Luminescent auxiliary material as well as preparation method and application thereof

Abstract

The invention provides a light-emitting auxiliary material as well as a preparation method and application thereof, and belongs to the field of organic electroluminescent materials, the structural general formula of the light-emitting auxiliary material is a chemical formula I. An organic electroluminescent device using the light-emitting auxiliary material provided by the invention has high light-emitting efficiency under the condition of keeping relatively low driving voltage. The material has excellent thermal stability, high luminous efficiency and long service life.

Description

Technical Field

[0001] The invention belongs to the field of organic electroluminescent materials and relates to a luminescent auxiliary material and a preparation method and application thereof. Background Art

[0002] The organic electroluminescent device converts electrical energy into light by applying power to an organic electroluminescent material, and generally includes an anode, a cathode, and an organic layer formed between the two electrodes.

[0003] In order to solve the problems of lifespan and efficiency, a luminescent auxiliary layer is usually added between the hole transport layer and the light-emitting layer. However, the materials used as the luminescent auxiliary layer (second hole transport layer material) are currently limited. Most of these materials use a fluorene-based structure. The chemical structure of fluorene is characterized by fixing two benzene rings on a plane through methylene groups. The structure has stronger rigidity, better thermal stability, a larger conjugated absorption wavelength, and a more obvious electroluminescence phenomenon. They have a higher hole mobility and a higher energy barrier to prevent the excitons after recombination from expanding to the transport layer. The appropriate HOMO value reduces the transmission barrier of holes from the transport layer to the light-emitting layer. However, the performance of the existing compounds containing fluorene groups as luminescent auxiliary layer materials needs to be further improved. In particular, the lifespan and luminescence efficiency of the device are not significantly improved. Therefore, the development of a luminescent auxiliary material with high luminescence efficiency, long service life, and low driving voltage is a goal that technicians in this field need to study now. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a luminescent auxiliary material and a preparation method and application thereof. The organic electroluminescent device using the luminescent auxiliary material of the present invention has excellent thermal stability, high luminescent efficiency and long service life while maintaining a low driving voltage.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In one aspect, the present invention provides a luminescence auxiliary material, the general structural formula of the luminescence auxiliary material is Chemical Formula I:

[0007]

[0008] Ar is selected from phenyl, and the dotted line indicates that it can be fused to any position of the benzene ring of the fluorene;

[0009] Ar 1 ,Ar 2 Each is independently selected from any one or a combination of at least two of the following groups:

[0010]

[0011] The position of * is the attachment site of the group;

[0012] R 1 -R 13 Each is independently selected from hydrogen, deuterium, unsubstituted C1-C6 alkyl, and C1-C6 alkyl fully or partially substituted by deuterium;

[0013] n 1 、n 8 Each is independently selected from 0, 1, 2, 3, 4, 5;

[0014] n 2 、n 5 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9;

[0015] n 3 、n 11 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13;

[0016] n 4 、n 6 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7;

[0017] n 7 、n 13 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8;

[0018] n 9 Independently selected from 0, 1, 2, 3, 4;

[0019] n 10 、n 12 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

[0020] A benzofluorene group is introduced into the structure of the luminescent auxiliary material of the present invention to enhance the conjugation of the overall molecular structure to improve the hole migration ability of the compound, and an adamantyl group with a rigid electron-rich group is connected to the 9th position of the fluorene to balance the overall molecular weight of the molecule and adjust the molecular stacking, and then a triarylamine group is further connected to make the material have a higher hole transfer efficiency.

[0021] Further preferably, the luminescence auxiliary material is selected from the following compounds having any one of the structures of Chemical Formula I-A to Chemical Formula I-C:

[0022] .

[0023] In the above technical solution, it is further preferred that the light-emitting auxiliary material is any one of the following structures, but not limited thereto:

[0024] .

[0025] The luminescence auxiliary material of the present invention can be prepared by a synthesis method known to those skilled in the art. Alternatively, the following reaction process is preferred for preparation.

[0026]

[0027] In the above formula, Ar, Ar 1 ,Ar 2 As defined in the above chemical formula I, Hal is independently selected from chlorine or bromine.

[0028] With respect to the complex raw materials which are not disclosed, the classical Buchwald–Hartwig coupling reaction will be adopted and applied to the present invention.

[0029] Specific preparation method:

[0030] Add raw material A (1.0 eq), raw material B (1.0-1.3 eq), toluene and sodium tert-butoxide or potassium tert-butoxide (2.0-4.0 eq) into a three-necked flask, add tri(dibenzylideneacetone)dipalladium (0.01-0.03 eq) and tri-tert-butylphosphine (0.02-0.15 eq) under nitrogen, raise the temperature to 100-120° C. and stir to react for 1-15 hours; detect the reaction by thin layer chromatography, after confirming that the reaction is complete, add water and dichloromethane for extraction and separation, combine the organic phases and concentrate, and purify by column chromatography using a mixed solution of dichloromethane and petroleum ether (volume ratio of 1:4-1:10) to obtain chemical formula I.

[0031] On the other hand, the present invention provides a red organic light-emitting device, comprising a first electrode, a second electrode and at least one organic layer disposed between the first electrode and the second electrode, wherein the organic layer comprises the light-emitting auxiliary material as described above.

[0032] Preferably, the organic layer includes a light-emitting auxiliary layer, and the light-emitting auxiliary layer contains the light-emitting auxiliary material as described above.

[0033] The organic layer of the red organic light-emitting device of the present invention may be formed as a single-layer structure, but may also be formed as a multilayer structure having two or more organic material layers. For example, the organic light-emitting device of the present invention may have a structure including a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting auxiliary layer, a light-emitting layer, an electron transport layer, an electron injection layer, a hole blocking layer, etc. as an organic layer. However, the structure of the organic light-emitting device is not limited thereto, and may include a smaller number of organic material layers or a larger number of organic layers.

[0034] Except that the light-emitting auxiliary layer disclosed herein includes the compound represented by Chemical Formula I, there is no special limitation on the materials of other layers in the OLED device.

[0035] In another aspect, the present invention provides an organic light-emitting device, comprising the organic electroluminescent device as described above.

[0036] The organic light-emitting device described in the present invention includes but is not limited to flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for internal or external lighting and / or signals, head-up displays, fully transparent or partially transparent displays, flexible displays, laser printers, telephones, mobile phones, photo albums, personal digital assistants (PDAs), wearable devices, laptops, digital cameras, camcorders, viewfinders, microdisplays, three-dimensional displays, virtual reality or augmented reality displays, vehicles, video walls including multiple displays tiled together, theater or stadium screens, light therapy devices and signs, etc.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The luminescent auxiliary material of the present invention is a benzofluorene group and a 9-position adamantane group connected to the fluorene as a parent core, and the unannulated side of the fluorene is connected to a triarylamine group. As a luminescent auxiliary layer material of a device, the device can have excellent luminescent efficiency and long service life, while maintaining a low driving voltage.

[0039] The fluorene group itself has good thermal stability, a larger conjugated absorption wavelength, and obvious electroluminescence. Further fusing a benzene ring, the resulting benzofluorene structure is more rigid and thus has more excellent properties, making the material better in film forming and stability during the evaporation process, thereby significantly improving the life of the device. The benzofluorene group has strong conjugation, which can improve the hole migration ability of the compound.

[0040] In addition, further connecting an electron-rich group, adamantyl, to the 9th position of fluorene can further increase the electron density of the system through the hyperconjugation effect, thereby further improving the hole migration ability of the compound. Since the adamantyl group has a large steric hindrance, it can reduce the intermolecular stacking effect and the molecular symmetry of the compound, thereby improving the morphology of the compound during film formation, increasing the evaporation temperature of the compound, making it less likely to crack during high-temperature evaporation, and having good thermal stability, thereby increasing the service life of the device. Moreover, the adamantyl group with large steric hindrance is located at the 9th position of fluorene. As one of the branches of the triarylamine, it can adjust the bonding angle and conjugation degree between the branches, thereby adjusting the HOMO energy level of the compound, so that the compound has a stronger hole migration ability, and can make the material better match other layers in the device.

[0041] The lone pair of electrons on the nitrogen atom of triarylamine is transferred by transition under the action of an external electric field, so the molecule generates holes and has good hole transmission ability. Further connection with other groups is to add geometric structure to the non-planar molecular structure, which is more conducive to the transmission of holes and obtains better hole transmission efficiency. Connecting triarylamine N to the 1st position of fluorene reduces the planarity of the molecular structure and increases the twist angle between the benzofluorene plane and the aromatic amine plane, so that the molecules can be more densely stacked, further improving the thermal stability of the material and enhancing the service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound 1 provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0044] In addition, it should be noted that the numerical values ​​given in the following examples are as accurate as possible, but those skilled in the art understand that due to unavoidable measurement errors and experimental operation problems, each number should be understood as an approximate number rather than an absolutely accurate value.

[0045] Example 1

[0046]

[0047] Raw material A-1 (1.0 eq, CAS number: 2566427-70-9), raw material B-1 (1.1 eq, CAS number: 1309601-64-6), toluene and sodium tert-butoxide (2.0 eq) were added into a three-necked flask, and tri(dibenzylideneacetone)dipalladium (0.02 eq) and tri-tert-butylphosphine (0.05 eq) were added under nitrogen. The temperature was raised to 120°C and stirred for reaction for 12 h. The reaction was detected by thin layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction and separation. The organic phases were combined and concentrated, and a mixed solution of dichloromethane and petroleum ether (volume ratio of 1:4) was used for purification by column chromatography to obtain compound 1 (yield: 81.3%).

[0048] The obtained compound 1 was tested and analyzed, and the results were as follows:

[0049] HPLC purity: >99.8%.

[0050] Mass spectrometry test: The model is Waters XEVO TQD mass spectrometer, using ESI source.

[0051] Test value MS (ESI, m / Z): [M+H] + =655.52.

[0052] Elemental Analysis:

[0053] Calculated values: C, 91.56; H, 6.30; N, 2.14;

[0054] The test values ​​are: C, 91.26; H, 6.46; N, 2.31.

[0055] The H NMR spectrum of compound 1 is as follows Figure 1 shown.

[0056] Example 2

[0057]

[0058] Raw material A-107 (1.0 eq, CAS number: 2716192-99-1), raw material B-107 (1.1 eq, CAS number: 897671-69-1), toluene and potassium tert-butoxide (2.0 eq) were added into a three-necked flask, and tri(dibenzylideneacetone)dipalladium (0.01 eq) and tri-tert-butylphosphine (0.05 eq) were added under nitrogen. The temperature was raised to 110°C and stirred for reaction for 13 h. The reaction was detected by thin layer chromatography. After the reaction was completed, water and dichloromethane were added for extraction and separation. The organic phases were combined and concentrated, and a mixed solution of dichloromethane and petroleum ether (volume ratio of 1:4) was used for purification by column chromatography to obtain compound 107 (yield: 80.6%).

[0059] The obtained compound 107 was tested and analyzed, and the results were as follows:

[0060] HPLC purity: >99.7%.

[0061] Mass spectrometry test: The model is Waters XEVO TQD mass spectrometer, using ESI source.

[0062] Test value MS (ESI, m / Z): [M+H] + =695.55.

[0063] Elemental Analysis:

[0064] Calculated values: C, 91.47; H, 6.52; N, 2.01;

[0065] Test values ​​are: C, 91.16; H, 6.69; N, 2.17.

[0066] In addition, it should be noted that other compounds of the present invention can be obtained by referring to the synthesis methods of the above-mentioned embodiments, so they are not listed one by one here.

[0067] Device Example 1: Preparation of red organic electroluminescent device

[0068] The structure of the prepared OLED device is: ITO anode / HIL / HTL / Prime / EML / HBL / ETL / EIL / cathode / CPL.

[0069] a. ITO anode: The ITO (indium tin oxide)-Ag-ITO (indium tin oxide) glass substrate with a coating thickness of 1500Å was cleaned in distilled water for 3 times, ultrasonically washed for 40 minutes, and then repeatedly cleaned with distilled water for 3 times, ultrasonically washed for 20 minutes. After washing, it was ultrasonically washed with methanol, acetone, and isopropanol in sequence (5 minutes each time), dried, and then transferred to a plasma cleaning machine for washing for 5 minutes. It was then sent to a vapor deposition machine, and the substrate was used as the anode, and other functional layers were deposited on it in sequence.

[0070] b. HIL (hole injection layer): Hole injection layer materials HT and P-dopant were vacuum evaporated at an evaporation rate of 1Å / s. The evaporation rate ratio of HT to P-dopant was 97:3, and the thickness was 10nm.

[0071] c. HTL (hole transport layer): 130nm HT was vacuum-deposited on the hole injection layer at a deposition rate of 1.5Å / s as the hole transport layer.

[0072] d. Prime (luminescence auxiliary layer): 90 nm of the compound 1 provided in the above embodiment was vacuum-deposited on the hole transport layer at a deposition rate of 1.0 Å / s as a luminescence auxiliary layer.

[0073] e. EML (light-emitting layer): Then, on the above-mentioned light-emitting auxiliary layer, the host material (Host) and the dopant material (Dopant) with a thickness of 40nm are vacuum evaporated at a deposition rate of 1Å / s as the light-emitting layer, wherein the deposition rate ratio of Host and Dopant is 97:3.

[0074] f. HBL (hole blocking layer): A hole blocking layer HB with a thickness of 5 nm was vacuum-deposited at a deposition rate of 0.5 Å / s.

[0075] g. ETL (electron transport layer): ET and Liq with a thickness of 30 nm were vacuum evaporated at an evaporation rate of 1Å / s as the electron transport layer, where the evaporation rate ratio of ET to Liq was 50:50.

[0076] h. EIL (electron injection layer): 1 nm of Yb film was evaporated at a deposition rate of 0.5 Å / s to form an electron injection layer.

[0077] i. Cathode: 13 nm of magnesium and silver were evaporated at an evaporation rate ratio of 1 Å / s, and the evaporation rate ratio was 1:9 to obtain an OLED device.

[0078] j. CPL (light extraction layer): CPL with a thickness of 65 nm is vacuum-deposited on the cathode at a deposition rate of 1Å / s as a light extraction layer.

[0079] k. Then the vapor-deposited substrate is packaged. First, the cleaned cover is coated with UV glue using glue coating equipment, and then the coated cover is moved to the pressing section, the vapor-deposited substrate is placed on the upper end of the cover, and finally the substrate and cover are bonded by bonding equipment, and the UV glue is cured by light.

[0080] The structures of HT, P-dopant, Host, Dopant, HB, ET, and CPL used in the device embodiment 1 are as follows:

[0081]

[0082] Referring to the method provided in the above device embodiment 1, the corresponding compounds in Table 1 were selected to replace compound 1, and the luminescent auxiliary layer was evaporated to prepare the corresponding organic electroluminescent devices, which were respectively recorded as device embodiments 2 to 31.

[0083] Device Comparison Examples 1-8:

[0084] This comparative example provides an organic electroluminescent device. The only difference between the preparation method of the organic electroluminescent device and the device embodiment 1 is that the organic electroluminescent device uses the existing comparative compound ah to replace the compound 1 in the device embodiment 1 as the light-emitting auxiliary material for evaporation. The chemical structure of the comparative compound ah is as follows:

[0085]

[0086] The driving voltage, luminous efficiency and life of the organic electroluminescent devices obtained in the above device embodiments 1 to 31 and device comparative examples 1 to 8 were characterized at a brightness of 6000 (nits). The test results are as follows

[0087] Table 1.

[0088] Table 1

[0089]

[0090]

[0091] It can be seen from Table 1 that, compared with the organic electroluminescent device prepared using the luminescent auxiliary material provided by the present invention and the organic electroluminescent device prepared using the comparative example compound, the luminescent efficiency and service life of the device are effectively improved while maintaining a lower driving voltage.

[0092]

[0093] Comparative compounds a, b and compounds 61, 105 are parallel comparative examples, respectively, the difference being that the parent core structure in comparative compounds a, b is fluorene, while the parent core structure in compounds 61, 105 of the present invention is a benzofluorene structure, forming a larger π-conjugated system, and this extended conjugation effect helps to reduce the band gap, thereby achieving emission of longer wavelengths (such as red light). And due to the introduction of additional benzene rings, the range of electron delocalization is expanded, making the charge distribution within the molecule more uniform, which is beneficial to improving carrier mobility. The larger π-conjugated system also increases the π-π interaction between molecules, allowing the molecules to be more densely packed, enhancing the overall rigidity of the molecules, thereby improving the thermal stability and chemical stability of the material, allowing the material to maintain structural stability during high-temperature evaporation, thereby enhancing the service life of the device. It can also better adjust the energy level structure, promote the effective transmission of holes and electrons, and help reduce the probability of non-radiative transitions and improve luminous efficiency.

[0094]

[0095] Comparative compounds c, d and compounds 80, 103 are parallel comparative examples, respectively, the difference being that there are no other substituents on the adamantane group and the benzofluorene group in the parent core structure of compounds 80 and 103 of the present invention, while a phenyl group is connected to the adamantane in comparative compound c, and a phenyl group is connected to the ring side of the benzofluorene group in comparative compound d. The introduction of the phenyl group will increase the steric hindrance of the molecule, affect the close packing between molecules, and cause the molecular arrangement to be inferior to that of the unsubstituted compound, which will affect the overall performance of the material. The phenyl group in compound c does not have the effect of extending the conjugated system. Although the phenyl group in compound d can extend the π-conjugated system, the excessive steric hindrance may cause the π-π interaction between molecules to be not strong enough, thereby affecting the effective transmission of carriers.

[0096]

[0097] The substitution position of the fluorenyl group in the compound is defined as follows: The comparison compounds e, f, g and compounds 9, 134, 83 are parallel comparative examples, respectively. The difference between them is that the positions where the triarylamine groups in the comparison compounds e, f, g are connected to benzofluorene are 2, 3, and 4, respectively, while the triarylamine groups in the compounds 9, 134, 83 of the present invention are connected to the 1 position of benzofluorene, so that the molecules can be stacked more closely, the π-π interaction between the molecules is enhanced, the thermal stability of the material is improved, and the service life of the device is thereby enhanced.

[0098]

[0099] Comparative compound h and compound 34 are parallel comparative examples, the difference between them is that in comparative compound h, there is a terphenyl group between the triarylamine group and the benzofluorene group, while in compound 34 of the present invention, the triarylamine group is directly connected to the benzofluorene group, the molecular structure is more compact, and a more closely arranged structure is formed, which improves the thermal stability of the material, makes the material less likely to crack under high-temperature evaporation, and thereby enhances the service life of the device.

[0100] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the luminescent auxiliary material and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A luminescent auxiliary material, characterized in that: The general structural formula of the luminescence auxiliary material is Chemical Formula I: Ar is selected from phenyl, and the dotted line indicates that it can be fused to any position of the benzene ring of the fluorene; Ar1 and Ar2 are each independently selected from any one or a combination of at least two of the following groups: The position of * is the connection site of the group; R1-R 13 Each is independently selected from hydrogen, deuterium, unsubstituted C1-C6 alkyl, and C1-C6 alkyl fully or partially substituted by deuterium; n1 and n8 are each independently selected from 0, 1, 2, 3, 4, and 5; n2 and n5 are each independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9; n3、n 11 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13; n4 and n6 are each independently selected from 0, 1, 2, 3, 4, 5, 6, 7; n7、n 13 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8; n9 is independently selected from 0, 1, 2, 3, 4; n 10 、n 12 Each is independently selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

2. The luminescence auxiliary material according to claim 1, characterized in that: The luminescence auxiliary material is selected from the following compounds having any one of the structures of Chemical Formula I-A to Chemical Formula I-C: 。 3. The luminescence auxiliary material according to claim 1, characterized in that: The light-emitting auxiliary material is any one of the following structures: 。 4. A red organic light emitting device, characterized in that: The red organic light emitting device comprises a first electrode, a second electrode and at least one organic layer disposed between the first electrode and the second electrode, wherein the organic layer comprises the light emitting auxiliary material according to any one of claims 1 to 3.

5. The red organic light emitting device according to claim 4, characterized in that: The organic layer includes a luminescence-assisting layer, and the luminescence-assisting layer includes the luminescence-assisting material according to any one of claims 1 to 3.

6. The red organic light emitting device according to claim 4, characterized in that: The organic layer further includes any one of a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, an electron transport layer, an electron injection layer or a hole blocking layer, or a combination of at least two of them.

Images