schematic diagram of the double light-emitting layer organic electroluminescent device of the present application, wherein 201 is a substrate, 202 is an anode, 203 is a hole injection layer, 204 is a hole transport layer, 205 is a light-emitting auxiliary layer, 206 is a first light-emitting layer, 207 is a second light-emitting layer, 208 is a hole blocking layer, 209 is an electron transport layer, 2010 is an electron injection layer, and 2011 is a cathode. DETAILED DESCRIPTION

[0077] In order to more clearly understand the content of the present application, the embodiments will be described in detail in conjunction with the drawings.

[0078] The compounds of the present application are suitable for use in light-emitting elements, display panels and electronic devices, in particular in organic electroluminescent devices. The electronic devices described in the present application are devices comprising at least one layer of an organic compound, which devices can also comprise layers of inorganic materials or be formed entirely from inorganic materials. The electronic devices are preferably organic electroluminescent devices (OLEDs), organic integrated circuits (O-ICs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic light-emitting transistors (O-LETs), organic solar cells (O-SCs), organic dye-sensitised solar cells (O-DSSCs), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) and organic plasmonic devices. The electronic devices are preferably organic electroluminescent devices (OLEDs). A schematic structural diagram of an exemplary organic electroluminescent device is shown in Figure 1 or Figure 5

[0079] Experimental Section

[0080] For a more clear understanding of the present application, the polycyclic compounds, the preparation method of the compounds and the light-emitting properties of the device will be explained in detail with reference to the examples. Various chemical reactions can be applied to the synthesis method of the compounds of one embodiment of the present application. However, it should be noted that the synthesis method of the compounds of one embodiment of the present application is not limited to the synthesis methods described below. Unless otherwise specified, the following synthesis is performed in anhydrous solvents under a protective gas atmosphere. Solvents and reagents can be purchased from conventional reagent suppliers.

[0081] Synthesis of intermediates

[0082]

[0083] In a 250 mL three-necked flask, 50 mL of toluene, 25 mL of ethanol and 25 mL of water were added under nitrogen atmosphere, and then Dn (10 mmol), En (10 mmol), potassium carbonate (4.15 g, 30 mmol) and tetrakis-triphenylphosphine palladium (0.35 g, 0.3 mmol) were added, heated to 80 °C for 12 h, after the reaction was completed, the reaction was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble matter, and then recrystallized to obtain the product Fn.

[0084] ​In a 250 mL flask, 100 mL of toluene was added under nitrogen protection, then Fn (20 mmol), Gn (10 mmol), cesium carbonate (9.78 g, 30 mmol) and [Cp*RhCl2]2 (0.31 g, 0.5 mmol), Cu(OAc)2·H2O (4.00 g, 20 mmol) were added, heated to 125°C for 12 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble matter, and then recrystallized to obtain the product Hn.

[0085] To a round-bottom flask purged with nitrogen, intermediate Hn (10 mmol), trimethyl borate (1.03 g, 10 mmol), tetrahydrofuran (30 mL) were added, and under nitrogen protection, tert-butyllithium (8.00 mL, 20 mmol) was added dropwise at -50°C, dropwise addition was completed within 2 h, and the temperature was kept for 3 h, then 3.5 mL of 5% hydrochloric acid solution was added, and stirring was continued for 2 h, tetrahydrofuran was distilled off under reduced pressure, and the temperature was lowered to 10°C to obtain solid precipitate, which was filtered and dried to obtain intermediate Jn.

[0086] In a 250 mL flask, 50 mL of toluene, 25 mL of ethanol and 25 mL of water were added under nitrogen protection, then Jn (10 mmol), Kn (10 mmol), potassium carbonate (4.15 g, 30 mmol) and tetrakis triphenyl phosphine palladium (0.35 g, 0.3 mmol) were added, heated to 80°C for 12 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble matter, and then recrystallized to obtain the product An.

[0087] The preparation process of intermediate A1 is exemplarily shown below, and the preparation of intermediates A2-A20 can be prepared by referring to the process.

[0088]

[0089] In a 250 mL flask, 50 mL of toluene, 25 mL of ethanol and 25 mL of water were added under nitrogen protection, then D1 (2.31 g, 10 mmol), E1 (1.27 g, 10 mmol), potassium carbonate (4.15 g, 30 mmol) and tetrakis triphenyl phosphine palladium (0.35 g, 0.3 mmol) were added, heated to 80°C for 12 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble matter, and then recrystallized to obtain the product F1: 2.37 g, yield: 85%, MS (m / z) (M+): 279.

[0090] In a 250 mL three-necked flask, 100 mL of toluene was added under nitrogen protection, then F1 (5.58 g, 20 mmol), G1 (1.78 g, 10 mmol), cesium carbonate (9.78 g, 30 mmol) and [Cp*RhCl2]2 (0.31 g, 0.5 mmol), Cu(OAc)2·H2O (4.00 g, 20 mmol) were added, heated to 125 °C for 24 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble, and then recrystallized to obtain product H1: 2.50 g, yield: 55%, MS (m / z) (M+): 455.

[0091] To a round-bottom flask purged and maintained with nitrogen, intermediate H1 (4.55 g, 10 mmol), trimethyl borate (1.03 g, 10 mmol), tetrahydrofuran (30 mL) were added, and under nitrogen protection, tert-butyllithium (8.00 mL, 20 mmol) was added dropwise at -50 °C, the dropwise addition was completed within 2 h, and the mixture was incubated for 3 h, then 3.5 mL of 5% hydrochloric acid solution was added, and the stirring was continued for 2 h, tetrahydrofuran was distilled off under reduced pressure, and the mixture was cooled to 10 °C, solid precipitate appeared, and the mixture was filtered and dried to obtain intermediate J1: 3.78 g, yield: 90%, MS (m / z) (M+): 420.

[0092] In a 250 mL three-necked flask, 50 mL of toluene, 25 mL of ethanol and 25 mL of water were added under nitrogen protection, then J1 (4.20 g, 10 mmol), K1 (3.36 g, 10 mmol), potassium carbonate (4.15 g, 30 mmol) and tetrakis(triphenylphosphine)palladium (0.35 g, 0.3 mmol) were added, heated to 80 °C for 12 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble, and then recrystallized to obtain product A1: 5.81 g, yield: 86%, MS (m / z) (M+): 675.

[0093] Synthesis Example 1

[0094]

[0095] In a 250 mL three-necked flask, 50 mL of toluene, 25 mL of ethanol and 25 mL of water were added under nitrogen protection, then A1 (6.76 g; 10 mmol), B1 (1.53 g; 10 mmol), potassium carbonate (4.15 g, 30 mmol) and tetrakis(triphenylphosphine)palladium (0.35 g, 0.3 mmol) were added, heated to 80 °C for 12 h, after the reaction was completed, it was cooled to room temperature, filtered, the filter cake was dissolved in toluene and heated, then filtered to remove solid insoluble, and then recrystallized to obtain product C1: 6.67 g, yield: 89%, MS (m / z) (M+): 749.

[0096] Synthesis Example 2

[0097]

[0098] Synthesis procedure as in Synthesis Example 1, except that A2 (6.76 g; 10 mmol), B2 (1.53 g; 10 mmol) were used instead of Al and Bl, resulting in product C2: 6.44 g (yield: 86%), MS (m / z) (M+): 749.

[0099] Synthesis Example 3

[0100]

[0101] Synthesis procedure as in Example 1, except that A3 (6.26 g; 10 mmol), B3 (0.77 g; 10 mmol) were used instead of Al and Bl, resulting in product C3: 5.48 g, yield: 88%, MS (m / z) (M+): 623.

[0102] Synthesis Example 4

[0103]

[0104] Synthesis procedure as in Synthesis Example 1, except that A4 (6.84 g; 10 mmol), B4 (0.77 g; 10 mmol) were used instead of Al and Bl, resulting in product C4: 5.86 g (yield: 86%), MS (m / z) (M+): 681.

[0105] Synthesis Example 5

[0106]

[0107] Synthesis procedure as in Example 1, except that A5 (6.84 g; 10 mmol), B5 (1.27 g; 10 mmol) were used instead of Al and Bl, resulting in product C5: 6.51 g (yield: 89%), MS (m / z) (M+): 731.

[0108] Synthesis Example 6

[0109]

[0110] Synthesis procedure as in Example 1, except that A6 (6.26 g; 10 mmol), B6 (1.77 g; 10 mmol) were used instead of Al and Bl, resulting in product C6: 6.15 g, yield: 85%, MS (m / z) (M+): 723.

[0111] Synthesis Example 7

[0112]

[0113] Preparation method same as example 1, except that A7 (6.29 g; 10 mmol), B7 (2.01 g; 10 mmol) replace Al and Bl, finally product C7: 6.38 g, yield: 85%, MS (m / z) (M+): 750.

[0114] Synthesis example 8

[0115]

[0116] Preparation method same as example 1, except that A8 (6.34 g; 10 mmol), B8 (2.29 g; 10 mmol) replace Al and Bl, finally product C8: 6.89 g, yield: 88%, MS (m / z) (M+): 783.

[0117] Synthesis example 9

[0118]

[0119] Preparation method same as example 1, except that A9 (6.29 g; 10 mmol), B9 (2.32 g; 10 mmol) replace Al and Bl, finally product C9: 6.93 g, yield: 88%, MS (m / z) (M+): 788.

[0120] Synthesis example 10

[0121]

[0122] Preparation method same as example 1, except that A10 (6.79 g; 10 mmol), B10 (2.03 g; 10 mmol) replace Al and Bl, finally product C10: 7.06 g (yield: 88%), MS (m / z) (M+): 802.

[0123] Synthesis example 11

[0124]

[0125] Preparation method same as example 1, except that A11 (6.84 g; 10 mmol), B11 (1.93 g; 10 mmol) replace Al and Bl, finally product C11: 7.09 g (yield: 89%), MS (m / z) (M+): 797.

[0126] Synthesis example 12

[0127]

[0128] Preparation method same as example 1, except that A12 (6.76 g; 10 mmol), B12 (0.82 g; 10 mmol) replace Al and Bl, finally product C12 is obtained: 5.9 g (yield: 87%), MS (m / z) (M+): 678.

[0129] Synthesis example 13

[0130]

[0131] Preparation method same as example 1, except that A13 (6.34 g; 10 mmol), B13 (0.82 g; 10 mmol) replace Al and Bl, finally product C13 is obtained: 5.6 g, yield: 88%, MS (m / z) (M+): 636.

[0132] Synthesis example 14

[0133]

[0134] Preparation method same as example 1, except that A14 (6.26 g; 10 mmol), B14 (3.15 g; 10 mmol) replace Al and Bl, finally product C14 is obtained: 7.4 g, yield: 86%, MS (m / z) (M+): 861.

[0135] Synthesis example 15

[0136]

[0137] Preparation method same as example 1, except that A15 (6.76 g; 10 mmol), B15 (2.03 g; 10 mmol) replace Al and Bl, finally product C15 is obtained: 7.19 g (yield: 90%), MS (m / z) (M+): 799.

[0138] Synthesis example 16

[0139]

[0140] Preparation method same as example 1, except that A16 (7.26 g; 10 mmol), B16 (0.82 g; 10 mmol) replace Al and Bl, finally product C16 is obtained: 6.41 g (yield: 88%), MS (m / z) (M+): 728.

[0141] Synthesis example 17

[0142]

[0143] Preparation method same as example 1 except that A17 (6.76 g; 10 mmol), B17 (0.77 g; 10 mmol) replaced Al and Bl, finally product C17 was obtained: 6.06 g, yield: 90%, MS (m / z) (M+): 673.

[0144] Synthesis of example 18

[0145]

[0146] Preparation method same as example 1 except that A18 (7.26 g; 10 mmol), B18 (1.27 g; 10 mmol) replaced Al and Bl, finally product C18 was obtained: 6.8 g, yield: 88%, MS (m / z) (M+): 773.

[0147] Synthesis of example 19

[0148]

[0149] Preparation method same as example 1 except that A19 (7.26 g; 10 mmol), B19 (1.27 g; 10 mmol) replaced Al and Bl, finally product C19 was obtained: 6.65 g, yield: 86%, MS (m / z) (M+): 773.

[0150] Synthesis of example 20

[0151]

[0152] Preparation method same as example 1 except that A20 (6.76 g; 10 mmol), B20 (3.15 g; 10 mmol) replaced Al and Bl, finally product C20 was obtained: 7.74 g, yield: 85%, MS (m / z) (M+): 911.

[0153] Comparative compound

[0154]

[0155]

[0156]

[0157] .

[0158] Compound properties

[0159] To prove the advantage of the material of the present application in carrier recombination energy (including hole recombination energy and electron recombination energy), the carrier recombination energy of different compounds is tested. Generally, the smaller the carrier recombination energy, the faster the carrier transport, and the device test results tend to show the effect of low driving voltage. Through ORCA software, based on the density functional theory (DFT) calculation method (the basis group level is set to: b3lyp / 6-31g(d), the charge number is 0), the molecular structure is optimized (Optimization), and on this basis, the recombination energy (eV) of the compound under positive charge and negative charge is further calculated. Generally, the smaller the recombination energy, the faster the mobility, which means that the probability of carrier being trapped by the dopant is lower, and the utilization rate of the carrier is higher, which is beneficial to improve the efficiency.

[0160] To illustrate the improvement of the material stability of the present application by substitution, the thermal stability of the material is determined by thermal stability test, and the specific method is as follows: the material to be tested is placed at 280℃ for 240h for thermal stability test, and the change of the purity of the material before and after the thermal stability test is tested by high performance liquid chromatograph. The smaller the difference in purity, the smaller the degree of decomposition, coupling and other degradation reactions of the material in a long time high temperature environment, and the better the thermal stability of the material. When the difference in purity before and after the thermal stability is large, it indicates that the material has coupling degradation in high heat environment, and the luminescent performance of the material itself changes, which affects the device life performance, and seriously, the polarization and exciton quenching of the deteriorated material. Since the compound developed by the present application as the host material accounts for a large proportion in the light-emitting layer, the purity requirement is more stringent than that of the guest material, and generally the purity of the compound needs to be greater than 99.99%. Therefore, when the purity change is less than 0.01%, the thermal stability is evaluated as excellent, and when the purity change is greater than or equal to 0.01%, the thermal stability is evaluated as poor.

[0161] Table 1

[0162]

[0163] The above results are analyzed, and compound C3 is taken as an example. It can be seen that, compared with the comparative compounds DB02 to DB08 which have only one aryl substituent on naphthalene benzofuran, compound C3 has the same phenyl-substituted anthracene fragment, and only the number and position of the phenyl group substituted on naphthalene benzofuran are different, but the hole / electron recombination energy of the material of the present application is 0.19 and 0.29, respectively, which is significantly smaller than that of the comparative compounds DB02 to DB08. Moreover, the thermal stability of compound C3 is basically equivalent to that of comparative compound DB01, which shows that the introduction of aryl group at the key position can effectively improve the stability of the material. In particular, from the perspective of the molecular conformation of C3 shown in Figure 2 Figure 3 ​As can be seen from the molecular conformation of the shown DB01, the two substituted phenyls greatly limit the twist of the naphthobenzofuran, increase the rigidity of the molecule, and reduce the reorganization energy. In addition, the substituted benzene ring and the π electron cloud of the anthracene nucleus present a certain overlap, which is conducive to carrier transport, and in turn reduces the voltage of the device. Compared with the comparative compound DB09, although the electronic reorganization energy of the comparative compound DB09 is improved to a certain extent, the comparative compound DB09 contains two large steric substituents at the ortho positions of the substituted phenyl of the anthracene nucleus (see the dashed circle part in the third structure below), which makes the synthesis yield of the related structure not high. In addition, due to the large steric hindrance in close proximity, the single bond connecting the anthracene nucleus and the lower furan part is weakened, and the stability of the molecular structure changes. Compared with the comparative compound DB10, the naphthobenzofuran substituted at position 7 (see the first structure below) is used in the present application. The naphthyl structure of the present application is more electron-rich, and the substitution mode of the present application can make the naphthobenzofuran based on the anthracene nucleus present a perpendicular structure, which has large steric hindrance. The benzene ring substituted thereon can overlap with the π electron cloud of the anthracene nucleus to a certain extent, so that the reorganization energy change of the structure of the present application is small when the hole is transported (that is, the molecule loses an electron). The patent document CN107531661B also states that the position 7 is similar to the position 1 of the dibenzofuran, which can also reduce the affinity potential, which is conducive to electron injection. The dibenzofuran structure of the comparative compound DB10 lacks a fused ring and thus has low electron cloud density. The substitution mode used cannot form a perpendicular structure (see Figure 4 ), and the phenyl-substituted dibenzofuran fragment can rotate around the single bond at the 2-substituted position (see the second structure below). This substitution mode improves the reorganization energy of electron transport, but significantly increases the reorganization energy of hole transport. Generally, the hole transport speed is faster than the electron transport speed, which can cause the accumulation of holes at the interface between the hole transport layer and the light-emitting layer, which is not conducive to the recombination of excitons.

[0164]

[0165] Manufacture and characterization of OLEDs

[0166] Device embodiments

[0167] The organic electroluminescent device provided by the present application comprises an anode, a hole transport zone, a light-emitting layer, an electron transport zone, and a cathode arranged in sequence on a substrate.

[0168] Further, the hole transport zone comprises a hole injection layer, a hole transport layer, and a light-emitting auxiliary layer; and the electron transport zone comprises an electron transport layer and an electron injection layer.

[0169] Further, the light-emitting layer is composed of a host material and a guest material. The light-emitting layer host material can be composed of one kind of molecular material or multiple kinds of molecular materials.

[0170] The composition of the present application can be used in the light-emitting layer of the organic electroluminescent device.

[0171] The anode in the embodiment adopts the anode material commonly used in the art, such as ITO, Ag or a multi-layer structure thereof. The hole injection layer adopts the hole injection material commonly used in the art, while F4TCNQ, HATCN, NDP-9 and the like are added for doping. The hole transport layer adopts the hole transport material commonly used in the art. The light-emitting layer adopts the host-guest material composition provided by the present application. The electron transport layer adopts the electron transport material commonly used in the art. The electron injection layer adopts the electron injection material commonly used in the art, such as LiQ, LiF, Yb and the like. The cathode adopts the material commonly used in the art, such as metal Al, Ag or a metal mixture (Ag-doped Mg, Ag-doped Ca and the like).

[0172] The electrode preparation method and the deposition method of each functional layer in the embodiment are the conventional methods in the art, such as vacuum thermal evaporation or inkjet printing, and will not be described here again. Only some process details in the preparation process and test methods are described as follows:

[0173] Device embodiment 1

[0174] The substrate used in the present application is subjected to the following operations: after the ITO substrate is patterned to have a light-emitting area with a size of 3 mm x 3 mm, it is subjected to water / isopropanol ultrasonic treatment, UV / ozone irradiation, and then 100°C drying. After that, the ITO substrate is installed on the substrate support of a vacuum deposition device and the pressure is adjusted to make the vacuum rate 1 x 10 -7torr. Then, a hole injection layer was formed by vacuum depositing compound HT01 and compound PD01 (mass ratio of compound HT01 to compound PD01 was 97:3) on the ITO layer (anode) of the substrate at a thickness of 10 nm, a hole transport layer was formed by vacuum depositing compound HT01 on the hole injection layer at a thickness of 100 nm, a light-emitting auxiliary layer was formed by vacuum depositing compound BP01 on the hole transport layer at a thickness of 5 nm, a light-emitting layer was formed by vacuum depositing a mixture of compound C1 provided by the application and compound BD01 on the light-emitting auxiliary layer at a thickness of 20 nm, wherein compound C1 was used as a host material and compound BD01 was used as a guest material, and the mass ratio of the host material to the guest material was 98:2, a hole blocking layer was formed by vacuum depositing compound HB01 on the light-emitting layer at a thickness of 5 nm, an electron transport layer was formed by vacuum depositing compound ET01 and compound LiQ (mass ratio of compound ET01 to compound LiQ was 1:1) on the hole blocking layer at a thickness of 30 nm, an electron injection layer was formed by vacuum depositing Yb on the electron transport layer at a thickness of 1 nm, a cathode was formed by depositing Mg and Ag (mass ratio of Mg to Ag was 1:9) on the electron injection layer at a thickness of 15 nm, and a cover layer was formed by depositing compound CP01 on the cathode at a thickness of 50 nm. Finally, the substrate on which the deposition was completed was encapsulated, a cleaning cover plate was coated with UV glue using a gluing device, the coated cover plate was moved to a pressing section, the substrate on which the deposition was completed was placed on the upper end of the cover plate, and the substrate and the cover plate were laminated under the action of a laminating device, and the UV glue was cured by light irradiation, thereby preparing a top-emission organic electroluminescent device. The device structure is shown in Figure 1 .

[0175] In addition to the host and guest materials of the light-emitting layer, the molecular structures of the materials of the other layers are as follows:

[0176]

[0177] Device Example 2-20

[0178] The compounds described in other examples in Table 2 were used to prepare organic electroluminescent devices by the above method. Specifically, blue organic electroluminescent devices Example 2-20 were prepared by replacing C1 in Device Example 1 with the host materials shown in Table 2.

[0179] Device Comparative Example 1-10

[0180] The compound described in the comparative example of Table 2 was made into an organic electroluminescent device by the above method, specifically, the blue light organic electroluminescent device comparative examples 1-10 were made by replacing the host material shown in the comparative example of Table 2 with C1 in device example 1.

[0181] The OLED device described above was tested by standard methods. To this end, the driving voltage, luminous efficiency of the organic electroluminescent device were determined at a current density of J = 10 mA / cm 2 The LT97 indicates that the luminous intensity of the prepared blue light device decreases to 97% of its initial value L0 after time LT97 when working at J = 20 mA / cm 2

[0182] The test instruments and methods for testing the performance of the above-mentioned example, comparative example OLED device are as follows:

[0183] The luminous efficiency C.E (cd / A) and color coordinates (CIEy) were tested using a spectral scanner PhotoResearch PR-635;

[0184] Current density and turn-on voltage: tested using a digital source meter Keithley 2400;

[0185] The luminous efficiency of the blue light device is greatly affected by the chromaticity, and the industry generally uses BI value as the basis for the efficiency of the blue light device, BI (Blue index) is obtained by dividing the luminous efficiency C.E (cd / A) by the color coordinates (CIEy);

[0186] Lifetime test: silicon photovoltaic OLED device lifetime test system was used.

[0187] The performance detection results of the above-mentioned device are shown in Table 2.

[0188] Table 2 Blue light device performance test results

[0189]

[0190] ​From the above device results, it can be seen that the test life of the material of the application on the device reaches a level basically equivalent to that of device comparative example 1, and is obviously superior to that of device comparative examples 2-8, because the aryl substituents (i.e. Ar2 and Ar3) are introduced at two specific positions in the application, forming a special molecular structure, taking C3 as an example, on the one hand, the carbon-hydrogen bond of the naphthalene fragment of the relatively weak naphthalene-benzofuran is changed to a more stable carbon-carbon bond after being substituted by aryl, and on the other hand, the special spatial stereostructure can improve the transport of carriers, reduce the residence of polaron on a single molecule in the device, and reduce the probability of interaction between polaron, exciton, carrier and the like, thereby reducing the quenching and degradation of the host material in the process of device operation, so as to improve the device life while ensuring high efficiency; more obviously, as shown in Table 1, due to the increase in molecular rigidity caused by aryl steric hindrance, the recombination energy of the carriers is reduced, and the transport of the carriers is accelerated, thereby improving the voltage performance of the application in the device. Compared with device comparative examples 9-10, although these two comparative examples have smaller recombination energy due to structural factors, they achieve a similar effect of reducing voltage as the application, but due to poor stability, they may be affected by material degradation, quenching and the like, and show relatively low efficiency and life.

[0191] Double-host device example 21

[0192] Similar to the preparation method of device example 1, the difference is that when preparing the light-emitting layer, a mixture of the compound C3 provided by the application, the compound BHB01 and the compound BD01 is vacuum deposited to form a light-emitting layer with a thickness of 20 nm, wherein BHB01 is used as the first host material, compound C3 is used as the second host material, and BD01 is used as the guest material, and the mass ratio of the three materials is 58:40:2 in turn; the rest is the same as the preparation method of device example 1.

[0193] Double-host device comparative example 11

[0194] Similar to the preparation method of device example 1, the difference is that when preparing the light-emitting layer, a mixture of the compound DB10 provided by the application, the compound BHB01 and the compound BD01 is vacuum deposited to form a light-emitting layer with a thickness of 20 nm, wherein BHB01 is used as the first host material, compound DB10 is used as the second host material, and BD01 is used as the guest material, and the mass ratio of the three materials is 58:40:2 in turn; the rest is the same as the preparation method of device example 1.

[0195] Other molecular structural formulas that can be used in double-host devices are as follows:

[0196]

[0197] The OLED devices described above are tested by standard methods. For this purpose, the OLED devices are tested in a glove box under nitrogen at J = 10 mA / cm2 the driving voltage, luminous efficiency of the organic electroluminescent device are determined, LT97 refers to the luminous brightness of the prepared blue light device is reduced to 97% of its initial value L0 after time LT97 when J = 20 mA / cm 2

[0198] The test instrument and method for testing the performance of the above-mentioned example, comparative example OLED device are as follows:

[0199] The luminous efficiency C.E (cd / A) and color coordinates (CIEy) are tested using a spectral scanner PhotoResearch PR-635;

[0200] Current density and turn-on voltage: tested using a digital source meter Keithley 2400;

[0201] The luminous efficiency of the blue light device is greatly affected by the chromaticity, and the industry generally uses BI value as the basis for the efficiency of the blue light device, BI (Blue index) is obtained by dividing the luminous efficiency C.E (cd / A) by the color coordinates (CIEy);

[0202] Lifetime test: a silicon photovoltaic OLED device lifetime test system is used.

[0203] The performance detection results of the above-mentioned device are listed in Table 3.

[0204] Table 3

[0205]

[0206] From the above Table 3 data, it can be seen that the material of the present application can also be used in double host devices, and by combining with different transmission characteristics of the condensed ring type host, the carrier recombination probability can be improved, and thus the luminous efficiency of the device can be significantly improved; DB10 also uses a double phenyl substitution scheme, and due to the small difference in hole and electron recombination energy, the transmission characteristics of the two carriers are not significantly different, and after combining with the condensed ring type host, the carrier recombination is not significantly improved, and the efficiency is not significantly improved.

[0207] Double light-emitting layer device example 22

[0208] ​In a similar manner to the preparation of device example 1, except that the light-emitting layer is prepared by vacuum depositing a mixture of compound BHA01 and compound BD01 to form a first light-emitting layer with a thickness of 5 nm, wherein compound BHA01 is used as the first host material and compound BD01 is used as the guest material, and the mass ratio of compound BHA01 and compound BD01 is 97:3; and vacuum depositing a mixture of compound C3 and compound BD01 to form a second light-emitting layer with a thickness of 15 nm on the first light-emitting layer, wherein compound C3 is used as the second host material and compound BD01 is used as the guest material, and the mass ratio of compound C3 and compound BD01 is 98:2; the first light-emitting layer is adjacent to the light-emitting auxiliary layer, and the second light-emitting layer is adjacent to the hole blocking layer, and the rest is the same as the preparation method of example 1. The device structure is shown in Figure 5 .

[0209] Double-host device comparative example 12

[0210] In a similar manner to the preparation of device example 1, except that the light-emitting layer is prepared by vacuum depositing a mixture of compound BHA01 and compound BD01 to form a first light-emitting layer with a thickness of 5 nm, wherein compound BHA01 is used as the first host material and compound BD01 is used as the guest material, and the mass ratio of compound BHA01 and compound BD01 is 97:3; and vacuum depositing a mixture of compound DB10 and compound BD01 to form a second light-emitting layer with a thickness of 15 nm on the first light-emitting layer, wherein compound DB10 is used as the second host material and compound BD01 is used as the guest material, and the mass ratio of compound DB10 and compound BD01 is 98:2; the first light-emitting layer is adjacent to the light-emitting auxiliary layer, and the second light-emitting layer is adjacent to the hole blocking layer, and the rest is the same as the preparation method of example 1.

[0211] The other molecular structures used in the double light-emitting layer device are as follows:

[0212]

[0213] The OLED devices described above are tested by standard methods. For this purpose, the driving voltage, luminous efficiency, LT97 of the organic electroluminescent device is determined at a current density of J = 10 mA / cm 2 . 2 LT97 is the time after which the luminous intensity of the prepared blue light device decreases to 97% of its initial value L0 when working at J = 20 mA / cm 2 .

[0214] The test instruments and methods for testing the performance of the above-mentioned example, comparative example OLED devices are as follows:

[0215] The luminous efficiency C.E (cd / A) and the color coordinate (CIEy) are tested by using a spectral scanner PhotoResearch PR-635;

[0216] The current density and the turn-on voltage are tested by using a digital source table Keithley 2400;

[0217] The luminous efficiency of the blue light device is greatly affected by the chromaticity, and the industry generally adopts the BI value as the basis for the efficiency of the blue light device, and the BI (Blue index) is obtained by dividing the luminous efficiency C.E (cd / A) by the color coordinate (CIEy);

[0218] The lifetime test is performed by using a silicon photoelectric OLED device lifetime test system.

[0219] The performance test results of the above device are listed in Table 4.

[0220] Table 4

[0221]

[0222] It can be seen from the above device that the material of the present application can also be used in a double light-emitting layer device, the first light-emitting layer in the double light-emitting layer undertakes carrier recombination, and the second light-emitting layer undertakes triplet-triplet fusion (TTF), thereby improving the luminous efficiency; the structure of the present application is unique due to the molecular structure, such as Figure 2 The substituted phenyl group of the molecular conformation of C3 in the middle has a certain overlap with the anthracene nucleus, which is beneficial to the TTF process, and further significantly improves the luminous efficiency.

[0223] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present application still fall within the protection scope of the present application.

Claims

1. An organic electroluminescent compound, characterized by The organic electroluminescent compound is selected from one of the following structures: I； wherein, Ar1 is selected from any one of substituted or unsubstituted phenyl, biphenyl, naphthyl, phenanthryl, pyrenyl, dimethylfluorenyl, spirofluorenyl, when Ar1 is substituted, the substituent is selected from deuterium or phenyl; Ar4 is selected from one of the following structures of formula II-1 to II-4: II-1, II-2, II-3, II-4; Ar2, Ar3 are each independently selected from phenyl; D represents deuterium, and represents a bonding site with anthracene in formula I; n is selected from 0 or 8, n2, n4, n5 are each independently selected from 0 or 6, n3 is selected from 0 or 3, and n6 is selected from 0 or 4.

2. The organic electroluminescence compound according to claim 1, wherein The Ar1 is selected from phenyl.

3. The organic electroluminescence compound according to claim 1, wherein The organic electroluminescent compound is selected from one of the following structures: 。 4. An organic electroluminescent device, characterized by comprising The organic electroluminescent compound is selected from one of the following structures:

5. The organic electroluminescent device according to claim 4, characterized in that The organic electroluminescent compound is selected from one of the following structures:

6. The organic electroluminescent device according to claim 4, wherein The organic electroluminescent compound is selected from one of the following structures: III; Ar5 is selected from any one of aryl with carbon number of 6 to 30, phenyl-substituted aryl with carbon number of 6 to 30, condensed ring aryl with carbon number of 10 to 30, phenyl-substituted condensed ring aryl with carbon number of 10 to 30; Ar6 is selected from any one of aryl with carbon number of 6 to 30, phenyl-substituted aryl with carbon number of 6 to 30, condensed ring aryl with carbon number of 10 to 30, phenyl-substituted condensed ring aryl with carbon number of 10 to 30, or 2-dibenzofuran.

7. The organic electroluminescent device according to claim 4, wherein The organic electroluminescent compound is selected from one of the following structures: IV; Ar7 is selected from any one of H, aryl with carbon number of 6 to 30, condensed ring aryl with carbon number of 10 to 30; Ar8 is selected from any one of H, aryl with carbon number of 6 to 30, condensed ring aryl with carbon number of 10 to 30; L is selected from one of phenyl and biphenyl.

Images