Organic compounds containing benzoxazole groups and spirocyclic structures and their use as electron transport materials

Abstract

The present disclosure relates to an organic compound including a benzoxazole group and a spirocyclic structure shown in Formula I and its use as an electron transport material. In the disclosed compound structure, the benzoxazole group has a higher electron affinity, so that it has excellent electron conduction characteristics, and the benzoxazole group has a lower LUMO energy level, and the electrons can be effectively transmitted to the light-emitting layer, so that the recombination probability of electrons and holes in the light-emitting layer is increased, and the device shows a high luminous efficiency; the spirocyclic structure has an orthogonal spatial stereo configuration, and the van der Waals force between molecules can be reduced, which is beneficial to prevent the crystallization of the electron transport material, and the structure is made more rigid at the same time, so that the compound has a higher glass transition temperature, and the film forming property and thermal stability of the compound are improved. Therefore, the disclosed compound is used as an electron transport material for an organic electroluminescent device, and the device can be made to have a lower voltage and good luminous efficiency and a longer service life.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescent materials, and specifically relates to an organic compound containing a benzoxazole group and a spiro ring structure, a preparation method thereof, use thereof as an electron transport material, and an organic electroluminescent device and a display device containing the same. Background Art

[0002] Organic light-emitting diodes (OLED) refer to the phenomenon that organic electroluminescent materials emit light under electrical excitation. Compared with traditional LCD displays, as the latest display technology, OLED has the advantages of self-luminescence, wide viewing angle, low power consumption, full black display, full color, etc., and has a wide range of commercial application potential. In recent years, organic electroluminescent materials have also made remarkable progress. After the commercialization of OLED flexible devices, related scientific research institutions and enterprises are carrying out work in this area. At present, great results have been achieved in the research of organic electroluminescent materials, but there are still some problems that need to be solved in the process of commercialization of OLED.

[0003] The efficiency and lifespan of currently disclosed electron transport materials need to be improved, so developing stable and efficient electron transport materials, improving device efficiency, and extending device life has very important practical application value. Summary of the invention

[0004] The inventor believes that during the operation of the organic electroluminescent device, under the driving action of the electric field, holes are injected from the anode and gradually transferred to the EML via the HOMO energy level of the functional layers such as the HIL and HTL. At the same time, electrons are injected from the cathode and gradually transferred to the EML via the LUMO energy level of the functional layers such as the EIL and ETL. Holes and electrons recombine in the EML to generate excitons. When the excitons return to the ground state from the excited state, the energy is emitted in the form of light. Therefore, how to balance the injection and recombination of holes and electrons is an important research content to enable OLEDs to have excellent luminous efficiency.

[0005] The inventors also believe that organic electroluminescent devices are carrier injection devices, and the recombination efficiency of carriers affects the efficiency of the device. In order to achieve effective recombination of carriers in the light-emitting layer and prevent excitons from diffusing to the surrounding functional layers, the functional layer adjacent to the light-emitting layer is required to have a higher T1 energy level. Therefore, it is particularly important to develop electron transport materials with a suitable T1 energy level to effectively improve the efficiency of the device.

[0006] The inventors also believe that in OLED materials, since most organic electroluminescent materials transfer holes faster than electrons, it is easy to cause an imbalance in the number of electrons and holes in the light-emitting layer, which results in a relatively low efficiency of the device. Therefore, it is very important to develop electron transport materials with high electron mobility.

[0007] In addition, the inventors also believe that since OLED devices generate Joule heat when voltage is applied, the organic material is prone to crystallization, affecting the life and efficiency of the device. Therefore, it is also necessary to develop stable and efficient organic electroluminescent materials.

[0008] Moreover, the inventors also believe that the electron transport material is an electron-deficient system in molecular structure and has a strong electronic group, which makes the electron transport material have a certain polarity. Compared with the hole transport material, the electron transport material is easier to crystallize, which will make the electron transport material have poor film-forming ability due to crystallization during the film-forming process, and even cause the material to block holes, which is not conducive to the mass production of OLED devices. Therefore, in the process of developing and designing electron transport materials, the crystallization performance of the material is also an important measurement indicator.

[0009] In short, the inventors believe that excellent electron transport materials should have the following characteristics:

[0010] 1. Appropriate HOMO and LUMO energy levels. A lower LUMO energy level is conducive to the injection of electrons from the cathode and reduces the turn-on voltage of the device. A lower HOMO energy level can more effectively confine hole carriers in the light-emitting layer, thereby improving the recombination efficiency of holes and electrons.

[0011] 2. Higher triplet energy level. Since triplet excitons have a longer lifetime and a larger diffusion distance, the higher triplet energy level of the electron transport material can prevent the triplet excitons from diffusing from the light-emitting layer to the electron transport layer, thus improving the efficiency of the device.

[0012] 3. Higher electron mobility. Mobility will affect the driving voltage of the device. Low electron mobility will increase the driving voltage of the device, thereby reducing the power efficiency of the device. In addition, if the driving voltage of the device is too high, it will also have a significant impact on the stability of the device.

[0013] 4. It can form a good amorphous film to avoid the performance degradation caused by crystallization.

[0014] Based on the above viewpoints, the present invention designs an electron transport material comprising a benzoxazole group and a spirocyclic group, and uses it in an organic electroluminescent device, showing good electroluminescent performance. Without being limited to any theory, the inventor believes that the compound disclosed in the present invention belongs to a typical electron-deficient system, and the selected azine group has a suitable LUMO energy level, which can effectively reduce the injection barrier between the electron transport layer and the adjacent functional layer, and improve the electron injection ability of the molecule; the rigid three-dimensional structure of the spirocyclic structure can effectively inhibit the crystallization of the thin film, therefore, the electron transport material developed in the present invention is used in an organic electroluminescent device, which can make the device have a lower voltage and good luminous efficiency and a longer service life.

[0015] One embodiment of the present disclosure provides a compound of the following formula I:

[0016]

[0017] In Formula I,

[0018] Ar1 is represented by formula II, Ar2 is represented by formula III, and Ar1 and Ar2 are not simultaneously connected to the same benzene ring;

[0019] X1 is selected from a single bond, O, S, Se, C=O, S(=O)2, CR5R6, SiR5R6, NR5, PR5, P(=O)R5,

[0020] One of BR5;

[0021] X2 is selected from direct disconnection, or single bond, O, S, Se, C=O, S(=O)2, CR7R8, SiR7R8, NR7, PR7,

[0022] One of P(=O)R7 and BR7;

[0023] A1 and A2 are each independently selected from a substituted or unsubstituted C5-C30 aromatic ring, a substituted or unsubstituted 5-30 membered heteroaromatic ring;

[0024] L1 and L2 are each independently selected from a single bond, a substituted or unsubstituted C6-C30 arylene group; a substituted or unsubstituted 5-30 membered heteroarylene group;

[0025] Y1, Y2, and Y3 are each independently C or N, and at least one is N;

[0026] Z1 is O or S;

[0027] R1, R2, R3, R4, R7 and R8 each independently represent one or more substituents, for example, one, two or three substituents, each independently selected from hydrogen, deuterium, halogen, cyano, nitro, hydroxyl, substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted C3-C18 cycloalkyl, substituted or unsubstituted C1-C18 alkoxy, substituted or unsubstituted C6-C18 aryl, substituted or unsubstituted 5-18 membered heteroaryl, substituted or unsubstituted 5-18 membered heterocyclyl, or two adjacent substituents together form a 5-18 membered ring;

[0028] R5 and R6 are each independently selected from substituted or unsubstituted C1-C18 alkyl, substituted or unsubstituted C2-C18 alkenyl, substituted or unsubstituted C2-C18 alkynyl, substituted or unsubstituted C3-C18 cycloalkyl, substituted or unsubstituted C1-C18 alkoxy, substituted or unsubstituted C6-C18 aryl, substituted or unsubstituted 5-18 membered heteroaryl, substituted or unsubstituted 5-18 membered heterocyclyl, or R5 and R6 together with the atoms to which they are attached form a 5-18 membered ring.

[0029] In some embodiments, Formula II is selected from the following structures:

[0030]

[0031] In some embodiments, Formula III is selected from the following structures:

[0032]

[0033] In some embodiments, X1 is selected from a single bond, O, S, C=O, C(CH3)2.

[0034] In some embodiments, X2 is selected from direct disconnection, single bond, C(CH3)2, O, S, BR7; R7 is selected from phenyl, naphthyl; or X2 and the adjacent substituents on the A1 ring together form a benzene ring.

[0035] In some embodiments, A1 and A2 are each independently selected from a benzene ring, a naphthalene ring, a quinoline ring, a furan ring, a thiopyran ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, and a pyridazine ring.

[0036] In some embodiments, L1 is selected from a single bond, a phenylene group, a pyridylene group, and a pyrazine ring.

[0037] In some embodiments, L2 is a single bond.

[0038] In some embodiments, R1 and R2 are hydrogen, or two adjacent R1s or two adjacent R2s together form a benzene ring or a pyridine ring; or R1 adjacent to X2 and X2 together form a benzene ring.

[0039] In some embodiments, Formula I is selected from the following structures:

[0040]

[0041] wherein Ar1, L1, Ar2, X1, and X2 are as defined above, and Y4, Y5, Y6, and Y7 are each independently C or N,

[0042] Z2 and Z3 are each independently O or S.

[0043] In some embodiments, Formula I is selected from the following structures:

[0044]

[0045]

[0046]

[0047]

[0048]

[0049] One embodiment of the present disclosure also provides a method for synthesizing the compound of formula I as described above, and the method is shown in the following reaction formula 1, comprising:

[0050]

[0051] (1) Compound a reacts with compound b to obtain compound c;

[0052] (2) Compound c reacts with bis(pinacol)diboron and then reacts with compound d to obtain a compound of formula I,

[0053] The definitions of the substituents are the same as those above.

[0054] The above step (1) can be carried out in the presence of a catalyst (e.g., Pd(PPh3)4) and a base (e.g., potassium carbonate) in a mixed solvent such as tetrahydrofuran (THF) and water under the protection of an inert gas such as nitrogen or argon, but the present disclosure is not limited thereto.

[0055] The reaction of the first step of step (2) with bis(pinacolato)diboron can be carried out in the presence of a catalyst (e.g., Pd(dppf)Cl2) and a base (e.g., potassium acetate) in a solvent such as 1,4-dioxane under the protection of an inert gas such as nitrogen or argon, but the present disclosure is not limited thereto.

[0056] The second step of step (2) above with compound d can be carried out in the presence of a catalyst (e.g., Pd(PPh3)4) and a base (e.g., potassium carbonate) in a mixed solvent such as tetrahydrofuran (THF) and water under the protection of an inert gas such as nitrogen or argon, but the present disclosure is not limited thereto.

[0057] In addition, according to the structure of the compound of formula I disclosed in the present invention, those skilled in the art can design a new synthesis route with reference to the synthesis methods known in the prior art. Therefore, the synthesis method of the compound of formula I is not limited to the above method.

[0058] In the present disclosure, the description method of "each independently" should be understood in a broad sense, which can mean that in different groups, the specific options expressed by the same symbols do not affect each other, or that in the same group, the specific options expressed by the same symbols do not affect each other.

[0059] The non-positioning substituent in the present disclosure refers to a substituent connected through a single bond extending from the center of the ring system, which means that the substituent can be connected at any possible position in the ring system.

[0060] In the present disclosure, when a certain group is defined as a "single bond", it means that the groups on both sides of the group are directly connected together.

[0061] In the present disclosure, when a certain group is defined as "directly disconnected", it means that the group does not exist, and the groups on both sides of the group are not connected together at this position.

[0062] In the present disclosure, "C1-C18", "C2-C18", "C3-C18", "C6-C18", etc. before a group refers to the number of carbon atoms contained in the group. For example, a C7 aryl group can be a tolyl group, which has 7 carbon atoms.

[0063] In the present disclosure, "5-18 members" before a ring group refers to the number of ring atoms contained in the ring group. For example, a 5-membered ring refers to a ring with 5 ring atoms.

[0064] In the present disclosure, when no specific definition is otherwise provided, "hetero" means including at least one heteroatom selected from B, N, O, S, Se, Si, P, etc. in one functional group.

[0065] In the present disclosure, "alkyl" may include straight or branched alkyl. Unless otherwise specified, the alkyl may have 1 to 10 carbon atoms, and in the present disclosure, a numerical range such as "1 to 10" refers to each integer in a given range; for example, "1 to 10 carbon atoms" refers to an alkyl that may contain 1 carbon atom, 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, or 10 carbon atoms. The alkyl may also be a lower alkyl having 1 to 6 carbon atoms. In addition, the alkyl may be substituted or unsubstituted. An unsubstituted alkyl may be a "saturated alkyl group" without any double or triple bonds. Optionally, the alkyl is selected from an alkyl having 1-6 carbon atoms, including, but not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl.

[0066] In the present disclosure, "alkenyl" may include straight or branched alkenyl groups containing at least one carbon-carbon double bond. Unless otherwise specified, alkenyl groups may have 2 to 10 carbon atoms, and in the present disclosure, numerical ranges such as "2 to 10" refer to individual integers in a given range; for example, "2 to 10 carbon atoms" refers to alkenyl groups that may contain 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, or 10 carbon atoms. Alkenyl groups may also be lower alkenyl groups having 2 to 6 carbon atoms. In addition, alkenyl groups may be substituted or unsubstituted. Optionally, alkenyl groups are selected from alkenyl groups having 2 to 6 carbon atoms, including but not limited to vinyl, propene-1-yl, propene-2-yl, butenyl, pentenyl, hexenyl, etc.

[0067] In the present disclosure, "alkynyl" may include straight or branched alkynyl groups containing at least one carbon-carbon triple bond. Unless otherwise specified, the alkynyl group may have 2 to 10 carbon atoms, and in the present disclosure, a numerical range such as "2 to 10" refers to each integer in a given range; for example, "2 to 10 carbon atoms" refers to an alkynyl group that may contain 2 carbon atoms, 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, or 10 carbon atoms. The alkynyl group may also be a lower alkynyl group having 2 to 6 carbon atoms. In addition, the alkynyl group may be substituted or unsubstituted. Optionally, the alkynyl group is selected from alkynyl groups having 2-6 carbon atoms, including but not limited to ethynyl, propynyl, butynyl, pentynyl, hexynyl, etc.

[0068] In the present disclosure, cycloalkyl refers to a group derived from a saturated cyclic carbon chain structure. Unless otherwise specified, a cycloalkyl may have 3 to 10 carbon atoms. In the present disclosure, a numerical range such as "3 to 10" refers to each integer in a given range; for example, "3 to 10 carbon atoms" refers to a cycloalkyl that may contain 3 carbon atoms, 4 carbon atoms, 5 carbon atoms, 6 carbon atoms, 7 carbon atoms, 8 carbon atoms, 9 carbon atoms, 10 carbon atoms. The cycloalkyl may be substituted or unsubstituted. Alternatively, specific examples of cycloalkyl include, but are not limited to, cyclopentyl, cyclohexyl, etc.

[0069] In the present disclosure, aryl refers to an optional functional group or substituent derived from an aromatic carbocyclic ring. Aryl can be a monocyclic aryl (e.g., phenyl) or a polycyclic aryl. In other words, aryl can be a monocyclic aryl, a condensed ring aryl, two or more monocyclic aryl groups connected by carbon-carbon bond conjugation, a monocyclic aryl and a condensed ring aryl connected by carbon-carbon bond conjugation, and two or more condensed ring aryl groups connected by carbon-carbon bond conjugation. That is, unless otherwise specified, two or more aromatic groups connected by carbon-carbon bond conjugation can also be regarded as aryl of the present disclosure. Among them, condensed ring aryl can include, for example, a bicyclic condensed aryl (e.g., naphthyl), a tricyclic condensed aryl (e.g., phenanthrenyl, fluorenyl, anthracenyl), etc. Aryl does not contain heteroatoms such as B, N, O, S, P, Se, and Si. For example, in the present disclosure, biphenyl, terphenyl, etc. are aryl. Examples of aryl groups may include, but are not limited to, phenyl, naphthyl, fluorenyl, anthracenyl, phenanthrenyl, biphenyl, terphenyl, quaterphenyl, pentphenyl, benzo[9,10]phenanthrenyl, pyrenyl, benzofluoranthenyl, Unless otherwise specified, the "aryl" of the present disclosure may contain 6-30 carbon atoms. In some examples, the number of carbon atoms in the aryl may be 6-25, in other examples the number of carbon atoms in the aryl may be 6-18, and in other examples the number of carbon atoms in the aryl may be 6-13. For example, in the present disclosure, the number of carbon atoms in the aryl may be 6, 10, 12, 13, 14, 15, 18, 20, 24, 25, 30, and of course, the number of carbon atoms may also be other numbers, which are not listed here one by one. In the present disclosure, biphenyl may be understood as an aryl substituted with a phenyl group, or may be understood as an unsubstituted aryl group.

[0070] In the present disclosure, heteroaryl refers to a monovalent aromatic ring containing at least one, for example 1, 2, 3, 4 or 5 heteroatoms in the ring, and the heteroatoms can be at least one selected from B, O, N, P, Si, Se and S. The heteroaryl can be a monocyclic heteroaryl or a polycyclic heteroaryl. In other words, the heteroaryl can be a single aromatic ring system or a plurality of aromatic ring systems connected by conjugation, and any aromatic ring system is an aromatic monocyclic ring or an aromatic condensed ring. For example, the heteroaryl can include thienyl, furanyl, pyrrolyl, imidazolyl, thiazolyl, oxazolyl, oxadiazolyl, triazolyl, pyridyl, bipyridyl, pyrimidyl, triazine, acridinyl, pyridazinyl, pyrazinyl, quinolyl, quinazolinyl, quinoxalinyl, phenoxazinyl, phthalazinyl, pyridopyrimidinyl, pyridopyrazinyl, pyrazinopyrazinyl, isoquinolyl, indolyl, carbazolyl, benzoxazolyl, benzimidazolyl, benzo Thiazolyl, benzotriazolyl, benzocarbazolyl, benzothiophenyl, dibenzothiophenyl, thienothiphenyl, benzofuranyl, phenanthroline, isoxazolyl, thiadiazolyl, benzothiazolyl, phenothiazinyl, silafluorenyl, dibenzofuranyl, and N-arylcarbazolyl (such as N-phenylcarbazolyl), N-heteroarylcarbazolyl (such as N-pyridylcarbazolyl), N-alkylcarbazolyl (such as N-methylcarbazolyl), etc., but not limited thereto. Among them, thiophenyl, furanyl, phenanthroline, etc. are heteroaryl groups of a single aromatic ring system type, and N-arylcarbazolyl and N-heteroarylcarbazolyl are heteroaryl groups of a polycyclic system type connected by conjugation. Unless otherwise specified, the "heteroaryl" of the present application may contain 5-30 ring atoms. In some examples, the number of ring atoms in the heteroaryl may be 5-23, and in other examples, the number of ring atoms in the heteroaryl may be 5-19. For example, the number of ring atoms may be 5, 6, 7, 10, 11, 12, 13, 18, 19, 20, 21, 22, 23, 25 or 30. Of course, the number of ring atoms may also be other numbers, which are not listed here one by one. In the present disclosure, the substituted heteroaryl may be one or more hydrogen atoms in the heteroaryl replaced by groups such as deuterium atoms, halogen groups, cyano groups, aryl groups, heteroaryl groups, alkyl groups, cycloalkyl groups, etc. Specific examples of aryl-substituted heteroaryl groups include, but are not limited to, phenyl-substituted dibenzofuranyl, phenyl-substituted dibenzothienyl, N-phenylcarbazolyl, etc. It should be understood that the number of carbon atoms in a substituted heteroaryl group refers to the total number of carbon atoms in the heteroaryl group and the substituents on the heteroaryl group.

[0071] In the present disclosure, a heterocyclic group is a monovalent non-aromatic ring containing at least one, for example 1, 2, 3, 4 or 5 heteroatoms in the ring, and the heteroatoms may be at least one selected from B, O, N, P, Si, Se and S. The heterocyclic group may be a monocyclic or polycyclic ring. For example, heterocyclic groups can include, but are not limited to, dihydropyridinyl, piperidinyl, tetrahydrothiophenyl, thiooxytetrahydrothiophenyl, 4-piperidonyl, pyrrolidinyl, 2-pyrrolidinonyl, pyrrolinyl, tetrahydrofuranyl, bis-tetrahydrofuranyl, tetrahydropyranyl, bis-tetrahydropyranyl, tetrahydroquinolyl, tetrahydroisoquinolyl, decahydroquinolyl, octahydroisoquinolyl, azocinyl, phenanthridinyl, acridinyl, pyrimidinyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, piperazinyl, indolyl, isoindolyl, quinuclidinyl, morpholinyl, oxazolidinyl, and the like.

[0072] In the present disclosure, the alkoxy group referred to refers to a group formed by connecting an oxygen atom to the terminal of the above alkyl group.

[0073] In the present disclosure, the arylene group and heteroarylene group refer to a divalent group formed by the above-mentioned aryl group and heteroaryl group losing a hydrogen atom.

[0074] In the present disclosure, the halogen group may include fluorine, iodine, bromine, chlorine, and the like.

[0075] In the present disclosure, "ring" includes rings of cycloalkyl, aryl, heteroaryl, heterocyclyl, etc. as defined above.

[0076] In the present disclosure, substituted alkyl, alkylene, alkenyl, alkynyl, cycloalkyl, alkoxy, aryl, arylene, heteroaryl, heteroarylene, heterocyclic group, etc. can be a group in which one or more hydrogen atoms are replaced by groups such as deuterium, halogen groups, cyano groups, nitro groups, amino groups, hydroxyl groups, C6-C12 aromatic groups, 5-12 membered heteroaryl groups, C1-C6 alkyl groups, C1-C6 alkoxy groups, C3-C6 cycloalkyl groups, etc.

[0077] According to the structure of the compound of formula I comprising a benzoxazole group and a spirocyclic group disclosed in the present invention, the benzoxazole group has a high electron affinity, so that it has excellent electron conduction characteristics; at the same time, the benzoxazole group has a low LUMO energy level, can effectively transmit electrons to the light-emitting layer, so that the recombination probability of electrons and holes in the light-emitting layer increases, and the device shows a high luminous efficiency; the spirocyclic group has an orthogonal spatial stereo configuration, can reduce the van der Waals force between molecules, is conducive to preventing the crystallization of the electron transport material, and at the same time, makes the structure more rigid, so that the compound has a higher glass transition temperature, improves the film-forming property and thermal stability of the compound. Therefore, the compound of formula I developed by the present disclosure is used as an electron transport material for an organic electroluminescent device, which can make the device have a lower voltage and good luminous efficiency and a longer service life.

[0078] Therefore, another embodiment of the present disclosure provides use of the above-mentioned compound of the present disclosure as an electron transport material.

[0079] Yet another embodiment of the present disclosure provides use of the above-mentioned compound of the present disclosure for preparing an organic electroluminescent device.

[0080] Yet another embodiment of the present disclosure provides an organic electroluminescent device, which includes an electron transport layer, wherein the electron transport layer includes the compound of the present disclosure.

[0081] The electron transport layer may further include other materials as required.

[0082] In addition to the electron transport layer, the organic electroluminescent device may also include one or more layers of a cathode, an anode, an electron blocking layer, a light-emitting layer, an electron injection layer, a hole injection layer, a hole transport layer, a hole blocking layer, a covering layer, an encapsulation layer, etc., but is not limited thereto. The organic electroluminescent device may have a structure of a conventional organic electroluminescent device without particular limitation. For example, the organic electroluminescent device may have a structure of an anode / hole injection layer / hole transport layer / electron blocking layer / light-emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode, but is not limited thereto.

[0083] Figure 1 An organic electroluminescent device according to an embodiment of the present disclosure is shown. As shown in the figure, it includes 1: a substrate, 2: a first electrode (anode), 3: a hole injection layer, 4: a hole transport layer, 5: an electron blocking layer, 6: a light-emitting layer, 7: a hole blocking layer, 8: an electron transport layer, 9: an electron injection layer, and 10: a second electrode (cathode) stacked in sequence.

[0084] In this embodiment, the first electrode may be a transparent oxide ITO, IZO, or a composite electrode formed by ITO / Ag / ITO, Ag / IZO, CNT / ITO, CNT / IZO, etc.; the second electrode may be a silver-magnesium composite electrode or an Al electrode. In some embodiments, the anode is made of ITO glass and the cathode is made of Ag:Mg composite electrode.

[0085] The organic electroluminescent device according to the present disclosure further includes a substrate 1 disposed on a side of the first electrode 2 away from the second electrode 10 . The substrate 1 may be a transparent rigid or flexible material, such as glass, polyimide, etc., and may realize rigid substrate display and flexible display.

[0086] The organic electroluminescent device according to the present disclosure further includes a hole injection layer, a hole transport layer, an electron blocking layer and a light emitting layer stacked in sequence on a side of the first electrode 2 close to the hole blocking layer; and further includes an electron injection layer arranged on a side of the electron transport layer away from the hole blocking layer.

[0087] The material of the hole injection layer can be an inorganic oxide, such as oxides of metals such as molybdenum, titanium, vanadium, rhenium, ruthenium, chromium, zirconium, hafnium, tantalum, silver, tungsten, and manganese, or a dopant of a strong electron-withdrawing system, such as F4TCNQ, HAT-CN, etc., or P-type doping can be performed in the hole transport layer. The thickness of the hole injection layer can be 5nm to 30nm.

[0088] The material of the hole transport layer is a material with good hole transport properties, and may be an aromatic amine or carbazole material, such as NPB, TPD, BAFLP, DFLDPBi, etc. The thickness of the hole transport layer may be 300 nm to 100 nm.

[0089] The electron blocking layer, i.e., the light-emitting auxiliary layer, has hole transport properties and can be a red light-emitting auxiliary layer, a green light-emitting auxiliary layer, or a blue light-emitting auxiliary layer. The material of the electron blocking layer can be an aromatic amine or carbazole material, such as CBP, PCzPA, etc. The thickness of the electron blocking layer can be 5nm to 50nm.

[0090] The material of the light emitting layer may be a red fluorescent host material and a red light dopant, a green fluorescent host material and a green light dopant, or a blue fluorescent host and a blue light dopant. The fluorescent host material of the light-emitting layer may include one material or a mixture of two or more materials, wherein the fluorescent host material of the blue light-emitting layer may be selected from anthracene derivatives ADN, MADN, etc., and the blue light dopant may be pyrene derivatives, fluorene derivatives, perylene derivatives, styrylamine derivatives, metal complexes, etc., such as TBPe, BDAVBi, DPAVBi, FIrpic, etc.; the fluorescent host material of the green light-emitting layer may be selected from coumarin dyes, quinacrine copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, such as DMQA, BA-NPB, Alq3, etc., and the green light dopant may be a metal complex, such as Ir(ppy)3, Ir(ppy)2(acac), etc.; the fluorescent host material of the red light-emitting layer may be selected from DCM series materials, such as DCM, DCJTB, DCJTI, etc., and the red light dopant may be a metal complex, such as Ir(piq)2(acac), PtOEP, Ir(btp)2(acac), etc. The thickness of the light-emitting layer may be 20 nm to 100 nm.

[0091] The thickness of the hole blocking layer can be 5nm to 100nm. The material of the hole blocking layer can be selected from aromatic heterocyclic compounds, such as imidazole derivatives such as benzimidazole derivatives, imidazopyridine derivatives, benzimidazolephenanthridine derivatives, and oxazine derivatives such as pyrimidine derivatives and triazine derivatives, as well as compounds containing nitrogen-containing six-membered ring structures such as quinoline derivatives, isoquinoline derivatives, and phenanthroline derivatives, and can also include compounds having phosphine oxide-based substituents on the heterocyclic ring, such as OXD-7, TAZ, p-EtTAZ, BPhen, BCP, etc.

[0092] The thickness of the electron transport layer can be 20nm to 100nm. The material of the electron transport layer can be selected from the compounds according to the present disclosure. In addition to the compounds according to the present disclosure, the material of the electron transport layer may also include electron transport materials commonly used in the art. For example, the material of the electron transport layer may also include aromatic heterocyclic compounds, such as imidazole derivatives such as benzimidazole derivatives, imidazopyridine derivatives, benzimidazolephenanthridine derivatives, and pyrimidine derivatives, triazine derivatives and other azine derivatives, as well as quinoline derivatives, isoquinoline derivatives, phenanthroline derivatives and other nitrogen-containing six-membered ring structures, and may also include compounds having phosphine oxide-based substituents on heterocyclic rings, such as: OXD-7, TAZ, p-EtTAZ, BPhen, BCP, etc.

[0093] The thickness of the electron injection layer may be 1 nm to 10 nm. The electron injection layer material includes alkali metals or metals, such as LiF, Yb, Mg, Ca or compounds thereof.

[0094] In some embodiments, HAT-CN is selected as the hole injection layer material, NPB is selected as the hole transport layer material, TCTA is selected as the electron blocking layer material, DPEPO is selected as the hole blocking layer material, AND is selected as the blue light host material, and DPAVBi is selected as the blue light dopant.

[0095] Except that the electron transport layer contains the compound according to the present disclosure, the specific structure, material composition and preparation method of the cathode, anode, electron blocking layer, electron transport layer, electron injection layer, light-emitting layer, hole injection layer, hole transport layer, hole blocking layer, covering layer and encapsulation layer of the organic electroluminescent device of the embodiment of the present disclosure can adopt any suitable structure, material composition and preparation method without special limitation. The present disclosure does not involve the improvement of these components, so these components are not described in detail to avoid blurring the main technical ideas of the present disclosure.

[0096] Yet another embodiment of the present disclosure provides a display device including the organic electroluminescent device according to the present disclosure.

[0097] In some embodiments, the display device may include a plurality of organic electroluminescent devices, at least one of which is an organic electroluminescent device according to the present disclosure. For example, the organic electroluminescent device in the display device may be a blue, green or red organic electroluminescent device, but is not limited thereto.

[0098] The display device disclosed herein may be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a laptop computer, a digital photo frame, a navigator, a car display, a smart watch, a smart bracelet, etc. Other essential components of the display device are well understood by those skilled in the art, and are not described in detail herein, nor should they be used as a limitation to the present invention.

[0099] In the present disclosure, the word "comprise" or its variations, such as "include", "contain", "have", will be understood to include the stated elements, integers or steps, or a combination of elements, integers or steps, but does not exclude the addition of other elements, integers or steps, or a combination of elements, integers or steps.

[0100] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those of ordinary skill in the art to which the present invention belongs. Although those similar or equivalent to the methods and materials described herein may be used in the practice or testing of the present invention, suitable methods and materials will be described below. In the event of a conflict, this specification (including definitions) shall prevail. In addition, the materials, methods and embodiments are merely illustrative and are not intended to be restrictive.

[0101] “At least one of A, B, and C” has the same meaning as “at least one of A, B, or C” and both include the following combinations of A, B, and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0102] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0103] In the present disclosure, unless otherwise specified, "plurality" means two or more.

[0104] Beneficial Effects

[0105] The present disclosure provides a class of compounds including benzoxazole groups and spirocyclic groups, which can be used as electron transport materials in organic electroluminescent devices. In the structure of such compounds, the benzoxazole group has a higher electron affinity, so that it has excellent electron conduction characteristics; At the same time, the benzoxazole group has a lower LUMO energy level, and can effectively transfer electrons to the luminescent layer, so that the recombination probability of electrons and holes in the luminescent layer increases, and the device shows a high luminous efficiency; The spirocyclic group has an orthogonal spatial stereo configuration, which can reduce the van der Waals force between molecules, is conducive to preventing the crystallization of electron transport materials, and at the same time, makes the structure more rigid, so that the compound has a higher glass transition temperature, improves the film forming property and thermal stability of the compound. Therefore, the compounds including benzoxazole groups and spirocyclic groups disclosed in the present disclosure are used as electron transport materials for organic electroluminescent devices, which can make the device have a lower voltage and good luminous efficiency and a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Figure 1 A schematic structural diagram of an organic electroluminescent device according to one embodiment of the present application is shown.

[0107] Figure numerals: 1: substrate; 2: first electrode; 3: hole injection layer; 4: hole transport layer; 5: electron blocking layer; 6: light emitting layer; 7: hole blocking layer; 8: electron transport layer; 9: electron injection layer; 10: second electrode. DETAILED DESCRIPTION

[0108] In order to objectively evaluate the technical effects of the embodiments of the present disclosure, the technical solutions provided by the present disclosure will be described in detail and exemplarily through embodiments below. These embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the exemplary embodiments are fully conveyed to those skilled in the art. The features, structures or characteristics described in these exemplary embodiments can be combined in one or more embodiments in any suitable manner, so that they can be implemented in various forms, and therefore should not be understood as being limited to the examples set forth herein. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by those of ordinary skill in the art are within the scope of protection of the present disclosure.

[0109] Example

[0110] Provided below are some exemplary embodiments of the present disclosure, the synthesis process of compounds containing a benzoxazole group and a spiro group, and the results of testing and comparing the performance of the prepared organic electroluminescent devices.

[0111] Synthesis Example 1: Synthesis of Compound 1:

[0112]

[0113] Synthesis of intermediate M-1

[0114] 2,4-diphenyl-6-pinacol ester-1,3,5-triazine (3.59 g, 10 mmol), 2,7-dibromo-9,9-diphenylfluorene (5.0 g, 10.5 mmol), Pd(PPh3)4 (0.58 g, 0.5 mmol), potassium carbonate (2.76 g, 20 mmol) and THF / H2O (60 mL / 12 mL) were added to a 200 mL pressure bottle, and heated to 100 ° C under argon protection for 12 h. After the reaction was completed, it was cooled to room temperature, and a large amount of solid precipitated. The reaction solution was filtered, and the filtered solid was washed with ethanol (100 mL) and dried to obtain a white powder solid (4.7 g, 7.5 mmol). Yield: 75%. 1 H NMR (500MHz, Chloroform-D) δ8.43 (s, 1H), 8.36 (s, 4H), 8.06 (m, 2H), 7.79 (d, J = 5.0Hz, 2H), 7.64 (s, 1H), 7.50 (s, 6H), 7.22 (m, 6H), 7.10 (s, 4H).

[0115] Synthesis of compound 1

[0116] M-1 (4.5 g, 7.2 mmol), bis(pinacolato)diboron (2.13 g, 8.40 mmol), Pd(dppf)Cl2 (256 mg, 0.35 mmol), potassium acetate (2.06 g, 21.1 mmol) and 1,4-dioxane (35 mL) were added to a 125 mL round-bottom flask, and heated to 100 ° C under argon protection for 12 h of reflux reaction. After the reaction was completed, it was cooled to room temperature, and 1,4-dioxane was removed by vacuum rotary evaporation, and then separated and purified by chromatography on a silica gel column (petroleum ether: DCM = 20:1) to obtain a light yellow powdery solid. Add the light yellow powdery solid, 4-bromobenzo[d]oxazole (1.6 g, 8 mmol), Pd(PPh3)4 (0.58 g, 0.5 mmol), potassium carbonate (2.76 g, 20 mmol) and THF / H2O (60 mL / 12 mL) into a 200 mL pressure bottle, and heat to 100°C for 12 h under argon protection. After the reaction is completed, cool to room temperature, and a large amount of solid precipitates. Filter the reaction solution, wash the filtered solid with ethanol (100 mL), and dry to obtain a yellow powdery solid (3.75 g, 7.5 mmol). Yield: 78%. 1H NMR(500MHz,Chloroform-D)δ8.45(s,1H),8.36(s,4H),8.26(s,1H),8.09(s,2H),7.90(s ,1H),7.84(s,1H),7.78(d,J=5.0Hz,3H),7.51(d,J=5.0Hz,7H),7.22(m,6H),7.10(s,4H).

[0117] Synthesis Example 2: Synthesis of Compound 2:

[0118]

[0119] Synthesis of intermediate M-2

[0120] The synthesis of intermediate M-2 is similar to that of intermediate M-1, except that 2,7-dibromo-9,9-diphenylfluorene is replaced by 2,7-dibromo-9,9'-spirobifluorene. Yield: 79%. 1 H NMR(500MHz,Chloroform-D)δ8.36(s,4H),8.24(s,1H),8.09(s,1H),7.87(m,3H),7 .79(d,J=5.0Hz,2H),7.64(s,1H),7.60(s,2H),7.50(s,6H),7.24(d,J=5.0Hz,4H).

[0121] Synthesis of compound 2

[0122] The synthesis of compound 2 is similar to that of compound 1, except that M-1 is replaced by M-2. Yield: 72%. 1 H NMR(500MHz,Chloroform-D)δ8.36(s,4H),8.20(s,1H),8.08(s,2H),8.02(s,1H),7.90(s,3H),7 .84(s,1H),7.77(s,1H),7.70(d,J=15.5Hz,4H),7.51(d,J=5.0Hz,7H),7.34(s,2H),7.24(s,2H).

[0123] Synthesis Example 3: Synthesis of Compound 4:

[0124]

[0125] Synthesis of intermediate M-3

[0126] The synthesis of intermediate M-3 is similar to that of intermediate M-1, except that 2,7-dibromo-9,9-diphenylfluorene is replaced by 2,7-dibromospiro[9H-fluorene-9,9'-[9H]xanthene]. Yield: 76%. 1 H NMR(500MHz,Chloroform-D)δ8.36(s,4H),8.26(s,1H),8.09(s,1H),7.87(s,1H),7.79(d, J=5.0Hz,2H),7.65(s,1H),7.50(s,6H),7.31(s,2H),7.18(d,J=15.0Hz,4H),7.00(s,2H).

[0127] Synthesis of compound 4

[0128] The synthesis of compound 4 is similar to that of compound 1, except that M-1 is replaced by M-3. Yield: 78%. 1 H NMR(500MHz,Chloroform-D)δ8.36(s,4H),8.27(s,1H),8.10(d,J=8.5Hz,3H),7.90(s,1H),7.84(s, 1H),7.78(d,J=5.0Hz,3H),7.51(d,J=5.0Hz,7H),7.31(s,2H),7.18(d,J=15.0Hz,4H),7.00(s,2H).

[0129] Synthesis Example 4: Synthesis of Compound 25:

[0130]

[0131] The synthesis of compound 25 is similar to that of compound 1, except that 4-bromobenzo[d]oxazole is replaced by 7-bromobenzo[d]oxazole. Yield: 75%. 1 H NMR(500MHz,Chloroform-D)δ8.46(s,1H),8.36(s,4H),8.30(s,1H),8.09(s,2H),7.90(s ,1H),7.78(d,J=5.0Hz,3H),7.71(s,1H),7.51(d,J=5.0Hz,7H),7.22(m,6H),7.10(s,4H).

[0132] Synthesis Example 5: Synthesis of Compound 26:

[0133]

[0134] The synthesis of compound 26 was similar to that of compound 2, except that 4-bromobenzo[d]oxazole was replaced by 7-bromobenzo[d]oxazole. Yield: 72%. 1 H NMR(500MHz,Chloroform-D)δ8.36(s,4H),8.20(s,1H),8.10(s,1H),8.07(d,J=14.0Hz ,2H),7.90(s,3H),7.81–7.64(m,6H),7.51(d,J=5.0Hz,7H),7.34(s,2H),7.24(s,2H).

[0135] Synthesis Example 6: Synthesis of Compound 28:

[0136]

[0137] The synthesis of compound 28 is similar to that of compound 4, except that 4-bromobenzo[d]oxazole is replaced by 7-bromobenzo[d]oxazole. Yield: 74%. 1 H NMR (500MHz, Chloroform-D) δ8.36 (s, 4H), 8.28 (s, 1H), 8.11 (m, 3H), 7.90 (s, 1H), 7.78 (d, J = 5. 0Hz,3H),7.71(s,1H),7.51(d,J=5.0Hz,7H),7.31(s,2H),7.18(d,J=15.0Hz,4H),7.00(s,2H).

[0138] Synthesis Example 7: Synthesis of Compound 73:

[0139]

[0140] Synthesis of intermediate M-4

[0141] The synthesis of intermediate M-4 is similar to that of intermediate M-1, except that 2,7-dibromo-9,9-diphenylfluorene is replaced by 2',7'-dibromospiro[benzo[mn]anthracene-7,9'-fluorene]; 2,4-diphenyl-6-pinacol ester-1,3,5-triazine is replaced by 2,4-diphenyl-6-[3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl]-1,3,5-triazine. Yield: 70%. 1H NMR(500MHz,Chloroform-D)δ8.50(s,1H),8.37(d,J=10.0Hz,5H),8.32(s,1H),8.09(s,1H),8.05(s,1H),7.87(s ,1H),7.83–7.68(m,7H),7.65(s,1H),7.61(s,1H),7.50(s,6H),7.40(t,J=12.5Hz,3H),7.20(s,1H),6.86(s,1H).

[0142] Synthesis of compound 73

[0143] The synthesis of compound 73 is similar to that of compound 25, except that intermediate M-1 is replaced by M-4. Yield: 75%. 1 H NMR(500MHz,Chloroform-D)δ9.55(s,1H),8.50(s,1H),8.37(d,J=10.0Hz,5H),8.09(d,J=3.9Hz,3H),7 .95(s,1H),7.90(s,1H),7.84–7.66(m,9H),7.61(s,1H),7.57–7.31(m,10H),7.20(s,1H),6.86(s,1H).

[0144] Synthesis Example 8: Synthesis of Compound 75:

[0145]

[0146] Synthesis of intermediate M-5

[0147] The synthesis of intermediate M-5 was similar to that of intermediate M-4, except that 2',7'-dibromospiro[benzo[mn]anthracene-7,9'-fluorene] was replaced by 2,7-dibromospiro[fluorene-9,4'-indeno[1,2-b]thiophene]. Yield: 76%. 1 H NMR(500MHz,Chloroform-D)δ8.43–8.28(m,6H),8.18(s,1H),8.09(s,1H),7.96(s ,1H),7.84–7.57(m,6H),7.50(s,6H),7.46–7.29(m,3H),7.13(s,1H),6.98(s,1H).

[0148] Synthesis of compound 75

[0149] The synthesis of compound 75 is similar to that of compound 25, except that intermediate M-1 is replaced by M-5. Yield: 68% 1HNMR(500MHz,Chloroform-D)δ8.42–8.29(m,6H),8.23(s,1H),8.15(s,1H),8.09(s,2H),7.90(s,1H) ,7.88–7.66(m,6H),7.61(s,1H),7.51(d,J=5.0Hz,7H),7.46–7.26(m,3H),7.13(s,1H),6.98(s,1H).

[0150] Some performance parameters of some compounds disclosed in the present invention were measured: the HOMO / LUMO energy levels, reorganization energies, and HOMO / LUMO energy level data of these compounds were calculated using AC-3 & CV & UV spectroscopy tests and are listed in Table 1 below:

[0151] Table 1

[0152]

[0153]

[0154] Device Embodiment

[0155] The structure of the organic electroluminescent device prepared in the embodiment is as follows Figure 1 As shown, specifically: substrate / first electrode (ITO) / hole injection layer (5nm) / hole transport layer (30nm) / electron blocking layer (10nm) / light-emitting layer (20nm) / hole blocking layer (10nm) / electron transport layer (40nm) / electron injection layer (1nm) / second electrode (100nm).

[0156] The organic electroluminescent device uses the following functional layer materials: HAT-CN is a hole injection layer material, NPB is a hole transport layer material, TCTA is an electron blocking layer material, DPEPO is a hole blocking layer material, ADN is a blue light host material, DPAVBi is a blue light dopant, and the electron transport layer material uses the compound prepared in the embodiment of the present disclosure or Ref1.

[0157] The chemical structures of the specific materials are shown below:

[0158]

[0159] The general preparation process of organic electroluminescent devices is as follows:

[0160] The base substrate (glass plate) provided with the first electrode 1 (ITO) is ultrasonically treated in a cleaning agent, rinsed in deionized water, ultrasonically degreased in an acetone-ethanol mixed solvent, and baked in a clean environment until the moisture is completely removed.

[0161] The glass plate with ITO was placed in a vacuum chamber and evacuated to 1×10 -5 ~1×10 -6 A hole injection material is vacuum-deposited on the side of the ITO away from the glass plate to form a hole injection layer.

[0162] A hole transport material is evaporated on the side of the hole injection layer away from the ITO to form a hole transport layer.

[0163] An electron blocking material is vacuum-deposited on a side of the hole transport layer away from the hole injection layer to form an electron blocking layer.

[0164] A light-emitting material is vacuum evaporated on one side of the electron blocking layer away from the hole transport layer to form a light-emitting layer. The light-emitting material includes a host material and a guest material. The weight ratio of the host material to the guest material is 95:5 using a multi-source co-evaporation method.

[0165] A hole blocking material is vacuum-deposited on a side of the light-emitting layer away from the electron blocking layer to form a hole blocking layer.

[0166] An electron transport material is vacuum evaporated on a side of the hole blocking layer away from the light-emitting layer to form an electron transport layer.

[0167] An inorganic substance (LiF) as an electron injection material was vacuum-deposited to a thickness of 1 nm on the side of the electron transport layer away from the hole blocking layer to form an electron injection layer.

[0168] An Al layer is vacuum-deposited on the side of the electron injection layer away from the electron transport layer as a cathode.

[0169] Example 1

[0170] The device structure is:

[0171] Substrate / ITO / HAT-CN (20nm) / NPB (50nm) / TCTA (6nm) / ADN+5%DPAVBi (20nm) / DPEPO (10nm) / Compound 1 (40nm) / LiF (1nm) / Al (100nm); Compound 1 is used as the electron transport layer material.

[0172] Example 2

[0173] Except that the electron transport layer uses compound 2 to replace compound 1 in embodiment 1, everything else is the same as embodiment 1.

[0174] Example 3

[0175] Except that the electron transport layer uses compound 4 instead of compound 1 in embodiment 1, the rest is the same as embodiment 1.

[0176] Example 4

[0177] Except that the electron transport layer uses compound 25 instead of compound 1 in Example 1, everything else is the same as Example 1.

[0178] Example 5

[0179] Except that the electron transport layer uses compound 26 instead of compound 1 in Example 1, everything else is the same as Example 1.

[0180] Example 6

[0181] Except that the electron transport layer uses compound 28 instead of compound 1 in Example 1, everything else is the same as Example 1.

[0182] Example 7

[0183] Except that the electron transport layer uses compound 73 instead of compound 1 in Example 1, everything else is the same as Example 1.

[0184] Example 8

[0185] Except that the electron transport layer uses compound 75 instead of compound 1 in Example 1, everything else is the same as Example 1.

[0186] Comparative Example

[0187] Except that the electron transport layer uses compound Ref.1 to replace compound 1 in Example 1, everything else is the same as Example 1.

[0188] The performance of the organic electroluminescent devices prepared in the embodiments and comparative examples is shown in Table 2:

[0189] Table 2

[0190]

[0191] As can be seen from Table 2, the compound disclosed in the present invention is an electron transport material with good device performance. OLED devices using it as an electron transport layer material all show high efficiency, low driving voltage, and long life electroluminescent performance.

[0192] Although the present disclosure has been described above, the contents described are only embodiments adopted to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. Any person skilled in the art may make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present disclosure, but the scope of patent protection of this application shall still be subject to the scope defined in the attached claims.

Claims

1. A compound of the following formula I: In Formula I, Ar1 is represented by formula II, Ar2 is represented by Indicates that Ar1 and Ar2 are not connected to the same benzene ring at the same time; X1 is selected from a single bond; X2 is selected from one of direct disconnection, single bond, and O; or X2 and the adjacent substituent on the A1 ring together form a benzene ring; A1 and A2 are each independently selected from a benzene ring and a thiophene ring; L1 and L2 are each independently selected from a single bond, a phenylene group; Y1, Y2, Y3 are N; R1, R2, R3, and R4 each independently represent 1, 2 or 3 substituents, and the substituents are each independently selected from hydrogen, deuterium, halogen, cyano, nitro, hydroxyl, substituted or unsubstituted C1-C18 alkyl, and the substituted C1-C18 alkyl means that one or more hydrogen atoms in the group are substituted by a group selected from deuterium, halogen, cyano, nitro, amino, hydroxyl, C6-C12 aryl, 5-12 membered heteroaryl, C1-C6 alkyl, C1-C6 alkoxy, and C3-C6 cycloalkyl; or R1 adjacent to X2 and X2 together form a benzene ring.

2. The compound according to claim 1, wherein Formula II is selected from the following structures:

3. The compound according to claim 1, wherein Formula I is selected from the following structures: Wherein, Ar1, L1, Ar2, and X2 are defined as in claim 1, Y4, Y5, Y6, Y7 are C, Z2 and Z3 are S.

4. The compound according to claim 1, wherein Formula I is selected from the following structures:

5. Use of the compound according to any one of claims 1 to 4 as an electron transport material.

6. Use of the compound according to any one of claims 1 to 4 for preparing an organic electroluminescent device.

7. An organic electroluminescent device comprising an electron transport layer, wherein the electron transport layer comprises the compound according to any one of claims 1 to 4.

8. A display device comprising the organic electroluminescent device according to claim 7.

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