CN114591257B - Spirocyclic compounds, electron transport materials and light-emitting devices - Google Patents

Abstract

The embodiment of the application provides a spiro compound, an electron transport material and a light-emitting device, wherein the structural general formula of the spiro compound is shown as the following general formula (I), and R1-R8 in the general formula (I) respectively and independently comprise a substituted or unsubstituted group; ar1 and Ar2 contain at least one electron withdrawing group and cannot be hydrogen at the same time; the a and B rings each independently comprise a substituted or unsubstituted monocyclic or polycyclic aromatic ring, or comprise a substituted or unsubstituted phenyl, naphthyl, phenanthrene, fluoranthene, fluorene, thiophene, or furanyl group; n is 0 or 1; when N is 1, X is one of a direct bond, O, S, C and N, wherein when X is a direct bond, both the a ring and the B ring cannot be unsubstituted phenyl groups, and the spiro compound has an orthogonal spatial stereo configuration, which can reduce intermolecular van der waals force, facilitate the prevention of crystallization of an electron transport material, and has a rigid structure, which can improve the light emitting efficiency of a light emitting device.

Description

Spirocyclic compounds, electron transport materials and light-emitting devices

Technical Field

The present application relates to the technical field of luminescent materials, and in particular to a spiro compound, an electron transport material and a luminescent device.

Background Art

With the progress of information industry, organic light-emitting diodes (OLEDs) in light-emitting devices have the advantages of all-solid-state, autonomous light emission, high brightness, high resolution, wide viewing angle, fast response speed, thin thickness, small size, light weight, flexible substrate, low voltage DC drive, low power consumption, wide operating temperature range, etc. They can be used in lighting systems, communication systems, vehicle displays, portable electronic devices, high-definition displays and military fields, etc.

However, the electron transport materials in current light-emitting devices are prone to crystallization and lack rigidity, which reduces the display performance and luminous efficiency of the light-emitting devices.

Summary of the invention

In view of the shortcomings of the existing methods, the present application proposes a spiro compound, an electron transport material and a light-emitting device to solve the technical problems that the electron transport material in the existing light-emitting device is easy to crystallize and lacks rigidity, thereby reducing the display performance and luminous efficiency of the light-emitting device.

In the first aspect, the embodiments of the present application provide a spiro compound, the general structural formula of the spiro compound is shown in the following general formula (I):

In the general formula (I), R1 to R8 each independently include substituted or unsubstituted design groups; Ar1 and Ar2 contain at least one electron-withdrawing group and cannot be hydrogen at the same time; Ring A and Ring B each independently include substituted or unsubstituted monocyclic or polycyclic aromatic rings, or include substituted or unsubstituted phenyl, naphthyl, phenanthrene, fluoranthene, fluorene, thiophene or furanyl; n is 0 or 1; when n is 1, X is a direct bond, O, S, C and N, wherein when X is a direct bond, Ring A and Ring B cannot both be unsubstituted phenyl.

Optionally, when n in the general formula (I) is 0, the general structural formula is as shown in the following general formula (II):

Optionally, when X in the general formula (I) is a direct bond, the general structural formula is as shown in the following general formula (III):

Optionally, in the general formula (I), when n is 1 and X is one of O, S, C and N, the general structural formula is as shown in the following general formula (IV):

Optionally, the spiro compound comprises at least one of the following:

The electron withdrawing group is independently one of pyridyl, pyrimidinyl, triazine, phosphinoyl, nitrile, nitro, oxazolyl, quinoxalinyl, thiazolyl, quinolyl, imidazole, phenylpyrimidine, oxaborinyl, sulfone and derivatives thereof;

The Ar1 and the Ar2 are each independently one of the following: hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amine, arylphosphine, phosphine oxide, aryl, heteroaryl, or adjacent groups are combined to form a ring.

Optionally, the design groups of R1 to R8 are each independently one of the following: hydrogen, deuterium, cyano, halogen, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amine, phosphine oxide, aryl, heteroaryl, pyridyl, pyrimidinyl, triazine, phosphinoyl, nitrile, nitro, oxazolyl, quinoxalinyl, thiazolyl, quinolyl, imidazole, phenylpyrimidine, borocyclic group, sulfone group and derivatives thereof.

Optionally, the A ring and the B ring are each independently one of the following structural formulas:

In a second aspect, an embodiment of the present application provides an electron transport material, comprising the above-mentioned spiro compound.

In a third aspect, an embodiment of the present application provides a light-emitting device, comprising a first electrode, a light-emitting functional layer, and a second electrode stacked in sequence, wherein the light-emitting functional layer comprises an electron transport layer, and the electron transport layer comprises the above-mentioned electron transport material.

Optionally, the light-emitting functional layer further includes a hole blocking layer disposed on a side of the electron transport layer close to the first electrode, and the hole blocking layer includes the above-mentioned electron transport material.

The beneficial technical effects brought about by the technical solution provided by the embodiments of the present application include:

The present application provides a spiro compound, which has an orthogonal spatial stereo configuration, can reduce the van der Waals force between molecules, is beneficial to preventing the crystallization of the electron transport material containing the spiro compound, and can further improve the display performance of the light-emitting device containing the electron transport material; the spiro compound has a rigid structure, so that the electron transport material containing the spiro compound has a higher glass transition temperature, which is beneficial to improving the stability of the electron transport material, and can further improve the luminous efficiency of the light-emitting device and extend the service life of the light-emitting device; introducing an electron-withdrawing group into the spiro compound can achieve effective separation of HOMO and LUMO, which is beneficial to adjusting the matching of adjacent functional layers, making carrier transmission smoother, and further reducing the driving voltage of the light-emitting device.

Additional aspects and advantages of the present application will be partially given in the following description, which will become apparent from the following description, or will be understood through the practice of the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

FIG1 is a schematic diagram of a cross-sectional film structure of a light-emitting device provided in an embodiment of the present application.

Description of reference numerals:

1- first electrode;

2-light-emitting functional layer; 21-hole injection layer; 22-hole transport layer; 23-electron blocking layer; 24-light-emitting layer; 25-hole blocking layer; 26-electron transport layer; 27-electron injection layer.

3-substrate;

4- second electrode;

100 - light emitting device.

DETAILED DESCRIPTION

The embodiments of the present application are described below in conjunction with the drawings in the present application. It should be understood that the implementation methods described below in conjunction with the drawings are exemplary descriptions for explaining the technical solutions of the embodiments of the present application and do not constitute a limitation on the technical solutions of the embodiments of the present application.

Those skilled in the art will appreciate that, unless expressly stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of the features, integers, steps, operations, elements and/or components, but does not exclude the implementation of other features, information, data, steps, operations, elements, components and/or combinations thereof supported by the technical field. The term "and/or" used herein refers to at least one of the items defined by the term, for example, "A and/or B" may be implemented as "A", or as "B", or as "A and B".

In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example" or "some examples" are intended to indicate that a specific feature, structure, material or characteristic associated with the embodiment or example is included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

In order to make the objectives, technical solutions and advantages of the present application more clear, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

The research and development ideas of this application include: Generally, the mobility of holes in light-emitting devices is higher than that of electrons. In order to achieve balanced charge transfer and effective recombination of carriers and prevent single carrier accumulation, electron transport materials play an important role. Currently, electron transport materials are prone to crystallization and lack rigidity, which reduces the display performance and luminous efficiency of light-emitting devices.

The following is a detailed description of the technical solution of the present application and how the technical solution of the present application solves the above technical problems with specific embodiments. It should be noted that the following implementations can refer to, draw on or combine with each other, and the same terms, similar features and similar implementation steps in different implementations will not be described repeatedly.

The present application provides a spiro compound, which has a structural formula shown in general formula (I):

In the general formula (I), R1 to R8 each independently include substituted or unsubstituted design groups; Ar1 and Ar2 contain at least one electron withdrawing group and cannot be hydrogen at the same time; Ring A and Ring B each independently include substituted or unsubstituted monocyclic or polycyclic aromatic rings, or include substituted or unsubstituted phenyl, naphthyl, phenanthrene, fluoranthene, fluorene, thiophene or furanyl; n is 0 or 1; when n is 1, X is a direct bond, O, S, C and N, wherein when X is a direct bond, Ring A and Ring B cannot both be unsubstituted phenyl.

It should be noted that the A ring and the B ring each independently include a substituted or unsubstituted monocyclic or polycyclic aromatic ring, which means that the A ring and the B ring each independently include a substituted monocyclic aromatic ring, an unsubstituted monocyclic aromatic ring, a substituted polycyclic aromatic ring or an unsubstituted polycyclic aromatic ring; polycyclic means at least two rings.

In this embodiment, the spiro compound has an orthogonal spatial stereo configuration, which can reduce the van der Waals force between molecules, which is beneficial to preventing the crystallization of the electron transport material containing the spiro compound, and thus can improve the display performance of the light-emitting device; the spiro compound has a higher triplet energy level, and the electron transport material containing the spiro compound has a higher triplet energy level, which can prevent the excitons generated in the light-emitting layer from diffusing to the electron transport layer, thereby improving the luminous efficiency of the light-emitting device.

Furthermore, by utilizing the SP3 hybridization of the central C atom in the spiro compound, the conjugation of the molecule can be interrupted, so that the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels are distributed in the upper and lower parts, which is beneficial to the regulation of the energy level of the electron transport material and to preventing the triplet level from decreasing; the spiro compound has a rigid structure, so that the electron transport material containing the spiro compound has a higher glass transition temperature, which is beneficial to improving the stability of the electron transport material, thereby improving the luminous efficiency and service life of the light-emitting device; at the same time, the spiro compound adopts an asymmetric spiro structure, which can reduce the symmetry of the molecule and is beneficial to improving the film-forming property of the molecule.

Optionally, the electron-withdrawing group is independently pyridyl, pyrimidinyl, triazine, phosphinoxy, nitrile, nitro, oxazolyl, quinoxalinyl, thiazolyl, quinolyl, imidazole, phenylpyrimidine, oxaborinyl, sulfone and derivatives thereof, wherein the derivative refers to a derivative of pyridyl, pyrimidinyl, triazine, phosphinoxy, nitrile, nitro, oxazolyl, quinoxalinyl, thiazolyl, quinolyl, imidazole, phenylpyrimidine, oxaborinyl and sulfone.

In this embodiment, an electron-withdrawing group is introduced into the spiro compound, and the electron-withdrawing group is connected to the electron group, which can achieve effective separation of HOMO and LUMO, facilitate adjustment of the energy level of the light-emitting layer to match the adjacent functional layer, and make carrier transmission smoother.

Optionally, introducing specific electron-withdrawing groups, such as phosphino, cyano, and imidazole groups, into the spiro compound can improve the injectability of the electron transport material and thereby reduce the driving voltage of the light-emitting device.

Optionally, Ar1 and Ar2 are each independently one of the following: hydrogen, deuterium, nitrile, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amine, arylphosphine, phosphine oxide, aryl, heteroaryl, or adjacent groups are combined to form a ring, wherein adjacent groups refer to any two adjacent groups in the compound structure.

Optionally, the design groups of R1 to R8 are each independently one of the following: hydrogen, deuterium, cyano, halogen, nitro, hydroxyl, carbonyl, ester, imide, amide, alkyl, cycloalkyl, alkoxy, aryloxy, alkylthio, arylthio, alkylsulfonyl, arylsulfonyl, alkenyl, silyl, boron, amine, phosphine oxide, aryl, heteroaryl, pyridyl, pyrimidinyl, triazine, phosphinoyl, nitrile, nitro, oxazolyl, quinoxalinyl, thiazolyl, quinolyl, imidazole, phenylpyrimidine, borocyclic group, sulfone group and derivatives thereof.

Optionally, ring A and ring B are each independently one of the following structural formulas:

The structures of the A and B rings are not limited to the above structures, and a specific appropriate structure can be selected according to actual conditions.

Optionally, when n in the general formula (I) is 0, the general structural formula is as shown in the following general formula (II):

In this embodiment, the compound having the general formula (II) may include the following compounds 1 to 3:

It should be noted that the structure of the compound of general formula (II) is not limited to the above structure.

Optionally, when X in the general formula (I) is a direct bond, the general structural formula is as shown in the general formula (III):

In this embodiment, the compound having the general formula (III) may include the following compounds 4 to 60:

It should be noted that the structure of the compound of general formula (III) is not limited to the above structure.

Optionally, in the general formula (I), when n is 1 and X is one of O, S, C and N, the general structural formula is as shown in the following general formula (IV):

In this embodiment, the compound having the general formula (IV) may include the following compounds 61 to 87:

It should be noted that the structure of the compound of general formula (IV) is not limited to the above structure.

The specific preparation method of the spirocyclic compound of the present application will be described in detail below using multiple synthesis examples as examples, but the preparation method of the present application is not limited to these multiple synthesis examples.

Various chemicals used in this application, such as 4-bromophenanthrene, tetrahydrofuran, butyl lithium, acetic acid, sulfuric acid, dioxane, potassium acetate, potassium carbonate aqueous solution, anhydrous magnesium sulfate and other basic chemical raw materials can be purchased in the domestic chemical product market.

Synthesis Example 1

Synthesis of compound E1:

Step 1: Synthesize intermediate 1 as follows:

In a three-necked flask, 70 mmol of compound 1a (4-bromophenanthrene) was dissolved in 200 mL of tetrahydrofuran (THF) and cooled to -78°C; 64 mmol of butyl lithium (n-BuLi) was slowly added dropwise at a temperature not exceeding -75°C, and after the addition of butyl lithium, the temperature was raised to room temperature and reacted for 1 hour; 200 mL of THF solution containing 60 mmol of compound 1b was added to the reaction flask, and the mixture was refluxed for reaction for 3 hours; after the reaction was detected by TLC (Thin Layer Chromatography), extraction was performed with ethyl acetate; after the extraction was completed, concentration was performed to obtain compound 1c.

50 mmol of the above compound 1c was added to 200 mL of acetic acid, stirred at 80°C and 1-2 drops of sulfuric acid were added; after reflux for 3 hours, the temperature was lowered to room temperature, and after the reaction was completed, compound 1d was separated by extraction with dichloromethane.

After completely dissolving the above 38 mmol of compound 1d and 40.5 mmol of compound 1e in 170 mL of dioxane, 110.5 mmol of potassium acetate was added and heated with stirring. The temperature was lowered to room temperature. After the reaction was completed, the potassium carbonate solution was removed and the potassium acetate was filtered out; the filtrate was solidified with ethanol and filtered; the white solid was washed twice with ethanol, respectively, to obtain intermediate 1 with a yield of 82%.

Step 2: Synthesize compound E1 as follows:

Under nitrogen atmosphere, in a 500ml round-bottom flask, 15mmol of intermediate 1 and 13mmol of compound A1 were completely dissolved in 300ml of tetrahydrofuran, and then 100ml of 2M potassium carbonate aqueous solution was added; 0.39mmol of tetrakis(triphenylphosphine)palladium (Pd(PPh3)4) was added, and the mixture was heated and stirred for 4 hours; the temperature was lowered to room temperature, the water layer was removed, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure; and recrystallized with 250ml of ethyl acetate to obtain compound E1 with a yield of 76%.

Synthesis Example 2

Synthesis of compound E2:

Step 1: Synthesize intermediate 2 as follows:

The synthesis steps were the same as those of intermediate 1, except that compound 1b was changed to compound 2b, and other reagents remained unchanged to obtain intermediate 2 with a yield of 72.3%.

Step 2: Synthesize compound E1 as follows:

Under nitrogen atmosphere, in a 500ml round-bottom flask, 18.9mmol of intermediate 2 and 16.47mmol of compound B1 were completely dissolved in 150ml of tetrahydrofuran, and then 100ml of 2M potassium carbonate aqueous solution was added; 0.48mmol of tetrakis(triphenylphosphine)palladium was added, and the mixture was heated and stirred for 4 hours; the temperature was lowered to room temperature, the water layer was removed, and the mixture was dried over anhydrous magnesium sulfate, concentrated under reduced pressure, and recrystallized with 250ml of ethyl acetate to obtain compound E2 with a yield of 75.8%.

Synthesis Example 3

Synthesis of compound E3:

Step 1: Synthesis of intermediate 3, as follows:

The synthesis steps were the same as those of intermediate 1, except that compound 1b was changed to 3b, and other reagents remained unchanged to obtain intermediate 3 with a yield of 79.5%.

Step 2: Synthesize compound E3 as follows:

Under nitrogen atmosphere, in a 500 ml round-bottom flask, 18.9 mmol of intermediate 3 and 16.47 mmol of compound C1 were completely dissolved in 150 ml of tetrahydrofuran, and then 100 ml of 2M potassium carbonate aqueous solution was added. After adding 0.48 mmol of tetrakis(triphenylphosphine)palladium, heating and stirring were performed for 4 hours; the temperature was lowered to room temperature, the water layer was removed, and after drying with anhydrous magnesium sulfate, it was concentrated under reduced pressure and recrystallized with 250 ml of ethyl acetate to obtain compound E2 with a yield of 75.8%.

Synthesis Example 4

Synthesis of compound E4:

Step 1: Synthesis of intermediate 4, as follows:

The synthesis steps were the same as those of intermediate 1, except that compound 1b was changed to 4b, and other reagents remained unchanged to obtain intermediate 4 with a yield of 83.6%.

Step 2: Synthesize compound E4 as follows:

Under nitrogen atmosphere, in a 500 ml round-bottom flask, 16.7 mmol of intermediate 4 and 13.26 mmol of compound D1 were completely dissolved in 150 ml of tetrahydrofuran, and then 100 ml of 2M potassium carbonate aqueous solution was added. After adding 0.41 mmol of tetrakis(triphenylphosphine)palladium, heating and stirring were performed for 4 hours; the temperature was lowered to room temperature, the water layer was removed, and after drying with anhydrous magnesium sulfate, it was concentrated under reduced pressure and recrystallized with 250 ml of ethyl acetate to obtain compound E4 with a yield of 81.3%.

As shown in Table 1 below, the spatial stereo configurations of the spiro compounds of formula (II), formula (III) and formula (IV) were simulated using molecular simulation software, as follows:

Table 1

It can be seen from Table 1 that the spiro compound of the present application belongs to an orthogonal spatial stereo configuration. The use of electron transport materials containing the spiro compound allows the molecule to have a better spatial stereo structure, reduces the van der Waals force between molecules, can effectively prevent the crystallization of the electron transport material, and improve the luminescence performance of the light-emitting device.

As shown in Table 2 below, the distribution of the electron clouds of the spiro compounds of the general formula (II), the general formula (III) and the general formula (IV) were simulated using molecular simulation software, as follows:

Table 2

It can be seen from Table 2 that the SP3 hybridization of the central C atom in the spiro compound can interrupt the conjugation of the molecule, so that the HOMO and LUMO energy levels are distributed in the upper and lower parts, which is beneficial to the regulation of the energy level of the electron transport material and to prevent the triplet level from decreasing, and can achieve matching with the adjacent functional layer. At the same time, the spiro compound adopts an asymmetric spiro structure, which can reduce the symmetry of the molecule and is beneficial to improving the film-forming property of the molecule.

As shown in Table 3 below, the glass transition temperature (Tg) of the spiro compounds of formula (II), formula (III) and formula (IV) was tested using a DSC differential scanning calorimeter, a nitrogen atmosphere, a heating rate of 10°C/min, and a temperature range of 50 to 380°C. The specific results are as follows:

Table 3

It can be seen from Table 3 that the spiro compound of the present application has a rigid three-dimensional structure, and the electron transport material containing the spiro compound has a higher glass transition temperature, which is beneficial to improving the thermodynamic stability of the electron transport material; during the evaporation process, the electron transport material does not undergo cracking changes, has good moldability, and extends the service life of the electron transport material. The use of electron transport materials with high glass transition temperatures in light-emitting devices can significantly improve the performance of the device.

Based on the same inventive concept, an embodiment of the present application provides an electron transport material, which includes the spiro compound provided in the above embodiment.

In this embodiment, the electron transport material includes the above-mentioned spiro compound, and the beneficial effects of the electron transport material include the beneficial effects of the above-mentioned spiro compound, which will not be repeated here.

Based on the same inventive concept, an embodiment of the present application provides a light-emitting device 100, as shown in FIG. 1 , comprising a first electrode 1, a light-emitting functional layer 2, and a second electrode 4 stacked in sequence, the light-emitting functional layer 2 comprising an electron transport layer 26, and the electron transport layer 26 comprising the electron transport material provided in the above embodiment.

In this embodiment, the first electrode 1 is an anode, which can be a transparent oxide ITO, IZO, or a composite electrode formed by ITO/Ag/ITO, Ag/IZO, CNT/ITO, CNT/IZO, GO/ITO, GO/IZO, etc.; the second electrode 4 is a cathode. The electron transport material in the light-emitting device 100 introduces a spiro compound, so that the electron transport material has a higher triplet energy level, which can prevent the excitons generated in the light-emitting layer 24 from diffusing to the electron transport layer 26, thereby improving the luminous efficiency of the light-emitting device 100; the electron transport material introduces a spiro compound to improve the injectability of the electron transport material, thereby reducing the driving voltage of the light-emitting device 100; the electron transport material has a higher glass transition temperature, which is conducive to improving the stability of the electron transport material, thereby improving the luminous efficiency of the light-emitting device 100 and extending the service life of the light-emitting device 100.

Optionally, the light-emitting functional layer 2 further includes a hole blocking layer 25 disposed on a side of the electron transport layer 26 close to the first electrode 1 , and the hole blocking layer 25 includes the electron transport material provided in the above embodiment.

Optionally, the light emitting device 100 further comprises a substrate 3 disposed on a side of the first electrode 1 away from the second electrode 4 . The substrate 3 may be made of a transparent rigid or flexible substrate 3 material, such as glass, polyimide, and the like.

Optionally, the light-emitting functional layer 2 also includes a hole injection layer 21, a hole transport layer 22, an electron blocking layer 23 and a light-emitting layer 24 which are stacked in sequence on a side of the first electrode 1 close to the hole blocking layer 25; the light-emitting functional layer 2 also includes an electron injection layer 27 which is arranged on a side of the electron transport layer 26 away from the hole blocking layer 25.

In this embodiment, the hole injection layer 21 can be an inorganic oxide, such as molybdenum oxide, titanium oxide, vanadium oxide, rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungsten oxide, manganese oxide, etc., or it can also be a dopant of a strong electron-withdrawing system, such as F4TCNQ, HATCN, etc., or it can also be P-type doped in the hole transport material, and the thickness of the hole injection layer 21 can be 5nm (nanometer) to 30nm (nanometer). The material of the hole transport layer 22 has good hole transport properties, and can be an aromatic amine or carbazole material, such as NPB, TPD, BAFLP, DFLDPBi, etc., and the thickness of the hole transport layer 22 can be 100nm to 2000nm. The electron blocking layer 23, 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 light-emitting auxiliary layer can be aromatic amine or carbazole material, such as CBP, PCzPA, etc. The thickness of the electron blocking layer 23 can be 5nm to 100nm.

The light-emitting layer 24 can be a phosphorescent host and a red phosphorescent dopant, a phosphorescent host and a green phosphorescent dopant, or a fluorescent host and a fluorescent dopant. The host material of the light-emitting layer 24 can include one material or a mixture of two or more materials. The host material of the blue light-emitting layer 24 can be selected from anthracene derivatives ADN, MADN, etc., and the guest material can be pyrene derivatives, fluorene derivatives, perylene derivatives, styrylamine derivatives, metal complexes, etc., such as TBPe, BDAVBi, DPAVBi, FIrpic, etc.; the host material of the green light-emitting layer 24 can be selected from coumarin dyes, quinacridone copper derivatives, polycyclic aromatic hydrocarbons, diamine anthracene derivatives, carbazole derivatives, such as DMQA, BA-NPB, Alq3, etc., and the guest material can be a metal complex, such as Ir(ppy)3, Ir(ppy)2(acac), etc.; the red light-emitting host material can be selected from DCM series materials, such as DCM, DCJTB, DCJTI, etc., the guest material can be a metal complex, such as Ir(piq)2(acac), PtOEP, Ir(btp)2(acac), etc., and the thickness of the light-emitting layer 24 can be 20nm~100nm.

The thickness of the hole blocking layer 25 can be 5nm to 100nm, and the thickness of the electron transport layer 26 can be 20nm to 100nm. The hole blocking layer 25 and the electron transport layer 26 independently include 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 quinoline derivatives, isoquinoline derivatives, phenanthroline derivatives and other compounds containing nitrogen-containing six-membered ring structures, and can also include compounds having phosphine oxide-based substituents on heterocyclic rings, such as: OXD-7, TAZ, p-EtTAZ), BPhen, BCP, the electron transport material of the present application, etc. The thickness of the electron injection layer 27 can be 1nm to 10nm, and the material of the electron injection layer 27 includes alkali metals or metals, such as LiF, Yb, Mg, Ca or compounds thereof.

Taking Figure 1 as an example, the structure of the light-emitting device 100 is: substrate 3 (glass plate)/first electrode 1 (ITO)/hole injection layer 21 (10nm)/hole transport layer 22 (100nm)/electron blocking layer 23 (35nm)/light-emitting layer 24 (20nm)/hole blocking layer 25 (5nm)/electron transport layer 26 (30nm)/electron injection layer 27 (1nm)/second electrode 4 (100nm).

The following is a detailed description of the preparation process of the light emitting device 100 in FIG. 1 :

The substrate 3 (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.

The glass plate with ITO is 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 21 .

A hole transport material is deposited on the side of the hole injection layer 21 away from the ITO to form the hole transport layer 22 .

An electron blocking material is vacuum-deposited on a side of the hole transport layer 22 away from the hole injection layer 21 to form an electron blocking layer 23 .

A light-emitting material is vacuum evaporated on one side of the electron blocking layer 23 away from the hole transport layer 22 to form a light-emitting layer 24. The light-emitting material includes a host material and a guest material. The weight ratio of the host material to the guest material is 97:3 by a multi-source co-evaporation method.

A hole blocking material is vacuum-deposited on a side of the light-emitting layer 24 away from the electron blocking layer 23 to form a hole blocking layer 25 .

An electron transporting material is vacuum-deposited on a side of the hole blocking layer 25 away from the light-emitting layer 24 to form an electron transporting layer 26 .

An inorganic substance (LiF) as an electron injection material is vacuum-deposited to a thickness of 1 nm on the side of the electron transport layer 26 away from the hole blocking layer 25 to form the electron injection layer 27 .

An Al layer is plated on the electron injection layer 27 away from the evaporated electron transport layer 26 as a cathode.

As shown in Table 4 below, these are compounds in the materials used for the hole injection layer 21 , the hole transport layer 22 , the electron blocking layer 23 , the light emitting layer 24 , the hole blocking layer 25 and the electron transport layer 26 .

Table 4

The driving voltage and luminous efficiency of the following five light-emitting devices were measured at a fixed current density. At a current density of 15 mA/ ^cm2 , the service life of the light-emitting devices was tested. The electron transport material in the light-emitting device of Example 1 includes compound E1; the electron transport layer material in the light-emitting device of Example 2 includes compound E2; the electron transport material in the light-emitting device of Example 3 includes compound E3; the electron transport material in the light-emitting device of Example 4 includes compound E4; the electron transport material in the light-emitting device of Example 5 includes compound 83; the electron transport material in the light-emitting device of Example 6 includes a comparative compound. The test results are shown in Table 5.

Table 5

It can be seen from Table 5 that the driving voltages of Examples 1 to 5 are lower than the driving voltage of Example 6. This is because Compound E1, Compound E2, Compound E3, Compound E4 and Compound 83 contained in the electron transport layer utilize the SP3 hybridization of their central C atoms to interrupt the conjugation of the molecule, which is beneficial to the separation of HOMO and LUMO, and is convenient for regulating the energy level, which is beneficial to the matching of adjacent functional layers, and thus the light-emitting device has a lower driving voltage.

It can also be seen from Table 5 that the luminous efficiency and service life of Examples 1 to 5 are higher than the luminous efficiency and service life of Example 6. This is because compound E1, compound E2, compound E3, compound E4 and compound 83 contained in the electron transport layer have an orthogonal spatial stereo configuration, which can reduce the van der Waals force between molecules, which is beneficial to prevent the crystallization of the electron transport material, thereby improving the display performance of the light-emitting device, and compound E1, compound E2, compound E3, compound E4 and compound 83 have a rigid structure, so that the electron transport material has a higher glass transition temperature, which is beneficial to improve the stability of the electron transport material, thereby improving the luminous efficiency and service life of the light-emitting device.

By applying the embodiments of the present application, at least the following beneficial effects can be achieved:

1. The spiro compound provided in the embodiment of the present application has an orthogonal spatial configuration, which can reduce the van der Waals force between molecules, help prevent the crystallization of the electron transport material containing the spiro compound, and thus can improve the display performance of the light-emitting device.

2. The spiro compound provided in the embodiment of the present application has a higher triplet energy level, and the electron transport material containing the spiro compound has a higher triplet energy level, which can prevent the excitons generated in the light-emitting layer from diffusing to the electron transport layer, thereby improving the luminous efficiency of the light-emitting device.

3. The SP3 hybridization of the central C atom in the spirocyclic compound provided in the embodiment of the present application can interrupt the conjugation of the molecule, so that the HOMO and LUMO energy levels are distributed in the upper and lower parts, which is beneficial to the regulation of the energy level of the electron transport material and to prevent the triplet level from decreasing.

4. The spiro compound provided in the embodiment of the present application has a rigid structure, so that the electron transport material containing the spiro compound has a higher glass transition temperature, which is beneficial to improving the stability of the electron transport material. At the same time, the spiro compound adopts an asymmetric spiro structure, which can reduce the symmetry of the molecule and help improve the film-forming property of the molecule.

It will be appreciated by those skilled in the art that the various operations, methods, steps, measures, and schemes in the processes discussed in this application may be alternated, altered, combined, or deleted. Furthermore, other steps, measures, and schemes in the various operations, methods, and processes discussed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted. Furthermore, the steps, measures, and schemes in the prior art that are similar to those disclosed in this application may also be alternated, altered, rearranged, decomposed, combined, or deleted.

The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

The above is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the technical concept of the scheme of the present application, other similar implementation methods based on the technical ideas of the present application also fall within the protection scope of the embodiments of the present application.

Claims (4)

1. A spiro compound, characterized in that the structural formula of the spiro compound is as follows: The spiro compound includes at least one of Compound 1 to Compound 88: Compound 1 to Compound 3: Compound 4 to Compound 60: Compound 61 to Compound 88: 2. An electron transport material, characterized in that it comprises: the spiro compound as described in claim 1. 3. A light-emitting device, characterized in that it comprises a first electrode, a light-emitting functional layer and a second electrode which are stacked in sequence, wherein the light-emitting functional layer comprises an electron transport layer, and the electron transport layer comprises the electron transport material according to claim 2. 4 . The light-emitting device according to claim 3 , characterized in that the light-emitting functional layer further comprises a hole blocking layer arranged on a side of the electron transport layer close to the first electrode, and the hole blocking layer comprises the electron transport material according to claim 2 .